WorldWideScience

Sample records for arabidopsis leaf cells

  1. Chloroplast Dysfunction Causes Multiple Defects in Cell Cycle Progression in the Arabidopsis crumpled leaf Mutant

    KAUST Repository

    Hudik, Elodie

    2014-07-18

    The majority of research on cell cycle regulation is focused on the nuclear events that govern the replication and segregation of the genome between the two daughter cells. However, eukaryotic cells contain several compartmentalized organelles with specialized functions, and coordination among these organelles is required for proper cell cycle progression, as evidenced by the isolation of several mutants in which both organelle function and overall plant development were affected. To investigate how chloroplast dysfunction affects the cell cycle, we analyzed the crumpled leaf (crl) mutant of Arabidopsis (Arabidopsis thaliana), which is deficient for a chloroplastic protein and displays particularly severe developmental defects. In the crl mutant, we reveal that cell cycle regulation is altered drastically and that meristematic cells prematurely enter differentiation, leading to reduced plant stature and early endoreduplication in the leaves. This response is due to the repression of several key cell cycle regulators as well as constitutive activation of stress-response genes, among them the cell cycle inhibitor SIAMESE-RELATED5. One unique feature of the crl mutant is that it produces aplastidic cells in several organs, including the root tip. By investigating the consequence of the absence of plastids on cell cycle progression, we showed that nuclear DNA replication occurs in aplastidic cells in the root tip, which opens future research prospects regarding the dialogue between plastids and the nucleus during cell cycle regulation in higher plants.

  2. Hormonal Regulation of Leaf Morphogenesis in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Lin-Chuan Li; Ding-Ming Kang; Zhang-Liang Chen; Li-Jia Qu

    2007-01-01

    Leaf morphogenesis is strictly controlled not only by intrinsic genetic factors, such as transcriptional factors, but also by environmental cues, such as light, water and pathogens. Nevertheless, the molecular mechanism of how leaf rnorphogenesis is regulated by genetic programs and environmental cues is far from clear. Numerous series of events demonstrate that plant hormones, mostly small and simple molecules,play crucial roles in plant growth and development, and in responses of plants to environmental cues such as light. With more and more genetics and molecular evidence obtained from the model plant Arabidopsis,several fundamental aspects of leaf rnorphogenesis including the initiation of leaf primordia, the determination of leaf axes, the regulation of cell division and expansion in leaves have been gradually unveiled.Among these phytohormones, auxin is found to be essential in the regulation of leaf morphogenesis.

  3. Effects of mutations in the Arabidopsis Cold Shock Domain Protein 3 (AtCSP3) gene on leaf cell expansion.

    Science.gov (United States)

    Yang, Yongil; Karlson, Dale

    2012-08-01

    The cold shock domain is among the most evolutionarily conserved nucleic acid binding domains from prokaryotes to higher eukaryotes, including plants. Although eukaryotic cold shock domain proteins have been extensively studied as transcriptional and post-transcriptional regulators during various developmental processes, their functional roles in plants remains poorly understood. In this study, AtCSP3 (At2g17870), which is one of four Arabidopsis thaliana c old s hock domain proteins (AtCSPs), was functionally characterized. Quantitative RT-PCR analysis confirmed high expression of AtCSP3 in reproductive and meristematic tissues. A homozygous atcsp3 loss-of-function mutant exhibits an overall reduced seedling size, stunted and orbicular rosette leaves, reduced petiole length, and curled leaf blades. Palisade mesophyll cells are smaller and more circular in atcsp3 leaves. Cell size analysis indicated that the reduced size of the circular mesophyll cells appears to be generated by a reduction of cell length along the leaf-length axis, resulting in an orbicular leaf shape. It was also determined that leaf cell expansion is impaired for lateral leaf development in the atcsp3 loss-of-function mutant, but leaf cell proliferation is not affected. AtCSP3 loss-of-function resulted in a dramatic reduction of LNG1 transcript, a gene that is involved in two-dimensional leaf polarity regulation. Transient subcellular localization of AtCSP3 in onion epidermal cells confirmed a nucleocytoplasmic localization pattern. Collectively, these data suggest that AtCSP3 is functionally linked to the regulation of leaf length by affecting LNG1 transcript accumulation during leaf development. A putative function of AtCSP3 as an RNA binding protein is also discussed in relation to leaf development.

  4. Blue light-dependent nuclear positioning in Arabidopsis thaliana leaf cells.

    Science.gov (United States)

    Iwabuchi, Kosei; Sakai, Tatsuya; Takagi, Shingo

    2007-09-01

    The plant nucleus changes its intracellular position not only upon cell division and cell growth but also in response to environmental stimuli such as light. We found that the nucleus takes different intracellular positions depending on blue light in Arabidopsis thaliana leaf cells. Under dark conditions, nuclei in mesophyll cells were positioned at the center of the bottom of cells (dark position). Under blue light at 100 mumol m(-2) s(-1), in contrast, nuclei were located along the anticlinal walls (light position). The nuclear positioning from the dark position to the light position was fully induced within a few hours of blue light illumination, and it was a reversible response. The response was also observed in epidermal cells, which have no chloroplasts, suggesting that the nucleus has the potential actively to change its position without chloroplasts. Light-dependent nuclear positioning was induced specifically by blue light at >50 mumol m(-2) s(-1). Furthermore, the response to blue light was induced in phot1 but not in phot2 and phot1phot2 mutants. Unexpectedly, we also found that nuclei as well as chloroplasts in phot2 and phot1phot2 mutants took unusual intracellular positions under both dark and light conditions. The lack of the response and the unusual positioning of nuclei and chloroplasts in the phot2 mutant were recovered by externally introducing the PHOT2 gene into the mutant. These results indicate that phot2 mediates the blue light-dependent nuclear positioning and the proper positioning of nuclei and chloroplasts. This is the first characterization of light-dependent nuclear positioning in spermatophytes.

  5. High-contrast three-dimensional imaging of the Arabidopsis leaf enables the analysis of cell dimensions in the epidermis and mesophyll

    Directory of Open Access Journals (Sweden)

    Granier Christine

    2010-07-01

    Full Text Available Abstract Background Despite the wide spread application of confocal and multiphoton laser scanning microscopy in plant biology, leaf phenotype assessment still relies on two-dimensional imaging with a limited appreciation of the cells' structural context and an inherent inaccuracy of cell measurements. Here, a successful procedure for the three-dimensional imaging and analysis of plant leaves is presented. Results The procedure was developed based on a range of developmental stages, from leaf initiation to senescence, of soil-grown Arabidopsis thaliana (L. Heynh. Rigorous clearing of tissues, made possible by enhanced leaf permeability to clearing agents, allowed the optical sectioning of the entire leaf thickness by both confocal and multiphoton microscopy. The superior image quality, in resolution and contrast, obtained by the latter technique enabled the three-dimensional visualisation of leaf morphology at the individual cell level, cell segmentation and the construction of structural models. Image analysis macros were developed to measure leaf thickness and tissue proportions, as well as to determine for the epidermis and all layers of mesophyll tissue, cell density, volume, length and width. For mesophyll tissue, the proportion of intercellular spaces and the surface areas of cells were also estimated. The performance of the procedure was demonstrated for the expanding 6th leaf of the Arabidopsis rosette. Furthermore, it was proven to be effective for leaves of another dicotyledon, apple (Malus domestica Borkh., which has a very different cellular organisation. Conclusions The pipeline for the three-dimensional imaging and analysis of plant leaves provides the means to include variables on internal tissues in leaf growth studies and the assessment of leaf phenotypes. It also allows the visualisation and quantification of alterations in leaf structure alongside changes in leaf functioning observed under environmental constraints. Data

  6. Characterization of temperature-sensitive mutants reveals a role for receptor-like kinase SCRAMBLED/STRUBBELIG in coordinating cell proliferation and differentiation during Arabidopsis leaf development.

    Science.gov (United States)

    Lin, Lin; Zhong, Si-Hui; Cui, Xiao-Feng; Li, Jianming; He, Zu-Hua

    2012-12-01

    The balance between cell proliferation and cell differentiation is essential for leaf patterning. However, identification of the factors coordinating leaf patterning and cell growth behavior is challenging. Here, we characterized a temperature-sensitive Arabidopsis mutant with leaf blade and venation defects. We mapped the mutation to the sub-2 allele of the SCRAMBLED/STRUBBELIG (SCM/SUB) receptor-like kinase gene whose functions in leaf development have not been demonstrated. The sub-2 mutant displayed impaired blade development, asymmetric leaf shape and altered venation patterning under high ambient temperature (30°C), but these defects were less pronounced at normal growth temperature (22°C). Loss of SCM/SUB function results in reduced cell proliferation and abnormal cell expansion, as well as altered auxin patterning. SCM/SUB is initially expressed throughout leaf primordia and becomes restricted to the vascular cells, coinciding with its roles in early leaf patterning and venation formation. Furthermore, constitutive expression of the SCM/SUB gene also restricts organ growth by inhibiting the transition from cell proliferation to expansion. We propose the existence of a SCM/SUB-mediated developmental stage-specific signal for leaf patterning, and highlight the importance of the balance between cell proliferation and differentiation for leaf morphogenesis.

  7. CCR1, an enzyme required for lignin biosynthesis in Arabidopsis, mediates cell proliferation exit for leaf development

    DEFF Research Database (Denmark)

    Xue, Jingshi; Luo, Dexian; Xu, Deyang;

    2015-01-01

    exit in leaves. CCR1 is expressed basipetally in the leaf, and ccr1 mutants exhibited multiple abnormalities, including increased cell proliferation. The ccr1 phenotypes are not due to the reduced lignin content, but instead are due to the dramatically increased level of ferulic acid (FeA......), an intermediate in lignin biosynthesis. FeA is known to have antioxidant activity, and the levels of reactive oxygen species (ROS) in ccr1 were markedly reduced. We also characterized another double mutant in CAFFEIC ACID O-METHYLTRANSFERASE (comt) and CAFFEOYL CoA 3-O-METHYLTRANSFERASE (ccoaomt), in which the FeA...... level was dramatically reduced. Cell proliferation in comt ccoaomt leaves was decreased, accompanied by elevated ROS levels, and the mutant phenotypes were partially rescued by treatment with FeA or another antioxidant (N-acetyl-L-cysteine). Taken together, our results suggest that CCR1, FeA and ROS...

  8. Expression of potato RNA-binding proteins StUBA2a/b and StUBA2c induces hypersensitive-like cell death and early leaf senescence in Arabidopsis.

    Science.gov (United States)

    Na, Jong-Kuk; Kim, Jae-Kwang; Kim, Dool-Yi; Assmann, Sarah M

    2015-07-01

    The Arabidopsis thaliana genome encodes three RNA-binding proteins (RBPs), UBP1-associated protein 2a (UBA2a), UBA2b, and UBA2c, that contain two RNA-recognition motif (RRM) domains. They play important roles in wounding response and leaf senescence, and are homologs of Vicia faba abscisic-acid-activated protein kinase-interacting protein 1 (VfAKIP1). The potato (Solanum tuberosum) genome encodes at least seven AKIP1-like RBPs. Here, two potato RBPs have been characterized, StUBA2a/b and StUBA2c, that are homologous to VfAKIP1 and Arabidopsis UBA2s. Transient expression of StUBA2s induced a hypersensitive-like cell death phenotype in tobacco leaves, and an RRM-domain deletion assay of StUBA2s revealed that the first RRM domain is crucial for the phenotype. Unlike overexpression of Arabidopsis UBA2s, constitutive expression of StUBA2a/b in Arabidopsis did not cause growth arrest and lethality at the young seedling stage, but induced early leaf senescence. This phenotype was associated with increased expression of defence- and senescence-associated genes, including pathogen-related genes (PR) and a senescence-associated gene (SAG13), and it was aggravated upon flowering and ultimately resulted in a shortened life cycle. Leaf senescence of StUBA2a/b Arabidopsis plants was enhanced under darkness and was accompanied by H2O2 accumulation and altered expression of autophagy-associated genes, which likely cause cellular damage and are proximate causes of the early leaf senescence. Expression of salicylic acid signalling and biosynthetic genes was also upregulated in StUBA2a/b plants. Consistent with the localization of UBA2s-GFPs and VfAKIP1-GFP, soluble-modified GFP-StUBA2s localized in the nucleus within nuclear speckles. StUBA2s potentially can be considered for transgenic approaches to induce potato shoot senescence, which is desirable at harvest. PMID:25944928

  9. Leaf Positioning of Arabidopsis in Response to Blue Light

    Institute of Scientific and Technical Information of China (English)

    Shin-ichiro Inoue; Toshinori Kinoshita; Atsushi Takemiya; Michio Doi; Ken-ichiro Shimazaki

    2008-01-01

    Appropriate leaf positioning is essential for optimizing photosynthesis and plant growth. However, it has not been elucidated how green leaves reach and maintain their position for capturing light. We show here the regulation of leaf positioning under blue light stimuli. When 1-week-old Arabidopsis seedlings grown under white light were transferred to red light (25 μmol m-2s-t) for 5 d, new petioles that appeared were almost horizontal and their leaves were curled and slanted downward. However, when a weak blue light from above (0.1 μmol m-2s-1) was superimposed on red light, the new petioles grew obliquely upward and the leaves were flat and horizontal. The leaf positioning required both phototropin1 (phot1) and nonphototropic hypocotyl 3 (NPH3), and resulted in enhanced plant growth. In an nph3 mutant, neither optimal leaf positioning nor leaf flattening by blue light was found, and blue light-induced growth enhancement was drastically reduced. When blue light was increased from 0.1 to 5 μmol m-2s-1, normal leaf positioning and leaf flattening were induced in both phot1 and nph3 mutants, suggesting that phot2 signaling became functional and that the signaling was independent of phot1 and NPH3 in these responses. When plants were irradiated with blue light (0.1 μmol m-2s-1) from the side and red light from above, the new leaves became oriented toward the source of blue light. When we transferred these plants to both blue light and red light from above, the leaf surface changed its orientation to the new blue light source within a few hours, whereas the petioles initially were unchanged but then gradually rotated, suggesting the plasticity of leaf positioning in response to blue light. We showed the tissue expression of NPH3 and its plasma membrane localization via the coiled-coil domain and the C-terminal region. We conclude that NPH3-mediated phototropin signaling optimizes the efficiency of light perception by inducing both optimal leaf positioning and leaf

  10. The TORNADO1 and TORNADO2 genes function in several patterning processes during early leaf development in Arabidopsis thaliana

    OpenAIRE

    Cnops, Gerda; Neyt, Pia; Raes, Jeroen; Petrarulo, Marica; Nelissen, Hilde; Malenica, Nenad; Luschnig, Christian; Tietz, Olaf; Ditengou, Franck; Palme, Klaus; Azmi, Abdelkrim; Prinsen, Els; Van Lijsebettens, Maria

    2006-01-01

    In multicellular organisms, patterning is a process that generates axes in the primary body plan, creates domains upon organ formation, and finally leads to differentiation into tissues and cell types. We identified the Arabidopsis thaliana TORNADO1 (TRN1) and TRN2 genes and their role in leaf patterning processes such as lamina venation, symmetry, and lateral growth. In trn mutants, the leaf venation network had a severely reduced complexity: incomplete loops, no tertiary or quaternary veins...

  11. Stem cell organization in Arabidopsis

    OpenAIRE

    Wendrich, J.R.

    2016-01-01

    Growth of plant tissues and organs depends on continuous production of new cells, by niches of stem cells. Stem cells typically divide to give rise to one differentiating daughter and one non-differentiating daughter. This constant process of self-renewal ensures that the niches of stem cells or meristems stay active throughout plant-life. Specification of stem cells occurs very early during development of the emrbyo and they are maintained during later stages. The Arabidopsis embryo is a hig...

  12. Testing models for the leaf economics spectrum with leaf and whole-plant traits in Arabidopsis thaliana.

    Science.gov (United States)

    Blonder, Benjamin; Vasseur, François; Violle, Cyrille; Shipley, Bill; Enquist, Brian J; Vile, Denis

    2015-05-08

    The leaf economics spectrum (LES) describes strong relationships between multiple functional leaf traits that determine resource fluxes in vascular plants. Five models have been proposed to explain these patterns: two based on patterns of structural allocation, two on venation networks and one on resource allocation to cell walls and cell contents. Here we test these models using data for leaf and whole-plant functional traits. We use structural equation modelling applied to multiple ecotypes, recombinant inbred lines, near isogenic lines and vascular patterning mutants of Arabidopsis thaliana that express LES trait variation. We show that a wide variation in multiple functional traits recapitulates the LES at the whole-plant scale. The Wright et al. (2004) model and the Blonder et al. (2013) venation network model cannot be rejected by data, while two simple models and the Shipley et al. (2006) allocation model are rejected. Venation networks remain a key hypothesis for the origin of the LES, but simpler explanations also cannot be ruled out.

  13. A VAMP-associated protein, PVA31 is involved in leaf senescence in Arabidopsis.

    Science.gov (United States)

    Ichikawa, Mie; Nakai, Yusuke; Arima, Keita; Nishiyama, Sayo; Hirano, Tomoko; Sato, Masa H

    2015-01-01

    VAMP-associated proteins (VAPs) are highly conserved among eukaryotes. Here, we report a functional analysis of one of the VAPs, PVA31, and demonstrate its novel function on leaf senescence in Arabidopsis. The expression of PVA31 is highly induced in senescence leaves, and localizes to the plasma membrane as well as the ARA7-positive endosomes. Yeast two-hybrid analysis demonstrates that PVA31 is interacted with the plasma membrane localized-VAMP proteins, VAMP721/722/724 but not with the endosome-localized VAMPs, VAMP711 and VAMP727, indicating that PVA31 is associated with VAMP721/722/724 on the plasma membrane. Strong constitutive expression of PVA31 under the control of the Cauliflower mosaic virus 35S promoter induces the typical symptom of leaf senescence earlier than WT in normal growth and an artificially induced senescence conditions. In addition, the marker genes for the SA-mediated signaling pathways, PR-1, is promptly expressed with elicitor application. These data indicate that PVA31-overexpressing plants exhibit the early senescence phenotype in their leaves, and suggest that PVA31 is involved in the SA-mediated programmed cell death process during leaf senescence and PR-protein secretion during pathogen infection in Arabidopsis.

  14. Leaf hydraulic conductance varies with vein anatomy across Arabidopsis thaliana wild-type and leaf vein mutants.

    Science.gov (United States)

    Caringella, Marissa A; Bongers, Franca J; Sack, Lawren

    2015-12-01

    Leaf venation is diverse across plant species and has practical applications from paleobotany to modern agriculture. However, the impact of vein traits on plant performance has not yet been tested in a model system such as Arabidopsis thaliana. Previous studies analysed cotyledons of A. thaliana vein mutants and identified visible differences in their vein systems from the wild type (WT). We measured leaf hydraulic conductance (Kleaf ), vein traits, and xylem and mesophyll anatomy for A. thaliana WT (Col-0) and four vein mutants (dot3-111 and dot3-134, and cvp1-3 and cvp2-1). Mutant true leaves did not possess the qualitative venation anomalies previously shown in the cotyledons, but varied quantitatively in vein traits and leaf anatomy across genotypes. The WT had significantly higher mean Kleaf . Across all genotypes, there was a strong correlation of Kleaf with traits related to hydraulic conductance across the bundle sheath, as influenced by the number and radial diameter of bundle sheath cells and vein length per area. These findings support the hypothesis that vein traits influence Kleaf , indicating the usefulness of this mutant system for testing theory that was primarily established comparatively across species, and supports a strong role for the bundle sheath in influencing Kleaf .

  15. In vivo packaging of triacylglycerols enhances Arabidopsis leaf biomass and energy density.

    Science.gov (United States)

    Winichayakul, Somrutai; Scott, Richard William; Roldan, Marissa; Hatier, Jean-Hugues Bertrand; Livingston, Sam; Cookson, Ruth; Curran, Amy Christina; Roberts, Nicholas John

    2013-06-01

    Our dependency on reduced carbon for energy has led to a rapid increase in the search for sustainable alternatives and a call to focus on energy densification and increasing biomass yields. In this study, we generated a uniquely stabilized plant structural protein (cysteine [Cys]-oleosin) that encapsulates triacylglycerol (TAG). When coexpressed with diacylglycerol O-acyltransferase (DGAT1) in Arabidopsis (Arabidopsis thaliana), we observed a 24% increase in the carbon dioxide (CO2) assimilation rate per unit of leaf area and a 50% increase in leaf biomass as well as approximately 2-, 3-, and 5-fold increases in the fatty acid content of the mature leaves, senescing leaves, and roots, respectively. We propose that the coexpression led to the formation of enduring lipid droplets that prevented the futile cycle of TAG biosynthesis/lipolysis and instead created a sustained demand for de novo lipid biosynthesis, which in turn elevated CO2 recycling in the chloroplast. Fatty acid profile analysis indicated that the formation of TAG involved acyl cycling in Arabidopsis leaves and roots. We also demonstrate that the combination of Cys-oleosin and DGAT1 resulted in the highest accumulation of fatty acids in the model single-cell eukaryote, Saccharomyces cerevisiae. Our results support the notion that the prevention of lipolysis is vital to enabling TAG accumulation in vegetative tissues and confirm the earlier speculation that elevating fatty acid biosynthesis in the leaf would lead to an increase in CO2 assimilation. The Cys-oleosins have applications in biofuels, animal feed, and human nutrition as well as in providing a tool for investigating fatty acid biosynthesis and catabolism. PMID:23616604

  16. Hpa1 harpin needs nitroxyl terminus to promote vegetative growth and leaf photosynthesis in Arabidopsis

    Indian Academy of Sciences (India)

    Xiaojie Li; Liping Han; Yanying Zhao; Zhenzhen You; Chunling Zhang; Zhenzhen You; Hansong Dong; Chunling Zhang

    2014-03-01

    Hpa1 is a harpin protein produced by Xanthomonas oryzae, an important bacterial pathogen of rice, and has the growth-promoting activity in plants. To understand the molecular basis for the function of Hpa1, we generated an inactive variant protein, Hpa1NT, by deleting the nitroxyl-terminal region of the Hpa1 sequence and compared Hpa1NT with the full-length protein in terms of the effects on vegetative growth and related physiological responses in Arabidopsis. When Hpa1 was applied to plants, it acted to enhance the vegetative growth but did not affect the floral development. Enhanced plant growth was accompanied by induced expression of growth-promoting genes in plant leaves. The growth-promoting activity of Hpa1 was further correlated with a physiological consequence shown as promoted leaf photosynthesis as a result of facilitated CO2 conduction through leaf stomata and mesophyll cells. On the contrary, plant growth, growth-promoting gene expression, and the physiological consequence changed little in response to the Hpa1NT treatment. These analyses suggest that Hpa1 requires the nitroxyl-terminus to facilitate CO2 transport inside leaf cells and promote leaf photosynthesis and vegetative growth of the plant.

  17. Structural assessment of the impact of environmental constraints on Arabidopsis thaliana leaf growth: a 3D approach.

    Science.gov (United States)

    Wuyts, Nathalie; Massonnet, Catherine; Dauzat, Myriam; Granier, Christine

    2012-09-01

    Light and soil water content affect leaf surface area expansion through modifications in epidermal cell numbers and area, while effects on leaf thickness and mesophyll cell volumes are far less documented. Here, three-dimensional imaging was applied in a study of Arabidopsis thaliana leaf growth to determine leaf thickness and the cellular organization of mesophyll tissues under moderate soil water deficit and two cumulative light conditions. In contrast to surface area, thickness was highly conserved in response to water deficit under both low and high cumulative light regimes. Unlike epidermal and palisade mesophyll tissues, no reductions in cell number were observed in the spongy mesophyll; cells had rather changed in volume and shape. Furthermore, leaf features of a selection of genotypes affected in leaf functioning were analysed. The low-starch mutant pgm had very thick leaves because of unusually large palisade mesophyll cells, together with high levels of photosynthesis and stomatal conductance. By means of an open stomata mutant and a 9-cis-epoxycarotenoid dioxygenase overexpressor, it was shown that stomatal conductance does not necessarily have a major impact on leaf dimensions and cellular organization, pointing to additional mechanisms for the control of CO(2) diffusion under high and low stomatal conductance, respectively.

  18. The cyclic nucleotide gated cation channel AtCNGC10 traffics from the ER via Golgi vesicles to the plasma membrane of Arabidopsis root and leaf cells

    Directory of Open Access Journals (Sweden)

    Andres Marilou A

    2007-09-01

    Full Text Available Abstract Background The cyclic nucleotide-gated ion channels (CNGCs maintain cation homeostasis essential for a wide range of physiological processes in plant cells. However, the precise subcellular locations and trafficking of these membrane proteins are poorly understood. This is further complicated by a general deficiency of information about targeting pathways of membrane proteins in plants. To investigate CNGC trafficking and localization, we have measured Atcngc5 and Atcngc10 expression in roots and leaves, analyzed AtCNGC10-GFP fusions transiently expressed in protoplasts, and conducted immunofluorescence labeling of protoplasts and immunoelectron microscopic analysis of high pressure frozen leaves and roots. Results AtCNGC10 mRNA and protein levels were 2.5-fold higher in roots than leaves, while AtCNGC5 mRNA and protein levels were nearly equal in these tissues. The AtCNGC10-EGFP fusion was targeted to the plasma membrane in leaf protoplasts, and lightly labeled several intracellular structures. Immunofluorescence microscopy with affinity purified CNGC-specific antisera indicated that AtCNGC5 and AtCNGC10 are present in the plasma membrane of protoplasts. Immunoelectron microscopy demonstrated that AtCNGC10 was associated with the plasma membrane of mesophyll, palisade parenchyma and epidermal cells of leaves, and the meristem, columella and cap cells of roots. AtCNCG10 was also observed in the endoplasmic reticulum and Golgi cisternae and vesicles of 50–150 nm in size. Patch clamp assays of an AtCNGC10-GFP fusion expressed in HEK293 cells measured significant cation currents. Conclusion AtCNGC5 and AtCNGC10 are plasma membrane proteins. We postulate that AtCNGC10 traffics from the endoplasmic reticulum via the Golgi apparatus and associated vesicles to the plasma membrane. The presence of the cation channel, AtCNGC10, in root cap meristem cells, cell plate, and gravity-sensing columella cells, combined with the previously reported

  19. The developmental transition to flowering in Arabidopsis is associated with an increase in leaf chloroplastic lipoxygenase activity.

    Science.gov (United States)

    Bañuelos, Gloria Rodriguez; Argumedo, Ruby; Patel, Komal; Ng, Vicky; Zhou, Feimeng; Vellanoweth, Robert Luis

    2008-03-01

    The developmental transition from vegetative growth to flowering in Arabidopsis is associated with a precipitous decline in the activity of leaf ascorbate peroxidase (APx), an enzymatic scavenger of hydrogen peroxide, and an increase in specific lipid peroxidation leading to the accumulation of 13-hydroperoxy-9,11,15 (Z,E,Z) octadecatrienoic acid (13 HOO-FA). The appearance of this specific isomer suggests that it is of enzymatic origin and may represent the activation of an oxylipin signaling pathway. We thus hypothesized that leaf 13-lipoxygenase (LOX) activity increases at the floral transition and leads to the observed elevation of 13-HOO-FA levels. Leaf protein extracts were prepared from seven distinct life stages of Arabidopsis plants and used to assay for LOX activity. We report that leaf 13-LOX enzymatic activity increases two- to three-fold from the vegetative stage to the immediate post-floral transition stage. We found two forms of LOX activity in cell extracts and show that the higher pH optimum form is the isoenzyme activated. This increase is correlated with a small increase in H(2)O(2), perhaps resulting from the previously reported decline in leaf APx activity. Very low levels of exogenous H(2)O(2) activate the induced form in vegetative leaf extracts in vitro, suggesting that the floral transition-dependent APx decline and subsequent H(2)O(2) elevation are involved in activating plastid 13-LOX and thus a second messenger oxylipin pathway.

  20. Distinct palisade tissue development processes promoted by leaf autonomous signalling and long-distance signalling in Arabidopsis thaliana.

    Science.gov (United States)

    Munekage, Yuri Nakajima; Inoue, Shio; Yoneda, Yuki; Yokota, Akiho

    2015-06-01

    Plants develop palisade tissue consisting of cylindrical mesophyll cells located at the adaxial side of leaves in response to high light. To understand high light signalling in palisade tissue development, we investigated leaf autonomous and long-distance signal responses of palisade tissue development using Arabidopsis thaliana. Illumination of a developing leaf with high light induced cell height elongation, whereas illumination of mature leaves with high light increased cell density and suppressed cell width expansion in palisade tissue of new leaves. Examination using phototropin1 phototropin2 showed that blue light signalling mediated by phototropins was involved in cell height elongation of the leaf autonomous response rather than the cell density increase induced by long-distance signalling. Hydrogen peroxide treatment induced cylindrical palisade tissue cell formation in both a leaf autonomous and long-distance manner, suggesting involvement of oxidative signals. Although constitutive expression of transcription factors involved in systemic-acquired acclimation to excess light, ZAT10 and ZAT12, induced cylindrical palisade tissue cell formation, knockout of these genes did not affect cylindrical palisade tissue cell formation. We conclude that two distinct signalling pathways - leaf autonomous signalling mostly dependent on blue light signalling and long-distance signalling from mature leaves that sense high light and oxidative stress - control palisade tissue development in A. thaliana.

  1. Ethylene Response Factor6 acts as a central regulator of leaf growth under water-limiting conditions in Arabidopsis.

    Science.gov (United States)

    Dubois, Marieke; Skirycz, Aleksandra; Claeys, Hannes; Maleux, Katrien; Dhondt, Stijn; De Bodt, Stefanie; Vanden Bossche, Robin; De Milde, Liesbeth; Yoshizumi, Takeshi; Matsui, Minami; Inzé, Dirk

    2013-05-01

    Leaf growth is a complex developmental process that is continuously fine-tuned by the environment. Various abiotic stresses, including mild drought stress, have been shown to inhibit leaf growth in Arabidopsis (Arabidopsis thaliana), but the underlying mechanisms remain largely unknown. Here, we identify the redundant Arabidopsis transcription factors ETHYLENE RESPONSE FACTOR5 (ERF5) and ERF6 as master regulators that adapt leaf growth to environmental changes. ERF5 and ERF6 gene expression is induced very rapidly and specifically in actively growing leaves after sudden exposure to osmotic stress that mimics mild drought. Subsequently, enhanced ERF6 expression inhibits cell proliferation and leaf growth by a process involving gibberellin and DELLA signaling. Using an ERF6-inducible overexpression line, we demonstrate that the gibberellin-degrading enzyme GIBBERELLIN 2-OXIDASE6 is transcriptionally induced by ERF6 and that, consequently, DELLA proteins are stabilized. As a result, ERF6 gain-of-function lines are dwarfed and hypersensitive to osmotic stress, while the growth of erf5erf6 loss-of-function mutants is less affected by stress. Besides its role in plant growth under stress, ERF6 also activates the expression of a plethora of osmotic stress-responsive genes, including the well-known stress tolerance genes STZ, MYB51, and WRKY33. Interestingly, activation of the stress tolerance genes by ERF6 occurs independently from the ERF6-mediated growth inhibition. Together, these data fit into a leaf growth regulatory model in which ERF5 and ERF6 form a missing link between the previously observed stress-induced 1-aminocyclopropane-1-carboxylic acid accumulation and DELLA-mediated cell cycle exit and execute a dual role by regulating both stress tolerance and growth inhibition.

  2. Gradual shifts in sites of free-auxin production during leaf-primordium development and their role in vascular differentiation and leaf morphogenesis in Arabidopsis.

    Science.gov (United States)

    Aloni, Roni; Schwalm, Katja; Langhans, Markus; Ullrich, Cornelia I

    2003-03-01

    The major regulatory shoot signal is auxin, whose synthesis in young leaves has been a mystery. To test the leaf-venation hypothesis [R. Aloni (2001) J Plant Growth Regul 20: 22-34], the patterns of free-auxin production, movement and accumulation in developing leaf primordia of DR5::GUS-transformed Arabidopsis thaliana (L.) Heynh. were visualized. DR5::GUS expression was regarded to reflect sites of free auxin, while immunolocalization with specific monoclonal antibodies indicated total auxin distribution. The mRNA expression of key enzymes involved in the synthesis, conjugate hydrolysis, accumulation and basipetal transport of auxin, namely indole-3-glycerol-phosphate-synthase, nitrilase, IAA-amino acid hydrolase, chalcone synthase and PIN1 as an essential component of the basipetal IAA carrier, was investigated by reverse transcription-polymerase chain reaction. Near the shoot apex, stipules were the earliest sites of high free-auxin production. During early stages of primordium development, leaf apical dominance was evident from strong beta-glucuronidase activity in the elongating tip, possibly suppressing the production of free auxin in the leaf tissues below it. Hydathodes, which develop in the tip and later in the lobes, were apparently primary sites of high free-auxin production, the latter supported by auxin-conjugate hydrolysis, auxin retention by the chalcone synthase-dependent action of flavonoids and also by the PIN1-component of the carrier-mediated basipetal transport. Trichomes and mesophyll cells were secondary sites of free-auxin production. During primordium development there are gradual shifts in sites and concentrations of free-auxin production occurring first in the tip of a leaf primordium, then progressing basipetally along the margins, and finally appearing also in the central regions of the lamina. This developmental pattern of free-auxin production is suggested to control the basipetal maturation sequence of leaf development and vascular

  3. A fluorescent reporter protein containing AtRMR1 domains is targeted to the storage and central vacuoles in Arabidopsis thaliana and tobacco leaf cells.

    Science.gov (United States)

    Scabone, Camila María; Frigerio, Lorenzo; Petruccelli, Silvana

    2011-10-01

    To develop a new strategy to target recombinant proteins to the vacuolar storage system in transgenic plants, the ability of the transmembrane and cytosolic domains of Arabidopsis receptor homology-transmembrane-RING H2-1 (AtRMR1) was evaluated. A secreted version of RFP (secRFP) and a fusion of it to the transmembrane and cytosolic domains of AtRMR1 (RFP-TMCT) were produced and studied both in transient and stable expression assays. Transient expression in leaves of Nicotiana tabacum showed that secRFP is secreted to the apoplast while its fusion to TMCT of AtRMR1 is sufficient to prevent secretion of the reporter. In tobacco leaves, RFP-TMCT reporter showed an endoplasmic reticulum pattern in early expression stages while in late expression stages, it was found in the vacuolar lumen. For the first time, the role of TM and CT domains of AtRMR1 in stable expression in Arabidopsis thaliana is presented; the fusion of TMCT to secRFP is sufficient to sort RFP to the lumen of the central vacuoles in leaves and roots and to the lumen of PSV in cotyledons of mature embryos. In addition, biochemical studies performed in extract from transgenic plants showed that RFP-TMCT is an integral membrane protein. Full-length RFP-TMCT was also found in the vacuolar lumen, suggesting internalization into destination vacuole. Not colocalization of RFP-TMCT with tonoplast and plasma membrane markers were observed. This membrane vacuolar determinant sorting signal could be used for future application in molecular pharming as an alternative means to sort proteins of interest to vacuoles. PMID:21611741

  4. A fluorescent reporter protein containing AtRMR1 domains is targeted to the storage and central vacuoles in Arabidopsis thaliana and tobacco leaf cells.

    Science.gov (United States)

    Scabone, Camila María; Frigerio, Lorenzo; Petruccelli, Silvana

    2011-10-01

    To develop a new strategy to target recombinant proteins to the vacuolar storage system in transgenic plants, the ability of the transmembrane and cytosolic domains of Arabidopsis receptor homology-transmembrane-RING H2-1 (AtRMR1) was evaluated. A secreted version of RFP (secRFP) and a fusion of it to the transmembrane and cytosolic domains of AtRMR1 (RFP-TMCT) were produced and studied both in transient and stable expression assays. Transient expression in leaves of Nicotiana tabacum showed that secRFP is secreted to the apoplast while its fusion to TMCT of AtRMR1 is sufficient to prevent secretion of the reporter. In tobacco leaves, RFP-TMCT reporter showed an endoplasmic reticulum pattern in early expression stages while in late expression stages, it was found in the vacuolar lumen. For the first time, the role of TM and CT domains of AtRMR1 in stable expression in Arabidopsis thaliana is presented; the fusion of TMCT to secRFP is sufficient to sort RFP to the lumen of the central vacuoles in leaves and roots and to the lumen of PSV in cotyledons of mature embryos. In addition, biochemical studies performed in extract from transgenic plants showed that RFP-TMCT is an integral membrane protein. Full-length RFP-TMCT was also found in the vacuolar lumen, suggesting internalization into destination vacuole. Not colocalization of RFP-TMCT with tonoplast and plasma membrane markers were observed. This membrane vacuolar determinant sorting signal could be used for future application in molecular pharming as an alternative means to sort proteins of interest to vacuoles.

  5. Decreased glutathione reductase2 leads to early leaf senescence in Arabidopsis.

    Science.gov (United States)

    Ding, Shunhua; Wang, Liang; Yang, Zhipan; Lu, Qingtao; Wen, Xiaogang; Lu, Congming

    2016-01-01

    Glutathione reductase (GR) catalyzes the reduction of glutathione disulfide (GSSG) to reduced glutathione (GSH) and participates in the ascorbate-glutathione cycle, which scavenges H2 O2 . Here, we report that chloroplastic/mitochondrial GR2 is an important regulator of leaf senescence. Seed development of the homozygous gr2 knockout mutant was blocked at the globular stage. Therefore, to investigate the function of GR2 in leaf senescence, we generated transgenic Arabidopsis plants with decreased GR2 using RNAi. The GR2 RNAi plants displayed early onset of age-dependent and dark- and H2 O2 -induced leaf senescence, which was accompanied by the induction of the senescence-related marker genes SAG12 and SAG13. Furthermore, transcriptome analysis revealed that genes related to leaf senescence, oxidative stress, and phytohormone pathways were upregulated directly before senescence in RNAi plants. In addition, H2 O2 accumulated to higher levels in RNAi plants than in wild-type plants and the levels of H2 O2 peaked in RNAi plants directly before the early onset of leaf senescence. RNAi plants showed a greater decrease in GSH/GSSG levels than wild-type plants during leaf development. Our results suggest that GR2 plays an important role in leaf senescence by modulating H2 O2 and glutathione signaling in Arabidopsis.

  6. Programming of Plant Leaf Senescence with Temporal and Inter-Organellar Coordination of Transcriptome in Arabidopsis.

    Science.gov (United States)

    Woo, Hye Ryun; Koo, Hee Jung; Kim, Jeongsik; Jeong, Hyobin; Yang, Jin Ok; Lee, Il Hwan; Jun, Ji Hyung; Choi, Seung Hee; Park, Su Jin; Kang, Byeongsoo; Kim, You Wang; Phee, Bong-Kwan; Kim, Jin Hee; Seo, Chaehwa; Park, Charny; Kim, Sang Cheol; Park, Seongjin; Lee, Byungwook; Lee, Sanghyuk; Hwang, Daehee; Nam, Hong Gil; Lim, Pyung Ok

    2016-05-01

    Plant leaves, harvesting light energy and fixing CO2, are a major source of foods on the earth. Leaves undergo developmental and physiological shifts during their lifespan, ending with senescence and death. We characterized the key regulatory features of the leaf transcriptome during aging by analyzing total- and small-RNA transcriptomes throughout the lifespan of Arabidopsis (Arabidopsis thaliana) leaves at multidimensions, including age, RNA-type, and organelle. Intriguingly, senescing leaves showed more coordinated temporal changes in transcriptomes than growing leaves, with sophisticated regulatory networks comprising transcription factors and diverse small regulatory RNAs. The chloroplast transcriptome, but not the mitochondrial transcriptome, showed major changes during leaf aging, with a strongly shared expression pattern of nuclear transcripts encoding chloroplast-targeted proteins. Thus, unlike animal aging, leaf senescence proceeds with tight temporal and distinct interorganellar coordination of various transcriptomes that would be critical for the highly regulated degeneration and nutrient recycling contributing to plant fitness and productivity. PMID:26966169

  7. Whole organ, venation and epidermal cell morphological variations are correlated in the leaves of Arabidopsis mutants.

    Science.gov (United States)

    Pérez-Pérez, José Manuel; Rubio-Díaz, Silvia; Dhondt, Stijn; Hernández-Romero, Diana; Sánchez-Soriano, Joaquín; Beemster, Gerrit T S; Ponce, María Rosa; Micol, José Luis

    2011-12-01

    Despite the large number of genes known to affect leaf shape or size, we still have a relatively poor understanding of how leaf morphology is established. For example, little is known about how cell division and cell expansion are controlled and coordinated within a growing leaf to eventually develop into a laminar organ of a definite size. To obtain a global perspective of the cellular basis of variations in leaf morphology at the organ, tissue and cell levels, we studied a collection of 111 non-allelic mutants with abnormally shaped and/or sized leaves, which broadly represent the mutational variations in Arabidopsis thaliana leaf morphology not associated with lethality. We used image-processing techniques on these mutants to quantify morphological parameters running the gamut from the palisade mesophyll and epidermal cells to the venation, whole leaf and rosette levels. We found positive correlations between epidermal cell size and leaf area, which is consistent with long-standing Avery's hypothesis that the epidermis drives leaf growth. In addition, venation parameters were positively correlated with leaf area, suggesting that leaf growth and vein patterning share some genetic controls. Positional cloning of the genes affected by the studied mutations will eventually establish functional links between genotypes, molecular functions, cellular parameters and leaf phenotypes.

  8. Effect of plant growth regulators on leaf anatomy of the has mutant of Arabidopsis thaliana.

    Science.gov (United States)

    Janosević, D; Uzelac, B; Budimir, S

    2008-12-01

    In this study, the effect of plant growth regulators on leaf morphogenesis of the recessive T-DNA insertion mutant of Arabidopsis thaliana was analyzed. The morpho-anatomical analysis revealed that leaves of the has mutant are small and narrow, with lobed blades and disrupted tissue organization. When has plants were grown on the medium supplied with plant growth regulators: benzylaminopurine (BAP) or ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), the leaf anatomy was partially restored to the wild type, although plants still exhibited morphological abnormalities.

  9. Individual Leaf Development in Arabidopsis thaliana: a Stable Thermal‐time‐based Programme

    OpenAIRE

    GRANIER, CHRISTINE; Massonnet, Catherine; TURC, OLIVIER; Muller, Bertrand; Chenu, Karine; Tardieu, François

    2002-01-01

    In crop species, the impact of temperature on plant development is classically modelled using thermal time. We examined whether this method could be used in a non‐crop species, Arabidopsis thaliana, to analyse the response to temperature of leaf initiation rate and of the development of two leaves of the rosette. The results confirmed the large plant‐to‐plant variability in the studied isogenic line of the Columbia ecotype: 100‐fold differences in leaf area among plants sown on the same date ...

  10. Overexpression of the Rap2.4f transcriptional factor in Arabidopsis promotes leaf senescence

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Senescence is a complex and highly regulated process. Leaf senescence is influenced by endogenous developmental and external environmental signals. In this work, we found that expression of an Ap2/DREB-type transcription factor gene, Arabidopsis Rap2.4f (At4g28140), was upregulated by salt, mannitol, and dark treatments. Constitutively overexpressing Rap2.4f under the control of the CaMV 35S promoter led to an increased chlorophyll degradation rate and upregulation of many senescence-associated genes in the transgenic Arabidopsis lines. Our results show that Rap2.4f is a positive regulator of senescence, promoting both developmental and dark-induced leaf senescence.

  11. Modulation of leaf conductance by root to shoot signaling under water stress in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Fan Yi-juan; Liu Qing; Wei Kai-fa; Li Bing-bing; Ren Hui-bo; Gao Zhi-hui; Jia Wen-suo

    2006-01-01

    Signal communication between root and shoot plays a crucial role in plant resistance to water stress. While many studies on root to shoot signals have been carried out in many plant species, no information is available for the model plant, Arabidopsis, whose adoption has great significance for further probing the molecular aspects of long distance stress signals. Here, we introduced the establishment of techniques for investigations of root to shoot signals in Arabidopsis. Stomatal movements in relation to root signals were probed by using these techniques. The results show that Arabidopsis is a suitable plant species for partial roots drying (PRD)experiments. In the PRD system, while no significant differences were found in leaf water potential between well-watered and stressed plants, water stress led to a decrease in leaf conductance, which suggests a regulation of stomatal movements by root to shoot signals. While water stress caused a significant increase in the concentration of sap abscisic acid (ABA) of xylem, no increase in xylem sap pH was observed. Moreover, the increase in the ABA content of xylem coincided with the decrease in leaf conductance,which suggests a possible role of ABA in the regulation of stomatal movements. Infrared temperature images showed that leaf temperatures of PRD plant were higher compared with those of well-watered plants, which further indicates that stomatal movements can be modulated by root signals. The confirmation of root to shoot signaling in Arabidopsis has established a basis for further investigation into the molecular mechanisms of the root to shoot signaling under water stress.

  12. Altered gene expression changes in Arabidopsis leaf tissues and protoplasts in response to Plum pox virus infection

    Directory of Open Access Journals (Sweden)

    Griffiths Jonathan S

    2008-07-01

    Full Text Available Abstract Background Virus infection induces the activation and suppression of global gene expression in the host. Profiling gene expression changes in the host may provide insights into the molecular mechanisms that underlie host physiological and phenotypic responses to virus infection. In this study, the Arabidopsis Affymetrix ATH1 array was used to assess global gene expression changes in Arabidopsis thaliana plants infected with Plum pox virus (PPV. To identify early genes in response to PPV infection, an Arabidopsis synchronized single-cell transformation system was developed. Arabidopsis protoplasts were transfected with a PPV infectious clone and global gene expression changes in the transfected protoplasts were profiled. Results Microarray analysis of PPV-infected Arabidopsis leaf tissues identified 2013 and 1457 genes that were significantly (Q ≤ 0.05 up- (≥ 2.5 fold and downregulated (≤ -2.5 fold, respectively. Genes associated with soluble sugar, starch and amino acid, intracellular membrane/membrane-bound organelles, chloroplast, and protein fate were upregulated, while genes related to development/storage proteins, protein synthesis and translation, and cell wall-associated components were downregulated. These gene expression changes were associated with PPV infection and symptom development. Further transcriptional profiling of protoplasts transfected with a PPV infectious clone revealed the upregulation of defence and cellular signalling genes as early as 6 hours post transfection. A cross sequence comparison analysis of genes differentially regulated by PPV-infected Arabidopsis leaves against uniEST sequences derived from PPV-infected leaves of Prunus persica, a natural host of PPV, identified orthologs related to defence, metabolism and protein synthesis. The cross comparison of genes differentially regulated by PPV infection and by the infections of other positive sense RNA viruses revealed a common set of 416 genes

  13. Individual Leaf Development in Arabidopsis thaliana: a Stable Thermal‐time‐based Programme

    Science.gov (United States)

    GRANIER, CHRISTINE; MASSONNET, CATHERINE; TURC, OLIVIER; MULLER, BERTRAND; CHENU, KARINE; TARDIEU, FRANÇOIS

    2002-01-01

    In crop species, the impact of temperature on plant development is classically modelled using thermal time. We examined whether this method could be used in a non‐crop species, Arabidopsis thaliana, to analyse the response to temperature of leaf initiation rate and of the development of two leaves of the rosette. The results confirmed the large plant‐to‐plant variability in the studied isogenic line of the Columbia ecotype: 100‐fold differences in leaf area among plants sown on the same date were commonly observed at a given date. These differences disappeared in mature leaves, suggesting that they were due to a variability in plant developmental stage. The whole population could therefore be represented by any group of synchronous plants labelled at the two‐leaf stage and followed during their development. Leaf initiation rate, duration of leaf expansion and maximal relative leaf expansion rate varied considerably among experiments performed at different temperatures (from 6 to 26 °C) but they were linearly related to temperature in the range 6–26 °C, with a common x‐intercept of 3 °C. Expressing time in thermal time with a threshold temperature of 3 °C unified the time courses of leaf initiation and of individual leaf development for plants grown at different temperatures and experimental conditions. The two leaves studied (leaf 2 and leaf 6) had a two‐phase development, with an exponential phase followed by a phase with decreasing relative elongation rate. Both phases had constant durations for a given leaf position if expressed in thermal time. Changes in temperature caused changes in both the rate of development and in the expansion rate which mutually compensated such that they had no consequence on leaf area at a given thermal time. The resulting model of leaf development was applied to ten experiments carried out in a glasshouse or in a growth chamber, with plants grown in soil or hydroponically. Because it predicts accurately the stage

  14. Comparison of Leaf Plastochron Index and Allometric Analyses of Tooth Development in Arabidopsis thaliana.

    Science.gov (United States)

    Groot; Meicenheimer

    2000-03-01

    Two methods of analyses were used to investigate tooth development in serrate (se) mutant and wild-type Columbia-1 (Col-1) Arabidopsis thaliana leaves. There were almost twice as many teeth with deeper sinuses and two orders of toothing on the margins of serrate compared with Columbia-1 leaves. The main objective of this study was to test three hypotheses relative to the source of polymorphism in tooth development: (i) Teeth share similar growth rates and initial sizes, but the deeper teeth are initiated earlier in leaf development. (ii) Teeth share similar timing of initiation and growth rates, but the deeper teeth have a larger initial size. (iii) Teeth share similar timing of initiation and initial sizes, but the deeper teeth have a faster growth rate. Leaf plastochron index (LPI) was used as the time variable for leaf development. Results showed teeth in se were initiated at -27 LPI, 15 plastochrons earlier than those of Col-1. Serrate leaf expansion was biphasic, with the early phase expanding at half the relative plastochron rate of the later phase, which equaled the constant relative expansion rate of Col-1 leaves. Allometric analyses of tooth development obscured the interactions between time of tooth and leaf initiation and the early phase of leaf expansion characteristic of serrate leaves and teeth. Timing of developmental events that allometric analysis obscured can be readily detected with the LPI as a developmental index.

  15. Identification and genetic mapping of four novel genes that regulate leaf development in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    SUNYUE; YingLiGuo; 等

    2000-01-01

    Molecular and genetic characterizations of mutants have led to a better understanding of many developmental processes in the model system Arabidopsis thaliana.However,the leaf development that is specific to plants has been little studies.With the aim of contributing to the genetic dissection of leaf development,we have performed a large-scare screening for mutants with abnormal leaves.Among a great number of leaf mutants we have generated by T-DNA and transposon tagging and ethylmethae sulfonate (EMS) mutagenesis,four independent mutant lines have been identified and studied genetically.Phenotypes of these mutant lines represent the defects of four novel muclear genes designated LL1(LOTUS LEAF 1),LL2(LOTUS LEAF2),URO(UPRIGHT ROSETTE),and EIL(ENVIRONMENT CONDITION INDUCED LESION).The phenotypic analysis indicates that these genes play important roles during leaf development.For the further genetic analysis of these genes and the map-based cloning of LL1 and LL2,we have mapped these genes to chromosome regions with an efficient and rapid mapping method.

  16. The Arabidopsis synaptotagmin SYTA regulates the cell-to-cell movement of diverse plant viruses

    Directory of Open Access Journals (Sweden)

    Asako eUchiyama

    2014-11-01

    Full Text Available Synaptotagmins are a large gene family in animals that have been extensively characterized due to their role as calcium sensors to regulate synaptic vesicle exocytosis and endocytosis in neurons, and dense core vesicle exocytosis for hormone secretion from neuroendocrine cells. Thought to be exclusive to animals, synaptotagmins have recently been characterized in Arabidopsis thaliana, in which they comprise a five gene family. Using infectivity and leaf-based functional assays, we have shown that Arabidopsis SYTA regulates endocytosis and marks an endosomal vesicle recycling pathway to regulate movement protein-mediated trafficking of the Begomovirus Cabbage leaf curl virus (CaLCuV and the Tobamovirus Tobacco mosaic virus (TMV through plasmodesmata (Lewis and Lazarowitz, 2010. To determine whether SYTA has a central role in regulating the cell-to-cell trafficking of a wider range of diverse plant viruses, we extended our studies here to examine the role of SYTA in the cell-to-cell movement of additional plant viruses that employ different modes of movement, namely the Potyvirus Turnip mosaic virus (TuMV, the Caulimovirus Cauliflower mosaic virus (CaMV and the Tobamovirus Turnip vein clearing virus (TVCV, which in contrast to TMV does efficiently infect Arabidopsis. We found that both TuMV and TVCV systemic infection, and the cell-to-cell trafficking of the their movement proteins, were delayed in the Arabidopsis Col-0 syta-1 knockdown mutant. In contrast, CaMV systemic infection was not inhibited in syta-1. Our studies show that SYTA is a key regulator of plant virus intercellular movement, being necessary for the ability of diverse cell-to-cell movement proteins encoded by Begomoviruses (CaLCuV MP, Tobamoviruses (TVCV and TMV 30K protein and Potyviruses (TuMV P3N-PIPO to alter PD and thereby mediate virus cell-to-cell spread.

  17. Leaf biomechanical properties in Arabidopsis thaliana polysaccharide mutants affect drought survival.

    Science.gov (United States)

    Balsamo, Ronald; Boak, Merewyn; Nagle, Kayla; Peethambaran, Bela; Layton, Bradley

    2015-11-26

    Individual sugars are the building blocks of cell wall polysaccharides, which in turn comprise a plant׳s overall architectural structure. But which sugars play the most prominent role in maintaining a plant׳s mechanical stability during large cellular deformations induced by drought? We investigated the individual contributions of several genes that are involved in the synthesis of monosaccharides which are important for cell wall structure. We then measured drought tolerance and mechanical integrity during simulated drought in Arabidopsis thaliana. To assess mechanical properties, we designed a small-scale tensile tester for measuring failure strain, ultimate tensile stress, work to failure, toughness, and elastic modulus of 6-week-old leaves in both hydrated and drought-simulated states. Col-0 mutants used in this study include those deficient in lignin, cellulose, components of hemicellulose such as xylose and fucose, the pectic components arabinose and rhamnose, as well as mutants with enhanced arabinose and total pectin content. We found that drought tolerance is correlated to the mechanical and architectural stability of leaves as they experience dehydration. Of the mutants, S096418 with mutations for reduced xylose and galactose was the least drought tolerant, while the arabinose-altered CS8578 mutants were the least affected by water loss. There were also notable correlations between drought tolerance and mechanical properties in the diminished rhamnose mutant, CS8575 and the dehydrogenase-disrupted S120106. Our findings suggest that components of hemicellulose and pectins affect leaf biomechanical properties and may play an important role in the ability of this model system to survive drought.

  18. Influence of atmospheric oxygen on leaf structure and starch deposition in Arabidopsis thaliana

    Science.gov (United States)

    Ramonell, K. M.; Kuang, A.; Porterfield, D. M.; Crispi, M. L.; Xiao, Y.; McClure, G.; Musgrave, M. E.

    2001-01-01

    Plant culture in oxygen concentrations below ambient is known to stimulate vegetative growth, but apart from reports on increased leaf number and weight, little is known about development at subambient oxygen concentrations. Arabidopsis thaliana (L.) Heynh. (cv. Columbia) plants were grown full term in pre-mixed atmospheres with oxygen partial pressures of 2.5, 5.1, 10.1, 16.2, and 21.3 kPa O2, 0.035 kPa CO2 and the balance nitrogen under continuous light. Fully expanded leaves were harvested and processed for light and transmission electron microscopy or for starch quantification. Growth in subambient oxygen concentrations caused changes in leaf anatomy (increased thickness, stomatal density and starch content) that have also been described for plants grown under carbon dioxide enrichment. However, at the lowest oxygen treatment (2.5 kPa), developmental changes occurred that could not be explained by changes in carbon budget caused by suppressed photorespiration, resulting in very thick leaves and a dwarf morphology. This study establishes the leaf parameters that change during growth under low O2, and identifies the lower concentration at which O2 limitation on transport and biosynthetic pathways detrimentally affects leaf development. Grant numbers: NAG5-3756, NAG2-1020, NAG2-1375.

  19. Leaf Downward Curvature and Delayed Flowering Caused by AtLH Overexpression in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    WUHao; YULin; TANGXiang-Rong; SHENRui-Juan; HEYu-Ke

    2004-01-01

    AtLHgene of Arabidopsis is a BcpLH(leafy head) homolog of Chinese cabbage, which encodes a double-stranded RNA-binding protein related to the curvature of folding leaf leading to the formation of leafy head. In order to elucidate the regulatory function of AtLH in the development of leaf curvature, we made a construct of 35S::AtLHand transformed it to Arabidopsis. In transgenic plants for sense-AtLH, transcripts of AtLH gene were increased significantly in leaves and flowers, giving rise to the AtLH-overexpressed plants in which the rosette leaves curved downward or outward in a manner of enhanced epinastic growth. Compared with normal plants, bolting and flowering time of the transgenic plants was significantly delayed. Moreover, the apical dominance of transgenic plants was weaker in vegetative shoots since more axillary shoots emerged from axil of rosette leaves, while stronger in flowering shoots because fewer cauline inflorescences were observed on the main inflorescence. In other aspects, these transgenic plants exhibited an increase in root-stimulating response to IAA and decrease in root-inhibitory reaction on ABA. It indicates that overexpression of AtLH causes downward curvature of transgenic plants.

  20. Ectopic expression of soybean GmKNT1 in Arabidopsis results in altered leaf morphology and flower identity

    Institute of Scientific and Technical Information of China (English)

    Jun Liu; Da Ha; Zongming Xie; Chunmei Wang; Huiwen Wang; Wanke Zhang; Jinsong Zhang; Shouyi Chen

    2008-01-01

    Plant morphology is specified by leaves and flowers, and the shoot apical meristem (SAM) defines the architecture of plant leaves and flowers. Here, we reported the characterization of a soybean KNOX gene GmKNT1, which was highly homologous to Arabidopsis STM. The GmKNT1 was strongly expressed in roots, flowers and developing seeds. Its expression could be induced by IAA, ABA and JA, but inhibited by GA or cytokinin. Staining of the transgenic plants overexpressing GmKNT1-GUS fusion protein revealed that the GmKNT1 was mainly expressed at lobe region, SAM of young leaves, sepal and carpel, not in seed and mature leaves. Scanning electron micros- copy (SEM) disclosed multiple changes in morphology of the epidermal cells and stigma. The transgenic Arabidopsis plants overexpress- ing the GmKNT1 showed small and lobed leaves, shortened internodes and small clustered inflorescence. The lobed leaves might result from the function of the meristems located at the boundary of the leaf. Compared with wild type plants, transgenic plants had higher ex- pression of the SAM-related genes including the CUP, WUS, CUC1, KNAT2 and KNAT6. These results indicated that the GmKNT1 could affect multiple aspects of plant growth and development by regulation of downstream genes expression.

  1. Stem cell organization in Arabidopsis

    NARCIS (Netherlands)

    Wendrich, J.R.

    2016-01-01

    Growth of plant tissues and organs depends on continuous production of new cells, by niches of stem cells. Stem cells typically divide to give rise to one differentiating daughter and one non-differentiating daughter. This constant process of self-renewal ensures that the niches of stem cells or mer

  2. Gene Network Analysis and Functional Studies of Senescence-associated Genes Reveal Novel Regulators of Arabidopsis Leaf Senescence

    Institute of Scientific and Technical Information of China (English)

    Zhonghai Li; Jinying Peng; Xing Wen; Hongwei Guo

    2012-01-01

    Plant leaf senescence has been recognized as the last phase of plant development,a highly ordered process regulated by genes known as senescence associated genes (SAGs).However,the function of most of SAGs in regulating leaf senescence as well as regulators of those functionally known SAGs are still unclear.We have previously developed a curated database of genes potentially associated with leaf senescence,the Leaf Senescence Database (LSD).In this study,we built gene networks to identify common regulators of leaf senescence in Arabidopsis thaliana using promoting or delaying senescence genes in LSD.Our results demonstrated that plant hormones cytokinin,auxin,nitric oxide as well as small molecules,such as Ca2+,delay leaf senescence.By contrast,ethylene,ABA,SA and JA as well as small molecules,such as oxygen,promote leaf senescence,altogether supporting the idea that phytohormones play a critical role in regulating leaf senescence.Functional analysis of candidate SAGs in LSD revealed that a WRKY transcription factor WRKY75 and a Cys2/His2-type transcription factor AZF2 are positive regulators of leaf senescence and loss-of-function of WRKY75 or AZF2 delayed leaf senescence.We also found that silencing of a protein phosphatase,AtMKP2,promoted early senescence.Collectively,LSD can serve as a comprehensive resource for systematic study of the molecular mechanism of leaf senescence as well as offer candidate genes for functional analyses.

  3. Programming of Plant Leaf Senescence with Temporal and Inter-Organellar Coordination of Transcriptome in Arabidopsis1[OPEN

    Science.gov (United States)

    Koo, Hee Jung; Kim, Jeongsik; Jeong, Hyobin; Yang, Jin Ok; Lee, Il Hwan; Jun, Ji Hyung; Choi, Seung Hee; Park, Su Jin; Kang, Byeongsoo; Kim, You Wang; Phee, Bong-Kwan; Kim, Jin Hee; Seo, Chaehwa; Park, Charny; Kim, Sang Cheol; Park, Seongjin; Lee, Byungwook; Lee, Sanghyuk; Hwang, Daehee; Lim, Pyung Ok

    2016-01-01

    Plant leaves, harvesting light energy and fixing CO2, are a major source of foods on the earth. Leaves undergo developmental and physiological shifts during their lifespan, ending with senescence and death. We characterized the key regulatory features of the leaf transcriptome during aging by analyzing total- and small-RNA transcriptomes throughout the lifespan of Arabidopsis (Arabidopsis thaliana) leaves at multidimensions, including age, RNA-type, and organelle. Intriguingly, senescing leaves showed more coordinated temporal changes in transcriptomes than growing leaves, with sophisticated regulatory networks comprising transcription factors and diverse small regulatory RNAs. The chloroplast transcriptome, but not the mitochondrial transcriptome, showed major changes during leaf aging, with a strongly shared expression pattern of nuclear transcripts encoding chloroplast-targeted proteins. Thus, unlike animal aging, leaf senescence proceeds with tight temporal and distinct interorganellar coordination of various transcriptomes that would be critical for the highly regulated degeneration and nutrient recycling contributing to plant fitness and productivity. PMID:26966169

  4. Branching patterns in leaf starches from Arabidopsis mutants deficient in diverse starch synthases.

    Science.gov (United States)

    Zhu, Fan; Bertoft, Eric; Szydlowski, Nicolas; d'Hulst, Christophe; Seetharaman, Koushik

    2015-01-12

    This is the first report on the cluster structure of transitory starch from Arabidopsis leaves. In addition to wild type, the molecular structures of leaf starch from mutants deficient in starch synthases (SS) including single enzyme mutants ss1-, ss2-, or ss3-, and also double mutants ss1-ss2- and ss1-ss3- were characterized. The mutations resulted in increased amylose content. Clusters from whole starch were isolated by partial hydrolysis using α-amylase of Bacillus amyloliquefaciens. The clusters were then further hydrolyzed with concentrated α-amylase of B. amyloliquefaciens to produce building blocks (α-limit dextrins). Structures of the clusters and their building blocks were characterized by chromatography of samples before and after debranching treatment. While the mutations increased the size of clusters, the reasons were different as reflected by the composition of their unit chains and building blocks. In general, all mutants contained more of a-chains that preferentially increased the number of small building blocks with only two chains. The clusters of the double mutant ss1-ss3- were very large and possessed also more of large building blocks with four or more chains. The results from transitory starch are compared with those from agriculturally important crops in the context that to what extent the Arabidopsis can be a true biotechnological reflection for starch modifications through genetic means.

  5. Arabidopsis Type II Phosphatidylinositol 4-Kinase PI4Kγ5 Regulates Auxin Biosynthesis and Leaf Margin Development through Interacting with Membrane-Bound Transcription Factor ANAC078.

    Science.gov (United States)

    Tang, Yong; Zhao, Chun-Yan; Tan, Shu-Tang; Xue, Hong-Wei

    2016-08-01

    Normal leaf margin development is important for leaf morphogenesis and contributes to diverse leaf shapes in higher plants. We here show the crucial roles of an atypical type II phosphatidylinositol 4-kinase, PI4Kγ5, in Arabidopsis leaf margin development. PI4Kγ5 presents a dynamics expression pattern along with leaf development and a T-DNA mutant lacking PI4Kγ5, pi4kγ5-1, presents serrated leaves, which is resulted from the accelerated cell division and increased auxin concentration at serration tips. Studies revealed that PI4Kγ5 interacts with and phosphorylates a membrane-bound NAC transcription factor, ANAC078. Previous studies demonstrated that membrane-bound transcription factors regulate gene transcription by undergoing proteolytic process to translocate into nucleus, and ANAC078 undergoes proteolysis by cleaving off the transmembrane region and carboxyl terminal. Western blot analysis indeed showed that ANAC078 deleting of carboxyl terminal is significantly reduced in pi4kγ5-1, indicating that PI4Kγ5 is important for the cleavage of ANAC078. This is consistent with the subcellular localization observation showing that fluorescence by GFP-ANAC078 is detected at plasma membrane but not nucleus in pi4kγ5-1 mutant and that expression of ANAC078 deleting of carboxyl terminal, driven by PI4Kγ5 promoter, could rescue the leaf serration defects of pi4kγ5-1. Further analysis showed that ANAC078 suppresses the auxin synthesis by directly binding and regulating the expression of auxin synthesis-related genes. These results indicate that PI4Kγ5 interacts with ANAC078 to negatively regulate auxin synthesis and hence influences cell proliferation and leaf development, providing informative clues for the regulation of in situ auxin synthesis and cell division, as well as the cleavage and functional mechanism of membrane-bound transcription factors. PMID:27529511

  6. Three-dimensional patterns of cell division and expansion throughout the development of Arabidopsis thaliana leaves.

    Science.gov (United States)

    Kalve, Shweta; Fotschki, Joanna; Beeckman, Tom; Vissenberg, Kris; Beemster, Gerrit T S

    2014-12-01

    Variations in size and shape of multicellular organs depend on spatio-temporal regulation of cell division and expansion. Here, cell division and expansion rates were quantified relative to the three spatial axes in the first leaf pair of Arabidopsis thaliana. The results show striking differences in expansion rates: the expansion rate in the petiole is higher than in the leaf blade; expansion rates in the lateral direction are higher than longitudinal rates between 5 and 10 days after stratification, but become equal at later stages of leaf blade development; and anticlinal expansion co-occurs with, but is an order of magnitude slower than periclinal expansion. Anticlinal expansion rates also differed greatly between tissues: the highest rates occurred in the spongy mesophyll and the lowest in the epidermis. Cell division rates were higher and continued for longer in the epidermis compared with the palisade mesophyll, causing a larger increase of palisade than epidermal cell area over the course of leaf development. The cellular dynamics underlying the effect of shading on petiole length and leaf thickness were then investigated. Low light reduced leaf expansion rates, which was partly compensated by increased duration of the growth phase. Inversely, shading enhanced expansion rates in the petiole, so that the blade to petiole ratio was reduced by 50%. Low light reduced leaf thickness by inhibiting anticlinal cell expansion rates. This effect on cell expansion was preceded by an effect on cell division, leading to one less layer of palisade cells. The two effects could be uncoupled by shifting plants to contrasting light conditions immediately after germination. This extended kinematic analysis maps the spatial and temporal heterogeneity of cell division and expansion, providing a framework for further research to understand the molecular regulatory mechanisms involved.

  7. The ABCG transporter PEC1/ABCG32 is required for the formation of the developing leaf cuticle in Arabidopsis.

    Science.gov (United States)

    Fabre, Guillaume; Garroum, Imène; Mazurek, Sylwester; Daraspe, Jean; Mucciolo, Antonio; Sankar, Martial; Humbel, Bruno M; Nawrath, Christiane

    2016-01-01

    The cuticle is an essential diffusion barrier on aerial surfaces of land plants whose structural component is the polyester cutin. The PERMEABLE CUTICLE1/ABCG32 (PEC1) transporter is involved in plant cuticle formation in Arabidopsis. The gpat6 pec1 and gpat4 gapt8 pec1 double and triple mutants are characterized. Their PEC1-specific contributions to aliphatic cutin composition and cuticle formation during plant development are revealed by gas chromatography/mass spectrometry and Fourier-transform infrared spectroscopy. The composition of cutin changes during rosette leaf expansion in Arabidopsis. C16:0 monomers are in higher abundance in expanding than in fully expanded leaves. The atypical cutin monomer C18:2 dicarboxylic acid is more prominent in fully expanded leaves. Findings point to differences in the regulation of several pathways of cutin precursor synthesis. PEC1 plays an essential role during expansion of the rosette leaf cuticle. The reduction of C16 monomers in the pec1 mutant during leaf expansion is unlikely to cause permeability of the leaf cuticle because the gpat6 mutant with even fewer C16:0 monomers forms a functional rosette leaf cuticle at all stages of development. PEC1/ABCG32 transport activity affects cutin composition and cuticle structure in a specific and non-redundant fashion.

  8. Cytokinin signaling regulates pavement cell morphogenesis in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Hongjiang Li; Tongda Xu; Deshu Lin; Mingzhang Wen; Mingtang Xie; Jér(o)me Duclercq; Agnieszka Bielach

    2013-01-01

    The puzzle piece-shaped Arabidopsis leaf pavement cells (PCs) with interdigitated lobes and indents is a good model system to investigate the mechanisms that coordinate cell polarity and shape formation within a tissue.Auxin has been shown to coordinate the interdigitation by activating ROP GTPase-dependent signaling pathways.To identify additional components or mechanisms,we screened for mutants with abnormal PC morphogenesis and found that cytokinin signaling regulates the PC interdigitation pattern.Reduction in cytokinin accumulation and defects in cytokinin signaling (such as in ARR7-over-expressing lines,the ahk3cre1 cytokinin receptor mutant,and the ahp12345 cytokinin signaling mutant) enhanced PC interdigitation,whereas over-production of cytokinin and over-activation of cytokinin signaling in an ARR20 over-expression line delayed or abolished PC interdigitation throughout the cotyledon.Genetic and biochemical analyses suggest that cytokinin signaling acts upstream of ROPs to suppress the formation of interdigitated pattern.Our results provide novel mechanistic understanding of the pathways controlling PC shape and uncover a new role for cytokinin signaling in cell morphogenesis.

  9. Selection of valine-resistance in callus culture of Arabidopsis thaliana (L.) Heynh. derived from leaf explants

    OpenAIRE

    Małgorzata D. Gaj; Grzegorz Czaja; Małgorzata Nawrot

    2014-01-01

    The selection of valine-resistant mutants was carried out in leaf explant cultures of three Arabidopsis thaliana (L.) Heynh. ecotypes: C-24, RLD and Columbia. The valine concentration used for in vitro selection, lethal for seed-growing plants, has not affected callus formation and growth. However, strong inhibition of shoot regeneration ability of calli growing under selection pressure was noticed. In total, 1043 explants were cultured on valine medium and 18 shoots were regenerated with an ...

  10. Starch synthase 4 is essential for coordination of starch granule formation with chloroplast division during Arabidopsis leaf expansion

    OpenAIRE

    Crumpton-Taylor, Matilda; Pike, Marilyn; Lu, Kuan-Jen; Hylton, Christopher M.; Feil, Regina; Eicke, Simona; Lunn, John E.; Zeeman, Samuel C.; Smith, Alison M.

    2013-01-01

    Arabidopsis thaliana mutants lacking the SS4 isoform of starch synthase have strongly reduced numbers of starch granules per chloroplast, suggesting that SS4 is necessary for the normal generation of starch granules. To establish whether it plays a direct role in this process, we investigated the circumstances in which granules are formed in ss4 mutants. Starch granule numbers and distribution and the accumulation of starch synthase substrates and products were investigated during ss4 leaf de...

  11. YUCCA6 over-expression demonstrates auxin function in delaying leaf senescence in Arabidopsis thaliana

    KAUST Repository

    Kim, Jeong Im

    2011-04-21

    The Arabidopsis thaliana YUCCA family of flavin monooxygenase proteins catalyses a rate-limiting step in de novo auxin biosynthesis. A YUCCA6 activation mutant, yuc6-1D, has been shown to contain an elevated free IAA level and to display typical high-auxin phenotypes. It is reported here that Arabidopsis plants over-expressing YUCCA6, such as the yuc6-1D activation mutant and 35S:YUC6 transgenic plants, displayed dramatic longevity. In addition, plants over-expressing YUCCA6 exhibited classical, delayed dark-induced and hormone-induced senescence in assays using detached rosette leaves. However, plants over-expressing an allele of YUCCA6, that carries mutations in the NADPH cofactor binding site, exhibited neither delayed leaf senescence phenotypes nor phenotypes typical of auxin overproduction. When the level of free IAA was reduced in yuc6-1D by conjugation to lysine, yuc6-1D leaves senesced at a rate similar to the wild-type leaves. Dark-induced senescence in detached leaves was accompanied by a decrease in their free IAA content, by the reduced expression of auxin biosynthesis enzymes such as YUCCA1 and YUCCA6 that increase cellular free IAA levels, and by the increased expression of auxin-conjugating enzymes encoded by the GH3 genes that reduce the cellular free auxin levels. Reduced transcript abundances of SAG12, NAC1, and NAC6 during senescence in yuc6-1D compared with the wild type suggested that auxin delays senescence by directly or indirectly regulating the expression of senescence-associated genes. 2011 The Author(s).

  12. Effect of clinorotation on the leaf mesophyll structure and pigment content in Arabidopsis thaliana L. and Pisum sativum L.

    Science.gov (United States)

    Adamchuk, N I

    2004-07-01

    Properties of mesophyll cells and photosynthetic membranes of Arabidopsis thaliana (L.) Heynh. and Pisum sativum (L.) plants grown in a horizontal clinostat and in control conditions were compared. Obtained data have show that under clinorotation conditions seedlings have experienced the following cell morphology changes structural chloroplast rearrangement in palisade cells, pigment content alteration, and cell aging acceleration.

  13. A workflow for mathematical modeling of subcellular metabolic pathways in leaf metabolism of Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Thomas eNägele

    2013-12-01

    Full Text Available During the last decade genome sequencing has experienced a rapid technological development resulting in numerous sequencing projects and applications in life science. In plant molecular biology, the availability of sequence data on whole genomes has enabled the reconstruction of metabolic networks. Enzymatic reactions are predicted by the sequence information. Pathways arise due to the participation of chemical compounds as substrates and products in these reactions. Although several of these comprehensive networks have been reconstructed for the genetic model plant Arabidopsis thaliana, the integration of experimental data is still challenging. Particularly the analysis of subcellular organization of plant cells limits the understanding of regulatory instances in these metabolic networks in vivo. In this study, we develop an approach for the functional integration of experimental high-throughput data into such large-scale networks. We present a subcellular metabolic network model comprising 524 metabolic intermediates and 548 metabolic interactions derived from a total of 2769 reactions. We demonstrate how to link the metabolite covariance matrix of different Arabidopsis thaliana accessions with the subcellular metabolic network model for the inverse calculation of the biochemical Jacobian, finally resulting in the calculation of a matrix which satisfies a Lyaponov equation involving a covariance matrix. In this way, differential strategies of metabolite compartmentation and involved reactions were identified in the accessions when exposed to low temperature.

  14. Higher peroxidase activity, leaf nutrient contents and carbon isotope composition changes in Arabidopsis thaliana are related to rutin stress.

    Science.gov (United States)

    Hussain, M Iftikhar; Reigosa, Manuel J

    2014-09-15

    Rutin, a plant secondary metabolite that is used in cosmetics and food additive and has known medicinal properties, protects plants from UV-B radiation and diseases. Rutin has been suggested to have potential in weed management, but its mode of action at physiological level is unknown. Here, we report the biochemical, physiological and oxidative response of Arabidopsis thaliana to rutin at micromolar concentrations. It was found that fresh weight; leaf mineral contents (nitrogen, sodium, potassium, copper and aluminum) were decreased following 1 week exposure to rutin. Arabidopsis roots generate significant amounts of reactive oxygen species after rutin treatment, consequently increasing membrane lipid peroxidation, decreasing leaf Ca(2+), Mg(2+), Zn(2+), Fe(2+) contents and losing root viability. Carbon isotope composition in A. thaliana leaves was less negative after rutin application than the control. Carbon isotope discrimination values were decreased following rutin treatment, with the highest reduction compared to the control at 750μM rutin. Rutin also inhibited the ratio of CO2 from leaf to air (ci/ca) at all concentrations. Total protein contents in A. thaliana leaves were decreased following rutin treatment. It was concluded carbon isotope discrimination coincided with protein degradation, increase lipid peroxidation and a decrease in ci/ca values may be the primary action site of rutin. The present results suggest that rutin possesses allelopathic potential and could be used as a candidate to develop environment friendly natural herbicide.

  15. Dynamics of Jasmonate Metabolism upon Flowering and across Leaf Stress Responses in Arabidopsis thaliana.

    Science.gov (United States)

    Widemann, Emilie; Smirnova, Ekaterina; Aubert, Yann; Miesch, Laurence; Heitz, Thierry

    2016-01-01

    The jasmonic acid (JA) signaling pathway plays important roles in adaptation of plants to environmental cues and in specific steps of their development, particularly in reproduction. Recent advances in metabolic studies have highlighted intricate mechanisms that govern enzymatic conversions within the jasmonate family. Here we analyzed jasmonate profile changes upon Arabidopsis thaliana flower development and investigated the contribution of catabolic pathways that were known to turnover the active hormonal compound jasmonoyl-isoleucine (JA-Ile) upon leaf stress. We report a rapid decline of JA-Ile upon flower opening, concomitant with the massive accumulation of its most oxidized catabolite, 12COOH-JA-Ile. Detailed genetic analysis identified CYP94C1 as the major player in this process. CYP94C1 is one out of three characterized cytochrome P450 enzymes that define an oxidative JA-Ile turnover pathway, besides a second, hydrolytic pathway represented by the amido-hydrolases IAR3 and ILL6. Expression studies combined with reporter gene analysis revealed the dominant expression of CYP94C1 in mature anthers, consistent with the established role of JA signaling in male fertility. Significant CYP94B1 expression was also evidenced in stamen filaments, but surprisingly, CYP94B1 deficiency was not associated with significant changes in JA profiles. Finally, we compared global flower JA profiles with those previously reported in leaves reacting to mechanical wounding or submitted to infection by the necrotrophic fungus Botrytis cinerea. These comparisons revealed distinct dynamics of JA accumulation and conversions in these three biological systems. Leaf injury boosts a strong and transient JA and JA-Ile accumulation that evolves rapidly into a profile dominated by ω-oxidized and/or Ile-conjugated derivatives. In contrast, B. cinerea-infected leaves contain mostly unconjugated jasmonates, about half of this content being ω-oxidized. Finally, developing flowers present an

  16. Dynamics of Jasmonate Metabolism upon Flowering and across Leaf Stress Responses in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Emilie Widemann

    2016-01-01

    Full Text Available The jasmonic acid (JA signaling pathway plays important roles in adaptation of plants to environmental cues and in specific steps of their development, particularly in reproduction. Recent advances in metabolic studies have highlighted intricate mechanisms that govern enzymatic conversions within the jasmonate family. Here we analyzed jasmonate profile changes upon Arabidopsis thaliana flower development and investigated the contribution of catabolic pathways that were known to turnover the active hormonal compound jasmonoyl-isoleucine (JA-Ile upon leaf stress. We report a rapid decline of JA-Ile upon flower opening, concomitant with the massive accumulation of its most oxidized catabolite, 12COOH-JA-Ile. Detailed genetic analysis identified CYP94C1 as the major player in this process. CYP94C1 is one out of three characterized cytochrome P450 enzymes that define an oxidative JA-Ile turnover pathway, besides a second, hydrolytic pathway represented by the amido-hydrolases IAR3 and ILL6. Expression studies combined with reporter gene analysis revealed the dominant expression of CYP94C1 in mature anthers, consistent with the established role of JA signaling in male fertility. Significant CYP94B1 expression was also evidenced in stamen filaments, but surprisingly, CYP94B1 deficiency was not associated with significant changes in JA profiles. Finally, we compared global flower JA profiles with those previously reported in leaves reacting to mechanical wounding or submitted to infection by the necrotrophic fungus Botrytis cinerea. These comparisons revealed distinct dynamics of JA accumulation and conversions in these three biological systems. Leaf injury boosts a strong and transient JA and JA-Ile accumulation that evolves rapidly into a profile dominated by ω-oxidized and/or Ile-conjugated derivatives. In contrast, B. cinerea-infected leaves contain mostly unconjugated jasmonates, about half of this content being ω-oxidized. Finally, developing

  17. SENESCENCE-SUPPRESSED PROTEIN PHOSPHATASE Directly Interacts with the Cytoplasmic Domain of SENESCENCE-ASSOCIATED RECEPTOR-LIKE KINASE and Negatively Regulates Leaf Senescence in Arabidopsis.

    Science.gov (United States)

    Xiao, Dong; Cui, Yanjiao; Xu, Fan; Xu, Xinxin; Gao, Guanxiao; Wang, Yaxin; Guo, Zhaoxia; Wang, Dan; Wang, Ning Ning

    2015-10-01

    Reversible protein phosphorylation mediated by protein kinases and phosphatases plays an important role in the regulation of leaf senescence. We previously reported that the leucine-rich repeat receptor-like kinase SENESCENCE-ASSOCIATED RECEPTOR-LIKE KINASE (AtSARK) positively regulates leaf senescence in Arabidopsis (Arabidopsis thaliana). Here, we report the involvement of a protein serine/threonine phosphatase 2C-type protein phosphatase, SENESCENCE-SUPPRESSED PROTEIN PHOSPHATASE (SSPP), in the negative regulation of Arabidopsis leaf senescence. SSPP transcript levels decreased greatly during both natural senescence and SARK-induced precocious senescence. Overexpression of SSPP significantly delayed leaf senescence in Arabidopsis. Protein pull-down and bimolecular fluorescence complementation assays demonstrated that the cytosol-localized SSPP could interact with the cytoplasmic domain of the plasma membrane-localized AtSARK. In vitro assays showed that SSPP has protein phosphatase function and can dephosphorylate the cytosolic domain of AtSARK. Consistent with these observations, overexpression of SSPP effectively rescued AtSARK-induced precocious leaf senescence and changes in hormonal responses. All our results suggested that SSPP functions in sustaining proper leaf longevity and preventing early senescence by suppressing or perturbing SARK-mediated senescence signal transduction.

  18. Acetylsalicylic acid induces programmed cell death in Arabidopsis cell cultures.

    Science.gov (United States)

    García-Heredia, José M; Hervás, Manuel; De la Rosa, Miguel A; Navarro, José A

    2008-06-01

    Acetylsalicylic acid (ASA), a derivative from the plant hormone salicylic acid (SA), is a commonly used drug that has a dual role in animal organisms as an anti-inflammatory and anticancer agent. It acts as an inhibitor of cyclooxygenases (COXs), which catalyze prostaglandins production. It is known that ASA serves as an apoptotic agent on cancer cells through the inhibition of the COX-2 enzyme. Here, we provide evidences that ASA also behaves as an agent inducing programmed cell death (PCD) in cell cultures of the model plant Arabidopsis thaliana, in a similar way than the well-established PCD-inducing agent H(2)O(2), although the induction of PCD by ASA requires much lower inducer concentrations. Moreover, ASA is herein shown to be a more efficient PCD-inducing agent than salicylic acid. ASA treatment of Arabidopsis cells induces typical PCD-linked morphological and biochemical changes, namely cell shrinkage, nuclear DNA degradation, loss of mitochondrial membrane potential, cytochrome c release from mitochondria and induction of caspase-like activity. However, the ASA effect can be partially reverted by jasmonic acid. Taking together, these results reveal the existence of common features in ASA-induced animal apoptosis and plant PCD, and also suggest that there are similarities between the pathways of synthesis and function of prostanoid-like lipid mediators in animal and plant organisms.

  19. Cell- and stimulus type-specific intracellular free Ca2+ signals in Arabidopsis.

    Science.gov (United States)

    Martí, María C; Stancombe, Matthew A; Webb, Alex A R

    2013-10-01

    Appropriate stimulus-response coupling requires that each signal induces a characteristic response, distinct from that induced by other signals, and that there is the potential for individual signals to initiate different downstream responses dependent on cell type. How such specificity is encoded in plant signaling is not known. One possibility is that information is encoded in signal transduction pathways to ensure stimulus- and cell type-specific responses. The calcium ion acts as a second messenger in response to mechanical stimulation, hydrogen peroxide, NaCl, and cold in plants and also in circadian timing. We use GAL4 transactivation of aequorin in enhancer trap lines of Arabidopsis (Arabidopsis thaliana) to test the hypothesis that stimulus- and cell-specific information can be encoded in the pattern of dynamic alterations in the concentration of intracellular free Ca(2+) ([Ca(2+)]i). We demonstrate that mechanically induced increases in [Ca(2+)]i are largely restricted to the epidermal pavement cells of leaves, that NaCl induces oscillatory [Ca(2+)]i signals in spongy mesophyll and vascular bundle cells, but not other cell types, and detect circadian rhythms of [Ca(2+)]i only in the spongy mesophyll. We demonstrate stimulus-specific [Ca(2+)]i dynamics in response to touch, cold, and hydrogen peroxide, which in the case of the latter two signals are common to all cell types tested. GAL4 transactivation of aequorin in specific leaf cell types has allowed us to bypass the technical limitations associated with fluorescent Ca(2+) reporter dyes in chlorophyll-containing tissues to identify the cell- and stimulus-specific complexity of [Ca(2+)]i dynamics in leaves of Arabidopsis and to determine from which tissues stress- and circadian-regulated [Ca(2+)]i signals arise.

  20. Modulation of ethylene- and heat-controlled hyponastic leaf movement in Arabidopsis thaliana by the plant defence hormones jasmonate and salicylate

    NARCIS (Netherlands)

    Zanten, M. van; Ritsema, T.; Polko, J.K.; Leon-Reyes, A.; Voesenek, L.A.C.J.; Millenaar, F.F.; Pieterse, C.M.J.; Peeters, A.J.M.

    2012-01-01

    Upward leaf movement (hyponastic growth) is adopted by several plant species including Arabidopsis thaliana, as a mechanism to escape adverse growth conditions. Among the signals that trigger hyponastic growth are, the gaseous hormone ethylene, low light intensities, and supra-optimal temperatures (

  1. In Silico Identification of Co-transcribed Core Cell Cycle Regulators and Transcription Factors in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Regulatory networks involving transcription factors and core cell cycle regulators are expected to play crucial roles in plant growth and development. In this report, we describe the identification of two groups of co-transcribed core cell cycle regulators and transcription factors via a two-step in silico screening. The core cell cycle regulators include TARDY ASYNCHRONOUS MEIOSIS (CYCA1;2), CYCB1;1, CYCB2;1, CDKB1;2, and CDKB2;2 while the transcription factors include CURLY LEAF, AINTEGUMENTA, a MYB protein, two Forkhead-associated domain proteins, and a SCARECROW family protein. Promoter analysis revealed a potential web of cross- and self-regulations among the identified proteins. Because one criterion for screening for these genes is that they are predominantly transcribed in young organs but not in mature organs, these genes are likely to be particularly involved in Arabidopsis organ growth.

  2. YUCCA-mediated auxin biogenesis is required for cell fate transition occurring during de novo root organogenesis in Arabidopsis.

    Science.gov (United States)

    Chen, Lyuqin; Tong, Jianhua; Xiao, Langtao; Ruan, Ying; Liu, Jingchun; Zeng, Minhuan; Huang, Hai; Wang, Jia-Wei; Xu, Lin

    2016-07-01

    Many plant organs have the ability to regenerate a new plant after detachment or wounding via de novo organogenesis. During de novo root organogenesis from Arabidopsis thaliana leaf explants, endogenic auxin is essential for the fate transition of regeneration-competent cells to become root founder cells via activation of WUSCHEL-RELATED HOMEOBOX 11 (WOX11). However, the molecular events from leaf explant detachment to auxin-mediated cell fate transition are poorly understood. In this study, we used an assay to determine the concentration of indole-3-acetic acid (IAA) to provide direct evidence that auxin is produced after leaf explant detachment, a process that involves YUCCA (YUC)-mediated auxin biogenesis. Inhibition of YUC prevents expression of WOX11 and fate transition of competent cells, resulting in the blocking of rooting. Further analysis showed that YUC1 and YUC4 act quickly (within 4 hours) in response to wounding after detachment in both light and dark conditions and promote auxin biogenesis in both mesophyll and competent cells, whereas YUC5, YUC8, and YUC9 primarily respond in dark conditions. In addition, YUC2 and YUC6 contribute to rooting by providing a basal auxin level in the leaf. Overall, our study indicates that YUC genes exhibit a division of labour during de novo root organogenesis from leaf explants in response to multiple signals. PMID:27255928

  3. Arabidopsis EDS1 connects pathogen effector recognition to cell compartment-specific immune responses.

    Science.gov (United States)

    Heidrich, Katharina; Wirthmueller, Lennart; Tasset, Céline; Pouzet, Cécile; Deslandes, Laurent; Parker, Jane E

    2011-12-01

    Pathogen effectors are intercepted by plant intracellular nucleotide binding-leucine-rich repeat (NB-LRR) receptors. However, processes linking receptor activation to downstream defenses remain obscure. Nucleo-cytoplasmic basal resistance regulator EDS1 (ENHANCED DISEASE SUSCEPTIBILITY1) is indispensible for immunity mediated by TIR (Toll-interleukin-1 receptor)-NB-LRR receptors. We show that Arabidopsis EDS1 molecularly connects TIR-NB-LRR disease resistance protein RPS4 recognition of bacterial effector AvrRps4 to defense pathways. RPS4-EDS1 and AvrRps4-EDS1 complexes are detected inside nuclei of living tobacco cells after transient coexpression and in Arabidopsis soluble leaf extracts after resistance activation. Forced AvrRps4 localization to the host cytoplasm or nucleus reveals cell compartment-specific RPS4-EDS1 defense branches. Although nuclear processes restrict bacterial growth, programmed cell death and transcriptional resistance reinforcement require nucleo-cytoplasmic coordination. Thus, EDS1 behaves as an effector target and activated TIR-NB-LRR signal transducer for defenses across cell compartments.

  4. Ectopic expression of a tobacco vacuolar invertase inhibitor in guard cells confers drought tolerance in Arabidopsis.

    Science.gov (United States)

    Chen, Su-Fen; Liang, Ke; Yin, Dong-Mei; Ni, Di-An; Zhang, Zhi-Guo; Ruan, Yong-Ling

    2016-12-01

    There are several hypotheses that explain stomatal behavior. These include the concept of osmoregulation mediated by potassium and its counterions malate and chlorine and the more recent starch-sugar hypothesis. We have previously reported that the activity of the sucrose cleavage enzyme, vacuolar invertase (VIN), is significantly higher in guard cells than in other leaf epidermal cells and its activity is correlated with stomatal aperture. Here, we examined whether VIN indeed controls stomatal movement under normal and drought conditions by transforming Arabidopsis with a tobacco vacuolar invertase inhibitor homolog (Nt-inhh) under the control of an abscisic acid-sensitive and guard cell-specific promoter (AtRab18). The data obtained showed that guard cells of transgenic Arabidopsis plants had lower VIN activity, stomatal aperture and conductance than that of wild-type plants. Moreover, the transgenic plants also displayed higher drought tolerance than wild-type plants. The data indicate that VIN is a promising target for manipulating stomatal function to increase drought tolerance. PMID:26899912

  5. A mutation in the cytosolic O-acetylserine (thiol lyase induces a genome-dependent early leaf death phenotype in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Schippers Jos HM

    2010-04-01

    Full Text Available Abstract Background Cysteine is a component in organic compounds including glutathione that have been implicated in the adaptation of plants to stresses. O-acetylserine (thiol lyase (OAS-TL catalyses the final step of cysteine biosynthesis. OAS-TL enzyme isoforms are localised in the cytoplasm, the plastids and mitochondria but the contribution of individual OAS-TL isoforms to plant sulphur metabolism has not yet been fully clarified. Results The seedling lethal phenotype of the Arabidopsis onset of leaf death3-1 (old3-1 mutant is due to a point mutation in the OAS-A1 gene, encoding the cytosolic OAS-TL. The mutation causes a single amino acid substitution from Gly162 to Glu162, abolishing old3-1 OAS-TL activity in vitro. The old3-1 mutation segregates as a monogenic semi-dominant trait when backcrossed to its wild type accession Landsberg erecta (Ler-0 and the Di-2 accession. Consistent with its semi-dominant behaviour, wild type Ler-0 plants transformed with the mutated old3-1 gene, displayed the early leaf death phenotype. However, the old3-1 mutation segregates in an 11:4:1 (wild type: semi-dominant: mutant ratio when backcrossed to the Colombia-0 and Wassilewskija accessions. Thus, the early leaf death phenotype depends on two semi-dominant loci. The second locus that determines the old3-1 early leaf death phenotype is referred to as odd-ler (for old3 determinant in the Ler accession and is located on chromosome 3. The early leaf death phenotype is temperature dependent and is associated with increased expression of defence-response and oxidative-stress marker genes. Independent of the presence of the odd-ler gene, OAS-A1 is involved in maintaining sulphur and thiol levels and is required for resistance against cadmium stress. Conclusions The cytosolic OAS-TL is involved in maintaining organic sulphur levels. The old3-1 mutation causes genome-dependent and independent phenotypes and uncovers a novel function for the mutated OAS-TL in cell

  6. Antiphase light and temperature cycles affect PHYTOCHROME B-controlled ethylene sensitivity and biosynthesis, limiting leaf movement and growth of Arabidopsis.

    Science.gov (United States)

    Bours, Ralph; van Zanten, Martijn; Pierik, Ronald; Bouwmeester, Harro; van der Krol, Alexander

    2013-10-01

    In the natural environment, days are generally warmer than the night, resulting in a positive day/night temperature difference (+DIF). Plants have adapted to these conditions, and when exposed to antiphase light and temperature cycles (cold photoperiod/warm night [-DIF]), most species exhibit reduced elongation growth. To study the physiological mechanism of how light and temperature cycles affect plant growth, we used infrared imaging to dissect growth dynamics under +DIF and -DIF in the model plant Arabidopsis (Arabidopsis thaliana). We found that -DIF altered leaf growth patterns, decreasing the amplitude and delaying the phase of leaf movement. Ethylene application restored leaf growth in -DIF conditions, and constitutive ethylene signaling mutants maintain robust leaf movement amplitudes under -DIF, indicating that ethylene signaling becomes limiting under these conditions. In response to -DIF, the phase of ethylene emission advanced 2 h, but total ethylene emission was not reduced. However, expression analysis on members of the 1-aminocyclopropane-1-carboxylic acid (ACC) synthase ethylene biosynthesis gene family showed that ACS2 activity is specifically suppressed in the petiole region under -DIF conditions. Indeed, petioles of plants under -DIF had reduced ACC content, and application of ACC to the petiole restored leaf growth patterns. Moreover, acs2 mutants displayed reduced leaf movement under +DIF, similar to wild-type plants under -DIF. In addition, we demonstrate that the photoreceptor PHYTOCHROME B restricts ethylene biosynthesis and constrains the -DIF-induced phase shift in rhythmic growth. Our findings provide a mechanistic insight into how fluctuating temperature cycles regulate plant growth.

  7. Urea retranslocation from senescing Arabidopsis leaves is promoted by DUR3-mediated urea retrieval from leaf apoplast.

    Science.gov (United States)

    Bohner, Anne; Kojima, Soichi; Hajirezaei, Mohammad; Melzer, Michael; von Wirén, Nicolaus

    2015-02-01

    In plants, urea derives either from root uptake or protein degradation. Although large quantities of urea are released during senescence, urea is mainly seen as a short-lived nitrogen (N) catabolite serving urease-mediated hydrolysis to ammonium. Here, we investigated the roles of DUR3 and of urea in N remobilization. During natural leaf senescence urea concentrations and DUR3 transcript levels showed a parallel increase with senescence markers like ORE1 in a plant age- and leaf age-dependent manner. Deletion of DUR3 decreased urea accumulation in leaves, whereas the fraction of urea lost to the leaf apoplast was enhanced. Under natural and N deficiency-induced senescence DUR3 promoter activity was highest in the vasculature, but was also found in surrounding bundle sheath and mesophyll cells. An analysis of petiole exudates from wild-type leaves revealed that N from urea accounted for >13% of amino acid N. Urea export from senescent leaves further increased in ureG-2 deletion mutants lacking urease activity. In the dur3 ureG double insertion line the absence of DUR3 reduced urea export from leaf petioles. These results indicate that urea can serve as an early metabolic marker for leaf senescence, and that DUR3-mediated urea retrieval contributes to the retranslocation of N from urea during leaf senescence.

  8. The action spectrum in chloroplast translocation in multilayer leaf cells

    Directory of Open Access Journals (Sweden)

    Zbigniew Lechowski

    2015-05-01

    Full Text Available By measurement of light transmittance through a leaf as criterion of chloroplast translocation, the action spectrum of Ajuga reptans was established. In the spectrum obtained, a correction was introduced for leaf autoabsorption calculated on the basis of the Beer-Lambert law. The action spectrum has two maxima: at λ= 375 nm and λ= 481 nm. The range above 502 nm has no significant effect on chloroplast translocation. Comparison with other objects examined demonstrated that in multilayer leaf cells riboflavin seems also to be a photoreceptor active in this process.

  9. Isolation of a strong Arabidopsis guard cell promoter and its potential as a research tool

    Directory of Open Access Journals (Sweden)

    Siegel Robert S

    2008-02-01

    Full Text Available Abstract Background A common limitation in guard cell signaling research is that it is difficult to obtain consistent high expression of transgenes of interest in Arabidopsis guard cells using known guard cell promoters or the constitutive 35S cauliflower mosaic virus promoter. An additional drawback of the 35S promoter is that ectopically expressing a gene throughout the organism could cause pleiotropic effects. To improve available methods for targeted gene expression in guard cells, we isolated strong guard cell promoter candidates based on new guard cell-specific microarray analyses of 23,000 genes that are made available together with this report. Results A promoter, pGC1(At1g22690, drove strong and relatively specific reporter gene expression in guard cells including GUS (beta-glucuronidase and yellow cameleon YC3.60 (GFP-based calcium FRET reporter. Reporter gene expression was weaker in immature guard cells. The expression of YC3.60 was sufficiently strong to image intracellular Ca2+ dynamics in guard cells of intact plants and resolved spontaneous calcium transients in guard cells. The GC1 promoter also mediated strong reporter expression in clustered stomata in the stomatal development mutant too-many-mouths (tmm. Furthermore, the same promoter::reporter constructs also drove guard cell specific reporter expression in tobacco, illustrating the potential of this promoter as a method for high level expression in guard cells. A serial deletion of the promoter defined a guard cell expression promoter region. In addition, anti-sense repression using pGC1 was powerful for reducing specific GFP gene expression in guard cells while expression in leaf epidermal cells was not repressed, demonstrating strong cell-type preferential gene repression. Conclusion The pGC1 promoter described here drives strong reporter expression in guard cells of Arabidopsis and tobacco plants. It provides a potent research tool for targeted guard cell expression or

  10. Leaf Epidermal Cells: A Trap for Lipophilic Xenobiotics

    Institute of Scientific and Technical Information of China (English)

    Zhiqian Liu

    2006-01-01

    Plant surfaces are covered by a layer of cuticle, which functions as a natural barrier to protect plants from mechanical damage, desiccation, and microbial invasion. Results presented in this report show that the epicuticular wax and the cuticle of plant leaves also play an important role in resisting xenobiotic invasion.Although the epicuticular wax is impermeableto hydrophilic xenobiotics, the cuticle not only restricts the penetration of hydrophilic compounds into leaf cells, but also traps lipophilic ones. The role of the epidermal cells of plant leaves in resisting xenobiotic invasion has been neglected until now. The present study shows, for the first time, that the epidermal cells may reduce or retard the transport of lipophilic xenobiotics into the internal tissues through vacuolar sequestration. Although the guard cells appear to be an easy point of entry for xenobiotics, only a very small proportion of xenobiotics present on the leaf surface actually moves into leaf tissues via the guard cells.

  11. Modulation of ethylene and heat-controlled hyponastic leaf movement in Arabidopsis thaliana by the plant defense hormones jasmonate and salicylate

    OpenAIRE

    van Zanten, Martijn; Ritsema, Tita; Polko, Joanna K.; Leon-Reyes, Antonio; Voesenek, Laurentius A C J; Frank F Millenaar; Pieterse, Corné M. J.; Peeters, Anton J. M.

    2012-01-01

    Upward leaf movement (hyponastic growth) is adopted by several plant species including Arabidopsis thaliana, as a mechanism to escape adverse growth conditions. Among the signals that trigger hyponastic growth are, the gaseous hormone ethylene, low light intensities, and supra-optimal temperatures (heat). Recent studies indicated that the defence-related phytohormones jasmonic acid (JA) and salicylic acid (SA) synthesized by the plant upon biotic infestation repress low light-induced hyponast...

  12. Improvements in the transformation of Arabidopsis thaliana C24 leaf-discs by Agrobacterium tumefaciens

    DEFF Research Database (Denmark)

    van der Graaff, Eric; Hooykaas, P J

    1996-01-01

    We report here an efficient Arabidopsis leafdisc transformation protocol yielding an average transformation frequency of 1.6 transgenic shoots per leaf explant 4 weeks after the bacterial infection period. Subsequent cultivation in vitro is such that a high percentage (85-90%) of the primary tran...... harboring an activator T-DNA construct in a gene tagging approach to isolate genes involved in morphogenesis and auxin signal transduction....

  13. Differential Roles of Two Homologous Cyclin-Dependent Kinase Inhibitor Genes in Regulating Cell Cycle and Innate Immunity in Arabidopsis.

    Science.gov (United States)

    Hamdoun, Safae; Zhang, Chong; Gill, Manroop; Kumar, Narender; Churchman, Michelle; Larkin, John C; Kwon, Ashley; Lu, Hua

    2016-01-01

    Precise cell-cycle control is critical for plant development and responses to pathogen invasion. Two homologous cyclin-dependent kinase inhibitor genes, SIAMESE (SIM) and SIM-RELATED 1 (SMR1), were recently shown to regulate Arabidopsis (Arabidopsis thaliana) defense based on phenotypes conferred by a sim smr1 double mutant. However, whether these two genes play differential roles in cell-cycle and defense control is unknown. In this report, we show that while acting synergistically to promote endoreplication, SIM and SMR1 play different roles in affecting the ploidy of trichome and leaf cells, respectively. In addition, we found that the smr1-1 mutant, but not sim-1, was more susceptible to a virulent Pseudomonas syringae strain, and this susceptibility could be rescued by activating salicylic acid (SA)-mediated defense. Consistent with these results, smr1-1 partially suppressed the dwarfism, high SA levels, and cell death phenotypes in acd6-1, a mutant used to gauge the change of defense levels. Thus, SMR1 functions partly through SA in defense control. The differential roles of SIM and SMR1 are due to differences in temporal and spatial expression of these two genes in Arabidopsis tissues and in response to P. syringae infection. In addition, flow-cytometry analysis of plants with altered SA signaling revealed that SA is necessary, but not sufficient, to change cell-cycle progression. We further found that a mutant with three CYCD3 genes disrupted also compromised disease resistance to P. syringae. Together, this study reveals differential roles of two homologous cyclin-dependent kinase inhibitors in regulating cell-cycle progression and innate immunity in Arabidopsis and provides insights into the importance of cell-cycle control during host-pathogen interactions. PMID:26561564

  14. Does Arabidopsis thaliana DREAM of cell cycle control?

    Science.gov (United States)

    Fischer, Martin; DeCaprio, James A

    2015-08-01

    Strict temporal control of cell cycle gene expression is essential for all eukaryotes including animals and plants. DREAM complexes have been identified in worm, fly, and mammals, linking several distinct transcription factors to coordinate gene expression throughout the cell cycle. In this issue of The EMBO Journal, Kobayashi et al (2015) identify distinct activator and repressor complexes for genes expressed during the G2 and M phases in Arabidopsis that can be temporarily separated during proliferating and post‐mitotic stages of development. The complexes incorporate specific activator and repressor MYB and E2F transcription factors and indicate the possibility of the existence of multiple DREAM complexes in plants. PMID:26089020

  15. Abscisic acid as an internal integrator of multiple physiological processes modulates leaf senescence onset in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Yuwei eSong

    2016-02-01

    Full Text Available Many studies have shown that exogenous abscisic acid (ABA promotes leaf abscission and senescence. However, owing to a lack of genetic evidence, ABA function in plant senescence has not been clearly defined. Here, two-leaf early-senescence mutants (eas that were screened by chlorophyll fluorescence imaging and named eas1-1 and eas1-2 showed high photosynthetic capacity in the early stage of plant growth compared with the wild type. Gene mapping showed that eas1-1 and eas1-2 are two novel ABA2 allelic mutants. Under unstressed conditions, the eas1 mutations caused plant dwarf, early germination, larger stomatal apertures, and early leaf senescence compared with those of the wild type. Flow cytometry assays showed that the cell apoptosis rate in eas1 mutant leaves was higher than that of the wild type after day 30. A significant increase in the transcript levels of several senescence-associated genes, especially SAG12, was observed in eas1 mutant plants in the early stage of plant growth. More importantly, ABA-activated calcium channel activity in plasma membrane and induced the increase of cytoplasmic calcium concentration in guard cells are suppressed due to the mutation of EAS1. In contrast, the eas1 mutants lost chlorophyll and ion leakage significant faster than in the wild type under treatment with calcium channel blocker. Hence, our results indicate that endogenous ABA level is an important factor controlling the onset of leaf senescence through Ca2+ signaling.

  16. Specific localization and measurement of hydrogen peroxide in Arabidopsis thaliana cell suspensions and protoplasts elicited by COS-OGA.

    Science.gov (United States)

    Ledoux, Quentin; Van Cutsem, Pierre; Markό, Istvan E; Veys, Pascal

    2014-01-01

    H2O2 acts as an important signaling molecule during plant/pathogen interactions but its study remains a challenge due to the current shortcomings in H2O2-responsive probes. In this work, ContPY1, a new molecular probe developed to specifically detect H2O2 was used to study the elicitation of Arabidopsis thaliana cells by a complex of chitosan oligomers (COS) and oligogalacturonides (OGA). The comparison of cell suspensions, protoplasts of cell suspensions and leaf protoplasts treated with different inhibitors gave indications on the potential sources of hydrogen peroxide in plant cells. The relative contribution of the cell wall, of membrane dehydrogenases and of peroxidases depended on cell type and treatment and proved to be variable. Our present protocol can be used to study hydrogen peroxide production in a large variety of plant species by simple protocol adaptation.

  17. A genetic link between epigenetic repressor AS1-AS2 and a putative small subunit processome in leaf polarity establishment of Arabidopsis.

    Science.gov (United States)

    Matsumura, Yoko; Ohbayashi, Iwai; Takahashi, Hiro; Kojima, Shoko; Ishibashi, Nanako; Keta, Sumie; Nakagawa, Ayami; Hayashi, Rika; Saéz-Vásquez, Julio; Echeverria, Manuel; Sugiyama, Munetaka; Nakamura, Kenzo; Machida, Chiyoko; Machida, Yasunori

    2016-01-01

    Although the DEAD-box RNA helicase family is ubiquitous in eukaryotes, its developmental role remains unelucidated. Here, we report that cooperative action between the Arabidopsis nucleolar protein RH10, an ortholog of human DEAD-box RNA helicase DDX47, and the epigenetic repressor complex of ASYMMETRIC-LEAVES1 (AS1) and AS2 (AS1-AS2) is critical to repress abaxial (ventral) genes ETT/ARF3 and ARF4, which leads to adaxial (dorsal) development in leaf primordia at shoot apices. Double mutations of rh10-1 and as2 (or as1) synergistically up-regulated the abaxial genes, which generated abaxialized filamentous leaves with loss of the adaxial domain. DDX47 is part of the small subunit processome (SSUP) that mediates rRNA biogenesis. In rh10-1 we found various defects in SSUP-related events, such as: accumulation of 35S/33S rRNA precursors; reduction in the 18S/25S ratio; and nucleolar hypertrophy. Double mutants of as2 with mutations of genes that encode other candidate SSUP-related components such as nucleolin and putative rRNA methyltransferase exhibited similar synergistic defects caused by up-regulation of ETT/ARF3 and ARF4 These results suggest a tight link between putative SSUP and AS1-AS2 in repression of the abaxial-determining genes for cell fate decisions for adaxial development. PMID:27334696

  18. A genetic link between epigenetic repressor AS1-AS2 and a putative small subunit processome in leaf polarity establishment of Arabidopsis

    Directory of Open Access Journals (Sweden)

    Yoko Matsumura

    2016-07-01

    Full Text Available Although the DEAD-box RNA helicase family is ubiquitous in eukaryotes, its developmental role remains unelucidated. Here, we report that cooperative action between the Arabidopsis nucleolar protein RH10, an ortholog of human DEAD-box RNA helicase DDX47, and the epigenetic repressor complex of ASYMMETRIC-LEAVES1 (AS1 and AS2 (AS1-AS2 is critical to repress abaxial (ventral genes ETT/ARF3 and ARF4, which leads to adaxial (dorsal development in leaf primordia at shoot apices. Double mutations of rh10-1 and as2 (or as1 synergistically up-regulated the abaxial genes, which generated abaxialized filamentous leaves with loss of the adaxial domain. DDX47 is part of the small subunit processome (SSUP that mediates rRNA biogenesis. In rh10-1 we found various defects in SSUP-related events, such as: accumulation of 35S/33S rRNA precursors; reduction in the 18S/25S ratio; and nucleolar hypertrophy. Double mutants of as2 with mutations of genes that encode other candidate SSUP-related components such as nucleolin and putative rRNA methyltransferase exhibited similar synergistic defects caused by up-regulation of ETT/ARF3 and ARF4. These results suggest a tight link between putative SSUP and AS1-AS2 in repression of the abaxial-determining genes for cell fate decisions for adaxial development.

  19. Salicylic acid 3-hydroxylase regulates Arabidopsis leaf longevity by mediating salicylic acid catabolism.

    Science.gov (United States)

    Zhang, Kewei; Halitschke, Rayko; Yin, Changxi; Liu, Chang-Jun; Gan, Su-Sheng

    2013-09-01

    The plant hormone salicylic acid (SA) plays critical roles in plant defense, stress responses, and senescence. Although SA biosynthesis is well understood, the pathways by which SA is catabolized remain elusive. Here we report the identification and characterization of an SA 3-hydroxylase (S3H) involved in SA catabolism during leaf senescence. S3H is associated with senescence and is inducible by SA and is thus a key part of a negative feedback regulation system of SA levels during senescence. The enzyme converts SA (with a Km of 58.29 µM) to both 2,3-dihydroxybenzoic acid (2,3-DHBA) and 2,5-DHBA in vitro but only 2,3-DHBA in vivo. The s3h knockout mutants fail to produce 2,3-DHBA sugar conjugates, accumulate very high levels of SA and its sugar conjugates, and exhibit a precocious senescence phenotype. Conversely, the gain-of-function lines contain high levels of 2,3-DHBA sugar conjugates and extremely low levels of SA and its sugar conjugates and display a significantly extended leaf longevity. This research reveals an elegant SA catabolic mechanism by which plants regulate SA levels by converting it to 2,3-DHBA to prevent SA overaccumulation. The research also provides strong molecular genetic evidence for an important role of SA in regulating the onset and rate of leaf senescence.

  20. Lipid profiling demonstrates that suppressing Arabidopsis phospholipase Dδ retards ABA-promoted leaf senescence by attenuating lipid degradation.

    Directory of Open Access Journals (Sweden)

    Yanxia Jia

    Full Text Available Senescence is the last phase of the plant life cycle and has an important role in plant development. Degradation of membrane lipids is an essential process during leaf senescence. Several studies have reported fundamental changes in membrane lipids and phospholipase D (PLD activity as leaves senesce. Suppression of phospholipase Dα1 (PLDα1 retards abscisic acid (ABA-promoted senescence. However, given the absence of studies that have profiled changes in the compositions of membrane lipid molecules during leaf senescence, there is no direct evidence that PLD affects lipid composition during the process. Here, we show that application of n-butanol, an inhibitor of PLD, and N-Acylethanolamine (NAE 12∶0, a specific inhibitor of PLDα1, retarded ABA-promoted senescence to different extents. Furthermore, phospholipase Dδ (PLDδ was induced in leaves treated with ABA, and suppression of PLDδ retarded ABA-promoted senescence in Arabidopsis. Lipid profiling revealed that detachment-induced senescence had different effects on plastidic and extraplastidic lipids. The accelerated degradation of plastidic lipids during ABA-induced senescence in wild-type plants was attenuated in PLDδ-knockout (PLDδ-KO plants. Dramatic increases in phosphatidic acid (PA and decreases in phosphatidylcholine (PC during ABA-induced senescence were also suppressed in PLDδ-KO plants. Our results suggest that PLDδ-mediated hydrolysis of PC to PA plays a positive role in ABA-promoted senescence. The attenuation of PA formation resulting from suppression of PLDδ blocks the degradation of membrane lipids, which retards ABA-promoted senescence.

  1. Virtual microstructural leaf tissue generation based on cell growth modeling

    NARCIS (Netherlands)

    Abera, M.K.; Retta, M.A.; Verboven, P.; Nicolai, B.M.; Berghuijs, H.; Struik, P.

    2016-01-01

    A cell growth algorithm for virtual leaf tissue generation is presented based on the biomechanics of plant cells in tissues. The algorithm can account for typical differences in epidermal layers, palisade mesophyll layer and spongy mesophyll layer which have characteristic differences in the shap

  2. Impacts of high ATP supply from chloroplasts and mitochondria on the leaf metabolism of Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Chao eLiang

    2015-10-01

    Full Text Available Chloroplasts and mitochondria are the major ATP producing organelles in plant leaves. Arabidopsis thaliana purple acid phosphatase 2 (AtPAP2 is a phosphatase dually targeted to the outer membranes of both organelles and it plays a role in the import of selected nuclear-encoded proteins into these two organelles. Overexpression (OE of AtPAP2 in Arabidopsis thaliana accelerates plant growth and promotes flowering, seed yield and biomass at maturity. Measurement of ADP/ATP/NADP+/NADPH contents in the leaves of 20-day-old OE and wild-type lines at the end of night and at 1 and 8 h following illumination in a 16/8 h photoperiod revealed that the ATP levels and ATP/NADPH ratios were significantly increased in the OE line at all three time points. The AtPAP2 OE line is therefore a good model to investigate the impact of high energy on the global molecular status of Arabidopsis. In this study, transcriptome, proteome and metabolome profiles of the high ATP transgenic line were examined and compared with those of wild-type plants. A comparison of OE and WT at the end of the night provide valuable information on the impact of higher ATP output from mitochondria on plant physiology, as mitochondrial respiration is the major source of ATP in the dark in leaves. Similarly, comparison of OE and WT following illumination will provide information on the impact of higher energy output from chloroplasts on plant physiology. Overexpression of AtPAP2 was found to significantly affect the transcript and protein abundances of genes encoded by the two organellar genomes. For example, the protein abundances of many ribosomal proteins encoded by the chloroplast genome were higher in the AtPAP2 OE line under both light and dark conditions, while the protein abundances of multiple components of the photosynthetic complexes were lower. RNA-seq data also showed that the transcription of the mitochondrial genome is greatly affected by the availability of energy. These data

  3. Genome-wide analysis of the Arabidopsis leaf transcriptome reveals interaction of phosphate and sugar metabolism

    DEFF Research Database (Denmark)

    Muller, Renate; Morant, Marc; Jarmer, Hanne Østergaard;

    2007-01-01

    factors individually. The genes exhibiting interactions form three main clusters with different response patterns and functionality of genes. One cluster (cluster 1) most likely represents a regulatory program to support increased growth and development when both P and carbohydrates are ample. Another...... cluster (cluster 3) represents genes induced to alleviate P starvation and these are further induced by carbohydrate accumulation. Thus, interactions between P and Suc reveal two different signaling programs and novel interactions in gene regulation in response to environmental factors. cis......-Regulatory elements were analyzed for each factor and for interaction clusters. PHR1 binding sites were more frequent in promoters of P-regulated genes as compared to the entire Arabidopsis genome, and E2F and PHR1 binding sites were more frequent in interaction clusters 1 and 3, respectively....

  4. Chromatin Remodeling in Stem Cell Maintenance in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Lin Xu; Wen-Hui Shen

    2009-01-01

    Pluripotent stem cells are able to both self-renew and generate undifferentiated cells for the formation of new tissues and organs.In higher plants,stem cells found in the shoot apical meristem (SAM) and the root apical meristem (RAM) are origins of organogenesis occurring post-embryonically.It is important to understand how the regulation of stem cell fate is coordinated to enable the meristem to constantly generate different types of lateral organs.Much knowledge has accumulated on specific transcription factors controlling SAM and RAM activity.Here,we review recent evidences for a role of chromatin remodeling in the maintenance of stable expression states of transcription factor genes and the control of stem cell activity in Arabidopsis.

  5. Light-dependent intracellular positioning of mitochondria in Arabidopsis thaliana mesophyll cells.

    Science.gov (United States)

    Islam, Md Sayeedul; Niwa, Yasuo; Takagi, Shingo

    2009-06-01

    Mitochondria, the power house of the cell, are one of the most dynamic cell organelles. Although there are several reports on actin- or microtubule-dependent movement of mitochondria in plant cells, intracellular positioning and motility of mitochondria under different light conditions remain open questions. Mitochondria were visualized in living Arabidopsis thaliana leaf cells using green fluorescent protein fused to a mitochondrion-targeting signal. In darkness, mitochondria were distributed randomly in palisade cells. In contrast, mitochondria accumulated along the periclinal walls, similar to the accumulation response of chloroplasts, when treated with weak blue light (470 nm, 4 micromol m(-2) s(-1)). Under strong blue light (100 micromol m(-2) s(-1)), mitochondria occupied the anticlinal positions similar to the avoidance response of chloroplasts and nuclei. While strong red light (660 nm, 100 micromol m(-2) s(-1)) induced the accumulation of mitochondria along the inner periclinal walls, green light exhibited little effect on the distribution of mitochondria. In addition, the mode of movement of individual mitochondria along the outer periclinal walls under different light conditions was precisely analyzed by time-lapse fluorescence microscopy. A gradual increase in the number of static mitochondria located in the vicinity of chloroplasts with a time period of blue light illumination clearly demonstrated the accumulation response of mitochondria. Light-induced co-localization of mitochondria with chloroplasts strongly suggested their mutual metabolic interactions. This is the first characterization of the light-dependent redistribution of mitochondria in plant cells.

  6. Additive and non-additive effects of simulated leaf and inflorescence damage on survival, growth and reproduction of the perennial herb Arabidopsis lyrata.

    Science.gov (United States)

    Puentes, Adriana; Ågren, Jon

    2012-08-01

    Herbivores may damage both leaves and reproductive structures, and although such combined damage may affect plant fitness non-additively, this has received little attention. We conducted a 2-year field experiment with a factorial design to examine the effects of simulated leaf (0, 12.5, 25, or 50% of leaf area removed) and inflorescence damage (0 vs. 50% of inflorescences removed) on survival, growth and reproduction in the perennial herb Arabidopsis lyrata. Leaf and inflorescence damage negatively and independently reduced flower, fruit and seed production in the year of damage; leaf damage also reduced rosette size by the end of the first season and flower production in the second year. Leaf damage alone reduced the proportion of flowers forming a fruit and fruit production per plant the second year, but when combined with inflorescence damage no such effect was observed (significant leaf × inflorescence damage interaction). Damage to leaves (sources) caused a greater reduction in future reproduction than did simultaneous damage to leaves and inflorescences (sinks). This demonstrates that a full understanding of the effects of herbivore damage on plant fitness requires that consequences of damage to vegetative and reproductive structures are evaluated over more than 1 year and that non-additive effects are considered. PMID:22349755

  7. Autophagic components contribute to hypersensitive cell death in Arabidopsis

    DEFF Research Database (Denmark)

    Hofius, Daniel; Schultz-Larsen, Torsten; Joensen, Jan;

    2009-01-01

    Autophagy has been implicated as a prosurvival mechanism to restrict programmed cell death (PCD) associated with the pathogen-triggered hypersensitive response (HR) during plant innate immunity. This model is based on the observation that HR lesions spread in plants with reduced autophagy gene...... expression. Here, we examined receptor-mediated HR PCD responses in autophagy-deficient Arabidopsis knockout mutants (atg), and show that infection-induced lesions are contained in atg mutants. We also provide evidence that HR cell death initiated via Toll/Interleukin-1 (TIR)-type immune receptors through...... the defense regulator EDS1 is suppressed in atg mutants. Furthermore, we demonstrate that PCD triggered by coiled-coil (CC)-type immune receptors via NDR1 is either autophagy-independent or engages autophagic components with cathepsins and other unidentified cell death mediators. Thus, autophagic cell death...

  8. AtPGL3 is an Arabidopsis BURP domain protein that is localized to the cell wall and promotes cell enlargement.

    Science.gov (United States)

    Park, Jiyoung; Cui, Yong; Kang, Byung-Ho

    2015-01-01

    The BURP domain is a plant-specific domain that has been identified in secretory proteins, and some of these are involved in cell wall modification. The tomato polygalacturonase I complex involved in pectin degradation in ripening fruits has a non-catalytic subunit that has a BURP domain. This protein is called polygalacturonase 1 beta (PG1β) and the Arabidopsis genome encodes three proteins that exhibit strong amino acid similarities with PG1β? We generated Arabidopsis lines in which expression levels of AtPGLs are altered in order to investigate the biological roles of the Arabidopsis PG1β-like proteins (AtPGLs). Among the three AtPGLs (AtPGL1-3), AtPGL3 exhibited the highest transcriptional activity throughout all developmental stages. AtPGL triple mutant plants have smaller rosette leaves than those of wild type plants because the leaf cells are smaller in the mutant plants. Interestingly, when we overexpressed AtPGL3 using a 35S promoter, leaf cells in transgenic plants grew larger than those of the wild type. A C-terminal GFP fusion protein of AtPGL3 complemented phenotypes of the triple mutant plants and it localized to the cell wall. A truncated AtPGL3-GFP fusion protein lacking the BURP domain failed to rescue the mutant phenotypes even though the GFP protein was targeted to the cell wall, indicating that the BURP domain is required for the protein's effect on cell expansion. Quantitative RT-PCR and immunoblot analyses indicated that the α-expansin 6 gene is up-regulated in the overexpressor plants. Taken together, these results indicate that AtPGL3 is an apoplastic BURP domain protein playing a role in cell expansion. PMID:26106400

  9. Changes in leaf proteome profile of Arabidopsis thaliana in response to salicylic acid

    Indian Academy of Sciences (India)

    Riddhi Datta; Ragini Sinha; Sharmila Chattopadhyay

    2013-06-01

    Salicylic acid (SA) has been implicated in determining the outcome of interactions between many plants and their pathogens. Global changes in response to this phytohormone have been observed at the transcript level, but little is known of how it induces changes in protein abundance. To this end we have investigated the effect of 1 mM SA on soluble proteins of Arabidopsis thaliana leaves by proteomic analysis. An initial study at transcript level has been performed on temporal landscape, which revealed that induction of most of the SA-responsive genes occurs within 3 to 6 h post treatment (HPT) and the expression peaked within 24 HPT. Two-dimensional gel electrophoresis (2-DE) coupled with MALDI-TOF MS/MS analysis has been used to identify differentially expressed proteins and 63 spots have been identified successfully. This comparative proteomic profiling of SA treated leaves versus control leaves demonstrated the changes of many defence related proteins like pathogenesis related protein 10a (PR10a), disease-resistance-like protein, putative late blight-resistance protein, WRKY4, MYB4, etc. along with gross increase in the rate of energy production, while other general metabolism rate is slightly toned down, presumably signifying a transition from ‘normal mode’ to ‘defence mode’.

  10. Leaf development: A cellular perspective

    Directory of Open Access Journals (Sweden)

    Gerrit TS Beemster

    2014-07-01

    Full Text Available Through its photosynthetic capacity the leaf provides the basis for growth of the whole plant. In order to improve crops for higher productivity and resistance for future climate scenarios, it is important to obtain a mechanistic understanding of leaf growth and development and the effect of genetic and environmental factors on the process. Cells are both the basic building blocks of the leaf and the regulatory units that integrate genetic and environmental information into the developmental program. Therefore, to fundamentally understand leaf development, one needs to be able to reconstruct the developmental pathway of individual cells (and their progeny from the stem cell niche to their final position in the mature leaf. To build the basis for such understanding, we review current knowledge on the spatial and temporal regulation mechanisms operating on cells, contributing to the formation of a leaf. We focus on the molecular networks that control exit from stem cell fate, leaf initiation, polarity, cytoplasmic growth, cell division, endoreduplication, transition between division and expansion, expansion and differentiation and their regulation by intercellular signaling molecules, including plant hormones, sugars, peptides, proteins and microRNAs. We discuss to what extent the knowledge available in the literature is suitable to be applied in systems biology approaches to model the process of leaf growth, in order to better understand and predict leaf growth starting with the model species Arabidopsis thaliana.

  11. Transcriptional Wiring of Cell Wall-Related Genes in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Marek Mutwil; Colin Ruprecht; Federico M. Giorgi; Martin Bringmann; Bj(o)rn Usadel; Staffan Persson

    2009-01-01

    Transcriptional coordination, or co-expression, of genes may signify functional relatedness of the correspond-ing proteins. For example, several genes involved in secondary cell wall cellulose biosynthesis are co-expressed with genes engaged in the synthesis of xylan, which is a major component of the secondary cell wall. To extend these types of anal-yses, we investigated the co-expression relationships of all Carbohydrate-Active enZYmes (CAZy)-related genes for Arabidopsis thaliana. Thus, the intention was to transcriptionally link different cell wall-related processes to each other, and also to other biological functions. To facilitate easy manual inspection, we have displayed these interactions as networks and matrices, and created a web-based interface (http://aranet.mpimp-golm.mpg.de/corecarb) containing downloadable files for all the transcriptional associations.

  12. 3D Plant Cell Architecture of Arabidopsis thaliana (Brassicaceae Using Focused Ion Beam–Scanning Electron Microscopy

    Directory of Open Access Journals (Sweden)

    Bhawana

    2014-06-01

    Full Text Available Premise of the study: Focused ion beam–scanning electron microscopy (FIB-SEM combines the ability to sequentially mill the sample surface and obtain SEM images that can be used to create 3D renderings with micron-level resolution. We have applied FIB-SEM to study Arabidopsis cell architecture. The goal was to determine the efficacy of this technique in plant tissue and cellular studies and to demonstrate its usefulness in studying cell and organelle architecture and distribution. Methods: Seed aleurone, leaf mesophyll, stem cortex, root cortex, and petal lamina from Arabidopsis were fixed and embedded for electron microscopy using protocols developed for animal tissues and modified for use with plant cells. Each sample was sectioned using the FIB and imaged with SEM. These serial images were assembled to produce 3D renderings of each cell type. Results: Organelles such as nuclei and chloroplasts were easily identifiable, and other structures such as endoplasmic reticula, lipid bodies, and starch grains were distinguishable in each tissue. Discussion: The application of FIB-SEM produced 3D renderings of five plant cell types and offered unique views of their shapes and internal content. These results demonstrate the usefulness of FIB-SEM for organelle distribution and cell architecture studies.

  13. Molecule mechanism of stem cells in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Wenjin Zhang

    2014-01-01

    Full Text Available Plants possess the ability to continually produce new tissues and organs throughout their life. Unlike animals, plants are exposed to extreme variations in environmental conditions over the course of their lives. The vitality of plants is so powerful that they can survive several hundreds of years or even more making it an amazing miracle that comes from plant stem cells. The stem cells continue to divide to renew themselves and provide cells for the formation of leaves, stems, and flowers. Stem cells are not only quiescent but also immortal, pluripotent and homeostatic. Stem cells are the magic cells that repair tissues and regenerate organs. During the past decade, scholars around the world have paid more and more attention toward plant stem cells. At present, the major challenge is in relating molecule action mechanism to root apical meristem, shoot apical meristem and vascular system. The coordination between stem cells maintenance and differentiation is critical for normal plant growth and development. Elements such as phytohormones, transcription factors and some other known or unknown genes cooperate to balance this process. In this review, Arabidopsis thaliana as a pioneer system, we highlight recent developments in molecule modulating, illustrating how plant stem cells generate new mechanistic insights into the regulation of plants growth and development.

  14. The FRIABLE1 gene product affects cell adhesion in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Lutz Neumetzler

    Full Text Available Cell adhesion in plants is mediated predominantly by pectins, a group of complex cell wall associated polysaccharides. An Arabidopsis mutant, friable1 (frb1, was identified through a screen of T-DNA insertion lines that exhibited defective cell adhesion. Interestingly, the frb1 plants displayed both cell and organ dissociations and also ectopic defects in organ separation. The FRB1 gene encodes a Golgi-localized, plant specific protein with only weak sequence similarities to known proteins (DUF246. Unlike other cell adhesion deficient mutants, frb1 mutants do not have reduced levels of adhesion related cell wall polymers, such as pectins. Instead, FRB1 affects the abundance of galactose- and arabinose-containing oligosaccharides in the Golgi. Furthermore, frb1 mutants displayed alteration in pectin methylesterification, cell wall associated extensins and xyloglucan microstructure. We propose that abnormal FRB1 action has pleiotropic consequences on wall architecture, affecting both the extensin and pectin matrices, with consequent changes to the biomechanical properties of the wall and middle lamella, thereby influencing cell-cell adhesion.

  15. Profilin Plays a Role in Cell Elongation, Cell Shape Maintenance, and Flowering in Arabidopsis

    DEFF Research Database (Denmark)

    Ramachandran, S.; Christensen, Hans Erik Mølager; Ishimaru, Y.;

    2000-01-01

    carrying a 35S-PFN-1 or 35S-antisense PFN-1 transgene. Etiolated seedlings underexpressing PFN (PFN-U) displayed an overall dwarf phenotype with short hypocotyls whose lengths were 20% to 25% that of wild type (WT) at low temperatures. Light-grown PFN-U plants were smaller in stature and flowered early......Profilin (PFN) is an ubiquitous, low-M-r, actin-binding protein involved in the organization of the cytoskeleton of eukaryotes including higher plants. PFNs are encoded by a multigene family in Arabidopsis. We have analyzed in vivo functions of Arabidopsis PFN by generating transgenic plants...... expressed in the vascular bundles of cotyledons and leaves. Our results show that Arabidopsis PFNs play a role in cell elongation, cell shape maintenance, polarized growth of root hair, and unexpectedly, in determination of flowering time....

  16. Does Arabidopsis thaliana DREAM of cell cycle control?

    Science.gov (United States)

    Fischer, Martin; DeCaprio, James A

    2015-01-01

    Strict temporal control of cell cycle gene expression is essential for all eukaryotes including animals and plants. DREAM complexes have been identified in worm, fly, and mammals, linking several distinct transcription factors to coordinate gene expression throughout the cell cycle. In this issue of The EMBO Journal, Kobayashi et al (2015) identify distinct activator and repressor complexes for genes expressed during the G2 and M phases in Arabidopsis that can be temporarily separated during proliferating and post-mitotic stages of development. The complexes incorporate specific activator and repressor MYB and E2F transcription factors and indicate the possibility of the existence of multiple DREAM complexes in plants. PMID:26089020

  17. Endogenous TasiRNAs mediate non-cell autonomous effects on gene regulation in Arabidopsis thaliana.

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    Rebecca Schwab

    Full Text Available BACKGROUND: Different classes of small RNAs (sRNAs refine the expression of numerous genes in higher eukaryotes by directing protein partners to complementary nucleic acids, where they mediate gene silencing. Plants encode a unique class of sRNAs, called trans-acting small interfering RNAs (tasiRNAs, which post-transcriptionally regulate protein-coding transcripts, as do microRNAs (miRNAs, and both sRNA classes control development through their targets. TasiRNA biogenesis requires multiple components of the siRNA pathway and also miRNAs. But while 21mer siRNAs originating from transgenes can mediate silencing across several cell layers, miRNA action seems spatially restricted to the producing or closely surrounding cells. PRINCIPAL FINDINGS: We have previously described the isolation of a genetrap reporter line for TAS3a, the major locus producing AUXIN RESPONS FACTOR (ARF-regulating tasiRNAs in the Arabidopsis shoot. Its activity is limited to the adaxial (upper side of leaf primordia, thus spatially isolated from ARF-activities, which are located in the abaxial (lower side. We show here by in situ hybridization and reporter fusions that the silencing activities of ARF-regulating tasiRNAs are indeed manifested non-cell autonomously to spatially control ARF activities. CONCLUSIONS/SIGNIFICANCE: Endogenous tasiRNAs are thus mediators of a mobile developmental signal and might provide effective gene silencing at a distance beyond the reach of most miRNAs.

  18. Looking Deep Inside: Detection of Low-Abundance Proteins in Leaf Extracts of Arabidopsis and Phloem Exudates of Pumpkin1[W

    Science.gov (United States)

    Fröhlich, Andreas; Gaupels, Frank; Sarioglu, Hakan; Holzmeister, Christian; Spannagl, Manuel; Durner, Jörg; Lindermayr, Christian

    2012-01-01

    The field of proteomics suffers from the immense complexity of even small proteomes and the enormous dynamic range of protein concentrations within a given sample. Most protein samples contain a few major proteins, which hamper in-depth proteomic analysis. In the human field, combinatorial hexapeptide ligand libraries (CPLL; such as ProteoMiner) have been used for reduction of the dynamic range of protein concentrations; however, this technique is not established in plant research. In this work, we present the application of CPLL to Arabidopsis (Arabidopsis thaliana) leaf proteins. One- and two-dimensional gel electrophoresis showed a decrease in high-abundance proteins and an enrichment of less abundant proteins in CPLL-treated samples. After optimization of the CPLL protocol, mass spectrometric analyses of leaf extracts led to the identification of 1,192 proteins in control samples and an additional 512 proteins after the application of CPLL. Upon leaf infection with virulent Pseudomonas syringae DC3000, CPLL beads were also used for investigating the bacterial infectome. In total, 312 bacterial proteins could be identified in infected Arabidopsis leaves. Furthermore, phloem exudates of pumpkin (Cucurbita maxima) were analyzed. CPLL prefractionation caused depletion of the major phloem proteins 1 and 2 and improved phloem proteomics, because 67 of 320 identified proteins were detectable only after CPLL treatment. In sum, our results demonstrate that CPLL beads are a time- and cost-effective tool for reducing major proteins, which often interfere with downstream analyses. The concomitant enrichment of less abundant proteins may facilitate a deeper insight into the plant proteome. PMID:22555880

  19. Acetylation of cell wall is required for structural integrity of the leaf surface and exerts a global impact on plant stress responses

    DEFF Research Database (Denmark)

    Nafisi, Majse; Stranne, Maria; Fimognari, Lorenzo;

    2015-01-01

    The epidermis on leaves protects plants from pathogen invasion and provides a waterproof barrier. It consists of a layer of cells that is surrounded by thick cell walls, which are partially impregnated by highly hydrophobic cuticular components. We show that the Arabidopsis T-DNA insertion mutants...... to abiotic stress, particularly detoxification of reactive oxygen species and defense against microbial pathogens (e.g., lipid transfer proteins, peroxidases). In accordance, peroxidase activities were found to be elevated in rwa2 as compared to the wild type. These results indicate that cell wall...... acetylation is essential for maintaining the structural integrity of leaf epidermis, and that reduction of cell wall acetylation leads to global stress responses in Arabidopsis....

  20. Elucidating the role of transport processes in leaf glucosinolate distribution.

    Science.gov (United States)

    Madsen, Svend Roesen; Olsen, Carl Erik; Nour-Eldin, Hussam Hassan; Halkier, Barbara Ann

    2014-11-01

    In Arabidopsis (Arabidopsis thaliana), a strategy to defend its leaves against herbivores is to accumulate glucosinolates along the midrib and at the margin. Although it is generally assumed that glucosinolates are synthesized along the vasculature in an Arabidopsis leaf, thereby suggesting that the margin accumulation is established through transport, little is known about these transport processes. Here, we show through leaf apoplastic fluid analysis and glucosinolate feeding experiments that two glucosinolate transporters, GTR1 and GTR2, essential for long-distance transport of glucosinolates in Arabidopsis, also play key roles in glucosinolate allocation within a mature leaf by effectively importing apoplastically localized glucosinolates into appropriate cells. Detection of glucosinolates in root xylem sap unambiguously shows that this transport route is involved in root-to-shoot glucosinolate allocation. Detailed leaf dissections show that in the absence of GTR1 and GTR2 transport activity, glucosinolates accumulate predominantly in leaf margins and leaf tips. Furthermore, we show that glucosinolates accumulate in the leaf abaxial epidermis in a GTR-independent manner. Based on our results, we propose a model for how glucosinolates accumulate in the leaf margin and epidermis, which includes symplasmic movement through plasmodesmata, coupled with the activity of putative vacuolar glucosinolate importers in these peripheral cell layers. PMID:25209984

  1. Promoter DNA hypermethylation and gene repression in undifferentiated Arabidopsis cells.

    Directory of Open Access Journals (Sweden)

    María Berdasco

    Full Text Available Maintaining and acquiring the pluripotent cell state in plants is critical to tissue regeneration and vegetative multiplication. Histone-based epigenetic mechanisms are important for regulating this undifferentiated state. Here we report the use of genetic and pharmacological experimental approaches to show that Arabidopsis cell suspensions and calluses specifically repress some genes as a result of promoter DNA hypermethylation. We found that promoters of the MAPK12, GSTU10 and BXL1 genes become hypermethylated in callus cells and that hypermethylation also affects the TTG1, GSTF5, SUVH8, fimbrin and CCD7 genes in cell suspensions. Promoter hypermethylation in undifferentiated cells was associated with histone hypoacetylation and primarily occurred at CpG sites. Accordingly, we found that the process specifically depends on MET1 and DRM2 methyltransferases, as demonstrated with DNA methyltransferase mutants. Our results suggest that promoter DNA methylation may be another important epigenetic mechanism for the establishment and/or maintenance of the undifferentiated state in plant cells.

  2. Fine-mapping of an Arabidopsis cell death mutation locus

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    An Arabidopsis cell death mutation locus was mapped to chromosome 2 between IGS1 and mi421. The YAC clone ends, CIC9A3R, CIC11C7L, CIC2G5R and RFLP marker CDs3 within this interval, were used to probe TAMU BAC library and 31 BAC clones were obtained. A BAC contig encompassing the mutation locus, which consists of T6P5, T7M23, T12A21, T8L6 and T18A18, was identified by Southern hybridization with the BAC ends as probes. 11 CAPS and 12 STS markers were developed in this region. These results will facilitate map-based cloning of the genes and sequencing of the genomic DNA in this region.

  3. Fine-mapping of an Arabidopsis cell death mutation locus

    Institute of Scientific and Technical Information of China (English)

    牟中林; 戴亚; 李家洋

    2000-01-01

    An Arabidopsis cell death mutation locus was mapped to chromosome 2 between lGS1 and mi421. The YAC clone ends, CIC9A3R, CIC11C7L, CIC2G5R and RFLP marker CDs3 within this interval, were used to probe TAMU BAC library and 31 BAC clones were obtained. A BAC contig encompassing the mutation locus, which consists of T6P5, T7M23, T12A21, T8L6 and T18A18, was identified by Southern hybridization with the BAC ends as probes. 11 CAPS and 12 STS markers were developed in this region. These results will facilitate map-based cloning of the genes and sequencing of the genomic DNA in this region.

  4. Elucidating the Role of Transport Processes in Leaf Glucosinolate Distribution

    DEFF Research Database (Denmark)

    Madsen, Svend Roesen; Olsen, Carl Erik; Nour-Eldin, Hussam Hassan;

    2014-01-01

    In Arabidopsis (Arabidopsis thaliana), a strategy to defend its leaves against herbivores is to accumulate glucosinolates along the midrib and at the margin. Although it is generally assumed that glucosinolates are synthesized along the vasculature in an Arabidopsis leaf, thereby suggesting...... that the margin accumulation is established through transport, little is known about these transport processes. Here, we show through leaf apoplastic fluid analysis and glucosinolate feeding experiments that two glucosinolate transporters, GTR1 and GTR2, essential for long-distance transport of glucosinolates...... in Arabidopsis, also play key roles in glucosinolate allocation within a mature leaf by effectively importing apoplastically localized glucosinolates into appropriate cells. Detection of glucosinolates in root xylem sap unambiguously shows that this transport route is involved in root-to-shoot glucosinolate...

  5. Long-distance movement of Cauliflower mosaic virus and host defence responses in Arabidopsis follow a predictable pattern that is determined by the leaf orthostichy.

    Science.gov (United States)

    Roberts, Karen; Love, Andrew J; Laval, Valérie; Laird, Janet; Tomos, A Deri; Hooks, Mark A; Milner, Joel J

    2007-01-01

    Long-distance virus transport takes place through the vascular system and is dependent on the movement of photoassimilates. Here, patterns of symptom development, virus movement and gene expression were analysed in Arabidopsis following inoculation with Cauliflower mosaic virus (CaMV) on a single leaf. Virus accumulation and expression of markers for the salicylic acid (SA) and ethylene/jasmonate (Et/JA) defence pathways, PR-1 and PDF1.2, were analysed on a leaf-by-leaf basis by real-time reverse transcription polymerase chain reaction (qRT-PCR). Virus spread followed a strictly defined pattern identical to that of a source-sink relationship. This was exploited to study differences between local and systemic defence responses in a developmental and spatial manner. In infected plants, PR-1 transcripts accumulated primarily but not exclusively in leaves with a direct vascular connection to the inoculated leaf. Abundances fell significantly as virus accumulated. By contrast, PDF1.2 transcripts were significantly lower than in controls in all leaves at early stages of infection, but recovered as virus accumulated. Virus and PR-1 transcript abundances are negatively correlated, and SA- and Et/JA-mediated signalling of gene expression occurs independently of the presence of virus. Although SA-dependent signalling responses were mainly linked to the orthostichy, Et/JA-dependent responses were independent of vascular connections. PMID:17688586

  6. Exploring Arabidopsis thaliana Root Endophytes via Single-Cell Genomics

    Energy Technology Data Exchange (ETDEWEB)

    Lundberg, Derek; Woyke, Tanja; Tringe, Susannah; Dangl, Jeff

    2014-03-19

    Land plants grow in association with microbial communities both on their surfaces and inside the plant (endophytes). The relationships between microbes and their host can vary from pathogenic to mutualistic. Colonization of the endophyte compartment occurs in the presence of a sophisticated plant immune system, implying finely tuned discrimination of pathogens from mutualists and commensals. Despite the importance of the microbiome to the plant, relatively little is known about the specific interactions between plants and microbes, especially in the case of endophytes. The vast majority of microbes have not been grown in the lab, and thus one of the few ways of studying them is by examining their DNA. Although metagenomics is a powerful tool for examining microbial communities, its application to endophyte samples is technically difficult due to the presence of large amounts of host plant DNA in the sample. One method to address these difficulties is single-cell genomics where a single microbial cell is isolated from a sample, lysed, and its genome amplified by multiple displacement amplification (MDA) to produce enough DNA for genome sequencing. This produces a single-cell amplified genome (SAG). We have applied this technology to study the endophytic microbes in Arabidopsis thaliana roots. Extensive 16S gene profiling of the microbial communities in the roots of multiple inbred A. thaliana strains has identified 164 OTUs as being significantly enriched in all the root endophyte samples compared to their presence in bulk soil.

  7. Rapid and simple isolation of vascular, epidermal and mesophyll cells from plant leaf tissue.

    Science.gov (United States)

    Endo, Motomu; Shimizu, Hanako; Araki, Takashi

    2016-08-01

    To understand physiological phenomena at the tissue level, elucidation of tissue-specific molecular functions in vivo is required. As an example of the current state of affairs, many genes in plants have been reported to have discordant levels of expression between bulk tissues and the specific tissues in which the respective gene product is principally functional. The principal challenge in deciphering such tissue-specific functions lies in separating tissues with high spatiotemporal resolution to evaluate accurate gene expression profiles. Here, we provide a simple and rapid tissue isolation protocol to isolate all three major leaf tissues (mesophyll, vasculature and epidermis) from Arabidopsis within 30 min with high purity. On the basis of the different cell-to-cell connectivities of tissues, the mesophyll isolation is achieved by making protoplasts, and the vasculature and epidermis isolation is achieved through sonication and enzymatic digestion of leaves. We have successfully tested the protocol on several other plant species, including crop plants such as soybean, tomato and wheat. Furthermore, isolated tissues can be used not only for tissue-specific transcriptome assays but also potentially for tissue-specific proteome and methylome assays. PMID:27388555

  8. Impaired Chloroplast Biogenesis in Immutans, an Arabidopsis Variegation Mutant, Modifies Developmental Programming, Cell Wall Composition and Resistance to Pseudomonas syringae.

    Science.gov (United States)

    Pogorelko, Gennady V; Kambakam, Sekhar; Nolan, Trevor; Foudree, Andrew; Zabotina, Olga A; Rodermel, Steven R

    2016-01-01

    The immutans (im) variegation mutation of Arabidopsis has green- and white- sectored leaves due to action of a nuclear recessive gene. IM codes for PTOX, a plastoquinol oxidase in plastid membranes. Previous studies have revealed that the green and white sectors develop into sources (green tissues) and sinks (white tissues) early in leaf development. In this report we focus on white sectors, and show that their transformation into effective sinks involves a sharp reduction in plastid number and size. Despite these reductions, cells in the white sectors have near-normal amounts of plastid RNA and protein, and surprisingly, a marked amplification of chloroplast DNA. The maintenance of protein synthesis capacity in the white sectors might poise plastids for their development into other plastid types. The green and white im sectors have different cell wall compositions: whereas cell walls in the green sectors resemble those in wild type, cell walls in the white sectors have reduced lignin and cellulose microfibrils, as well as alterations in galactomannans and the decoration of xyloglucan. These changes promote susceptibility to the pathogen Pseudomonas syringae. Enhanced susceptibility can also be explained by repressed expression of some, but not all, defense genes. We suggest that differences in morphology, physiology and biochemistry between the green and white sectors is caused by a reprogramming of leaf development that is coordinated, in part, by mechanisms of retrograde (plastid-to-nucleus) signaling, perhaps mediated by ROS. We conclude that variegation mutants offer a novel system to study leaf developmental programming, cell wall metabolism and host-pathogen interactions. PMID:27050746

  9. LeafJ: an ImageJ plugin for semi-automated leaf shape measurement.

    Science.gov (United States)

    Maloof, Julin N; Nozue, Kazunari; Mumbach, Maxwell R; Palmer, Christine M

    2013-01-01

    High throughput phenotyping (phenomics) is a powerful tool for linking genes to their functions (see review and recent examples). Leaves are the primary photosynthetic organ, and their size and shape vary developmentally and environmentally within a plant. For these reasons studies on leaf morphology require measurement of multiple parameters from numerous leaves, which is best done by semi-automated phenomics tools. Canopy shade is an important environmental cue that affects plant architecture and life history; the suite of responses is collectively called the shade avoidance syndrome (SAS). Among SAS responses, shade induced leaf petiole elongation and changes in blade area are particularly useful as indices. To date, leaf shape programs (e.g. SHAPE, LAMINA, LeafAnalyzer, LEAFPROCESSOR) can measure leaf outlines and categorize leaf shapes, but can not output petiole length. Lack of large-scale measurement systems of leaf petioles has inhibited phenomics approaches to SAS research. In this paper, we describe a newly developed ImageJ plugin, called LeafJ, which can rapidly measure petiole length and leaf blade parameters of the model plant Arabidopsis thaliana. For the occasional leaf that required manual correction of the petiole/leaf blade boundary we used a touch-screen tablet. Further, leaf cell shape and leaf cell numbers are important determinants of leaf size. Separate from LeafJ we also present a protocol for using a touch-screen tablet for measuring cell shape, area, and size. Our leaf trait measurement system is not limited to shade-avoidance research and will accelerate leaf phenotyping of many mutants and screening plants by leaf phenotyping. PMID:23380664

  10. Proteomics of loosely bound cell wall proteins of Arabidopsis thaliana cell suspension cultures: a critical analysis.

    OpenAIRE

    Borderies, Gisèle; Jamet, Elisabeth; Lafitte, Claude; Rossignol, Michel; Jauneau, Alain; Boudart, Georges; Monsarrat, Bernard; Esquerré-Tugayé, Marie-Thérèse; Boudet, Alain; Pont-Lezica, Rafael

    2003-01-01

    The complete sequencing of the Arabidopsis thaliana genome allows the use of the recently developed mass spectrometry techniques to identify the cell wall proteins (CWPs). Most proteomic approaches depend on the quality of sample preparation. Extraction of CWPs is particularly complex since the proteins may be free in the apoplast or are embedded in a polysaccharide matrix where they are retained by Van der Waals interactions, hydrogen bonds, hydrophobic or ionic interactions, or cross-linked...

  11. Overexpression of the Transcription Factors GmSHN1 and GmSHN9 Differentially Regulates Wax and Cutin Biosynthesis, Alters Cuticle Properties, and Changes Leaf Phenotypes in Arabidopsis.

    Science.gov (United States)

    Xu, Yangyang; Wu, Hanying; Zhao, Mingming; Wu, Wang; Xu, Yinong; Gu, Dan

    2016-04-21

    SHINE (SHN/WIN) clade proteins, transcription factors of the plant-specific APETALA 2/ethylene-responsive element binding factor (AP2/ERF) family, have been proven to be involved in wax and cutin biosynthesis. Glycine max is an important economic crop, but its molecular mechanism of wax biosynthesis is rarely characterized. In this study, 10 homologs of Arabidopsis SHN genes were identified from soybean. These homologs were different in gene structures and organ expression patterns. Constitutive expression of each of the soybean SHN genes in Arabidopsis led to different leaf phenotypes, as well as different levels of glossiness on leaf surfaces. Overexpression of GmSHN1 and GmSHN9 in Arabidopsis exhibited 7.8-fold and 9.9-fold up-regulation of leaf cuticle wax productions, respectively. C31 and C29 alkanes contributed most to the increased wax contents. Total cutin contents of leaves were increased 11.4-fold in GmSHN1 overexpressors and 5.7-fold in GmSHN9 overexpressors, mainly through increasing C16:0 di-OH and dioic acids. GmSHN1 and GmSHN9 also altered leaf cuticle membrane ultrastructure and increased water loss rate in transgenic Arabidopsis plants. Transcript levels of many wax and cutin biosynthesis and leaf development related genes were altered in GmSHN1 and GmSHN9 overexpressors. Overall, these results suggest that GmSHN1 and GmSHN9 may differentially regulate the leaf development process as well as wax and cutin biosynthesis.

  12. Overexpression of the Transcription Factors GmSHN1 and GmSHN9 Differentially Regulates Wax and Cutin Biosynthesis, Alters Cuticle Properties, and Changes Leaf Phenotypes in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Yangyang Xu

    2016-04-01

    Full Text Available SHINE (SHN/WIN clade proteins, transcription factors of the plant-specific APETALA 2/ethylene-responsive element binding factor (AP2/ERF family, have been proven to be involved in wax and cutin biosynthesis. Glycine max is an important economic crop, but its molecular mechanism of wax biosynthesis is rarely characterized. In this study, 10 homologs of Arabidopsis SHN genes were identified from soybean. These homologs were different in gene structures and organ expression patterns. Constitutive expression of each of the soybean SHN genes in Arabidopsis led to different leaf phenotypes, as well as different levels of glossiness on leaf surfaces. Overexpression of GmSHN1 and GmSHN9 in Arabidopsis exhibited 7.8-fold and 9.9-fold up-regulation of leaf cuticle wax productions, respectively. C31 and C29 alkanes contributed most to the increased wax contents. Total cutin contents of leaves were increased 11.4-fold in GmSHN1 overexpressors and 5.7-fold in GmSHN9 overexpressors, mainly through increasing C16:0 di-OH and dioic acids. GmSHN1 and GmSHN9 also altered leaf cuticle membrane ultrastructure and increased water loss rate in transgenic Arabidopsis plants. Transcript levels of many wax and cutin biosynthesis and leaf development related genes were altered in GmSHN1 and GmSHN9 overexpressors. Overall, these results suggest that GmSHN1 and GmSHN9 may differentially regulate the leaf development process as well as wax and cutin biosynthesis.

  13. AtHSPR may function in salt-induced cell death and ER stress in Arabidopsis.

    Science.gov (United States)

    Yang, Tao; Zhang, Peng; Wang, Chongying

    2016-07-01

    Salt stress is a harmful and global abiotic stress to plants and has an adverse effect on all physiological processes of plants. Recently, we cloned and identified a novel AtHSPR (Arabidopsis thaliana Heat Shock Protein Related), which encodes a nuclear-localized protein with ATPase activity, participates in salt and drought tolerance in Arabidopsis. Transcript profiling analysis revealed a differential expression of genes involved in accumulation of reactive oxygen species (ROS), abscisic acid (ABA) signaling, stress response and photosynthesis between athspr mutant and WT under salt stress. Here, we provide further analysis of the data showing the regulation of salt-induced cell death and endoplasmic reticulum (ER) stress response in Arabidopsis and propose a hypothetical model for the role of AtHSPR in the regulation of the salt tolerance in Arabidopsis. PMID:27302034

  14. Regulation of Jasmonate-Induced Leaf Senescence by Antagonism between bHLH Subgroup IIIe and IIId Factors in Arabidopsis.

    Science.gov (United States)

    Qi, Tiancong; Wang, Jiaojiao; Huang, Huang; Liu, Bei; Gao, Hua; Liu, Yule; Song, Susheng; Xie, Daoxin

    2015-06-01

    Plants initiate leaf senescence to relocate nutrients and energy from aging leaves to developing tissues or storage organs for growth, reproduction, and defense. Leaf senescence, the final stage of leaf development, is regulated by various environmental stresses, developmental cues, and endogenous hormone signals. Jasmonate (JA), a lipid-derived phytohormone essential for plant defense and plant development, serves as an important endogenous signal to activate senescence-associated gene expression and induce leaf senescence. This study revealed one of the mechanisms underlying JA-induced leaf senescence: antagonistic interactions of the bHLH subgroup IIIe factors MYC2, MYC3, and MYC4 with the bHLH subgroup IIId factors bHLH03, bHLH13, bHLH14, and bHLH17. We showed that MYC2, MYC3, and MYC4 function redundantly to activate JA-induced leaf senescence. MYC2 binds to and activates the promoter of its target gene SAG29 (SENESCENCE-ASSOCIATED GENE29) to activate JA-induced leaf senescence. Interestingly, plants have evolved an elaborate feedback regulation mechanism to modulate JA-induced leaf senescence: The bHLH subgroup IIId factors (bHLH03, bHLH13, bHLH14, and bHLH17) bind to the promoter of SAG29 and repress its expression to attenuate MYC2/MYC3/MYC4-activated JA-induced leaf senescence. The antagonistic regulation by activators and repressors would mediate JA-induced leaf senescence at proper level suitable for plant survival in fluctuating environmental conditions. PMID:26071420

  15. Isolation and RNA gel blot analysis of genes that could serve as potential molecular markers for leaf senescence in Arabidopsis thaliana.

    Science.gov (United States)

    Yoshida, S; Ito, M; Nishida, I; Watanabe, A

    2001-02-01

    Nine cDNAs, representing genes in which the transcripts accumulated in senescent leaves of Arabidopsis thaliana, were isolated by differential display reverse transcription polymerase chain reaction (DDRT-PCR) and the genes were designated yellow-leaf-specific gene 1 to 9 (YLS1-YLS9). Sequence analysis revealed that none of the YLS genes, except YLS6, had been reported as senescence-up-regulated genes. RNA gel blot analysis revealed that the transcripts of YLS3 accumulated at the highest level at an early senescence stage, whereas the transcripts from the other YLS genes reached their maximum levels in late senescence stages. Transcripts of YLS genes showed various accumulation patterns under natural senescence, and under artificial senescence induced by darkness, ethylene or ABA. These expression characteristics of YLS genes will be useful as potential molecular markers, which will enhance our understanding of natural and artificial senescence processes.

  16. The intrinsically disordered protein LEA7 from Arabidopsis thaliana protects the isolated enzyme lactate dehydrogenase and enzymes in a soluble leaf proteome during freezing and drying.

    Science.gov (United States)

    Popova, Antoaneta V; Rausch, Saskia; Hundertmark, Michaela; Gibon, Yves; Hincha, Dirk K

    2015-10-01

    The accumulation of Late Embryogenesis Abundant (LEA) proteins in plants is associated with tolerance against stresses such as freezing and desiccation. Two main functions have been attributed to LEA proteins: membrane stabilization and enzyme protection. We have hypothesized previously that LEA7 from Arabidopsis thaliana may stabilize membranes because it interacts with liposomes in the dry state. Here we show that LEA7, contrary to this expectation, did not stabilize liposomes during drying and rehydration. Instead, it partially preserved the activity of the enzyme lactate dehydrogenase (LDH) during drying and freezing. Fourier-transform infrared (FTIR) spectroscopy showed no evidence of aggregation of LDH in the dry or rehydrated state under conditions that lead to complete loss of activity. To approximate the complex influence of intracellular conditions on the protective effects of a LEA protein in a convenient in-vitro assay, we measured the activity of two Arabidopsis enzymes (glucose-6-P dehydrogenase and ADP-glucose pyrophosphorylase) in total soluble leaf protein extract (Arabidopsis soluble proteome, ASP) after drying and rehydration or freezing and thawing. LEA7 partially preserved the activity of both enzymes under these conditions, suggesting its role as an enzyme protectant in vivo. Further FTIR analyses indicated the partial reversibility of protein aggregation in the dry ASP during rehydration. Similarly, aggregation in the dry ASP was strongly reduced by LEA7. In addition, mixtures of LEA7 with sucrose or verbascose reduced aggregation more than the single additives, presumably through the effects of the protein on the H-bonding network of the sugar glasses. PMID:25988244

  17. Efeitos da radiação ultravioleta-B sobre a morfologia foliar de Arabidopsis thaliana (L. Heynh. (Brassicaceae Effects of ultraviolet-B radiation on leaf morphology of Arabidopsis thaliana (L. Heynh. (Brassicaceae

    Directory of Open Access Journals (Sweden)

    Maria Regina Torres Boeger

    2006-06-01

    Full Text Available A redução da camada de ozônio resulta no aumento da radiação ultravioleta que atinge a superfície terrestre, especialmente a radiação ultravioletaB (UV-B. O aumento da radiação poderá induzir a mudanças estruturais e fisiológicas nas plantas, influenciando no seu crescimento e desenvolvimento. O objetivo deste trabalho foi determinar os efeitos da radiação UV-B ambiente sobre a morfologia das folhas de Arabidopsis thaliana desenvolvidas em condições controladas. As sementes de A. thaliana cresceram em câmaras de crescimento, com 300 µmol m-2s-1 de radiação fotossinteticamente ativa (PAR com ou sem 6 kJ m-2 s-1 de radiação UV-Bbe (UV-Bbe; UV-B biologicamente efetiva. Após 21 dias, 10 folhas de cada tratamento (com e sem radiação UV-B foram coletadas para avaliar área foliar, massa fresca e seca, AEF, densidades estomáticas e de tricomas de ambas as faces da folha, espessura da lâmina foliar e concentração de compostos fenólicos e de clorofila total, a e b. As folhas tratadas com radiação UV-B apresentaram menor área foliar, massa fresca e seca, densidade de tricomas na face adaxial e densidade de estômatos na face abaxial da folha. Entretanto, apresentaram os maiores valores médios de espessura total da lâmina e do mesofilo, maior concentração de clorofila total, clorofila a e clorofila b e compostos fenólicos foliares do que as folhas não tratadas com radiação UV-B. Essas diferenças morfológicas significativas (p Reduction of the ozone layer results in the increase in ultraviolet radiation reaching the earth's surface, especially the ultraviolet-B (UV-B. The increase of radiation may induce structural and physiological changes in plants, influencing their growth and development. This paper evaluates the effects of ambient UV-B radiation upon to the leaf morphology of Arabidopsis thaliana developed under controlled conditions. The seeds of A. thaliana grown in environmental chamber, with 300 µmol m-2

  18. Nitric Oxide Deficiency Accelerates Chlorophyll Breakdown and Stability Loss of Thylakoid Membranes during Dark-Induced Leaf Senescence in Arabidopsis

    OpenAIRE

    Liu, Fang(Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China); Guo, Fang-Qing

    2013-01-01

    Nitric oxide (NO) has been known to preserve the level of chlorophyll (Chl) during leaf senescence. However, the mechanism by which NO regulates Chl breakdown remains unknown. Here we report that NO negatively regulates the activities of Chl catabolic enzymes during dark-induced leaf senescence. The transcriptional levels of the major enzyme genes involving Chl breakdown pathway except for RED CHL CATABOLITE REDUCTASE (RCCR) were dramatically up-regulated during dark-induced Chl degradation i...

  19. Rapid kinetic labeling of Arabidopsis cell suspension cultures: Implications for models of lipid export from plastids

    Science.gov (United States)

    T-87 suspension cell cultures are increasingly used in Arabidopsis research, but there are no reports describing their lipid composition or biosynthesis. To evaluate if T-87 cell cultures as a model system for analysis of lipid metabolism, including tests of gene candidate functions, we have deter...

  20. Cell fate in the Arabidopsis root epidermis is determined by competition between WEREWOLF and CAPRICE.

    Science.gov (United States)

    Song, Sang-Kee; Ryu, Kook Hui; Kang, Yeon Hee; Song, Jae Hyo; Cho, Young-Hee; Yoo, Sang-Dong; Schiefelbein, John; Lee, Myeong Min

    2011-11-01

    The root hair and nonhair cells in the Arabidopsis (Arabidopsis thaliana) root epidermis are specified by a suite of transcriptional regulators. Two of these are WEREWOLF (WER) and CAPRICE (CPC), which encode MYB transcription factors that are required for promoting the nonhair cell fate and the hair cell fate, respectively. However, the precise function and relationship between these transcriptional regulators have not been fully defined experimentally. Here, we examine these issues by misexpressing the WER gene using the GAL4-upstream activation sequence transactivation system. We find that WER overexpression in the Arabidopsis root tip is sufficient to cause epidermal cells to adopt the nonhair cell fate through direct induction of GLABRA2 (GL2) gene expression. We also show that GLABRA3 (GL3) and ENHANCER OF GLABRA3 (EGL3), two closely related bHLH proteins, are required for the action of the overexpressed WER and that WER interacts with these bHLHs in plant cells. Furthermore, we find that CPC suppresses the WER overexpression phenotype quantitatively. These results show that WER acts together with GL3/EGL3 to induce GL2 expression and that WER and CPC compete with one another to define cell fates in the Arabidopsis root epidermis.

  1. SCARECROW, SCR-LIKE 23 and SHORT-ROOT control bundle sheath cell fate and function in Arabidopsis thaliana.

    Science.gov (United States)

    Cui, Hongchang; Kong, Danyu; Liu, Xiuwen; Hao, Yueling

    2014-04-01

    Bundle sheath (BS) cells form a single cell layer surrounding the vascular tissue in leaves. In C3 plants, photosynthesis occurs in both the BS and mesophyll cells, but the BS cells are the major sites of photosynthesis in C4 plants, whereas the mesophyll cells are only involved in CO2 fixation. Because C4 plants are more efficient photosynthetically, introduction of the C4 mechanism into C3 plants is considered a key strategy to improve crop yield. One prerequisite for such C3-to-C4 engineering is the ability to manipulate the number and physiology of the BS cells, but the molecular basis of BS cell-fate specification remains unclear. Here we report that mutations in three GRAS family transcription factors, SHORT-ROOT (SHR), SCARECROW (SCR) and SCARECROW-LIKE 23 (SCL23), affect BS cell fate in Arabidopsis thaliana. SCR and SCL23 are expressed specifically in the BS cells and act redundantly in BS cell-fate specification, but their expression pattern and function diverge at later stages of leaf development. Using ChIP-chip experiments and sugar assays, we show that SCR is primarily involved in sugar transport whereas SCL23 functions in mineral transport. SHR is also essential for BS cell-fate specification, but it is expressed in the central vascular tissue. However, the SHR protein moves into the BS cells, where it directly regulates SCR and SCL23 expression. SHR, SCR and SCL23 homologs are present in many plant species, suggesting that this developmental pathway for BS cell-fate specification is likely to be evolutionarily conserved.

  2. Arabidopsis NRT1.5 Mediates the Suppression of Nitrate Starvation-Induced Leaf Senescence by Modulating Foliar Potassium Level.

    Science.gov (United States)

    Meng, Shuan; Peng, Jia-Shi; He, Ya-Ni; Zhang, Guo-Bin; Yi, Hong-Ying; Fu, Yan-Lei; Gong, Ji-Ming

    2016-03-01

    Nitrogen deficiency induces leaf senescence. However, whether or how nitrate might affect this process remains to be investigated. Here, we report an interesting finding that nitrate-instead of nitrogen-starvation induced early leaf senescence in nrt1.5 mutant, and present genetic and physiological data demonstrating that nitrate starvation-induced leaf senescence is suppressed by NRT1.5. NRT1.5 suppresses the senescence process dependent on its function from roots, but not the nitrate transport function. Further analyses using nrt1.5 single and nia1 nia2 nrt1.5-4 triple mutant showed a negative correlation between nitrate concentration and senescence rate in leaves. Moreover, when exposed to nitrate starvation, foliar potassium level decreased in nrt1.5, but adding potassium could essentially restore the early leaf senescence phenotype of nrt1.5 plants. Nitrate starvation also downregulated the expression of HAK5, RAP2.11, and ANN1 in nrt1.5 roots, and appeared to alter potassium level in xylem sap from nrt1.5. These data suggest that NRT1.5 likely perceives nitrate starvation-derived signals to prevent leaf senescence by facilitating foliar potassium accumulation. PMID:26732494

  3. A multidirectional non-cell autonomous control and a genetic interaction restricting tobacco etch virus susceptibility in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Suresh Gopalan

    Full Text Available BACKGROUND: Viruses constitute a major class of pathogens that infect a variety of hosts. Understanding the intricacies of signaling during host-virus interactions should aid in designing disease prevention strategies and in understanding mechanistic aspects of host and pathogen signaling machinery. METHODOLOGY/PRINCIPAL FINDINGS: An Arabidopsis mutant, B149, impaired in susceptibility to Tobacco etch virus (TEV, a positive strand RNA virus of picoRNA family, was identified using a high-throughput genetic screen and a counterselection scheme. The defects include initiation of infection foci, rate of cell-to-cell movement and long distance movement. CONCLUSIONS/SIGNIFICANCE: The defect in infectivity is conferred by a recessive locus. Molecular genetic analysis and complementation analysis with three alleles of a previously published mutant lsp1 (loss of susceptibility to potyviruses indicate a genetic interaction conferring haploinsufficiency between the B149 locus and certain alleles of lsp1 resulting in impaired host susceptibility. The pattern of restriction of TEV foci on leaves at or near the boundaries of certain cell types and leaf boundaries suggest dysregulation of a multidirectional non-cell autonomous regulatory mechanism. Understanding the nature of this multidirectional signal and the molecular genetic mechanism conferring it should potentially reveal a novel arsenal in the cellular machinery.

  4. Human GLTP and mutant forms of ACD11 suppress cell death in the Arabidopsis acd11 mutant

    DEFF Research Database (Denmark)

    Petersen, Nikolaj H T; McKinney, Lea V; Pike, Helen;

    2008-01-01

    The Arabidopsis acd11 mutant exhibits runaway, programmed cell death due to the loss of a putative sphingosine transfer protein (ACD11) with homology to mammalian GLTP. We demonstrate that transgenic expression in Arabidopsis thaliana of human GLTP partially suppressed the phenotype of the acd11 ...

  5. Plastid distribution in columella cells of a starchless Arabidopsis mutant grown in microgravity

    Science.gov (United States)

    Hilaire, E.; Paulsen, A. Q.; Brown, C. S.; Guikema, J. A.; Spooner, B. S. (Principal Investigator)

    1997-01-01

    Wild-type and starchless Arabidopsis thaliana mutant seedlings (TC7) were grown and fixed in the microgravity environment of a U.S. Space Shuttle spaceflight. Computer image analysis of longitudinal sections from columella cells suggest a different plastid positioning mechanism for mutant and wild-type in the absence of gravity.

  6. A new picture of cell wall protein dynamics in elongating cells of Arabidopsis thaliana: Confirmed actors and newcomers

    OpenAIRE

    Jamet Elisabeth; Pont-Lezica Rafael; Borderies Gisèle; Canut Hervé; Irshad Muhammad

    2008-01-01

    Abstract Background Cell elongation in plants requires addition and re-arrangements of cell wall components. Even if some protein families have been shown to play roles in these events, a global picture of proteins present in cell walls of elongating cells is still missing. A proteomic study was performed on etiolated hypocotyls of Arabidopsis used as model of cells undergoing elongation followed by growth arrest within a short time. Results Two developmental stages (active growth and after g...

  7. Induction of cell death by graphene in Arabidopsis thaliana (Columbia ecotype) T87 cell suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Begum, Parvin, E-mail: parvinchy@ees.hokudai.ac.jp; Fugetsu, Bunshi

    2013-09-15

    Highlights: • This study was set up to explore potential influence of graphene on T87 cells. • Fragmented nuclei, membrane damage, mitochondrial dysfunction were observed. • ROS increased, ROS are key mediators in the cell death signaling pathway. • Translocation of graphene into cells and an endocytosis-like structure was observed. • Graphene entering into the cells by endocytosis. -- Abstract: The toxicity of graphene on suspensions of Arabidopsis thaliana (Columbia ecotype) T87 cells was investigated by examining the morphology, mitochondrial dysfunction, reactive oxygen species generation (ROS), and translocation of graphene as the toxicological endpoints. The cells were grown in Jouanneau and Péaud-Lenoel (JPL) media and exposed to graphene at concentrations 0–80 mg/L. Morphological changes were observed by scanning electron microscope and the adverse effects such as fragmented nuclei, membrane damage, mitochondrial dysfunction was observed with fluorescence microscopy by staining with Hoechst 33342/propidium iodide and succinate dehydrogenase (mitochondrial bioenergetic enzyme). Analysis of intracellular ROS by 2′,7′-dichlorofluorescein diacetate demonstrated that graphene induced a 3.3-fold increase in ROS, suggesting that ROS are key mediators in the cell death signaling pathway. Transmission electron microscopy verified the translocation of graphene into cells and an endocytosis-like structure was observed which suggested graphene entering into the cells by endocytosis. In conclusion, our results show that graphene induced cell death in T87 cells through mitochondrial damage mediated by ROS.

  8. Two-Step Regulation of a Meristematic Cell Population Acting in Shoot Branching in Arabidopsis.

    Science.gov (United States)

    Shi, Bihai; Zhang, Cui; Tian, Caihuan; Wang, Jin; Wang, Quan; Xu, Tengfei; Xu, Yan; Ohno, Carolyn; Sablowski, Robert; Heisler, Marcus G; Theres, Klaus; Wang, Ying; Jiao, Yuling

    2016-07-01

    Shoot branching requires the establishment of new meristems harboring stem cells; this phenomenon raises questions about the precise regulation of meristematic fate. In seed plants, these new meristems initiate in leaf axils to enable lateral shoot branching. Using live-cell imaging of leaf axil cells, we show that the initiation of axillary meristems requires a meristematic cell population continuously expressing the meristem marker SHOOT MERISTEMLESS (STM). The maintenance of STM expression depends on the leaf axil auxin minimum. Ectopic expression of STM is insufficient to activate axillary buds formation from plants that have lost leaf axil STM expressing cells. This suggests that some cells undergo irreversible commitment to a developmental fate. In more mature leaves, REVOLUTA (REV) directly up-regulates STM expression in leaf axil meristematic cells, but not in differentiated cells, to establish axillary meristems. Cell type-specific binding of REV to the STM region correlates with epigenetic modifications. Our data favor a threshold model for axillary meristem initiation, in which low levels of STM maintain meristematic competence and high levels of STM lead to meristem initiation. PMID:27398935

  9. Vascular Cell Induction Culture System Using Arabidopsis Leaves (VISUAL) Reveals the Sequential Differentiation of Sieve Element-Like Cells.

    Science.gov (United States)

    Kondo, Yuki; Nurani, Alif Meem; Saito, Chieko; Ichihashi, Yasunori; Saito, Masato; Yamazaki, Kyoko; Mitsuda, Nobutaka; Ohme-Takagi, Masaru; Fukuda, Hiroo

    2016-06-01

    Cell differentiation is a complex process involving multiple steps, from initial cell fate specification to final differentiation. Procambial/cambial cells, which act as vascular stem cells, differentiate into both xylem and phloem cells during vascular development. Recent studies have identified regulatory cascades for xylem differentiation. However, the molecular mechanism underlying phloem differentiation is largely unexplored due to technical challenges. Here, we established an ectopic induction system for phloem differentiation named Vascular Cell Induction Culture System Using Arabidopsis Leaves (VISUAL). Our results verified similarities between VISUAL-induced Arabidopsis thaliana phloem cells and in vivo sieve elements. We performed network analysis using transcriptome data with VISUAL to dissect the processes underlying phloem differentiation, eventually identifying a factor involved in the regulation of the master transcription factor gene APL Thus, our culture system opens up new avenues not only for genetic studies of phloem differentiation, but also for future investigations of multidirectional differentiation from vascular stem cells. PMID:27194709

  10. Single Walled Carbon Nanotubes Exhibit Dual-Phase Regulation to Exposed Arabidopsis Mesophyll Cells

    Science.gov (United States)

    Yuan, Hengguang; Hu, Shanglian; Huang, Peng; Song, Hua; Wang, Kan; Ruan, Jing; He, Rong; Cui, Daxiang

    2011-12-01

    Herein we are the first to report that single-walled carbon nanotubes (SWCNTs) exhibit dual-phase regulation to Arabidopsis mesophyll cells exposed to different concentration of SWCNTs. The mesophyll protoplasts were prepared by enzyme digestion, and incubated with 15, 25, 50, 100 μg/ml SWCNTs for 48 h, and then were observed by optical microscopy and transmission electron microscopy, the reactive oxygen species (ROS) generation was measured. Partial protoplasts were stained with propidium iodide and 4'-6- diamidino-2-phenylindole, partial protoplasts were incubated with fluorescein isothiocyanate-labeled SWCNTs, and observed by fluorescence microscopy. Results showed that SWCNTs could traverse both the plant cell wall and cell membrane, with less than or equal to 50 μg/ml in the culture medium, SWCNTs stimulated plant cells to grow out trichome clusters on their surface, with more than 50 μg/ml SWCNTs in the culture medium, SWCNTs exhibited obvious toxic effects to the protoplasts such as increasing generation of ROS, inducing changes of protoplast morphology, changing green leaves into yellow, and inducing protoplast cells' necrosis and apoptosis. In conclusion, single walled carbon nanotubes can get through Arabidopsis mesophyll cell wall and membrane, and exhibit dose-dependent dual-phase regulation to Arabidopsis mesophyll protoplasts such as low dose stimulating cell growth, and high dose inducing cells' ROS generation, necrosis or apoptosis.

  11. Single Walled Carbon Nanotubes Exhibit Dual-Phase Regulation to Exposed Arabidopsis Mesophyll Cells

    Directory of Open Access Journals (Sweden)

    Huang Peng

    2011-01-01

    Full Text Available Abstract Herein we are the first to report that single-walled carbon nanotubes (SWCNTs exhibit dual-phase regulation to Arabidopsis mesophyll cells exposed to different concentration of SWCNTs. The mesophyll protoplasts were prepared by enzyme digestion, and incubated with 15, 25, 50, 100 μg/ml SWCNTs for 48 h, and then were observed by optical microscopy and transmission electron microscopy, the reactive oxygen species (ROS generation was measured. Partial protoplasts were stained with propidium iodide and 4'-6- diamidino-2-phenylindole, partial protoplasts were incubated with fluorescein isothiocyanate-labeled SWCNTs, and observed by fluorescence microscopy. Results showed that SWCNTs could traverse both the plant cell wall and cell membrane, with less than or equal to 50 μg/ml in the culture medium, SWCNTs stimulated plant cells to grow out trichome clusters on their surface, with more than 50 μg/ml SWCNTs in the culture medium, SWCNTs exhibited obvious toxic effects to the protoplasts such as increasing generation of ROS, inducing changes of protoplast morphology, changing green leaves into yellow, and inducing protoplast cells' necrosis and apoptosis. In conclusion, single walled carbon nanotubes can get through Arabidopsis mesophyll cell wall and membrane, and exhibit dose-dependent dual-phase regulation to Arabidopsis mesophyll protoplasts such as low dose stimulating cell growth, and high dose inducing cells' ROS generation, necrosis or apoptosis.

  12. Regulation of Arabidopsis Early Anther Development by Putative Cell-Cell Signaling Molecules and Transcriptional Regulators

    Institute of Scientific and Technical Information of China (English)

    Yu-Jin Sun; Carey LH Hord; Chang-Bin Chen; Hong Ma

    2007-01-01

    Anther development in flowering plants involves the formation of several cell types, including the tapetal and pollen mother cells. The use of genetic and molecular tools has led to the identification and characterization of genes that are critical for normal cell division and differentiation in Arabidopsis early anther development. We review here several recent studies on these genes, including the demonstration that the putative receptor protein kinases BAM1 and BAM2 together play essential roles in the control of early cell division and differentiation. In addition, we discuss the hypothesis that BAM1/2 may form a positive-negative feedback regulatory loop with a previously identified key regulator, SPOROCYTELESS (also called NOZZLE),to control the balance between sporogenous and somatic cell types in the anther. Furthermore, we summarize the isolation and functional analysis of the DYSFUNCTIONAL TAPETUM1 (DYT1) gene in promoting proper tapetal cell differentiation. Our finding that DYT1 encodes a putative transcription factor of the bHLH family, as well as relevant expression analyses, strongly supports a model that DYT1 serves as a critical link between upstream factors and downstream target genes that are critical for normal tapetum development and function. These studies, together with other recently published works, indicate that cell-cell communication and transcriptional control are key processes essential for cell fate specification in anther development.

  13. Transcriptional analyses of natural leaf senescence in maize.

    Directory of Open Access Journals (Sweden)

    Wei Yang Zhang

    Full Text Available Leaf senescence is an important biological process that contributes to grain yield in crops. To study the molecular mechanisms underlying natural leaf senescence, we harvested three different developmental ear leaves of maize, mature leaves (ML, early senescent leaves (ESL, and later senescent leaves (LSL, and analyzed transcriptional changes using RNA-sequencing. Three sets of data, ESL vs. ML, LSL vs. ML, and LSL vs. ESL, were compared, respectively. In total, 4,552 genes were identified as differentially expressed. Functional classification placed these genes into 18 categories including protein metabolism, transporters, and signal transduction. At the early stage of leaf senescence, genes involved in aromatic amino acids (AAAs biosynthetic process and transport, cellular polysaccharide biosynthetic process, and the cell wall macromolecule catabolic process, were up-regulated. Whereas, genes involved in amino acid metabolism, transport, apoptosis, and response to stimulus were up-regulated at the late stage of leaf senescence. Further analyses reveals that the transport-related genes at the early stage of leaf senescence potentially take part in enzyme and amino acid transport and the genes upregulated at the late stage are involved in sugar transport, indicating nutrient recycling mainly takes place at the late stage of leaf senescence. Comparison between the data of natural leaf senescence in this study and previously reported data for Arabidopsis implies that the mechanisms of leaf senescence in maize are basically similar to those in Arabidopsis. A comparison of natural and induced leaf senescence in maize was performed. Athough many basic biological processes involved in senescence occur in both types of leaf senescence, 78.07% of differentially expressed genes in natural leaf senescence were not identifiable in induced leaf senescence, suggesting that differences in gene regulatory network may exist between these two leaf senescence

  14. Determination of Inter-leaf Translocated Free Glyphosate in Arabidopsis thaliana using Liquid Chromatography Tandem Mass Spectrometry (LCMS/MS) after Derivatization with Fluorenylmethyloxycarbonyl Chloride (FMOC-Cl)

    KAUST Repository

    Raji, Misjudeen

    2014-02-03

    Glyphosate is a broad-spectrum herbicide widely used for eliminating weeds in crop fields. Its mode of action is believed to be via translocation from the source to the sink tissues where it then interferes with the activities of 5-enol-pyruvylshikimate-3-phosphate synthase (EPSPS). In this study, the translocation of glyphosate in the leaves of Arabidopsis thaliana was investigated using an HPLC-MS/MS method following derivatization of the secondary amino group in the analyte using N-(9-fluorenylmethoxycarbonyloxy) chloride. To eliminate the errant precipitation that occurred when the reagent and the analyte are mixed, optimization of this method was required. The method linearity has a correlation coefficient higher than 0.99 over the concentration range of 0.005-2 μM. The limits of detection and quantitation were estimated to be 0.002 μM and 0.008 μM respectively. The repeatability of the method (as%R.S.D) ranged from 10% to 13%. The presented method was employed for the determination of free glyphosate in young untreated leaves of the specimen plants after treating a single leaf and allowing it to stand for 12 hours.

  15. Overexpression of Medicago sativa TMT elevates the α-tocopherol content in Arabidopsis seeds, alfalfa leaves, and delays dark-induced leaf senescence.

    Science.gov (United States)

    Jiang, Jishan; Jia, Huili; Feng, Guangyan; Wang, Zan; Li, Jun; Gao, Hongwen; Wang, Xuemin

    2016-08-01

    Alfalfa (Medicago sativa L.) is a major forage legume for livestock and a target for improving their dietary quality. Vitamin E is an essential vitamin that animals must obtain from their diet for proper growth and development. γ-tocopherol methyltransferase (γ-TMT), which catalyzes the conversion of δ- and γ-tocopherols (or tocotrienols) to β- and α-tocopherols (or tocotrienols), respectively, is the final enzyme involved in the vitamin E biosynthetic pathway. The overexpression of M. sativa L.'s γ-TMT (MsTMT) increased the α-tocopherol content 10-15 fold above that of wild type Arabidopsis seeds without altering the total content of vitamin E. Additionally, in response to osmotic stress, the biomass and the expression levels of several osmotic marker genes were significantly higher in the transgenic lines compared with wild type. Overexpression of MsTMT in alfalfa led to a modest, albeit significant, increase in α-tocopherol in leaves and was also responsible for a delayed leaf senescence phenotype. Additionally, the crude protein content was increased, while the acid and neutral detergent fiber contents were unchanged in these transgenic lines. Thus, increased α-tocopherol content occurred in transgenic alfalfa without compromising the nutritional qualities. The targeted metabolic engineering of vitamin E biosynthesis through MsTMT overexpression provides a promising approach to improve the α-tocopherol content of forage crops. PMID:27297993

  16. Mechanistic evaluation of Ginkgo biloba leaf extract-induced genotoxicity in L5178Y cells.

    Science.gov (United States)

    Lin, Haixia; Guo, Xiaoqing; Zhang, Suhui; Dial, Stacey L; Guo, Lei; Manjanatha, Mugimane G; Moore, Martha M; Mei, Nan

    2014-06-01

    Ginkgo biloba has been used for many thousand years as a traditional herbal remedy and its extract has been consumed for many decades as a dietary supplement. Ginkgo biloba leaf extract is a complex mixture with many constituents, including flavonol glycosides and terpene lactones. The National Toxicology Program 2-year cancer bioassay found that G. biloba leaf extract targets the liver, thyroid gland, and nose of rodents; however, the mechanism of G. biloba leaf extract-associated carcinogenicity remains unclear. In the current study, the in vitro genotoxicity of G. biloba leaf extract and its eight constituents was evaluated using the mouse lymphoma assay (MLA) and Comet assay. The underlying mechanisms of G. biloba leaf extract-associated genotoxicity were explored. Ginkgo biloba leaf extract, quercetin, and kaempferol resulted in a dose-dependent increase in the mutant frequency and DNA double-strand breaks (DSBs). Western blot analysis confirmed that G. biloba leaf extract, quercetin, and kaempferol activated the DNA damage signaling pathway with increased expression of γ-H2AX and phosphorylated Chk2 and Chk1. In addition, G. biloba leaf extract produced reactive oxygen species and decreased glutathione levels in L5178Y cells. Loss of heterozygosity analysis of mutants indicated that G. biloba leaf extract, quercetin, and kaempferol treatments resulted in extensive chromosomal damage. These results indicate that G. biloba leaf extract and its two constituents, quercetin and kaempferol, are mutagenic to the mouse L5178Y cells and induce DSBs. Quercetin and kaempferol likely are major contributors to G. biloba leaf extract-induced genotoxicity.

  17. Chemical Characterization and in Vitro Cytotoxicity on Squamous Cell Carcinoma Cells of Carica Papaya Leaf Extracts

    Directory of Open Access Journals (Sweden)

    Thao T. Nguyen

    2015-12-01

    Full Text Available In traditional medicine, Carica papaya leaf has been used for a wide range of therapeutic applications including skin diseases and cancer. In this study, we investigated the in vitro cytotoxicity of aqueous and ethanolic extracts of Carica papaya leaves on the human oral squamous cell carcinoma SCC25 cell line in parallel with non-cancerous human keratinocyte HaCaT cells. Two out of four extracts showed a significantly selective effect towards the cancer cells and were found to contain high levels of phenolic and flavonoid compounds. The chromatographic and mass spectrometric profiles of the extracts obtained with Ultra High Performance Liquid Chromatography-Quadrupole Time of Flight-Mass Spectrometry were used to tentatively identify the bioactive compounds using comparative analysis. The principal compounds identified were flavonoids or flavonoid glycosides, particularly compounds from the kaempferol and quercetin families, of which several have previously been reported to possess anticancer activities. These results confirm that papaya leaf is a potential source of anticancer compounds and warrant further scientific investigation to validate the traditional use of papaya leaf to treat cancer.

  18. Chemical Characterization and in Vitro Cytotoxicity on Squamous Cell Carcinoma Cells of Carica papaya Leaf Extracts.

    Science.gov (United States)

    Nguyen, Thao T; Parat, Marie-Odile; Hodson, Mark P; Pan, Jenny; Shaw, Paul N; Hewavitharana, Amitha K

    2015-12-24

    In traditional medicine, Carica papaya leaf has been used for a wide range of therapeutic applications including skin diseases and cancer. In this study, we investigated the in vitro cytotoxicity of aqueous and ethanolic extracts of Carica papaya leaves on the human oral squamous cell carcinoma SCC25 cell line in parallel with non-cancerous human keratinocyte HaCaT cells. Two out of four extracts showed a significantly selective effect towards the cancer cells and were found to contain high levels of phenolic and flavonoid compounds. The chromatographic and mass spectrometric profiles of the extracts obtained with Ultra High Performance Liquid Chromatography-Quadrupole Time of Flight-Mass Spectrometry were used to tentatively identify the bioactive compounds using comparative analysis. The principal compounds identified were flavonoids or flavonoid glycosides, particularly compounds from the kaempferol and quercetin families, of which several have previously been reported to possess anticancer activities. These results confirm that papaya leaf is a potential source of anticancer compounds and warrant further scientific investigation to validate the traditional use of papaya leaf to treat cancer.

  19. The DOF transcription factor Dof5.1 influences leaf axial patterning by promoting Revoluta transcription in Arabidopsis

    KAUST Repository

    Kim, Hyungsae

    2010-10-05

    Dof proteins are transcription factors that have a conserved single zinc finger DNA-binding domain. In this study, we isolated an activation tagging mutant Dof5.1-D exhibiting an upward-curling leaf phenotype due to enhanced expression of the REV gene that is required for establishing adaxialabaxial polarity. Dof5.1-D plants also had reduced transcript levels for IAA6 and IAA19 genes, indicating an altered auxin biosynthesis in Dof5.1-D. An electrophoretic mobility shift assay using the Dof5.1 DNA-binding motif and the REV promoter region indicated that the DNA-binding domain of Dof5.1 binds to a TAAAGT motif located in the 5′-distal promoter region of the REV promoter. Further, transient and chromatin immunoprecipitation assays verified binding activity of the Dof5.1 DNA-binding motif with the REV promoter. Consistent with binding assays, constitutive over-expression of the Dof5.1 DNA-binding domain in wild-type plants caused a downward-curling phenotype, whereas crossing Dof5.1-D to a rev mutant reverted the upward-curling phenotype of the Dof5.1-D mutant leaf to the wild-type. These results suggest that the Dof5.1 protein directly binds to the REV promoter and thereby regulates adaxialabaxial polarity. © 2010 Blackwell Publishing Ltd.

  20. A dynamic model for stem cell homeostasis and patterning in Arabidopsis meristems.

    Directory of Open Access Journals (Sweden)

    Tim Hohm

    Full Text Available Plants maintain stem cells in their meristems as a source for new undifferentiated cells throughout their life. Meristems are small groups of cells that provide the microenvironment that allows stem cells to prosper. Homeostasis of a stem cell domain within a growing meristem is achieved by signalling between stem cells and surrounding cells. We have here simulated the origin and maintenance of a defined stem cell domain at the tip of Arabidopsis shoot meristems, based on the assumption that meristems are self-organizing systems. The model comprises two coupled feedback regulated genetic systems that control stem cell behaviour. Using a minimal set of spatial parameters, the mathematical model allows to predict the generation, shape and size of the stem cell domain, and the underlying organizing centre. We use the model to explore the parameter space that allows stem cell maintenance, and to simulate the consequences of mutations, gene misexpression and cell ablations.

  1. Root border-like cells of Arabidopsis. Microscopical characterization and role in the interaction with rhizobacteria.

    Science.gov (United States)

    Vicré, Maïté; Santaella, Catherine; Blanchet, Sandrine; Gateau, Aurélien; Driouich, Azeddine

    2005-06-01

    Plant roots of many species produce thousands of cells that are released daily into the rhizosphere. These cells are commonly termed border cells because of their major role in constituting a biotic boundary layer between the root surface and the soil. In this study, we investigated the occurrence and ultrastructure of such cells in Arabidopsis (Arabidopsis thaliana) using light and electron microscopy coupled to high-pressure freezing. The secretion of cell wall molecules including pectic polysaccharides and arabinogalactan-proteins (AGPs) was examined also using immunofluorescence microscopy and a set of anticarbohydrate antibodies. We show that root tips of Arabidopsis seedlings released cell layers in an organized pattern that differs from the rather randomly dispersed release observed in other plant species studied to date. Therefore, we termed such cells border-like cells (BLC). Electron microscopical results revealed that BLC are rich in mitochondria, Golgi stacks, and Golgi-derived vesicles, suggesting that these cells are actively engaged in secretion of materials to their cell walls. Immunocytochemical data demonstrated that pectins as well as AGPs are among secreted material as revealed by the high level of expression of AGP-epitopes. In particular, the JIM13-AGP epitope was found exclusively associated with BLC and peripheral cells in the root cap region. In addition, we investigated the function of BLC and root cap cell AGPs in the interaction with rhizobacteria using AGP-disrupting agents and a strain of Rhizobium sp. expressing a green fluorescent protein. Our findings demonstrate that alteration of AGPs significantly inhibits the attachment of the bacteria to the surface of BLC and root tip.

  2. Disc size regulation in the brood cell building behavior of leaf-cutter bee, Megachile tsurugensis

    Science.gov (United States)

    Kim, Jong-Yoon

    2007-12-01

    The leaf-cutter bee, Megachile tsurugensis, builds a brood cell in a preexisting tunnel with leaf discs that she cuts in decreasing sizes and assembles them like a Russian matryoshka doll. By experimentally manipulating the brood cell, it was investigated how she regulates the size of leaf discs that fit in the brood cell’s internal volume. When the internal volume was artificially increased by removing a bulk of leaf discs, she decreased the leaf disc size, although increasing it would have made the leaf disc more fitting in the increased internal volume. As a reverse manipulation, when the internal volume was decreased by inserting a group of inner layers of preassembled leaf discs to a brood cell, she decreased the leaf disc size, so that the leaf disc could fit in the decreased internal volume. These results suggest that she uses at least two different mechanisms to regulate the disc size: the use of some internal memory about the degree of building work accomplished in the first and of sensory feedback of dimensional information at the construction site in the second manipulation, respectively. It was concluded that a stigmergic mechanism, an immediate sensory feedback from the brood cell changed by the building work, alone cannot explain the details of the bee’s behavior particularly with respect to her initial response to the first manipulation. For a more complete explanation of the behavior exhibited by the solitary bee, two additional behavioral elements, reinforcement of building activity and processing of dimensional information, were discussed along with stigmergy.

  3. Cortical microtubule patterning in roots of Arabidopsis thaliana primary cell wall mutants reveals the bidirectional interplay with cell expansion.

    Science.gov (United States)

    Panteris, Emmanuel; Adamakis, Ioannis-Dimosthenis S; Daras, Gerasimos; Rigas, Stamatis

    2015-01-01

    Cell elongation requires directional deposition of cellulose microfibrils regulated by transverse cortical microtubules. Microtubules respond differentially to suppression of cell elongation along the developmental zones of Arabidopsis thaliana root apex. Cortical microtubule orientation is particularly affected in the fast elongation zone but not in the meristematic or transition zones of thanatos and pom2-4 cellulose-deficient mutants of Arabidopsis thaliana. Here, we report that a uniform phenotype is established among the primary cell wall mutants, as cortical microtubules of root epidermal cells of rsw1 and prc1 mutants exhibit the same pattern described in thanatos and pom2-4. Whether cortical microtubules assume transverse orientation or not is determined by the demand for cellulose synthesis, according to each root zone's expansion rate. It is suggested that cessation of cell expansion may provide a biophysical signal resulting in microtubule reorientation. PMID:26042727

  4. 盐胁迫对拟南芥叶片和下表皮细胞大小的影响%Effects of Salt Stress on Epidermal Cell Expansion in Leaves of Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    侯蕾; 陈龙俊

    2011-01-01

    [目的]探讨盐胁迫对拟南芥叶片发育的影响.[方法]用浓度分别为0、100和150 mmol/L的NaCl溶液处理拟南芥幼苗7和14d后,用改进的指甲油印迹法并借助计算机软件,测量了不同处理的叶片面积和下表皮细胞面积.并对不同处理的叶片和细胞面积进行了差异性检验和比较.[结果]盐胁迫下,拟南芥叶片的生长受到显著抑制.叶片大小、叶片下表皮细胞的大小都相应减小.[结论]叶片及表皮细胞的减小是植物盐胁迫条件下的重要生理反映.%[ Objective ] The aim of this study was to investigate the effects of salt stress on cell expansion in Arabidopsis rosette leaves. [ Method] Arabidopsis rosetle seedlings were treated by sodium chloride at the concentration of 0, 100 or 150 mmol/L. At the 7 and 14 d of treatment, with colorless nail polish printing mark method and computer software, the leaf blades area and abaxial epidermal pavement cells area were measured and compared using statistical analysis in Excel. [ Result ] The growth of Arabidopsis rosette leaves was inhibited under salt stress. Leaves treated for 7 or 14 d expanded less compared with controls. The salt-mediated decrease in leaf expansion is associated with a decrease in abaxial pavement cell expansion. [ Conclusion] The decreased leaf and epidermal cell expansion under salt stress was the most important characteristic of plant physiological response to salt stress.

  5. Meiotic and Mitotic Cell Cycle Mutants Involved in Gametophyte Development in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Jingjing Liu; Li-Jia Qu

    2008-01-01

    The alternation between diploid and haploid generations is fundamentalin the life cycles of both animals and plants.The meiotic cell cycle is common to both animals and plants gamete formation, but in animals the products of meiosis are gametes,whereas for most plants,subsequent mitotic cell cycles are needed for their formation. Clarifying the regulatory mechanisms of mitotic cell cycle progression during gametophyte development will help understanding of sexual reproduction in plants.Many mutants defective in gametophyte development and,in particular,many meiotic and mitotic cell cycle mutants in Arabidopsis male and female gametophyte development were identified through both forward and reverse genetics approaches.

  6. Kunitz Trypsin Inhibitor: An Antagonist of Cell Death Triggered by Phytopathogens and Fumonisin B1 in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Jing Li; Günter Brader; E. Tapio Palva

    2008-01-01

    Programmed cell death (PCD) is a central regulatory process in both plant development and in plant responses to pathogens. PCD requires a coordinate activation of pro-apoptotic factors such as proteases and suppressors inhibiting and modulating these processes. In plants, various caspase-like cysteine proteases as well as serine proteases have been implicated in PCD. Here, we show that a serine protease (Kunitz trypsin) inhibitor (KTI1) of Arabidopsis acts as a functional KTI when produced in bacteria and in planta. Expression of AtKTI1 is induced late in response to bacterial and fungal elicitors and to salicylic acid. RNAi silencing of the AtKTI1 gene results in enhanced lesion development after infiltration of leaf tissue with the PCD-eliciting fungal toxin fumonisin B1 (FB1) or the avirulent bacterial pathogen Pseudomonas syringae pv tomato DC3000 carrying avrB (Pst avrB). Overexpression of AtKTI1 results in reduced lesion development after Pst avrB and FB1 infiltration. Interestingly, RNAi silencing of AtKTI1 leads to enhanced resistance to the virulent pathogen Erwinia carotovora subsp, carotovora SCC1, while overexpression of AtKTI1 leads to higher susceptibility towards this pathogen. Together, these data indicate that AtKTI1 is involved in modulating PCD in plant-pathogen interactions.

  7. Yeast cell wall extract induces disease resistance against bacterial and fungal pathogens in Arabidopsis thaliana and Brassica crop.

    Directory of Open Access Journals (Sweden)

    Mari Narusaka

    Full Text Available Housaku Monogatari (HM is a plant activator prepared from a yeast cell wall extract. We examined the efficacy of HM application and observed that HM treatment increased the resistance of Arabidopsis thaliana and Brassica rapa leaves to bacterial and fungal infections. HM reduced the severity of bacterial leaf spot and anthracnose on A. thaliana and Brassica crop leaves with protective effects. In addition, gene expression analysis of A. thaliana plants after treatment with HM indicated increased expression of several plant defense-related genes. HM treatment appears to induce early activation of jasmonate/ethylene and late activation of salicylic acid (SA pathways. Analysis using signaling mutants revealed that HM required SA accumulation and SA signaling to facilitate resistance to the bacterial pathogen Pseudomonas syringae pv. maculicola and the fungal pathogen Colletotrichum higginsianum. In addition, HM-induced resistance conferred chitin-independent disease resistance to bacterial pathogens in A. thaliana. These results suggest that HM contains multiple microbe-associated molecular patterns that activate defense responses in plants. These findings suggest that the application of HM is a useful tool that may facilitate new disease control methods.

  8. Functional Analysis of Cellulose and Xyloglucan in the Walls of Stomatal Guard Cells of Arabidopsis.

    Science.gov (United States)

    Rui, Yue; Anderson, Charles T

    2016-03-01

    Stomatal guard cells are pairs of specialized epidermal cells that control water and CO2 exchange between the plant and the environment. To fulfill the functions of stomatal opening and closure that are driven by changes in turgor pressure, guard cell walls must be both strong and flexible, but how the structure and dynamics of guard cell walls enable stomatal function remains poorly understood. To address this question, we applied cell biological and genetic analyses to investigate guard cell walls and their relationship to stomatal function in Arabidopsis (Arabidopsis thaliana). Using live-cell spinning disk confocal microscopy, we measured the motility of cellulose synthase (CESA)-containing complexes labeled by green fluorescent protein (GFP)-CESA3 and observed a reduced proportion of GFP-CESA3 particles colocalizing with microtubules upon stomatal closure. Imaging cellulose organization in guard cells revealed a relatively uniform distribution of cellulose in the open state and a more fibrillar pattern in the closed state, indicating that cellulose microfibrils undergo dynamic reorganization during stomatal movements. In cesa3(je5) mutants defective in cellulose synthesis and xxt1 xxt2 mutants lacking the hemicellulose xyloglucan, stomatal apertures, changes in guard cell length, and cellulose reorganization were aberrant during fusicoccin-induced stomatal opening or abscisic acid-induced stomatal closure, indicating that sufficient cellulose and xyloglucan are required for normal guard cell dynamics. Together, these results provide new insights into how guard cell walls allow stomata to function as responsive mediators of gas exchange at the plant surface. PMID:26729799

  9. Calcium dynamics in root cells of Arabidopsis thaliana visualized with selective plane illumination microscopy.

    Directory of Open Access Journals (Sweden)

    Alex Costa

    Full Text Available Selective Plane Illumination Microscopy (SPIM is an imaging technique particularly suited for long term in-vivo analysis of transparent specimens, able to visualize small organs or entire organisms, at cellular and eventually even subcellular resolution. Here we report the application of SPIM in Calcium imaging based on Förster Resonance Energy Transfer (FRET. Transgenic Arabidopsis plants expressing the genetically encoded-FRET-based Ca(2+ probe Cameleon, in the cytosol or nucleus, were used to demonstrate that SPIM enables ratiometric fluorescence imaging at high spatial and temporal resolution, both at tissue and single cell level. The SPIM-FRET technique enabled us to follow nuclear and cytosolic Ca(2+ dynamics in Arabidopsis root tip cells, deep inside the organ, in response to different stimuli. A relevant physiological phenomenon, namely Ca(2+ signal percolation, predicted in previous studies, has been directly visualized.

  10. Classification and identification of arabidopsis cell wall mutants using fourier transfrom infrared (FT-IR) microspectroscopy

    OpenAIRE

    Mouille, Grégory; Lecomte, Mannaïg; Pagant, Sylvère; Höfte, Hermanus

    2003-01-01

    We have developed a novel procedure for the rapid classification and identification of Arabidopsis mutants with altered cell wall architecture based on Fourier-Transform infrared (FT-IR) micro-spectroscopy. FT-IR transmission spectra were sampled from native 4 day-old dark-grown hypocotyls of 46 mutants and wild type treated with various drugs. The Mahalanobis distance between mutants, calculated from the spectral information after compression with the Discriminant Variables Selection procedu...

  11. Leaf anatomy of Cinnamomum schaeffer (Lauraceae) with special reference to oil and mucilage cells

    NARCIS (Netherlands)

    Bakker, M.E.; Gerritsen, A.F.; Schaaf, van der P.J.

    1992-01-01

    The morphology and distribution patterns of oil and mucilage cells in the leaf of 150 species of Cinnamomum are described. Idioblasts are always present in the palisade and the spongy parenchyma. Usually both oil and mucilage cells occur; in some species either oil or mucilage cells are present. Bot

  12. Plant cell wall proteomics: the leadership of Arabidopsis thaliana

    OpenAIRE

    Albenne, Cécile; Canut, Hervé; Jamet, Elisabeth

    2013-01-01

    Plant cell wall proteins (CWPs) progressively emerged as crucial components of cell walls although present in minor amounts. Cell wall polysaccharides such as pectins, hemicelluloses, and cellulose represent more than 90% of primary cell wall mass, whereas hemicelluloses, cellulose, and lignins are the main components of lignified secondary walls. All these polymers provide mechanical properties to cell walls, participate in cell shape and prevent water loss in aerial organs. However, cell wa...

  13. Cell Wall Heterogeneity in Root Development of Arabidopsis

    Science.gov (United States)

    Somssich, Marc; Khan, Ghazanfar Abbas; Persson, Staffan

    2016-01-01

    Plant cell walls provide stability and protection to plant cells. During growth and development the composition of cell walls changes, but provides enough strength to withstand the turgor of the cells. Hence, cell walls are highly flexible and diverse in nature. These characteristics are important during root growth, as plant roots consist of radial patterns of cells that have diverse functions and that are at different developmental stages along the growth axis. Young stem cell daughters undergo a series of rapid cell divisions, during which new cell walls are formed that are highly dynamic, and that support rapid anisotropic cell expansion. Once the cells have differentiated, the walls of specific cell types need to comply with and support different cell functions. For example, a newly formed root hair needs to be able to break through the surrounding soil, while endodermal cells modify their walls at distinct positions to form Casparian strips between them. Hence, the cell walls are modified and rebuilt while cells transit through different developmental stages. In addition, the cell walls of roots readjust to their environment to support growth and to maximize nutrient uptake. Many of these modifications are likely driven by different developmental and stress signaling pathways. However, our understanding of how such pathways affect cell wall modifications and what enzymes are involved remain largely unknown. In this review we aim to compile data linking cell wall content and re-modeling to developmental stages of root cells, and dissect how root cell walls respond to certain environmental changes. PMID:27582757

  14. Cell Wall Heterogeneity in Root Development of Arabidopsis.

    Science.gov (United States)

    Somssich, Marc; Khan, Ghazanfar Abbas; Persson, Staffan

    2016-01-01

    Plant cell walls provide stability and protection to plant cells. During growth and development the composition of cell walls changes, but provides enough strength to withstand the turgor of the cells. Hence, cell walls are highly flexible and diverse in nature. These characteristics are important during root growth, as plant roots consist of radial patterns of cells that have diverse functions and that are at different developmental stages along the growth axis. Young stem cell daughters undergo a series of rapid cell divisions, during which new cell walls are formed that are highly dynamic, and that support rapid anisotropic cell expansion. Once the cells have differentiated, the walls of specific cell types need to comply with and support different cell functions. For example, a newly formed root hair needs to be able to break through the surrounding soil, while endodermal cells modify their walls at distinct positions to form Casparian strips between them. Hence, the cell walls are modified and rebuilt while cells transit through different developmental stages. In addition, the cell walls of roots readjust to their environment to support growth and to maximize nutrient uptake. Many of these modifications are likely driven by different developmental and stress signaling pathways. However, our understanding of how such pathways affect cell wall modifications and what enzymes are involved remain largely unknown. In this review we aim to compile data linking cell wall content and re-modeling to developmental stages of root cells, and dissect how root cell walls respond to certain environmental changes. PMID:27582757

  15. Conserved cis-regulatory elements for DNA-binding-with-one-finger and homeo-domain-leucine-zipper transcription factors regulate companion cell-specific expression of the Arabidopsis thaliana SUCROSE TRANSPORTER 2 gene.

    Science.gov (United States)

    Schneidereit, Alexander; Imlau, Astrid; Sauer, Norbert

    2008-09-01

    The transition from young carbon-importing sink leaves of higher plants to mature carbon-exporting source leaves is paralleled by a complete reversal of phloem function. While sink-leaf phloem mediates the influx of reduced carbon from older source leaves and the release of this imported carbon to the sink-leaf mesophyll, source-leaf phloem catalyzes the uptake of photoassimilates into companion cells (CCs) and sieve elements (SEs) and the net carbon export from the leaf. Phloem loading in source leaves with sucrose, the main or exclusive transport form for fixed carbon in most higher plants, is catalyzed by plasma membrane-localized sucrose transporters. Consistent with the described physiological switch from sink to source, the promoter of the Arabidopsis AtSUC2 gene is active only in source-leaf CCs of Arabidopsis or of transgenic tobacco (Nicotiana tabacum). For the identification of regulatory elements involved in this companion cell-specific and source-specific gene expression, we performed detailed analyses of the AtSUC2 promoter by truncation and mutagenesis. A 126-bp promoter fragment was identified, which seems to contain these fragments and which drives AtSUC2-typical expression when combined with a 35S minimal promoter. Within this fragment, linker-scanning analyses revealed two cis-regulatory elements that were further characterized as putative binding sites for transcription factors of the DNA-binding-with-one-finger or the homeo-domain-leucine-zipper families. Similar or identical binding sites are found in other genes and in different plant species, suggesting an ancient regulatory mechanism for this important physiological switch. PMID:18551303

  16. PD trafficking of potato leaf roll virus movement protein in Arabidopsis depends on site-specific protein phosphorylation

    Directory of Open Access Journals (Sweden)

    Katrin eLink

    2011-06-01

    Full Text Available Many plant viruses encode for specialised movement proteins (MP to facilitate passage of viral material to and through plasmodesmata (PD. To analyse intracellular trafficking of potato leaf roll virus (PLRV movement protein (MP17 we performed GFP fusion experiments with distinct deletion variants of MP17. These studies revealed that the C-terminus of MP17 is essential but not sufficient for PD targeting. Interestingly, fusion of GFP to three C-terminal MP17 deletion variants resulted in the accumulation of GFP in chloroplasts. This indicates that MP17 harbours hidden plastid targeting sequences. Previous studies showed that posttranslational protein phosphorylation influences PD targeting of MP and virus spread. Analysis of MP17-derived phospho-peptides by mass spectrometry revealed four phosphorylated serine residues (S71, S79, S137 and S140. Site-directed mutagenesis of S71/S79 and S137/S140 showed that the C-terminal serine residues S137/S140 are dispensable for PD targeting. However, exchange of S71/S79 to A71/A79 abolished PD targeting of the mutated MP17 protein. To mimic phosphorylation of S71/S79 both amino acids were substituted by aspartic acid. The resulting D71/D79 variant of MP17 was efficiently targeted to PD. Further deletion analysis showed that PD targeting of MP17 is dependent on the C-terminus, phosphorylation of S71 and/or S79 and a N-terminal domain.

  17. Levels of Arabidopsis thaliana leaf phosphatidic acids, phosphatidylserines, and most trienoate-containing polar lipid molecular species increase during the dark period of the diurnal cycle

    Directory of Open Access Journals (Sweden)

    Sara eMaatta

    2012-03-01

    Full Text Available Previous work has demonstrated that plant leaf polar lipid fatty acid composition varies during the diurnal (dark-light cycle. Fatty acid synthesis occurs primarily during the light, but fatty acid desaturation continues in the absence of light, resulting in polyunsaturated fatty acids reaching their highest levels toward the end of the dark period. In this work, Arabidopsis thaliana were grown at constant (21°C temperature with 12-h light and 12-h dark periods. Collision induced dissociation time-of-flight mass spectrometry demonstrated that 16:3 and 18:3 fatty acid content in membrane lipids of leaves are higher at the end of the dark than at the end of the light period, while 16:1, 16:2, 18:0, and 18:1 content are higher at the end of the light period. Lipid profiling of membrane galactolipids, phospholipids, and lysophospholipids by electrospray ionization triple quadrupole mass spectrometry indicated that the monogalactosyldiacylglycerol, phosphatidylglycerol, and phosphatidylcholine classes include molecular species whose levels are highest at end of the light period and others that are highest at the end of the dark period. The levels of phosphatidic acid and phosphatidylserine classes were higher at the end of the dark period, and molecular species within these classes either followed the class pattern or were not significantly changed in the diurnal cycle. Phospholipase D (PLD is a family of enzymes that hydrolyzes phospholipids to produce phosphatidic acid. Analysis of several PLD mutant lines suggests that PLDζ2 and possibly PLDα1 may contribute to diurnal cycling of phosphatidic acid. The polar lipid compositional changes are considered in relation to recent data that demonstrate phosphatidylcholine acyl editing.

  18. Comprehensive analysis of single-repeat R3 MYB proteins in epidermal cell patterning and their transcriptional regulation in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Schiefelbein John

    2008-07-01

    Full Text Available Abstract Background Single-repeat R3 MYB transcription factors are critical components of the lateral inhibition machinery that mediates epidermal cell patterning in plants. Sequence analysis of the Arabidopsis genome using the BLAST program reveals that there are a total of six genes, including TRIPTYCHON (TRY, CAPRICE (CPC, TRICHOMELESS1 (TCL1, and ENHANCER of TRY and CPC 1, 2, and 3 (ETC1, ETC2 and ETC3 encoding single-repeat R3 MYB transcription factors that are approximately 50% identical to one another at the amino acid level. Previous studies indicate that these single-repeat R3 MYBs regulate epidermal cell patterning. However, each of the previous studies of these single-repeat R3 MYBs has been limited to an analysis of only a subset of these six genes, and furthermore, they have limited their attention to epidermal development in only one or two of the organs. In addition, the transcriptional regulation of these single-repeat R3 MYB genes remains largely unknown. Results By analyzing multiple mutant lines, we report here that TCL1 functions redundantly with other single-repeat R3 MYB transcription factors to control both leaf trichome and root hair formation. On the other hand, ETC1 and ETC3 participate in controlling trichome formation on inflorescence stems and pedicles. Further, we discovered that single-repeat R3 MYBs suppress trichome formation on cotyledons and siliques, organs that normally do not bear any trichomes. By using Arabidopsis protoplast transfection assays, we found that all single-repeat R3 MYBs examined interact with GL3, and that GL1 or WER and GL3 or EGL3 are required and sufficient to activate the transcription of TRY, CPC, ETC1 and ETC3, but not TCL1 and ETC2. Furthermore, only ETC1's transcription was greatly reduced in the gl3 egl3 double mutants. Conclusion Our comprehensive analysis enables us to draw broader conclusions about the role of single-repeat R3 MYB gene family than were possible in the earlier

  19. Evaluation of cytotoxicity of Moringa oleifera Lam. callus and leaf extracts on Hela cells

    Directory of Open Access Journals (Sweden)

    Abbas Jafarain

    2014-01-01

    Full Text Available Background: There are considerable attempts worldwide on herbal and traditional compounds to validate their use as anti-cancer drugs. Plants from Moringaceae family including Moringa oleifera possess several activities such as antitumor effect on tumor cell lines. In this study we sought to determine if callus and leaf extracts of M. oleifera possess any cytotoxicity. Materials and Methods: Ethanol-water (70-30 extracts of callus and leaf of M. oleifera were prepared by maceration method. The amount of phenolic compounds of the extracts was determined by Folin Ciocalteu method. The cytotoxicity of the extracts against Hela tumor cells was carried out using MTT assay. Briefly, cells were seeded in microplates and different concentrations of the extract were added. Cells were incubated for 48 h and their viability was evaluated by addition of tetrazolium salt solution. After 3 h medium was aspirated, dimethyl sulfoxide was added and absorbance was determined at 540 nm with an ELISA plate reader. Cytotoxicity was considered when more than 50% reduction on cell survival was observed. Results: Callus and leaf extracts of M. oleifera significantly decreased the viability of Hela cells in a concentration-dependent manner. However, leaf extract of M. oleifera were more potent than that of callus extract. Conclusion: As the content of phenolic compounds of leaf extract was higher than that of callus extract, it can be concluded that phenolic compounds are involved in the cytotoxicity of M. oleifera.

  20. Does ploidy level directly control cell size? Counterevidence from Arabidopsis genetics.

    Directory of Open Access Journals (Sweden)

    Hirokazu Tsukaya

    Full Text Available Ploidy level affects cell size in many organisms, and ploidy-dependent cell enlargement has been used to breed many useful organisms. However, how polyploidy affects cell size remains unknown. Previous studies have explored changes in transcriptome data caused by polyploidy, but have not been successful. The most naïve theory explaining ploidy-dependent cell enlargement is that increases in gene copy number increase the amount of protein, which in turn increases the cell volume. This hypothesis can be evaluated by examining whether any strains, mutants, or transgenics show the same cell size before and after a tetraploidization event. I performed this experiment by tetraploidizing various mutants and transgenics of Arabidopsis thaliana, which show a wide range in cell size, and found that the ploidy-dependent increase in cell volume is genetically regulated. This result is not in agreement with the theory described above.

  1. Nitric oxide suppresses stomatal opening by inhibiting inward-rectifying Kin channels in Arabidopsis guard cells

    Institute of Scientific and Technical Information of China (English)

    XUE ShaoWu; YANG Pin; HE YiKun

    2008-01-01

    We explore nitric oxide (NO) effect on K+in channels in Arabidopsis guard cells. We observed NO inhib-ited K+in currents when Ca2+ chelator EGTA (Ethylene glycol-bis(2-aminoethylether)-N,N,N',N'tetraacetic acid) was not added in the pipette solution; K+in currents were not sensitive to NO when cytosolic Ca2+ was chelated by EGTA. NO inhibited the Arabidopsis stomatal opening, but when EGTA was added in the bath solution, inhibition effect of NO on stomatal opening vanished. Thus, it implies that NO ele-vates cytosolic Ca2+ by activating plasma membrane Ca2+ channels firstly, then inactivates K+in chan-nels, resulting in stomatal opening suppressed subsequently.

  2. Immunoprofiling reveals unique cell-specific patterns of wall epitopes in the expanding Arabidopsis stem.

    Science.gov (United States)

    Hall, Hardy C; Cheung, Jingling; Ellis, Brian E

    2013-04-01

    The Arabidopsis inflorescence stem undergoes rapid directional growth, requiring massive axial cell-wall extension in all its tissues, but, at maturity, these tissues are composed of cell types that exhibit markedly different cell-wall structures. It is not clear whether the cell-wall compositions of these cell types diverge rapidly following axial growth cessation, or whether compositional divergence occurs at earlier stages in differentiation, despite the common requirement for cell-wall extensibility. To examine this question, seven cell types were assayed for the abundance and distribution of 18 major cell-wall glycan classes at three developmental stages along the developing inflorescence stem, using a high-throughput immunolabelling strategy. These stages represent a phase of juvenile growth, a phase displaying the maximum rate of stem extension, and a phase in which extension growth is ceasing. The immunolabelling patterns detected demonstrate that the cell-wall composition of most stem tissues undergoes pronounced changes both during and after rapid extension growth. Hierarchical clustering of the immunolabelling signals identified cell-specific binding patterns for some antibodies, including a sub-group of arabinogalactan side chain-directed antibodies whose epitope targets are specifically associated with the inter-fascicular fibre region during the rapid cell expansion phase. The data reveal dynamic, cell type-specific changes in cell-wall chemistry across diverse cell types during cell-wall expansion and maturation in the Arabidopsis inflorescence stem, and highlight the paradox between this structural diversity and the uniform anisotropic cell expansion taking place across all tissues during stem growth.

  3. Spatiotemporal relationships between growth and microtubule orientation as revealed in living root cells of Arabidopsis thaliana transformed with green-fluorescent-protein gene construct GFP-MBD

    Science.gov (United States)

    Granger, C. L.; Cyr, R. J.

    2001-01-01

    Arabidopsis thaliana plants were transformed with GFP-MBD (J. Marc et al., Plant Cell 10: 1927-1939, 1998) under the control of a constitutive (35S) or copper-inducible promoter. GFP-specific fluorescence distributions, levels, and persistence were determined and found to vary with age, tissue type, transgenic line, and individual plant. With the exception of an increased frequency of abnormal roots of 35S GFP-MBD plants grown on kanamycin-containing media, expression of GFP-MBD does not appear to affect plant phenotype. The number of leaves, branches, bolts, and siliques as well as overall height, leaf size, and seed set are similar between wild-type and transgenic plants as is the rate of root growth. Thus, we conclude that the transgenic plants can serve as a living model system in which the dynamic behavior of microtubules can be visualized. Confocal microscopy was used to simultaneously monitor growth and microtubule behavior within individual cells as they passed through the elongation zone of the Arabidopsis root. Generally, microtubules reoriented from transverse to oblique or longitudinal orientations as growth declined. Microtubule reorientation initiated at the ends of the cell did not necessarily occur simultaneously in adjacent neighboring cells and did not involve complete disintegration and repolymerization of microtubule arrays. Although growth rates correlated with microtubule reorientation, the two processes were not tightly coupled in terms of their temporal relationships, suggesting that other factor(s) may be involved in regulating both events. Additionally, microtubule orientation was more defined in cells whose growth was accelerating and less stringent in cells whose growth was decelerating, indicating that microtubule-orienting factor(s) may be sensitive to growth acceleration, rather than growth per se.

  4. An arabidopsis gene regulatory network for secondary cell wall synthesis

    Science.gov (United States)

    The plant cell wall is an important factor for determining cell shape, function and response to the environment. Secondary cell walls, such as those found in xylem, are composed of cellulose, hemicelluloses and lignin and account for the bulk of plant biomass. The coordination between transcriptiona...

  5. Embryonic control of epidermal cell patterning in the root and hypocotyl of Arabidopsis.

    Science.gov (United States)

    Lin, Y; Schiefelbein, J

    2001-10-01

    A position-dependent pattern of epidermal cell types is produced during the development of the Arabidopsis seedling root and hypocotyl. To understand the origin and regulation of this patterning mechanism, we have examined the embryonic expression of the GLABRA2 (GL2) gene, which encodes a cell-type-specific transcription factor. Using in situ RNA hybridization and a sensitive GL2::GFP reporter, we discovered that a position-dependent pattern of GL2 expression is established within protodermal cells at the heart stage and is maintained throughout the remainder of embryogenesis. In addition, we show that an exceptional GL2 expression character and epidermal cell pattern arises during development of the root-hypocotyl junction, which represents an anatomical transition zone. Furthermore, we find that two of the genes regulating seedling epidermal patterning, TRANSPARENT TESTA GLABRA (TTG) and WEREWOLF (WER), also control the embryonic GL2 pattern, whereas the CAPRICE (CPC) and GL2 genes are not required to establish this pattern. These results indicate that position-dependent patterning of epidermal cell types begins at an early stage of embryogenesis, before formation of the apical meristems and shortly after the cellular anatomy of the protoderm and outer ground tissue layer is established. Thus, epidermal cell specification in the Arabidopsis seedling relies on the embryonic establishment of a patterning mechanism that is perpetuated postembryonically.

  6. Single-Cell Telomere-Length Quantification Couples Telomere Length to Meristem Activity and Stem Cell Development in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Mary-Paz González-García

    2015-05-01

    Full Text Available Telomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at the stem cells. The defects in meristem and stem cell renewal observed in tert mutants demonstrate that telomere lengthening by TERT sets a replicative limit in the root meristem. Conversely, the long telomeres of the columella cells and the premature stem cell differentiation plt1,2 mutants suggest that differentiation can prevent telomere erosion. Overall, our results indicate that telomere dynamics are coupled to meristem activity and continuous growth, disclosing a critical association between telomere length, stem cell function, and the extended lifespan of plants.

  7. Single-cell telomere-length quantification couples telomere length to meristem activity and stem cell development in Arabidopsis.

    Science.gov (United States)

    González-García, Mary-Paz; Pavelescu, Irina; Canela, Andrés; Sevillano, Xavier; Leehy, Katherine A; Nelson, Andrew D L; Ibañes, Marta; Shippen, Dorothy E; Blasco, Maria A; Caño-Delgado, Ana I

    2015-05-12

    Telomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at the stem cells. The defects in meristem and stem cell renewal observed in tert mutants demonstrate that telomere lengthening by TERT sets a replicative limit in the root meristem. Conversely, the long telomeres of the columella cells and the premature stem cell differentiation plt1,2 mutants suggest that differentiation can prevent telomere erosion. Overall, our results indicate that telomere dynamics are coupled to meristem activity and continuous growth, disclosing a critical association between telomere length, stem cell function, and the extended lifespan of plants. PMID:25937286

  8. Single-cell telomere-length quantification couples telomere length to meristem activity and stem cell development in Arabidopsis.

    Science.gov (United States)

    González-García, Mary-Paz; Pavelescu, Irina; Canela, Andrés; Sevillano, Xavier; Leehy, Katherine A; Nelson, Andrew D L; Ibañes, Marta; Shippen, Dorothy E; Blasco, Maria A; Caño-Delgado, Ana I

    2015-05-12

    Telomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at the stem cells. The defects in meristem and stem cell renewal observed in tert mutants demonstrate that telomere lengthening by TERT sets a replicative limit in the root meristem. Conversely, the long telomeres of the columella cells and the premature stem cell differentiation plt1,2 mutants suggest that differentiation can prevent telomere erosion. Overall, our results indicate that telomere dynamics are coupled to meristem activity and continuous growth, disclosing a critical association between telomere length, stem cell function, and the extended lifespan of plants.

  9. Changes in cell ultrastructure and morphology of Arabidopsis thaliana roots after coumarins treatment

    Directory of Open Access Journals (Sweden)

    Ewa Kupidłowska

    2014-02-01

    Full Text Available The ultrastructure and morphology of roots treated with coumarin and umbelliferone as well as the reversibility of the coumarins effects caused by exogenous GA, were studied in Arabidopsis thaliana. Both coumarins suppressed root elongation and appreciably stimulated radial expansion of epidermal and cortical cells in the upper part of the meristem and in the elongation zone. The gibberellic acid applied simultaneously with coumarins decreased their inhibitory effect on root elongation and reduced cells swelling.Microscopic observation showed intensive vacuolization of cells and abnormalities in the structure of the Golgi stacks and the nuclear envelope. The detection of active acid phosphatase in the cytosol of swollen cells indicated increased membrane permeability. Significant abnormalities of newly formed cell walls, e.g. the discontinuity of cellulose layer, uncorrect position of walls and the lack of their bonds with the mother cell wall suggest that coumarins affected the cytoskeleton.

  10. An Arabidopsis aspartic protease functions as an anti-cell-death component in reproduction and embryogenesis.

    Science.gov (United States)

    Ge, Xiaochun; Dietrich, Charles; Matsuno, Michiyo; Li, Guojing; Berg, Howard; Xia, Yiji

    2005-03-01

    The components and pathways that regulate and execute developmental cell death programmes in plants remain largely unknown. We have found that the PROMOTION OF CELL SURVIVAL 1 (PCS1) gene in Arabidopsis, which encodes an aspartic protease, has an important role in determining the fate of cells in embryonic development and in reproduction processes. The loss-of-function mutation of PCS1 causes degeneration of both male and female gametophytes and excessive cell death of developing embryos. Conversely, ectopic expression of PCS1 causes the septum and stomium cells that normally die in the anther wall to survive instead, leading to a failure in anther dehiscence and male sterility. PCS1 provides a new avenue for understanding the mechanisms of the programmed cell death processes that are associated with developmental pathways in plants and makes available a useful tool for engineering the male sterility trait for hybrid seed production.

  11. Molecule mechanism of stem cells in Arabidopsis thaliana

    OpenAIRE

    Wenjin Zhang; Rongming Yu

    2014-01-01

    Plants possess the ability to continually produce new tissues and organs throughout their life. Unlike animals, plants are exposed to extreme variations in environmental conditions over the course of their lives. The vitality of plants is so powerful that they can survive several hundreds of years or even more making it an amazing miracle that comes from plant stem cells. The stem cells continue to divide to renew themselves and provide cells for the formation of leaves, stems, and flowers. S...

  12. Differential survival of solitary and aggregated bacterial cells promotes aggregate formation on leaf surfaces

    Science.gov (United States)

    Monier, J.-M.; Lindow, S. E.

    2003-01-01

    The survival of individual Pseudomonas syringae cells was determined on bean leaf surfaces maintained under humid conditions or periodically exposed to desiccation stress. Cells of P. syringae strain B728a harboring a GFP marker gene were visualized by epifluorescence microscopy, either directly in situ or after recovery from leaves, and dead cells were identified as those that were stained with propidium iodide in such populations. Under moist, conducive conditions on plants, the proportion of total live cells was always high, irrespective of their aggregated state. In contrast, the proportion of the total cells that remained alive on leaves that were periodically exposed to desiccation stress decreased through time and was only ≈15% after 5 days. However, the fraction of cells in large aggregates that were alive on such plants in both condition was much higher than more solitary cells. Immediately after inoculation, cells were randomly distributed over the leaf surface and no aggregates were observed. However, a very aggregated pattern of colonization was apparent within 7 days, and >90% of the living cells were located in aggregates of 100 cells or more. Our results strongly suggest that, although conducive conditions favor aggregate formation, such cells are much more capable of tolerating environmental stresses, and the preferential survival of cells in aggregates promotes a highly clustered spatial distribution of bacteria on leaf surfaces. PMID:14665692

  13. Deciphering the responses of root border-like cells of Arabidopsis and flax to pathogen-derived elicitors.

    Science.gov (United States)

    Plancot, Barbara; Santaella, Catherine; Jaber, Rim; Kiefer-Meyer, Marie Christine; Follet-Gueye, Marie-Laure; Leprince, Jérôme; Gattin, Isabelle; Souc, Céline; Driouich, Azeddine; Vicré-Gibouin, Maïté

    2013-12-01

    Plant pathogens including fungi and bacteria cause many of the most serious crop diseases. The plant innate immune response is triggered upon recognition of microbe-associated molecular patterns (MAMPs) such as flagellin22 and peptidoglycan. To date, very little is known of MAMP-mediated responses in roots. Root border cells are cells that originate from root caps and are released individually into the rhizosphere. Root tips of Arabidopsis (Arabidopsis thaliana) and flax (Linum usitatissimum) release cells known as "border-like cells." Whereas root border cells of pea (Pisum sativum) are clearly involved in defense against fungal pathogens, the function of border-like cells remains to be established. In this study, we have investigated the responses of root border-like cells of Arabidopsis and flax to flagellin22 and peptidoglycan. We found that both MAMPs triggered a rapid oxidative burst in root border-like cells of both species. The production of reactive oxygen species was accompanied by modifications in the cell wall distribution of extensin epitopes. Extensins are hydroxyproline-rich glycoproteins that can be cross linked by hydrogen peroxide to enhance the mechanical strength of the cell wall. In addition, both MAMPs also caused deposition of callose, a well-known marker of MAMP-elicited defense. Furthermore, flagellin22 induced the overexpression of genes involved in the plant immune response in root border-like cells of Arabidopsis. Our findings demonstrate that root border-like cells of flax and Arabidopsis are able to perceive an elicitation and activate defense responses. We also show that cell wall extensin is involved in the innate immunity response of root border-like cells.

  14. The development and geometry of shape change in Arabidopsis thaliana cotyledon pavement cells

    Directory of Open Access Journals (Sweden)

    Halsey Leah E

    2011-02-01

    Full Text Available Abstract Background The leaf epidermis is an important architectural control element that influences the growth properties of underlying tissues and the overall form of the organ. In dicots, interdigitated pavement cells are the building blocks of the tissue, and their morphogenesis includes the assembly of specialized cell walls that surround the apical, basal, and lateral (anticlinal cell surfaces. The microtubule and actin cytoskeletons are highly polarized along the cortex of the anticlinal wall; however, the relationships between these arrays and cell morphogenesis are unclear. Results We developed new quantitative tools to compare population-level growth statistics with time-lapse imaging of cotyledon pavement cells in an intact tissue. The analysis revealed alternating waves of lobe initiation and a phase of lateral isotropic expansion that persisted for days. During lateral isotropic diffuse growth, microtubule organization varied greatly between cell surfaces. Parallel microtubule bundles were distributed unevenly along the anticlinal surface, with subsets marking stable cortical domains at cell indentations and others clearly populating the cortex within convex cell protrusions. Conclusions Pavement cell morphogenesis is discontinuous, and includes punctuated phases of lobe initiation and lateral isotropic expansion. In the epidermis, lateral isotropic growth is independent of pavement cell size and shape. Cortical microtubules along the upper cell surface and stable cortical patches of anticlinal microtubules may coordinate the growth behaviors of orthogonal cell walls. This work illustrates the importance of directly linking protein localization data to the growth behavior of leaf epidermal cells.

  15. Programmed cell death activated by Rose Bengal in Arabidopsis thaliana cell suspension cultures requires functional chloroplasts.

    Science.gov (United States)

    Gutiérrez, Jorge; González-Pérez, Sergio; García-García, Francisco; Daly, Cara T; Lorenzo, Oscar; Revuelta, José L; McCabe, Paul F; Arellano, Juan B

    2014-07-01

    Light-grown Arabidopsis thaliana cell suspension culture (ACSC) were subjected to mild photooxidative damage with Rose Bengal (RB) with the aim of gaining a better understanding of singlet oxygen-mediated defence responses in plants. Additionally, ACSC were treated with H2O2 at concentrations that induced comparable levels of protein oxidation damage. Under low to medium light conditions, both RB and H2O2 treatments activated transcriptional defence responses and inhibited photosynthetic activity, but they differed in that programmed cell death (PCD) was only observed in cells treated with RB. When dark-grown ACSC were subjected to RB in the light, PCD was suppressed, indicating that the singlet oxygen-mediated signalling pathway in ACSC requires functional chloroplasts. Analysis of up-regulated transcripts in light-grown ACSC, treated with RB in the light, showed that both singlet oxygen-responsive transcripts and transcripts with a key role in hormone-activated PCD (i.e. ethylene and jasmonic acid) were present. A co-regulation analysis proved that ACSC treated with RB exhibited higher correlation with the conditional fluorescence (flu) mutant than with other singlet oxygen-producing mutants or wild-type plants subjected to high light. However, there was no evidence for the up-regulation of EDS1, suggesting that activation of PCD was not associated with the EXECUTER- and EDS1-dependent signalling pathway described in the flu mutant. Indigo Carmine and Methylene Violet, two photosensitizers unable to enter chloroplasts, did not activate transcriptional defence responses in ACSC; however, whether this was due to their location or to their inherently low singlet oxygen quantum efficiencies was not determined.

  16. Distribution and regulation of auxin in Arabidopsis root cells

    OpenAIRE

    Petersson, Sara

    2011-01-01

    The plant hormone auxin (IAA) coordinates many of the important processes in plant development. For example, IAA is critical for normal embryogenesis, root development, cell elongation, and the tropic responses such as gravitropism and phototropism. IAA gradients are established and maintained in many tissues and it is thought that these gradients act as developmental cues, determining the fate of cells and tissues. Descriptions of auxin distribution patterns with cellular resolution h...

  17. Leaf apoplastic proteome composition in UV-B treated Arabidopsis thaliana mutants impaired in extracellular glutathione degradation

    Directory of Open Access Journals (Sweden)

    A. Masi

    2016-03-01

    We then compared the expression changes resulting from the mutation and from the UV-B treatment. Rearrangements occurring in apoplastic protein composition suggest the involvement of hydrogen peroxide, which may ultimately act as a signal. Other important changes related to hormonal effects, cell wall remodeling, and redox activities are also reported. We argue that oxidative stress conditions imposed by UV-B and by disruption of the gamma-glutamyl cycle result in similar stress-induced responses, to some degree at least. Data shown here are associated with the article from Trentin et al. (2015 [1]; protein data have been deposited to the PRIDE database (Vizcaíno et al., 2014 [2] with identifier PXD001807.

  18. Molecular and Genetic Analysis of Hormone-Regulated Differential Cell Elongation in Arabidopsis

    Energy Technology Data Exchange (ETDEWEB)

    Ecker, Joseph R.

    2002-12-03

    The authors have utilized the response of Arabidopsis seedlings to the plant hormone ethylene to identify new genes involved in the regulation of ethylene biosynthesis, perception, signal transduction and differential cell growth. In building a genetic framework for the action of these genes, they developed a molecular model that has facilitated the understanding of the molecular requirements of ethylene for cell elongation processes. The ethylene response pathway in Arabidopsis appears to be primarily linear and is defined by the genes: ETR1, ETR2, ERS1, ERS2, EIN4, CTR1, EIN2, EIN3, EIN5 EIN6, and EIN. Downstream branches identified by the HLS1, EIR1, and AUX1 genes involve interactions with other hormonal (auxin) signals in the process of differential cell elongation in the hypocotyl hook. Cloning and characterization of HLS1 and three HLS1-LIKE genes in the laboratory has been supported under this award. HLS1 is required for differential elongation of cells in the hypocotyl and may act in the establishment of hormone gradients. Also during the award period, they have identified and begun preliminary characterization of two genes that genetically act upstream of the ethylene receptors. ETO1 and RAN1 encode negative regulators of ethylene biosynthesis and signaling respectively. Progress on the analysis of these genes along with HOOKLESS1 is described.

  19. Expression of Arabidopsis hexokinase in citrus guard cells controls stomatal aperture and reduces transpiration

    Directory of Open Access Journals (Sweden)

    Nitsan eLugassi

    2015-12-01

    Full Text Available Hexokinase (HXK is a sugar-phosphorylating enzyme involved in sugar-sensing. It has recently been shown that HXK in guard cells mediates stomatal closure and coordinates photosynthesis with transpiration in the annual species tomato and Arabidopsis. To examine the role of HXK in the control of the stomatal movement of perennial plants, we generated citrus plants that express Arabidopsis HXK1 (AtHXK1 under KST1, a guard cell-specific promoter. The expression of KST1 in the guard cells of citrus plants has been verified using GFP as a reporter gene. The expression of AtHXK1 in the guard cells of citrus reduced stomatal conductance and transpiration with no negative effect on the rate of photosynthesis, leading to increased water-use efficiency. The effects of light intensity and humidity on stomatal behavior were examined in rooted leaves of the citrus plants. The optimal intensity of photosynthetically active radiation and lower humidity enhanced stomatal closure of AtHXK1-expressing leaves, supporting the role of sugar in the regulation of citrus stomata. These results suggest that HXK coordinates photosynthesis and transpiration and stimulates stomatal closure not only in annual species, but also in perennial species.

  20. A rapid chemical method for lysing Arabidopsis cells for protein analysis

    Directory of Open Access Journals (Sweden)

    Takano Tetsuo

    2011-07-01

    Full Text Available Abstract Background Protein extraction is a frequent procedure in biological research. For preparation of plant cell extracts, plant materials usually have to be ground and homogenized to physically break the robust cell wall, but this step is laborious and time-consuming when a large number of samples are handled at once. Results We developed a chemical method for lysing Arabidopsis cells without grinding. In this method, plants are boiled for just 10 minutes in a solution containing a Ca2+ chelator and detergent. Cell extracts prepared by this method were suitable for SDS-PAGE and immunoblot analysis. This method was also applicable to genomic DNA extraction for PCR analysis. Our method was applied to many other plant species, and worked well for some of them. Conclusions Our method is rapid and economical, and allows many samples to be prepared simultaneously for protein analysis. Our method is useful not only for Arabidopsis research but also research on certain other species.

  1. A Theoretical Model of Jigsaw-Puzzle Pattern Formation by Plant Leaf Epidermal Cells.

    Science.gov (United States)

    Higaki, Takumi; Kutsuna, Natsumaro; Akita, Kae; Takigawa-Imamura, Hisako; Yoshimura, Kenji; Miura, Takashi

    2016-04-01

    Plant leaf epidermal cells exhibit a jigsaw puzzle-like pattern that is generated by interdigitation of the cell wall during leaf development. The contribution of two ROP GTPases, ROP2 and ROP6, to the cytoskeletal dynamics that regulate epidermal cell wall interdigitation has already been examined; however, how interactions between these molecules result in pattern formation remains to be elucidated. Here, we propose a simple interface equation model that incorporates both the cell wall remodeling activity of ROP GTPases and the diffusible signaling molecules by which they are regulated. This model successfully reproduces pattern formation observed in vivo, and explains the counterintuitive experimental results of decreased cellulose production and increased thickness. Our model also reproduces the dynamics of three-way cell wall junctions. Therefore, this model provides a possible mechanism for cell wall interdigitation formation in vivo.

  2. Steroids are required for epidermal cell fate establishment in Arabidopsis roots.

    Science.gov (United States)

    Kuppusamy, Kavitha T; Chen, Andrew Y; Nemhauser, Jennifer L

    2009-05-12

    The simple structure of Arabidopsis roots provides an excellent model system to study epidermal cell fate specification. Epidermal cells in contact with 2 underlying cortical cells differentiate into hair cells (H cells; trichoblasts), whereas cells that contact only a single cortical cell differentiate into mature hairless cells (N cells; atrichoblasts). This position-dependent patterning, in combination with the constrained orientation of cell divisions, results in hair and nonhair cell files running longitudinally along the root epidermis. Here, we present strong evidence that steroid hormones called brassinosteroids (BRs) are required to maintain position-dependent fate specification in roots. We show that BRs are required for normal expression levels and patterns of WEREWOLF (WER) and GLABRA2 (GL2), master regulators of epidermal patterning. Loss of BR signaling results in loss of hair cells in H positions, likely as a consequence of reduced expression of CAPRICE (CPC), a direct downstream target of WER. Our observations demonstrate that in addition to their well-known role in cell expansion, BRs play an essential role in directing cell fate.

  3. Arabidopsis Heterotrimeric G-protein Regulates Cell Wall Defense and Resistance to Necrotrophic Fungi

    Institute of Scientific and Technical Information of China (English)

    Magdalena Delcado-Cerezo; Paul Schulze-Lefert; Shauna Somerville; José Manuel Estevez; Staffan Persson; Antonio Molina; Clara Sánchez-Rodríguez; Viviana Escudero; Eva Miedes; Paula Virginia Fernández; Lucía Jordá; Camilo Hernández-Blanco; Andrea Sánchez-Vallet; Pawel Bednarek

    2012-01-01

    The Arabidopsis heterotrimeric G-protein controls defense responses to necrotrophic and vascular fungi.The agb1 mutant impaired in the Gβ subunit displays enhanced susceptibility to these pathogens.Gβ/AGB1 forms an obligate dimer with either one of the Arabidopsis Gγ subunits (γ1/AGG1 and γ2/AGG2).Accordingly,we now demonstrate that the agg1 agg2 double mutant is as susceptible as agb1 plants to the necrotrophic fungus Plectosphaerella cucumerina.To elucidate the molecular basis of heterotrimeric G-protein-mediated resistance,we performed a comparative transcriptomic analysis of agb1-1 mutant and wild-type plants upon inoculation with P cucumerina.This analysis,together with metabolomic studies,demonstrated that G-protein-mediated resistance was independent of defensive pathways required for resistance to necrotrophic fungi,such as the salicylic acid,jasmonic acid,ethylene,abscisic acid,and tryptophan-derived metabolites signaling,as these pathways were not impaired in agb1 and agg1 agg2 mutants.Notably,many mis-regulated genes in agb1 plants were related with cell wall functions,which was also the case in agg1 agg2 mutant.Biochemical analyses and Fourier Transform InfraRed (FTIR) spectroscopy of cell walls from G-protein mutants revealed that the xylose content was lower in agb1 and agg1 agg2 mutants than in wild-type plants,and that mutant walls had similar FTIR spectratypes,which differed from that of wild-type plants.The data presented here suggest a canonical functionality of the Gβ and Gγ1/γ2 subunits in the control of Arabidopsis immune responses and the regulation of cell wall composition.

  4. Arabidopsis thaliana Somatic Embryogenesis Receptor Kinase I protein is present in sporophytic and gametophytic cells and undergoes endocytosis

    NARCIS (Netherlands)

    Kwaaitaal, M.A.C.J.; Vries, de S.C.; Russinova, E.T.

    2005-01-01

    Arabidopsis thaliana plants expressing AtSERK1 fused to yellow-fluorescent protein were generated. Fluorescence was detected predominantly at the cell periphery, most likely the plasma membrane, of cells in ovules, embryo sacs, anthers, and embryos and in seedlings. The AtSERK1 protein was detected

  5. Antiproliferation and induction of apoptosis by Moringa oleifera leaf extract on human cancer cells.

    Science.gov (United States)

    Sreelatha, S; Jeyachitra, A; Padma, P R

    2011-06-01

    Medicinal plants provide an inexhaustible source of anticancer drugs in terms of both variety and mechanism of action. Induction of apoptosis is the key success of plant products as anticancer agents. The present study was designed to determine the antiproliferative and apoptotic events of Moringa oleifera leaf extract (MLE) using human tumor (KB) cell line as a model system. KB cells were cultured in the presence of leaf extracts at various concentrations for 48 h and the percentage of cell viability was evaluated by MTT assay. MLE showed a dose-dependent inhibition of cell proliferation of KB cells. The antiproliferative effect of MLE was also associated with induction of apoptosis as well as morphological changes and DNA fragmentation. The morphology of apoptotic nuclei was quantified using DAPI and propidium iodide staining. The degree of DNA fragmentation was analyzed using agarose gel electrophoresis. In addition, MLE at various concentrations was found to induce ROS production suggesting modulation of redox-sensitive mechanism. Eventually, HPTLC analysis indicated the presence of phenolics such as quercetin and kaempferol. Thus, these findings suggest that the leaf extracts from M. oleifera had strong antiproliferation and potent induction of apoptosis. Thus, it indicates that M. oleifera leaf extracts has potential for cancer chemoprevention and can be claimed as a therapeutic target for cancer.

  6. Leaf anatomy of Cinnamomum schaeffer (Lauraceae) with special reference to oil and mucilage cells

    OpenAIRE

    Bakker, M.E.; Gerritsen, A.F.; Schaaf, van der, Martijn

    1992-01-01

    The morphology and distribution patterns of oil and mucilage cells in the leaf of 150 species of Cinnamomum are described. Idioblasts are always present in the palisade and the spongy parenchyma. Usually both oil and mucilage cells occur; in some species either oil or mucilage cells are present. Both types of idioblasts possess a suberized wall layer. The idioblasts vary between species in size/ shape, stainability and number. Variations in the distribution pattern can partly be explained by ...

  7. The organization pattern of root border-like cells of Arabidopsis is dependent on cell wall homogalacturonan.

    Science.gov (United States)

    Durand, Caroline; Vicré-Gibouin, Maïté; Follet-Gueye, Marie Laure; Duponchel, Ludovic; Moreau, Myriam; Lerouge, Patrice; Driouich, Azeddine

    2009-07-01

    Border-like cells are released by Arabidopsis (Arabidopsis thaliana) root tips as organized layers of several cells that remain attached to each other rather than completely detached from each other, as is usually observed in border cells of many species. Unlike border cells, cell attachment between border-like cells is maintained after their release into the external environment. To investigate the role of cell wall polysaccharides in the attachment and organization of border-like cells, we have examined their release in several well-characterized mutants defective in the biosynthesis of xyloglucan, cellulose, or pectin. Our data show that among all mutants examined, only quasimodo mutants (qua1-1 and qua2-1), which have been characterized as producing less homogalacturonan, had an altered border-like cell phenotype as compared with the wild type. Border-like cells in both lines were released as isolated cells separated from each other, with the phenotype being much more pronounced in qua1-1 than in qua2-1. Further analysis of border-like cells in the qua1-1 mutant using immunocytochemistry and a set of anti-cell wall polysaccharide antibodies showed that the loss of the wild-type phenotype was accompanied by (1) a reduction in homogalacturonan-JIM5 epitope in the cell wall of border-like cells, confirmed by Fourier transform infrared microspectrometry, and (2) the secretion of an abundant mucilage that is enriched in xylogalacturonan and arabinogalactan-protein epitopes, in which the cells are trapped in the vicinity of the root tip.

  8. Evaluation of diel patterns of relative changes in cell turgor of tomato plants using leaf patch clamp pressure probes

    NARCIS (Netherlands)

    Lee, K.M.; Driever, S.M.; Heuvelink, E.; Rüger, S.; Zimmermann, U.; Gelder, de A.; Marcelis, L.F.M.

    2012-01-01

    Relative changes in cell turgor of leaves of well-watered tomato plants were evaluated using the leaf patch clamp pressure probe (LPCP) under dynamic greenhouse climate conditions. Leaf patch clamp pressure changes, a measure for relative changes in cell turgor, were monitored at three different hei

  9. H2O2-induced Leaf Cell Death and the Crosstalk of Reactive Nitric/Oxygen Species([F])

    Institute of Scientific and Technical Information of China (English)

    Yiqin Wang; Aihong Lin; Gary J.Loake; Chengcai Chu

    2013-01-01

    In plants,the chloroplast is the main reactive oxygen species (ROS) producing site under high light stress.Catalase (CAT),which decomposes hydrogen peroxide (H2O2),is one of the controlling enzymes that maintains leaf redox homeostasis.The catalase mutants with reduced leaf catalase activity from different plant species exhibit an H2O2-induced leaf cell death phenotype.This phenotype was differently affected by light intensity or photoperiod,which may be caused by plant species,leaf redox status or growth conditions.In the rice CAT mutant nitric oxide excess 1 (noe1),higher H2O2 levels induced the generation of nitric oxide (NO) and higher S-nitrosothiol (SNO) levels,suggesting that NO acts as an important endogenous mediator in H2O2-induced leaf cell death.As a free radical,NO could also react with other intracellular and extracellular targets and form a series of related molecules,collectively called reactive nitrogen species (RNS).Recent studies have revealed that both RNS and ROS are important partners in plant leaf cell death.Here,we summarize the recent progress on H2O2-induced leaf cell death and the crosstalk of RNS and ROS signals in the plant hypersensitive response (HR),leaf senescence,and other forms of leaf cell death triggered by diverse environmental conditions.

  10. Identification and characterization of inward K ~+-channels in plasma membranes of Arabidopsis root cortex cells

    Institute of Scientific and Technical Information of China (English)

    于川江; 武维华

    1999-01-01

    Patch clamping whole-cell reeording techniques were apphed to study the inward K+ channels in Arabidopsis root cortex cells. The inward K+-channels in the plasma membranes of the root cortex cell protoplasts were activated by hyperpolarized membrane potentials. The channels were highly selective tor K+ ions over Na+ ions. The channel activity was significantly inbibited by the external TEA(?) or Ba(?) The changes in cytoplasmic Ca2+ concentrations did not affect the whole-cell inward K+-currents. The possible asso(?)ation betw(?)en the channel selectivity to K+ and Na(?) ions and plant salt-tolerance was also discussed.

  11. Cytoskeletal arrangement and its intercellular connection in wheat young leaf cells

    Institute of Scientific and Technical Information of China (English)

    SEIXIANGYUN; LINGCHENGJIAN

    1993-01-01

    By using the techniques of partial digestion of cell wall and selective extraction,we examined the cytoskeleton of wheat yong leaf cells under scanning electron microscope(SEM).A 3-dimensional cytoskeletal system,showing some new features,was observed.The cortical network located beneath the cross wall was an anastomosing organization.The association of nucleus with the cell wall by some skeletal filaments was also found.It is notice able that there were cytoskeletal filaments,which passed through cell wall and connected together with cytoskeletal arrays of adjacent cells,Thus,it is possible that an integral skeletal network existed within the yong leaf tissue of wheat.

  12. JACKDAW controls epidermal patterning in the Arabidopsis root meristem through a non-cell-autonomous mechanism.

    Science.gov (United States)

    Hassan, Hala; Scheres, Ben; Blilou, Ikram

    2010-05-01

    In Arabidopsis, specification of the hair and non-hair epidermal cell types is position dependent, in that hair cells arise over clefts in the underlying cortical cell layer. Epidermal patterning is determined by a network of transcriptional regulators that respond to an as yet unknown cue from underlying tissues. Previously, we showed that JACKDAW (JKD), a zinc finger protein, localizes in the quiescent centre and the ground tissue, and regulates tissue boundaries and asymmetric cell division by delimiting SHORT-ROOT movement. Here, we provide evidence that JKD controls position-dependent signals that regulate epidermal-cell-type patterning. JKD is required for appropriately patterned expression of the epidermal cell fate regulators GLABRA2, CAPRICE and WEREWOLF. Genetic interaction studies indicate that JKD operates upstream of the epidermal patterning network in a SCRAMBLED (SCM)-dependent fashion after embryogenesis, but acts independent of SCM in embryogenesis. Tissue-specific induction experiments indicate non-cell-autonomous action of JKD from the underlying cortex cell layer to specify epidermal cell fate. Our findings are consistent with a model where JKD induces a signal in every cortex cell that is more abundant in the hair cell position owing to the larger surface contact of cells located over a cleft.

  13. Analysis of chlorophyll fluorescence reveals stage specific patterns of chloroplast-containing cells during Arabidopsis embryogenesis.

    Science.gov (United States)

    Tejos, Ricardo I; Mercado, Ana V; Meisel, Lee A

    2010-01-01

    The basic body plan of a plant is established early in embryogenesis when cells differentiate, giving rise to the apical and basal regions of the embryo. Using chlorophyll fluorescence as a marker for chloroplasts, we have detected specific patterns of chloroplast-containing cells at specific stages of embryogenesis. Non-randomly distributed chloroplast-containing cells are seen as early as the globular stage of embryogenesis in Arabidopsis. In the heart stage of embryogenesis, chloroplast containing cells are detected in epidermal cells as well as a central region of the heart stage embryo, forming a triangular septum of chloroplast-containing cells that divides the embryo into three equal sectors. Torpedo stage embryos have chloroplast-containing epidermal cells and a central band of chloroplast-containing cells in the cortex layer, just below the shoot apical meristem. In the walking-stick stage of embryogenesis, chloroplasts are present in the epidermal, cortex and endodermal cells. The chloroplasts appear reduced or absent from the provascular and columella cells of walking-stick stage embryos. These results suggest that there is a tight regulation of plastid differentiation during embryogenesis that generates specific patterns of chloroplast-containing cells in specific cell layers at specific stages of embryogenesis.

  14. Ginkgo biloba leaf extract induces DNA damage by inhibiting topoisomerase II activity in human hepatic cells.

    Science.gov (United States)

    Zhang, Zhuhong; Chen, Si; Mei, Hu; Xuan, Jiekun; Guo, Xiaoqing; Couch, Letha; Dobrovolsky, Vasily N; Guo, Lei; Mei, Nan

    2015-09-30

    Ginkgo biloba leaf extract has been shown to increase the incidence in liver tumors in mice in a 2-year bioassay conducted by the National Toxicology Program. In this study, the DNA damaging effects of Ginkgo biloba leaf extract and many of its constituents were evaluated in human hepatic HepG2 cells and the underlying mechanism was determined. A molecular docking study revealed that quercetin, a flavonoid constituent of Ginkgo biloba, showed a higher potential to interact with topoisomerase II (Topo II) than did the other Ginkgo biloba constituents; this in silico prediction was confirmed by using a biochemical assay to study Topo II enzyme inhibition. Moreover, as measured by the Comet assay and the induction of γ-H2A.X, quercetin, followed by keampferol and isorhamnetin, appeared to be the most potent DNA damage inducer in HepG2 cells. In Topo II knockdown cells, DNA damage triggered by Ginkgo biloba leaf extract or quercetin was dramatically decreased, indicating that DNA damage is directly associated with Topo II. DNA damage was also observed when cells were treated with commercially available Ginkgo biloba extract product. Our findings suggest that Ginkgo biloba leaf extract- and quercetin-induced in vitro genotoxicity may be the result of Topo II inhibition.

  15. Ginkgo biloba leaf extract induces DNA damage by inhibiting topoisomerase II activity in human hepatic cells.

    Science.gov (United States)

    Zhang, Zhuhong; Chen, Si; Mei, Hu; Xuan, Jiekun; Guo, Xiaoqing; Couch, Letha; Dobrovolsky, Vasily N; Guo, Lei; Mei, Nan

    2015-01-01

    Ginkgo biloba leaf extract has been shown to increase the incidence in liver tumors in mice in a 2-year bioassay conducted by the National Toxicology Program. In this study, the DNA damaging effects of Ginkgo biloba leaf extract and many of its constituents were evaluated in human hepatic HepG2 cells and the underlying mechanism was determined. A molecular docking study revealed that quercetin, a flavonoid constituent of Ginkgo biloba, showed a higher potential to interact with topoisomerase II (Topo II) than did the other Ginkgo biloba constituents; this in silico prediction was confirmed by using a biochemical assay to study Topo II enzyme inhibition. Moreover, as measured by the Comet assay and the induction of γ-H2A.X, quercetin, followed by keampferol and isorhamnetin, appeared to be the most potent DNA damage inducer in HepG2 cells. In Topo II knockdown cells, DNA damage triggered by Ginkgo biloba leaf extract or quercetin was dramatically decreased, indicating that DNA damage is directly associated with Topo II. DNA damage was also observed when cells were treated with commercially available Ginkgo biloba extract product. Our findings suggest that Ginkgo biloba leaf extract- and quercetin-induced in vitro genotoxicity may be the result of Topo II inhibition. PMID:26419945

  16. Flat leaf formation realized by cell-division control and mutual recessive gene regulation.

    Science.gov (United States)

    Hayakawa, Yoshinori; Tachikawa, Masashi; Mochizuki, Atsushi

    2016-09-01

    Most of the land plants generally have dorsoventrally flat leaves, maximizing the surface area of both upper (adaxial) side and lower (abaxial) side. The former is specialized for light capturing for photosynthesis and the latter is specialized for gas exchange. From findings of molecular genetics, it has been considered that the coupled dynamics between tissue morphogenesis and gene regulation for cell identity is responsible for making flat leaves. The hypothesis claims that a flat leaf is generated under two assumptions, (i) two mutually recessive groups of genes specify adaxial and abaxial sides of a leaf, (ii) cell divisions are induced at the limited region in the leaf margin where both of two groups are expressed. We examined the plausibility and possibility of this hypothesis from the dynamical point of view. We studied a mathematical model where two processes are coupled, tissue morphogenesis induced by cell division and deformation, and dynamics of gene regulations. From the analysis of the model we found that the classically believed hypothesis is not sufficient to generate flat leaves with high probability. We examined several different modifications and revision of the model. Then we found that a simple additional rule of polarized cell division facilitates flat leaf formation. The result of our analysis gives prediction of possible mechanism, which can be easily verified in experiments. PMID:27287339

  17. AtPGL3 is an Arabidopsis BURP domain protein that is localized to the cell wall and promotes cell enlargement

    OpenAIRE

    Park, Jiyoung; Cui, Yong; Kang, Byung-Ho

    2015-01-01

    The BURP domain is a plant-specific domain that has been identified in secretory proteins, and some of these are involved in cell wall modification. The tomato polygalacturonase I complex involved in pectin degradation in ripening fruits has a non-catalytic subunit that has a BURP domain. This protein is called polygalacturonase 1 beta (PG1β) and the Arabidopsis genome encodes three proteins that exhibit strong amino acid similarities with PG1β? We generated Arabidopsis lines in which express...

  18. Genetic ablation of root cap cells in Arabidopsis

    OpenAIRE

    Tsugeki, Ryuji; Fedoroff, Nina V.

    1999-01-01

    The root cap is increasingly appreciated as a complex and dynamic plant organ. Root caps sense and transmit environmental signals, synthesize and secrete small molecules and macromolecules, and in some species shed metabolically active cells. However, it is not known whether root caps are essential for normal shoot and root development. We report the identification of a root cap-specific promoter and describe its use to genetically ablate root caps by directing root cap-specific expression of...

  19. Leaf-shape remodeling: programmed cell death in fistular leaves of Allium fistulosum.

    Science.gov (United States)

    Ni, Xi-Lu; Su, Hui; Zhou, Ya-fu; Wang, Feng-Hua; Liu, Wen-Zhe

    2015-03-01

    Some species of Allium in Liliaceae have fistular leaves. The fistular lamina of Allium fistulosum undergoes a process from solid to hollow during development. The aims were to reveal the process of fistular leaf formation involved in programmed cell death (PCD) and to compare the cytological events in the execution of cell death to those in the unusual leaf perforations or plant aerenchyma formation. In this study, light and transmission electron microscopy were used to characterize the development of fistular leaves and cytological events. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays and gel electrophoresis were used to determine nuclear DNA cleavage during the PCD. The cavity arises in the leaf blade by degradation of specialized cells, the designated pre-cavity cells, in the center of the leaves. Nuclei of cells within the pre-cavity site become TUNEL-positive, indicating that DNA cleavage is an early event. Gel electrophoresis revealed that DNA internucleosomal cleavage occurred resulting in a characteristic DNA ladder. Ultrastructural analysis of cells at the different stages showed disrupted vacuoles, misshapen nuclei with condensed chromatin, degraded cytoplasm and organelles and emergence of secondary vacuoles. The cell walls degraded last, and residue of degraded cell walls aggregated together. These results revealed that PCD plays a critical role in the development of A. fistulosum fistular leaves. The continuous cavity in A. fistulosum leaves resemble the aerenchyma in the pith of some gramineous plants to improve gas exchange.

  20. Investigating the Molecular Mechanism of TSO1 Function in Arabidopsis cell division and meristem development

    Energy Technology Data Exchange (ETDEWEB)

    Zhongchi Liu

    2004-10-01

    Unlike animals, plants are constantly exposed to environmental mutagens including ultraviolet light and reactive oxygen species. Further, plant cells are totipotent with highly plastic developmental programs. An understanding of molecular mechanisms underlying the ability of plants to monitor and repair its DNA and to eliminate damaged cells are of great importance. Previously we have identified two genes, TSO1 and TSO2, from a flowering plant Arabidopsis thaliana. Mutations in these two genes cause callus-like flowers, fasciated shoot apical meristems, and abnormal cell division, indicating that TSO1 and TSO2 may encode important cell cycle regulators. Previous funding from DOE led to the molecular cloning of TSO1, which was shown to encode a novel nuclear protein with two CXC domains suspected to bind DNA. This DOE grant has allowed us to characterize and isolate TSO2 that encodes the small subunit of the ribonucleotide reductase (RNR). RNR comprises two large subunits (R1) an d two small subunits (R2), catalyzes a rate-limiting step in the production of deoxyribonucleotides needed for DNA replication and repair. Previous studies in yeast and mammals indicated that defective RNR often led to cell cycle arrest, growth retardation and p53-dependent apoptosis while abnormally elevated RNR activities led to higher mutation rates. Subsequently, we identified two additional R2 genes, R2A and R2B in the Arabidopsis genome. Using reverse genetics, mutations in R2A and R2B were isolated, and double and triple mutants among the three R2 genes (TSO2, R2A and R2B) were constructed and analyzed. We showed that Arabidopsis tso2 mutants, with reduced dNTP levels, were more sensitive to UV-C. While r2a or r2b single mutants did not exhibit any phenotypes, tso2 r2b double mutants were embryonic lethal and tso2 r2a double mutants were seedling lethal indicating redundant functions among the three R2 genes. Furthermore, tso2 r2a double mutants exhibited increased DNA dam age

  1. Arabidopsis CDS blastp result: AK243493 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK243493 J100074A10 At2g23380.1 68415.m02792 curly leaf protein (CURLY LEAF) / poly...comb-group protein identical to polycomb group [Arabidopsis thaliana] GI:1903019 (curly leaf); contains Pfam profile PF00856: SET domain 0.0 ...

  2. Arabidopsis CDS blastp result: AK111743 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK111743 J023052J10 At2g23380.1 curly leaf protein (CURLY LEAF) / polycomb-group pr...otein identical to polycomb group [Arabidopsis thaliana] GI:1903019 (curly leaf); contains Pfam profile PF00856: SET domain 3e-22 ...

  3. The dynamics of plant cell-wall polysaccharide decomposition in leaf-cutting ant fungus gardens

    DEFF Research Database (Denmark)

    Moller, Isabel Eva; de Fine Licht, Henrik Hjarvard; Harholt, Jesper;

    2011-01-01

    The degradation of live plant biomass in fungus gardens of leaf-cutting ants is poorly characterised but fundamental for understanding the mutual advantages and efficiency of this obligate nutritional symbiosis. Controversies about the extent to which the garden-symbiont Leucocoprinus gongylophorus......, to map the occurrence of cell wall polymers in consecutive sections of the fungus garden of the leaf-cutting ant Acromyrmex echinatior. We show that pectin, xyloglucan and some xylan epitopes are degraded, whereas more highly substituted xylan and cellulose epitopes remain as residuals in the waste...

  4. Tape-Arabidopsis Sandwich - a simpler Arabidopsis protoplast isolation method

    Directory of Open Access Journals (Sweden)

    Lee Shu-Hong

    2009-11-01

    Full Text Available Abstract Background Protoplasts isolated from leaves are useful materials in plant research. One application, the transient expression of recombinant genes using Arabidopsis mesophyll protoplasts (TEAMP, is currently commonly used for studies of subcellular protein localization, promoter activity, and in vivo protein-protein interactions. This method requires cutting leaves into very thin slivers to collect mesophyll cell protoplasts, a procedure that often causes cell damage, may yield only a few good protoplasts, and is time consuming. In addition, this protoplast isolation method normally requires a large number of leaves derived from plants grown specifically under low-light conditions, which may be a concern when material availability is limited such as with mutant plants, or in large scale experiments. Results In this report, we present a new procedure that we call the Tape-Arabidopsis Sandwich. This is a simple and fast mesophyll protoplast isolation method. Two kinds of tape (Time tape adhered to the upper epidermis and 3 M Magic tape to the lower epidermis are used to make a "Tape-Arabidopsis Sandwich". The Time tape supports the top side of the leaf during manipulation, while tearing off the 3 M Magic tape allows easy removal of the lower epidermal layer and exposes mesophyll cells to cell wall digesting enzymes when the leaf is later incubated in an enzyme solution. The protoplasts released into solution are collected and washed for further use. For TEAMP, plasmids carrying a gene expression cassette for a fluorescent protein can be successfully delivered into protoplasts isolated from mature leaves grown under optimal conditions. Alternatively, these protoplasts may be used for bimolecular fluorescence complementation (BiFC to investigate protein-protein interactions in vivo, or for Western blot analysis. A significant advantage of this protocol over the current method is that it allows the generation of protoplasts in less than 1 hr

  5. The cell wall of the Arabidopsis pollen tube--spatial distribution, recycling, and network formation of polysaccharides.

    Science.gov (United States)

    Chebli, Youssef; Kaneda, Minako; Zerzour, Rabah; Geitmann, Anja

    2012-12-01

    The pollen tube is a cellular protuberance formed by the pollen grain, or male gametophyte, in flowering plants. Its principal metabolic activity is the synthesis and assembly of cell wall material, which must be precisely coordinated to sustain the characteristic rapid growth rate and to ensure geometrically correct and efficient cellular morphogenesis. Unlike other model species, the cell wall of the Arabidopsis (Arabidopsis thaliana) pollen tube has not been described in detail. We used immunohistochemistry and quantitative image analysis to provide a detailed profile of the spatial distribution of the major cell wall polymers composing the Arabidopsis pollen tube cell wall. Comparison with predictions made by a mechanical model for pollen tube growth revealed the importance of pectin deesterification in determining the cell diameter. Scanning electron microscopy demonstrated that cellulose microfibrils are oriented in near longitudinal orientation in the Arabidopsis pollen tube cell wall, consistent with a linear arrangement of cellulose synthase CESA6 in the plasma membrane. The cellulose label was also found inside cytoplasmic vesicles and might originate from an early activation of cellulose synthases prior to their insertion into the plasma membrane or from recycling of short cellulose polymers by endocytosis. A series of strategic enzymatic treatments also suggests that pectins, cellulose, and callose are highly cross linked to each other. PMID:23037507

  6. ROP GTPase-mediated auxin signaling regulates pavement cell interdigitation in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Deshu Lin; Huibo Ren; Ying Fu

    2015-01-01

    In multicel ular plant organs, cel shape formation depends on molecular switches to transduce developmental or environmental signals and to coordinate cel‐to‐cel communi-cation. Plants have a specific subfamily of the Rho GTPase family, usual y cal ed Rho of Plants (ROP), which serve as a critical signal transducer involved in many cel ular processes. In the last decade, important advances in the ROP‐mediated regulation of plant cel morphogenesis have been made by using Arabidopsis thaliana leaf and cotyledon pavement cel s. Especial y, the auxin‐ROP signaling networks have been demonstrated to control interdigitated growth of pavement cel s to form jigsaw‐puzzle shapes. Here, we review findings related to the discovery of this novel auxin‐signaling mecha-nism at the cel surface. This signaling pathway is to a large extent independent of the wel‐known Transport Inhibitor Response (TIR)–Auxin Signaling F‐Box (AFB) pathway, and instead requires Auxin Binding Protein 1 (ABP1) interaction with the plasma membrane‐localized, transmembrane kinase (TMK) receptor‐like kinase to regulate ROP proteins. Once activated, ROP influences cytoskeletal organization and inhibits endocytosis of the auxin transporter PIN1. The present review focuses on ROP signaling and its self‐organizing feature al owing ROP proteins to serve as a bustling signal decoder and integrator for plant cel morphogenesis.

  7. Cell pattern in the Arabidopsis root epidermis determined by lateral inhibition with feedback.

    Science.gov (United States)

    Lee, Myeong Min; Schiefelbein, John

    2002-03-01

    In the root epidermis of Arabidopsis, hair and nonhair cell types are specified in a distinct position-dependent pattern. Here, we show that transcriptional feedback loops between the WEREWOLF (WER), CAPRICE (CPC), and GLABRA2 (GL2) genes help to establish this pattern. Positional cues bias the expression of the WER MYB gene, leading to the induction of CPC and GL2 in cells located in a particular position (N) and adoption of the nonhair fate. The truncated MYB encoded by CPC mediates a lateral inhibition mechanism to negatively regulate WER, GL2, and its own gene in the alternative position (H) to induce the hair fate. These results provide a molecular genetic framework for understanding the determination of a cell-type pattern in plants.

  8. A feedback mechanism controlling SCRAMBLED receptor accumulation and cell-type pattern in Arabidopsis.

    Science.gov (United States)

    Kwak, Su-Hwan; Schiefelbein, John

    2008-12-23

    Cellular pattern formation in the root epidermis of Arabidopsis occurs in a position-dependent manner, generating root-hair (H) cells contacting two underlying cortical cells and nonhair (N) cells contacting one cortical cell. SCRAMBLED (SCM), a leucine-rich repeat receptor-like kinase (LRR-RLK), mediates this process through its effect on a downstream transcription factor regulatory network. After perception of a positional cue, the SCM signaling pathway is proposed to preferentially repress WEREWOLF (WER) transcription factor expression in H cells and thereby bias the outcome of mutual lateral inhibition acting between H and N cells. However, the molecular mechanism responsible for this preferential SCM signaling is unknown. Here, we analyze the distribution of the SCM receptor and the biological effect of altering its accumulation pattern. We find that SCM expression and accumulation in the epidermal cell layer is necessary and sufficient to direct the cell-type pattern. Further, SCM preferentially accumulates in H cells, and this accumulation pattern is dependent on the downstream transcription factors. Thus, SCM participates in an autoregulatory feedback loop, enabling cells engaged in SCM signaling to maintain high levels of SCM receptor, which provides a simple mechanism for reinforcing a bias in receptor-mediated signaling to ensure robust pattern formation.

  9. Microtubules Are Essential for Guard-Cell Function in Vicia and Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    William Eisinger; David Ehrhardt; Winslow Briggs

    2012-01-01

    Radially arranged cortical microtubules are a prominent feature of guard cells.Guard cells expressing GFPtubulin showed consistent changes in the appearance of microtubules when stomata opened or closed.Guard cells showed fewer microtubule structures as stomata closed,whether induced by transfer to darkness,ABA,hydrogen peroxide,or sodium hydrogen carbonate.Guard cells kept in the dark (closed stomata) showed increases in microtubule structures and stomatal aperture on light treatment.GFP-EB1,marking microtubule growing plus ends,showed no change in number of plus ends or velocity of assembly on stomatal closure.Since the number of growing plus ends and the rate of plus-end growth did not change when microtubule structure numbers declined,microtubule instability and/or rearrangement must be responsible for the apparent loss of microtubules.Guard cells with closed stomata showed more cytosolic GFP-fluorescence than those with open stomata as cortical microtubules became disassembled,although with a large net loss in total fluorescence.Microtubule-targeted drugs blocked guard-cell function in Vicia and Arabidopsis.Oryzalin disrupted guard-cell microtubules and prevented stomatal opening and taxol stabilized guard-cell microtubules and delayed stomatal closure.Gas exchange measurements indicated that the transgenes for fluorescent-labeled proteins did not disrupt normal stomatal function.These dynamic changes in guard-cell microtubules combined with our inhibitor studies provide evidence for an active role of microtubules in guard-cell function.

  10. Hydrogen Peroxide-induced Cell Death in Arabidopsis : Transcriptional and Mutant Analysis Reveals a Role of an Oxoglutarate-dependent Dioxygenase Gene in the Cell Death Process

    NARCIS (Netherlands)

    Gechev, Tsanko S.; Minkov, Ivan N.; Hille, Jacques

    2005-01-01

    Hydrogen peroxide is a major regulator of plant programmed cell death (PCD) but little is known about the downstream genes from the H2O2-signaling network that mediate the cell death. To address this question, a novel system for studying H2O2-induced programmed cell death in Arabidopsis thaliana was

  11. Motile apparatus in Vallisneria leaf cells. I. Organization of microfilaments.

    Science.gov (United States)

    Yamaguchi, Y; Nagai, R

    1981-04-01

    The organization of the microfilaments in epidermal cells of Vallisneria leaves was investigated with respect to the induction of cytoplasmic streaming (secondary streaming). In many of the epidermal cells, cytoplasm exhibited rotational streaming along the anticlinal wall of the cell after exposure around the anticlinal wall. The bundles were arrayed in parallel to the streaming direction. They were recognized usually as 10-40 closely packed dense dots in cross-section. The spacing between bundles was not even. Bundles tended to form groups of 4 to 5 in which the spacing between bundles was usually 0.3 to 0.5 micrometer. The microfilaments were identified as F-actin. Together with the fact that rotational streaming in Vallisneria cells by cytochalasin B, the motile mechanism of secondary streaming was concluded to be similar in its essential features to the cytoplasmic streaming seen in Characean cell (primary streaming). In epidermal cells that had been kept under low-intensity light the cytoplasm and the cytoplasmic streaming occurred in these cells. The bundles of microfilaments remained in the very thin layer of cytoplasm lining the anticlinal wall, although they were fewer and somewhat loosely packed. EGTA at appropriate concentration could induce cytoplasmic streaming in these cells. The mechanism of the induction is discussed on the basis of the effectiveness of EGTA and the requirement of a low concentration of free Ca2+ for cytoplasmic streaming in Characean cells. PMID:6792210

  12. AtGRIP protein locates to the secretory vesicles of trans Golgi-network in Arabidopsis root cap cells

    Institute of Scientific and Technical Information of China (English)

    CHEN Ying; ZHANG Wei; ZHAO Lei; LI Yan

    2008-01-01

    GRIP domain proteins, locating to the trans-Golgi network, are thought to play an essential role in Golgi apparatus trafficking in yeast and animal cells. In the present study, AtGRIP cDNA was amplified by reverse transcriptase PCR from RNA isolated from Arabidopsis seedling. The GST fusion protein of AtGRIP was affinity-purified and its rabbit polyclonal antibody was obtained. Immuno-blotting with the purified anti-AtGRIP polyclonal antibody demonstrated that the molecular mass of AtGRIP protein is about 92 kD, and its expression is not tissue-specific in Arabidopsis. Immunoflourescent labeling and confocal microscopy revealed that the AtGRIP protein was co-localized with Golgi stacks in Arabidop-sis root cells. Immuno-gold labeling and electron microscopy observation showed that AtGRIP protein was mainly located to the membrane of the secretory vesicles of trans-Golgi network in Arabidopsis root cap cells. Taken together, these results indicate that the localization of GRIP domain proteins be-tween plants and animal cells are conserved. These results also suggest that the AtGRIP may be in-volved in regulating the formation or sorting of Golgi-associated vesicles in plant cells.

  13. Apoplastic Alkalinization Is Instrumental for the Inhibition of Cell Elongation in the Arabidopsis Root by the Ethylene Precursor 1-Aminocyclopropane-1-Carboxylic Acid

    NARCIS (Netherlands)

    Staal, Marten; De Cnodder, Tinne; Simon, Damien; Vandenbussche, Filip; Van Der Straeten, Dominique; Verbelen, Jean-Pierre; Elzenga, Theo; Vissenberg, Kris

    2011-01-01

    In Arabidopsis (Arabidopsis thaliana; Columbia-0) roots, the so-called zone of cell elongation comprises two clearly different domains: the transition zone, a postmeristematic region (approximately 200-450 mu m proximal of the root tip) with a low rate of elongation, and a fast elongation zone, the

  14. Involvement of sphingoid bases in mediating reactive oxygen intermediate production and programmed cell death in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Lihua Shi; Yusuf A Hannun; Jianru Zuo; Jacek Bielawski; Jinye Mu; Haili Dong; Chong Teng; Jian Zhang; Xiaohui Yang; Nario Tomishige; Kentaro Hanada

    2007-01-01

    Sphingolipids have been suggested to act as second messengers for an array of cellular signaling activities in plant cells, including stress responses and programmed cell death (PCD). However, the mechanisms underpinning these processes are not well understood. Here, we report that an Arabidopsis mutant, fumonisin Bl resistant11-1 (fbr11-1), which fails to generate reactive oxygen intermediates (ROIs), is incapable of initiating PCD when the mutant is challenged by fumonisin B1 (FB1), a specific inhibitor of ceramide synthase. Molecular analysis indicated that FBR11 encodes a long-chain basel (LCB1) subunit of serine palmitoyltransferase (SPT), which catalyzes the first rate-limiting step of de novo sphingolipid synthesis. Mass spectrometric analysis of the sphingolipid concentrations revealed that whereas the fbrll-1 mutation did not affect basal levels of sphingoid bases, the mutant showed attenuated formation of sphingoid bases in response to FB1 By a direct feeding experiment, we show that the free sphingoid bases dihydrosphingosine, phytosphingosine and sphingosine efficiently induce ROI generation followed by cell death. Conversely, ROI generation and cell death induced by dihydrosphingosine were specifically blocked by its phosphorylated form dihydrosphingosine-1 -phosphate in a dose-dependent manner, suggesting that the maintenance of homeostasis between a free sphingoid base and its phosphorylated derivative is critical to determining the cell fate. Because alterations of the sphingolipid level occur prior to the ROI production, we propose that the free sphingoid bases are involved in the control of PCD in Arabidopsis, presumably through the regulation of the ROI level upon receiving different developmental or environmental cues.

  15. Cis-Regulatory Elements Determine Germline Specificity and Expression Level of an Isopentenyltransferase Gene in Sperm Cells of Arabidopsis.

    Science.gov (United States)

    Zhang, Jinghua; Yuan, Tong; Duan, Xiaomeng; Wei, Xiaoping; Shi, Tao; Li, Jia; Russell, Scott D; Gou, Xiaoping

    2016-03-01

    Flowering plant sperm cells transcribe a divergent and complex complement of genes. To examine promoter function, we chose an isopentenyltransferase gene known as PzIPT1. This gene is highly selectively transcribed in one sperm cell morphotype of Plumbago zeylanica, which preferentially fuses with the central cell during fertilization and is thus a founding cell of the primary endosperm. In transgenic Arabidopsis (Arabidopsis thaliana), PzIPT1 promoter displays activity in both sperm cells and upon progressive promoter truncation from the 5'-end results in a progressive decrease in reporter production, consistent with occurrence of multiple enhancer sites. Cytokinin-dependent protein binding motifs are identified in the promoter sequence, which respond with stimulation by cytokinin. Expression of PzIPT1 promoter in sperm cells confers specificity independently of previously reported Germline Restrictive Silencer Factor binding sequence. Instead, a cis-acting regulatory region consisting of two duplicated 6-bp Male Gamete Selective Activation (MGSA) motifs occurs near the site of transcription initiation. Disruption of this sequence-specific site inactivates expression of a GFP reporter gene in sperm cells. Multiple copies of the MGSA motif fused with the minimal CaMV35S promoter elements confer reporter gene expression in sperm cells. Similar duplicated MGSA motifs are also identified from promoter sequences of sperm cell-expressed genes in Arabidopsis, suggesting selective activation is possibly a common mechanism for regulation of gene expression in sperm cells of flowering plants. PMID:26739233

  16. The Changes of Photosynthetic Properties and Cell Microstructure in Peanut Leaves during Leaf Senescence

    Institute of Scientific and Technical Information of China (English)

    LI Xiang-dong; WANG Xiao-yun; YU Song-lie; ZHANG Gao-ying; WAN Yong-shan; LI Jun

    2002-01-01

    The changes of photosynthetic properties and cell microstructure in peanut leaves during leaf senescence were studied with two high-yielding peanut cultivars (cv. Luhua11 and Fu8707). The main results showed that during the whole process of leaf growth and senescence, changes in the photosynthesis rate (Pn)and contents of chlorophyll in leaves, could be described with a parabolic function, y = A + Bx + Cx2 (where y refers to the values of the above parameters and x to the days after leaf unfolding). During peanut leaf senescence, the shape of chloroplast changed gradually from long ellipses to circles. The starch globule in chloroplast altered gradually from more and larger sizes to fewer and smaller, but the oil globule from fewer and smaller to more and larger. The grana lamellae varied progressively: from thinness and length to thickness and shortness; from ranking along the long axle direction of chloroplast to disorderly arrangment and finally blurring.At last, the membrane envelope of chloroplast broke, so the inclusion seeped out to the cell and the chloroplast broke up.

  17. Proteomic characterization of golgi membranes enriched from Arabidopsis suspension cell cultures

    DEFF Research Database (Denmark)

    Hansen, Sara Fasmer; Ebert, Berit; Rautengarten, Carsten;

    2016-01-01

    from an Arabidopsis cell suspension culture that can be used to investigate the proteome of this organelle. We also provide a useful workflow for the examination of proteomic data as the result of multiple analyses. Finally, we highlight a simple technique to validate the subcellular localization......The plant Golgi apparatus has a central role in the secretory pathway and is the principal site within the cell for the assembly and processing of macromolecules. The stacked membrane structure of the Golgi apparatus along with its interactions with the cytoskeleton and endoplasmic reticulum has...... historically made the isolation and purification of this organelle difficult. Density centrifugation has typically been used to enrich Golgi membranes from plant microsomal preparations, and aside from minor adaptations, the approach is still widely employed. Here we outline the enrichment of Golgi membranes...

  18. Quantitative proteome changes in Arabidopsis thaliana suspension-cultured cells in response to plant natriuretic peptides

    KAUST Repository

    Turek, Ilona

    2015-06-30

    Proteome changes in the Arabidopsis thaliana suspension cells in response to the A. thaliana plant natriuretic peptide (PNP), AtPNP-A (At2g18660) were assessed using quantitative proteomics employing tandem mass tag (TMT) labeling and tandem mass spectrometry (LC–MS/MS). In this study, we characterized temporal responses of suspension-cultured cells to 1 nM and 10 pM AtPNP-A at 0, 10 and 30 min post-treatment. Both concentrations we found to yield a distinct differential proteome signature. The data shown in this article are associated with the article “Plant natriuretic peptides induce a specific set of proteins diagnostic for an adaptive response to abiotic stress” by Turek et al. (Front. Plant Sci. 5 (2014) 661) and have been deposited to the ProteomeXchange with identifier PXD001386.

  19. Substitution of L-fucose by L-galactose in cell walls of arabidopsis mur1

    Energy Technology Data Exchange (ETDEWEB)

    Zablackis, E.; York, W.S.; Pauly, M. [Univ. of Georgia, Athens (United States)

    1996-06-21

    An Arabidopsis thaliana mutant (mur1) has less than 2 percent of the normal amounts of L-fucose in the primary cell walls of aerial portions of the plant. The survival of mur1 plants challenged the hypothesis that fucose is a required component of biologically active oligosaccharides derived from cell wall xyloglucan. However, the replacement of L-fucose (that is, 6-deoxyl-L-galactose) by L-galactose does not detectably alter the biological activity of the oligosaccharides derived from xyloglucan. Thus, essential structural and conformational features of xyloglucan and xyloglucan-derived oligosaccharides are retained when L-galactose replaces L-fucose. 29 refs., 2 figs., 2 tabs.

  20. Quantitative proteome changes in Arabidopsis thaliana suspension-cultured cells in response to plant natriuretic peptides

    Directory of Open Access Journals (Sweden)

    Ilona Turek

    2015-09-01

    Full Text Available Proteome changes in the Arabidopsis thaliana suspension cells in response to the A. thaliana plant natriuretic peptide (PNP, AtPNP-A (At2g18660 were assessed using quantitative proteomics employing tandem mass tag (TMT labeling and tandem mass spectrometry (LC–MS/MS. In this study, we characterized temporal responses of suspension-cultured cells to 1 nM and 10 pM AtPNP-A at 0, 10 and 30 min post-treatment. Both concentrations we found to yield a distinct differential proteome signature. The data shown in this article are associated with the article “Plant natriuretic peptides induce a specific set of proteins diagnostic for an adaptive response to abiotic stress” by Turek et al. (Front. Plant Sci. 5 (2014 661 and have been deposited to the ProteomeXchange with identifier PXD001386.

  1. Arabidopsis FH1 Formin Affects Cotyledon Pavement Cell Shape by Modulating Cytoskeleton Dynamics.

    Science.gov (United States)

    Rosero, Amparo; Oulehlová, Denisa; Stillerová, Lenka; Schiebertová, Petra; Grunt, Michal; Žárský, Viktor; Cvrčková, Fatima

    2016-03-01

    Plant cell morphogenesis involves concerted rearrangements of microtubules and actin microfilaments. We previously reported that FH1, the main Arabidopsis thaliana housekeeping Class I membrane-anchored formin, contributes to actin dynamics and microtubule stability in rhizodermis cells. Here we examine the effects of mutations affecting FH1 (At3g25500) on cell morphogenesis and above-ground organ development in seedlings, as well as on cytoskeletal organization and dynamics, using a combination of confocal and variable angle epifluorescence microscopy with a pharmacological approach. Homozygous fh1 mutants exhibited cotyledon epinasty and had larger cotyledon pavement cells with more pronounced lobes than the wild type. The pavement cell shape alterations were enhanced by expression of the fluorescent microtubule marker GFP-microtubule-associated protein 4 (MAP4). Mutant cotyledon pavement cells exhibited reduced density and increased stability of microfilament bundles, as well as enhanced dynamics of microtubules. Analogous results were also obtained upon treatments with the formin inhibitor SMIFH2 (small molecule inhibitor of formin homology 2 domains). Pavement cell shape in wild-type (wt) and fh1 plants in some situations exhibited a differential response towards anti-cytoskeletal drugs, especially the microtubule disruptor oryzalin. Our observations indicate that FH1 participates in the control of microtubule dynamics, possibly via its effects on actin, subsequently influencing cell morphogenesis and macroscopic organ development. PMID:26738547

  2. Arabidopsis R-SNARE proteins VAMP721 and VAMP722 are required for cell plate formation.

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    Liang Zhang

    Full Text Available BACKGROUND: Cell plate formation during plant cytokinesis is facilitated by SNARE complex-mediated vesicle fusion at the cell-division plane. However, our knowledge regarding R-SNARE components of membrane fusion machinery for cell plate formation remains quite limited. METHODOLOGY/PRINCIPAL FINDINGS: We report the in vivo function of Arabidopsis VAMP721 and VAMP722, two closely sequence-related R-SNAREs, in cell plate formation. Double homozygous vamp721vamp722 mutant seedlings showed lethal dwarf phenotypes and were characterized by rudimentary roots, cotyledons and hypocotyls. Furthermore, cell wall stubs and incomplete cytokinesis were frequently observed in vamp721vamp722 seedlings. Confocal images revealed that green fluorescent protein-tagged VAMP721 and VAMP722 were preferentially localized to the expanding cell plates in dividing cells. Drug treatments and co-localization analyses demonstrated that punctuate organelles labeled with VAMP721 and VAMP722 represented early endosomes overlapped with VHA-a1-labeled TGN, which were distinct from Golgi stacks and prevacuolar compartments. In addition, protein traffic to the plasma membrane, but not to the vacuole, was severely disrupted in vamp721vamp722 seedlings by subcellular localization of marker proteins. CONCLUSION/SIGNIFICANCE: These observations suggest that VAMP721 and VAMP722 are involved in secretory trafficking to the plasma membrane via TGN/early endosomal compartment, which contributes substantially to cell plate formation during plant cytokinesis.

  3. The inhibition of Typhonium flagelliforme Lodd. Blume leaf extract on COX-2 expression of WiDr colon cancer cells

    OpenAIRE

    Agustina Setiawati; Handika Immanuel; Mery Tri Utami

    2016-01-01

    Objective: To determine the inhibition activity of Typhonium flagelliforme Lodd. Blume (T. flagelliforme) leaf extract on cyclooxygenase 2 (COX-2) expression of colon cancer cells. Methods: T. flagelliforme leaf extract was prepared to macerate in ethyl acetate. In vitro anticancer activity was assayed by MTT method on WiDr colon cancer cells. This study applied apoptosis induction assay to investigate the mechanism of cell death using double staining method. COX-2 expression was stained b...

  4. Involvement of C2H2 zinc finger proteins in the regulation of epidermal cell fate determination in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    An Yan; Minjie Wu; Yongqin Zhao; Aidong Zhang; Bohan Liu; John Schiefelbein; Yinbo Gan

    2014-01-01

    Cell fate determination is a basic developmental process during the growth of multicellular organisms. Trichomes and root hairs of Arabidopsis are both readily accessible structures originating from the epidermal cells of the aerial tissues and roots respectively, and they serve as excellent models for understanding the molecular mecha-nisms controlling cell fate determination and cell morphogen-esis. The regulation of trichome and root hair formation is a complex program that consists of the integration of hormonal signals with a large number of transcriptional factors, including MYB and bHLH transcriptional factors. Studies during recent years have uncovered an important role of C2H2 type zinc finger proteins in the regulation of epidermal cell fate determination. Here in this minireview we briefly summarize the involvement of C2H2 zinc finger proteins in the control of trichome and root hair formation in Arabidopsis.

  5. Variable-angle total internal reflection fluorescence microscopy of intact cells of Arabidopsis thaliana

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    Kim Myung K

    2011-09-01

    Full Text Available Abstract Background Total internal reflection fluorescence microscopy (TIRFM is a powerful tool for observing fluorescently labeled molecules on the plasma membrane surface of animal cells. However, the utility of TIRFM in plant cell studies has been limited by the fact that plants have cell walls, thick peripheral layers surrounding the plasma membrane. Recently, a new technique known as variable-angle epifluorescence microscopy (VAEM was developed to circumvent this problem. However, the lack of a detailed analysis of the optical principles underlying VAEM has limited its applications in plant-cell biology. Results Here, we present theoretical and experimental evidence supporting the use of variable-angle TIRFM in observations of intact plant cells. We show that when total internal reflection occurs at the cell wall/cytosol interface with an appropriate angle of incidence, an evanescent wave field of constant depth is produced inside the cytosol. Results of experimental TIRFM observations of the dynamic behaviors of phototropin 1 (a membrane receptor protein and clathrin light chain (a vesicle coat protein support our theoretical analysis. Conclusions These findings demonstrate that variable-angle TIRFM is appropriate for quantitative live imaging of cells in intact tissues of Arabidopsis thaliana.

  6. Decrease in Leaf Sucrose Synthesis Leads to Increased Leaf Starch Turnover and Decreased RuBP-limited Photosynthesis But Not Rubisco-limited Photosynthesis in Arabidopsis Null Mutants of SPSA1

    Science.gov (United States)

    SPS (Sucrose phosphate synthase) isoforms from dicots cluster into families A, B and C. In this study, we investigated the individual effect of null mutations of each of the four SPS genes in Arabidopsis (spsa1, spsa2, spsb and spsc) on photosynthesis and carbon partitioning. Null mutants spsa1 and ...

  7. Leaf-cutting ant fungi produce cell wall degrading pectinase complexes reminiscent of phytopathogenic fungi

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    Boomsma Jacobus J

    2010-12-01

    Full Text Available Abstract Background Leaf-cutting (attine ants use their own fecal material to manure fungus gardens, which consist of leaf material overgrown by hyphal threads of the basidiomycete fungus Leucocoprinus gongylophorus that lives in symbiosis with the ants. Previous studies have suggested that the fecal droplets contain proteins that are produced by the fungal symbiont to pass unharmed through the digestive system of the ants, so they can enhance new fungus garden growth. Results We tested this hypothesis by using proteomics methods to determine the gene sequences of fecal proteins in Acromyrmex echinatior leaf-cutting ants. Seven (21% of the 33 identified proteins were pectinolytic enzymes that originated from the fungal symbiont and which were still active in the fecal droplets produced by the ants. We show that these enzymes are found in the fecal material only when the ants had access to fungus garden food, and we used quantitative polymerase chain reaction analysis to show that the expression of six of these enzyme genes was substantially upregulated in the fungal gongylidia. These unique structures serve as food for the ants and are produced only by the evolutionarily advanced garden symbionts of higher attine ants, but not by the fungi reared by the basal lineages of this ant clade. Conclusions Pectinolytic enzymes produced in the gongylidia of the fungal symbiont are ingested but not digested by Acromyrmex leaf-cutting ants so that they end up in the fecal fluid and become mixed with new garden substrate. Substantial quantities of pectinolytic enzymes are typically found in pathogenic fungi that attack live plant tissue, where they are known to breach the cell walls to allow the fungal mycelium access to the cell contents. As the leaf-cutting ant symbionts are derived from fungal clades that decompose dead plant material, our results suggest that their pectinolytic enzymes represent secondarily evolved adaptations that are convergent to

  8. The WEREWOLF MYB protein directly regulates CAPRICE transcription during cell fate specification in the Arabidopsis root epidermis.

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    Ryu, Kook Hui; Kang, Yeon Hee; Park, Young-hwan; Hwang, Ildoo; Schiefelbein, John; Lee, Myeong Min

    2005-11-01

    The Arabidopsis root epidermis is composed of two types of cells, hair cells and non-hair cells, and their fate is determined in a position-dependent manner. WEREWOLF (WER), a R2R3 MYB protein, has been shown genetically to function as a master regulator to control both of the epidermal cell fates. To directly test the proposed role of WER in this system, we examined its subcellular localization and defined its transcriptional activation properties. We show that a WER-GFP fusion protein is functional and accumulates in the nucleus of the N-position cells in the Arabidopsis root epidermis, as expected for a transcriptional regulator. We also find that a modified WER protein with a strong activation domain (WER-VP16) promotes the formation of both epidermal cell types, supporting the view that WER specifies both cell fates. In addition, we used the glucocorticoid receptor (GR) inducible system to show that CPC transcription is regulated directly by WER. Using EMSA, we found two WER-binding sites (WBSs; WBSI and WBSII) in the CPC promoter. WER-WBSI binding was confirmed in vivo using the yeast one-hybrid assay. Binding between the WER protein and both WBSs (WBSI and WBSII), and the importance of the two WBSs in CPC promoter activity were confirmed in Arabidopsis. These results provide experimental support for the proposed role of WER as an activator of gene transcription during the specification of both epidermal cell fates.

  9. Assessing the regulation of leaf redox status under water stress conditions in Arabidopsis thaliana: Col-0 ecotype (wild-type and vtc-2), expressing mitochondrial and cytosolic roGFP1.

    Science.gov (United States)

    Brossa, Ricard; Pintó-Marijuan, Marta; Jiang, Keni; Alegre, Leonor; Feldman, Lewis J

    2013-07-01

    Using Arabidopsis plants Col-0 and vtc2 transformed with a redox sensitive green fluorescent protein, (c-roGFP) and (m-roGFP), we investigated the effects of a progressive water stress and re-watering on the redox status of the cytosol and the mitochondria. Our results establish that water stress affects redox status differently in these two compartments, depending on phenotype and leaf age, furthermore we conclude that ascorbate plays a pivotal role in mediating redox status homeostasis and that Col-0 Arabidopsis subjected to water stress increase the synthesis of ascorbate suggesting that ascorbate may play a role in buffering changes in redox status in the mitochondria and the cytosol, with the presumed buffering capacity of ascorbate being more noticeable in young compared with mature leaves. Re-watering of water-stressed plants was paralleled by a return of both the redox status and ascorbate to the levels of well-watered plants. In contrast to the effects of water stress on ascorbate levels, there were no significant changes in the levels of glutathione, thereby suggesting that the regeneration and increase in ascorbate in water-stressed plants may occur by other processes in addition to the regeneration of ascorbate via the glutathione. Under water stress in vtc2 lines it was observed stronger differences in redox status in relation to leaf age, than due to water stress conditions compared with Col-0 plants. In the vtc2 an increase in DHA was observed in water-stressed plants. Furthermore, this work confirms the accuracy and sensitivity of the roGFP1 biosensor as a reporter for variations in water stress-associated changes in redox potentials.

  10. The dynamics of plant cell-wall polysaccharide decomposition in leaf-cutting ant fungus gardens.

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    Isabel E Moller

    Full Text Available The degradation of live plant biomass in fungus gardens of leaf-cutting ants is poorly characterised but fundamental for understanding the mutual advantages and efficiency of this obligate nutritional symbiosis. Controversies about the extent to which the garden-symbiont Leucocoprinus gongylophorus degrades cellulose have hampered our understanding of the selection forces that induced large scale herbivory and of the ensuing ecological footprint of these ants. Here we use a recently established technique, based on polysaccharide microarrays probed with antibodies and carbohydrate binding modules, to map the occurrence of cell wall polymers in consecutive sections of the fungus garden of the leaf-cutting ant Acromyrmex echinatior. We show that pectin, xyloglucan and some xylan epitopes are degraded, whereas more highly substituted xylan and cellulose epitopes remain as residuals in the waste material that the ants remove from their fungus garden. These results demonstrate that biomass entering leaf-cutting ant fungus gardens is only partially utilized and explain why disproportionally large amounts of plant material are needed to sustain colony growth. They also explain why substantial communities of microbial and invertebrate symbionts have evolved associations with the dump material from leaf-cutting ant nests, to exploit decomposition niches that the ant garden-fungus does not utilize. Our approach thus provides detailed insight into the nutritional benefits and shortcomings associated with fungus-farming in ants.

  11. Pinoresinol reductase 1 impacts lignin distribution during secondary cell wall biosynthesis in Arabidopsis.

    Science.gov (United States)

    Zhao, Qiao; Zeng, Yining; Yin, Yanbin; Pu, Yunqiao; Jackson, Lisa A; Engle, Nancy L; Martin, Madhavi Z; Tschaplinski, Timothy J; Ding, Shi-You; Ragauskas, Arthur J; Dixon, Richard A

    2015-04-01

    Pinoresinol reductase (PrR) catalyzes the conversion of the lignan (-)-pinoresinol to (-)-lariciresinol in Arabidopsis thaliana, where it is encoded by two genes, PrR1 and PrR2, that appear to act redundantly. PrR1 is highly expressed in lignified inflorescence stem tissue, whereas PrR2 expression is barely detectable in stems. Co-expression analysis has indicated that PrR1 is co-expressed with many characterized genes involved in secondary cell wall biosynthesis, whereas PrR2 expression clusters with a different set of genes. The promoter of the PrR1 gene is regulated by the secondary cell wall related transcription factors SND1 and MYB46. The loss-of-function mutant of PrR1 shows, in addition to elevated levels of pinoresinol, significantly decreased lignin content and a slightly altered lignin structure with lower abundance of cinnamyl alcohol end groups. Stimulated Raman scattering (SRS) microscopy analysis indicated that the lignin content of the prr1-1 loss-of-function mutant is similar to that of wild-type plants in xylem cells, which exhibit a normal phenotype, but is reduced in the fiber cells. Together, these data suggest an association of the lignan biosynthetic enzyme encoded by PrR1 with secondary cell wall biosynthesis in fiber cells.

  12. Guard cell chloroplasts are essential for blue light-dependent stomatal opening in Arabidopsis.

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    Noriyuki Suetsugu

    Full Text Available Blue light (BL induces stomatal opening through the activation of H+-ATPases with subsequent ion accumulation in guard cells. In most plant species, red light (RL enhances BL-dependent stomatal opening. This RL effect is attributable to the chloroplasts of guard cell, the only cells in the epidermis possessing this organelle. To clarify the role of chloroplasts in stomatal regulation, we investigated the effects of RL on BL-dependent stomatal opening in isolated epidermis, guard cell protoplasts, and intact leaves of Arabidopsis thaliana. In isolated epidermal tissues and intact leaves, weak BL superimposed on RL enhanced stomatal opening while BL alone was less effective. In guard cell protoplasts, RL enhanced BL-dependent H+-pumping and DCMU, a photosynthetic electron transport inhibitor, eliminated this effect. RL enhanced phosphorylation levels of the H+-ATPase in response to BL, but this RL effect was not suppressed by DCMU. Furthermore, DCMU inhibited both RL-induced and BL-dependent stomatal opening in intact leaves. The photosynthetic rate in leaves correlated positively with BL-dependent stomatal opening in the presence of DCMU. We conclude that guard cell chloroplasts provide ATP and/or reducing equivalents that fuel BL-dependent stomatal opening, and that they indirectly monitor photosynthetic CO2 fixation in mesophyll chloroplasts by absorbing PAR in the epidermis.

  13. Cell division plane orientation based on tensile stress in Arabidopsis thaliana.

    Science.gov (United States)

    Louveaux, Marion; Julien, Jean-Daniel; Mirabet, Vincent; Boudaoud, Arezki; Hamant, Olivier

    2016-07-26

    Cell geometry has long been proposed to play a key role in the orientation of symmetric cell division planes. In particular, the recently proposed Besson-Dumais rule generalizes Errera's rule and predicts that cells divide along one of the local minima of plane area. However, this rule has been tested only on tissues with rather local spherical shape and homogeneous growth. Here, we tested the application of the Besson-Dumais rule to the divisions occurring in the Arabidopsis shoot apex, which contains domains with anisotropic curvature and differential growth. We found that the Besson-Dumais rule works well in the central part of the apex, but fails to account for cell division planes in the saddle-shaped boundary region. Because curvature anisotropy and differential growth prescribe directional tensile stress in that region, we tested the putative contribution of anisotropic stress fields to cell division plane orientation at the shoot apex. To do so, we compared two division rules: geometrical (new plane along the shortest path) and mechanical (new plane along maximal tension). The mechanical division rule reproduced the enrichment of long planes observed in the boundary region. Experimental perturbation of mechanical stress pattern further supported a contribution of anisotropic tensile stress in division plane orientation. Importantly, simulations of tissues growing in an isotropic stress field, and dividing along maximal tension, provided division plane distributions comparable to those obtained with the geometrical rule. We thus propose that division plane orientation by tensile stress offers a general rule for symmetric cell division in plants.

  14. METACASPASE9 modulates autophagy to confine cell death to the target cells during Arabidopsis vascular xylem differentiation

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    Sacha Escamez

    2016-02-01

    Full Text Available We uncovered that the level of autophagy in plant cells undergoing programmed cell death determines the fate of the surrounding cells. Our approach consisted of using Arabidopsis thaliana cell cultures capable of differentiating into two different cell types: vascular tracheary elements (TEs that undergo programmed cell death (PCD and protoplast autolysis, and parenchymatic non-TEs that remain alive. The TE cell type displayed higher levels of autophagy when expression of the TE-specific METACASPASE9 (MC9 was reduced using RNAi (MC9-RNAi. Misregulation of autophagy in the MC9-RNAi TEs coincided with ectopic death of the non-TEs, implying the existence of an autophagy-dependent intercellular signalling from within the TEs towards the non-TEs. Viability of the non-TEs was restored when AUTOPHAGY2 (ATG2 was downregulated specifically in MC9-RNAi TEs, demonstrating the importance of autophagy in the spatial confinement of cell death. Our results suggest that other eukaryotic cells undergoing PCD might also need to tightly regulate their level of autophagy to avoid detrimental consequences for the surrounding cells.

  15. A new picture of cell wall protein dynamics in elongating cells of Arabidopsis thaliana: Confirmed actors and newcomers

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    Jamet Elisabeth

    2008-09-01

    Full Text Available Abstract Background Cell elongation in plants requires addition and re-arrangements of cell wall components. Even if some protein families have been shown to play roles in these events, a global picture of proteins present in cell walls of elongating cells is still missing. A proteomic study was performed on etiolated hypocotyls of Arabidopsis used as model of cells undergoing elongation followed by growth arrest within a short time. Results Two developmental stages (active growth and after growth arrest were compared. A new strategy consisting of high performance cation exchange chromatography and mono-dimensional electrophoresis was established for separation of cell wall proteins. This work allowed identification of 137 predicted secreted proteins, among which 51 had not been identified previously. Apart from expected proteins known to be involved in cell wall extension such as xyloglucan endotransglucosylase-hydrolases, expansins, polygalacturonases, pectin methylesterases and peroxidases, new proteins were identified such as proteases, proteins related to lipid metabolism and proteins of unknown function. Conclusion This work highlights the CWP dynamics that takes place between the two developmental stages. The presence of proteins known to be related to cell wall extension after growth arrest showed that these proteins may play other roles in cell walls. Finally, putative regulatory mechanisms of protein biological activity are discussed from this global view of cell wall proteins.

  16. Antagonistic control of oxidative stress-induced cell death in Arabidopsis by two related, plant-specific zinc finger proteins

    OpenAIRE

    Epple, Petra; Mack, Amanda A.; Morris, Veronica R. F.; Dangl, Jeffery L.

    2003-01-01

    The most familiar form of plant programmed cell death is the hypersensitive response (HR) associated with successful plant immune responses. HR is preceded by an oxidative burst and the generation of both reactive oxygen intermediates (ROI) and NO. The Arabidopsis LSD1 gene encodes a negative regulator of plant programmed cell death that meets several criteria for a regulator of processes relevant to ROI management during pathogen responses. Here we demonstrate that a highly conserved L...

  17. Dehydration induced loss of photosynthesis in Arabidopsis leaves during senescence is accompanied by the reversible enhancement in the activity of cell wall β-glucosidase.

    Science.gov (United States)

    Patro, Lichita; Mohapatra, Pranab Kishor; Biswal, Udaya Chand; Biswal, Basanti

    2014-08-01

    The physiology of loss of photosynthetic production of sugar and the consequent cellular sugar reprogramming during senescence of leaves experiencing environmental stress largely remains unclear. We have shown that leaf senescence in Arabidopsis thaliana causes a significant reduction in the rate of oxygen evolution and net photosynthetic rate (Pn). The decline in photosynthesis is further aggravated by dehydration. During dehydration, primary photochemical reaction of thylakoids and net photosynthesis decrease in parallel with the increase in water deficit. Senescence induced loss in photosynthesis is accompanied by a significant increase in the activity of cell wall hydrolyzing enzyme such as β-glucosidase associated with cell wall catabolism. The activity of this enzyme is further enhanced when the senescing leaves experience dehydration stress. It is possible that both senescence and stress separately or in combination result in the loss in photosynthesis which could be a signal for an enhancement in the activity of β-glucosidase that breaks down cell wall polysaccharides to sugar to sustain respiration for metabolic activities of plants experiencing stress. Thus dehydration response of cell wall hydrolases of senescing leaves is considered as plants' strategy to have cell wall polysaccharides as an alternative energy source for completion of energy requiring senescence process, stress survival and maintenance of recovery potential of energy deficit cells in the background of loss in photosynthesis. Withdrawal of stress (rehydration) distinctly exhibits recovery of photosynthesis and suppression of enzyme activity. Retention of the signaling for sugar reprogramming through breakdown of cell wall polysaccharides in the senescing leaves exposed to severe drought stress suggests that senescing leaves like mature ones possess potential for stress recovery. The precise mechanism of stress adaptation of senescing leaves is yet to be known. A significant

  18. Effects of Waterlogging on Leaf Mesophyll Cell Ultrastructure and Photosynthetic Characteristics of Summer Maize.

    Science.gov (United States)

    Ren, Baizhao; Zhang, Jiwang; Dong, Shuting; Liu, Peng; Zhao, Bin

    2016-01-01

    A field experiment was performed to study the effects of waterlogging on the leaf mesophyll cell ultrastructure, chlorophyll content, gas exchange parameters, chlorophyll fluorescence, and malondialdehyde (MDA) content of summer maize (Zea mays L.) hybrids Denghai605 (DH605) and Zhengdan958 (ZD958). The waterlogging treatments were implemented for different durations (3 and 6 days) at the third leaf stage (V3), the sixth leaf stage (V6), and the 10th day after the tasseling stage (10VT). Leaf area index (LAI), chlorophyll content, photosynthetic rate (Pn), and actual photochemical efficiency (ΦPSII) were reduced after waterlogging, indicating that waterlogging significantly decreased photosynthetic capacity. The chloroplast shapes changed from long and oval to elliptical or circular after waterlogging. In addition, the internal structures of chloroplasts were degenerated after waterlogging. After waterlogging for 6 d at V3, the number of grana and grana lamellae of the third expanded leaf in DH605 were decreased by 26.83% and 55.95%, respectively, compared to the control (CK). Those in ZD958 were reduced by 30.08% and 31.94%, respectively. Waterlogging increased MDA content in both hybrids, suggesting an impact of waterlogging on membrane integrity and thus membrane deterioration. Waterlogging also damaged the biological membrane structure and mitochondria. Our results indicated that the physiological reactions to waterlogging were closely related to lower LAI, chlorophyll content, and Pn and to the destruction of chloroplast ultrastructure. These negative effects resulted in the decrease of grain yield in response to waterlogging. Summer maize was the most susceptible to damage when waterlogging occurred at V3, followed by V6 and 10VT, with damage increasing in the wake of waterlogging duration increasing. PMID:27583803

  19. Effects of Waterlogging on Leaf Mesophyll Cell Ultrastructure and Photosynthetic Characteristics of Summer Maize

    Science.gov (United States)

    Ren, Baizhao; Zhang, Jiwang; Dong, Shuting; Liu, Peng; Zhao, Bin

    2016-01-01

    A field experiment was performed to study the effects of waterlogging on the leaf mesophyll cell ultrastructure, chlorophyll content, gas exchange parameters, chlorophyll fluorescence, and malondialdehyde (MDA) content of summer maize (Zea mays L.) hybrids Denghai605 (DH605) and Zhengdan958 (ZD958). The waterlogging treatments were implemented for different durations (3 and 6 days) at the third leaf stage (V3), the sixth leaf stage (V6), and the 10th day after the tasseling stage (10VT). Leaf area index (LAI), chlorophyll content, photosynthetic rate (Pn), and actual photochemical efficiency (ΦPSII) were reduced after waterlogging, indicating that waterlogging significantly decreased photosynthetic capacity. The chloroplast shapes changed from long and oval to elliptical or circular after waterlogging. In addition, the internal structures of chloroplasts were degenerated after waterlogging. After waterlogging for 6 d at V3, the number of grana and grana lamellae of the third expanded leaf in DH605 were decreased by 26.83% and 55.95%, respectively, compared to the control (CK). Those in ZD958 were reduced by 30.08% and 31.94%, respectively. Waterlogging increased MDA content in both hybrids, suggesting an impact of waterlogging on membrane integrity and thus membrane deterioration. Waterlogging also damaged the biological membrane structure and mitochondria. Our results indicated that the physiological reactions to waterlogging were closely related to lower LAI, chlorophyll content, and Pn and to the destruction of chloroplast ultrastructure. These negative effects resulted in the decrease of grain yield in response to waterlogging. Summer maize was the most susceptible to damage when waterlogging occurred at V3, followed by V6 and 10VT, with damage increasing in the wake of waterlogging duration increasing. PMID:27583803

  20. A Mutation in Plant-Specific SWI2/SNF2-Like Chromatin-Remodeling Proteins, DRD1 and DDM1, Delays Leaf Senescence in Arabidopsis thaliana.

    Science.gov (United States)

    Cho, Eun Ju; Choi, Seung Hee; Kim, Ji Hong; Kim, Ji Eun; Lee, Min Hee; Chung, Byung Yeoup; Woo, Hye Ryun; Kim, Jin-Hong

    2016-01-01

    Leaf senescence is a finely regulated complex process; however, evidence for the involvement of epigenetic processes in the regulation of leaf senescence is still fragmentary. Therefore, we chose to examine the functions of DRD1, a SWI2/SNF2 chromatin remodeling protein, in epigenetic regulation of leaf senescence, particularly because drd1-6 mutants exhibited a delayed leaf senescence phenotype. Photosynthetic parameters such as Fv/Fm and ETRmax were decreased in WT leaves compared to leaves of drd1-6 mutants after dark treatment. The WT leaves remarkably lost more chlorophyll and protein content during dark-induced senescence (DIS) than the drd1-6 leaves did. The induction of senescence-associated genes was noticeably inhibited in the drd1-6 mutant after 5-d of DIS. We compared changes in epigenetic regulation during DIS via quantitative expression analysis of 180-bp centromeric (CEN) and transcriptionally silent information (TSI) repeats. Their expression levels significantly increased in both the WT and the drd1-6 mutant, but did much less in the latter. Moreover, the delayed leaf senescence was observed in ddm1-2 mutants as well as the drd1-6, but not in drd1-p mutants. These data suggest that SWI2/SNF2 chromatin remodeling proteins such as DRD1 and DDM1 may influence leaf senescence possibly via epigenetic regulation.

  1. Finding missing interactions of the Arabidopsis thaliana root stem cell niche gene regulatory network

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    Eugenio eAzpeitia

    2013-04-01

    Full Text Available AbstractOver the last few decades, the Arabidopsis thaliana root stem cell niche has become a model system for the study of plant development and the stem cell niche. Currently, many of the molecular mechanisms involved in root stem cell niche maintenance and development have been described. A few years ago, we published a gene regulatory network model integrating this information. This model suggested that there were missing components or interactions. Upon updating the model, the observed stable gene configurations of the root stem cell niche could not be recovered, indicating that there are additional missing components or interactions in the model. In fact, due to the lack of experimental data, gene regulatory networks inferred from published data are usually incomplete. However, predicting the location and nature of the missing data is a not trivial task. Here, we propose a set of procedures for detecting and predicting missing interactions in Boolean networks. We used these procedures to predict putative missing interactions in the A. thaliana root stem cell niche network model. Using our approach, we identified three necessary interactions to recover the reported gene activation configurations that have been experimentally uncovered for the different cell types within the root stem cell niche: 1 a regulation of PHABULOSA to restrict its expression domain to the vascular cells, 2 a self-regulation of WOX5, possibly by an indirect mechanism through the auxin signalling pathway and 3 a positive regulation of JACKDAW by MAGPIE. The procedures proposed here greatly reduce the number of possible Boolean functions that are biologically meaningful and experimentally testable and that do not contradict previous data. We believe that these procedures can be used on any Boolean network. However, because the procedures were designed for the specific case of the root stem cell niche, formal demonstrations of the procedures should be shown in future

  2. A theoretical model for ROP localisation by auxin in Arabidopsis root hair cells.

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    Robert J H Payne

    Full Text Available Local activation of Rho GTPases is important for many functions including cell polarity, morphology, movement, and growth. Although a number of molecules affecting Rho-of-Plants small GTPase (ROP signalling are known, it remains unclear how ROP activity becomes spatially organised. Arabidopsis root hair cells produce patches of ROP at consistent and predictable subcellular locations, where root hair growth subsequently occurs.We present a mathematical model to show how interaction of the plant hormone auxin with ROPs could spontaneously lead to localised patches of active ROP via a Turing or Turing-like mechanism. Our results suggest that correct positioning of the ROP patch depends on the cell length, low diffusion of active ROP, a gradient in auxin concentration, and ROP levels. Our theory provides a unique explanation linking the molecular biology to the root hair phenotypes of multiple mutants and transgenic lines, including OX-ROP, CA-rop, aux1, axr3, tip1, eto1, etr1, and the triple mutant aux1 ein2 gnom(eb.We show how interactions between Rho GTPases (in this case ROPs and regulatory molecules (in this case auxin could produce characteristic subcellular patterning that subsequently affects cell shape. This has important implications for research on the morphogenesis of plants and other eukaryotes. Our results also illustrate how gradient-regulated Turing systems provide a particularly robust and flexible mechanism for pattern formation.

  3. Chloride regulates leaf cell size and water relations in tobacco plants.

    Science.gov (United States)

    Franco-Navarro, Juan D; Brumós, Javier; Rosales, Miguel A; Cubero-Font, Paloma; Talón, Manuel; Colmenero-Flores, José M

    2016-02-01

    Chloride (Cl(-)) is a micronutrient that accumulates to macronutrient levels since it is normally available in nature and actively taken up by higher plants. Besides a role as an unspecific cell osmoticum, no clear biological roles have been explicitly associated with Cl(-) when accumulated to macronutrient concentrations. To address this question, the glycophyte tobacco (Nicotiana tabacum L. var. Habana) has been treated with a basal nutrient solution supplemented with one of three salt combinations containing the same cationic balance: Cl(-)-based (CL), nitrate-based (N), and sulphate+phosphate-based (SP) treatments. Under non-saline conditions (up to 5 mM Cl(-)) and no water limitation, Cl(-) specifically stimulated higher leaf cell size and led to a moderate increase of plant fresh and dry biomass mainly due to higher shoot expansion. When applied in the 1-5 mM range, Cl(-) played specific roles in regulating leaf osmotic potential and turgor, allowing plants to improve leaf water balance parameters. In addition, Cl(-) also altered water relations at the whole-plant level through reduction of plant transpiration. This was a consequence of a lower stomatal conductance, which resulted in lower water loss and greater photosynthetic and integrated water-use efficiency. In contrast to Cl(-), these effects were not observed for essential anionic macronutrients such as nitrate, sulphate, and phosphate. We propose that the abundant uptake and accumulation of Cl(-) responds to adaptive functions improving water homeostasis in higher plants.

  4. Live imaging of companion cells and sieve elements in Arabidopsis leaves.

    Directory of Open Access Journals (Sweden)

    Thibaud Cayla

    Full Text Available The phloem is a complex tissue composed of highly specialized cells with unique subcellular structures and a compact organization that is challenging to study in vivo at cellular resolution. We used confocal scanning laser microscopy and subcellular fluorescent markers in companion cells and sieve elements, for live imaging of the phloem in Arabidopsis leaves. This approach provided a simple framework for identifying phloem cell types unambiguously. It highlighted the compactness of the meshed network of organelles within companion cells. By contrast, within the sieve elements, unknown bodies were observed in association with the PP2-A1:GFP, GFP:RTM1 and RTM2:GFP markers at the cell periphery. The phloem lectin PP2-A1:GFP marker was found in the parietal ground matrix. Its location differed from that of the P-protein filaments, which were visualized with SEOR1:GFP and SEOR2:GFP. PP2-A1:GFP surrounded two types of bodies, one of which was identified as mitochondria. This location suggested that it was embedded within the sieve element clamps, specific structures that may fix the organelles to each another or to the plasma membrane in the sieve tubes. GFP:RTM1 was associated with a class of larger bodies, potentially corresponding to plastids. PP2-A1:GFP was soluble in the cytosol of immature sieve elements. The changes in its subcellular localization during differentiation provide an in vivo blueprint for monitoring this process. The subcellular features obtained with these companion cell and sieve element markers can be used as landmarks for exploring the organization and dynamics of phloem cells in vivo.

  5. Heterotrimeric G-protein is involved in phytochrome A-mediated cell death of Arabidopsis hypocotyls

    Institute of Scientific and Technical Information of China (English)

    Qing Wei; Wenbin Zhou; Guangzhen Hu; Jiamian Wei; Hongquan Yang; Jirong Huang

    2008-01-01

    The heterotrimeric guanine nucleotide-binding protein (G-protein) has been demonstrated to mediate various signaling pathways in plants. However,its role in phytochrome A (phyA) signaling remains elusive. In this study,we discover a new phyA-mediated phenotype designated far-red irradiation (FR) preconditioned cell death,which occurs only in the hypocotyls of FR-grown seedlings following exposure to white light (WL). The cell death is mitigated in the Ga mutant gpal but aggravated in the Gβ mutant agbl in comparison with the wild type (WT),indicative of antagonistic roles of GPAI and AGB1 in the phyA-mediated cell-death pathway. Further investigation indicates that FR-induced accumulation of nonphotoconvertible protochlorophyllide (Pchlide633),which generates reactive oxygen species (ROS)on exposure to WL,is required for FR-preconditioned cell death. Moreover,ROS is mainly detected in chloroplasts using the fluorescent probe. Interestingly,the application of H2O2 to dark-grown seedlings results in a phenotype similar to FR-preconditioned cell death. This reveals that ROS is a critical mediator for the cell death. In addition,we observe that agbl is more sensitive to H2O2 than WT seedlings,indicating that the G-protein may also modify the sensitivity of the seedlings to ROS stress. Taking these results together,we infer that the G-protein may be involved in the phyA signaling pathway to regulate FR-preconditioned cell death of Arabidopsis hypocotyls.Apossible mechanism underlying the involvement of the G-protein in phyA signaling is discussed in this study.

  6. Cytosolic Ca(2+) Signals Enhance the Vacuolar Ion Conductivity of Bulging Arabidopsis Root Hair Cells.

    Science.gov (United States)

    Wang, Yi; Dindas, Julian; Rienmüller, Florian; Krebs, Melanie; Waadt, Rainer; Schumacher, Karin; Wu, Wei-Hua; Hedrich, Rainer; Roelfsema, M Rob G

    2015-11-01

    Plant cell expansion depends on the uptake of solutes across the plasma membrane and their storage within the vacuole. In contrast to the well-studied plasma membrane, little is known about the regulation of ion transport at the vacuolar membrane. We therefore established an experimental approach to study vacuolar ion transport in intact Arabidopsis root cells, with multi-barreled microelectrodes. The subcellular position of electrodes was detected by imaging current-injected fluorescent dyes. Comparison of measurements with electrodes in the cytosol and vacuole revealed an average vacuolar membrane potential of -31 mV. Voltage clamp recordings of single vacuoles resolved the activity of voltage-independent and slowly deactivating channels. In bulging root hairs that express the Ca(2+) sensor R-GECO1, rapid elevation of the cytosolic Ca(2+) concentration was observed, after impalement with microelectrodes, or injection of the Ca(2+) chelator BAPTA. Elevation of the cytosolic Ca(2+) level stimulated the activity of voltage-independent channels in the vacuolar membrane. Likewise, the vacuolar ion conductance was enhanced during a sudden increase of the cytosolic Ca(2+) level in cells injected with fluorescent Ca(2+) indicator FURA-2. These data thus show that cytosolic Ca(2+) signals can rapidly activate vacuolar ion channels, which may prevent rupture of the vacuolar membrane, when facing mechanical forces. PMID:26232520

  7. Involvement of Arabidopsis Hexokinase1 in Cell Death Mediated by Myo -Inositol Accumulation

    KAUST Repository

    Bruggeman, Quentin

    2015-06-05

    Programmed cell death (PCD) is essential for several aspects of plant life, including development and stress responses. We recently identified the mips1 mutant of Arabidopsis thaliana, which is deficient for the enzyme catalyzing the limiting step of myo-inositol (MI) synthesis. One of the most striking features of mips1 is the light-dependent formation of lesions on leaves due to salicylic acid (SA)-dependent PCD. Here, we identified a suppressor of PCD by screening for mutations that abolish the mips1 cell death phenotype. Our screen identified the hxk1 mutant, mutated in the gene encoding the hexokinase1 (HXK1) enzyme that catalyzes sugar phosphorylation and acts as a genuine glucose sensor. We show that HXK1 is required for lesion formation in mips1 due to alterations in MI content, via SA-dependant signaling. Using two catalytically inactive HXK1 mutants, we also show that hexokinase catalytic activity is necessary for the establishment of lesions in mips1. Gas chromatography-mass spectrometry analyses revealed a restoration of the MI content in mips1 hxk1 that it is due to the activity of the MIPS2 isoform, while MIPS3 is not involved. Our work defines a pathway of HXK1-mediated cell death in plants and demonstrates that two MIPS enzymes act cooperatively under a particular metabolic status, highlighting a novel checkpoint of MI homeostasis in plants. © 2015 American Society of Plant Biologists. All rights reserved.

  8. Expression of NO scavenging hemoglobin is involved in the timing of bolting in Arabidopsis thaliana

    DEFF Research Database (Denmark)

    Hebelstrup, Kim Henrik; Jensen, Erik Østergaard

    2008-01-01

    -symbiotic hemoglobin gene, GLB2, in Arabidopsis thaliana. Lines with GLB1 silencing had a significant delay of bolting and after bolting, shoots reverted to the rosette vegetative phase by formation of aerial rosettes at lateral meristems. Lines with overexpression of GLB1 or GLB2 bolted earlier than wild type plants...... molecule, NO. So far, NO scavenging has only been demonstrated for class 1 non-symbiotic hemoglobins. A direct assay in Arabidopsis leaf cells shows that GLB1 as well as the class 2 non-symbiotic hemoglobin, GLB2, scavenge NO in vivo. NO has also been demonstrated to be a growth stimulating signal...

  9. 氮磷施肥对拟南芥叶片碳氮磷化学计量特征的影响%Effects of nitrogen and phosphorus fertilization on leaf carbon, nitrogen and phosphorus stoichiometry of Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    严正兵; 金南瑛; 韩廷申; 方精云; 韩文轩

    2013-01-01

    Aims Arabidopsis thaliana,a widely used model organism in plant biology,is an ideal plant to test the growth rate hypothesis (GRH) and homeostasis theory about plant nutrition.Our objectives are to test i) whether GRH applies to this plant species,ii) how leaf nitrogen (N) and phosphorus (P) of A.thaliana follow the homeostasis theory and iii) whether the allometric relationship between leaf N and P content is consistent with the 3/4 power function (N-P3/4) for individual plant species.Methods Based on a pot experiment in a phytotron with N and P fertilizer additions,we measured the leaf carbon (C),N and P content and leafbiomass ofA.thaliana.Specific growth rate (mg·mg-1·d-1) was the leafbiomass increment divided by the initial biomass at planting,and by the days after planting.The homeostasis of plant elements is indicated by the exponent (reciprocal of the regulation coefficient) of the power function of leaf nutrient against soil nutrient concentrations.Important findings P is the limiting nutrient of the culture substrate for A.thaliana,while N fertilization could cause toxic effects in cases of excessive N uptake.The growth ofA.thaliana is consistent with GRH—the specific growth rate decreases with increasing leaf N∶P or C∶P.Leaf P content shows a significant regulation coefficient (3.51) (leaf-P-substrate-p1/3.51),but leaf N content has no significant relationship with substrate N.There is a significant allometric relationship between leaf N and P content,which is inconsistent with the 3/4 power function (N-p3/4).The power exponent (0.209) between leaf N content and leaf P content in the P fertilization treatments is significantly lower than the exponent (0.466) in the N fertilization treatments,suggesting that fertilization may affect the allometry between nutrients.Our findings can offer reference for future field studies on plant ecological stoichiometry at scales from species to community to ecosystem.%研究植物碳(C)氮(N)磷(P)化学计量

  10. Cell division plane orientation based on tensile stress in Arabidopsis thaliana

    Science.gov (United States)

    Louveaux, Marion; Julien, Jean-Daniel; Mirabet, Vincent; Boudaoud, Arezki; Hamant, Olivier

    2016-01-01

    Cell geometry has long been proposed to play a key role in the orientation of symmetric cell division planes. In particular, the recently proposed Besson–Dumais rule generalizes Errera’s rule and predicts that cells divide along one of the local minima of plane area. However, this rule has been tested only on tissues with rather local spherical shape and homogeneous growth. Here, we tested the application of the Besson–Dumais rule to the divisions occurring in the Arabidopsis shoot apex, which contains domains with anisotropic curvature and differential growth. We found that the Besson–Dumais rule works well in the central part of the apex, but fails to account for cell division planes in the saddle-shaped boundary region. Because curvature anisotropy and differential growth prescribe directional tensile stress in that region, we tested the putative contribution of anisotropic stress fields to cell division plane orientation at the shoot apex. To do so, we compared two division rules: geometrical (new plane along the shortest path) and mechanical (new plane along maximal tension). The mechanical division rule reproduced the enrichment of long planes observed in the boundary region. Experimental perturbation of mechanical stress pattern further supported a contribution of anisotropic tensile stress in division plane orientation. Importantly, simulations of tissues growing in an isotropic stress field, and dividing along maximal tension, provided division plane distributions comparable to those obtained with the geometrical rule. We thus propose that division plane orientation by tensile stress offers a general rule for symmetric cell division in plants. PMID:27436908

  11. A gene regulatory network for root epidermis cell differentiation in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Angela Bruex

    2012-01-01

    Full Text Available The root epidermis of Arabidopsis provides an exceptional model for studying the molecular basis of cell fate and differentiation. To obtain a systems-level view of root epidermal cell differentiation, we used a genome-wide transcriptome approach to define and organize a large set of genes into a transcriptional regulatory network. Using cell fate mutants that produce only one of the two epidermal cell types, together with fluorescence-activated cell-sorting to preferentially analyze the root epidermis transcriptome, we identified 1,582 genes differentially expressed in the root-hair or non-hair cell types, including a set of 208 "core" root epidermal genes. The organization of the core genes into a network was accomplished by using 17 distinct root epidermis mutants and 2 hormone treatments to perturb the system and assess the effects on each gene's transcript accumulation. In addition, temporal gene expression information from a developmental time series dataset and predicted gene associations derived from a Bayesian modeling approach were used to aid the positioning of genes within the network. Further, a detailed functional analysis of likely bHLH regulatory genes within the network, including MYC1, bHLH54, bHLH66, and bHLH82, showed that three distinct subfamilies of bHLH proteins participate in root epidermis development in a stage-specific manner. The integration of genetic, genomic, and computational analyses provides a new view of the composition, architecture, and logic of the root epidermal transcriptional network, and it demonstrates the utility of a comprehensive systems approach for dissecting a complex regulatory network.

  12. Programmed cell death in the leaves of the Arabidopsis spontaneous necrotic spots (sns-D mutant correlates with increased expression of the eukaryotic translation initiation factor eIF4B2

    Directory of Open Access Journals (Sweden)

    Gwenael M.D.J.-M. Gaussand

    2011-04-01

    Full Text Available From a pool of transgenic Arabidopsis (Arabidopsis thaliana plants harboring an activator T-DNA construct, one mutant was identified that developed spontaneous necrotic spots (sns-D on the rosette leaves under aseptic conditions. The sns-D mutation is dominant and homozygous plants are embryo lethal. The mutant produced smaller rosettes with a different number of stomata than the wild-type. DNA fragmentation in the nuclei of cells in the necrotic spots and a significant increase of caspase-3 and caspase-6 like activities in sns-D leaf extracts indicated that the sns-D mutation caused programmed cell death (PCD. The integration of the activator T-DNA caused an increase of the expression level of At1g13020, which encodes the eukaryotic translation initiation factor eIF4B2. The expression level of eIF4B2 was positively correlated with the severity of sns-D mutant phenotype. Overexpression of the eIF4B2 cDNA mimicked phenotypic traits of the sns-D mutant indicating that the sns-D mutant phenotype is indeed caused by activation tagging of eIF4B2. Thus, incorrect regulation of translation initiation may result in PCD.

  13. Intraspecific variability of cadmium tolerance and accumulation, and cadmium-induced cell wall modifications in the metal hyperaccumulator Arabidopsis halleri

    OpenAIRE

    Meyer, Claire-Lise; Juraniec, Michal; Huguet, Stéphanie; Chaves-Rodriguez, Elena; Salis, Pietro; Isaure, Marie-Pierre; Goormaghtigh, Erik; Verbruggen, Nathalie

    2015-01-01

    Certain molecular mechanisms of Cd tolerance and accumulation have been identified in the model species Arabidopsis halleri, while intraspecific variability of these traits and the mechanisms of shoot detoxification were little addressed. The Cd tolerance and accumulation of metallicolous and non-metallicolous A. halleri populations from different genetic units were tested in controlled conditions. In addition, changes in shoot cell wall composition were investigated using Fourier transform i...

  14. Live cell imaging of FM4-64, a tool for tracing the endocytic pathways in Arabidopsis root cells.

    Science.gov (United States)

    Rigal, Adeline; Doyle, Siamsa M; Robert, Stéphanie

    2015-01-01

    Confocal live imaging of the amphiphilic styryl dye FM4-64 is a valuable technique to monitor organelle dynamics and in particular endocytic pathways. After application in plants, FM4-64 immediately stains the plasma membrane and is then integrated on vesicles following endomembrane system-dependent internalization processes. Over time, FM4-64 becomes distributed throughout the full vesicular network from the plasma membrane to the vacuole, including the components of the secretory pathways. Here we provide succinct examples of the many important developmental processes in plants that rely on endocytosis and describe two suitable methods to trace the endocytic pathways in Arabidopsis thaliana root cells based on the uptake of FM4-64. PMID:25408447

  15. Leaf hydraulics I: scaling transport properties from single cells to tissues.

    Science.gov (United States)

    Rockwell, Fulton E; Michele Holbrook, N; Stroock, Abraham D

    2014-01-01

    In leaf tissues, water may move through the symplast or apoplast as a liquid, or through the airspace as vapor, but the dominant path remains in dispute. This is due, in part, to a lack of models that describe these three pathways in terms of experimental variables. We show that, in plant water relations theory, the use of a hydraulic capacity in a manner analogous to a thermal capacity, though it ignores mechanical interactions between cells, is consistent with a special case of the more general continuum mechanical theory of linear poroelasticity. The resulting heat equation form affords a great deal of analytical simplicity at a minimal cost: we estimate an expected error of less than 12%, compared to the full set of equations governing linear poroelastic behavior. We next consider the case for local equilibrium between protoplasts, their cell walls, and adjacent air spaces during isothermal hydration transients to determine how accurately simple volume averaging of material properties (a 'composite' model) describes the hydraulic properties of leaf tissue. Based on typical hydraulic parameters for individual cells, we find that a composite description for tissues composed of thin walled cells with air spaces of similar size to the cells, as in photosynthetic tissues, is a reasonable preliminary assumption. We also expect isothermal transport in such cells to be dominated by the aquaporin-mediated cell-to-cell path. In the non-isothermal case, information on the magnitude of the thermal gradients is required to assess the dominant phase of water transport, liquid or vapor. PMID:24112968

  16. A subgroup of MATE transporter genes regulates hypocotyl cell elongation in Arabidopsis.

    Science.gov (United States)

    Wang, Rui; Liu, Xiayan; Liang, Shuang; Ge, Qing; Li, Yuanfeng; Shao, Jingxia; Qi, Yafei; An, Lijun; Yu, Fei

    2015-10-01

    The growth of higher plants is under complex regulation to ensure the elaboration of developmental programmes under a changing environment. To dissect these regulatory circuits, we carried out genetic screens for Arabidopsis abnormal shoot (abs) mutants with altered shoot development. Here, we report the isolation of two dominant mutants, abs3-1D and abs4-1D, through activation tagging. Both mutants showed a 'bushy' loss of apical dominance phenotype. ABS3 and ABS4 code for two closely related putative Multidrug and Toxic Compound Extrusion (MATE) family of efflux transporters, respectively. ABS3 and ABS4, as well as two related MATE genes, ABS3-Like1 (ABS3L1) and ABS3L2, showed diverse tissue expression profiles but their gene products all localized to the late endosome/prevacuole (LE/PVC) compartment. The over-expression of these four genes individually led to the inhibition of hypocotyl cell elongation in the light. On the other hand, the quadruple knockout mutant (mateq) showed the opposite phenotype of an enhanced hypocotyl cell elongation in the light. Hypocotyl cell elongation and de-etiolation processes in the dark were also affected by the mutations of these genes. Exogenously applied sucrose attenuated the inhibition of hypocotyl elongation caused by abs3-1D and abs4-1D in the dark, and enhanced the hypocotyl elongation of mateq under prolonged dark treatment. We determined that ABS3 genetically interacts with the photoreceptor gene PHYTOCHROME B (PHYB). Our results demonstrate that ABS3 and related MATE family transporters are potential negative regulators of hypocotyl cell elongation and support a functional link between the endomembrane system, particularly the LE/PVC, and the regulation of plant cell elongation. PMID:26160579

  17. Cell-free translation and purification of Arabidopsis thaliana regulator of G signaling 1 protein.

    Science.gov (United States)

    Li, Bo; Makino, Shin-Ichi; Beebe, Emily T; Urano, Daisuke; Aceti, David J; Misenheimer, Tina M; Peters, Jonathan; Fox, Brian G; Jones, Alan M

    2016-10-01

    Arabidopsis thaliana Regulator of G protein Signalling 1 (AtRGS1) is a protein with a predicted N-terminal 7-transmembrane (7TM) domain and a C-terminal cytosolic RGS1 box domain. The RGS1 box domain exerts GTPase activation (GAP) activity on Gα (AtGPA1), a component of heterotrimeric G protein signaling in plants. AtRGS1 may perceive an exogenous agonist to regulate the steady-state levels of the active form of AtGPA1. It is uncertain if the full-length AtRGS1 protein exerts any atypical effects on Gα, nor has it been established exactly how AtRGS1 contributes to perception of an extracellular signal and transmits this response to a G-protein dependent signaling cascade. Further studies on full-length AtRGS1 have been inhibited due to the extreme low abundance of the endogenous AtRGS1 protein in plants and lack of a suitable heterologous system to express AtRGS1. Here, we describe methods to produce full-length AtRGS1 by cell-free synthesis into unilamellar liposomes and nanodiscs. The cell-free synthesized AtRGS1 exhibits GTPase activating activity on Gα and can be purified to a level suitable for biochemical analyses. PMID:27164033

  18. Quantitative Proteomic Analysis of the Response to Zinc, Magnesium, and Calcium Deficiency in Specific Cell Types of Arabidopsis Roots

    Directory of Open Access Journals (Sweden)

    Yoichiro Fukao

    2016-01-01

    Full Text Available The proteome profiles of specific cell types have recently been investigated using techniques such as fluorescence activated cell sorting and laser capture microdissection. However, quantitative proteomic analysis of specific cell types has not yet been performed. In this study, to investigate the response of the proteome to zinc, magnesium, and calcium deficiency in specific cell types of Arabidopsis thaliana roots, we performed isobaric tags for relative and absolute quantification (iTRAQ-based quantitative proteomics using GFP-expressing protoplasts collected by fluorescence-activated cell sorting. Protoplasts were collected from the pGL2-GFPer and pMGP-GFPer marker lines for epidermis or inner cell lines (pericycle, endodermis, and cortex, respectively. To increase the number of proteins identified, iTRAQ-labeled peptides were separated into 24 fractions by OFFGFEL electrophoresis prior to high-performance liquid chromatography coupled with mass spectrometry analysis. Overall, 1039 and 737 proteins were identified and quantified in the epidermal and inner cell lines, respectively. Interestingly, the expression of many proteins was decreased in the epidermis by mineral deficiency, although a weaker effect was observed in inner cell lines such as the pericycle, endodermis, and cortex. Here, we report for the first time the quantitative proteomics of specific cell types in Arabidopsis roots.

  19. Single-cell and coupled GRN models of cell patterning in the Arabidopsis thaliana root stem cell niche

    Directory of Open Access Journals (Sweden)

    Alvarez-Buylla Elena R

    2010-10-01

    Full Text Available Abstract Background Recent experimental work has uncovered some of the genetic components required to maintain the Arabidopsis thaliana root stem cell niche (SCN and its structure. Two main pathways are involved. One pathway depends on the genes SHORTROOT and SCARECROW and the other depends on the PLETHORA genes, which have been proposed to constitute the auxin readouts. Recent evidence suggests that a regulatory circuit, composed of WOX5 and CLE40, also contributes to the SCN maintenance. Yet, we still do not understand how the niche is dynamically maintained and patterned or if the uncovered molecular components are sufficient to recover the observed gene expression configurations that characterize the cell types within the root SCN. Mathematical and computational tools have proven useful in understanding the dynamics of cell differentiation. Hence, to further explore root SCN patterning, we integrated available experimental data into dynamic Gene Regulatory Network (GRN models and addressed if these are sufficient to attain observed gene expression configurations in the root SCN in a robust and autonomous manner. Results We found that an SCN GRN model based only on experimental data did not reproduce the configurations observed within the root SCN. We developed several alternative GRN models that recover these expected stable gene configurations. Such models incorporate a few additional components and interactions in addition to those that have been uncovered. The recovered configurations are stable to perturbations, and the models are able to recover the observed gene expression profiles of almost all the mutants described so far. However, the robustness of the postulated GRNs is not as high as that of other previously studied networks. Conclusions These models are the first published approximations for a dynamic mechanism of the A. thaliana root SCN cellular pattering. Our model is useful to formally show that the data now available are not

  20. Inhibitive Effects of Mulberry Leaf-Related Extracts on Cell Adhesion and Inflammatory Response in Human Aortic Endothelial Cells

    Directory of Open Access Journals (Sweden)

    P.-Y. Chao

    2013-01-01

    Full Text Available Effects of mulberry leaf-related extracts (MLREs on hydrogen peroxide-induced DNA damage in human lymphocytes and on inflammatory signaling pathways in human aortic endothelial cells (HAECs were studied. The tested MLREs were rich in flavonols, especially bombyx faces tea (BT in quercetin and kaempferol. Polyphenols, flavonoids, and anthocyanidin also abounded in BT. The best trolox equivalent antioxidant capacity (TEAC was generated from the acidic methanolic extracts of BT. Acidic methanolic and water extracts of mulberry leaf tea (MT, mulberry leaf (M, and BT significantly inhibited DNA oxidative damage to lymphocytes based on the comet assay as compared to the H2O2-treated group. TNF-α-induced monocyte-endothelial cell adhesion was significantly suppressed by MLREs. Additionally, nuclear factor kappa B (NF-κB expression was significantly reduced by BT and MT. Significant reductions were also observed in both NF-κB and activator protein (AP-1 DNA binding by MLREs. Significant increases in peroxisome proliferator-activated receptor (PPAR α and γ DNA binding by MLREs were also detected in M and MT extracts, but no evidence for PPAR α DNA binding in 50 μg/mL MT extract was found. Apparently, MLREs can provide distinct cytoprotective mechanisms that may contribute to its putative beneficial effects on suppressing endothelial responses to cytokines during inflammation.

  1. Phytosulfokine-α controls hypocotyl length and cell expansion in Arabidopsis thaliana through phytosulfokine receptor 1.

    Directory of Open Access Journals (Sweden)

    Nils Stührwohldt

    Full Text Available The disulfated peptide growth factor phytosulfokine-α (PSK-α is perceived by LRR receptor kinases. In this study, a role for PSK signaling through PSK receptor PSKR1 in Arabidopsis thaliana hypocotyl cell elongation is established. Hypocotyls of etiolated pskr1-2 and pskr1-3 seedlings, but not of pskr2-1 seedlings were shorter than wt due to reduced cell elongation. Treatment with PSK-α did not promote hypocotyl growth indicating that PSK levels were saturating. Tyrosylprotein sulfotransferase (TPST is responsible for sulfation and hence activation of the PSK precursor. The tpst-1 mutant displayed shorter hypocotyls with shorter cells than wt. Treatment of tpst-1 seedlings with PSK-α partially restored elongation growth in a dose-dependent manner. Hypocotyl elongation was significantly enhanced in tpst-1 seedlings at nanomolar PSK-α concentrations. Cell expansion was studied in hypocotyl protoplasts. WT and pskr2-1 protoplasts expanded in the presence of PSK-α in a dose-dependent manner. By contrast, pskr1-2 and pskr1-3 protoplasts were unresponsive to PSK-α. Protoplast swelling in response to PSK-α was unaffected by ortho-vanadate, which inhibits the plasma membrane H(+-ATPase. In maize (Zea mays L., coleoptile protoplast expansion was similarly induced by PSK-α in a dose-dependent manner and was dependent on the presence of K(+ in the media. In conclusion, PSK-α signaling of hypocotyl elongation and protoplast expansion occurs through PSKR1 and likely involves K(+ uptake, but does not require extracellular acidification by the plasma membrane H(+-ATPase.

  2. Salt-mediated changes in leaf mesophyll cells of Lycopersicon esculentum Mill. plants

    Directory of Open Access Journals (Sweden)

    Magdalena Gapinska

    2014-09-01

    Full Text Available Five-week-old tomato plants (Lycopersicon esculentum cv. Perkoz grown in pots containing garden soil in a growth chamber were submitted to 50 or 150 mM NaCl for 1 h, 2 and 5 days. Tomato leaf anatomy generally did not change after short time salinity, except 5-day-treatment with 150 mM NaCl, where changed cell shape (shrunk and deformed simultaneously with increased volume of intercellular spaces (IS were observed. Although leaf hydration (H depleted only 1 h after 150 mM NaCl treatment both salt concentrations generated two coexisting populations of salt-affected mesophyll cells: (i slightly-affected (Sl-A which showed incipient plasmolysis or slightly changed shapes, and (ii severely-affected (Sv-A which showed severe plasmolysis; serious deformation of cell shape or disorganization including cell degeneration. In Sl-A cells salinity changed location and shape of chloroplasts which were: more rounded, with oversized starch grains (SG (2d or more flat (5d. Salt-mediated changes were becoming more distinguished and pronounced with length of 150 mM NaCl treatment. The amount of salt-affected cells was changing during the experiment and depended on the salt concentration. In 50 mM-treated plants salt-affected cells appeared 1 h after treatment (~40% and raised up to 78% on 2nd day, however the population of Sl-A cells dominated. In 150 mM NaCl-treated plants the percentage of affected cells raised during the experiment from 75% to 99%. Firstly Sl-A cells dominated, but on the 5th day the majority was Sv-A. Salt-affected cells were distributed quite evenly in palisade or spongy mesophyll, except 2 d after treatment with 50 mM NaCl, when their number was higher in the palisade mesophyll. Sv-A cells in the spongy mesophyll were located mostly near the bundle while in the palisade mesophyll more irregularly. Different susceptibility of cells to salt stress might be the consequence of an unequal distribution of osmotic stress and subsequent ionic

  3. The MYB23 gene provides a positive feedback loop for cell fate specification in the Arabidopsis root epidermis.

    Science.gov (United States)

    Kang, Yeon Hee; Kirik, Victor; Hulskamp, Martin; Nam, Kyoung Hee; Hagely, Katherine; Lee, Myeong Min; Schiefelbein, John

    2009-04-01

    The specification of cell fates during development requires precise regulatory mechanisms to ensure robust cell type patterns. Theoretical models of pattern formation suggest that a combination of negative and positive feedback mechanisms are necessary for efficient specification of distinct fates in a field of differentiating cells. Here, we examine the role of the R2R3-MYB transcription factor gene, AtMYB23 (MYB23), in the establishment of the root epidermal cell type pattern in Arabidopsis thaliana. MYB23 is closely related to, and is positively regulated by, the WEREWOLF (WER) MYB gene during root epidermis development. Furthermore, MYB23 is able to substitute for the function of WER and to induce its own expression when controlled by WER regulatory sequences. We also show that the MYB23 protein binds to its own promoter, suggesting a MYB23 positive feedback loop. The localization of MYB23 transcripts and MYB23-green fluorescent protein (GFP) fusion protein, as well as the effect of a chimeric MYB23-SRDX repressor construct, links MYB23 function to the developing non-hair cell type. Using mutational analyses, we find that MYB23 is necessary for precise establishment of the root epidermal pattern, particularly under conditions that compromise the cell specification process. These results suggest that MYB23 participates in a positive feedback loop to reinforce cell fate decisions and ensure robust establishment of the cell type pattern in the Arabidopsis root epidermis.

  4. AMIODARONE INDUCES THE SYNTHESIS OF HSPS IN SACCHAROMYCES CEREVISIAE AND ARABIDOPSIS THALIANA CELLS

    Directory of Open Access Journals (Sweden)

    Pyatrikas D.V.

    2012-08-01

    Full Text Available Many biotic and abiotic stresses cause an increase of cytosolic Ca2+ level in cells. Calcium is one of the most important second messengers, regulating many various activities in the cell and was known to affect expression of stress activated genes. Mild heat shock induces the expression of heat shock proteins (Hsps which protect cell from drastic heat shock exposure. There are some literature data permitting to suggest that transient elevation of cytosolic Ca2+ level in plant cells is important for activation of Hsps expression. On the other hand mitochondria are known to regulate the intracellular calcium and reactive oxygen species signaling. It has been shown recently that mild heat shock induces hyperpolarization of inner mitochondrial membrane in plant and yeast cells and this event is critically important for activation of Hsps expression. To reveal the relationship between mitochondrial activity, intracellular calcium homeostasis and Hsps expression an antiarrhythmic drug amiodarone (AMD have been used. AMD is known to cause transient increase of cytosolic Ca2+ level in Saccharomyces cerevisiae. Obtained results have showed that AMD treatment induced the synthesis of Hsp104p in S. cerevisiae cells and Hsp101p in A. thaliana cell culture. Induction of Hsp104p synthesis leads to enhanced yeast capability to survive lethal heat shock exposure. Development of S. cerevisiae thermotolerance depended significantly on the presence of Hsp104p. Elevation of Hsp104p level in the result of AMD treatment was shown to be governed by activity of Msn2p and Msn4p transcription factors. Deletion of the MSN2 and MSN4 genes abrogated the AMD ability to induce Hsp104p synthesis. Mild heat shock and AMD treatment induced the hyperpolarization of the inner mitochondrial membrane in yeast and Arabidopsis cells which accompanied by HSP synthesis and development of thermotolerance. It was suggested that increase of cytosolic Ca2+ level after AMD treatment

  5. The U-Box/ARM E3 ligase PUB13 regulates cell death, defense, and flowering time in Arabidopsis.

    Science.gov (United States)

    Li, Wei; Ahn, Il-Pyung; Ning, Yuese; Park, Chan-Ho; Zeng, Lirong; Whitehill, Justin G A; Lu, Haibin; Zhao, Qingzhen; Ding, Bo; Xie, Qi; Zhou, Jian-Min; Dai, Liangying; Wang, Guo-Liang

    2012-05-01

    The components in plant signal transduction pathways are intertwined and affect each other to coordinate plant growth, development, and defenses to stresses. The role of ubiquitination in connecting these pathways, particularly plant innate immunity and flowering, is largely unknown. Here, we report the dual roles for the Arabidopsis (Arabidopsis thaliana) Plant U-box protein13 (PUB13) in defense and flowering time control. In vitro ubiquitination assays indicated that PUB13 is an active E3 ubiquitin ligase and that the intact U-box domain is required for the E3 ligase activity. Disruption of the PUB13 gene by T-DNA insertion results in spontaneous cell death, the accumulation of hydrogen peroxide and salicylic acid (SA), and elevated resistance to biotrophic pathogens but increased susceptibility to necrotrophic pathogens. The cell death, hydrogen peroxide accumulation, and resistance to necrotrophic pathogens in pub13 are enhanced when plants are pretreated with high humidity. Importantly, pub13 also shows early flowering under middle- and long-day conditions, in which the expression of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 and FLOWERING LOCUS T is induced while FLOWERING LOCUS C expression is suppressed. Finally, we found that two components involved in the SA-mediated signaling pathway, SID2 and PAD4, are required for the defense and flowering-time phenotypes caused by the loss of function of PUB13. Taken together, our data demonstrate that PUB13 acts as an important node connecting SA-dependent defense signaling and flowering time regulation in Arabidopsis.

  6. Proteomic signature of arabidopsis cell cultures exposed to magnetically induced hyper- and microgravity environments

    NARCIS (Netherlands)

    R. Herranz; A.I. Manzano; J.J.W.A. van Loon; P.C.M. Christianen; F.J. Medina

    2013-01-01

    Earth-based microgravity simulation techniques are required due to space research constraints. Using diamagnetic levitation, we exposed Arabidopsis thaliana in vitro callus cultures to environments with different levels of effective gravity and magnetic field strengths (B) simultaneously. The enviro

  7. A lower content of de-methylesterified homogalacturonan improves enzymatic cell separation and isolation of mesophyll protoplasts in Arabidopsis.

    Science.gov (United States)

    Lionetti, Vincenzo; Cervone, Felice; De Lorenzo, Giulia

    2015-04-01

    Cell adhesion occurs primarily at the level of middle lamella which is mainly composed by pectin polysaccharides. These can be degraded by cell wall degrading enzymes (CWDEs) during developmental processes to allow a controlled separation of plant cells. Extensive cell wall degradation by CWDEs with consequent cell separation is performed when protoplasts are isolated from plant tissues by using mixtures of CWDEs. We have evaluated whether modification of pectin affects cell separation and protoplast isolation. Arabidopsis plants overexpressing the pectin methylesterase inhibitors AtPMEI-1 or AtPMEI-2, and Arabidopsis pme3 plants, mutated in the gene encoding pectin methylesterase 3, showed an increased efficiency of isolation of viable mesophyll protoplasts as compared with Wild Type Columbia-0 plants. The release of protoplasts was correlated with the reduced level of long stretches of de-methylesterified homogalacturonan (HGA) present in these plants. Response to elicitation, cell wall regeneration and efficiency of transfection in protoplasts from transgenic plants was comparable to those of wild type protoplasts.

  8. Proteomic signature of Arabidopsis cell cultures exposed to magnetically induced hyper- and microgravity environments.

    Science.gov (United States)

    Herranz, Raul; Manzano, Ana I; van Loon, Jack J W A; Christianen, Peter C M; Medina, F Javier

    2013-03-01

    Earth-based microgravity simulation techniques are required due to space research constraints. Using diamagnetic levitation, we exposed Arabidopsis thaliana in vitro callus cultures to environments with different levels of effective gravity and magnetic field strengths (B) simultaneously. The environments included simulated 0 g* at B=10.1 T, an internal 1 g* control (B=16.5 T), and hypergravity (2 g* at B=10.1 T). Furthermore, samples were also exposed to altered gravity environments that were created with mechanical devices, such as the Random Positioning Machine (simulated μg) and the Large Diameter Centrifuge (2 g). We have determined the proteomic signature of cell cultures exposed to these altered-gravity environments by means of the difference gel electrophoresis (DiGE) technique, and we have compared the results with microarray-based transcriptomes from the same samples. The magnetic field itself produced a low number of proteomic alterations, but the combination of gravitational alteration and magnetic field exposure produced synergistic effects on the proteome of plants (the number of significant changes is 3-7 times greater). Tandem mass spectrometry identification of 19 overlapping spots in the different conditions corroborates a major role of abiotic stress and secondary metabolism proteins in the molecular adaptation of plants to unusual environments, including microgravity.

  9. Enhanced arsenic accumulation by engineered yeast cells expressing Arabidopsis thaliana phytochelatin synthase.

    Science.gov (United States)

    Singh, Shailendra; Lee, Wonkyu; Dasilva, Nancy A; Mulchandani, Ashok; Chen, Wilfred

    2008-02-01

    Phytochelatins (PCs) are naturally occurring peptides with high-binding capabilities for a wide range of heavy metals including arsenic (As). PCs are enzymatically synthesized by phytochelatin synthases and contain a (gamma-Glu-Cys)(n) moiety terminated by a Gly residue that makes them relatively proteolysis resistant. In this study, PCs were introduced by expressing Arabidopsis thaliana Phytochelatin Synthase (AtPCS) in the yeast Saccharomyces cerevisiae for enhanced As accumulation and removal. PCs production in yeast resulted in six times higher As accumulation as compared to the control strain under a wide range of As concentrations. For the high-arsenic concentration, PCs production led to a substantial decrease in levels of PC precursors such as glutathione (GSH) and gamma-glutamyl cysteine (gamma-EC). The levels of As(III) accumulation were found to be similar between AtPCS-expressing wild type strain and AtPCS-expressing acr3Delta strain lacking the arsenic efflux system, suggesting that the arsenic uptake may become limiting. This is further supported by the roughly 1:3 stoichiometric ratio between arsenic and PC2 (n = 2) level (comparing with a theoretical value of 1:2), indicating an excess availability of PCs inside the cells. However, at lower As(III) concentration, PC production became limiting and an additive effect on arsenic accumulation was observed for strain lacking the efflux system. More importantly, even resting cells expressing AtPCS pre-cultured in Zn(2+) enriched media showed PCs production and two times higher arsenic removal than the control strain. These results open up the possibility of using cells expressing AtPCS as an inexpensive sorbent for the removal of toxic arsenic.

  10. Role of callose synthases in transfer cell wall development in tocopherol deficient Arabidopsis mutants

    Directory of Open Access Journals (Sweden)

    Hiroshi eMaeda

    2014-02-01

    Full Text Available Tocopherols (vitamin E are lipid-soluble antioxidants produced by all plants and algae, and many cyanobacteria, yet their functions in these photosynthetic organisms are still not fully understood. We have previously reported that the vitamin E deficient 2 (vte2 mutant of Arabidopsis thaliana is sensitive to low temperature (LT due to impaired transfer cell wall (TCW development and photoassimilate export, associated with massive callose deposition in transfer cells of the phloem. To further understand the role of tocopherols in LT induced TCW development we compared global transcript profiles of vte2 and wild type leaves during LT treatment. Tocopherol deficiency had no impact on global gene expression in permissive conditions, but affected expression of 77 genes after 48 hours of LT treatment. In vte2 relative to wild type, genes related with solute transport were repressed, while those involved in various pathogen responses and cell wall modifications, such as GLUCAN SYNTHASE LIKE genes (GSL4 and GSL11, were induced. However, introduction of gsl4 or gsl11 mutations into the vte2 background did not suppress callose deposition or the overall LT-induced phenotypes of vte2. Intriguingly, introduction of a mutation of GSL5, the major GSL responsible for pathogen-induced callose deposition, into vte2 substantially reduced vascular callose deposition at LT, but again had no effect on the photoassimilate export phenotype of LT-treated vte2. These results suggest that GSL5 plays a major role in TCW callose deposition in LT-treated vte2 but that this GSL5-dependent callose deposition is not the primary cause of the impaired photoassimilate export phenotype.

  11. SIMULATION OF THE LIGHT-INDUCED OSCILLATIONS OF THE MEMBRANE-POTENTIAL IN POTAMOGETON LEAF-CELLS

    NARCIS (Netherlands)

    MIEDEMA, H; PRINS, HBA

    1993-01-01

    An attempt has been made to simulate the light-induced oscillations of the membrane potential of Potamogeton lucens leaf cells in relation to the apoplastic pH changes. Previously it was demonstrated that the membrane potential of these cells can be described in terms of proton movements only. It is

  12. Calcium-calmodulin signalling is involved in light-induced acidification by epidermal leaf cells of pea, Pisum sativum L.

    NARCIS (Netherlands)

    Elzenga, JTM; Staal, M; Prins, HBA

    1997-01-01

    Pathways of signal transduction of red and blue light-dependent acidification by leaf epidermal cells were studied using epidermal strips of the Argenteum mutant of Pisum sativum. In these preparations the contribution of guard cells to the acidification is minimal. The hydroxypyridine nifedipine, a

  13. Tissue organization and cell ultrastructure in the roots of three Arabidopsis species grown at different zinc concentrations

    Directory of Open Access Journals (Sweden)

    M. Čiamporová

    2015-05-01

    Full Text Available The model plant Arabidopsis thaliana is known to be heavy metal-sensitive in contrast to its relative species A. arenosa and A. halleri classified as pseudometallophytes. Quantitative differences in primary root anatomy previously found between A. thaliana and the non-metallicolous (NM and metallicolous (M populations of the non-model Arabidopsis species necessitated further research at cellular and ultrastructural levels. Seedlings of A. thaliana, ecotype Columbia and a natural population Ratkovo, the NM and M populations of A. arenosa and A. halleri were grown on agar medium containing 10 μM (control and 1000 μM Zn2+ for 5 days. Light microscopy confirmed the higher number of cells in the endodermal, cortical and epidermal layers and a higher incidence of additional cell tiers, the so-called middle cortex (MC in the tolerant genotypes. Such differences were present in untreated plants and even more pronounced in plants exposed to excess of zinc (Zn. Electron microscopy of the root tissues at comparable distances from the root tip showed Casparian bands only in the radial cell walls of endodermis of A. halleri M population originating from severely (Cu, Cd and Pb contaminated site. Casparian bands were not differentiated yet in the roots of the other species and populations, and they were not formed in the cell walls between endodermis and MC cells. In the apical cytoplasm of trichoblast bulges, autophagic vacuoles were found only in the sensitive A. thaliana and small vacuoles in the other genotypes. The enhanced concentration of Zn confirmed the higher metal sensitivity of the model species and did not substantially disturb the root cell ultrastructure of the tolerant Arabidopsis species.

  14. Different myrosinase and idioblast distribution in Arabidopsis and Brassica napus

    DEFF Research Database (Denmark)

    Andreasson, Erik; Jørgensen, Lise Bolt; Höglund, Anna-Stina;

    2001-01-01

    Arabidopsis, Brassica napus, Myrosinase, Myrosinase Binding Protein, Glucosinolates, Myrosin Cell, Immunocytochemistry......Arabidopsis, Brassica napus, Myrosinase, Myrosinase Binding Protein, Glucosinolates, Myrosin Cell, Immunocytochemistry...

  15. Common and unique elements of the ABA-regulated transcriptome of Arabidopsis guard cells

    Directory of Open Access Journals (Sweden)

    Zhao Zhixin

    2011-05-01

    Full Text Available Abstract Background In the presence of drought and other desiccating stresses, plants synthesize and redistribute the phytohormone abscisic acid (ABA. ABA promotes plant water conservation by acting on specialized cells in the leaf epidermis, guard cells, which border and regulate the apertures of stomatal pores through which transpirational water loss occurs. Following ABA exposure, solute uptake into guard cells is rapidly inhibited and solute loss is promoted, resulting in inhibition of stomatal opening and promotion of stomatal closure, with consequent plant water conservation. There is a wealth of information on the guard cell signaling mechanisms underlying these rapid ABA responses. To investigate ABA regulation of gene expression in guard cells in a systematic genome-wide manner, we analyzed data from global transcriptomes of guard cells generated with Affymetrix ATH1 microarrays, and compared these results to ABA regulation of gene expression in leaves and other tissues. Results The 1173 ABA-regulated genes of guard cells identified by our study share significant overlap with ABA-regulated genes of other tissues, and are associated with well-defined ABA-related promoter motifs such as ABREs and DREs. However, we also computationally identified a unique cis-acting motif, GTCGG, associated with ABA-induction of gene expression specifically in guard cells. In addition, approximately 300 genes showing ABA-regulation unique to this cell type were newly uncovered by our study. Within the ABA-regulated gene set of guard cells, we found that many of the genes known to encode ion transporters associated with stomatal opening are down-regulated by ABA, providing one mechanism for long-term maintenance of stomatal closure during drought. We also found examples of both negative and positive feedback in the transcriptional regulation by ABA of known ABA-signaling genes, particularly with regard to the PYR/PYL/RCAR class of soluble ABA receptors and

  16. Oleuropein-Enriched Olive Leaf Extract Affects Calcium Dynamics and Impairs Viability of Malignant Mesothelioma Cells

    Directory of Open Access Journals (Sweden)

    Carla Marchetti

    2015-01-01

    Full Text Available Malignant mesothelioma is a poor prognosis cancer in urgent need of alternative therapies. Oleuropein, the major phenolic of olive tree (Olea europaea L., is believed to have therapeutic potentials for various diseases, including tumors. We obtained an oleuropein-enriched fraction, consisting of 60% w/w oleuropein, from olive leaves, and assessed its effects on intracellular Ca2+ and cell viability in mesothelioma cells. Effects of the oleuropein-enriched fraction on Ca2+ dynamics and cell viability were studied in the REN mesothelioma cell line, using fura-2 microspectrofluorimetry and MTT assay, respectively. Fura-2-loaded cells, transiently exposed to the oleuropein-enriched fraction, showed dose-dependent transient elevations of cytosolic Ca2+ concentration (Ca2+i. Application of standard oleuropein and hydroxytyrosol, and of the inhibitor of low-voltage T-type Ca2+ channels NNC-55-0396, suggested that the effect is mainly due to oleuropein acting through its hydroxytyrosol moiety on T-type Ca2+ channels. The oleuropein-enriched fraction and standard oleuropein displayed a significant antiproliferative effect, as measured on REN cells by MTT cell viability assay, with IC50 of 22 μg/mL oleuropein. Data suggest that our oleuropein-enriched fraction from olive leaf extract could have pharmacological application in malignant mesothelioma anticancer therapy, possibly by targeting T-type Ca2+ channels and thereby dysregulating intracellular Ca2+ dynamics.

  17. Hibiscus sabdariffa leaf polyphenolic extract induces human melanoma cell death, apoptosis, and autophagy.

    Science.gov (United States)

    Chiu, Chun-Tang; Hsuan, Shu-Wen; Lin, Hui-Hsuan; Hsu, Cheng-Chin; Chou, Fen-Pi; Chen, Jing-Hsien

    2015-03-01

    Melanoma is the least common but most fatal form of skin cancer. Previous studies have indicated that an aqueous extract of Hibiscus sabdariffa leaves possess hypoglycemic, hypolipidemic, and antioxidant effects. In this study, we want to investigate the anticancer activity of Hibiscus leaf polyphenolic (HLP) extract in melanoma cells. First, HLP was exhibited to be rich in epicatechin gallate (ECG) and other polyphenols. Apoptotic and autophagic activities of HLP and ECG were further evaluated by DAPI stain, cell-cycle analysis, and acidic vascular organelle (AVO) stain. Our results revealed that both HLP and ECG induced the caspases cleavages, Bcl-2 family proteins regulation, and Fas/FasL activation in A375 cells. In addition, we also revealed that the cells presented AVO-positive after HLP treatments. HLP could increase the expressions of autophagy-related proteins autophagy-related gene 5 (ATG5), Beclin1, and light chain 3-II (LC3-II), and induce autophagic cell death in A375 cells. These data indicated that the anticancer effect of HLP, partly contributed by ECG, in A375 cells. HLP potentially could be developed as an antimelanoma agent. PMID:25694272

  18. Cadmium uptake and sequestration kinetics in individual leaf cell protoplasts of the Cd/Zn hyperaccumulator Thlaspi caerulescens

    OpenAIRE

    Leitenmaier, Barbara; Küpper, Hendrik

    2011-01-01

    Hyperaccumulators store accumulated metals in the vacuoles of large leaf epidermal cells (storage cells). For investigating cadmium uptake, we incubated protoplasts obtained from leaves of Thlaspi caerulescens (Ganges ecotype) with a Cd-specific fluorescent dye. A fluorescence kinetic microscope was used for selectively measuring Cd-uptake and photosynthesis in different cell types, so that physical separation of cell types was not necessary. Few minutes after its addition, cadmium accumulate...

  19. Xyloglucan Metabolism Differentially Impacts the Cell Wall Characteristics of the Endosperm and Embryo during Arabidopsis Seed Germination.

    Science.gov (United States)

    Sechet, Julien; Frey, Anne; Effroy-Cuzzi, Delphine; Berger, Adeline; Perreau, François; Cueff, Gwendal; Charif, Delphine; Rajjou, Loïc; Mouille, Grégory; North, Helen M; Marion-Poll, Annie

    2016-03-01

    Cell wall remodeling is an essential mechanism for the regulation of plant growth and architecture, and xyloglucans (XyGs), the major hemicellulose, are often considered as spacers of cellulose microfibrils during growth. In the seed, the activity of cell wall enzymes plays a critical role in germination by enabling embryo cell expansion leading to radicle protrusion, as well as endosperm weakening prior to its rupture. A screen for Arabidopsis (Arabidopsis thaliana) mutants affected in the hormonal control of germination identified a mutant, xyl1, able to germinate on paclobutrazol, an inhibitor of gibberellin biosynthesis. This mutant also exhibited reduced dormancy and increased resistance to high temperature. The XYL1 locus encodes an α-xylosidase required for XyG maturation through the trimming of Xyl. The xyl1 mutant phenotypes were associated with modifications to endosperm cell wall composition that likely impact on its resistance, as further demonstrated by the restoration of normal germination characteristics by endosperm-specific XYL1 expression. The absence of phenotypes in mutants defective for other glycosidases, which trim Gal or Fuc, suggests that XYL1 plays the major role in this process. Finally, the decreased XyG abundance in hypocotyl longitudinal cell walls of germinating embryos indicates a potential role in cell wall loosening and anisotropic growth together with pectin de-methylesterification. PMID:26826221

  20. Constitutive activation of AtMEK5, a MAPK kinase, induces salicylic acid-independent cell death in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    LIU Hongxia; WANG Ying; ZHOU Tianhong; SUN Yujing; LIU Guoqin; REN Dongtao

    2004-01-01

    AtMEK5DD is an active mutant of AtMEK5, a MAP kinase kinase in Arabidopsis. Induction of AtMEK5DD expression in transgenic plants leads to activation of 44 and 48 kD MAPKs and causes a rapid cell death. To compare the cell death induced by the expression of AtMEK5DD with the HR-cell death induced by avirulence pathogen infection, we analyzed the activation of downstream MAP Kinase and induction of PR genes expression in permanent transgenic Arabidopsis plants. In-gel kinase activity assay revealed that the infection of Pseudomonas syringae DC3000 harboring Avr Rpt2 gene also lead to activation of 44 and 48 kD MAPKs. PAL, PR1 and PR5 were strongly induced in plants undergoing HR-cell death caused by the infection of P. Syringae DC3000, while only the expression of PR5 was strongly induced in transgenic plants expressing AtMEK5DD protein. NahG protein in AtMEK5DD×NahG plants cannot suppress the cell death induced by AtMEK5DD. And AtMEK5DD protein expressed AtMEK5DD×NahG plants showed no significant change in salicylic acid (SA)level.All these suggest that the cell death induced by the activation of AtMEK5 is salicylic acid-independent.

  1. Evaluation of cell wall preparations for proteomics: a new procedure for purifying cell walls from Arabidopsis hypocotyls

    Directory of Open Access Journals (Sweden)

    Canut Hervé

    2006-05-01

    Full Text Available Abstract Background The ultimate goal of proteomic analysis of a cell compartment should be the exhaustive identification of resident proteins; excluding proteins from other cell compartments. Reaching such a goal closely depends on the reliability of the isolation procedure for the cell compartment of interest. Plant cell walls possess specific difficulties: (i the lack of a surrounding membrane may result in the loss of cell wall proteins (CWP during the isolation procedure, (ii polysaccharide networks of cellulose, hemicelluloses and pectins form potential traps for contaminants such as intracellular proteins. Several reported procedures to isolate cell walls for proteomic analyses led to the isolation of a high proportion (more than 50% of predicted intracellular proteins. Since isolated cell walls should hold secreted proteins, one can imagine alternative procedures to prepare cell walls containing a lower proportion of contaminant proteins. Results The rationales of several published procedures to isolate cell walls for proteomics were analyzed, with regard to the bioinformatic-predicted subcellular localization of the identified proteins. Critical steps were revealed: (i homogenization in low ionic strength acid buffer to retain CWP, (ii purification through increasing density cushions, (iii extensive washes with a low ionic strength acid buffer to retain CWP while removing as many cytosolic proteins as possible, and (iv absence of detergents. A new procedure was developed to prepare cell walls from etiolated hypocotyls of Arabidopsis thaliana. After salt extraction, a high proportion of proteins predicted to be secreted was released (73%, belonging to the same functional classes as proteins identified using previously described protocols. Finally, removal of intracellular proteins was obtained using detergents, but their amount represented less than 3% in mass of the total protein extract, based on protein quantification. Conclusion The

  2. Glucosylceramides are critical for cell-type differentiation and organogenesis, but not for cell viability in Arabidopsis.

    Science.gov (United States)

    Msanne, Joseph; Chen, Ming; Luttgeharm, Kyle D; Bradley, Amanda M; Mays, Elizabeth S; Paper, Janet M; Boyle, Daniel L; Cahoon, Rebecca E; Schrick, Kathrin; Cahoon, Edgar B

    2015-10-01

    Glucosylceramides (GlcCer), glucose-conjugated sphingolipids, are major components of the endomembrane system and plasma membrane in most eukaryotic cells. Yet the quantitative significance and cellular functions of GlcCer are not well characterized in plants and other multi-organ eukaryotes. To address this, we examined Arabidopsis lines that were lacking or deficient in GlcCer by insertional disruption or by RNA interference (RNAi) suppression of the single gene for GlcCer synthase (GCS, At2g19880), the enzyme that catalyzes GlcCer synthesis. Null mutants for GCS (designated 'gcs-1') were viable as seedlings, albeit strongly reduced in size, and failed to develop beyond the seedling stage. Heterozygous plants harboring the insertion allele exhibited reduced transmission through the male gametophyte. Undifferentiated calli generated from gcs-1 seedlings and lacking GlcCer proliferated in a manner similar to calli from wild-type plants. However, gcs-1 calli, in contrast to wild-type calli, were unable to develop organs on differentiation media. Consistent with a role for GlcCer in organ-specific cell differentiation, calli from gcs-1 mutants formed roots and leaves on media supplemented with the glucosylated sphingosine glucopsychosine, which was readily converted to GlcCer independent of GCS. Underlying these phenotypes, gcs-1 cells had altered Golgi morphology and fewer cisternae per Golgi apparatus relative to wild-type cells, indicative of protein trafficking defects. Despite seedling lethality in the null mutant, GCS RNAi suppression lines with ≤2% of wild-type GlcCer levels were viable and fertile. Collectively, these results indicate that GlcCer are essential for cell-type differentiation and organogenesis, and plant cells produce amounts of GlcCer in excess of that required for normal development. PMID:26313010

  3. Arabidopsis brassinosteroid biosynthetic mutant dwarf7-1 exhibits slower rates of cell division and shoot induction

    Directory of Open Access Journals (Sweden)

    Schulz Burkhard

    2010-12-01

    Full Text Available Abstract Background Plant growth depends on both cell division and cell expansion. Plant hormones, including brassinosteroids (BRs, are central to the control of these two cellular processes. Despite clear evidence that BRs regulate cell elongation, their roles in cell division have remained elusive. Results Here, we report results emphasizing the importance of BRs in cell division. An Arabidopsis BR biosynthetic mutant, dwarf7-1, displayed various characteristics attributable to slower cell division rates. We found that the DWARF4 gene which encodes for an enzyme catalyzing a rate-determining step in the BR biosynthetic pathways, is highly expressed in the actively dividing callus, suggesting that BR biosynthesis is necessary for dividing cells. Furthermore, dwf7-1 showed noticeably slower rates of callus growth and shoot induction relative to wild-type control. Flow cytometric analyses of the nuclei derived from either calli or intact roots revealed that the cell division index, which was represented as the ratio of cells at the G2/M vs. G1 phases, was smaller in dwf7-1 plants. Finally, we found that the expression levels of the genes involved in cell division and shoot induction, such as PROLIFERATING CELL NUCLEAR ANTIGEN2 (PCNA2 and ENHANCER OF SHOOT REGENERATION2 (ESR2, were also lower in dwf7-1 as compared with wild type. Conclusions Taken together, results of callus induction, shoot regeneration, flow cytometry, and semi-quantitative RT-PCR analysis suggest that BRs play important roles in both cell division and cell differentiation in Arabidopsis.

  4. Stability and efficiency of dye-sensitized solar cells based on papaya-leaf dye

    Science.gov (United States)

    Suyitno, Suyitno; Saputra, Trisma Jaya; Supriyanto, Agus; Arifin, Zainal

    2015-09-01

    The present article reports on the enhancement of the performance and stability of natural dye-based dye-sensitized solar cells (DSSCs). Natural dyes extracted from papaya leaves (PL) were investigated as sensitizers in TiO2-based DSSCs and evaluated in comparison with N719 dye. The acidity of the papaya-leaf extract dyes was tuned by adding benzoic acid. The TiO2 film-coated fluorine-doped tin oxide glass substrates were prepared using the doctor-blade method, followed by sintering at 450 °C. The counter electrode was coated by chemically deposited catalytic platinum. The working electrodes were immersed in N719 dye and papaya dye solutions with concentrations of 8 g/100 mL. The absorbance spectra of the dyes were obtained by ultra-violet-visible spectroscopy. The energy levels of the dyes were measured by the method of cyclic voltammetry. In addition, Fourier transform infrared spectroscopy was used to determine the characteristic functionalities of the dye molecules. The DSSC based on the N719 dye displayed a highest efficiency of 0.87% whereas those based on papaya-leaf dye achieved 0.28% at pH 3.5. The observed improved efficiency of the latter was attributed to the increased current density value. Furthermore, the DSSCs based on papaya-leaf dye with pH 3.5-4 exhibited better stability than those based on N719 dye. However, further studies are required to improve the current density and stability of natural dye-based DSSCs, including the investigation of alternative dye extraction routes, such as isolating the pure chlorophyll from papaya leaves and stabilizing it.

  5. Fasciclin-like arabinogalactan proteins: specialization for stem biomechanics and cell wall architecture in Arabidopsis and Eucalyptus.

    Science.gov (United States)

    MacMillan, Colleen P; Mansfield, Shawn D; Stachurski, Zbigniew H; Evans, Rob; Southerton, Simon G

    2010-05-01

    The ancient cell adhesion fasciclin (FAS) domain is found in bacteria, fungi, algae, insects and animals, and occurs in a large family of fasciclin-like arabinogalactan proteins (FLAs) in higher plants. Functional roles for FAS-containing proteins have been determined for insects, algae and vertebrates; however, the biological functions of the various higher-plant FLAs are not clear. Expression of some FLAs has been correlated with the onset of secondary-wall cellulose synthesis in Arabidopsis stems, and also with wood formation in the stems and branches of trees, suggesting a biological role in plant stems. We examined whether FLAs contribute to plant stem biomechanics. Using phylogenetic, transcript abundance and promoter-GUS fusion analyses, we identified a conserved subset of single FAS domain FLAs (group A FLAs) in Eucalyptus and Arabidopsis that have specific and high transcript abundance in stems, particularly in stem cells undergoing secondary-wall deposition, and that the phylogenetic conservation appears to extend to other dicots and monocots. Gene-function analyses revealed that Arabidopsis T-DNA knockout double mutant stems had altered stem biomechanics with reduced tensile strength and a reduced tensile modulus of elasticity, as well as altered cell-wall architecture and composition, with increased cellulose microfibril angle and reduced arabinose, galactose and cellulose content. Using materials engineering concepts, we relate the effects of these FLAs on cell-wall composition with stem biomechanics. Our results suggest that a subset of single FAS domain FLAs contributes to plant stem strength by affecting cellulose deposition, and to the stem modulus of elasticity by affecting the integrity of the cell-wall matrix.

  6. Cell Geometry Guides the Dynamic Targeting of Apoplastic GPI-Linked Lipid Transfer Protein to Cell Wall Elements and Cell Borders in Arabidopsis thaliana

    Science.gov (United States)

    Wasteneys, Geoffrey

    2013-01-01

    During cellular morphogenesis, changes in cell shape and cell junction topology are fundamental to normal tissue and organ development. Here we show that apoplastic Glycophosphatidylinositol (GPI)-anchored Lipid Transfer Protein (LTPG) is excluded from cell junctions and flat wall regions, and passively accumulates around their borders in the epidermal cells of Arabidopsis thaliana. Beginning with intense accumulation beneath highly curved cell junction borders, this enrichment is gradually lost as cells become more bulbous during their differentiation. In fully mature epidermal cells, YFP-LTPG often shows a fibrous cellulose microfibril-like pattern within the bulging outer faces. Physical contact between a flat glass surface and bulbous cell surface induces rapid and reversible evacuation from contact sites and accumulation to the curved wall regions surrounding the contact borders. Thus, LTPG distribution is dynamic, responding to changes in cell shape and wall curvature during cell growth and differentiation. We hypothesize that this geometry-based mechanism guides wax-carrying LTPG to functional sites, where it may act to “seal” the vulnerable border surrounding cell-cell junctions and assist in cell wall fortification and cuticular wax deposition. PMID:24260561

  7. Role of SCHIZORIZA in asymmetric cell division, cell fate segregation and specification in Arabidopsis root development

    NARCIS (Netherlands)

    Jansweijer, V.M.A.

    2013-01-01

    Multicellular organisms develop their large variety of cell types from just one single cell, the zygote. Both plants and animals use asymmetric cell division to establish a multicellular body plan How different cell and tissue types are determined, how patterns are created and maintained, and which

  8. Genetic analysis of the Arabidopsis protein kinases MAP3Kε1 and MAP3Kε2 indicates roles in cell expansion and embryo development.

    Science.gov (United States)

    Chaiwongsar, Suraphon; Strohm, Allison K; Su, Shih-Heng; Krysan, Patrick J

    2012-01-01

    MAP3Kε1 and MAP3Kε2 are a pair of Arabidopsis thaliana genes that encode protein kinases related to cdc7p from Saccharomyces cerevisiae. We have previously shown that the map3kε1;map3kε2 double-mutant combination causes pollen lethality. In this study, we have used an ethanol-inducible promoter construct to rescue this lethal phenotype and create map3kε1(-/-);map3kε2(-/-) double-mutant plants in order to examine the function of these genes in the sporophyte. These rescued double-mutant plants carry a yellow fluorescent protein (YFP)-MAP3Kε1 transgene under the control of the alcohol-inducible AlcA promoter from Aspergillus nidulans. The double-mutant plants were significantly smaller and had shorter roots than wild-type when grown in the absence of ethanol treatment. Microscopic analysis indicated that cell elongation was reduced in the roots of the double-mutant plants and cell expansion was reduced in rosette leaves. Treatment with ethanol to induce expression of YFP-MAP3Kε1 largely rescued the leaf phenotypes. The double-mutant combination also caused embryos to arrest in the early stages of development. Through the use of YFP reporter constructs we determined that MAP3Kε1 and MAP3Kε2 are expressed during embryo development, and also in root tissue. Our results indicate that MAP3Kε1 and MAP3Kε2 have roles outside of pollen development and that these genes affect several aspects of sporophyte development.

  9. The MADS domain protein DIANA acts together with AGAMOUS-LIKE80 to specify the central cell in Arabidopsis ovules.

    Science.gov (United States)

    Bemer, Marian; Wolters-Arts, Mieke; Grossniklaus, Ueli; Angenent, Gerco C

    2008-08-01

    MADS box genes in plants consist of MIKC-type and type I genes. While MIKC-type genes have been studied extensively, the functions of type I genes are still poorly understood. Evidence suggests that type I MADS box genes are involved in embryo sac and seed development. We investigated two independent T-DNA insertion alleles of the Arabidopsis thaliana type I MADS box gene AGAMOUS-LIKE61 (AGL61) and showed that in agl61 mutant ovules, the polar nuclei do not fuse and central cell morphology is aberrant. Furthermore, the central cell begins to degenerate before fertilization takes place. Although pollen tubes are attracted and perceived by the mutant ovules, neither endosperm development nor zygote formation occurs. AGL61 is expressed in the central cell during the final stages of embryo sac development. An AGL61:green fluorescent protein-beta-glucoronidase fusion protein localizes exclusively to the polar nuclei and the secondary nucleus of the central cell. Yeast two-hybrid analysis showed that AGL61 can form a heterodimer with AGL80 and that the nuclear localization of AGL61 is lost in the agl80 mutant. Thus, AGL61 and AGL80 appear to function together to differentiate the central cell in Arabidopsis. We renamed AGL61 DIANA, after the virginal Roman goddess of the hunt.

  10. Novel nuclear protein ALC-INTERACTING PROTEIN1 is expressed in vascular and mesocarp cells in Arabidopsis.

    Science.gov (United States)

    Wang, Fang; Shi, Dong-Qiao; Liu, Jie; Yang, Wei-Cai

    2008-07-01

    Pod shattering is an agronomical trait that is a result of the coordinated action of cell differentiation and separation. In Arabidopsis, pod shattering is controlled by a complex genetic network in which ALCATRAZ (ALC), a member of the basic helix-loop-helix family, is critical for cell separation during fruit dehiscence. Herein, we report the identification of ALC-INTERACTING PROTEIN1 (ACI1) via the yeast two-hybrid screen. ACI1 encodes a nuclear protein with a lysine-rich domain and a C-terminal serine-rich domain. ACI1 is mainly expressed in the vascular system throughout the plant and mesocarp of the valve in siliques. Our data showed that ACI1 interacts strongly with the N-terminal portion of ALC in yeast cells and in plant cells in the nucleus as demonstrated by bimolecular fluorescence complementation assay. Both ACI1 and ALC share an overlapping expression pattern, suggesting that they likely function together in planta. However, no detectable phenotype was found in plants with reduced ACI1 expression by RNA interference technology, suggesting that ACI1 may be redundant. Taken together, these data indicate that ALC may interact with ACI1 and its homologs to control cell separation during fruit dehiscence in Arabidopsis. PMID:18713402

  11. Novel Nuclear Protein ALC-INTERACTING PROTEIN1 is Expressed in Vascular and Mesocarp Cells in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Fang Wang; Dong-Qiao Shi; Jie Liu; Wei-Cai Yang

    2008-01-01

    Pod shattering is an agronomical trait that is a result of the coordinated action of cell differentiation and separation. In Arabidopsis, pod shattering is controlled by a complex genetic network in which ALCATRAZ (ALC), a member of the basic helix-loop-helix family, is critical for cell separation during fruit dehiscence. Herein, we report the identification of ALC-INTERACTiNG PROTEIN1 (ACI1) via the yeast two-hybrid screen. ACI1 encodes a nuclear protein with a lysine-rich domain and a C-terminal serine-rich domain. ACI1 is mainly expressed in the vascular system throughout the plant and mesocarp of the valve in siliques. Our data showed that ACI1 interacts strongly with the N-terminal portion of ALC in yeast cells and in plant cells in the nucleus as demonstrated by bimolecular fluorescence complementation assay. Both ACl1 and ALC share an overlapping expression pattern, suggesting that they likely function together in planta. However, no detectable phenotype was found in plants with reduced ACI1 expression by RNA interference technology, suggesting that ACI1 may be redundant. Taken together, these data indicate that ALC may interact with ACll and its homologs to control cell separation during fruit dehiscence in Arabidopsis.

  12. EBE, an AP2/ERF transcription factor highly expressed in proliferating cells, affects shoot architecture in Arabidopsis.

    Science.gov (United States)

    Mehrnia, Mohammad; Balazadeh, Salma; Zanor, María-Inés; Mueller-Roeber, Bernd

    2013-06-01

    We report about ERF BUD ENHANCER (EBE; At5g61890), a transcription factor that affects cell proliferation as well as axillary bud outgrowth and shoot branching in Arabidopsis (Arabidopsis thaliana). EBE encodes a member of the APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) transcription factor superfamily; the gene is strongly expressed in proliferating cells and is rapidly and transiently up-regulated in axillary meristems upon main stem decapitation. Overexpression of EBE promotes cell proliferation in growing calli, while the opposite is observed in EBE-RNAi lines. EBE overexpression also stimulates axillary bud formation and outgrowth, while repressing it results in inhibition of bud growth. Global transcriptome analysis of estradiol-inducible EBE overexpression lines revealed 48 EBE early-responsive genes, of which 14 were up-regulated and 34 were down-regulated. EBE activates several genes involved in cell cycle regulation and dormancy breaking, including D-type cyclin CYCD3;3, transcription regulator DPa, and BRCA1-ASSOCIATED RING DOMAIN1. Among the down-regulated genes were DORMANCY-ASSOCIATED PROTEIN1 (AtDRM1), AtDRM1 homolog, MEDIATOR OF ABA-REGULATED DORMANCY1, and ZINC FINGER HOMEODOMAIN5. Our data indicate that the effect of EBE on shoot branching likely results from an activation of genes involved in cell cycle regulation and dormancy breaking.

  13. Cadmium uptake and sequestration kinetics in individual leaf cell protoplasts of the Cd/Zn hyperaccumulator Thlaspi caerulescens.

    Science.gov (United States)

    Leitenmaier, Barbara; Küpper, Hendrik

    2011-02-01

    Hyperaccumulators store accumulated metals in the vacuoles of large leaf epidermal cells (storage cells). For investigating cadmium uptake, we incubated protoplasts obtained from leaves of Thlaspi caerulescens (Ganges ecotype) with a Cd-specific fluorescent dye. A fluorescence kinetic microscope was used for selectively measuring Cd-uptake and photosynthesis in different cell types, so that physical separation of cell types was not necessary. Few minutes after its addition, cadmium accumulated in the cytoplasm before its transport into the vacuole. This demonstrated that vacuolar sequestration is the rate-limiting step in cadmium uptake into protoplasts of all leaf cell types. During accumulation in the cytoplasm, Cd-rich vesicle-like structures were observed. Cd uptake rates into epidermal storage cells were higher than into standard-sized epidermal cells and mesophyll cells. This shows that the preferential heavy metal accumulation in epidermal storage cells, previously observed for several metals in intact leaves of various hyperaccumulator species, is due to differences in active metal transport and not differences in passive mechanisms like transpiration stream transport or cell wall adhesion. Combining this with previous studies, it seems likely that the transport steps over the plasma and tonoplast membranes of leaf epidermal storage cells are driving forces behind the hyperaccumulation phenotype. PMID:20880204

  14. Biochemistry and cell ultrastructure changes during senescence of Beta vulgaris L. leaf.

    Science.gov (United States)

    Romanova, Alla K; Semenova, Galina A; Ignat'ev, Alexander R; Novichkova, Natalia S; Fomina, Irina R

    2016-05-01

    The comparative study of biochemical and ultrastructure features in senescing sugar beet (Beta vulgaris L.) leaves was carried out. One group of plants was grown under normal conditions in washed river sand and poured in turn with nitrate-containing mineral solution or water (N plants). Another group of plants, after 1 month of normal growth, was further grown with nitrate omitted in the nutritive solution (defN plants). The starting point of normal leaf senescence in N plants was identified by the maximal content of soluble protein. Soluble carbohydrate pools were statistically constant in senescing N plants, whereas glucose pools varied noticeably. A decrease in the contents of soluble protein and chlorophyll (a + b) in the course of senescing was typical for N plant leaves. The cell membrane in N plant leaves remained mostly intact; the central vacuoles in the leaf cells were large, and their membranes remained intact. The chloroplasts and mitochondria in senescing N plant leaves became swollen. The vesicles that were present in the cytoplasm of N plant leaves were especially large in the oldest leaves. It was concluded that senescing of sugar beet leaves at sufficient nitrate nutrition occurs according to a "vacuolar" scenario. In the case of nitrate deficiency, the content of soluble carbohydrates in defN leaves first reached maximum and then decreased in older leaves; the protein and chlorophyll (a + b) contents were totally lower than those in normal leaves and continuously decreased during the experiments. Chloroplasts in mesophyll cells of defN plant leaves became more rounded; starch grains in chloroplasts degraded and the number and size of lipid globules increased. The multitude of membrane impairments and lots of large vesicles-"crystals" appeared during the experiment. The results showed the controlling action of nitrogen nutrition in the senescing of sugar beet leaves. PMID:26666552

  15. WEREWOLF, a MYB-related protein in Arabidopsis, is a position-dependent regulator of epidermal cell patterning.

    Science.gov (United States)

    Lee, M M; Schiefelbein, J

    1999-11-24

    The formation of the root epidermis of Arabidopsis provides a simple and elegant model for the analysis of cell patterning. A novel gene, WEREWOLF (WER), is described here that is required for position-dependent patterning of the epidermal cell types. The WER gene encodes a MYB-type protein and is preferentially expressed within cells destined to adopt the non-hair fate. Furthermore, WER is shown to regulate the position-dependent expression of the GLABRA2 homeobox gene, to interact with a bHLH protein, and to act in opposition to the CAPRICE MYB. These results suggest a simple model to explain the specification of the two root epidermal cell types, and they provide insight into the molecular mechanisms used to control cell patterning.

  16. Catalase and NO CATALASE ACTIVITY1 Promote Autophagy-Dependent Cell Death in Arabidopsis

    DEFF Research Database (Denmark)

    Hackenberg, Thomas; Juul, Trine; Auzina, Aija;

    2013-01-01

    Programmed cell death often depends on generation of reactive oxygen species, which can be detoxified by antioxidative enzymes, including catalases. We previously isolated catalase-deficient mutants (cat2) in a screen for resistance to hydroxyurea-induced cell death. Here, we identify an Arabidop......Programmed cell death often depends on generation of reactive oxygen species, which can be detoxified by antioxidative enzymes, including catalases. We previously isolated catalase-deficient mutants (cat2) in a screen for resistance to hydroxyurea-induced cell death. Here, we identify...... an Arabidopsis thaliana hydroxyurea-resistant autophagy mutant, atg2, which also shows reduced sensitivity to cell death triggered by the bacterial effector avrRpm1. To test if catalase deficiency likewise affected both hydroxyurea and avrRpm1 sensitivity, we selected mutants with extremely low catalase...

  17. The Arabidopsis thaliana natriuretic peptide AtPNP-A is a systemic regulator of leaf dark respiration and signals via the phloem

    KAUST Repository

    Ruzvidzo, Oziniel

    2011-09-01

    Plant natriuretic peptides (PNPs) belong to a novel class of peptidic signaling molecules that share some structural similarity to the N-terminal domain of expansins and affect physiological processes such as water and ion homeostasis at nano-molar concentrations. Here we show that a recombinant Arabidopsis thaliana PNP (AtPNP-A) rapidly increased the rate of dark respiration in treated leaves after 5 min. In addition, we observed increases in lower leaves, and with a lag time of 10 min, the effect spread to the upper leaves and subsequently (after 15 min) to the opposite leaves. This response signature is indicative of phloem mobility of the signal, a hypothesis that was further strengthened by the fact that cold girdling, which affects phloem but not xylem or apoplastic processes, delayed the long distance AtPNP-A effect. We conclude that locally applied AtPNP-A can induce a phloem-mobile signal that rapidly modifies plant homeostasis in distal parts. © 2011 Elsevier GmbH.

  18. Dehydration induced loss of photosynthesis in Arabidopsis leaves during senescence is accompanied by the reversible enhancement in the activity of cell wall β-glucosidase.

    Science.gov (United States)

    Patro, Lichita; Mohapatra, Pranab Kishor; Biswal, Udaya Chand; Biswal, Basanti

    2014-08-01

    The physiology of loss of photosynthetic production of sugar and the consequent cellular sugar reprogramming during senescence of leaves experiencing environmental stress largely remains unclear. We have shown that leaf senescence in Arabidopsis thaliana causes a significant reduction in the rate of oxygen evolution and net photosynthetic rate (Pn). The decline in photosynthesis is further aggravated by dehydration. During dehydration, primary photochemical reaction of thylakoids and net photosynthesis decrease in parallel with the increase in water deficit. Senescence induced loss in photosynthesis is accompanied by a significant increase in the activity of cell wall hydrolyzing enzyme such as β-glucosidase associated with cell wall catabolism. The activity of this enzyme is further enhanced when the senescing leaves experience dehydration stress. It is possible that both senescence and stress separately or in combination result in the loss in photosynthesis which could be a signal for an enhancement in the activity of β-glucosidase that breaks down cell wall polysaccharides to sugar to sustain respiration for metabolic activities of plants experiencing stress. Thus dehydration response of cell wall hydrolases of senescing leaves is considered as plants' strategy to have cell wall polysaccharides as an alternative energy source for completion of energy requiring senescence process, stress survival and maintenance of recovery potential of energy deficit cells in the background of loss in photosynthesis. Withdrawal of stress (rehydration) distinctly exhibits recovery of photosynthesis and suppression of enzyme activity. Retention of the signaling for sugar reprogramming through breakdown of cell wall polysaccharides in the senescing leaves exposed to severe drought stress suggests that senescing leaves like mature ones possess potential for stress recovery. The precise mechanism of stress adaptation of senescing leaves is yet to be known. A significant

  19. Efficient and high-throughput vector construction and Agrobacterium-mediated transformation of Arabidopsis thaliana suspension-cultured cells for functional genomics.

    Science.gov (United States)

    Ogawa, Yoichi; Dansako, Tomoko; Yano, Kentaro; Sakurai, Nozomu; Suzuki, Hideyuki; Aoki, Koh; Noji, Masaaki; Saito, Kazuki; Shibata, Daisuke

    2008-02-01

    We established a large-scale, high-throughput protocol to construct Arabidopsis thaliana suspension-cultured cell lines, each of which carries a single transgene, using Agrobacterium-mediated transformation. We took advantage of RIKEN Arabidopsis full-length (RAFL) cDNA clones and the Gateway cloning system for high-throughput preparation of binary vectors carrying individual full-length cDNA sequences. Throughout all cloning steps, multiple-well plates were used to treat 96 samples simultaneously in a high-throughput manner. The optimal conditions for Agrobacterium-mediated transformation of 96 independent binary vector constructs were established to obtain transgenic cell lines efficiently. We evaluated the protocol by generating transgenic Arabidopsis T87 cell lines carrying individual 96 metabolism-related RAFL cDNA fragments, and showed that the protocol was useful for high-throughput and large-scale production of gain-of-function lines for functional genomics.

  20. Arabidopsis poly(A) polymerase PAPS1 limits founder-cell recruitment to organ primordia and suppresses the salicylic acid-independent immune response downstream of EDS1/PAD4.

    Science.gov (United States)

    Trost, Gerda; Vi, Son Lang; Czesnick, Hjördis; Lange, Peggy; Holton, Nick; Giavalisco, Patrick; Zipfel, Cyril; Kappel, Christian; Lenhard, Michael

    2014-03-01

    Polyadenylation of pre-mRNAs by poly(A) polymerase (PAPS) is a critical process in eukaryotic gene expression. As found in vertebrates, plant genomes encode several isoforms of canonical nuclear PAPS enzymes. In Arabidopsis thaliana these isoforms are functionally specialized, with PAPS1 affecting both organ growth and immune response, at least in part by the preferential polyadenylation of subsets of pre-mRNAs. Here, we demonstrate that the opposite effects of PAPS1 on leaf and flower growth reflect the different identities of these organs, and identify a role for PAPS1 in the elusive connection between organ identity and growth patterns. The overgrowth of paps1 mutant petals is due to increased recruitment of founder cells into early organ primordia, and suggests that PAPS1 activity plays unique roles in influencing organ growth. By contrast, the leaf phenotype of paps1 mutants is dominated by a constitutive immune response that leads to increased resistance to the biotrophic oomycete Hyaloperonospora arabidopsidis and reflects activation of the salicylic acid-independent signalling pathway downstream of ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1)/PHYTOALEXIN DEFICIENT4 (PAD4). These findings provide an insight into the developmental and physiological basis of the functional specialization amongst plant PAPS isoforms.

  1. Combinations of Ashwagandha leaf extracts protect brain-derived cells against oxidative stress and induce differentiation.

    Directory of Open Access Journals (Sweden)

    Navjot Shah

    Full Text Available Ashwagandha, a traditional Indian herb, has been known for its variety of therapeutic activities. We earlier demonstrated anticancer activities in the alcoholic and water extracts of the leaves that were mediated by activation of tumor suppressor functions and oxidative stress in cancer cells. Low doses of these extracts were shown to possess neuroprotective activities in vitro and in vivo assays.We used cultured glioblastoma and neuroblastoma cells to examine the effect of extracts (alcoholic and water as well as their bioactive components for neuroprotective activities against oxidative stress. Various biochemical and imaging assays on the marker proteins of glial and neuronal cells were performed along with their survival profiles in control, stressed and recovered conditions. We found that the extracts and one of the purified components, withanone, when used at a low dose, protected the glial and neuronal cells from oxidative as well as glutamate insult, and induced their differentiation per se. Furthermore, the combinations of extracts and active component were highly potent endorsing the therapeutic merit of the combinational approach.Ashwagandha leaf derived bioactive compounds have neuroprotective potential and may serve as supplement for brain health.

  2. Salt stress response triggers activation of the jasmonate signaling pathway leading to inhibition of cell elongation in Arabidopsis primary root.

    Science.gov (United States)

    Valenzuela, Camilo E; Acevedo-Acevedo, Orlando; Miranda, Giovanna S; Vergara-Barros, Pablo; Holuigue, Loreto; Figueroa, Carlos R; Figueroa, Pablo M

    2016-07-01

    Salinity is a severe abiotic stress that affects irrigated croplands. Jasmonate (JA) is an essential hormone involved in plant defense against herbivory and in responses to abiotic stress. However, the relationship between the salt stress response and the JA pathway in Arabidopsis thaliana is not well understood at molecular and cellular levels. In this work we investigated the activation of JA signaling by NaCl and its effect on primary root growth. We found that JA-responsive JAZ genes were up-regulated by salt stress in a COI1-dependent manner in the roots. Using a JA-Ile sensor we demonstrated that activation of JA signaling by salt stress occurs in the meristematic zone and stele of the differentiation zone and that this activation was dependent on JAR1 and proteasome functions. Another finding is that the elongation zone (EZ) and its cortical cells were significantly longer in JA-related mutants (AOS, COI1, JAZ3 and MYC2/3/4 genes) compared with wild-type plants under salt stress, revealing the participation of the canonical JA signaling pathway. Noteworthy, osmotic stress - a component of salt stress - inhibited cell elongation in the EZ in a COI1-dependent manner. We propose that salt stress triggers activation of the JA signaling pathway followed by inhibition of cell elongation in the EZ. We have shown that salt-inhibited root growth partially involves the jasmonate signaling pathway in Arabidopsis. PMID:27217545

  3. A TIR-NBS protein encoded by Arabidopsis Chilling Sensitive 1 (CHS1) limits chloroplast damage and cell death at low temperature.

    Science.gov (United States)

    Zbierzak, Anna Maria; Porfirova, Svetlana; Griebel, Thomas; Melzer, Michael; Parker, Jane E; Dörmann, Peter

    2013-08-01

    Survival of plants at low temperature depends on mechanisms for limiting physiological damage and maintaining growth. We mapped the chs1-1 (chilling sensitive1-1) mutation in Arabidopsis accession Columbia to the TIR-NBS gene At1g17610. In chs1-1, a single amino acid exchange at the CHS1 N-terminus close to the conserved TIR domain creates a stable mutant protein that fails to protect leaves against chilling stress. The sequence of another TIR-NBS gene (At5g40090) named CHL1 (CHS1-like 1) is related to that of CHS1. Over-expression of CHS1 or CHL1 alleviates chilling damage and enhances plant growth at moderate (24°C) and chilling (13°C) temperatures, suggesting a role for both proteins in growth homeostasis. chs1-1 mutants show induced salicylic acid production and defense gene expression at 13°C, indicative of autoimmunity. Genetic analysis of chs1-1 in combination with defense pathway mutants shows that chs1-1 chilling sensitivity requires the TIR-NBS-LRR and basal resistance regulators encoded by EDS1 and PAD4 but not salicylic acid. By following the timing of metabolic, physiological and chloroplast ultrastructural changes in chs1-1 leaves during chilling, we have established that alterations in photosynthetic complexes and thylakoid membrane integrity precede leaf cell death measured by ion leakage. At 24°C, the chs1-1 mutant appears normal but produces a massive necrotic response to virulent Pseudomonas syringae pv. tomato infection, although this does not affect bacterial proliferation. Our results suggest that CHS1 acts at an intersection between temperature sensing and biotic stress pathway activation to maintain plant performance over a range of conditions.

  4. Differential responsiveness of cortical microtubule orientation to suppression of cell expansion among the developmental zones of Arabidopsis thaliana root apex.

    Directory of Open Access Journals (Sweden)

    Emmanuel Panteris

    Full Text Available Τhe bidirectional relationship between cortical microtubule orientation and cell wall structure has been extensively studied in elongating cells. Nevertheless, the possible interplay between microtubules and cell wall elements in meristematic cells still remains elusive. Herein, the impact of cellulose synthesis inhibition and suppressed cell elongation on cortical microtubule orientation was assessed throughout the developmental zones of Arabidopsis thaliana root apex by whole-mount tubulin immunolabeling and confocal microscopy. Apart from the wild-type, thanatos and pom2-4 mutants of Cellulose SynthaseA3 and Cellulose Synthase Interacting1, respectively, were studied. Pharmacological and mechanical approaches inhibiting cell expansion were also applied. Cortical microtubules of untreated wild-type roots were predominantly transverse in the meristematic, transition and elongation root zones. Cellulose-deficient mutants, chemical inhibition of cell expansion, or growth in soil resulted in microtubule reorientation in the elongation zone, wherein cell length was significantly decreased. Combinatorial genetic and chemical suppression of cell expansion extended microtubule reorientation to the transition zone. According to the results, transverse cortical microtubule orientation is established in the meristematic root zone, persisting upon inhibition of cell expansion. Microtubule reorientation in the elongation zone could be attributed to conditional suppression of cell elongation. The differential responsiveness of microtubule orientation to genetic and environmental cues is most likely associated with distinct biophysical traits of the cells among each developmental root zone.

  5. Differential responsiveness of cortical microtubule orientation to suppression of cell expansion among the developmental zones of Arabidopsis thaliana root apex.

    Science.gov (United States)

    Panteris, Emmanuel; Adamakis, Ioannis-Dimosthenis S; Daras, Gerasimos; Hatzopoulos, Polydefkis; Rigas, Stamatis

    2013-01-01

    Τhe bidirectional relationship between cortical microtubule orientation and cell wall structure has been extensively studied in elongating cells. Nevertheless, the possible interplay between microtubules and cell wall elements in meristematic cells still remains elusive. Herein, the impact of cellulose synthesis inhibition and suppressed cell elongation on cortical microtubule orientation was assessed throughout the developmental zones of Arabidopsis thaliana root apex by whole-mount tubulin immunolabeling and confocal microscopy. Apart from the wild-type, thanatos and pom2-4 mutants of Cellulose SynthaseA3 and Cellulose Synthase Interacting1, respectively, were studied. Pharmacological and mechanical approaches inhibiting cell expansion were also applied. Cortical microtubules of untreated wild-type roots were predominantly transverse in the meristematic, transition and elongation root zones. Cellulose-deficient mutants, chemical inhibition of cell expansion, or growth in soil resulted in microtubule reorientation in the elongation zone, wherein cell length was significantly decreased. Combinatorial genetic and chemical suppression of cell expansion extended microtubule reorientation to the transition zone. According to the results, transverse cortical microtubule orientation is established in the meristematic root zone, persisting upon inhibition of cell expansion. Microtubule reorientation in the elongation zone could be attributed to conditional suppression of cell elongation. The differential responsiveness of microtubule orientation to genetic and environmental cues is most likely associated with distinct biophysical traits of the cells among each developmental root zone. PMID:24324790

  6. Cyclic programmed cell death stimulates hormone signaling and root development in Arabidopsis

    NARCIS (Netherlands)

    Xuan, Wei; Band, Leah R.; Kumpf, Robert P.; Rybel, De Bert

    2016-01-01

    The plant root cap, surrounding the very tip of the growing root, perceives and transmits environmental signals to the inner root tissues. In Arabidopsis thaliana, auxin released by the root cap contributes to the regular spacing of lateral organs along the primary root axis. Here, we show that t

  7. Xylogalacturonan exists in cell walls from various tissues of Arabidopsis thaliana

    NARCIS (Netherlands)

    Zandleven, J.S.; Sorensen, S.; Harbolt, J.; Beldman, G.; Schols, H.A.; Scheller, H.V.; Voragen, A.G.J.

    2007-01-01

    Evidence is presented for the presence of xylogalacturonan (XGA) in Arabidopsis thaliana. This evidence was obtained by extraction of pectin from the seeds, root, stem, young leaves and mature leaves of A. thaliana, followed by treatment of these pectin extracts with xylogalacturonan hydrolase (XGH)

  8. A role for AUXIN RESISTANT3 in the coordination of leaf growth.

    Science.gov (United States)

    Pérez-Pérez, José Manuel; Candela, Héctor; Robles, Pedro; López-Torrejón, Gema; del Pozo, Juan C; Micol, José Luis

    2010-10-01

    The characteristically flat structure of Arabidopsis thaliana vegetative leaves requires coordinating the growth of the epidermal, palisade mesophyll, spongy mesophyll and vascular tissues. Mutations disrupting such coordination or the specific growth properties of any of these tissues can cause hyponasty, epinasty, waviness or other deviations from flatness. Here, we show that the incurvata6 (icu6) semi-dominant allele of the AUXIN RESISTANT3 (AXR3) gene causes leaf hyponasty. Cotyledons and leaves of icu6/AXR3 plants exhibited reduced size of adaxial pavement cells, and abnormal expansion of palisade mesophyll cells. Enhanced auxin responses in the adaxial domain of icu6/AXR3 developing cotyledons and leaves correlated with increased cell divisions in the adaxial epidermis. Leaf incurvature in icu6/AXR3 leaves was alleviated by loss-of-function alleles of the ASYMMETRIC LEAVES1 (AS1) and AS2 genes, which restrict the expression of class I KNOX genes to the shoot apical meristem and regulate cell proliferation in leaf primordia. Taken together, our results suggest that an interaction between auxin responses and the AS1-AS2 pathway coordinates tissue growth during Arabidopsis thaliana leaf expansion.

  9. The Antiproliferative Effect of Moringa oleifera Crude Aqueous Leaf Extract on Human Esophageal Cancer Cells.

    Science.gov (United States)

    Tiloke, Charlette; Phulukdaree, Alisa; Chuturgoon, Anil A

    2016-04-01

    Esophageal cancer (EC) is commonly diagnosed in South Africa (SA), with high incidences occurring in SA's black population. Moringa oleifera (MO), a multipurpose tree, is used traditionally for its nutritional and medicinal properties. It has been used for the treatment of a variety of ailments, including cancer. We investigated the antiproliferative effect of MO crude aqueous leaf extract (MOE) on a cancerous esophageal cell line (SNO). SNO cells were exposed to a range of MOE dilutions to evaluate cytotoxicity (MTT assay). Oxidative stress was determined using the TBARS assay. The comet assay was used to assess DNA damage. We then determined cell death mechanisms by measuring phosphatidylserine (PS) externalization (flow cytometry), caspase-3/7 and caspase-9 activities, and adenosine triphosphate (ATP) levels (luminometry). Protein expression of Smac/DIABLO and PARP-1 was determined by western blotting. SNO cells were treated with a range of MOE dilutions to obtain an IC50 value of 389.2 μg/mL MOE (24 h), which was used in all subsequent assays. MOE significantly increased lipid peroxidation (P < .05) and DNA fragmentation (P < .0001) in SNO cells. The induction of apoptosis was confirmed by the increase in PS externalization (P < .0001), caspase-9 (P < .05) and caspase-3/7 (P = .22) activities, and decreased ATP levels (P < .0001). MOE significantly increased both the expression of Smac/DIABLO protein and cleavage of PARP-1, resulting in an increase in the 24-kDa fragment (P < .001). MOE possesses antiproliferative effects on SNO EC cells by increasing lipid peroxidation, DNA fragmentation, and induction of apoptosis. PMID:27074620

  10. Synthesis of zinc oxide nanoparticles using tea leaf extract and its application for solar cell

    Indian Academy of Sciences (India)

    Prasanta Sutradhar; Mitali Saha

    2015-06-01

    We report the synthesis of zinc oxide (ZnO) nanoparticles and its composite with natural graphite (NG) powder for application in solar cell. ZnO nanoparticles were synthesized using green tea leaf extract as non-toxic and eco-friendly reducing material under microwave irradiation. The formation of ZnO nanoparticles was monitored by the colour changes during the reaction. The synthesized ZnO nanoparticles were characterized by particle size analyzer (dynamic light scattering), scanning electron microscope, UV–visible spectroscopy, atomic force microscope and fluorescence spectroscopy. The average particle size of the ZnO nanoparticles was found to be 26 nm. The synthesized ZnO nanoparticles were further used to prepare ZnO/NG composite material with commercially available NG powder. The current–voltage (–) characteristics of thin film of ZnO/NG nanocomposite were investigated. JSC (short-circuit photocurrent), VOC (open-circuit photovoltage), FF (fill factor) and (efficiency of the solar cell) were measured for ZnO/NG nanocomposite. Interestingly, the cell showed a good power conversion efficiency of 3.54% with high stability.

  11. Salicylic acid antagonism of EDS1-driven cell death is important for immune and oxidative stress responses in Arabidopsis.

    Science.gov (United States)

    Straus, Marco R; Rietz, Steffen; Ver Loren van Themaat, Emiel; Bartsch, Michael; Parker, Jane E

    2010-05-01

    Reactive oxygen species (ROS) have emerged as signals in the responses of plants to stress. Arabidopsis Enhanced Disease Susceptibility1 (EDS1) regulates defense and cell death against biotrophic pathogens and controls cell death propagation in response to chloroplast-derived ROS. Arabidopsis Nudix hydrolase7 (nudt7) mutants are sensitized to photo-oxidative stress and display EDS1-dependent enhanced resistance, salicylic acid (SA) accumulation and initiation of cell death. Here we explored the relationship between EDS1, EDS1-regulated SA and ROS by examining gene expression profiles, photo-oxidative stress and resistance phenotypes of nudt7 mutants in combination with eds1 and the SA-biosynthetic mutant, sid2. We establish that EDS1 controls steps downstream of chloroplast-derived O(2)(*-) that lead to SA-assisted H(2)O(2) accumulation as part of a mechanism limiting cell death. A combination of EDS1-regulated SA-antagonized and SA-promoted processes is necessary for resistance to host-adapted pathogens and for a balanced response to photo-oxidative stress. In contrast to SA, the apoplastic ROS-producing enzyme NADPH oxidase RbohD promotes initiation of cell death during photo-oxidative stress. Thus, chloroplastic O(2)(*-) signals are processed by EDS1 to produce counter-balancing activities of SA and RbohD in the control of cell death. Our data strengthen the idea that EDS1 responds to the status of O(2)(*-) or O(2)(*-)-generated molecules to coordinate cell death and defense outputs. This activity may enable the plant to respond flexibly to different biotic and abiotic stresses in the environment.

  12. The age-dependent epigenetic and physiological changes in an Arabidopsis T87 cell suspension culture during long-term cultivation

    Energy Technology Data Exchange (ETDEWEB)

    Kwiatkowska, Aleksandra, E-mail: A.Kwiatkows@gmail.com [Department of Botany, University of Rzeszow, Kolbuszowa (Poland); Zebrowski, Jacek [Department of Plant Physiology, University of Rzeszow, Kolbuszowa (Poland); Oklejewicz, Bernadetta [Department of Genetics, University of Rzeszow, Kolbuszowa (Poland); Czarnik, Justyna [Department of Botany, University of Rzeszow, Kolbuszowa (Poland); Halibart-Puzio, Joanna [Department of Plant Physiology, University of Rzeszow, Kolbuszowa (Poland); Wnuk, Maciej [Department of Genetics, University of Rzeszow, Kolbuszowa (Poland)

    2014-05-02

    Highlights: • A decrease in proliferation rate during long-term cultivation of Arabidopsis cells. • Age-dependent increase in senescence-associated gene expression in Arabidopsis cells. • Age-related increase in DNA methylation, H3K9me2, and H3K27me3 in Arabidopsis cells. • High potential of photosynthetic efficiency of long-term cultured Arabidopsis cells. - Abstract: Plant cell suspension cultures represent good model systems applicable for both basic research and biotechnological purposes. Nevertheless, it is widely known that a prolonged in vitro cultivation of plant cells is associated with genetic and epigenetic instabilities, which may limit the usefulness of plant lines. In this study, the age-dependent epigenetic and physiological changes in an asynchronous Arabidopsis T87 cell culture were examined. A prolonged cultivation period was found to be correlated with a decrease in the proliferation rate and a simultaneous increase in the expression of senescence-associated genes, indicating that the aging process started at the late growth phase of the culture. In addition, increases in the heterochromatin-specific epigenetic markers, i.e., global DNA methylation, H3K9 dimethylation, and H3K27 trimethylation, were observed, suggesting the onset of chromatin condensation, a hallmark of the early stages of plant senescence. Although the number of live cells decreased with an increase in the age of the culture, the remaining viable cells retained a high potential to efficiently perform photosynthesis and did not exhibit any symptoms of photosystem II damage.

  13. Control of differential petiole growth in Arabidopsis thaliana

    NARCIS (Netherlands)

    van Zanten, M.

    2009-01-01

    Plants react quickly and profoundly to changes in their environment. For example, complete submergence and low light intensities induce differential petiole growth, resulting in upward leaf movement (hyponastic growth) in Arabidopsis thaliana. This thesis deals with the physiological-, genetic- and

  14. Conserved CDC20 cell cycle functions are carried out by two of the five isoforms in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Zoltán Kevei

    Full Text Available BACKGROUND: The CDC20 and Cdh1/CCS52 proteins are substrate determinants and activators of the Anaphase Promoting Complex/Cyclosome (APC/C E3 ubiquitin ligase and as such they control the mitotic cell cycle by targeting the degradation of various cell cycle regulators. In yeasts and animals the main CDC20 function is the destruction of securin and mitotic cyclins. Plants have multiple CDC20 gene copies whose functions have not been explored yet. In Arabidopsis thaliana there are five CDC20 isoforms and here we aimed at defining their contribution to cell cycle regulation, substrate selectivity and plant development. METHODOLOGY/PRINCIPAL FINDINGS: Studying the gene structure and phylogeny of plant CDC20s, the expression of the five AtCDC20 gene copies and their interactions with the APC/C subunit APC10, the CCS52 proteins, components of the mitotic checkpoint complex (MCC and mitotic cyclin substrates, conserved CDC20 functions could be assigned for AtCDC20.1 and AtCDC20.2. The other three intron-less genes were silent and specific for Arabidopsis. We show that AtCDC20.1 and AtCDC20.2 are components of the MCC and interact with mitotic cyclins with unexpected specificity. AtCDC20.1 and AtCDC20.2 are expressed in meristems, organ primordia and AtCDC20.1 also in pollen grains and developing seeds. Knocking down both genes simultaneously by RNAi resulted in severe delay in plant development and male sterility. In these lines, the meristem size was reduced while the cell size and ploidy levels were unaffected indicating that the lower cell number and likely slowdown of the cell cycle are the cause of reduced plant growth. CONCLUSIONS/SIGNIFICANCE: The intron-containing CDC20 gene copies provide conserved and redundant functions for cell cycle progression in plants and are required for meristem maintenance, plant growth and male gametophyte formation. The Arabidopsis-specific intron-less genes are possibly "retrogenes" and have hitherto undefined

  15. Defects in leaf carbohydrate metabolism compromise acclimation to high light and lead to a high chlorophyll fluorescence phenotype in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Schmitz Jessica

    2012-01-01

    Full Text Available Abstract Background We have studied the impact of carbohydrate-starvation on the acclimation response to high light using Arabidopsis thaliana double mutants strongly impaired in the day- and night path of photoassimilate export from the chloroplast. A complete knock-out mutant of the triose phosphate/phosphate translocator (TPT; tpt-2 mutant was crossed to mutants defective in (i starch biosynthesis (adg1-1, pgm1 and pgi1-1; knock-outs of ADP-glucose pyrophosphorylase, plastidial phosphoglucomutase and phosphoglucose isomerase or (ii starch mobilization (sex1-3, knock-out of glucan water dikinase as well as in (iii maltose export from the chloroplast (mex1-2. Results All double mutants were viable and indistinguishable from the wild type when grown under low light conditions, but - except for sex1-3/tpt-2 - developed a high chlorophyll fluorescence (HCF phenotype and growth retardation when grown in high light. Immunoblots of thylakoid proteins, Blue-Native gel electrophoresis and chlorophyll fluorescence emission analyses at 77 Kelvin with the adg1-1/tpt-2 double mutant revealed that HCF was linked to a specific decrease in plastome-encoded core proteins of both photosystems (with the exception of the PSII component cytochrome b559, whereas nuclear-encoded antennae (LHCs accumulated normally, but were predominantly not attached to their photosystems. Uncoupled antennae are the major cause for HCF of dark-adapted plants. Feeding of sucrose or glucose to high light-grown adg1-1/tpt-2 plants rescued the HCF- and growth phenotypes. Elevated sugar levels induce the expression of the glucose-6-phosphate/phosphate translocator2 (GPT2, which in principle could compensate for the deficiency in the TPT. A triple mutant with an additional defect in GPT2 (adg1-1/tpt-2/gpt2-1 exhibited an identical rescue of the HCF- and growth phenotype in response to sugar feeding as the adg1-1/tpt-2 double mutant, indicating that this rescue is independent from the

  16. Cell wall and enzyme changes during the graviresponse of the leaf-sheath pulvinus of oat (Avena sativa)

    Science.gov (United States)

    Gibeaut, David M.; Karuppiah, Nadarajah; Chang, S.-R.; Brock, Thomas G.; Vadlamudi, Babu; Kim, Donghern; Ghosheh, Najati S.; Rayle, David L.; Carpita, Nicholas C.; Kaufman, Peter B.

    1990-01-01

    The graviresponse of the leaf-sheath pulvinus of oat (Avena sativa) involves an asymmetric growth response and asymmetric processes involving degradation of starch and cell wall synthesis. Cellular and biochemical events were studied by investigation of the activities of related enzymes and changes in cell walls and their constituents. It is suggested that an osmotic potential gradient acts as the driving factor for growth, while wall extensibility is a limiting factor in pulvinus growth.

  17. Cell Wall Targeted in planta Iron Accumulation Enhances Biomass Conversion and Seed Iron Concentration in Arabidopsis and Rice

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Haibing; Wei, Hui; Ma, Guojie; Antunes, Mauricio S.; Vogt, Stefan; Cox, Joseph; Zhang, Xiao; Liu, Xiping; Bu, Lintao; Gleber, S. Charlotte; Carpita, Nicholas C.; Makowski, Lee; Himmel, Michael E.; Tucker, Melvin P.; McCann, Maureen C.; Murphy, Angus S.; Peer, Wendy A.

    2016-10-01

    Conversion of nongrain biomass into liquid fuel is a sustainable approach to energy demands as global population increases. Previously, we showed that iron can act as a catalyst to enhance the degradation of lignocellulosic biomass for biofuel production. However, direct addition of iron catalysts to biomass pretreatment is diffusion-limited, would increase the cost and complexity of biorefinery unit operations and may have deleterious environmental impacts. Here, we show a new strategy for in planta accumulation of iron throughout the volume of the cell wall where iron acts as a catalyst in the deconstruction of lignocellulosic biomass. We engineered CBM-IBP fusion polypeptides composed of a carbohydrate-binding module family 11 (CBM11) and an iron-binding peptide (IBP) for secretion into Arabidopsis and rice cell walls. CBM-IBP transformed Arabidopsis and rice plants show significant increases in iron accumulation and biomass conversion compared to respective controls. Further, CBM-IBP rice shows a 35% increase in seed iron concentration and a 40% increase in seed yield in greenhouse experiments. CBM-IBP rice potentially could be used to address iron deficiency, the most common and widespread nutritional disorder according to the World Health Organization.

  18. Co-localisation studies of Arabidopsis SR splicing factors reveal different types of speckles in plant cell nuclei

    International Nuclear Information System (INIS)

    SR proteins are multidomain splicing factors which are important for spliceosome assembly and for regulation of alternative splicing. In mammalian nuclei these proteins localise to speckles from where they are recruited to transcription sites. By using fluorescent protein fusion technology and different experimental approaches it has been shown that Arabidopsis SR proteins, in addition to diffuse nucleoplasmic staining, localise into an irregular nucleoplasmic network resembling speckles in mammalian cells. As Arabidopsis SR proteins fall into seven conserved sub-families we investigated co-localisation of members of the different sub-families in transiently transformed tobacco protoplast. Here we demonstrate the new finding that members of different SR protein sub-families localise into distinct populations of nuclear speckles with no, partial or complete co-localisation. This is particularly interesting as we also show that these proteins do interact in a yeast two-hybrid assay as well as in pull-down and in co-immunopreciptiation assays. Our data raise the interesting possibility that SR proteins are partitioned into distinct populations of nuclear speckles to allow a more specific recruitment to the transcription/pre-mRNA processing sites of particular genes depending on cell type and developmental stage

  19. Blue light-dependent changes in loosely bound calcium in Arabidopsis mesophyll cells: an X-ray microanalysis study.

    Science.gov (United States)

    Łabuz, Justyna; Samardakiewicz, Sławomir; Hermanowicz, Paweł; Wyroba, Elżbieta; Pilarska, Maria; Gabryś, Halina

    2016-06-01

    Calcium is involved in the signal transduction pathway from phototropins, the blue light photoreceptor kinases which mediate chloroplast movements. The chloroplast accumulation response in low light is controlled by both phot1 and phot2, while only phot2 is involved in avoidance movement induced by strong light. Phototropins elevate cytosolic Ca(2+) after activation by blue light. In higher plants, both types of chloroplast responses depend on Ca(2+), and internal calcium stores seem to be crucial for these processes. Yet, the calcium signatures generated after the perception of blue light by phototropins are not well understood. To characterize the localization of calcium in Arabidopsis mesophyll cells, loosely bound (exchangeable) Ca(2+) was precipitated with potassium pyroantimonate and analyzed by transmission electron microscopy followed by energy-dispersive X-ray microanalysis. In dark-adapted wild-type Arabidopsis leaves, calcium precipitates were observed at the cell wall, where they formed spherical structures. After strong blue light irradiation, calcium at the apoplast prevailed, and bigger, multilayer precipitates were found. Spherical calcium precipitates were also detected at the tonoplast. After red light treatment as a control, the precipitates at the cell wall were smaller and less numerous. In the phot2 and phot1phot2 mutants, calcium patterns were different from those of wild-type plants. In both mutants, no elevation of calcium after blue light treatment was observed at the cell periphery (including the cell wall and a fragment of cytoplasm). This result confirms the involvement of phototropin2 in the regulation of Ca(2+) homeostasis in mesophyll cells.

  20. Environmentally induced programmed cell death in leaf protoplasts of Aponogeton madagascariensis.

    Science.gov (United States)

    Lord, Christina E N; Gunawardena, Arunika H L A N

    2011-02-01

    Within plant systems, two main forms of programmed cell death (PCD) exist: developmentally regulated and environmentally induced. The lace plant (Aponogeton madagascariensis) naturally undergoes developmentally regulated PCD to form perforations between longitudinal and transverse veins over its leaf surface. Developmental PCD in the lace plant has been well characterized; however, environmental PCD has never before been studied in this plant species. The results presented here portray heat shock (HS) treatment at 55 °C for 20 min as a promising inducer of environmental PCD within lace plant protoplasts originally isolated from non-PCD areas of the plant. HS treatment produces cells displaying many characteristics of developmental PCD, including blebbing of the plasma membrane, increased number of hydrolytic vesicles and transvacuolar strands, nuclear condensation, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling positive nuclei, as well as increased Brownian motion within the vacuole. Results presented here for the first time provide evidence of chloroplasts in the vacuole of living protoplasts undergoing environmentally induced PCD. Findings suggest that the mitochondria play a critical role in the cell death process. Changes in mitochondrial dynamics were visualized in HS-treated cells, including loss of mitochondrial mobility, reduction in ΔΨ(m), as well as the proximal association with chloroplasts. The role of the mitochondrial permeability transition pore (PTP) was examined by pre-treatment with the PTP agonist cyclosporine A. Overall, HS is depicted as a reliable method to induce PCD within lace plant protoplasts, and proves to be a reliable technique to enable comparisons between environmentally induced and developmentally regulated PCD within one species of plant.

  1. Leaf-cutting ant fungi produce cell wall degrading pectinase complexes reminiscent of phytopathogenic fungi

    DEFF Research Database (Denmark)

    Schiøtt, Morten; Rogowska-Wrzesinska, Adelina; Roepstorff, Peter;

    2010-01-01

    Leaf-cutting (attine) ants use their own fecal material to manure fungus gardens, which consist of leaf material overgrown by hyphal threads of the basidiomycete fungus Leucocoprinus gongylophorus that lives in symbiosis with the ants. Previous studies have suggested that the fecal droplets conta...

  2. Comparison of the effects of fresh leaf and peel extracts of walnut (Juglans regia L. on blood glucose and β-cells of streptozotocin-induced diabetic rats

    Directory of Open Access Journals (Sweden)

    Somaye Javidanpour

    2012-12-01

    Full Text Available There is some report about the hypoglycemic effect of Juglans rejia L. leaf in alloxan induced diabetic rats and hypoglycemic effect of its fruit peel administered intra peritoneally. Thirty male Wistar rats divided into five groups, to evaluate the hypoglycemic and pancreas β-cells regenerative effects of oral methanolic extracts of leaf and fruit peel of walnut. Rats were made diabetic by intravenous (IV injection of 50 mg kg-1 streptozotocin (STZ. Negative control group did not get STZ and any treatment. Positive control, leaf extract, peel extract and insulin groups were treated orally by extract solvent, 200 mg kg-1 leaf extract, 200 mg kg-1 peel extract and 5 IU kg-1 of subcutaneous neutral protamine Hagedorn (NPH insulin, respectively. Four weeks later, blood was collected for biochemical analysis and pancreases were removed for β-cells counts in histological sections. Diabetes leads to increase of fast blood sugar (FBS and HbA1c, and decrease of β-cell number and insulin. FBS decreased only in leaf extract group. HbA1c decreased in leaf extract and insulin groups. The β-cells number increased in leaf and peel extract groups. Insulin increased moderately in all treatment groups. We showed the proliferative properties of leaves and peel of Juglans regia L. methanolic extract in STZ- induced diabetic rats, which was accompanied by hypoglycemic effect of leaf extract.

  3. Relationship between pentatricopeptide repeat gene PPRs and rosette leaf senescence in Arabidopsis%拟南芥PPRs基因与莲座叶衰老之间的关系

    Institute of Scientific and Technical Information of China (English)

    朱正火; 任育军; 李燕云; 缪颖

    2016-01-01

    Pentatricopeptide repeats ( PPR) play important roles in plant growth, development and dealing with endogenous and ex-ogenous stresses. To elucidate the function of a PPR gene ( PPRs) on the regulation of rosette leaf senescence in Arabidopsis, real-time qPCR analysis was applied to evaluate the relative transcription level of PPRs gene in different tissues and organs in 7-week-old wild-type Arabidopsis. Meanwhile, the 4th week old plants were treated with phytohormones, including jasmonic acid ( JA) , salicylic acid ( SA) , abscisic acid ( ABA) , auxin ( IAA) and gibberellins ( GA3 ) , and abiotic treatments ( coldness, hotness, wounding, drought, darkness and H2 O2 ) for 24 hours. Results showed that the relative expression of PPRs gene was higher in rosette leaves, flowers and siliques than in the other tissues of the wide-type plants, and the relative expression decreased significantly in rosette leaves when their senescence initiated. After being treated with various stresses, the relative expression of PPRs gene in 4-week-old plants dropped to that of 6-week-old plants compared with the control plants, though JA, coldness, hotness, and drought-treated plants had significantly higher expression of PPRs gene than other treatments. Phenotypes of rosette leaf at senescence period were almost the same among over-expressing ( OE-PPRs) , antisense-PPRs ( AN-PPRs) , and wild-type plants. Nevertheless, leaf senes-cence of JA-treated OE-PPRs plants was significantly retarded compared with the wild-type, and it was consistent with variations in the expression of senescence-associated genes between OE-PPRs and wild-type plants. This study has provided insight into the nega-tive regulation of PPRs gene in rosette leaf senescence period.%研究了拟南芥中一个PPR(称PPRs)基因与莲座叶片衰老之间的关系。实时定量PCR分析发现这个基因在生长7周的拟南芥各种组织中几乎都有表达,在莲座叶、花序和角果中

  4. Arabidopsis VARIEGATED 3 encodes a chloroplast-targeted, zinc-finger protein required for chloroplast and palisade cell development

    DEFF Research Database (Denmark)

    Næsted, Henrik; Holm, Agnethe; Jenkins, Tom;

    2004-01-01

    The stable, recessive Arabidopsis variegated 3 (var3) mutant exhibits a variegated phenotype due to somatic areas lacking or containing developmentally retarded chloroplasts and greatly reduced numbers of palisade cells. The VAR3 gene, isolated by transposon tagging, encodes the 85.9 kDa VAR3...... protein containing novel repeats and zinc fingers described as protein interaction domains. VAR3 interacts specifically in yeast and in vitro with NCED4, a putative polyene chain or carotenoid dioxygenase, and both VAR3 and NCED4 accumulate in the chloroplast stroma. Metabolic profiling demonstrates...... that pigment profiles are qualitatively similar in wild type and var3, although var3 accumulates lower levels of chlorophylls and carotenoids. These results indicate that VAR3 is a part of a protein complex required for normal chloroplast and palisade cell development....

  5. Arabidopsis VARIEGATED 3 encodes a chloroplasttargeted, zinc-finger protein required for chloroplast and palisade cell development

    DEFF Research Database (Denmark)

    Næsted, Henrik; Holm, A.; Jenkins, T.;

    2004-01-01

    The stable, recessive Arabidopsis variegated 3 (var3) mutant exhibits a variegated phenotype due to somatic areas lacking or containing developmentally retarded chloroplasts and greatly reduced numbers of palisade cells. The VAR3 gene, isolated by transposon tagging, encodes the 85.9 kDa VAR3...... protein containing novel repeats and zinc fingers described as protein interaction domains. VAR3 interacts specifically in yeast and in vitro with NCED4, a putative polyene chain or carotenoid dioxygenase, and both VAR3 and NCED4 accumulate in the chloroplast stroma. Metabolic profiling demonstrates...... that pigment profiles are qualitatively similar in wild type and var3, although var3 accumulates lower levels of chlorophylls and carotenoids. These results indicate that VAR3 is a part of a protein complex required for normal chloroplast and palisade cell development....

  6. Ethylene Antagonizes Salt-Induced Growth Retardation and Cell Death Process via Transcriptional Controlling of Ethylene-, BAG- and Senescence-Associated Genes in Arabidopsis

    OpenAIRE

    Pan, Ya-Jie; Liu, Ling; Lin, Ying-Chao; Zu, Yuan-Gang; Li, Lei-Peng; Tang, Zhong-Hua

    2016-01-01

    The existing question whether ethylene is involved in the modulation of salt-induced cell death to mediate plant salt tolerance is important for understanding the salt tolerance mechanisms. Here, we employed Arabidopsis plants to study the possible role of ethylene in salt-induced growth inhibition and programmed cell death (PCD) profiles. The root length, DNA ladder and cell death indicated by Evan's blue detection were measured by compared to the control or salt-stressed seedlings. Secondly...

  7. Ethylene antagonizes salt-induced growth retardation and cell death process via transcriptional controlling of ethylene-, BAG- and senescence-associated genes in Arabidopsis

    OpenAIRE

    YaJie ePan; Ling eLiu; YingChao eLin; YuanGang eZu; Zhonghua eTang; LeiPeng eLi

    2016-01-01

    The existing question whether ethylene is involved in the modulation of salt-induced cell death to mediate plant salt tolerance is important for understanding the salt tolerance mechanisms. Here, we employed Arabidopsis plants to study the possible role of ethylene in salt-induced growth inhibition and programmed cell death (PCD) profiles. The root length, DNA ladder and cell death indicated by Evan’s blue detection were measured by compared to the control or salt-stressed seedlings. Secondly...

  8. Localization of the Arabidopsis Senescence- and Cell Death-Associated BFN1 Nuclease: From the ER to Fragmented Nuclei

    Institute of Scientific and Technical Information of China (English)

    Sarit Farage-Barhom; Shaul Burd; Lilian Sonego; Ana Mett; Eduard Belausov; David Gidoni; Amnon Lers

    2011-01-01

    Plant senescence- or PCD-associated nucleases share significant homology with nucleases from different organisms.However,knowledge of their function is limited.Intracellular localization of the Arabidopsis senescenceand PCD-associated nuclease BFN1 was investigated.Analysis of BFN1-GFP localization in transiently transformed tobacco protoplasts revealed initial localization in filamentous structures spread throughout the cytoplasm,which then clustered around the nuclei as the protoplasts senesced.These filamentous structures were identified as being of ER origin.In BFN1GFP-transgenic Arabidopsis plants,similar localization of BFN1-GFP was observed in young leaves,that is,in filamentous structures that reorganized around the nuclei only in senescing cells.In late senescence,BFN1-GFP was localized with fragmented nuclei in membrane-wrapped vesicles.BFN1's postulated function as a nucleic acid-degrading enzyme in senescence and PCD is supported by its localization pattern.Our results suggest the existence of a dedicated compartment mediating nucleic acid degradation in senescence and PCD processes.

  9. Arabidopsis thaliana T-DNA Mutants Implicate GAUT Genes in the Biosynthesis of Pectin and Xylan in Cell Walls and Seed Testa

    Institute of Scientific and Technical Information of China (English)

    Kerry H. Caffall; Sivakumar Pattathil; Sarah E. Phillips; Michael G. Hahn; Debra Mohnen

    2009-01-01

    Galacturonosyltransferase 1 (GAUT1) is an α1,4-D-galacturonosyltransferase that transfers galacturonic acid from uridine 5'-diphosphogalacturonic acid onto the pectic polysaccharide homogalacturonan (Sterling et al., 2006). The 25-member Arabidopsis thaliana GAUT1-related gene family encodes 15 GAUT and 10 GAUT-like (GATL) proteins with, respectively, 56-84 and 42-53% amino acid sequence similarity to GAUT1. Previous phylogenetic analyses of AtGAUTs indicated three clades: A through C. A comparative phylogenetic analysis of the Arabidopsis, poplar and rice GAUT families has sub-classified the GAUTs into seven clades: clade A-1 (GAUTs 1 to 3); A-2 (GAUT4); A-3 (GAUTs 5 and 6); A-4 (GAUT7); B-1(GAUTs 8 and 9); B-2 (GAUTs 10 and 11); and clade C (GAUTs 12 to 15). The Arabidopsis GAUTs have a distribution com-parable to the poplar orthologs, with the exception of GAUT2, which is absent in poplar. Rice, however, has no orthologs of GAUTs 2 and 12 and has multiple apparent orthologs of GAUTs 1, 4, and 7 compared with eitherArabidopsis or poplar. The cell wall glycosyl residue compositions of 26 homozygous T-DNA insertion mutants for 13 of 15 Arabidopsis GAUTgenes reveal significantly and reproducibly different cell walls in specific tissues of gaut mutants 6, 8, 9, 10, 11, 12, 13, and 14 from that of wild-type Arabidopsis walls. Pectin and xylan polysaccharides are affected by the loss of GAUT function, as dem-onstrated by the altered galacturonic acid, xylose, rhamnose, galactose, and arabinose composition of distinct gaut mu-tant walls. The wall glycosyl residue compositional phenotypes observed among the gaut mutants suggest that at least six different biosynthetic linkages in pectins and/or xylans are affected by the lesions in these GAUTgenes. Evidence is also presented to support a role for GAUT11 in seed mucilage expansion and in seed wall and mucilage composition.

  10. Membrane Potentials of Vallisneria Leaf Cells and Their Relation to Photosynthesis 1

    Science.gov (United States)

    Prins, Hidde B. A.; Harper, James R.; Higinbotham, Noe

    1980-01-01

    A study has been made of the effects of the inhibitors carbonylcyanide m-chlorophenylhydrazone (CCCP), 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), and of anoxia on the light-sensitive membrane potential of Vallisneria leaf cells. The present results are compared with the known effects of these inhibitors on ion transport and photosynthesis (Prins 1974 Ph.D thesis). The membrane potential is composed of a diffusion potential plus an electrogenic component. The electrogenic potential is about −13 millivolts in the dark and −80 millivolts in the light. The inhibitory effect of DCMU and CCCP on the electrogenic mechanisms strongly depends on the light intensity used, the inhibition being less at a higher light intensity. This is of significance in view of the often conflicting results obtained with these inhibitors. With ion transport in Vallisneria the electrogenic pump derives its energy from phosphorylation; however, the process which causes the initial light-induced hyperpolarization and the process that keeps the membrane potential at a steady hyperpolarized state in the light have different energy requirements. The action of photosystem I alone is sufficient to induce the initial hyperpolarization. For continuous operation in the light the activity of photosystem II also is needed. PMID:16661121

  11. Membrane potentials of vallisneria leaf cells and their relation to photosynthesis.

    Science.gov (United States)

    Prins, H B; Harper, J R; Higinbotham, N

    1980-01-01

    A study has been made of the effects of the inhibitors carbonylcyanide m-chlorophenylhydrazone (CCCP), 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), and of anoxia on the light-sensitive membrane potential of Vallisneria leaf cells. The present results are compared with the known effects of these inhibitors on ion transport and photosynthesis (Prins 1974 Ph.D thesis). The membrane potential is composed of a diffusion potential plus an electrogenic component. The electrogenic potential is about -13 millivolts in the dark and -80 millivolts in the light. The inhibitory effect of DCMU and CCCP on the electrogenic mechanisms strongly depends on the light intensity used, the inhibition being less at a higher light intensity. This is of significance in view of the often conflicting results obtained with these inhibitors. With ion transport in Vallisneria the electrogenic pump derives its energy from phosphorylation; however, the process which causes the initial light-induced hyperpolarization and the process that keeps the membrane potential at a steady hyperpolarized state in the light have different energy requirements. The action of photosystem I alone is sufficient to induce the initial hyperpolarization. For continuous operation in the light the activity of photosystem II also is needed. PMID:16661121

  12. A correlative microscopy approach relates microtubule behaviour, local organ geometry, and cell growth at the Arabidopsis shoot apical meristem.

    Science.gov (United States)

    Burian, Agata; Ludynia, Michal; Uyttewaal, Magalie; Traas, Jan; Boudaoud, Arezki; Hamant, Olivier; Kwiatkowska, Dorota

    2013-12-01

    Cortical microtubules (CMTs) are often aligned in a particular direction in individual cells or even in groups of cells and play a central role in the definition of growth anisotropy. How the CMTs themselves are aligned is not well known, but two hypotheses have been proposed. According to the first hypothesis, CMTs align perpendicular to the maximal growth direction, and, according to the second, CMTs align parallel to the maximal stress direction. Since both hypotheses were formulated on the basis of mainly qualitative assessments, the link between CMT organization, organ geometry, and cell growth is revisited using a quantitative approach. For this purpose, CMT orientation, local curvature, and growth parameters for each cell were measured in the growing shoot apical meristem (SAM) of Arabidopsis thaliana. Using this approach, it has been shown that stable CMTs tend to be perpendicular to the direction of maximal growth in cells at the SAM periphery, but parallel in the cells at the boundary domain. When examining the local curvature of the SAM surface, no strict correlation between curvature and CMT arrangement was found, which implies that SAM geometry, and presumed geometry-derived stress distribution, is not sufficient to prescribe the CMT orientation. However, a better match between stress and CMTs was found when mechanical stress derived from differential growth was also considered.

  13. Cell wall pectic arabinans influence the mechanical properties of Arabidopsis thaliana inflorescence stems and their response to mechanical stress.

    Science.gov (United States)

    Verhertbruggen, Yves; Marcus, Susan E; Chen, Jianshe; Knox, J Paul

    2013-08-01

    Little is known of the dynamics of plant cell wall matrix polysaccharides in response to the impact of mechanical stress on plant organs. The capacity of the imposition of a mechanical stress (periodic brushing) to reduce the height of the inflorescence stem of Arabidopsis thaliana seedlings has been used to study the role of pectic arabinans in the mechanical properties and stress responsiveness of a plant organ. The arabinan-deficient-1 (arad1) mutation that affects arabinan structures in epidermal cell walls of inflorescence stems is demonstrated to reduce the impact on inflorescence stem heights caused by mechanical stress. The arabinan-deficient-2 (arad2) mutation, that does not have detectable impact on arabinan structures, is also shown to reduce the impact on stem heights caused by mechanical stress. The LM13 linear arabinan epitope is specifically detected in epidermal cell walls of the younger, flexible regions of inflorescence stems and increases in abundance at the base of inflorescence stems in response to an imposed mechanical stress. The strain (percentage deformation) of stem epidermal cells in the double mutant arad1 × arad2 is lower in unbrushed plants than in wild-type plants, but rises to wild-type levels in response to brushing. The study demonstrates the complexity of arabinan structures within plant cell walls and also that their contribution to cell wall mechanical properties is a factor influencing responsiveness to mechanical stress.

  14. Arabidopsis Kinesins HINKEL and TETRASPORE Act Redundantly to Control Cell Plate Expansion during Cytokinesis in the Male Garnetophyte

    Institute of Scientific and Technical Information of China (English)

    Sung-Aeong Oh; Valérie Bourdon; Madhumita Das'Pal; Hugh Dickinson; David Twell

    2008-01-01

    Asymmetric cell division at pollen mitosis I(PMI)is required to specify the differentiaI fate of the daughter vegetative and generative cells.Cytokinesis at PMI displays specialized features,and it has been suggested that there might be distinct molecular pathways underpinning different modes of cytokinesis in plants.Activation of the NACKPQR MAP kinase signaling pathway,which is essentiaI for somatic cell cytokinesis in tobacco,depends upon the NACK1and NACK2 kinesin-related proteins.Their Arabidopsis orthologs.HINKEL(HIK)and TETRAsPORE(TES).were reported to be essential for cytokinesis in somatic cells and in microsporoctes.respectively.More recently,HIK and TES were shown to have a functionally redundant role in female gametophytic cvtokinesis.We report here that HIK and TES are co-expressed in microspores and developing pollen,and,through analysis of microspore and pollen development in double heterozygote mutants.the occurrence of cell plate expansion defects during cytokinesis at PMI.The data demonstrate a functionally redundant role for HIK and TES in cell plate expansion during male gametophytic cytokinesis.extending the concept that different modes of cytokinesis are executed by a common signaling pathway,but reinforcing the individuality of gametophytic cytokinesis in its requirement for either TES or HIK.

  15. Gravitational field related changes in gene expression after short-term exposure of Arabidopsis thaliana cell cultures

    Science.gov (United States)

    Babbick, Maren; Cogoli-Greuter, Marianne; Lowe, Kenneth C.; Power, J. Brian; Anthony, Paul; Dijkstra, Camelia; Davey, Michael R.; Hampp, Rüdiger

    2005-08-01

    Cell cultures of Arabidopsis thaliana (cv. Columbia) were used to screen for early changes in gene expression in response to altered gravitatonal fields. Genes of interest (mainly components of signalling chains) were selected from a larger group, the expression of which was affected under hypergravity [Martzivanou M. and Hampp R., Physiol. Plant., 118, 221-231, 2003]. Transcriptional changes of these genes were studied within a period of up to 10 min of exposure to clinorotation (random positioning machine), magnetophoresis, and hypergravity (8 g). Microarrays identified a set of transcription factor genes which responded in a treatment-specific way. The respective transcripts were quantified by real time RT PCR. As most responses occurred within 10 min of treatment, such genes can be used for the investigation of microgravity-related alterations in gene expression under sounding rocket conditions (TEXUS, MAXUS).

  16. Function of type-2 Arabidopsis hemoglobin in the auxin-mediated formation of embryogenic cells during morphogenesis

    DEFF Research Database (Denmark)

    Elhiti, Mohamed; Hebelstrup, Kim; Wang, Aiming;

    2013-01-01

    Suppression of the Arabidopsis GLB2, a type-2 nonsymbiotic hemoglobin, enhances somatic embryogenesis by increasing auxin production. In the glb2 knock-out line (GLB2 -/-) polarization of PIN1 proteins and auxin maxima occurred at the base of the cotyledons of the zygotic explants, which...... are the sites of embryogenic tissue formation. These changes were also accompanied by a transcriptional up-regulation of WUSCHEL (WUS) and SOMATIC EMBRYOGENESIS RECEPTOR KINASE (SERK1), markers of embryogenic competence. The increased auxin levels in the GLB2 -/- line were ascribed to the induction of several...... the embryogenic cells, which repress the expression of the transcription factor MYC2, a well characterized repressor of the auxin biosynthetic pathway. A model is proposed in which the suppression of GLB2 reduces the degree of NO scavenging by oxyhemoglobin, thereby increasing the cellular NO concentration...

  17. Anti-angiogenic effect of Nelumbo nucifera leaf extracts in human umbilical vein endothelial cells with antioxidant potential.

    Directory of Open Access Journals (Sweden)

    Jong Suk Lee

    Full Text Available Nelumbo nucifera Gaertn (Nymphaeaceae has long been used as a traditional herb in Chinese, Japanese, Indian, and Korean medicinal practices since prehistoric times and flourishes today as the primary form of medicine. This study reports for the first time the potent ability of N. nucifera leaf extracts to inhibit vascular endothelial growth factor (VEGF-induced angiogenesis in vitro and in vivo, as well as their antioxidant efficacy in various scavenging models and an analysis of their chemical composition. In vivo anti-angiogenic activity was evaluated in a chick chorioallantoic membrane (CAM model using fertilized chicken eggs, in human umbilical vein endothelial cells (HUVECs by using cell viability, cell proliferation and tube formation assays, and by determining intracellular reactive oxygen species (ROS in vitro. The antioxidant efficacy of N. nucifera leaf extracts was determined in various scavenging models, including total phenolic and flavonoid content. The chemical composition of N. nucifera leaf extracts was determined by GC-MS analysis, which revealed the presence of different phytochemicals. The IC50 values for the DPPH radical scavenging activities of water and methanol extracts were found to be 1699.47 and 514.36 μg ml(-1, and their total phenolic and flavonoid contents were 85.01 ± 2.32 and 147.63 ± 2.23 mg GAE g dry mass(-1 and 35.38 ± 1.32 and 41.86 ± 1.07 mg QA g dry mass(-1, respectively. N. nucifera leaf extracts (10-100 μg ml(-1 exhibited significant dose-dependent inhibition of VEGF-induced angiogenesis, as well as VEGF-induced proliferation and tube formation in HUVECs. In this study, N. nucifera leaf extracts displayed potent antioxidant and inhibitory effects on VEGF-induced angiogenesis. N. nucifera exerted an inhibitory effect on VEGF-induced proliferation and tube formation, as well as CAM angiogenesis in vivo. Moreover, N. nucifera leaf extracts significantly blocked VEGF-induced ROS production in HUVECs

  18. Chromatin dynamics in pollen mother cells underpin a common scenario at the somatic-to-reproductive fate transition of both the male and female lineages in Arabidopsis

    OpenAIRE

    She, Wenjing; Baroux, Célia

    2015-01-01

    Unlike animals, where the germline is established early during embryogenesis, plants set aside their reproductive lineage late in development in dedicated floral organs. The specification of pollen mother cells (PMC) committed to meiosis takes place in the sporogenous tissue in anther locules and marks the somatic-to-reproductive cell fate transition toward the male reproductive lineage. Here we show that Arabidopsis PMC differentiation is accompanied by large-scale changes in chromatin organ...

  19. Salicylic acid modulates levels of phosphoinositide dependent-phospholipase C substrates and products to remodel the Arabidopsis suspension cell transcriptome

    Directory of Open Access Journals (Sweden)

    Eric eRuelland

    2014-11-01

    Full Text Available Basal phosphoinositide-dependent phospholipase C (PI-PLC activity controls gene expression in Arabidopsis suspension cells and seedlings. PI-PLC catalyzes the production of phosphorylated inositol and diacylglycerol (DAG from phosphoinositides. It is not known how PI-PLC regulates the transcriptome although the action of DAG-kinase (DGK on DAG immediately downstream from PI-PLC is responsible for some of the regulation. We previously established a list of genes whose expression is affected in the presence of PI-PLC inhibitors. Here this list of genes was used as a signature in similarity searches of curated plant hormone response transcriptome data. The strongest correlations obtained with the inhibited PI-PLC signature were with salicylic acid (SA treatments. We confirm here that in Arabidopsis suspension cells SA treatment leads to an increase in phosphoinositides, then demonstrate that SA leads to a significant 20% decrease in phosphatidic acid, indicative of a decrease in PI-PLC products. Previous sets of microarray data were re-assessed. The SA response of one set of genes was dependent on phosphoinositides. Alterations in the levels of a second set of genes, mostly SA-repressed genes, could be related to decreases in PI-PLC products that occur in response to SA action. Together, the two groups of genes comprise at least 40% of all SA-responsive genes. Overall these two groups of genes are distinct in the functional categories of the proteins they encode, their promoter cis-elements and their regulation by DGK or phospholipase D. SA-regulated genes dependent on phosphoinositides are typical SA response genes while those with an SA response that is possibly dependent on PI-PLC products are less SA-specific. We propose a model in which SA inhibits PI-PLC activity and alters levels of PI-PLC products and substrates, thereby regulating gene expression divergently.

  20. The WD40 repeat protein NEDD1 functions in microtubule organization during cell division in Arabidopsis thaliana.

    Science.gov (United States)

    Zeng, C J Tracy; Lee, Y-R Julie; Liu, Bo

    2009-04-01

    Although cells of flowering plants lack a structurally defined microtubule-organizing center like the centrosome, organization of the spindles and phragmoplasts in mitosis is known to involve the evolutionarily conserved gamma-tubulin complex. We have investigated the function of Arabidopsis thaliana NEDD1, a WD40 repeat protein related to the animal NEDD1/GCP-WD protein, which interacts with the gamma-tubulin complex. The NEDD1 protein decorates spindle microtubules (MTs) preferentially toward spindle poles and phragmoplast MTs toward their minus ends. A T-DNA insertional allele of the single NEDD1 gene was isolated and maintained in heterozygous sporophytes, and NEDD1's function in cell division was analyzed in haploid microspores produced by the heterozygote. In approximately half of the dividing microspores exhibiting aberrant MT organization, spindles were no longer restricted to the cell periphery and became abnormally elongated. After mitosis, MTs aggregated between reforming nuclei but failed to appear in a bipolar configuration. Consequently, defective microspores did not form a continuous cell plate, and two identical nuclei were produced with no differentiation into generative and vegetative cells. Our results support the notion that the plant NEDD1 homolog plays a critical role in MT organization during mitosis, and its function is likely linked to that of the gamma-tubulin complex. PMID:19383896

  1. Plastid position in Arabidopsis columella cells is similar in microgravity and on a random-positioning machine

    Science.gov (United States)

    Kraft, T. F.; van Loon, J. J.; Kiss, J. Z.

    2000-01-01

    In order to study gravity effects on plant structure and function, it may become necessary to remove the g-stimulus. On Earth, various instruments such as clinostats have been used by biologists in an attempt to neutralize the effects of gravity. In this study, the position of amyloplasts was assayed in columella cells in the roots of Arabidopsis thaliana (L.) Heynh. seedlings grown in the following conditions: on Earth, on a two-dimensional clinostat at 1 rpm, on a three-dimensional clinostat (also called a random-positioning machine, or an RPM), and in space (true microgravity). In addition, the effects of these gravity treatments on columella cell area and plastid area also were measured. In terms of the parameters measured, only amyloplast position was affected by the gravity treatments. Plastid position was not significantly different between spaceflight and RPM conditions but was significantly different between spaceflight and the classical two-dimensional clinostat treatments. Flanking columella cells showed a greater susceptibility to changes in gravity compared to the central columella cells. In addition, columella cells of seedlings that were grown on the RPM did not exhibit deleterious effects in terms of their ultrastructure as has been reported previously for seedlings grown on a two-dimensional clinostat. This study supports the hypothesis that the RPM provides a useful simulation of weightlessness.

  2. Anti-Cancer Effects of Imperata cylindrica Leaf Extract on Human Oral Squamous Carcinoma Cell Line SCC-9 in Vitro.

    Science.gov (United States)

    Keshava, Rohini; Muniyappa, Nagesh; Gope, Rajalakshmi; Ramaswamaiah, Ananthanarayana Saligrama

    2016-01-01

    Imperata cylindrica, a tall tufted grass which has multiple pharmacological applications is one of the key ingredients in various traditional medicinal formula used in India. Previous reports have shown that I. cylindrica plant extract inhibited cell proliferation and induced apoptosis in various cancer cell lines. To our knowledge, no studies have been published on the effect of I. cylindrica leaf extract on human oral cancers. The present study was undertaken in order to evaluate the anticancer properties of the leaf extract of I. cylindrica using an oral squamous cell carcinoma cell line SCC-9 as an in vitro model system. A methanol extract from dried leaves of I. cylindrica (ICL) was prepared by standard procedures. Effects of the ICL extract on the morphology of SCC-9 cells was visualized by microscopy. Cytotoxicity was determined by MTT assay. Effects of the ICL extract on colony forming ability of SCC-9 cells was evaluated using clonogenic assay. Cell cycle analysis was performed by flow cytometry and induction of apoptosis was determined by DNA fragmentation assay. The ICL extract treatment caused cytotoxicity and induced cell death in vitro in SCC-9 cells in a dose-dependent manner. This treatment also significantly reduced the clonogenic potential and inhibited cell proliferation by arresting the cell cycle in the G2/M phase. Furthermore, DNA fragmentation assays showed that the observed cell death was caused by apoptosis. This is the first report showing the anticancer activity of the methanol extracts from the leaves of I. cylindrica in human oral cancer cell line. Our data indicates that ICL extract could be considered as one of the lead compounds for the formulation of anticancer therapeutic agents to treat/manage human oral cancers. The natural abundance of I. cylindrica and its wide geographic distribution could render it one of the primary resource materials for preparation of anticancer therapeutic agents. PMID:27221872

  3. Death of mitochondria during programmed cell death of leaf mesophyll cells.

    Science.gov (United States)

    Selga, Tūrs; Selga, Maija; Pāvila, Vineta

    2005-12-01

    The role of plant mitochondria in the programmed cell death (PCD) is widely discussed. However, spectrum and sequence of mitochondrial structural changes during different types of PCD in leaves are poorly described. Pea, cucumber and rye plants were grown under controlled growing conditions. A part of them were sprinkled with ethylene releaser to accelerate cell death. During yellowing the palisade parenchyma mitochondria were attracted to nuclear envelope. Mitochondrial matrix became electron translucent. Mitochondria entered vacuole by invagination of tonoplast and formed multivesicular bodies. Ethephon treatment increased the frequency of sticking of mitochondria to the nuclear envelope or chloroplasts and peroxisomes. Mitochondria divided by different mechanisms and became enclosed in Golgi and ER derived authopagic vacuoles or in the central vacuole. Several fold increase of the diameter of cristae became typical. In all cases mitochondria were attached to nuclear envelope. It can be considered as structural mechanism of promoting of PCD.

  4. Genome-wide Expression Profiling in Seedlings of the Arabidopsis Mutant uro that is Defective in the Secondary Cell Wall Formation

    Institute of Scientific and Technical Information of China (English)

    Zheng Yuan; Xuan Yao; Dabing Zhang; Yue Sun; Hai Huang

    2007-01-01

    Plant secondary growth is of tremendous importance, not only for plant growth and development but also for economic usefulness.Secondary tissues such as xylem and phloem are the conducting tissues in plant vascular systems, essentially for water and nutrient transport, respectively.On the other hand, products of plant secondary growth are important raw materials and renewable sources of energy.Although advances have been recently made towards describing molecular mechanisms that regulate secondary growth, the genetic control for this process is not yet fully understood.Secondary cell wall formation in plants shares some common mechanisms with other plant secondary growth processes.Thus, studies on the secondary cell wall formation using Arabidopsis may help to understand the regulatory mechanisms for plant secondary growth.We previously reported phenotypic characterizations of an Arabidopsis semi-dominant mutant,upright rosette (uro), which is defective in secondary cell wall growth and has an unusually soft stem.Here, we show that lignification in the secondary cell wall in uro is aberrant by analyzing hypocotyl and stem.We also show genome-wide expression profiles of uro seedlings, using the Affymetrix GeneChip that contains approximately 24 000 Arabidopsis genes.Genes identified with altered expression levels include those that function in plant hormone biosynthesis and signaling,cell division and plant secondary tissue growth.These results provide useful information for further characterizations of the regulatory network in plant secondary cell wall formation.

  5. Transient gibberellin application promotes Arabidopsis thaliana hypocotyl cell elongation without maintaining transverse orientation of microtubules on the outer tangential wall of epidermal cells

    KAUST Repository

    Sauret-Güeto, Susanna

    2011-11-25

    The phytohormone gibberellin (GA) promotes plant growth by stimulating cellular expansion. Whilst it is known that GA acts by opposing the growth-repressing effects of DELLA proteins, it is not known how these events promote cellular expansion. Here we present a time-lapse analysis of the effects of a single pulse of GA on the growth of Arabidopsis hypocotyls. Our analyses permit kinetic resolution of the transient growth effects of GA on expanding cells. We show that pulsed application of GA to the relatively slowly growing cells of the unexpanded light-grown Arabidopsis hypocotyl results in a transient burst of anisotropic cellular growth. This burst, and the subsequent restoration of initial cellular elongation rates, occurred respectively following the degradation and subsequent reappearance of a GFP-tagged DELLA (GFP-RGA). In addition, we used a GFP-tagged α-tubulin 6 (GFP-TUA6) to visualise the behaviour of microtubules (MTs) on the outer tangential wall (OTW) of epidermal cells. In contrast to some current hypotheses concerning the effect of GA on MTs, we show that the GA-induced boost of hypocotyl cell elongation rate is not dependent upon the maintenance of transverse orientation of the OTW MTs. This confirms that transverse alignment of outer face MTs is not necessary to maintain rapid elongation rates of light-grown hypocotyls. Together with future studies on MT dynamics in other faces of epidermal cells and in cells deeper within the hypocotyl, our observations advance understanding of the mechanisms by which GA promotes plant cell and organ growth. © 2011 Blackwell Publishing Ltd.

  6. AtHKT1;1 mediates nernstian sodium channel transport properties in Arabidopsis root stelar cells.

    Directory of Open Access Journals (Sweden)

    Shaowu Xue

    Full Text Available The Arabidopsis AtHKT1;1 protein was identified as a sodium (Na⁺ transporter by heterologous expression in Xenopus laevis oocytes and Saccharomyces cerevisiae. However, direct comparative in vivo electrophysiological analyses of a plant HKT transporter in wild-type and hkt loss-of-function mutants has not yet been reported and it has been recently argued that heterologous expression systems may alter properties of plant transporters, including HKT transporters. In this report, we analyze several key functions of AtHKT1;1-mediated ion currents in their native root stelar cells, including Na⁺ and K⁺ conductances, AtHKT1;1-mediated outward currents, and shifts in reversal potentials in the presence of defined intracellular and extracellular salt concentrations. Enhancer trap Arabidopsis plants with GFP-labeled root stelar cells were used to investigate AtHKT1;1-dependent ion transport properties using patch clamp electrophysiology in wild-type and athkt1;1 mutant plants. AtHKT1;1-dependent currents were carried by sodium ions and these currents were not observed in athkt1;1 mutant stelar cells. However, K⁺ currents in wild-type and athkt1;1 root stelar cell protoplasts were indistinguishable correlating with the Na⁺ over K⁺ selectivity of AtHKT1;1-mediated transport. Moreover, AtHKT1;1-mediated currents did not show a strong voltage dependence in vivo. Unexpectedly, removal of extracellular Na⁺ caused a reduction in AtHKT1;1-mediated outward currents in Columbia root stelar cells and Xenopus oocytes, indicating a role for external Na⁺ in regulation of AtHKT1;1 activity. Shifting the NaCl gradient in root stelar cells showed a Nernstian shift in the reversal potential providing biophysical evidence for the model that AtHKT1;1 mediates passive Na⁺ channel transport properties.

  7. DNA Damage in Euonymus japonicus Leaf Cells Caused by Roadside Pollution in Beijing.

    Science.gov (United States)

    Li, Tianxin; Zhang, Minjie; Gu, Ke; Herman, Uwizeyimana; Crittenden, John; Lu, Zhongming

    2016-07-22

    The inhalable particles from vehicle exhaust can cause DNA damage to exposed organisms. Research on DNA damage is primarily focused on the influence of specific pollutants on certain species or the effect of environmental pollution on human beings. To date, little research has quantitatively studied the relationship between roadside pollution and DNA damage. Based on an investigation of the roadside pollution in Beijing, Euonymus japonicus leaves of differing ages grown in heavily-polluted sections were chosen as biomonitors to detect DNA damage using the comet assay technique. The percentage of DNA in the tail and tail moment was chosen as the analysis index based on SPSS data analysis. The roadside samples showed significantly higher levels of DNA damage than non-roadside samples, which increased in older leaves, and the DNA damage to Euonymus japonicus leaf cells was positively correlated with haze-aggravated roadside pollution. The correlation between damage and the Air Quality Index (AQI) are 0.921 (one-year-old leaves), 0.894 (two-year-old leaves), and 0.878 (three-year-old leaves). Over time, the connection between DNA damage and AQI weakened, with the sensitivity coefficient for δyear 1 being larger than δyear 2 and δyear 3. These findings support the suitability and sensitivity of the comet assay for surveying plants for an estimation of DNA damage induced by environmental genotoxic agents. This study might be applied as a preliminary quantitative method for Chinese urban air pollution damage assessment caused by environmental stress.

  8. DNA Damage in Euonymus japonicus Leaf Cells Caused by Roadside Pollution in Beijing.

    Science.gov (United States)

    Li, Tianxin; Zhang, Minjie; Gu, Ke; Herman, Uwizeyimana; Crittenden, John; Lu, Zhongming

    2016-01-01

    The inhalable particles from vehicle exhaust can cause DNA damage to exposed organisms. Research on DNA damage is primarily focused on the influence of specific pollutants on certain species or the effect of environmental pollution on human beings. To date, little research has quantitatively studied the relationship between roadside pollution and DNA damage. Based on an investigation of the roadside pollution in Beijing, Euonymus japonicus leaves of differing ages grown in heavily-polluted sections were chosen as biomonitors to detect DNA damage using the comet assay technique. The percentage of DNA in the tail and tail moment was chosen as the analysis index based on SPSS data analysis. The roadside samples showed significantly higher levels of DNA damage than non-roadside samples, which increased in older leaves, and the DNA damage to Euonymus japonicus leaf cells was positively correlated with haze-aggravated roadside pollution. The correlation between damage and the Air Quality Index (AQI) are 0.921 (one-year-old leaves), 0.894 (two-year-old leaves), and 0.878 (three-year-old leaves). Over time, the connection between DNA damage and AQI weakened, with the sensitivity coefficient for δyear 1 being larger than δyear 2 and δyear 3. These findings support the suitability and sensitivity of the comet assay for surveying plants for an estimation of DNA damage induced by environmental genotoxic agents. This study might be applied as a preliminary quantitative method for Chinese urban air pollution damage assessment caused by environmental stress. PMID:27455298

  9. DNA Damage in Euonymus japonicus Leaf Cells Caused by Roadside Pollution in Beijing

    Science.gov (United States)

    Li, Tianxin; Zhang, Minjie; Gu, Ke; Herman, Uwizeyimana; Crittenden, John; Lu, Zhongming

    2016-01-01

    The inhalable particles from vehicle exhaust can cause DNA damage to exposed organisms. Research on DNA damage is primarily focused on the influence of specific pollutants on certain species or the effect of environmental pollution on human beings. To date, little research has quantitatively studied the relationship between roadside pollution and DNA damage. Based on an investigation of the roadside pollution in Beijing, Euonymus japonicus leaves of differing ages grown in heavily-polluted sections were chosen as biomonitors to detect DNA damage using the comet assay technique. The percentage of DNA in the tail and tail moment was chosen as the analysis index based on SPSS data analysis. The roadside samples showed significantly higher levels of DNA damage than non-roadside samples, which increased in older leaves, and the DNA damage to Euonymus japonicus leaf cells was positively correlated with haze-aggravated roadside pollution. The correlation between damage and the Air Quality Index (AQI) are 0.921 (one-year-old leaves), 0.894 (two-year-old leaves), and 0.878 (three-year-old leaves). Over time, the connection between DNA damage and AQI weakened, with the sensitivity coefficient for δyear 1 being larger than δyear 2 and δyear 3. These findings support the suitability and sensitivity of the comet assay for surveying plants for an estimation of DNA damage induced by environmental genotoxic agents. This study might be applied as a preliminary quantitative method for Chinese urban air pollution damage assessment caused by environmental stress. PMID:27455298

  10. Overexpression of the carbohydrate binding module of strawberry expansin2 in Arabidopsis thaliana modifies plant growth and cell wall metabolism.

    Science.gov (United States)

    Nardi, Cristina F; Villarreal, Natalia M; Rossi, Franco R; Martínez, Santiago; Martínez, Gustavo A; Civello, Pedro M

    2015-05-01

    Several cell wall enzymes are carbohydrate active enzymes that contain a putative Carbohydrate Binding Module (CBM) in their structures. The main function of these non-catalitic modules is to facilitate the interaction between the enzyme and its substrate. Expansins are non-hydrolytic proteins present in the cell wall, and their structure includes a CBM in the C-terminal that bind to cell wall polymers such as cellulose, hemicelluloses and pectins. We studied the ability of the Expansin2 CBM (CBMFaEXP2) from strawberry (Fragaria x ananassa, Duch) to modify the cell wall of Arabidopsis thaliana. Plants overexpressing CBMFaEXP2 were characterized phenotypically and biochemically. Transgenic plants were taller than wild type, possibly owing to a faster growth of the main stem. Cell walls of CBMFaEXP2-expressing plants were thicker and contained higher amount of pectins. Lower activity of a set of enzymes involved in cell wall degradation (PG, β-Gal, β-Xyl) was found, and the expression of the corresponding genes (AtPG, Atβ-Gal, Atβ-Xyl5) was reduced also. In addition, a decrease in the expression of two A. thaliana Expansin genes (AtEXP5 and AtEXP8) was observed. Transgenic plants were more resistant to Botrytis cinerea infection than wild type, possibly as a consequence of higher cell wall integrity. Our results support the hypothesis that the overexpression of a putative CBM is able to modify plant cell wall structure leading to modulation of wall loosening and plant growth. These findings might offer a tool to controlling physiological processes where cell wall disassembly is relevant, such as fruit softening. PMID:25837738

  11. Desaturase mutants reveal that membrane rigidification acts as a cold perception mechanism upstream of the diacylglycerol kinase pathway in Arabidopsis cells.

    Science.gov (United States)

    Vaultier, Marie-Noëlle; Cantrel, Catherine; Vergnolle, Chantal; Justin, Anne-Marie; Demandre, Chantal; Benhassaine-Kesri, Ghouziel; Ciçek, Dominique; Zachowski, Alain; Ruelland, Eric

    2006-07-24

    Membrane rigidification could be the first step of cold perception in poikilotherms. We have investigated its implication in diacylglycerol kinase (DAGK) activation by cold stress in suspension cells from Arabidopsis mutants altered in desaturase activities. By lateral diffusion assay, we showed that plasma membrane rigidification with temperature decrease was steeper in cells deficient in oleate desaturase than in wild type cells and in cells overexpressing linoleate desaturase. The threshold for the activation of the DAGK pathway in each type of cells correlated with this order of rigidification rate, suggesting that cold induced-membrane rigidification is upstream of DAGK pathway activation. PMID:16839551

  12. A Novel Function for Arabidopsis CYCLASE1 in Programmed Cell Death Revealed by Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) Analysis of Extracellular Matrix Proteins.

    Science.gov (United States)

    Smith, Sarah J; Kroon, Johan T M; Simon, William J; Slabas, Antoni R; Chivasa, Stephen

    2015-06-01

    Programmed cell death is essential for plant development and stress adaptation. A detailed understanding of the signal transduction pathways that regulate plant programmed cell death requires identification of the underpinning protein networks. Here, we have used a protagonist and antagonist of programmed cell death triggered by fumonisin B1 as probes to identify key cell death regulatory proteins in Arabidopsis. Our hypothesis was that changes in the abundance of cell death-regulatory proteins induced by the protagonist should be blocked or attenuated by concurrent treatment with the antagonist. We focused on proteins present in the mobile phase of the extracellular matrix on the basis that they are important for cell-cell communications during growth and stress-adaptive responses. Salicylic acid, a plant hormone that promotes programmed cell death, and exogenous ATP, which can block fumonisin B1-induced cell death, were used to treat Arabidopsis cell suspension cultures prior to isobaric-tagged relative and absolute quantitation analysis of secreted proteins. A total of 33 proteins, whose response to salicylic acid was suppressed by ATP, were identified as putative cell death-regulatory proteins. Among these was CYCLASE1, which was selected for further analysis using reverse genetics. Plants in which CYCLASE1 gene expression was knocked out by insertion of a transfer-DNA sequence manifested dramatically increased cell death when exposed to fumonisin B1 or a bacterial pathogen that triggers the defensive hypersensitive cell death. Although pathogen inoculation altered CYCLASE1 gene expression, multiplication of bacterial pathogens was indistinguishable between wild type and CYCLASE1 knockout plants. However, remarkably severe chlorosis symptoms developed on gene knockout plants in response to inoculation with either a virulent bacterial pathogen or a disabled mutant that is incapable of causing disease in wild type plants. These results show that CYCLASE1, which

  13. Shotgun Proteomic Analysis of Arabidopsis thaliana Leaves

    Science.gov (United States)

    Two shotgun tandem mass spectrometry proteomics approaches, Multidimensional Protein Identification Technology (MudPIT) and 1D-Gel-LC-MS/MS, were used to identify Arabidopsis thaliana leaf proteins. These methods utilize different protein/peptide separation strategies. Detergents not compatible wit...

  14. Arabidopsis CDS blastp result: AK287576 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK287576 J065037D19 At1g28300.1 68414.m03473 transcriptional factor B3 family protein / leaf...y cotyledon 2 (LEC2) nearly identical to LEAFY COTYLEDON 2 [Arabidopsis thaliana] GI:15987516; contains Pfam profile PF02362: B3 DNA binding domain 5e-13 ...

  15. An early nodulin-like protein accumulates in the sieve element plasma membrane of Arabidopsis

    DEFF Research Database (Denmark)

    Khan, Junaid A.; Wang, Qi; Sjölund, Richard D.;

    2007-01-01

    Membrane proteins within the sieve element-companion cell complex have essential roles in the physiological functioning of the phloem. The monoclonal antibody line RS6, selected from hybridomas raised against sieve elements isolated from California shield leaf (Streptanthus tortuosus; Brassicaceae......) tissue cultures, recognizes an antigen in the Arabidopsis (Arabidopsis thaliana) ecotype Columbia that is associated specifically with the plasma membrane of sieve elements, but not companion cells, and accumulates at the earliest stages of sieve element differentiation. The identity of the RS6 antigen...... floral and vegetative tissues, the sieve element-specific ENOD is expressed only within the phloem. Members of the ENOD subfamily of the cupredoxin superfamily do not appear to bind copper and have unknown functions. Phenotypic analysis of homozygous T-DNA insertion mutants for the gene At3g20570 shows...

  16. Amino acid substitution converts WEREWOLF function from an activator to a repressor of Arabidopsis non-hair cell development.

    Science.gov (United States)

    Tominaga-Wada, Rumi; Nukumizu, Yuka; Wada, Takuji

    2012-02-01

    Root hair cell or non-hair cell fate determination in Arabidopsis thaliana root epidermis is model system for plant cell development. Two types of MYB transcription factors, the R2R3-type MYB, WEREWOLF (WER), and an R3-type MYB, CAPRICE (CPC), are involved in this cell fate determination process. To study the molecular basis of this process, we analyzed the functional relationship of WER and CPC. WER-CPC chimeric constructs were made from WER where all or parts of the MYB R3 region were replaced with the corresponding regions from CPC R3, and the constructs were introduced into the cpc-2 mutant. Although, the WER gene did not rescue the cpc-2 mutant 'small number of root hairs' phenotype, the WER-CPC chimera with two amino acids substitution (WC6) completely rescued the cpc-2 mutant phenotype. Furthermore, the WER-CPC chimera with 37 amino acids substitution (WC5) excessively rescued the cpc-2 mutant and induced 2.5 times more root hairs than wild-type. Consistent with this phenotype, GL2 gene expression was strongly reduced in WC5 in a cpc-2 background. Our results suggest that swapping at least two amino acids is sufficient to convert WER to CPC function. Therefore, these key residues may have strongly contributed to the selection of these important functions over evolution.

  17. Control of patterns of symmetric cell division in the epidermal and cortical tissues of the Arabidopsis root.

    Science.gov (United States)

    Zhang, Yanwen; Iakovidis, Michail; Costa, Silvia

    2016-03-15

    Controlled cell division is central to the growth and development of all multicellular organisms. Within the proliferating zone of the Arabidopsis root, regular symmetric divisions give rise to patterns of parallel files of cells, the genetic basis of which remains unclear. We found that genotypes impaired in the TONNEAU1a (TON1a) gene display misoriented symmetric divisions in the epidermis and have no division defects in the underlying cortical tissue. The TON1a gene encodes a microtubule-associated protein. We show that in the ton1a mutant, epidermal and cortical cells do not form narrow, ring-like preprophase bands (PPBs), which are plant-specific, cytoskeletal structures that predict the position of the division plane before mitosis. The results indicate that in the cortex but not in the epidermis, division plane positioning and patterning can proceed correctly in the absence of both a functional TON1a and PPB formation. Differences between tissues in how they respond to the signals that guide symmetric division orientation during patterning might provide the basis for organised organ growth in the absence of cell movements.

  18. Transcriptome profiling in Arabidopsis inflorescence stems grown under hypergravity in terms of cell walls and plant hormones

    Science.gov (United States)

    Tamaoki, D.; Karahara, I.; Nishiuchi, T.; De Oliveira, S.; Schreiber, L.; Wakasugi, T.; Yamada, K.; Yamaguchi, K.; Kamisaka, S.

    2009-07-01

    Land plants rely on lignified secondary cell walls in supporting their body weight on the Earth. Although gravity influences the formation of the secondary cell walls, the regulatory mechanism of their formation by gravity is not yet understood. We carried out a comprehensive analysis of gene expression in inflorescence stems of Arabidopsis thaliana L. using microarray (22 K) to identify genes whose expression is modulated under hypergravity condition (300 g). Total RNA was isolated from the basal region of inflorescence stems of plants grown for 24 h at 300 g or 1 g. Microarray analysis showed that hypergravity up-regulated the expression of 403 genes to more than 2-fold. Hypergravity up-regulated the genes responsible for the biosynthesis or modification of cell wall components such as lignin, xyloglucan, pectin and structural proteins. In addition, hypergravity altered the expression of genes related to the biosynthesis of plant hormones such as auxin and ethylene and that of genes encoding hormone-responsive proteins. Our transcriptome profiling indicates that hypergravity influences the formation of secondary cell walls by modulating the pattern of gene expression, and that auxin and/or ethylene play an important role in signaling hypergravity stimulus.

  19. Leaf extracts from Moricandia arvensis promote antiproliferation of human cancer cells, induce apoptosis, and enhance antioxidant activity.

    Science.gov (United States)

    Skandrani, Ines; Boubaker, Jihed; Bhouri, Wissem; Limem, Ilef; Kilani, Soumaya; Ben Sghaier, Mohamed; Neffati, Aicha; Bouhlel, Ines; Ghedira, Kamel; Chekir-Ghedira, Leila

    2010-01-01

    The in vitro antiproliferative, apoptotic, and antioxidant activities from leaf extracts of Moricandia arvensis, which are used in traditional cooking and medicines, were investigated. The MTT assay revealed that only TOF (total oligomer flavonoids), ethyl acetate (EA), chloroform (Chl), and petroleum ether (PE) extracts inhibited the proliferation of K562 cells. Apoptosis plays a very important role in the treatment of cancer by promoting the apoptosis of cancer cells and limiting the concurrent death of normal cells. Thus, the possible effects of M. arvensis extracts on the induction of apoptosis in human leukemic cells (K562 cells) were investigated. The electrophoretic analysis of DNA fragmentation confirms that TOF, Chl, PE, and EA extracts provoke DNA fragmentation. Using the lipid peroxidation inhibitory assay, the antioxidant capacity of M. arvensis extracts was evaluated by the ability of each extract to inhibit malondialdehyde formation. It was revealed that EA and TOF extracts are the most active in scavenging the hydroxyl radicals. PMID:19995267

  20. Turgor Regulation in Osmotically Stressed Arabidopsis Epidermal Root Cells. Direct Support for the Role of Inorganic Ion Uptake as Revealed by Concurrent Flux and Cell Turgor Measurements1

    Science.gov (United States)

    Shabala, Sergey N.; Lew, Roger R.

    2002-01-01

    Hyperosmotic stress is known to significantly enhance net uptake of inorganic ions into plant cells. Direct evidence for cell turgor recovery via such a mechanism, however, is still lacking. In the present study, we performed concurrent measurements of net ion fluxes (with the noninvasive microelectrode ion flux estimation technique) and cell turgor changes (with the pressure-probe technique) to provide direct evidence that inorganic ion uptake regulates turgor in osmotically stressed Arabidopsis epidermal root cells. Immediately after onset of hyperosmotic stress (100/100 mm mannitol/sorbitol treatment), the cell turgor dropped from 0.65 to about 0.25 MPa. Turgor recovery started within 2 to 10 min after the treatment and was accompanied by a significant (30–80 nmol m−2 s−1) increase in uptake of K+, Cl−, and Na+ by root cells. In most cells, almost complete (>90% of initial values) recovery of the cell turgor was observed within 40 to 50 min after stress onset. In another set of experiments, we combined the voltage-clamp and the microelectrode ion flux estimation techniques to show that this process is, in part, mediated by voltage-gated K+ transporters at the cell plasma membrane. The possible physiological significance of these findings is discussed. PMID:12011359

  1. Double Fertilization in Arabidopsis thaliana Involves a Polyspermy Block on the Egg but Not the Central Cell

    Institute of Scientific and Technical Information of China (English)

    Rod J.Scott; Susan J.Armstrong; James Doughty; Melissa Spielman

    2008-01-01

    In animal reproduction,thousands of sperm may compete to fertilize a single egg,but polyspermy blocks prevent multiple fertilization that would otherwise lead to death of the embryo.In flowering plants,successfuI seed development requires that only two sperm are delivered to the embryo sac,where each must fertilize a female gamete(egg or central cell)to produce the embryo and endosperm.Therefore,polyspermy must be avoided,not only to prevent abnormalities in offspring,but to ensure double fertilization.It is not understood how each sperm fertilizes only one female gamete,nor has the existence of polyspermy barriers been directly tested in vivo.Here,we sought evidence for poly-spermy blocks in angiosperms using the polyspermic tetraspore(tes)mutant of Arabidopsis,which allows in-vivo challenge of egg and central cell with multiple male gametes.We show that tes mutant pollen tubes can transmit more than one sperm pair to an embryo sac,and that sperm from more than one pair can participate in fertilization.We detected endosperms but not embryos with ploidies that could only result from multiple fertilization.Our results therefore dem-onstrate an in-vivo polyspermy block on the egg,but not the central cell of a flowering plant.

  2. Plastidial Glycolytic Glyceraldehyde-3-Phosphate Dehydrogenase Is an Important Determinant in the Carbon and Nitrogen Metabolism of Heterotrophic Cells in Arabidopsis.

    Science.gov (United States)

    Anoman, Armand D; Muñoz-Bertomeu, Jesús; Rosa-Téllez, Sara; Flores-Tornero, María; Serrano, Ramón; Bueso, Eduardo; Fernie, Alisdair R; Segura, Juan; Ros, Roc

    2015-11-01

    This study functionally characterizes the Arabidopsis (Arabidopsis thaliana) plastidial glycolytic isoforms of glyceraldehyde-3-phosphate dehydrogenase (GAPCp) in photosynthetic and heterotrophic cells. We expressed the enzyme in gapcp double mutants (gapcp1gapcp2) under the control of photosynthetic (Rubisco small subunit RBCS2B [RBCS]) or heterotrophic (phosphate transporter PHT1.2 [PHT]) cell-specific promoters. Expression of GAPCp1 under the control of RBCS in gapcp1gapcp2 had no significant effect on the metabolite profile or growth in the aerial part (AP). GAPCp1 expression under the control of the PHT promoter clearly affected Arabidopsis development by increasing the number of lateral roots and having a major effect on AP growth and metabolite profile. Our results indicate that GAPCp1 is not functionally important in photosynthetic cells but plays a fundamental role in roots and in heterotrophic cells of the AP. Specifically, GAPCp activity may be required in root meristems and the root cap for normal primary root growth. Transcriptomic and metabolomic analyses indicate that the lack of GAPCp activity affects nitrogen and carbon metabolism as well as mineral nutrition and that glycerate and glutamine are the main metabolites responding to GAPCp activity. Thus, GAPCp could be an important metabolic connector of glycolysis with other pathways, such as the phosphorylated pathway of serine biosynthesis, the ammonium assimilation pathway, or the metabolism of γ-aminobutyrate, which in turn affect plant development. PMID:26134167

  3. Regulation of secondary cell wall biosynthesis by poplar R2R3 MYB transcription factor PtrMYB152 in Arabidopsis

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shucai [Northeast Normal Univ., Changchun (China); Univ. of British Columbia, Vancouver, BC (Canada); Li, Eryang [Univ. of British Columbia, Vancouver, BC (Canada); Porth, Ilga [Univ. of British Columbia, Vancouver, BC (Canada); Chen, Jin-Gui [Univ. of British Columbia, Vancouver, BC (Canada); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Mansfield, Shawn D. [Univ. of British Columbia, Vancouver, BC (Canada); Douglas, Carl [Univ. of British Columbia, Vancouver, BC (Canada)

    2014-05-23

    Poplar has 192 annotated R2R3 MYB genes, of which only three have been shown to play a role in the regulation of secondary cell wall formation. Here we report the characterization of PtrMYB152, a poplar homolog of the Arabidopsis R2R3 MYB transcription factor AtMYB43, in the regulation of secondary cell wall biosynthesis. The expression of PtrMYB152 in secondary xylem is about 18 times of that in phloem. When expressed in Arabidopsis under the control of either 35S or PtrCesA8 promoters, PtrMYB152 increased secondary cell wall thickness, which is likely caused by increased lignification. Accordingly, elevated expression of genes encoding sets of enzymes in secondary wall biosynthesis were observed in transgenic plants expressing PtrMYB152. Arabidopsis protoplast transfection assays suggested that PtrMYB152 functions as a transcriptional activator. Taken together, our results suggest that PtrMYB152 may be part of a regulatory network activating expression of discrete sets of secondary cell wall biosynthesis genes.

  4. [Valve-like structures in motor cells of the leaf of Distichlis spicata "Yesen 4A" (Poaceae)].

    Science.gov (United States)

    Semenova, G A

    2015-01-01

    The salt gland of the leaf of Distichlis directly contacts the cells of interfascicular aquiferous parenchyma (motor cells). The cytoplasmic strand of motor cells produce deep invaginations, which form with the participation of mitochondria. The constriction of the cytoplasmic strand at the site of the localization of mitochondria leads to the fusion of the tonoplast and plasmalemma with mitochondrial membranes and the formation of a thin one-layer plate, a valve. At this locus, vacuolar and apoplast spaces are separated only by a valve. The cytoplasm of motor cells is filled with electron dense granules, which are considered as contractile elements. It is assumed that the cytoplasmic strand is involved in the reduction of the volume, which results in the generation of pressure on the valve. This leads to the direct throw-in of water into the apoplast space adjacent to the salt gland.

  5. Influence of Flavonoid of Astragalus Membranaceus's Stem and Leaf on the Function of Cell Mediated Immunity in Mice

    Institute of Scientific and Technical Information of China (English)

    焦艳; 闻杰; 于晓红; 张德山

    2001-01-01

    Objective: To investigate the immune regulation of flavonoid of Astragalus membranaceus's stem and leaf(FAM-sl). Methods: Changes of total T cell count and subsets in mice were determined by monoclonal antibody assay before and after treatment with FAM-sl, and the lymphokine activated killer cell (LAK) activity was tested simultaneously by isotope label method.Results: FAM-sl could promote the proliferation of lymphocytes induced by ConA, raise the total T cell count and regulate the T cell subsets disturbance, and elevate the LAK activity induced by recombinant interleukin-2 (rIL-2).Conclusion: FAM-sl possesses effects of immune stimulation and immune regulation in treating immunosuppressive mice. This study provides experimental evidence for clinical application of FAM-sl.

  6. Intraspecific variability of cadmium tolerance and accumulation, and cadmium-induced cell wall modifications in the metal hyperaccumulator Arabidopsis halleri.

    Science.gov (United States)

    Meyer, Claire-Lise; Juraniec, Michal; Huguet, Stéphanie; Chaves-Rodriguez, Elena; Salis, Pietro; Isaure, Marie-Pierre; Goormaghtigh, Erik; Verbruggen, Nathalie

    2015-06-01

    Certain molecular mechanisms of Cd tolerance and accumulation have been identified in the model species Arabidopsis halleri, while intraspecific variability of these traits and the mechanisms of shoot detoxification were little addressed. The Cd tolerance and accumulation of metallicolous and non-metallicolous A. halleri populations from different genetic units were tested in controlled conditions. In addition, changes in shoot cell wall composition were investigated using Fourier transform infrared spectroscopy. Indeed, recent works on A. halleri suggest Cd sequestration both inside cells and in the cell wall/apoplast. All A. halleri populations tested were hypertolerant to Cd, and the metallicolous populations were on average the most tolerant. Accumulation was highly variable between and within populations, and populations that were non-accumulators of Cd were identified. The effect of Cd on the cell wall composition was quite similar in the sensitive species A. lyrata and in A. halleri individuals; the pectin/polysaccharide content of cell walls seems to increase after Cd treatment. Nevertheless, the changes induced by Cd were more pronounced in the less tolerant individuals, leading to a correlation between the level of tolerance and the extent of modifications. This work demonstrated that Cd tolerance and accumulation are highly variable traits in A. halleri, suggesting adaptation at the local scale and involvement of various molecular mechanisms. While in non-metallicolous populations drastic modifications of the cell wall occur due to higher Cd toxicity and/or Cd immobilization in this compartment, the increased tolerance of metallicolous populations probably involves other mechanisms such as vacuolar sequestration. PMID:25873677

  7. ARGONAUTE10 and ARGONAUTE1 regulate the termination of floral stem cells through two microRNAs in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Lijuan Ji

    2011-03-01

    Full Text Available Stem cells are crucial in morphogenesis in plants and animals. Much is known about the mechanisms that maintain stem cell fates or trigger their terminal differentiation. However, little is known about how developmental time impacts stem cell fates. Using Arabidopsis floral stem cells as a model, we show that stem cells can undergo precise temporal regulation governed by mechanisms that are distinct from, but integrated with, those that specify cell fates. We show that two microRNAs, miR172 and miR165/166, through targeting APETALA2 and type III homeodomain-leucine zipper (HD-Zip genes, respectively, regulate the temporal program of floral stem cells. In particular, we reveal a role of the type III HD-Zip genes, previously known to specify lateral organ polarity, in stem cell termination. Both reduction in HD-Zip expression by over-expression of miR165/166 and mis-expression of HD-Zip genes by rendering them resistant to miR165/166 lead to prolonged floral stem cell activity, indicating that the expression of HD-Zip genes needs to be precisely controlled to achieve floral stem cell termination. We also show that both the ubiquitously expressed ARGONAUTE1 (AGO1 gene and its homolog AGO10, which exhibits highly restricted spatial expression patterns, are required to maintain the correct temporal program of floral stem cells. We provide evidence that AGO10, like AGO1, associates with miR172 and miR165/166 in vivo and exhibits "slicer" activity in vitro. Despite the common biological functions and similar biochemical activities, AGO1 and AGO10 exert different effects on miR165/166 in vivo. This work establishes a network of microRNAs and transcription factors governing the temporal program of floral stem cells and sheds light on the relationships among different AGO genes, which tend to exist in gene families in multicellular organisms.

  8. Hibiscus sabdariffa Leaf Extract Inhibits Human Prostate Cancer Cell Invasion via Down-Regulation of Akt/NF-κB/MMP-9 Pathway

    OpenAIRE

    Chun-Tang Chiu; Jing-Hsien Chen; Fen-Pi Chou; Hui-Hsuan Lin

    2015-01-01

    Hibiscus sabdariffa leaf has been previously shown to possess hypoglycemic, hypolipidemic, and antioxidant effects, and induce tumor cell apoptosis. However, the molecular mechanisms involved in the anticancer activity of H. sabdariffa leaf extract (HLE) are poorly understood. The object of the study was to examine the anti-invasive potential of HLE. First, HLE was demonstrated to be rich in polyphenols. The results of wound-healing assay and in vitro transwell assay revealed that HLE dose-de...

  9. Salicylic acid-independent ENHANCED DISEASE SUSCEPTIBILITY1 signaling in Arabidopsis immunity and cell death is regulated by the monooxygenase FMO1 and the Nudix hydrolase NUDT7.

    Science.gov (United States)

    Bartsch, Michael; Gobbato, Enrico; Bednarek, Pawel; Debey, Svenja; Schultze, Joachim L; Bautor, Jaqueline; Parker, Jane E

    2006-04-01

    Arabidopsis thaliana ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) controls defense activation and programmed cell death conditioned by intracellular Toll-related immune receptors that recognize specific pathogen effectors. EDS1 is also needed for basal resistance to invasive pathogens by restricting the progression of disease. In both responses, EDS1, assisted by its interacting partner, PHYTOALEXIN-DEFICIENT4 (PAD4), regulates accumulation of the phenolic defense molecule salicylic acid (SA) and other as yet unidentified signal intermediates. An Arabidopsis whole genome microarray experiment was designed to identify genes whose expression depends on EDS1 and PAD4, irrespective of local SA accumulation, and potential candidates of an SA-independent branch of EDS1 defense were found. We define two new immune regulators through analysis of corresponding Arabidopsis loss-of-function insertion mutants. FLAVIN-DEPENDENT MONOOXYGENASE1 (FMO1) positively regulates the EDS1 pathway, and one member (NUDT7) of a family of cytosolic Nudix hydrolases exerts negative control of EDS1 signaling. Analysis of fmo1 and nudt7 mutants alone or in combination with sid2-1, a mutation that severely depletes pathogen-induced SA production, points to SA-independent functions of FMO1 and NUDT7 in EDS1-conditioned disease resistance and cell death. We find instead that SA antagonizes initiation of cell death and stunting of growth in nudt7 mutants.

  10. TIR1/AFB-Aux/IAA auxin perception mediates rapid cell wall acidification and growth of Arabidopsis hypocotyls

    Science.gov (United States)

    Fendrych, Matyáš; Leung, Jeffrey; Friml, Jiří

    2016-01-01

    Despite being composed of immobile cells, plants reorient along directional stimuli. The hormone auxin is redistributed in stimulated organs leading to differential growth and bending. Auxin application triggers rapid cell wall acidification and elongation of aerial organs of plants, but the molecular players mediating these effects are still controversial. Here we use genetically-encoded pH and auxin signaling sensors, pharmacological and genetic manipulations available for Arabidopsis etiolated hypocotyls to clarify how auxin is perceived and the downstream growth executed. We show that auxin-induced acidification occurs by local activation of H+-ATPases, which in the context of gravity response is restricted to the lower organ side. This auxin-stimulated acidification and growth require TIR1/AFB-Aux/IAA nuclear auxin perception. In addition, auxin-induced gene transcription and specifically SAUR proteins are crucial downstream mediators of this growth. Our study provides strong experimental support for the acid growth theory and clarified the contribution of the upstream auxin perception mechanisms. DOI: http://dx.doi.org/10.7554/eLife.19048.001 PMID:27627746

  11. PIN2 turnover in Arabidopsis root epidermal cells explored by the photoconvertible protein Dendra2.

    Directory of Open Access Journals (Sweden)

    Ján Jásik

    Full Text Available The steady state level of integral membrane proteins is dependent on a strictly controlled delivery and removal. Here we show that Dendra2, a green-to-red photoconvertible fluorescent protein, is a suitable tool to study protein turnover in plants. We characterized the fluorescence properties of Dendra2 expressed either as a free protein or as a tag in Arabidopsis thaliana roots and optimized photoconversion settings to study protein turnover. Dendra2 was fused to the PIN2 protein, an auxin transporter in the root tip, and by time-lapse imaging and assessment of red and green signal intensities in the membrane after photoconversion we quantified directly and simultaneously the rate of PIN2 delivery of the newly synthesized protein into the plasma membrane as well as the disappearance of the protein from the plasma membrane due to degradation. Additionally we have verified several factors which are expected to affect PIN2 protein turnover and therefore potentially regulate root growth.

  12. A P-Loop NTPase Regulates Quiescent Center Cell Division and Distal Stem Cell Identity through the Regulation of ROS Homeostasis in Arabidopsis Root.

    Science.gov (United States)

    Yu, Qianqian; Tian, Huiyu; Yue, Kun; Liu, Jiajia; Zhang, Bing; Li, Xugang; Ding, Zhaojun

    2016-09-01

    Reactive oxygen species (ROS) are recognized as important regulators of cell division and differentiation. The Arabidopsis thaliana P-loop NTPase encoded by APP1 affects root stem cell niche identity through its control of local ROS homeostasis. The disruption of APP1 is accompanied by a reduction in ROS level, a rise in the rate of cell division in the quiescent center (QC) and the promotion of root distal stem cell (DSC) differentiation. Both the higher level of ROS induced in the app1 mutant by exposure to methyl viologen (MV), and treatment with hydrogen peroxide (H2O2) rescued the mutant phenotype, implying that both the increased rate of cell division in the QC and the enhancement in root DSC differentiation can be attributed to a low level of ROS. APP1 is expressed in the root apical meristem cell mitochondria, and its product is associated with ATP hydrolase activity. The key transcription factors, which are defining root distal stem niche, such as SCARECROW (SCR) and SHORT ROOT (SHR) are both significantly down-regulated at both the transcriptional and protein level in the app1 mutant, indicating that SHR and SCR are important downstream targets of APP1-regulated ROS signaling to control the identity of root QC and DSCs. PMID:27583367

  13. A P-Loop NTPase Regulates Quiescent Center Cell Division and Distal Stem Cell Identity through the Regulation of ROS Homeostasis in Arabidopsis Root

    Science.gov (United States)

    Yu, Qianqian; Tian, Huiyu; Liu, Jiajia; Zhang, Bing; Li, Xugang; Ding, Zhaojun

    2016-01-01

    Reactive oxygen species (ROS) are recognized as important regulators of cell division and differentiation. The Arabidopsis thaliana P-loop NTPase encoded by APP1 affects root stem cell niche identity through its control of local ROS homeostasis. The disruption of APP1 is accompanied by a reduction in ROS level, a rise in the rate of cell division in the quiescent center (QC) and the promotion of root distal stem cell (DSC) differentiation. Both the higher level of ROS induced in the app1 mutant by exposure to methyl viologen (MV), and treatment with hydrogen peroxide (H2O2) rescued the mutant phenotype, implying that both the increased rate of cell division in the QC and the enhancement in root DSC differentiation can be attributed to a low level of ROS. APP1 is expressed in the root apical meristem cell mitochondria, and its product is associated with ATP hydrolase activity. The key transcription factors, which are defining root distal stem niche, such as SCARECROW (SCR) and SHORT ROOT (SHR) are both significantly down-regulated at both the transcriptional and protein level in the app1 mutant, indicating that SHR and SCR are important downstream targets of APP1-regulated ROS signaling to control the identity of root QC and DSCs. PMID:27583367

  14. A unique HEAT repeat-containing protein SHOOT GRAVITROPISM6 is involved in vacuolar membrane dynamics in gravity-sensing cells of Arabidopsis inflorescence stem.

    Science.gov (United States)

    Hashiguchi, Yasuko; Yano, Daisuke; Nagafusa, Kiyoshi; Kato, Takehide; Saito, Chieko; Uemura, Tomohiro; Ueda, Takashi; Nakano, Akihiko; Tasaka, Masao; Terao Morita, Miyo

    2014-04-01

    Plant vacuoles play critical roles in development, growth and stress responses. In mature cells, vacuolar membranes (VMs) display several types of structures, which are formed by invagination and folding of VMs into the lumenal side and can gradually move and change shape. Although such VM structures are observed in a broad range of tissue types and plant species, the molecular mechanism underlying their formation and maintenance remains unclear. Here, we report that a novel HEAT-repeat protein, SHOOT GRAVITROPISM6 (SGR6), of Arabidopsis is involved in the control of morphological changes and dynamics of VM structures in endodermal cells, which are the gravity-sensing cells in shoots. SGR6 is a membrane-associated protein that is mainly localized to the VM in stem endodermal cells. The sgr6 mutant stem exhibits a reduced gravitropic response. Higher plants utilize amyloplast sedimentation as a means to sense gravity direction. Amyloplasts are surrounded by VMs in Arabidopsis endodermal cells, and the flexible and dynamic structure of VMs is important for amyloplast sedimentation. We demonstrated that such dynamic features of VMs are gradually lost in sgr6 endodermal cells during a 30 min observation period. Histological analysis revealed that amyloplast sedimentation was impaired in sgr6. Detailed live-cell imaging analyses revealed that the VM structures in sgr6 had severe defects in morphological changes and dynamics. Our results suggest that SGR6 is a novel protein involved in the formation and/or maintenance of invaginated VM structures in gravity-sensing cells.

  15. Antagonistic regulation of growth and immunity by the Arabidopsis basic helix-loop-helix transcription factor homolog of brassinosteroid enhanced expression2 interacting with increased leaf inclination1 binding bHLH1

    DEFF Research Database (Denmark)

    Malinovsky, Frederikke Gro; Batoux, Martine; Schwessinger, Benjamin;

    2014-01-01

    mechanisms is needed. Here, we identify the basic helix-loop-helix (bHLH) transcription factor homolog of brassinosteroid enhanced expression2 interacting with IBH1 (HBI1) as a negative regulator of PTI signaling in Arabidopsis (Arabidopsis thaliana). HBI1 expression is down-regulated in response...... to different PAMPs. HBI1 overexpression leads to reduced PAMP-triggered responses. This inhibition correlates with reduced steady-state expression of immune marker genes, leading to increased susceptibility to the bacterium Pseudomonas syringae. Overexpression of the HBI1-related bHLHs brassinosteroid enhanced...

  16. Bioactive Profiles, Antioxidant Activities, Nitrite Scavenging Capacities and Protective Effects on H2O2-Injured PC12 Cells of Glycyrrhiza Glabra L. Leaf and Root Extracts

    Directory of Open Access Journals (Sweden)

    Yi Dong

    2014-06-01

    Full Text Available This study compared the total flavonoid content of Glycyrrhiza glabra L. leaf and root extracts. Results suggested that the total flavonoid content in the leaf extract was obviously higher than that in the root extract. Pinocembrin, the main compound in the leaf extract after purification by column chromatography, showed good antioxidant activity and nitrite scavenging capacity, but moderate inhibitory effect on mushroom tyrosinase. Liquiritin was the main compound in root extract and possessed strong inhibitory effect on mushroom tyrosinase. Both compounds exhibited significant protection effect on H2O2-injured PC12 cells at a low concentration. These results indicate that Glycyrrhiza glabra L. leaf is potential as an important raw material for functional food.

  17. Exploring the use of cDNA-AFLP with leaf protoplasts as a tool to study primary cell wall biosynthesis in potato

    NARCIS (Netherlands)

    Oomen, R.J.F.J.; Bergervoet-van Deelen, J.E.M.; Bachem, C.W.B.; Visser, R.G.F.; Vincken, J.P.

    2003-01-01

    An RNA fingerprinting study of potato leaf protoplasts was performed to explore its suitability for identifying candidate genes involved in primary cell wall biosynthesis. Microscopic analysis, using calcofluor white to stain cellulose, showed that the protoplasts generated a new cell wall in the fi

  18. The combined effects of CO2 concentration and enhanced UV-B radiation on faba bean. 3. Leaf optical properties, pigments, stomatal index and epidermal cell density

    International Nuclear Information System (INIS)

    Seedlings of Vicia faba L. (cv. Minica) were grown in a factorial experiment in a greenhouse. The purpose of the study was to determine whether CO2 enrichment and supplemental UV-B radiation affect leaf optical properties and whether the combined effects differ from single factor effects. Seedlings were grown at either 380 μmol mol-1 or 750 μmol mol-1 CO2 and at four levels of UV-B radiation. After 20 and 40 days of treatment, absorptance, transmittance and reflectance of photosynthetically active radiation (PAR) were measured on the youngest fully developed leaf. On the same leaf, the specific leaf area on a fresh weight basis (SLAfw), chlorophyll content, UV-B absorbance, transmittance of UV light and stomatal index were measured. UV-B radiation significantly increased PAR absorptance and decreased PAR transmittance. The increased PAR absorptance can be explained by an increased chlorophyll content in response to UV-B radiation. Leaf transmittance of UV radiation decreased with increasing UV-B levels mainly caused by increased absorbance of UV absorbing compounds. UV-B radiation decreased both the stomatal density and epidermal cell density of the abaxial leaf surface, leaving the stomatal index unchanged. Effects of CO2 enrichment were less pronounced than those of UV-B radiation. The most important CO2 effect was an increase in stomatal density and epidermal cell density of the adaxial leaf surface. The stomatal index was not affected. No interaction between CO2 and UV-B radiation was found. The results are discussed in relation to the internal light environment of the leaf. (author)

  19. Glucose alleviates cadmium toxicity by increasing cadmium fixation in root cell wall and sequestration into vacuole in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Yuan-Zhi Shi; Xiao-Fang Zhu; Jiang-Xue Wan; Gui-Xin Li; Shao-Jian Zheng

    2015-01-01

    Glucose (Glu) is involved in not only plant physiological and developmental events but also plant responses to abiotic stresses. Here, we found that the exogenous Glu improved root and shoot growth, reduced shoot cadmium (Cd) concentration, and rescued Cd-induced chlorosis in Arabidopsis thaliana (Columbia ecotype, Col-0) under Cd stressed conditions. Glucose increased Cd retained in the roots, thus reducing its translocation from root to shoot significantly. The most Cd retained in the roots was found in the hemicellulose 1. Glucose combined with Cd (Glu þ Cd) treatment did not affect the content of pectin and its binding capacity of Cd while it increased the content of hemicelluloses 1 and the amount of Cd retained in it significantly. Furthermore, Leadmium Green staining indicated that more Cd was compartmented into vacuoles in Glu þ Cd treatment compared with Cd treatment alone, which was in accordance with the significant upregulation of the expression of tonoplast-localized metal transporter genes, suggesting that com-partmentation of Cd into vacuoles also contributes to the Glu-alleviated Cd toxicity. Taken together, we demonstrated that Glu-alleviated Cd toxicity is mediated through increas-ing Cd fixation in the root cell wall and sequestration into the vacuoles.

  20. Multiple abiotic stress tolerance of the transformants yeast cells and the transgenic Arabidopsis plants expressing a novel durum wheat catalase.

    Science.gov (United States)

    Feki, Kaouthar; Kamoun, Yosra; Ben Mahmoud, Rihem; Farhat-Khemakhem, Ameny; Gargouri, Ali; Brini, Faiçal

    2015-12-01

    Catalases are reactive oxygen species scavenging enzymes involved in response to abiotic and biotic stresses. In this study, we described the isolation and functional characterization of a novel catalase from durum wheat, designed TdCAT1. Molecular Phylogeny analyses showed that wheat TdCAT1 exhibited high amino acids sequence identity to other plant catalases. Sequence homology analysis showed that TdCAT1 protein contained the putative calmodulin binding domain and a putative conserved internal peroxisomal targeting signal PTS1 motif around its C-terminus. Predicted three-dimensional structural model revealed the presence of four putative distinct structural regions which are the N-terminal arm, the β-barrel, the wrapping and the α-helical domains. TdCAT1 protein had the heme pocket that was composed by five essential residues. TdCAT1 gene expression analysis showed that this gene was induced by various abiotic stresses in durum wheat. The expression of TdCAT1 in yeast cells and Arabidopsis plants conferred tolerance to several abiotic stresses. Compared with the non-transformed plants, the transgenic lines maintained their growth and accumulated more proline under stress treatments. Furthermore, the amount of H2O2 was lower in transgenic lines, which was due to the high CAT and POD activities. Taken together, these data provide the evidence for the involvement of durum wheat catalase TdCAT1 in tolerance to multiple abiotic stresses in crop plants. PMID:26555900

  1. Acyl chains of phospholipase D transphosphatidylation products in Arabidopsis cells: a study using multiple reaction monitoring mass spectrometry.

    Directory of Open Access Journals (Sweden)

    Dominique Rainteau

    Full Text Available BACKGROUND: Phospholipases D (PLD are major components of signalling pathways in plant responses to some stresses and hormones. The product of PLD activity is phosphatidic acid (PA. PAs with different acyl chains do not have the same protein targets, so to understand the signalling role of PLD it is essential to analyze the composition of its PA products in the presence and absence of an elicitor. METHODOLOGY/PRINCIPAL FINDINGS: Potential PLD substrates and products were studied in Arabidopsis thaliana suspension cells treated with or without the hormone salicylic acid (SA. As PA can be produced by enzymes other than PLD, we analyzed phosphatidylbutanol (PBut, which is specifically produced by PLD in the presence of n-butanol. The acyl chain compositions of PBut and the major glycerophospholipids were determined by multiple reaction monitoring (MRM mass spectrometry. PBut profiles of untreated cells or cells treated with SA show an over-representation of 160/18:2- and 16:0/18:3-species compared to those of phosphatidylcholine and phosphatidylethanolamine either from bulk lipid extracts or from purified membrane fractions. When microsomal PLDs were used in in vitro assays, the resulting PBut profile matched exactly that of the substrate provided. Therefore there is a mismatch between the acyl chain compositions of putative substrates and the in vivo products of PLDs that is unlikely to reflect any selectivity of PLDs for the acyl chains of substrates. CONCLUSIONS: MRM mass spectrometry is a reliable technique to analyze PLD products. Our results suggest that PLD action in response to SA is not due to the production of a stress-specific molecular species, but that the level of PLD products per se is important. The over-representation of 160/18:2- and 16:0/18:3-species in PLD products when compared to putative substrates might be related to a regulatory role of the heterogeneous distribution of glycerophospholipids in membrane sub-domains.

  2. Functional analysis of the theobroma cacao NPR1 gene in arabidopsis

    Directory of Open Access Journals (Sweden)

    Verica Joseph

    2010-11-01

    Full Text Available Abstract Background The Arabidopsis thaliana NPR1 gene encodes a transcription coactivator (NPR1 that plays a major role in the mechanisms regulating plant defense response. After pathogen infection and in response to salicylic acid (SA accumulation, NPR1 translocates from the cytoplasm into the nucleus where it interacts with other transcription factors resulting in increased expression of over 2000 plant defense genes contributing to a pathogen resistance response. Results A putative Theobroma cacao NPR1 cDNA was isolated by RT-PCR using degenerate primers based on homologous sequences from Brassica, Arabidopsis and Carica papaya. The cDNA was used to isolate a genomic clone from Theobroma cacao containing a putative TcNPR1 gene. DNA sequencing revealed the presence of a 4.5 kb coding region containing three introns and encoding a polypeptide of 591 amino acids. The predicted TcNPR1 protein shares 55% identity and 78% similarity to Arabidopsis NPR1, and contains each of the highly conserved functional domains indicative of this class of transcription factors (BTB/POZ and ankyrin repeat protein-protein interaction domains and a nuclear localization sequence (NLS. To functionally define the TcNPR1 gene, we transferred TcNPR1 into an Arabidopsis npr1 mutant that is highly susceptible to infection by the plant pathogen Pseudomonas syringae pv. tomato DC3000. Driven by the constitutive CaMV35S promoter, the cacao TcNPR1 gene partially complemented the npr1 mutation in transgenic Arabidopsis plants, resulting in 100 fold less bacterial growth in a leaf infection assay. Upon induction with SA, TcNPR1 was shown to translocate into the nucleus of leaf and root cells in a manner identical to Arabidopsis NPR1. Cacao NPR1 was also capable of participating in SA-JA signaling crosstalk, as evidenced by the suppression of JA responsive gene expression in TcNPR1 overexpressing transgenic plants. Conclusion Our data indicate that the TcNPR1 is a functional

  3. Studies on the Rice LEAF INCLINATION1 (LC1),an IAA-amido Synthetase, Reveal the Effects of Auxin in Leaf Inclination Control

    Institute of Scientific and Technical Information of China (English)

    Shu-Qing Zhao; Jing-Jing Xiang; Hong-Wei Xue

    2013-01-01

    The angle of rice leaf inclination is an important agronomic trait and closely related to the yields and architecture of crops.Although few mutants with altered leaf angles have been reported,the molecular mechanism remains to be elucidated,especially whether hormones are involved in this process.Through genetic screening,a rice gain-offunction mutant leaf inclination1,Ic1-D,was identified from the Shanghai T-DNA Insertion Population (SHIP).Phenotypic analysis confirmed the exaggerated leaf angles of Ic1-D due to the stimulated cell elongation at the lamina joint.LC1 is transcribed in various tissues and encodes OsGH3-1,an indole-3-acetic acid (IAA) amido synthetase,whose homolog of Arabidopsis functions in maintaining the auxin homeostasis by conjugating excess IAA to various amino acids.Indeed,recombinant LC1 can catalyze the conjugation of IAA to Ala,Asp,and Asn in vitro,which is consistent with the decreased free IAA amount in Ic1-D mutant.Ic1-D is insensitive to IAA and hypersensitive to exogenous BR,in agreement with the microarray analysis that reveals the altered transcriptions of genes involved in auxin signaling and BR biosynthesis.These results indicate the crucial roles of auxin homeostasis in the leaf inclination control.

  4. Cell biological analyses of anther morphogenesis and pollen viability in Arabidopsis and rice.

    Science.gov (United States)

    Chang, Fang; Zhang, Zaibao; Jin, Yue; Ma, Hong

    2014-01-01

    Major advances have been made in recent years in our understanding of anther development through a combination of genetic studies, cell biological technologies, biochemical analysis, microarray and high-throughput sequencing-based approaches. In this chapter, we summarize the widely used protocols for pollen viability staining; the investigation of anther morphogenesis by light microscopy of semi-thin sections; TUNEL assay for programmed tapetum cell death; and laser microdissection procedures to obtain specialized cells or cell layers for carrying out transcriptomics.

  5. A survey of cellulose microfibril patterns in dividing, expanding, and differentiating cells of Arabidopsis thaliana.

    Science.gov (United States)

    Fujita, Miki; Wasteneys, Geoffrey O

    2014-05-01

    Cellulose microfibrils are critical for plant cell specialization and function. Recent advances in live cell imaging of fluorescently tagged cellulose synthases to track cellulose synthesis have greatly advanced our understanding of cellulose biosynthesis. Nevertheless, cellulose deposition patterns remain poorly described in many cell types, including those in the process of division or differentiation. In this study, we used field emission scanning electron microscopy analysis of cryo-planed tissues to determine the arrangement of cellulose microfibrils in various faces of cells undergoing cytokinesis or specialized development, including cell types in which cellulose cannot be imaged by conventional approaches. In dividing cells, we detected microfibrillar meshworks in the cell plates, consistent with the concentration at the cell plate of cellulose synthase complexes, as detected by fluorescently tagged CesA6. We also observed a loss of parallel cellulose microfibril orientation in walls of the mother cell during cytokinesis, which corresponded with the loss of fluorescently tagged cellulose synthase complexes from these surfaces. In recently formed guard cells, microfibrils were randomly organized and only formed a highly ordered circumferential pattern after pore formation. In pit fields, cellulose microfibrils were arranged in circular patterns around plasmodesmata. Microfibrils were random in most cotyledon cells except the epidermis and were parallel to the growth axis in trichomes. Deposition of cellulose microfibrils was spatially delineated in metaxylem and protoxylem cells of the inflorescence stem, supporting recent studies on microtubule exclusion mechanisms.

  6. A chemical screen for suppressors of the avrRpm1-RPM1-dependent hypersensitive cell death response in Arabidopsis thaliana

    OpenAIRE

    Serrano, M; Hubert, D.; Dangl, J.; Schulze-Lefert, P; Kombrink, E.

    2010-01-01

    Arabidopsis thaliana RPM1 encodes an intracellular immune sensor that conditions disease resistance to Pseudomonas syringae expressing the type III effector protein AvrRpm1. Conditional expression of this type III effector in a transgenic line carrying avrRpm1 under the control of a steroid-inducible promoter results in RPM1-dependent cell death that resembles the cell death response of the incompatible RPM1-avrRpm1 plant–bacterium interaction. This line was previously used in a genetic scree...

  7. Gibberellin-Regulation and Genetic Variations in Leaf Elongation for Tall Fescue in Association with Differential Gene Expression Controlling Cell Expansion.

    Science.gov (United States)

    Xu, Qian; Krishnan, Sanalkumar; Merewitz, Emily; Xu, Jichen; Huang, Bingru

    2016-01-01

    Leaf elongation rate (LER) is an important factor controlling plant growth and productivity. The objective of this study was to determine whether genetic variation in LER for a fast-growing ('K-31'), and a dwarf cultivar ('Bonsai') of tall fescue (Festuca arundinacea) and gibberellic acid (GA) regulation of LER were associated with differential expression of cell-expansion genes. Plants were treated with GA3, trinexapac-ethyl (TE) (GA inhibitor), or water (untreated control) in a hydroponic system. LER of 'K-31' was 63% greater than that of 'Bonsai', which corresponded with 32% higher endogenous GA4 content in leaf and greater cell elongation and production rates under the untreated control condition. Exogenous application of GA3 significantly enhanced LER while TE treatment inhibited leaf elongation due to GA3-stimulation or TE-inhibition of cell elongation and production rate in leaves for both cultivars. Real-time quantitative polymerase chain reaction analysis revealed that three α-expansins, one β-expansin, and three xyloglucan endotransglycosylase (XET) genes were associated with GA-stimulation of leaf elongation, of which, the differential expression of EXPA4 and EXPA7 was related to the genotypic variation in LER of two cultivars. Those differentially-expressed expansin and XET genes could play major roles in genetic variation and GA-regulated leaf elongation in tall fescue. PMID:27457585

  8. Alterations in protein expression of Arabidopsis thaliana cell cultures during hyper- , simulated and sounding rocket micro-gravity

    Science.gov (United States)

    Hampp, Ruediger; Barjaktarović, Žarko; Babbick, Maren; Magel, Elisabeth; Nordheim, Alfred; Lamkemeyer, Tobias; Hampp, Ruediger

    Callus cell cultures of Arabidopsis thaliana exposed to hypergravity (8g), 2D clinorotation and random positioning exhibit changes in gene expression (Martzivanou et al., Protoplasma 229:155-162, 2003). In a recent investigation we could show that after 2 hrs of exposure also the protein complement shows treatment-related changes. These are indicative for reactive oxygen species being involved in the perception of / response to changes in the gravitational field. In the present study we have extended these investigations for a period of up to 16 hrs of exposure. We report on changes in abundance of 28 proteins which have been identified by nano HPLC-ESI-MS/MS, and which were altered in amount after 2 hrs of treatment. According to changes between 2 and 16 hrs we could distinguish four groups of proteins which either declined, increased from down-regulated to control levels, showed a transient decline or a transient increase. With regard to function, our data indicate stress relief or adaption to a new gravitational steady state under prolonged exposure. The latter assumption is supported by the appearance of a new set of 19 proteins which is changed in abundance after 8 hrs of hypergravity. A comparative analysis of the different treatments showed some similarities in response between 8g centrifugation and 2D clinorotation, while random positioning showed the least responses. In addition, we report on the impact of reduced gravitation on the phospho proteom. Cell cultures exposed to 12 min of microgravity as obtained on board of sounding rockets do not respond with alterations in total protein but in the degree of phosphorylation as demonstrated after 2D SDS PAGE separation and sequencing. On this basis we give evidence for signaling cascades involved in the transduction of gravitational signals.

  9. Genome-scale identification of cell-wall related genes in Arabidopsis based on co-expression network analysis

    Directory of Open Access Journals (Sweden)

    Wang Shan

    2012-08-01

    Full Text Available Abstract Background Identification of the novel genes relevant to plant cell-wall (PCW synthesis represents a highly important and challenging problem. Although substantial efforts have been invested into studying this problem, the vast majority of the PCW related genes remain unknown. Results Here we present a computational study focused on identification of the novel PCW genes in Arabidopsis based on the co-expression analyses of transcriptomic data collected under 351 conditions, using a bi-clustering technique. Our analysis identified 217 highly co-expressed gene clusters (modules under some experimental conditions, each containing at least one gene annotated as PCW related according to the Purdue Cell Wall Gene Families database. These co-expression modules cover 349 known/annotated PCW genes and 2,438 new candidates. For each candidate gene, we annotated the specific PCW synthesis stages in which it is involved and predicted the detailed function. In addition, for the co-expressed genes in each module, we predicted and analyzed their cis regulatory motifs in the promoters using our motif discovery pipeline, providing strong evidence that the genes in each co-expression module are transcriptionally co-regulated. From the all co-expression modules, we infer that 108 modules are related to four major PCW synthesis components, using three complementary methods. Conclusions We believe our approach and data presented here will be useful for further identification and characterization of PCW genes. All the predicted PCW genes, co-expression modules, motifs and their annotations are available at a web-based database: http://csbl.bmb.uga.edu/publications/materials/shanwang/CWRPdb/index.html.

  10. Variable-angle total internal reflection fluorescence microscopy of intact cells of Arabidopsis thaliana

    OpenAIRE

    Kim Myung K; Hao Huaiqin; Fan Lusheng; Ash William M; Wan Yinglang; Lin Jinxing

    2011-01-01

    Abstract Background Total internal reflection fluorescence microscopy (TIRFM) is a powerful tool for observing fluorescently labeled molecules on the plasma membrane surface of animal cells. However, the utility of TIRFM in plant cell studies has been limited by the fact that plants have cell walls, thick peripheral layers surrounding the plasma membrane. Recently, a new technique known as variable-angle epifluorescence microscopy (VAEM) was developed to circumvent this problem. However, the ...

  11. A SCARECROW-RETINOBLASTOMA protein network controls protective quiescence in the Arabidopsis root stem cell organizer.

    OpenAIRE

    Alfredo Cruz-Ramírez; Sara Díaz-Triviño; Guy Wachsman; Yujuan Du; Mario Arteága-Vázquez; Hongtao Zhang; Rene Benjamins; Ikram Blilou; Neef, Anne B.; Vicki Chandler; Ben Scheres

    2013-01-01

    Author Summary In the plant Arabidposis thaliana, root meristems (in the growing tip of the root) contain slowly dividing cells that act as an organizing center for the root stem cells that surround them. This centre is called the quiescent centre (QC). In this study, we show that the slow rate of division in the QC is regulated by the interaction between two proteins: Retinoblastoma homolog (RBR) and SCARECROW (SCR), a transcription factor that controls stem cell maintenance. RBR and SCR reg...

  12. Meristematic competence is disrupted by microgravity, real or simulated, in seedlings and cultured cells of Arabidopsis

    Science.gov (United States)

    Medina, Francisco Javier; Herranz, Raul; Van Loon, ing.. Jack J. W. A.; Kiss, John; Valbuena, Miguel A.; Youssef, Khaled

    In actively proliferating plant cells, the rate of cell proliferation is strictly coordinated with cell growth, and this coordination is called “meristematic competence”. Cell proliferation consists of the adequate progression of the cell division cycle throughout specific regulatory checkpoints, and cell growth consists of reaching the critical size making possible cell division, based on the increase of biomass, essentially by means of protein synthesis. There are two cellular models in which these processes can be studied, namely the meristematic tissues of plants and seedlings and the in vitro suspension cell cultures. Meristems are essential for the determination of the developmental pattern of the plant, which is primarily based on the balance between proliferating (meristematic) and differentiated cells. Auxin is a fundamental phytohormone, responsible for the maintenance of meristematic competence and for the control of the rate of differentiation. We first studied the proliferating activity of root meristematic cells in the International Space Station (ISS) and in a random positioning machine (RPM), a ground-based device for simulated microgravity. The result in both experiments was the increase of mitotic activity (cell proliferation) and the depletion of ribosome synthesis (cell growth), that is, the disruption of meristematic competence. We found these effects associated with changes in the auxin levels and polar transport, which is related to the role of auxin as a mediator of the transduction of the gravitropic signal sensed in the root columella. We plan to advance in the investigation of mechanisms of the auxin control of meristematic competence in microgravity conditions in a new experiment, “Seedling Growth”, to be performed in the ISS. We will use mutants of the auxin transport pathway and we will also test the potential activating role of red light, known to be a cell proliferation and gene expression enhancer. The role played by

  13. The MADS Domain Protein DIANA Acts Together with AGAMOUS-LIKE80 to Specify the Central Cell in Arabidopsis Ovules[W

    Science.gov (United States)

    Bemer, Marian; Wolters-Arts, Mieke; Grossniklaus, Ueli; Angenent, Gerco C.

    2008-01-01

    MADS box genes in plants consist of MIKC-type and type I genes. While MIKC-type genes have been studied extensively, the functions of type I genes are still poorly understood. Evidence suggests that type I MADS box genes are involved in embryo sac and seed development. We investigated two independent T-DNA insertion alleles of the Arabidopsis thaliana type I MADS box gene AGAMOUS-LIKE61 (AGL61) and showed that in agl61 mutant ovules, the polar nuclei do not fuse and central cell morphology is aberrant. Furthermore, the central cell begins to degenerate before fertilization takes place. Although pollen tubes are attracted and perceived by the mutant ovules, neither endosperm development nor zygote formation occurs. AGL61 is expressed in the central cell during the final stages of embryo sac development. An AGL61:green fluorescent protein–β-glucoronidase fusion protein localizes exclusively to the polar nuclei and the secondary nucleus of the central cell. Yeast two-hybrid analysis showed that AGL61 can form a heterodimer with AGL80 and that the nuclear localization of AGL61 is lost in the agl80 mutant. Thus, AGL61 and AGL80 appear to function together to differentiate the central cell in Arabidopsis. We renamed AGL61 DIANA, after the virginal Roman goddess of the hunt. PMID:18713950

  14. BEL1-LIKE HOMEODOMAIN6 and KNOTTED ARABIDOPSIS THALIANA7 interact and regulate secondary cell wall formation via repression of REVOLUTA.

    Science.gov (United States)

    Liu, Yuanyuan; You, Shijun; Taylor-Teeples, Mallorie; Li, Wenhua L; Schuetz, Mathias; Brady, Siobhan M; Douglas, Carl J

    2014-12-01

    The TALE homeodomain transcription factor KNOTTED ARABIDOPSIS THALIANA7 (KNAT7) is part of a regulatory network governing the commitment to secondary cell wall biosynthesis of Arabidopsis thaliana, where it contributes to negative regulation of this process. Here, we report that BLH6, a BELL1-LIKE HOMEODOMAIN protein, specifically interacts with KNAT7, and this interaction influences secondary cell wall development. BLH6 is a transcriptional repressor, and BLH6-KNAT7 physical interaction enhances KNAT7 and BLH6 repression activities. The overlapping expression patterns of BLH6 and KNAT7 and phenotypes of blh6, knat7, and blh6 knat7 loss-of-function mutants are consistent with the existence of a BLH6-KNAT7 heterodimer that represses commitment to secondary cell wall biosynthesis in interfascicular fibers. BLH6 and KNAT7 overexpression results in thinner interfascicular fiber secondary cell walls, phenotypes that are dependent on the interacting partner. A major impact of the loss of BLH6 and KNAT7 function is enhanced expression of the homeodomain-leucine zipper transcription factor REVOLUTA/INTERFASCICULAR FIBERLESS1 (REV/IFL1). BLH6 and KNAT7 bind to the REV promoter and repress REV expression, while blh6 and knat7 interfascicular fiber secondary cell wall phenotypes are suppressed in blh6 rev and knat7 rev double mutants, suggesting that BLH6/KNAT7 signaling acts through REV as a direct target.

  15. Cellulose-Pectin Spatial Contacts Are Inherent to Never-Dried Arabidopsis Primary Cell Walls: Evidence from Solid-State Nuclear Magnetic Resonance.

    Science.gov (United States)

    Wang, Tuo; Park, Yong Bum; Cosgrove, Daniel J; Hong, Mei

    2015-07-01

    The structural role of pectins in plant primary cell walls is not yet well understood because of the complex and disordered nature of the cell wall polymers. We recently introduced multidimensional solid-state nuclear magnetic resonance spectroscopy to characterize the spatial proximities of wall polysaccharides. The data showed extensive cross peaks between pectins and cellulose in the primary wall of Arabidopsis (Arabidopsis thaliana), indicating subnanometer contacts between the two polysaccharides. This result was unexpected because stable pectin-cellulose interactions are not predicted by in vitro binding assays and prevailing cell wall models. To investigate whether the spatial contacts that give rise to the cross peaks are artifacts of sample preparation, we now compare never-dried Arabidopsis primary walls with dehydrated and rehydrated samples. One-dimensional (13)C spectra, two-dimensional (13)C-(13)C correlation spectra, water-polysaccharide correlation spectra, and dynamics data all indicate that the structure, mobility, and intermolecular contacts of the polysaccharides are indistinguishable between never-dried and rehydrated walls. Moreover, a partially depectinated cell wall in which 40% of homogalacturonan is extracted retains cellulose-pectin cross peaks, indicating that the cellulose-pectin contacts are not due to molecular crowding. The cross peaks are observed both at -20 °C and at ambient temperature, thus ruling out freezing as a cause of spatial contacts. These results indicate that rhamnogalacturonan I and a portion of homogalacturonan have significant interactions with cellulose microfibrils in the native primary wall. This pectin-cellulose association may be formed during wall biosynthesis and may involve pectin entrapment in or between cellulose microfibrils, which cannot be mimicked by in vitro binding assays.

  16. Exogenous auxin alleviates cadmium toxicity in Arabidopsis thaliana by stimulating synthesis of hemicellulose 1 and increasing the cadmium fixation capacity of root cell walls

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiao Fang [Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, College of Life Sciences, Zhejiang University, Hangzhou 310058 (China); State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058 (China); Wang, Zhi Wei [Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, College of Life Sciences, Zhejiang University, Hangzhou 310058 (China); Dong, Fang; Lei, Gui Jie [State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058 (China); Shi, Yuan Zhi [The Key Laboratory of Tea Chemical Engineering, Ministry of Agriculture, Yunqi Road 1, Hangzhou 310008 (China); Li, Gui Xin, E-mail: guixinli@zju.edu.cn [College of Agronomy and Biotechnology, Zhejiang University, Hangzhou 310058 (China); Zheng, Shao Jian [Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, College of Life Sciences, Zhejiang University, Hangzhou 310058 (China); State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058 (China)

    2013-12-15

    Highlights: • Cd reduces endogenous auxin levels in Arabidopsis. • Exogenous applied auxin NAA increases Cd accumulation in the roots but decreases in the shoots. • NAA increases cell wall hemicellulose 1 content. • Hemicellulose 1 retains Cd and makes it difficult to be translocated to shoots. • NAA rescues Cd-induced chlorosis. -- Abstract: Auxin is involved in not only plant physiological and developmental processes but also plant responses to abiotic stresses. In this study, cadmium (Cd{sup 2+}) stress decreased the endogenous auxin level, whereas exogenous auxin (α-naphthaleneacetic acid, NAA, a permeable auxin analog) reduced shoot Cd{sup 2+} concentration and rescued Cd{sup 2+}-induced chlorosis in Arabidopsis thaliana. Under Cd{sup 2+} stress conditions, NAA increased Cd{sup 2+} retention in the roots and most Cd{sup 2+} in the roots was fixed in hemicellulose 1 of the cell wall. NAA treatment did not affect pectin content and its binding capacity for Cd{sup 2+}, whereas it significantly increased the content of hemicellulose 1 and the amount of Cd{sup 2+} retained in it. There were highly significant correlations between Cd{sup 2+} concentrations in the root, cell wall and hemicellulose 1 when the plants were subjected to Cd{sup 2+} or NAA + Cd{sup 2+} treatment for 1 to 7 d, suggesting that the increase in hemicellulose 1 contributes greatly to the fixation of Cd{sup 2+} in the cell wall. Taken together, these results demonstrate that auxin-induced alleviation of Cd{sup 2+} toxicity in Arabidopsis is mediated through increasing hemicellulose 1 content and Cd{sup 2+} fixation in the root, thus reducing the translocation of Cd{sup 2+} from roots to shoots.

  17. Cell edges accumulate gamma tubulin complex components and nucleate microtubules following cytokinesis in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Chris Ambrose

    Full Text Available Microtubules emanate from distinct organizing centers in fungal and animal cells. In plant cells, by contrast, microtubules initiate from dispersed sites in the cell cortex, where they then self-organize into parallel arrays. Previous ultrastructural evidence suggested that cell edges participate in microtubule nucleation but so far there has been no direct evidence for this. Here we use live imaging to show that components of the gamma tubulin nucleation complex (GCP2 and GCP3 localize at distinct sites along the outer periclinal edge of newly formed crosswalls, and that microtubules grow predominantly away from these edges. These data confirm a role for cell edges in microtubule nucleation, and suggest that an asymmetric distribution of microtubule nucleation factors contributes to cortical microtubule organization in plants, in a manner more similar to other kingdoms than previously thought.

  18. Reciprocal responses in the interaction between Arabidopsis and the cell-content-feeding chelicerate herbivore spider mite.

    Science.gov (United States)

    Zhurov, Vladimir; Navarro, Marie; Bruinsma, Kristie A; Arbona, Vicent; Santamaria, M Estrella; Cazaux, Marc; Wybouw, Nicky; Osborne, Edward J; Ens, Cherise; Rioja, Cristina; Vermeirssen, Vanessa; Rubio-Somoza, Ignacio; Krishna, Priti; Diaz, Isabel; Schmid, Markus; Gómez-Cadenas, Aurelio; Van de Peer, Yves; Grbic, Miodrag; Clark, Richard M; Van Leeuwen, Thomas; Grbic, Vojislava

    2014-01-01

    Most molecular-genetic studies of plant defense responses to arthropod herbivores have focused on insects. However, plant-feeding mites are also pests of diverse plants, and mites induce different patterns of damage to plant tissues than do well-studied insects (e.g. lepidopteran larvae or aphids). The two-spotted spider mite (Tetranychus urticae) is among the most significant mite pests in agriculture, feeding on a staggering number of plant hosts. To understand the interactions between spider mite and a plant at the molecular level, we examined reciprocal genome-wide responses of mites and its host Arabidopsis (Arabidopsis thaliana). Despite differences in feeding guilds, we found that transcriptional responses of Arabidopsis to mite herbivory resembled those observed for lepidopteran herbivores. Mutant analysis of induced plant defense pathways showed functionally that only a subset of induced programs, including jasmonic acid signaling and biosynthesis of indole glucosinolates, are central to Arabidopsis's defense to mite herbivory. On the herbivore side, indole glucosinolates dramatically increased mite mortality and development times. We identified an indole glucosinolate dose-dependent increase in the number of differentially expressed mite genes belonging to pathways associated with detoxification of xenobiotics. This demonstrates that spider mite is sensitive to Arabidopsis defenses that have also been associated with the deterrence of insect herbivores that are very distantly related to chelicerates. Our findings provide molecular insights into the nature of, and response to, herbivory for a representative of a major class of arthropod herbivores.

  19. Quantitative Changes in Microtubule Distribution Correlate with Guard Cell Function in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    William R. Eisinger; Viktor Kirik; Charlotte Lewis; David W. Ehrhardt; Winslow R. Briggs

    2012-01-01

    Radially arranged cortical microtubules are a prominent feature of guard cells.We observed guard cells expressing GFP-tubulin (GFP-TUA6) with confocal microscopy and found recognizable changes in the appearance of microtubules when stomata open or close (Eisinger et al.,2012).In the present study,analysis of fluorescence distribution showed a dramatic increase in peak intensities of microtubule bundles within guard cells as stomata open.This increase was correlated with an increase in the total fluorescence that could be attributed to polymerized tubulin.Adjacent pavement cells did not show similar changes in peak intensities or integrated fluorescence when stomatal apertures changed.Imaging of RFP-tagged end binding protein 1 (EB1) and YFP-tagged α-tubulin expressed in the same cell revealed that the number of microtubules with growing ends remained constant,although the total amount of polymerized tubulin was higher in open than in closed guard cells.Taken together,these results indicate that the changes in microtubule array organization that are correlated with and required for normal guard cell function are characterized by changes in microtubule clustering or bundling.

  20. Ectopic Expression of BnaC.CP20.1 Results in Premature Tapetal Programmed Cell Death in Arabidopsis.

    Science.gov (United States)

    Song, Liping; Zhou, Zhengfu; Tang, Shan; Zhang, Zhiqiang; Xia, Shengqian; Qin, Maomao; Li, Bao; Wen, Jing; Yi, Bin; Shen, Jinxiong; Ma, Chaozhi; Fu, Tingdong; Tu, Jinxing

    2016-09-01

    Tapetal programmed cell death (PCD) is essential in pollen grain development, and cysteine proteases are ubiquitous enzymes participating in plant PCD. Although the major papain-like cysteine proteases (PLCPs) have been investigated, the exact functions of many PLCPs are still poorly understood in PCD. Here, we identified a PLCP gene, BnaC.CP20.1, which was closely related to XP_013596648.1 from Brassica oleracea. Quantitative real-time PCR analysis revealed that BnaC.CP20.1 expression was down-regulated in male-sterile lines in oilseed rape, suggesting a connection between this gene and male sterility. BnaC.CP20.1 is especially active in the tapetum and microspores in Brassica napus from the uninucleate stage until formation of mature pollen grains during anther development. On expression of BnaC.CP20.1 prior to the tetrad stage, BnA9::BnaC.CP20.1 transgenic lines in Arabidopsis thaliana showed a male-sterile phenotype with shortened siliques containing fewer or no seeds by self-crossing. Scanning electron microscopy indicated that the reticulate exine was defective in aborted microspores. Callose degradation was delayed and microspores were not released from the tetrad in a timely fashion. Additionally, the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay indicated that BnaC.CP20.1 ectopic expression led to premature tapetal PCD. Transmission electron microscopy analyses further demonstrated that the pollen abortion was due to the absence of tectum connections to the bacula in the transgenic anthers. These findings suggest that timely expression of BnaC.CP20.1 is necessary for tapetal degeneration and pollen wall formation. PMID:27388342

  1. Activation of Tag1 transposable elements in Arabidopsis dedifferentiating cells and their regulation by CHROMOMETHYLASE 3-mediated CHG methylation.

    Science.gov (United States)

    Khan, Asif; Yadav, Narendra Singh; Morgenstern, Yaakov; Zemach, Assaf; Grafi, Gideon

    2016-10-01

    Dedifferentiation, that is, the acquisition of stem cell-like state, commonly induced by stress (e.g., protoplasting), is characterized by open chromatin conformation, a chromatin state that could lead to activation of transposable elements (TEs). Here, we studied the activation of the Arabidopsis class II TE Tag1, in which two copies, situated close to each other (near genes) on chromosome 1 are found in Landsberg erecta (Ler) but not in Columbia (Col). We first transformed protoplasts with a construct in which a truncated Tag1 (ΔTag1 non-autonomous) blocks the expression of a reporter gene AtMBD5-GFP and found a relatively high ectopic excision of ΔTag1 accompanied by expression of AtMBD5-GFP in protoplasts derived from Ler compared to Col; further increase was observed in ddm1 (decrease in DNA methylation1) protoplasts (Ler background). Ectopic excision was associated with transcription of the endogenous Tag1 and changes in histone H3 methylation at the promoter region. Focusing on the endogenous Tag1 elements we found low level of excision in Ler protoplasts, which was slightly and strongly enhanced in ddm1 and cmt3 (chromomethylase3) protoplasts, respectively, concomitantly with reduction in Tag1 gene body (GB) CHG methylation and increased Tag1 transcription; strong activation of Tag1 was also observed in cmt3 leaves. Notably, in cmt3, but not in ddm1, Tag1 elements were excised out from their original sites and transposed elsewhere in the genome. Our results suggest that dedifferentiation is associated with Tag1 activation and that CMT3 rather than DDM1 plays a central role in restraining Tag1 activation via inducing GB CHG methylation. PMID:27475038

  2. Callus cell proliferation from broccoli leaf slice using IBA and BAP in vitro culture: Its biochemical and antioxidant properties.

    Science.gov (United States)

    Sharif Hossain, A B M; Haq, Imdadul; Ibrahim, Nasir A; Aleissa, Mohammed Saad

    2016-03-01

    Plant tissue or cell culture keeps a significant role in micro-propagation in the plant production industry. Combination of 6-Benzylaminopurine (BAP) and other plant growth regulators like 1-Naphthaleneacetic acid (NAA) or Indole-3-acetic acid (IAA) or indole-3-butyric acid (IBA) was used in the most of the research in tissue culture. The study was carried out to investigate the optimization of the concentration of IBA and BAP combination (0, 0.25, 0.50, 1.0, 1.50, 2.0, 2.5, 3.0 and 3.5 mg/l) for the root, callus and leaf proliferation from the leaf cutting slice. The highest number (6.75) of root proliferation was observed in the concentration of 2.0 mg/l IBA+0.25 mg/l BAP combination. The callus initiation was found in the concentration of IBA 1.0-3.5 mg/l+BAP 1.0-2.0 mg/l. However, the highest callus weight was observed at the concentration of IBA 1.5 mg/l+BAP 1.0 mg/l combination than other combination of concentrations. Positively leaf initiation and formation was better in the concentration of IBA 1-3.5 mg/l+BAP 1.0-2.0 mg/l combination. In addition, the 2,2-diphenyl-2-picrylhydarzyl (DPPH) free radical scavenging potential was higher (70.1%) in leaves extract than in callus extracts (46.3%) at the concentration of 10 mg/ml though both extracts had lower DPPH free radical scavenging activity compared to the positive control, vitamin C and BHT. Theresults conclude that the optimum concentration was IBA 1.5 mg/l+BAP 1.0 mg/l combination to produce callus cell proliferation and concentration of 2.0 mg/l IBA+0.25 mg/l BAP combination was the optimum for root proliferation of broccoli in vitro.

  3. Callus cell proliferation from broccoli leaf slice using IBA and BAP in vitro culture: Its biochemical and antioxidant properties

    Directory of Open Access Journals (Sweden)

    A.B.M. Sharif Hossain

    2016-03-01

    Full Text Available Plant tissue or cell culture keeps a significant role in micro-propagation in the plant production industry. Combination of 6-Benzylaminopurine (BAP and other plant growth regulators like 1-Naphthaleneacetic acid (NAA or Indole-3-acetic acid (IAA or indole-3-butyric acid (IBA was used in the most of the research in tissue culture. The study was carried out to investigate the optimization of the concentration of IBA and BAP combination (0, 0.25, 0.50, 1.0, 1.50, 2.0, 2.5, 3.0 and 3.5 mg/l for the root, callus and leaf proliferation from the leaf cutting slice. The highest number (6.75 of root proliferation was observed in the concentration of 2.0 mg/l IBA+0.25 mg/l BAP combination. The callus initiation was found in the concentration of IBA 1.0–3.5 mg/l+BAP 1.0–2.0 mg/l. However, the highest callus weight was observed at the concentration of IBA 1.5 mg/l+BAP 1.0 mg/l combination than other combination of concentrations. Positively leaf initiation and formation was better in the concentration of IBA 1–3.5 mg/l+BAP 1.0–2.0 mg/l combination. In addition, the 2,2-diphenyl-2-picrylhydarzyl (DPPH free radical scavenging potential was higher (70.1% in leaves extract than in callus extracts (46.3% at the concentration of 10 mg/ml though both extracts had lower DPPH free radical scavenging activity compared to the positive control, vitamin C and BHT. Theresults conclude that the optimum concentration was IBA 1.5 mg/l+BAP 1.0 mg/l combination to produce callus cell proliferation and concentration of 2.0 mg/l IBA+0.25 mg/l BAP combination was the optimum for root proliferation of broccoli in vitro.

  4. Zinc distribution and speciation in Arabidopsis halleri x Arabidops is lyrata progenies presenting various zinc accumulation capacities

    Energy Technology Data Exchange (ETDEWEB)

    Sarret, Geraldine; Willems, Glenda; Isaure, Marie-Pierre; Marcus, Matthew A.; Fakra, Sirine C.; Frerot, Helene; Pairis, Sebastien; Geoffroy, Nicolas; Manceau, Alain; Saumitou-Laprade, Pierre

    2010-04-08

    - The purpose of this study was to investigate the relationship between the chemical form and localization of zinc (Zn) in plant leaves and their Zn accumulationcapacity. - An interspecific cross between Arabidopsis halleri sp. halleri and Arabidopsis lyrata sp. petrea segregating for Zn accumulation was used. Zinc (Zn) speciation and Zn distribution in the leaves of the parent plants and of selected F1 and F2 progenies were investigated by spectroscopic and microscopic techniques and chemical analyses. - A correlation was observed between the proportion of Zn being in octahedral coordination complexed to organic acids and free in solution (Zn?OAs + Znaq) and Zn content in the leaves. This pool varied between 40percent and 80percent of total leaf Zn depending on the plant studied. Elemental mapping of the leaves revealed different Zn partitioning between the veins and the leaf tissue. The vein : tissue fluorescence ratio was negatively correlated with Zn accumulation. - The higher proportion of Zn?OAs + Znaq and the depletion of the veins in the stronger accumulators are attributed to a higher xylem unloading and vacuolar sequestration in the leaf cells. Elemental distributions in the trichomes were also investigated, and results support the role of carboxyl and⁄ or hydroxyl groups as major Zn ligands in these cells.

  5. Reactive oxygen species regulate leaf pulvinus abscission zone cell separation in response to water-deficit stress in cassava.

    Science.gov (United States)

    Liao, Wenbin; Wang, Gan; Li, Yayun; Wang, Bin; Zhang, Peng; Peng, Ming

    2016-01-01

    Cassava (Manihot esculenta Crantz) plant resists water-deficit stress by shedding leaves leading to adaptive water-deficit condition. Transcriptomic, physiological, cellular, molecular, metabolic, and transgenic methods were used to study the mechanism of cassava abscission zone (AZ) cell separation under water-deficit stress. Microscopic observation indicated that AZ cell separation initiated at the later stages during water-deficit stress. Transcriptome profiling of AZ suggested that differential expression genes of AZ under stress mainly participate in reactive oxygen species (ROS) pathway. The key genes involved in hydrogen peroxide biosynthesis and metabolism showed significantly higher expression levels in AZ than non-separating tissues adjacent to the AZ under stress. Significantly higher levels of hydrogen peroxide correlated with hydrogen peroxide biosynthesis related genes and AZ cell separation was detected by microscopic observation, colorimetric detection and GC-MS analyses under stress. Co-overexpression of the ROS-scavenging proteins SOD and CAT1 in cassava decreased the levels of hydrogen peroxide in AZ under water-deficit stress. The cell separation of the pulvinus AZ also delayed in co-overexpression of the ROS-scavenging proteins SOD and CAT1 plants both in vitro and at the plant level. Together, the results indicated that ROS play an important regulatory role in the process of cassava leaf abscission under water-deficit stress.

  6. Reactive oxygen species regulate leaf pulvinus abscission zone cell separation in response to water-deficit stress in cassava.

    Science.gov (United States)

    Liao, Wenbin; Wang, Gan; Li, Yayun; Wang, Bin; Zhang, Peng; Peng, Ming

    2016-01-01

    Cassava (Manihot esculenta Crantz) plant resists water-deficit stress by shedding leaves leading to adaptive water-deficit condition. Transcriptomic, physiological, cellular, molecular, metabolic, and transgenic methods were used to study the mechanism of cassava abscission zone (AZ) cell separation under water-deficit stress. Microscopic observation indicated that AZ cell separation initiated at the later stages during water-deficit stress. Transcriptome profiling of AZ suggested that differential expression genes of AZ under stress mainly participate in reactive oxygen species (ROS) pathway. The key genes involved in hydrogen peroxide biosynthesis and metabolism showed significantly higher expression levels in AZ than non-separating tissues adjacent to the AZ under stress. Significantly higher levels of hydrogen peroxide correlated with hydrogen peroxide biosynthesis related genes and AZ cell separation was detected by microscopic observation, colorimetric detection and GC-MS analyses under stress. Co-overexpression of the ROS-scavenging proteins SOD and CAT1 in cassava decreased the levels of hydrogen peroxide in AZ under water-deficit stress. The cell separation of the pulvinus AZ also delayed in co-overexpression of the ROS-scavenging proteins SOD and CAT1 plants both in vitro and at the plant level. Together, the results indicated that ROS play an important regulatory role in the process of cassava leaf abscission under water-deficit stress. PMID:26899473

  7. Chloroplasts activity and PAP-signaling regulate programmed cell death in Arabidopsis

    KAUST Repository

    Bruggeman, Quentin

    2016-01-09

    Programmed cell death (PCD) is a crucial process both for plant development and responses to biotic and abiotic stress. There is accumulating evidence that chloroplasts may play a central role during plant PCD as for mitochondria in animal cells, but it is still unclear whether they participate in PCD onset, execution, or both. To tackle this question, we have analyzed the contribution of chloroplast function to the cell death phenotype of the myoinositol phosphate synthase1 (mips1) mutant that forms spontaneous lesions in a light-dependent manner. We show that photosynthetically active chloroplasts are required for PCD to occur in mips1, but this process is independent of the redox state of the chloroplast. Systematic genetic analyses with retrograde signaling mutants reveal that 3’-phosphoadenosine 5’-phosphate, a chloroplast retrograde signal that modulates nuclear gene expression in response to stress, can inhibit cell death and compromises plant innate immunity via inhibition of the RNA-processing 5’-3’ exoribonucleases. Our results provide evidence for the role of chloroplast-derived signal and RNA metabolism in the control of cell death and biotic stress response. © 2016 American Society of Plant Biologists. All Rights Reserved.

  8. Tissue-autonomous promotion of palisade cell development by phototropin 2 in Arabidopsis.

    Science.gov (United States)

    Kozuka, Toshiaki; Kong, Sam-Geun; Doi, Michio; Shimazaki, Ken-ichiro; Nagatani, Akira

    2011-10-01

    Light is an important environmental information source that plants use to modify their growth and development. Palisade parenchyma cells in leaves develop cylindrical shapes in response to blue light; however, the photosensory mechanism for this response has not been elucidated. In this study, we analyzed the palisade cell response in phototropin-deficient mutants. First, we found that two different light-sensing mechanisms contributed to the response in different proportions depending on the light intensity. One response observed under lower intensities of blue light was mediated exclusively by a blue light photoreceptor, phototropin 2 (PHOT2). Another response was elicited under higher intensities of light in a phototropin-independent manner. To determine the tissue in which PHOT2 perceives the light stimulus to regulate the response, green fluorescent protein (GFP)-tagged PHOT2 (P2G) was expressed under the control of tissue-specific promoters in the phot1 phot2 mutant background. The results revealed that the expression of P2G in the mesophyll, but not in the epidermis, promoted palisade cell development. Furthermore, a constitutively active C-terminal kinase fragment of PHOT2 fused to GFP (P2CG) promoted the development of cylindrical palisade cells in the proper direction without the directional cue provided by light. Hence, in response to blue light, PHOT2 promotes the development of cylindrical palisade cells along a predetermined axis in a tissue-autonomous manner.

  9. RED AND BLUE LIGHT-STIMULATED PROTON EFFLUX BY EPIDERMAL LEAF-CELLS OF THE ARGENTEUM MUTANT OF PISUM-SATIVUM

    NARCIS (Netherlands)

    STAAL, M; ELZENGA, JTM; VANELK, AG; PRINS, HBA; VANVOLKENBURGH, E

    1994-01-01

    Light stimulates leaf expansion in dicotyledons by increasing apoplastic acidification, cell wall loosening and solute accumulation for turgor maintenance. Red and blue light enhance growth via different photosystems, but the cellular location and modes of action of these systems is not known. Here,

  10. The nucleolar structure and nucleolar proteins in proliferating cells of Arabidopsis seeds germinated in the International Space Station

    Science.gov (United States)

    Matía, I.; González-Camacho, F.; Marco, R.; Kiss, J. Z.; Gasset, G.; Medina, F. J.

    Seeds of Arabidopsis thaliana were sent to the ISS in the ``Cervantes Mission'' (Spanish Soyuz Mission) within MAMBA Biocontainers (Dutch Space B.V.). These Biocontainers are capable of supplying liquids to the biosample by means of a motorized mechanism based on the ``Berlingot-Ampoule'' concept. Seed germination was activated by supplying culture medium to them, and the process progressed for 4 days at 22°C. Then, growth was stopped by the addition of paraformaldehyde (PFA) fixative. Once back on the ground, samples were immediately processed for microscopical observation. A parallel ground control experiment was simultaneously replicated, following the same schedule and conditions. Seed germination occurred at a high rate in the Space. No differences in the germination rate were observed with respect to the ground control, although Space-grown seedlings were substantially longer (affecting the roots and also the hypocotyl) than the parallel samples grown at 1 g. The mitotic index and the cellular morphometric parameters (length, width, nuclear size) were measured and compared in both the experimental and control conditions. Bidimensional protein electrophoresis was performed on samples in which PFA fixation was reverted by prolonged (two weeks) storage in PBS buffer. The total proteomic profile of seedlings showed differences between the Space sample and the ground control, affecting to nearly one third of the spots. Remarkably, a set of spots around 35 kDa and pI 8.0 are conspicuous in the Space sample and do not appear in the ground control. A more specialized proteomic analysis, with functional significance, was carried out using the AgNOR staining method on Western blots, a technique revealing nucleolar proteins associated with cell proliferation. Immunocytochemical experiments showed the in situ distribution of nucleolin, a nucleolar multifunctional protein regulated by kinases related with cell cycle and proliferation control mechanisms. Finally, the

  11. Information flow during gene activation by signaling molecules: ethylene transduction in Arabidopsis cells as a study system

    Directory of Open Access Journals (Sweden)

    Díaz José

    2009-05-01

    Full Text Available Abstract Background We study root cells from the model plant Arabidopsis thaliana and the communication channel conformed by the ethylene signal transduction pathway. A basic equation taken from our previous work relates the probability of expression of the gene ERF1 to the concentration of ethylene. Results The above equation is used to compute the Shannon entropy (H or degree of uncertainty that the genetic machinery has during the decoding of the message encoded by the ethylene specific receptors embedded in the endoplasmic reticulum membrane and transmitted into the nucleus by the ethylene signaling pathway. We show that the amount of information associated with the expression of the master gene ERF1 (Ethylene Response Factor 1 can be computed. Then we examine the system response to sinusoidal input signals with varying frequencies to determine if the cell can distinguish between different regimes of information flow from the environment. Our results demonstrate that the amount of information managed by the root cell can be correlated with the frequency of the input signal. Conclusion The ethylene signaling pathway cuts off very low and very high frequencies, allowing a window of frequency response in which the nucleus reads the incoming message as a sinusoidal input. Out of this window the nucleus reads the input message as an approximately non-varying one. From this frequency response analysis we estimate: a the gain of the system during the synthesis of the protein ERF1 (~-5.6 dB; b the rate of information transfer (0.003 bits during the transport of each new ERF1 molecule into the nucleus and c the time of synthesis of each new ERF1 molecule (~21.3 s. Finally, we demonstrate that in the case of the system of a single master gene (ERF1 and a single slave gene (HLS1, the total Shannon entropy is completely determined by the uncertainty associated with the expression of the master gene. A second proposition shows that the Shannon entropy

  12. Expression of the Arabidopsis high-affinity hexose transporter STP13 correlates with programmed cell death

    DEFF Research Database (Denmark)

    Nørholm, Morten Helge Hauberg; Nour-Eldin, Hussam H; Brodersen, Peter;

    2006-01-01

    GFP expression only in the vascular tissue in emerging petals under non-stressed conditions. Quantitative PCR and the pSTP13-GFP plants show induction of STP13 in programmed cell death (PCD) obtained by treatments with the fungal toxin fumonisin B1 and the pathogen Pseudomonas syringae. A role for STP......13 in PCD is supported by microarray data from e.g. plants undergoing senescence and a strong correlation between STP13 transcripts and the PCD phenotype in different accelerated cell death (acd11) mutants....

  13. Live and let die: a REM complex promotes fertilization through synergid cell death in Arabidopsis.

    Science.gov (United States)

    Mendes, Marta Adelina; Guerra, Rosalinda Fiorella; Castelnovo, Beatrice; Silva-Velazquez, Yuriria; Morandini, Piero; Manrique, Silvia; Baumann, Nadine; Groß-Hardt, Rita; Dickinson, Hugh; Colombo, Lucia

    2016-08-01

    Fertilization in flowering plants requires a complex series of coordinated events involving interaction between the male and female gametophyte. We report here molecular data on one of the key events underpinning this process - the death of the receptive synergid cell and the coincident bursting of the pollen tube inside the ovule to release the sperm. We show that two REM transcription factors, VALKYRIE (VAL) and VERDANDI (VDD), both targets of the ovule identity MADS-box complex SEEDSTICK-SEPALLATA3, interact to control the death of the receptive synergid cell. In vdd-1/+ mutants and VAL_RNAi lines, we find that GAMETOPHYTIC FACTOR 2 (GFA2), which is required for synergid degeneration, is downregulated, whereas expression of FERONIA (FER) and MYB98, which are necessary for pollen tube attraction and perception, remain unaffected. We also demonstrate that the vdd-1/+ phenotype can be rescued by expressing VDD or GFA2 in the synergid cells. Taken together, our findings reveal that the death of the receptive synergid cell is essential for maintenance of the following generations, and that a complex comprising VDD and VAL regulates this event.

  14. Live and let die: a REM complex promotes fertilization through synergid cell death in Arabidopsis.

    Science.gov (United States)

    Mendes, Marta Adelina; Guerra, Rosalinda Fiorella; Castelnovo, Beatrice; Silva-Velazquez, Yuriria; Morandini, Piero; Manrique, Silvia; Baumann, Nadine; Groß-Hardt, Rita; Dickinson, Hugh; Colombo, Lucia

    2016-08-01

    Fertilization in flowering plants requires a complex series of coordinated events involving interaction between the male and female gametophyte. We report here molecular data on one of the key events underpinning this process - the death of the receptive synergid cell and the coincident bursting of the pollen tube inside the ovule to release the sperm. We show that two REM transcription factors, VALKYRIE (VAL) and VERDANDI (VDD), both targets of the ovule identity MADS-box complex SEEDSTICK-SEPALLATA3, interact to control the death of the receptive synergid cell. In vdd-1/+ mutants and VAL_RNAi lines, we find that GAMETOPHYTIC FACTOR 2 (GFA2), which is required for synergid degeneration, is downregulated, whereas expression of FERONIA (FER) and MYB98, which are necessary for pollen tube attraction and perception, remain unaffected. We also demonstrate that the vdd-1/+ phenotype can be rescued by expressing VDD or GFA2 in the synergid cells. Taken together, our findings reveal that the death of the receptive synergid cell is essential for maintenance of the following generations, and that a complex comprising VDD and VAL regulates this event. PMID:27338615

  15. The zinc finger protein ZAT11 modulates paraquat-induced programmed cell death in Arabidopsis thaliana

    NARCIS (Netherlands)

    Qureshi, Muhammad Kamran; Sujeeth, Neerakkal; Gechev, Tsanko S.; Hille, Jacques; Liu, J.-H.

    2013-01-01

    Plants use programmed cell death (PCD) as a tool in their growth and development. PCD is also involved in defense against different kinds of stresses including pathogen attack. In both types of PCD, reactive oxygen species (ROS) play an important role. ROS is not only a toxic by-product but also act

  16. Probabilistic mapping and image clustering for quantitative assessment of fluorescent protein localizations in Arabidopsis guard cells

    OpenAIRE

    sprotocols

    2015-01-01

    Authors: Takumi Higaki, Natsumaro Kutsuna & Seiichiro Hasezawa ### Abstract The protocol reported here describes a method to quantitatively evaluate fluorescently-tagged protein localizations from fluorescent microscopic images with a combination of probabilistic mapping and image clustering. We demonstrate the use of this protocol using kidney-shaped guard cells of plants. ### Introduction Microscopic assessment of protein localizations with fluorescent protein taggin...

  17. AcEBP1, an ErbB3-Binding Protein (EBP1) from halophyte Atriplex canescens, negatively regulates cell growth and stress responses in Arabidopsis.

    Science.gov (United States)

    Li, Jingtao; Yu, Gang; Sun, Xinhua; Zhang, Xianghui; Liu, Jinliang; Pan, Hongyu

    2016-07-01

    An ErbB-3-binding protein gene AcEBP1, also known as proliferation-associated 2G4 gene (PA2G4s) belonging to the M24 superfamily, was obtained from the saltbush Atriplex canescens. Subcellular localization imaging showed the fusion protein AcEBP1-eGFP was located in the nucleus of epidermal cells in Nicotiana benthamiana. The AcEBP1 gene expression levels were up-regulated under salt, osmotic stress, and hormones treatment as revealed by qRT-PCR. Overexpression of AcEBP1 in Arabidopsis demonstrated that AcEBP1 was involved in root cell growth and stress responses (NaCl, osmotic stress, ABA, low temperature, and drought). These phenotypic data were correlated with the expression patterns of stress responsive genes and PR genes. The AcEBP1 transgenic Arabidopsis plants also displayed increased sensitivity under low temperature and evaluated resistance to drought stress. Together, these results demonstrate that AcEBP1 negatively affects cell growth and is a regulator under stress conditions. PMID:27181948

  18. A temperature-sensitive allele of a putative mRNA splicing helicase down-regulates many cell wall genes and causes radial swelling in Arabidopsis thaliana.

    Science.gov (United States)

    Howles, Paul A; Gebbie, Leigh K; Collings, David A; Varsani, Arvind; Broad, Ronan C; Ohms, Stephen; Birch, Rosemary J; Cork, Ann H; Arioli, Tony; Williamson, Richard E

    2016-05-01

    The putative RNA helicase encoded by the Arabidopsis gene At1g32490 is a homolog of the yeast splicing RNA helicases Prp2 and Prp22. We isolated a temperature-sensitive allele (rsw12) of the gene in a screen for root radial swelling mutants. Plants containing this allele grown at the restrictive temperature showed weak radial swelling, were stunted with reduced root elongation, and contained reduced levels of cellulose. The role of the protein was further explored by microarray analysis. By using both fold change cutoffs and a weighted gene coexpression network analysis (WGCNA) to investigate coexpression of genes, we found that the radial swelling phenotype was not linked to genes usually associated with primary cell wall biosynthesis. Instead, the mutation has strong effects on expression of secondary cell wall related genes. Many genes potentially associated with secondary walls were present in the most significant WGCNA module, as were genes coding for arabinogalactans and proteins with GPI anchors. The proportion of up-regulated genes that possess introns in rsw12 was above that expected if splicing was unrelated to the activity of the RNA helicase, suggesting that the helicase does indeed play a role in splicing in Arabidopsis. The phenotype may be due to a change in the expression of one or more genes coding for cell wall proteins.

  19. Lesion simulating disease 1 and enhanced disease susceptibility 1 differentially regulate UV-C-induced photooxidative stress signalling and programmed cell death in Arabidopsis thaliana.

    Science.gov (United States)

    Wituszyńska, Weronika; Szechyńska-Hebda, Magdalena; Sobczak, Mirosław; Rusaczonek, Anna; Kozłowska-Makulska, Anna; Witoń, Damian; Karpiński, Stanisław

    2015-02-01

    As obligate photoautotrophs, plants are inevitably exposed to ultraviolet (UV) radiation. Because of stratospheric ozone depletion, UV has become more and more dangerous to the biosphere. Therefore, it is important to understand UV perception and signal transduction in plants. In the present study, we show that lesion simulating disease 1 (LSD1) and enhanced disease susceptibility 1 (EDS1) are antagonistic regulators of UV-C-induced programmed cell death (PCD) in Arabidopsis thaliana. This regulatory dependence is manifested by a complex deregulation of photosynthesis, reactive oxygen species homeostasis, antioxidative enzyme activity and UV-responsive genes expression. We also prove that a UV-C radiation episode triggers apoptotic-like morphological changes within the mesophyll cells. Interestingly, chloroplasts are the first organelles that show features of UV-C-induced damage, which may indicate their primary role in PCD development. Moreover, we show that Arabidopsis Bax inhibitor 1 (AtBI1), which has been described as a negative regulator of plant PCD, is involved in LSD1-dependent cell death in response to UV-C. Our results imply that LSD1 and EDS1 regulate processes extinguishing excessive energy, reactive oxygen species formation and subsequent PCD in response to different stresses related to impaired electron transport.

  20. A temperature-sensitive allele of a putative mRNA splicing helicase down-regulates many cell wall genes and causes radial swelling in Arabidopsis thaliana.

    Science.gov (United States)

    Howles, Paul A; Gebbie, Leigh K; Collings, David A; Varsani, Arvind; Broad, Ronan C; Ohms, Stephen; Birch, Rosemary J; Cork, Ann H; Arioli, Tony; Williamson, Richard E

    2016-05-01

    The putative RNA helicase encoded by the Arabidopsis gene At1g32490 is a homolog of the yeast splicing RNA helicases Prp2 and Prp22. We isolated a temperature-sensitive allele (rsw12) of the gene in a screen for root radial swelling mutants. Plants containing this allele grown at the restrictive temperature showed weak radial swelling, were stunted with reduced root elongation, and contained reduced levels of cellulose. The role of the protein was further explored by microarray analysis. By using both fold change cutoffs and a weighted gene coexpression network analysis (WGCNA) to investigate coexpression of genes, we found that the radial swelling phenotype was not linked to genes usually associated with primary cell wall biosynthesis. Instead, the mutation has strong effects on expression of secondary cell wall related genes. Many genes potentially associated with secondary walls were present in the most significant WGCNA module, as were genes coding for arabinogalactans and proteins with GPI anchors. The proportion of up-regulated genes that possess introns in rsw12 was above that expected if splicing was unrelated to the activity of the RNA helicase, suggesting that the helicase does indeed play a role in splicing in Arabidopsis. The phenotype may be due to a change in the expression of one or more genes coding for cell wall proteins. PMID:27008640

  1. Alpha-picolinic Acid Activates Diverse Defense Responses of Salicylic Acid-, Jasmonic Acid/Ethylene- and Ca2 -dependent Pathways in Arabidopsis and Rice Suspension Cells

    Institute of Scientific and Technical Information of China (English)

    ZHANGHai-Kuo; ZHANGXin; LIQun; HEZu-Hua

    2004-01-01

    Alpha-picolinic acid (PA) is an apoptosis inducer in animal cells, and could elicit hypersensitiv eresponse (HR) in rice, a monocotyledonous model plant. Here we report that PA is an HR inducer in plants. It induced HR in Arabidopsis, a dicotyledonous model plant, including the oxidative burst and cell death. We investigated defense signal transduction activated by PA through marker genes of particular defense pathways in Arabidopsis. The result indicated that both the salicylic acid-dependent and jasmonic acid/ethylene-dependent pathways were activated by PA, in which the marker defense genes PR-1, PR-2 and PDF 1.2 were all induced in dose-dependent and time-course manners. We also observed that the PAinduced reactive oxygen species (ROS) production in rice suspension cells was Ca2+-dependent. Together with our previous studies of PA-induced defense activation in rice, we conclude that PA acts as a nonspecific elicitor in plant defense and has a potential utilization in cellular model establishment of systemicac quired resistance (SAR) activation.

  2. Requirement of KNAT1/BP for the Development of Abscission Zones in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Xiao-Qun Wang; Wei-Hui Xu; Li-Geng Ma; Zhi-Ming Fu; Xing-Wang Deng; Jia-Yang Li; Yong-Hong Wang

    2006-01-01

    The KNAT1 gene is a member of the Class Ⅰ KNOXhomeobox gene family and is thought to play an important role in meristem development and leaf morphogenesis. Recent studies have demonstrated that KNAT1/BP regulates the architecture of the inflorescence by affecting pedicle development in Arabidopsis thaliana.Herein, we report the characterization of an Arabidopsis T-DNA insertion mutant that shares considerable phenotypic similarity to the previously identified mutant brevipedicle (bp). Molecular and genetic analyses showed that the mutant is allelic to bp and that the T-DNA is located within the first helix of the KNAT1homeodomain (HD). Although the mutation causes a typical abnormality of short pedicles, propendent siliques,and semidwarfism, no obvious defects are observed in the vegetative stage. A study on cell morphology showed that asymmetrical division and inhibition of cell elongation contribute to the downward-pointing and shorter pedicle phenotype. Loss of KNAT/BPfunction results in the abnormal development of abscission zones. Microarray analysis of gene expression profiling suggests that KNAT1/BP may regulate abscission zone development through hormone signaling and hormone metabolism in Arabidopsis.

  3. Isolation of protoplasts from tissues of 14-day-old seedlings of Arabidopsis thaliana.

    Science.gov (United States)

    Zhai, Zhiyang; Jung, Ha-Il; Vatamaniuk, Olena K

    2009-08-17

    Protoplasts are plant cells that have had their cell walls enzymatically removed. Isolation of protoplasts from different plant tissues was first reported more than 40 years ago and has since been adapted to study a variety of cellular processes, such as subcellular localization of proteins, isolation of intact organelles and targeted gene-inactivation by double stranded RNA interference (RNAi). Most of the protoplast isolation protocols use leaf tissues of mature Arabidopsis (e.g. 35-day-old plants). We modified existing protocols by employing 14-day-old Arabidopsis seedlings. In this procedure, one gram of 14-day-old seedlings yielded 5 10(6)-10(7) protoplasts that remain intact at least 96 hours. The yield of protoplasts from seedlings is comparable with preparations from leaves of mature Arabidopsis, but instead of 35-36 days, isolation of protoplasts is completed in 15 days. This allows decreasing the time and growth chamber space that are required for isolating protoplasts when mature plants are used, and expedites the downstream studies that require intact protoplasts.

  4. Ashwagandha leaf derived withanone protects normal human cells against the toxicity of methoxyacetic acid, a major industrial metabolite.

    Directory of Open Access Journals (Sweden)

    Didik Priyandoko

    Full Text Available The present day lifestyle heavily depends on industrial chemicals in the form of agriculture, cosmetics, textiles and medical products. Since the toxicity of the industrial chemicals has been a concern to human health, the need for alternative non-toxic natural products or adjuvants that serve as antidotes are in high demand. We have investigated the effects of Ayurvedic herb Ashwagandha (Withania somnifera leaf extract on methoxyacetic acid (MAA induced toxicity. MAA is a major metabolite of ester phthalates that are commonly used in industry as gelling, viscosity and stabilizer reagents. We report that the MAA cause premature senescence of normal human cells by mechanisms that involve ROS generation, DNA and mitochondrial damage. Withanone protects cells from MAA-induced toxicity by suppressing the ROS levels, DNA and mitochondrial damage, and induction of cell defense signaling pathways including Nrf2 and proteasomal degradation. These findings warrant further basic and clinical studies that may promote the use of withanone as a health adjuvant in a variety of consumer products where the toxicity has been a concern because of the use of ester phthalates.

  5. UV-B inhibition of hypocotyl growth in etiolated Arabidopsis thaliana seedlings is a consequence of cell cycle arrest initiated by photodimer accumulation.

    Science.gov (United States)

    Biever, Jessica J; Brinkman, Doug; Gardner, Gary

    2014-06-01

    Ultraviolet (UV) radiation is an important constituent of sunlight that determines plant morphology and growth. It induces photomorphogenic responses but also causes damage to DNA. Arabidopsis mutants of the endonucleases that function in nucleotide excision repair, xpf-3 and uvr1-1, showed hypersensitivity to UV-B (280-320nm) in terms of inhibition of hypocotyl growth. SOG1 is a transcription factor that functions in the DNA damage signalling response after γ-irradiation. xpf mutants that carry the sog1-1 mutation showed hypocotyl growth inhibition after UV-B irradiation similar to the wild type. A DNA replication inhibitor, hydroxyurea (HU), also inhibited hypocotyl growth in etiolated seedlings, but xpf-3 was not hypersensitive to HU. UV-B irradiation induced accumulation of the G2/M-specific cell cycle reporter construct CYCB1;1-GUS in wild-type Arabidopsis seedlings that was consistent with the expected accumulation of photodimers and coincided with the time course of hypocotyl growth inhibition after UV-B treatment. Etiolated mutants of UVR8, a recently described UV-B photoreceptor gene, irradiated with UV-B showed inhibition of hypocotyl growth that was not different from that of the wild type, but they lacked UV-B-specific expression of chalcone synthase (CHS), as expected from previous reports. CHS expression after UV-B irradiation was not different in xpf-3 compared with the wild type, nor was it altered after HU treatment. These results suggest that hypocotyl growth inhibition by UV-B light in etiolated Arabidopsis seedlings, a photomorphogenic response, is dictated by signals originating from UV-B absorption by DNA that lead to cell cycle arrest. This process occurs distinct from UVR8 and its signalling pathway responsible for CHS induction.

  6. Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTERS 1 and 2: fructose and xylitol/H+ symporters in pollen and young xylem cells

    Science.gov (United States)

    Klepek, Yvonne-Simone; Konrad, Kai R.; Wippel, Kathrin; Hoth, Stefan; Hedrich, Rainer; Sauer, Norbert

    2010-01-01

    The genome of Arabidopsis thaliana contains six genes, AtPMT1 to AtPMT6 (Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTER 1–6), which form a distinct subfamily within the large family of more than 50 monosaccharide transporter-like (MST-like) genes. So far, only AtPMT5 [formerly named AtPLT5 (At3g18830)] has been characterized and was shown to be a plasma membrane-localized H+-symporter with broad substrate specificity. The characterization of AtPMT1 (At2g16120) and AtPMT2 (At2g16130), two other, almost identical, members of this transporter subfamily, are presented here. Expression of the AtPMT1 and AtPMT2 cDNAs in baker's yeast (Saccharomyces cerevisiae) revealed that these proteins catalyse the energy-dependent, high-capacity transport of fructose and xylitol, and the transport of several other compounds with lower rates. Expression of their cRNAs in Xenopus laevis oocytes showed that both proteins are voltage-dependent and catalyse the symport of their substrates with protons. Fusions of AtPMT1 or AtPMT2 with the green fluorescent protein (GFP) localized to Arabidopsis plasma membranes. Analyses of reporter genes performed with AtPMT1 or AtPMT2 promoter sequences showed expression in mature (AtPMT2) or germinating (AtPMT1) pollen grains, as well as in growing pollen tubes, hydathodes, and young xylem cells (both genes). The expression was confirmed with an anti-AtPMT1/AtPMT2 antiserum (αAtPMT1/2) raised against peptides conserved in AtPMT1 and AtPMT2. The physiological roles of the proteins are discussed and related to plant cell wall modifications. PMID:19969532

  7. Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTERS 1 and 2: fructose and xylitol/H+ symporters in pollen and young xylem cells.

    Science.gov (United States)

    Klepek, Yvonne-Simone; Volke, Melanie; Konrad, Kai R; Wippel, Kathrin; Hoth, Stefan; Hedrich, Rainer; Sauer, Norbert

    2010-01-01

    The genome of Arabidopsis thaliana contains six genes, AtPMT1 to AtPMT6 (Arabidopsis thaliana POLYOL/MONOSACCHARIDE TRANSPORTER 1-6), which form a distinct subfamily within the large family of more than 50 monosaccharide transporter-like (MST-like) genes. So far, only AtPMT5 [formerly named AtPLT5 (At3g18830)] has been characterized and was shown to be a plasma membrane-localized H(+)-symporter with broad substrate specificity. The characterization of AtPMT1 (At2g16120) and AtPMT2 (At2g16130), two other, almost identical, members of this transporter subfamily, are presented here. Expression of the AtPMT1 and AtPMT2 cDNAs in baker's yeast (Saccharomyces cerevisiae) revealed that these proteins catalyse the energy-dependent, high-capacity transport of fructose and xylitol, and the transport of several other compounds with lower rates. Expression of their cRNAs in Xenopus laevis oocytes showed that both proteins are voltage-dependent and catalyse the symport of their substrates with protons. Fusions of AtPMT1 or AtPMT2 with the green fluorescent protein (GFP) localized to Arabidopsis plasma membranes. Analyses of reporter genes performed with AtPMT1 or AtPMT2 promoter sequences showed expression in mature (AtPMT2) or germinating (AtPMT1) pollen grains, as well as in growing pollen tubes, hydathodes, and young xylem cells (both genes). The expression was confirmed with an anti-AtPMT1/AtPMT2 antiserum (alphaAtPMT1/2) raised against peptides conserved in AtPMT1 and AtPMT2. The physiological roles of the proteins are discussed and related to plant cell wall modifications. PMID:19969532

  8. Heat shock, visible light or high calcium augment the cytotoxic effects of Ailanthus altissima (Swingle) leaf extracts against Saccharomyces cerevisiae cells.

    Science.gov (United States)

    Popa, Claudia Valentina; Lungu, Liliana; Cristache, Ligia Florentina; Ciuculescu, Crinu; Danet, Andrei Florin; Farcasanu, Ileana Cornelia

    2015-01-01

    To gain new insight into the antimicrobial potential of Ailanthus altissima Swingle, ethanol leaf extracts were evaluated for the antifungal effects against the model yeast Saccharomyces cerevisae. The extracts inhibited the yeast growth in a dose-dependent manner, and this effect could be augmented by heat shock, exposure to visible light or exposure to high concentrations of Ca(2+). Using transgenic yeast cells expressing the Ca(2+)-dependent photoprotein, aequorin, it was found that the leaf extracts induced cytosolic Ca(2+) elevation. Experiments on yeast mutants with defects in Ca(2+) transport demonstrated that the cytotoxicity of the A. altissima leaf extracts (AaLEs) was mediated by transient pulses of Ca(2+) ions which were released into the cytosol predominantly from the vacuole. The investigation of the antifungal synergies involving AaLEs may contribute to the development of optimal and safe combination therapies for the treatment of drug-resistant fungal infections. PMID:25587627

  9. Aqueous Extract of Solanum nigrum Leaf Activates Autophagic Cell Death and Enhances Docetaxel-Induced Cytotoxicity in Human Endometrial Carcinoma Cells

    Directory of Open Access Journals (Sweden)

    Cheng-Jeng Tai

    2012-01-01

    Full Text Available Chemotherapy is the main approach in dealing with advanced and recurrent endometrial cancer. An effective complementary ingredient can be helpful in improving the clinical outcome. Aqueous extract of Solanum nigrum leaf (AE-SN is a principal ingredient for treating cancer patients in traditional Chinese medicinal practice but lacks sufficient evidence to verify its tumor suppression efficacy. This study evaluated the antitumor effects of AE-SN and also assessed the synergistic effects of AE-SN with docetaxel On the human endometrial cancer cell lines, HEC1A, HEC1B, and KLE. The activation of apoptotic markers, caspase-3 and poly-ADP-ribose polymerase, and autophagic marker, microtubule-associated protein 1 light chain 3 A/B, wAS determined to clarify the cell death pathways responsible for AE-SN induced tumor cell death. Results indicated that AE-SN-treatment has significant cytotoxicity on the tested endometrial cancer cells with accumulation of LC3 A/B II and demonstrated a synergistic effect of AE-SN and docetaxel in HEC1A and HEC1B cells, but not KLE cells. In conclusion, AE-SN treatment was effective in suppressing endometrial cancer cells via the autophagic pathway and was also capable of enhancing the cytotoxicity of docetaxel in human endometrial cancer cells. Our results provide meaningful evidence for integrative cancer therapy in the future.

  10. Arabidopsis RAV1 is down-regulated by brassinosteroid and may act as a negative regulator during plant development

    Institute of Scientific and Technical Information of China (English)

    Yu Xin HU; Yong Hong WANG; Xin Fang LIU; Jia Yang LI

    2004-01-01

    RAV1 is a novel DNA-binding protein with two distinct DNA-binding domains unique in higher plants,but its role in plant growth and development remains unknown. Using cDNA array,we found that transcription of RAV1 is downregulated by epibrassinolide (epiBL) in Arabidopsis suspension cells. RNA gel blot analysis revealed that epiBL-regulated RAV1 transcription involves neither protein phosphorylation/dephosphorylation nor newly synthesized protein,and does not require the functional BRI1,suggesting that this regulation might be through a new BR signaling pathway.Overexpressing RAV1 in Arabidopsis results in a retardation of lateral root and rosette leaf development,and the underexpression causes an earlier flowering phenotype,implying that RAV1 may function as a negative regulatory component of growth and development.

  11. Evaluation of Three Protein-Extraction Methods for Proteome Analysis of Maize Leaf Midrib, a Compound Tissue Rich in Sclerenchyma Cells.

    Science.gov (United States)

    Wang, Ning; Wu, Xiaolin; Ku, Lixia; Chen, Yanhui; Wang, Wei

    2016-01-01

    Leaf morphology is closely related to the growth and development of maize (Zea mays L.) plants and final kernel production. As an important part of the maize leaf, the midrib holds leaf blades in the aerial position for maximum sunlight capture. Leaf midribs of adult plants contain substantial sclerenchyma cells with heavily thickened and lignified secondary walls and have a high amount of phenolics, making protein extraction and proteome analysis difficult in leaf midrib tissue. In the present study, three protein-extraction methods that are commonly used in plant proteomics, i.e., phenol extraction, TCA/acetone extraction, and TCA/acetone/phenol extraction, were qualitatively and quantitatively evaluated based on 2DE maps and MS/MS analysis using the midribs of the 10th newly expanded leaves of maize plants. Microscopy revealed the existence of substantial amounts of sclerenchyma underneath maize midrib epidermises (particularly abaxial epidermises). The spot-number order obtained via 2DE mapping was as follows: phenol extraction (655) > TCA/acetone extraction (589) > TCA/acetone/phenol extraction (545). MS/MS analysis identified a total of 17 spots that exhibited 2-fold changes in abundance among the three methods (using phenol extraction as a control). Sixteen of the proteins identified were hydrophilic, with GRAVY values ranging from -0.026 to -0.487. For all three methods, we were able to obtain high-quality protein samples and good 2DE maps for the maize leaf midrib. However, phenol extraction produced a better 2DE map with greater resolution between spots, and TCA/acetone extraction produced higher protein yields. Thus, this paper includes a discussion regarding the possible reasons for differential protein extraction among the three methods. This study provides useful information that can be used to select suitable protein extraction methods for the proteome analysis of recalcitrant plant tissues that are rich in sclerenchyma cells. PMID:27379139

  12. Ethylene signaling is required for the acceleration of cell death induced by the activation of At ME K5 in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Hongxia Liu; Ying Wang; Juan Xu; Tongbing Su; Guoqin Liu; Dongtao Ren

    2008-01-01

    Mitogen-activated protein kinases (MAPKs) are involved in the regulation of plant growth, development and responses to a wide variety of stimuli. In a conditional gain-of-function transgenic system, the activation of AtM£K5, a MAPK kinase, can in turn activate endogenous AtMAPK3 and AtMAPK6, and can lead to a striking increase in ethylene production and induce hypersensitive response (HR)-like cell death in Arabidopsis. However, the role of the increased ethylene production in regulating this HR-like cell death remains unknown. Using Arabidopsis transgenic plants that express AtMEK5DD , an active mutant of AtMEK5 that is under the control of a steroid-inducible promoter, we tested the contribution of ethylene to cell death. We found that ethylene biosynthesis occurs before cell death. Cell death was delayed by inhibiting AtMEK5-induced ethylene production using inhibitors of ACC-synthases, ACC-oxidases or ethylene receptors. In the mutants AtMEK5DDletrl-1 and AtMEK5DDlein2-l, both of which showed insen-sitivity to ethylene, the expression of AtMEKSDD protein, activity of AtMAPK3 and AtMAPK6, and ethylene production were the same as those seen in AtMEK.5 transgenic plants, but cell death was also delayed. These data suggest that ethylene signaling perception is required to accelerate cell death that is induced by AtMEK5 activation.

  13. Ectopic Expression of Arabidopsis Phospholipase A Genes Elucidates Role of Phospholipase Bs in S. cerevisiae Cells

    OpenAIRE

    Zhang, Meng; Zhang, Yan; Giblin, E Michael; Taylor, David C.

    2009-01-01

    In S. cerevisiae neither disruption of the phospholipase B triple knockout mutant (plb1plb2plb3; plb123) nor over-expression of phospholipase Bs (PLBs) result in a phenotype different from wild type. In performing experiments to characterize candidate plant phospholipase (PLA) genes, we found, surprisingly, that ectopic expression of either of two different A. thaliana PLA2 or PLA1 genes in the yeast plb123 mutant completely inhibited cell growth. We proposed that while PLBs might not be esse...

  14. Gasotransmitters are emerging as new guard cell signaling molecules and regulators of leaf gas exchange.

    Science.gov (United States)

    García-Mata, Carlos; Lamattina, Lorenzo

    2013-03-01

    Specialized guard cells modulate plant gas exchange through the regulation of stomatal aperture. The size of the stomatal pore is a direct function of the volume of the guard cells. The transport of solutes across channels in plasma membrane is a crucial process in the maintenance of guard cell water status. The fine tuned regulation of that transport requires an integrated convergence of multiple endogenous and exogenous signals perceived at both the cellular and the whole plant level. Gasotransmitters are novel signaling molecules with key functions in guard cell physiology. Three gasotransmitters, nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H(2)S) are involved in guard cell regulatory processes. These molecules are endogenously produced by plant cells and are part of the guard cells responses to drought stress conditions through ABA-dependent pathways. In this review, we summarize the current knowledge of gasotransmitters as versatile molecules interacting with different components of guard cell signaling network and propose them as players in new paradigms to study ABA-independent guard cell responses to water deficit.

  15. Study of genes induced by ionizing radiations at Arabidopsis thaliana: identification and molecular characterization of the ATGR1 gene, a new gene encoding a protein involved in plant cell division

    International Nuclear Information System (INIS)

    DNA damage, that can be experimentally introduced by ionizing radiation (IR), induces complex signal transduction pathways leading to cell recovery or, alternatively to programmed cell death if damages are too severe. To identify the inducible components of the response to genotoxic stress in plants, we have screened by Differential Display for mRNAs that rapidly and strongly accumulate after IR treatment in A. thaliana cells. We have characterized ATGR1, a new single copy Arabidopsis gene encoding a PEST-box protein of unknown function. In unstressed plant organs the ATGR1 mRNA is hardly detectable, whereas the protein is present in extracts prepared from roots, shoot meristems and inflorescences, that all contain large amounts of actively dividing cells. This pattern is confirmed by immuno localisation on tissue sections that shows constitutive ATGR1 protein expression covering the root elongation zone, the shoot meristem, leaf primordial and the ovules of developing flowers. Histochemical analysis of transgenic plants expressing the GUS reporter gene under the control of the ATGR1 promoter, demonstrate that the developmental and tissue-specific profile of ATGR1 protein expression is conferred by the gene promoter. The massive, transient and dose-dependent accumulation of ATGR1 transcripts after IR treatment observed in all plant organs does not lead to significant changes in ATGR1 protein pattern. Stable ATGR1 protein overexpression, as exemplified by transgenic A. thaliana plants that contain a 35S promoter-ATGR1 gene fusion, does not induce notable changes of the overall ATGR1 protein level, but leads to male and female sterility. The cause of sterility is a lack of correct chromosome assembly and distribution at the stage metaphase II of meiosis. Taken together our results show that i) ATGR1 gene expression is associated to cell division during plant development ii) the ATGR1 protein level is regulated at the transcriptional and post-transcriptional level iii

  16. Polyphenol stabilized colloidal gold nanoparticles from Abutilon indicum leaf extract induce apoptosis in HT-29 colon cancer cells.

    Science.gov (United States)

    Mata, Rani; Nakkala, Jayachandra Reddy; Sadras, Sudha Rani

    2016-07-01

    Green synthesized gold nanoparticles have received substantial attention owing to their biomedical applications, particularly in cancer therapy. Although anticancer activities of green synthesized gold nanoparticles have been reported earlier, the underlying mechanism behind their anticancer activity is still to be understood. The present study, describes the green synthesis of Abutilon indicum gold nanoparticles (AIGNPs) from Abutilon indicum leaf extract (AILE) and their cytotoxic mechanism in colon cancer cells. Dimensions of spherical shaped AIGNPs were found to be in the range of 1-20nm as determined by TEM. GC-MS and FTIR analysis indicated the presence of polyphenolic groups in AILE, which might have been involved in the stabilization of AIGNPs. In vitro free radical scavenging analysis revealed the radical quenching activity of AIGNPs. Further, the AIGNPs exhibited cytotoxicity in HT-29 colon cancer cells with IC50 values of 210 and 180μg/mL after 24 and 48h. This was mediated through nuclear morphological changes and cell membrane damage as evidenced by acridine orange/ethidium bromide, propidium iodide and AnnexinV-Cy3 staining methods. Mechanism of the observed cytotoxicity of AIGNPs was explained on the basis of increased levels of reactive oxygen species and simultaneous reduction in cellular antioxidants, which might have caused mitochondrial membrane potential loss, DNA damage and G1/S phase cell cycle arrest. Expression of cleaved Caspase-9, Caspase-8, Caspase-3, Lamin A/C and PARP, provided the clues for the induction of intrinsic and extrinsic apoptosis pathways in AIGNPs treated HT-29 cells. The study provides a preliminary guidance towards the development of colon cancer therapy using green synthesized gold nanoparticles. PMID:27038915

  17. Anti-inflammatory effects of Perilla frutescens leaf extract on lipopolysaccharide-stimulated RAW264.7 cells.

    Science.gov (United States)

    Huang, Bee-Piao; Lin, Chun-Hsiang; Chen, Yi-Ching; Kao, Shao-Hsuan

    2014-08-01

    Perilla leaves are widely used in Chinese herbal medicine and in Japanese herbal agents used to treat respiratory diseases. This study aimed to investigate the anti‑inflammatory effects and the underlying mechanisms of Perilla frutescens leaf extract (PLE). Murine macrophage RAW264.7 cells were used as a model. Cell viability and morphological changes were studied by the MTT assay and microscopy. mRNA expression of pro‑inflammatory mediators was assessed by both semi‑quantitative reverse transcription‑polymerase chain reaction (RT‑PCR) and quantitative (q) RT‑PCR. Nitric oxide (NO) and prostaglandin E2 (PGE2) production were analyzed by the Griess test and sandwich enzyme‑linked immunosorbent assay (ELISA), respectively. The activation of kinase cascades was studied by immunoblotting. Our findings showed that PLE slightly affects cell viability, but alleviates LPS‑induced activation of RAW264.7 cells. Furthermore, PLE significantly reduced the LPS‑induced mRNA expression of the interleukin (IL)‑6, IL‑8, tumor necrosis factor‑α (TNF‑α), cyclooxygenase‑2 (COX‑2) and inducible nitric oxide synthase (iNOS), genes in a dose‑dependent manner. In addition, PLE reduced NO production and PGE2 secretion induced by LPS. PLE also inhibited activation of mitogen‑activated protein kinases (MAPKs), increased the cytosolic IκBα level, and reduced the level of nuclear factor (NF)‑κB. Taken together, these findings indicate that PLE significantly decreases the mRNA expression and protein production of pro‑inflammatory mediators, via the inhibition of extracellular‑signal‑regulated kinase (ERK)1/2, c‑Jun N‑terminal kinase (JNK), p38, as well as NF‑κB signaling in RAW264.7 cells stimulated with LPS. PMID:24898576

  18. LSD1 and HY5 Antagonistically Regulate Red Light induced-Programmed Cell Death in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Tingting eChai

    2015-05-01

    Full Text Available Programmed cell death (PCD in plant is triggered by abiotic and biotic stress. Light-dependent PCD is unique to plants. Light-induced PCD also requires reactive oxygen species (ROS and salicylic acid (SA. In this study, lesion simulating disease1 (LSD1 and elongated hypocotyl 5 (HY5 perform opposite roles to regulate excess red light (RL-triggered PCD associated with ROS and SA production. Under RL, the lsd1 mutant released more ROS and SA and displayed a stronger cell death rate than the hy5 mutant. It was shown that active LSD1 converted into inactive form by changing the redox status of the plastoquinone pool, and HY5 interacted with phytochrome B (phyB to promote PCD in response to RL. LSD1 inhibited the enhanced disease susceptibility 1 (EDS1 expression by upregulating SR1, whereas HY5 enhanced the enhanced EDS1 expression by binding to the G-box of the EDS1 promoter. This study suggested that LSD1 and HY5 antagonistically modulated EDS1-dependent ROS and SA signaling; thus, PCD was mediated in response to RL.

  19. LSD1 and HY5 antagonistically regulate red light induced-programmed cell death in Arabidopsis.

    Science.gov (United States)

    Chai, Tingting; Zhou, Jun; Liu, Jian; Xing, Da

    2015-01-01

    Programmed cell death (PCD) in plant is triggered by abiotic and biotic stress. Light-dependent PCD is unique to plants. Light-induced PCD also requires reactive oxygen species (ROS) and salicylic acid (SA). In this study, lesion simulating disease1 (LSD1) and elongated hypocotyl 5 (HY5) perform opposite roles to regulate excess red light (RL)-triggered PCD associated with ROS and SA production. Under RL, the lsd1 mutant released more ROS and SA and displayed a stronger cell death rate than the hy5 mutant. It was shown that active LSD1 converted into inactive form by changing the redox status of the plastoquinone pool, and HY5 interacted with phytochrome B (phyB) to promote PCD in response to RL. LSD1 inhibited the enhanced disease susceptibility 1 (EDS1) expression by upregulating SR1, whereas HY5 enhanced the enhanced EDS1 expression by binding to the G-box of the EDS1 promoter. This study suggested that LSD1 and HY5 antagonistically modulated EDS1-dependent ROS and SA signaling; thus, PCD was mediated in response to RL.

  20. Electrophoretic assay for ribulose 1,5-bisphosphate carboxylase/oxygenase in guard cells and other leaf cells of Vicia faba L

    Energy Technology Data Exchange (ETDEWEB)

    Tarczynski, M.C.; Outlaw, W.H. Jr.; Arold, N.; Neuhoff, V.; Hampp, R. (Florida State Univ., Tallahassee (USA) Max-Planck-Institute fuer Experimentelle Medizin, Goettingen (West Germany) Universitaet Tuebingen (West Germany))

    1989-04-01

    The ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) contents of guard cells and other cells of Vicia faba L. leaflet were determined. To prevent proteolysis, proteins of frozen protoplast preparations or of cells excised from freeze-dried leaf were extracted directly in a sodium-dodecyl-sulfate-containing solution which was heated immediately after sample addition. Protein profiles of the different cell types were obtained by electrophoresis of the extracts and subsequent densitometry of the stained protein bands. About one-third of the protein of palisade parenchyma and of spongy parenchyma was Rubisco large subunit. Using chlorophyll (Chl):protein ratios previously obtained, we calculate mesophyll contained ca. 22 millimoles Rubisco per mole Chl. In contrast, guard-cell protoplast preparations were calculated to contain from 0.7 to 2.2 millimoles Rubisco per mole Chl. The upper end of this range is an overestimate resulting from contamination by mesophyll and to the method of peak integration. Extracts of excised guard cells were calculated to contain 0.05 to 0.17 millimole Rubisco per mole Chl. We conclude that Rubisco is absent, or virtually so, in guard cells of V. faba.

  1. Extraction and Characterization of Extracellular Proteins and Their Post-Translational Modifications from Arabidopsis thaliana Suspension Cell Cultures and Seedlings: A Critical Review

    Directory of Open Access Journals (Sweden)

    Mina Ghahremani

    2016-09-01

    Full Text Available Proteins secreted by plant cells into the extracellular space, consisting of the cell wall, apoplastic fluid, and rhizosphere, play crucial roles during development, nutrient acquisition, and stress acclimation. However, isolating the full range of secreted proteins has proven difficult, and new strategies are constantly evolving to increase the number of proteins that can be detected and identified. In addition, the dynamic nature of the extracellular proteome presents the further challenge of identifying and characterizing the post-translational modifications (PTMs of secreted proteins, particularly glycosylation and phosphorylation. Such PTMs are common and important regulatory modifications of proteins, playing a key role in many biological processes. This review explores the most recent methods in isolating and characterizing the plant extracellular proteome with a focus on the model plant Arabidopsis thaliana, highlighting the current challenges yet to be overcome. Moreover, the crucial role of protein PTMs in cell wall signalling, development, and plant responses to biotic and abiotic stress is discussed.

  2. The Arabidopsis thaliana homeobox gene ATHB12 is involved in symptom development caused by geminivirus infection.

    Directory of Open Access Journals (Sweden)

    Jungan Park

    Full Text Available BACKGROUND: Geminiviruses are single-stranded DNA viruses that infect a number of monocotyledonous and dicotyledonous plants. Arabidopsis is susceptible to infection with the Curtovirus, Beet severe curly top virus (BSCTV. Infection of Arabidopsis with BSCTV causes severe symptoms characterized by stunting, leaf curling, and the development of abnormal inflorescence and root structures. BSCTV-induced symptom development requires the virus-encoded C4 protein which is thought to interact with specific plant-host proteins and disrupt signaling pathways important for controlling cell division and development. Very little is known about the specific plant regulatory factors that participate in BSCTV-induced symptom development. This study was conducted to identify specific transcription factors that are induced by BSCTV infection. METHODOLOGY/PRINCIPAL FINDINGS: Arabidopsis plants were inoculated with BSCTV and the induction of specific transcription factors was monitored using quantitative real-time polymerase chain reaction assays. We found that the ATHB12 and ATHB7 genes, members of the homeodomain-leucine zipper family of transcription factors previously shown to be induced by abscisic acid and water stress, are induced in symptomatic tissues of Arabidopsis inoculated with BSCTV. ATHB12 expression is correlated with an array of morphological abnormalities including leaf curling, stunting, and callus-like structures in infected Arabidopsis. Inoculation of plants with a BSCTV mutant with a defective c4 gene failed to induce ATHB12. Transgenic plants expressing the BSCTV C4 gene exhibited increased ATHB12 expression whereas BSCTV-infected ATHB12 knock-down plants developed milder symptoms and had lower ATHB12 expression compared to the wild-type plants. Reporter gene studies demonstrated that the ATHB12 promoter was responsive to BSCTV infection and the highest expression levels were observed in symptomatic tissues where cell cycle genes also were

  3. Cell polarity and patterning by PIN trafficking through early endosomal compartments in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Hirokazu Tanaka

    2013-05-01

    Full Text Available PIN-FORMED (PIN proteins localize asymmetrically at the plasma membrane and mediate intercellular polar transport of the plant hormone auxin that is crucial for a multitude of developmental processes in plants. PIN localization is under extensive control by environmental or developmental cues, but mechanisms regulating PIN localization are not fully understood. Here we show that early endosomal components ARF GEF BEN1 and newly identified Sec1/Munc18 family protein BEN2 are involved in distinct steps of early endosomal trafficking. BEN1 and BEN2 are collectively required for polar PIN localization, for their dynamic repolarization, and consequently for auxin activity gradient formation and auxin-related developmental processes including embryonic patterning, organogenesis, and vasculature venation patterning. These results show that early endosomal trafficking is crucial for cell polarity and auxin-dependent regulation of plant architecture.

  4. Gene trap-based identification of a guard cell promoter in Arabidopsis.

    Science.gov (United States)

    Francia, Priscilla; Simoni, Laura; Cominelli, Eleonora; Tonelli, Chiara; Galbiati, Massimo

    2008-09-01

    Preserving crop yield under drought stress is a major challenge for modern agriculture. To cope with the detrimental effects of water scarcity on crop productivity it is important to develop new plants with a more sustainable use of water and capable of higher performance under stress conditions. Transpiration through stomatal pores accounts for over 90% of water loss in land plants. Recent studies have increased our understanding of the networks that control stomatal activity and have led to practical approaches for enhancing drought tolerance. Genetic engineering of target genes in stomata requires effective expression systems, including suitable promoters, because constitutive promoters (i.e., CaMV35S) are not always functional or can have negative effects on plant growth and productivity. Here we describe the identification of the CYP86A2 guard cell promoter and discuss its potential for gene expression in stomata.

  5. Nanoparticles of Selaginella doederleinii leaf extract inhibit human lung cancer cells A549

    Science.gov (United States)

    Syaefudin; Juniarti, A.; Rosiyana, L.; Setyani, A.; Khodijah, S.

    2016-01-01

    The aim of the present study is to evaluate cytotoxicity effect of nanoparticles of Selaginella doederleinii (S. doederleinii) leaves extract. S. doederleinii was extracted by maceration method using 70%(v/v) ethanol as solvent. Phytochemical content was analyzed qualitatively by using Harborne and Thin Layer Chromatography (TLC) methods. Nanoparticle extract was prepared by ionic gelation using chitosan as encapsulant agent. Anticancer activity was performed by using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The results showed that S. doederleinii contains of flavonoids. Nanoparticle of S. doederleinii leaves extract greatly inhibited A549 cells growth (cancer cells), with IC50 of 3% or 1020 μg/ml. These nanoparticles extract also inhibited the growth of Chang cells (normal cells), with IC50 of 4% or 1442 μg/ml. The effective concentration of nanoparticles extract which inhibits cancer cells without harming the normal cells is 0.5% or 167 μg/ml. Further studies are needed to obtain the concentration of nanoparticles extract which can selectively suppress cancer cells.

  6. Arabidopsis ECERIFERUM9 involvement in cuticle formation and maintenance of plant water status

    Science.gov (United States)

    A unique set of allelic Arabidopsis mutants are described that exhibit either suppressed or completely inhibited expression of a gene designated ECERIFERUM9 (CER9). These mutants exhibit a dramatic elevation in the total amount of leaf cutin monomers, and a dramatic shift in the leaf cuticular wax p...

  7. 7 CFR 29.3035 - Leaf structure.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See...

  8. 7 CFR 29.2278 - Leaf structure.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2278 Leaf structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2351.)...

  9. 7 CFR 29.2530 - Leaf structure.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.2530 Section 29.2530 Agriculture...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2601.)...

  10. 7 CFR 29.6023 - Leaf structure.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by...

  11. 7 CFR 29.1030 - Leaf structure.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.1030 Section 29.1030 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity....

  12. 7 CFR 29.3527 - Leaf structure.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity....

  13. Reassessment of an Arabidopsis cell wall invertase inhibitor AtCIF1 reveals its role in seed germination and early seedling growth.

    Science.gov (United States)

    Su, Tao; Wolf, Sebastian; Han, Mei; Zhao, Hongbo; Wei, Hongbin; Greiner, Steffen; Rausch, Thomas

    2016-01-01

    In higher plants, cell wall invertase (CWI) and vacuolar invertase (VI) are recognized as essential players in sugar metabolism and sugar signaling, thereby affecting source-sink interactions, plant development and responses to environmental cues. CWI and VI expression levels are transcriptionally controlled; however, both enzymes are also subject to posttranslational control by invertase inhibitor proteins. The physiological significances of inhibitor proteins during seed germination and early seedling development are not yet fully understood. Here, we demonstrate that the inhibitor isoform AtCIF1 impacted on seed germination and early seedling growth in Arabidopsis. The primary target of AtCIF1 was shown to be localized to the apoplast after expressing an AtCIF1 YFP-fusion construct in tobacco epidermis and transgenic Arabidopsis root. The analysis of expression patterns showed that AtCWI1 was co-expressed spatiotemporally with AtCIF1 within the early germinating seeds. Seed germination was observed to be accelerated independently of exogenous abscisic acid (ABA) in the AtCIF1 loss-of-function mutant cif1-1. This effect coincided with a drastic increase of CWI activity in cif1-1 mutant seeds by 24 h after the onset of germination, both in vitro and in planta. Accordingly, quantification of sugar content showed that hexose levels were significantly boosted in germinating seeds of the cif1-1 mutant. Further investigation of AtCIF1 overexpressors in Arabidopsis revealed a markedly suppressed CWI activity as well as delayed seed germination. Thus, we conclude that the posttranslational modulation of CWI activity by AtCIF1 helps to orchestrate seed germination and early seedling growth via fine-tuning sucrose hydrolysis and, possibly, sugar signaling. PMID:26546341

  14. Analysis of Circadian Leaf Movements.

    Science.gov (United States)

    Müller, Niels A; Jiménez-Gómez, José M

    2016-01-01

    The circadian clock is a molecular timekeeper that controls a wide variety of biological processes. In plants, clock outputs range from the molecular level, with rhythmic gene expression and metabolite content, to physiological processes such as stomatal conductance or leaf movements. Any of these outputs can be used as markers to monitor the state of the circadian clock. In the model plant Arabidopsis thaliana, much of the current knowledge about the clock has been gained from time course experiments profiling expression of endogenous genes or reporter constructs regulated by the circadian clock. Since these methods require labor-intensive sample preparation or transformation, monitoring leaf movements is an interesting alternative, especially in non-model species and for natural variation studies. Technological improvements both in digital photography and image analysis allow cheap and easy monitoring of circadian leaf movements. In this chapter we present a protocol that uses an autonomous point and shoot camera and free software to monitor circadian leaf movements in tomato. PMID:26867616

  15. The disease resistance signaling components EDS1 and PAD4 are essential regulators of the cell death pathway controlled by LSD1 in Arabidopsis.

    Science.gov (United States)

    Rustérucci, C; Aviv, D H; Holt, B F; Dangl, J L; Parker, J E

    2001-10-01

    Specific recognition of pathogens is mediated by plant disease resistance (R) genes and translated into a successful defense response. The extent of associated hypersensitive cell death varies from none to an area encompassing cells surrounding an infection site, depending on the R gene activated. We constructed double mutants in Arabidopsis between positive regulators of R function and a negative regulator of cell death, LSD1, to address whether genes required for normal R function also regulate the runaway cell death observed in lsd1 mutants. We report here that EDS1 and PAD4, two signaling genes that mediate some but not all R responses, also are required for runaway cell death in the lsd1 mutant. Importantly, this novel function of EDS1 and PAD4 is operative when runaway cell death in lsd1 is initiated through an R gene that does not require EDS1 or PAD4 for disease resistance. NDR1, another component of R signaling, also contributes to the control of plant cell death. The roles of EDS1 and PAD4 in regulating lsd1 runaway cell death are related to the interpretation of reactive oxygen intermediate-derived signals at infection sites. We further demonstrate that the fate of superoxide at infection sites is different from that observed at the leading margins of runaway cell death lesions in lsd1 mutants.

  16. Lhcb transcription is coordinated with cell size and chlorophyll accumulation. Studies on fluorescence-activated, cell-sorter-purified single cells from wild-type and immutans Arabidopsis thaliana

    Energy Technology Data Exchange (ETDEWEB)

    Meehan, L.; Harkins, K.; Rodermel, S. [Iowa State Univ., Ames, IA (United States)] [and others

    1996-11-01

    To study the mechanisms that integrate pigment and chlorophyll a/b-binding apoprotein biosynthesis during light-harvesting complex II assembly, we have examined {beta}-glucuronidase (GUS) enzyme activities, cell-sorting-separated single cells sizes in fluorescence activated, cell-sorting-separated single cells from transgenic Arabidopsis thaliana wild-type and immutans variegation mutant plants that express an Lhcb (photosystem II chlorophyll a/b-binding polypeptide gene)/GUS promoter fusion. We found that GUS activities are positively correlated with chlorophyll content and cell size in green cells from the control and immutans plants, indicating that Lhcb gene transcription is coordinated with cell size in this species. Compared with the control plants, however, chlorophyll production is enhanced in the green cells of immutans; this may represent part of a strategy to maximize photosynthesis in the white sectors of the mutant. Lhcb transcription is significantly higher in pure-white cells of the transgenic immutans plants than in pure-white cells from norflurazon-treated, photooxidized A. thaliana leaves. This suggests that immutans partially uncouples Lhcb transcription from its normal dependence on chlorophyll accumulation and chloroplast development. We conclude that immutans may play a role in regulating Lhcb transcription, and may be a key component in the signal transduction pathways that control chloroplast biogenesis. 58 refs., 5 figs., 2 tabs.

  17. AtCDC5 regulates the G2 to M transition of the cell cycle and is critical for the function of Arabidopsis shoot apical meristem

    Institute of Scientific and Technical Information of China (English)

    Zhiqiang Lin; Kangquan Yin; Danling Zhu; Zhangliang Chen; Hongya Gu; LiJia Qu

    2007-01-01

    As a cell cycle regulator, the Myb-related CDC5 protein was reported to be essential for the G2 phase of the cell cycle in yeast and animals, but little is known about its function in plants. Here we report the functional characterization of the CDC5 gene in Arabidopsis thaliana. Arabidopsis CDC5 {AtCDCS) is mainly expressed in tissues with high cell division activity, and is expressed throughout the entire process of embryo formation. The AtCDCS loss-of-function mutant is embryonic lethal. In order to investigate the function of AtCDCS in vivo, we generated AtCDC5-RNAi plants in which the expression of AtCDCS was reduced by RNA interference. We found that the G2 to M (G2/M) phase transition was affected in the AtCDC5-RNAi plants, and that endoreduplication was increased. Additionally, the maintenance of shoot apical meristem (SAM) function was disturbed in the AtCDC5-KNAi plants, in which both the WUSCHEL (WUS)-CLAVATA (CLV) and the SHOOT MERISTEMLESS (STM) pathways were impaired. In situ hybridization analysis showed that the expression of STM was greatly reduced in the shoot apical cells of the AtCDC5-KNAi plants. Moreover, cyclinBl or Histone4 was found to be expressed in some of these cells when the transcript of STM was undetectable. These results suggest that AtCDC5 is essential for the G2/M phase transition and may regulate the function of SAM by controlling the expression of STM and WUS.

  18. Cytotoxicity of Marchantia convoluta leaf extracts to human liver and lung cancer cells

    Directory of Open Access Journals (Sweden)

    Xiao J.B.

    2006-01-01

    Full Text Available The cytotoxicity of three extracts (petroleum ether, ethyl acetate and n-butanol from a plant used in folk medicine, Marchantia convoluta, to human non-small cell lung carcinoma (H1299 and liver carcinoma (HepG2 cell lines was tested. After 72-h incubation of lung and liver cancer cell cultures with varying concentrations of extracts (15 to 200 µg/mL, cytotoxicity was determined by the 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide assay and reported in terms of cell viability. The extracts that showed a significant cytotoxicity were subjected to gas chromatography-mass spectrometry analysis to identify the components. The ethyl acetate, but not the petroleum ether or n-butanol extract, had a significant cytotoxicity against lung and liver carcinoma cells with IC50 values of 100 and 30 µg/mL, respectively. A high concentration of ethyl acetate extract (100 µg/mL rapidly reduced the number of H1299 cells. At lower concentrations of ethyl acetate extract (15, 30, and 40 µg/mL, the numbers of HepG2 cells started to decrease markedly. Gas chromatography-mass spectrometry analysis of the ethyl acetate extract revealed the presence of several compounds such as phytol (23.42%, 1,2,4-tripropylbenzene (13.09%, 9-cedranone (12.75%, ledene oxide (7.22%, caryophyllene (1.82%, and caryophyllene oxide (1.15%. HPLC analysis result showed that there were no flavonoids in ethyl acetate extract, but flavonoids are abundant in n-butanol extract. Further studies are needed regarding the identification, toxicity, and mechanism of action of active compounds.

  19. Auxin-Independent NAC Pathway Acts in Response to Explant-Specific Wounding and Promotes Root Tip Emergence during de Novo Root Organogenesis in Arabidopsis.

    Science.gov (United States)

    Chen, Xiaodong; Cheng, Jingfei; Chen, Lyuqin; Zhang, Guifang; Huang, Hai; Zhang, Yijing; Xu, Lin

    2016-04-01

    Plants have powerful regenerative abilities that allow them to recover from damage and survive in nature. De novo organogenesis is one type of plant regeneration in which adventitious roots and shoots are produced from wounded and detached organs. By studying de novo root organogenesis using leaf explants of Arabidopsis (Arabidopsis thaliana), we previously suggested that wounding is the first event that provides signals to trigger the whole regenerative process. However, our knowledge of the role of wounding in regeneration remains limited. In this study, we show that wounding not only triggers the auxin-mediated fate transition of regeneration-competent cells, but also induces the NAC pathway for root tip emergence. The NAC1 transcription factor gene was specifically expressed in response to wounding in the leaf explant, but not in the wounded leaf residue of the source plant. Inhibition of the NAC1 pathway severely affected the emergence of adventitious root tips. However, the NAC1 pathway functioned independently of auxin-mediated cell fate transition and regulates expression of CEP genes, which encode proteins that might have a role in degradation of extensin proteins in the cell wall. Overall, our results suggest that wounding has multiple roles in de novo root organogenesis and that NAC1 acts as one downstream branch in regulating the cellular environment for organ emergence.

  20. Enhanced Expression and Activation of the Alternative Oxidase during Infection of Arabidopsis with Pseudomonas syringae pv tomato

    NARCIS (Netherlands)

    Simons, Bert H.; Millenaar, F.F.; Mulder, Lonneke; Loon, L.C. van; Lambers, Hans

    2002-01-01

    Cyanide-resistant ("alternative") respiration was studied in Arabidopsis during incompatible and compatible infection with Pseudomonas syringae pv tomato DC3000. Total leaf respiration increased as the leaves became necrotic, as did the cyanideresistant component that was sensitive to salicylhydroxa

  1. Perturbations in the Primary Metabolism of Tomato and Arabidopsis thaliana Plants Infected with the Soil-Borne Fungus Verticillium dahliae.

    Directory of Open Access Journals (Sweden)

    Anja Buhtz

    Full Text Available The hemibiotrophic soil-borne fungus Verticillium dahliae is a major pathogen of a number of economically important crop species. Here, the metabolic response of both tomato and Arabidopsis thaliana to V. dahliae infection was analysed by first using non-targeted GC-MS profiling. The leaf content of both major cell wall components glucuronic acid and xylose was reduced in the presence of the pathogen in tomato but enhanced in A. thaliana. The leaf content of the two tricarboxylic acid cycle intermediates fumaric acid and succinic acid was increased in the leaf of both species, reflecting a likely higher demand for reducing equivalents required for defence responses. A prominent group of affected compounds was amino acids and based on the targeted analysis in the root, it was shown that the level of 12 and four free amino acids was enhanced by the infection in, respectively, tomato and A. thaliana, with leucine and histidine being represented in both host species. The leaf content of six free amino acids was reduced in the leaf tissue of diseased A. thaliana plants, while that of two free amino acids was raised in the tomato plants. This study emphasizes the role of primary plant metabolites in adaptive responses when the fungus has colonized the plant.

  2. Metabolomics analysis of Cistus monspeliensis leaf extract on energy metabolism activation in human intestinal cells.

    Science.gov (United States)

    Shimoda, Yoichi; Han, Junkyu; Kawada, Kiyokazu; Smaoui, Abderrazak; Isoda, Hiroko

    2012-01-01

    Energy metabolism is a very important process to improve and maintain health from the point of view of physiology. It is well known that the intracellular ATP production is contributed to energy metabolism in cells. Cistus monspeliensis is widely used as tea, spices, and medical herb; however, it has not been focusing on the activation of energy metabolism. In this study, C. monspeliensis was investigated as the food resources by activation of energy metabolism in human intestinal epithelial cells. C. monspeliensis extract showed high antioxidant ability. In addition, the promotion of metabolites of glycolysis and TCA cycle was induced by C. monspeliensis treatment. These results suggest that C. monspeliensis extract has an ability to enhance the energy metabolism in human intestinal cells. PMID:22523469

  3. Metabolomics Analysis of Cistus monspeliensis Leaf Extract on Energy Metabolism Activation in Human Intestinal Cells

    Directory of Open Access Journals (Sweden)

    Yoichi Shimoda

    2012-01-01

    Full Text Available Energy metabolism is a very important process to improve and maintain health from the point of view of physiology. It is well known that the intracellular ATP production is contributed to energy metabolism in cells. Cistus monspeliensis is widely used as tea, spices, and medical herb; however, it has not been focusing on the activation of energy metabolism. In this study, C. monspeliensis was investigated as the food resources by activation of energy metabolism in human intestinal epithelial cells. C. monspeliensis extract showed high antioxidant ability. In addition, the promotion of metabolites of glycolysis and TCA cycle was induced by C. monspeliensis treatment. These results suggest that C. monspeliensis extract has an ability to enhance the energy metabolism in human intestinal cells.

  4. Isolation and characterization of an Arabidopsis biotin carboxylase gene and its promoter.

    Science.gov (United States)

    Bao, X; Shorrosh, B S; Ohlrogge, J B

    1997-11-01

    In the plastids of most plants, acetyl-CoA carboxylase (ACCase; EC 6.4.1.2) is a multisubunit complex consisting of biotin carboxylase (BC), biotin-carboxyl carrier protien (BCCP), and carboxytransferase (alpha-CT, beta-CT) subunits. To better understand the regulation of this enzyme, we have isolated and sequenced a BC genomic clone from Arabidopsis and partially characterized its promoter. Fifteen introns were identified. The deduced amino acid sequence of the mature BC protein is highly conserved between Arabidopsis and tobacco (92.6% identity). BC expression was evaluated using northern blots and BC/GUS fusion constructs in transgenic Arabidopsis. GUS activity in the BC/GUS transgenics as well as transcript level of the native gene were both found to be higher in silique and flower than in root and leaf. Analysis of tobacco suspension cells transformed with truncated BC promoter/GUS gene fusions indicated the region from -140 to +147 contained necessary promoter elements which supported basal gene expression. A positive regulatory region was found to be located between -2100 and -140, whereas a negative element was possibly located in the first intron. In addition, several conserved regulatory elements were identified in the BC promoter. Surprisingly, although BC is a low-abundance protein, the expression of BC/GUS fusion constructs was similar to 35S/GUS constructs.

  5. Comparative proteomics and physiological characterization of Arabidopsis thaliana seedlings in responses to Ochratoxin A.

    Science.gov (United States)

    Wang, Yan; Hao, Junran; Zhao, Weiwei; Yang, Zhuojun; Wu, Weihong; Zhang, Yu; Xu, Wentao; Luo, YunBo; Huang, Kunlun

    2013-07-01

    Ochratoxin A (OTA) is a mycotoxin that is primarily produced by Aspergillus ochraceus and Penicillium verrucosum. This mycotoxin is a contaminant of food and feedstock worldwide and may induce cell death in plants. To investigate the dynamic growth process of Arabidopsis seedlings in response to OTA stress and to obtain a better understanding of the mechanism of OTA toxicity towards Arabidopsis, a comparative proteomics study using 2-DE and MALDI-TOF/TOF MS/MS was performed. Mass spectrometry analysis identified 59 and 51 differentially expressed proteins in seedlings exposed to 25 and 45 μM OTA for 7 days, respectively. OTA treatment decreased root elongation and leaf area, increased anthocyanin accumulation, damaged the photosynthetic apparatus and inhibited photosynthesis. Treatment of the seedlings with 25 μM OTA enhanced energy metabolism, whereas higher concentration of OTA (45 μM) inhibited energy metabolism in the seedlings. OTA treatment caused an increase of ROS, an enhancement of antioxidant enzyme defense responses, disturbance of redox homeostasis and activation of lipid oxidation. Glutamine and S-adenosylmethionine metabolism may also play important roles in the response to OTA. In conclusion, our study provided novel insights regarding the response of Arabidopsis to OTA at the level of the proteome. These results are expected to be highly useful for understanding the physiological responses and dissecting the OTA response pathways in higher plants. PMID:23625346

  6. Protective effect of C. sativa leaf extract against UV mediated-DNA damage in a human keratinocyte cell line.

    Science.gov (United States)

    Almeida, I F; Pinto, A S; Monteiro, C; Monteiro, H; Belo, L; Fernandes, J; Bento, A R; Duarte, T L; Garrido, J; Bahia, M F; Sousa Lobo, J M; Costa, P C

    2015-03-01

    Toxic effects of ultraviolet (UV) radiation on skin include protein and lipid oxidation, and DNA damage. The latter is known to play a major role in photocarcinogenesis and photoaging. Many plant extracts and natural compounds are emerging as photoprotective agents. Castanea sativa leaf extract is able to scavenge several reactive species that have been associated to UV-induced oxidative stress. The aim of this work was to analyze the protective effect of C. sativa extract (ECS) at different concentrations (0.001, 0.01, 0.05 and 0.1 μg/mL) against the UV mediated-DNA damage in a human keratinocyte cell line (HaCaT). For this purpose, the cytokinesis-block micronucleus assay was used. Elucidation of the protective mechanism was undertaken regarding UV absorption, influence on (1)O₂ mediated effects or NRF2 activation. ECS presented a concentration-dependent protective effect against UV-mediated DNA damage in HaCaT cells. The maximum protection afforded (66.4%) was achieved with the concentration of 0.1 μg/mL. This effect was found to be related to a direct antioxidant effect (involving (1)O₂) rather than activation of the endogenous antioxidant response coordinated by NRF2. Electrochemical studies showed that the good antioxidant capacity of the ECS can be ascribed to the presence of a pool of different phenolic antioxidants. No genotoxic or phototoxic effects were observed after incubation of HaCaT cells with ECS (up to 0.1 μg/mL). Taken together these results reinforce the putative application of this plant extract in the prevention/minimization of UV deleterious effects on skin.

  7. Transcriptomic signatures of transfer cells in early developing nematode feeding cells of Arabidopsis focused on auxin and ethylene signalling.

    Directory of Open Access Journals (Sweden)

    Javier eCabrera

    2014-03-01

    Full Text Available Phyto-endoparasitic nematodes induce specialized feeding cells (NFCs in their hosts, termed syncytia and giant cells (GCs for cyst and root-knot nematodes, respectively. They differ in their ontogeny and global transcriptional signatures, but both develop cell wall ingrowths to facilitate high rates of apoplastic/symplastic solute exchange showing transfer cell (TC characteristics. Regulatory signals for TC differentiation are not still well known. The two-component signalling system (2CS and reactive oxygen species are proposed as inductors of TC identity, while, 2CSs-related genes are not major contributors to differential gene expression in early developing NFCs. Additionally, transcriptomic and functional studies have assigned a major role to auxin and ethylene as regulatory signals on early developing TCs. Genes encoding proteins with similar functions expressed in both early developing NFCs and typical TCs are putatively involved in upstream or downstream responses mediated by auxin and ethylene. Yet, no function directly associated to the TCs identity of NFCs, such as the formation of cell wall ingrowths is described for most of them. Thus we reviewed similarities between transcriptional changes observed during the early stages of NFCs formation and those described during differentiation of TCs to hypothesize about putative signals leading to TC-like differentiation of NFCs with particular emphasis on auxin an ethylene.

  8. Coupling the GAL4 UAS system with alcR for versatile cell type-specific chemically inducible gene expression in Arabidopsis.

    Science.gov (United States)

    Sakvarelidze, Lali; Tao, Zheng; Bush, Max; Roberts, Gethin R; Leader, David J; Doonan, John H; Rawsthorne, Stephen

    2007-07-01

    The Aspergillus alc regulon encodes a transcription factor, ALCR, which regulates transcription from cognate promoters such as alcA(p). In the presence of suitable chemical inducers, ALCR activates gene expression from alcA(p). The alc regulon can be transferred to other species and can be used to control the expression of reporter, metabolic and developmental genes in response to low-level ethanol exposure. In this paper, we describe a versatile system for targeting the alc regulon to specific cell types in Arabidopsis by driving ALCR expression from the GAL4 upstream activator sequence (UAS). Large numbers of Arabidopsis lines are available in which GAL4 is expressed in a variety of spatial patterns and, in turn, drives the expression of any gene cloned downstream of the UAS. We have used a previously characterized line that directs gene expression to the endosperm to demonstrate spatially restricted ethanol-inducible gene expression. We also show that the domain of inducible gene expression can easily be altered by crossing the UAS::ALCR cassette into different driver lines. We conclude that this gene switch can be used to drive gene expression in a highly responsive, but spatially restricted, manner.

  9. The Arabidopsis lue1 mutant defines a katanin p60 ortholog involved in hormonal control of microtubule orientation during cell growth

    DEFF Research Database (Denmark)

    Bouquin, Thomas; Mattsson, Ole; Naested, Henrik;

    2003-01-01

    The lue1 mutant was previously isolated in a bio-imaging screen for Arabidopsis mutants exhibiting inappropriate regulation of an AtGA20ox1 promoter-luciferase reporter fusion. Here we show that lue1 is allelic to fra2, bot1 and erh3, and encodes a truncated katanin-like microtubule-severing prot......The lue1 mutant was previously isolated in a bio-imaging screen for Arabidopsis mutants exhibiting inappropriate regulation of an AtGA20ox1 promoter-luciferase reporter fusion. Here we show that lue1 is allelic to fra2, bot1 and erh3, and encodes a truncated katanin-like microtubule......-severing protein (AtKSS). Complementation of lue1 with the wild-type AtKSS gene restored both wild-type stature and luciferase reporter levels. Hormonal responses of lue1 to ethylene and gibberellins revealed inappropriate cortical microtubule reorientation during cell growth. Moreover, a fusion between the At...

  10. Chloride regulates leaf cell size and water relations in tobacco plants

    OpenAIRE

    Franco-Navarro, Juan D.; Brumós Fuentes, Javier; Rosales Villegas, Miguel Á.; Cubero Font, Paloma; Talón Cubillo, Manuel; Colmenero Flores, José M.

    2015-01-01

    Chloride (Cl–) is a micronutrient that accumulates to macronutrient levels since it is normally available in nature and actively taken up by higher plants. Besides a role as an unspecific cell osmoticum, no clear biological roles have been explicitly associated with Cl– when accumulated to macronutrient concentrations. To address this question, the glycophyte tobacco (Nicotiana tabacum L. var. Habana) has been treated with a basal nutrient solution supplemented with one of three salt combinat...

  11. Anti-Ageing Effects of Sonchus oleraceus L. (pūhā) Leaf Extracts on H2O2-Induced Cell Senescence

    DEFF Research Database (Denmark)

    Ou, Zong-Quan; Rades, Thomas; McDowell, Arlene

    2015-01-01

    Antioxidants protect against damage from free radicals and are believed to slow the ageing process. Previously, we have reported the high antioxidant activity of 70% methanolic Sonchus oleraceus L. (Asteraceae) leaf extracts. We hypothesize that S. oleraceus extracts protect cells against H2O2-in......-induced premature senescence than the corresponding ascorbic acid treatments. These findings indicate the potential of S. oleraceus extracts to be formulated as an anti-ageing agent....

  12. Overexpression of PIP2;5 aquaporin alleviates effects of low root temperature on cell hydraulic conductivity and growth in Arabidopsis.

    Science.gov (United States)

    Lee, Seong Hee; Chung, Gap Chae; Jang, Ji Young; Ahn, Sung Ju; Zwiazek, Janusz J

    2012-05-01

    The effects of low root temperature on growth and root cell water transport were compared between wild-type Arabidopsis (Arabidopsis thaliana) and plants overexpressing plasma membrane intrinsic protein 1;4 (PIP1;4) and PIP2;5. Descending root temperature from 25°C to 10°C quickly reduced cell hydraulic conductivity (L(p)) in wild-type plants but did not affect L(p) in plants overexpressing PIP1;4 and PIP2;5. Similarly, when the roots of wild-type plants were exposed to 10°C for 1 d, L(p) was lower compared with 25°C. However, there was no effect of low root temperature on L(p) in PIP1;4- and PIP2;5-overexpressing plants after 1 d of treatment. When the roots were exposed to 10°C for 5 d, L(p) was reduced in wild-type plants and in plants overexpressing PIP1;4, whereas there was still no effect in PIP2;5-overexpressing plants. These results suggest that the gating mechanism in PIP1;4 may be more sensitive to prolonged low temperature compared with PIP2;5. The reduction of L(p) at 10°C in roots of wild-type plants was partly restored to the preexposure level by 5 mm Ca(NO(3))(2) and protein phosphatase inhibitors (75 nm okadaic acid or 1 μm Na(3)VO(4)), suggesting that aquaporin phosphorylation/dephosphorylation processes were involved in this response. The temperature sensitivity of cell water transport in roots was reflected by a reduction in shoot and root growth rates in the wild-type and PIP1;4-overexpressing plants exposed to 10°C root temperature for 5 d. However, low root temperature had no effect on growth in plants overexpressing PIP2;5. These results provide strong evidence for a link between growth at low root temperature and aquaporin-mediated root water transport in Arabidopsis.

  13. The polyadenylation factor subunit CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR30: A key factor of programmed cell death and a regulator of immunity in arabidopsis

    KAUST Repository

    Bruggeman, Quentin

    2014-04-04

    Programmed cell death (PCD) is essential for several aspects of plant life, including development and stress responses. Indeed, incompatible plant-pathogen interactions are well known to induce the hypersensitive response, a localized cell death. Mutational analyses have identified several key PCD components, and we recently identified the mips1 mutant of Arabidopsis (Arabidopsis thaliana), which is deficient for the key enzyme catalyzing the limiting step of myoinositol synthesis. One of the most striking features of mips1 is the light-dependent formation of lesions on leaves due to salicylic acid (SA)-dependent PCD, revealing roles for myoinositol or inositol derivatives in the regulation of PCD. Here, we identified a regulator of plant PCD by screening for mutants that display transcriptomic profiles opposing that of the mips1 mutant. Our screen identified the oxt6 mutant, which has been described previously as being tolerant to oxidative stress. In the oxt6 mutant, a transfer DNA is inserted in the CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR30 (CPSF30) gene, which encodes a polyadenylation factor subunit homolog. We show that CPSF30 is required for lesion formation in mips1 via SA-dependent signaling, that the prodeath function of CPSF30 is not mediated by changes in the glutathione status, and that CPSF30 activity is required for Pseudomonas syringae resistance. We also show that the oxt6 mutation suppresses cell death in other lesion-mimic mutants, including lesion-simulating disease1, mitogen-activated protein kinase4, constitutive expressor of pathogenesis-related genes5, and catalase2, suggesting that CPSF30 and, thus, the control of messenger RNA 3′ end processing, through the regulation of SA production, is a key component of plant immune responses. © 2014 American Society of Plant Biologists. All rights reserved.

  14. Combining proteomics and transcriptome sequencing to identify active plant-cell-wall-degrading enzymes in a leaf beetle

    Directory of Open Access Journals (Sweden)

    Kirsch Roy

    2012-11-01

    Full Text Available Abstract Background The primary plant cell wall is a complex mixture of polysaccharides and proteins encasing living plant cells. Among these polysaccharides, cellulose is the most abundant and useful biopolymer present on earth. These polysaccharides also represent a rich source of energy for organisms which have evolved the ability to degrade them. A growing body of evidence suggests that phytophagous beetles, mainly species from the superfamilies Chrysomeloidea and Curculionoidea, possess endogenous genes encoding complex and diverse families of so-called plant cell wall degrading enzymes (PCWDEs. The presence of these genes in phytophagous beetles may have been a key element in their success as herbivores. Here, we combined a proteomics approach and transcriptome sequencing to identify PCWDEs present in larval gut contents of the mustard leaf beetle, Phaedon cochleariae. Results Using a two-dimensional proteomics approach, we recovered 11 protein bands, isolated using activity assays targeting cellulose-, pectin- and xylan-degrading enzymes. After mass spectrometry analyses, a total of 13 proteins putatively responsible for degrading plant cell wall polysaccharides were identified; these proteins belong to three glycoside hydrolase (GH families: GH11 (xylanases, GH28 (polygalacturonases or pectinases, and GH45 (β-1,4-glucanases or cellulases. Additionally, highly stable and proteolysis-resistant host plant-derived proteins from various pathogenesis-related protein (PRs families as well as polygalacturonase-inhibiting proteins (PGIPs were also identified from the gut contents proteome. In parallel, transcriptome sequencing revealed the presence of at least 19 putative PCWDE transcripts encoded by the P. cochleariae genome. All of these were specifically expressed in the insect gut rather than the rest of the body, and in adults as well as larvae. The discrepancy observed in the number of putative PCWDEs between transcriptome and proteome

  15. Identifying the ionically bound cell wall and intracellular glycoside hydrolases in late growth stage Arabidopsis stems: implications for the genetic engineering of bioenergy crops

    Directory of Open Access Journals (Sweden)

    Hui eWEI

    2015-05-01

    Full Text Available Identifying the cell wall-ionically bound glycoside hydrolases (GHs in Arabidopsis stems is important for understanding the regulation of cell wall integrity. For cell wall proteomics studies, the preparation of clean cell wall fractions is a challenge since cell walls constitute an open compartment, which is more likely to contain a mixture of intracellular and extracellular proteins due to cell leakage at the late growth stage. Here, we utilize a CaCl2-extraction procedure to isolate non-structural proteins from Arabidopsis whole stems, followed by the in-solution and in-gel digestion methods coupled with Nano-LC-MS/MS, bioinformatic