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Sample records for arabidopsis root growth

  1. MES buffer affects Arabidopsis root apex zonation and root growth by suppressing superoxide generation in root apex

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    Tomoko eKagenishi

    2016-02-01

    Full Text Available In plants, growth of roots and root hairs is regulated by the fine cellular control of pH and reactive oxygen species. MES, 2-(N-morpholinoethanesulfonic acid as one of the Good’s buffers has broadly been used for buffering medium, and it is thought to suit for plant growth with the concentration at 0.1% (w/v because the buffer capacity of MES ranging pH 5.5-7.0 (for Arabidopsis, pH 5.8. However, many reports have shown that, in nature, roots require different pH values on the surface of specific root apex zones, namely meristem, transition zone and elongation zone. Despite the fact that roots always grow on a media containing buffer molecule, little is known about impact of MES on root growth. Here, we have checked the effects of different concentrations of MES buffer using growing roots of Arabidopsis thaliana. Our results show that 1% of MES significantly inhibited root growth, the number of root hairs and length of meristem, whereas 0.1% promoted root growth and root apex area (region spanning from the root tip up to the transition zone. Furthermore, superoxide generation in root apex disappeared at 1% of MES. These results suggest that MES disturbs normal root morphogenesis by changing the reactive oxygen species (ROS homeostasis in root apex.

  2. MES Buffer Affects Arabidopsis Root Apex Zonation and Root Growth by Suppressing Superoxide Generation in Root Apex.

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    Kagenishi, Tomoko; Yokawa, Ken; Baluška, František

    2016-01-01

    In plants, growth of roots and root hairs is regulated by the fine cellular control of pH and reactive oxygen species (ROS). MES, 2-(N-morpholino)ethanesulfonic acid as one of the Good's buffers has broadly been used for buffering medium, and it is thought to suit for plant growth with the concentration at 0.1% (w/v) because the buffer capacity of MES ranging pH 5.5-7.0 (for Arabidopsis, pH 5.8). However, many reports have shown that, in nature, roots require different pH values on the surface of specific root apex zones, namely meristem, transition zone, and elongation zone. Despite the fact that roots always grow on a media containing buffer molecule, little is known about impact of MES on root growth. Here, we have checked the effects of different concentrations of MES buffer using growing roots of Arabidopsis thaliana. Our results show that 1% of MES significantly inhibited root growth, the number of root hairs and length of meristem, whereas 0.1% promoted root growth and root apex area (region spanning from the root tip up to the transition zone). Furthermore, superoxide generation in root apex disappeared at 1% of MES. These results suggest that MES disturbs normal root morphogenesis by changing the ROS homeostasis in root apex. PMID:26925066

  3. Arabidopsis alcohol dehydrogenase expression in both shoots and roots is conditioned by root growth environment

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    Chung, H. J.; Ferl, R. J.

    1999-01-01

    It is widely accepted that the Arabidopsis Adh (alcohol dehydrogenase) gene is constitutively expressed at low levels in the roots of young plants grown on agar media, and that the expression level is greatly induced by anoxic or hypoxic stresses. We questioned whether the agar medium itself created an anaerobic environment for the roots upon their growing into the gel. beta-Glucuronidase (GUS) expression driven by the Adh promoter was examined by growing transgenic Arabidopsis plants in different growing systems. Whereas roots grown on horizontal-positioned plates showed high Adh/GUS expression levels, roots from vertical-positioned plates had no Adh/GUS expression. Additional results indicate that growth on vertical plates closely mimics the Adh/GUS expression observed for soil-grown seedlings, and that growth on horizontal plates results in induction of high Adh/GUS expression that is consistent with hypoxic or anoxic conditions within the agar of the root zone. Adh/GUS expression in the shoot apex is also highly induced by root penetration of the agar medium. This induction of Adh/GUS in shoot apex and roots is due, at least in part, to mechanisms involving Ca2+ signal transduction.

  4. Hydrogen peroxide modulates abscisic acid signaling in root growth and development in Arabidopsis

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    BAI Ling; ZHOU Yun; ZHANG XiaoRan; SONG ChunPeng; Gao MingQing

    2007-01-01

    Exogenous abscisic acid (ABA) can inhibit root growth and promote formation of more root hairs in the root tip of Arabidopsis. However, the molecular mechanisms that underlie root ABA signaling are largely unknown. We report here that hydrogen peroxide (H2O2) reduces the root growth of wild type,and the phenotype of H2O2 on the root growth is similar to ABA response. Meanwhile ABA-induced changes in the morphology of root system can be partly reversed by ascorbic acid in wild type and abolished in NADPH oxidase defective mutant atrbohF and atrbohC. Further, ABA can induce H2O2 accumulation in the root cells and enhance transcription level of OXI1, which is necessary for many more AOS-dependent processes such as root hair growth in Arabidopsis. Our results suggest that H2O2 as an important signal molecule is required for the ABA-regulated root growth and development in Arabidopsis.

  5. AtOPR3 specifically inhibits primary root growth in Arabidopsis under phosphate deficiency.

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    Zheng, Hongyan; Pan, Xiaoying; Deng, Yuxia; Wu, Huamao; Liu, Pei; Li, Xuexian

    2016-01-01

    The primary root plays essential roles in root development, nutrient absorption, and root architectural establishment. Primary root growth is generally suppressed by phosphate (P) deficiency in A. thaliana; however, the underlying molecular mechanisms are largely elusive to date. We found that AtOPR3 specifically inhibited primary root growth under P deficiency via suppressing root tip growth at the transcriptional level, revealing an important novel function of AtOPR3 in regulating primary root response to the nutrient stress. Importantly, AtOPR3 functioned to down-regulate primary root growth under P limitation mostly by its own, rather than depending on the Jasmonic acid signaling pathway. Further, AtOPR3 interacted with ethylene and gibberellin signaling pathways to regulate primary root growth upon P deficiency. In addition, the AtOPR3's function in inhibiting primary root growth upon P limitation was also partially dependent on auxin polar transport. Together, our studies provide new insights into how AtOPR3, together with hormone signaling interactions, modulates primary root growth in coping with the environmental stress in Arabidopsis.

  6. Glucose and auxin signaling interaction in controlling Arabidopsis thaliana seedlings root growth and development.

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    Bhuwaneshwar S Mishra

    Full Text Available BACKGROUND: Plant root growth and development is highly plastic and can adapt to many environmental conditions. Sugar signaling has been shown to affect root growth and development by interacting with phytohormones such as gibberellins, cytokinin and abscisic acid. Auxin signaling and transport has been earlier shown to be controlling plant root length, number of lateral roots, root hair and root growth direction. PRINCIPAL FINDINGS: Increasing concentration of glucose not only controls root length, root hair and number of lateral roots but can also modulate root growth direction. Since root growth and development is also controlled by auxin, whole genome transcript profiling was done to find out the extent of interaction between glucose and auxin response pathways. Glucose alone could transcriptionally regulate 376 (62% genes out of 604 genes affected by IAA. Presence of glucose could also modulate the extent of regulation 2 fold or more of almost 63% genes induced or repressed by IAA. Interestingly, glucose could affect induction or repression of IAA affected genes (35% even if glucose alone had no significant effect on the transcription of these genes itself. Glucose could affect auxin biosynthetic YUCCA genes family members, auxin transporter PIN proteins, receptor TIR1 and members of a number of gene families including AUX/IAA, GH3 and SAUR involved in auxin signaling. Arabidopsis auxin receptor tir1 and response mutants, axr2, axr3 and slr1 not only display a defect in glucose induced change in root length, root hair elongation and lateral root production but also accentuate glucose induced increase in root growth randomization from vertical suggesting glucose effects on plant root growth and development are mediated by auxin signaling components. CONCLUSION: Our findings implicate an important role of the glucose interacting with auxin signaling and transport machinery to control seedling root growth and development in changing nutrient

  7. Disentangling the intertwined genetic bases of root and shoot growth in Arabidopsis.

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    Bouteillé, Marie; Rolland, Gaëlle; Balsera, Crispulo; Loudet, Olivier; Muller, Bertrand

    2012-01-01

    Root growth and architecture are major components of plant nutrient and water use efficiencies and these traits are the matter of extensive genetic analysis in several crop species. Because root growth relies on exported assimilate from the shoot, and changes in assimilate supply are known to alter root architecture, we hypothesized (i) that the genetic bases of root growth could be intertwined with the genetic bases of shoot growth and (ii) that the link could be either positive, with alleles favouring shoot growth also favouring root growth, or negative, because of competition for assimilates. We tested these hypotheses using a quantitative genetics approach in the model species Arabidopsis thaliana and the Bay-0 × Shahdara recombinant inbred lines population. In accordance with our hypothesis, root and shoot growth traits were strongly correlated and most root growth quantitative trait loci (QTLs) colocalized with shoot growth QTLs with positive alleles originating from either the same or the opposite parent. In order to identify regions that could be responsible for root growth independently of the shoot, we generated new variables either based on root to shoot ratios, residuals of root to shoot correlations or coordinates of principal component analysis. These variables showed high heritability allowing genetic analysis. They essentially all yielded similar results pointing towards two regions involved in the root--shoot balance. Using Heterogeneous Inbred Families (a kind of near-isogenic lines), we validated part of the QTLs present in these two regions for different traits. Our study thus highlights the difficulty of disentangling intertwined genetic bases of root and shoot growth and shows that this difficulty can be overcome by using simple statistical tools.

  8. Disentangling the intertwined genetic bases of root and shoot growth in Arabidopsis.

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    Marie Bouteillé

    Full Text Available Root growth and architecture are major components of plant nutrient and water use efficiencies and these traits are the matter of extensive genetic analysis in several crop species. Because root growth relies on exported assimilate from the shoot, and changes in assimilate supply are known to alter root architecture, we hypothesized (i that the genetic bases of root growth could be intertwined with the genetic bases of shoot growth and (ii that the link could be either positive, with alleles favouring shoot growth also favouring root growth, or negative, because of competition for assimilates. We tested these hypotheses using a quantitative genetics approach in the model species Arabidopsis thaliana and the Bay-0 × Shahdara recombinant inbred lines population. In accordance with our hypothesis, root and shoot growth traits were strongly correlated and most root growth quantitative trait loci (QTLs colocalized with shoot growth QTLs with positive alleles originating from either the same or the opposite parent. In order to identify regions that could be responsible for root growth independently of the shoot, we generated new variables either based on root to shoot ratios, residuals of root to shoot correlations or coordinates of principal component analysis. These variables showed high heritability allowing genetic analysis. They essentially all yielded similar results pointing towards two regions involved in the root--shoot balance. Using Heterogeneous Inbred Families (a kind of near-isogenic lines, we validated part of the QTLs present in these two regions for different traits. Our study thus highlights the difficulty of disentangling intertwined genetic bases of root and shoot growth and shows that this difficulty can be overcome by using simple statistical tools.

  9. Arabidopsis root growth movements and their symmetry: progress and problems arising from recent work.

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    Migliaccio, Fernando; Fortunati, Alessio; Tassone, Paola

    2009-03-01

    Over the last fifteen years, an increasing number of plant scientists have become interested in the Arabidopsis root growth pattern, that is produced on the surface of an agar plate, inclined from the vertical. In this situation, the roots wave intensely and slant preferentially towards one side, showing torsions in the epidermal cell files alternately right-and left handed. In addition, the pattern switches to the formation of large or strict coils when the plate is set horizontally. After this finding, different hypotheses were advanced attempting to explain the forces that shape these patterns. These basically appear to be gravitropism, circumnutation and negative thigmotropism. With regard to the symmetry, the coils and the slanting in the wild-type are essentially right-handed, but mutants were also reported which show a left-handed symmetry, while some do not show a regular growth pattern at all. This review article discusses the earlier as well as the most recent findings on the topic, and investigates the possibility of describing the different mechanisms shaping the root growth patterns via unifying hypothesis.

  10. Overexpressing HRS1 Confers Hypersensitivity to Low Phosphate-Elicited Inhibition of Primary Root Growth in Arabidopsis thaliana

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    Hong Liu; Huixia Yang; Chongming Wu; Juanjuan Feng; Xin Liu; Huanju Qin; Daowen Wang

    2009-01-01

    Phosphate (Pi) deficiency causes dramatic root system architecture (RSA) changes in higher plants.Here we report that overexpression of HRS1 leads to enhanced sensitivity to low Pi-elicited inhibition of primary root growth in Arabidopsis thaliana seedlings.Bioinformatic investigations uncovered that HRS1 and its six homologs encode putative G2-1ike transcription factors in Arabidopsis.Analysis of promoter::GUS reporter lines revealed that HRS1 transcripts were present mainly in the root hair region and root hair cells under Pi-sufficient conditions.Pi deprivation Increased HRS1 expression level and expanded its expression domain.Although HRS1 knockout mutant did not differ from wild type (WT) control irrespective of Pi status,its overexpreesion lines were significantly more susceptible to low Pi-elicited primary root shortening.In both WT and HRS1 overexpression seedlings,low Pi-induced primary root shortening was accompanied by enhanced root hair cell differentiation,but this enhancement occurred to a greater extent in the latter genotype.Collectively,our data suggest that HRS1 may be involved in the modulation of primary root and root hair growth in Pi-deprived Arabidopsis seedlings,and provide useful clues for further research into the function of HRS1 and its homologs and the mechanisms behind RSA changes under Pi-deficient conditions.

  11. Glucose and Auxin Signaling Interaction in Controlling Arabidopsis thaliana Seedlings Root Growth and Development

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    Mishra, Bhuwaneshwar S.; Manjul Singh; Priyanka Aggrawal; Ashverya Laxmi

    2009-01-01

    BACKGROUND: Plant root growth and development is highly plastic and can adapt to many environmental conditions. Sugar signaling has been shown to affect root growth and development by interacting with phytohormones such as gibberellins, cytokinin and abscisic acid. Auxin signaling and transport has been earlier shown to be controlling plant root length, number of lateral roots, root hair and root growth direction. PRINCIPAL FINDINGS: Increasing concentration of glucose not only controls root ...

  12. Trichoderma spp. Improve growth of Arabidopsis seedlings under salt stress through enhanced root development, osmolite production, and Na⁺ elimination through root exudates.

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    Contreras-Cornejo, Hexon Angel; Macías-Rodríguez, Lourdes; Alfaro-Cuevas, Ruth; López-Bucio, José

    2014-06-01

    Salt stress is an important constraint to world agriculture. Here, we report on the potential of Trichoderma virens and T. atroviride to induce tolerance to salt in Arabidopsis seedlings. We first characterized the effect of several salt concentrations on shoot biomass production and root architecture of Arabidopsis seedlings. We found that salt repressed plant growth and root development in a dose-dependent manner by blocking auxin signaling. Analysis of the wild type and eir1, aux1-7, arf7arf19, and tir1abf2abf19 auxin-related mutants revealed a key role for indole-3-acetic acid (IAA) signaling in mediating salt tolerance. We also found that T. virens (Tv29.8) and T. atroviride (IMI 206040) promoted plant growth in both normal and saline conditions, which was related to the induction of lateral roots and root hairs through auxin signaling. Arabidopsis seedlings grown under saline conditions inoculated with Trichoderma spp. showed increased levels of abscissic acid, L-proline, and ascorbic acid, and enhanced elimination of Na⁺ through root exudates. Our data show the critical role of auxin signaling and root architecture to salt tolerance in Arabidopsis and suggest that these fungi may enhance the plant IAA level as well as the antioxidant and osmoprotective status of plants under salt stress. PMID:24502519

  13. Ethylene is critical to the maintenance of primary root growth and Fe homeostasis under Fe stress in Arabidopsis.

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    Li, Guangjie; Xu, Weifeng; Kronzucker, Herbert J; Shi, Weiming

    2015-04-01

    Iron (Fe) is an essential microelement but is highly toxic when in excess. The response of plant roots to Fe toxicity and the nature of the regulatory pathways engaged are poorly understood. Here, we examined the response to excess Fe exposure in Arabidopsis wild type and ethylene mutants with a focus on primary root growth and the role of ethylene. We showed that excess Fe arrested primary root growth by decreasing both cell elongation and division, and principally resulteds from direct external Fe contact at the root tip. Pronounced ethylene, but not abscisic acid, evolution was associated with excess Fe exposure. Ethylene antagonists intensified root growth inhibition in the wild type, while the inhibition was significantly reduced in ethylene-overproduction mutants. We showed that ethylene plays a positive role in tissue Fe homeostasis, even in the absence of iron-plaque formation. Ethylene reduced Fe concentrations in the stele, xylem, and shoot. Furthermore, ethylene increased the expression of genes encoding Fe-sequestering ferritins. Additionally, ethylene significantly enhanced root K(+) status and upregulated K(+)-transporter (HAK5) expression. Our findings highlight the important role of ethylene in tissue Fe and K homeostasis and primary root growth under Fe stress in Arabidopsis.

  14. Arabidopsis thaliana root elongation growth is sensitive to lunisolar tidal acceleration and may also be weakly correlated with geomagnetic variations

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    Barlow, Peter W.; Fisahn, Joachim; Yazdanbakhsh, Nima; Moraes, Thiago A.; Khabarova, Olga V.; Gallep, Cristiano M.

    2013-01-01

    Background Correlative evidence suggests a relationship between the lunisolar tidal acceleration and the elongation rate of arabidopsis roots grown under free-running conditions of constant low light. Methods Seedlings of Arabidopsis thaliana were grown in a controlled-climate chamber maintained at a constant temperature and subjected to continuous low-level illumination from fluorescent tubes, conditions that approximate to a ‘free-running’ state in which most of the abiotic factors that entrain root growth rates are excluded. Elongation of evenly spaced, vertical primary roots was recorded continuously over periods of up to 14 d using high temporal- and spatial-resolution video imaging and were analysed in conjunction with geophysical variables. Key Results and Conclusions The results confirm the lunisolar tidal/root elongation relationship. Also presented are relationships between the hourly elongation rates and the contemporaneous variations in geomagnetic activity, as evaluated from the disturbance storm time and ap indices. On the basis of time series of root elongation rates that extend over ≥4 d and recorded at different seasons of the year, a provisional conclusion is that root elongation responds to variation in the lunisolar force and also appears to adjust in accordance with variations in the geomagnetic field. Thus, both lunisolar tidal acceleration and the geomagnetic field should be considered as modulators of root growth rate, alongside other, stronger and more well-known abiotic environmental regulators, and perhaps unexplored factors such as air ions. Major changes in atmospheric pressure are not considered to be a factor contributing to oscillations of root elongation rate. PMID:23532042

  15. Proteomics in deciphering the auxin commitment in the Arabidopsis thaliana root growth.

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    Mattei, Benedetta; Sabatini, Sabrina; Schininà, M Eugenia

    2013-11-01

    The development of plant root systems is characterized by a high plasticity, made possible by the continual propagation of new meristems. Root architecture is fundamental for overall plant growth, abiotic stress resistance, nutrient uptake, and response to environmental changes. Understanding the function of genes and proteins that control root architecture and stress resistance will contribute to the development of more sustainable systems of intensified crop production. To meet these challenges, proteomics provide the genome-wide scale characterization of protein expression pattern, subcellular localization, post-translational modifications, activity regulation, and molecular interactions. In this review, we describe a variety of proteomic strategies that have been applied to study the proteome of the whole organ and of specific cell types during root development. Each has advantages and limitations, but collectively they are providing important insights into the mechanisms by which auxin structures and patterns the root system and into the interplay between signaling networks, auxin transport and growth. The acquisition of proteomic, transcriptomic, and metabolomic data sets of the root apex on the cell scale has revealed the high spatial complexity of regulatory networks and fosters the use of new powerful proteomic tools for a full understanding of the control of root developmental processes and environmental responses.

  16. Molecular genetic investigations of root gravitropism and other complex growth behaviors using Arabidopsis and Brachypodium as models

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    Masson, Patrick; Barker, Richard; Miller, Nathan; Su, Shih-Hao; Su, Shih-Heng

    2016-07-01

    When growing on hard surfaces, Arabidopsis roots tend to grown downward, as dictated by positive gravitropism. At the same time, surface-derived stimuli promote a wavy pattern of growth that is superimposed to a rightward root-skewing trend. This behavior is believed to facilitate obstacle avoidance in soil. To better understand these complex behaviors, we have isolated and characterized mutations that affect them. Some of these mutations were shown to affect gravitropism whereas others did not. Within the latter group, most of the mutations affected mechanisms that control anisotropic cell expansion. We have also characterized mutations that affect early steps of gravity signal transduction within the gravity-sensing columella cells of the root cap. Upon reorientation within the gravity field, starch-filled plastids sediment to the bottom-side of these cells, triggering a pathway that leads to re-localization of auxin efflux facilitators to the bottom membrane. Lateral auxin transport toward the bottom flank ensues, leading to gravitropic curvature. Several of the mutations we characterized affect genes that encode proteins associated with the vesicle trafficking pathway needed for this cell polarization. Other mutations were shown to affect components of the plastid outer envelope protein import complex (TOC). Their functional analysis suggests an active role for plastids in gravity signal transduction, beyond a simple contribution as sedimenting gravity susceptors. Because most cultivated crops are monocots, not dicots like Arabidopsis, we have also initiated studies of root-growth behavior with Brachypodium distachyon. When responding to a gravistimulus, the roots of Brachypodium seedlings develop a strong downward curvature that proceeds until the tip reaches a ~50-degree curvature. At that time, an oscillatory tip movement occurs while the root continues its downward reorientation. These root-tip oscillations also occur if roots are allowed to simply grow

  17. Microfilament Dynamics is Required for Root Growth under Alkaline Stress in Arabidopsis

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    Yue Zhou; Zijun Yang; Guangqin Guo; Yan Guo

    2010-01-01

    The microfilament (MF) cytoskeleton has crucial functions in plant development. Recent studies have revealed the function of MFs in diverse stress response. Alkaline stress is harmful to plant growth;however, it remains unclear whether the MFs play a role in alkaline stress. In the present study, we find that blocking MF assembly with latrunculin B (Lat B) leads to inhibition of plant root growth, and stabilization of MFs with phalloidin does not significantly affect plant root growth under normal conditions. In high external pH conditions, MF de-polymerization is induced and that associates with the reduction of root growth; phalloidin treatment partially rescues this reduction. Moreover, Lat B treatment further decreases the survival rate of seedlings growing in high external pH conditions. However, a high external pH (8.0) does not affect MF stability in vitro. Taken together, our results suggest that alkaline stress may trigger a signal that leads the dynamics of MFs and in turn regulates root growth.

  18. Growth performance and root transcriptome remodeling of Arabidopsis in response to Mars-like levels of magnesium sulfate.

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    Anne M Visscher

    Full Text Available BACKGROUND: Martian regolith (unconsolidated surface material is a potential medium for plant growth in bioregenerative life support systems during manned missions on Mars. However, hydrated magnesium sulfate mineral levels in the regolith of Mars can reach as high as 10 wt%, and would be expected to be highly inhibitory to plant growth. METHODOLOGY AND PRINCIPAL FINDINGS: Disabling ion transporters AtMRS2-10 and AtSULTR1;2, which are plasma membrane localized in peripheral root cells, is not an effective way to confer tolerance to magnesium sulfate soils. Arabidopsis mrs2-10 and sel1-10 knockout lines do not mitigate the growth inhibiting impacts of high MgSO(4.7H(2O concentrations observed with wildtype plants. A global approach was used to identify novel genes with potential to enhance tolerance to high MgSO(4.7H(2O (magnesium sulfate stress. The early Arabidopsis root transcriptome response to elevated concentrations of magnesium sulfate was characterized in Col-0, and also between Col-0 and the mutant line cax1-1, which was confirmed to be relatively tolerant of high levels of MgSO(4.7H(2O in soil solution. Differentially expressed genes in Col-0 treated for 45 min. encode enzymes primarily involved in hormone metabolism, transcription factors, calcium-binding proteins, kinases, cell wall related proteins and membrane-based transporters. Over 200 genes encoding transporters were differentially expressed in Col-0 up to 180 min. of exposure, and one of the first down-regulated genes was CAX1. The importance of this early response in wildtype Arabidopsis is exemplified in the fact that only four transcripts were differentially expressed between Col-0 and cax1-1 at 180 min. after initiation of treatment. CONCLUSIONS/SIGNIFICANCE: The results provide a solid basis for the understanding of the metabolic response of plants to elevated magnesium sulfate soils; it is the first transcriptome analysis of plants in this environment. The results foster

  19. Lysine63-linked ubiquitylation of PIN2 auxin carrier protein governs hormonally controlled adaptation of Arabidopsis root growth.

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    Leitner, Johannes; Petrášek, Jan; Tomanov, Konstantin; Retzer, Katarzyna; Pařezová, Markéta; Korbei, Barbara; Bachmair, Andreas; Zažímalová, Eva; Luschnig, Christian

    2012-05-22

    Cross-talk between plant cells and their surroundings requires tight regulation of information exchange at the plasma membrane (PM), which involves dynamic adjustments of PM protein localization and turnover to modulate signal perception and solute transport at the interface between cells and their surroundings. In animals and fungi, turnover of PM proteins is controlled by reversible ubiquitylation, which signals endocytosis and delivery to the cell's lytic compartment, and there is emerging evidence for related mechanisms in plants. Here, we describe the fate of Arabidopsis PIN2 protein, required for directional cellular efflux of the phytohormone auxin, and identify cis- and trans-acting mediators of PIN2 ubiquitylation. We demonstrate that ubiquitin acts as a principal signal for PM protein endocytosis in plants and reveal dynamic adjustments in PIN2 ubiquitylation coinciding with variations in vacuolar targeting and proteolytic turnover. We show that control of PIN2 proteolytic turnover via its ubiquitylation status is of significant importance for auxin distribution in root meristems and for environmentally controlled adaptations of root growth. Moreover, we provide experimental evidence indicating that PIN2 vacuolar sorting depends on modification specifically by lysine(63)-linked ubiquitin chains. Collectively, our results establish lysine(63)-linked PM cargo ubiquitylation as a regulator of polar auxin transport and adaptive growth responses in higher plants.

  20. Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation

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    Lili Fu

    2016-06-01

    Full Text Available Plant myrosinases (β-thioglucoside glucohydrolases are classified into two subclasses, Myr I and Myr II. The biological function of Myr I has been characterized as a major biochemical defense against insect pests and pathogens in cruciferous plants. However, the biological function of Myr II remains obscure. We studied the function of two Myr II member genes AtTGG4 and AtTGG5 in Arabidopsis. RT-PCR showed that both genes were specifically expressed in roots. GUS-assay revealed that both genes were expressed in the root-tip but with difference: AtTGG4 was expressed in the elongation zone of the root-tip, while AtTGG5 was expressed in the whole root-tip. Moreover, myrosin cells that produce and store the Myr I myrosinases in aboveground organs were not observed in roots, and AtTGG4 and AtTGG5 were expressed in all cells of the specific region. A homozygous double mutant line tgg4tgg5 was obtained through cross-pollination between two T-DNA insertion lines, tgg4E8 and tgg5E12, by PCR-screening in the F2 and F3 generations. Analysis of myrosinase activity in roots of mutants revealed that AtTGG4 and AtTGG5 had additive effects and contributed 35% and 65% myrosinase activity in roots of the wild type Col-0, respectively, and myrosinase activity in tgg4tgg5 was severely repressed. When grown in Murashiege & Skoog (MS medium or in soil with sufficient water, Col-0 had the shortest roots, and tgg4tgg5 had the longest roots, while tgg4E8 and tgg5E12 had intermediate root lengths. In contrast, when grown in soil with excessive water, Col-0 had the longest roots, and tgg4tgg5 had the shortest roots. These results suggested that AtTGG4 and AtTGG5 regulated root growth and had a role in flood tolerance. The auxin-indicator gene DR5::GUS was then introduced into tgg4tgg5 by cross-pollination. DR5::GUS expression patterns in seedlings of F1, F2, and F3 generations indicated that AtTGG4 and AtTGG5 contributed to auxin biosynthesis in roots. The proposed

  1. Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation.

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    Fu, Lili; Wang, Meng; Han, Bingying; Tan, Deguan; Sun, Xuepiao; Zhang, Jiaming

    2016-01-01

    Plant myrosinases (β-thioglucoside glucohydrolases) are classified into two subclasses, Myr I and Myr II. The biological function of Myr I has been characterized as a major biochemical defense against insect pests and pathogens in cruciferous plants. However, the biological function of Myr II remains obscure. We studied the function of two Myr II member genes AtTGG4 and AtTGG5 in Arabidopsis. RT-PCR showed that both genes were specifically expressed in roots. GUS-assay revealed that both genes were expressed in the root-tip but with difference: AtTGG4 was expressed in the elongation zone of the root-tip, while AtTGG5 was expressed in the whole root-tip. Moreover, myrosin cells that produce and store the Myr I myrosinases in aboveground organs were not observed in roots, and AtTGG4 and AtTGG5 were expressed in all cells of the specific region. A homozygous double mutant line tgg4tgg5 was obtained through cross-pollination between two T-DNA insertion lines, tgg4E8 and tgg5E12, by PCR-screening in the F2 and F3 generations. Analysis of myrosinase activity in roots of mutants revealed that AtTGG4 and AtTGG5 had additive effects and contributed 35% and 65% myrosinase activity in roots of the wild type Col-0, respectively, and myrosinase activity in tgg4tgg5 was severely repressed. When grown in Murashiege & Skoog (MS) medium or in soil with sufficient water, Col-0 had the shortest roots, and tgg4tgg5 had the longest roots, while tgg4E8 and tgg5E12 had intermediate root lengths. In contrast, when grown in soil with excessive water, Col-0 had the longest roots, and tgg4tgg5 had the shortest roots. These results suggested that AtTGG4 and AtTGG5 regulated root growth and had a role in flood tolerance. The auxin-indicator gene DR5::GUS was then introduced into tgg4tgg5 by cross-pollination. DR5::GUS expression patterns in seedlings of F1, F2, and F3 generations indicated that AtTGG4 and AtTGG5 contributed to auxin biosynthesis in roots. The proposed mechanism is that

  2. Genetic identification of a second site modifier of ctr1-1 that controls ethylene-responsive and gravitropic root growth in Arabidopsis thaliana.

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    Shin, Kihye; Lee, Rin-A; Lee, Inhye; Lee, Sumin; Park, Soon Ki; Soh, Moon-Soo

    2013-07-01

    Ethylene controls myriad aspects of plant growth throughout developmental stages in higher plants. It has been well established that ethylene-responsive growth entails extensive crosstalk with other plant hormones, particularly auxin. Here, we report a genetic mutation, named 1-aminocyclopropane carboxylic acid (ACC) resistant root1-1 (are1-1) in Arabidopsis thaliana (L.) Heynh. The CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) encodes a Raf-related protein, functioning as an upstream negative regulator of ethylene signaling in Arabidopsis thaliana. We found that the ctr1-1, a kinase-inactive allele exhibited slightly, but significantly, longer root length, compared to ACC-treated wild-type or ctr1-3, a null allele. Our genetic studies unveiled the existence of are1-1 mutation in the ctr1-1 mutant, as a second-site modifier which confers root-specific ethylene-resistance. Based on well-characterized crosstalk between ethylene and auxin during ethylene-responsive root growth, we performed various physiological analyses. Whereas are1-1 displayed normal sensitivity to synthetic auxins, it showed modest resistance to an auxin transport inhibitor, 1-Nnaphthylphthalamic acid. In addition, are1-1 mutant exhibited ectopically altered DR5:GUS activity upon ethylenetreatment. The results implicated the involvement of are1-1 in auxin-distribution, but not in auxin-biosynthesis, -uptake, or -sensitivity. In agreement, are1-1 mutant exhibited reduced gravitropic root growth and defective redistribution of DR5:GUS activity upon gravi-stimulation. Taken together with genetic and molecular analysis, our results suggest that ARE1 defines a novel locus to control ethylene-responsive root growth as well as gravitropic root growth presumably through auxin distribution in Arabidopsis thaliana.

  3. Defining the core Arabidopsis thaliana root microbiome

    Science.gov (United States)

    Gehring, Jase; Malfatti, Stephanie; Tremblay, Julien; Engelbrektson, Anna; Kunin, Victor; del Rio, Tijana Glavina; Edgar, Robert C.; Eickhorst, Thilo; Ley, Ruth E.; Hugenholtz, Philip; Tringe, Susannah Green; Dangl, Jeffery L.

    2014-01-01

    Land plants associate with a root microbiota distinct from the complex microbial community present in surrounding soil. The microbiota colonizing therhizosphere(immediately surroundingthe root) and the endophytic compartment (within the root) contribute to plant growth, productivity, carbon sequestration and phytoremediation1-3. Colonization of the root occurs despite a sophisticated plant immune system4,5, suggesting finely tuned discrimination of mutualists and commensals from pathogens. Genetic principles governing the derivation of host-specific endophyte communities from soil communities are poorly understood. Here we report the pyrosequencing of the bacterial 16S ribosomal RNA gene of more than 600 Arabidopsis thaliana plants to test the hypotheses that the root rhizosphere and endophytic compartment microbiota of plants grown under controlled conditions in natural soils are sufficiently dependent on the host to remain consistent across different soil types and developmental stages, and sufficiently dependent on host genotype to vary between inbred Arabidopsis accessions. We describe different bacterial communities in two geochemically distinct bulk soils and in rhizosphere and endophytic compartments prepared from roots grown in these soils. The communities in each compartment are strongly influenced by soil type. Endophytic compartments from both soils feature overlapping, low-complexity communities that are markedly enriched in Actinobacteria and specific families from other phyla, notably Proteobacteria. Some bacteria vary quantitatively between plants of different developmental stage and genotype. Our rigorous definition of an endophytic compartment microbiome should facilitate controlled dissection of plantmicrobe interactions derived from complex soil communities. PMID:22859206

  4. Expression of GhNAC2 from G. herbaceum, improves root growth and imparts tolerance to drought in transgenic cotton and Arabidopsis.

    Science.gov (United States)

    Gunapati, Samatha; Naresh, Ram; Ranjan, Sanjay; Nigam, Deepti; Hans, Aradhana; Verma, Praveen C; Gadre, Rekha; Pathre, Uday V; Sane, Aniruddha P; Sane, Vidhu A

    2016-01-01

    NAC proteins are plant-specific transcription factors that play essential roles in regulating development and responses to abiotic and biotic stresses. We show that over-expression of the cotton GhNAC2 under the CaMV35S promoter increases root growth in both Arabidopsis and cotton under unstressed conditions. Transgenic Arabidopsis plants also show improved root growth in presence of mannitol and NaCl while transgenic cotton expressing GhNAC2 show reduced leaf abscission and wilting upon water stress compared to control plants. Transgenic Arabidopsis plants also have larger leaves, higher seed number and size under well watered conditions, reduced transpiration and higher relative leaf water content. Micro-array analysis of transgenic plants over-expressing GhNAC2 reveals activation of the ABA/JA pathways and a suppression of the ethylene pathway at several levels to reduce expression of ERF6/ERF1/WRKY33/ MPK3/MKK9/ACS6 and their targets. This probably suppresses the ethylene-mediated inhibition of organ expansion, leading to larger leaves, better root growth and higher yields under unstressed conditions. Suppression of the ethylene pathway and activation of the ABA/JA pathways also primes the plant for improved stress tolerance by reduction in transpiration, greater stomatal control and suppression of growth retarding factors. PMID:27113714

  5. Expression of GhNAC2 from G. herbaceum, improves root growth and imparts tolerance to drought in transgenic cotton and Arabidopsis.

    Science.gov (United States)

    Gunapati, Samatha; Naresh, Ram; Ranjan, Sanjay; Nigam, Deepti; Hans, Aradhana; Verma, Praveen C; Gadre, Rekha; Pathre, Uday V; Sane, Aniruddha P; Sane, Vidhu A

    2016-04-26

    NAC proteins are plant-specific transcription factors that play essential roles in regulating development and responses to abiotic and biotic stresses. We show that over-expression of the cotton GhNAC2 under the CaMV35S promoter increases root growth in both Arabidopsis and cotton under unstressed conditions. Transgenic Arabidopsis plants also show improved root growth in presence of mannitol and NaCl while transgenic cotton expressing GhNAC2 show reduced leaf abscission and wilting upon water stress compared to control plants. Transgenic Arabidopsis plants also have larger leaves, higher seed number and size under well watered conditions, reduced transpiration and higher relative leaf water content. Micro-array analysis of transgenic plants over-expressing GhNAC2 reveals activation of the ABA/JA pathways and a suppression of the ethylene pathway at several levels to reduce expression of ERF6/ERF1/WRKY33/ MPK3/MKK9/ACS6 and their targets. This probably suppresses the ethylene-mediated inhibition of organ expansion, leading to larger leaves, better root growth and higher yields under unstressed conditions. Suppression of the ethylene pathway and activation of the ABA/JA pathways also primes the plant for improved stress tolerance by reduction in transpiration, greater stomatal control and suppression of growth retarding factors.

  6. 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.

  7. Joint genetic and network analyses identify loci associated with root growth under NaCl stress in Arabidopsis thaliana.

    Science.gov (United States)

    Kobayashi, Yuriko; Sadhukhan, Ayan; Tazib, Tanveer; Nakano, Yuki; Kusunoki, Kazutaka; Kamara, Mohamed; Chaffai, Radhouane; Iuchi, Satoshi; Sahoo, Lingaraj; Kobayashi, Masatomo; Hoekenga, Owen A; Koyama, Hiroyuki

    2016-04-01

    Plants have evolved a series of tolerance mechanisms to saline stress, which perturbs physiological processes throughout the plant. To identify genetic mechanisms associated with salinity tolerance, we performed linkage analysis and genome-wide association study (GWAS) on maintenance of root growth of Arabidopsis thaliana in hydroponic culture with weak and severe NaCl toxicity. The top 200 single-nucleotide polymorphisms (SNPs) determined by GWAS could cumulatively explain approximately 70% of the variation observed at each stress level. The most significant SNPs were linked to the genes of ATP-binding cassette B10 and vacuolar proton ATPase A2. Several known salinity tolerance genes such as potassium channel KAT1 and calcium sensor SOS3 were also linked to SNPs in the top 200. In parallel, we constructed a gene co-expression network to independently verify that particular groups of genes work together to a common purpose. We identify molecular mechanisms to confer salt tolerance from both predictable and novel physiological sources and validate the utility of combined genetic and network analysis. Additionally, our study indicates that the genetic architecture of salt tolerance is responsive to the severity of stress. These gene datasets are a significant information resource for a following exploration of gene function. PMID:26667381

  8. Spiralizations and tropisms in Arabidopsis roots.

    Science.gov (United States)

    Migliaccio, F; Piconese, S

    2001-12-01

    When Arabidopsis seedlings are grown on a hard-agar plate, their primary roots show characteristic spiralling movements, apparent as waves, coils and torsions, together with a slanting toward the right-hand side. All these movements are believed to be the result of three different processes acting on the roots: circumnutation, positive gravitropism and negative thigmotropism. The basic movement of the roots is described as that of a growing right-handed helix, which, because of the root tip hitting the agar plate, is continuously switched from the right-hand to the left-hand of the growth direction, and vice versa. This movement also produces a slanting root-growth direction toward the right-hand because of the incomplete waves made by the right-handed root to the left-hand. By contrast, the torsions seen in the coils and waves are interpreted as artefacts that form as an adaptation of the three-dimensional root helix to the flat two-dimensional agar surface.

  9. Natural variation in small molecule-induced TIR-NB-LRR signaling induces root growth arrest via EDS1- and PAD4-complexed R protein VICTR in Arabidopsis.

    Science.gov (United States)

    Kim, Tae-Houn; Kunz, Hans-Henning; Bhattacharjee, Saikat; Hauser, Felix; Park, Jiyoung; Engineer, Cawas; Liu, Amy; Ha, Tracy; Parker, Jane E; Gassmann, Walter; Schroeder, Julian I

    2012-12-01

    In a chemical genetics screen we identified the small-molecule [5-(3,4-dichlorophenyl)furan-2-yl]-piperidine-1-ylmethanethione (DFPM) that triggers rapid inhibition of early abscisic acid signal transduction via PHYTOALEXIN DEFICIENT4 (PAD4)- and ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1)-dependent immune signaling mechanisms. However, mechanisms upstream of EDS1 and PAD4 in DFPM-mediated signaling remain unknown. Here, we report that DFPM generates an Arabidopsis thaliana accession-specific root growth arrest in Columbia-0 (Col-0) plants. The genetic locus responsible for this natural variant, VICTR (VARIATION IN COMPOUND TRIGGERED ROOT growth response), encodes a TIR-NB-LRR (for Toll-Interleukin1 Receptor-nucleotide binding-Leucine-rich repeat) protein. Analyses of T-DNA insertion victr alleles showed that VICTR is necessary for DFPM-induced root growth arrest and inhibition of abscisic acid-induced stomatal closing. Transgenic expression of the Col-0 VICTR allele in DFPM-insensitive Arabidopsis accessions recapitulated the DFPM-induced root growth arrest. EDS1 and PAD4, both central regulators of basal resistance and effector-triggered immunity, as well as HSP90 chaperones and their cochaperones RAR1 and SGT1B, are required for the DFPM-induced root growth arrest. Salicylic acid and jasmonic acid signaling pathway components are dispensable. We further demonstrate that VICTR associates with EDS1 and PAD4 in a nuclear protein complex. These findings show a previously unexplored association between a TIR-NB-LRR protein and PAD4 and identify functions of plant immune signaling components in the regulation of root meristematic zone-targeted growth arrest. PMID:23275581

  10. Natural variation in small molecule-induced TIR-NB-LRR signaling induces root growth arrest via EDS1- and PAD4-complexed R protein VICTR in Arabidopsis.

    Science.gov (United States)

    Kim, Tae-Houn; Kunz, Hans-Henning; Bhattacharjee, Saikat; Hauser, Felix; Park, Jiyoung; Engineer, Cawas; Liu, Amy; Ha, Tracy; Parker, Jane E; Gassmann, Walter; Schroeder, Julian I

    2012-12-01

    In a chemical genetics screen we identified the small-molecule [5-(3,4-dichlorophenyl)furan-2-yl]-piperidine-1-ylmethanethione (DFPM) that triggers rapid inhibition of early abscisic acid signal transduction via PHYTOALEXIN DEFICIENT4 (PAD4)- and ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1)-dependent immune signaling mechanisms. However, mechanisms upstream of EDS1 and PAD4 in DFPM-mediated signaling remain unknown. Here, we report that DFPM generates an Arabidopsis thaliana accession-specific root growth arrest in Columbia-0 (Col-0) plants. The genetic locus responsible for this natural variant, VICTR (VARIATION IN COMPOUND TRIGGERED ROOT growth response), encodes a TIR-NB-LRR (for Toll-Interleukin1 Receptor-nucleotide binding-Leucine-rich repeat) protein. Analyses of T-DNA insertion victr alleles showed that VICTR is necessary for DFPM-induced root growth arrest and inhibition of abscisic acid-induced stomatal closing. Transgenic expression of the Col-0 VICTR allele in DFPM-insensitive Arabidopsis accessions recapitulated the DFPM-induced root growth arrest. EDS1 and PAD4, both central regulators of basal resistance and effector-triggered immunity, as well as HSP90 chaperones and their cochaperones RAR1 and SGT1B, are required for the DFPM-induced root growth arrest. Salicylic acid and jasmonic acid signaling pathway components are dispensable. We further demonstrate that VICTR associates with EDS1 and PAD4 in a nuclear protein complex. These findings show a previously unexplored association between a TIR-NB-LRR protein and PAD4 and identify functions of plant immune signaling components in the regulation of root meristematic zone-targeted growth arrest.

  11. Involvement of Arabidopsis thaliana phospholipase Dzeta2 in root hydrotropism through the suppression of root gravitropism.

    OpenAIRE

    Taniguchi, Yukimi Y; Taniguchi, Masatoshi; Tsuge, Tomohiko; Oka, Atsuhiro; Aoyama, Takashi

    2010-01-01

    Root hydrotropism is the phenomenon of directional root growth toward moisture under water-deficient conditions. Although physiological and genetic studies have revealed the involvement of the root cap in the sensing of moisture gradients, and those of auxin and abscisic acid (ABA) in the signal transduction for asymmetric root elongation, the overall mechanism of root hydrotropism is still unclear. We found that the promoter activity of the Arabidopsis phospholipase Dzeta2 gene (PLDzeta2) wa...

  12. 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.

  13. Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation

    OpenAIRE

    Lili Fu; Meng Wang; Bingying Han; Deguan Tan; Xuepiao Sun; Jiaming Zhang

    2016-01-01

    Plant myrosinases (β-thioglucoside glucohydrolases) are classified into two subclasses, Myr I and Myr II. The biological function of Myr I has been characterized as a major biochemical defense against insect pests and pathogens in cruciferous plants. However, the biological function of Myr II remains obscure. We studied the function of two Myr II member genes AtTGG4 and AtTGG5 in Arabidopsis. RT-PCR showed that both genes were specifically expressed in roots. GUS-assay revealed that both gene...

  14. Strigolactones suppress adventitious rooting in Arabidopsis and pea.

    Science.gov (United States)

    Rasmussen, Amanda; Mason, Michael Glenn; De Cuyper, Carolien; Brewer, Philip B; Herold, Silvia; Agusti, Javier; Geelen, Danny; Greb, Thomas; Goormachtig, Sofie; Beeckman, Tom; Beveridge, Christine Anne

    2012-04-01

    Adventitious root formation is essential for the propagation of many commercially important plant species and involves the formation of roots from nonroot tissues such as stems or leaves. Here, we demonstrate that the plant hormone strigolactone suppresses adventitious root formation in Arabidopsis (Arabidopsis thaliana) and pea (Pisum sativum). Strigolactone-deficient and response mutants of both species have enhanced adventitious rooting. CYCLIN B1 expression, an early marker for the initiation of adventitious root primordia in Arabidopsis, is enhanced in more axillary growth2 (max2), a strigolactone response mutant, suggesting that strigolactones restrain the number of adventitious roots by inhibiting the very first formative divisions of the founder cells. Strigolactones and cytokinins appear to act independently to suppress adventitious rooting, as cytokinin mutants are strigolactone responsive and strigolactone mutants are cytokinin responsive. In contrast, the interaction between the strigolactone and auxin signaling pathways in regulating adventitious rooting appears to be more complex. Strigolactone can at least partially revert the stimulatory effect of auxin on adventitious rooting, and auxin can further increase the number of adventitious roots in max mutants. We present a model depicting the interaction of strigolactones, cytokinins, and auxin in regulating adventitious root formation. PMID:22323776

  15. Identification and characterization of Arabidopsis AtNUDX9 as a GDP-d-mannose pyrophosphohydrolase: its involvement in root growth inhibition in response to ammonium

    OpenAIRE

    Tanaka, Hiroyuki; Maruta, Takanori; Ogawa, Takahisa; Tanabe, Noriaki; Tamoi, Masahiro; Yoshimura, Kazuya; Shigeoka, Shigeru

    2015-01-01

    Highlight AtNUDX9, a GDP-d-Man pyrophosphohydrolase in Arabidopsis, is involved in the regulation of GDP-d-Man levels affecting ammonium sensitivity via modulation of protein N-glycosylation in the roots.

  16. Nuclear ribosome biogenesis mediated by the DIM1A rRNA dimethylase is required for organized root growth and epidermal patterning in Arabidopsis.

    Science.gov (United States)

    Wieckowski, Yana; Schiefelbein, John

    2012-07-01

    Position-dependent patterning of hair and non-hair cells in the Arabidopsis thaliana root epidermis is a powerful system to study the molecular basis of cell fate specification. Here, we report an epidermal patterning mutant affecting the ADENOSINE DIMETHYL TRANSFERASE 1A (DIM1A) rRNA dimethylase gene, predicted to participate in rRNA posttranscriptional processing and base modification. Consistent with a role in ribosome biogenesis, DIM1A is preferentially expressed in regions of rapid growth, and its product is nuclear localized with nucleolus enrichment. Furthermore, DIM1A preferentially accumulates in the developing hair cells, and the dim1A point mutant alters the cell-specific expression of the transcriptional regulators GLABRA2, CAPRICE, and WEREWOLF. Together, these findings suggest that establishment of cell-specific gene expression during root epidermis development is dependent upon proper ribosome biogenesis, possibly due to the sensitivity of the cell fate decision to relatively small differences in gene regulatory activities. Consistent with its effect on the predicted S-adenosyl-l-Met binding site, dim1A plants lack the two 18S rRNA base modifications but exhibit normal pre-rRNA processing. In addition to root epidermal defects, the dim1A mutant exhibits abnormal root meristem division, leaf development, and trichome branching. Together, these findings provide new insights into the importance of rRNA base modifications and translation regulation for plant growth and development.

  17. Arabidopsis: an adequate model for dicot root systems?

    OpenAIRE

    Zobel, Richard W.

    2016-01-01

    The Arabidopsis root system is frequently considered to have only three classes of root: primary, lateral, and adventitious. Research with other plant species has suggested up to 8 different developmental/functional classes of root for a given plant root system. If Arabidopsis has only three classes of root, it may not be an adequate model for eudicot plant root systems. Recent research, however, can be interpreted to suggest that pre-flowering Arabidopsis does have at least five (5) of th...

  18. Arabidopsis: An Adequate Model for Dicot Root Systems?

    OpenAIRE

    Zobel, Richard W.

    2016-01-01

    The Arabidopsis root system is frequently considered to have only three classes of root: primary, lateral, and adventitious. Research with other plant species has suggested up to eight different developmental/functional classes of root for a given plant root system. If Arabidopsis has only three classes of root, it may not be an adequate model for eudicot plant root systems. Recent research, however, can be interpreted to suggest that pre-flowering Arabidopsis does have at least five (5) of t...

  19. Identification of MicroRNA 395a in 24-Epibrassinolide-Regulated Root Growth of Arabidopsis thaliana Using MicroRNA Arrays

    Directory of Open Access Journals (Sweden)

    Hsueh-Fen Juan

    2013-07-01

    Full Text Available Brassinosteroids (BRs are endogenous plant hormones and are essential for normal plant growth and development. MicroRNAs (miRNAs of Arabidopsis thaliana are involved in mediating cell proliferation in leaves, stress tolerance, and root development. The specifics of BR mechanisms involving miRNAs are unknown. Using customized miRNA array analysis, we identified miRNAs from A. thaliana ecotype Columbia (Col-0 regulated by 24-epibrassinolide (EBR, a highly active BR. We found that miR395a was significantly up-regulated by EBR treatment and validated its expression under these conditions. miR395a was over expressed in leaf veins and root tissues in EBR-treated miR395a promoter::GUS plants. We integrated bioinformatics methods and publicly available DNA microarray data to predict potential targets of miR395a. GUN5—a multifunctional protein involved in plant metabolic functions such as chlorophyll synthesis and the abscisic acid (ABA pathway—was identified as a possible target. ABI4 and ABI5, both genes positively regulated by ABA, were down-regulated by EBR treatment. In summary, our results suggest that EBR regulates seedling development and root growth of A. thaliana through miR395a by suppressing GUN5 expression and its downstream signal transduction.

  20. Identification and characterization of Arabidopsis AtNUDX9 as a GDP-d-mannose pyrophosphohydrolase: its involvement in root growth inhibition in response to ammonium.

    Science.gov (United States)

    Tanaka, Hiroyuki; Maruta, Takanori; Ogawa, Takahisa; Tanabe, Noriaki; Tamoi, Masahiro; Yoshimura, Kazuya; Shigeoka, Shigeru

    2015-09-01

    GDP-d-mannose (GDP-d-Man) is an important intermediate in ascorbic acid (AsA) synthesis, cell wall synthesis, protein N-glycosylation, and glycosylphosphatidylinositol-anchoring in plants. Thus, the modulation of intracellular levels of GDP-d-Man could be important for maintaining various cellular processes. Here an Arabidopsis GDP-d-Man pyrophosphohydrolase, AtNUDX9 (AtNUDT9; At3g46200), which hydrolysed GDP-d-Man to GMP and mannose 1-phosphate, was identified. The K m and V max values for GDP-d-Man of AtNUDX9 were 376±24 μM and 1.61±0.15 μmol min(-1) mg(-1) protein, respectively. Among various tissues, the expression levels of AtNUDX9 and the total activity of GDP-d-Man pyrophosphohydrolase were the highest in the roots. The GDP-d-Man pyrophosphohydrolase activity was increased in the root of plants grown in the presence of ammonium. No difference was observed in the levels of AsA in the leaf and root tissues of the wild-type and knockout-nudx9 (KO-nudx9) plants, whereas a marked increase in N-glycoprotein levels and enhanced growth were detected in the roots of KO-nudx9 plants in the presence of ammonium. These results suggest that AtNUDX9 is involved in the regulation of GDP-d-Man levels affecting ammonium sensitivity via modulation of protein N-glycosylation in the roots.

  1. Constitutive salicylic acid accumulation in pi4kIIIβ1β2 Arabidopsis plants stunts rosette but not root growth.

    Science.gov (United States)

    Sašek, Vladimír; Janda, Martin; Delage, Elise; Puyaubert, Juliette; Guivarc'h, Anne; López Maseda, Encarnación; Dobrev, Petre I; Caius, José; Bóka, Károly; Valentová, Olga; Burketová, Lenka; Zachowski, Alain; Ruelland, Eric

    2014-08-01

    Phospholipids have recently been found to be integral elements of hormone signalling pathways. An Arabidopsis thaliana double mutant in two type III phosphatidylinositol-4-kinases (PI4Ks), pi4kIIIβ1β2, displays a stunted rosette growth. The causal link between PI4K activity and growth is unknown. Using microarray analysis, quantitative reverse transcription polymerase chain reaction (RT-qPCR) and multiple phytohormone analysis by LC-MS we investigated the mechanism responsible for the pi4kIIIβ1β2 phenotype. The pi4kIIIβ1β2 mutant accumulated a high concentration of salicylic acid (SA), constitutively expressed SA marker genes including PR-1, and was more resistant to Pseudomonas syringae. pi4kIIIβ1β2 was crossed with SA signalling mutants eds1 and npr1 and SA biosynthesis mutant sid2 and NahG. The dwarf phenotype of pi4kIIIβ1β2 rosettes was suppressed in all four triple mutants. Whereas eds1 pi4kIIIβ1β2, sid2 pi4kIIIβ1β2 and NahG pi4kIIIβ1β2 had similar amounts of SA as the wild-type (WT), npr1pi4kIIIβ1β2 had more SA than pi4kIIIβ1β2 despite being less dwarfed. This indicates that PI4KIIIβ1 and PI4KIIIβ2 are genetically upstream of EDS1 and need functional SA biosynthesis and perception through NPR1 to express the dwarf phenotype. The slow root growth phenotype of pi4kIIIβ1β2 was not suppressed in any of the triple mutants. The pi4kIIIβ1β2 mutations together cause constitutive activation of SA signalling that is responsible for the dwarf rosette phenotype but not for the short root phenotype.

  2. Piriformospora indica Stimulates Root Metabolism of Arabidopsis thaliana.

    Science.gov (United States)

    Strehmel, Nadine; Mönchgesang, Susann; Herklotz, Siska; Krüger, Sylvia; Ziegler, Jörg; Scheel, Dierk

    2016-01-01

    Piriformospora indica is a root-colonizing fungus, which interacts with a variety of plants including Arabidopsis thaliana. This interaction has been considered as mutualistic leading to growth promotion of the host. So far, only indolic glucosinolates and phytohormones have been identified as key players. In a comprehensive non-targeted metabolite profiling study, we analyzed Arabidopsis thaliana's roots, root exudates, and leaves of inoculated and non-inoculated plants by ultra performance liquid chromatography/electrospray ionization quadrupole-time-of-flight mass spectrometry (UPLC/(ESI)-QTOFMS) and gas chromatography/electron ionization quadrupole mass spectrometry (GC/EI-QMS), and identified further biomarkers. Among them, the concentration of nucleosides, dipeptides, oligolignols, and glucosinolate degradation products was affected in the exudates. In the root profiles, nearly all metabolite levels increased upon co-cultivation, like carbohydrates, organic acids, amino acids, glucosinolates, oligolignols, and flavonoids. In the leaf profiles, we detected by far less significant changes. We only observed an increased concentration of organic acids, carbohydrates, ascorbate, glucosinolates and hydroxycinnamic acids, and a decreased concentration of nitrogen-rich amino acids in inoculated plants. These findings contribute to the understanding of symbiotic interactions between plant roots and fungi of the order of Sebacinales and are a valid source for follow-up mechanistic studies, because these symbioses are particular and clearly different from interactions of roots with mycorrhizal fungi or dark septate endophytes. PMID:27399695

  3. SDG2-Mediated H3K4 Methylation Is Required for Proper Arabidopsis Root Growth and Development

    OpenAIRE

    Xiaozhen Yao; Haiyang Feng; Yu Yu; Aiwu Dong; Wen-Hui Shen

    2013-01-01

    Trithorax group (TrxG) proteins are evolutionarily conserved in eukaryotes and play critical roles in transcriptional activation via deposition of histone H3 lysine 4 trimethylation (H3K4me3) in chromatin. Several Arabidopsis TrxG members have been characterized, and among them SET DOMAIN GROUP 2 (SDG2) has been shown to be necessary for global genome-wide H3K4me3 deposition. Although pleiotropic phenotypes have been uncovered in the sdg2 mutants, SDG2 function in the regulation of stem cell ...

  4. Capturing Arabidopsis Root Architecture Dynamics with root-fit Reveals Diversity in Responses to Salinity1[W][OPEN

    Science.gov (United States)

    Julkowska, Magdalena M.; Hoefsloot, Huub C.J.; Mol, Selena; Feron, Richard; de Boer, Gert-Jan; Haring, Michel A.; Testerink, Christa

    2014-01-01

    The plant root is the first organ to encounter salinity stress, but the effect of salinity on root system architecture (RSA) remains elusive. Both the reduction in main root (MR) elongation and the redistribution of the root mass between MRs and lateral roots (LRs) are likely to play crucial roles in water extraction efficiency and ion exclusion. To establish which RSA parameters are responsive to salt stress, we performed a detailed time course experiment in which Arabidopsis (Arabidopsis thaliana) seedlings were grown on agar plates under different salt stress conditions. We captured RSA dynamics with quadratic growth functions (root-fit) and summarized the salt-induced differences in RSA dynamics in three growth parameters: MR elongation, average LR elongation, and increase in number of LRs. In the ecotype Columbia-0 accession of Arabidopsis, salt stress affected MR elongation more severely than LR elongation and an increase in LRs, leading to a significantly altered RSA. By quantifying RSA dynamics of 31 different Arabidopsis accessions in control and mild salt stress conditions, different strategies for regulation of MR and LR meristems and root branching were revealed. Different RSA strategies partially correlated with natural variation in abscisic acid sensitivity and different Na+/K+ ratios in shoots of seedlings grown under mild salt stress. Applying root-fit to describe the dynamics of RSA allowed us to uncover the natural diversity in root morphology and cluster it into four response types that otherwise would have been overlooked. PMID:25271266

  5. Effects of natural and synthetic auxins on the gravitropic growth habit of roots in two auxin-resistant mutants of Arabidopsis, axr1 and axr4: evidence for defects in the auxin influx mechanism of axr4

    Science.gov (United States)

    Yamamoto, M.; Yamamoto, K. T.

    1999-01-01

    The partially agravitropic growth habit of roots of an auxin-resistant mutant of Arabidopsis thaliana, axr4, was restored by the addition of 30-300 nM 1-naphthaleneacetic acid (NAA) to the growth medium. Neither indole 3-acetic acid (IAA) nor 2,4-dichlorophenoxyacetic acid (2,4-D) showed such an effect. Growth of axr4 roots was resistant to IAA and 2,4-D, but not at all to NAA. The differential effects of the three auxins suggest that the defects of axr4 result from a lower auxin influx into its cells. The partially agravitropic growth habit of axr1 roots, which was less severe than that of axr4 roots, was only slightly affected by the three auxins in the growth medium at concentrations up to 300 nM; growth of axr1 roots was resistant to all three of the auxins. These results suggest that the lesion of axrl mutants is different from that of axr4.

  6. Natural genetic variation in Arabidopsis for responsiveness to plant growth-promoting rhizobacteria

    OpenAIRE

    Wintermans, P.C.A.; Bakker, P.A.H.M.; Pieterse, C.M.J.

    2016-01-01

    The plant growth-promoting rhizobacterium (PGPR) Pseudomonas simiae WCS417r stimulates lateral root formation and increases shoot growth in Arabidopsis thaliana (Arabidopsis). These plant growth-stimulating effects are partly caused by volatile organic compounds (VOCs) produced by the bacterium. Here, we performed a genome-wide association (GWA) study on natural genetic variation in Arabidopsis for the ability to profit from rhizobacteria-mediated plant growth-promotion. To this end, 302 Arab...

  7. Natural genetic variation in Arabidopsis for responsiveness to plant growth-promoting rhizobacteria

    NARCIS (Netherlands)

    Wintermans, P.C.A.; Bakker, P.A.H.M.; Pieterse, C.M.J.

    2016-01-01

    The plant growth-promoting rhizobacterium (PGPR) Pseudomonas simiae WCS417r stimulates lateral root formation and increases shoot growth in Arabidopsis thaliana (Arabidopsis). These plant growth-stimulating effects are partly caused by volatile organic compounds (VOCs) produced by the bacterium. Her

  8. Genetic analysis of the gravitropic set-point angle in lateral roots of arabidopsis

    Science.gov (United States)

    Mullen, J. L.; Hangarter, R. P.

    2003-05-01

    Research on gravity responses in plants has mostly focused on primary roots and shoots, which typically orient to a vertical orientation. However, the distribution of lateral organs and their characteristically non-vertical growth orientation are critical for the determination of plant form. For example, in Arabidopsis, when lateral roots emerge from the primary root, they grow at a nearly horizontal orientation. As they elongate, the roots slowly curve until they eventually reach a vertical orientation. The regulation of this lateral root orientation is an important component affecting overall root system architecture. We found that this change in orientation is not simply due to the onset of gravitropic competence, as non-vertical lateral roots are capable of both positive and negative gravitropism. Thus, the horizontal growth of new lateral roots appears to be determined by what is called the gravitropic set-point angle (GSA). This developmental control of the GSA of lateral roots in Arabidopsis provides a useful system for investigating the components involved in regulating gravitropic responses. Using this system, we have identified several Arabidopsis mutants that have altered lateral root orientations but maintain normal primary root orientation.

  9. “Rhizoponics”: a novel hydroponic rhizotron for root system analyses on mature Arabidopsis thaliana plants

    OpenAIRE

    Mathieu, Laura; Lobet, Guillaume; Tocquin, Pierre; Périlleux, Claire

    2015-01-01

    Background Well-developed and functional roots are critical to support plant life and reach high crop yields. Their study however, is hampered by their underground growth and characterizing complex root system architecture (RSA) therefore remains a challenge. In the last few years, several phenotyping methods, including rhizotrons and x-ray computed tomography, have been developed for relatively thick roots. But in the model plant Arabidopsis thaliana, in vitro culture remains the easiest and...

  10. Glycerol Affects Root Development through Regulation of Multiple Pathways in Arabidopsis

    OpenAIRE

    Jun Hu; Yonghong Zhang; Jinfang Wang; Yongming Zhou

    2014-01-01

    Glycerol metabolism has been well studied biochemically. However, the means by which glycerol functions in plant development is not well understood. This study aimed to investigate the mechanism underlying the effects of glycerol on root development in Arabidopsis thaliana. Exogenous glycerol inhibited primary root growth and altered lateral root development in wild-type plants. These phenotypes appeared concurrently with increased endogenous glycerol-3-phosphate (G3P) and H2O2 contents in se...

  11. Phytochrome mediates red-light-based positive phototropism in Arabidopsis roots

    Science.gov (United States)

    Correll, M.; Mullen, J.; Hangarter, R.; Kiss, J.

    Plants rely on sophisticated mechanisms to interpret the constant bombardment of incoming signals so they can adjust their growth accordingly. The environmental cues of gravity and light are particularly important for plant growth and development. While gravitropism has been extensively studied in roots, there has been increased emphasis on understanding the cellular and molecular basis of root phototropism. In addition to the blue-light-based negative phototropism, roots also exhibit a recently discovered positive phototropism in response to red light. In this paper, we characterize this red-light-based phototropism in roots of Arabidopsis.

  12. Mechanical touch responses of Arabidopsis TCH1-3 mutant roots on inclined hard-agar surface

    Science.gov (United States)

    Zha, Guodong; Wang, Bochu; Liu, Junyu; Yan, Jie; Zhu, Liqing; Yang, Xingyan

    2016-01-01

    The gravity-induced mechanical touch stimulus can affect plant root architecture. Mechanical touch responses of plant roots are an important aspect of plant root growth and development. Previous studies have reported that Arabidopsis TCH1-3 genes are involved in mechano-related events, how-ever, the physiological functions of TCH1-3 genes in Arabidopsis root mechanoresponses remain unclear. In the present study, we applied an inclined hard agar plate method to produce mechanical touch stimulus, and provided evidence that altered mechanical environment could influence root growth. Furthermore, tch1-3 Arabidopsis mutants were investigated on inclined agar surfaces to explore the functions of TCH1-3 genes on Arabidopsis root mechanoresponses. The results showed that two tch2 mutants, cml24-2 and cml24-4, exhibited significantly reduced root length, biased skewing, and decreased density of lateral root. In addition, primary root length and density of lateral root of tch3 (cml12-2) was significantly decreased on inclined agar surfaces. This study indicates that the tch2 and tch3 mutants are hypersensitive to mechanical touch stimulus, and TCH2 (CML24-2 and CML24-4) and TCH3 (CML12-2) genes may participate in the mechanical touch response of Arabidopsis roots.

  13. Control of root meristem size by DA1-RELATED PROTEIN2 in Arabidopsis.

    Science.gov (United States)

    Peng, Yuancheng; Ma, Wenying; Chen, Liangliang; Yang, Lei; Li, Shengjun; Zhao, Hongtao; Zhao, Yankun; Jin, Weihuan; Li, Na; Bevan, Michael W; Li, Xia; Tong, Yiping; Li, Yunhai

    2013-03-01

    The control of organ growth by coordinating cell proliferation and differentiation is a fundamental developmental process. In plants, postembryonic root growth is sustained by the root meristem. For maintenance of root meristem size, the rate of cell differentiation must equal the rate of cell division. Cytokinin and auxin interact to affect the cell proliferation and differentiation balance and thus control root meristem size. However, the genetic and molecular mechanisms that determine root meristem size still remain largely unknown. Here, we report that da1-related protein2 (dar2) mutants produce small root meristems due to decreased cell division and early cell differentiation in the root meristem of Arabidopsis (Arabidopsis thaliana). dar2 mutants also exhibit reduced stem cell niche activity in the root meristem. DAR2 encodes a Lin-11, Isl-1, and Mec-3 domain-containing protein and shows an expression peak in the border between the transition zone and the elongation zone. Genetic analyses show that DAR2 functions downstream of cytokinin and SHORT HYPOCOTYL2 to maintain normal auxin distribution by influencing auxin transport. Further results indicate that DAR2 acts through the PLETHORA pathway to influence root stem cell niche activity and therefore control root meristem size. Collectively, our findings identify the role of DAR2 in root meristem size control and provide a novel link between several key regulators influencing root meristem size.

  14. The secretion of the bacterial phytase PHY-US417 by Arabidopsis roots reveals its potential for increasing phosphate acquisition and biomass production during co-growth.

    Science.gov (United States)

    Belgaroui, Nibras; Berthomieu, Pierre; Rouached, Hatem; Hanin, Moez

    2016-09-01

    Phytic acid (PA) is a major source of inorganic phosphate (Pi) in the soil; however, the plant lacks the capacity to utilize it for Pi nutrition and growth. Microbial phytases constitute a group of enzymes that are able to remobilize Pi from PA. Thus, the use of these phytases to increase the capacity of higher plants to remobilize Pi from PA is of agronomical interest. In the current study, we generate transgenic Arabidopsis lines (ePHY) overexpressing an extracellular form of the phytase PHY-US417 of Bacillus subtilis, which are characterized by high levels of secreted phytase activity. In the presence of PA as sole source of Pi, while the wild-type plants show hallmark of Pi deficiency phenotypes, including the induction of the expression of Pi starvation-induced genes (PSI, e.g. PHT1;4) and the inhibition of growth capacity, the ePHY overexpressing lines show a higher biomass production and no PSI induction. Interestingly, when co-cultured with ePHY overexpressors, wild-type Arabidopsis plants (or tobacco) show repression of the PSI genes, improvement of Pi content and increases in biomass production. In line with these results, mutants in the high-affinity Pi transporters, namely pht1;1 and pht1;1-1;4, both fail to accumulate Pi and to grow when co-cultured with ePHY overexpressors. Taken together, these data demonstrate the potential of secreted phytases in improving the Pi content and enhancing growth of not only the transgenic lines but also the neighbouring plants. PMID:26914451

  15. Statistical modeling of nitrogen-dependent modulation of root system architecture in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Takao Araya; Takuya Kubo; Nicolaus von Wiren; Hideki Takahashi

    2016-01-01

    Plant root development is strongly affected by nutrient availability. Despite the importance of structure and function of roots in nutrient acquisition, statistical modeling approaches to evaluate dynamic and temporal modulations of root system architecture in response to nutrient availability have remained as widely open and exploratory areas in root biology. In this study, we developed a statistical modeling approach to investigate modulations of root system archi-tecture in response to nitrogen availability. Mathematical models were designed for quantitative assessment of root growth and root branching phenotypes and their dynamic relationships based on hierarchical configuration of primary and lateral roots formulating the fishbone-shaped root system architecture in Arabidopsis thaliana. Time-series datasets reporting dynamic changes in root developmental traits on different nitrate or ammonium concentrations were gener-ated for statistical analyses. Regression analyses unraveled key parameters associated with:(i) inhibition of primary root growth under nitrogen limitation or on ammonium;(i ) rapid progression of lateral root emergence in response to ammonium; and (i i) inhibition of lateral root elongation in the presence of excess nitrate or ammonium. This study provides a statistical framework for interpreting dynamic modulation of root system architecture, supported by meta-analysis of datasets displaying morphological responses of roots to diverse nitrogen supplies.

  16. ABA modulates root growth through regulating auxin in Arabidopsis thaliana%脱落酸通过影响生长素合成及分布抑制拟南芥主根伸长

    Institute of Scientific and Technical Information of China (English)

    袁冰剑; 张森磊; 曹萌萌; 王志娟; 李霞

    2014-01-01

    脱落酸(ABA)在介导植物生长发育及逆境响应中发挥重要功能,但ABA抑制根伸长的机制尚不清楚。本文以拟南芥为材料,通过研究 ABA 对拟南芥根伸长的影响以及 ABA 受体突变体根发育表型的鉴定,探讨ABA抑制植物主根的机制。研究发现:ABA能够抑制主根生长及伸长,并且经典受体PYR1/PRL介导了ABA抑制根伸长的过程;ABA能够改变细胞周期蛋白CycB1;1:GUS表达模式,并影响根中生长素分布和响应。结果表明, ABA可能通过影响生长素在根部的分布和剂量,进而影响根尖分生区细胞分裂,从而抑制根伸长。%As sessile organism, plants exhibit an amazing developmental plasticity in adapting to changing growth conditions in response to environmental stimuli. As an important organ of plants, roots variously make active changes in the face of different stimuli. It is well known that ABA (abscisic acid) is an important molecule that inhibits root growth. ABA receptor PYR1/PYL mediates ABA signaling transduction by binding with PP2C proteins and activating kinases SnRK2s. However, little is known about how ABA regulates root growth and plastic development. In order to understand the mechanism underlying root growth inhibition by ABA, the effects of ABA on the size and activity of root meristem, meristematic cell cycle, and auxin amount and distribution patterns were analyzed with Arabidopsis thaliana as materials. The results showed that ABA inhibited the growth of primary roots and reduced the size of meristems of primary roots. The inhibition effect of ABA on pyr1/pyl1/pyl2 root growth reduced, which showed that ABA receptor PYR1/PYL was involved in the inhibition of root growth. Further analysis showed that ABA treatment blocked G2/M-phase transition during cell division with the accumulation of cyclin protein CYCB1;1::GUS expression. In addition, we noted that the amounts and distribution patterns of auxin in the roots

  17. Phototropism and gravitropism in lateral roots of Arabidopsis.

    Science.gov (United States)

    Kiss, John Z; Miller, Kelley M; Ogden, Lisa A; Roth, Kelly K

    2002-01-01

    Gravitropism and, to a lesser extent, phototropism have been characterized in primary roots, but little is known about structural/functional aspects of these tropisms in lateral roots. Therefore, in this study, we report on tropistic responses in lateral roots of Arabidopsis thaliana. Lateral roots initially are plagiogravitropic, but when they reach a length of approximately 10 mm, these roots grow downward and exhibit positive orthogravitropism. Light and electron microscopic studies demonstrate a correlation between positive gravitropism and development of columella cells with large, sedimented amyloplasts in wild-type plants. Lateral roots display negative phototropism in response to white and blue light and positive phototropism in response to red light. As is the case with primary roots, the photoresponse is weak relative to the graviresponse, but phototropism is readily apparent in starchless mutant plants, which are impaired in gravitropism. To our knowledge, this is the first report of phototropism of lateral roots in any plant species.

  18. Amyloplasts are necessary for full gravitropic sensitivity in roots of Arabidopsis thaliana

    Science.gov (United States)

    Kiss, J. Z.; Hertel, R.; Sack, F. D.

    1989-01-01

    The observation that a starchless mutant (TC7) of Arabidopsis thaliana (L.) Heynh. is gravitropic (T. Caspar and B.G. Pickard, 1989, Planta 177, 185-197) raises questions about the hypothesis that starch and amyloplasts play a role in gravity perception. We compared the kinetics of gravitropism in this starchless mutant and the wild-type (WT). Wild-type roots are more responsive to gravity than TC7 roots as judged by several parameters: (1) Vertically grown TC7 roots were not as oriented with respect to the gravity vector as WT roots. (2) In the time course of curvature after gravistimulation, curvature in TC7 roots was delayed and reduced compared to WT roots. (3) TC7 roots curved less than WT roots following a single, short (induction) period of gravistimulation, and WT, but not TC7, roots curved in response to a 1-min period of horizontal exposure. (4) Wild-type roots curved much more than TC7 roots in response to intermittent stimulation (repeated short periods of horizontal exposure); WT roots curved in response to 10 s of stimulation or less, but TC7 roots required 2 min of stimulation to produce a curvature. The growth rates were equal for both genotypes. We conclude that WT roots are more sensitive to gravity than TC7 roots. Starch is not required for gravity perception in TC7 roots, but is necessary for full sensitivity; thus it is likely that amyloplasts function as statoliths in WT Arabidopsis roots. Furthermore, since centrifugation studies using low gravitational forces indicated that starchless plastids are relatively dense and are the most movable component in TC7 columella cells, the starchless plastids may also function as statoliths.

  19. Somatic Embryogenesis Receptor Kinases Control Root Development Mainly via Brassinosteroid Independent Actions in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Junbo Du; Hongju Yin; Shasha Zhang; ZhuoyunWei; Baolin Zhao; Jinghua Zhang; Xiaoping Gou; Honghui Lin; Jia Li

    2012-01-01

    Brassinosteroids (BRs),a group of plant steroidal hormones,play critical roles in many aspects of plant growth and development.Previous studies showed that BRI1-mediated BR signaling regulates cell division and differentiation during Arabidopsis root development via interplaying with auxin and other phytohormones.Arabidopsis somatic embryogenesis receptor-like kinases (SERKs),as co-receptors of BRI1,were found to play a fundamental role in an early activation step of BR signaling pathway.Here we report a novel function of SERKs in regulating Arabidopsis root development.Genetic analyses indicated that SERKs control root growth mainly via a BR-independent pathway.Although BR signaling pathway is completely disrupted in the serk1 bak1 bkk1 triple mutant,the root growth of the triple mutant is much severely damaged than the BR deficiency or signaling null mutants.More detailed analyses indicated that the triple mutant exhibited drastically reduced expression of a number of genes critical to polar auxin transport,cell cycle,endodermis development and root meristem differentiation,which were not observed in null BR biosynthesis mutant cpd and null BR signaling mutant bri1-701.

  20. Regulation of Arabidopsis root development by small signaling peptides

    Directory of Open Access Journals (Sweden)

    Christina eDelay

    2013-09-01

    Full Text Available Plant root systems arise de novo from a single embryonic root. Complex and highly coordinated developmental networks are required to ensure the formation of lateral organs maximises plant fitness. The Arabidopsis root is well suited to dissection of regulatory and developmental networks due to its highly ordered, predictable structure. A myriad of regulatory signalling networks control the development of plant roots, from the classical hormones such as auxin and cytokinin to short-range positional signalling molecules that relay information between neighbouring cells. Small signaling peptides are a growing class of regulatory molecules involved in many aspects of root development including meristem maintenance, the gravitropic response, lateral root development and vascular formation. Here, recent findings on the roles of regulatory peptides in these aspects of root development are discussed.

  1. Effects of externally supplied protein on root morphology and biomass allocation in Arabidopsis.

    Science.gov (United States)

    Lonhienne, Thierry G A; Trusov, Yuri; Young, Anthony; Rentsch, Doris; Näsholm, Torgny; Schmidt, Susanne; Paungfoo-Lonhienne, Chanyarat

    2014-01-01

    Growth, morphogenesis and function of roots are influenced by the concentration and form of nutrients present in soils, including low molecular mass inorganic N (IN, ammonium, nitrate) and organic N (ON, e.g. amino acids). Proteins, ON of high molecular mass, are prevalent in soils but their possible effects on roots have received little attention. Here, we investigated how externally supplied protein of a size typical of soluble soil proteins influences root development of axenically grown Arabidopsis. Addition of low to intermediate concentrations of protein (bovine serum albumen, BSA) to IN-replete growth medium increased root dry weight, root length and thickness, and root hair length. Supply of higher BSA concentrations inhibited root development. These effects were independent of total N concentrations in the growth medium. The possible involvement of phytohormones was investigated using Arabidopsis with defective auxin (tir1-1 and axr2-1) and ethylene (ein2-1) responses. That no phenotype was observed suggests a signalling pathway is operating independent of auxin and ethylene responses. This study expands the knowledge on N form-explicit responses to demonstrate that ON of high molecular mass elicits specific responses. PMID:24852366

  2. MASSUGU2 encodes Aux/IAA19, an auxin-regulated protein that functions together with the transcriptional activator NPH4/ARF7 to regulate differential growth responses of hypocotyl and formation of lateral roots in Arabidopsis thaliana.

    Science.gov (United States)

    Tatematsu, Kiyoshi; Kumagai, Satoshi; Muto, Hideki; Sato, Atsuko; Watahiki, Masaaki K; Harper, Reneé M; Liscum, Emmanuel; Yamamoto, Kotaro T

    2004-02-01

    We have isolated a dominant, auxin-insensitive mutant of Arabidopsis thaliana, massugu2 (msg2), that displays neither hypocotyl gravitropism nor phototropism, fails to maintain an apical hook as an etiolated seedling, and is defective in lateral root formation. Yet other aspects of growth and development of msg2 plants are almost normal. These characteristics of msg2 are similar to those of another auxin-insensitive mutant, non-phototropic hypocotyl4 (nph4), which is a loss-of-function mutant of AUXIN RESPONSE FACTOR7 (ARF7) (Harper et al., 2000). Map-based cloning of the MSG2 locus reveals that all four mutant alleles result in amino acid substitutions in the conserved domain II of an Auxin/Indole-3-Acetic Acid protein, IAA19. Interestingly, auxin inducibility of MSG2/IAA19 gene expression is reduced by 65% in nph4/arf7. Moreover, MSG2/IAA19 protein binds to the C-terminal domain of NPH4/ARF7 in a Saccharomyces cerevisiae (yeast) two-hybrid assay and to the whole latter protein in vitro by pull-down assay. These results suggest that MSG2/IAA19 and NPH4/ARF7 may constitute a negative feedback loop to regulate differential growth responses of hypocotyls and lateral root formation.

  3. Abscisic acid is a negative regulator of root gravitropism in Arabidopsis thaliana.

    Science.gov (United States)

    Han, Woong; Rong, Honglin; Zhang, Hanma; Wang, Myeong-Hyeon

    2009-01-23

    The plant hormone abscisic acid (ABA) plays a role in root gravitropism and has led to an intense debate over whether ABA acts similar to auxin by translating the gravitational signal into directional root growth. While tremendous advances have been made in the past two decades in establishing the role of auxin in root gravitropism, little progress has been made in characterizing the role of ABA in this response. In fact, roots of plants that have undetectable levels of ABA and that display a normal gravitropic response have raised some serious doubts about whether ABA plays any role in root gravitropism. Here, we show strong evidence that ABA plays a role opposite to that of auxin and that it is a negative regulator of the gravitropic response of Arabidopsis roots.

  4. Effects of elevated carbon dioxide and sucrose concentrations on Arabidopsis thaliana root architecture and anatomy

    Energy Technology Data Exchange (ETDEWEB)

    Lee-Ho, E.; Walton, L.J.; Reid, D.M.; Yeung, E.C.; Kurepin, L.V. [Calgary Univ., AB (Canada). Dept. of Biology

    2007-03-15

    Plant root growth is known to be influenced by higher levels of atmospheric carbon dioxide (CO{sub 2}). Roots of some species grown in hydroponics under elevated CO{sub 2} concentrations may be more competitive sinks for photosynthetic assimilates than roots grown under lower CO{sub 2} conditions. Root branching patterns may also be influenced by elevated CO{sub 2} concentrations. Studies have also shown that factors such as soil compaction, salinity and the availability of nitrate, phosphorous, oxygen and water also influence root growth, and the effects of higher CO{sub 2} on roots can be confounded by such environmental factors. This study evaluated the effects of elevated carbon dioxide and sucrose concentrations on Arabidopsis thaliana root growth, morphology, and architecture. Both ambient and elevated CO{sub 2} levels were used along with various sucrose concentrations. The study revealed that A. thaliana plants grown on a phytagar medium in small chambers with elevated CO{sub 2} had longer roots, more lateral root growth than plants grown in ambient CO{sub 2}. Roots in elevated CO{sub 2} were found to have wider root diameters, and more secondary growth. The addition of sucrose to the media closely resembled the effects of elevated CO{sub 2}. In addition, the increase in sucrose concentration had a bigger effect on root morphology under ambient, than elevated CO{sub 2}. Therefore, both elevated CO{sub 2} and increased sucrose concentrations promote root growth by increasing their number, length, and diameter. The dichotomy branching index (DBI) also dropped resulting in a more dichotomous branching pattern. 34 refs., 5 figs.

  5. Natural genetic variation in Arabidopsis for responsiveness to plant growth-promoting rhizobacteria.

    Science.gov (United States)

    Wintermans, Paul C A; Bakker, Peter A H M; Pieterse, Corné M J

    2016-04-01

    The plant growth-promoting rhizobacterium (PGPR) Pseudomonas simiae WCS417r stimulates lateral root formation and increases shoot growth in Arabidopsis thaliana (Arabidopsis). These plant growth-stimulating effects are partly caused by volatile organic compounds (VOCs) produced by the bacterium. Here, we performed a genome-wide association (GWA) study on natural genetic variation in Arabidopsis for the ability to profit from rhizobacteria-mediated plant growth-promotion. To this end, 302 Arabidopsis accessions were tested for root architecture characteristics and shoot fresh weight in response to exposure to WCS417r. Although virtually all Arabidopsis accessions tested responded positively to WCS417r, there was a large variation between accessions in the increase in shoot fresh weight, the extra number of lateral roots formed, and the effect on primary root length. Correlation analyses revealed that the bacterially-mediated increase in shoot fresh weight is related to alterations in root architecture. GWA mapping for WCS417r-stimulated changes in root and shoot growth characteristics revealed 10 genetic loci highly associated with the responsiveness of Arabidopsis to the plant growth-promoting activity of WCS417r. Several of the underlying candidate genes have been implicated in important plant growth-related processes. These results demonstrate that plants possess natural genetic variation for the capacity to profit from the plant growth-promoting function of a beneficial rhizobacterium in their rhizosphere. This knowledge is a promising starting point for sustainable breeding strategies for future crops that are better able to maximize profitable functions from their root microbiome.

  6. Natural genetic variation in Arabidopsis for responsiveness to plant growth-promoting rhizobacteria.

    Science.gov (United States)

    Wintermans, Paul C A; Bakker, Peter A H M; Pieterse, Corné M J

    2016-04-01

    The plant growth-promoting rhizobacterium (PGPR) Pseudomonas simiae WCS417r stimulates lateral root formation and increases shoot growth in Arabidopsis thaliana (Arabidopsis). These plant growth-stimulating effects are partly caused by volatile organic compounds (VOCs) produced by the bacterium. Here, we performed a genome-wide association (GWA) study on natural genetic variation in Arabidopsis for the ability to profit from rhizobacteria-mediated plant growth-promotion. To this end, 302 Arabidopsis accessions were tested for root architecture characteristics and shoot fresh weight in response to exposure to WCS417r. Although virtually all Arabidopsis accessions tested responded positively to WCS417r, there was a large variation between accessions in the increase in shoot fresh weight, the extra number of lateral roots formed, and the effect on primary root length. Correlation analyses revealed that the bacterially-mediated increase in shoot fresh weight is related to alterations in root architecture. GWA mapping for WCS417r-stimulated changes in root and shoot growth characteristics revealed 10 genetic loci highly associated with the responsiveness of Arabidopsis to the plant growth-promoting activity of WCS417r. Several of the underlying candidate genes have been implicated in important plant growth-related processes. These results demonstrate that plants possess natural genetic variation for the capacity to profit from the plant growth-promoting function of a beneficial rhizobacterium in their rhizosphere. This knowledge is a promising starting point for sustainable breeding strategies for future crops that are better able to maximize profitable functions from their root microbiome. PMID:26830772

  7. Red-light-induced positive phototropism in Arabidopsis roots.

    Science.gov (United States)

    Ruppel, N J; Hangarter, R P; Kiss, J Z

    2001-02-01

    The interaction between light and gravity is critical in determining the final form of a plant. For example, the competing activities of gravitropism and phototropism can determine the final orientation of a stem or root. The results reported here indicate that, in addition to the previously described blue-light-dependent negative phototropic response in roots, roots of Arahidopsis thaliana (L.) Heynh. display a previously unknown red-light-dependent positive phototropic response. Both phototropic responses in roots are considerably weaker than the graviresponse, which often masks phototropic curvature. However, through the use of mutant strains with impaired gravitropism, we were able to identify a red-light-dependent positive phototropic response in Arabidopsis roots. The red-induced positive phototropic response is considerably weaker than the blue-light response and is barely detectable in plants with a normal gravitropic response.

  8. Bacterial Traits Involved in Colonization of Arabidopsis thaliana Roots by Bacillus amyloliquefaciens FZB42.

    Science.gov (United States)

    Dietel, Kristin; Beator, Barbara; Budiharjo, Anto; Fan, Ben; Borriss, Rainer

    2013-03-01

    Colonization studies previously performed with a green-fluorescent-protein, GFP, labeled derivative of Bacillus amyloliquefaciens FZB42 revealed that the bacterium behaved different in colonizing surfaces of plant roots of different species (Fan et al., 2012). In order to extend these studies and to elucidate which genes are crucial for root colonization, we applied targeted mutant strains to Arabidopsis seedlings. The fates of root colonization in mutant strains impaired in synthesis of alternative sigma factors, non-ribosomal synthesis of lipopeptides and polyketides, biofilm formation, swarming motility, and plant growth promoting activity were analyzed by confocal laser scanning microscopy. Whilst the wild-type strain heavily colonized surfaces of root tips and lateral roots, the mutant strains were impaired in their ability to colonize root tips and most of them were unable to colonize lateral roots. Ability to colonize plant roots is not only dependent on the ability to form biofilms or swarming motility. Six mutants, deficient in abrB-, sigH-, sigD-, nrfA-, yusV and RBAM017410, but not affected in biofilm formation, displayed significantly reduced root colonization. The nrfA- and yusV-mutant strains colonized border cells and, partly, root surfaces but did not colonize root tips or lateral roots.

  9. Piriformospora indica antagonizes cyst nematode infection and development in Arabidopsis roots

    OpenAIRE

    Daneshkhah, R.; Cabello, S.; Rozanska, E.; Sobczak, M.; Grundler, F. M. W.; Wieczorek, K.; Hofmann, J.

    2013-01-01

    The beneficial endophytic fungus Piriformospora indica colonizes the roots of many plant species, including the model plant Arabidopsis thaliana. Its colonization promotes plant growth, development, and seed production as well as resistance to various biotic and abiotic stresses. In the present work, P. indica was tested as potential antagonist of the sedentary plant-parasitic nematode Heterodera schachtii. This biotrophic cyst-forming nematode induces severe host plant damage by changing the...

  10. Water Deficit Enhances C Export to the Roots in Arabidopsis thaliana Plants with Contribution of Sucrose Transporters in Both Shoot and Roots.

    Science.gov (United States)

    Durand, Mickaël; Porcheron, Benoît; Hennion, Nils; Maurousset, Laurence; Lemoine, Rémi; Pourtau, Nathalie

    2016-03-01

    Root high plasticity is an adaptation to its changing environment. Water deficit impairs growth, leading to sugar accumulation in leaves, part of which could be available to roots via sucrose (Suc) phloem transport. Phloem loading is widely described in Arabidopsis (Arabidopsis thaliana), while unloading in roots is less understood. To gain information on leaf-to-root transport, a soil-based culture system was developed to monitor root system architecture in two dimensions. Under water deficit (50% of soil water-holding capacity), total root length was strongly reduced but the depth of root foraging and the shape of the root system were less affected, likely to improve water uptake. (14)CO2 pulse-chase experiments confirmed that water deficit enhanced carbon (C) export to the roots, as suggested by the increased root-to-shoot ratio. The transcript levels of AtSWEET11 (for sugar will eventually be exported transporter), AtSWEET12, and AtSUC2 (for Suc carrier) genes, all three involved in Suc phloem loading, were significantly up-regulated in leaves of water deficit plants, in accordance with the increase in C export from the leaves to the roots. Interestingly, the transcript levels of AtSUC2 and AtSWEET11 to AtSWEET15 were also significantly higher in stressed roots, underlying the importance of Suc apoplastic unloading in Arabidopsis roots and a putative role for these Suc transporters in Suc unloading. These data demonstrate that, during water deficit, plants respond to growth limitation by allocating relatively more C to the roots to maintain an efficient root system and that a subset of Suc transporters is potentially involved in the flux of C to and in the roots. PMID:26802041

  11. A no hydrotropic response root mutant that responds positively to gravitropism in Arabidopsis.

    Science.gov (United States)

    Eapen, Delfeena; Barroso, María Luisa; Campos, María Eugenia; Ponce, Georgina; Corkidi, Gabriel; Dubrovsky, Joseph G; Cassab, Gladys I

    2003-02-01

    For most plants survival depends upon the capacity of root tips to sense and move towards water and other nutrients in the soil. Because land plants cannot escape environmental stress they use developmental solutions to remodel themselves in order to better adapt to the new conditions. The primary site for perception of underground signals is the root cap (RC). Plant roots have positive hydrotropic response and modify their growth direction in search of water. Using a screening system with a water potential gradient, we isolated a no hydrotropic response (nhr) semi-dominant mutant of Arabidopsis that continued to grow downwardly into the medium with the lowest water potential contrary to the positive hydrotropic and negative gravitropic response seen in wild type-roots. The lack of hydrotropic response of nhr1 roots was confirmed in a system with a gradient in air moisture. The root gravitropic response of nhr1 seedlings was significantly faster in comparison with those of wild type. The frequency of the waving pattern in nhr1 roots was increased compared to those of wild type. nhr1 seedlings had abnormal root cap morphogenesis and reduced root growth sensitivity to abscisic acid (ABA) and the polar auxin transport inhibitor N-(1-naphtyl)phtalamic acid (NPA). These results showed that hydrotropism is amenable to genetic analysis and that an ABA signaling pathway participates in sensing water potential gradients through the root cap.

  12. Shoot-supplied ammonium targets the root auxin influx carrier AUX1 and inhibits lateral root emergence in Arabidopsis

    KAUST Repository

    Li, Baohai

    2011-03-24

    Deposition of ammonium (NH4 +) from the atmosphere is a substantial environmental problem. While toxicity resulting from root exposure to NH4 + is well studied, little is known about how shoot-supplied ammonium (SSA) affects root growth. In this study, we show that SSA significantly affects lateral root (LR) development. We show that SSA inhibits lateral root primordium (LRP) emergence, but not LRP initiation, resulting in significantly impaired LR number. We show that the inhibition is independent of abscisic acid (ABA) signalling and sucrose uptake in shoots but relates to the auxin response in roots. Expression analyses of an auxin-responsive reporter, DR5:GUS, and direct assays of auxin transport demonstrated that SSA inhibits root acropetal (rootward) auxin transport while not affecting basipetal (shootward) transport or auxin sensitivity of root cells. Mutant analyses indicated that the auxin influx carrier AUX1, but not the auxin efflux carriers PIN-FORMED (PIN)1 or PIN2, is required for this inhibition of LRP emergence and the observed auxin response. We found that AUX1 expression was modulated by SSA in vascular tissues rather than LR cap cells in roots. Taken together, our results suggest that SSA inhibits LRP emergence in Arabidopsis by interfering with AUX1-dependent auxin transport from shoot to root. © 2011 Blackwell Publishing Ltd.

  13. In Vitro Morphogenesis of Arabidopsis to Search for Novel Endophytic Fungi Modulating Plant Growth.

    Directory of Open Access Journals (Sweden)

    Francesco Dovana

    Full Text Available Fungal endophytes have shown to affect plant growth and to confer stress tolerance to the host; however, effects of endophytes isolated from water plants have been poorly investigated. In this study, fungi isolated from stems (stem-E and roots (root-E of Mentha aquatica L. (water mint were identified, and their morphogenetic properties analysed on in vitro cultured Arabidopsis (L. Heynh., 14 and 21 days after inoculation (DAI. Nineteen fungi were analysed and, based on ITS analysis, 17 isolates showed to be genetically distinct. The overall effect of water mint endophytes on Arabidopsis fresh (FW and dry weight (DW was neutral and positive, respectively, and the increased DW, mainly occurring 14 DAI, was possibly related to plant defence mechanism. Only three fungi increased both FW and DW of Arabidopsis at 14 and 21 DAI, thus behaving as plant growth promoting (PGP fungi. E-treatment caused a reduction of root depth and primary root length in most cases and inhibition-to-promotion of root area and lateral root length, from 14 DAI. Only Phoma macrostoma, among the water mint PGP fungi, increased both root area and depth, 21 DAI. Root depth and area 14 DAI were shown to influence DWs, indicating that the extension of the root system, and thus nutrient uptake, was an important determinant of plant dry biomass. Reduction of Arabidopsis root depth occurred to a great extent when plants where treated with stem-E while root area decreased or increased under the effects of stem-E and root-E, respectively, pointing to an influence of the endophyte origin on root extension. M. aquatica and many other perennial hydrophytes have growing worldwide application in water pollution remediation. The present study provided a model for directed screening of endophytes able to modulate plant growth in the perspective of future field applications of these fungi.

  14. Root Architecture Diversity and Meristem Dynamics in Different Populations of Arabidopsis thaliana.

    Science.gov (United States)

    Aceves-García, Pamela; Álvarez-Buylla, Elena R; Garay-Arroyo, Adriana; García-Ponce, Berenice; Muñoz, Rodrigo; Sánchez, María de la Paz

    2016-01-01

    Arabidopsis thaliana has been an excellent model system for molecular genetic approaches to development and physiology. More recently, the potential of studying various accessions collected from diverse habitats has been started to exploit. Col-0 has been the best-studied accession but we now know that several traits show significant divergences among them. In this work, we focused in the root that has become a key system for development. We studied root architecture and growth dynamics of 12 Arabidopsis accessions. Our data reveal a wide variability in root architecture and root length among accessions. We also found variability in the root apical meristem (RAM), explained mainly by cell size at the RAM transition domain and possibly by peculiar forms of organization at the stem cell niche in some accessions. Contrary to Col-0 reports, in some accessions the RAM size not always explains the variations in the root length; indicating that elongated cell size could be more relevant in the determination of root length than the RAM size itself. This study contributes to investigations dealing with understanding the molecular and cellular basis of phenotypic variation, the role of plasticity on adaptation, and the developmental mechanisms that may restrict phenotypic variation in response to contrasting environmental conditions. PMID:27379140

  15. Quiescent center initiation in the Arabidopsis lateral root primordia is dependent on the SCARECROW transcription factor.

    Science.gov (United States)

    Goh, Tatsuaki; Toyokura, Koichi; Wells, Darren M; Swarup, Kamal; Yamamoto, Mayuko; Mimura, Tetsuro; Weijers, Dolf; Fukaki, Hidehiro; Laplaze, Laurent; Bennett, Malcolm J; Guyomarc'h, Soazig

    2016-09-15

    Lateral root formation is an important determinant of root system architecture. In Arabidopsis, lateral roots originate from pericycle cells, which undergo a program of morphogenesis to generate a new lateral root meristem. Despite its importance for root meristem organization, the onset of quiescent center (QC) formation during lateral root morphogenesis remains unclear. Here, we used live 3D confocal imaging to monitor cell organization and identity acquisition during lateral root development. Our dynamic observations revealed an early morphogenesis phase and a late meristem formation phase as proposed in the bi-phasic growth model. Establishment of lateral root QCs coincided with this developmental phase transition. QC precursor cells originated from the outer layer of stage II lateral root primordia, within which the SCARECROW (SCR) transcription factor was specifically expressed. Disrupting SCR function abolished periclinal divisions in this lateral root primordia cell layer and perturbed the formation of QC precursor cells. We conclude that de novo QC establishment in lateral root primordia operates via SCR-mediated formative cell division and coincides with the developmental phase transition. PMID:27510971

  16. Physiological characterization and genetic modifiers of aberrant root thigmomorphogenesis in mutants of Arabidopsis thaliana MILDEW LOCUS O genes.

    Science.gov (United States)

    Bidzinski, Przemyslaw; Noir, Sandra; Shahi, Shermineh; Reinstädler, Anja; Gratkowska, Dominika Marta; Panstruga, Ralph

    2014-12-01

    Root architecture and growth patterns are plant features that are still poorly understood. When grown under in vitro conditions, seedlings with mutations in Arabidopsis thaliana genes MLO4 or MLO11 exhibit aberrant root growth patterns upon contact with hard surfaces, exemplified as tight root spirals. We used a set of physiological assays and genetic tools to characterize this thigmomorphogenic defect in detail. We observed that the mlo4/mlo11-associated root curling phenotype is not recapitulated in a set of mutants with altered root growth patterns or architecture. We further found that mlo4/mlo11-conditioned root curling is not dependent upon light and endogenous flavonoids, but is pH-sensitive and affected by exogenous calcium levels. Based upon the latter two characteristics, mlo4-associated root coiling appears to be mechanistically different from the natural strong root curvature of the Arabidopsis ecotype Landsberg erecta. Gravistimulation reversibly overrides the aberrant thigmomorphogenesis of mlo4 seedlings. Mutants with dominant negative defects in α-tubulin modulate the extent and directionality of mlo4/mlo11-conditioned root coils, whereas mutants defective in polar auxin transport (axr4, aux1) or gravitropism (pgm1) completely suppress the mlo4 root curling phenotype. Our data implicate a joint contribution of calcium signalling, pH regulation, microtubular function, polar auxin transport and gravitropism in root thigmomorphogenesis.

  17. Ethylene modulates flavonoid accumulation and gravitropic responses in roots of Arabidopsis.

    Science.gov (United States)

    Buer, Charles S; Sukumar, Poornima; Muday, Gloria K

    2006-04-01

    Plant organs change their growth direction in response to reorientation relative to the gravity vector. We explored the role of ethylene in Arabidopsis (Arabidopsis thaliana) root gravitropism. Treatment of wild-type Columbia seedlings with the ethylene precursor 1-aminocyclopropane carboxylic acid (ACC) reduced root elongation and gravitropic curvature. The ethylene-insensitive mutants ein2-5 and etr1-3 had wild-type root gravity responses, but lacked the growth and gravity inhibition by ACC found in the wild type. We examined the effect of ACC on tt4(2YY6) seedlings, which have a null mutation in the gene encoding chalcone synthase, the first enzyme in flavonoid synthesis. The tt4(2YY6) mutant makes no flavonoids, has elevated indole-3-acetic acid transport, and exhibits a delayed gravity response. Roots of tt4(2YY6), the backcrossed line tt4-2, and two other tt4 alleles had wild-type sensitivity to growth inhibition by ACC, whereas the root gravitropic curvature of these tt4 alleles was much less inhibited by ACC than wild-type roots, suggesting that ACC may reduce gravitropic curvature by altering flavonoid synthesis. ACC treatment induced flavonoid accumulation in root tips, as judged by a dye that becomes fluorescent upon binding flavonoids in wild type, but not in ein2-5 and etr1-3. ACC also prevented a transient peak in flavonoid synthesis in response to gravity. Together, these experiments suggest that elevated ethylene levels negatively regulate root gravitropism, using EIN2- and ETR1-dependent pathways, and that ACC inhibition of gravity response occurs through altering flavonoid synthesis. PMID:16489132

  18. An auxin-responsive endogenous peptide regulates root development in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Fengxi Yang; Yu Song; Hao Yang; Zhibin Liu; Genfa Zhu; Yi Yang

    2014-01-01

    Auxin plays critical roles in root formation and development. The components involved in this process, however, are not well understood. Here, we newly identified a peptide encoding gene, auxin-responsive endogenous polypeptide 1 (AREP1), which is induced by auxin, and mediates root development in Arabidopsis. Expression of AREP1 was specific to the cotyledon and to root and shoot meristem tissues. Amounts of AREP1 transcripts and AREP1-green fluorescent protein fusion proteins were elevated in response to indoleacetic acid treatment. Suppression of AREP1 through RNAi silencing resulted in reduction of primary root length, increase of lateral root number, and expansion of adventitious roots, compared to the observations in wild-type plants in the presence of auxin. By contrast, transgenic plants overexpressing AREP1 showed enhanced growth of the primary root under auxin treatment. Additionally, rootmorphology, including lateral root number and adventitious roots, differed greatly between transgenic and wildtype plants. Further analysis indicated that the expression of auxin-responsive genes, such as IAA3, IAA7, IAA17, GH3.2, GH3.3, and SAUR-AC1, was significantly higher in AREP1 RNAi plants, and was slightly lower in AREP1 overexpressing plants than in wildtype plants. These results suggest that the novel endogenous peptide AREP1 plays an important role in the process of auxinmediated root development.

  19. In Vitro Morphogenesis of Arabidopsis to Search for Novel Endophytic Fungi Modulating Plant Growth

    OpenAIRE

    Francesco Dovana; Marco Mucciarelli; Maurizio Mascarello; Anna Fusconi

    2015-01-01

    Fungal endophytes have shown to affect plant growth and to confer stress tolerance to the host; however, effects of endophytes isolated from water plants have been poorly investigated. In this study, fungi isolated from stems (stem-E) and roots (root-E) of Mentha aquatica L. (water mint) were identified, and their morphogenetic properties analysed on in vitro cultured Arabidopsis (L.) Heynh., 14 and 21 days after inoculation (DAI). Nineteen fungi were analysed and, based on ITS analysis, 17 i...

  20. Integrating roots into a whole plant network of flowering time genes in Arabidopsis thaliana.

    Science.gov (United States)

    Bouché, Frédéric; D'Aloia, Maria; Tocquin, Pierre; Lobet, Guillaume; Detry, Nathalie; Périlleux, Claire

    2016-01-01

    Molecular data concerning the involvement of roots in the genetic pathways regulating floral transition are lacking. In this study, we performed global analyses of the root transcriptome in Arabidopsis in order to identify flowering time genes that are expressed in the roots and genes that are differentially expressed in the roots during the induction of flowering. Data mining of public microarray experiments uncovered that about 200 genes whose mutations are reported to alter flowering time are expressed in the roots (i.e. were detected in more than 50% of the microarrays). However, only a few flowering integrator genes passed the analysis cutoff. Comparison of root transcriptome in short days and during synchronized induction of flowering by a single 22-h long day revealed that 595 genes were differentially expressed. Enrichment analyses of differentially expressed genes in root tissues, gene ontology categories, and cis-regulatory elements converged towards sugar signaling. We concluded that roots are integrated in systemic signaling, whereby carbon supply coordinates growth at the whole plant level during the induction of flowering. This coordination could involve the root circadian clock and cytokinin biosynthesis as a feed forward loop towards the shoot. PMID:27352932

  1. Hormonal response and root architecture in Arabidopsis thaliana subjected to heavy metals

    Directory of Open Access Journals (Sweden)

    Antonella Vitti

    2014-05-01

    Full Text Available In this work, specific concentrations of cadmium, copper and zinc in double combination, were supplied for 12 days to growing seedlings of the model species Arabidopsis thaliana. Metal accumulation was measured in roots and shoots. Microscopic analyses revealed that root morphology was affected by metals, and that the root and shoot levels of indole-3-acetic acid, trans-zeatin riboside and dihydrozeatin riboside varied accordingly. Minor modifications in gibberellic acid levels occurred in the Zinc treatments, whereas abscisic acid level did not change after the exposition to metals. Reverse transcription polymerase chain reaction analysis of some genes involved in auxin and cytokinin synthesis (AtAAO, AtNIT and AtIPT revealed that their expression were not affected by metal treatments. The root morphological alterations that resulted in an increased surface area, due to the formation of root hairs and lateral roots, could be signs of the response to metal stress in terms of a functionally-addressed reorientation of root growth. The root system plasticity observed could be important for better understanding the manner in which the root architecture is shaped by environmental and hormonal stimuli.

  2. 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

  3. In vivo localization in Arabidopsis protoplasts and root tissue.

    Science.gov (United States)

    Lee, Myoung Hui; Lee, Yongjik; Hwang, Inhwan

    2013-01-01

    In eukaryotic cells, a large number of proteins are transported to their final destination after translation by a process called intracellular trafficking. Transient gene expression, either in plant protoplasts or in specific plant tissues, is a fast, flexible, and reproducible approach to study the cellular function of proteins, protein subcellular localizations, and protein-protein interactions. Here we describe the general method of protoplast isolation, polyethylene glycol-mediated protoplast transformation and immunostaining of protoplast or intact root tissues for studying the localization of protein in Arabidopsis.

  4. Recent Advances in Understanding the Molecular Mechanisms Regulating the Root System Response to Phosphate Deficiency in Arabidopsis.

    Science.gov (United States)

    Bouain, Nadia; Doumas, Patrick; Rouached, Hatem

    2016-08-01

    Phosphorus (P) is an essential macronutrient for plant growth and development. Inorganic phosphate (Pi) is the major form of P taken up from the soil by plant roots. It is well established that under Pi deficiency condition, plant roots undergo striking morphological changes; mainly a reduction in primary root length while increase in lateral root length as well as root hair length and density. This typical phenotypic change reflects complex interactions with other nutrients such as iron, and involves the activity of a large spectrum of plant hormones. Although, several key proteins involved in the regulation of root growth under Pi-deficiency have been identified in Arabidopsis, how plants adapt roots system architecture in response to Pi availability remains an open question. In the current post-genomic era, state of the art technologies like high-throughput phenotyping and sequencing platforms,"omics" methods, together with the widespread use of system biology and genome-wide association studies will help to elucidate the genetic architectures of root growth on different Pi regimes. It is clear that the large-scale characterization of molecular systems will improve our understanding of nutrient stress phenotype and biology. Herein, we summarize the recent advances and future directions towards a better understanding of Arabidopsis root developmental programs functional under Pi deficiency. Such a progress is necessary to devise strategies to improve the Pi use efficiency in plants that is an important issue for agriculture. PMID:27499680

  5. Phytochromes play a role in phototropism and gravitropism in Arabidopsis roots

    Science.gov (United States)

    Correll, Melanie J.; Coveney, Katrina M.; Raines, Steven V.; Mullen, Jack L.; Hangarter, Roger P.; Kiss, John Z.

    2003-05-01

    Phototropism as well as gravitropism plays a role in the oriented growth of roots in flowering plants. In blue or white light, roots exhibit negative phototropism, but red light induces positive phototropism in Arabidopsis roots. Phytochrome A (phyA) and phyB mediate the positive red-light-based photoresponse in roots since single mutants (and the double phyAB mutant) were severely impaired in this response. In blue-light-based negative phototropism, phyA and phyAB (but not phyB) were inhibited in the response relative to the WT. In root gravitropism, phyB and phyAB (but not phyA) were inhibited in the response compared to the WT. The differences observed in tropistic responses were not due to growth limitations since the growth rates among all the mutants tested were not significantly different from that of the WT. Thus, our study shows that the blue-light and red-light systems interact in roots and that phytochrome plays a key role in plant development by integrating multiple environmental stimuli.

  6. Signaling in Arabidopsis roots in response to beneficial rhizobacteria

    NARCIS (Netherlands)

    Zamioudis, C

    2012-01-01

    Root colonization by selected strains of beneficial soil-resident bacteria is known to improve plant growth, influence root system architecture and trigger a systemic immune response that is effective against a broad range of pathogens, known as induced systemic resistance (ISR). In this thesis we e

  7. Arabidopsis Growth Simulation Using Image Processing Technology

    Directory of Open Access Journals (Sweden)

    Junmei Zhang

    2014-01-01

    Full Text Available This paper aims to provide a method to represent the virtual Arabidopsis plant at each growth stage. It includes simulating the shape and providing growth parameters. The shape is described with elliptic Fourier descriptors. First, the plant is segmented from the background with the chromatic coordinates. With the segmentation result, the outer boundary series are obtained by using boundary tracking algorithm. The elliptic Fourier analysis is then carried out to extract the coefficients of the contour. The coefficients require less storage than the original contour points and can be used to simulate the shape of the plant. The growth parameters include total area and the number of leaves of the plant. The total area is obtained with the number of the plant pixels and the image calibration result. The number of leaves is derived by detecting the apex of each leaf. It is achieved by using wavelet transform to identify the local maximum of the distance signal between the contour points and the region centroid. Experiment result shows that this method can record the growth stage of Arabidopsis plant with fewer data and provide a visual platform for plant growth research.

  8. Systems analysis of transcriptome data provides new hypotheses about Arabidopsis root response to nitrate treatments

    Directory of Open Access Journals (Sweden)

    Javier eCanales

    2014-02-01

    Full Text Available Nitrogen (N is an essential macronutrient for plant growth and development. Plants adapt to changes in N availability partly by changes in global gene expression. We integrated publicly available root microarray data under contrasting nitrate conditions to identify new genes and functions important for adaptive nitrate responses in Arabidopsis thaliana roots. Overall, more than two thousand genes exhibited changes in expression in response to nitrate treatments in Arabidopsis thaliana root organs. Global regulation of gene expression by nitrate depends largely on the experimental context. However, despite significant differences from experiment to experiment in the identity of regulated genes, there is a robust nitrate response of specific biological functions. Integrative gene network analysis uncovered relationships between nitrate-responsive genes and eleven highly co-expressed gene clusters (modules. Four of these gene network modules have robust nitrate responsive functions such as transport, signaling and metabolism. Network analysis hypothesized G2-like transcription factors are key regulatory factors controlling transport and signaling functions. Our meta-analysis highlights the role of biological processes not studied before in the context of the nitrate response such as root hair development and provides testable hypothesis to advance our understanding of nitrate responses in plants.

  9. Proteomic alterations in root tips of Arabidopsis thaliana seedlings under altered gravity conditions

    Science.gov (United States)

    Zheng, H. Q.; Wang, H.

    Gravity has a profound influence on plant growth and development Removed the influence of gravitational acceleration by spaceflight caused a wide range of cellular changes in plant Whole seedling that germinated and grown on clinostats showed the absent of gravitropism At the cellular level clinostat treatment has specific effects on plant cells such as induce alterations in cell wall composition increase production of heat-soluble proteins impact on the cellular energy metabolism facilitate a uniform distribution of plastids amyloplasts and increase number and volume of nucleoli A number of recent studies have shown that the exposure of Arabidopsis seedlings and callus cells to gravity stimulation hyper g-forces or clinostat rotation induces alterations in gene expression In our previous study the proteome of the Arabidopsis thaliana callus cells were separated by high resolution two-dimensional electrophoresis 2-DE Image analysis revealed that 80 protein spots showed quantitative and qualitative variations after exposure to clinostat rotation treatment We report here a systematic proteomic approach to investigate the altered gravity responsive proteins in root tip of Arabidopsis thaliana cv Landsberg erecta Three-day-old seedlings were exposed for 12h to a horizontal clinostat rotation H simulated weightlessness altered g-forces by centrifugation 7g hypergravity a vertical clinostat rotation V clinostat control or a stationary control grown conditions Total proteins of roots were extracted

  10. Analysis of gene expression during parabolic flights reveals distinct early gravity responses in Arabidopsis roots.

    Science.gov (United States)

    Aubry-Hivet, D; Nziengui, H; Rapp, K; Oliveira, O; Paponov, I A; Li, Y; Hauslage, J; Vagt, N; Braun, M; Ditengou, F A; Dovzhenko, A; Palme, K

    2014-01-01

    Plant roots are among most intensively studied biological systems in gravity research. Altered gravity induces asymmetric cell growth leading to root bending. Differential distribution of the phytohormone auxin underlies root responses to gravity, being coordinated by auxin efflux transporters from the PIN family. The objective of this study was to compare early transcriptomic changes in roots of Arabidopsis thaliana wild type, and pin2 and pin3 mutants under parabolic flight conditions and to correlate these changes to auxin distribution. Parabolic flights allow comparison of transient 1-g, hypergravity and microgravity effects in living organisms in parallel. We found common and mutation-related genes differentially expressed in response to transient microgravity phases. Gene ontology analysis of common genes revealed lipid metabolism, response to stress factors and light categories as primarily involved in response to transient microgravity phases, suggesting that fundamental reorganisation of metabolic pathways functions upstream of a further signal mediating hormonal network. Gene expression changes in roots lacking the columella-located PIN3 were stronger than in those deprived of the epidermis and cortex cell-specific PIN2. Moreover, repetitive exposure to microgravity/hypergravity and gravity/hypergravity flight phases induced an up-regulation of auxin responsive genes in wild type and pin2 roots, but not in pin3 roots, suggesting a critical function of PIN3 in mediating auxin fluxes in response to transient microgravity phases. Our study provides important insights towards understanding signal transduction processes in transient microgravity conditions by combining for the first time the parabolic flight platform with the transcriptome analysis of different genetic mutants in the model plant, Arabidopsis.

  11. Bacterial communities associated with the leaves and the roots of Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Natacha Bodenhausen

    Full Text Available Diverse communities of bacteria inhabit plant leaves and roots and those bacteria play a crucial role for plant health and growth. Arabidopsis thaliana is an important model to study plant pathogen interactions, but little is known about its associated bacterial community under natural conditions. We used 454 pyrosequencing to characterize the bacterial communities associated with the roots and the leaves of wild A. thaliana collected at 4 sites; we further compared communities on the outside of the plants with communities in the endophytic compartments. We found that the most heavily sequenced bacteria in A. thaliana associated community are related to culturable species. Proteobacteria, Actinobacteria, and Bacteroidetes are the most abundant phyla in both leaf and root samples. At the genus level, sequences of Massilia and Flavobacterium are prevalent in both samples. Organ (leaf vs root and habitat (epiphytes vs endophytes structure the community. In the roots, richness is higher in the epiphytic communities compared to the endophytic compartment (P = 0.024, while the reverse is true for the leaves (P = 0.032. Interestingly, leaf and root endophytic compartments do not differ in richness, diversity and evenness, while they differ in community composition (P = 0.001. The results show that although the communities associated with leaves and roots share many bacterial species, the associated communities differ in structure.

  12. SABRE is required for stabilization of root hair patterning in Arabidopsis thaliana.

    Science.gov (United States)

    Pietra, Stefano; Lang, Patricia; Grebe, Markus

    2015-03-01

    Patterned differentiation of distinct cell types is essential for the development of multicellular organisms. The root epidermis of Arabidopsis thaliana is composed of alternating files of root hair and non-hair cells and represents a model system for studying the control of cell-fate acquisition. Epidermal cell fate is regulated by a network of genes that translate positional information from the underlying cortical cell layer into a specific pattern of differentiated cells. While much is known about the genes of this network, new players continue to be discovered. Here we show that the SABRE (SAB) gene, known to mediate microtubule organization, anisotropic cell growth and planar polarity, has an effect on root epidermal hair cell patterning. Loss of SAB function results in ectopic root hair formation and destabilizes the expression of cell fate and differentiation markers in the root epidermis, including expression of the WEREWOLF (WER) and GLABRA2 (GL2) genes. Double mutant analysis reveal that wer and caprice (cpc) mutants, defective in core components of the epidermal patterning pathway, genetically interact with sab. This suggests that SAB may act on epidermal patterning upstream of WER and CPC. Hence, we provide evidence for a role of SAB in root epidermal patterning by affecting cell-fate stabilization. Our work opens the door for future studies addressing SAB-dependent functions of the cytoskeleton during root epidermal patterning.

  13. The root-specific glutamate decarboxylase (GAD1) is essential for sustaining GABA levels in Arabidopsis.

    Science.gov (United States)

    Bouché, Nicolas; Fait, Aaron; Zik, Moriyah; Fromm, Hillel

    2004-05-01

    In plants, as in most eukaryotes, glutamate decarboxylase catalyses the synthesis of GABA. The Arabidopsis genome contains five glutamate decarboxylase genes and one of these genes (glutamate decarboxylase1; i.e. GAD1 ) is expressed specifically in roots. By isolating and analyzing three gad1 T-DNA insertion alleles, derived from two ecotypes, we investigated the potential role of GAD1 in GABA production. We also analyzed a promoter region of the GAD1 gene and show that it confers root-specific expression when fused to reporter genes. Phenotypic analysis of the gad1 insertion mutants revealed that GABA levels in roots were drastically reduced compared with those in the wild type. The roots of the wild type contained about sevenfold more GABA than roots of the mutants. Disruption of the GAD1 gene also prevented the accumulation of GABA in roots in response to heat stress. Our results show that the root-specific calcium/calmodulin-regulated GAD1 plays a major role in GABA synthesis in plants under normal growth conditions and in response to stress.

  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. 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

  16. Beneficial Bacteria Isolated from Grapevine Inner Tissues Shape Arabidopsis thaliana Roots.

    Science.gov (United States)

    Baldan, Enrico; Nigris, Sebastiano; Romualdi, Chiara; D'Alessandro, Stefano; Clocchiatti, Anna; Zottini, Michela; Stevanato, Piergiorgio; Squartini, Andrea; Baldan, Barbara

    2015-01-01

    We investigated the potential plant growth-promoting traits of 377 culturable endophytic bacteria, isolated from Vitis vinifera cv. Glera, as good biofertilizer candidates in vineyard management. Endophyte ability in promoting plant growth was assessed in vitro by testing ammonia production, phosphate solubilization, indole-3-acetic acid (IAA) and IAA-like molecule biosynthesis, siderophore and lytic enzyme secretion. Many of the isolates were able to mobilize phosphate (33%), release ammonium (39%), secrete siderophores (38%) and a limited part of them synthetized IAA and IAA-like molecules (5%). Effects of each of the 377 grapevine beneficial bacteria on Arabidopsis thaliana root development were also analyzed to discern plant growth-promoting abilities (PGP) of the different strains, that often exhibit more than one PGP trait. A supervised model-based clustering analysis highlighted six different classes of PGP effects on root architecture. A. thaliana DR5::GUS plantlets, inoculated with IAA-producing endophytes, resulted in altered root growth and enhanced auxin response. Overall, the results indicate that the Glera PGP endospheric culturable microbiome could contribute, by structural root changes, to obtain water and nutrients increasing plant adaptation and survival. From the complete cultivable collection, twelve promising endophytes mainly belonging to the Bacillus but also to Micrococcus and Pantoea genera, were selected for further investigations in the grapevine host plants towards future application in sustainable management of vineyards. PMID:26473358

  17. Beneficial Bacteria Isolated from Grapevine Inner Tissues Shape Arabidopsis thaliana Roots.

    Directory of Open Access Journals (Sweden)

    Enrico Baldan

    Full Text Available We investigated the potential plant growth-promoting traits of 377 culturable endophytic bacteria, isolated from Vitis vinifera cv. Glera, as good biofertilizer candidates in vineyard management. Endophyte ability in promoting plant growth was assessed in vitro by testing ammonia production, phosphate solubilization, indole-3-acetic acid (IAA and IAA-like molecule biosynthesis, siderophore and lytic enzyme secretion. Many of the isolates were able to mobilize phosphate (33%, release ammonium (39%, secrete siderophores (38% and a limited part of them synthetized IAA and IAA-like molecules (5%. Effects of each of the 377 grapevine beneficial bacteria on Arabidopsis thaliana root development were also analyzed to discern plant growth-promoting abilities (PGP of the different strains, that often exhibit more than one PGP trait. A supervised model-based clustering analysis highlighted six different classes of PGP effects on root architecture. A. thaliana DR5::GUS plantlets, inoculated with IAA-producing endophytes, resulted in altered root growth and enhanced auxin response. Overall, the results indicate that the Glera PGP endospheric culturable microbiome could contribute, by structural root changes, to obtain water and nutrients increasing plant adaptation and survival. From the complete cultivable collection, twelve promising endophytes mainly belonging to the Bacillus but also to Micrococcus and Pantoea genera, were selected for further investigations in the grapevine host plants towards future application in sustainable management of vineyards.

  18. 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.

  19. Two seven-transmembrane domain MILDEW RESISTANCE LOCUS O proteins cofunction in Arabidopsis root thigmomorphogenesis.

    Science.gov (United States)

    Chen, Zhongying; Noir, Sandra; Kwaaitaal, Mark; Hartmann, H Andreas; Wu, Ming-Jing; Mudgil, Yashwanti; Sukumar, Poornima; Muday, Gloria; Panstruga, Ralph; Jones, Alan M

    2009-07-01

    Directional root expansion is governed by nutrient gradients, positive gravitropism and hydrotropism, negative phototropism and thigmotropism, as well as endogenous oscillations in the growth trajectory (circumnutation). Null mutations in phylogenetically related Arabidopsis thaliana genes MILDEW RESISTANCE LOCUS O 4 (MLO4) and MLO11, encoding heptahelical, plasma membrane-localized proteins predominantly expressed in the root tip, result in aberrant root thigmomorphogenesis. mlo4 and mlo11 mutant plants show anisotropic, chiral root expansion manifesting as tightly curled root patterns upon contact with solid surfaces. The defect in mlo4 and mlo11 mutants is nonadditive and dependent on light and nutrients. Genetic epistasis experiments demonstrate that the mutant phenotype is independently modulated by the Gbeta subunit of the heterotrimeric G-protein complex. Analysis of expressed chimeric MLO4/MLO2 proteins revealed that the C-terminal domain of MLO4 is necessary but not sufficient for MLO4 action in root thigmomorphogenesis. The expression of the auxin efflux carrier fusion, PIN1-green fluorescent protein, the pattern of auxin-induced gene expression, and acropetal as well as basipetal auxin transport are altered at the root tip of mlo4 mutant seedlings. Moreover, addition of auxin transport inhibitors or the loss of EIR1/AGR1/PIN2 function abolishes root curling of mlo4, mlo11, and wild-type seedlings. These results demonstrate that the exaggerated root curling phenotypes of the mlo4 and mlo11 mutants depend on auxin gradients and suggest that MLO4 and MLO11 cofunction as modulators of touch-induced root tropism.

  20. Root suberin forms an extracellular barrier that affects water relations and mineral nutrition in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Ivan Baxter

    2009-05-01

    Full Text Available Though central to our understanding of how roots perform their vital function of scavenging water and solutes from the soil, no direct genetic evidence currently exists to support the foundational model that suberin acts to form a chemical barrier limiting the extracellular, or apoplastic, transport of water and solutes in plant roots. Using the newly characterized enhanced suberin1 (esb1 mutant, we established a connection in Arabidopsis thaliana between suberin in the root and both water movement through the plant and solute accumulation in the shoot. Esb1 mutants, characterized by increased root suberin, were found to have reduced day time transpiration rates and increased water-use efficiency during their vegetative growth period. Furthermore, these changes in suberin and water transport were associated with decreases in the accumulation of Ca, Mn, and Zn and increases in the accumulation of Na, S, K, As, Se, and Mo in the shoot. Here, we present direct genetic evidence establishing that suberin in the roots plays a critical role in controlling both water and mineral ion uptake and transport to the leaves. The changes observed in the elemental accumulation in leaves are also interpreted as evidence that a significant component of the radial root transport of Ca, Mn, and Zn occurs in the apoplast.

  1. NPY Genes Play an Essential Role in Root Gravitropic Responses in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Yuanting Li; Xinhua Dai; Youfa Cheng; Yunde Zhao

    2011-01-01

    Plants can sense the direction of gravity and orient their growth to ensure that roots are anchored in soil and that shoots grow upward. Gravitropism has been studied extensively using Arabidopsis genetics, but the exact mechanisms for gravitropism are not fully understood. Here, we demonstrate that five NPY genes play a key role in Arabidopsis root gravitropism. NPY genes were previously identified as regulators of auxin-mediated organogenesis in way with the AGC kinases PID, PID2, WAG1, and WAG2. We show that all five NPY genes are highly expressdd in primary root tips. The single npy mutants do not display obvious gravitropism defects, but the npyl npy2 npy3 npy5 quinntuple mutants show dramatic gravitropic phenotypes. Systematic analysis of all the npy double, triple, and qudruple combinations demonstrates that the five NPY genes all contribute to gravitropism. Our work indicates that gravitropism,phototropism, and organogenesis use analogous mechanisms in which at least one AGC kinase, one NPH3/NPY gene, and one ARF are required.

  2. Inference of the Genetic Network Regulating Lateral Root Initiation in Arabidopsis thaliana

    KAUST Repository

    Muraro, D.

    2013-01-01

    Regulation of gene expression is crucial for organism growth, and it is one of the challenges in systems biology to reconstruct the underlying regulatory biological networks from transcriptomic data. The formation of lateral roots in Arabidopsis thaliana is stimulated by a cascade of regulators of which only the interactions of its initial elements have been identified. Using simulated gene expression data with known network topology, we compare the performance of inference algorithms, based on different approaches, for which ready-to-use software is available. We show that their performance improves with the network size and the inclusion of mutants. We then analyze two sets of genes, whose activity is likely to be relevant to lateral root initiation in Arabidopsis, and assess causality of their regulatory interactions by integrating sequence analysis with the intersection of the results of the best performing methods on time series and mutants. The methods applied capture known interactions between genes that are candidate regulators at early stages of development. The network inferred from genes significantly expressed during lateral root formation exhibits distinct scale free, small world and hierarchical properties and the nodes with a high out-degree may warrant further investigation. © 2004-2012 IEEE.

  3. 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

  4. Novel software for analysis of root gravitropism: comparative response patterns of Arabidopsis wild-type and axr1 seedlings

    Science.gov (United States)

    Ishikawa, H.; Evans, M. L.

    1997-01-01

    In an earlier study (Evans, Ishikawa & Estelle 1994, Planta 194, 215-222) we used a video digitizer system to compare the kinetics of auxin action on root elongation in wild-type seedlings and seedlings of auxin response mutants of Arabidopsis thaliana (L.) Heynh. We have since modified the system software to allow determination of elongation on opposite sides of vertical or gravistimulated roots and to allow continuous measurement of the angle of orientation of sequential subsections of the root during the response. We used this technology to compare the patterns of differential growth that generate curvature in roots of the Columbia ecotype and in the mutants axr1-3, axr1-12 and axr2, which show reduced gravitropic responsiveness and reduced sensitivity to inhibition by auxin. The pattern of differential growth during gravitropism differed in roots of wild-type and axr1 seedlings. In wild-type roots, initial curvature resulted from differential inhibition of elongation in the distal elongation zone (DEZ). This was followed by an acceleration of elongation along the top side of the DEZ. In roots of axr1-3, curvature resulted from differential stimulation of elongation whereas in roots of axr1-12 the response was variable. Roots of axr2 did not exhibit gravitropic curvature. The observation that the pattern of differential growth causing curvature is dramatically altered by a change in sensitivity to auxin is consistent with the classical Cholodny-Went theory of gravitropism which maintains that differential growth patterns induced by gravistimulation are mediated primarily by gravi-induced shifts in auxin distribution. The new technology introduced with this report allows automated determination of stimulus response patterns in the small but experimentally popular roots of Arabidopsis.

  5. New theories of root growth modelling

    Science.gov (United States)

    Landl, Magdalena; Schnepf, Andrea; Vanderborght, Jan; Huber, Katrin; Javaux, Mathieu; Bengough, A. Glyn; Vereecken, Harry

    2016-04-01

    In dynamic root architecture models, root growth is represented by moving root tips whose line trajectory results in the creation of new root segments. Typically, the direction of root growth is calculated as the vector sum of various direction-affecting components. However, in our simulations this did not reproduce experimental observations of root growth in structured soil. We therefore developed a new approach to predict the root growth direction. In this approach we distinguish between, firstly, driving forces for root growth, i.e. the force exerted by the root which points in the direction of the previous root segment and gravitropism, and, secondly, the soil mechanical resistance to root growth or penetration resistance. The latter can be anisotropic, i.e. depending on the direction of growth, which leads to a difference between the direction of the driving force and the direction of the root tip movement. Anisotropy of penetration resistance can be caused either by microscale differences in soil structure or by macroscale features, including macropores. Anisotropy at the microscale is neglected in our model. To allow for this, we include a normally distributed random deflection angle α to the force which points in the direction of the previous root segment with zero mean and a standard deviation σ. The standard deviation σ is scaled, so that the deflection from the original root tip location does not depend on the spatial resolution of the root system model. Similarly to the water flow equation, the direction of the root tip movement corresponds to the water flux vector while the driving forces are related to the water potential gradient. The analogue of the hydraulic conductivity tensor is the root penetrability tensor. It is determined by the inverse of soil penetration resistance and describes the ease with which a root can penetrate the soil. By adapting the three dimensional soil and root water uptake model R-SWMS (Javaux et al., 2008) in this way

  6. Comparative pathobiology of Heterobasidion annosum during challenge on Pinus sylvestris and Arabidopsis roots: an analysis of defensin gene expression in two pathosystems.

    Science.gov (United States)

    Jaber, Emad; Xiao, Chaowen; Asiegbu, Fred O

    2014-03-01

    Heterobasidion annosum is widely known as a major root and butt rot pathogen of conifer trees, but little information is available on its interaction with the roots of herbaceous angiosperm plants. We investigated the infection biology of H. annosum during challenge with the angiosperm model Arabidopsis and monitored the host response after exposure to different hormone elicitors, chemicals (chitin, glucan and chitosan) and fungal species that represent diverse basidiomycete life strategies [e.g., pathogen (H. annosum), saprotroph (Stereum sanguinolentum) and mutualist (Lactarius rufus)]. The results revealed that the tree pathogen (H. annosum) and the saprotroph (S. sanguinolentum) could infect the Col-8 (Columbia) ecotype of Arabidopsis in laboratory inoculation experiments. Germinated H. annosum spores had appressorium-like penetration structures attached to the surface of the Arabidopsis roots. Subsequent invasive fungal growth led to the disintegration of the vascular region of the root tissues. Progression of root rot symptoms in Arabidopsis was similar to the infection development that was previously documented in Scots pine seedlings. Scots pine PsDef1 and Arabidopsis DEFLs (AT5G44973.1) and PDF1.2 were induced at the initial stage of the infection. However, differences in the expression patterns of the defensin gene homologs from the two plant groups were observed under various conditions, suggesting functional differences in their regulation. The potential use of the H. annosum-Arabidopsis pathosystem as a model for studying forest tree diseases is discussed. PMID:24366684

  7. Glycerol affects root development through regulation of multiple pathways in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Jun Hu

    Full Text Available Glycerol metabolism has been well studied biochemically. However, the means by which glycerol functions in plant development is not well understood. This study aimed to investigate the mechanism underlying the effects of glycerol on root development in Arabidopsis thaliana. Exogenous glycerol inhibited primary root growth and altered lateral root development in wild-type plants. These phenotypes appeared concurrently with increased endogenous glycerol-3-phosphate (G3P and H2O2 contents in seedlings, and decreased phosphate levels in roots. Upon glycerol treatment, G3P level and root development did not change in glycerol kinase mutant gli1, but G3P level increased in gpdhc1 and fad-gpdh mutants, which resulted in more severely impaired root development. Overexpression of the FAD-GPDH gene attenuated the alterations in G3P, phosphate and H2O2 levels, leading to increased tolerance to exogenous glycerol, which suggested that FAD-GPDH plays an important role in modulating this response. Free indole-3-acetic acid (IAA content increased by 46%, and DR5pro::GUS staining increased in the stele cells of the root meristem under glycerol treatment, suggesting that glycerol likely alters normal auxin distribution. Decreases in PIN1 and PIN7 expression, β-glucuronidase (GUS staining in plants expressing PIN7pro::GUS and green fluorescent protein (GFP fluorescence in plants expressing PIN7pro::PIN7-GFP were observed, indicating that polar auxin transport in the root was downregulated under glycerol treatment. Analyses with auxin-related mutants showed that TIR1 and ARF7 were involved in regulating root growth under glycerol treatment. Glycerol-treated plants showed significant reductions in root meristem size and cell number as revealed by CYCB1;1pro::GUS staining. Furthermore, the expression of CDKA and CYCB1 decreased significantly in treated plants compared with control plants, implying possible alterations in cell cycle progression. Our data

  8. Glycerol affects root development through regulation of multiple pathways in Arabidopsis.

    Science.gov (United States)

    Hu, Jun; Zhang, Yonghong; Wang, Jinfang; Zhou, Yongming

    2014-01-01

    Glycerol metabolism has been well studied biochemically. However, the means by which glycerol functions in plant development is not well understood. This study aimed to investigate the mechanism underlying the effects of glycerol on root development in Arabidopsis thaliana. Exogenous glycerol inhibited primary root growth and altered lateral root development in wild-type plants. These phenotypes appeared concurrently with increased endogenous glycerol-3-phosphate (G3P) and H2O2 contents in seedlings, and decreased phosphate levels in roots. Upon glycerol treatment, G3P level and root development did not change in glycerol kinase mutant gli1, but G3P level increased in gpdhc1 and fad-gpdh mutants, which resulted in more severely impaired root development. Overexpression of the FAD-GPDH gene attenuated the alterations in G3P, phosphate and H2O2 levels, leading to increased tolerance to exogenous glycerol, which suggested that FAD-GPDH plays an important role in modulating this response. Free indole-3-acetic acid (IAA) content increased by 46%, and DR5pro::GUS staining increased in the stele cells of the root meristem under glycerol treatment, suggesting that glycerol likely alters normal auxin distribution. Decreases in PIN1 and PIN7 expression, β-glucuronidase (GUS) staining in plants expressing PIN7pro::GUS and green fluorescent protein (GFP) fluorescence in plants expressing PIN7pro::PIN7-GFP were observed, indicating that polar auxin transport in the root was downregulated under glycerol treatment. Analyses with auxin-related mutants showed that TIR1 and ARF7 were involved in regulating root growth under glycerol treatment. Glycerol-treated plants showed significant reductions in root meristem size and cell number as revealed by CYCB1;1pro::GUS staining. Furthermore, the expression of CDKA and CYCB1 decreased significantly in treated plants compared with control plants, implying possible alterations in cell cycle progression. Our data demonstrated that glycerol

  9. Mutations in exocyst complex subunit SEC6 gene impaired polar auxin transport and PIN protein recycling in Arabidopsis primary root.

    Science.gov (United States)

    Tan, Xiaoyun; Feng, Yihong; Liu, Yulong; Bao, Yiqun

    2016-09-01

    Polar auxin transport, which is critical for land plant pattern formation and directional growth, is largely depended on asymmetric distribution of PIN proteins at the plasma membrane (PM). Endocytosis and recycling processes play important roles in regulating PIN protein distribution and abundance at the PM. Two subunits (SEC8, EXO70A1) of exocyst, an octameric vesicle-tethering complex, have been reported to be involved in PIN protein recycling in Arabidopsis. However, the function of exocyst complex in PIN protein recycling and polar auxin transport remains incompletely understood. In this study, we utilized two SEC6 down-regulation mutants (PRsec6-1 and PRsec6-2) to investigate the role of exocyst subunit SEC6 in the primary root development, polar auxin transport and PIN proteins recycling. We found that in PRsec6 mutants: 1. Primary root growth was retarded, and lateral root initiation were compromised. 2. Primary roots were sensitive to exogenous auxin 1-napthalene acetic acid (NAA) but not 2,4-dichlorophenoxy (2.4-D). 3. Recycling of PIN1 and PIN2 proteins from the Brefeldin A (BFA) compartment to the PM was delayed. 4. Vesicles accumulated in the primary root tip cells, especially accumulated in the cytosol closed to the PM. These results further demonstrated that the exocyst complex plays an important role in PIN protein recycling and polar auxin transport in Arabidopsis primary root.

  10. Mutations in exocyst complex subunit SEC6 gene impaired polar auxin transport and PIN protein recycling in Arabidopsis primary root.

    Science.gov (United States)

    Tan, Xiaoyun; Feng, Yihong; Liu, Yulong; Bao, Yiqun

    2016-09-01

    Polar auxin transport, which is critical for land plant pattern formation and directional growth, is largely depended on asymmetric distribution of PIN proteins at the plasma membrane (PM). Endocytosis and recycling processes play important roles in regulating PIN protein distribution and abundance at the PM. Two subunits (SEC8, EXO70A1) of exocyst, an octameric vesicle-tethering complex, have been reported to be involved in PIN protein recycling in Arabidopsis. However, the function of exocyst complex in PIN protein recycling and polar auxin transport remains incompletely understood. In this study, we utilized two SEC6 down-regulation mutants (PRsec6-1 and PRsec6-2) to investigate the role of exocyst subunit SEC6 in the primary root development, polar auxin transport and PIN proteins recycling. We found that in PRsec6 mutants: 1. Primary root growth was retarded, and lateral root initiation were compromised. 2. Primary roots were sensitive to exogenous auxin 1-napthalene acetic acid (NAA) but not 2,4-dichlorophenoxy (2.4-D). 3. Recycling of PIN1 and PIN2 proteins from the Brefeldin A (BFA) compartment to the PM was delayed. 4. Vesicles accumulated in the primary root tip cells, especially accumulated in the cytosol closed to the PM. These results further demonstrated that the exocyst complex plays an important role in PIN protein recycling and polar auxin transport in Arabidopsis primary root. PMID:27457987

  11. Redirection of auxin flow in Arabidopsis thaliana roots after infection by root-knot nematodes.

    Science.gov (United States)

    Kyndt, Tina; Goverse, Aska; Haegeman, Annelies; Warmerdam, Sonja; Wanjau, Cecilia; Jahani, Mona; Engler, Gilbert; de Almeida Engler, Janice; Gheysen, Godelieve

    2016-08-01

    Plant-parasitic root-knot nematodes induce the formation of giant cells within the plant root, and it has been recognized that auxin accumulates in these feeding sites. Here, we studied the role of the auxin transport system governed by AUX1/LAX3 influx proteins and different PIN efflux proteins during feeding site development in Arabidopsis thaliana roots. Data generated via promoter-reporter line and protein localization analyses evoke a model in which auxin is being imported at the basipetal side of the feeding site by the concerted action of the influx proteins AUX1 and LAX3, and the efflux protein PIN3. Mutants in auxin influx proteins AUX1 and LAX3 bear significantly fewer and smaller galls, revealing that auxin import into the feeding sites is needed for their development and expansion. The feeding site development in auxin export (PIN) mutants was only slightly hampered. Expression of some PINs appears to be suppressed in galls, probably to prevent auxin drainage. Nevertheless, a functional PIN4 gene seems to be a prerequisite for proper nematode development and gall expansion, most likely by removing excessive auxin to stabilize the hormone level in the feeding site. Our data also indicate a role of local auxin peaks in nematode attraction towards the root. PMID:27312670

  12. Redirection of auxin flow in Arabidopsis thaliana roots after infection by root-knot nematodes

    Science.gov (United States)

    Kyndt, Tina; Goverse, Aska; Haegeman, Annelies; Warmerdam, Sonja; Wanjau, Cecilia; Jahani, Mona; Engler, Gilbert; de Almeida Engler, Janice; Gheysen, Godelieve

    2016-01-01

    Plant-parasitic root-knot nematodes induce the formation of giant cells within the plant root, and it has been recognized that auxin accumulates in these feeding sites. Here, we studied the role of the auxin transport system governed by AUX1/LAX3 influx proteins and different PIN efflux proteins during feeding site development in Arabidopsis thaliana roots. Data generated via promoter–reporter line and protein localization analyses evoke a model in which auxin is being imported at the basipetal side of the feeding site by the concerted action of the influx proteins AUX1 and LAX3, and the efflux protein PIN3. Mutants in auxin influx proteins AUX1 and LAX3 bear significantly fewer and smaller galls, revealing that auxin import into the feeding sites is needed for their development and expansion. The feeding site development in auxin export (PIN) mutants was only slightly hampered. Expression of some PINs appears to be suppressed in galls, probably to prevent auxin drainage. Nevertheless, a functional PIN4 gene seems to be a prerequisite for proper nematode development and gall expansion, most likely by removing excessive auxin to stabilize the hormone level in the feeding site. Our data also indicate a role of local auxin peaks in nematode attraction towards the root. PMID:27312670

  13. Potassium Transporter KUP7 Is Involved in K(+) Acquisition and Translocation in Arabidopsis Root under K(+)-Limited Conditions.

    Science.gov (United States)

    Han, Min; Wu, Wei; Wu, Wei-Hua; Wang, Yi

    2016-03-01

    Potassium (K(+)) is one of the essential macronutrients for plant growth and development. K(+) uptake from environment and K(+) translocation in plants are conducted by K(+) channels and transporters. In this study, we demonstrated that KT/HAK/KUP transporter KUP7 plays crucial roles in K(+) uptake and translocation in Arabidopsis root. The kup7 mutant exhibited a sensitive phenotype on low-K(+) medium, whose leaves showed chlorosis symptoms compared with wild-type plants. Loss of function of KUP7 led to a reduction of K(+) uptake rate and K(+) content in xylem sap under K(+)-deficient conditions. Thus, the K(+) content in kup7 shoot was significantly reduced under low-K(+) conditions. Localization analysis revealed that KUP7 was predominantly targeted to the plasma membrane. The complementation assay in yeast suggested that KUP7 could mediate K(+) transport. In addition, phosphorylation on S80, S719, and S721 was important for KUP7 activity. KUP7 was ubiquitously expressed in many organs/tissues, and showed a higher expression level in Arabidopsis root. Together, our data demonstrated that KUP7 is crucial for K(+) uptake in Arabidopsis root and might be also involved in K(+) transport into xylem sap, affecting K(+) translocation from root toward shoot, especially under K(+)-limited conditions. PMID:26851373

  14. Phosphate availability alters architecture and causes changes in hormone sensitivity in the Arabidopsis root system.

    Science.gov (United States)

    López-Bucio, José; Hernández-Abreu, Esmeralda; Sánchez-Calderón, Lenin; Nieto-Jacobo, María Fernanda; Simpson, June; Herrera-Estrella, Luis

    2002-05-01

    The postembryonic developmental program of the plant root system is plastic and allows changes in root architecture to adapt to environmental conditions such as water and nutrient availability. Among essential nutrients, phosphorus (P) often limits plant productivity because of its low mobility in soil. Therefore, the architecture of the root system may determine the capacity of the plant to acquire this nutrient. We studied the effect of P availability on the development of the root system in Arabidopsis. We found that at P-limiting conditions (increase in auxin sensitivity in the roots of P-deprived Arabidopsis seedlings. It was also found that the axr1-3, axr2-1, and axr4-1 Arabidopsis mutants have normal responses to low P availability conditions, whereas the iaa28-1 mutant shows resistance to the stimulatory effects of low P on root hair and lateral root formation. Analysis of ethylene signaling mutants and treatments with 1-aminocyclopropane-1-carboxylic acid showed that ethylene does not promote lateral root formation under P deprivation. These results suggest that in Arabidopsis, auxin sensitivity may play a fundamental role in the modifications of root architecture by P availability. PMID:12011355

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

    Directory of Open Access Journals (Sweden)

    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.

  16. Interaction of PLS and PIN and hormonal crosstalk in Arabidopsis root developmentHormonal crosstalk in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Junli eLiu

    2013-04-01

    Full Text Available Understanding how hormones and genes interact to coordinate plant growth is a major challenge in developmental biology. The activities of auxin, ethylene and cytokinin depend on cellular context and exhibit either synergistic or antagonistic interactions. Here we use experimentation and network construction to elucidate the role of the interaction of the POLARIS peptide (PLS and the auxin efflux carrier PIN proteins in the crosstalk of three hormones (auxin, ethylene and cytokinin in Arabidopsis root development. In ethylene hypersignalling mutants such as polaris (pls, we show experimentally that expression of both PIN1 and PIN2 significantly increases. This relationship is analysed in the context of the crosstalk between auxin, ethylene and cytokinin: in pls, endogenous auxin, ethylene and cytokinin concentration decreases, approximately remains unchanged and increases, respectively. Experimental data are integrated into a hormonal crosstalk network through combination with information in literature. Network construction reveals that the regulation of both PIN1 and PIN2 is predominantly via ethylene signalling. In addition, it is deduced that the relationship between cytokinin and PIN1 and PIN2 levels implies a regulatory role of cytokinin in addition to its regulation to auxin, ethylene and PLS levels. We discuss how the network of hormones and genes coordinates plant growth by simultaneously regulating the activities of auxin, ethylene and cytokinin signalling pathways.

  17. SAGE ANALYSIS OF TRANSCRIPTOME RESPONSES IN ARABIDOPSIS ROOTS EXPOSED TO 2,4,6-TRINITROTOLUENE

    Science.gov (United States)

    Serial Analysis of Gene Expression (SAGE) was used to profile transcript levels in Arabidopsis thaliana roots and assess their responses to 2,4,6-trinitrotoluene (TNT) exposure. SAGE libraries representing control and TNT-exposed seedling root transcripts were constructed, and ea...

  18. Vacuolar invertase regulates elongation of Arabidopsis thaliana roots as revealed by QTL and mutant analysis.

    NARCIS (Netherlands)

    Sergeeva, L.I.; Keurentjes, J.J.B.; Bentsink, L.; Vonk, J.; Plas, van der L.H.W.; Koornneef, M.; Vreugdenhil, D.

    2006-01-01

    The possible role of the sucrose-splitting enzymes sucrose synthase and invertase in elongating roots and hypocotyls of Arabidopsis was tested by using a combination of histochemical methods and quantitative trait locus (QTL) analysis. Lengths of roots and hypocotyls correlated better with invertase

  19. Geometric analysis of Arabidopsis root apex reveals a new aspect of the ethylene signal transduction pathway in development

    Science.gov (United States)

    Cervantes, Emilio; Tocino, Angel

    2005-01-01

    Structurally, ethylene is the simplest phytohormone and regulates multiple aspects of plant growth and development. Its effects are mediated by a signal transduction cascade involving receptors, MAP kinases and transcription factors. Many morphological effects of ethylene in plant development, including root size, have been previously described. In this article a combined geometric and algebraic approach has been used to analyse the shape and the curvature in the root apex of Arabidopsis seedlings. The process requires the fitting of Bezier curves that reproduce the root apex shape, and the calculation of the corresponding curvatures. The application of the method has allowed us to identify significant differences in the root curvatures of ethylene insensitive mutants (ein2-1 and etr1-1) with respect to the wild-type Columbia.

  20. Comparison between Arabidopsis and Rice for Main Pathways of K(+) and Na(+) Uptake by Roots.

    Science.gov (United States)

    Nieves-Cordones, Manuel; Martínez, Vicente; Benito, Begoña; Rubio, Francisco

    2016-01-01

    K(+) is an essential macronutrient for plants. It is acquired by specific uptake systems located in roots. Although the concentrations of K(+) in the soil solution are widely variable, K(+) nutrition is secured by uptake systems that exhibit different affinities for K(+). Two main systems have been described for root K(+) uptake in several species: the high-affinity HAK5-like transporter and the inward-rectifier AKT1-like channel. Other unidentified systems may be also involved in root K(+) uptake, although they only seem to operate when K(+) is not limiting. The use of knock-out lines has allowed demonstrating their role in root K(+) uptake in Arabidopsis and rice. Plant adaptation to the different K(+) supplies relies on the finely tuned regulation of these systems. Low K(+)-induced transcriptional up-regulation of the genes encoding HAK5-like transporters occurs through a signal cascade that includes changes in the membrane potential of root cells and increases in ethylene and reactive oxygen species concentrations. Activation of AKT1 channels occurs through phosphorylation by the CIPK23/CBL1 complex. Recently, activation of the Arabidopsis HAK5 by the same complex has been reported, pointing to CIPK23/CBL as a central regulator of the plant's adaptation to low K(+). Na(+) is not an essential plant nutrient but it may be beneficial for some plants. At low concentrations, Na(+) improves growth, especially under K(+) deficiency. Thus, high-affinity Na(+) uptake systems have been described that belong to the HKT and HAK families of transporters. At high concentrations, typical of saline environments, Na(+) accumulates in plant tissues at high concentrations, producing alterations that include toxicity, water deficit and K(+) deficiency. Data concerning pathways for Na(+) uptake into roots under saline conditions are still scarce, although several possibilities have been proposed. The apoplast is a significant pathway for Na(+) uptake in rice grown under salinity

  1. Comparison between Arabidopsis and Rice for Main Pathways of K+ and Na+ Uptake by Roots

    Science.gov (United States)

    Nieves-Cordones, Manuel; Martínez, Vicente; Benito, Begoña; Rubio, Francisco

    2016-01-01

    K+ is an essential macronutrient for plants. It is acquired by specific uptake systems located in roots. Although the concentrations of K+ in the soil solution are widely variable, K+ nutrition is secured by uptake systems that exhibit different affinities for K+. Two main systems have been described for root K+ uptake in several species: the high-affinity HAK5-like transporter and the inward-rectifier AKT1-like channel. Other unidentified systems may be also involved in root K+ uptake, although they only seem to operate when K+ is not limiting. The use of knock-out lines has allowed demonstrating their role in root K+ uptake in Arabidopsis and rice. Plant adaptation to the different K+ supplies relies on the finely tuned regulation of these systems. Low K+-induced transcriptional up-regulation of the genes encoding HAK5-like transporters occurs through a signal cascade that includes changes in the membrane potential of root cells and increases in ethylene and reactive oxygen species concentrations. Activation of AKT1 channels occurs through phosphorylation by the CIPK23/CBL1 complex. Recently, activation of the Arabidopsis HAK5 by the same complex has been reported, pointing to CIPK23/CBL as a central regulator of the plant’s adaptation to low K+. Na+ is not an essential plant nutrient but it may be beneficial for some plants. At low concentrations, Na+ improves growth, especially under K+ deficiency. Thus, high-affinity Na+ uptake systems have been described that belong to the HKT and HAK families of transporters. At high concentrations, typical of saline environments, Na+ accumulates in plant tissues at high concentrations, producing alterations that include toxicity, water deficit and K+ deficiency. Data concerning pathways for Na+ uptake into roots under saline conditions are still scarce, although several possibilities have been proposed. The apoplast is a significant pathway for Na+ uptake in rice grown under salinity conditions, but in other plant species

  2. Arabidopsis ERF1 Mediates Cross-Talk between Ethylene and Auxin Biosynthesis during Primary Root Elongation by Regulating ASA1 Expression.

    Directory of Open Access Journals (Sweden)

    Jie-Li Mao

    2016-01-01

    Full Text Available The gaseous phytohormone ethylene participates in the regulation of root growth and development in Arabidopsis. It is known that root growth inhibition by ethylene involves auxin, which is partially mediated by the action of the WEAK ETHYLENE INSENSITIVE2/ANTHRANILATE SYNTHASE α1 (WEI2/ASA1, encoding a rate-limiting enzyme in tryptophan (Trp biosynthesis, from which auxin is derived. However, the molecular mechanism by which ethylene decreases root growth via ASA1 is not understood. Here we report that the ethylene-responsive AP2 transcription factor, ETHYLENE RESPONSE FACTOR1 (ERF1, plays an important role in primary root elongation of Arabidopsis. Using loss- and gain-of-function transgenic lines as well as biochemical analysis, we demonstrate that ERF1 can directly up-regulate ASA1 by binding to its promoter, leading to auxin accumulation and ethylene-induced inhibition of root growth. This discloses one mechanism linking ethylene signaling and auxin biosynthesis in Arabidopsis roots.

  3. Arabidopsis ERF1 Mediates Cross-Talk between Ethylene and Auxin Biosynthesis during Primary Root Elongation by Regulating ASA1 Expression

    Science.gov (United States)

    Wang, Zhen; Yu, Lin-Hui; Cai, Xiao-Teng; Xiang, Cheng-Bin

    2016-01-01

    The gaseous phytohormone ethylene participates in the regulation of root growth and development in Arabidopsis. It is known that root growth inhibition by ethylene involves auxin, which is partially mediated by the action of the WEAK ETHYLENE INSENSITIVE2/ANTHRANILATE SYNTHASE α1 (WEI2/ASA1), encoding a rate-limiting enzyme in tryptophan (Trp) biosynthesis, from which auxin is derived. However, the molecular mechanism by which ethylene decreases root growth via ASA1 is not understood. Here we report that the ethylene-responsive AP2 transcription factor, ETHYLENE RESPONSE FACTOR1 (ERF1), plays an important role in primary root elongation of Arabidopsis. Using loss- and gain-of-function transgenic lines as well as biochemical analysis, we demonstrate that ERF1 can directly up-regulate ASA1 by binding to its promoter, leading to auxin accumulation and ethylene-induced inhibition of root growth. This discloses one mechanism linking ethylene signaling and auxin biosynthesis in Arabidopsis roots. PMID:26745809

  4. 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...

  5. Vacuolar invertase regulates elongation of Arabidopsis thaliana roots as revealed by QTL and mutant analysis

    OpenAIRE

    Sergeeva, L.I.; Keurentjes, J. J. B.; Bentsink, L.; Vonk, J.; Plas, van der, M..; Koornneef, M; Vreugdenhil, D.

    2006-01-01

    The possible role of the sucrose-splitting enzymes sucrose synthase and invertase in elongating roots and hypocotyls of Arabidopsis was tested by using a combination of histochemical methods and quantitative trait locus (QTL) analysis. Lengths of roots and hypocotyls correlated better with invertase activities than with sucrose synthase activities. The highest correlations were observed with activities in the elongating zones of roots. The genetic basis of these correlations was studied by us...

  6. Different Degree in Proteasome Malfunction Has Various Effects on Root Growth Possibly through Preventing Cell Division and Promoting Autophagic Vacuolization

    OpenAIRE

    Xianyong Sheng; Qian Wei; Liping Jiang; Xue Li; Yuan Gao; Li Wang

    2012-01-01

    The ubiquitin/proteasome pathway plays a vital role in plant development. But the effects of proteasome malfunction on root growth, and the mechanism underlying this involvement remains unclear. In the present study, the effects of proteasome inhibitors on Arabidopsis root growth were studied through the analysis of the root length, and meristem size and cell length in maturation zone using FM4-64, and cell-division potential using GFP fusion cyclin B, and accumulation of ubiquitinated protei...

  7. 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.

  8. Use of Rhizosphere Metabolomics to Investigate Exudation of Phenolics by Arabidopsis Roots

    Science.gov (United States)

    Lee, Yong Jian; Rai, Amit; Reuben, Sheela; Nesati, Victor; Almeida, Reinaldo; Swarup, Sanjay

    2013-04-01

    The rhizosphere is a specialised micro-niche for bacteria that have an active exchange of signals and nutrients with the host plant. Nearly 20% of photosynthates are released as root exudates, which consist of primary metabolites and products of secondary metabolism which are largely phenolic in nature. Previously, using rhizosphere metabolomics, we showed that nearly 50% of organic carbon in the exudates is in the form of phenolic compounds, of which the largest fraction is from the phenylpropanoid synthesis pathway. Using Arabidopsis as a model, we have demonstrated that a biased rhizosphere can be created using plants with varying levels of phenylpropanoids due to mutations in the biosynthetic or regulatory genes. These phenylpropanoids levels are reflected in the exudates, and exudates from lines with regulatory gene mutations, tt8 and ttg, have higher levels of phenylpropanoids, whereas biosynthetic mutant line, tt4, has very low and undetectable levels of phenylpropanoids. The biased rhizosphere of tt8 and ttg lines provides a nutritional advantage to rhizobacteria that can utilize these phenylpropanoids such as quercetin. With such a strategy to increase the competitiveness of plant growth-promoting rhizobacteria (PGPR) such as Pseudomonas putida, this system can be applied to improve plant performance. In order to better understand the metabolic basis of the nutritional advantage behind the competitiveness of the favoured P. putida, we elucidated its quercetin utilization pathway. We have recently cloned the gene for quercetin oxidoreductase (QuoA) and expressed it in transgenic Arabidopsis lines to alter the plant phenylpropanoid metabolism, using a gain of function approach. Since phenylpropanoid biosynthesis in plants involve formation of quercetin from naringenin, we envisaged that QuoA expression in plants will provide us with a genetic tool to "reverse" this biosynthetic step. This perturbation led to a decrease in flavonoids and an increase in lignin

  9. Winter Wheat Root Growth and Nitrogen Relations

    DEFF Research Database (Denmark)

    Rasmussen, Irene Skovby

    Root growth is an essential parameter regarding nitrogen (N) uptake efficiency, as more and deeper roots may improve the uptake from deeper soil layers and reduce nitrate leaching losses. During this PhD project, it was studied how different agronomic practices influence root growth and N relations...... in winter wheat (Triticum aestivum L). Field experiments on the effect of sowing date, N fertilization and cultivars were conducted on a sandy loam soil in Taastrup, Denmark. The root studies were conducted by means of the minirhizotron method. Also, a field experiment on the effect of defoliation and N...... fertilization was conducted in Canberra, Australia. Here the root studies were done by means of the core-break method and root washing....

  10. The role of Arabidopsis 5PTase13 in root gravitropism through modulation of vesicle trafficking

    Institute of Scientific and Technical Information of China (English)

    Yuan Wang; Wen-Hui Lin; Xu Chen; Hong-Wei Xue

    2009-01-01

    Inositol polyphosphate 5-phosphatases (5PTases) are enzymes of phosphatidylinositoi metabolism that affect various aspects of plant growth and development. Arabidopsis 5PTasel3 regulates auxin homeostasis and hormone-related cotyledon vein development, and here we demonstrate that its knockout mutant 5pt13 has elevated sensitivity to gravistimulation in root gravitropic responses. The altered responses of 5pt13 mutants to 1-N-naphthylphthalamic acid (an auxin transport inhibitor) indicate that 5PTasel3 might be involved in the regulation of auxin transport. Indeed, the auxin efflux carrier PIN2 is expressed more broadly under 5PTasel3 deficiency, and observations of the internalization of the membrane-selective dye FM4-64 reveal altered vesicle trafficking in 5pt13 mutants. Compared with wild-type, 5pt13 mutant seedlings are less sensitive to the inhibition by brefeldin A of vesicle cycling, seedling growth, and the intracellular cycling of the PINI and PIN2 proteins. Further, auxin redistribution upon gravitropic stimulation is stimulated under 5PTasel3 deficiency. These results suggest that 5PTasel3 may modulate auxin trans-port by regulating vesicle trafficking and thereby play a role in root gravitropism.

  11. L-Cysteine inhibits root elongation through auxin/PLETHORA and SCR/SHR pathway in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Zhen Wang; Jie-Li Mao; Ying-Jun Zhao; Chuan-You Li; Cheng-Bin Xiang

    2015-01-01

    L‐Cysteine plays a prominent role in sulfur metabo-lism of plants. However, its role in root development is largely unknown. Here, we report that L‐cysteine reduces primary root growth in a dosage‐dependent manner. Elevating cel ular L‐cysteine level by exposing Arabidopsis thaliana seedlings to high L‐cysteine, buthionine sulphoximine, or O‐acetylserine leads to altered auxin maximum in root tips, the expression of quiescent center cel marker as wel as the decrease of the auxin carriers PIN1, PIN2, PIN3, and PIN7 of primary roots. We also show that high L‐cysteine significantly reduces the protein level of two sets of stem cel specific transcription factors PLETHORA1/2 and SCR/SHR. However, L‐cysteine does not downregulate the transcript level of PINs, PLTs, or SCR/SHR, suggesting that an uncharacterized post‐transcriptional mech-anism may regulate the accumulation of PIN, PLT, and SCR/SHR proteins and auxin transport in the root tips. These results suggest that endogenous L‐cysteine level acts to maintain root stem cel niche by regulating basal‐and auxin‐induced expression of PLT1/2 and SCR/SHR. L‐Cysteine may serve as a link between sulfate assimilation and auxin in regulating root growth.

  12. L-Cysteine inhibits root elongation through auxin/PLETHORA and SCR/SHR pathway in Arabidopsis thaliana.

    Science.gov (United States)

    Wang, Zhen; Mao, Jie-Li; Zhao, Ying-Jun; Li, Chuan-You; Xiang, Cheng-Bin

    2015-02-01

    L-Cysteine plays a prominent role in sulfur metabolism of plants. However, its role in root development is largely unknown. Here, we report that L-cysteine reduces primary root growth in a dosage-dependent manner. Elevating cellular L-cysteine level by exposing Arabidopsis thaliana seedlings to high L-cysteine, buthionine sulphoximine, or O-acetylserine leads to altered auxin maximum in root tips, the expression of quiescent center cell marker as well as the decrease of the auxin carriers PIN1, PIN2, PIN3, and PIN7 of primary roots. We also show that high L-cysteine significantly reduces the protein level of two sets of stem cell specific transcription factors PLETHORA1/2 and SCR/SHR. However, L-cysteine does not downregulate the transcript level of PINs, PLTs, or SCR/SHR, suggesting that an uncharacterized post-transcriptional mechanism may regulate the accumulation of PIN, PLT, and SCR/SHR proteins and auxin transport in the root tips. These results suggest that endogenous L-cysteine level acts to maintain root stem cell niche by regulating basal- and auxin-induced expression of PLT1/2 and SCR/SHR. L-Cysteine may serve as a link between sulfate assimilation and auxin in regulating root growth.

  13. Genetic Analysis of Gravity Signal Transduction in Arabidopsis Roots

    Science.gov (United States)

    Masson, Patrick; Strohm, Allison; Barker, Richard; Su, Shih-Heng

    Like most other plant organs, roots use gravity as a directional guide for growth. Specialized cells within the columella region of the root cap (the statocytes) sense the direction of gravity through the sedimentation of starch-filled plastids (amyloplasts). Amyloplast movement and/or pressure on sensitive membranes triggers a gravity signal transduction pathway within these cells, which leads to a fast transcytotic relocalization of plasma-membrane associated auxin-efflux carrier proteins of the PIN family (PIN3 and PIN7) toward the bottom membrane. This leads to a polar transport of auxin toward the bottom flank of the cap. The resulting lateral auxin gradient is then transmitted toward the elongation zones where it triggers a curvature that ultimately leads to a restoration of vertical downward growth. Our laboratory is using strategies derived from genetics and systems biology to elucidate the molecular mechanisms that modulate gravity sensing and signal transduction in the columella cells of the root cap. Our previous research uncovered two J-domain-containing proteins, ARG1 and ARL2, as contributing to this process. Mutations in the corresponding paralogous genes led to alterations of root and hypocotyl gravitropism accompanied by an inability for the statocytes to develop a cytoplasmic alkalinization, relocalize PIN3, and transport auxin laterally, in response to gravistimulation. Both proteins are associated peripherally to membranes belonging to various compartments of the vesicular trafficking pathway, potentially modulating the trafficking of defined proteins between plasma membrane and endosomes. MAR1 and MAR2, on the other end, are distinct proteins of the plastidic outer envelope protein import TOC complex (the transmembrane channel TOC75 and the receptor TOC132, respectively). Mutations in the corresponding genes enhance the gravitropic defects of arg1. Using transformation-rescue experiments with truncated versions of TOC132 (MAR2), we have shown

  14. Indole-3-acetaldoxime-derived compounds restrict root colonization in the beneficial interaction between Arabidopsis roots and the endophyte Piriformospora indica.

    Science.gov (United States)

    Nongbri, Pyniarlang L; Johnson, Joy Michal; Sherameti, Irena; Glawischnig, Erich; Halkier, Barbara Ann; Oelmüller, Ralf

    2012-09-01

    The growth-promoting and root-colonizing endophyte Piriformospora indica induces camalexin and the expression of CYP79B2, CYP79B3, CYP71A13, PAD3, and WRKY33 required for the synthesis of indole-3-acetaldoxime (IAOx)-derived compounds in the roots of Arabidopsis seedlings. Upregulation of the mRNA levels by P. indica requires cytoplasmic calcium elevation and mitogen-activated protein kinase 3 but not root-hair-deficient 2, radical oxygen production, or the 3-phosphoinositide-dependent kinase 1/oxidative signal-inducible 1 pathway. Because P. indica-mediated growth promotion is impaired in cyp79B2 cyp79B3 seedlings, while pad3 seedlings-which do not accumulate camalexin-still respond to the fungus, IAOx-derived compounds other than camalexin (e.g., indole glucosinolates) are required during early phases of the beneficial interaction. The roots of cyp79B2 cyp79B3 seedlings are more colonized than wild-type roots, and upregulation of the defense genes pathogenesis-related (PR)-1, PR-3, PDF1.2, phenylalanine ammonia lyase, and germin indicates that the mutant responds to the lack of IAOx-derived compounds by activating other defense processes. After 6 weeks on soil, defense genes are no longer upregulated in wild-type, cyp79B2 cyp79B3, and pad3 roots. This results in uncontrolled fungal growth in the mutant roots and reduced performance of the mutants. We propose that a long-term harmony between the two symbionts requires restriction of root colonization by IAOx-derived compounds.

  15. 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.

  16. UV-B Induced Generation of Reactive Oxygen Species Promotes Formation of BFA-Induced Compartments in Cells of Arabidopsis Root Apices.

    Science.gov (United States)

    Yokawa, Ken; Kagenishi, Tomoko; Baluška, František

    2015-01-01

    UV-B radiation is an important part of the electromagnetic spectrum emitted by the sun. For much of the period of biological evolution organisms have been exposed to UV radiation, and have developed diverse mechanisms to cope with this potential stress factor. Roots are usually shielded from exposure to UV by the surrounding soil, but may nevertheless be exposed to high energy radiation on the soil surface. Due to their high sensitivity to UV-B radiation, plant roots need to respond rapidly in order to minimize exposure on the surface. In addition to root gravitropism, effective light perception by roots has recently been discovered to be essential for triggering negative root phototropism in Arabidopsis. However, it is not fully understood how UV-B affects root growth and phototropism. Here, we report that UV-B induces rapid generation of reactive oxygen species which in turn promotes the formation of BFA-induced compartments in the Arabidopsis root apex. During unilateral UV-B irradiation of roots changes in auxin concentration on the illuminated side have been recorded. In conclusion, UV-B-induced and ROS-mediated stimulation of vesicle recycling promotes root growth and induces negative phototropism.

  17. UV-B induced generation of reactive oxygen species promotes formation of BFA-induced compartments in cells of Arabidopsis root apices

    Directory of Open Access Journals (Sweden)

    Ken eYokawa

    2016-01-01

    Full Text Available UV-B radiation is an important part of the electromagnetic spectrum emitted by the sun. For much of the period of biological evolution organisms have been exposed to UV radiation, and have developed diverse mechanisms to cope with this potential stress factor. Roots are usually shielded from exposure to UV by the surrounding soil, but may nevertheless be exposed to high energy radiationon the soil surface. Due to their high sensitivity to UV-B radiation, plant roots need to respond rapidly in order to minimize exposure on the surface. In addition to root gravitropism, effective light perception by roots has recently been discovered to be essential for triggering negative root phototropism in Arabidopsis. However, it is not fully understood how UV-B affects root growth and phototropism. Here, we report that UV-B induces rapid generation of reactive oxygen species which in turn promotes the formation of BFA-induced compartments in the Arabidopsis root apex. During unilateral UV-B irradiation of roots changes in auxin concentration on the illuminated side have been recorded. In conclusion, UV-B-induced and ROS-mediated stimulation of vesicle recycling promotes root growth and induces negative phototropism.

  18. Arabidopsis NIP3;1 Plays an Important Role in Arsenic Uptake and Root-to-Shoot Translocation under Arsenite Stress Conditions.

    Science.gov (United States)

    Xu, Wenzhong; Dai, Wentao; Yan, Huili; Li, Sheng; Shen, Hongling; Chen, Yanshan; Xu, Hua; Sun, Yangyang; He, Zhenyan; Ma, Mi

    2015-05-01

    In Arabidopsis, the nodulin 26-like intrinsic protein (NIP) subfamily of aquaporin proteins consists of nine members, five of which (NIP1;1, NIP1;2, NIP5;1, NIP6;1, and NIP7;1) were previously identified to be permeable to arsenite. However, the roles of NIPs in the root-to-shoot translocation of arsenite in plants remain poorly understood. In this study, using reverse genetic strategies, Arabidopsis NIP3;1 was identified to play an important role in both the arsenic uptake and root-to-shoot distribution under arsenite stress conditions. The nip3;1 loss-of-function mutants displayed obvious improvements in arsenite tolerance for aboveground growth and accumulated less arsenic in shoots than those of the wild-type plants, whereas the nip3;1 nip1;1 double mutant showed strong arsenite tolerance and improved growth of both roots and shoots under arsenite stress conditions. A promoter-β-glucuronidase analysis revealed that NIP3;1 was expressed almost exclusively in roots (with the exception of the root tips), and heterologous expression in the yeast Saccharomyces cerevisiae demonstrated that NIP3;1 was able to mediate arsenite transport. Taken together, our results suggest that NIP3;1 is involved in arsenite uptake and root-to-shoot translocation in Arabidopsis, probably as a passive and bidirectional arsenite transporter.

  19. 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

  20. Root cap specific expression of an endo-beta-1,4-D-glucanase (cellulase): a new marker to study root development in Arabidopsis.

    Science.gov (United States)

    del Campillo, Elena; Abdel-Aziz, Amal; Crawford, Damian; Patterson, Sara E

    2004-09-01

    The sloughing of root cap cells from the root tip is important because it assists the growing root in penetrating the soil. Using a promoter-reporter (GUS) and RT-PCR analysis, we identified an endo-beta-1,4-glucanase (AtCel5) of Arabidopsis thaliana that is expressed exclusively in root cap cells of both primary and secondary roots. Expression is inhibited by high concentrations of IAA, both exogenous and internal, as well as by ABA. AtCel5 expression begins once the mature tissue pattern is established and continues for 3 weeks. GUS staining is observed in both root cap cells that are still attached and cells that have already been shed. Using AtCel5-GUS as a marker, we observed that the root cap cells begin to separate at the sides of the tip while the cells of the central region of the tip separate last. Separation involves sequential tiers of intact cells that separate from the periphery of the root tip. A homozygous T-DNA insertion mutant that does not express AtCel5 forms the root cap and sheds root cap cells but sloughing is less efficient compared to wild type. The reduction in sloughing in the mutant does not affect the overall growth performance of the plant in loose media. The modest effect of abolishing AtCel5 expression suggests that there are multiple redundant genes regulating the process of sloughing of the root cap, including AtCel3/At1g71380, the paralog of the AtCel5 gene that is also expressed in the root cap cells. Thus, these two endo-1,4-beta-D-glucanases may have a role in the sloughing of border cells from the root tip. We propose that AtCel5, provides a new molecular marker to further analyze the process of root cap cell separation and a root cap specific promoter for targeting to the environment genes with beneficial properties for plant growth.

  1. Auxin and Cytokinin Metabolism and Root Morphological Modifications in Arabidopsis thaliana Seedlings Infected with Cucumber mosaic virus (CMV or Exposed to Cadmium

    Directory of Open Access Journals (Sweden)

    Adriano Sofo

    2013-03-01

    Full Text Available Arabidopsis thaliana L. is a model plant but little information is available about morphological root changes as part of a phytohormonal common response against both biotic and abiotic stressors. For this purpose, two-week-old Arabidopsis seedlings were treated with 10 µM CdSO4 or infected with CMV. After 12 days the entire aerial parts and the root system were analyzed, and the presence of CMV or the accumulation of Cd were detected. Microscopic analysis revealed that both CMV and Cd influenced root morphology by a marked development in the length of root hairs and an intense root branching if compared to controls. Among the three treatments, Cd-treated seedlings showed a shorter root axis length and doubled their lateral root diameter, while the lateral roots of CMV-infected seedlings were the longest. The root growth patterns were accompanied by significant changes in the levels of indole-3-acetic acid, trans-zeatin riboside, dihydrozeatin riboside, as a probable consequence of the regulation of some genes involved in their biosynthesis/degradation. The opposite role on root development played by the phythormones studied is discussed in detail. The results obtained could provide insights into novel strategies for plant defense against pathogens and plant protection against pollutants.

  2. Corn-on-a-chip: Mini-channel Device for Corn Root Growth

    Science.gov (United States)

    Kreis, Kevin; Ryu, Sangjin

    2015-11-01

    Plant growth heavily relies on interactions between the root and the soil environment, but it is impossible to observe such interactions because of opaqueness of soil. Microfluidics has been successfully utilized to monitor the root growth behaviors of Arabidopsis. In this study we have chosen Maize as a model plant because of its economic significance, and aim to develop transparent mini-channel devices accommodating the root growth of corn seedlings in a controlled environment. To mimic aspects of the soil environment, we try to impose concentration gradients of key chemical ions to the growing root using the device, and to investigate how the root responds to the applied stimuli. We acknowledge support from NASA Nebraska Space Grant Fellowship.

  3. Stochastic roots of growth phenomena

    Science.gov (United States)

    De Lauro, E.; De Martino, S.; De Siena, S.; Giorno, V.

    2014-05-01

    We show that the Gompertz equation describes the evolution in time of the median of a geometric stochastic process. Therefore, we induce that the process itself generates the growth. This result allows us further to exploit a stochastic variational principle to take account of self-regulation of growth through feedback of relative density variations. The conceptually well defined framework so introduced shows its usefulness by suggesting a form of control of growth by exploiting external actions.

  4. 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.

  5. Effect of lead on root growth.

    Science.gov (United States)

    Fahr, Mouna; Laplaze, Laurent; Bendaou, Najib; Hocher, Valerie; Mzibri, Mohamed El; Bogusz, Didier; Smouni, Abdelaziz

    2013-01-01

    Lead (Pb) is one of the most widespread heavy metal contaminant in soils. It is highly toxic to living organisms. Pb has no biological function but can cause morphological, physiological, and biochemical dysfunctions in plants. Plants have developed a wide range of tolerance mechanisms that are activated in response to Pb exposure. Pb affects plants primarily through their root systems. Plant roots rapidly respond either (i) by the synthesis and deposition of callose, creating a barrier that stops Pb entering (ii) through the uptake of large amounts of Pb and its sequestration in the vacuole accompanied by changes in root growth and branching pattern or (iii) by its translocation to the aboveground parts of plant in the case of hyperaccumulators plants. Here we review the interactions of roots with the presence of Pb in the rhizosphere and the effect of Pb on the physiological and biochemical mechanisms of root development.

  6. Gibberellins inhibit adventitious rooting in hybrid aspen and Arabidopsis by affecting auxin transport.

    Science.gov (United States)

    Mauriat, Mélanie; Petterle, Anna; Bellini, Catherine; Moritz, Thomas

    2014-05-01

    Knowledge of processes involved in adventitious rooting is important to improve both fundamental understanding of plant physiology and the propagation of numerous plants. Hybrid aspen (Populus tremula × tremuloïdes) plants overexpressing a key gibberellin (GA) biosynthesis gene (AtGA20ox1) grow rapidly but have poor rooting efficiency, which restricts their clonal propagation. Therefore, we investigated the molecular basis of adventitious rooting in Populus and the model plant Arabidopsis. The production of adventitious roots (ARs) in tree cuttings is initiated from the basal stem region, and involves the interplay of several endogenous and exogenous factors. The roles of several hormones in this process have been characterized, but the effects of GAs have not been fully investigated. Here, we show that a GA treatment negatively affects the numbers of ARs produced by wild-type hybrid aspen cuttings. Furthermore, both hybrid aspen plants and intact Arabidopsis seedlings overexpressing AtGA20ox1, PttGID1.1 or PttGID1.3 genes (with a 35S promoter) produce few ARs, although ARs develop from the basal stem region of hybrid aspen and the hypocotyl of Arabidopsis. In Arabidopsis, auxin and strigolactones are known to affect AR formation. Our data show that the inhibitory effect of GA treatment on adventitious rooting is not mediated by perturbation of the auxin signalling pathway, or of the strigolactone biosynthetic and signalling pathways. Instead, GAs appear to act by perturbing polar auxin transport, in particular auxin efflux in hybrid aspen, and both efflux and influx in Arabidopsis.

  7. Phenotypical and molecular responses of Arabidopsis thaliana roots as a result of inoculation with the auxin-producing bacterium Azospirillum brasilense.

    Science.gov (United States)

    Spaepen, Stijn; Bossuyt, Stijn; Engelen, Kristof; Marchal, Kathleen; Vanderleyden, Jos

    2014-02-01

    The auxin-producing bacterium Azospirillum brasilense Sp245 can promote the growth of several plant species. The model plant Arabidopsis thaliana was chosen as host plant to gain an insight into the molecular mechanisms that govern this interaction. The determination of differential gene expression in Arabidopsis roots after inoculation with either A. brasilense wild-type or an auxin biosynthesis mutant was achieved by microarray analysis. Arabidopsis thaliana inoculation with A. brasilense wild-type increases the number of lateral roots and root hairs, and elevates the internal auxin concentration in the plant. The A. thaliana root transcriptome undergoes extensive changes on A. brasilense inoculation, and the effects are more pronounced at later time points. The wild-type bacterial strain induces changes in hormone- and defense-related genes, as well as in plant cell wall-related genes. The A. brasilense mutant, however, does not elicit these transcriptional changes to the same extent. There are qualitative and quantitative differences between A. thaliana responses to the wild-type A. brasilense strain and the auxin biosynthesis mutant strain, based on both phenotypic and transcriptomic data. This illustrates the major role played by auxin in the Azospirillum-Arabidopsis interaction, and possibly also in other bacterium-plant interactions.

  8. Chromium-Induced Ultrastructural Changes and Oxidative Stress in Roots of Arabidopsis thaliana.

    Science.gov (United States)

    Eleftheriou, Eleftherios P; Adamakis, Ioannis-Dimosthenis S; Panteris, Emmanuel; Fatsiou, Maria

    2015-01-01

    Chromium (Cr) is an abundant heavy metal in nature, toxic to living organisms. As it is widely used in industry and leather tanning, it may accumulate locally at high concentrations, raising concerns for human health hazards. Though Cr effects have extensively been investigated in animals and mammals, in plants they are poorly understood. The present study was then undertaken to determine the ultrastructural malformations induced by hexavalent chromium [Cr(VI)], the most toxic form provided as 100 μM potassium dichromate (K2Cr2O7), in the root tip cells of the model plant Arabidopsis thaliana. A concentration-dependent decrease of root growth and a time-dependent increase of dead cells, callose deposition, hydrogen peroxide (H2O2) production and peroxidase activity were found in Cr(VI)-treated seedlings, mostly at the transition root zone. In the same zone, nuclei remained ultrastructurally unaffected, but in the meristematic zone some nuclei displayed bulbous outgrowths or contained tubular structures. Endoplasmic reticulum (ER) was less affected under Cr(VI) stress, but Golgi bodies appeared severely disintegrated. Moreover, mitochondria and plastids became spherical and displayed translucent stroma with diminished internal membranes, but noteworthy is that their double-membrane envelopes remained structurally intact. Starch grains and electron dense deposits occurred in the plastids. Amorphous material was also deposited in the cell walls, the middle lamella and the vacuoles. Some vacuoles were collapsed, but the tonoplast appeared integral. The plasma membrane was structurally unaffected and the cytoplasm contained opaque lipid droplets and dense electron deposits. All electron dense deposits presumably consisted of Cr that is sequestered from sensitive sites, thus contributing to metal tolerance. It is concluded that the ultrastructural changes are reactive oxygen species (ROS)-correlated and the malformations observed are organelle specific. PMID:26204828

  9. Chromium-Induced Ultrastructural Changes and Oxidative Stress in Roots of Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Eleftherios P. Eleftheriou

    2015-07-01

    Full Text Available Chromium (Cr is an abundant heavy metal in nature, toxic to living organisms. As it is widely used in industry and leather tanning, it may accumulate locally at high concentrations, raising concerns for human health hazards. Though Cr effects have extensively been investigated in animals and mammals, in plants they are poorly understood. The present study was then undertaken to determine the ultrastructural malformations induced by hexavalent chromium [Cr(VI], the most toxic form provided as 100 μM potassium dichromate (K2Cr2O7, in the root tip cells of the model plant Arabidopsis thaliana. A concentration-dependent decrease of root growth and a time-dependent increase of dead cells, callose deposition, hydrogen peroxide (H2O2 production and peroxidase activity were found in Cr(VI-treated seedlings, mostly at the transition root zone. In the same zone, nuclei remained ultrastructurally unaffected, but in the meristematic zone some nuclei displayed bulbous outgrowths or contained tubular structures. Endoplasmic reticulum (ER was less affected under Cr(VI stress, but Golgi bodies appeared severely disintegrated. Moreover, mitochondria and plastids became spherical and displayed translucent stroma with diminished internal membranes, but noteworthy is that their double-membrane envelopes remained structurally intact. Starch grains and electron dense deposits occurred in the plastids. Amorphous material was also deposited in the cell walls, the middle lamella and the vacuoles. Some vacuoles were collapsed, but the tonoplast appeared integral. The plasma membrane was structurally unaffected and the cytoplasm contained opaque lipid droplets and dense electron deposits. All electron dense deposits presumably consisted of Cr that is sequestered from sensitive sites, thus contributing to metal tolerance. It is concluded that the ultrastructural changes are reactive oxygen species (ROS-correlated and the malformations observed are organelle specific.

  10. The OXI1 kinase pathway mediates Piriformospora indica-induced growth promotion in Arabidopsis.

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    Iris Camehl

    2011-05-01

    Full Text Available Piriformospora indica is an endophytic fungus that colonizes roots of many plant species and promotes growth and resistance to certain plant pathogens. Despite its potential use in agriculture, little is known on the molecular basis of this beneficial plant-fungal interaction. In a genetic screen for plants, which do not show a P. indica- induced growth response, we isolated an Arabidopsis mutant in the OXI1 (Oxidative Signal Inducible1 gene. OXI1 has been characterized as a protein kinase which plays a role in pathogen response and is regulated by H₂O₂ and PDK1 (3-PHOSPHOINOSITIDE-DEPENDENT PROTEIN KINASE1. A genetic analysis showed that double mutants of the two closely related PDK1.1 and PDK1.2 genes are defective in the growth response to P. indica. While OXI1 and PDK1 gene expression is upregulated in P. indica-colonized roots, defense genes are downregulated, indicating that the fungus suppresses plant defense reactions. PDK1 is activated by phosphatidic acid (PA and P. indica triggers PA synthesis in Arabidopsis plants. Under beneficial co-cultivation conditions, H₂O₂ formation is even reduced by the fungus. Importantly, phospholipase D (PLDα1 or PLDδ mutants, which are impaired in PA synthesis do not show growth promotion in response to fungal infection. These data establish that the P. indica-stimulated growth response is mediated by a pathway consisting of the PLD-PDK1-OXI1 cascade.

  11. Root system architecture: insights from Arabidopsis and cereal crops

    OpenAIRE

    Smith, Stephanie; De Smet, Ive

    2012-01-01

    Roots are important to plants for a wide variety of processes, including nutrient and water uptake, anchoring and mechanical support, storage functions, and as the major interface between the plant and various biotic and abiotic factors in the soil environment. Understanding the development and architecture of roots holds potential for the exploitation and manipulation of root characteristics to both increase food plant yield and optimize agricultural land use. This theme issue highlights the...

  12. In vivo imaging of the tonoplast intrinsic protein family in Arabidopsis roots

    Directory of Open Access Journals (Sweden)

    Khonsari Roman H

    2009-11-01

    Full Text Available Abstract Background Tonoplast intrinsic proteins (TIPs are widely used as markers for vacuolar compartments in higher plants. Ten TIP isoforms are encoded by the Arabidopsis genome. For several isoforms, the tissue and cell specific pattern of expression are not known. Results We generated fluorescent protein fusions to the genomic sequences of all members of the Arabidopsis TIP family whose expression is predicted to occur in root tissues (TIP1;1 and 1;2; TIP2;1, 2;2 and 2;3; TIP4;1 and expressed these fusions, both individually and in selected pairwise combinations, in transgenic Arabidopsis. Analysis by confocal microscopy revealed that TIP distribution varied between different cell layers within the root axis, with extensive co-expression of some TIPs and more restricted expression patterns for other isoforms. TIP isoforms whose expression overlapped appeared to localise to the tonoplast of the central vacuole, vacuolar bulbs and smaller, uncharacterised structures. Conclusion We have produced a comprehensive atlas of TIP expression in Arabidopsis roots, which reveals novel expression patterns for not previously studied TIPs.

  13. The acquisition of cell fate in the Arabidopsis thaliana root meristem

    NARCIS (Netherlands)

    Scheres, B.J.G.; Berg, C. van den; Hage, W.; Willemsen, V.; Werff, N. van der; Wolkenfelt, H.; McKhann, H.; Weisbeek, P.

    1997-01-01

    During plant embryogenesis an embryo with cotyledons, a shoot apical meristem, a hypocotyl and a root apical meristem, is formed. The primary root and shoot meristems initiate post-embryonic growth generating all plant organs. The root meristem forms the primary root, and the shoot meristem forms th

  14. Oscillating Gene Expression Determines Competence for Periodic Arabidopsis Root Branching

    Science.gov (United States)

    Moreno-Risueno, Miguel A.; Van Norman, Jaimie M.; Moreno, Antonio; Zhang, Jingyuan; Ahnert, Sebastian E.; Benfey, Philip N.

    2010-01-01

    Plants and animals produce modular developmental units in a periodic fashion. In plants, lateral roots form as repeating units along the root primary axis; however, the developmental mechanism regulating this process is unknown. We found that cyclic expression pulses of a reporter gene mark the position of future lateral roots by establishing prebranch sites and that prebranch site production and root bending are periodic. Microarray and promoter-luciferase studies revealed two sets of genes oscillating in opposite phases at the root tip. Genetic studies show that some oscillating transcriptional regulators are required for periodicity in one or both developmental processes. This molecular mechanism has characteristics that resemble molecular clock–driven activities in animal species. PMID:20829477

  15. Gene Networks Involved in Hormonal Control of Root Development in Arabidopsis thaliana: A Framework for Studying Its Disturbance by Metal Stress.

    Science.gov (United States)

    De Smet, Stefanie; Cuypers, Ann; Vangronsveld, Jaco; Remans, Tony

    2015-01-01

    Plant survival under abiotic stress conditions requires morphological and physiological adaptations. Adverse soil conditions directly affect root development, although the underlying mechanisms remain largely to be discovered. Plant hormones regulate normal root growth and mediate root morphological responses to abiotic stress. Hormone synthesis, signal transduction, perception and cross-talk create a complex network in which metal stress can interfere, resulting in root growth alterations. We focus on Arabidopsis thaliana, for which gene networks in root development have been intensively studied, and supply essential terminology of anatomy and growth of roots. Knowledge of gene networks, mechanisms and interactions related to the role of plant hormones is reviewed. Most knowledge has been generated for auxin, the best-studied hormone with a pronounced primary role in root development. Furthermore, cytokinins, gibberellins, abscisic acid, ethylene, jasmonic acid, strigolactones, brassinosteroids and salicylic acid are discussed. Interactions between hormones that are of potential importance for root growth are described. This creates a framework that can be used for investigating the impact of abiotic stress factors on molecular mechanisms related to plant hormones, with the limited knowledge of the effects of the metals cadmium, copper and zinc on plant hormones and root development included as case example.

  16. Capturing Arabidopsis Root Architecture Dynamics with root-fit Reveals Diversity in Responses to Salinity

    NARCIS (Netherlands)

    M.M. Julkowska; H.C.J. Hoefsloot; S. Mol; R. Feron; G.J. de Boer; M.A. Haring; C. Testerink

    2014-01-01

    The plant root is the first organ to encounter salinity stress, but the effect of salinity on root system architecture (RSA) remains elusive. Both the reduction in main root (MR) elongation and the redistribution of the root mass between MRs and lateral roots (LRs) are likely to play crucial roles i

  17. Low temperature inhibits root growth by reducing auxin accumulation via ARR1/12.

    Science.gov (United States)

    Zhu, Jiang; Zhang, Kun-Xiao; Wang, Wen-Shu; Gong, Wen; Liu, Wen-Cheng; Chen, Hong-Guo; Xu, Heng-Hao; Lu, Ying-Tang

    2015-04-01

    Plants exhibit reduced root growth when exposed to low temperature; however, how low temperature modulates root growth remains to be understood. Our study demonstrated that low temperature reduces both meristem size and cell number, repressing the division potential of meristematic cells by reducing auxin accumulation, possibly through the repressed expression of PIN1/3/7 and auxin biosynthesis-related genes, although the experiments with exogenous auxin application also suggest the involvement of other factor(s). In addition, we verified that ARABIDOPSIS RESPONSE REGULATOR 1 (ARR1) and ARR12 are involved in low temperature-mediated inhibition of root growth by showing that the roots of arr1-3 arr12-1 seedlings were less sensitive than wild-type roots to low temperature, in terms of changes in root length and meristem cell number. Furthermore, low temperature reduced the levels of PIN1/3 transcripts and the auxin level to a lesser extent in arr1-3 arr12-1 roots than in wild-type roots, suggesting that cytokinin signaling is involved in the low-temperature-mediated reduction of auxin accumulation. Taken together, our data suggest that low temperature inhibits root growth by reducing auxin accumulation via ARR1/12.

  18. TORNADO1 regulates root epidermal patterning through the WEREWOLF pathway in Arabidopsis thaliana.

    Science.gov (United States)

    Kwak, Su-Hwan; Song, Sang-Kee; Lee, Myeong Min; Schiefelbein, John

    2015-01-01

    Cell fate in the root epidermis of Arabidopsis thaliana is determined in a position-dependent manner. SCRAMBLED (SCM), an atypical leucine-rich repeat receptor-like kinase, mediates this positional regulation via its effect on WEREWOLF (WER) expression, and subsequently, its downstream transcription factor, GLABRA2 (GL2), which are required for nonhair cell development. Previously, TORNADO1 (TRN1), a plant-specific protein with a leucine-rich repeat ribonuclease inhibitor-like domain, was shown to be required for proper epidermal patterning in Arabidopsis roots. In this work, we analyzed the possible involvement of TRN1 in the known root epidermal gene network. We discovered that the trn1 mutant caused the ectopic expression of WER and the randomized expression of GL2 and EGL3. This suggests that TRN1 regulates the position-dependent cell fate determination by affecting WER expression in Arabidopsis root epidermis. Additionally, the distinct phenotypes of the aerial parts of the trn1-t and scm-2 mutant suggest that TRN1 and SCM might have different functions in the development of aerial parts.

  19. Quest for Continual Growth Takes Root

    Science.gov (United States)

    Surdey, Mary M.; Hashey, Jane M.

    2006-01-01

    In this article, the authors describe how the quest for continual growth has taken its root at Vestal Central School district. Located at the heart of upstate New York, educators at Vestal Central School district have created a spirit of "kaizen," a Japanese word meaning the relentless quest for continual improvement and higher-quality…

  20. Identification of a root-specific glycosyltransferase from Arabidopsis and characterization of its promoter

    Indian Academy of Sciences (India)

    Virupapuram Vijaybhaskar; Veeraputhiran Subbiah; Jagreet Kaur; Pagadala Vijayakumari; Imran Siddiqi

    2008-06-01

    A set of Ds-element enhancer trap lines of Arabidopsis thaliana was generated and screened for expression patterns leading to the identification of a line that showed root-specific expression of the bacterial uidA reporter gene encoding -glucuronidase (GUS). The insertion of the Ds element was found to be immediately downstream to a glycosyltransferase gene At1g73160. Analysis of At1g73160 expression showed that it is highly root-specific. Isolation and characterization of the upstream region of the At1g73160 gene led to the definition of a 218 bp fragment that is sufficient to confer root-specific expression. Sequence analysis revealed that several regulatory elements were implicated in expression in root tissue. The promoter identified and characterized in this study has the potential to be applied in crop biotechnology for directing the root-specific expression of transgenes.

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

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    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.

  2. 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

  3. 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.

  4. Touch and gravitropic set-point angle interact to modulate gravitropic growth in roots

    Science.gov (United States)

    Massa, G. D.; Gilroy, S.

    2003-01-01

    Plant roots must sense and respond to a variety of environmental stimuli as they grow through the soil. Touch and gravity represent two of the mechanical signals that roots must integrate to elicit the appropriate root growth patterns and root system architecture. Obstacles such as rocks will impede the general downwardly directed gravitropic growth of the root system and so these soil features must be sensed and this information processed for an appropriate alteration in gravitropic growth to allow the root to avoid the obstruction. We show that primary and lateral roots of Arabidopsis do appear to sense and respond to mechanical barriers placed in their path of growth in a qualitatively similar fashion. Both types of roots exhibited a differential growth response upon contacting the obstacle that directed the main axis of elongation parallel to the barrier. This growth habit was maintained until the obstacle was circumvented, at which point normal gravitropic growth was resumed. Thus, the gravitational set-point angle of the primary and lateral roots prior to encountering the barrier were 95 degrees and 136 degrees respectively and after growing off the end of the obstacle identical set-point angles were reinstated. However, whilst tracking across the barrier, quantitative differences in response were observed between these two classes of roots. The root tip of the primary root maintained an angle of 136 degrees to the horizontal as it traversed the barrier whereas the lateral roots adopted an angle of 154 degrees. Thus, this root tip angle appeared dependent on the gravitropic set-point angle of the root type with the difference in tracking angle quantitatively reflecting differences in initial set-point angle. Concave and convex barriers were also used to analyze the response of the root to tracking along a continuously varying surface. The roots maintained the a fairly fixed angle to gravity on the curved surface implying a constant resetting of this tip angle

  5. Interaction of root gravitropism and phototropism in Arabidopsis wild-type and starchless mutants.

    Science.gov (United States)

    Vitha, S; Zhao, L; Sack, F D

    2000-02-01

    Root gravitropism in wild-type Arabidopsis and in two starchless mutants, pgm1-1 and adg1-1, was evaluated as a function of light position to determine the relative strengths of negative phototropism and of gravitropism and how much phototropism affects gravitropic measurements. Gravitropism was stronger than phototropism in some but not all light positions in wild-type roots grown for an extended period, indicating that the relationship between the two tropisms is more complex than previously reported. Root phototropism significantly influenced the time course of gravitropic curvature and the two measures of sensitivity. Light from above during horizontal exposure overestimated all three parameters for all three genotypes except the wild-type perception time. At the irradiance used (80 micromol m(-2) s(-1)), the shortest periods of illumination found to exaggerate gravitropism were 45 min of continuous illumination and 2-min doses of intermittent illumination. By growing roots in circumlateral light or by gravistimulating in the dark, corrected values were obtained for each gravitropic parameter. Roots of both starchless mutants were determined to be about three times less sensitive than prior estimates. This study demonstrates the importance of accounting for phototropism in the design of root gravitropism experiments in Arabidopsis.

  6. An improved grafting technique for mature Arabidopsis plants demonstrates long-distance shoot-to-root transport of phytochelatins in Arabidopsis.

    Science.gov (United States)

    Chen, Alice; Komives, Elizabeth A; Schroeder, Julian I

    2006-05-01

    Phytochelatins (PCs) are peptides that function in heavy-metal chelation and detoxification in plants and fungi. A recent study showed that PCs have the ability to undergo long-distance transport in a root-to-shoot direction in transgenic Arabidopsis (Arabidopsis thaliana). To determine whether long-distance transport of PCs can occur in the opposite direction, from shoots to roots, the wheat (Triticum aestivum) PC synthase (TaPCS1) gene was expressed under the control of a shoot-specific promoter (CAB2) in an Arabidopsis PC-deficient mutant, cad1-3 (CAB2TaPCS1/cad1-3). Analyses demonstrated that TaPCS1 is expressed only in shoots and that CAB2TaPCS1/cad1-3 lines complement the cadmium (Cd) and arsenic metal sensitivity of cad1-3 shoots. CAB2TaPCS1/cad1-3 plants exhibited higher Cd accumulation in roots and lower Cd accumulation in shoots compared to wild type. Fluorescence HPLC coupled to mass spectrometry analyses directly detected PC2 in the roots of CAB2:TaPCS1/cad1-3 but not in cad1-3 controls, suggesting that PC2 is transported over long distances in the shoot-to-root direction. In addition, wild-type shoot tissues were grafted onto PC synthase cad1-3 atpcs2-1 double loss-of-function mutant root tissues. An Arabidopsis grafting technique for mature plants was modified to obtain an 84% success rate, significantly greater than a previous rate of approximately 11%. Fluorescence HPLC-mass spectrometry showed the presence of PC2, PC3, and PC4 in the root tissue of grafts between wild-type shoots and cad1-3 atpcs2-1 double-mutant roots, demonstrating that PCs are transported over long distances from shoots to roots in Arabidopsis.

  7. Measuring whole plant CO2 exchange with the environment reveals opposing effects of the gin2-1 mutation in shoots and roots of Arabidopsis thaliana.

    Science.gov (United States)

    Brauner, Katrin; Stutz, Simon; Paul, Martin; Heyer, Arnd G

    2015-01-01

    Using a cuvette for simultaneous measurement of net photosynthesis in above ground plant organs and root respiration we investigated the effect of reduced leaf glucokinase activity on plant carbon balance. The gin2-1 mutant of Arabidopsis thaliana is characterized by a 50% reduction of glucokinase activity in the shoot, while activity in roots is about fivefold higher and similar to wild type plants. High levels of sucrose accumulating in leaves during the light period correlated with elevated root respiration in gin2-1. Despite substantial respiratory losses in roots, growth retardation was moderate, probably because photosynthetic carbon fixation was simultaneously elevated in gin2-1. Our data indicate that futile cycling of sucrose in shoots exerts a reduction on net CO2 gain, but this is over-compensated by the prevention of exaggerated root respiration resulting from high sucrose concentration in leaf tissue.

  8. Photosynthesis of root chloroplasts developed in Arabidopsis lines overexpressing GOLDEN2-LIKE transcription factors.

    Science.gov (United States)

    Kobayashi, Koichi; Sasaki, Daichi; Noguchi, Ko; Fujinuma, Daiki; Komatsu, Hirohisa; Kobayashi, Masami; Sato, Mayuko; Toyooka, Kiminori; Sugimoto, Keiko; Niyogi, Krishna K; Wada, Hajime; Masuda, Tatsuru

    2013-08-01

    In plants, genes involved in photosynthesis are encoded separately in nuclei and plastids, and tight cooperation between these two genomes is therefore required for the development of functional chloroplasts. Golden2-like (GLK) transcription factors are involved in chloroplast development, directly targeting photosynthesis-associated nuclear genes for up-regulation. Although overexpression of GLKs leads to chloroplast development in non-photosynthetic organs, the mechanisms of coordination between the nuclear gene expression influenced by GLKs and the photosynthetic processes inside chloroplasts are largely unknown. To elucidate the impact of GLK-induced expression of photosynthesis-associated nuclear genes on the construction of photosynthetic systems, chloroplast morphology and photosynthetic characteristics in greenish roots of Arabidopsis thaliana lines overexpressing GLKs were compared with those in wild-type roots and leaves. Overexpression of GLKs caused up-regulation of not only their direct targets but also non-target nuclear and plastid genes, leading to global induction of chloroplast biogenesis in the root. Large antennae relative to reaction centers were observed in wild-type roots and were further enhanced by GLK overexpression due to the increased expression of target genes associated with peripheral light-harvesting antennae. Photochemical efficiency was lower in the root chloroplasts than in leaf chloroplasts, suggesting that the imbalance in the photosynthetic machinery decreases the efficiency of light utilization in root chloroplasts. Despite the low photochemical efficiency, root photosynthesis contributed to carbon assimilation in Arabidopsis. Moreover, GLK overexpression increased CO₂ fixation and promoted phototrophic performance of the root, showing the potential of root photosynthesis to improve effective carbon utilization in plants.

  9. 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.

  10. Transcription factor movement and tissue patterning in Arabidopsis root meristem

    NARCIS (Netherlands)

    Long, Y.

    2015-01-01

    Cell-cell communication is key to coordinated cellular functions in multicellular organisms. In addition to the signaling molecules found in animals, plants also frequently recruit mobile transcription factors to deliver positional information. The best studied example is SHORT-ROOT (SHR), a transcr

  11. Bacterial volatiles promote growth in Arabidopsis

    OpenAIRE

    Ryu, Choong-Min; Mohamed A. Farag; Hu, Chia-Hui; Reddy, Munagala S.; Wei, Han-Xun; Paré, Paul W.; Kloepper, Joseph W.

    2003-01-01

    Several chemical changes in soil are associated with plant growth-promoting rhizobacteria (PGPR). Some bacterial strains directly regulate plant physiology by mimicking synthesis of plant hormones, whereas others increase mineral and nitrogen availability in the soil as a way to augment growth. Identification of bacterial chemical messengers that trigger growth promotion has been limited in part by the understanding of how plants respond to external stimuli. With an increasing appreciation of...

  12. Hydrogen peroxide is involved in cGMP modulating the lateral root development of Arabidopsis thaliana

    OpenAIRE

    Li, Jisjeng; Jia, Honglei

    2013-01-01

    3′,5′-cyclic guanosine monophosphate (cGMP) and hydrogen peroxide (H2O2) function as the important signaling molecule which promote the lateral root development of Arabidopsis thaliana. In this study, interestingly, application of 8-Br-cGMP (the membrane permeable cGMP analog) promoted the endogenous H2O2 production. In addition, the decrease of endogenous H2O2 also inhibited the effect of cGMP on the lateral root development. Thus, H2O2 maybe act as a downstream signaling of cGMP molecule wh...

  13. BES1 regulates the localization of the brassinosteroid receptor BRL3 within the provascular tissue of the Arabidopsis primary root.

    Science.gov (United States)

    Salazar-Henao, Jorge E; Lehner, Reinhard; Betegón-Putze, Isabel; Vilarrasa-Blasi, Josep; Caño-Delgado, Ana I

    2016-09-01

    Brassinosteroid (BR) hormones are important regulators of plant growth and development. Recent studies revealed the cell-specific role of BRs in vascular and stem cell development by the action of cell-specific BR receptor complexes and downstream signaling components in Arabidopsis thaliana Despite the importance of spatiotemporal regulation of hormone signaling in the control of plant vascular development, the mechanisms that confer cellular specificity to BR receptors within the vascular cells are not yet understood. The present work shows that BRI1-like receptor genes 1 and 3 (BRL1 and BRL3) are differently regulated by BRs. By using promoter deletion constructs of BRL1 and BRL3 fused to GFP/GUS (green fluorescent protein/β-glucuronidase) reporters in Arabidopsis, analysis of their cell-specific expression and regulation by BRs in the root apex has been carried out. We found that BRL3 expression is finely modulated by BRs in different root cell types, whereas the location of BRL1 appears to be independent of this hormone. Physiological and genetic analysis show a BR-dependent expression of BRL3 in the root meristem. In particular, BRL3 expression requires active BES1, a central transcriptional effector within the BRI1 pathway. ChIP analysis showed that BES1 directly binds to the BRRE present in the BRL3 promoter region, modulating its transcription in different subsets of cells of the root apex. Overall our study reveals the existence of a cell-specific negative feedback loop from BRI1-mediated BES1 transcription factor to BRL3 in phloem cells, while contributing to a general understanding of the spatial control of steroid signaling in plant development. PMID:27511026

  14. EFFECT OF SEED XYLOGLUCANS AND DERIVATES ON THE GROWTH OF Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Adriana Tourinho Salamoni

    2009-10-01

    Full Text Available Studies on xyloglucan (XG extracted from Hymenaea courbaril L. (jatoba seeds showed that this biopolymer has biological activity that enhanced wheat coleoptiles growth. In apple tree micropropagation, the culture medium containing XG combined with agar induced a higher multiplication rate, rooting rate and root length than medium solidified with agar only. The purpose of this study was to determine the effect of XG from jatobá seeds extracted from jatoba seeds collected in Sinope/MT (XGS and Cuiabá/MT (XGC, and from XGC hydrolysed with a cellulase (XGCH, as well from Tamarindus indica seeds (XGT collected in Bahia/BA, on the growth of in vitro cultured Arabidopsis thaliana plantlets. In the first experiment, XGCH (0.25, 25 and 250 nM or XGC (0.5, 50 and 500 nM were added to a liquid half-strength MS medium. In the second experiment, XGs from several origins were compared: XGC (500 nM, XGS (1200 nM and XGT (800 nM, using culture medium solidified with 6 g.L-1agar. Arabidopsis thaliana L. seeds germinated in Petri plates for 4 to 5 days were transferred to culture media containing the different concentrations of XGs and cultured in a growing room. When the plantlets were cultured in a liquid medium, their growth was very slow in the presence of XGC and XGCH at the highest concentration tested, and it was faster at the lowest concentration. In the semi-solid culture medium, XGs also reduced growth. It was concluded that XGs can play a biological role in Arabidopsis thaliana (L. Heynh. plantlets, stimulating or inhibiting the root system growth and the lateral root formation. These opposite effects varied according to the plant specie that furnished the seeds containing XG, as well as the place where the seeds were collected, to the XG form used (hydrolyzed or not and to its concentration in the culture media. 

  15. Complexation of arsenite with phytochelatins reduces arsenite efflux and translocation from roots to shoots in Arabidopsis.

    Science.gov (United States)

    Liu, Wen-Ju; Wood, B Alan; Raab, Andrea; McGrath, Steve P; Zhao, Fang-Jie; Feldmann, Jörg

    2010-04-01

    Complexation of arsenite [As(III)] with phytochelatins (PCs) is an important mechanism employed by plants to detoxify As; how this complexation affects As mobility was little known. We used high-resolution inductively coupled plasma-mass spectrometry and accurate mass electrospray ionization-mass spectrometry coupled to HPLC to identify and quantify As(III)-thiol complexes and free thiol compounds in Arabidopsis (Arabidopsis thaliana) exposed to arsenate [As(V)]. As(V) was efficiently reduced to As(III) in roots. In wild-type roots, 69% of As was complexed as As(III)-PC4, As(III)-PC3, and As(III)-(PC2)2. Both the glutathione (GSH)-deficient mutant cad2-1 and the PC-deficient mutant cad1-3 were approximately 20 times more sensitive to As(V) than the wild type. In cad1-3 roots, only 8% of As was complexed with GSH as As(III)-(GS)3 and no As(III)-PCs were detected, while in cad2-1 roots, As(III)-PCs accounted for only 25% of the total As. The two mutants had a greater As mobility, with a significantly higher accumulation of As(III) in shoots and 4.5 to 12 times higher shoot-to-root As concentration ratio than the wild type. Roots also effluxed a substantial proportion of the As(V) taken up as As(III) to the external medium, and this efflux was larger in the two mutants. Furthermore, when wild-type plants were exposed to l-buthionine sulfoximine or deprived of sulfur, both As(III) efflux and root-to-shoot translocation were enhanced. The results indicate that complexation of As(III) with PCs in Arabidopsis roots decreases its mobility for both efflux to the external medium and for root-to-shoot translocation. Enhancing PC synthesis in roots may be an effective strategy to reduce As translocation to the edible organs of food crops.

  16. Chiral and non-chiral nutations in Arabidopsis roots grown on the random positioning machine.

    Science.gov (United States)

    Piconese, S; Tronelli, G; Pippia, P; Migliaccio, F

    2003-08-01

    Arabidopsis thaliana roots grown on a vertically set plate do not elongate straight down the gravitational vector, but by making waves and coils, and by conspicuously slanting towards the right-hand. This behaviour, in a previous paper, was ascribed to the simultaneous effect of three processes: circumnutation, positive gravitropism and negative thigmotropism. However, when the plants are grown on the Random Positioning Machine (RPM), in conditions that are believed to simulate space microgravitational conditions closely, the roots do not show the usual pattern. In the wild type, the roots make large loops to the right-hand side, whereas in the gravitropic and auxinic mutants aux1, eir1, rha1, they just move randomly around the initial direction. Therefore, if the movements made on the RPM are those produced by the exclusion of gravitropism and negative thigmotropism, as is apparent, the conclusion is that Arabidopsis roots are animated by a form of chiral circumnutation, that is lacking in the auxinic and gravitropic mutants aux1, eir1 and rha1. In addition, the 1 g condition appears to reduce the scatter among the circumnutating tracks produced by the roots of the wild types, but not among those of the mutants. Because there is a scarcity of literature regarding circumnutation in roots, it is not known how widely root chiral circumnutation is spread, but it is known that, in some previously studied species, just random nutations are observed. Two kinds of nutating movements seem to exist in plant roots and, whereas the random process does not seem to be connected with auxin physiology and transport, the chiral process appears to be connected in the same way as gravitropism is.

  17. 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...

  18. High throughput selection of novel plant growth regulators: Assessing the translatability of small bioactive molecules from Arabidopsis to crops.

    Science.gov (United States)

    Rodriguez-Furlán, Cecilia; Miranda, Giovanna; Reggiardo, Martín; Hicks, Glenn R; Norambuena, Lorena

    2016-04-01

    Plant growth regulators (PGRs) have become an integral part of agricultural and horticultural practices. Accordingly, there is an increased demand for new and cost-effective products. Nevertheless, the market is limited by insufficient innovation. In this context chemical genomics has gained increasing attention as a powerful approach addressing specific traits. Here is described the successful implementation of a highly specific, sensitive and efficient high throughput screening approach using Arabidopsis as a model. Using a combination of techniques, 10,000 diverse compounds were screened and evaluated for several important plant growth traits including root and leaf growth. The phenotype-based selection allowed the compilation of a collection of putative Arabidopsis growth regulators with a broad range of activities and specificities. A subset was selected for evaluating their bioactivity in agronomically valuable plants. Their validation as growth regulators in commercial species such as tomato, lettuce, carrot, maize and turfgrasses reinforced the success of the screening in Arabidopsis and indicated that small molecules activity can be efficiently translated to commercial species. Therefore, the chemical genomics approach in Arabidopsis is a promising field that can be incorporated in PGR discovery programs and has a great potential to develop new products that can be efficiently used in crops.

  19. High throughput selection of novel plant growth regulators: Assessing the translatability of small bioactive molecules from Arabidopsis to crops.

    Science.gov (United States)

    Rodriguez-Furlán, Cecilia; Miranda, Giovanna; Reggiardo, Martín; Hicks, Glenn R; Norambuena, Lorena

    2016-04-01

    Plant growth regulators (PGRs) have become an integral part of agricultural and horticultural practices. Accordingly, there is an increased demand for new and cost-effective products. Nevertheless, the market is limited by insufficient innovation. In this context chemical genomics has gained increasing attention as a powerful approach addressing specific traits. Here is described the successful implementation of a highly specific, sensitive and efficient high throughput screening approach using Arabidopsis as a model. Using a combination of techniques, 10,000 diverse compounds were screened and evaluated for several important plant growth traits including root and leaf growth. The phenotype-based selection allowed the compilation of a collection of putative Arabidopsis growth regulators with a broad range of activities and specificities. A subset was selected for evaluating their bioactivity in agronomically valuable plants. Their validation as growth regulators in commercial species such as tomato, lettuce, carrot, maize and turfgrasses reinforced the success of the screening in Arabidopsis and indicated that small molecules activity can be efficiently translated to commercial species. Therefore, the chemical genomics approach in Arabidopsis is a promising field that can be incorporated in PGR discovery programs and has a great potential to develop new products that can be efficiently used in crops. PMID:26940491

  20. Genetic analysis of growth-regulator-induced parthenocarpy in Arabidopsis.

    Science.gov (United States)

    Vivian-Smith, A; Koltunow, A M

    1999-10-01

    In Arabidopsis, seedless silique development or parthenocarpy can be induced by the application of various plant growth regulators (PGRs) to unfertilized pistils. Ecotype-specific responses were observed in the Arabidopsis ecotypes Columbia and Landsberg relative to the type of PGR and level applied. The parthenocarpic response was greatest in ecotype Landsberg, and comparisons of fruit growth and morphology were studied primarily in this ecotype. Gibberellic acid application (10 micromol pistil(-1)) caused development similar to that in pollinated pistils, while benzyladenine (1 micromol pistil(-1)) and naphthylacetic acid (10 micromol pistil(-1)) treatment produced shorter siliques. Naphthylacetic acid primarily modified mesocarp cell expansion. Arabidopsis mutants were employed to examine potential dependencies on gibberellin biosynthesis (ga1-3, ga4-1, and ga5-1) and perception (spy-4 and gai) during parthenocarpic silique development. Emasculated spy-4 pistils were neither obviously parthenocarpic nor deficient in PGR perception. By contrast, emasculated gai mutants did not produce parthenocarpic siliques following gibberellic acid application, but silique development occurred following pollination or application of auxin and cytokinin. Pollinated gai siliques had decreased cell numbers and morphologically resembled auxin-induced parthenocarpic siliques. This shows that a number of independent and possibly redundant pathways can direct hormone-induced parthenocarpy, and that endogenous gibberellins play a role in regulating cell expansion and promoting cell division in carpels. PMID:10517835

  1. A novel high efficiency, low maintenance, hydroponic system for synchronous growth and flowering of Arabidopsis thaliana

    Science.gov (United States)

    Tocquin, Pierre; Corbesier, Laurent; Havelange, Andrée; Pieltain, Alexandra; Kurtem, Emile; Bernier, Georges; Périlleux, Claire

    2003-01-01

    Background Arabidopsis thaliana is now the model organism for genetic and molecular plant studies, but growing conditions may still impair the significance and reproducibility of the experimental strategies developed. Besides the use of phytotronic cabinets, controlling plant nutrition may be critical and could be achieved in hydroponics. The availability of such a system would also greatly facilitate studies dealing with root development. However, because of its small size and rosette growth habit, Arabidopsis is hardly grown in standard hydroponic devices and the systems described in the last years are still difficult to transpose at a large scale. Our aim was to design and optimize an up-scalable device that would be adaptable to any experimental conditions. Results An hydroponic system was designed for Arabidopsis, which is based on two units: a seed-holder and a 1-L tank with its cover. The original agar-containing seed-holder allows the plants to grow from sowing to seed set, without transplanting step and with minimal waste. The optimum nitrate supply was determined for vegetative growth, and the flowering response to photoperiod and vernalization was characterized to show the feasibility and reproducibility of experiments extending over the whole life cycle. How this equipment allowed to overcome experimental problems is illustrated by the analysis of developmental effects of nitrate reductase deficiency in nia1nia2 mutants. Conclusion The hydroponic device described in this paper allows to drive small and large scale cultures of homogeneously growing Arabidopsis plants. Its major advantages are its flexibility, easy handling, fast maintenance and low cost. It should be suitable for many experimental purposes. PMID:12556248

  2. A novel high efficiency, low maintenance, hydroponic system for synchronous growth and flowering of Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Bernier Georges

    2003-01-01

    Full Text Available Abstract Background Arabidopsis thaliana is now the model organism for genetic and molecular plant studies, but growing conditions may still impair the significance and reproducibility of the experimental strategies developed. Besides the use of phytotronic cabinets, controlling plant nutrition may be critical and could be achieved in hydroponics. The availability of such a system would also greatly facilitate studies dealing with root development. However, because of its small size and rosette growth habit, Arabidopsis is hardly grown in standard hydroponic devices and the systems described in the last years are still difficult to transpose at a large scale. Our aim was to design and optimize an up-scalable device that would be adaptable to any experimental conditions. Results An hydroponic system was designed for Arabidopsis, which is based on two units: a seed-holder and a 1-L tank with its cover. The original agar-containing seed-holder allows the plants to grow from sowing to seed set, without transplanting step and with minimal waste. The optimum nitrate supply was determined for vegetative growth, and the flowering response to photoperiod and vernalization was characterized to show the feasibility and reproducibility of experiments extending over the whole life cycle. How this equipment allowed to overcome experimental problems is illustrated by the analysis of developmental effects of nitrate reductase deficiency in nia1nia2 mutants. Conclusion The hydroponic device described in this paper allows to drive small and large scale cultures of homogeneously growing Arabidopsis plants. Its major advantages are its flexibility, easy handling, fast maintenance and low cost. It should be suitable for many experimental purposes.

  3. Plastid sedimentation kinetics in roots of wild-type and starch-deficient mutants of Arabidopsis

    Science.gov (United States)

    MacCleery, S. A.; Kiss, J. Z.

    1999-01-01

    Sedimentation and movement of plastids in columella cells of the root cap were measured in seedlings of wild-type, a reduced starch mutant, and a starchless mutant of Arabidopsis. To assay for sedimentation, we used both linear measurements and the change of angle from the cell center as indices in vertical and reoriented plants with the aid of computer-assisted image analysis. Seedlings were fixed at short periods after reorientation, and plastid sedimentation correlated with starch content in the three strains of Arabidopsis. Amyloplasts of wild-type seedlings showed the greatest sedimentation, whereas plastids of the starchless mutant showed no significant sedimentation in the vertically grown and reoriented seedlings. Because previous research has shown that a full complement of starch is needed for full gravitropic sensitivity, this study correlates increased sensitivity with plastid sedimentation. However, although plastid sedimentation contributed to gravisensitivity, it was not required, because the gravitropic starchless mutant had plastids that did not sediment. This is the first study, to our knowledge, to measure plastid sedimentation in Arabidopsis roots after reorientation of seedlings. Taken together, the results of this study are consistent with the classic plastid-based and protoplast-based models of graviperception and suggest that multiple systems of perception exist in plant cells.

  4. AtGRP3 Is Implicated in Root Size and Aluminum Response Pathways in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Amanda Mangeon

    Full Text Available AtGRP3 is a glycine-rich protein (GRP from Arabidopsis thaliana shown to interact with the receptor-like kinase AtWAK1 in yeast, in vitro and in planta. In this work, phenotypic analyses using transgenic plants were performed in order to better characterize this GRP. Plants of two independent knockout alleles of AtGRP3 develop longer roots suggesting its involvement in root size determination. Confocal microscopy analysis showed an abnormal cell division and elongation in grp3-1 knockout mutants. Moreover, we also show that grp3-1 exhibits an enhanced Aluminum (Al tolerance, a feature also described in AtWAK1 overexpressing plants. Together, these results implicate AtGRP3 function root size determination during development and in Al stress.

  5. 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.

  6. Cyclic mononucleotides modulate potassium and calcium flux responses to H2O2 in Arabidopsis roots

    KAUST Repository

    Ordoñez, Natalia Maria

    2014-02-13

    Cyclic mononucleotides are messengers in plant stress responses. Here we show that hydrogen peroxide (H2O2) induces rapid net K+-efflux and Ca2+-influx in Arabidopsis roots. Pre-treatment with either 10 μM cAMP or cGMP for 1 or 24 h does significantly reduce net K+-leakage and Ca2+-influx, and in the case of the K+-fluxes, the cell permeant cyclic mononucleotides are more effective. We also examined the effect of 10 μM of the cell permeant 8-Br-cGMP on the Arabidopsis microsomal proteome and noted a specific increase in proteins with a role in stress responses and ion transport, suggesting that cGMP is sufficient to directly and/or indirectly induce complex adaptive changes to cellular stresses induced by H2O2. © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  7. 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.

  8. 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.

  9. Arabidopsis growth under prolonged high temperature and water deficit: independent or interactive effects?

    Science.gov (United States)

    Vile, Denis; Pervent, Marjorie; Belluau, Michaël; Vasseur, François; Bresson, Justine; Muller, Bertrand; Granier, Christine; Simonneau, Thierry

    2012-04-01

    High temperature (HT) and water deficit (WD) are frequent environmental constraints restricting plant growth and productivity. These stresses often occur simultaneously in the field, but little is known about their combined impacts on plant growth, development and physiology. We evaluated the responses of 10 Arabidopsis thaliana natural accessions to prolonged elevated air temperature (30 °C) and soil WD applied separately or in combination. Plant growth was significantly reduced under both stresses and their combination was even more detrimental to plant performance. The effects of the two stresses were globally additive, but some traits responded specifically to one but not the other stress. Root allocation increased in response to WD, while reproductive allocation, hyponasty and specific leaf area increased under HT. All the traits that varied in response to combined stresses also responded to at least one of them. Tolerance to WD was higher in small-sized accessions under control temperature and HT and in accessions with high biomass allocation to root under control conditions. Accessions that originate from sites with higher temperature have less stomatal density and allocate less biomass to the roots when cultivated under HT. Independence and interaction between stresses as well as the relationships between traits and stress responses are discussed.

  10. Redirection of auxin flow in Arabidopsis thaliana roots after infection by root-knot nematodes

    NARCIS (Netherlands)

    Kyndt, Tina; Goverse, Aska; Haegeman, Annelies; Warmerdam, Sonja; Wanjau, Cecilia; Jahani, Mona; Engler, Gilbert; Almeida Engler, De Janice; Gheysen, Godelieve

    2016-01-01

    Plant-parasitic root-knot nematodes induce the formation of giant cells within the plant root, and it has been recognized that auxin accumulates in these feeding sites. Here, we studied the role of the auxin transport system governed by AUX1/LAX3 influx proteins and different PIN efflux proteins dur

  11. Plant growth in Arabidopsis is assisted by compost soil-derived microbial communities.

    Science.gov (United States)

    Carvalhais, Lilia C; Muzzi, Frederico; Tan, Chin-Hong; Hsien-Choo, Jin; Schenk, Peer M

    2013-01-01

    Plants in natural and agricultural environments are continuously exposed to a plethora of diverse microorganisms resulting in microbial colonization of roots and the rhizosphere. This process is believed to be accompanied by an intricate network of ongoing simultaneous interactions. In this study, we examined Arabidopsis thaliana roots and shoots in the presence or absence of whole microbial communities extracted from compost soil. The results show a clear growth promoting effect on Arabidopsis shoots in the presence of soil microbes compared to plants grown in microbe-free soil under otherwise identical conditions. Element analyses showed that iron uptake was facilitated by these mixed microbial communities which also led to transcriptional downregulation of genes required for iron transport. In addition, soil microbial communities suppressed the expression of marker genes involved in nitrogen uptake, oxidative stress/redox signaling, and salicylic acid (SA)-mediated plant defense while upregulating jasmonate (JA) signaling, cell wall organization/biosynthesis and photosynthesis. Multi-species analyses such as simultaneous transcriptional profiling of plants and their interacting microorganisms (metatranscriptomics) coupled to metagenomics may further increase our understanding of the intricate networks underlying plant-microbe interactions. PMID:23847639

  12. The transparent testa4 mutation prevents flavonoid synthesis and alters auxin transport and the response of Arabidopsis roots to gravity and light.

    Science.gov (United States)

    Buer, Charles S; Muday, Gloria K

    2004-05-01

    We examined whether flavonoids act as endogenous auxin transport regulators during gravity vector and light intensity changes in Arabidopsis thaliana roots. Flavonoid deficient transparent testa4 [tt4(2YY6)] seedlings had elevated root basipetal auxin transport compared with the wild type, consistent with the absence of a negative auxin transport regulator. The tt4(2YY6) roots had delayed gravitropism that was chemically complemented with a flavonoid intermediate. Flavonoid accumulation was found in wild-type columella cells, the site of gravity perception, and in epidermal and cortical cells, the site of differential growth, but flavonoid accumulation was absent in tt4(2YY6) roots. Flavonoid accumulation was higher in gravity-stimulated root tips as compared with vertical controls, with maximum differences coinciding with the timing of gravitropic bending, and was located in epidermal cells. Exogenous indole-3-acetic acid (IAA) also elevated flavonoid accumulation, suggesting that flavonoid changes in response to gravity might be partly as a result of changing IAA distribution. Acropetal IAA transport was also elevated in roots of tt4(2YY6). Flavonoid synthesis was repressed in the dark, as were differences in root acropetal transport in tt4(2YY6). These results are consistent with light- and gravity-induced flavonoid stimulation that alters auxin transport in roots and dependent physiological processes, including gravitropic bending and root development.

  13. NITRIC OXIDE-ASSOCIATED PROTEIN1 (AtNOA1) is essential for salicylic acid-induced root waving in Arabidopsis thaliana.

    Science.gov (United States)

    Zhao, Xiang; Wang, Jin; Yuan, Jing; Wang, Xi-Li; Zhao, Qing-Ping; Kong, Pei-Tao; Zhang, Xiao

    2015-07-01

    Root waving responses have been attributed to both environmental and genetics factors, but the potential inducers and transducers of root waving remain elusive. Thus, the identification of novel signal elements related to root waving is an intriguing field of research. Genetic, physiological, cytological, live cell imaging, and pharmacological approaches provide strong evidence for the involvement of Arabidopsis thaliana NITRIC OXIDE-ASSOCIATED PROTEIN1 (AtNOA1) in salicylic acid (SA)-induced root waving. SA specially induced root waving, with an overall decrease in root elongation in A. thaliana, and this SA-induced response was disrupted in the Atnoa1 mutant, as well as in nonexpresser of pathogenesis-related genes 1 (npr1), which is defective in SA-mediated plant defense signal transduction, but not in npr3/4 single and double mutants. The expression assays revealed that the abundance of AtNOA1 was significantly increased by application of SA. Genetic and pharmacological analyses showed that SA-induced root waving involved an AtNOA1-dependent Ca(2+) signal transduction pathway, and PIN-FORMED2 (PIN2) -based polar auxin transport possibly plays a crucial role in this process. Our work suggests that SA signaling through NPR1 and AtNOA1 is involved in the control of root waving, which provides new insights into the mechanisms that control root growth behavior on a hard agar surface.

  14. Long-distance root-to-shoot transport of phytochelatins and cadmium in Arabidopsis.

    Science.gov (United States)

    Gong, Ji-Ming; Lee, David A; Schroeder, Julian I

    2003-08-19

    Phytochelatin synthases (PCS) mediate cellular heavy-metal resistance in plants, fungi, and worms. However, phytochelatins (PCs) are generally considered to function as intracellular heavy-metal detoxification mechanisms, and whether long-distance transport of PCs occurs during heavy-metal detoxification remains unknown. Here, wheat TaPCS1 cDNA expression was either targeted to Arabidopsis roots with the Arabidopsis alcohol dehydrogenase (Adh) promoter (Adh::TaPCS1/cad1-3) or ectopically expressed with the cauliflower mosaic virus 35S promoter (35S::TaPCS1/cad1-3) in the PC-deficient mutant cad1-3. Adh::TaPCS1/cad1-3 and 35S::TaPCS1/cad1-3 complemented the cadmium, mercury, and arsenic sensitivities of the cad1-3 mutant. Northern blot, RT-PCR, and Western blot analyses showed Adh promoter-driven TaPCS1 expression only in roots and thus demonstrated lack of long-distance TaPCS1 mRNA and protein transport in plants. Fluorescence HPLC analyses showed that under Cd2+ stress, no PCs were detectable in cad1-3. However, in Adh::TaPCS1/cad1-3 plants, PCs were detected in roots and in rosette leaves and stems. Inductively coupled plasma atomic emission spectrometer analyses showed that either root-specific or ectopic expression of TaPCS1 significantly enhanced long-distance Cd2+ transport into stems and rosette leaves. Unexpectedly, transgenic expression of TaPCS1 reduced Cd2+ accumulation in roots compared with cad1-3. The reduced Cd2+ accumulation in roots and enhanced root-to-shoot Cd2+ transport in transgenic plants were abrogated by l-buthionine sulfoximine. The presented findings show that (i) transgenic expression of TaPCS1 suppresses the heavy-metal sensitivity of cad1-3, (ii) PCs can be transported from roots to shoots, and (iii) transgenic expression of the TaPCS1 gene increases long-distance root-to-shoot Cd2+ transport and reduces Cd2+ accumulation in roots.

  15. 土壤食细菌线虫对拟南芥根系生长的影响及机理%The impact of bacterial-feeding nematodes on root growth of Arabidopsis thaliana L.and the possible mechanisms

    Institute of Scientific and Technical Information of China (English)

    成艳红; 陈小云; 刘满强; 胡锋; 李辉信

    2011-01-01

    hormonal effects as seen for protozoan grazing.To study the impacts andmechanisms of bacterial-feeding nematodes on the growth of plant, namely Arabidopsis thaliana L. ( Ecotype Columbia ) , a selected soil sample (sandy-loam alluvial soil) was mixed with pig manure and placed in mesh bags. In order to get greater populations of bacterial-feeding nematodes (SMI ) , the diameters of the openings were lmm and 5 μm. Then the mesh bags were buried under the soil ( SM5 ) which was surrounded with outer layer of un-amended soil seedlings. Nematodes were able to migrate through the 1 mm diameter mesh bag into the outer soil, thus giving greater populations than the soil surrounded by a control treatment with the mesh bag openings 5 jxm in diameter, through which nematodes could not migrate.After 35 days incubation, the outer soil contained a 4. 1-fold increase of nematode numbers in the lmm treatment compared to the 5μm treatment. The root parameters (total length, average diameter, total surface area and number of tips) of the seedlings grown in the outer soil were measured after 15 days. Soil NH^-N and NO3-N contents were determined using a continuous flow auto-analyzer ( AA3, Germany). Soil auxins were measured using high performance liquid chromatography ( HPLC). Soil bacterial community structure was analyzed by a Community-level physiological profile (CLPP) , using Biolog ECO microplates (Biolog, Hayward, CA, USA).Results showed that the Arabidopsis thaliana seedlings grown in the soil with more bacterial-feeding nematodes ( SMI ) could develop a highly branched root system with longer roots and bigger surface area. Soil NH^-N and auxin ( GA3 and IAA) contents were increased significantly in the presence of more nematodes. Furthermore, the potential for utilization of substrates of the Biolog system obtained by BIOLOG ecoplate assay indicated that the presence of nematodes made large differences in the catabolic capability of soil microbial communities. The mechanism was

  16. Aluminium toxicity targets PIN2 in Arabidopsis root apices: Effects on PIN2 endocytosis, vesicular recycling,and polar auxin transport

    Institute of Scientific and Technical Information of China (English)

    SHEN Hong; HOU NingYan; Markus SCHLICHT; WAN YingLang; Stefano MANCUSO; Frantisek BALUSKA

    2008-01-01

    The most obvious symptom of AI toxicity is the inhibition of root growth.However,the mechanism of AI-inhibiting root growth remains to be elucidated.In this study,auxin transport and vesicle movement of an auxin-efflux carrier (PIN2) were investigated in Arabidopsis roots in response to AI stress.Results indicated that AI inhibited the apical transport of auxin in root tips of Arabidopsis significantly.The severe inhibition was localized in the cells of transition zone,where the concentration of auxin was only 34% that of the control.Brefeldin A (BFA),an inhibitor of vesicle transport,induced the dot-like structure of PIN2 vesicle significantly.Al decreased the size of dot-like structure of PIN2 vesicles.Re-sults of real-time RT-PCR and Western-blotting analysis showed that Al increased the transcript level of PIN2 and the accumulation of PIN2 protein in horizontal direction of plasma membrane,but decreased its distribution in endosomes,suggesting that AI inhibited the transport of PIN2 vesicles from plasma membrane to endosomes.Results of cytoskeleton-depolymering drugs indicated that it was via the pathway of disruption of actin microfilaments that AI inhibited the transport of PIN2 vesicles.Exposed to AI stress,the cells of elongation zone had less AI uptake and less transport frequency of vesicles than cells of transition zone.Taken together,our results suggested that AI inhibited root growth mainly by modulating the transport of PIN2 vesicles between plasma membrane and endosomes,thus block-ing auxin transport and root growth.

  17. The role of the SCRAMBLED receptor-like kinase in patterning the Arabidopsis root epidermis.

    Science.gov (United States)

    Kwak, Su-Hwan; Schiefelbein, John

    2007-02-01

    Cell-type patterning in the Arabidopsis root epidermis is achieved by a network of transcription factors and influenced by a position-dependent mechanism. The SCRAMBLED receptor-like kinase is required for the normal pattern to arise, but its precise role is not understood. Here we describe genetic and molecular studies to define the spatial and temporal role of SCM in epidermal patterning and its relationship to the transcriptional network. Our results suggest that SCM helps unspecified epidermal cells interpret their position in relation to the underlying cortical cells and establish distinct cell identities. Furthermore, SCM loss-of-function and overexpression analyses suggest that SCM influences cell fate through its negative transcriptional regulation of the WEREWOLF MYB gene in epidermal cells at the H position. We also find that SCM function is specifically required for patterning the post-embryonic root epidermis and not for the analogous epidermal cell-type patterning during embryogenesis or hypocotyl development. In addition, we show that two closely related SCM-like genes in Arabidopsis (SRF1 and SRF3) are not required alone or together with SCM for proper epidermal patterning. These findings help define the developmental and mechanistic role of SCM and suggest a new model for its action in root epidermal cell patterning.

  18. The role of auxin and cytokinin signalling in specifying the root architecture of Arabidopsis thaliana

    KAUST Repository

    Muraro, Daniele

    2013-01-01

    Auxin and cytokinin are key hormonal signals that control the cellular architecture of the primary root and the initiation of new lateral root organs in the plant Arabidopsis thaliana. Both developmental processes are regulated by cross-talk between these hormones and their signalling pathways. In this paper, sub-cellular and multi-cellular mathematical models are developed to investigate how interactions between auxin and cytokinin influence the size and location of regions of division and differentiation within the primary root, and describe how their cross-regulation may cause periodic branching of lateral roots. We show how their joint activity may influence tissue-specific oscillations in gene expression, as shown in Moreno-Risueno et al. (2010) and commented upon in Traas and Vernoux (2010), and we propose mechanisms that may generate synchronisation of such periodic behaviours inside a cell and with its neighbours. Using a multi-cellular model, we also analyse the roles of cytokinin and auxin in specifying the three main regions of the primary root (elongation, transition and division zones), our simulation results being in good agreement with independent experimental observations. We then use our model to generate testable predictions concerning the effect of varying the concentrations of the auxin efflux transporters on the sizes of the different root regions. In particular, we predict that over-expression of the transporters will generate a longer root with a longer elongation zone and a smaller division zone than that of a wild type root. This root will contain fewer cells than its wild type counterpart. We conclude that our model can provide a useful tool for investigating the response of cell division and elongation to perturbations in hormonal signalling. © 2012 Elsevier Ltd.

  19. Carotenoid crystal formation in Arabidopsis and carrot roots caused by increased phytoene synthase protein levels.

    Directory of Open Access Journals (Sweden)

    Dirk Maass

    Full Text Available BACKGROUND: As the first pathway-specific enzyme in carotenoid biosynthesis, phytoene synthase (PSY is a prime regulatory target. This includes a number of biotechnological approaches that have successfully increased the carotenoid content in agronomically relevant non-green plant tissues through tissue-specific PSY overexpression. We investigated the differential effects of constitutive AtPSY overexpression in green and non-green cells of transgenic Arabidopsis lines. This revealed striking similarities to the situation found in orange carrot roots with respect to carotenoid amounts and sequestration mechanism. METHODOLOGY/PRINCIPAL FINDINGS: In Arabidopsis seedlings, carotenoid content remained unaffected by increased AtPSY levels although the protein was almost quantitatively imported into plastids, as shown by western blot analyses. In contrast, non-photosynthetic calli and roots overexpressing AtPSY accumulated carotenoids 10 and 100-fold above the corresponding wild-type tissues and contained 1800 and 500 microg carotenoids per g dry weight, respectively. This increase coincided with a change of the pattern of accumulated carotenoids, as xanthophylls decreased relative to beta-carotene and carotene intermediates accumulated. As shown by polarization microscopy, carotenoids were found deposited in crystals, similar to crystalline-type chromoplasts of non-green tissues present in several other taxa. In fact, orange-colored carrots showed a similar situation with increased PSY protein as well as carotenoid levels and accumulation patterns whereas wild white-rooted carrots were similar to Arabidopsis wild type roots in this respect. Initiation of carotenoid crystal formation by increased PSY protein amounts was further confirmed by overexpressing crtB, a bacterial PSY gene, in white carrots, resulting in increased carotenoid amounts deposited in crystals. CONCLUSIONS: The sequestration of carotenoids into crystals can be driven by the

  20. Effects of externally supplied protein on root morphology and biomass allocation in Arabidopsis

    OpenAIRE

    Thierry G. A. Lonhienne; Yuri Trusov; Anthony Young; Doris Rentsch; Torgny Näsholm; Susanne Schmidt; Chanyarat Paungfoo-Lonhienne

    2014-01-01

    Growth, morphogenesis and function of roots are influenced by the concentration and form of nutrients present in soils, including low molecular mass inorganic N (IN, ammonium, nitrate) and organic N (ON, e.g. amino acids). Proteins, ON of high molecular mass, are prevalent in soils but their possible effects on roots have received little attention. Here, we investigated how externally supplied protein of a size typical of soluble soil proteins influences root development of axenically grown A...

  1. 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.

  2. 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

  3. APC/C-CCS52A complexes control meristem maintenance in the Arabidopsis root.

    Science.gov (United States)

    Vanstraelen, Marleen; Baloban, Mikhail; Da Ines, Olivier; Cultrone, Antonietta; Lammens, Tim; Boudolf, Véronique; Brown, Spencer C; De Veylder, Lieven; Mergaert, Peter; Kondorosi, Eva

    2009-07-14

    Plant organs originate from meristems where stem cells are maintained to produce continuously daughter cells that are the source of different cell types. The cell cycle switch gene CCS52A, a substrate specific activator of the anaphase promoting complex/cyclosome (APC/C), controls the mitotic arrest and the transition of mitotic cycles to endoreduplication (ER) cycles as part of cell differentiation. Arabidopsis, unlike other organisms, contains 2 CCS52A isoforms. Here, we show that both of them are active and regulate meristem maintenance in the root tip, although through different mechanisms. The CCS52A1 activity in the elongation zone of the root stimulates ER and mitotic exit, and contributes to the border delineation between dividing and expanding cells. In contrast, CCS52A2 acts directly in the distal region of the root meristem to control identity of the quiescent center (QC) cells and stem cell maintenance. Cell proliferation assays in roots suggest that this control involves CCS52A2 mediated repression of mitotic activity in the QC cells. The data indicate that the CCS52A genes favor a low mitotic state in different cell types of the root tip that is required for meristem maintenance, and reveal a previously undescribed mechanism for APC/C mediated control in plant development.

  4. 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.

  5. Comprehensive transcriptional profiling of NaCl-stressed Arabidopsis roots reveals novel classes of responsive genes

    Directory of Open Access Journals (Sweden)

    Deyholos Michael K

    2006-10-01

    Full Text Available Abstract Background Roots are an attractive system for genomic and post-genomic studies of NaCl responses, due to their primary importance to agriculture, and because of their relative structural and biochemical simplicity. Excellent genomic resources have been established for the study of Arabidopsis roots, however, a comprehensive microarray analysis of the root transcriptome following NaCl exposure is required to further understand plant responses to abiotic stress and facilitate future, systems-based analyses of the underlying regulatory networks. Results We used microarrays of 70-mer oligonucleotide probes representing 23,686 Arabidopsis genes to identify root transcripts that changed in relative abundance following 6 h, 24 h, or 48 h of hydroponic exposure to 150 mM NaCl. Enrichment analysis identified groups of structurally or functionally related genes whose members were statistically over-represented among up- or down-regulated transcripts. Our results are consistent with generally observed stress response themes, and highlight potentially important roles for underappreciated gene families, including: several groups of transporters (e.g. MATE, LeOPT1-like; signalling molecules (e.g. PERK kinases, MLO-like receptors, carbohydrate active enzymes (e.g. XTH18, transcription factors (e.g. members of ZIM, WRKY, NAC, and other proteins (e.g. 4CL-like, COMT-like, LOB-Class 1. We verified the NaCl-inducible expression of selected transcription factors and other genes by qRT-PCR. Conclusion Micorarray profiling of NaCl-treated Arabidopsis roots revealed dynamic changes in transcript abundance for at least 20% of the genome, including hundreds of transcription factors, kinases/phosphatases, hormone-related genes, and effectors of homeostasis, all of which highlight the complexity of this stress response. Our identification of these transcriptional responses, and groups of evolutionarily related genes with either similar or divergent

  6. 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.

  7. Natural variation of root exudates in Arabidopsis thaliana-linking metabolomic and genomic data.

    Science.gov (United States)

    Mönchgesang, Susann; Strehmel, Nadine; Schmidt, Stephan; Westphal, Lore; Taruttis, Franziska; Müller, Erik; Herklotz, Siska; Neumann, Steffen; Scheel, Dierk

    2016-01-01

    Many metabolomics studies focus on aboveground parts of the plant, while metabolism within roots and the chemical composition of the rhizosphere, as influenced by exudation, are not deeply investigated. In this study, we analysed exudate metabolic patterns of Arabidopsis thaliana and their variation in genetically diverse accessions. For this project, we used the 19 parental accessions of the Arabidopsis MAGIC collection. Plants were grown in a hydroponic system, their exudates were harvested before bolting and subjected to UPLC/ESI-QTOF-MS analysis. Metabolite profiles were analysed together with the genome sequence information. Our study uncovered distinct metabolite profiles for root exudates of the 19 accessions. Hierarchical clustering revealed similarities in the exudate metabolite profiles, which were partly reflected by the genetic distances. An association of metabolite absence with nonsense mutations was detected for the biosynthetic pathways of an indolic glucosinolate hydrolysis product, a hydroxycinnamic acid amine and a flavonoid triglycoside. Consequently, a direct link between metabolic phenotype and genotype was detected without using segregating populations. Moreover, genomics can help to identify biosynthetic enzymes in metabolomics experiments. Our study elucidates the chemical composition of the rhizosphere and its natural variation in A. thaliana, which is important for the attraction and shaping of microbial communities. PMID:27363486

  8. Annexin 1 regulates the H2O2-induced calcium signature in Arabidopsis thaliana roots.

    Science.gov (United States)

    Richards, Siân L; Laohavisit, Anuphon; Mortimer, Jennifer C; Shabala, Lana; Swarbreck, Stéphanie M; Shabala, Sergey; Davies, Julia M

    2014-01-01

    Hydrogen peroxide is the most stable of the reactive oxygen species (ROS) and is a regulator of development, immunity and adaptation to stress. It frequently acts by elevating cytosolic free Ca(2+) ([Ca(2+) ]cyt ) as a second messenger, with activation of plasma membrane Ca(2+) -permeable influx channels as a fundamental part of this process. At the genetic level, to date only the Ca(2) (+) -permeable Stelar K(+) Outward Rectifier (SKOR) channel has been identified as being responsive to hydrogen peroxide. We show here that the ROS-regulated Ca(2+) transport protein Annexin 1 in Arabidopsis thaliana (AtANN1) is involved in regulating the root epidermal [Ca(2+) ]cyt response to stress levels of extracellular hydrogen peroxide. Peroxide-stimulated [Ca(2+) ]cyt elevation (determined using aequorin luminometry) was aberrant in roots and root epidermal protoplasts of the Atann1 knockout mutant. Similarly, peroxide-stimulated net Ca(2+) influx and K(+) efflux were aberrant in Atann1 root mature epidermis, determined using extracellular vibrating ion-selective microelectrodes. Peroxide induction of GSTU1 (Glutathione-S-Transferase1 Tau 1), which is known to be [Ca(2+) ]cyt -dependent was impaired in mutant roots, consistent with a lesion in signalling. Expression of AtANN1 in roots was suppressed by peroxide, consistent with the need to restrict further Ca(2+) influx. Differential regulation of annexin expression was evident, with AtANN2 down-regulation but up-regulation of AtANN3 and AtANN4. Overall the results point to involvement of AtANN1 in shaping the root peroxide-induced [Ca(2+) ]cyt signature and downstream signalling.

  9. Cinnamic Acid Increases Lignin Production and Inhibits Soybean Root Growth

    OpenAIRE

    Victor Hugo Salvador; Rogério Barbosa Lima; Wanderley Dantas dos Santos; Anderson Ricardo Soares; Paulo Alfredo Feitoza Böhm; Rogério Marchiosi; Maria de Lourdes Lucio Ferrarese; Osvaldo Ferrarese-Filho

    2013-01-01

    Cinnamic acid is a known allelochemical that affects seed germination and plant root growth and therefore influences several metabolic processes. In the present work, we evaluated its effects on growth, indole-3-acetic acid (IAA) oxidase and cinnamate 4-hydroxylase (C4H) activities and lignin monomer composition in soybean ( Glycine max ) roots. The results revealed that exogenously applied cinnamic acid inhibited root growth and increased IAA oxidase and C4H activities. The allelochemical in...

  10. Plant growth-promoting rhizobacteria and root system functioning

    OpenAIRE

    Vacheron, Jordan; Desbrosses, Guilhem; Bouffaud, Marie-Lara; Touraine, Bruno; Moënne-Loccoz, Yvan; Muller, Daniel; Legendre, Laurent; Wisniewski-Dyé, Florence; Prigent-Combaret, Claire

    2013-01-01

    The rhizosphere supports the development and activity of a huge and diversified microbial community, including microorganisms capable to promote plant growth. Among the latter, plant growth-promoting rhizobacteria (PGPR) colonize roots of monocots and dicots, and enhance plant growth by direct and indirect mechanisms. Modification of root system architecture by PGPR implicates the production of phytohormones and other signals that lead, mostly, to enhanced lateral root branching and developme...

  11. Plant growth-promoting rhizobacteria and root system functioning

    OpenAIRE

    Jordan eVacheron; Guilhem eDesbrosses; Marie-Lara eBouffaud; Bruno eTouraine; Yvan eMoënne-Loccoz; Daniel eMuller; Laurent eLegendre; Florence eWisniewski-Dyé; Claire ePrigent-Combaret

    2013-01-01

    The rhizosphere supports the development and activity of a huge and diversified microbial community, including microorganisms capable to promote plant growth. Among the latter, Plant Growth-Promoting Rhizobacteria (PGPR) colonize roots of monocots and dicots, and enhance plant growth by direct and indirect mechanisms. Modification of root system architecture by PGPR implicates the production of phytohormones and other signals that lead, mostly, to enhanced lateral root branching and developme...

  12. Phene synergism between root hair length and basal root growth angle for phosphorus acquisition.

    Science.gov (United States)

    Miguel, Magalhaes Amade; Postma, Johannes Auke; Lynch, Jonathan Paul

    2015-04-01

    Shallow basal root growth angle (BRGA) increases phosphorus acquisition efficiency by enhancing topsoil foraging because in most soils, phosphorus is concentrated in the topsoil. Root hair length and density (RHL/D) increase phosphorus acquisition by expanding the soil volume subject to phosphorus depletion through diffusion. We hypothesized that shallow BRGA and large RHL/D are synergetic for phosphorus acquisition, meaning that their combined effect is greater than the sum of their individual effects. To evaluate this hypothesis, phosphorus acquisition in the field in Mozambique was compared among recombinant inbred lines of common bean (Phaseolus vulgaris) having four distinct root phenotypes: long root hairs and shallow basal roots, long root hairs and deep basal roots, short root hairs and shallow basal roots, and short root hairs and deep basal roots. The results revealed substantial synergism between BRGA and RHL/D. Compared with short-haired, deep-rooted phenotypes, long root hairs increased shoot biomass under phosphorus stress by 89%, while shallow roots increased shoot biomass by 58%. Genotypes with both long root hairs and shallow roots had 298% greater biomass accumulation than short-haired, deep-rooted phenotypes. Therefore, the utility of shallow basal roots and long root hairs for phosphorus acquisition in combination is twice as large as their additive effects. We conclude that the anatomical phene of long, dense root hairs and the architectural phene of shallower basal root growth are synergetic for phosphorus acquisition. Phene synergism may be common in plant biology and can have substantial importance for plant fitness, as shown here.

  13. Strigolactone regulates anthocyanin accumulation, acid phosphatases production and plant growth under low phosphate condition in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Shinsaku Ito

    Full Text Available Phosphate is an essential macronutrient in plant growth and development; however, the concentration of inorganic phosphate (Pi in soil is often suboptimal for crop performance. Accordingly, plants have developed physiological strategies to adapt to low Pi availability. Here, we report that typical Pi starvation responses in Arabidopsis are partially dependent on the strigolactone (SL signaling pathway. SL treatment induced root hair elongation, anthocyanin accumulation, activation of acid phosphatase, and reduced plant weight, which are characteristic responses to phosphate starvation. Furthermore, the expression profile of SL-response genes correlated with the expression of genes induced by Pi starvation. These results suggest a potential overlap between SL signaling and Pi starvation signaling pathways in plants.

  14. The GLABRA2 homeodomain protein directly regulates CESA5 and XTH17 gene expression in Arabidopsis roots.

    Science.gov (United States)

    Tominaga-Wada, Rumi; Iwata, Mineko; Sugiyama, Junji; Kotake, Toshihisa; Ishida, Tetsuya; Yokoyama, Ryusuke; Nishitani, Kazuhiko; Okada, Kiyotaka; Wada, Takuji

    2009-11-01

    Arabidopsis root hair formation is determined by the patterning genes CAPRICE (CPC), GLABRA3 (GL3), WEREWOLF (WER) and GLABRA2 (GL2), but little is known about the later changes in cell wall material during root hair formation. A combined Fourier-transform infrared microspectroscopy-principal components analysis (FTIR-PCA) method was used to detect subtle differences in the cell wall material between wild-type and root hair mutants in Arabidopsis. Among several root hair mutants, only the gl2 mutation affected root cell wall polysaccharides. Five of the 10 genes encoding cellulose synthase (CESA1-10) and 4 of 33 xyloglucan endotransglucosylase (XTH1-33) genes in Arabidopsis are expressed in the root, but only CESA5 and XTH17 were affected by the gl2 mutation. The L1-box sequence located in the promoter region of these genes was recognized by the GL2 protein. These results indicate that GL2 directly regulates cell wall-related gene expression during root development.

  15. Root exudation of phytochemicals in Arabidopsis follows specific patterns that are developmentally programmed and correlate with soil microbial functions.

    Directory of Open Access Journals (Sweden)

    Jacqueline M Chaparro

    Full Text Available Plant roots constantly secrete compounds into the soil to interact with neighboring organisms presumably to gain certain functional advantages at different stages of development. Accordingly, it has been hypothesized that the phytochemical composition present in the root exudates changes over the course of the lifespan of a plant. Here, root exudates of in vitro grown Arabidopsis plants were collected at different developmental stages and analyzed using GC-MS. Principle component analysis revealed that the composition of root exudates varied at each developmental stage. Cumulative secretion levels of sugars and sugar alcohols were higher in early time points and decreased through development. In contrast, the cumulative secretion levels of amino acids and phenolics increased over time. The expression in roots of genes involved in biosynthesis and transportation of compounds represented in the root exudates were consistent with patterns of root exudation. Correlation analyses were performed of the in vitro root exudation patterns with the functional capacity of the rhizosphere microbiome to metabolize these compounds at different developmental stages of Arabidopsis grown in natural soils. Pyrosequencing of rhizosphere mRNA revealed strong correlations (p<0.05 between microbial functional genes involved in the metabolism of carbohydrates, amino acids and secondary metabolites with the corresponding compounds released by the roots at particular stages of plant development. In summary, our results suggest that the root exudation process of phytochemicals follows a developmental pattern that is genetically programmed.

  16. ARGONAUTE1 acts in Arabidopsis root radial pattern formation independently of the SHR/SCR pathway.

    Science.gov (United States)

    Miyashima, Shunsuke; Hashimoto, Takashi; Nakajima, Keiji

    2009-03-01

    The formation of radially symmetric tissue patterns is one of the most basic processes in the development of vascular plants. In Arabidopsis thaliana, plant-specific GRAS-type transcription factors, SHORT-ROOT (SHR) and SCARECROW (SCR), are required for asymmetric cell divisions that separate two ground tissue cell layers, the endodermis and cortex, as well as for endodermal cell fate specification. While loss of SHR or SCR results in a single-layered ground tissue, radially symmetric cellular patterns are still maintained, suggesting that unknown regulatory mechanisms act independently of the SHR/SCR-dependent pathway. In this study, we identified a novel root radial pattern mutant and found that it is a new argonaute1 (ago1) allele. Multiple ago1 mutant alleles contained supernumerary ground tissue cell layers lacking a concentric organization, while expression patterns of SHR and SCR were not affected, revealing a previously unreported role for AGO1 in root ground tissue patterning. Analyses of ago1 scr double mutants demonstrated that the simultaneous loss of the two pathways caused a dramatic reduction in cellular organization and ground tissue identity as compared with the single mutants. Based on these results, we propose that highly symmetric root ground tissue patterns are maintained by the actions of two independent pathways, one using post-transcriptional regulation mediated by AGO1 and the other using the SHR/SCR transcriptional regulator.

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

    Directory of Open Access Journals (Sweden)

    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

  18. Coordinated post-translational responses of aquaporins to abiotic and nutritional stimuli in Arabidopsis roots.

    Science.gov (United States)

    di Pietro, Magali; Vialaret, Jérôme; Li, Guo-Wei; Hem, Sonia; Prado, Karine; Rossignol, Michel; Maurel, Christophe; Santoni, Véronique

    2013-12-01

    In plants, aquaporins play a crucial role in regulating root water transport in response to environmental and physiological cues. Controls achieved at the post-translational level are thought to be of critical importance for regulating aquaporin function. To investigate the general molecular mechanisms involved, we performed, using the model species Arabidopsis, a comprehensive proteomic analysis of root aquaporins in a large set of physiological contexts. We identified nine physiological treatments that modulate root hydraulics in time frames of minutes (NO and H2O2 treatments), hours (mannitol and NaCl treatments, exposure to darkness and reversal with sucrose, phosphate supply to phosphate-starved roots), or days (phosphate or nitrogen starvation). All treatments induced inhibition of root water transport except for sucrose supply to dark-grown plants and phosphate resupply to phosphate-starved plants, which had opposing effects. Using a robust label-free quantitative proteomic methodology, we identified 12 of 13 plasma membrane intrinsic protein (PIP) aquaporin isoforms, 4 of the 10 tonoplast intrinsic protein isoforms, and a diversity of post-translational modifications including phosphorylation, methylation, deamidation, and acetylation. A total of 55 aquaporin peptides displayed significant changes after treatments and enabled the identification of specific and as yet unknown patterns of response to stimuli. The data show that the regulation of PIP and tonoplast intrinsic protein abundance was involved in response to a few treatments (i.e. NaCl, NO, and nitrate starvation), whereas changes in the phosphorylation status of PIP aquaporins were positively correlated to changes in root hydraulic conductivity in the whole set of treatments. The identification of in vivo deamidated forms of aquaporins and their stimulus-induced changes in abundance may reflect a new mechanism of aquaporin regulation. The overall work provides deep insights into the in vivo post

  19. Transcriptomic Analysis of Soil-Grown Arabidopsis thaliana Roots and Shoots in Response to a Drought Stress

    OpenAIRE

    Sultana eRasheed; Khurram eBashir; Akihiro eMatsui; Maho eTanaka; Motoaki eSeki

    2016-01-01

    Drought stress has a negative impact on crop yield. Thus, understanding the molecular mechanisms responsible for plant drought stress tolerance is essential for improving this beneficial trait in crops. In the current study, a transcriptional analysis was conducted of gene regulatory networks in roots of soil-grown Arabidopsis plants in response to a drought stress treatment. A microarray analysis of drought-stressed roots and shoots was performed at 0, 1, 3, 5, 7 and 9 days. Results indicat...

  20. [Effects nutrients on the seedlings root hair development and root growth of Poncirus trifoliata under hydroponics condition].

    Science.gov (United States)

    Cao, Xiu; Xia, Ren-Xue; Zhang, De-Jian; Shu, Bo

    2013-06-01

    Ahydroponics experiment was conducted to study the effects of nutrients (N, P, K, Ca, Mg, Fe, and Mn) deficiency on the length of primary root, the number of lateral roots, and the root hair density, length, and diameter on the primary root and lateral roots of Poncirus trifoliata seedlings. Under the deficiency of each test nutrient, root hair could generate, but was mainly concentrated on the root base and fewer on the root tip. The root hair density on lateral roots was significantly larger than that on primary root, but the root hair length was in adverse. The deficiency of each test nutrient had greater effects on the growth and development of root hairs, with the root hair density on primary root varied from 55.0 to 174.3 mm(-2). As compared with the control, Ca deficiency induced the significant increase of root hair density and length on primary root, P deficiency promoted the root hair density and length on the base and middle part of primary root and on the lateral roots significantly, Fe deficiency increased the root hair density but decreased the root hair length on the tip of primary root significantly, K deficiency significantly decreased the root hair density, length, and diameter on primary root and lateral roots, whereas Mg deficiency increased the root hair length of primary root significantly. In all treatments of nutrient deficiency, the primary root had the similar growth rate, but, with the exceptions of N and Mg deficiency, the lateral roots exhibited shedding and regeneration.

  1. Colonization of Arabidopsis roots by Pseudomonas fluorescens primes the plant to produce higher levels of ethylene upon pathogen infection

    NARCIS (Netherlands)

    Hase, S.; Pelt, J.A. van; Loon, L.C. van; Pieterse, C.M.J.

    2003-01-01

    Plants develop an enhanced defensive capacity against a broad spectrum of plant pathogens after colonization of the roots by selected strains of non-pathogenic, fluorescent Pseudomonas spp. In Arabidopsis thaliana, this rhizobacteria-induced systemic resistance (ISR) functions independently of salic

  2. Lateral Root Development of Related Genes in Arabidopsis thaliana%拟南芥侧根生长发育相关的基因

    Institute of Scientific and Technical Information of China (English)

    张方亮; 高亚梅; 王占斌; 韩毅强; 郑殿峰; 何俊华

    2015-01-01

    侧根是植物吸收水分和养分的重要器官,随着人们对植物侧根研究的不断深入,在植物中发现了大量与侧根发育相关的基因.不完全统计了从2000至2014年发表的与拟南芥侧根生长发育相关的69个基因,按照突变体表型分为三类,结果显示,在69个基因中有57个基因与侧根数目相关,7个基因与侧根长度有关,5个基因影响侧根形态.这些基因中有48个基因与激素相关,其中生长素相关基因36个,说明生长素对侧根发育具有重要作用.从侧根数目、侧根长度、侧根形态3个方面论述了基因对侧根生长发育的作用,为系统揭示拟南芥侧根形成的调控网络提供参考.%Lateral roots are important organs of plant to absorb water and nutrients,a lot of genes associated with lateral root development were found in the plant with more and more researches. 69 lateral root development of related genes in Arabidopsis thaliana were incompletely got from 2000 to 2014,and classified into three categories according to the mutant phenotype. The results showed that 56 genes of 69 genes were associated with the number of lateral roots,7 genes were associated with the lateral root length,and 6 genes affected lateral root morphology. There were 48 hormone-related genes,including 36 auxin-related genes,which indicated that auxin played an important role in lateral root development. This article summarized lateral root growth and development genes from lateral roots number,lateral root length,lateral root morphology,which provided the basis for further study of regulatory network of Arabidopsis lateral root development.

  3. Root Growth and Water distribution in living walls

    DEFF Research Database (Denmark)

    Jørgensen, Lars

    for root growth. This thesis investigates the correlations between the growing media and root and shoots growth, and studies root growth patterns of different plant species and effects of planting position and root interactions of plants growing in living walls. There are a number of challenges with living...... walls; the vertical orientation of the growing medium, plants are growing vertically above or below each other in a limited rooting volume; there is an increased exposure to weather and the plants can react differently to water conditions and competition from other plants. Plant growth is the core...... of functional living walls and this thesis is a first step of understanding the essential but hidden part inside the growing medium, i.e. the roots. Ensuring successful performance of the plants in a living wall is complex and the choice of growing medium, plant species and planting position are important....

  4. Metabolome analysis of Arabidopsis thaliana roots identifies a key metabolic pathway for iron acquisition.

    Directory of Open Access Journals (Sweden)

    Holger Schmidt

    Full Text Available Fe deficiency compromises both human health and plant productivity. Thus, it is important to understand plant Fe acquisition strategies for the development of crop plants which are more Fe-efficient under Fe-limited conditions, such as alkaline soils, and have higher Fe density in their edible tissues. Root secretion of phenolic compounds has long been hypothesized to be a component of the reduction strategy of Fe acquisition in non-graminaceous plants. We therefore subjected roots of Arabidopsis thaliana plants grown under Fe-replete and Fe-deplete conditions to comprehensive metabolome analysis by gas chromatography-mass spectrometry and ultra-pressure liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry. Scopoletin and other coumarins were found among the metabolites showing the strongest response to two different Fe-limited conditions, the cultivation in Fe-free medium and in medium with an alkaline pH. A coumarin biosynthesis mutant defective in ortho-hydroxylation of cinnamic acids was unable to grow on alkaline soil in the absence of Fe fertilization. Co-cultivation with wild-type plants partially rescued the Fe deficiency phenotype indicating a contribution of extracellular coumarins to Fe solubilization. Indeed, coumarins were detected in root exudates of wild-type plants. Direct infusion mass spectrometry as well as UV/vis spectroscopy indicated that coumarins are acting both as reductants of Fe(III and as ligands of Fe(II.

  5. 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.

  6. Uranium perturbs signaling and iron uptake response in Arabidopsis thaliana roots.

    Science.gov (United States)

    Doustaly, Fany; Combes, Florence; Fiévet, Julie B; Berthet, Serge; Hugouvieux, Véronique; Bastien, Olivier; Aranjuelo, Iker; Leonhardt, Nathalie; Rivasseau, Corinne; Carrière, Marie; Vavasseur, Alain; Renou, Jean-Pierre; Vandenbrouck, Yves; Bourguignon, Jacques

    2014-04-01

    Uranium is a natural element which is mainly redistributed in the environment due to human activity, including accidents and spillages. Plants may be useful in cleaning up after incidents, although little is yet known about the relationship between metal speciation and plant response. Here, J-Chess modeling was used to predict U speciation and exposure conditions affecting U bioavailability for plants. The model was confirmed by exposing Arabidopsis thaliana plants to U under hydroponic conditions. The early root response was characterized using complete Arabidopsis transcriptome microarrays (CATMA). Expression of 111 genes was modified at the three timepoints studied. The associated biological processes were further examined by real-time quantitative RT-PCR. Annotation revealed that oxidative stress, cell wall and hormone biosynthesis, and signaling pathways (including phosphate signaling) were affected by U exposure. The main actors in iron uptake and signaling (IRT1, FRO2, AHA2, AHA7 and FIT1) were strongly down-regulated upon exposure to uranyl. A network calculated using IRT1, FRO2 and FIT1 as bait revealed a set of genes whose expression levels change under U stress. Hypotheses are presented to explain how U perturbs the iron uptake and signaling response. These results give preliminary insights into the pathways affected by uranyl uptake, which will be of interest for engineering plants to help clean areas contaminated with U.

  7. 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.

  8. Photosynthate Regulation of the Root System Architecture Mediated by the Heterotrimeric G Protein Complex in Arabidopsis.

    Science.gov (United States)

    Mudgil, Yashwanti; Karve, Abhijit; Teixeira, Paulo J P L; Jiang, Kun; Tunc-Ozdemir, Meral; Jones, Alan M

    2016-01-01

    Assimilate partitioning to the root system is a desirable developmental trait to control but little is known of the signaling pathway underlying partitioning. A null mutation in the gene encoding the Gβ subunit of the heterotrimeric G protein complex, a nexus for a variety of signaling pathways, confers altered sugar partitioning in roots. While fixed carbon rapidly reached the roots of wild type and agb1-2 mutant seedlings, agb1 roots had more of this fixed carbon in the form of glucose, fructose, and sucrose which manifested as a higher lateral root density. Upon glucose treatment, the agb1-2 mutant had abnormal gene expression in the root tip validated by transcriptome analysis. In addition, PIN2 membrane localization was altered in the agb1-2 mutant. The heterotrimeric G protein complex integrates photosynthesis-derived sugar signaling incorporating both membrane-and transcriptional-based mechanisms. The time constants for these signaling mechanisms are in the same range as photosynthate delivery to the root, raising the possibility that root cells are able to use changes in carbon fixation in real time to adjust growth behavior. PMID:27610112

  9. 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.

  10. Separation of ballistic and diffusive fluorescence photons in confocal Light-Sheet Microscopy of Arabidopsis roots.

    Science.gov (United States)

    Meinert, Tobias; Tietz, Olaf; Palme, Klaus J; Rohrbach, Alexander

    2016-01-01

    Image quality in light-sheet fluorescence microscopy is strongly affected by the shape of the illuminating laser beam inside embryos, plants or tissue. While the phase of Gaussian or Bessel beams propagating through thousands of cells can be partly controlled holographically, the propagation of fluorescence light to the detector is difficult to control. With each scatter process a fluorescence photon loses information necessary for the image generation. Using Arabidopsis root tips we demonstrate that ballistic and diffusive fluorescence photons can be separated by analyzing the image spectra in each plane without a priori knowledge. We introduce a theoretical model allowing to extract typical scattering parameters of the biological material. This allows to attenuate image contributions from diffusive photons and to amplify the relevant image contributions from ballistic photons through a depth dependent deconvolution. In consequence, image contrast and resolution are significantly increased and scattering artefacts are minimized especially for Bessel beams with confocal line detection. PMID:27553506

  11. Separation of ballistic and diffusive fluorescence photons in confocal Light-Sheet Microscopy of Arabidopsis roots

    Science.gov (United States)

    Meinert, Tobias; Tietz, Olaf; Palme, Klaus J.; Rohrbach, Alexander

    2016-01-01

    Image quality in light-sheet fluorescence microscopy is strongly affected by the shape of the illuminating laser beam inside embryos, plants or tissue. While the phase of Gaussian or Bessel beams propagating through thousands of cells can be partly controlled holographically, the propagation of fluorescence light to the detector is difficult to control. With each scatter process a fluorescence photon loses information necessary for the image generation. Using Arabidopsis root tips we demonstrate that ballistic and diffusive fluorescence photons can be separated by analyzing the image spectra in each plane without a priori knowledge. We introduce a theoretical model allowing to extract typical scattering parameters of the biological material. This allows to attenuate image contributions from diffusive photons and to amplify the relevant image contributions from ballistic photons through a depth dependent deconvolution. In consequence, image contrast and resolution are significantly increased and scattering artefacts are minimized especially for Bessel beams with confocal line detection. PMID:27553506

  12. Potential involvement of drought-induced Ran GTPase CLRan1 in root growth enhancement in a xerophyte wild watermelon.

    Science.gov (United States)

    Akashi, Kinya; Yoshimura, Kazuya; Kajikawa, Masataka; Hanada, Kouhei; Kosaka, Rina; Kato, Atsushi; Katoh, Akira; Nanasato, Yoshihiko; Tsujimoto, Hisashi; Yokota, Akiho

    2016-10-01

    Enhanced root growth is known as the survival strategy of plants under drought. Previous proteome analysis in drought-resistant wild watermelon has shown that Ran GTPase, an essential regulator of cell division and proliferation, was induced in the roots under drought. In this study, two cDNAs were isolated from wild watermelon, CLRan1 and CLRan2, which showed a high degree of structural similarity with those of other plant Ran GTPases. Quantitative RT-PCR and promoter-GUS assays suggested that CLRan1 was expressed mainly in the root apex and lateral root primordia, whereas CLRan2 was more broadly expressed in other part of the roots. Immunoblotting analysis confirmed that the abundance of CLRan proteins was elevated in the root apex region under drought stress. Transgenic Arabidopsis overexpressing CLRan1 showed enhanced primary root growth, and the growth was maintained under osmotic stress, indicating that CLRan1 functions as a positive factor for maintaining root growth under stress conditions. PMID:27310473

  13. Root growth, secondary root formation and root gravitropism in carotenoid-deficient seedlings of Zea mays L

    Science.gov (United States)

    Ng, Y. K.; Moore, R.

    1985-01-01

    The effect of ABA on root growth, secondary-root formation and root gravitropism in seedlings of Zea mays was investigated by using Fluridone-treated seedlings and a viviparous mutant, both of which lack carotenoids and ABA. Primary roots of seedlings grown in the presence of Fluridone grew significantly slower than those of control (i.e. untreated) roots. Elongation of Fluridone-treated roots was inhibited significantly by the exogenous application of 1 mM ABA. Exogenous application of 1 micromole and 1 nmole ABA had either no effect or only a slight stimulatory effect on root elongation, depending on the method of application. The absence of ABA in Fluridone-treated plants was not an important factor in secondary-root formation in seedlings less than 9-10 d old. However, ABA may suppress secondary-root formation in older seedlings, since 11-d-old control seedlings had significantly fewer secondary roots than Fluridone-treated seedlings. Roots of Fluridone-treated and control seedlings were graviresponsive. Similar data were obtained for vp-9 mutants of Z. mays, which are phenotypically identical to Fluridone-treated seedlings. These results indicate that ABA is necessary for neither secondary-root formation nor for positive gravitropism by primary roots.

  14. An ABA down-regulated bHLH transcription repressor gene, bHLH129 regulates root elongation and ABA response when overexpressed in Arabidopsis

    Science.gov (United States)

    Tian, Hainan; Guo, Hongyan; Dai, Xuemei; Cheng, Yuxin; Zheng, Kaijie; Wang, Xiaoping; Wang, Shucai

    2015-01-01

    Plant hormone abscisic acid (ABA) plays a crucial role in modulating plant responses to environmental stresses. Basic helix-loop-helix (bHLH) transcription factors are one of the largest transcription factor families that regulate multiple aspects of plant growth and development, as well as of plant metabolism in Arabidopsis. Several bHLH transcription factors have been shown to be involved in the regulation of ABA signaling. We report here the characterization of bHLH129, a bHLH transcription factor in Arabidopsis. We found that the expression level of bHLH129 was reduced in response to exogenously applied ABA, and elevated in the ABA biosynthesis mutant aba1-5. Florescence observation of transgenic plants expressing bHLH129-GFP showed that bHLH129 was localized in the nucleus, and transient expression of bHLH129 in protoplasts inhibited reporter gene expression. When expressed in Arabidopsis under the control of the 35S promoter, bHLH129 promoted root elongation, and the transgenic plants were less sensitivity to ABA in root elongation assays. Quantitative RT-PCR results showed that ABA response of several genes involved in ABA signaling, including ABI1, SnRK2.2, SnRK2.3 and SnRK2.6 were altered in the transgenic plants overexpressing bHLH129. Taken together, our study suggests that bHLH129 is a transcription repressor that negatively regulates ABA response in Arabidopsis. PMID:26625868

  15. Perturbation of cytokinin and ethylene-signalling pathways explain the strong rooting phenotype exhibited by Arabidopsis expressing the Schizosaccharomyces pombe mitotic inducer, cdc25

    Directory of Open Access Journals (Sweden)

    Spadafora Natasha D

    2012-03-01

    Full Text Available Abstract Background Entry into mitosis is regulated by cyclin dependent kinases that in turn are phosphoregulated. In most eukaryotes, phosphoregulation is through WEE1 kinase and CDC25 phosphatase. In higher plants a homologous CDC25 gene is unconfirmed and hence the mitotic inducer Schizosaccharomyces pombe (Sp cdc25 has been used as a tool in transgenic plants to probe cell cycle function. Expression of Spcdc25 in tobacco BY-2 cells accelerates entry into mitosis and depletes cytokinins; in whole plants it stimulates lateral root production. Here we show, for the first time, that alterations to cytokinin and ethylene signaling explain the rooting phenotype elicited by Spcdc25 expression in Arabidopsis. Results Expressing Spcdc25 in Arabidopsis results in increased formation of lateral and adventitious roots, a reduction of primary root width and more isodiametric cells in the root apical meristem (RAM compared with wild type. Furthermore it stimulates root morphogenesis from hypocotyls when cultured on two way grids of increasing auxin and cytokinin concentrations. Microarray analysis of seedling roots expressing Spcdc25 reveals that expression of 167 genes is changed by > 2-fold. As well as genes related to stress responses and defence, these include 19 genes related to transcriptional regulation and signaling. Amongst these was the up-regulation of genes associated with ethylene synthesis and signaling. Seedlings expressing Spcdc25 produced 2-fold more ethylene than WT and exhibited a significant reduction in hypocotyl length both in darkness or when exposed to 10 ppm ethylene. Furthermore in Spcdc25 expressing plants, the cytokinin receptor AHK3 was down-regulated, and endogenous levels of iPA were reduced whereas endogeous IAA concentrations in the roots increased. Conclusions We suggest that the reduction in root width and change to a more isodiametric cell phenotype in the RAM in Spcdc25 expressing plants is a response to ethylene over

  16. The Root Cap Determines Ethylene-Dependent Growth and Development in Maize Roots

    Institute of Scientific and Technical Information of China (English)

    Achim Hahn; Roman Zimmermann; Dierk Wanke; Klaus Harter; Hans G.Edelmann

    2008-01-01

    Besides providing protection against mechanical damage to the root tip,the root cap is involved in the perception and processing of diverse external and internal stimuli resulting in altered growth and development.The transduction of these stimuli includes hormonal signaling pathways such as those of auxin,ethylene and cytokinin.Here,we show that the root cap is essential for the ethylene-induced regulation of elongation growth and root hair formation in maize.Exogenously applied ethylene is no longer able to inhibit elongation growth when the root cap has been surgically removed prior to hormone treatment.Reconstitution of the cap positively correlates with the developing capacity of the roots to respond to ethylene again.In contrast,the removal of the root cap does not per se affect growth inhibition controlled by auxin and cytokinin.Furthermore,our semi-quantitative RT-PCR results support earlier findings that the maize root cap is a site of high gene expression activity with respect to sensing and responding to hormones such as ethylene.From these data,we propose a novel function of the root cap which is the establishment of competence to respond to ethylene in the distal zones of the root.

  17. Plant development in space: Observations on root formation and growth

    Science.gov (United States)

    Levine, H. G.; Kann, R. P.; Krikorian, Abraham D.

    1990-01-01

    Root growth in space is discussed and observations on root production from plants flown as part of the Chromex project that were defined as to their origin, stage of development and physiological status, are presented. Roots were generated from fully differentiated, aseptically maintained individuals of Haplopappus gracilis (Compositae) under spaceflight conditions. Results are compared for tissue culture generated plantlets and comparably sized seedling clone individuals, both of which had their roots trimmed on Earth before they were loaded into NASA's plant growth unit and subjected to a 5 day shuttle flight (STS-29). Asepsis was maintained throughout the experiment. Overall root production was 40 to 50 percent greater under spaceflight conditions than during ground control tests. However, root formation slowed down towards the end of the flight. This decrease in new roots did not occur in the ground controls that sought to simulate flight except for microgravity.

  18. A complex molecular interplay of auxin and ethylene signaling pathways is involved in Arabidopsis growth promotion by Burkholderia phytofirmans PsJN

    Directory of Open Access Journals (Sweden)

    María Josefina Poupin

    2016-04-01

    Full Text Available Modulation of phytohormones homeostasis is one of the proposed mechanisms to explain plant growth promotion induced by beneficial rhizobacteria (PGPR. However, there is still limited knowledge about the molecular signals and pathways underlying these beneficial interactions. Even less is known concerning the interplay between phytohormones in plants inoculated with PGPR. Auxin and ethylene are crucial hormones in the control of plant growth and development, and recent studies report an important and complex crosstalk between them in the regulation of different plant developmental processes. The objective of this work was to study the role of both hormones in the growth promotion of Arabidopsis thaliana plants induced by the well-known PGPR Burkholderia phytofirmans PsJN. For this, the spatiotemporal expression patterns of several genes related to auxin biosynthesis, perception and response and ethylene biosynthesis were studied, finding that most of these genes showed specific transcriptional regulations after inoculation in roots and shoots. PsJN-growth promotion was not observed in Arabidopsis mutants with an impaired ethylene (ein2-1 or auxin (axr1-5 signaling. Even, PsJN did not promote growth in an ethylene overproducer (eto2, indicating that a fine regulation of both hormones signaling and homeostasis is necessary to induce growth of the aerial and root tissues. Auxin polar transport is also involved in growth promotion, since PsJN did not promote primary root growth in the pin2 mutant or under chemical inhibition of transport in wild type plants. Finally, a key role for ethylene biosynthesis was found in the PsJN-mediated increase in root hair number. These results not only give new insights of PGPR regulation of plant growth but also are also useful to understand key aspects of Arabidopsis growth control.

  19. A Complex Molecular Interplay of Auxin and Ethylene Signaling Pathways Is Involved in Arabidopsis Growth Promotion by Burkholderia phytofirmans PsJN.

    Science.gov (United States)

    Poupin, María J; Greve, Macarena; Carmona, Vicente; Pinedo, Ignacio

    2016-01-01

    Modulation of phytohormones homeostasis is one of the proposed mechanisms to explain plant growth promotion induced by beneficial rhizobacteria (PGPR). However, there is still limited knowledge about the molecular signals and pathways underlying these beneficial interactions. Even less is known concerning the interplay between phytohormones in plants inoculated with PGPR. Auxin and ethylene are crucial hormones in the control of plant growth and development, and recent studies report an important and complex crosstalk between them in the regulation of different plant developmental processes. The objective of this work was to study the role of both hormones in the growth promotion of Arabidopsis thaliana plants induced by the well-known PGPR Burkholderia phytofirmans PsJN. For this, the spatiotemporal expression patterns of several genes related to auxin biosynthesis, perception and response and ethylene biosynthesis were studied, finding that most of these genes showed specific transcriptional regulations after inoculation in roots and shoots. PsJN-growth promotion was not observed in Arabidopsis mutants with an impaired ethylene (ein2-1) or auxin (axr1-5) signaling. Even, PsJN did not promote growth in an ethylene overproducer (eto2), indicating that a fine regulation of both hormones signaling and homeostasis is necessary to induce growth of the aerial and root tissues. Auxin polar transport is also involved in growth promotion, since PsJN did not promote primary root growth in the pin2 mutant or under chemical inhibition of transport in wild type plants. Finally, a key role for ethylene biosynthesis was found in the PsJN-mediated increase in root hair number. These results not only give new insights of PGPR regulation of plant growth but also are also useful to understand key aspects of Arabidopsis growth control. PMID:27148317

  20. 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

  1. Mathematical modeling and experimental validation of the spatial distribution of boron in the root of Arabidopsis thaliana identify high boron accumulation in the tip and predict a distinct root tip uptake function.

    Science.gov (United States)

    Shimotohno, Akie; Sotta, Naoyuki; Sato, Takafumi; De Ruvo, Micol; Marée, Athanasius F M; Grieneisen, Verônica A; Fujiwara, Toru

    2015-04-01

    Boron, an essential micronutrient, is transported in roots of Arabidopsis thaliana mainly by two different types of transporters, BORs and NIPs (nodulin26-like intrinsic proteins). Both are plasma membrane localized, but have distinct transport properties and patterns of cell type-specific accumulation with different polar localizations, which are likely to affect boron distribution. Here, we used mathematical modeling and an experimental determination to address boron distributions in the root. A computational model of the root is created at the cellular level, describing the boron transporters as observed experimentally. Boron is allowed to diffuse into roots, in cells and cell walls, and to be transported over plasma membranes, reflecting the properties of the different transporters. The model predicts that a region around the quiescent center has a higher concentration of soluble boron than other portions. To evaluate this prediction experimentally, we determined the boron distribution in roots using laser ablation-inductivity coupled plasma-mass spectrometry. The analysis indicated that the boron concentration is highest near the tip and is lower in the more proximal region of the meristem zone, similar to the pattern of soluble boron distribution predicted by the model. Our model also predicts that upward boron flux does not continuously increase from the root tip toward the mature region, indicating that boron taken up in the root tip is not efficiently transported to shoots. This suggests that root tip-absorbed boron is probably used for local root growth, and that instead it is the more mature root regions which have a greater role in transporting boron toward the shoots. PMID:25670713

  2. Arabidopsis thaliana cdd1 mutant uncouples the constitutive activation of salicylic acid signalling from growth defects

    NARCIS (Netherlands)

    Swain, S.; Roy, S.; Shah, J.; Wees, S.C.M. van; Pieterse, C.M.J.; Nandi, A.K.

    2011-01-01

    Arabidopsis genotypes with a hyperactive salicylic acidmediated signalling pathway exhibit enhanced disease resistance, which is often coupled with growth and developmental defects, such as dwarfing and spontaneous necrotic lesions on the leaves, resulting in reduced biomass yield. In this article,

  3. The S-Domain Receptor Kinase Arabidopsis Receptor Kinase2 and the U Box/Armadillo Repeat-Containing E3 Ubiquitin Ligase9 Module Mediates Lateral Root Development under Phosphate Starvation in Arabidopsis.

    Science.gov (United States)

    Deb, Srijani; Sankaranarayanan, Subramanian; Wewala, Gayathri; Widdup, Ellen; Samuel, Marcus A

    2014-06-25

    When plants encounter nutrient-limiting conditions in the soil, the root architecture is redesigned to generate numerous lateral roots (LRs) that increase the surface area of roots, promoting efficient uptake of these deficient nutrients. Of the many essential nutrients, reduced availability of inorganic phosphate has a major impact on plant growth because of the requirement of inorganic phosphate for synthesis of organic molecules, such as nucleic acids, ATP, and phospholipids, that function in various crucial metabolic activities. In our screens to identify a potential role for the S-domain receptor kinase1-6 and its interacting downstream signaling partner, the Arabidopsis (Arabidopsis thaliana) plant U box/armadillo repeat-containing E3 ligase9 (AtPUB9), we identified a role for this module in regulating LR development under phosphate-starved conditions. Our results show that Arabidopsis double mutant plants lacking AtPUB9 and Arabidopsis Receptor Kinase2 (AtARK2; ark2-1/pub9-1) display severely reduced LRs when grown under phosphate-starved conditions. Under these starvation conditions, these plants accumulated very low to no auxin in their primary root and LR tips as observed through expression of the auxin reporter DR5::uidA transgene. Exogenous auxin was sufficient to rescue the LR developmental defects in the ark2-1/pub9-1 lines, indicating a requirement of auxin accumulation for this process. Our subcellular localization studies with tobacco (Nicotiana tabacum) suspension-cultured cells indicate that interaction between ARK2 and AtPUB9 results in accumulation of AtPUB9 in the autophagosomes. Inhibition of autophagy in wild-type plants resulted in reduction of LR development and auxin accumulation under phosphate-starved conditions, suggesting a role for autophagy in regulating LR development. Thus, our study has uncovered a previously unknown signaling module (ARK2-PUB9) that is required for auxin-mediated LR development under phosphate-starved conditions

  4. 生长素类化合物及6-苯甲基腺嘌呤对拟南芥主根生长的抑制效应比较%Comparison of the Inhibit Effects of Auxins and 6-Benzyladenine on Arabidopsis Main Root Growth

    Institute of Scientific and Technical Information of China (English)

    李晓峰; 孟广目; 梁城磊; 李丹; 张瑞婷; 牟长军; 陈倪; 刘恒

    2012-01-01

    To study the effect of auxins and 6-BA on cell divison and cell elongation, we compared the inhibit effects of 1AA, NAA, 2,4-D and 6-BA on Arabidopsis main root development. We found that IAA and NAA has similar effects on root development that can increases the length of root meristem zone through promotes cell division and decreases the length of root elongation zone, but 2,4-D and 6-BA decreases both the length of root meristem zone through inhibit cell division and root elongation zone.%为更好的研究生长素类化合物及6-苯甲基腺嘌呤(6-BA)对细胞分裂和细胞伸长的影响,以拟南芥主根为材料,从组织学水平比较了IAA、NAA、2,4-D和6-BA对拟南芥主根分生区和伸长区的抑制效应,发现IAA和NAA效果是相似的,可以通过促进细胞分裂显著增加根分生区长度,但也显著缩短主根伸长区长度,而2,4-D和6-BA则通过抑制细胞分裂来显著缩短根分生区长度,同时也显著缩短根伸长区的长度.

  5. A proteomic approach to analyzing responses of Arabidopsis thaliana root cells to different gravitational conditions using an agravitropic mutant, pin2 and its wild type

    Directory of Open Access Journals (Sweden)

    Tan Chao

    2011-11-01

    Full Text Available Abstract Background Root gravitropsim has been proposed to require the coordinated, redistribution of the plant signaling molecule auxin within the root meristem, but the underlying molecular mechanisms are still unknown. PIN proteins are membrane transporters that mediate the efflux of auxin from cells. The PIN2 is important for the basipetal transport of auxin in roots and plays a critical role in the transmission of gravity signals perceived in the root cap to the root elongation zone. The loss of function pin2 mutant exhibits a gravity-insensitive root growth phenotype. By comparing the proteomes of wild type and the pin2 mutant root tips under different gravitational conditions, we hope to identify proteins involved in the gravity-related signal transduction. Results To identify novel proteins involved in the gravity signal transduction pathway we have carried out a comparative proteomic analysis of Arabidopsis pin2 mutant and wild type (WT roots subjected to different gravitational conditions. These conditions included horizontal (H and vertical (V clinorotation, hypergravity (G and the stationary control (S. Analysis of silver-stained two-dimensional SDS-PAGE gels revealed 28 protein spots that showed significant expression changes in altered gravity (H or G compared to control roots (V and S. Whereas the majority of these proteins exhibited similar expression patterns in WT and pin2 roots, a significant number displayed different patterns of response between WT and pin2 roots. The latter group included 11 protein spots in the H samples and two protein spots in the G samples that exhibited an altered expression exclusively in WT but not in pin2 roots. One of these proteins was identified as annexin2, which was induced in the root cap columella cells under altered gravitational conditions. Conclusions The most interesting observation in this study is that distinctly different patterns of protein expression were found in WT and pin2 mutant

  6. Handling Arabidopsis plants: growth, preservation of seeds, transformation, and genetic crosses.

    Science.gov (United States)

    Rivero, Luz; Scholl, Randy; Holomuzki, Nicholas; Crist, Deborah; Grotewold, Erich; Brkljacic, Jelena

    2014-01-01

    Growing healthy plants is essential for the advancement of Arabidopsis thaliana (Arabidopsis) research. Over the last 20 years, the Arabidopsis Biological Resource Center (ABRC) has collected and developed a series of best-practice protocols, some of which are presented in this chapter. Arabidopsis can be grown in a variety of locations, growth media, and environmental conditions. Most laboratory accessions and their mutant or transgenic derivatives flower after 4-5 weeks and set seeds after 7-8 weeks, under standard growth conditions (soil, long day, 23 ºC). Some mutant genotypes, natural accessions, and Arabidopsis relatives require strict control of growth conditions best provided by growth rooms, chambers, or incubators. Other lines can be grown in less-controlled greenhouse settings. Although the majority of lines can be grown in soil, certain experimental purposes require utilization of sterile solid or liquid growth media. These include the selection of primary transformants, identification of homozygous lethal individuals in a segregating population, or bulking of a large amount of plant material. The importance of controlling, observing, and recording growth conditions is emphasized and appropriate equipment required to perform monitoring of these conditions is listed. Proper conditions for seed harvesting and preservation, as well as seed quality control, are also described. Plant transformation and genetic crosses, two of the methods that revolutionized Arabidopsis genetics, are introduced as well.

  7. Proteomic analyses of the interaction between the plant-growth promoting rhizobacterium Paenibacillus polymyxa E681 and Arabidopsis thaliana.

    Science.gov (United States)

    Kwon, Young Sang; Lee, Dong Yeol; Rakwal, Randeep; Baek, Seong-Bum; Lee, Jeom Ho; Kwak, Youn-Sig; Seo, Jong-Su; Chung, Woo Sik; Bae, Dong-Won; Kim, Sang Gon

    2016-01-01

    Plant growth-promoting rhizobacteria (PGPR) facilitate the plant growth and enhance their induced systemic resistance (ISR) against a variety of environmental stresses. In this study, we carried out integrative analyses on the proteome, transcriptome, and metabolome to investigate Arabidopsis root and shoot responses to the well-known PGPR strain Paenibacillus polymyxa (P. polymyxa) E681. Shoot fresh and root dry weights were increased, whereas root length was decreased by treatment with P. polymyxa E681. 2DE approach in conjunction with MALDI-TOF/TOF analysis revealed a total of 41 (17 spots in root, 24 spots in shoot) that were differentially expressed in response to P. polymyxa E681. Biological process- and molecular function-based bioinformatics analysis resulted in their classification into seven different protein groups. Of these, 36 proteins including amino acid metabolism, antioxidant, defense and stress response, photosynthesis, and plant hormone-related proteins were up-regulated, whereas five proteins including three carbohydrate metabolism- and one amino acid metabolism-related, and one unknown protein were down-regulated, respectively. A good correlation was observed between protein and transcript abundances for the 12 differentially expressed proteins during interactions as determined by qPCR analysis. Metabolite analysis using LC-MS/MS revealed highly increased levels of tryptophan, indole-3-acetonitrile (IAN), indole-3-acetic acid (IAA), and camalexin in the treated plants. Arabidopsis plant inoculated P. polymyxa E681 also showed resistance to Botrytis cinerea infection. Taken together these results suggest that P. polymyxa E681 may promote plant growth by induced metabolism and activation of defense-related proteins against fungal pathogen.

  8. 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

  9. Genes of the most conserved WOX clade in plants affect root and flower development in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Moreau Hervé

    2008-10-01

    Full Text Available Abstract Background The Wuschel related homeobox (WOX family proteins are key regulators implicated in the determination of cell fate in plants by preventing cell differentiation. A recent WOX phylogeny, based on WOX homeodomains, showed that all of the Physcomitrella patens and Selaginella moellendorffii WOX proteins clustered into a single orthologous group. We hypothesized that members of this group might preferentially share a significant part of their function in phylogenetically distant organisms. Hence, we first validated the limits of the WOX13 orthologous group (WOX13 OG using the occurrence of other clade specific signatures and conserved intron insertion sites. Secondly, a functional analysis using expression data and mutants was undertaken. Results The WOX13 OG contained the most conserved plant WOX proteins including the only WOX detected in the highly proliferating basal unicellular and photosynthetic organism Ostreococcus tauri. A large expansion of the WOX family was observed after the separation of mosses from other land plants and before monocots and dicots have arisen. In Arabidopsis thaliana, AtWOX13 was dynamically expressed during primary and lateral root initiation and development, in gynoecium and during embryo development. AtWOX13 appeared to affect the floral transition. An intriguing clade, represented by the functional AtWOX14 gene inside the WOX13 OG, was only found in the Brassicaceae. Compared to AtWOX13, the gene expression profile of AtWOX14 was restricted to the early stages of lateral root formation and specific to developing anthers. A mutational insertion upstream of the AtWOX14 homeodomain sequence led to abnormal root development, a delay in the floral transition and premature anther differentiation. Conclusion Our data provide evidence in favor of the WOX13 OG as the clade containing the most conserved WOX genes and established a functional link to organ initiation and development in Arabidopsis, most

  10. Identification of a Stelar-Localized Transport Protein That Facilitates Root-to-Shoot Transfer of Chloride in Arabidopsis

    KAUST Repository

    Li, Bo

    2015-12-11

    Under saline conditions, higher plants restrict the accumulation of chloride ions (Cl–) in the shoot by regulating their transfer from the root symplast into the xylem-associated apoplast. To identify molecular mechanisms underpinning this phenomenon, we undertook a transcriptional screen of salt stressed Arabidopsis (Arabidopsis thaliana) roots. Microarrays, quantitative RT-PCR, and promoter-GUS fusions identified a candidate gene involved in Cl– xylem loading from the Nitrate transporter 1/Peptide Transporter family (NPF2.4). This gene was highly expressed in the root stele compared to the cortex, and its expression decreased after exposure to NaCl or abscisic acid. NPF2.4 fused to fluorescent proteins, expressed either transiently or stably, was targeted to the plasma membrane. Electrophysiological analysis of NPF2.4 in Xenopus laevis oocytes suggested that NPF2.4 catalyzed passive Cl– efflux out of cells and was much less permeable to NO3−. Shoot Cl– accumulation was decreased following NPF2.4 artificial microRNA knockdown, whereas it was increased by overexpression of NPF2.4. Taken together, these results suggest that NPF2.4 is involved in long-distance transport of Cl– in plants, playing a role in the loading and the regulation of Cl– loading into the xylem of Arabidopsis roots during salinity stress.

  11. 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...

  12. 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...

  13. Growth, Nitrogen Uptake and Flow in Maize Plants Affected by Root Growth Restriction

    Institute of Scientific and Technical Information of China (English)

    Liang-zheng Xu; Jun-fang Niu; Chun-jian Li; Fu-suo Zhang

    2009-01-01

    The objective of the present study was to investigate the influence of a reduced maize root-system size on root growth and nitrogen (N) uptake and flow within plants. Restriction of shoot-borne root growth caused a strong decrease in the absorption of root: shoot dry weight ratio and a reduction in shoot growth. On the other hand, compensatory growth and an increased N uptake rate in the remaining roots were observed. Despite the limited long-distance transport pathway in the mesocotyl with restriction of shoot-borne root growth, N cycling within these plants was higher than those in control plants, implying that xylem and phloem flow velocities via the mesocotyl were considerably higher than in plants with an intact root system. The removal of the seminal roots in addition to restricting shoot-borne root development did not affect whole plant growth and N uptake, except for the stronger compensatory growth of the primary roots. Our results suggest that an adequate N supply to maize plant is maintained by compensatory growth of the remaining roots, increased N uptake rate and flow velocities within the xylem and phloem via the mesocotyl, and reduction in the shoot growth rate.

  14. Ectopic expression of a stress-inducible glycosyltransferase from saffron enhances salt and oxidative stress tolerance in Arabidopsis while alters anchor root formation.

    Science.gov (United States)

    Ahrazem, Oussama; Rubio-Moraga, Angela; Trapero-Mozos, Almudena; Climent, María Fernanda López; Gómez-Cadenas, Aurelio; Gómez-Gómez, Lourdes

    2015-05-01

    Glycosyltransferases play diverse roles in cellular metabolism by modifying the activities of regulatory metabolites. Three stress-regulated UDP-glucosyltransferase-encoding genes have been isolated from the stigmas of saffron, UGT85U1, UGT85U2 and UGT85V1, which belong to the UGT85 family that includes members associated with stress responses and cell cycle regulation. Arabidopsis constitutively expressing UGT85U1 exhibited and increased anchor root development. No differences were observed in the timing of root emergence, in leaf, stem and flower morphology or flowering time. However, salt and oxidative stress tolerance was enhanced in these plants. Levels of glycosylated compounds were measured in these plants and showed changes in the composition of several indole-derivatives. Moreover, auxin levels in the roots were higher compared to wild type. The expression of several key genes related to root development and auxin homeostasis, including CDKB2.1, CDKB2.2, PIN2, 3 and 4; TIR1, SHR, and CYCD6, were differentially regulated with an increase of expression level of SHR, CYCD6, CDKB2.1 and PIN2. The obtained results showed that UGT85U1 takes part in root growth regulation via auxin signal alteration and the modified expression of cell cycle-related genes, resulting in significantly improved survival during oxidative and salt stress treatments.

  15. Transcriptional Activation and Production of Tryptophan-Derived Secondary Metabolites in Arabidopsis Roots Contributes to the Defense against the Fungal Vascular Pathogen Verticillium Iongisporum

    Institute of Scientific and Technical Information of China (English)

    Tim Iven; Wolfgang Dr(o)ge-Laser; Stefanie K(o)nig; Seema Singh; Susanna A.Braus-Stromeyer; Matthias Bischoff; Lutz F.Tietze; Gerhard H.Braus; Volker Lipka; Ivo Feussner

    2012-01-01

    The soil-borne fungal pathogen Verticillium Iongisporum causes vascular disease on Brassicaceae host plants such as oilseed rape.The fungus colonizes the root xylem and moves upwards to the foliage where disease symptoms become visible.Using Arabidopsis as a model for early gene induction,we performed root transcriptome analyses in response to hyphal growth immediately after spore germination and during penetration of the root cortex,respectively.Infected roots showed a rapid reprogramming of gene expression such as activation of transcription factors,stress-,and defense-related genes.Here,we focused on the highly coordinated gene induction resulting in the production of tryptophan-derived secondary metabolites.Previous studies in leaves showed that enzymes encoded by CYP81F2 and PEN2 (PENETRATION2) execute the formation of antifungal indole glucosinolate (IGS) metabolites.In Verticillium-infected roots.we found transcriptional activation of CYP81F2 and the PEN2 homolog PEL1 (PEN2-LIKE1),but no increase in antifungal IGS breakdown products.In contrast,indole-3-carboxylic acid (I3CA) and the phytoalexin camalexin accumulated in infected roots but only camalexin inhibited Verticillium growth in vitro.Whereas genetic disruption of the individual metabolic pathways leading to either camalexin or CYP81F2-dependent IGS metabolites did not alter Verticillium-induced disease symptoms,a cyp79b2 cyp79b3 mutant impaired in both branches resulted in significantly enhanced susceptibility.Hence,our data provide an insight into root-specific early defenses and suggest tryptophan-derived metabolites as active antifungal compounds against a vascular pathogen.

  16. 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.

  17. SOMBRERO, BEARSKIN1, and BEARSKIN2 regulate root cap maturation in Arabidopsis.

    Science.gov (United States)

    Bennett, Tom; van den Toorn, Albert; Sanchez-Perez, Gabino F; Campilho, Ana; Willemsen, Viola; Snel, Berend; Scheres, Ben

    2010-03-01

    The root cap has a central role in root growth, determining the growth trajectory and facilitating penetration into the soil. Root cap cells have specialized functions and morphologies, and border cells are released into the rhizosphere by specific cell wall modifications. Here, we demonstrate that the cellular maturation of root cap is redundantly regulated by three genes, SOMBRERO (SMB), BEARSKIN1 (BRN1), and BRN2, which are members of the Class IIB NAC transcription factor family, together with the VASCULAR NAC DOMAIN (VND) and NAC SECONDARY WALL THICKENING PROMOTING FACTOR (NST) genes that regulate secondary cell wall synthesis in specialized cell types. Lateral cap cells in smb-3 mutants continue to divide and fail to detach from the root, phenotypes that are independent of FEZ upregulation in smb-3. In brn1-1 brn2-1 double mutants, columella cells fail to detach, while in triple mutants, cells fail to mature in all parts of the cap. This complex genetic redundancy involves differences in expression, protein activity, and target specificity. All three genes have very similar overexpression phenotypes to the VND/NST genes, indicating that members of this family are largely functionally equivalent. Our results suggest that Class IIB NAC proteins regulate cell maturation in cells that undergo terminal differentiation with strong cell wall modifications.

  18. Jatropha curcas L. Root Structure and Growth in Diverse Soils

    Directory of Open Access Journals (Sweden)

    Ofelia Andrea Valdés-Rodríguez

    2013-01-01

    Full Text Available Unlike most biofuel species, Jatropha curcas has promise for use in marginal lands, but it may serve an additional role by stabilizing soils. We evaluated the growth and structural responsiveness of young J. curcas plants to diverse soil conditions. Soils included a sand, a sandy-loam, and a clay-loam from eastern Mexico. Growth and structural parameters were analyzed for shoots and roots, although the focus was the plasticity of the primary root system architecture (the taproot and four lateral roots. The sandy soil reduced the growth of both shoot and root systems significantly more than sandy-loam or clay-loam soils; there was particularly high plasticity in root and shoot thickness, as well as shoot length. However, the architecture of the primary root system did not vary with soil type; the departure of the primary root system from an index of perfect symmetry was 14±5% (mean ± standard deviation. Although J. curcas developed more extensively in the sandy-loam and clay-loam soils than in sandy soil, it maintained a consistent root to shoot ratio and root system architecture across all types of soil. This strong genetic determination would make the species useful for soil stabilization purposes, even while being cultivated primarily for seed oil.

  19. Auxin modulates the enhanced development of root hairs in Arabidopsis thaliana (L.) Heynh. under elevated CO(2).

    Science.gov (United States)

    Niu, Yaofang; Jin, Chongwei; Jin, Gulei; Zhou, Qingyan; Lin, Xianyong; Tang, Caixian; Zhang, Yongsong

    2011-08-01

    Root hairs may play a critical role in nutrient acquisition of plants grown under elevated CO(2) . This study investigated how elevated CO(2) enhanced the development of root hairs in Arabidopsis thaliana (L.) Heynh. The plants under elevated CO(2) (800 µL L(-1)) had denser and longer root hairs, and more H-positioned cells in root epidermis than those under ambient CO(2) (350 µL L(-1)). The elevated CO(2) increased auxin production in roots. Under elevated CO(2) , application of either 1-naphthoxyacetic acid (1-NOA) or N-1-naphthylphthalamic acid (NPA) blocked the enhanced development of root hairs. The opposite was true when the plants under ambient CO(2) were treated with 1-naphthylacetic acid (NAA), an auxin analogue. Furthermore, the elevated CO(2) did not enhance the development of root hairs in auxin-response mutants, axr1-3, and auxin-transporter mutants, axr4-1, aux1-7 and pin1-1. Both elevated CO(2) and NAA application increased expressions of caprice, triptychon and rho-related protein from plants 2, and decreased expressions of werewolf, GLABRA2, GLABRA3 and the transparent testa glabra 1, genes related to root-hair development, while 1-NOA and NPA application had an opposite effect. Our study suggests that elevated CO(2) enhanced the development of root hairs in Arabidopsis via the well-characterized auxin signalling and transport that modulate the initiation of root hairs and the expression of its specific genes.

  20. An ethylene and ROS-dependent pathway is involved in low ammonium-induced root hair elongation in Arabidopsis seedlings.

    Science.gov (United States)

    Zhu, Changhua; Yang, Na; Guo, Zhengfei; Qian, Meng; Gan, Lijun

    2016-08-01

    Root hairs are plastic in response to nutrient supply, but relatively little is known about their development under low ammonium (NH4(+)) conditions. This study showed that reducing NH4(+) for 3 days in wild-type Arabidopsis seedlings resulted in drastic elongation of root hairs. To investigate the possible mediation of ethylene and auxin in this process, seedlings were treated with 2,3,5-triiodobenzoic acid (TIBA, auxin transport inhibitor), 1-naphthylphthalamic acid (NPA, auxin transport inhibitor), p-chlorophenoxy isobutyric acid (PCIB, auxin action inhibitor), aminoethoxyvinylglycine (AVG, chemical inhibitor of ethylene biosynthesis), or silver ions (Ag(+), ethylene perception antagonist) under low NH4(+) conditions. Our results showed that TIBA, NPA and PCIB did not inhibit root hair elongation under low NH4(+) conditions, while AVG and Ag(+) completely inhibited low NH4(+)-induced root hair elongation. This suggested that low NH4(+)-induced root hair elongation was dependent on the ethylene pathway, but not the auxin pathway. Further genetic studies revealed that root hair elongation in auxin-insensitive mutants was sensitive to low NH4(+) treatment, but elongation was less sensitive in ethylene-insensitive mutants than wild-type plants. In addition, low NH4(+)-induced root hair elongation was accompanied by reactive oxygen species (ROS) accumulation. Diphenylene iodonium (DPI, NADPH oxidase inhibitor) and dimethylthiourea (DMTU, ROS scavenger) inhibited low NH4(+)-induced root hair elongation, suggesting that ROS were involved in this process. Moreover, ethylene acted together with ROS to modulate root hair elongation under low NH4(+) conditions. These results demonstrate that a signaling pathway involving ethylene and ROS participates in regulation of root hair elongation when Arabidopsis seedlings are subjected to low NH4(+) conditions. PMID:27074220

  1. Differential regulation of GS-GOGAT gene expression by plant growth regulators in Arabidopsis seedlings

    Directory of Open Access Journals (Sweden)

    Dragićević Milan

    2016-01-01

    Full Text Available Primary and secondary ammonium assimilation is catalyzed by the glutamine synthetase-glutamate synthase (GS-GOGAT pathway in plants. The Arabidopsis genome contains five cytosolic GS1 genes (GLN1;1 - GLN1;5, one nuclear gene for chloroplastic GS2 isoform (GLN2, two Fd-GOGAT genes (GLU1 and GLU2 and a GLT1 gene coding for NADH-GOGAT. Even though the regulation of GS and GOGAT isoforms has been extensively studied in response to various environmental and metabolic cues in many plant species, little is known about the effects of phytohormones on their regulation. The objective of this study was to investigate the impact of representative plant growth regulators, kinetin (KIN, abscisic acid (ABA, gibberellic acid (GA3 and 2,4-dichlorophenoxyacetic acid (2,4-D, on the expression of A. thaliana GS and GOGAT genes. The obtained results indicate that GS and GOGAT genes are differentially regulated by growth regulators in shoots and roots. KIN and 2,4-D repressed GS and GOGAT expression in roots, with little effect on transcript levels in shoots. KIN affected all tested genes; 2,4-D was apparently more selective and less potent. ABA induced the expression of GLN1;1 and GLU2 in whole seedlings, while GA3 enhanced the expression of all tested genes in shoots, except GLU2. The observed expression patterns are discussed in relation to physiological roles of investigated plant growth regulators and N-assimilating enzymes. [Projekat Ministarstva nauke Republike Srbije, br. ON173024

  2. 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.

  3. Light as stress factor to plant roots - case of root halotropism.

    Science.gov (United States)

    Yokawa, Ken; Fasano, Rossella; Kagenishi, Tomoko; Baluška, František

    2014-01-01

    Despite growing underground, largely in darkness, roots emerge to be very sensitive to light. Recently, several important papers have been published which reveal that plant roots not only express all known light receptors but also that their growth, physiology and adaptive stress responses are light-sensitive. In Arabidopsis, illumination of roots speeds-up root growth via reactive oxygen species-mediated and F-actin dependent process. On the other hand, keeping Arabidopsis roots in darkness alters F-actin distribution, polar localization of PIN proteins as well as polar transport of auxin. Several signaling components activated by phytohormones are overlapping with light-related signaling cascade. We demonstrated that the sensitivity of roots to salinity is altered in the light-grown Arabidopsis roots. Particularly, light-exposed roots are less effective in their salt-avoidance behavior known as root halotropism. Here we discuss these new aspects of light-mediated root behavior from cellular, physiological and evolutionary perspectives.

  4. Differences in photosynthesis and terpene content in leaves and roots of wild-type and transgenic Arabidopsis thaliana plants

    OpenAIRE

    Blanch Roure, Josep-Salvador; Peñuelas, Josep; Llusià Benet, Joan; Sardans i Galobart, Jordi; Owen, Susan M.

    2015-01-01

    We investigated the hypotheses that two different varieties of Arabidopsis thaliana show differences in physiology and terpene production. The two varieties of A. thaliana used in this study were wildtype (WT) and transgenic line (CoxIVFaNES I) genetically modified to emit nerolidol with linalool/nerolidol synthase (COX). Photosynthetic rate, electron transport rate, fluorescence, leaf volatile terpene contents and root volatile terpene contents were analyzed. For both types, we found coeluti...

  5. RNAi-mediated gene silencing reveals involvement of Arabidopsis chromatin-related genes in Agrobacterium-mediated root transformation

    OpenAIRE

    Crane, Yan Ma; Gelvin, Stanton B

    2007-01-01

    We investigated the effect of RNAi-mediated gene silencing of 109 Arabidopsis thaliana chromatin-related genes (termed “chromatin genes” hereafter) on Agrobacterium-mediated root transformation. Each of the RNAi lines contains a single- or low-copy-number insertion of a hairpin construction that silences the endogenous copy of the target gene. We used three standard transient and stable transformation assays to screen 340 independent RNAi lines, representing 109 target genes, for the rat (res...

  6. Response of Arabidopsis thaliana Roots with Altered Lipid Transfer Protein (LTP) Gene Expression to the Clubroot Disease and Salt Stress

    OpenAIRE

    Sabine Jülke; Jutta Ludwig-Müller

    2015-01-01

    The clubroot disease of Brassicaceae is caused by the obligate biotrophic protist Plasmodiophora brassicae. The disease is characterized by abnormal tumorous swellings of infected roots that result in reduced drought resistance and insufficient distribution of nutrients, leading to reduced crop yield. It is one of the most damaging diseases among cruciferous crops worldwide. The acquisition of nutrients by the protist is not well understood. Gene expression profiles in Arabidopsis thaliana cl...

  7. Putting theory to the test: which regulatory mechanisms can drive realistic growth of a root?

    Science.gov (United States)

    De Vos, Dirk; Vissenberg, Kris; Broeckhove, Jan; Beemster, Gerrit T S

    2014-10-01

    In recent years there has been a strong development of computational approaches to mechanistically understand organ growth regulation in plants. In this study, simulation methods were used to explore which regulatory mechanisms can lead to realistic output at the cell and whole organ scale and which other possibilities must be discarded as they result in cellular patterns and kinematic characteristics that are not consistent with experimental observations for the Arabidopsis thaliana primary root. To aid in this analysis, a 'Uniform Longitudinal Strain Rule' (ULSR) was formulated as a necessary condition for stable, unidirectional, symplastic growth. Our simulations indicate that symplastic structures are robust to differences in longitudinal strain rates along the growth axis only if these differences are small and short-lived. Whereas simple cell-autonomous regulatory rules based on counters and timers can produce stable growth, it was found that steady developmental zones and smooth transitions in cell lengths are not feasible. By introducing spatial cues into growth regulation, those inadequacies could be avoided and experimental data could be faithfully reproduced. Nevertheless, a root growth model based on previous polar auxin-transport mechanisms violates the proposed ULSR due to the presence of lateral gradients. Models with layer-specific regulation or layer-driven growth offer potential solutions. Alternatively, a model representing the known cross-talk between auxin, as the cell proliferation promoting factor, and cytokinin, as the cell differentiation promoting factor, predicts the effect of hormone-perturbations on meristem size. By down-regulating PIN-mediated transport through the transcription factor SHY2, cytokinin effectively flattens the lateral auxin gradient, at the basal boundary of the division zone, (thereby imposing the ULSR) to signal the exit of proliferation and start of elongation. This model exploration underlines the value of

  8. Over-expression of the Arabidopsis proton-pyrophosphatase AVP1 enhances transplant survival, root mass, and fruit development under limiting phosphorus conditions.

    Science.gov (United States)

    Yang, Haibing; Zhang, Xiao; Gaxiola, Roberto A; Xu, Guohua; Peer, Wendy Ann; Murphy, Angus S

    2014-07-01

    Phosphorus (P), an element required for plant growth, fruit set, fruit development, and fruit ripening, can be deficient or unavailable in agricultural soils. Previously, it was shown that over-expression of a proton-pyrophosphatase gene AVP1/AVP1D (AVP1DOX) in Arabidopsis, rice, and tomato resulted in the enhancement of root branching and overall mass with the result of increased mineral P acquisition. However, although AVP1 over-expression also increased shoot biomass in Arabidopsis, this effect was not observed in tomato under phosphate-sufficient conditions. AVP1DOX tomato plants exhibited increased rootward auxin transport and root acidification compared with control plants. AVP1DOX tomato plants were analysed in detail under limiting P conditions in greenhouse and field trials. AVP1DOX plants produced 25% (P=0.001) more marketable ripened fruit per plant under P-deficient conditions compared with the controls. Further, under low phosphate conditions, AVP1DOX plants displayed increased phosphate transport from leaf (source) to fruit (sink) compared to controls. AVP1DOX plants also showed an 11% increase in transplant survival (Ptomato cultivars for increased proton pyrophosphatase gene expression could be useful when selecting for cultivars to be grown on marginal soils.

  9. Auxin Resistant1 and PIN-FORMED2 Protect Lateral Root Formation in Arabidopsis under Iron Stress.

    Science.gov (United States)

    Li, Guangjie; Song, Haiyan; Li, Baohai; Kronzucker, Herbert J; Shi, Weiming

    2015-12-01

    A stunted root system is a significant symptom of iron (Fe) toxicity, yet little is known about the effects of excess Fe on lateral root (LR) development. In this work, we show that excess Fe has different effects on LR development in different portions of the Arabidopsis (Arabidopsis thaliana) root system and that inhibitory effects on the LR initiation are only seen in roots newly formed during excess Fe exposure. We show that root tip contact with Fe is both necessary and sufficient for LR inhibition and that the auxin, but not abscisic acid, pathway is engaged centrally in the initial stages of excess Fe exposure. Furthermore, Fe stress significantly reduced PIN-FORMED2 (PIN2)-green fluorescent protein (GFP) expression in root tips, and pin2-1 mutants exhibited significantly fewer LR initiation events under excess Fe than the wild type. Exogenous application of both Fe and glutathione together increased PIN2-GFP expression and the number of LR initiation events compared with Fe treatment alone. The ethylene inhibitor aminoethoxyvinyl-glycine intensified Fe-dependent inhibition of LR formation in the wild type, and this inhibition was significantly reduced in the ethylene overproduction mutant ethylene overproducer1-1. We show that Auxin Resistant1 (AUX1) is a critical component in the mediation of endogenous ethylene effects on LR formation under excess Fe stress. Our findings demonstrate the relationship between excess Fe-dependent PIN2 expression and LR formation and the potential role of AUX1 in ethylene-mediated LR tolerance and suggest that AUX1 and PIN2 protect LR formation in Arabidopsis during the early stages of Fe stress.

  10. A Cold-Inducible DEAD-Box RNA Helicase from Arabidopsis thaliana Regulates Plant Growth and Development under Low Temperature.

    Science.gov (United States)

    Liu, Yuelin; Tabata, Daisuke; Imai, Ryozo

    2016-01-01

    DEAD-box RNA helicases comprise a large family and are involved in a range of RNA processing events. Here, we identified one of the Arabidopsis thaliana DEAD-box RNA helicases, AtRH7, as an interactor of Arabidopsis COLD SHOCK DOMAIN PROTEIN 3 (AtCSP3), which is an RNA chaperone involved in cold adaptation. Promoter:GUS transgenic plants revealed that AtRH7 is expressed ubiquitously and that its levels of the expression are higher in rapidly growing tissues. Knockout mutant lines displayed several morphological alterations such as disturbed vein pattern, pointed first true leaves, and short roots, which resemble ribosome-related mutants of Arabidopsis. In addition, aberrant floral development was also observed in rh7 mutants. When the mutants were germinated at low temperature (12°C), both radicle and first leaf emergence were severely delayed; after exposure of seedlings to a long period of cold, the mutants developed aberrant, fewer, and smaller leaves. RNA blots and circular RT-PCR revealed that 35S and 18S rRNA precursors accumulated to higher levels in the mutants than in WT under both normal and cold conditions, suggesting the mutants are partially impaired in pre-rRNA processing. Taken together, the results suggest that AtRH7 affects rRNA biogenesis and plays an important role in plant growth under cold.

  11. Establishment of embryonic shoot–root axis is involved in auxin and cytokinin response during Arabidopsis somatic embryogenesis

    Directory of Open Access Journals (Sweden)

    Ying Hua eSu

    2015-01-01

    Full Text Available Auxin and cytokinin signaling participates in regulating a large spectrum of developmental and physiological processes in plants. The shoots and roots of plants have specific and sometimes even contrary responses to these hormones. Recent studies have clearly shown that establishing the spatiotemporal distribution of auxin and cytokinin response signals is central for the control of shoot apical meristem (SAM induction in cultured tissues. However, little is known about the role of these hormones in root apical meristem (RAM initiation. Here, we found that the expression patterns of several regulatory genes critical for RAM formation were correlated with the establishment of the embryonic root meristem during somatic embryogenesis in Arabidopsis. Interestingly, the early expression of the WUS-RELATED HOMEOBOX 5 (WOX5 and WUSCHEL (WUS genes was induced and was nearly overlapped within the embryonic callus when somatic embryos (SEs could not be identified morphologically. Their correct expression was essential for RAM and SAM initiation and embryonic shoot–root axis establishment. Furthermore, we analyzed the auxin and cytokinin response during SE initiation. Notably, cytokinin response signals were detected in specific regions that were correlated with induced WOX5 expression and subsequent SE formation. Overexpression of the ARABIDOPSIS RESPONSE REGULATOR genes ARR7 and ARR15 (feedback repressors of cytokinin signaling, disturbed RAM initiation and SE induction. These results provide new information on auxin and cytokinin-regulated apical–basal polarity formation of shoot–root axis during somatic embryogenesis.

  12. Arabidopsis ROOT HAIR DEFECTIVE3 is involved in nitrogen starvation-induced anthocyanin accumulation

    Institute of Scientific and Technical Information of China (English)

    Jing Wang; Yan Wang; Ju Yang; Chunli Ma; Ying Zhang; Ting Ge; Zhi Qi; Yan Kang

    2015-01-01

    Anthocyanin accumulation is a common phenom-enon seen in plants under environmental stress. In this study, we identified a new allele of ROOT HAIR DEFECTIVE3 (RHD3) showing an anthocyanin overaccumulation phenotype under nitrogen starvation conditions. It is known that ethylene negatively regulates light- and sucrose-induced anthocyanin biosynthesis. We hypothesized that RHD3 achieves its negative effect on anthocyanin biosynthesis via an ethylene-regulating pathway. In support of this, similar to rhd3 mutants, the Arabidopsis ethylene signaling mutants etr1, ein2, and ein3/eil1 showed an anthocyanin overaccumulation phenotype under nitrogen starvation conditions. The ethylene precursor ACC strongly suppressed anthocyanin accumulation, dependent on ETR1, EIN2, EIN3/EIL1, and, partially, RHD3. In addition, inactivating RHD3 partially reversed the suppressive effect of ETO1 inactivation-evoked endogenous ethylene production on anthocyanin accumulation. The expression of nitrogen starva-tion-induced anthocyanin biosynthesis genes was negatively regulated by RHD3, but ethylene response genes were positively regulated by RHD3. Wild-type seedlings overexpress-ing RHD3 showed similar phenotypes to rhd3 mutants, indicating the existence of a fine-tuned relationship between gene expression and function. RHD3 was initial y identified as a gene involved in root hair development. This study uncovered a new physiological function of RHD3 in nitrogen starvation-induced anthocyanin accumulation and ethylene homeostasis. Correction added on 6 August 2015, after first online publica-tion:“RND3”corrected to“RHD3”.

  13. Involvement of 14-3-3 protein GRF9 in root growth and response under polyethylene glycol-induced water stress.

    Science.gov (United States)

    He, Yuchi; Wu, Jingjing; Lv, Bing; Li, Jia; Gao, Zhiping; Xu, Weifeng; Baluška, František; Shi, Weiming; Shaw, Pang Chui; Zhang, Jianhua

    2015-04-01

    Plant 14-3-3 proteins are phosphoserine-binding proteins that regulate a wide array of targets via direct protein-protein interactions. In this study, the role of a 14-3-3 protein, GRF9, in plant response to water stress was investigated. Arabidopsis wild-type, GRF9-deficient mutant (grf9), and GRF9-overexpressing (OE) plants were treated with polyethylene glycol (PEG) to induce mild water stress. OE plant showed better whole-plant growth and root growth than the wild type under normal or water stress conditions while the grf9 mutant showed worse growth. In OE plants, GRF9 favours the allocation of shoot carbon to roots. In addition, GRF9 enhanced proton extrusion, mainly in the root elongation zone and root hair zone, and maintained root growth under mild water stress. Grafting among the wild type, OE, and grf9 plants showed that when OE plants were used as the scion and GRF9 was overexpressed in the shoot, it enhanced sucrose transport into the root, and when OE plants were used as rootstock and GRF9 was overexpressed in the root, it caused more release of protons into the root surface under water stress. Taken together, the results suggest that under PEG-induced water stress, GRF9 is involved in allocating more carbon from the shoot to the root and enhancing proton secretion in the root growing zone, and this process is important for root response to mild water stress.

  14. Tracking transcription factor mobility and interaction in Arabidopsis roots with fluorescence correlation spectroscopy.

    Science.gov (United States)

    Clark, Natalie M; Hinde, Elizabeth; Winter, Cara M; Fisher, Adam P; Crosti, Giuseppe; Blilou, Ikram; Gratton, Enrico; Benfey, Philip N; Sozzani, Rosangela

    2016-06-11

    To understand complex regulatory processes in multicellular organisms, it is critical to be able to quantitatively analyze protein movement and protein-protein interactions in time and space. During Arabidopsis development, the intercellular movement of SHORTROOT (SHR) and subsequent interaction with its downstream target SCARECROW (SCR) control root patterning and cell fate specification. However, quantitative information about the spatio-temporal dynamics of SHR movement and SHR-SCR interaction is currently unavailable. Here, we quantify parameters including SHR mobility, oligomeric state, and association with SCR using a combination of Fluorescent Correlation Spectroscopy (FCS) techniques. We then incorporate these parameters into a mathematical model of SHR and SCR, which shows that SHR reaches a steady state in minutes, while SCR and the SHR-SCR complex reach a steady-state between 18 and 24 hr. Our model reveals the timing of SHR and SCR dynamics and allows us to understand how protein movement and protein-protein stoichiometry contribute to development.

  15. Regulation of CAPRICE transcription by MYB proteins for root epidermis differentiation in Arabidopsis.

    Science.gov (United States)

    Koshino-Kimura, Yoshihiro; Wada, Takuji; Tachibana, Tatsuhiko; Tsugeki, Ryuji; Ishiguro, Sumie; Okada, Kiyotaka

    2005-06-01

    Epidermal cell differentiation in Arabidopsis root is studied as a model system for understanding cell fate specification. Two types of MYB-related transcription factors are involved in this cell differentiation. One of these, CAPRICE (CPC), encoding an R3-type MYB protein, is a positive regulator of hair cell differentiation and is preferentially transcribed in hairless cells. We analyzed the regulatory mechanism of CPC transcription. Deletion analyses of the CPC promoter revealed that hairless cell-specific transcription of the CPC gene required a 69 bp sequence, and a tandem repeat of this region was sufficient for its expression in epidermis. This region includes two MYB-binding sites, and the epidermis-specific transcription of CPC was abolished when base substitutions were introduced in these sites. We showed by gel mobility shift experiments and by yeast one-hybrid assay that WEREWOLF (WER), which is an R2R3-type MYB protein, directly binds to this region. We showed that WER also binds to the GL2 promoter region, indicating that WER directly regulates CPC and GL2 transcription by binding to their promoter regions.

  16. 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.

  17. Tracking transcription factor mobility and interaction in Arabidopsis roots with fluorescence correlation spectroscopy.

    Science.gov (United States)

    Clark, Natalie M; Hinde, Elizabeth; Winter, Cara M; Fisher, Adam P; Crosti, Giuseppe; Blilou, Ikram; Gratton, Enrico; Benfey, Philip N; Sozzani, Rosangela

    2016-01-01

    To understand complex regulatory processes in multicellular organisms, it is critical to be able to quantitatively analyze protein movement and protein-protein interactions in time and space. During Arabidopsis development, the intercellular movement of SHORTROOT (SHR) and subsequent interaction with its downstream target SCARECROW (SCR) control root patterning and cell fate specification. However, quantitative information about the spatio-temporal dynamics of SHR movement and SHR-SCR interaction is currently unavailable. Here, we quantify parameters including SHR mobility, oligomeric state, and association with SCR using a combination of Fluorescent Correlation Spectroscopy (FCS) techniques. We then incorporate these parameters into a mathematical model of SHR and SCR, which shows that SHR reaches a steady state in minutes, while SCR and the SHR-SCR complex reach a steady-state between 18 and 24 hr. Our model reveals the timing of SHR and SCR dynamics and allows us to understand how protein movement and protein-protein stoichiometry contribute to development. PMID:27288545

  18. Osmotic Effects on the Electrical Properties of Arabidopsis Root Hair Vacuoles in Situ1

    Science.gov (United States)

    Lew, Roger R.

    2004-01-01

    To assess the role of the vacuole in responses to hyperosmotic and hypo-osmotic stress, the electrical properties of the vacuole were measured in situ. A double-barrel micropipette was inserted into the vacuole for voltage clamping. A second double-barrel micropipette was inserted into the cytoplasm to provide a virtual ground that separated the electrical properties of the vacuole from those of the plasma membrane. Osmotic stress causes immediate electrical responses at the plasma membrane (Lew RR [1996] Plant Physiol 97: 2002-2005) and ion flux changes and turgor recovery (Shabala SN, Lew RR [2002] 129: 290-299) in Arabidopsis root cells. In situ, the vacuole also responds rapidly to changes in extracellular osmotic potential. Hyperosmotic treatment caused a very large increase in the ionic conductance of the vacuole. Hypo-osmotic treatment did not affect the vacuolar conductance. In either case, the vacuolar electrical potential was unchanged. Taken in concert with previous studies of changes at the plasma membrane, these results demonstrate a highly coordinated system in which the vacuole and plasma membrane are primed to respond immediately to hyperosmotic stress before changes in gene expression. PMID:14730070

  19. 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.

  20. Root Growth Optimizer with Self-Similar Propagation

    Directory of Open Access Journals (Sweden)

    Xiaoxian He

    2015-01-01

    Full Text Available Most nature-inspired algorithms simulate intelligent behaviors of animals and insects that can move spontaneously and independently. The survival wisdom of plants, as another species of biology, has been neglected to some extent even though they have evolved for a longer period of time. This paper presents a new plant-inspired algorithm which is called root growth optimizer (RGO. RGO simulates the iterative growth behaviors of plant roots to optimize continuous space search. In growing process, main roots and lateral roots, classified by fitness values, implement different strategies. Main roots carry out exploitation tasks by self-similar propagation in relatively nutrient-rich areas, while lateral roots explore other places to seek for better chance. Inhibition mechanism of plant hormones is applied to main roots in case of explosive propagation in some local optimal areas. Once resources in a location are exhausted, roots would shrink away from infertile conditions to preserve their activity. In order to validate optimization effect of the algorithm, twelve benchmark functions, including eight classic functions and four CEC2005 test functions, are tested in the experiments. We compared RGO with other existing evolutionary algorithms including artificial bee colony, particle swarm optimizer, and differential evolution algorithm. The experimental results show that RGO outperforms other algorithms on most benchmark functions.

  1. Melatonin in Arabidopsis thaliana acts as plant growth regulator at low concentrations and preserves seed viability at high concentrations.

    Science.gov (United States)

    Hernández, Ismaél Gatica; Gomez, Federico José Vicente; Cerutti, Soledad; Arana, María Verónica; Silva, María Fernanda

    2015-09-01

    Since the discovery of melatonin in plants, several roles have been described for different species, organs, and developmental stages. Arabidopsis thaliana, being a model plant species, is adequate to contribute to the elucidation of the role of melatonin in plants. In this work, melatonin was monitored daily by UHPLC-MS/MS in leaves, in order to study its diurnal accumulation as well as the effects of natural and artificial light treatments on its concentration. Furthermore, the effects of exogenous application of melatonin to assess its role in seed viability after heat stress and as a regulator of growth and development of vegetative tissues were evaluated. Our results indicate that melatonin contents in Arabidopsis were higher in plants growing under natural radiation when compared to those growing under artificial conditions, and its levels were not diurnally-regulated. Exogenous melatonin applications prolonged seed viability after heat stress conditions. In addition, melatonin applications retarded leaf senescence. Its effects as growth promoter were dose and tissue-dependent; stimulating root growth at low concentrations and decreasing leaf area at high doses.

  2. Impact of elevated CO2 on growth and development of Arabidopsis thaliana L

    NARCIS (Netherlands)

    van der Kooij, T.A W; De Kok, L.J.

    1996-01-01

    After germination, Arabidopsis thaliana L (cv. Landsberg) was grown at 350 mu l l(-1) (control) or 700 mu l l(-1) (elevated) CO2. Total shoot biomass at the end of the vegetative growth period was increased by 56% due to a short transient stimulation of the relative growth rate by elevated CO2 at th

  3. Quantitative trait local analysis of growth-related traits in a new Arabidopsis recombinant inbred population

    NARCIS (Netherlands)

    El-Lithy, M.E.M.; Clerkx, E.J.M.; Ruijs, G.J.; Koornneef, M.; Vreugdenhil, D.

    2004-01-01

    Arabidopsis natural variation was used to analyze the genetics of plant growth rate. Screening of 22 accessions revealed a large variation for seed weight, plant dry weight and relative growth rate but not for water content. A positive correlation was observed between seed weight and plant area 10 d

  4. Plant growth-promoting rhizobacteria and root system functioning

    Directory of Open Access Journals (Sweden)

    Jordan eVacheron

    2013-09-01

    Full Text Available The rhizosphere supports the development and activity of a huge and diversified microbial community, including microorganisms capable to promote plant growth. Among the latter, Plant Growth-Promoting Rhizobacteria (PGPR colonize roots of monocots and dicots, and enhance plant growth by direct and indirect mechanisms. Modification of root system architecture by PGPR implicates the production of phytohormones and other signals that lead, mostly, to enhanced lateral root branching and development of root hairs. PGPR also modify root functioning, improve plant nutrition and influence the physiology of the whole plant. Recent results provided first clues as to how PGPR signals could trigger these plant responses. Whether local and/or systemic, the plant molecular pathways involved remain often unknown. From an ecological point of view, it emerged that PGPR form coherent functional groups, whose rhizosphere ecology is influenced by a myriad of abiotic and biotic factors in natural and agricultural soils, and these factors can in turn modulate PGPR effects on roots. In this paper, we address novel knowledge and gaps on PGPR modes of action and signals, and highlight recent progress on the links between plant morphological and physiological effects induced by PGPR. We also show the importance of taking into account the size, diversity and gene expression patterns of PGPR assemblages in the rhizosphere to better understand their impact on plant growth and functioning. Integrating mechanistic and ecological knowledge on PGPR populations in soil will be a prerequisite to develop novel management strategies for sustainable agriculture.

  5. Synergistic growth effect among bacteria recovered from root canal infections

    Directory of Open Access Journals (Sweden)

    Gil Moreira Júnior

    2011-09-01

    Full Text Available The objective of this study was to determine the ecological relationships between bacterial species that colonize infected root canals. Root canal bacteria recovered from one patient with pulp canal necrosis were evaluated in vitro for synergistic and antagonistic activities determined by mono and co-culture growth kinetics and the production of bacteriocin-like substances using the double layer diffusion method. Peptostreptococcus prevotii triggered a significant increase of Fusobacterium nucleatum growth, while the former bacteria did not affect the growth of P. prevotii. The bacterial species did not produce antagonism activity against itself or against any of the other two species. Despite many studies have demonstrated the capability of root canal microorganisms to produce antagonistic substances, these in vitro experimental tests show the synergistic effect of P. prevotii on the growth of F. nucleatum.

  6. Constitutive expression of OsIAA9 affects starch granules accumulation and root gravitropic response in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Sha eLuo

    2015-12-01

    Full Text Available Auxin/Indole-3-Acetic Acid (Aux/IAA genes are early auxin response genes ecoding short-lived transcriptional repressors, which regulate auxin signaling in plants by interplay with Auxin Response Factors (ARFs. Most of the Aux/IAA proteins contain four different domains, namely Domain I, Domain II, Domain III and Domain IV. So far all Aux/IAA mutants with auxin-related phenotypes identified in both Arabidopsis and rice (Oryza sativa are dominant gain-of-function mutants with mutations in Domain II of the corresponding Aux/IAA proteins, suggest that Aux/IAA proteins in both Arabidopsis and rice are largely functional redundantly, and they may have conserved functions. We report here the functional characterization of a rice Aux/IAA gene, OsIAA9. RT-PCR results showed that expression of OsIAA9 was induced by exogenously applied auxin, suggesting that OsIAA9 is an auxin response gene. Bioinformatic analysis showed that OsIAA9 has a repressor motif in Domain I, a degron in Domain II, and the conserved amino acid signatures for protein-protein interactions in Domain III and Domain IV. By generating transgenic plants expressing GFP-OsIAA9 and examining florescence in the transgenic plants, we found that OsIAA9 is localized in the nucleus. When transfected into protoplasts isolated from rosette leaves of Arabidopsis, OsIAA9 repressed reporter gene expression, and the repression was partially released by exogenously IAA. These results suggest that OsIAA9 is a canonical Aux/IAA protein. Protoplast transfection assays showed that OsIAA9 interacted ARF5, but not ARF6, 7, 8 and 19. Transgenic Arabidopsis plants expressing OsIAA9 have increased number of lateral roots, and reduced gravitropic response. Further analysis showed that OsIAA9 transgenic Arabidopsis plants accumulated fewer granules in their root tips and the distribution of granules was also affected. Taken together, our study showed that OsIAA9 is a transcriptional repressor, and it regulates

  7. Different degree in proteasome malfunction has various effects on root growth possibly through preventing cell division and promoting autophagic vacuolization.

    Directory of Open Access Journals (Sweden)

    Xianyong Sheng

    Full Text Available The ubiquitin/proteasome pathway plays a vital role in plant development. But the effects of proteasome malfunction on root growth, and the mechanism underlying this involvement remains unclear. In the present study, the effects of proteasome inhibitors on Arabidopsis root growth were studied through the analysis of the root length, and meristem size and cell length in maturation zone using FM4-64, and cell-division potential using GFP fusion cyclin B, and accumulation of ubiquitinated proteins using immunofluorescence labeling, and autophagy activity using LysoTracker and MDC. The results indicated that lower concentration of proteasome inhibitors promoted root growth, whereas higher concentration of inhibitors had the opposite effects. The accumulation of cyclin B was linked to MG132-induced decline in meristem size, indicating that proteasome malfunction prevented cell division. Besides, MG132-induced accumulation of the ubiquitinated proteins was associated with the increasing fluorescence signal of LysoTracker and MDC in the elongation zone, revealing a link between the activation of autophagy and proteasome malfunction. These results suggest that weak proteasome malfunction activates moderate autophagy and promotes cell elongation, which compensates the inhibitor-induced reduction of cell division, resulting in long roots. Whereas strong proteasome malfunction induces severe autophagy and disturbs cell elongation, resulting in short roots.

  8. 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.

  9. Responses to Iron-Deficiency in Arabidopsis-Thaliana - The Turbo Iron Reductase does not depend on the Formation of Root Hairs and Transfer Cells.

    NARCIS (Netherlands)

    Moog, P.R.; Van der Kooij, T.A.W.; Bruggemann, W.; Schiefelbein, J.W.; Kuiper, P.J.C.

    1995-01-01

    Arabidopsis thaliana (L.) Heynh. Columbia wild type and a root hair-less mutant RM57 were grown on iron-containing and iron-deficient nutrient solutions. In both genotypes, ferric chelate reductase (FCR) of intact roots was induced upon iron deficiency and followed a Michaelis-Menten kinetic with a

  10. Plasma membrane proteomics in the maize primary root growth zone: novel insights into root growth adaptation to water stress.

    Science.gov (United States)

    Voothuluru, Priyamvada; Anderson, Jeffrey C; Sharp, Robert E; Peck, Scott C

    2016-09-01

    Previous work on maize (Zea mays L.) primary root growth under water stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex. These responses involve spatially differential and coordinated regulation of osmotic adjustment, modification of cell wall extensibility, and other cellular growth processes that are required for root growth under water-stressed conditions. As the interface between the cytoplasm and the apoplast (including the cell wall), the plasma membrane likely plays critical roles in these responses. Using a simplified method for enrichment of plasma membrane proteins, the developmental distribution of plasma membrane proteins was analysed in the growth zone of well-watered and water-stressed maize primary roots. The results identified 432 proteins with differential abundances in well-watered and water-stressed roots. The majority of changes involved region-specific patterns of response, and the identities of the water stress-responsive proteins suggest involvement in diverse biological processes including modification of sugar and nutrient transport, ion homeostasis, lipid metabolism, and cell wall composition. Integration of the distinct, region-specific plasma membrane protein abundance patterns with results from previous physiological, transcriptomic and cell wall proteomic studies reveals novel insights into root growth adaptation to water stress.

  11. Plasma membrane proteomics in the maize primary root growth zone: novel insights into root growth adaptation to water stress.

    Science.gov (United States)

    Voothuluru, Priyamvada; Anderson, Jeffrey C; Sharp, Robert E; Peck, Scott C

    2016-09-01

    Previous work on maize (Zea mays L.) primary root growth under water stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex. These responses involve spatially differential and coordinated regulation of osmotic adjustment, modification of cell wall extensibility, and other cellular growth processes that are required for root growth under water-stressed conditions. As the interface between the cytoplasm and the apoplast (including the cell wall), the plasma membrane likely plays critical roles in these responses. Using a simplified method for enrichment of plasma membrane proteins, the developmental distribution of plasma membrane proteins was analysed in the growth zone of well-watered and water-stressed maize primary roots. The results identified 432 proteins with differential abundances in well-watered and water-stressed roots. The majority of changes involved region-specific patterns of response, and the identities of the water stress-responsive proteins suggest involvement in diverse biological processes including modification of sugar and nutrient transport, ion homeostasis, lipid metabolism, and cell wall composition. Integration of the distinct, region-specific plasma membrane protein abundance patterns with results from previous physiological, transcriptomic and cell wall proteomic studies reveals novel insights into root growth adaptation to water stress. PMID:27341663

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

    Science.gov (United States)

    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.

  13. A novel bioassay using root re-growth in Lemna.

    Science.gov (United States)

    Park, Areum; Kim, Youn-Jung; Choi, Eun-Mi; Brown, Murray T; Han, Taejun

    2013-09-15

    A new phytotoxicity test method based on root elongation of three Lemna species (Lemna gibba, L. minor, and L. paucicostata) has been developed. Tests with aquatic plants have, typically, favored measurements on fronds (e.g. frond number, area, biomass) rather than on roots, due, in part, to issues associated with handling fragile roots and the time-consuming procedures of selecting roots with identical root lengths. The present method differs in that roots were excised prior to exposure with subsequent measurements on newly developed roots. Results show that there were species-specific difference in sensitivity to the five metals tested (Ag, Cd, Cr, Cu and Hg), with Ag being the most toxic (EC50=5.3-37.6 μgL(-1)) to all three species, and Cr the least toxic for L. gibba and L. minor (1148.3 and 341.8 μgL(-1), respectively) and Cu for L. paucicostata (470.4 μgL(-1)). Direct comparisons were made with measurements of frond area, which were found to be less sensitive. More generally, root re-growth was shown to reflect the toxic responses of all three Lemna species to these five important metals. The root growth bioassay differs from three internationally standardized methods (ISO, OCED and US EPA) in that it is completed in 48 h, the required volume of test solutions is only 3 ml and non-axenic plants are used. Our results show that the Lemna root method is a simple, rapid, cost-effective, sensitive and precise bioassay to assess the toxic risks of metals and has practical application for monitoring municipal and industrial waste waters where metals are common constituents. PMID:23917640

  14. cGMP regulates hydrogen peroxide accumulation in calcium-dependent salt resistance pathway in Arabidopsis thaliana roots.

    Science.gov (United States)

    Li, Jisheng; Wang, Xiaomin; Zhang, Yanli; Jia, Honglei; Bi, Yurong

    2011-10-01

    3',5'-cyclic guanosine monophosphate (cGMP) is an important second messenger in plants. In the present study, roles of cGMP in salt resistance in Arabidopsis roots were investigated. Arabidopsis roots were sensitive to 100 mM NaCl treatment, displaying a great increase in electrolyte leakage and Na(+)/K(+) ratio and a decrease in gene expression of the plasma membrane (PM) H(+)-ATPase. However, application of exogenous 8Br-cGMP (an analog of cGMP), H(2)O(2) or CaCl(2) alleviated the NaCl-induced injury by maintaining a lower Na(+)/K(+) ratio and increasing the PM H(+)-ATPase gene expression. In addition, the inhibition of root elongation and seed germination under salt stress was removed by 8Br-cGMP. Further study indicated that 8Br-cGMP-induced higher NADPH levels for PM NADPH oxidase to generate H(2)O(2) by regulating glucose-6-phosphate dehydrogenase (G6PDH) activity. The effect of 8Br-cGMP and H(2)O(2) on ionic homeostasis was abolished when Ca(2+) was eliminated by glycol-bis-(2-amino ethyl ether)-N,N,N',N'-tetraacetic acid (EGTA, a Ca(2+) chelator) in Arabidopsis roots under salt stress. Taken together, cGMP could regulate H(2)O(2) accumulation in salt stress, and Ca(2+) was necessary in the cGMP-mediated signaling pathway. H(2)O(2), as the downstream component of cGMP signaling pathway, stimulated PM H(+)-ATPase gene expression. Thus, ion homeostasis was modulated for salt tolerance.

  15. Involvement of calmodulin in regulation of primary root elongation by N-3-oxo-hexanoyl homoserine lactone in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Qian eZhao

    2015-01-01

    Full Text Available Many bacteria use signal molecules of low molecular weight to monitor their local population density and to coordinate their collective behavior in a process called quorum sensing (QS. N-acyl-homoserine lactones (AHLs are the primary QS signals among Gram-negative bacteria. AHL-mediated QS plays an essential role in diverse bacterial physiological processes. Recent evidence shows that plants are able to sense bacterial AHLs and respond to them appropriately. However, little is known about the mechanism by which plants perceive and transduce the bacterial AHLs within cells. In this study, we found that the stimulatory effect of N-3-oxo-hexanoyl homoserine lactone (3OC6-HSL on primary root elongation of Arabidopsis was abolished by the calmodulin (CaM antagonists N-(6-aminohexyl-5-chloro-1-naphthalene sulfonamide (W-7 and trifluoperazine (TFP. Western-blot and ELISA analysis revealed that the concentration of CaM protein in Arabidopsis roots increased after treatment with 1 μM 3OC6-HSL. Results from quantitative RT-PCR demonstrated that the transcription of all nine CaM genes in Arabidopsis genome was up-regulated in the plants treated with 3OC6-HSL. The loss-of-function mutants of each AtCaM gene (AtCaM1-9 were insensitive to 3OC6-HSL-stimulation of primary root elongation. On the other hand, the genetic evidence showed that CaM may not participates the inhibition of primary root length caused by application of long-chained AHLs such as C10-HSL and C12-HSL. Nevertheless, our results suggest that CaM is involved in the bacterial 3OC6-HSL signaling in plant cells. These data offer new insight into the mechanism of plant response to bacterial QS signals.

  16. Root growth regulation and gravitropism in maize roots does not require the epidermis

    Science.gov (United States)

    Bjorkman, T.; Cleland, R. E.

    1991-01-01

    We have earlier published observations showing that endogenous alterations in growth rate during gravitropism in maize roots (Zea mays L.) are unaffected by the orientation of cuts which remove epidermal and cortical tissue in the growing zone (Bjorkman and Cleland, 1988, Planta 176, 513-518). We concluded that the epidermis and cortex are not essential for transporting a growth-regulating signal in gravitropism or straight growth, nor for regulating the rate of tissue expansion. This conclusion has been challenged by Yang et al. (1990, Planta 180, 530-536), who contend that a shallow girdle around the entire perimeter of the root blocks gravitropic curvature and that this inhibition is the result of a requirement for epidermal cells to transport the growth-regulating signal. In this paper we demonstrate that the entire epidermis can be removed without blocking gravitropic curvature and show that the position of narrow girdles does not affect the location of curvature. We therefore conclude that the epidermis is not required for transport of a growth-regulating substance from the root cap to the growing zone, nor does it regulate the growth rate of the elongating zone of roots.

  17. Microtubules guide root hair tip growth

    NARCIS (Netherlands)

    Sieberer, B.; Ketelaar, M.J.; Esseling, J.J.; Emons, A.M.C.

    2005-01-01

    The ability to establish cell polarity is crucial to form and function of an individual cell. Polarity underlies critical processes during cell development, such as cell growth, cell division, cell differentiation and cell signalling. Interphase cytoplasmic microtubules in tip-growing fission yeast

  18. A root-specific wall-associated kinase gene, HvWAK1, regulates root growth and is highly divergent in barley and other cereals.

    Science.gov (United States)

    Kaur, Ravneet; Singh, Kashmir; Singh, Jaswinder

    2013-06-01

    Wall-associated receptor-like kinases (WAKs) are important candidates for directly linking the extracellular matrix with intracellular compartments and are involved in developmental processes and stress response. WAK gene family has been identified in plants such as Arabidopsis and rice. Here, we present a detailed analysis of the WAK1 gene from barley cv. Golden Promise, mapped to chromosome 5H. Three BAC clones corresponding to the WAK fragment were sequenced and the full-length WAK1 gene was characterized. The gene has three exons and two short introns with a coding region of 2,178 bp encoding a protein of 725 amino acids. A regulatory region was analyzed in -1,000 bp sequence upstream to start codon. Using conserved domains database and SMART, various conserved domains such as GUB WAK Bind, epidermal growth factor CA, and protein kinase C as well as other regions like signal peptides, active sites, and transmembrane domains were identified. The gene organization of HvWAK1 was compared with wheat (TaWAK1) and Arabidopsis (AtWAK1), suggesting that the WAK1 gene organization has remained highly conserved. Nonetheless, WAK1 was found to be highly divergent when compared with sequences available from barley cv. Haruna Nijo (50 %), rice (46 %), wheat (21 %), Arabidopsis (25 %), and maize (19 %). This divergence may have facilitated a better adaptation to surrounding environments due to its role in communication between the extracellular matrix, cell, and outer environment. Semiquantitative RT-PCR-based expression analysis indicates HvWAK1 expression is specific to roots. Significant differences in root growth between GP wild type and GP-Ds mutant seedlings were observed under control and salt stress conditions. PMID:23443578

  19. The COW1 locus of arabidopsis acts after RHD2, and in parallel with RHD3 and TIP1, to determine the shape, rate of elongation, and number of root hairs produced from each site of hair formation.

    Science.gov (United States)

    Grierson, C S; Roberts, K; Feldmann, K A; Dolan, L

    1997-11-01

    Two recessive mutant alleles at CAN OF WORMS1 (COW1), a new locus involved in root hair morphogenesis, have been identified in Arabidopsis thaliana L. Heynh. Root hairs on Cow1- mutants are short and wide and occasionally formed as pairs at a single site of hair formation. The COW1 locus maps to chromosome 4. Root hairs on Cow1- plants form in the usual positions, suggesting that the phenotype is not the result of abnormal positional signals. Root hairs on Cow1- roots begin hair formation normally, forming a small bulge, or root hair initiation site, of normal size and shape and in the usual position on the hair-forming cell. However, when Cow1- root hairs start to elongate by tip growth, abnormalities in the shape and elongation rate of the hairs become apparent. Genetic evidence from double-mutant analysis of cow1-1 and other loci involved in root hair development supports our conclusion that COW1 is required during root hair elongation.

  20. Development of test method for evaluating root resistance of pavement used for roof garden caused by thickening growth of root

    Energy Technology Data Exchange (ETDEWEB)

    Ishihara, Saori; Tanaka, Kyoji [Tokyo Institute of Technology, Tokyo, (Japan)

    2010-07-01

    The growth of roots of plants can damage roof garden components, such as pavements. This paper developed a test method for evaluating the resistance of pavement used in roof gardens to damage from a thickening growth of roots. The study assessed the behaviour of plant roots and evaluated the force of root growth subjected to hypertrophy. A system to measure the enlargement force of roots was designed and used for measurements over a period of 8 months on a cherry blossom of 21 years growth. The enlargement force was approximately 440 N/cm. A mechanical simulated root was designed and used to carry out experimental tests on asphalt pavements. The tests results demonstrated the viability of simulated root for evaluation of root resistances in pavements and various components of roof gardens.

  1. Hemoglobin is essential for normal growth of Arabidopsis organs

    DEFF Research Database (Denmark)

    Hebelstrup, Kim Henrik; Hunt, Peter; Dennis, Elizabeth;

    2006-01-01

    lines are viable but show a mutant phenotype affecting the regions where AHb1 is expressed. Arabidopsis lines with an insertional knockout or overexpression of AHb2, a class II 3-on-3 hemoglobin, were generated. Seedlings overexpressing AHb2 show enhanced survival of hypoxic stress. The AHb2 knockout...... lines develop normally. However, when AHb2 knockout is combined with AHb1 silencing, seedlings die at an early vegetative stage suggesting that the two 3-on-3 hemoglobins, AHb1 and AHb2, together play an essential role for normal development of Arabidopsis seedlings. In conclusion, these results...... suggests that 3-on-3 hemoglobins apart from a role in hypoxic stress play a general role under non-stressed conditions where they are essential for normal development by controlling the level of NO which tends to accumulate in floral buds and leaf hydathodes of plants...

  2. AINTEGUMENTA and the D-type cyclin CYCD3;1 regulate root secondary growth and respond to cytokinins.

    Science.gov (United States)

    Randall, Ricardo S; Miyashima, Shunsuke; Blomster, Tiina; Zhang, Jing; Elo, Annakaisa; Karlberg, Anna; Immanen, Juha; Nieminen, Kaisa; Lee, Ji-Young; Kakimoto, Tatsuo; Blajecka, Karolina; Melnyk, Charles W; Alcasabas, Annette; Forzani, Celine; Matsumoto-Kitano, Miho; Mähönen, Ari Pekka; Bhalerao, Rishikesh; Dewitte, Walter; Helariutta, Ykä; Murray, James A H

    2015-01-01

    Higher plant vasculature is characterized by two distinct developmental phases. Initially, a well-defined radial primary pattern is established. In eudicots, this is followed by secondary growth, which involves development of the cambium and is required for efficient water and nutrient transport and wood formation. Regulation of secondary growth involves several phytohormones, and cytokinins have been implicated as key players, particularly in the activation of cell proliferation, but the molecular mechanisms mediating this hormonal control remain unknown. Here we show that the genes encoding the transcription factor AINTEGUMENTA (ANT) and the D-type cyclin CYCD3;1 are expressed in the vascular cambium of Arabidopsis roots, respond to cytokinins and are both required for proper root secondary thickening. Cytokinin regulation of ANT and CYCD3 also occurs during secondary thickening of poplar stems, suggesting this represents a conserved regulatory mechanism. PMID:26340943

  3. AINTEGUMENTA and the D-type cyclin CYCD3;1 regulate root secondary growth and respond to cytokinins

    Directory of Open Access Journals (Sweden)

    Ricardo S. Randall

    2015-10-01

    Full Text Available Higher plant vasculature is characterized by two distinct developmental phases. Initially, a well-defined radial primary pattern is established. In eudicots, this is followed by secondary growth, which involves development of the cambium and is required for efficient water and nutrient transport and wood formation. Regulation of secondary growth involves several phytohormones, and cytokinins have been implicated as key players, particularly in the activation of cell proliferation, but the molecular mechanisms mediating this hormonal control remain unknown. Here we show that the genes encoding the transcription factor AINTEGUMENTA (ANT and the D-type cyclin CYCD3;1 are expressed in the vascular cambium of Arabidopsis roots, respond to cytokinins and are both required for proper root secondary thickening. Cytokinin regulation of ANT and CYCD3 also occurs during secondary thickening of poplar stems, suggesting this represents a conserved regulatory mechanism.

  4. Gravitropism in Arabidopsis thaliana: Root-specific action of the EHB gene and violation of the resultant law.

    Science.gov (United States)

    Dümmer, Michaela; Forreiter, Christoph; Galland, Paul

    2015-09-15

    Gravitropic bending of seedlings of Arabidopsis thaliana in response to centrifugal accelerations was determined in a range between 0.0025 and 4×g to revisit and validate the so-called resultant law, which claims that centrifugation causes gravitropic organs to orient parallel to the resultant stimulus vector. We show here for seedlings of A. thaliana that this empirical law holds for hypocotyls but surprisingly fails for roots. While the behavior of hypocotyls could be modeled by an arc tangent function predicted by the resultant law, roots displayed a sharp maximum at 1.8×g that substantially overshoots the predicted value and that represents a novel phenomenon, diagravitropism elicited by centrifugal acceleration. The gravitropic bending critically depended on the orientation of the seedling relative to the centrifugal acceleration. If the centrifugal vector pointed toward the cotyledons, gravitropic bending of hypocotyls and roots was substantially enhanced. The complex behavior of Arabidopsis seedlings provides strong evidence that gravitropic bending entails a cosine component (longitudinal stimulus) to which the seedlings were more sensitive than to the classical sine component. The absolute gravitropic thresholds of hypocotyls and roots were determined in a clinostat-centrifuge and found to be below 0.015×g. A tropism mutant lacking the EHB1 protein, which interacts with ARF-GAP (ARF GTPase-activating protein) and thus indirectly with a small ARF-type G protein, displayed a lower gravitropic threshold for roots and also enhanced bending, while the responses of the hypocotyls remained nearly unaffected. PMID:26496692

  5. ROOT-GROWTH AND FUNCTIONING UNDER ATMOSPHERIC CO2 ENRICHMENT

    NARCIS (Netherlands)

    STULEN, [No Value; DENHERTOG, J

    1993-01-01

    This paper examines the extent to which atmospheric CO2 enrichment may influence growth of plant roots and function in terms of uptake of water and nutrients, and carbon allocation towards symbionts. It is concluded that changes in dry matter allocation greatly depend on the experimental conditions

  6. Cinnamic acid increases lignin production and inhibits soybean root growth.

    Directory of Open Access Journals (Sweden)

    Victor Hugo Salvador

    Full Text Available Cinnamic acid is a known allelochemical that affects seed germination and plant root growth and therefore influences several metabolic processes. In the present work, we evaluated its effects on growth, indole-3-acetic acid (IAA oxidase and cinnamate 4-hydroxylase (C4H activities and lignin monomer composition in soybean (Glycine max roots. The results revealed that exogenously applied cinnamic acid inhibited root growth and increased IAA oxidase and C4H activities. The allelochemical increased the total lignin content, thus altering the sum and ratios of the p-hydroxyphenyl (H, guaiacyl (G, and syringyl (S lignin monomers. When applied alone or with cinnamic acid, piperonylic acid (PIP, a quasi-irreversible inhibitor of C4H reduced C4H activity, lignin and the H, G, S monomer content compared to the cinnamic acid treatment. Taken together, these results indicate that exogenously applied cinnamic acid can be channeled into the phenylpropanoid pathway via the C4H reaction, resulting in an increase in H lignin. In conjunction with enhanced IAA oxidase activity, these metabolic responses lead to the stiffening of the cell wall and are followed by a reduction in soybean root growth.

  7. 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

  8. Flavonoids modify root growth and modulate expression of SHORT-ROOT and HD-ZIP III.

    Science.gov (United States)

    Franco, Danilo Miralha; Silva, Eder Marques; Saldanha, Luiz Leonardo; Adachi, Sérgio Akira; Schley, Thayssa Rabelo; Rodrigues, Tatiane Maria; Dokkedal, Anne Ligia; Nogueira, Fabio Tebaldi Silveira; Rolim de Almeida, Luiz Fernando

    2015-09-01

    Flavonoids are a class of distinct compounds produced by plant secondary metabolism that inhibit or promote plant development and have a relationship with auxin transport. We showed that, in terms of root development, Copaifera langsdorffii leaf extracts has an inhibitory effect on most flavonoid components compared with the application of exogenous flavonoids (glycosides and aglycones). These compounds alter the pattern of expression of the SHORT-ROOT and HD-ZIP III transcription factor gene family and cause morpho-physiological alterations in sorghum roots. In addition, to examine the flavonoid auxin interaction in stress, we correlated the responses with the effects of exogenous application of auxin and an auxin transport inhibitor. The results show that exogenous flavonoids inhibit primary root growth and increase the development of lateral roots. Exogenous flavonoids also change the pattern of expression of specific genes associated with root tissue differentiation. These findings indicate that flavonoid glycosides can influence the polar transport of auxin, leading to stress responses that depend on auxin.

  9. Effects of plant growth promoting rhizobacteria (PGPR) on rooting and root growth of kiwifruit (Actinidia deliciosa) stem cuttings.

    Science.gov (United States)

    Erturk, Yasar; Ercisli, Sezai; Haznedar, Ayhan; Cakmakci, Ramazan

    2010-01-01

    The effects of plant growth promoting rhizobacteria (PGPR) on the rooting and root growth of semi-hardwood and hardwood kiwifruit stem cuttings were investigated. The PGPR used were Bacillus RC23, Paenibacillus polymyxa RC05, Bacillus subtilis OSU142, Bacillus RC03, Comamonas acidovorans RC41, Bacillus megaterium RC01 and Bacillus simplex RC19. All the bacteria showed indole-3-acetic acid (IAA) producing capacity. Among the PGPR used, the highest rooting ratios were obtained at 47.50% for semi-hardwood stem cuttings from Bacillus RC03 and Bacillus simplex RC19 treatments and 42.50% for hardwood stem cuttings from Bacillus RC03. As well, Comamonas acidovorans RC41 inoculations indicated higher value than control treatments. The results suggest that these PGPR can be used in organic nursery material production and point to the feasibility of synthetic auxin (IBA) replacement by organic management based on PGPR. PMID:21157636

  10. Phytotoxicity of nanoparticles: Inhibition of seed germination and root growth

    International Nuclear Information System (INIS)

    Plants need to be included to develop a comprehensive toxicity profile for nanoparticles. Effects of five types of nanoparticles (multi-walled carbon nanotube, aluminum, alumina, zinc, and zinc oxide) on seed germination and root growth of six higher plant species (radish, rape, ryegrass, lettuce, corn, and cucumber) were investigated. Seed germination was not affected except for the inhibition of nanoscale zinc (nano-Zn) on ryegrass and zinc oxide (nano-ZnO) on corn at 2000 mg/L. Inhibition on root growth varied greatly among nanoparticles and plants. Suspensions of 2000 mg/L nano-Zn or nano-ZnO practically terminated root elongation of the tested plant species. Fifty percent inhibitory concentrations (IC50) of nano-Zn and nano-ZnO were estimated to be near 50 mg/L for radish, and about 20 mg/L for rape and ryegrass. The inhibition occurred during the seed incubation process rather than seed soaking stage. These results are significant in terms of use and disposal of engineered nanoparticles. - Engineered nanoparticles can inhibit the seed germination and root growth

  11. Signal molecules mediate the impact of the earthworm Aporrectodea caliginosa on growth, development and defence of the plant Arabidopsis thaliana.

    Science.gov (United States)

    Puga-Freitas, Ruben; Barot, Sébastien; Taconnat, Ludivine; Renou, Jean-Pierre; Blouin, Manuel

    2012-01-01

    Earthworms have generally a positive impact on plant growth, which is often attributed to a trophic mechanism: namely, earthworms increase the release of mineral nutrients from soil litter and organic matter. An alternative hypothesis has been proposed since the discovery of a signal molecule (Indole Acetic Acid) in earthworm faeces. In this study, we used methodologies developed in plant science to gain information on ecological mechanisms involved in plant-earthworm interaction, by looking at plant response to earthworm presence at a molecular level. First, we looked at plant overall response to earthworm faeces in an in vitro device where only signal molecules could have an effect on plant growth; we observed that earthworms were inducing positive or negative effects on different plant species. Then, using an Arabidopsis thaliana mutant with an impaired auxin transport, we demonstrated the potential of earthworms to stimulate root growth and to revert the dwarf mutant phenotype. Finally, we performed a comparative transcriptomic analysis of Arabidopsis thaliana in the presence and absence of earthworms; we found that genes modulated in the presence of earthworms are known to respond to biotic and abiotic stresses, or to the application of exogenous hormones. A comparison of our results with other studies found in databases revealed strong analogies with systemic resistance, induced by signal molecules emitted by Plant Growth Promoting Rhizobacteria and/or elicitors emitted by non-virulent pathogens. Signal molecules such as auxin and ethylene, which are considered as major in plant-microorganisms interactions, can also be of prior importance to explain plant-macroinvertebrates interactions. This could imply revisiting ecological theories which generally stress on the role of trophic relationships. PMID:23226498

  12. Signal molecules mediate the impact of the earthworm Aporrectodea caliginosa on growth, development and defence of the plant Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Ruben Puga-Freitas

    Full Text Available Earthworms have generally a positive impact on plant growth, which is often attributed to a trophic mechanism: namely, earthworms increase the release of mineral nutrients from soil litter and organic matter. An alternative hypothesis has been proposed since the discovery of a signal molecule (Indole Acetic Acid in earthworm faeces. In this study, we used methodologies developed in plant science to gain information on ecological mechanisms involved in plant-earthworm interaction, by looking at plant response to earthworm presence at a molecular level. First, we looked at plant overall response to earthworm faeces in an in vitro device where only signal molecules could have an effect on plant growth; we observed that earthworms were inducing positive or negative effects on different plant species. Then, using an Arabidopsis thaliana mutant with an impaired auxin transport, we demonstrated the potential of earthworms to stimulate root growth and to revert the dwarf mutant phenotype. Finally, we performed a comparative transcriptomic analysis of Arabidopsis thaliana in the presence and absence of earthworms; we found that genes modulated in the presence of earthworms are known to respond to biotic and abiotic stresses, or to the application of exogenous hormones. A comparison of our results with other studies found in databases revealed strong analogies with systemic resistance, induced by signal molecules emitted by Plant Growth Promoting Rhizobacteria and/or elicitors emitted by non-virulent pathogens. Signal molecules such as auxin and ethylene, which are considered as major in plant-microorganisms interactions, can also be of prior importance to explain plant-macroinvertebrates interactions. This could imply revisiting ecological theories which generally stress on the role of trophic relationships.

  13. AGO6 functions in RNA-mediated transcriptional gene silencing in shoot and root meristems in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Changho Eun

    Full Text Available RNA-directed DNA methylation (RdDM is a small interfering RNA (siRNA-mediated epigenetic modification that contributes to transposon silencing in plants. RdDM requires a complex transcriptional machinery that includes specialized RNA polymerases, named Pol IV and Pol V, as well as chromatin remodelling proteins, transcription factors, RNA binding proteins, and other plant-specific proteins whose functions are not yet clarified. In Arabidopsis thaliana, DICER-LIKE3 and members of the ARGONAUTE4 group of ARGONAUTE (AGO proteins are involved, respectively, in generating and using 24-nt siRNAs that trigger methylation and transcriptional gene silencing of homologous promoter sequences. AGO4 is the main AGO protein implicated in the RdDM pathway. Here we report the identification of the related AGO6 in a forward genetic screen for mutants defective in RdDM and transcriptional gene silencing in shoot and root apical meristems in Arabidopsis thaliana. The identification of AGO6, and not AGO4, in our screen is consistent with the primary expression of AGO6 in shoot and root growing points.

  14. A mutual support mechanism through intercellular movement of CAPRICE and GLABRA3 can pattern the Arabidopsis root epidermis.

    Science.gov (United States)

    Savage, Natasha Saint; Walker, Tom; Wieckowski, Yana; Schiefelbein, John; Dolan, Liam; Monk, Nicholas A M

    2008-09-23

    The patterning of the Arabidopsis root epidermis depends on a genetic regulatory network that operates both within and between cells. Genetic studies have identified a number of key components of this network, but a clear picture of the functional logic of the network is lacking. Here, we integrate existing genetic and biochemical data in a mathematical model that allows us to explore both the sufficiency of known network interactions and the extent to which additional assumptions about the model can account for wild-type and mutant data. Our model shows that an existing hypothesis concerning the autoregulation of WEREWOLF does not account fully for the expression patterns of components of the network. We confirm the lack of WEREWOLF autoregulation experimentally in transgenic plants. Rather, our modelling suggests that patterning depends on the movement of the CAPRICE and GLABRA3 transcriptional regulators between epidermal cells. Our combined modelling and experimental studies show that WEREWOLF autoregulation does not contribute to the initial patterning of epidermal cell fates in the Arabidopsis seedling root. In contrast to a patterning mechanism relying on local activation, we propose a mechanism based on lateral inhibition with feedback. The active intercellular movements of proteins that are central to our model underlie a mechanism for pattern formation in planar groups of cells that is centred on the mutual support of two cell fates rather than on local activation and lateral inhibition.

  15. A mutual support mechanism through intercellular movement of CAPRICE and GLABRA3 can pattern the Arabidopsis root epidermis.

    Directory of Open Access Journals (Sweden)

    Natasha Saint Savage

    2008-09-01

    Full Text Available The patterning of the Arabidopsis root epidermis depends on a genetic regulatory network that operates both within and between cells. Genetic studies have identified a number of key components of this network, but a clear picture of the functional logic of the network is lacking. Here, we integrate existing genetic and biochemical data in a mathematical model that allows us to explore both the sufficiency of known network interactions and the extent to which additional assumptions about the model can account for wild-type and mutant data. Our model shows that an existing hypothesis concerning the autoregulation of WEREWOLF does not account fully for the expression patterns of components of the network. We confirm the lack of WEREWOLF autoregulation experimentally in transgenic plants. Rather, our modelling suggests that patterning depends on the movement of the CAPRICE and GLABRA3 transcriptional regulators between epidermal cells. Our combined modelling and experimental studies show that WEREWOLF autoregulation does not contribute to the initial patterning of epidermal cell fates in the Arabidopsis seedling root. In contrast to a patterning mechanism relying on local activation, we propose a mechanism based on lateral inhibition with feedback. The active intercellular movements of proteins that are central to our model underlie a mechanism for pattern formation in planar groups of cells that is centred on the mutual support of two cell fates rather than on local activation and lateral inhibition.

  16. 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.

  17. CYTOKININ RESPONSE FACTOR2 (CRF2) and CRF3 Regulate Lateral Root Development in Response to Cold Stress in Arabidopsis.

    Science.gov (United States)

    Jeon, Jin; Cho, Chuloh; Lee, Mi Rha; Van Binh, Nguyen; Kim, Jungmook

    2016-08-01

    Lateral roots (LRs) are a major determinant of the root system architecture in plants, and developmental plasticity of LR formation is critical for the survival of plants in changing environmental conditions. In Arabidopsis thaliana, genetic pathways have been identified that regulate LR branching in response to numerous environmental cues, including some nutrients, salt, and gravity. However, it is not known how genetic components are involved in the LR adaptation response to cold. Here, we demonstrate that CYTOKININ RESPONSE FACTOR2 (CRF2) and CRF3, encoding APETALA2 transcription factors, play an important role in regulating Arabidopsis LR initiation under cold stress. Analysis of LR developmental kinetics demonstrated that both CRF2 and CRF3 regulate LR initiation. crf2 and crf3 single mutants exhibited decreased LR initiation under cold stress compared with the wild type, and the crf2 crf3 double mutants showed additively decreased LR densities compared with the single mutants. Conversely, CRF2 or CRF3 overexpression caused increased LR densities. CRF2 was induced by cold via a subset of the cytokinin two-component signaling (TCS) pathway, whereas CRF3 was upregulated by cold via TCS-independent pathways. Our results suggest that CRF2 and CRF3 respond to cold via TCS-dependent and TCS-independent pathways and control LR initiation and development, contributing to LR adaptation to cold stress. PMID:27432872

  18. Overexpression of a glycosyltransferase gene SrUGT74G1 from Stevia improved growth and yield of transgenic Arabidopsis by catechin accumulation.

    Science.gov (United States)

    Guleria, Praveen; Yadav, Sudesh Kumar

    2014-03-01

    Steviol glycoside and gibberellin biosynthetic routes are known as divergent branches of a common origin in Stevia. A UDP-glycosyltransferase encoded by SrUGT74G1 catalyses the conversion of steviolbioside into stevioside in Stevia rebaudiana leaves. In the present study, transgenic Arabidopsis thaliana overexpressing SrUGT74G1 cDNA from Stevia were developed to check the probability of stevioside biosynthesis in them. However, stevioside accumulation was not evident in transgenics. Also, the transgenic Arabidopsis showed no change in GA3 content on SrUGT74G1 overexpression. Surprisingly, significant accumulation of catechin was noticed in transgenics. The transgenics showed a considerable increase in shoot length, root length and rosette area. An increase in free radical scavenging activity of transgenics was noticed. Moreover, the seed yield of transgenics was also increased by 6-15% than control. Additionally, variation in trichome branching pattern on leaf surface of transgenics was observed. The trichome branching pattern was also validated by exogenous catechin exposure (10, 50, 100 ng ml(-1)) to control plants. Hence, present study reports the probable role of SrUGT74G1 from Stevia in catechin accumulation of transgenic Arabidopsis thaliana. Thus, detailed study in present perspective has revealed the role of Stevia SrUGT74G1 gene in trichome branching pattern, improved vegetative growth, scavenging potential and seed yield by catechin accumulation in transgenic Arabidopsis.

  19. Arabidopsis COPPER MODIFIED RESISTANCE1/PATRONUS1 is essential for growth adaptation to stress and required for mitotic onset control.

    Science.gov (United States)

    Juraniec, Michal; Heyman, Jefri; Schubert, Veit; Salis, Pietrino; De Veylder, Lieven; Verbruggen, Nathalie

    2016-01-01

    The mitotic checkpoint (MC) guards faithful sister chromatid segregation by monitoring the attachment of spindle microtubules to the kinetochores. When chromosome attachment errors are detected, MC delays the metaphase-to-anaphase transition through the inhibition of the anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase. In contrast to yeast and mammals, our knowledge on the proteins involved in MC in plants is scarce. Transient synchronization of root tips as well as promoter-reporter gene fusions were performed to analyze temporal and spatial expression of COPPER MODIFIED RESISTANCE1/PATRONUS1 (CMR1/PANS1) in developing Arabidopsis thaliana seedlings. Functional analysis of the gene was carried out, including CYCB1;2 stability in CMR1/PANS1 knockout and overexpressor background as well as metaphase-anaphase chromosome status. CMR1/PANS1 is transcriptionally active during M phase. Its deficiency provokes premature cell cycle exit and in consequence a rapid consumption of the number of meristematic cells in particular under stress conditions that are known to affect spindle microtubules. Root growth impairment is correlated with a failure to delay the onset of anaphase, resulting in anaphase bridges and chromosome missegregation. CMR1/PANS1 overexpression stabilizes the mitotic CYCB1;2 protein. Likely, CMR1/PANS1 coordinates mitotic cell cycle progression by acting as an APC/C inhibitor and plays a key role in growth adaptation to stress.

  20. Functional analysis of water stress-responsive soybean GmNAC003 and GmNAC004 transcription factors in lateral root development in arabidopsis.

    Directory of Open Access Journals (Sweden)

    Truyen N Quach

    Full Text Available In Arabidopsis, NAC (NAM, ATAF and CUC transcription factors have been found to promote lateral root number through the auxin signaling pathway. In the present study, the role of water stress-inducible soybean GmNAC003 and GmNAC004 genes in the enhancement of lateral root development under water deficit conditions was investigated. Both genes were highly expressed in roots, leaves and flowers of soybean and were strongly induced by water stress and moderately induced by a treatment with abscisic acid (ABA. They showed a slight response to treatment with 2,4-dichlorophenoxyacetic acid (2,4-D. The transgenic Arabidopsis plants overexpressing GmNAC004 showed an increase in lateral root number and length under non-stress conditions and maintained higher lateral root number and length under mild water stress conditions compared to the wild-type (WT, while the transgenic plants overexpressing GmNAC003 did not show any response. However, LR development of GmNAC004 transgenic Arabidopsis plants was not enhanced in the water-stressed compared to the well-watered treatment. In the treatment with ABA, LR density of the GmNAC004 transgenic Arabidopsis was less suppressed than that of the WT, suggesting that GmNAC004 counteracts ABA-induced inhibition of lateral root development. In the treatment with 2,4-D, lateral root density was enhanced in both GmNAC004 transgenic Arabidopsis and WT plants but the promotion was higher in the transgenic plants. Conversely, in the treatment with naphthylphthalamic acid (NPA, lateral root density was inhibited and there was no difference in the phenotype of the GmNAC004 transgenic Arabidopsis and WT plants, indicating that auxin is required for the action of GmNAC004. Transcript analysis for a number of known auxin and ABA related genes showed that GmNAC004's role may suppress ABA signaling but promote auxin signaling to increase lateral root development in the Arabidopsis heterologous system.

  1. A Simple Technique for Recording Root and Shoot Growth in Plants.

    Science.gov (United States)

    Murray, Philip J.; Bristow, Andrew W.

    1997-01-01

    Presents a simple method of recording root growth which can be used in schools. A slant board system was designed to facilitate access to roots to enable measurements to be made, essentially forcing the roots to grow in a two-dimensional form which allows each student to observe and record root growth over several weeks. (AIM)

  2. A Glycine soja 14-3-3 protein GsGF14o participates in stomatal and root hair development and drought tolerance in Arabidopsis thaliana.

    Science.gov (United States)

    Sun, Xiaoli; Luo, Xiao; Sun, Mingzhe; Chen, Chao; Ding, Xiaodong; Wang, Xuedong; Yang, Shanshan; Yu, Qingyue; Jia, Bowei; Ji, Wei; Cai, Hua; Zhu, Yanming

    2014-01-01

    It is well established that 14-3-3 proteins are key regulators of multiple stress signal transduction cascades. However, the biological functions of soybean 14-3-3 proteins, especially in plant drought response, are not yet known. In this study, we characterized a Glycine soja 14-3-3 gene, GsGF14o, which is involved in plant development and drought response. GsGF14o expression was greatly induced by drought stress, as evidenced by the quantitative real-time PCR and β-glucuronidase (GUS) activity analysis. GsGF14o overexpression in Arabidopsis thaliana resulted in decreased drought tolerance during seed germination and seedling growth. Furthermore, silencing of AtGF14µ, the most homologous 14-3-3 gene of GsGF14o, led to enhanced drought tolerance at both the seed germination and seedling stage. Unexpectedly, GsGF14o transgenic lines showed reduced water loss and transpiration rates compared with wild-type plants, which was demonstrated to be the consequence of the decreased stomatal size. At the same time, the smaller stomata due to GsGF14o overexpression led to a relatively slow net photosynthesis rate, which led to a growth penalty under drought stress. We further demonstrated that GsGF14o overexpression caused deficits in root hair formation and development, and thereby reduced the water intake capacity of the transgenic root system. In addition, GsGF14o overexpression down-regulated the transcript levels of drought-responsive marker genes. Finally, we also investigated the tissue-specific accumulation of GsGF14o by using a GUS activity assay. Collectively, the results presented here confirm that GsGF14o plays a dual role in drought stress responses through its involvement in the regulation of stomatal size and root hair development.

  3. Transcriptional profile of maize roots under acid soil growth

    Directory of Open Access Journals (Sweden)

    Mattiello Lucia

    2010-09-01

    Full Text Available Abstract Background Aluminum (Al toxicity is one of the most important yield-limiting factors of many crops worldwide. The primary symptom of Al toxicity syndrome is the inhibition of root growth leading to poor water and nutrient absorption. Al tolerance has been extensively studied using hydroponic experiments. However, unlike soil conditions, this method does not address all of the components that are necessary for proper root growth and development. In the present study, we grew two maize genotypes with contrasting tolerance to Al in soil containing toxic levels of Al and then compared their transcriptomic responses. Results When grown in acid soil containing toxic levels of Al, the Al-sensitive genotype (S1587-17 showed greater root growth inhibition, more Al accumulation and more callose deposition in root tips than did the tolerant genotype (Cat100-6. Transcriptome profiling showed a higher number of genes differentially expressed in S1587-17 grown in acid soil, probably due to secondary effects of Al toxicity. Genes involved in the biosynthesis of organic acids, which are frequently associated with an Al tolerance response, were not differentially regulated in both genotypes after acid soil exposure. However, genes related to the biosynthesis of auxin, ethylene and lignin were up-regulated in the Al-sensitive genotype, indicating that these pathways might be associated with root growth inhibition. By comparing the two maize lines, we were able to discover genes up-regulated only in the Al-tolerant line that also presented higher absolute levels than those observed in the Al-sensitive line. These genes encoded a lipase hydrolase, a retinol dehydrogenase, a glycine-rich protein, a member of the WRKY transcriptional family and two unknown proteins. Conclusions This work provides the first characterization of the physiological and transcriptional responses of maize roots when grown in acid soil containing toxic levels of Al. The

  4. Modulation of root branching by a coumarin derivative

    OpenAIRE

    Li, Xiang; Gao, Ming-Jun

    2011-01-01

    A healthy root system is crucial to plant growth and survival. To maintain efficiency of root function, plants have to dynamically modulate root system architecture through various adaptive mechanisms such as lateral root formation to respond to a changing and diversified soil environment. Exogenous application of a coumarin derivative, 4-methylumbelliferone (4-MU), in Arabidopsis thaliana inhibits seed germination by mainly reducing primary root growth. UDP-glycosyltransferases play an integ...

  5. Impact of root growth and root hydraulic conductance on water availability of young walnut trees

    Science.gov (United States)

    Jerszurki, Daniela; Couvreur, Valentin; Hopmans, Jan W.; Silva, Lucas C. R.; Shackel, Kenneth A.; de Souza, Jorge L. M.

    2015-04-01

    Walnut (Juglans regia L.) is a tree species of high economic importance in the Central Valley of California. This crop has particularly high water requirements, which makes it highly dependent on irrigation. The context of decreasing water availability in the state calls for efficient water management practices, which requires improving our understanding of the relationship between water application and walnut water availability. In addition to the soil's hydraulic conductivity, two plant properties are thought to control the supply of water from the bulk soil to the canopy: (i) root distribution and (ii) plant hydraulic conductance. Even though these properties are clearly linked to crop water requirements, their quantitative relation remains unclear. The aim of this study is to quantitatively explain walnut water requirements under water deficit from continuous measurements of its water consumption, soil and stem water potential, root growth and root system hydraulic conductance. For that purpose, a greenhouse experiment was conducted for a two month period. Young walnut trees were planted in transparent cylindrical pots, equipped with: (i) rhizotron tubes, which allowed for non-invasive monitoring of root growth, (ii) pressure transducer tensiometers for soil water potential, (iii) psychrometers attached to non-transpiring leaves for stem water potential, and (iv) weighing scales for plant transpiration. Treatments consisted of different irrigation rates: 100%, 75% and 50% of potential crop evapotranspiration. Plant responses were compared to predictions from three simple process-based soil-plant-atmosphere models of water flow: (i) a hydraulic model of stomatal regulation based on stem water potential and vapor pressure deficit, (ii) a model of plant hydraulics predicting stem water potential from soil-root interfaces water potential, and (iii) a model of soil water depletion predicting the water potential drop between the bulk soil and soil-root interfaces

  6. CEP5 and XIP1/CEPR1 regulate lateral root initiation in Arabidopsis.

    Science.gov (United States)

    Roberts, Ianto; Smith, Stephanie; Stes, Elisabeth; De Rybel, Bert; Staes, An; van de Cotte, Brigitte; Njo, Maria Fransiska; Dedeyne, Lise; Demol, Hans; Lavenus, Julien; Audenaert, Dominique; Gevaert, Kris; Beeckman, Tom; De Smet, Ive

    2016-08-01

    Roots explore the soil for water and nutrients through the continuous production of lateral roots. Lateral roots are formed at regular distances in a steadily elongating organ, but how future sites for lateral root formation become established is not yet understood. Here, we identified C-TERMINALLY ENCODED PEPTIDE 5 (CEP5) as a novel, auxin-repressed and phloem pole-expressed signal assisting in the formation of lateral roots. In addition, based on genetic and expression data, we found evidence for the involvement of its proposed receptor, XYLEM INTERMIXED WITH PHLOEM 1 (XIP1)/CEP RECEPTOR 1 (CEPR1), during the process of lateral root initiation. In conclusion, we report here on the existence of a peptide ligand-receptor kinase interaction that impacts lateral root initiation. Our results represent an important step towards the understanding of the cellular communication implicated in the early phases of lateral root formation. PMID:27296247

  7. Tracking transcription factor mobility and interaction in arabidopsis roots with fluorescence correlation spectroscopy

    NARCIS (Netherlands)

    Clark, Natalie M.; Hinde, Elizabeth; Hinde, Elizabeth; Fisher, Adam P.; Crosti, Giuseppe; Blilou, Ikram; Gratton, Enrico; Benfey, Philip N.; Sozzani, Rosangela

    2016-01-01

    To understand complex regulatory processes in multicellular organisms, it is critical to be able to quantitatively analyze protein movement and protein-protein interactions in time and space. During Arabidopsis development, the intercellular movement of SHORTROOT (SHR) and subsequent interaction

  8. Rhizobacterial volatiles and photosynthesis-related signals coordinate MYB72 in Arabidopsis roots during onset of induced systemic resistance and iron deficiency responses

    NARCIS (Netherlands)

    Zamioudis, C.; Korteland, J.; Van Pelt, J.A.; Van Hamersveld, M.; Dombrowski, N.; Bai, Y.; Hanson, J.; Van Verk, M.C.; Ling, H.-Q.; Schulze-Lefert, P.; Pieterse, C.M.J.

    2015-01-01

    In Arabidopsis roots, the transcription factor MYB72 plays a dual role in the onset of rhizobacteria-induced systemic resistance (ISR) and plant survival under conditions of limited iron availability. Previously, it was shown that MYB72 coordinates the expression of a gene module that promotes synth

  9. Colonization of the Arabidopsis rhizosphere by fluorescent Pseudomonas spp. activates a root-specific, ethylene-responsive PR-5 gene in the vascular bundle

    NARCIS (Netherlands)

    Léon-Kloosterziel, K.M.; Verhagen, B.W.M.; Keurentjes, J.J.B.; Pelt, J.A. van; Rep, M.; Loon, L.C. van; Pieterse, C.M.J.

    2005-01-01

    Plants of which the roots are colonized by selected strains of non-pathogenic, fluorescent Pseudomonas spp. develop an enhanced defensive capacity against a broad spectrum of foliar pathogens. In Arabidopsis thaliana, this rhizobacteria-induced systemic resistance (ISR) functions independently of sa

  10. A root chicory MADS box sequence and the Arabidopsis flowering repressor FLC share common features that suggest conserved function in vernalization and de-vernalization responses.

    Science.gov (United States)

    Périlleux, Claire; Pieltain, Alexandra; Jacquemin, Guillaume; Bouché, Frédéric; Detry, Nathalie; D'Aloia, Maria; Thiry, Laura; Aljochim, Pierre; Delansnay, Martin; Mathieu, Anne-Sophie; Lutts, Stanley; Tocquin, Pierre

    2013-08-01

    Root chicory (Cichorium intybus var. sativum) is a biennial crop, but is harvested to obtain root inulin at the end of the first growing season before flowering. However, cold temperatures may vernalize seeds or plantlets, leading to incidental early flowering, and hence understanding the molecular basis of vernalization is important. A MADS box sequence was isolated by RT-PCR and named FLC-LIKE1 (CiFL1) because of its phylogenetic positioning within the same clade as the floral repressor Arabidopsis FLOWERING LOCUS C (AtFLC). Moreover, over-expression of CiFL1 in Arabidopsis caused late flowering and prevented up-regulation of the AtFLC target FLOWERING LOCUS T by photoperiod, suggesting functional conservation between root chicory and Arabidopsis. Like AtFLC in Arabidopsis, CiFL1 was repressed during vernalization of seeds or plantlets of chicory, but repression of CiFL1 was unstable when the post-vernalization temperature was favorable to flowering and when it de-vernalized the plants. This instability of CiFL1 repression may be linked to the bienniality of root chicory compared with the annual lifecycle of Arabidopsis. However, re-activation of AtFLC was also observed in Arabidopsis when a high temperature treatment was used straight after seed vernalization, eliminating the promotive effect of cold on flowering. Cold-induced down-regulation of a MADS box floral repressor and its re-activation by high temperature thus appear to be conserved features of the vernalization and de-vernalization responses in distant species. PMID:23581257

  11. Hydrogen sulfide is involved in maintaining ion homeostasis via regulating plasma membrane Na+/H+ antiporter system in the hydrogen peroxide-dependent manner in salt-stress Arabidopsis thaliana root.

    Science.gov (United States)

    Li, Jisheng; Jia, Honglei; Wang, Jue; Cao, Qianhua; Wen, Zichao

    2014-07-01

    Hydrogen sulfide (H2S) and hydrogen peroxide (H2O2) function as the signaling molecules in plants responding to salt stresses. The present study presents a signaling network involving H2S and H2O2 in salt resistance pathway of the Arabidopsis root. Arabidopsis roots were sensitive to 100 mM NaCl treatment, which displayed a great increase in electrolyte leakage (EL) and Na(+)/K(+) ratio under salt stress. The treatment of H2S donors sodium hydrosulfide (NaHS) enhanced the salt tolerance by maintaining a lower Na(+)/K(+) ratio. In addition, the inhibition of root growth under salt stress was removed by H2S. Further studies indicated that H2O2 was involved in H2S-induced salt tolerance pathway. H2S induced the production of the endogenous H2O2 via regulating the activities of glucose-6-phosphate dehydrogenase (G6PDH) and plasma membrane (PM) NADPH oxidase, with the treatment with dimethylthiourea (DMTU, an ROS scavenger), diphenylene iodonium (DPI, a PM NADPH oxidase inhibitor), or glycerol (G6PDH inhibitor) removing the effect of H2S. Treatment with amiloride (an inhibitor of PM Na(+)/H(+) antiporter) and vanadate (an inhibitor of PM H(+)-ATPase) also inhibited the activity of H2S on Na(+)/K(+) ratio. Through an analysis of quantitative real-time polymerase chain reaction and Western blot, we found that H2S promoted the genes expression and the phosphorylation level of PM H(+)-ATPase and Na(+)/H(+) antiporter protein level. However, when the endogenous H2O2 level was inhibited by DPI or DMTU, the effect of H2S on the PM Na(+)/H(+) antiporter system was removed. Taken together, H2S maintains ion homeostasis in the H2O2-dependent manner in salt-stress Arabidopsis root.

  12. Growth enhancement and gene expression of Arabidopsis thaliana irradiated with active oxygen species

    Science.gov (United States)

    Watanabe, Satoshi; Ono, Reoto; Hayashi, Nobuya; Shiratani, Masaharu; Tashiro, Kosuke; Kuhara, Satoru; Inoue, Asami; Yasuda, Kaori; Hagiwara, Hiroko

    2016-07-01

    The characteristics of plant growth enhancement effect and the mechanism of the enhancement induced by plasma irradiation are investigated using various active species in plasma. Active oxygen species in oxygen plasma are effective for growth enhancement of plants. DNA microarray analysis of Arabidopsis thaliana indicates that the genes coding proteins that counter oxidative stresses by eliminating active oxygen species are expressed at significantly high levels. The size of plant cells increases owing to oxygen plasma irradiation. The increases in gene expression levels and cell size suggest that the increase in the expression level of the expansin protein is essential for plant growth enhancement phenomena.

  13. 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.

  14. The Protein Elicitor PevD1 Enhances Resistance to Pathogens and Promotes Growth in Arabidopsis.

    Science.gov (United States)

    Liu, Mengjie; Khan, Najeeb Ullah; Wang, Ningbo; Yang, Xiufen; Qiu, Dewen

    2016-01-01

    The protein elicitor PevD1, isolated from Verticillium dahlia, could enhance resistance to TMV in tobacco and Verticillium wilt in cotton. Here, the pevd1 gene was over-expressed in wild type (WT) Arabidopsis, and its biological functions were investigated. Our results showed that the transgenic lines were more resistant to Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000 than the WT line was. In transgenic plants, both the germination time and bolting time required were significantly shorter and fresh weights and plant heights were significantly higher than those in the WT line. A transcriptomics study using digital gene expression profiling (DGE) was performed in transgenic and WT Arabidopsis. One hundred and thirty-six differentially expressed genes were identified. In transgenic Arabidopsis, three critical regulators of JA biosynthesis were up-regulated and JA levels were slightly increased. Three important repressors of the ABA-responsive pathway were up-regulated, indicating that ABA signal transduction may be suppressed. One CML and two WRKY TFs involved in Ca(2+)-responsive pathways were up-regulated, indicating that this pathway may have been triggered. In conclusion, we show that PevD1 is involved in regulating several plant endogenous signal transduction pathways and regulatory networks to enhance resistance and promote growth and development in Arabidopsis. PMID:27489497

  15. Sustained exposure to abscisic acid enhances the colonization potential of the mutualist fungus Piriformospora indica on Arabidopsis thaliana roots.

    Science.gov (United States)

    Peskan-Berghöfer, Tatjana; Vilches-Barro, Amaya; Müller, Teresa M; Glawischnig, Erich; Reichelt, Michael; Gershenzon, Jonathan; Rausch, Thomas

    2015-11-01

    Root colonization by the beneficial fungus Piriformospora indica is controlled by plant innate immunity, but factors that channel this interaction into a mutualistic relationship are not known. We have explored the impact of abscisic acid (ABA) and osmotic stress on the P. indica interaction with Arabidopsis thaliana. The activation of plant innate immunity in roots was determined by measuring the concentration of the phytoalexin camalexin and expression of transcription factors regulating the biosynthesis of tryptophan-related defence metabolites. Furthermore, the impact of the fungus on the content of ABA, salicylic acid, jasmonic acid (JA) and JA-related metabolites was examined. We demonstrated that treatment with exogenous ABA or the ABA analogue pyrabactin increased fungal colonization efficiency without impairment of plant fitness. Concomitantly, ABA-deficient mutants of A. thaliana (aba1-6 and aba2-1) were less colonized, while plants exposed to moderate stress were more colonized than corresponding controls. Sustained exposure to ABA attenuated expression of transcription factors MYB51, MYB122 and WRKY33 in roots upon P. indica challenge or chitin treatment, and prevented an increase in camalexin content. The results indicate that ABA can strengthen the interaction with P. indica as a consequence of its impact on plant innate immunity. Consequently, ABA will be relevant for the establishment and outcome of the symbiosis under stress conditions.

  16. Response of Arabidopsis thaliana Roots with Altered Lipid Transfer Protein (LTP) Gene Expression to the Clubroot Disease and Salt Stress.

    Science.gov (United States)

    Jülke, Sabine; Ludwig-Müller, Jutta

    2015-01-01

    The clubroot disease of Brassicaceae is caused by the obligate biotrophic protist Plasmodiophora brassicae. The disease is characterized by abnormal tumorous swellings of infected roots that result in reduced drought resistance and insufficient distribution of nutrients, leading to reduced crop yield. It is one of the most damaging diseases among cruciferous crops worldwide. The acquisition of nutrients by the protist is not well understood. Gene expression profiles in Arabidopsis thaliana clubroots indicate that lipid transfer proteins (LTPs) could be involved in disease development or at least in adaptation to the disease symptoms. Therefore, the aim of the study was to examine the role of some, of the still enigmatic LTPs during clubroot development. For a functional approach, we have generated transgenic plants that overexpress LTP genes in a root specific manner or show reduced LTP gene expression. Our results showed that overexpression of some of the LTP genes resulted in reduced disease severity whereas the lipid content in clubs of LTP mutants seems to be unaffected. Additional studies indicate a role for some LTPs during salt stress conditions in roots of A. thaliana. PMID:27135222

  17. Response of Arabidopsis thaliana Roots with Altered Lipid Transfer Protein (LTP Gene Expression to the Clubroot Disease and Salt Stress

    Directory of Open Access Journals (Sweden)

    Sabine Jülke

    2015-12-01

    Full Text Available The clubroot disease of Brassicaceae is caused by the obligate biotrophic protist Plasmodiophora brassicae. The disease is characterized by abnormal tumorous swellings of infected roots that result in reduced drought resistance and insufficient distribution of nutrients, leading to reduced crop yield. It is one of the most damaging diseases among cruciferous crops worldwide. The acquisition of nutrients by the protist is not well understood. Gene expression profiles in Arabidopsis thaliana clubroots indicate that lipid transfer proteins (LTPs could be involved in disease development or at least in adaptation to the disease symptoms. Therefore, the aim of the study was to examine the role of some, of the still enigmatic LTPs during clubroot development. For a functional approach, we have generated transgenic plants that overexpress LTP genes in a root specific manner or show reduced LTP gene expression. Our results showed that overexpression of some of the LTP genes resulted in reduced disease severity whereas the lipid content in clubs of LTP mutants seems to be unaffected. Additional studies indicate a role for some LTPs during salt stress conditions in roots of A. thaliana.

  18. Plant hormone cross-talk: the pivot of root growth.

    Science.gov (United States)

    Pacifici, Elena; Polverari, Laura; Sabatini, Sabrina

    2015-02-01

    Root indeterminate growth and its outstanding ability to produce new tissues continuously make this organ a highly dynamic structure able to respond promptly to external environmental stimuli. Developmental processes therefore need to be finely tuned, and hormonal cross-talk plays a pivotal role in the regulation of root growth. In contrast to what happens in animals, plant development is a post-embryonic process. A pool of stem cells, placed in a niche at the apex of the meristem, is a source of self-renewing cells that provides cells for tissue formation. During the first days post-germination, the meristem reaches its final size as a result of a balance between cell division and cell differentiation. A complex network of interactions between hormonal pathways co-ordinates such developmental inputs. In recent years, by means of molecular and computational approaches, many efforts have been made aiming to define the molecular components of these networks. In this review, we focus our attention on the molecular mechanisms at the basis of hormone cross-talk during root meristem size determination.

  19. The Arabidopsis nitrate transporter AtNRT2.1 is targeted to the root plasma membrane.

    Science.gov (United States)

    Chopin, Franck; Wirth, Judith; Dorbe, Marie-France; Lejay, Laurence; Krapp, Anne; Gojon, Alain; Daniel-Vedele, Françoise

    2007-08-01

    Arabidopsis AtNRT2.1 protein is the best characterized high affinity nitrate transporter in higher plants. However, nothing is known about its sub-cellular localization. In this work, we used GFP imaging to follow the targeting of the AtNRT2.1 protein to the different cell membranes. A polyclonal antibody was also raised against a peptide derived from the AtNRT2.1 sequence. Comparison of wild type and mutant plant extracts showed that this antibody recognized specifically the AtNRT2.1 protein. Microsomal membranes were fractionated on sucrose gradients and immunological detections were performed on the different fractions. Altogether, our results demonstrate that the AtNRT2.1 protein is located in the plasma membrane of the root cells.

  20. 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

  1. An improved, simple, inexpensive and highly flexible hydroponic setup for root mitochondria isolation from arabidopsis and nicotiana pants

    International Nuclear Information System (INIS)

    Hydroponic setups are frequently developed and improved as they are convenient platforms for studying whole plant physiology. Mostly, the available systems produce small amounts of plant material and are therefore, unsuitable for studies requiring large quantities of plant material like isolation of mitochondria. To address this issue, we have modified a hydroponic setup that can sustain hundreds of Arabidopsis and tobacco plants until adult plants are established. The setup is very flexible and easy to construct. It is based on the use of recyclable and sterilizable plastic-net-pots and media containers, which are easily available from the local suppliers. The modified seed-pots and styrofoam sheets facilitate the transfer and harvesting of seedlings. We have used the Percoll based two-step density gradient centrifugation method for the isolation of root mitochondria from the hydroponically grown plants. (author)

  2. 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...

  3. The RHG gene is involved in root and hypocotyl gravitropism in Arabidopsis thaliana.

    Science.gov (United States)

    Fukaki, H; Fujisawa, H; Tasaka, M

    1997-07-01

    In higher plants, shoots show negative gravitropism and roots show positive gravitropism. To elucidate the molecular mechanisms of root and hypocotyl gravitropism, we segregated the second mutation from the original phyB-1 mutant line which impaired both root and hypocotyl gravitropism and characterized this novel mutation named rhg (for root and hypocotyl gravitropism). The rhg is a single recessive nuclear mutation and it is mapped on the lower part of the chromosome 1. Analyses on the gravitropic responses of the rhg mutant indicate that root and hypocotyl gravitropism are severely impaired but inflorescence stem gravitropism is not affected by the rhg mutation. In the rhg mutant seedlings, amyloplasts (statoliths for gravity-perception) were present in the presumptive statocytes of roots and hypocotyls. Phototropism by roots and hypocotyls was not impaired in the rhg mutant. These results suggest that the RHG gene product probably acts on the gravity-perception and/or the gravity-signal transduction in root and hypocotyl gravitropism. This is the first report about the genetic locus specifically involved in both root and hypocotyl gravitropism but not inflorescence stem gravitropism, supporting our hypothesis that the mechanisms of gravitropism are genetically different between hypocotyls and inflorescence stems.

  4. 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.

  5. Tomato root growth, gravitropism, and lateral development: correlation with auxin transport

    Science.gov (United States)

    Muday, G. K.; Haworth, P.

    1994-01-01

    Tomato (Lycopersicon esculentum, Mill.) roots were analyzed during growth on agar plates. Growth of these roots was inhibited by the auxin transport inhibitors naphthylphthalamic acid (NPA) and semicarbazone derivative I (SCB-1). The effect of auxin transport inhibitors on root gravitropism was analyzed by measurement of the angle of gravitropic curvature after the roots were reoriented 90 degrees from the vertical. NPA and SCB-1 abolished both the response of these roots to gravity and the formation of lateral roots, with SCB-1 being the more effective at inhibition. Auxins also inhibited root growth. Both auxins tested has a slight effect on the gravity response, but this effect is probably indirect, since auxins reduced the growth rate. Auxins also stimulated lateral root growth at concentration where primary root growth was inhibited. When roots were treated with both IAA and NPA simultaneously, a cumulative inhibition of root growth was found. When both compounds were applied together, analysis of gravitropism and lateral root formation indicated that the dominant effect was exerted by auxin transport inhibitors. Together, these data suggest a model for the role of auxin transport in controlling both primary and lateral root growth.

  6. Uncovering genes and ploidy involved in the high diversity in root hair density, length and response to local scarce phosphate in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Markus G Stetter

    Full Text Available Plant root hairs increase the root surface to enhance the uptake of sparingly soluble and immobile nutrients, such as the essential nutrient phosphorus, from the soil. Here, root hair traits and the response to scarce local phosphorus concentration were studied in 166 accessions of Arabidopsis thaliana using split plates. Root hair density and length were correlated, but highly variable among accessions. Surprisingly, the well-known increase in root hair density under low phosphorus was mostly restricted to genotypes that had less and shorter root hairs under P sufficient conditions. By contrast, several accessions with dense and long root hairs even had lower hair density or shorter hairs in local scarce phosphorus. Furthermore, accessions with whole-genome duplications developed more dense but phosphorus-insensitive root hairs. The impact of genome duplication on root hair density was confirmed by comparing tetraploid accessions with their diploid ancestors. Genome-wide association mapping identified candidate genes potentially involved in root hair responses tp scarce local phosphate. Knock-out mutants in identified candidate genes (CYR1, At1g32360 and RLP48 were isolated and differences in root hair traits in the mutants were confirmed. The large diversity in root hair traits among accessions and the diverse response when local phosphorus is scarce is a rich resource for further functional analyses.

  7. Unraveling uranium induced oxidative stress related responses in Arabidopsis thaliana seedlings. Part I: responses in the roots

    Energy Technology Data Exchange (ETDEWEB)

    Vanhoudt, Nathalie, E-mail: nvanhoud@sckcen.be [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Hasselt University, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium); Vandenhove, Hildegarde; Horemans, Nele [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Remans, Tony; Opdenakker, Kelly; Smeets, Karen [Hasselt University, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium); Bello, Daniel Martinez [Hasselt University, Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Agoralaan Building D, 3590 Diepenbeek (Belgium); Wannijn, Jean; Van Hees, May [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Vangronsveld, Jaco; Cuypers, Ann [Hasselt University, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium)

    2011-06-15

    When aiming to evaluate the environmental impact of uranium contamination, it is important to unravel the mechanisms by which plants respond to uranium stress. As oxidative stress seems an important modulator under other heavy metal stress, this study aimed to investigate oxidative stress related responses in Arabidopsis thaliana exposed to uranium concentrations ranging from 0.1 to 100 {mu}M for 1, 3 and 7 days. Besides analyzing relevant reactive oxygen species-producing and -scavenging enzymes at protein and transcriptional level, the importance of the ascorbate-glutathione cycle under uranium stress was investigated. These results are reported separately for roots and leaves in two papers: Part I dealing with responses in the roots and Part II unraveling responses in the leaves and presenting general conclusions. Results of Part I indicate that oxidative stress related responses in the roots were only triggered following exposure to the highest uranium concentration of 100 {mu}M. A fast oxidative burst was suggested based on the observed enhancement of lipoxygenase (LOX1) and respiratory burst oxydase homolog (RBOHD) transcript levels already after 1 day. The first line of defense was attributed to superoxide dismutase (SOD), also triggered from the first day. The enhanced SOD-capacity observed at protein level corresponded with an enhanced expression of iron SOD (FSD1) located in the plastids. For the detoxification of H{sub 2}O{sub 2}, an early increase in catalase (CAT1) transcript levels was observed while peroxidase capacities were enhanced at the later stage of 3 days. Although the ascorbate peroxidase capacity and gene expression (APX1) increased, the ascorbate/dehydroascorbate redox balance was completely disrupted and shifted toward the oxidized form. This disrupted balance could not be inverted by the glutathione part of the cycle although the glutathione redox balance could be maintained. - Highlights: > Unravel response mechanisms to uranium stress

  8. Ectopic expression of R3 MYB transcription factor gene OsTCL1 in Arabidopsis, but not rice, affects trichome and root hair formation

    Science.gov (United States)

    Zheng, Kaijie; Tian, Hainan; Hu, Qingnan; Guo, Hongyan; Yang, Li; Cai, Ling; Wang, Xutong; Liu, Bao; Wang, Shucai

    2016-01-01

    In Arabidopsis, a MYB-bHLH-WD40 (MBW) transcriptional activator complex activates the homeodomain protein gene GLABRA2 (GL2), leading to the promotion of trichome formation and inhibition of root hair formation. The same MBW complex also activates single-repeat R3 MYB genes. R3 MYBs in turn, play a negative feedback role by competing with R2R3 MYB proteins for binding bHLH proteins, thus blocking the formation of the MBW complex. By BLASTing the rice (Oryza sativa) protein database using the entire amino acid sequence of Arabidopsis R3 MYB transcription factor TRICHOMELESS1 (TCL1), we found that there are two genes in rice genome encoding R3 MYB transcription factors, namely Oryza sativa TRICHOMELESS1 (OsTCL1) and OsTCL2. Expressing OsTCL1 in Arabidopsis inhibited trichome formation and promoted root hair formation, and OsTCL1 interacted with GL3 when tested in Arabidopsis protoplasts. Consistent with these observations, expression levels of GL2, R2R3 MYB transcription factor gene GLABRA1 (GL1) and several R3 MYB genes were greatly reduced, indicating that OsTCL1 is functional R3 MYB. However, trichome and root hair formation in transgenic rice plants overexpressing OsTCL1 remained largely unchanged, and elevated expression of OsGL2 was observed in the transgenic rice plants, indicating that rice may use different mechanisms to regulate trichome formation. PMID:26758286

  9. Fruit growth in Arabidopsis occurs via DELLA-dependent and DELLA-independent gibberellin responses.

    Science.gov (United States)

    Fuentes, Sara; Ljung, Karin; Sorefan, Karim; Alvey, Elizabeth; Harberd, Nicholas P; Østergaard, Lars

    2012-10-01

    Fruit growth and development depend on highly coordinated hormonal activities. The phytohormone gibberellin (GA) promotes growth by inducing degradation of the growth-repressing DELLA proteins; however, the extent to which DELLA proteins contribute to GA-mediated gynoecium and fruit development remains to be clarified. Here, we provide an in-depth characterization of the role of DELLA proteins in Arabidopsis thaliana fruit growth. We show that DELLA proteins are key regulators of reproductive organ size and important for ensuring optimal fertilization. We demonstrate that the seedless fruit growth (parthenocarpy) observed in della mutants can be directly attributed to the constitutive activation of GA signaling. It has been known for >75 years that another hormone, auxin, can induce formation of seedless fruits. Using mutants with complete lack of DELLA activity, we show here that auxin-induced parthenocarpy occurs entirely through GA signaling in Arabidopsis. Finally, we uncover the existence of a DELLA-independent GA response that promotes fruit growth. This response requires GIBBERELLIN-INSENSITIVE DWARF1-mediated GA perception and a functional 26S proteasome and involves the basic helix-loop-helix protein SPATULA as a key component. Taken together, our results describe additional complexities in GA signaling during fruit development, which may be particularly important to optimize the conditions for successful reproduction. PMID:23064323

  10. 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

  11. Stimulation of Armillaria rhizomorph growth by oak root fungi

    Directory of Open Access Journals (Sweden)

    Hanna Kwaśna

    2014-08-01

    Full Text Available Thirty one different genera of fungi were isolated from the wood of roots of 5O·year·old oak (Quercus robur. The most frequently isolated fungi were: Mycelium radicis atrovirens alpha (MRAA, Clonostachys sp. and Penicillium daleae, Beauveria bassiana, Clonostachys sp., Cryplosporiopsis rodicicolo, Geotrichum candidum, Mortierella vinacea, MRAA, P. daleae, P. janczewskii P. spinulosum, Sporothrix schenckii and Tolypocladium niveum significantly enhanced Armillaria mellea rhizomorph initiation and growth from oak branch segments in vitro. The biggest stimulation effect was noticed when the dematiaceous hyphomycetes, e.g. MRAA, P. dimorphospora and S. schenckii were studied.

  12. Arabidopsis NAC1 transduces auxin signal downstream of TIR1 to promote lateral root development.

    Science.gov (United States)

    Xie, Q; Frugis, G; Colgan, D; Chua, N H

    2000-12-01

    Auxin plays a key role in lateral root formation, but the signaling pathway for this process is poorly understood. We show here that NAC1, a new member of the NAC family, is induced by auxin and mediates auxin signaling to promote lateral root development. NAC1 is a transcription activator consisting of an N-terminal conserved NAC-domain that binds to DNA and a C-terminal activation domain. This factor activates the expression of two downstream auxin-responsive genes, DBP and AIR3. Transgenic plants expressing sense or antisense NAC1 cDNA show an increase or reduction of lateral roots, respectively. Finally, TIR1-induced lateral root development is blocked by expression of antisense NAC1 cDNA, and NAC1 overexpression can restore lateral root formation in the auxin-response mutant tir1, indicating that NAC1 acts downstream of TIR1.

  13. 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.

  14. Effect of indole-3-acetic acid on pea root growth, peroxidase profiles and hydroxyl radical formation

    Directory of Open Access Journals (Sweden)

    Kukavica Biljana

    2007-01-01

    Full Text Available Changes in growth, peroxidase profiles, and hydroxyl radical formation were examined in IAA (0.5-10 mg/l treated pea plants grown hydroponically and in isolated roots in liquid in vitro culture. IAA inhibited root elongation, both in hydroponically grown pea plants and in isolated roots in vitro. A remarkable increase in the number of POD iso­forms was noticed in isolated roots grown in vitro, compared to the roots from plants grown hydroponically. IAA induced both disappearance of several root POD isoforms and hydroxyl radical formation in the root and the root cell wall.

  15. Positional signaling and expression of ENHANCER OF TRY AND CPC1 are tuned to increase root hair density in response to phosphate deficiency in Arabidopsis thaliana.

    Science.gov (United States)

    Savage, Natasha; Yang, Thomas J W; Chen, Chung Ying; Lin, Kai-Lan; Monk, Nicholas A M; Schmidt, Wolfgang

    2013-01-01

    Phosphate (Pi) deficiency induces a multitude of responses aimed at improving the acquisition of Pi, including an increased density of root hairs. To understand the mechanisms involved in Pi deficiency-induced alterations of the root hair phenotype in Arabidopsis (Arabidopsis thaliana), we analyzed the patterning and length of root epidermal cells under control and Pi-deficient conditions in wild-type plants and in four mutants defective in the expression of master regulators of cell fate, CAPRICE (CPC), ENHANCER OF TRY AND CPC 1 (ETC1), WEREWOLF (WER) and SCRAMBLED (SCM). From this analysis we deduced that the longitudinal cell length of root epidermal cells is dependent on the correct perception of a positional signal ('cortical bias') in both control and Pi-deficient plants; mutants defective in the receptor of the signal, SCM, produced short cells characteristic of root hair-forming cells (trichoblasts). Simulating the effect of cortical bias on the time-evolving probability of cell fate supports a scenario in which a compromised positional signal delays the time point at which non-hair cells opt out the default trichoblast pathway, resulting in short, trichoblast-like non-hair cells. Collectively, our data show that Pi-deficient plants increase root hair density by the formation of shorter cells, resulting in a higher frequency of hairs per unit root length, and additional trichoblast cell fate assignment via increased expression of ETC1.

  16. Positional signaling and expression of ENHANCER OF TRY AND CPC1 are tuned to increase root hair density in response to phosphate deficiency in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Natasha Savage

    Full Text Available Phosphate (Pi deficiency induces a multitude of responses aimed at improving the acquisition of Pi, including an increased density of root hairs. To understand the mechanisms involved in Pi deficiency-induced alterations of the root hair phenotype in Arabidopsis (Arabidopsis thaliana, we analyzed the patterning and length of root epidermal cells under control and Pi-deficient conditions in wild-type plants and in four mutants defective in the expression of master regulators of cell fate, CAPRICE (CPC, ENHANCER OF TRY AND CPC 1 (ETC1, WEREWOLF (WER and SCRAMBLED (SCM. From this analysis we deduced that the longitudinal cell length of root epidermal cells is dependent on the correct perception of a positional signal ('cortical bias' in both control and Pi-deficient plants; mutants defective in the receptor of the signal, SCM, produced short cells characteristic of root hair-forming cells (trichoblasts. Simulating the effect of cortical bias on the time-evolving probability of cell fate supports a scenario in which a compromised positional signal delays the time point at which non-hair cells opt out the default trichoblast pathway, resulting in short, trichoblast-like non-hair cells. Collectively, our data show that Pi-deficient plants increase root hair density by the formation of shorter cells, resulting in a higher frequency of hairs per unit root length, and additional trichoblast cell fate assignment via increased expression of ETC1.

  17. Plant-growth promoting effect of newly isolated rhizobacteria varies between two Arabidopsis ecotypes

    OpenAIRE

    Schwachtje, Jens; Karojet, Silke; Kunz, Sabine; Brouwer, Stephan; van Dongen, Joost T.

    2012-01-01

    Various rhizobacteria are known for their beneficial effects on plants, i. e. promotion of growth and induction of systemic resistance against pathogens. These bacteria are categorized as plant growth promoting rhizobacteria (PGPR) and are associated with plant roots. Knowledge of the underlying mechanisms of plant growth promotion in vivo is still very limited, but interference of bacteria with plant hormone metabolism is suggested to play a major role. To obtain new growth promoting bacteri...

  18. Improving root-zone soil moisture estimations using dynamic root growth and crop phenology

    Science.gov (United States)

    Hashemian, Minoo; Ryu, Dongryeol; Crow, Wade T.; Kustas, William P.

    2015-12-01

    Water Energy Balance (WEB) Soil Vegetation Atmosphere Transfer (SVAT) modelling can be used to estimate soil moisture by forcing the model with observed data such as precipitation and solar radiation. Recently, an innovative approach that assimilates remotely sensed thermal infrared (TIR) observations into WEB-SVAT to improve the results has been proposed. However, the efficacy of the model-observation integration relies on the model's realistic representation of soil water processes. Here, we explore methods to improve the soil water processes of a simple WEB-SVAT model by adopting and incorporating an exponential root water uptake model with water stress compensation and establishing a more appropriate soil-biophysical linkage between root-zone moisture content, above-ground states and biophysical indices. The existing WEB-SVAT model is extended to a new Multi-layer WEB-SVAT with Dynamic Root distribution (MWSDR) that has five soil layers. Impacts of plant root depth variations, growth stages and phenological cycle of the vegetation on transpiration are considered in developing stages. Hydrometeorological and biogeophysical measurements collected from two experimental sites, one in Dookie, Victoria, Australia and the other in Ponca, Oklahoma, USA, are used to validate the new model. Results demonstrate that MWSDR provides improved soil moisture, transpiration and evaporation predictions which, in turn, can provide an improved physical basis for assimilating remotely sensed data into the model. Results also show the importance of having an adequate representation of vegetation-related transpiration process for an appropriate simulation of water transfer in a complicated system of soil, plants and atmosphere.

  19. Induction of Root Hair Growth in a Phosphorus-Buffered Culture Solution

    Institute of Scientific and Technical Information of China (English)

    LIU Guo-dong; James Dunlop; Thai Phung

    2006-01-01

    A system to control the release of phosphate in water was successfully established, based on solubility product of [Ca2+] and [PO43-] using tricalcium phosphate as P source in the hydroponic solution, and adding CaC12 for supplementing extra Ca2+. The system, similar to soil solutions, was a P nutrient buffer solution with very low bioavailable P. The buffer solution induced the roots of both monocotyledon and dicotyledon species to grow abundant root hairs, 3 mm in maximum length. The monocotyledons were corn (Zea mays L.) (var. Yellow Rose), wheat (Triticum aestivum L.) (var.Yanzhong 144), Triticale secale L. (var. Jingsong 5), and ryegrass (Lolium rigidum L.) (var. Ruanni), and the dicotyledons were Arabidopsis thaliana L. (var. Columbia), white clover (Trifolium repens) (var. Kopu), Lotus (Lotus peduncucatus Cav. Luliginosus Schkuhr) (var. Grasslands Maku). For these species we proved that the root environment controls the induction of root hair formation. However, the hydroponic buffer solution failed to induce root hairs on the roots of onion (Allium cepa L.). Other investigators have concluded that corn does not form root hairs in hydroponics, but abundant long root hairs on corn were induced by this buffer system. The roots with abundant long root hairs are called "hedgehog roots" because they have hairs everywhere just like a hedgehog.

  20. Nano titania aided clustering and adhesion of beneficial bacteria to plant roots to enhance crop growth and stress management.

    Science.gov (United States)

    Palmqvist, N G M; Bejai, S; Meijer, J; Seisenbaeva, G A; Kessler, V G

    2015-01-01

    A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection.

  1. Nano titania aided clustering and adhesion of beneficial bacteria to plant roots to enhance crop growth and stress management

    Science.gov (United States)

    Palmqvist, N. G. M.; Bejai, S.; Meijer, J.; Seisenbaeva, G. A.; Kessler, V. G.

    2015-05-01

    A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection.

  2. How grow-and-switch gravitropism generates root coiling and root waving growth responses in Medicago truncatula.

    Science.gov (United States)

    Tan, Tzer Han; Silverberg, Jesse L; Floss, Daniela S; Harrison, Maria J; Henley, Christopher L; Cohen, Itai

    2015-10-20

    Experimental studies show that plant root morphologies can vary widely from straight gravity-aligned primary roots to fractal-like root architectures. However, the opaqueness of soil makes it difficult to observe how environmental factors modulate these patterns. Here, we combine a transparent hydrogel growth medium with a custom built 3D laser scanner to directly image the morphology of Medicago truncatula primary roots. In our experiments, root growth is obstructed by an inclined plane in the growth medium. As the tilt of this rigid barrier is varied, we find Medicago transitions between randomly directed root coiling, sinusoidal root waving, and normal gravity-aligned morphologies. Although these root phenotypes appear morphologically distinct, our analysis demonstrates the divisions are less well defined, and instead, can be viewed as a 2D biased random walk that seeks the path of steepest decent along the inclined plane. Features of this growth response are remarkably similar to the widely known run-and-tumble chemotactic behavior of Escherichia coli bacteria, where biased random walks are used as optimal strategies for nutrient uptake.

  3. On the role of a Lipid-Transfer Protein. Arabidopsis ltp3 mutant is compromised in germination and seedling growth.

    OpenAIRE

    Pagnussat, Luciana A; Oyarburo, Natalia; Cimmino, Carlos; Pinedo, Marcela L; de la Canal, Laura

    2015-01-01

    Plant Lipid-Transfer Proteins (LTPs) exhibit the ability to reversibly bind/transport lipids in vitro. LTPs have been involved in diverse physiological processes but conclusive evidence on their role has only been presented for a few members, none of them related to seed physiology. Arabidopsis seeds rely on storage oil breakdown to supply carbon skeletons and energy for seedling growth. Here, Arabidopsis ltp3 mutant was analyzed for its ability to germinate and for seedling establishment. Lt...

  4. Integration of hormonal signaling networks and mobile microRNAs is required for vascular patterning in Arabidopsis roots

    KAUST Repository

    Muraro, D.

    2013-12-31

    As multicellular organisms grow, positional information is continually needed to regulate the pattern in which cells are arranged. In the Arabidopsis root, most cell types are organized in a radially symmetric pattern; however, a symmetry-breaking event generates bisymmetric auxin and cytokinin signaling domains in the stele. Bidirectional cross-talk between the stele and the surrounding tissues involving a mobile transcription factor, SHORT ROOT (SHR), and mobile microRNA species also determines vascular pattern, but it is currently unclear how these signals integrate. We use a multicellular model to determine a minimal set of components necessary for maintaining a stable vascular pattern. Simulations perturbing the signaling network show that, in addition to the mutually inhibitory interaction between auxin and cytokinin, signaling through SHR, microRNA165/6, and PHABULOSA is required to maintain a stable bisymmetric pattern. We have verified this prediction by observing loss of bisymmetry in shr mutants. The model reveals the importance of several features of the network, namely the mutual degradation of microRNA165/6 and PHABULOSA and the existence of an additional negative regulator of cytokinin signaling. These components form a plausible mechanism capable of patterning vascular tissues in the absence of positional inputs provided by the transport of hormones from the shoot.

  5. Plant-to-Plant Variability in Root Metabolite Profiles of 19 Arabidopsis thaliana Accessions Is Substance-Class-Dependent

    Science.gov (United States)

    Mönchgesang, Susann; Strehmel, Nadine; Trutschel, Diana; Westphal, Lore; Neumann, Steffen; Scheel, Dierk

    2016-01-01

    Natural variation of secondary metabolism between different accessions of Arabidopsis thaliana (A. thaliana) has been studied extensively. In this study, we extended the natural variation approach by including biological variability (plant-to-plant variability) and analysed root metabolic patterns as well as their variability between plants and naturally occurring accessions. To screen 19 accessions of A. thaliana, comprehensive non-targeted metabolite profiling of single plant root extracts was performed using ultra performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC/ESI-QTOF-MS) and gas chromatography/electron ionization quadrupole mass spectrometry (GC/EI-QMS). Linear mixed models were applied to dissect the total observed variance. All metabolic profiles pointed towards a larger plant-to-plant variability than natural variation between accessions and variance of experimental batches. Ratios of plant-to-plant to total variability were high and distinct for certain secondary metabolites. None of the investigated accessions displayed a specifically high or low biological variability for these substance classes. This study provides recommendations for future natural variation analyses of glucosinolates, flavonoids, and phenylpropanoids and also reference data for additional substance classes. PMID:27649165

  6. Root growth dynamics linked to aboveground growth in walnuts (Juglans regia L.)

    Science.gov (United States)

    Background and Aims: Examination of belowground plant responses to canopy and soil moisture manipulation is scant compared to that aboveground but needed to understand whole plant responses to environmental factors. Plasticity in the seasonal timing and vertical distribution of root growth in respon...

  7. Gene Networks Involved in Hormonal Control of Root Development in Arabidopsis thaliana: A Framework for Studying Its Disturbance by Metal Stress

    OpenAIRE

    Stefanie De Smet; Ann Cuypers; Jaco Vangronsveld; Tony Remans

    2015-01-01

    Plant survival under abiotic stress conditions requires morphological and physiological adaptations. Adverse soil conditions directly affect root development, although the underlying mechanisms remain largely to be discovered. Plant hormones regulate normal root growth and mediate root morphological responses to abiotic stress. Hormone synthesis, signal transduction, perception and cross-talk create a complex network in which metal stress can interfere, resulting in root growth alterations...

  8. Root growth and soil nitrogen depletion by onion, lettuce, early cabbage and carrot

    OpenAIRE

    Thorup-Kristensen, K

    2001-01-01

    Experiments examining root growth, the utilization of N and the effect of green manures were carried out on four vegetable crops. Large differences were observed both in rooting depth penetration rates, and in final rooting depth and distribution. Onion had a very low depth penetration rate, carrot an intermediate rate, and lettuce and cabbage showed high rates. A combination of depth penetration rates and duration of growth determined rooting depth at harvest. Therefore, lettuce, which had a...

  9. GH3-mediated auxin homeostasis links growth regulation with stress adaptation response in Arabidopsis.

    Science.gov (United States)

    Park, Jung-Eun; Park, Ju-Young; Kim, Youn-Sung; Staswick, Paul E; Jeon, Jin; Yun, Ju; Kim, Sun-Young; Kim, Jungmook; Lee, Yong-Hwan; Park, Chung-Mo

    2007-03-30

    Plants constantly monitor environmental fluctuations to optimize their growth and metabolism. One example is adaptive growth occurring in response to biotic and abiotic stresses. Here, we demonstrate that GH3-mediated auxin homeostasis is an essential constituent of the complex network of auxin actions that regulates stress adaptation responses in Arabidopsis. Endogenous auxin pool is regulated, at least in part, through negative feedback by a group of auxin-inducible GH3 genes encoding auxin-conjugating enzymes. An Arabidopsis mutant, wes1-D, in which a GH3 gene WES1 is activated by nearby insertion of the (35)S enhancer, exhibited auxin-deficient traits, including reduced growth and altered leaf shape. Interestingly, WES1 is also induced by various stress conditions as well as by salicylic acid and abscisic acid. Accordingly, wes1-D was resistant to both biotic and abiotic stresses, and stress-responsive genes, such as pathogenesis-related genes and CBF genes, were upregulated in this mutant. In contrast, a T-DNA insertional mutant showed reduced stress resistance. We therefore propose that GH3-mediated growth suppression directs reallocation of metabolic resources to resistance establishment and represents the fitness costs of induced resistance.

  10. High REDOX RESPONSIVE TRANSCRIPTION FACTOR1 Levels Result in Accumulation of Reactive Oxygen Species in Arabidopsis thaliana Shoots and Roots.

    Science.gov (United States)

    Matsuo, Mitsuhiro; Johnson, Joy Michal; Hieno, Ayaka; Tokizawa, Mutsutomo; Nomoto, Mika; Tada, Yasuomi; Godfrey, Rinesh; Obokata, Junichi; Sherameti, Irena; Yamamoto, Yoshiharu Y; Böhmer, Frank-D; Oelmüller, Ralf

    2015-08-01

    Redox Responsive Transcription Factor1 (RRTF1) in Arabidopsis is rapidly and transiently upregulated by H2O2, as well as biotic- and abiotic-induced redox signals. RRTF1 is highly conserved in angiosperms, but its physiological role remains elusive. Here we show that inactivation of RRTF1 restricts and overexpression promotes reactive oxygen species (ROS) accumulation in response to stress. Transgenic lines overexpressing RRTF1 are impaired in root and shoot development, light sensitive, and susceptible to Alternaria brassicae infection. These symptoms are diminished by the beneficial root endophyte Piriformospora indica, which reduces ROS accumulation locally in roots and systemically in shoots, and by antioxidants and ROS inhibitors that scavenge ROS. More than 800 genes were detected in mature leaves and seedlings of transgenic lines overexpressing RRTF1; ∼ 40% of them have stress-, redox-, ROS-regulated-, ROS-scavenging-, defense-, cell death- and senescence-related functions. Bioinformatic analyses and in vitro DNA binding assays demonstrate that RRTF1 binds to GCC-box-like sequences in the promoter of RRTF1-responsive genes. Upregulation of RRTF1 by stress stimuli and H2O2 requires WRKY18/40/60. RRTF1 is co-regulated with the phylogenetically related RAP2.6, which contains a GCC-box-like sequence in its promoter, but transgenic lines overexpressing RAP2.6 do not accumulate higher ROS levels. RRTF1 also stimulates systemic ROS accumulation in distal non-stressed leaves. We conclude that the elevated levels of the highly conserved RRTF1 induce ROS accumulation in response to ROS and ROS-producing abiotic and biotic stress signals.

  11. Pseudomonas fluorescens and Pseudomonas putida for Promoting Growth of Jatropha curcas Seedling Root

    Directory of Open Access Journals (Sweden)

    Sri Sumarsih

    2012-05-01

    Full Text Available Pseudomonas fluorescens and P. putida are Plant Growth Promoting Rhizobacteria (PGPR that can produce growth hormone. The objective of this study is to know the effects of those two combined species of PGPR on seedling root growth of Jatropha curcas. The condition of the seedling root determines the success of dry land cultivation. The root which has wider coverage, is larger in number, and is bigger in diameter makes seedling more resistant to stress in dry land environment. In the experiment, two kinds of plant materials are used for seedling, the Jatropha seed and stem material, which are treated in a mixed culture of PGPR. For the Jatropha seed, this mixed culture of PGPR is given at the same time of cultivating the sprout on the seedling medium. For the stem cutting, the PGPR is poured in together during the first watering of the seedling cultivation medium. In the fourthweek, the observed growth parameters are root length, root diameter, primary and secondary lateral root numbers, Root Length Density (RLD, Frequency of Lateral Root (FLR, and Specific Root Length (SRL. These data are analyzed using analysis of variant with DMRT test at 0.05 level of significance. The result of this study shows that PGPR tend to reduce FLR values on the seedling root made from seeds. On the seedling root made from stem cutting, PGPR increase the root length, primary and secondary lateral root numbers, root diameter, FLR and SRL values as well.

  12. Arabidopsis thaliana as a tool to identify traits involved in Verticillium dahliae biocontrol by the olive root endophyte Pseudomonas fluorescens PICF7

    Science.gov (United States)

    Maldonado-González, M. Mercedes; Bakker, Peter A. H. M.; Prieto, Pilar; Mercado-Blanco, Jesús

    2015-01-01

    The effective management of Verticillium wilts (VW), diseases affecting many crops and caused by some species of the soil-borne fungus Verticillium, is problematic. The use of microbial antagonists to control these pathologies fits modern sustainable agriculture criteria. Pseudomonas fluorescens PICF7 is an endophytic bacterium isolated from olive roots with demonstrated ability to control VW of olive caused by the highly virulent, defoliating (D) pathotype of Verticillium dahliae Kleb. However, the study of the PICF7-V. dahliae-olive tripartite interaction poses difficulties because of the inherent characteristics of woody, long-living plants. To overcome these problems we explored the use of the model plant Arabidopsis thaliana. Results obtained in this study showed that: (i) olive D and non-defoliating V. dahliae pathotypes produce differential disease severity in A. thaliana plants; (ii) strain PICF7 is able to colonize and persist in the A. thaliana rhizosphere but is not endophytic in Arabidopsis; and (iii) strain PICF7 controls VW in Arabidopsis. Additionally, as previously observed in olive, neither swimming motility nor siderophore production by PICF7 are required for VW control in A. thaliana, whilst cysteine auxotrophy decreased the effectiveness of PICF7. Moreover, when applied to the roots PICF7 controlled Botrytis cinerea infection in the leaves of Arabidopsis, suggesting that this strain is able to induce systemic resistance. A. thaliana is therefore a suitable alternative to olive bioassays to unravel biocontrol traits involved in biological control of V. dahliae by P. fluorescens PICF7. PMID:25904904

  13. Arabidopsis thaliana as a tool to identify traits involved in Verticillium dahliae biocontrol by the olive root endophyte Pseudomonas fluorescens PICF7.

    Science.gov (United States)

    Maldonado-González, M Mercedes; Bakker, Peter A H M; Prieto, Pilar; Mercado-Blanco, Jesús

    2015-01-01

    The effective management of Verticillium wilts (VW), diseases affecting many crops and caused by some species of the soil-borne fungus Verticillium, is problematic. The use of microbial antagonists to control these pathologies fits modern sustainable agriculture criteria. Pseudomonas fluorescens PICF7 is an endophytic bacterium isolated from olive roots with demonstrated ability to control VW of olive caused by the highly virulent, defoliating (D) pathotype of Verticillium dahliae Kleb. However, the study of the PICF7-V. dahliae-olive tripartite interaction poses difficulties because of the inherent characteristics of woody, long-living plants. To overcome these problems we explored the use of the model plant Arabidopsis thaliana. Results obtained in this study showed that: (i) olive D and non-defoliating V. dahliae pathotypes produce differential disease severity in A. thaliana plants; (ii) strain PICF7 is able to colonize and persist in the A. thaliana rhizosphere but is not endophytic in Arabidopsis; and (iii) strain PICF7 controls VW in Arabidopsis. Additionally, as previously observed in olive, neither swimming motility nor siderophore production by PICF7 are required for VW control in A. thaliana, whilst cysteine auxotrophy decreased the effectiveness of PICF7. Moreover, when applied to the roots PICF7 controlled Botrytis cinerea infection in the leaves of Arabidopsis, suggesting that this strain is able to induce systemic resistance. A. thaliana is therefore a suitable alternative to olive bioassays to unravel biocontrol traits involved in biological control of V. dahliae by P. fluorescens PICF7. PMID:25904904

  14. Advancements in Root Growth Measurement Technologies and Observation Capabilities for Container-Grown Plants

    Directory of Open Access Journals (Sweden)

    Lesley A. Judd

    2015-07-01

    Full Text Available The study, characterization, observation, and quantification of plant root growth and root systems (Rhizometrics has been and remains an important area of research in all disciplines of plant science. In the horticultural industry, a large portion of the crops grown annually are grown in pot culture. Root growth is a critical component in overall plant performance during production in containers, and therefore it is important to understand the factors that influence and/or possible enhance it. Quantifying root growth has varied over the last several decades with each method of quantification changing in its reliability of measurement and variation among the results. Methods such as root drawings, pin boards, rhizotrons, and minirhizotrons initiated the aptitude to measure roots with field crops, and have been expanded to container-grown plants. However, many of the published research methods are monotonous and time-consuming. More recently, computer programs have increased in use as technology advances and measuring characteristics of root growth becomes easier. These programs are instrumental in analyzing various root growth characteristics, from root diameter and length of individual roots to branching angle and topological depth of the root architecture. This review delves into the expanding technologies involved with expertly measuring root growth of plants in containers, and the advantages and disadvantages that remain.

  15. Effects of N fertilizer on root growth in Zea mays L. seedlings

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z. R.; Rui, Y. R.; Shen, J. B.; Zhang, F. S.

    2008-07-01

    This paper reports the effects of different nitrogen (N) fertilizer levels on the growth of maize (Zea mays L.) under field conditions. The N supply was found to influence the growth of the plants, especially the roots. A high N supply significantly inhibited root elongation, and was associated with reduced root dry weight compared to controls and to plants grown with smaller supplies of N. However, no differences were seen in lateral primary root density under the different N supply conditions, nor did plant N concentration increase with high N supply. In conclusion, a high N supply not only wastes resources and pollutes the environment, it may also inhibit root growth. (Author)

  16. Growth of AM fungi on in vitro root organ culture of Sorghum vulgare and Saccharum officinarum.

    Science.gov (United States)

    Raman, N; Sahadevan, C; Srinivasan, V

    2001-12-01

    Spores of Gl mosseae and Gig gigantea germinated on minimal medium produced extraradical mycelium. Gl. mosseae infected roots of S. officinarum in in vitro condition were inoculated in M medium with in vitro cultured roots of Sorghum vulgare (test roots). From the infected root of S. officinarum, the mycelium developed and it infected the test roots. The roots developed new mycelia and further the mycelia produced a few hyaline spores. In MS medium combined with soil extract, root exudate, thiamine HCl and inositol combination, spore germination and germ tube growth were higher when compared with other media. PMID:12018527

  17. Arabidopsis CAP1-mediated ammonium sensing required reactive oxygen species in plant cell growth.

    Science.gov (United States)

    Bai, Ling; Zhou, Yun; Ma, Xiaonan; Gao, Lijie; Song, Chun-Peng

    2014-06-18

    [Ca (2+)]cyt-associated protein kinase (CAP) gene 1 is a receptor-like kinase that belongs to CrRLK1L (Catharanthus roseus Receptor like kinase) subfamily. CAP1 has been identified as a novel modulator of NH 4(+) in the tonoplast, which regulates root hair growth by maintaining the cytoplasmic Ca (2+) gradients. Different expression pattern of tonoplast intrinsic protein (TIP2;3) in the CAP1 knock out mutant and wild type on Murashige and Skoog (MS) medium suggested that CAP1 influences transport activity to regulate the compartmentalization of NH 4(+) into vacuole. Lower expression level of Oxidative Signal-Inducible1(OXI1) in the cap1-1 root and the abnormal reactive oxygen species (ROS) gradient in root hair of cap1-1 on MS medium indicated that ROS signaling involve in CAP1-regulated root hair growth. Wild-type-like ROS distribution pattern in the cap1-1 root hair can be reestablished in seedlings grown on NH 4(+) deficient medium, which indicated that CAP1 functions as a sensor for NH 4(+) signaling in maintaining tip-focused ROS gradient in root hairs polar growth. PMID:24940875

  18. 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.

  19. 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.

  20. Pseudomonas fluorescens and Pseudomonas putida for Promoting Growth of Jatropha curcas Seedling Root

    OpenAIRE

    Sri Sumarsih; Darban Haryanto

    2012-01-01

    Pseudomonas fluorescens and P. putida are Plant Growth Promoting Rhizobacteria (PGPR) that can produce growth hormone. The objective of this study is to know the effects of those two combined species of PGPR on seedling root growth of Jatropha curcas. The condition of the seedling root determines the success of dry land cultivation. The root which has wider coverage, is larger in number, and is bigger in diameter makes seedling more resistant to stress in dry land environment. In the experime...

  1. Ectopic Expression of the Chinese Cabbage Malate Dehydrogenase Gene Promotes Growth and Aluminum Resistance in Arabidopsis.

    Science.gov (United States)

    Li, Qing-Fei; Zhao, Jing; Zhang, Jing; Dai, Zi-Hui; Zhang, Lu-Gang

    2016-01-01

    Malate dehydrogenases (MDHs) are key metabolic enzymes that play important roles in plant growth and development. In the present study, we isolated the full-length and coding sequences of BraMDH from Chinese cabbage [Brassica campestris L. ssp. pekinensis (Lour) Olsson]. We conducted bioinformatics analysis and a subcellular localization assay, which revealed that the BraMDH gene sequence contained no introns and that BraMDH is localized to the chloroplast. In addition, the expression pattern of BraMDH in Chinese cabbage was investigated, which revealed that BraMDH was heavily expressed in inflorescence apical meristems, as well as the effect of BraMDH overexpression in two homozygous transgenic Arabidopsis lines, which resulted in early bolting and taller inflorescence stems. Furthermore, the fresh and dry weights of aerial tissue from the transgenic Arabidopsis plants were significantly higher than those from the corresponding wild-type plants, as were plant height, the number of rosette leaves, and the number of siliques produced, and the transgenic plants also exhibited stronger aluminum resistance when treated with AlCl3. Therefore, our results suggest that BraMDH has a dramatic effect on plant growth and that the gene is involved in both plant growth and aluminum resistance. PMID:27536317

  2. Hydroxyproline O-arabinosyltransferase mutants oppositely alter tip growth in Arabidopsis thaliana and Physcomitrella patens.

    Science.gov (United States)

    MacAlister, Cora A; Ortiz-Ramírez, Carlos; Becker, Jörg D; Feijó, José A; Lippman, Zachary B

    2016-01-01

    Hydroxyproline O-arabinosyltransferases (HPATs) are members of a small, deeply conserved family of plant-specific glycosyltransferases that add arabinose sugars to diverse proteins including cell wall-associated extensins and small signaling peptides. Recent genetic studies in flowering plants suggest that different HPAT homologs have been co-opted to function in diverse species-specific developmental contexts. However, nothing is known about the roles of HPATs in basal plants. We show that complete loss of HPAT function in Arabidopsis thaliana and the moss Physcomitrella patens results in a shared defect in gametophytic tip cell growth. Arabidopsis hpat1/2/3 triple knockout mutants suffer from a strong male sterility defect as a consequence of pollen tubes that fail to fully elongate following pollination. Knocking out the two HPAT genes of Physcomitrella results in larger multicellular filamentous networks due to increased elongation of protonemal tip cells. Physcomitrella hpat mutants lack cell-wall associated hydroxyproline arabinosides and can be rescued with exogenous cellulose, while global expression profiling shows that cell wall-associated genes are severely misexpressed, implicating a defect in cell wall formation during tip growth. Our findings point to a major role for HPATs in influencing cell elongation during tip growth in plants.

  3. SEUSS Integrates Gibberellin Signaling with Transcriptional Inputs from the SHR-SCR-SCL3 Module to Regulate Middle Cortex Formation in the Arabidopsis Root.

    Science.gov (United States)

    Gong, Xue; Flores-Vergara, Miguel A; Hong, Jing Han; Chu, Huangwei; Lim, Jun; Franks, Robert G; Liu, Zhongchi; Xu, Jian

    2016-03-01

    A decade of studies on middle cortex (MC) formation in the root endodermis of Arabidopsis (Arabidopsis thaliana) have revealed a complex regulatory network that is orchestrated by several GRAS family transcription factors, including SHORT-ROOT (SHR), SCARECROW (SCR), and SCARECROW-LIKE3 (SCL3). However, how their functions are regulated remains obscure. Here we show that mutations in the SEUSS (SEU) gene led to a higher frequency of MC formation. seu mutants had strongly reduced expression of SHR, SCR, and SCL3, suggesting that SEU positively regulates these genes. Our results further indicate that SEU physically associates with upstream regulatory sequences of SHR, SCR, and SCL3; and that SEU has distinct genetic interactions with these genes in the control of MC formation, with SCL3 being epistatic to SEU. Similar to SCL3, SEU was repressed by the phytohormone GA and induced by the GA biosynthesis inhibitor paclobutrazol, suggesting that SEU acts downstream of GA signaling to regulate MC formation. Consistently, we found that SEU mediates the regulation of SCL3 by GA signaling. Together, our study identifies SEU as a new critical player that integrates GA signaling with transcriptional inputs from the SHR-SCR-SCL3 module to regulate MC formation in the Arabidopsis root.

  4. Detecting autophagy in Arabidopsis roots by membrane-permeable cysteine protease inhibitor E-64d and endocytosis tracer FM4–64

    OpenAIRE

    Oh-ye, Yuumi; Inoue, Yuko; Moriyasu, Yuji

    2011-01-01

    Autophagy is the process by which cells degrade their own components in lysosomes or vacuoles. Autophagy in tobacco BY-2 cells cultured in sucrose-free medium takes place in formed, autolysosomes in the presence of a cysteine protease inhibitor. The autolysosomes in BY-2 cells are located in the endocytotic pathway and thus can be stained with fluorescent endocytosis marker FM4–64. In the present study, in order to detect autophagy in the root cells of Arabidopsis, we incubated root tips from...

  5. The overexpression of an Amaranthus hypochondriacus NF-YC gene modifies growth and confers water deficit stress resistance in Arabidopsis.

    Science.gov (United States)

    Palmeros-Suárez, Paola A; Massange-Sánchez, Julio A; Martínez-Gallardo, Norma A; Montero-Vargas, Josaphat M; Gómez-Leyva, Juan F; Délano-Frier, John P

    2015-11-01

    Nuclear factor-Y (NF-Y), is a plant heterotrimeric transcription factor constituted by NF-YA, NF-YB and NF-YC subunits. The function of many NF-Y subunits, mostly of the A and B type, has been studied in plants, but knowledge regarding the C subunit remains fragmentary. Here, a water stress-induced NF-YC gene from Amaranthus hypochondriacus (AhNF-YC) was further characterized by its overexpression in transgenic Arabidospis thaliana plants. A role in development was inferred from modified growth rates in root, rosettes and inflorescences recorded in AhNF-YC overexpressing Arabidopsis plants, in addition to a delayed onset of flowering. Also, the overexpression of AhNF-YC caused increased seedling sensitivity to abscisic acid (ABA), and influenced the expression of several genes involved in secondary metabolism, development and ABA-related responses. An altered expression of the latter in water stressed and recovered transgenic plants, together with the observed increase in ABA sensitivity, suggested that their increased water stress resistance was partly ABA-dependent. An untargeted metabolomic analysis also revealed an altered metabolite pattern, both in normal and water stress/recovery conditions. These results suggest that AhNF-YC may play an important regulatory role in both development and stress, and represents a candidate gene for the engineering of abiotic stress resistance in commercial crops. PMID:26475185

  6. Comparison of the toxicity of silver nanoparticles and silver ions on the growth of terrestrial plant model Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Haifeng Qian; Xiaofeng Peng; Xiao Han; Jie Ren; Liwei Sun; Zhengwei Fu

    2013-01-01

    Silver nanoparticles (AgNPs) are one of the most widely used nanomaterials,but the mechanism of AgNP toxicity in terrestrial plants is still unclear.We compared the toxic effects of AgNPs and Ag+ on Arabidopsis thaliana at the physiological,ultrastructural and molecular levels.AgNPs did not affect seed germination; however,they showed stronger inhibitory effect on root elongation than Ag+.The results of transmission electron microscopy and metal content analysis showed that AgNPs could be accumulated in leaves.These absorbed AgNPs disrupted the thylakoid membrane structure and decreased chlorophyll content,which can inhibit plant growth.By comparison,a small amount of Ag+ was absorbed by seedlings,and it did not pronouncedly affect chloroplast structure and other metal ion absorption as AgNPs did.Compared with Ag+,AgNPs could alter the transcription of antioxidant and aquaporin genes,indicating that AgNPs changed the balance between the oxidant and antioxidant systems,and also affected the homeostasis of water and other small molecules within the plant body.All the data from physiological,ultrastructural and molecular levels suggest that AgNPs were more toxic than Ag+.

  7. Effect of calmodulin antagonists on the growth and graviresponsiveness of primary roots of maize

    Science.gov (United States)

    Stinemetz, C. L.; Hasenstein, K. H.; Young, L. M.; Evans, M. L.

    1992-01-01

    We examined the effect of calmodulin (CaM) antagonists applied at the root tip on root growth, gravity-induced root curvature, and the movement of calcium across the root tip and auxin (IAA) across the elongation zone of gravistimulated roots. All of the CaM antagonists used in these studies delayed gravity-induced curvature at a concentration (1 micromole) that did not affect root growth. Calmodulin antagonists (> or = 1 micromole) inhibited downward transport of label from 45Ca2+ across the caps of gravistimulated roots relative to the downward transport of 45Ca2+ in gravistimulated roots which were not treated with CaM antagonists. Application of CaM antagonists at the root tip (> or = 1 micromole) also decreased the relative downward movement of label from 3H-IAA applied to the upper side of the elongation zone of gravistimulated roots. In general, tip application of antagonists inhibited neither the upward transport of 45Ca2+ in the root tip nor the upward movement of label from 3H-IAA in the elongation zone of gravistimulated roots. Thus, roots treated with CaM antagonists > or = 1 micromole become less graviresponsive and exhibit reduced or even a reversal of downward polarity of calcium transport across the root tip and IAA transport across the elongation zone. The results indicate that calmodulin-regulated events play a role in root gravitropism.

  8. The Equilibrium and Growth Stability of Winter Wheat Root and Shoot Under Different Soil Water Conditions

    Institute of Scientific and Technical Information of China (English)

    GAO Zhi-hong; CHEN Xiao-yuan; LUO Yuan-pei

    2007-01-01

    The equilibrium between root, shoot and growth stability under different soil water conditions were investigated in a tube experiment of winter wheat. The water supplying treatments included: sufficient irrigation at whole growth phase, moderate deficiency irrigation at whole growth phase, serious deficiency irrigation at whole growth phase, sufficient irrigation at jointing stage, tillering stage, flowering stage, and fillering respectively, after moderate and serious water deficit during their previous growth stage. Root and shoot biomass were measured. On the basis of the cooperative root-shoot interactions model, the equilibrium and growth stability were studied on the strength of the kinetics system theory. There was only one varying equilibrium point between the root and shoot over the life time of the winter wheat plant. Water stress prolonged the duration of stable growth, the more serious the water deficit, the longer the period of stable growth.The duration of stable growth was shortened and that of unstable growth was prolonged after water recovery. The growth behavior of the plants exposed to moderate water deficit shifted from stable to unstable until the end of the growth,after rewatering at flowering. In the life-time of the crop, the root and shoot had been adjusting themselves in structure and function so as to maintain an equilibrium, but could not achieve the equilibrium state for long. They were always in an unbalanced state from the beginning to the end of growth. This was the essence of root-shoot equilibrium. Water stress inhibited the function of root and shoot, reduced root shoot interactions, and as a result, the plant growth gradually tended to stabilize. Rewatering enhanced root shoot interactions, prolonged duration of instable growth. Rewatering at flowering could upset the inherent relativity during the long time of stable growth from flowering to filling stage, thus leading to unstable growth and enhanced dry matter accumulating rate

  9. Mathematical Modeling and Experimental Validation of the Spatial Distribution of Boron in the Root of Arabidopsis thaliana Identify High Boron Accumulation in the Tip and Predict a Distinct Root Tip Uptake Function

    OpenAIRE

    Shimotohno, Akie; Sotta, Naoyuki; Sato, Takafumi; De Ruvo, Micol; Marée, Athanasius F.M.; Verônica A Grieneisen; Fujiwara, Toru

    2015-01-01

    Boron, an essential micronutrient, is transported in roots of Arabidopsis thaliana mainly by two different types of transporters, BORs and NIPs (nodulin26-like intrinsic proteins). Both are plasma membrane localized, but have distinct transport properties and patterns of cell type-specific accumulation with different polar localizations, which are likely to affect boron distribution. Here, we used mathematical modeling and an experimental determination to address boron distributions in the ro...

  10. Life-cycle chronic gamma exposure of Arabidopsis thaliana induces growth effects but no discernable effects on oxidative stress pathways.

    Science.gov (United States)

    Vandenhove, Hildegarde; Vanhoudt, Nathalie; Cuypers, Ann; van Hees, May; Wannijn, Jean; Horemans, Nele

    2010-09-01

    Arabidopsis thaliana was exposed to low-dose chronic gamma irradiation during a full life cycle (seed to seed) and several biological responses were investigated. Applied dose rates were 2336, 367 and 81 microGy h(-1). Following 24 days (inflorescence emergence), 34 days (approximately 50% of flowers open) and 54 days (silice ripening) exposure, plants were harvested and monitored for biometric parameters, capacities of enzymes involved in the antioxidative defence mechanisms (SOD, APOD, GLUR, GPOD, SPOD, CAT, ME), glutathione and ascorbate pool, lipid peroxidation products, altered gene expression of selected genes encoding for antioxidative enzymes or reactive oxygen species production, and DNA integrity. Root fresh weight was significantly reduced after gamma exposure compared to the control at all stages monitored but no significant differences in root weight for the different dose rates applied was observed. Leaf and stem fresh weight were significantly reduced at the highest irradiation level after 54 days exposure only. Also total plant fresh was significantly lower at silice riping and this for the highest and medium dose rate applied. The dose rate estimated to result in a 10% reduction in growth (EDR-10) ranged between 60 and 80 microGy h(-1). Germination of seeds from the gamma irradiated plants was not hampered. For several of the antioxidative defence enzymes studied, the enzyme capacity was generally stimulated towards flowering but generally no significant effect of dose rate on enzyme capacity was observed. Gene analysis revealed a significant transient and dose dependent change in expression of RBOHC indicating active reactive oxygen production induced by gamma irradiation. No effect of irradiation was observed on concentration or reduction state of the non-enzymatic antioxidants, ascorbate and glutathione. The level of lipid peroxidation products remained constant throughout the observation period and was not affected by dose rate. The comet assay

  11. Life-cycle chronic gamma exposure of Arabidopsis thaliana induces growth effects but no discernable effects on oxidative stress pathways.

    Science.gov (United States)

    Vandenhove, Hildegarde; Vanhoudt, Nathalie; Cuypers, Ann; van Hees, May; Wannijn, Jean; Horemans, Nele

    2010-09-01

    Arabidopsis thaliana was exposed to low-dose chronic gamma irradiation during a full life cycle (seed to seed) and several biological responses were investigated. Applied dose rates were 2336, 367 and 81 microGy h(-1). Following 24 days (inflorescence emergence), 34 days (approximately 50% of flowers open) and 54 days (silice ripening) exposure, plants were harvested and monitored for biometric parameters, capacities of enzymes involved in the antioxidative defence mechanisms (SOD, APOD, GLUR, GPOD, SPOD, CAT, ME), glutathione and ascorbate pool, lipid peroxidation products, altered gene expression of selected genes encoding for antioxidative enzymes or reactive oxygen species production, and DNA integrity. Root fresh weight was significantly reduced after gamma exposure compared to the control at all stages monitored but no significant differences in root weight for the different dose rates applied was observed. Leaf and stem fresh weight were significantly reduced at the highest irradiation level after 54 days exposure only. Also total plant fresh was significantly lower at silice riping and this for the highest and medium dose rate applied. The dose rate estimated to result in a 10% reduction in growth (EDR-10) ranged between 60 and 80 microGy h(-1). Germination of seeds from the gamma irradiated plants was not hampered. For several of the antioxidative defence enzymes studied, the enzyme capacity was generally stimulated towards flowering but generally no significant effect of dose rate on enzyme capacity was observed. Gene analysis revealed a significant transient and dose dependent change in expression of RBOHC indicating active reactive oxygen production induced by gamma irradiation. No effect of irradiation was observed on concentration or reduction state of the non-enzymatic antioxidants, ascorbate and glutathione. The level of lipid peroxidation products remained constant throughout the observation period and was not affected by dose rate. The comet assay

  12. Colonization of Greek olive cultivars' root system by arbuscular mycorrhiza fungus: root morphology, growth, and mineral nutrition of olive plants

    Directory of Open Access Journals (Sweden)

    Theocharis Chatzistathis

    2013-06-01

    Full Text Available Rooted leafy cuttings of three Greek olive (Olea europaea L. cultivars (Koroneiki, Kothreiki and Chondrolia Chalkidikis were grown for six months in three soil types, in an experimental greenhouse, in order to investigate: i if their root system was colonized by arbuscular mycorrhiza fungus (AMF genus and, ii if genotypic differences concerning growth and mineral nutrition of olive plants existed. Gigaspora sp. colonized the root system of the three cultivars studied, while Glomus sp. colonized only the root system of 'Koroneiki'. Furthermore, in most cases root colonization by AMF differed among cultivars and soil types. The maximum root colonization, in all soils, was found in 'Chondrolia Chalkidikis'. In the three soils studied, the ratio shoot dry weight (SDW/ root dry weight (RDW was higher in 'Chondrolia Chalkidikis' than in the other two cultivars. Furthermore, root system morphology of the three olive cultivars was completely different, irrespectively of soil type. Leaf Mn, Fe, Zn, Ca, Mg, K and P concentrations, as well as total per plant nutrient content and nutrient use efficiency, differed among cultivars under the same soil conditions. These differences concerning root morphology, SDW/RDW, as well as nutrient uptake and use efficiency, could be possibly ascribed to the differential AMF colonization by Glomus sp. and Gigaspora sp.

  13. Arabidopsis thaliana AtUTr7 Encodes a Golgi-Localized UDP-Glucose/UDP-Galactose Transporter that Affects Lateral Root Emergence

    Institute of Scientific and Technical Information of China (English)

    Michael Handford; Cecilia Rodríguez-Furlán; Lorena Marchant; Marcelo Segura; Daniela Gómez; Elena Alvarez-Buyll; Guang-Yan Xiong; Markus Pauly; Ariel Orellana

    2012-01-01

    Nucleotide sugar transporters (NSTs) are antiporters comprising a gene family that plays a fundamental role in the biosynthesis of complex cell wall polysaccharides and glycoproteins in plants.However,due to the limited number of related mutants that have observable phenotypes,the biological function(s) of most NSTs in cell wall biosynthesis and assembly have remained elusive.Here,we report the characterization of AtUTr7 from Arabidopsis (Arabidopsis thaliana (L.) Heynh.),which is homologous to multi-specific UDP-sugar transporters from Drosophila melanogaster,humans,and Caenorhabditis elegans.We show that AtUTr7 possesses the common structural characteristics conserved among NSTs.Using a green fluorescent protein (GFP) tagged version,we demonstrate that AtUTr7 is localized in the Golgi apparatus.We also show that AtUTr7 is widely expressed,especially in the roots and in specific floral organs.Additionally,the results of an in vitro nucleotide sugar transport assay carried out with a tobacco and a yeast expression system suggest that AtUTr7 is capable of transferring UDP-Gal and UDP-GIc,but not a range of other UDP-and GDP-sugars,into the Golgi lumen.Mutants lacking expression of AtUTr7 exhibited an early proliferation of lateral roots as well as distorted root hairs when cultivated at high sucrose concentrations.Furthermore,the distribution of homogalacturonan with a low degree of methyl esterification differed in lateral root tips of the mutant compared to wild-type plants,although additional analytical procedures revealed no further differences in the composition of the root cell walls.This evidence suggests that the transport of UDP-Gal and UDP-GIc into the Golgi under conditions of high root biomass production plays a role in lateral root and root hair development.

  14. Arabidopsis thaliana as a tool to identify traits involved in Verticillium dahliae biocontrol by the olive root endophyte Pseudomonas fluorescens PICF7

    Directory of Open Access Journals (Sweden)

    M. Mercedes eMaldonado-González

    2015-04-01

    Full Text Available The effective management of Verticillium wilts, diseases affecting many crops and caused by some species of the soil-borne fungus Verticillium, is problematic. The use of microbial antagonists to control these pathologies fits modern sustainable agriculture criteria. Pseudomonas fluorescens PICF7 is an endophytic bacterium isolated from olive roots with demonstrated ability to control Verticillium wilt of olive caused by the highly-virulent, defoliating (D pathotype of Verticillium dahliae Kleb. However, the study of the PICF7-V.dahliae-olive tripartite interaction poses difficulties because of the inherent characteristics of woody, long-living plants. To overcome these problems we explored the use of the model plant Arabidopsis thaliana. Results obtained in this study showed that: (i olive D and non-defoliating (ND V. dahliae pathotypes produce differential disease severity in A. thaliana plants; (ii strain PICF7 is able to colonize and persist in the A. thaliana rhizosphere but is not endophytic in Arabidopsis; and (iii strain PICF7 controls Verticillium wilt (VW in Arabidopsis. Additionally, as previously observed in olive, neither swimming motility nor siderophore production by PICF7 are required for VW control in A. thaliana, whilst cysteine auxotrophy decreased the effectiveness of PICF7. Moreover, when applied to the roots PICF7 controlled Botrytis cinerea infection in the leaves of Arabidopsis, suggesting that this strain is able to induce systemic resistance. Arabidopsis thaliana is therefore a suitable alternative to olive bioassays to unravel biocontrol traits involved in biological control of V. dahliae by P. fluorescens PICF7.

  15. Analyzing Arabidopsis thaliana root proteome provides insights into the molecular bases of enantioselective imazethapyr toxicity

    Science.gov (United States)

    Qian, Haifeng; Lu, Haiping; Ding, Haiyan; Lavoie, Michel; Li, Yali; Liu, Weiping; Fu, Zhengwei

    2015-07-01

    Imazethapyr (IM) is a widely used chiral herbicide that inhibits the synthesis of branched-chain amino acids (BCAAs). IM is thought to exert its toxic effects on amino acid synthesis mainly through inhibition of acetolactate synthase activity, but little is known about the potential effects of IM on other key biochemical pathways. Here, we exposed the model plant Arabidospsis thaliana to trace S- and R-IM enantiomer concentrations and examined IM toxicity effects on the root proteome using iTRAQ. Conventional analyses of root carbohydrates, organic acids, and enzyme activities were also performed. We discovered several previously unknown key biochemical pathways targeted by IM in Arabidospsis. 1,322 and 987 proteins were differentially expressed in response to R- and S-IM treatments, respectively. Bioinformatics and physiological analyses suggested that IM reduced the BCAA tissue content not only by strongly suppressing BCAA synthesis but also by increasing BCAA catabolism. IM also affected sugar and starch metabolism, changed the composition of root cell walls, increased citrate production and exudation, and affected the microbial community structure of the rhizosphere. The present study shed new light on the multiple toxicity mechanisms of a selective herbicide on a model plant.

  16. Overexpression of Arabidopsis VIT1 increases accumulation of iron in cassava roots and stems.

    Science.gov (United States)

    Narayanan, Narayanan; Beyene, Getu; Chauhan, Raj Deepika; Gaitán-Solis, Eliana; Grusak, Michael A; Taylor, Nigel; Anderson, Paul

    2015-11-01

    Iron is extremely abundant in the soil, but its uptake in plants is limited due to low solubility in neutral or alkaline soils. Plants can rely on rhizosphere acidification to increase iron solubility. AtVIT1 was previously found to be involved in mediating vacuolar sequestration of iron, which indicates a potential application for iron biofortification in crop plants. Here, we have overexpressed AtVIT1 in the starchy root crop cassava using a patatin promoter. Under greenhouse conditions, iron levels in mature cassava storage roots showed 3-4 times higher values when compared with wild-type plants. Significantly, the expression of AtVIT1 showed a positive correlation with the increase in iron concentration of storage roots. Conversely, young leaves of AtVIT1 transgenic plants exhibit characteristics of iron deficiency such as interveinal chlorosis of leaves (yellowing) and lower iron concentration when compared with the wild type plants. Interestingly, the AtVIT1 transgenic plants showed 4 and 16 times higher values of iron concentration in the young stem and stem base tissues, respectively. AtVIT1 transgenic plants also showed 2-4 times higher values of iron content when compared with wild-type plants, with altered partitioning of iron between source and sink tissues. These results demonstrate vacuolar iron sequestration as a viable transgenic strategy to biofortify crops and to help eliminate micronutrient malnutrition in at-risk human populations.

  17. Oxidative stress response in Arabidopsis thaliana roots and leaves exposed to cadmium, uranium or a combination of both stressors

    Energy Technology Data Exchange (ETDEWEB)

    Horemans, N.; Saenen, E.; Vandenhove, H. [Belgian Nuclear Research Centre, SCK.CEN, Boeretang 200, 2400 Mol (Belgium); Hendrix, S.; Keunen, E.; Cuypers, A. [Hasselt University, Centre for Environmental Sciences, Agoralaan, Building D, 3590 Diepenbeek (Belgium)

    2014-07-01

    Nuclear energy production or NORM industry released low amounts of radioactive substances together with non-radioactive substances (e.g., heavy metals, organic chemicals) to the environment. As sessile organisms, plants are commonly exposed to a number of adverse conditions and therefore it is interesting to study the stress responses of plants induced by the single stressors as well as in a in a multi-pollution set-up. The aim of this study was to understand and predict fast induced oxidative stress responses in plants exposed to Cd and U or a combination of both stressors. Arabidopsis thaliana plants grown hydroponically for 18 days were exposed to a Cd (5 μM) or {sup 238}U (25 μM) or an equi-toxic mixture of Cd and {sup 238}U (2.5 μM + 12.5 μM) for 24 h. As expected both metals were taken up into the plants with Cd being more readily transported to the leaves than U. The root-to-shoot ratio was approximately 1,3 for Cd whereas it was above 3500 for U. For both U and Cd the root-to-shoot ratio was not affected under multiple exposure conditions used here. Notwithstanding the limited exposure time, leave and root fresh weight was already decreasing in U-treated plants. For Cd or Cd+U a decreasing but at this point not significant trend was visible. As U concentrations in the leaves were very low the decrease in leaf fresh weight is possibly due to signaling from the roots rather than a direct toxicity of U. The oxidative stress response was investigated by measuring the transcription of selected pro- and anti-oxidative genes, anti-oxidative enzyme capacities and concentration and redox status of major anti-oxidative metabolites. Cd strongly up-regulated lipoxygenase (LOX1) and NADPH-oxidases (RBOHD or C in roots and leaves, respectively) whereas this was not found in the U-treated plants. For the anti-oxidative response related enzymes both Cd and U induced a decrease in Cu/Zn superoxide dismutases (CSD1,2) and a concomitant increase in Fe-SOD (FSD1). However

  18. Light regulation of the growth response in corn root gravitropism

    Science.gov (United States)

    Kelly, M. O.; Leopold, A. C.

    1992-01-01

    Roots of Merit variety corn (Zea mays L.) require red light for orthogravitropic curvature. Experiments were undertaken to identify the step in the pathway from gravity perception to asymmetric growth on which light may act. Red light was effective in inducing gravitropism whether it was supplied concomitant with or as long as 30 minutes after the gravity stimulus (GS). The presentation time was the same whether the GS was supplied in red light or in darkness. Red light given before the GS slightly enhanced the rate of curvature but had little effect on the lag time or on the final curvature. This enhancement was expanded by a delay between the red light pulse and the GS. These results indicate that gravity perception and at least the initial transduction steps proceed in the dark. Light may regulate the final growth (motor) phase of gravitropism. The time required for full expression of the light enhancement of curvature is consistent with its involvement in some light-stimulated biosynthetic event.

  19. Tree growth and management in Ugandan agroforestry systems: effects of root pruning on tree growth and crop yield.

    Science.gov (United States)

    Wajja-Musukwe, Tellie-Nelson; Wilson, Julia; Sprent, Janet I; Ong, Chin K; Deans, J Douglas; Okorio, John

    2008-02-01

    Tree root pruning is a potential tool for managing belowground competition when trees and crops are grown together in agroforestry systems. We investigated the effects of tree root pruning on shoot growth and root distribution of Alnus acuminata (H.B. & K.), Casuarina equisetifolia L., Grevillea robusta A. Cunn. ex R. Br., Maesopsis eminii Engl. and Markhamia lutea (Benth.) K. Schum. and on yield of adjacent crops in sub-humid Uganda. The trees were 3 years old at the commencement of the study, and most species were competing strongly with crops. Tree roots were pruned 41 months after planting by cutting and back-filling a trench to a depth of 0.3 m, at a distance of 0.3 m from the trees, on one side of the tree row. The trench was reopened and roots recut at 50 and 62 months after planting. We assessed the effects on tree growth and root distribution over a 3 year period, and crop yield after the third root pruning at 62 months. Overall, root pruning had only a slight effect on aboveground tree growth: height growth was unaffected and diameter growth was reduced by only 4%. A substantial amount of root regrowth was observed by 11 months after pruning. Tree species varied in the number and distribution of roots, and C. equisetifolia and M. lutea had considerably more roots per unit of trunk volume than the other species, especially in the surface soil layers. Casuarina equisetifolia and M. eminii were the tree species most competitive with crops and G. robusta and M. lutea the least competitive. Crop yield data provided strong evidence of the redistribution of root activity following root pruning, with competition increasing on the unpruned side of tree rows. Thus, one-sided root pruning will be useful in only a few circumstances.

  20. Tree growth and management in Ugandan agroforestry systems: effects of root pruning on tree growth and crop yield.

    Science.gov (United States)

    Wajja-Musukwe, Tellie-Nelson; Wilson, Julia; Sprent, Janet I; Ong, Chin K; Deans, J Douglas; Okorio, John

    2008-02-01

    Tree root pruning is a potential tool for managing belowground competition when trees and crops are grown together in agroforestry systems. We investigated the effects of tree root pruning on shoot growth and root distribution of Alnus acuminata (H.B. & K.), Casuarina equisetifolia L., Grevillea robusta A. Cunn. ex R. Br., Maesopsis eminii Engl. and Markhamia lutea (Benth.) K. Schum. and on yield of adjacent crops in sub-humid Uganda. The trees were 3 years old at the commencement of the study, and most species were competing strongly with crops. Tree roots were pruned 41 months after planting by cutting and back-filling a trench to a depth of 0.3 m, at a distance of 0.3 m from the trees, on one side of the tree row. The trench was reopened and roots recut at 50 and 62 months after planting. We assessed the effects on tree growth and root distribution over a 3 year period, and crop yield after the third root pruning at 62 months. Overall, root pruning had only a slight effect on aboveground tree growth: height growth was unaffected and diameter growth was reduced by only 4%. A substantial amount of root regrowth was observed by 11 months after pruning. Tree species varied in the number and distribution of roots, and C. equisetifolia and M. lutea had considerably more roots per unit of trunk volume than the other species, especially in the surface soil layers. Casuarina equisetifolia and M. eminii were the tree species most competitive with crops and G. robusta and M. lutea the least competitive. Crop yield data provided strong evidence of the redistribution of root activity following root pruning, with competition increasing on the unpruned side of tree rows. Thus, one-sided root pruning will be useful in only a few circumstances. PMID:18055434

  1. Gravitational force regulates elongation growth of arabidopsis hypocotyls by modifying xyloglucan metabolism

    Science.gov (United States)

    Soga, K.; Wakabayashi, K.; Hoson, T.; Kamisaka, S.

    Growth of dark-grown Arabidopsis hypocotyls was suppressed under hypergravity conditions (300 g), or was stimulated under microgravity conditions in space (Space Shuttle STS-95). The mechanical extensibility of cell walls decreased and increased under hypergravity and microgravity conditions, respectively. The amounts of cell wall polysaccharides (pectin, hemicellulose-I, hemicellulose-II and cellulose) per unit length of hypocotyls increased under hypergravity conditions, and decreased under microgravity conditions. The amount and the molecular mass of xyloglucans also increased under the hypergravity conditions, while those decreased under microgravity conditions. The activity of xyloglucan-degrading enzymes extracted from hypocotyl cell walls decreased and increased under hypergravity and microgravity conditions, respectively. These results indicate that the amount and the molecular mass of xyloglucans are affected by the magnitude of gravity and that such changes are caused by changes in xyloglucan-degrading activity. Modifications of xyloglucan metabolism as well as the thickness of cell walls by gravity stimulus may be the primary event determining the cell wall extensibility, thereby regulating the growth rate of Arabidopsis hypocotyls.

  2. Cytokinin modulates proteomic, transcriptomic and growth responses to temperature shocks in Arabidopsis.

    Science.gov (United States)

    Cerný, Martin; Jedelský, Petr L; Novák, Jan; Schlosser, Andreas; Brzobohatý, Břetislav

    2014-07-01

    As sessile organisms, plants must sense environmental conditions and adjust their growth and development processes accordingly, through adaptive responses regulated by various internal factors, including hormones. A key environmental factor is temperature, but temperature-sensing mechanisms are not fully understood despite intense research. We investigated proteomic responses to temperature shocks (15 min cold or heat treatments) with and without exogenous applications of cytokinin in Arabidopsis. Image and mass spectrometric analysis of the two-dimensionally separated proteins detected 139 differentially regulated spots, in which 148 proteins were identified, most of which have not been previously linked to temperature perception. More than 70% of the temperature-shock response proteins were modulated by cytokinin, mostly in a similar manner as heat shock. Data mining of previous transcriptomic datasets supported extensive interactions between temperature and cytokinin signalling. The biological significance of this finding was tested by assaying an independent growth response of Arabidopsis seedlings to heat stress: hypocotyl elongation. This response was strongly inhibited in mutants with deficiencies in cytokinin signalling or endogenous cytokinin levels. Thus, cytokinins may directly participate in heat signalling in plants. Finally, large proportions of both temperature-shock and cytokinin responsive proteomes co-localize to the chloroplast, which might therefore host a substantial proportion of the temperature response machinery.

  3. Transcript profiling of cytokinin action in Arabidopsis roots and shoots discovers largely similar but also organ-specific responses

    Directory of Open Access Journals (Sweden)

    Brenner Wolfram G

    2012-07-01

    Full Text Available Abstract Background The plant hormone cytokinin regulates growth and development of roots and shoots in opposite ways. In shoots it is a positive growth regulator whereas it inhibits growth in roots. It may be assumed that organ-specific regulation of gene expression is involved in these differential activities, but little is known about it. To get more insight into the transcriptional events triggered by cytokinin in roots and shoots, we studied genome-wide gene expression in cytokinin-treated and cytokinin-deficient roots and shoots. Results It was found by principal component analysis of the transcriptomic data that the immediate-early response to a cytokinin stimulus differs from the later response, and that the transcriptome of cytokinin-deficient plants is different from both the early and the late cytokinin induction response. A higher cytokinin status in the roots activated the expression of numerous genes normally expressed predominantly in the shoot, while a lower cytokinin status in the shoot reduced the expression of genes normally more active in the shoot to a more root-like level. This shift predominantly affected nuclear genes encoding plastid proteins. An organ-specific regulation was assigned to a number of genes previously known to react to a cytokinin signal, including root-specificity for the cytokinin hydroxylase gene CYP735A2 and shoot specificity for the cell cycle regulator gene CDKA;1. Numerous cytokinin-regulated genes were newly discovered or confirmed, including the meristem regulator genes SHEPHERD and CLAVATA1, auxin-related genes (IAA7, IAA13, AXR1, PIN2, PID, several genes involved in brassinosteroid (CYP710A1, CYP710A2, DIM/DWF and flavonol (MYB12, CHS, FLS1 synthesis, various transporter genes (e.g. HKT1, numerous members of the AP2/ERF transcription factor gene family, genes involved in light signalling (PhyA, COP1, SPA1, and more than 80 ribosomal genes. However, contrasting with the fundamental difference of

  4. 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

  5. A novel high efficiency, low maintenance, hydroponic system for synchronous growth and flowering of Arabidopsis thaliana

    OpenAIRE

    Bernier Georges; Kurtem Emile; Pieltain Alexandra; Havelange Andrée; Corbesier Laurent; Tocquin Pierre; Périlleux Claire

    2003-01-01

    Abstract Background Arabidopsis thaliana is now the model organism for genetic and molecular plant studies, but growing conditions may still impair the significance and reproducibility of the experimental strategies developed. Besides the use of phytotronic cabinets, controlling plant nutrition may be critical and could be achieved in hydroponics. The availability of such a system would also greatly facilitate studies dealing with root development. However, because of its small size and roset...

  6. Adaptive growth of tree root systems in response to wind action and site conditions.

    Science.gov (United States)

    Nicoll, Bruce C.; Ray, Duncan

    1996-01-01

    Soil-root plate dimensions and structural root architecture were examined on 46-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) trees that had been mechanically uprooted. Rooting depth was restricted by a water table, and root system morphology had adapted to resist the wind movement associated with shallow rooting. The spread of the root system and the ratio of root mass to shoot mass (root/shoot ratio) were both negatively related to soil-root plate depth. Root systems had more structural root mass on the leeward side than the windward side of the tree relative to the prevailing wind direction. Cross sections of structural roots were obtained at distances of 0.5, 0.75, 1.0, and 1.25 m from the tree center. Buttressed parts of roots had greater lateral and vertical secondary thickening above rather than below the biological center. This uneven growth, which produced a shape similar in cross section to a T-beam, was greater on the leeward side of the tree, and was greatest at 0.5 m from the tree center of shallow rooted trees. Further from the tree, particularly on the windward side, many roots developed eccentric cross-sectional shapes comparable to I-beams, which would efficiently resist vertical flexing. Roots became more ovoid in shape with increasing distance from the tree, especially on deep rooted trees where lateral roots tapered rapidly to a small diameter. We conclude that these forms of adaptive growth in response to wind movement improve the rigidity of the soil-root plate and counteract the increasing vulnerability to windthrow as the tree grows.

  7. Cytotypes of Centaurea stoebe found to differ in root growth using growth pouches

    OpenAIRE

    Alexandra R. Collins; Thalmann, Daniela; Müller-Schärer, Heinz

    2013-01-01

    Centaurea stoebe is native to Europe and Western Asia and was introduced into North America in the late 19th century, where it has become highly invasive. In its native range, C. stoebe occurs in two cytotypes, namely diploids (2n = 18) and tetraploids (2n = 36), but only the tetraploid form has been identified in the invaded range. We used special growth pouches to determine whether diploid and tetraploid cytotypes from the native range differed in root growth and architecture. We grew seeds...

  8. 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

  9. ARG1 and ARL2 contribute to gravity signal transduction in the statocytes of Arabidopsis thaliana roots and hypocotyls

    Science.gov (United States)

    Masson, Patrick; Harrison, Benjamin; Stanga, John; Otegui, Marisa; Sedbrook, John

    Gravity is an important cue that plant organs use to guide their growth. Each organ is characterized by a defined gravity set point angle that dictates its optimal orientation within the gravity field. Specialized cells, named statocytes, enable this directional growth response by perceiving gravity via the sedimentation of, and/or tension/pressure exerted by, starch-filled plastids within their cytoplasm. Located in the columella region of the cap in roots and in the endodermis of hypocotyls and stems, these cells modulate the lateral transport of auxin across the corresponding organ in a gravistimulus-dependent manner. Upon plant reorientation within the gravity field, a gravity signal transduction pathway is activated within those cells, which in roots leads to a relocalization of the PIN3 auxin efflux carrier toward the lower membrane and an alkalinization of the cytoplasm. In turn, these events appear to promote a lateral transport of auxin toward the bottom side of the stimulated organ, which promotes a curvature. We previously uncovered ARG1 and ARL2 as essential contributors to these cellular processes. Mutations in these genes result in altered root and hypocotyl gravitropism. In roots, this abnormal growth behavior is associated with a lack of PIN3 relocalization within the statocytes and an absence of preferential downward auxin transport upon gravistimulation. These two genes encode paralogous J-domain proteins that are associated with the plasma membrane and other membranes of the vesicular trafficking pathway, and appear to modulate protein trafficking within the statocytes. An analysis of the root gravitropic phenotypes associated with different double mutant configurations affecting ARG1, ARL2 and PIN3 suggest that all three proteins function in a common gravity-signaling pathway. Surprisingly, when a mutation that affects starch biosynthesis (pgm) is introgressed into an arg1-2 mutant, the gravitropic defects are dramatically enhanced relative to

  10. The beet cyst nematode Heterodera schachtii modulates the expression of WRKY transcription factors in syncytia to favour its development in Arabidopsis roots.

    Science.gov (United States)

    Ali, Muhammad Amjad; Wieczorek, Krzysztof; Kreil, David P; Bohlmann, Holger

    2014-01-01

    Cyst nematodes invade the roots of their host plants as second stage juveniles and induce a syncytium which is the only source of nutrients throughout their life. A recent transcriptome analysis of syncytia induced by the beet cyst nematode Heterodera schachtii in Arabidopsis roots has shown that thousands of genes are up-regulated or down-regulated in syncytia as compared to root segments from uninfected plants. Among the down-regulated genes are many which code for WRKY transcription factors. Arabidopsis contains 66 WRKY genes with 59 represented by the ATH1 GeneChip. Of these, 28 were significantly down-regulated and 6 up-regulated in syncytia as compared to control root segments. We have studied here the down-regulated genes WRKY6, WRKY11, WRKY17 and WRKY33 in detail. We confirmed the down-regulation in syncytia with promoter::GUS lines. Using various overexpression lines and mutants it was shown that the down-regulation of these WRKY genes is important for nematode development, probably through interfering with plant defense reactions. In case of WRKY33, this might involve the production of the phytoalexin camalexin.

  11. The beet cyst nematode Heterodera schachtii modulates the expression of WRKY transcription factors in syncytia to favour its development in Arabidopsis roots.

    Directory of Open Access Journals (Sweden)

    Muhammad Amjad Ali

    Full Text Available Cyst nematodes invade the roots of their host plants as second stage juveniles and induce a syncytium which is the only source of nutrients throughout their life. A recent transcriptome analysis of syncytia induced by the beet cyst nematode Heterodera schachtii in Arabidopsis roots has shown that thousands of genes are up-regulated or down-regulated in syncytia as compared to root segments from uninfected plants. Among the down-regulated genes are many which code for WRKY transcription factors. Arabidopsis contains 66 WRKY genes with 59 represented by the ATH1 GeneChip. Of these, 28 were significantly down-regulated and 6 up-regulated in syncytia as compared to control root segments. We have studied here the down-regulated genes WRKY6, WRKY11, WRKY17 and WRKY33 in detail. We confirmed the down-regulation in syncytia with promoter::GUS lines. Using various overexpression lines and mutants it was shown that the down-regulation of these WRKY genes is important for nematode development, probably through interfering with plant defense reactions. In case of WRKY33, this might involve the production of the phytoalexin camalexin.

  12. Beneficial Bacteria Isolated from Grapevine Inner Tissues Shape Arabidopsis thaliana Roots

    OpenAIRE

    Enrico Baldan; Sebastiano Nigris; Chiara Romualdi; Stefano D'Alessandro; Anna Clocchiatti; Michela Zottini; Piergiorgio Stevanato; Andrea Squartini; Barbara Baldan

    2015-01-01

    We investigated the potential plant growth-promoting traits of 377 culturable endophytic bacteria, isolated from Vitis vinifera cv. Glera, as good biofertilizer candidates in vineyard management. Endophyte ability in promoting plant growth was assessed in vitro by testing ammonia production, phosphate solubilization, indole-3-acetic acid (IAA) and IAA-like molecule biosynthesis, siderophore and lytic enzyme secretion. Many of the isolates were able to mobilize phosphate (33%), release ammoniu...

  13. Root cooling strongly affects diel leaf growth dynamics, water and carbohydrate relations in Ricinus communis.

    Science.gov (United States)

    Poiré, Richard; Schneider, Heike; Thorpe, Michael R; Kuhn, Arnd J; Schurr, Ulrich; Walter, Achim

    2010-03-01

    In laboratory and greenhouse experiments with potted plants, shoots and roots are exposed to temperature regimes throughout a 24 h (diel) cycle that can differ strongly from the regime under which these plants have evolved. In the field, roots are often exposed to lower temperatures than shoots. When the root-zone temperature in Ricinus communis was decreased below a threshold value, leaf growth occurred preferentially at night and was strongly inhibited during the day. Overall, leaf expansion, shoot biomass growth, root elongation and ramification decreased rapidly, carbon fluxes from shoot to root were diminished and carbohydrate contents of both root and shoot increased. Further, transpiration rate was not affected, yet hydrostatic tensions in shoot xylem increased. When root temperature was increased again, xylem tension reduced, leaf growth recovered rapidly, carbon fluxes from shoot to root increased, and carbohydrate pools were depleted. We hypothesize that the decreased uptake of water in cool roots diminishes the growth potential of the entire plant - especially diurnally, when the growing leaf loses water via transpiration. As a consequence, leaf growth and metabolite concentrations can vary enormously, depending on root-zone temperature and its heterogeneity inside pots. PMID:19968824

  14. Myo-inositol oxygenase is important for the removal of excess myo-inositol from syncytia induced by Heterodera schachtii in Arabidopsis roots.

    Science.gov (United States)

    Siddique, Shahid; Endres, Stefanie; Sobczak, Miroslaw; Radakovic, Zoran S; Fragner, Lena; Grundler, Florian M W; Weckwerth, Wolfram; Tenhaken, Raimund; Bohlmann, Holger

    2014-01-01

    The enzyme myo-inositol oxygenase is the key enzyme of a pathway leading from myo-inositol to UDP-glucuronic acid. In Arabidopsis, myo-inositol oxygenase is encoded by four genes. All genes are strongly expressed in syncytia induced by the beet cyst nematode Heterodera schachtii in Arabidopsis roots. Here, we studied the effect of a quadruple myo-inositol oxygenase mutant on nematode development. We performed metabolite profiling of syncytia induced in roots of the myo-inositol oxygenase quadruple mutant. The role of galactinol in syncytia was studied using Arabidopsis lines with elevated galactinol levels and by supplying galactinol to wild-type seedlings. The quadruple myo-inositol oxygenase mutant showed a significant reduction in susceptibility to H. schachtii, and syncytia had elevated myo-inositol and galactinol levels and an elevated expression level of the antimicrobial thionin gene Thi2.1. This reduction in susceptibility could also be achieved by exogenous application of galactinol to wild-type seedlings. The primary function of myo-inositol oxygenase for syncytium development is probably not the production of UDP-glucuronic acid as a precursor for cell wall polysaccharides, but the reduction of myo-inositol levels and thereby a reduction in the galactinol level to avoid the induction of defence-related genes. PMID:24117492

  15. On the role of a Lipid-Transfer Protein. Arabidopsis ltp3 mutant is compromised in germination and seedling growth.

    Science.gov (United States)

    Pagnussat, Luciana A; Oyarburo, Natalia; Cimmino, Carlos; Pinedo, Marcela L; de la Canal, Laura

    2015-01-01

    Plant Lipid-Transfer Proteins (LTPs) exhibit the ability to reversibly bind/transport lipids in vitro. LTPs have been involved in diverse physiological processes but conclusive evidence on their role has only been presented for a few members, none of them related to seed physiology. Arabidopsis seeds rely on storage oil breakdown to supply carbon skeletons and energy for seedling growth. Here, Arabidopsis ltp3 mutant was analyzed for its ability to germinate and for seedling establishment. Ltp3 showed delayed germination and reduced germination frequency. Seedling growth appeared reduced in the mutant but this growth restriction was rescued by the addition of an exogenous carbon supply, suggesting a defective oil mobilization. Lipid breakdown analysis during seedling growth revealed a differential profile in the mutant compared to the wild type. The involvement of LTP3 in germination and seedling growth and its relationship with the lipid transfer ability of this protein is discussed. PMID:26479260

  16. Overexpression of Arabidopsis NLP7 improves plant growth under both nitrogen-limiting and -sufficient conditions by enhancing nitrogen and carbon assimilation

    Science.gov (United States)

    Yu, Lin-Hui; Wu, Jie; Tang, Hui; Yuan, Yang; Wang, Shi-Mei; Wang, Yu-Ping; Zhu, Qi-Sheng; Li, Shi-Gui; Xiang, Cheng-Bin

    2016-01-01

    Nitrogen is essential for plant survival and growth. Excessive application of nitrogenous fertilizer has generated serious environment pollution and increased production cost in agriculture. To deal with this problem, tremendous efforts have been invested worldwide to increase the nitrogen use ability of crops. However, only limited success has been achieved to date. Here we report that NLP7 (NIN-LIKE PROTEIN 7) is a potential candidate to improve plant nitrogen use ability. When overexpressed in Arabidopsis, NLP7 increases plant biomass under both nitrogen-poor and -rich conditions with better-developed root system and reduced shoot/root ratio. NLP7–overexpressing plants show a significant increase in key nitrogen metabolites, nitrogen uptake, total nitrogen content, and expression levels of genes involved in nitrogen assimilation and signalling. More importantly, overexpression of NLP7 also enhances photosynthesis rate and carbon assimilation, whereas knockout of NLP7 impaired both nitrogen and carbon assimilation. In addition, NLP7 improves plant growth and nitrogen use in transgenic tobacco (Nicotiana tabacum). Our results demonstrate that NLP7 significantly improves plant growth under both nitrogen-poor and -rich conditions by coordinately enhancing nitrogen and carbon assimilation and sheds light on crop improvement. PMID:27293103

  17. Overexpression of Arabidopsis NLP7 improves plant growth under both nitrogen-limiting and -sufficient conditions by enhancing nitrogen and carbon assimilation.

    Science.gov (United States)

    Yu, Lin-Hui; Wu, Jie; Tang, Hui; Yuan, Yang; Wang, Shi-Mei; Wang, Yu-Ping; Zhu, Qi-Sheng; Li, Shi-Gui; Xiang, Cheng-Bin

    2016-01-01

    Nitrogen is essential for plant survival and growth. Excessive application of nitrogenous fertilizer has generated serious environment pollution and increased production cost in agriculture. To deal with this problem, tremendous efforts have been invested worldwide to increase the nitrogen use ability of crops. However, only limited success has been achieved to date. Here we report that NLP7 (NIN-LIKE PROTEIN 7) is a potential candidate to improve plant nitrogen use ability. When overexpressed in Arabidopsis, NLP7 increases plant biomass under both nitrogen-poor and -rich conditions with better-developed root system and reduced shoot/root ratio. NLP7-overexpressing plants show a significant increase in key nitrogen metabolites, nitrogen uptake, total nitrogen content, and expression levels of genes involved in nitrogen assimilation and signalling. More importantly, overexpression of NLP7 also enhances photosynthesis rate and carbon assimilation, whereas knockout of NLP7 impaired both nitrogen and carbon assimilation. In addition, NLP7 improves plant growth and nitrogen use in transgenic tobacco (Nicotiana tabacum). Our results demonstrate that NLP7 significantly improves plant growth under both nitrogen-poor and -rich conditions by coordinately enhancing nitrogen and carbon assimilation and sheds light on crop improvement. PMID:27293103

  18. The signal transducer NPH3 integrates the phototropin1 photosensor with PIN2-based polar auxin transport in Arabidopsis root phototropism.

    Science.gov (United States)

    Wan, Yinglang; Jasik, Jan; Wang, Li; Hao, Huaiqing; Volkmann, Dieter; Menzel, Diedrik; Mancuso, Stefano; Baluška, František; Lin, Jinxing

    2012-02-01

    Under blue light (BL) illumination, Arabidopsis thaliana roots grow away from the light source, showing a negative phototropic response. However, the mechanism of root phototropism is still unclear. Using a noninvasive microelectrode system, we showed that the BL sensor phototropin1 (phot1), the signal transducer NONPHOTOTROPIC HYPOCOTYL3 (NPH3), and the auxin efflux transporter PIN2 were essential for BL-induced auxin flux in the root apex transition zone. We also found that PIN2-green fluorescent protein (GFP) localized to vacuole-like compartments (VLCs) in dark-grown root epidermal and cortical cells, and phot1/NPH3 mediated a BL-initiated pathway that caused PIN2 redistribution to the plasma membrane. When dark-grown roots were exposed to brefeldin A (BFA), PIN2-GFP remained in VLCs in darkness, and BL caused PIN2-GFP disappearance from VLCs and induced PIN2-GFP-FM4-64 colocalization within enlarged compartments. In the nph3 mutant, both dark and BL BFA treatments caused the disappearance of PIN2-GFP from VLCs. However, in the phot1 mutant, PIN2-GFP remained within VLCs under both dark and BL BFA treatments, suggesting that phot1 and NPH3 play different roles in PIN2 localization. In conclusion, BL-induced root phototropism is based on the phot1/NPH3 signaling pathway, which stimulates the shootward auxin flux by modifying the subcellular targeting of PIN2 in the root apex transition zone. PMID:22374399

  19. 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

  20. 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

  1. Root growth conditions in the topsoil as affected by tillage intensity

    DEFF Research Database (Denmark)

    Kadziene, Grazina; Munkholm, Lars Juhl; Mutegi, James

    2011-01-01

    Many studies have reported impeded root growth in topsoil under reduced tillage or direct drilling, but few have quantified the effects on the least limiting water range for root growth. This study explored the effects of tillage intensity on critical soil physical conditions for root growth...... radish could be a promising tool in the amelioration of soil compaction. Highlights We explored root growth conditions in the topsoil as affected by tillage intensity ► For this purpose we applied the least limiting water range concept. ► We found clear differences in estimated critical aeration limits......–16 cm depths. We estimated the critical aeration limit from either 10% air-filled porosity (εa) or relative gas diffusivity (D/D0) of 0.005 or 0.02 and found a difference between the two methods. The critical limit of soil aeration was best assessed by measuring gas diffusivity directly. Root growth...

  2. Activation of NADPH-recycling systems in leaves and roots of Arabidopsis thaliana under arsenic-induced stress conditions is accelerated by knock-out of Nudix hydrolase 19 (AtNUDX19) gene.

    Science.gov (United States)

    Corpas, Francisco J; Aguayo-Trinidad, Simeón; Ogawa, Takahisa; Yoshimura, Kazuya; Shigeoka, Shigeru

    2016-03-15

    NADPH is an important cofactor in cell growth, proliferation and detoxification. Arabidopsis thaliana Nudix hydrolase 19 (AtNUDX19) belongs to a family of proteins defined by the conserved amino-acid sequence GX5-EX7REUXEEXGU which has the capacity to hydrolyze NADPH as a physiological substrate in vivo. Given the importance of NADPH in the cellular redox homeostasis of plants, the present study compares the responses of the main NADPH-recycling systems including NADP-isocitrate dehydrogenase (ICDH), glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH) and NADP-malic enzyme (ME) in the leaves and roots of Arabidopsis wild-type (Wt) and knock-out (KO) AtNUDX19 mutant (Atnudx19) plants under physiological and arsenic-induced stress conditions. Two major features were observed in the behavior of the main NADPH-recycling systems: (i) under optimal conditions in both organs, the levels of these activities were higher in nudx19 mutants than in Wt plants; and, (ii) under 500μM AsV conditions, these activities increase, especially in nudx19 mutant plants. Moreover, G6PDH activity in roots was the most affected enzyme in both Wt and nudx19 mutant plants, with a 4.6-fold and 5.0-fold increase, respectively. In summary, the data reveals a connection between the absence of chloroplastic AtNUDX19 and the rise in all NADP-dehydrogenase activities under physiological and arsenic-induced stress conditions, particularly in roots. This suggests that AtNUDX19 could be a key factor in modulating the NADPH pool in plants and consequently in redox homeostasis. PMID:26878367

  3. Modeling the hydraulics of root growth in three dimensions with phloem water sources.

    Science.gov (United States)

    Wiegers, Brandy S; Cheer, Angela Y; Silk, Wendy K

    2009-08-01

    Primary growth is characterized by cell expansion facilitated by water uptake generating hydrostatic (turgor) pressure to inflate the cell, stretching the rigid cell walls. The multiple source theory of root growth hypothesizes that root growth involves transport of water both from the soil surrounding the growth zone and from the mature tissue higher in the root via phloem and protophloem. Here, protophloem water sources are used as boundary conditions in a classical, three-dimensional model of growth-sustaining water potentials in primary roots. The model predicts small radial gradients in water potential, with a significant longitudinal gradient. The results improve the agreement of theory with empirical studies for water potential in the primary growth zone of roots of maize (Zea mays). A sensitivity analysis quantifies the functional importance of apical phloem differentiation in permitting growth and reveals that the presence of phloem water sources makes the growth-sustaining water relations of the root relatively insensitive to changes in root radius and hydraulic conductivity. Adaptation to drought and other environmental stresses is predicted to involve more apical differentiation of phloem and/or higher phloem delivery rates to the growth zone. PMID:19542299

  4. Indole-3-butyric acid synthesis in ecotypes and mutants of Arabidopsis thaliana under different growth conditions.

    Science.gov (United States)

    Ludwig-Müller, Jutta

    2007-01-01

    Although IBA is a naturally occurring auxin, its role in plant development is still under debate. In this study a set of Arabidopsis mutants was used to analyze the biosynthesis of IBA in vitro. The mutants chosen for this study can be classified as: (1) involvement in auxin metabolism, transport or synthesis (amt1, aux1, ilr1, nit1, rib1, sur1, trp1-100); (2) other hormones possibly involved in the regulation of IBA synthesis (aba1, aba3, eto2, fae1, hls1, jar1); (3) photomorphogenesis (det1, det2, det3); and (4) root architecture (cob1, cob2, scr1). In addition, two transgenic lines overexpressing the IAA glucose synthase (iaglu) gene from maize were analyzed. The ecotypes No-0 and Wassilewskija showed the highest IBA synthetase activity under control conditions, followed by Columbia, Enkheim and Landsberg erecta. In the mutant lines IBA synthetase activity differed in most cases from the wild type, however no particular pattern of up- or down-regulation, which could be correlated to their possible function, was found. For rib1 mutant seedlings it was tested whether reduced IBA synthetase activity correlates with the endogenous IBA levels. Free IBA differed only depending on the culture conditions, but gave no clear correlation with IBA synthetase activity compared to the wild type. Since drought and osmotic stress as well as abscisic acid (ABA) application enhanced IBA synthesis in maize, it was tested whether IBA synthetase from Arabidopsis is also inducible by drought stress conditions. This was confirmed for the two ecotypes Col and Ler which showed different IBA synthetase activity when cultivated with various degrees of drought stress. IBA synthetase was also determined in photomorphogenic mutants under different light regimes. Induction of IBA synthetase in det1 and det3 plants was found under short day plus a red light pulse or in the dark, respectively. The results are discussed with respect to the functions of the mutated genes. PMID:16325963

  5. TOR Signaling Promotes Accumulation of BZR1 to Balance Growth with Carbon Availability in Arabidopsis.

    Science.gov (United States)

    Zhang, Zhenzhen; Zhu, Jia-Ying; Roh, Jeehee; Marchive, Chloé; Kim, Seong-Ki; Meyer, Christian; Sun, Yu; Wang, Wenfei; Wang, Zhi-Yong

    2016-07-25

    For maintenance of cellular homeostasis, the actions of growth-promoting hormones must be attenuated when nutrient and energy become limiting. The molecular mechanisms that coordinate hormone-dependent growth responses with nutrient availability remain poorly understood in plants [1, 2]. The target of rapamycin (TOR) kinase is an evolutionarily conserved master regulator that integrates nutrient and energy signaling to regulate growth and homeostasis in both animals and plants [3-7]. Here, we show that sugar signaling through TOR controls the accumulation of the brassinosteroid (BR)-signaling transcription factor BZR1, which is essential for growth promotion by multiple hormonal and environmental signals [8-11]. Starvation, caused by shifting of light-grown Arabidopsis seedlings into darkness, as well as inhibition of TOR by inducible RNAi, led to plant growth arrest and reduced expression of BR-responsive genes. The growth arrest caused by TOR inactivation was partially recovered by BR treatment and the gain-of-function mutation bzr1-1D, which causes accumulation of active forms of BZR1 [12]. Exogenous sugar promoted BZR1 accumulation and seedling growth, but such sugar effects were largely abolished by inactivation of TOR, whereas the effect of TOR inactivation on BZR1 degradation is abolished by inhibition of autophagy and by the bzr1-1D mutation. These results indicate that cellular starvation leads sequentially to TOR inactivation, autophagy, and BZR1 degradation. Such regulation of BZR1 accumulation by glucose-TOR signaling allows carbon availability to control the growth promotion hormonal programs, ensuring supply-demand balance in plant growth.

  6. TOR Signaling Promotes Accumulation of BZR1 to Balance Growth with Carbon Availability in Arabidopsis.

    Science.gov (United States)

    Zhang, Zhenzhen; Zhu, Jia-Ying; Roh, Jeehee; Marchive, Chloé; Kim, Seong-Ki; Meyer, Christian; Sun, Yu; Wang, Wenfei; Wang, Zhi-Yong

    2016-07-25

    For maintenance of cellular homeostasis, the actions of growth-promoting hormones must be attenuated when nutrient and energy become limiting. The molecular mechanisms that coordinate hormone-dependent growth responses with nutrient availability remain poorly understood in plants [1, 2]. The target of rapamycin (TOR) kinase is an evolutionarily conserved master regulator that integrates nutrient and energy signaling to regulate growth and homeostasis in both animals and plants [3-7]. Here, we show that sugar signaling through TOR controls the accumulation of the brassinosteroid (BR)-signaling transcription factor BZR1, which is essential for growth promotion by multiple hormonal and environmental signals [8-11]. Starvation, caused by shifting of light-grown Arabidopsis seedlings into darkness, as well as inhibition of TOR by inducible RNAi, led to plant growth arrest and reduced expression of BR-responsive genes. The growth arrest caused by TOR inactivation was partially recovered by BR treatment and the gain-of-function mutation bzr1-1D, which causes accumulation of active forms of BZR1 [12]. Exogenous sugar promoted BZR1 accumulation and seedling growth, but such sugar effects were largely abolished by inactivation of TOR, whereas the effect of TOR inactivation on BZR1 degradation is abolished by inhibition of autophagy and by the bzr1-1D mutation. These results indicate that cellular starvation leads sequentially to TOR inactivation, autophagy, and BZR1 degradation. Such regulation of BZR1 accumulation by glucose-TOR signaling allows carbon availability to control the growth promotion hormonal programs, ensuring supply-demand balance in plant growth. PMID:27345161

  7. Root exudate-induced alterations in Bacillus cereus cell wall contribute to root colonization and plant growth promotion.

    Directory of Open Access Journals (Sweden)

    Swarnalee Dutta

    Full Text Available The outcome of an interaction between plant growth promoting rhizobacteria and plants may depend on the chemical composition of root exudates (REs. We report the colonization of tobacco, and not groundnut, roots by a non-rhizospheric Bacillus cereus (MTCC 430. There was a differential alteration in the cell wall components of B. cereus in response to the REs from tobacco and groundnut. Attenuated total reflectance infrared spectroscopy revealed a split in amide I region of B. cereus cells exposed to tobacco-root exudates (TRE, compared to those exposed to groundnut-root exudates (GRE. In addition, changes in exopolysaccharides and lipid-packing were observed in B. cereus grown in TRE-amended minimal media that were not detectable in GRE-amended media. Cell-wall proteome analyses revealed upregulation of oxidative stress-related alkyl hydroperoxide reductase, and DNA-protecting protein chain (Dlp-2, in response to GRE and TRE, respectively. Metabolism-related enzymes like 2-amino-3-ketobutyrate coenzyme A ligase and 2-methylcitrate dehydratase and a 60 kDa chaperonin were up-regulated in response to TRE and GRE. In response to B. cereus, the plant roots altered their exudate-chemodiversity with respect to carbohydrates, organic acids, alkanes, and polyols. TRE-induced changes in surface components of B. cereus may contribute to successful root colonization and subsequent plant growth promotion.

  8. Change of water use efficiency and its relation with root system growth in wheat evolution

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Raising crop water use efficiency (WUE) is the physiological basis to implement crop high efficiently using water. The present soil column and field experiments are designed to investigate the change of wheat WUE (Triticum aestivum L.) at whole plant level and root system growth in evolution and the relationship between WUE and its root system growth using 10 wheat evolution genotypes with different ploidy chromosomes sets. Results show that in wheat evolution from 2n→6n, WUE at whole plant level increases with the increase of ploidy chromosomes, and root system growth (root weight, root length) and root/shoot ratio of wheat decrease with the increase of ploidy chromosomes under dry and irrigated conditions. WUE is negatively correlated with root weight and root/shoot ratio of wheat in evolution, significantly. Root system growth has an adverse redundancy for WUE in wheat evolution, and the root redundancy reduces with the increase of ploidy chromosomes, which result in the increase of wheat WUE at whole plant level.

  9. 高铵胁迫对拟南芥根系向重性的影响及机制初探%Effect and Mechanism of High Ammonium on Root Gravitropic Response in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    邹娜; 李保海; 强晓敏; 施卫明

    2013-01-01

    Gravitropism is an important factor in determining root architecture and directs roots to grow downward in soil and thus may have a great affect on the uptake of water and mineral ions required for plant growth and development. Ammonium profoundly affects root architecture of Arabidopsis thaliana. Despite the inhibitory effects of high ammonium on root length and the number of lateral roots, however, very little is known concerning the influence of ammonium on root growth direction. Experiments were performed with Arabidopsis thaliana using indoor agar media for a simulation to study the effects of high ammonium on root growth direction. It was found that NH4+ stress not only inhibited plant growth, but also affected root growth direction. Kinetics results for a 30-h assay window showed that 10 mmol/L (NH4)2SO4 delayed root gravitropism, while 30 mmol/L (NH4)2SO4 significantly reduced root gravitropic curvature. Reduction the nutrients in basic medium, root agravitropic response induced by NH4+ occurred at a lower concentration. Adding Ca(NO3)2 partially restored the inhibition of NH4+ on root elongation, but had no effects on NH4+ induced root gravitropic angle. When NH4+ was supplied separately to different parts of the plants, the effect of NH4+ on root gravitropism was mainly from the root-supplied NH4+. These results preliminarily indicate that the influence of ammonium on root growth direction is partially independent of its effect on root elongation and is not due to the deficiency of cations such as Ca2+, but may be related with the alteration of root physiological processes when root exposed to high NH4+.%向重性是决定植物根系构型的主要因素之一,对根系锚定及水分养分吸收具有重要影响.铵显著影响拟南芥根构型,尽管高铵抑制主根伸长和侧根数,然而铵对主根生长方向的研究却少有报道.本文以拟南芥为材料,利用室内培养基模拟试验,研究了高铵胁迫对根系向重性生长的

  10. Grazing and nitrogen on the growth of roots in the mixture of oat and ryegrass

    Directory of Open Access Journals (Sweden)

    Hugo von Linsingen Piazzetta

    2014-09-01

    Full Text Available This study evaluated the effect of grazing and its absence, and the nitrogen on the morphology of roots of black oat (Avena strigosa Schreb. mixed with Italian ryegrass (Lolium multiflorum Lam.. The experimental design was a randomized block design in split-split, the main portion was study the effects of grazing and its absence, in the subplots the nitrogen doses of 75 and 150 kg ha-1 and in the sub-subplots were at sampling period. There was used the cylinder method to collect the root, being measured the length, surface area, mean diameter and volume by image analysis system Win / MacRizho (4.1c. Determined the dry mass of roots and shoot, and estimated the density of the root tissue and shoot:root ratio. From these results we determined the rate of root growth relative (RGR, relative root expansion rate (RRER and rate of accumulation of dry matter daily (RADM. In the first period, was higher RGR, RRER, the second period there was a reduction of the same, probably due to the period of drought and plant senescence. There was also reduced due to grazing RADM. With grazing, the length, surface area, mean diameter and root volume were higher, indicating that there was greater root growth of plants grazed compared to ungrazed. The systems studied had no effect on the dry weight of roots. There were found greater specific mass and shot:root ratio in the system without grazing. There was no significant difference between the nitrogen studied. At mixed of black oat and ryegrass, the grazing and nitrogen dose until 150 kg ha-1 little affect root growth. The nitrogen dose changed a little the growth rates and expansion of the roots. On the other hand, the grazing favored the length, area, volume and root diameter.

  11. The influence of calcium and pH on growth in primary roots of Zea mays

    Science.gov (United States)

    Hasenstein, K. H.; Evans, M. L.

    1988-01-01

    We investigated the interaction of Ca2+ and pH on root elongation in Zea mays L. cv. B73 x Missouri 17 and cv. Merit. Seedlings were raised to contain high levels of Ca2+ (HC, imbibed and raised in 10 mM CaCl2) or low levels of Ca2+ (LC, imbibed and raised in distilled water). In HC roots, lowering the pH (5 mM MES/Tris) from 6.5 to 4.5 resulted in strong, long-lasting growth promotion. Surprisingly, increasing the pH from 6.5 to 8.5 also resulted in strong growth promotion. In LC roots acidification of the medium (pH 6.5 to 4.5) resulted in transient growth stimulation followed by a gradual decline in the growth rate toward zero. Exposure of LC roots to high pH (pH shift from 6.5 to 8.5) also promoted growth. Addition of EGTA resulted in strong growth promotion in both LC and HC roots. The ability of EGTA to stimulate growth appeared not to be related to H+ release from EGTA upon Ca2+ chelation since, 1) LC roots showed a strong and prolonged response to EGTA, but only a transient response to acid pH, and 2) promotion of growth by EGTA was observed in strongly buffered solutions. We also examined the pH dependence of the release of 45Ca2+ from roots of 3-day-old seedlings grown from grains imbibed in 45Ca2+. Release of 45Ca2+ from the root into agar blocks placed on the root surface was greater the more acidic the pH of the blocks. The results indicate that Ca2+ may be necessary for the acid growth response in roots.

  12. 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.

  13. Effects of some plant growth promoting rhizobacteria (PGPR on rooting of grapevine rootstocks

    Directory of Open Access Journals (Sweden)

    Cafer Köse

    2013-12-01

    Full Text Available In this study. effects of topical applications of two plant growth promoting rhizobacteria (PGPR strains and their combination (Bacillus BA16, OSU142 and BA16+OSU142 on the rooting of 41B and Rupestris du Lot rootstocks were investigated. The results showed that none of the bacterial strains have significant effects on success rate at 41B and Rupestris du Lot alone, but BA16+0SU142 combination significantly increased the rooting rate and rooting degree of 41B, and decreased the rooting rate and rooting degree of Rupestris du Lot compared with control. In addition, none of the applications had significant effects in number, length and weight of roots on cuttings of both 41B and Rupestris du Lot. Our results suggest that PGPR may have a great potential to stimulate the rooting of hardwood cuttings of grapevine rootstocks, with low rooting capability.

  14. Vigorous Root Growth Is a Better Indicator of Early Nutrient Uptake than Root Hair Traits in Spring Wheat Grown under Low Fertility

    OpenAIRE

    Wang, Yaosheng; Thorup-Kristensen, Kristian; Jensen, Lars Stoumann; Magid, Jakob

    2016-01-01

    A number of root and root hair traits have been proposed as important for nutrient acquisition. However, there is still a need for knowledge on which traits are most important in determining macro- and micronutrient uptake at low soil fertility. This study investigated the variations in root growth vigor and root hair length (RHL) and density (RHD) among spring wheat genotypes and their relationship to nutrient concentrations and uptake during early growth. Six spring wheat genotypes were gro...

  15. Tracking soil structural changes during root growth with sequential X-Ray CT scanning

    Science.gov (United States)

    Schmidt, Sonja; Bengough, Glyn; Hallett, Paul

    2014-05-01

    Crop productivity is highly dependent on a good supply of water and nutrients. With increasing demand for food and variable water regimes due to climate change, it is important to get a better understanding on the processes involved in water and nutrient uptake by roots. Changes in soil structure affect water and nutrient availabilities for plants. It is known that roots change their environment during growth but little is known on how soil structural properties change as roots penetrate soils. More detailed information on root growth induced changes in the rhizosphere will help us to model water and nutrient uptake by plants. The objective of this study was to measure directly how soil structure changes in close proximity to the root as a seedling root penetrates through the soil. 3D volumetric images of maize root growth during six hours were obtained using X-ray microtomography at a resolution of 21 μm. Roots were grown in soils of two different compaction levels (50 kPa and 200 kPa uniaxial load) and matric potentials (10 kPa and 100 kPa). Changes in porosity, pore connectivity and root-soil contact were determined from 2D cross sections for each time step. The 2D cross sections were chosen at 4 different positions in the sample, and each section was divided into sections of 64 voxels (1.3 mm2) to determine changes in porosity and connectivity with distance from the root. Soil movement caused by root growth was quantified from 2D cross sections at different positions along the sample using Particle image velocimetry (PIV). Changes in soil structure during root growth were observed. Porosity in close proximity to the root decreased whereas root-soil contact increased with time. The PIV showed a radial deformation of the soil. Greatest deformation was found close to the root. Some aggregates fractured during root growth whereas others were pushed into the pore space. These data on the changes in soil structure will help us to predict water and nutrient

  16. Nitrogen source interacts with ROP signalling in root hair tip-growth.

    Science.gov (United States)

    Bloch, Daria; Monshausen, Gabriele; Singer, Meromit; Gilroy, Simon; Yalovsky, Shaul

    2011-01-01

    Root hairs elongate in a highly polarized manner known as tip growth. Overexpression of constitutively active Rho of Plant (ROP)/RAC GTPases mutants induces swelling of root hairs. Here, we demonstrate that Atrop11(CA)-induced swelling of root hairs depends on the composition of the growth medium. Depletion of ammonium allowed normal root hair elongation in Atrop11(CA) plants, induced the development of longer root hairs in wild-type plants and suppressed the effect of Atrop11(CA) expression on actin organization and reactive oxygen species distribution, whereas membrane localization of the protein was not affected. Ammonium at concentrations higher than 1 mM and the presence of nitrate were required for induction of swelling. Oscillations in wall and cytoplasmic pH are known to accompany tip growth in root hairs, and buffering of the growth medium decreased Atrop11(CA)-induced swelling. Fluorescence ratio imaging experiments revealed that in wild-type root hairs, the addition of NH₄NO₃ to the growth medium induced an increase in the amplitude of extracellular and intracellular pH oscillations and an overall decrease in cytoplasmic pH at the cell apex. Based on these results, we suggest a model in which ROP GTPases and nitrogen-dependent pH oscillations function in parallel pathways, creating a positive feedback loop during root hair growth.

  17. Growth Rings of Roots in Perennial Forbs in Duolun Grassland, Inner Mongolia, China

    Institute of Scientific and Technical Information of China (English)

    Yong-Bo Liu; Qi-Bin Zhang

    2007-01-01

    Annual growth rings of roots in perennial forbs have been used in studies of climate change and the ecology of grasslands. However, little has been done in this aspect of research in China. In this study, we report the characteristics of growth rings in the main roots of 13 herb species sampled in Duolun of the Inner Mongolia grassland in northern China. The results show that around two thirds of the species possess clearly demarcated annual rings in the root xylem. Some species of the same genera show different patterns in anatomical structure of the root xylem. Standardized annual ring widths of three species, Potentilla anserine L., Cymbaria dahurica L. and Lespedeza daurica (Laxm.) Schindl., show a common linear trend, indicating a continued favorable growth condition in the sampling sites. Our results provide evidence that growth rings in roots of some perennial forbs in the Inner Mongolia grassland can serve as a new and useful indicator of past changes in the grassland environment.

  18. Kinetics of Growth and Nutrient Consumption in the Culture of Trichosanthes kirilowii Hairy Root

    Institute of Scientific and Technical Information of China (English)

    郭志刚; 郑明智; 刘瑞芝

    2003-01-01

    Ribosome-inactivating proteins in Trichosanthes kirilowii having high anti-HIV activity can be efficiently obtained by culturing Trichosanthes kirilowii hairy root. A hairy root line from Trichosanthes kirilowii was cultivated in flasks and in a 5-L bioreactor. The results show that a logistic equation can be used to describe the relationship between the hairy root biomass and the culture time. The medium conductivity decrease is linearly related to the biomass amount. In the suspension culture, the hairy root growth is closely related to the nutrient consumption. The biomass to nitrate yield is 0.352 g/mmol. The growth rate of the hairy root in the bioreactor is higher than that in the flasks, and after a 12-day culture its growth rate enters a high-speed period when the growth rate is 0.738 g/(L * d).

  19. Effect of fast neutrons and gamma radiation on seedling and root growth of barley varieties

    International Nuclear Information System (INIS)

    Seven varieties of barley were irradiated with 10-80 krad of gamma rays and 0.3-1.2 krad of fast neutrons. Their radiosensitivity was compared on the basis of 50% reduction in seedling and root growth. The RBE (ratio: gamma/neutron, 50% growth reduction dose) for roots was twice as high as for seedling growth reduction. (author). 3 refs, 2 figs, 1 tab

  20. Interact to survive: Phyllobacterium brassicacearum improves Arabidopsis tolerance to severe water deficit and growth recovery.

    Directory of Open Access Journals (Sweden)

    Justine Bresson

    Full Text Available Mutualistic bacteria can alter plant phenotypes and confer new abilities to plants. Some plant growth-promoting rhizobacteria (PGPR are known to improve both plant growth and tolerance to multiple stresses, including drought, but reports on their effects on plant survival under severe water deficits are scarce. We investigated the effect of Phyllobacterium brassicacearum STM196 strain, a PGPR isolated from the rhizosphere of oilseed rape, on survival, growth and physiological responses of Arabidopsis thaliana to severe water deficits combining destructive and non-destructive high-throughput phenotyping. Soil inoculation with STM196 greatly increased the survival rate of A. thaliana under several scenarios of severe water deficit. Photosystem II efficiency, assessed at the whole-plant level by high-throughput fluorescence imaging (Fv/Fm, was related to the probability of survival and revealed that STM196 delayed plant mortality. Inoculated surviving plants tolerated more damages to the photosynthetic tissues through a delayed dehydration and a better tolerance to low water status. Importantly, STM196 allowed a better recovery of plant growth after rewatering and stressed plants reached a similar biomass at flowering than non-stressed plants. Our results highlight the importance of plant-bacteria interactions in plant responses to severe drought and provide a new avenue of investigations to improve drought tolerance in agriculture.

  1. Improved Growth and Stress Tolerance in the Arabidopsis oxt1 Mutant Triggered by Altered Adenine Metabolism

    Institute of Scientific and Technical Information of China (English)

    Suchada Sukrong; Kil-Young Yun; Patrizia Stadler; Charan Kumar; Tony Facciuolo; Barbara A.Moffatt; Deane L.Falcone

    2012-01-01

    Plants perceive and respond to environmental stresses with complex mechanisms that are often associated with the activation of antioxidant defenses.A genetic screen aimed at isolating oxidative stress-tolerant lines of Arabidopsis thaliana has identified oxt1,a line that exhibits improved tolerance to oxidative stress and elevated temperature but displays no apparent deleterious growth effects under non-stress conditions.Oxt1 harbors a mutation that arises from the altered expression of a gene encoding adenine phosphoribosyltransferase (APT1),an enzyme that converts adenine to adenosine monophosphate (AMP),indicating a link between purine metabolism,whole-plant growth responses,and stress acclimation.The oxt1 mutation results in decreased APT1 expression that leads to reduced enzymatic activity.Correspondingly,oxt1 plants possess elevated levels of adenine.Decreased APT enzyme activity directly correlates with stress resistance in transgenic lines that ectopically express APT1.The metabolic alteration in oxt1 plants also alters the expression of several antioxidant defense genes and the response of these genes to oxidative challenge.Finally,it is shown that manipulation of adenine levels can induce stress tolerance to wild-type plants.Collectively,these results show that alterations in cellular adenine levels can trigger stress tolerance and improve growth,leading to increases in plant biomass.The results also suggest that adenine might play a part in the signals that modulate responses to abiotic stress and plant growth.

  2. Aluminium localization and toxicity symptoms related to root growth inhibition in rice (Oryza sativa L.) seedlings

    Indian Academy of Sciences (India)

    M N Alvim; F T Ramos; D C Oliveira; R M S Isaias; M G C França

    2012-12-01

    We correlated root growth inhibition with aluminium (Al3+) localization and toxicity symptoms in rice roots using seedlings of two genotypes (tolerant and sensitive) that were exposed to different AlCl3 concentrations. Al3+ localization was evaluated by hematoxylin in primary roots and by morin in cross-sections of the root tips. Neutral invertase enzyme activity and callose (1$\\to$3, -D-glucan) accumulation were observed and compared with Al3+ accumulation sites. Root growth was inhibited by Al3+ in a concentration-specific manner and proportional to the increase of hematoxylin staining, being more pronounced in the sensitive genotype. Morin staining showed the presence of Al3+ deep within the roots of the sensitive genotype, indicating that the metal was able to penetrate beyond the first few cell layers. In the tolerant genotype, Al3+ penetration was restricted to the first two cell layers. Ruptures in exodermis and epidermis layers by lateral root protrusions in both genotypes allowed Al3+ to enter into the roots. More intense activity of invertase in roots of the tolerant genotype was also observed, which could be related to greater root growth of this cultivar when submitted to Al3+ stress. Moreover, Al3+-induced callose accumulation was a late response occurring in the same areas where Al3+ was present.

  3. Analysis of root growth from a phenotyping data set using a density-based model.

    Science.gov (United States)

    Kalogiros, Dimitris I; Adu, Michael O; White, Philip J; Broadley, Martin R; Draye, Xavier; Ptashnyk, Mariya; Bengough, A Glyn; Dupuy, Lionel X

    2016-02-01

    Major research efforts are targeting the improved performance of root systems for more efficient use of water and nutrients by crops. However, characterizing root system architecture (RSA) is challenging, because roots are difficult objects to observe and analyse. A model-based analysis of RSA traits from phenotyping image data is presented. The model can successfully back-calculate growth parameters without the need to measure individual roots. The mathematical model uses partial differential equations to describe root system development. Methods based on kernel estimators were used to quantify root density distributions from experimental image data, and different optimization approaches to parameterize the model were tested. The model was tested on root images of a set of 89 Brassica rapa L. individuals of the same genotype grown for 14 d after sowing on blue filter paper. Optimized root growth parameters enabled the final (modelled) length of the main root axes to be matched within 1% of their mean values observed in experiments. Parameterized values for elongation rates were within ±4% of the values measured directly on images. Future work should investigate the time dependency of growth parameters using time-lapse image data. The approach is a potentially powerful quantitative technique for identifying crop genotypes with more efficient root systems, using (even incomplete) data from high-throughput phenotyping systems. PMID:26880747

  4. Gravity-dependent differentiation and root coils in Arabidopsis thaliana wild type and phospholipase-A-I knockdown mutant grown on the International Space Station.

    Science.gov (United States)

    Scherer, G F E; Pietrzyk, P

    2014-01-01

    Arabidopsis roots on 45° tilted agar in 1-g grow in wave-like figures. In addition to waves, formation of root coils is observed in several mutants compromised in gravitropism and/or auxin transport. The knockdown mutant ppla-I-1 of patatin-related phospholipase-A-I is delayed in root gravitropism and forms increased numbers of root coils. Three known factors contribute to waving: circumnutation, gravisensing and negative thigmotropism. In microgravity, deprivation of wild type (WT) and mutant roots of gravisensing and thigmotropism and circumnutation (known to slow down in microgravity, and could potentially lead to fewer waves or increased coiling in both WT and mutant). To resolve this, mutant ppla-I-1 and WT were grown in the BIOLAB facility in the International Space Station. In 1-g, roots of both types only showed waving. In the first experiment in microgravity, the mutant after 9 days formed far more coils than in 1-g but the WT also formed several coils. After 24 days in microgravity, in both types the coils were numerous with slightly more in the mutant. In the second experiment, after 9 days in microgravity only the mutant formed coils and the WT grew arcuated roots. Cell file rotation (CFR) on the mutant root surface in microgravity decreased in comparison to WT, and thus was not important for coiling. Several additional developmental responses (hypocotyl elongation, lateral root formation, cotyledon expansion) were found to be gravity-influenced. We tentatively discuss these in the context of disturbances in auxin transport, which are known to decrease through lack of gravity.

  5. Non-targeted profiling of semi-polar metabolites in Arabidopsis root exudates uncovers a role for coumarin secretion and lignification during the local response to phosphate limitation.

    Science.gov (United States)

    Ziegler, Jörg; Schmidt, Stephan; Chutia, Ranju; Müller, Jens; Böttcher, Christoph; Strehmel, Nadine; Scheel, Dierk; Abel, Steffen

    2016-03-01

    Plants have evolved two major strategies to cope with phosphate (Pi) limitation. The systemic response, mainly comprising increased Pi uptake and metabolic adjustments for more efficient Pi use, and the local response, enabling plants to explore Pi-rich soil patches by reorganization of the root system architecture. Unlike previous reports, this study focused on root exudation controlled by the local response to Pi deficiency. To approach this, a hydroponic system separating the local and systemic responses was developed. Arabidopsis thaliana genotypes exhibiting distinct sensitivities to Pi deficiency could be clearly distinguished by their root exudate composition as determined by non-targeted reversed-phase ultraperformance liquid chromatography electrospray ionization quadrupole-time-of-flight mass spectrometry metabolite profiling. Compared with wild-type plants or insensitive low phosphate root 1 and 2 (lpr1 lpr2) double mutant plants, the hypersensitive phosphate deficiency response 2 (pdr2) mutant exhibited a reduced number of differential features in root exudates after Pi starvation, suggesting the involvement of PDR2-encoded P5-type ATPase in root exudation. Identification and analysis of coumarins revealed common and antagonistic regulatory pathways between Pi and Fe deficiency-induced coumarin secretion. The accumulation of oligolignols in root exudates after Pi deficiency was inversely correlated with Pi starvation-induced lignification at the root tips. The strongest oligolignol accumulation in root exudates was observed for the insensitive lpr1 lpr2 double mutant, which was accompanied by the absence of Pi deficiency-induced lignin deposition, suggesting a role of LPR ferroxidases in lignin polymerization during Pi starvation. PMID:26685189

  6. [Effects of cinnamic acid and vanillin on grafted eggplant root growth and physiological characteristics].

    Science.gov (United States)

    Chen, Shao-Li; Zhou, Bao-Li; Lin, Shan-Shan; Li, Xia; Ye, Xue-Ling

    2010-06-01

    Choosing Solanum torvum as rootstock and cultivated Xi'anlü eggplant as scion, a pot culture experiment was conducted to study the effects of autotoxic substances (cinnamic acid and vanillin) on the root growth, antioxidase activity, and osmoregulation substances content of grafted eggplant, own-rooted eggplant, and rootstock eggplant. Cinnamic acid and vanillin had allelopathic effects on the root system of test eggplants, with low concentration promoting and higher concentration inhibiting the root growth and physiological metabolism. For own-rooted eggplant, the critical concentration of cinnamic acid and vanillin for promotion or inhibition was 0.1 mmol x kg(-1) and 0.5 mmol x kg(-1), respectively; whereas for grafted and rootstock eggplants, it was 0.5 mmol x kg(-1) and 1 mmol x kg(-1), respectively. The root resistance to autotoxic substances was in the order of root-stock eggplant > grafted eggplant > own-rooted eggplant. Higher concentration cinamic acid (0.5-4 mmol x kg(-1)) and vanillin (1-4 mmol x kg(-1)) enhanced the SOD enzyme activity and the proline and soluble sugar contents of grafted eggplant root by 8.50%-24.50%; 9.39%-27.64%, and 12.77%-81.81%, respectively, compared with own-rooted eggplant. The soluble protein content, fresh mass, dry mass, and root activity of grafted eggplant roots were significantly higher than those of own-rooted eggplant, suggesting that grafted eggplant had a strong resistance of rootstocks to autotoxic substances, which alleviated the negative effect of autotoxic substances on root growth.

  7. Effect of N Fertilizers on Root Growth and Endogenous Hormones in Strawberry

    Institute of Scientific and Technical Information of China (English)

    WANG Bo; LAI Tao; HUANG Qi-Wei; YANG Xing-Ming; SHEN Qi-Rong

    2009-01-01

    Endogenous hormones play an important role in the growth and development of roots. The objective of this research was to study the effect of four types of N fertilizers on the root growth of strawberry (Fragaria ananassa Duchesne) and the endogenous enzymes of indole-3-acetic acid (IAA), abscisic acid (ABA), and isopentenyl adenosine (iPA) in its roots and leaves using enzyme-linked immunosorbent assay. Application of all types of N fertilizers significantly depressed (P ≤ 0.05) root growth at 20 d after transplanting. Application of organic-inorganic fertilizer (OIF) as basal fertilizer had a significant negative effect (P ≤ 0.05) on root growth. The application of OIF and urea lowered the lateral root frequency in strawberry plants at 60 d (P ≤ 0.05) compared with the application of two organic fertilizers (OFA and OFB) and the control (CK). With the fertilizer treatments, there were the same concentrations of IAA and ABA in both roots and leaves at the initial growth stage (20 d), lower levels of IAA and ABA at the later stage (60 d), and higher iPA levels at all seedling stages as compared to those of CK. Thus, changes in the concentrations of endogenous phytohormones in strawberry plants could be responsible for the morphological changes of roots due to fertilization.

  8. Arabidopsis phosphatidylinositol monophosphate 5-kinase 2 is involved in root gravitropism through regulation of polar auxin transport by affecting the cycling of PIN proteins

    OpenAIRE

    Mei, Yu; Jia, Wen-Jing; Chu, Yu-Jia; Xue, Hong-Wei

    2011-01-01

    Phosphatidylinositol monophosphate 5-kinase (PIP5K) catalyzes the synthesis of PI-4,5-bisphosphate (PtdIns(4,5)P2) by phosphorylation of PI-4-phosphate at the 5 position of the inositol ring, and is involved in regulating multiple developmental processes and stress responses. We here report on the functional characterization of Arabidopsis PIP5K2, which is expressed during lateral root initiation and elongation, and whose expression is enhanced by exogenous auxin. The knockout mutant pip5k...

  9. MiRNA398b and miRNA398c are involved in the regulation of the SOD response in uranium-exposed Arabidopsis thaliana roots

    OpenAIRE

    Saenen, Eline; Horemans, Nele; Vanhoudt, Nathalie; Vandenhove, H.; Biermans, Geert; Hees, M. van; WANNIJN, J.; Vangronsveld, Jaco; Cuypers, Ann

    2015-01-01

    The chemical speciation of uranium (U), and hence its toxicity, is strongly dependent on pH. However, oxidative stress responses after U exposure have mainly been investigated in Arabidopsis thaliana plants at pH 5.5, the ideal pH for growing plants in a hydroponic setup. As the pH of pore water can vary strongly, the aim of this study is to investigate oxidative stress responses induced in roots of A. thaliana plants exposed to different U concentrations at pH 4.5 and hence at a high free...

  10. Consequences of insect herbivory on grape fine root systems with different growth rates.

    Science.gov (United States)

    Bauerle, T L; Eissenstat, D M; Granett, J; Gardner, D M; Smart, D R

    2007-07-01

    Herbivory tolerance has been linked to plant growth rate where plants with fast growth rates are hypothesized to be more tolerant of herbivory than slower-growing plants. Evidence supporting this theory has been taken primarily from observations of aboveground organs but rarely from roots. Grapevines differing in overall rates of new root production, were studied in Napa Valley, California over two growing seasons in an established vineyard infested with the sucking insect, grape phylloxera (Daktulosphaira vitifoliae Fitch). The experimental vineyard allowed for the comparison of two root systems that differed in rates of new root tip production (a 'fast grower', Vitis berlandieri x Vitis rupestris cv. 1103P, and a slower-growing stock, Vitis riparia x Vitis rupestris cv. 101-14 Mgt). Each root system was grafted with a genetically identical shoot system (Vitis vinifera cv. Merlot). Using minirhizotrons, we did not observe any evidence of spatial or temporal avoidance of insect populations by root growth. Insect infestations were abundant throughout the soil profile, and seasonal peaks in phylloxera populations generally closely followed peaks in new root production. Our data supported the hypothesis that insect infestation was proportional to the number of growing tips, as indicated by similar per cent infestation in spite of a threefold difference in root tip production. In addition, infested roots of the fast-growing rootstock exhibited somewhat shorter median lifespans (60 d) than the slower-growing rootstock (85 d). Lifespans of uninfested roots were similar for the two rootstocks (200 d). As a consequence of greater root mortality of younger roots, infested root populations in the fast-growing rootstock had an older age structure. While there does not seem to be a trade-off between potential growth rate and relative rate of root infestation in these cultivars, our study indicates that a fast-growing root system may more readily shed infested roots that are

  11. Root growth of Lotus corniculatus interacts with P distribution in young sandy soil

    OpenAIRE

    Felderer, B.; K. M. Boldt-Burisch; Schneider, B.U.; R. F. J. Hüttl; R. Schulin

    2013-01-01

    Large areas of land are restored with unweathered soil substrates following mining activities in eastern Germany and elsewhere. In the initial stages of colonization of such land by vegetation, plant roots may become key agents in generating soil formation patterns by introducing gradients in chemical and physical soil properties. On the other hand, such patterns may be influenced by root growth responses to pre-existing substrate heterogeneities. In particular, the roots of many plants were ...

  12. Vitamin D3 affects growth and Ca2+ uptake by Phaseolus vulgaris roots cultured in vitro

    International Nuclear Information System (INIS)

    Vitamin D3 at low concentration (10−9 M) inhibited the growth of Phaseolus vulgaris L. (cv. Contrancha) roots in vitro as measured by elongation (14 h) and [3H]-leucine incorporation into protein (2 h), and increased their labelling with 45Ca2+ (2 h). Cycloheximide and puromycin (50 u.M) blocked vitamin D3 stimulation of root 45Ca2+ labelling, indicating that it is mediated by de novo protein synthesis. The calcium ionophore X-537A (10−5JW) induced similar changes both in root elongation and 45Ca2+ uptake (14 h). This may indicate that the inhibitory effects of the sterol on root growth are mediated by changes in Ca2+ fluxes. However, this interpretation should be further strengthened by additional studies as the ionophore may have acted on root growth, affecting physiological processes other than Ca2+ transport. (author)

  13. Auxin, the organizer of the environmental/hormonal signals for root hair growth

    Directory of Open Access Journals (Sweden)

    Hyung-Taeg eCho

    2013-11-01

    Full Text Available The root hair development is controlled by diverse factors such as fate-determining developmental cues, auxin-related environmental factors, and hormones. In particular, the soil environmental factors are important as they maximize their absorption by modulating root hair development. These environmental factors affect the root hair developmental process by making use of diverse hormones. These hormonal factors interact with each other to modulate root hair development in which auxin appears to form the most intensive networks with the pathways from environmental factors and hormones. Moreover, auxin action for root hair development is genetically located immediately upstream of the root hair-morphogenetic genes. These observations suggest that auxin plays as an organizing node for environmental/hormonal pathways to modulate root hair growth.

  14. Root responses to soil physical conditions; growth dynamics from field to cell.

    Science.gov (United States)

    Bengough, A Glyn; Bransby, M Fraser; Hans, Joachim; McKenna, Stephen J; Roberts, Tim J; Valentine, Tracy A

    2006-01-01

    Root growth in the field is often slowed by a combination of soil physical stresses, including mechanical impedance, water stress, and oxygen deficiency. The stresses operating may vary continually, depending on the location of the root in the soil profile, the prevailing soil water conditions, and the degree to which the soil has been compacted. The dynamics of root growth responses are considered in this paper, together with the cellular responses that underlie them. Certain root responses facilitate elongation in hard soil, for example, increased sloughing of border cells and exudation from the root cap decreases friction; and thickening of the root relieves stress in front of the root apex and decreases buckling. Whole root systems may also grow preferentially in loose versus dense soil, but this response depends on genotype and the spatial arrangement of loose and compact soil with respect to the main root axes. Decreased root elongation is often accompanied by a decrease in both cell flux and axial cell extension, and recent computer-based models are increasing our understanding of these processes. In the case of mechanical impedance, large changes in cell shape occur, giving rise to shorter fatter cells. There is still uncertainty about many aspects of this response, including the changes in cell walls that control axial versus radial extension, and the degree to which the epidermis, cortex, and stele control root elongation. Optical flow techniques enable tracking of root surfaces with time to yield estimates of two-dimensional velocity fields. It is demonstrated that these techniques can be applied successfully to time-lapse sequences of confocal microscope images of living roots, in order to determine velocity fields and strain rates of groups of cells. In combination with new molecular approaches this provides a promising way of investigating and modelling the mechanisms controlling growth perturbations in response to environmental stresses.

  15. Arabidopsis thaliana glyoxalase 2-1 is required during abiotic stress but is not essential under normal plant growth.

    Directory of Open Access Journals (Sweden)

    Sriram Devanathan

    Full Text Available The glyoxalase pathway, which consists of the two enzymes, GLYOXALASE 1 (GLX 1 (E.C.: 4.4.1.5 and 2 (E.C.3.1.2.6, has a vital role in chemical detoxification. In Arabidopsis thaliana there are at least four different isoforms of glyoxalase 2, two of which, GLX2-1 and GLX2-4 have not been characterized in detail. Here, the functional role of Arabidopsis thaliana GLX2-1 is investigated. Glx2-1 loss-of-function mutants and plants that constitutively over-express GLX2-1 resemble wild-type plants under normal growth conditions. Insilico analysis of publicly available microarray datasets with ATTEDII, Mapman and Genevestigator indicate potential role(s in stress response and acclimation. Results presented here demonstrate that GLX2-1 gene expression is up-regulated in wild type Arabidopsis thaliana by salt and anoxia stress, and by excess L-Threonine. Additionally, a mutation in GLX2-1 inhibits growth and survival during abiotic stresses. Metabolic profiling studies show alterations in the levels of sugars and amino acids during threonine stress in the plants. Elevated levels of polyamines, which are known stress markers, are also observed. Overall our results suggest that Arabidopsis thaliana GLX2-1 is not essential during normal plant life, but is required during specific stress conditions.

  16. Cyclin-like F-box protein plays a role in growth and development of the three model species Medicago truncatula, Lotus japonicus, and Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Boycheva I

    2015-08-01

    Full Text Available Irina Boycheva,1 Valya Vassileva,2 Miglena Revalska,1 Grigor Zehirov,2 Anelia Iantcheva1 1Department of Functional Genetics Legumes, 2AgroBioInstitute, Department of Plant Stress Molecular Biology, Institute of Plant Physiology and Genetics, Sofia, Bulgaria Abstract: In eukaryotes, F-box proteins are one of the main components of the SCF complex that belongs to the family of ubiquitin E3 ligases, which catalyze protein ubiquitination and maintain the balance between protein synthesis and degradation. In the present study, we clarified the role and function of the gene encoding cyclin-like F-box protein from Medicago truncatula using transgenic plants of the model species M. truncatula, Lotus japonicas, and Arabidopsis thaliana generated by Agrobacterium-mediated transformation. Morphological and transcriptional analyses combined with flow cytometry and histochemistry demonstrated the participation of this protein in many aspects of plant growth and development, including processes of indirect somatic embryogenesis and symbiotic nodulation. The cyclin-like F-box gene showed expression in all plant organs and tissues comprised of actively dividing cells. The observed variations in root and hypocotyl growth, leaf and silique development, ploidy levels, and leaf parameters in the obtained transgenic lines demonstrated the effects of this gene on organ development. Furthermore, knockdown of cyclin-like F-box led to accumulation of higher levels of the G2/M transition-specific gene cyclin B1:1 (CYCB1:1, suggesting its possible role in cell cycle control. Together, the collected data suggest a similar role of the cyclin-like F-box protein in the three model species, providing evidence for the functional conservation of the studied gene. Keywords: cyclin-like F-box, model legumes, Arabidopsis thaliana, plant growth, plant development, cell cycle

  17. Acclimation of Arabidopsis thaliana to long-term CO{sub 2} enrichment and nitrogen supply is basically a matter of growth rate adjustment

    Energy Technology Data Exchange (ETDEWEB)

    Tocquin, P.; Ormenese, S.; Pieltain, A.; Detry, N.; Bernier, G.; Perilleux, C. [Univ. of Liege, Dept. of Life Sciences, Lab. of Plant Physiology, Liege (Belgium)

    2006-12-15

    The long-term response of Arabidopsis thaliana to increasing CO{sub 2} was evaluated in plants grown in 800 {mu}l l{sup -1} CO{sub 2} from sowing and maintained, in hydroponics, on three nitrogen supplies: 'low', 'medium' and 'high'. The global response to high CO{sub 2} and N-supply was evaluated by measuring growth parameters in parallel with photosynthetic activity, leaf carbohydrates, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) messenger RNA and protein, stomatal conductance (g-s) and density. CO{sub 2} enrichment was found to stimulate biomass production, whatever the N-supply. This stimulation was transient on low N-supply and persisted throughout the whole vegetative growth only in high N-supply. Acclimation on low N-high C0{sub 2} was not associated with carbohydrate accumulation or with a strong reduction in Rubisco amount or activity. At high N-supply, growth stimulation by high CO{sub 2} was mainly because of the acceleration of leaf production and expansion while other parameters such as specific leaf area, root/shoot ratio and g{sub s} appeared to be correlated with total leaf area. Our results thus suggest that, in strictly controlled and stable growing conditions, acclimation of A. thaliana to long-term CO{sub 2} enrichment is mostly controlled by growth rate adjustment. (au)

  18. Genetic Improvement of Root Growth Contributes to Efficient Phosphorus Acquisition in maize (Zea mays L.)

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi-kai; CHEN Fan-jun; CHEN Xiao-chao; LONG Li-zhi; GAO Kun; YUAN Li-xing; ZHANG Fu-suo; MI Guo-hua

    2013-01-01

    Maize plants adapt to low phosphorus (P) stress by increasing root growth. It is of importance to know the extent to which genetic improvement of root growth can enhance P acquisiton. In the present study, the contribution of root growth improvement to efficient P acquisition was evaluated in two soils using T149 and T222, a pair of near isogenic maize testcrosses which were derived from a backcross BC4F3 population. T149 and T222 showed no difference in shoot biomass and leaf area under normal growth conditions, but differed greatly in root growth. T149 had longer lateral roots and a larger root surface area compared to T222. In calcareous soil, when P was insufficient, i.e., when P was either supplied as KH2PO4 at a concentration of 50 mg P kg-1 soil, or in the form of Phy-P, Ca3-P or Ca10-P, a 43%increase in root length in T149 compared to T222 resulted in an increase in P uptake by 53%, and shoot biomass by 48%. In acid soil, however, when P supply was insufficient, i.e., when P was supplied as KH2PO4 at a concentration of 100 mg P kg-1 soil, or in the form of Phy-P, Fe-P or Al-P, a 32%increase in root length in T149 compared to T222 resulted in an increase in P uptake by only 12%, and shoot biomass by 7%. No significant differences in the exudation of organic acids and APase activity were found between the two genotypes. It is concluded that genetic improvement of root growth can efficiently increase P acquisition in calcareous soils. In acid soils, however, improvements in the physiological traits of roots, in addition to their size, seem to be required for efficient P acquisition.

  19. Expression of the Beet necrotic yellow vein virus p25 protein induces hormonal changes and a root branching phenotype in Arabidopsis thaliana.

    Science.gov (United States)

    Peltier, Claire; Schmidlin, Laure; Klein, Elodie; Taconnat, Ludivine; Prinsen, Els; Erhardt, Mathieu; Heintz, Dimitri; Weyens, Guy; Lefebvre, Marc; Renou, Jean-Pierre; Gilmer, David

    2011-06-01

    The RNA-3-encoded p25 protein was previously characterized as one of the major symptom determinants of the Beet necrotic yellow vein virus. Previous analyses reported the influence of the p25 protein in root proliferation phenotype observed in rhizomania disease on infected sugar beets (Beta vulgaris). A transgenic approach was developed, in which the p25 protein was constitutively expressed in Arabidopsis thaliana Columbia (Col-0) ecotype in order to provide new clues as to how the p25 protein might promote alone disease development and symptom expression. Transgenic plants were characterized by Southern blot and independent lines carrying single and multiple copies of the transgene were selected. Mapping of the T-DNA insertion was performed on the monocopy homozygote lines. P25 protein was localized both in the nucleus and in the cytoplasm of epidermal and root cells of transgenic plants. Although A. thaliana was not described as a susceptible host for BNYVV infection, abnormal root branching was observed on p25 protein-expressing A. thaliana plants. Moreover, these transgenic plants were more susceptible than wild-type plants to auxin analog treatment (2,4-D) but more resistant to methyl jasmonate (MeJA), abscisic acid (ABA) and to lesser extend to salicylic acid (SA). Hormonal content assays measuring plant levels of auxin (IAA), jasmonate (JA) and ethylene precursor (ACC) revealed major hormonal changes. Global transcript profiling analyses on roots displayed differential gene expressions that could corroborate root branching phenotype and stress signaling modifications.

  20. Expression of the Beet necrotic yellow vein virus p25 protein induces hormonal changes and a root branching phenotype in Arabidopsis thaliana.

    Science.gov (United States)

    Peltier, Claire; Schmidlin, Laure; Klein, Elodie; Taconnat, Ludivine; Prinsen, Els; Erhardt, Mathieu; Heintz, Dimitri; Weyens, Guy; Lefebvre, Marc; Renou, Jean-Pierre; Gilmer, David

    2011-06-01

    The RNA-3-encoded p25 protein was previously characterized as one of the major symptom determinants of the Beet necrotic yellow vein virus. Previous analyses reported the influence of the p25 protein in root proliferation phenotype observed in rhizomania disease on infected sugar beets (Beta vulgaris). A transgenic approach was developed, in which the p25 protein was constitutively expressed in Arabidopsis thaliana Columbia (Col-0) ecotype in order to provide new clues as to how the p25 protein might promote alone disease development and symptom expression. Transgenic plants were characterized by Southern blot and independent lines carrying single and multiple copies of the transgene were selected. Mapping of the T-DNA insertion was performed on the monocopy homozygote lines. P25 protein was localized both in the nucleus and in the cytoplasm of epidermal and root cells of transgenic plants. Although A. thaliana was not described as a susceptible host for BNYVV infection, abnormal root branching was observed on p25 protein-expressing A. thaliana plants. Moreover, these transgenic plants were more susceptible than wild-type plants to auxin analog treatment (2,4-D) but more resistant to methyl jasmonate (MeJA), abscisic acid (ABA) and to lesser extend to salicylic acid (SA). Hormonal content assays measuring plant levels of auxin (IAA), jasmonate (JA) and ethylene precursor (ACC) revealed major hormonal changes. Global transcript profiling analyses on roots displayed differential gene expressions that could corroborate root branching phenotype and stress signaling modifications. PMID:20602166

  1. Soil acidification effects on fine root growth of Douglas-fir on sandy soils.

    NARCIS (Netherlands)

    Olsthoorn, A.F.M.

    1998-01-01

    The ammonium sulphate deposited in forest ecosystems in the Netherlands as a result of air pollution currently exceeds 80 kg N ha -1yr -1locally. To study the influence of this air pollution on fine root density and its dynamics, fine root growth was monitored for three years i