Plant-specific Histone Deacetylases HDT½ Regulate GIBBERELLIN 2-OXIDASE 2 Expression to Control Arabidopsis Root Meristem Cell Number

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Li, Huchen; Torres-Garcia, Jesus; latrasse, David; Benhamed, Moussa; Schilderink, Stefan; Zhou, Wenkun; Kulikova, Olga; Hirt, Heribert; Bisseling, Ton

2017-01-01

Root growth is modulated by environmental factors and depends on cell production in the root meristem (RM). New cells in the meristem are generated by stem cells and transit-amplifying cells, which together determine RM cell number. Transcription

Identification of genes involved in the ACC-mediated control of root cell elongation in Arabidopsis thaliana

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Markakis Marios

2012-11-01

Full Text Available Abstract Background Along the root axis of Arabidopsis thaliana, cells pass through different developmental stages. In the apical meristem repeated cycles of division increase the numbers of cells. Upon leaving the meristem, these cells pass the transition zone where they are physiologically and mechanically prepared to undergo subsequent rapid elongation. During the process of elongation epidermal cells increase their length by 300% in a couple of hours. When elongation ceases, the cells acquire their final size, shape and functions (in the differentiation zone. Ethylene administered as its precursor 1-aminocyclopropane-1-carboxylic acid (ACC is capable of inhibiting elongation in a concentration-dependent way. Using a microarray analysis, genes and/or processes involved in this elongation arrest are identified. Results Using a CATMA-microarray analysis performed on control and 3h ACC-treated roots, 240 differentially expressed genes were identified. Quantitative Real-Time RT-PCR analysis of the 10 most up and down regulated genes combined with literature search confirmed the accurateness of the analysis. This revealed that inhibition of cell elongation is, at least partly, caused by restricting the events that under normal growth conditions initiate elongation and by increasing the processes that normally stop cellular elongation at the end of the elongation/onset of differentiation zone. Conclusions ACC interferes with cell elongation in the Arabidopsis thaliana roots by inhibiting cells from entering the elongation process and by immediately stimulating the formation of cross-links in cell wall components, diminishing the remaining elongation capacity. From the analysis of the differentially expressed genes, it becomes clear that many genes identified in this response, are also involved in several other kind of stress responses. This suggests that many responses originate from individual elicitors, but that somewhere in the downstream

Inhibition of tobacco mosaic virus replication in lateral roots is dependent on an activated meristem-derived signal.

Science.gov (United States)

Valentine, T A; Roberts, I M; Oparka, K J

2002-05-01

Viral invasion of the root system of Nicotiana benthamiana was studied noninvasively with a tobacco mosaic virus (TMV) vector expressing the green-fluorescent protein (GFP). Lateral root primordia, which developed from the pericycle of primary roots, became heavily infected as they emerged from the root cortex. However, following emergence, a progressive wave of viral inhibition occurred that originated in the lateral-root meristem and progressed towards its base. Excision of source and sink tissues suggested that the inhibition of virus replication was brought about by the basipetal movement of a root meristem signal. When infected plants were inoculated with tobacco rattle virus (TRV) expressing the red-fluorescent protein, DsRed, TRV entered the lateral roots and suppressed the host response, leading to a reestablishment of TMV infection in lateral roots. By infecting GFP-expressing transgenic plants with TMV carrying the complementary GFP sequence it was possible to silence the host GFP, leading to the complete loss of fluorescence in lateral roots. The data suggest that viral inhibition in lateral roots occurs by a gene-silencing-like mechanism that is dependent on the activation of a lateral-root meristem.

Improved and Reproducible Flow Cytometry Methodology for Nuclei Isolation from Single Root Meristem

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Thaís Cristina Ribeiro Silva

2010-01-01

Full Text Available Root meristems have increasingly been target of cell cycle studies by flow cytometric DNA content quantification. Moreover, roots can be an alternative source of nuclear suspension when leaves become unfeasible and for chromosome analysis and sorting. In the present paper, a protocol for intact nuclei isolation from a single root meristem was developed. This proceeding was based on excision of the meristematic region using a prototypical slide, followed by short enzymatic digestion and mechanical isolation of nuclei during homogenization with a hand mixer. Such parameters were optimized for reaching better results. Satisfactory nuclei amounts were extracted and analyzed by flow cytometry, producing histograms with reduced background noise and CVs between 3.2 and 4.1%. This improved and reproducible technique was shown to be rapid, inexpensive, and simple for nuclear extraction from a single root tip, and can be adapted for other plants and purposes.

Cell radiosensitivity variation in synchronously-dividing root meristems of Pisum sativum L. and Zea mays L. during the mitotic cycle

International Nuclear Information System (INIS)

Gudkov, I.N.; Grodzinsky, D.M.

1982-01-01

The cell divisions in pea and maize seedling root meristems were synchronized by treatment with 0.03 per cent hydroxyurea for 24 hours. At different times after block cessation (removing seedlings from hydroxyurea), i.e. according to certain phases and subphases of the mitotic cycle, the seedlings were treated with 60 Co γ-radiation at doses from 3 to 32 Gy. Evaluation of seedling radioresistance by the survival of the main root meristem on the tenth day after irradiation led to the following sequence of cell stages in order of increasing resistance. For the pea root meristem: G 2 , M, late G 1 , early S, late S, middle S and early G 1 . For the maize root meristem: late G 2 , M, G 1 , early S, early G 2 , late S and middle S. (author)

Adsorption and inhibition of CuO nanoparticles on Arabidopsis thaliana root

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Xu, Lina

2018-02-01

CuO NPs, the size ranging from 20 to 80 nm were used to detect the adsorption and inhibition on the Arabidopsis thaliana roots. In this study, CuO NPs were adsorbed and agglomerated on the surface of root top after exposed for 7 days. With the increasing of CuO NPs concentrations, CuO NPs also adsorbed on the meristernatic zone. The growth of Arabidopsis thaliana lateral roots were also inhibited by CuO NPs exposure. The Inhibition were concentration dependent. The number of root top were 246, 188 and 123 per Arabidopsis thaliana, respectively. The number of root tops after CuO NPs exposure were significantly decreased compared with control groups. This results suggested the phytotoxicity of CuO NPs on Arabidopsis thaliana roots.

Cell radiosensitivity variation in synchronously-dividing root meristems of Pisum sativum L. and Zea mays L. during the mitotic cycle

Energy Technology Data Exchange (ETDEWEB)

Gudkov, I.N.; Grodzinsky, D.M. (AN Ukrainskoj SSR, Kiev. Inst. Fiziologii Rastenij)

1982-04-01

The cell divisions in pea and maize seedling root meristems were synchronized by treatment with 0.03 per cent hydroxyurea for 24 hours. At different times after block cessation (removing seedlings from hydroxyurea), i.e. according to certain phases and subphases of the mitotic cycle, the seedlings were treated with /sup 60/Co ..gamma..-radiation at doses from 3 to 32 Gy. Evaluation of seedling radioresistance by the survival of the main root meristem on the tenth day after irradiation led to the following sequence of cell stages in order of increasing resistance. For the pea root meristem: G/sub 2/, M, late G/sub 1/, early S, late S, middle S and early G/sub 1/. For the maize root meristem: late G/sub 2/, M, G/sub 1/, early S, early G/sub 2/, late S and middle S.

Plant-specific histone deacetylases HDT1/2 regulate GIBBERELLIN 2-OXIDASE2 expression to control arabidopsis root meristem cell number

NARCIS (Netherlands)

Li, Huchen; Torres-Garcia, Jesus; Latrasse, David; Benhamed, Moussa; Schilderink, Stefan; Zhou, Wenkun; Kulikova, Olga; Hirt, Heribert; Bisseling, Ton

2017-01-01

Root growth is modulated by environmental factors and depends on cell production in the root meristem (RM). New cells in the meristem are generated by stem cells and transit-amplifying cells, which together determine RM cell number. Transcription factors and chromatin-remodeling factors have been

Cadmium cytotoxity: study of Allium sativum L. root meristems

Energy Technology Data Exchange (ETDEWEB)

Clain, E.; Deysson, G.

1976-01-01

Three cadmium salts, CdSO/sub 4/, Cd(NO/sub 3/)/sub 2/, and Cd(OAc)/sub 2/ were tested on garlic root meristems. CdSO/sub 4/ was the most toxic of the three; when 10/sup -7/ mol/ml was used, mitostasis resulted within 24 hours and cellular death after forty-eight hours. Cd(NO/sub 3/)/sub 2/ and Cd(OAc)/sub 2/ were lethal at 5 x 10/sup -7/ mol/ml. 1 figure, 1 table.

A 3D digital atlas of the Nicotiana tabacum root tip and its use to investigate changes in the root apical meristem induced by the Agrobacterium 6b oncogene.

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Pasternak, Taras; Haser, Thomas; Falk, Thorsten; Ronneberger, Olaf; Palme, Klaus; Otten, Léon

2017-10-01

Using the intrinsic Root Coordinate System (iRoCS) Toolbox, a digital atlas at cellular resolution has been constructed for Nicotiana tabacum roots. Mitotic cells and cells labeled for DNA replication with 5-ethynyl-2'-deoxyuridine (EdU) were mapped. The results demonstrate that iRoCS analysis can be applied to roots that are thicker than those of Arabidopsis thaliana without histological sectioning. A three-dimensional (3-D) analysis of the root tip showed that tobacco roots undergo several irregular periclinal and tangential divisions. Irrespective of cell type, rapid cell elongation starts at the same distance from the quiescent center, however, boundaries between cell proliferation and transition domains are cell-type specific. The data support the existence of a transition domain in tobacco roots. Cell endoreduplication starts in the transition domain and continues into the elongation zone. The tobacco root map was subsequently used to analyse root organization changes caused by the inducible expression of the Agrobacterium 6b oncogene. In tobacco roots that express the 6b gene, the root apical meristem was shorter and radial cell growth was reduced, but the mitotic and DNA replication indexes were not affected. The epidermis of 6b-expressing roots produced less files and underwent abnormal periclinal divisions. The periclinal division leading to mature endodermis and cortex3 cell files was delayed. These findings define additional targets for future studies on the mode of action of the Agrobacterium 6b oncogene. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

Lateral root initiation and formation within the parental root meristem of Cucurbita pepo: is auxin a key player?

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Ilina, Elena L; Kiryushkin, Alexey S; Semenova, Victoria A; Demchenko, Nikolay P; Pawlowski, Katharina; Demchenko, Kirill N

2018-04-19

In some plant families, including Cucurbitaceae, initiation and development of lateral roots (LRs) occur in the parental root apical meristem. The objective of this study was to identify the general mechanisms underlying LR initiation (LRI). Therefore, the first cellular events leading to LRI as well as the role of auxin in this process were studied in the Cucurbita pepo root apical meristem. Transgenic hairy roots harbouring the auxin-responsive promoter DR5 fused to different reporter genes were used for visualizing of cellular auxin response maxima (ARMs) via confocal laser scanning microscopy and 3-D imaging. The effects of exogenous auxin and auxin transport inhibitors on root branching were analysed. The earliest LRI event involved a group of symmetric anticlinal divisions in pericycle cell files at a distance of 250-350 µm from the initial cells. The visualization of the ARMs enabled the precise detection of cells involved in determining the site of LR primordium formation. A local ARM appeared in sister cells of the pericycle and endodermis files before the first division. Cortical cells contributed to LR development after the anticlinal divisions in the pericycle via the formation of an ARM. Exogenous auxins did not increase the total number of LRs and did not affect the LRI index. Although exogenous auxin transport inhibitors acted in different ways, they all reduced the number of LRs formed. Literature data, as well as results obtained in this study, suggest that the formation of a local ARM before the first anticlinal formative divisions is the common mechanism underlying LRI in flowering plants. We propose that the mechanisms of the regulation of root branching are independent of the position of the LRI site relative to the parental root tip.

ROOT HAIR DEFECTIVE SIX-LIKE Class I Genes Promote Root Hair Development in the Grass Brachypodium distachyon.

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Chul Min Kim

2016-08-01

Full Text Available Genes encoding ROOT HAIR DEFECTIVE SIX-LIKE (RSL class I basic helix loop helix proteins are expressed in future root hair cells of the Arabidopsis thaliana root meristem where they positively regulate root hair cell development. Here we show that there are three RSL class I protein coding genes in the Brachypodium distachyon genome, BdRSL1, BdRSL2 and BdRSL3, and each is expressed in developing root hair cells after the asymmetric cell division that forms root hair cells and hairless epidermal cells. Expression of BdRSL class I genes is sufficient for root hair cell development: ectopic overexpression of any of the three RSL class I genes induces the development of root hairs in every cell of the root epidermis. Expression of BdRSL class I genes in root hairless Arabidopsis thaliana root hair defective 6 (Atrhd6 Atrsl1 double mutants, devoid of RSL class I function, restores root hair development indicating that the function of these proteins has been conserved. However, neither AtRSL nor BdRSL class I genes is sufficient for root hair development in A. thaliana. These data demonstrate that the spatial pattern of class I RSL activity can account for the pattern of root hair cell differentiation in B. distachyon. However, the spatial pattern of class I RSL activity cannot account for the spatial pattern of root hair cells in A. thaliana. Taken together these data indicate that that the functions of RSL class I proteins have been conserved among most angiosperms-monocots and eudicots-despite the dramatically different patterns of root hair cell development.

A plant U-box protein, PUB4, regulates asymmetric cell division and cell proliferation in the root meristem

NARCIS (Netherlands)

Kinoshita, A.; Hove, ten C.A.; Tabata, R.; Yamada, M.; Shimizu, N.; Ishida, T.; Yamaguchi, K.; Shigenobu, S.; Takebayashi, Y.; Luchies, J.; Kobayashi, M.; Kurata, T.; Wada, T.; Seo, M.; Hasebe, M.; Blilou, I.; Fukuda, H.; Scheres, B.; Heidstra, R.; Kamiya, Y.; Sawa, S.

2015-01-01

The root meristem (RM) is a fundamental structure that is responsible for postembryonic root growth. The RM contains the quiescent center (QC), stem cells and frequently dividing meristematic cells, in which the timing and the frequency of cell division are tightly regulated. In Arabidopsis

Distinct modes of adventitious rooting in Arabidopsis thaliana.

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Correa, L da Rocha; Troleis, J; Mastroberti, A A; Mariath, J E A; Fett-Neto, A G

2012-01-01

The literature describes different rooting protocols for Arabidopsis thaliana as models to study adventitious rooting, and results are generally perceived as comparable. However, there is a lack of investigations focusing on the distinct features, advantages and limitations of each method in the study of adventitious rooting with both wild-type (WT) ecotypes and their respective mutants. This investigation was undertaken to evaluate the adventitious rooting process in three different experimental systems, all using A. thaliana, analysing the same rooting parameters after transient exposure to auxin (indole-3-acetic acid) and control conditions: excised leaves, de-rooted plants and etiolated seedlings. The founding tissues and sites of origin of roots differed depending on the system used, whereas all rooting patterns were of the direct type (i.e., without callus formation). None of the systems had an absolute requirement for exogenous auxin, although rooting was enhanced by this phytohormone, with the exception of de-rooted plants, which had adventitious rooting strongly inhibited by exogenous auxin. Root elongation was much favoured in isolated leaves. Auxin-overproducing mutants could not be used in the detached leaf system due to precocious senescence; in the de-rooted plant system, these mutants had a WT-like rooting response, whereas the expression of the 'rooty' phenotype was only evident in the etiolated seedling system. Adventitious rooting of etiolated WT seedlings in the presence of exogenous auxin was inhibited by exogenous flavonoids, which act as auxin transport inhibitors; surprisingly, the flavonoid-deficient mutant chs had a lower rooting response compared to WT. Although Arabidopsis is an excellent model system to study adventitious rooting, physiological and developmental responses differed significantly, underlining the importance of avoiding data generalisation on rooting responses derived from different experimental systems with this species. �

Repression of BLADE-ON-PETIOLE genes by KNOX homeodomain protein BREVIPEDICELLUS is essential for differentiation of secondary xylem in Arabidopsis root.

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Woerlen, Natalie; Allam, Gamalat; Popescu, Adina; Corrigan, Laura; Pautot, Véronique; Hepworth, Shelley R

2017-06-01

Repression of boundary genes by KNOTTED1-like homeodomain transcription factor BREVIPEDICELLUS promotes the differentiation of phase II secondary xylem in Arabidopsis roots. Plant growth and development relies on the activity of meristems. Boundaries are domains of restricted growth that separate forming organs and the meristem. Class I KNOX homeodomain transcription factors are important regulators of meristem maintenance. Members of this class including BREVIDICELLUS also called KNOTTED-LIKE FROM ARABIDOPSIS THALIANA1 (BP/KNAT1) fulfill this function in part by spatially regulating boundary genes. The vascular cambium is a lateral meristem that allows for radial expansion of organs during secondary growth. We show here that BP/KNAT1 repression of boundary genes plays a crucial role in root secondary growth. In particular, exclusion of BLADE-ON-PETIOLE1/2 (BOP1/2) and other members of this module from xylem is required for the differentiation of lignified fibers and vessels during the xylem expansion phase of root thickening. These data reveal a previously undiscovered role for boundary genes in the root and shed light on mechanisms controlling wood development in trees.

Primary root growth in Arabidopsis thaliana is inhibited by the miR159 mediated repression of MYB33, MYB65 and MYB101.

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Xue, Tao; Liu, Zhenhua; Dai, Xuehuan; Xiang, Fengning

2017-09-01

Organ growth is a fundamental developmental process basing on cell proliferation and differentiation. The growth of the plant root is sustained by the activity of the root meristem, a process controlled in part by various transcription factors. Here, the miR159 has been identified as a post transcriptional repressor of root growth, on the basis that the mir159ab double mutant developed a larger meristem than did the wild type, and that it formed longer roots. In the mutant, the abundance of MYB33, MYB65 and MYB101 transcript was substantially increased. When MYB33, MYB65 and MYB101 were replaced by the miR159-resistant forms mMYB33, mMYB65 and mMYB101 respectively, the root meristem was similarly enlarged and the growth of the primary root enhanced. MYB65 activity promoted cell division in the root meristem by accelerating the cell cycle. The data suggest that miR159 acts as a key repressor of the primary root's growth, acting through its repression of MYB65 and consequent blocking of the cell cycle. Copyright © 2017 Elsevier B.V. All rights reserved.

Multi-element bioimaging of Arabidopsis thaliana roots

DEFF Research Database (Denmark)

Persson, Daniel Olof; Chen, Anle; Aarts, Mark G.M.

2016-01-01

Better understanding of root function is central for the development of plants with more efficient nutrient uptake and translocation. We here present a method for multielement bioimaging at the cellular level in roots of the genetic model system Arabidopsis (Arabidopsis thaliana). Using conventio......Better understanding of root function is central for the development of plants with more efficient nutrient uptake and translocation. We here present a method for multielement bioimaging at the cellular level in roots of the genetic model system Arabidopsis (Arabidopsis thaliana). Using...... omics techniques. To demonstrate the potential of the method, we analyzed a mutant of Arabidopsis unable to synthesize the metal chelator nicotianamine. The mutant accumulated substantially more zinc and manganese than the wild type in the tissues surrounding the vascular cylinder. For iron, the images...... looked completely different, with iron bound mainly in the epidermis of the wild-type plants but confined to the cortical cell walls of the mutant. The method offers the power of inductively coupled plasma-mass spectrometry to be fully employed, thereby providing a basis for detailed studies of ion...

Transcriptomic characterization of a synergistic genetic interaction during carpel margin meristem development in Arabidopsis thaliana.

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April N Wynn

Full Text Available In flowering plants the gynoecium is the female reproductive structure. In Arabidopsis thaliana ovules initiate within the developing gynoecium from meristematic tissue located along the margins of the floral carpels. When fertilized the ovules will develop into seeds. SEUSS (SEU and AINTEGUMENTA (ANT encode transcriptional regulators that are critical for the proper formation of ovules from the carpel margin meristem (CMM. The synergistic loss of ovule initiation observed in the seu ant double mutant suggests that SEU and ANT share overlapping functions during CMM development. However the molecular mechanism underlying this synergistic interaction is unknown. Using the ATH1 transcriptomics platform we identified transcripts that were differentially expressed in seu ant double mutant relative to wild type and single mutant gynoecia. In particular we sought to identify transcripts whose expression was dependent on the coordinated activities of the SEU and ANT gene products. Our analysis identifies a diverse set of transcripts that display altered expression in the seu ant double mutant tissues. The analysis of overrepresented Gene Ontology classifications suggests a preponderance of transcriptional regulators including multiple members of the REPRODUCTIVE MERISTEMS (REM and GROWTH-REGULATING FACTOR (GRF families are mis-regulated in the seu ant gynoecia. Our in situ hybridization analyses indicate that many of these genes are preferentially expressed within the developing CMM. This study is the first step toward a detailed description of the transcriptional regulatory hierarchies that control the development of the CMM and ovule initiation. Understanding the regulatory hierarchy controlled by SEU and ANT will clarify the molecular mechanism of the functional redundancy of these two genes and illuminate the developmental and molecular events required for CMM development and ovule initiation.

Autoradiographic study of gamma-ray induced unscheduled DNA synthesis in bean root meristem cells

International Nuclear Information System (INIS)

Liu Zhenshen; Qiu Quanfa; Chen Dongli

1989-01-01

The gamma-ray induced unscheduled DNA synthesis in root meristem cells of Vica faba was studied autoradiographically by calculating the number of cells with different 3H-thymidine labelling degree. It was found that the level of unscheduled synthesis in cells with intermediate dose (500 R) irradiation was higher than that in cells with lower dose (250 R) irradiation; however, higher dose (1000 R) irradiation would inhibit the reparative replication

Repression of Lateral Organ Boundary Genes by PENNYWISE and POUND-FOOLISH Is Essential for Meristem Maintenance and Flowering in Arabidopsis

NARCIS (Netherlands)

Khan, Madiha; Ragni, Laura; Tabb, Paul; Salasini, Brenda C; Chatfield, Steven; Datla, Raju; Lock, John; Kuai, Xiahezi; Després, Charles; Proveniers, Marcel; Yongguo, Cao; Xiang, Daoquan; Morin, Halima; Rullière, Jean-Pierre; Citerne, Sylvie; Hepworth, Shelley R; Pautot, Véronique

2015-01-01

In the model plant Arabidopsis (Arabidopsis thaliana), endogenous and environmental signals acting on the shoot apical meristem cause acquisition of inflorescence meristem fate. This results in changed patterns of aerial development seen as the transition from making leaves to the production of

Root hair defective4 encodes a phosphatidylinositol-4-phosphate phosphatase required for proper root hair development in Arabidopsis thaliana

NARCIS (Netherlands)

Thole, J.M.; Vermeer, J.E.M.; Zhang, Y.; Gadella, Th.W.J.; Nielsen, E.

2008-01-01

Polarized expansion of root hair cells in Arabidopsis thaliana is improperly controlled in root hair-defective rhd4-1 mutant plants, resulting in root hairs that are shorter and randomly form bulges along their length. Using time-lapse fluorescence microscopy in rhd4-1 root hairs, we analyzed

Organization of the root apical meristem in Linum usitatissimum L. grown at 25°C and 7°C

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A. Kadej

2015-01-01

Full Text Available In the first days of intensive growth of the Linum usitatissimum root, the central part of the apical meristem exhibits usually a 4-tier organization. When growth ceases reorganization of the cell arrangement occurs. It starts by periclinal division of the subprotodermal initials, whose derivatives are forming the secondary columella in the central part of the root cap.

Effect of nickel on the organization of actin filaments in Arabidopsis thaliana primary root cells

International Nuclear Information System (INIS)

Goryunova, I.I.; Krasilenko, Yu.A.; Emets, A.I.; Blyum, Ya.B.

2016-01-01

The influence of one of the most toxic heavy metals - nickel (Ni 2+ ) - on the organization of actin filaments (microfilaments) of different types of Arabidopsis thaliana (L.) root cells is studied in living cells by the laser scanning microscopy. To visualize microfilaments, the A. thaliana line expressing chimeric gene gfp-fabd2 was used. Ni 2+ leads to a significant inhibition of the growth of the main root and disturbs its morphology, causing the swelling of epidermal cells and inducing a large number of abnormally long root hairs. For the first time, it has been shown that Ni 2+ disturbs the organization of actin filaments in cells, leading to morphological changes of a root as the main organ, being the first exposed to the intoxication by soil pollutants. It is found that the most sensitive to its action are actin filaments of epidermal cells of all growth zones of A. thaliana root

Transcriptomics insights into the genetic regulation of root apical meristem exhaustion and determinate primary root growth in Pachycereus pringlei (Cactaceae).

Science.gov (United States)

Rodriguez-Alonso, Gustavo; Matvienko, Marta; López-Valle, Mayra L; Lázaro-Mixteco, Pedro E; Napsucialy-Mendivil, Selene; Dubrovsky, Joseph G; Shishkova, Svetlana

2018-06-04

Many Cactaceae species exhibit determinate growth of the primary root as a consequence of root apical meristem (RAM) exhaustion. The genetic regulation of this growth pattern is unknown. Here, we de novo assembled and annotated the root apex transcriptome of the Pachycereus pringlei primary root at three developmental stages, with active or exhausted RAM. The assembled transcriptome is robust and comprehensive, and was used to infer a transcriptional regulatory network of the primary root apex. Putative orthologues of Arabidopsis regulators of RAM maintenance, as well as putative lineage-specific transcripts were identified. The transcriptome revealed putative orthologues of most proteins involved in housekeeping processes, hormone signalling, and metabolic pathways. Our results suggest that specific transcriptional programs operate in the root apex at specific developmental time points. Moreover, the transcriptional state of the P. pringlei root apex as the RAM becomes exhausted is comparable to the transcriptional state of cells from the meristematic, elongation, and differentiation zones of Arabidopsis roots along the root axis. We suggest that the transcriptional program underlying the drought stress response is induced during Cactaceae root development, and that lineage-specific transcripts could contribute to RAM exhaustion in Cactaceae.

Meristem identity and phyllotaxis in inflorescence development.

Science.gov (United States)

Bartlett, Madelaine E; Thompson, Beth

2014-01-01

Inflorescence morphology is incredibly diverse. This diversity of form has been a fruitful source of inquiry for plant morphologists for more than a century. Work in the grasses (Poaceae), the tomato family (Solanaceae), and Arabidopsis thaliana (Brassicaceae) has led to a richer understanding of the molecular genetics underlying this diversity. The character of individual meristems, a combination of the number (determinacy) and nature (identity) of the products a meristem produces, is key in the development of plant form. A framework that describes inflorescence development in terms of shifting meristem identities has emerged and garnered empirical support in a number of model systems. We discuss this framework and highlight one important aspect of meristem identity that is often considered in isolation, phyllotaxis. Phyllotaxis refers to the arrangement of lateral organs around a central axis. The development and evolution of phyllotaxis in the inflorescence remains underexplored, but recent work analyzing early inflorescence development in the grasses identified an evolutionary shift in primary branch phyllotaxis in the Pooideae. We discuss the evidence for an intimate connection between meristem identity and phyllotaxis in both the inflorescence and vegetative shoot, and touch on what is known about the establishment of phyllotactic patterns in the meristem. Localized auxin maxima are instrumental in determining the position of lateral primordia. Upstream factors that regulate the position of these maxima remain unclear, and how phyllotactic patterns change over the course of a plant's lifetime and evolutionary time, is largely unknown. A more complete understanding of the molecular underpinnings of phyllotaxis and architectural diversity in inflorescences will require capitalizing on the extensive resources available in existing genetic systems, and developing new model systems that more fully represent the diversity of plant morphology.

Cell fate in the Arabidopsis root meristem determined by directional signalling

NARCIS (Netherlands)

Berg, C. van den; Willemsen, V.; Hage, W.; Weisbeek, P.; Scheres, B.J.G.

1995-01-01

Postembryonic development in plants is achieved by apical meristems. Surgical studies and clonal analysis have revealed indirectly that cells in shoot meristems have no predictable destiny and that position is likely to play a role in the acquisition of cell identity . In contrast to animal

Differential spatial expression of A- and B-type CDKs, and distribution of auxins and cytokinins in the open transverse root apical meristem of Cucurbita maxima.

Science.gov (United States)

Chiappetta, Adriana; Bruno, Leonardo; Salimonti, Amelia; Muto, Antonella; Jones, Jessica; Rogers, Hilary J; Francis, Dennis; Bitonti, Maria Beatrice

2011-05-01

Aside from those on Arabidopsis, very few studies have focused on spatial expression of cyclin-dependent kinases (CDKs) in root apical meristems (RAMs), and, indeed, none has been undertaken for open meristems. The extent of interfacing between cell cycle genes and plant growth regulators is also an increasingly important issue in plant cell cycle studies. Here spatial expression/localization of an A-type and B-type CDK, auxin and cytokinins are reported in relation to the hitherto unexplored anatomy of RAMs of Cucurbita maxima. Median longitudinal sections were cut from 1-cm-long primary root tips of C. maxima. Full-length A-type CDKs and a B-type CDK were cloned from C. maxima using degenerate primers, probes of which were localized on sections of RAMs using in situ hybridization. Isopentenyladenine (iPA), trans-zeatin (t-Z) and indole-3yl-acetic acid (IAA) were identified on sections by immunolocalization. The C. cucurbita RAM conformed to an open transverse (OT) meristem typified by an absence of a clear boundary between the eumeristem and root cap columella, but with a distinctive longitudinally thickened epidermis. Cucma;CDKA;1 expression was detected strongly in the longitudinally thickened epidermis, a tissue with mitotic competence that contributes cells radially to the root cap of OT meristems. Cucma;CDKB2 was expressed mainly in proliferative regions of the RAM and in lateral root primordia. iPA and t-Z were mainly distributed in differentiated cells whilst IAA was distributed more uniformly in all tissues of the RAM. Cucma;CDKA;1 was expressed most strongly in cells that have proliferative competence whereas Cucma;CDKB2 was confined mainly to mitotic cells. iPA and t-Z marked differentiated cells in the RAM, consistent with the known effect of cytokinins in promoting differentiation in root systems. iPA/t-Z were distributed in a converse pattern to Cucma;CDKB2 expression whereas IAA was detected in most cells in the RAM regardless of their proliferative

The Ca2+ pump inhibitor, thapsigargin, inhibits root gravitropism in Arabidopsis thaliana

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DANIELA C URBINA

2006-01-01

Full Text Available Thapsigargin, a specific inhibitor of most animal intracellular SERCA-type Ca2+ pumps present in the sarcoplasmic/endoplasmic reticulum, was originally isolated from the roots of the Mediterranean plant Thapsia gargancia L. Here, we demonstrate that this root-derived compound is capable of altering root gravitropism in Arabidopsis thaliana. Thapsigargin concentrations as low as 0.1 µM alter root gravitropism whereas under similar conditions cyclopiazonic acid does not. Furthermore, a fluorescently conjugated thapsigargin (BODIPY FL thapsigargin suggests that target sites for thapsigargin are located in intracellular organelles in the root distal elongation zone and the root cap, regions known to regulate root gravitropism

Investigation of protective effects of Erythrina velutina extract against MMS induced damages in the root meristem cells of Allium cepa

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Deborah S. B. S. Silva

2013-04-01

Full Text Available Erythrina velutina Willd., Fabaceae, is a medicinal plant that can be found in the tropics and subtropics, including in the semi-arid northeastern Brazil. It is commonly used in folk medicine to treat anxiety, agitation and insomnia. E. velutina has been known to present analgesic, anti-inflammatory and antibacterial activities, however, it is unknown if this plant present a protective effect on DNA. We assessed the antigenotoxic effect of E. velutina against the genotoxic effects induced by MMS in the root meristem cells of Allium cepa. Three concentrations of the aqueous extract (100, 200 and 400 mg/L of this medicinal plant were used in three different types of treatment (pre-, post- and simultaneous. The effects of the extracts on the root meristem cells of A. cepa were analyzed at both macroscopic and microscopic levels. Protective effects were observed at higher concentrations in pre-treatment and in simultaneous treatment. The results suggest that E. velutina may present antigenotoxic properties and demonstrate its chemopreventive potential.

Arabidopsis thaliana Somatic Embryogenesis Receptor Kinase 1 protein is present in sporophytic and gametophytic cells and undergoes endocytosis

DEFF Research Database (Denmark)

Kwaaitaal, Mark Adrianus Cornelis J; de Vries, S C; Russinova, E

2005-01-01

Arabidopsis thaliana plants expressing AtSERK1 fused to yellow-fluorescent protein were generated. Fluorescence was detected predominantly at the cell periphery, most likely the plasma membrane, of cells in ovules, embryo sacs, anthers, and embryos and in seedlings. The AtSERK1 protein was detected...... in diverse cell types including the epidermis and the vascular bundles. In some cells, fluorescent receptors were seen in small vesicle-like compartments. After application of the fungal toxin Brefeldin A, the fluorescent receptors were rapidly internalized in the root meristem and root vascular tissue. We...... conclude that the AtSERK1 receptor functions in a common signalling pathway employed in both sporophytic and gametophytic cells....

Cytogenetical and ultrastructural effects of copper on root meristem cells of Allium sativum L.

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Liu, Donghua; Jiang, Wusheng; Meng, Qingmin; Zou, Jin; Gu, Jiegang; Zeng, Muai

2009-04-01

Different copper concentrations, as well as different exposure times, were applied to investigate both cytogenetical and ultrastructural alterations in garlic (Allium sativum L.) meristem cells. Results showed that the mitotic index decreased progressively when either copper concentration or exposure time increased. C-mitosis, anaphase bridges, chromosome stickiness and broken nuclei were observed in the copper treated root tip cells. Some particulates containing the argyrophilic NOR-associated proteins were distributed in the nucleus of the root-tip cells and the amount of this particulate material progressively increased with increasing exposure time. Finally, the nucleolar material was extruded from the nucleus into the cytoplasm. Also, increased dictyosome vesicles in number, formation of cytoplasmic vesicles containing electron dense granules, altered mitochondrial shape, disruption of nuclear membranes, condensation of chromatin material, disintegration of organelles were observed. The mechanisms of detoxification and tolerance of copper are briefly discussed.

Overexpression of Arabidopsis plasmodesmata germin-like proteins disrupts root growth and development.

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Ham, Byung-Kook; Li, Gang; Kang, Byung-Ho; Zeng, Fanchang; Lucas, William J

2012-09-01

In plants, a population of non-cell-autonomous proteins (NCAPs), including numerous transcription factors, move cell to cell through plasmodesmata (PD). In many cases, the intercellular trafficking of these NCAPs is regulated by their interaction with specific PD components. To gain further insight into the functions of this NCAP pathway, coimmunoprecipitation experiments were performed on a tobacco (Nicotiana tabacum) plasmodesmal-enriched cell wall protein preparation using as bait the NCAP, pumpkin (Cucurbita maxima) PHLOEM PROTEIN16 (Cm-PP16). A Cm-PP16 interaction partner, Nt-PLASMODESMAL GERMIN-LIKE PROTEIN1 (Nt-PDGLP1) was identified and shown to be a PD-located component. Arabidopsis thaliana putative orthologs, PDGLP1 and PDGLP2, were identified; expression studies indicated that, postgermination, these proteins were preferentially expressed in the root system. The PDGLP1 signal peptide was shown to function in localization to the PD by a novel mechanism involving the endoplasmic reticulum-Golgi secretory pathway. Overexpression of various tagged versions altered root meristem function, leading to reduced primary root but enhanced lateral root growth. This effect on root growth was corrected with an inability of these chimeric proteins to form stable PD-localized complexes. PDGLP1 and PDGLP2 appear to be involved in regulating primary root growth by controlling phloem-mediated allocation of resources between the primary and lateral root meristems.

miR396 affects mycorrhization and root meristem activity in the legume Medicago truncatula.

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Bazin, Jérémie; Khan, Ghazanfar Abbas; Combier, Jean-Philippe; Bustos-Sanmamed, Pilar; Debernardi, Juan Manuel; Rodriguez, Ramiro; Sorin, Céline; Palatnik, Javier; Hartmann, Caroline; Crespi, Martin; Lelandais-Brière, Christine

2013-06-01

The root system is crucial for acquisition of resources from the soil. In legumes, the efficiency of mineral and water uptake by the roots may be reinforced due to establishment of symbiotic relationships with mycorrhizal fungi and interactions with soil rhizobia. Here, we investigated the role of miR396 in regulating the architecture of the root system and in symbiotic interactions in the model legume Medicago truncatula. Analyses with promoter-GUS fusions suggested that the mtr-miR396a and miR396b genes are highly expressed in root tips, preferentially in the transition zone, and display distinct expression profiles during lateral root and nodule development. Transgenic roots of composite plants that over-express the miR396b precursor showed lower expression of six growth-regulating factor genes (MtGRF) and two bHLH79-like target genes, as well as reduced growth and mycorrhizal associations. miR396 inactivation by mimicry caused contrasting tendencies, with increased target expression, higher root biomass and more efficient colonization by arbuscular mycorrhizal fungi. In contrast to MtbHLH79, repression of three GRF targets by RNA interference severely impaired root growth. Early activation of mtr-miR396b, concomitant with post-transcriptional repression of MtGRF5 expression, was also observed in response to exogenous brassinosteroids. Growth limitation in miR396 over-expressing roots correlated with a reduction in cell-cycle gene expression and the number of dividing cells in the root apical meristem. These results link the miR396 network to the regulation of root growth and mycorrhizal associations in plants. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

CLE peptides regulate lateral root development in response to nitrogen nutritional status of plants.

Science.gov (United States)

Araya, Takao; von Wirén, Nicolaus; Takahashi, Hideki

2014-01-01

CLE (CLAVATA3/embryo surrounding region (ESR)) peptides control meristem functions in plants. Our recent study highlights the critical role of a peptide-receptor signaling module composed of nitrogen (N)-responsive CLE peptides and the CLAVATA1 (CLV1) leucine-rich repeat receptor-like kinase in controlling lateral root development in Arabidopsis thaliana. CLE1, -3, -4 and -7 are expressed in root pericycle cells in Arabidopsis roots under N-limited growth conditions. Overexpression of these CLE genes inhibits lateral root emergence from the primary root. The inhibitory action of N-responsive CLE peptides on lateral root development requires the function of CLV1 expressed in phloem companion cells in roots, suggesting that downstream signals are transferred through phloem for systemic regulation of root system architecture. An additional mechanism downstream of CLV1 feedback-regulates transcript levels of N-responsive CLE genes in roots for fine-tuning the signal amplitude.

An aeroponic culture system for the study of root herbivory on Arabidopsis thaliana

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Vaughan Martha M

2011-03-01

Full Text Available Abstract Background Plant defense against herbivory has been studied primarily in aerial tissues. However, complex defense mechanisms have evolved in all parts of the plant to combat herbivore attack and these mechanisms are likely to differ in the aerial and subterranean environment. Research investigating defense responses belowground has been hindered by experimental difficulties associated with the accessibility and quality of root tissue and the lack of bioassays using model plants with altered defense profiles. Results We have developed an aeroponic culture system based on a calcined clay substrate that allows insect herbivores to feed on plant roots while providing easy recovery of the root tissue. The culture method was validated by a root-herbivore system developed for Arabidopsis thaliana and the herbivore Bradysia spp. (fungus gnat. Arabidopsis root mass obtained from aeroponically grown plants was comparable to that from other culture systems, and the plants were morphologically normal. Bradysia larvae caused considerable root damage resulting in reduced root biomass and water absorption. After feeding on the aeroponically grown root tissue, the larvae pupated and emerged as adults. Root damage of mature plants cultivated in aeroponic substrate was compared to that of Arabidopsis seedlings grown in potting mix. Seedlings were notably more susceptible to Bradysia feeding than mature plants and showed decreased overall growth and survival rates. Conclusions A root-herbivore system consisting of Arabidopsis thaliana and larvae of the opportunistic herbivore Bradysia spp. has been established that mimics herbivory in the rhizosphere. Bradysia infestation of Arabidopsis grown in this culture system significantly affects plant performance. The culture method will allow simple profiling and in vivo functional analysis of root defenses such as chemical defense metabolites that are released in response to belowground insect attack.

Sites and regulation of auxin biosynthesis in Arabidopsis roots.

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Ljung, Karin; Hull, Anna K; Celenza, John; Yamada, Masashi; Estelle, Mark; Normanly, Jennifer; Sandberg, Göran

2005-04-01

Auxin has been shown to be important for many aspects of root development, including initiation and emergence of lateral roots, patterning of the root apical meristem, gravitropism, and root elongation. Auxin biosynthesis occurs in both aerial portions of the plant and in roots; thus, the auxin required for root development could come from either source, or both. To monitor putative internal sites of auxin synthesis in the root, a method for measuring indole-3-acetic acid (IAA) biosynthesis with tissue resolution was developed. We monitored IAA synthesis in 0.5- to 2-mm sections of Arabidopsis thaliana roots and were able to identify an important auxin source in the meristematic region of the primary root tip as well as in the tips of emerged lateral roots. Lower but significant synthesis capacity was observed in tissues upward from the tip, showing that the root contains multiple auxin sources. Root-localized IAA synthesis was diminished in a cyp79B2 cyp79B3 double knockout, suggesting an important role for Trp-dependent IAA synthesis pathways in the root. We present a model for how the primary root is supplied with auxin during early seedling development.

Ethylene-auxin interactions regulate lateral root initiation and emergence in Arabidopsis thaliana.

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Ivanchenko, Maria G; Muday, Gloria K; Dubrovsky, Joseph G

2008-07-01

Plant root systems display considerable plasticity in response to endogenous and environmental signals. Auxin stimulates pericycle cells within elongating primary roots to enter de novo organogenesis, leading to the establishment of new lateral root meristems. Crosstalk between auxin and ethylene in root elongation has been demonstrated, but interactions between these hormones in root branching are not well characterized. We find that enhanced ethylene synthesis, resulting from the application of low concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), promotes the initiation of lateral root primordia. Treatment with higher doses of ACC strongly inhibits the ability of pericycle cells to initiate new lateral root primordia, but promotes the emergence of existing lateral root primordia: behaviour that is also seen in the eto1 mutation. These effects are correlated with decreased pericycle cell length and increased lateral root primordia cell width. When auxin is applied simultaneously with ACC, ACC is unable to prevent the auxin stimulation of lateral root formation in the root tissues formed prior to ACC exposure. However, in root tissues formed after transfer to ACC, in which elongation is reduced, auxin does not rescue the ethylene inhibition of primordia initiation, but instead increases it by several fold. Mutations that block auxin responses, slr1 and arf7 arf19, render initiation of lateral root primordia insensitive to the promoting effect of low ethylene levels, and mutations that inhibit ethylene-stimulated auxin biosynthesis, wei2 and wei7, reduce the inhibitory effect of higher ethylene levels, consistent with ethylene regulating root branching through interactions with auxin.

Cytokinin-Deficient Transgenic Arabidopsis Plants Show Multiple Developmental Alterations Indicating Opposite Functions of Cytokinins in the Regulation of Shoot and Root Meristem Activity

Czech Academy of Sciences Publication Activity Database

Werner, T.; Motyka, Václav; Laucou, V.; Smets, R.; Onckelen, H. V.; Schmülling, T.

2003-01-01

Roč. 15, č. 11 (2003), s. 2532-2550 ISSN 1040-4651 R&D Projects: GA AV ČR IAA6038002 Institutional research plan: CEZ:AV0Z5038910 Keywords : Transgenic Arabidopsis Plants * Cytokinins * Root Meristem Activity Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 10.679, year: 2003

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

International Nuclear Information System (INIS)

Lee-Ho, E.; Walton, L.J.; Reid, D.M.; Yeung, E.C.; Kurepin, L.V.

2007-01-01

Plant root growth is known to be influenced by higher levels of atmospheric carbon dioxide (CO 2 ). Roots of some species grown in hydroponics under elevated CO 2 concentrations may be more competitive sinks for photosynthetic assimilates than roots grown under lower CO 2 conditions. Root branching patterns may also be influenced by elevated CO 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 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 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 2 had longer roots, more lateral root growth than plants grown in ambient CO 2 . Roots in elevated CO 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 2 . In addition, the increase in sucrose concentration had a bigger effect on root morphology under ambient, than elevated CO 2 . Therefore, both elevated CO 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

Nitrate induction of root hair density is mediated by TGA1/TGA4 and CPC transcription factors in Arabidopsis thaliana.

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Canales, Javier; Contreras-López, Orlando; Álvarez, José M; Gutiérrez, Rodrigo A

2017-10-01

Root hairs are specialized cells that are important for nutrient uptake. It is well established that nutrients such as phosphate have a great influence on root hair development in many plant species. Here we investigated the role of nitrate on root hair development at a physiological and molecular level. We showed that nitrate increases root hair density in Arabidopsis thaliana. We found that two different root hair defective mutants have significantly less nitrate than wild-type plants, suggesting that in A. thaliana root hairs have an important role in the capacity to acquire nitrate. Nitrate reductase-null mutants exhibited nitrate-dependent root hair phenotypes comparable with wild-type plants, indicating that nitrate is the signal that leads to increased formation of root hairs. We examined the role of two key regulators of root hair cell fate, CPC and WER, in response to nitrate treatments. Phenotypic analyses of these mutants showed that CPC is essential for nitrate-induced responses of root hair development. Moreover, we showed that NRT1.1 and TGA1/TGA4 are required for pathways that induce root hair development by suppression of longitudinal elongation of trichoblast cells in response to nitrate treatments. Our results prompted a model where nitrate signaling via TGA1/TGA4 directly regulates the CPC root hair cell fate specification gene to increase formation of root hairs in A. thaliana. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

Bacillus subtilis Early Colonization of Arabidopsis thaliana Roots Involves Multiple Chemotaxis Receptors.

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Allard-Massicotte, Rosalie; Tessier, Laurence; Lécuyer, Frédéric; Lakshmanan, Venkatachalam; Lucier, Jean-François; Garneau, Daniel; Caudwell, Larissa; Vlamakis, Hera; Bais, Harsh P; Beauregard, Pascale B

2016-11-29

Colonization of plant roots by Bacillus subtilis is mutually beneficial to plants and bacteria. Plants can secrete up to 30% of their fixed carbon via root exudates, thereby feeding the bacteria, and in return the associated B. subtilis bacteria provide the plant with many growth-promoting traits. Formation of a biofilm on the root by matrix-producing B. subtilis is a well-established requirement for long-term colonization. However, we observed that cells start forming a biofilm only several hours after motile cells first settle on the plant. We also found that intact chemotaxis machinery is required for early root colonization by B. subtilis and for plant protection. Arabidopsis thaliana root exudates attract B. subtilis in vitro, an activity mediated by the two characterized chemoreceptors, McpB and McpC, as well as by the orphan receptor TlpC. Nonetheless, bacteria lacking these chemoreceptors are still able to colonize the root, suggesting that other chemoreceptors might also play a role in this process. These observations suggest that A. thaliana actively recruits B. subtilis through root-secreted molecules, and our results stress the important roles of B. subtilis chemoreceptors for efficient colonization of plants in natural environments. These results demonstrate a remarkable strategy adapted by beneficial rhizobacteria to utilize carbon-rich root exudates, which may facilitate rhizobacterial colonization and a mutualistic association with the host. Bacillus subtilis is a plant growth-promoting rhizobacterium that establishes robust interactions with roots. Many studies have now demonstrated that biofilm formation is required for long-term colonization. However, we observed that motile B. subtilis mediates the first contact with the roots. These cells differentiate into biofilm-producing cells only several hours after the bacteria first contact the root. Our study reveals that intact chemotaxis machinery is required for the bacteria to reach the

Genetic and Phenotypic Analysis of Lateral Root Development in Arabidopsis thaliana.

Science.gov (United States)

Napsucialy-Mendivil, Selene; Dubrovsky, Joseph G

2018-01-01

Root system formation to a great extent depends on lateral root (LR) formation. In Arabidopsis thaliana, LRs are initiated within a parent root in pericycle that is an external tissue of the stele. LR initiation takes place in a strictly acropetal pattern, whereas posterior lateral root primordium (LRP) formation is asynchronous. In this chapter, we focus on methods of genetic and phenotypic analysis of LR initiation, LRP morphogenesis, and LR emergence in Arabidopsis. We provide details on how to make cleared root preparations and how to identify the LRP stages. We also pay attention to the categorization of the LRP developmental stages and their variations and to the normalization of the number of LRs and LRPs formed, per length of the primary root, and per number of cells produced within a root. Hormonal misbalances and mutations affect LRP morphogenesis significantly, and the evaluation of LRP abnormalities is addressed as well. Finally, we deal with various molecular markers that can be used for genetic and phenotypic analyses of LR development.

Analysis of AtGUS1 and AtGUS2 in Arabidopsis root apex by a highly sensitive TSA-MISH method.

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Bruno, Leonardo; Ronchini, Matteo; Gagliardi, Olimpia; Corinti, Tamara; Chiappetta, Adriana; Gerola, Paolo; Bitonti, Maria B

2015-01-01

A new highly sensitive whole-mount in situ hybridization method, based on tyramide signal amplification (TSA-MISH) was developed and a combined GFP detection and TSA-MISH procedure was applied for the first time in plants, to precisely define the spatial pattern of AtGUS1 and AtGUS2 expression in the root apex. β-glucuronidases (GUSs) belonging to the glycosyl hydrolases (GHs) 79 family, are widely distributed in plants, but their functional role has not yet been fully investigated. In the model system Arabidopsis Thaliana, three different AtGUS genes have been identified which encode proteins with putative different fates. Endogenous GUS expression has been detected in different organs and tissues, but the cyto-histological domains of gene expression remain unclear. The results here reported show co-expression of AtGUS1 and AtGUS2 in different functional zones of the root apex (the cap central zone, the root cap meristem, the staminal cell niche and the cortical cell layers of the proximal meristem), while AtGUS2 is exclusively expressed in the cap peripheral layer and in the epidermis in the elongation zone. Interestingly, both genes are not expressed in the stelar portion of the proximal meristem. A spatial (cortex vs. stele) and temporal (proximal meristem vs. transition zone) regulation of AtGUS1 and AtGUS2 expression is therefore active in the root apex. This expression pattern, although globally consistent with the involvement of GUS activity in both cell proliferation and elongation, clearly indicates that AtGUS1 and AtGUS2 could control distinct downstream process depending on the developmental context and the interaction with other players of root growth control. In the future, the newly developed approaches may well be very useful to dissect such interactions.

Identification of novel miRNAs and miRNA dependent developmental shifts of gene expression in Arabidopsis thaliana.

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Shuhua Zhan

Full Text Available microRNAs (miRNAs are small, endogenous RNAs of 20 approximately 25 nucleotides, processed from stem-loop regions of longer RNA precursors. Plant miRNAs act as negative regulators of target mRNAs predominately by slicing target transcripts, and a number of miRNAs play important roles in development. We analyzed a number of published datasets from Arabidopsis thaliana to characterize novel miRNAs, novel miRNA targets, and miRNA-regulated developmental changes in gene expression. These data include microarray profiling data and small RNA (sRNA deep sequencing data derived from miRNA biogenesis/transport mutants, microarray profiling data of mRNAs in a developmental series, and computational predictions of conserved genomic stem-loop structures. Our conservative analyses identified five novel mature miRNAs and seven miRNA targets, including one novel target gene. Two complementary miRNAs that target distinct mRNAs were encoded by one gene. We found that genes targeted by known miRNAs, and genes up-regulated or down-regulated in miRNA mutant inflorescences, are highly expressed in the wild type inflorescence. In addition, transcripts upregulated within the mutant inflorescences were abundant in wild type leaves and shoot meristems and low in pollen and seed. Downregulated transcripts were abundant in wild type pollen and seed and low in shoot meristems, roots and leaves. Thus, disrupting miRNA function causes the inflorescence transcriptome to resemble the leaf and meristem and to differ from pollen and seed. Applications of our computational approach to other species and the use of more liberal criteria than reported here will further expand the number of identified miRNAs and miRNA targets. Our findings suggest that miRNAs have a global role in promoting vegetative to reproductive transitions in A. thaliana.

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.

Repression of Lateral Organ Boundary Genes by PENNYWISE and POUND-FOOLISH Is Essential for Meristem Maintenance and Flowering in Arabidopsis.

Science.gov (United States)

Khan, Madiha; Ragni, Laura; Tabb, Paul; Salasini, Brenda C; Chatfield, Steven; Datla, Raju; Lock, John; Kuai, Xiahezi; Després, Charles; Proveniers, Marcel; Yongguo, Cao; Xiang, Daoquan; Morin, Halima; Rullière, Jean-Pierre; Citerne, Sylvie; Hepworth, Shelley R; Pautot, Véronique

2015-11-01

In the model plant Arabidopsis (Arabidopsis thaliana), endogenous and environmental signals acting on the shoot apical meristem cause acquisition of inflorescence meristem fate. This results in changed patterns of aerial development seen as the transition from making leaves to the production of flowers separated by elongated internodes. Two related BEL1-like homeobox genes, PENNYWISE (PNY) and POUND-FOOLISH (PNF), fulfill this transition. Loss of function of these genes impairs stem cell maintenance and blocks internode elongation and flowering. We show here that pny pnf apices misexpress lateral organ boundary genes BLADE-ON-PETIOLE1/2 (BOP1/2) and KNOTTED-LIKE FROM ARABIDOPSIS THALIANA6 (KNAT6) together with ARABIDOPSIS THALIANA HOMEOBOX GENE1 (ATH1). Inactivation of genes in this module fully rescues pny pnf defects. We further show that BOP1 directly activates ATH1, whereas activation of KNAT6 is indirect. The pny pnf restoration correlates with renewed accumulation of transcripts conferring floral meristem identity, including FD, SQUAMOSA PROMOTER-BINDING PROTEIN LIKE genes, LEAFY, and APETALA1. To gain insight into how this module blocks flowering, we analyzed the transcriptome of BOP1-overexpressing plants. Our data suggest a central role for the microRNA156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE-microRNA172 module in integrating stress signals conferred in part by promotion of jasmonic acid biosynthesis. These data reveal a potential mechanism by which repression of lateral organ boundary genes by PNY-PNF is essential for flowering. © 2015 American Society of Plant Biologists. All Rights Reserved.

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. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Cis-regulatory PLETHORA promoter elements directing root and nodule expression are conserved between Arabidopsis thaliana and Medicago truncatula

NARCIS (Netherlands)

Franssen, H.G.J.M.; Kulikova, O.; Willemsen, V.A.; Heidstra, R.

2017-01-01

Nodules are unique organs formed on roots of legumes by soil-borne bacteria, collectively known as rhizobium. Recently, we have shown that orthologs of the AINTEGUMENTA-like (AIL) AP2 transcription factors PLETHORA (PLT) 1 to 4, that redundantly regulate Arabidopsis thaliana root development are

Requirement of B2-Type Cyclin-Dependent Kinases for Meristem Integrity in Arabidopsis thaliana

Czech Academy of Sciences Publication Activity Database

Andersen, S.U.; Buechel, S.; Zhao, Z.; Ljung, K.; Novák, Ondřej; Busch, W.; Schuster, Ch.; Lohmann, J.U.

2008-01-01

Roč. 20, č. 1 (2008), s. 88-100 ISSN 1040-4651 Institutional research plan: CEZ:AV0Z50380511 Keywords : SHOOT APICAL MERISTEM * CELL-CYCLE * PLANT DEVELOPMENT Subject RIV: CE - Biochemistry Impact factor: 9.296, year: 2008

Brachytic2/ZmABCB1 functions in IAA export from intercalary meristems

Science.gov (United States)

Knöller, Anne Sophie; Richards, Elizabeth L.; Peer, Wendy Ann; Murphy, Angus S.

2010-01-01

Dwarfism traits in Zea mays are regulated by multiple factors including the hormone auxin. Dwarf brachytic2 (br2) mutants harbour lesions in the gene encoding an orthologue of Arabidopsis thaliana ABCB1 which functions in auxin efflux out of meristematic regions in the shoot and root. br2 mesocotyls and coleoptiles exhibit reduced auxin transport. However, the dwarf stature of br2 derives from shortened lower internodes whilst the upper portion of the plant is completely normal. As such, it is counter-intuitive to attribute br2 dwarfism exclusively to reduced auxin export out of the shoot apex. Arabidopsis abcb1 mutants exhibit only minor reductions in auxin transport and plant height unless combined with mutations in the ABCB19 auxin transporter. Phylogenetic modelling analysis excludes the possibility that BR2 is more closely related to ABCB19 which has three more closely related orthologues in maize. BR2 is expressed in nodal meristems, and analyses of auxin transport and content indicate that BR2 function in these grass-specific tissues is analogous to ABCB1 function in the shoot and root apex of Arabidopsis. These results indicate that ABCB1/BR2 function is conserved between dicots and monocots, but also suggests that this function must be understood in the context of the segmental organization of grass plants. PMID:20581123

Caffeine-Induced Premature Chromosome Condensation Results in the Apoptosis-Like Programmed Cell Death in Root Meristems of Vicia faba.

Directory of Open Access Journals (Sweden)

Dorota Rybaczek

Full Text Available We have demonstrated that the activation of apoptosis-like programmed cell death (AL-PCD was a secondary result of caffeine (CF induced premature chromosome condensation (PCC in hydroxyurea-synchronized Vicia faba root meristem cells. Initiation of the apoptotic-like cell degradation pathway seemed to be the result of DNA damage generated by treatment with hydroxyurea (HU [double-stranded breaks (DSBs mostly] and co-treatment with HU/CF [single-stranded breaks (SSBs mainly]. A single chromosome comet assay was successfully used to study different types of DNA damage (neutral variant-DSBs versus alkaline-DSBs or SSBs. The immunocytochemical detection of H2AXS139Ph and PARP-2 were used as markers for DSBs and SSBs, respectively. Acridine orange and ethidium bromide (AO/EB were applied for quantitative immunofluorescence measurements of dead, dying and living cells. Apoptotic-type DNA fragmentation and positive TUNEL reaction finally proved that CF triggers AL-PCD in stressed V. faba root meristem cells. In addition, the results obtained under transmission electron microscopy (TEM further revealed apoptotic-like features at the ultrastructural level of PCC-type cells: (i extensive vacuolization; (ii abnormal chromatin condensation, its marginalization and concomitant degradation; (iii formation of autophagy-like vesicles (iv protoplast shrinkage (v fragmentation of cell nuclei and (vi extensive degeneration of the cells. The results obtained have been discussed with respect to the vacuolar/autolytic type of plant-specific AL-PCD.

Revealing the importance of meristems and roots for the development of hypersensitive responses and full foliar resistance to Phytophthora infestans in the resistant potato cultivar Sarpo Mira

DEFF Research Database (Denmark)

Orlowska, Elzbieta Zofia; Basile, Alessio; Kandzia, Izabela

2012-01-01

The defence responses of potato against Phytophthora infestans were studied using the highly resistant Sarpo Mira cultivar. The effects of plant integrity, meristems, and roots on the hypersensitive response (HR), plant resistance, and the regulation of PR genes were analysed. Sarpo Mira shoots a...

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

Science.gov (United States)

Araya, Takao; Kubo, Takuya; von Wirén, Nicolaus; Takahashi, Hideki

2016-03-01

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 architecture 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 generated for statistical analyses. Regression analyses unraveled key parameters associated with: (i) inhibition of primary root growth under nitrogen limitation or on ammonium; (ii) rapid progression of lateral root emergence in response to ammonium; and (iii) 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. © 2015 Institute of Botany, Chinese Academy of Sciences.

Effect of modeled microgravity on radiation-induced adaptive response of root growth in Arabidopsis thaliana

International Nuclear Information System (INIS)

Deng, Chenguang; Wang, Ting; Wu, Jingjing; Xu, Wei; Li, Huasheng; Liu, Min

2017-01-01

Highlights: • The radio-adaptive response (RAR) of A. thaliana root growth is modulated in microgravity. • The DNA damage repairs in RAR are regulated by microgravity. • The phytohormone auxin plays a regulatory role in the modulation of microgravity on RAR of root growth. - Abstract: Space particles have an inevitable impact on organisms during space missions; radio-adaptive response (RAR) is a critical radiation effect due to both low-dose background and sudden high-dose radiation exposure during solar storms. Although it is relevant to consider RAR within the context of microgravity, another major space environmental factor, there is no existing evidence as to its effects on RAR. In the present study, we established an experimental method for detecting the effects of gamma-irradiation on the primary root growth of Arabidopsis thaliana, in which RAR of root growth was significantly induced by several dose combinations. Microgravity was simulated using a two-dimensional rotation clinostat. It was shown that RAR of root growth was significantly inhibited under the modeled microgravity condition, and was absent in pgm-1 plants that had impaired gravity sensing in root tips. These results suggest that RAR could be modulated in microgravity. Time course analysis showed that microgravity affected either the development of radio-resistance induced by priming irradiation, or the responses of plants to challenging irradiation. After treatment with the modeled microgravity, attenuation in priming irradiation-induced expressions of DNA repair genes (AtKu70 and AtRAD54), and reduced DNA repair efficiency in response to challenging irradiation were observed. In plant roots, the polar transportation of the phytohormone auxin is regulated by gravity, and treatment with an exogenous auxin (indole-3-acetic acid) prevented the induction of RAR of root growth, suggesting that auxin might play a regulatory role in the interaction between microgravity and RAR of root growth.

Effect of modeled microgravity on radiation-induced adaptive response of root growth in Arabidopsis thaliana

Energy Technology Data Exchange (ETDEWEB)

Deng, Chenguang [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences (China); Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province (China); Institute of Technical Biology and Agriculture Engineering, Chinese Academy of Sciences, 350 Shushanhu Road, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Wang, Ting [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences (China); Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province (China); Institute of Technical Biology and Agriculture Engineering, Chinese Academy of Sciences, 350 Shushanhu Road, Hefei 230031 (China); Wu, Jingjing [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences (China); Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province (China); Institute of Technical Biology and Agriculture Engineering, Chinese Academy of Sciences, 350 Shushanhu Road, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Xu, Wei [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences (China); Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province (China); Institute of Technical Biology and Agriculture Engineering, Chinese Academy of Sciences, 350 Shushanhu Road, Hefei 230031 (China); Li, Huasheng; Liu, Min [China Space Molecular Biological Lab, China Academy of Space Technology, Beijing 100086 (China); and others

2017-02-15

Highlights: • The radio-adaptive response (RAR) of A. thaliana root growth is modulated in microgravity. • The DNA damage repairs in RAR are regulated by microgravity. • The phytohormone auxin plays a regulatory role in the modulation of microgravity on RAR of root growth. - Abstract: Space particles have an inevitable impact on organisms during space missions; radio-adaptive response (RAR) is a critical radiation effect due to both low-dose background and sudden high-dose radiation exposure during solar storms. Although it is relevant to consider RAR within the context of microgravity, another major space environmental factor, there is no existing evidence as to its effects on RAR. In the present study, we established an experimental method for detecting the effects of gamma-irradiation on the primary root growth of Arabidopsis thaliana, in which RAR of root growth was significantly induced by several dose combinations. Microgravity was simulated using a two-dimensional rotation clinostat. It was shown that RAR of root growth was significantly inhibited under the modeled microgravity condition, and was absent in pgm-1 plants that had impaired gravity sensing in root tips. These results suggest that RAR could be modulated in microgravity. Time course analysis showed that microgravity affected either the development of radio-resistance induced by priming irradiation, or the responses of plants to challenging irradiation. After treatment with the modeled microgravity, attenuation in priming irradiation-induced expressions of DNA repair genes (AtKu70 and AtRAD54), and reduced DNA repair efficiency in response to challenging irradiation were observed. In plant roots, the polar transportation of the phytohormone auxin is regulated by gravity, and treatment with an exogenous auxin (indole-3-acetic acid) prevented the induction of RAR of root growth, suggesting that auxin might play a regulatory role in the interaction between microgravity and RAR of root growth.

Effects of 5-fluorouracil on the mitotic activity of onion root tips apical meristem

Directory of Open Access Journals (Sweden)

Waldemar Lechowicz

2015-01-01

Full Text Available The effects of various concentrations of 5-FU on the mitotic activity of onion root tips apical meristem were investigated during 24-hour incubation in 5-FU and postincubation in water. The incubation in 5-FU caused a reversible inhibition of mitotic activity, and waves of the partially synchronised mitoses were observed during the period of postincubation. The most pronounced synchronisation of mitoses was obtained after incubation in 100 mg/l. 5-FU but the mitotic index of the resumed mitotic activity amounted to only one half of the control value. 5-FU was found to cause some cytological changes in meristematic cells such as enlargement of the nucleoli, change in the interphasic nuclei structure, appearance of subchromatid and chromatid aberrations and micronuclei. The effects of 5-FU on nucleic acids and the cell division cycle ace discussed and compared with the effects of 5-FUdR.

Multimodal nonlinear imaging of arabidopsis thaliana root cell

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Jang, Bumjoon; Lee, Sung-Ho; Woo, Sooah; Park, Jong-Hyun; Lee, Myeong Min; Park, Seung-Han

2017-07-01

Nonlinear optical microscopy has enabled the possibility to explore inside the living organisms. It utilizes ultrashort laser pulse with long wavelength (greater than 800nm). Ultrashort pulse produces high peak power to induce nonlinear optical phenomenon such as two-photon excitation fluorescence (TPEF) and harmonic generations in the medium while maintaining relatively low average energy pre area. In plant developmental biology, confocal microscopy is widely used in plant cell imaging after the development of biological fluorescence labels in mid-1990s. However, fluorescence labeling itself affects the sample and the sample deviates from intact condition especially when labelling the entire cell. In this work, we report the dynamic images of Arabidopsis thaliana root cells. This demonstrates the multimodal nonlinear optical microscopy is an effective tool for long-term plant cell imaging.

Meristem culture and subsequent micropropagation of Chilean strawberry (Fragaria chiloensis (L.) Duch.).

Science.gov (United States)

Quiroz, Karla A; Berríos, Miguel; Carrasco, Basilio; Retamales, Jorge B; Caligari, Peter D S; García-Gonzáles, Rolando

2017-06-02

Vegetative propagation of Fragaria sp. is traditionally carried out using stolons. This system of propagation, in addition to being slow, can spread plant diseases, particularly serious being viral. In vitro culture of meristems and the establishment of micropropagation protocols are important tools for solving these problems. In recent years, considerable effort has been made to develop in vitro propagation of the commercial strawberry in order to produce virus-free plants of high quality. These previous results can serve as the basis for developing in vitro-based propagation technologies in the less studied species Fragaria chiloensis. In this context, we studied the cultivation of meristems and establishment of a micropropagation protocol for F. chiloensis. The addition of polyvinylpyrrolidone (PVP) improved the meristem regeneration efficiency of F. chiloensis accessions. Similarly, the use of 6-benzylaminopurine (BAP) in the culture media increased the average rate of multiplication to 3-6 shoots per plant. In addition, the use of 6-benzylaminopurine (BAP), had low levels (near zero) of explant losses due to oxidation. However, plant height as well as number of leaves and roots were higher in media without growth regulators, with average values of 0.5 cm, 9 leaves and 4 roots per plant. For the first time in Chilean strawberry, meristem culture demonstrated to be an efficient tool for eliminating virus from infected plants, giving the possibility to produce disease free propagation material. Also, the addition of PVP into the basal MS medium improved the efficiency of plant recovery from isolated meristems. Farmers can now access to high quality plant material produced by biotech tools which will improve their technological practices.

Novel features of radiation-induced bystander signaling in Arabidopsis thaliana demonstrated using root micro-grafting

Science.gov (United States)

Wang, Ting; Li, Fanghua; Xu, Wei; Bian, Po; Wu, Yuejin; Wu, Lijun

2012-01-01

Radiation-induced bystander effects (RIBE) have been well demonstrated in whole organisms, as well as in single-cell culture models in vitro and multi-cellular tissues models in vitro, however, the underlying mechanisms remain unclear, including the temporal and spatial course of bystander signaling. The RIBE in vivo has been shown to exist in the model plant Arabidopsis thaliana (A. thaliana). Importantly, the unique plant grafting provides a delicate approach for studying the temporal and spatial course of bystander signaling in the context of whole plants. In our previous study, the time course of bystander signaling in plants has been well demonstrated using the root micro-grafting technique. In this study, we further investigated the temporal cooperation pattern of multiple bystander signals, the directionality of bystander signaling, and the effect of bystander tissues on the bystander signaling. The results showed that the bystander response could also be induced efficiently when the asynchronously generated bystander signals reached the bystander tissues in the same period, but not when they entered into the bystander tissues in an inversed sequence. The absence of bystander response in root-inversed grafting indicated that the bystander signaling along roots might be of directionality. The bystander signaling was shown to be independent of the bystander tissues. PMID:23072991

Increased root hair density by loss of WRKY6 in Arabidopsis thaliana

Directory of Open Access Journals (Sweden)

Markus G. Stetter

2017-01-01

Full Text Available Root hairs are unicellular elongations of certain rhizodermal cells that improve the uptake of sparingly soluble and immobile soil nutrients. Among different Arabidopsis thaliana genotypes, root hair density, length and the local acclimation to low inorganic phosphate (Pi differs considerably, when analyzed on split agar plates. Here, genome-wide association fine mapping identified significant single nucleotide polymorphisms associated with the increased root hair density in the absence of local phosphate on chromosome 1. A loss-of-functionmutant of the candidate transcription factor gene WRKY6, which is involved in the acclimation of plants to low phosphorus, had increased root hair density. This is partially explained by a reduced cortical cell diameter in wrky6-3, reducing the rhizodermal cell numbers adjacent to the cortical cells. As a consequence, rhizodermal cells in positions that are in contact with two cortical cells are found more often, leading to higher hair density. Distinct cortical cell diameters and epidermal cell lengths distinguish other Arabidopsis accessions with distinct root hair density and −Pi response from diploid Col-0, while tetraploid Col-0 had generally larger root cell sizes, which explain longer hairs. A distinct radial root morphology within Arabidopsis accessions and wrky6-3explains some, but not all, differences in the root hair acclimation to –Pi.

Regulation of root development in Arabidopsis thaliana by phytohormone-secreting epiphytic methylobacteria.

Science.gov (United States)

Klikno, Jana; Kutschera, Ulrich

2017-09-01

In numerous experimental studies, seedlings of the model dicot Arabidopsis thaliana have been raised on sterile mineral salt agar. However, under natural conditions, no plant has ever grown in an environment without bacteria. Here, we document that germ-free (gnotobiotic) seedlings, raised on mineral salt agar without sucrose, develop very short root hairs. In the presence of a soil extract that contains naturally occurring microbes, root hair elongation is promoted; this effect can be mimicked by the addition of methylobacteria to germ-free seedlings. Using five different bacterial species (Methylobacterium mesophilicum, Methylobacterium extorquens, Methylobacterium oryzae, Methylobacterium podarium, and Methylobacterium radiotolerans), we show that, over 9 days of seedling development in a light-dark cycle, root development (hair elongation, length of the primary root, branching patterns) is regulated by these epiphytic microbes that occur in the rhizosphere of field-grown plants. In a sterile liquid culture test system, auxin (IAA) inhibited root growth with little effect on hair elongation and significantly stimulated hypocotyl enlargement. Cytokinins (trans-zeatin, kinetin) and ethylene (application of the precursor ACC) likewise exerted an inhibitory effect on root growth but, in contrast to IAA, drastically stimulated root hair elongation. Methylobacteria are phytosymbionts that produce/secrete cytokinins. We conclude that, under real-world conditions (soil), the provision of these phytohormones by methylobacteria (and other epiphytic microbes) regulates root development during seedling establishment.

Inhibition of primary roots and stimulation of lateral root development in Arabidopsis thaliana by the rhizobacterium Serratia marcescens 90-166 is through both auxin-dependent and -independent signaling pathways.

Science.gov (United States)

Shi, Chun-Lin; Park, Hyo-Bee; Lee, Jong Suk; Ryu, Sangryeol; Ryu, Choong-Min

2010-03-01

The rhizobacterium Serratia marcescens strain 90-166 was previously reported to promote plant growth and induce resistance in Arabidopsis thaliana. In this study, the influence of strain 90-166 on root development was studied in vitro. We observed inhibition of primary root elongation, enhanced lateral root emergence, and early emergence of second order lateral roots after inoculation with strain 90-166 at a certain distance from the root. Using the DR5::GUS transgenic A. thaliana plant and an auxin transport inhibitor, N-1-naphthylphthalamic acid, the altered root development was still elicited by strain 90-166, indicating that this was not a result of changes in plant auxin levels. Intriguingly, indole-3-acetic acid, a major auxin chemical, was only identified just above the detection limit in liquid culture of strain 90-166 using liquid chromatography-mass spectrometry. Focusing on bacterial determinants of the root alterations, we found that primary root elongation was inhibited in seedlings treated with cell supernatant (secreted compounds), while lateral root formation was induced in seedlings treated with lysate supernatant (intracellular compounds). Further study revealed that the alteration of root development elicited by strain 90-166 involved the jasmonate, ethylene, and salicylic acid signaling pathways. Collectively, our results suggest that strain 90-166 can contribute to plant root development via multiple signaling pathways.

Cytokinin response factors regulate PIN-FORMED auxin transporters

Czech Academy of Sciences Publication Activity Database

Šimášková, M.; O'Brien, J.A.; Khan, M.; Van Noorden, G.; Ötvös, K.; Vieten, A.; De Clercq, E.; Van Haperen, J.M.A.; Cuesta, C.; Hoyerová, Klára; Vanneste, S.; Marhavý, P.; Wabnik, K.; Van Breusegem, F.; Nowack, M.; Murphy, A.; Friml, J.; Weijers, D.; Beeckman, T.; Benková, E.

2015-01-01

Roč. 6, NOV (2015), s. 8717 ISSN 2041-1723 Institutional support: RVO:61389030 Keywords : ARABIDOPSIS -THALIANA * ROOT-MERISTEM * TRANSCRIPTION FACTORS Subject RIV: ED - Physiology Impact factor: 11.329, year: 2015

Dose rate, mitotic cycle duration, and sensitivity of cell transitions from G1 → S and G2 → M to protracted gamma radiation in root meristems

International Nuclear Information System (INIS)

Evans, L.S.; Hof, J.V.

1975-01-01

Experiments were designed to determine the relative radiosensitivity of the cell transition points of G1 → S and G2 → M in root meristems of several plant species. Label and mitotic indices and microspectrophotometry were used to measure the proportions of cells in each mitotic cycle stage in root meristems after protracted gamma radiation. The criterion of radiosensitivity was the dose rate needed to produce a tissue with less than 1 percent cells in S and none in M after 3 days of continuous exposure. The results show that DNA is the primary radiation target in proliferative root meristems and that the cycle duration stipulates the time interval of vulnerability. In each species, nonrandom reproducible cell proportions were established with 2C:4C:8C amounts of nuclear DNA after 3 days of exposure. Roots of Helianthus annuus, Crepis capillaris, and Tradescantia clone 02 had 80 percent cells with a 2C amount of DNA and 20 percent had a 4C amount of DNA. In these species the transition point of G1 → S was more radiosensitive than G2 → M. Roots of Pisum sativum and Triticum aestivum had cell proportions at 2C:4C:8C amounts of DNA in frequencies of 0.10 to 0.20:0.40 to 0.60:0.30 to 0.40. In these two species 0.30 to 0.40 cells underwent radiation-induced endoreduplication that resulted from a rapid inhibition of cell transit from G2 → M and a slower impairment of G1 → S. Cells increased from 2C to 4C and from 4C to 8C amounts of DNA during irradiation. The proportions of nuclei with 2C:4C:8C amounts of DNA were dependent in part upon the relative radiosensitivity of the G1 → S and G2 → M control points. The data show the relative radiosensitivity of the transition points from G1 → S and from G2 → M was species specific and unrelated to the cycle duration and mean nuclear DNA content of the plant species

S-nitrosoglutathione promotes cell wall remodelling, alters the transcriptional profile and induces root hair formation in the hairless root hair defective 6 (rhd6) mutant of Arabidopsis thaliana.

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Moro, Camila Fernandes; Gaspar, Marilia; da Silva, Felipe Rodrigues; Pattathil, Sivakumar; Hahn, Michael G; Salgado, Ione; Braga, Marcia Regina

2017-03-01

Nitric oxide (NO) exerts pleiotropic effects on plant development; however, its involvement in cell wall modification during root hair formation (RHF) has not yet been addressed. Here, mutants of Arabidopsis thaliana with altered root hair phenotypes were used to assess the involvement of S-nitrosoglutathione (GSNO), the primary NO source, in cell wall dynamics and gene expression in roots induced to form hairs. GSNO and auxin restored the root hair phenotype of the hairless root hair defective 6 (rhd6) mutant. A positive correlation was observed between increased NO production and RHF induced by auxin in rhd6 and transparent testa glabra (ttg) mutants. Deposition of an epitope within rhamnogalacturonan-I recognized by the CCRC-M2 antibody was delayed in root hair cells (trichoblasts) compared with nonhair cells (atrichoblasts). GSNO, but not auxin, restored the wild-type root glycome and transcriptome profiles in rhd6, modulating the expression of a large number of genes related to cell wall composition and metabolism, as well as those encoding ribosomal proteins, DNA and histone-modifying enzymes and proteins involved in post-translational modification. Our results demonstrate that NO plays a key role in cell wall remodelling in trichoblasts and suggest that it also participates in chromatin modification in root cells of A. thaliana. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Low glutathione regulates gene expression and the redox potentials of the nucleus and cytosol in Arabidopsis thaliana.

Science.gov (United States)

Schnaubelt, Daniel; Queval, Guillaume; Dong, Yingping; Diaz-Vivancos, Pedro; Makgopa, Matome Eugene; Howell, Gareth; De Simone, Ambra; Bai, Juan; Hannah, Matthew A; Foyer, Christine H

2015-02-01

Reduced glutathione (GSH) is considered to exert a strong influence on cellular redox homeostasis and to regulate gene expression, but these processes remain poorly characterized. Severe GSH depletion specifically inhibited root meristem development, while low root GSH levels decreased lateral root densities. The redox potential of the nucleus and cytosol of Arabidopsis thaliana roots determined using roGFP probes was between -300 and -320 mV. Growth in the presence of the GSH-synthesis inhibitor buthionine sulfoximine (BSO) increased the nuclear and cytosolic redox potentials to approximately -260 mV. GSH-responsive genes including transcription factors (SPATULA, MYB15, MYB75), proteins involved in cell division, redox regulation (glutaredoxinS17, thioredoxins, ACHT5 and TH8) and auxin signalling (HECATE), were identified in the GSH-deficient root meristemless 1-1 (rml1-1) mutant, and in other GSH-synthesis mutants (rax1-1, cad2-1, pad2-1) as well as in the wild type following the addition of BSO. Inhibition of auxin transport had no effect on organ GSH levels, but exogenous auxin decreased the root GSH pool. We conclude that GSH depletion significantly increases the redox potentials of the nucleus and cytosol, and causes arrest of the cell cycle in roots but not shoots, with accompanying transcript changes linked to altered hormone responses, but not oxidative stress. © 2013 John Wiley & Sons Ltd.

Lateral root formation and the multiple roles of auxin.

Science.gov (United States)

Du, Yujuan; Scheres, Ben

2018-01-04

Root systems can display variable architectures that contribute to survival strategies of plants. The model plant Arabidopsis thaliana possesses a tap root system, in which the primary root and lateral roots (LRs) are major architectural determinants. The phytohormone auxin fulfils multiple roles throughout LR development. In this review, we summarize recent advances in our understanding of four aspects of LR formation: (i) LR positioning, which determines the spatial distribution of lateral root primordia (LRP) and LRs along primary roots; (ii) LR initiation, encompassing the activation of nuclear migration in specified lateral root founder cells (LRFCs) up to the first asymmetric cell division; (iii) LR outgrowth, the 'primordium-intrinsic' patterning of de novo organ tissues and a meristem; and (iv) LR emergence, an interaction between LRP and overlaying tissues to allow passage through cell layers. We discuss how auxin signaling, embedded in a changing developmental context, plays important roles in all four phases. In addition, we discuss how rapid progress in gene network identification and analysis, modeling, and four-dimensional imaging techniques have led to an increasingly detailed understanding of the dynamic regulatory networks that control LR development. © The Author(s) 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Round-shape gold nanoparticles: effect of particle size and concentration on Arabidopsis thaliana root growth

Czech Academy of Sciences Publication Activity Database

Siegel, J.; Záruba, K.; Švorčík, V.; Kroumanová, Kristýna; Burketová, Lenka; Martinec, Jan

2018-01-01

Roč. 13, APR 10 (2018), č. článku 95. ISSN 1556-276X R&D Projects: GA ČR GA17-10907S; GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:61389030 Keywords : Arabidopsis thaliana * Concentration * Gold nanoparticles * Root growth * Size Subject RIV: JJ - Other Materials OBOR OECD: Plant sciences, botany Impact factor: 2.833, year: 2016

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

Science.gov (United States)

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

2015-05-12

Telomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at the stem cells. The defects in meristem and stem cell renewal observed in tert mutants demonstrate that telomere lengthening by TERT sets a replicative limit in the root meristem. Conversely, the long telomeres of the columella cells and the premature stem cell differentiation plt1,2 mutants suggest that differentiation can prevent telomere erosion. Overall, our results indicate that telomere dynamics are coupled to meristem activity and continuous growth, disclosing a critical association between telomere length, stem cell function, and the extended lifespan of plants. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Genotoxic Effects of Diuron Contaminated Soil on the Root Meristem Cells of Allium sativum: A Possible Mechanism of Chromosome Damage.

Science.gov (United States)

Saxena, P N; Chauhan, L K S; Chandra, Saurabh; Gupta, S K

2004-01-01

Diuron, a persistant substituted urea herbicide, was tested in the root meristem cells of Allium sativum for the possible cytogenetic effects and to compare the sensitivity with Allium cepa. Test concentrations of diuron 22.5, 45.0, and 90.0 ppm were mixed in soil and the cloves of A. sativum were placed over diuron-contaminated soils. Root meristematic cells were sampled at 48 h to score Mitotic/Chromosomal aberrations and to analyze the effect on mitotic index (MI). Microscopic analyses revealed significant and dose-dependent induction of mitotic as well as chromosomal breaks. The frequency of mitotic aberrations was every time found much higher than that of chromosomal aberrations. Mild percentage of Micronucleated and Binucleated cells was observed, as MI also declined during the analysis. Based on the data of valence charge densities on the atoms of herbicide molecule and spectroscopic studies, a possible mechanism of interaction of diuron with DNA molecule for chromosomal aberrations has been proposed.

Characteristics of a root hair-less line of Arabidopsis thaliana under physiological stresses.

Science.gov (United States)

Tanaka, Natsuki; Kato, Mariko; Tomioka, Rie; Kurata, Rie; Fukao, Yoichiro; Aoyama, Takashi; Maeshima, Masayoshi

2014-04-01

The plasma membrane-associated Ca(2+)-binding protein-2 of Arabidopsis thaliana is involved in the growth of root hair tips. Several transgenic lines that overexpress the 23 residue N-terminal domain of this protein under the control of the root hair-specific EXPANSIN A7 promoter lack root hairs completely. The role of root hairs under normal and stress conditions was examined in one of these root hair-less lines (NR23). Compared with the wild type, NR23 showed a 47% reduction in water absorption, decreased drought tolerance, and a lower ability to adapt to heat. Growth of NR23 was suppressed in media deficient in phosphorus, iron, calcium, zinc, copper, or potassium. Also, the content of an individual mineral in NR23 grown in normal medium, or in medium lacking a specific mineral, was relatively low. In wild-type plants, the primary and lateral roots produce numerous root hairs that become elongated under phosphate-deficient conditions; NR23 did not produce root hairs. Although several isoforms of the plasma membrane phosphate transporters including PHT1;1-PHT1;6 were markedly induced after growth in phosphate-deficient medium, the levels induced in NR23 were less than half those observed in the wild type. In phosphate-deficient medium, the amounts of acid phosphatase, malate, and citrate secreted from NR23 roots were 38, 9, and 16% of the levels secreted from wild-type roots. The present results suggest that root hairs play significant roles in the absorption of water and several minerals, secretion of acid phosphatase(s) and organic acids, and in penetration of the primary roots into gels.

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.

Primary root protophloem differentiation requires balanced phosphatidylinositol-4,5-biphosphate levels and systemically affects root branching.

NARCIS (Netherlands)

Rodriguez-Villalon, A.; Gujas, B.; van Wijk, R.; Munnik, T.; Hardtke, C.S.

2015-01-01

Protophloem is a specialized vascular tissue in growing plant organs, such as root meristems. In Arabidopsis mutants with impaired primary root protophloem differentiation, brevis radix (brx) and octopus (ops), meristematic activity and consequently overall root growth are strongly reduced. Second

FON2 SPARE1 redundantly regulates floral meristem maintenance with FLORAL ORGAN NUMBER2 in rice.

Directory of Open Access Journals (Sweden)

Takuya Suzaki

2009-10-01

Full Text Available CLAVATA signaling restricts stem cell identity in the shoot apical meristem (SAM in Arabidopsis thaliana. In rice (Oryza sativa, FLORAL ORGAN NUMBER2 (FON2, closely related to CLV3, is involved as a signaling molecule in a similar pathway to negatively regulate stem cell proliferation in the floral meristem (FM. Here we show that the FON2 SPARE1 (FOS1 gene encoding a CLE protein functions along with FON2 in maintenance of the FM. In addition, FOS1 appears to be involved in maintenance of the SAM in the vegetative phase, because constitutive expression of FOS1 caused termination of the vegetative SAM. Genetic analysis revealed that FOS1 does not need FON1, the putative receptor of FON2, for its action, suggesting that FOS1 and FON2 may function in meristem maintenance as signaling molecules in independent pathways. Initially, we identified FOS1 as a suppressor that originates from O. sativa indica and suppresses the fon2 mutation in O. sativa japonica. FOS1 function in japonica appears to be compromised by a functional nucleotide polymorphism (FNP at the putative processing site of the signal peptide. Sequence comparison of FOS1 in about 150 domesticated rice and wild rice species indicates that this FNP is present only in japonica, suggesting that redundant regulation by FOS1 and FON2 is commonplace in species in the Oryza genus. Distribution of the FNP also suggests that this mutation may have occurred during the divergence of japonica from its wild ancestor. Stem cell maintenance may be regulated by at least three negative pathways in rice, and each pathway may contribute differently to this regulation depending on the type of the meristem. This situation contrasts with that in Arabidopsis, where CLV signaling is the major single pathway in all meristems.

Mild salinity stimulates a stress-induced morphogenic response in Arabidopsis thaliana roots.

Science.gov (United States)

Zolla, Gaston; Heimer, Yair M; Barak, Simon

2010-01-01

Plant roots exhibit remarkable developmental plasticity in response to local soil conditions. It is shown here that mild salt stress stimulates a stress-induced morphogenic response (SIMR) in Arabidopsis thaliana roots characteristic of several other abiotic stresses: the proliferation of lateral roots (LRs) with a concomitant reduction in LR and primary root length. The LR proliferation component of the salt SIMR is dramatically enhanced by the transfer of seedlings from a low to a high NO3- medium, thereby compensating for the decreased LR length and maintaining overall LR surface area. Increased LR proliferation is specific to salt stress (osmotic stress alone has no stimulatory effect) and is due to the progression of more LR primordia from the pre-emergence to the emergence stage, in salt-stressed plants. In salt-stressed seedlings, greater numbers of LR primordia exhibit expression of a reporter gene driven by the auxin-sensitive DR5 promoter than in unstressed seedlings. Moreover, in the auxin transporter mutant aux1-7, the LR proliferation component of the salt SIMR is completely abrogated. The results suggest that salt stress promotes auxin accumulation in developing primordia thereby preventing their developmental arrest at the pre-emergence stage. Examination of ABA and ethylene mutants revealed that ABA synthesis and a factor involved in the ethylene signalling network also regulate the LR proliferation component of the salt SIMR.

Towards systems biology of the gravity response of higher plants -multiscale analysis of Arabidopsis thaliana root growth

Science.gov (United States)

Palme, Klaus; Aubry, D.; Bensch, M.; Schmidt, T.; Ronneberger, O.; Neu, C.; Li, X.; Wang, H.; Santos, F.; Wang, B.; Paponov, I.; Ditengou, F. A.; Teale, W. T.; Volkmann, D.; Baluska, F.; Nonis, A.; Trevisan, S.; Ruperti, B.; Dovzhenko, A.

Gravity plays a fundamental role in plant growth and development. Up to now, little is known about the molecular organisation of the signal transduction cascades and networks which co-ordinate gravity perception and response. By using an integrated systems biological approach, a systems analysis of gravity perception and the subsequent tightly-regulated growth response is planned in the model plant Arabidopsis thaliana. This approach will address questions such as: (i) what are the components of gravity signal transduction pathways? (ii) what are the dynamics of these components? (iii) what is their spatio-temporal regulation in different tis-sues? Using Arabidopsis thaliana as a model-we use root growth to obtain insights in the gravity response. New techniques enable identification of the individual genes affected by grav-ity and further integration of transcriptomics and proteomics data into interaction networks and cell communication events that operate during gravitropic curvature. Using systematic multiscale analysis we have identified regulatory networks consisting of transcription factors, the protein degradation machinery, vesicle trafficking and cellular signalling during the gravire-sponse. We developed approach allowing to incorporate key features of the root system across all relevant spatial and temporal scales to describe gene-expression patterns and correlate them with individual gene and protein functions. Combination of high-resolution microscopy and novel computational tools resulted in development of the root 3D model in which quantitative descriptions of cellular network properties and of multicellular interactions important in root growth and gravitropism can be integrated for the first time.

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

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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. © 2014 Institute of Botany, Chinese Academy of Sciences.

Exaggerated root respiration accounts for growth retardation in a starchless mutant of Arabidopsis thaliana.

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Brauner, Katrin; Hörmiller, Imke; Nägele, Thomas; Heyer, Arnd G

2014-07-01

The knock-out mutation of plastidial phosphoglucomutase (pgm) causes a starchless phenotype in Arabidopsis thaliana, and results in a severe growth reduction of plants cultivated under diurnal conditions. It has been speculated that high soluble sugar levels accumulating during the light phase in leaf mesophyll might cause a reduction of photosynthetic activity or that shortage of reduced carbon during the night is the reason for the slow biomass gain of pgm. Separate simultaneous measurements of leaf net photosynthesis and root respiration demonstrate that photosynthetic activity per unit fresh weight is not reduced in pgm, whereas root respiration is strongly elevated. Comparison with a mutant defective in the dominating vacuolar invertase (AtβFruct4) revealed that high sucrose concentration in the cytosol, but not in the vacuole, of leaf cells is responsible for elevated assimilate transport to the root. Increased sugar supply to the root, as observed in pgm mutants, forces substantial respiratory losses. Because root respiration accounts for 80% of total plant respiration under long-day conditions, this gives rise to retarded biomass formation. In contrast, reduced vacuolar invertase activity leads to reduced net photosynthesis in the shoot and lowered root respiration, and affords an increased root/shoot ratio. The results demonstrate that roots have very limited capacity for carbon storage but exert rigid control of supply for their maintenance metabolism. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Arabidopsis thaliana as a tool to identify traits involved in Verticillium dahliae biocontrol by the olive root endophyte Pseudomonas fluorescens PICF7

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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.

Evidence that L-glutamate can act as an exogenous signal to modulate root growth and branching in Arabidopsis thaliana.

Science.gov (United States)

Walch-Liu, Pia; Liu, Lai-Hua; Remans, Tony; Tester, Mark; Forde, Brian G

2006-08-01

The roots of many plant species are known to use inorganic nitrogen, in the form of , as a cue to initiate localized root proliferation within nutrient-rich patches of soil. We report here that, at micromolar concentrations and in a genotype-dependent manner, exogenous l-glutamate is also able to elicit complex changes in Arabidopsis root development. l-Glutamate is perceived specifically at the primary root tip and inhibits mitotic activity in the root apical meristem, but does not interfere with lateral root initiation or outgrowth. Only some time after emergence do lateral roots acquire l-glutamate sensitivity, indicating that their ability to respond to l-glutamate is developmentally regulated. Comparisons between different Arabidopsis ecotypes revealed a remarkable degree of natural variation in l-glutamate sensitivity, with C24 being the most sensitive. The aux1-7 auxin transport mutant had reduced l-glutamate sensitivity, suggesting a possible interaction between l-glutamate and auxin signaling. Surprisingly, two loss-of-function mutants at the AXR1 locus (axr1-3 and axr1-12) were hypersensitive to l-glutamate. A pharmacological approach, using agonists and antagonists of mammalian ionotropic glutamate receptors, was unable to provide evidence of a role for their plant homologs in sensing exogenous glutamate. We discuss the mechanism of l-glutamate sensing and the possible ecological significance of the observed l-glutamate-elicited changes in root architecture.

Regeneration of roots from callus reveals stability of the developmental program for determinate root growth in Sonoran Desert Cactaceae.

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Shishkova, Svetlana; García-Mendoza, Edith; Castillo-Díaz, Vicente; Moreno, Norma E; Arellano, Jesús; Dubrovsky, Joseph G

2007-05-01

In some Sonoran Desert Cactaceae the primary root has a determinate root growth: the cells of the root apical meristem undergo only a few cell division cycles and then differentiate. The determinate growth of primary roots in Cactaceae was found in plants cultivated under various growth conditions, and could not be reverted by any treatment tested. The mechanisms involved in root meristem maintenance and determinate root growth in plants remain poorly understood. In this study, we have shown that roots regenerated from the callus of two Cactaceae species, Stenocereus gummosus and Ferocactus peninsulae, have a determinate growth pattern, similar to that of the primary root. To demonstrate this, a protocol for root regeneration from callus was established. The determinate growth pattern of roots regenerated from callus suggests that the program of root development is very stable in these species. These findings will permit future analysis of the role of certain Cactaceae genes in the determinate pattern of root growth via the regeneration of transgenic roots from transformed calli.

GENE EXPRESSION CHANGES IN ARABIDOPSIS THALIANA SEEDLING ROOTS EXPOSED TO THE MUNITION HEXAHYDRO-1,3,5-TRINITRO-1,3,5-TRIAZINE

Science.gov (United States)

Arabidopsis thaliana root transcriptome responses to the munition, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), were assessed using serial analysis of gene expression (SAGE). Comparison of the transcriptional profile for the RDX response to a profile previously described for Ar...

Embryonic origin of the Arabidopsis primary root and root meristem initials

NARCIS (Netherlands)

Scheres, B.J.G.; Wolkenfelt, H.; Willemsen, V.; Terlouw, M.; Lawson, E.; Dean, C.; Weisbeek, P.

1994-01-01

The embryonic origin of the Arabidopsis root and hypocotyl region has been investigated using histological techniques and clonal analysis. Our data reveal the pattern of cell division in the embryo giving rise to the various initials within the root promeristem. A small region of the root at its

Cytotoxicity of Cheese and Cheddar Cheese food flavorings on Allim cepa L root meristems

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A. G. Moura

Full Text Available Abstract Despite their great importance for the food industry, flavorings, in general, raise a number of questions regarding their cytotoxicity, mutagenicity and carcinogenicity, since, in the literature, there are few studies found evaluating the toxicity on the systemic and cellular level, of these chemical compounds. The root meristems of Allium cepa (onion are widely used for the assessment of toxicity of chemical compounds of interest. Thus, this study aimed to evaluate, in A. cepa meristematic cells, individually and in combination at the cellular level, the toxicity of synthetic Cheese and Cheddar Cheese food flavorings, identical to the natural, at doses of 1.0 and 2.0 mL, at exposure times of 24 and 48 hours. In combination we used 0.5 mL of Cheese flavor associated with 0.5 mL of Cheddar flavor; and 1.0 mL of Cheese flavor associated with 1.0 mL of Cheddar flavor, at exposure times of 24 and 48 hours. For these evaluations, we used groups of five onion bulbs, which were first embedded in distilled water and then transferred to their respective doses. The root tips were collected and fixed in acetic acid (3:1 for 24 hours. The slides were prepared by crushing and were stained with 2% acetic orcein. Cells were analyzed throughout the cell cycle, totaling 5,000 for each control and exposure time. The mitotic indices calculated and cellular aberrations observed were subjected to statistical analysis using the chi-square test (p <0.05. No chromosomal abnormalities nor those of mitotic spindle were observed for the treatments performed. The results, both individually and in combination, showed that the flavorings under study significantly reduced the cell division rate of the test system cells used. Therefore, under the conditions studied, the two flavorings were cytotoxic.

Agave tequilana MADS genes show novel expression patterns in meristems, developing bulbils and floral organs.

Science.gov (United States)

Delgado Sandoval, Silvia del Carmen; Abraham Juárez, María Jazmín; Simpson, June

2012-03-01

Agave tequilana is a monocarpic perennial species that flowers after 5-8 years of vegetative growth signaling the end of the plant's life cycle. When fertilization is unsuccessful, vegetative bulbils are induced on the umbels of the inflorescence near the bracteoles from newly formed meristems. Although the regulation of inflorescence and flower development has been described in detail for monocarpic annuals and polycarpic species, little is known at the molecular level for these processes in monocarpic perennials, and few studies have been carried out on bulbils. Histological samples revealed the early induction of umbel meristems soon after the initiation of the vegetative to inflorescence transition in A. tequilana. To identify candidate genes involved in the regulation of floral induction, a search for MADS-box transcription factor ESTs was conducted using an A. tequilana transcriptome database. Seven different MIKC MADS genes classified into 6 different types were identified based on previously characterized A. thaliana and O. sativa MADS genes and sequences from non-grass monocotyledons. Quantitative real-time PCR analysis of the seven candidate MADS genes in vegetative, inflorescence, bulbil and floral tissues uncovered novel patterns of expression for some of the genes in comparison with orthologous genes characterized in other species. In situ hybridization studies using two different genes showed expression in specific tissues of vegetative meristems and floral buds. Distinct MADS gene regulatory patterns in A. tequilana may be related to the specific reproductive strategies employed by this species.

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

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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

Potential bud bank responses to apical meristem damage and environmental variables: matching or complementing axillary meristems?

Science.gov (United States)

Klimešová, Jitka; Malíková, Lenka; Rosenthal, Jonathan; Šmilauer, Petr

2014-01-01

Soil nutrients, dormant axillary meristem availability, and competition can influence plant tolerance to damage. However, the role of potential bud banks (adventitious meristems initiated only after injury) is not known. Examining Central European field populations of 22 species of short-lived monocarpic herbs exposed to various sources of damage, we hypothesized that: (1) with increasing injury severity, the number of axillary branches would decrease, due to axillary meristem limitation, whereas the number of adventitious shoots (typically induced by severe injury) would increase; (2) favorable environmental conditions would allow intact plants to branch more, resulting in stronger axillary meristem limitation than in unfavorable conditions; and (3) consequently, adventitious sprouting would be better enabled in favorable than unfavorable conditions. We found strong support for the first hypothesis, only limited support for the second, and none for the third. Our results imply that whereas soil nutrients and competition marginally influence plant tolerance to damage, potential bud banks enable plants to overcome meristem limitation from severe damage, and therefore better tolerate it. All the significant effects were found in intraspecific comparisons, whereas interspecific differences were not found. Monocarpic plants with potential bud banks therefore represent a distinct strategy occupying a narrow environmental niche. The disturbance regime typical for this niche remains to be examined, as do the costs associated with the banks of adventitious and axillary reserve meristems.

Potential bud bank responses to apical meristem damage and environmental variables: matching or complementing axillary meristems?

Directory of Open Access Journals (Sweden)

Jitka Klimešová

Full Text Available Soil nutrients, dormant axillary meristem availability, and competition can influence plant tolerance to damage. However, the role of potential bud banks (adventitious meristems initiated only after injury is not known. Examining Central European field populations of 22 species of short-lived monocarpic herbs exposed to various sources of damage, we hypothesized that: (1 with increasing injury severity, the number of axillary branches would decrease, due to axillary meristem limitation, whereas the number of adventitious shoots (typically induced by severe injury would increase; (2 favorable environmental conditions would allow intact plants to branch more, resulting in stronger axillary meristem limitation than in unfavorable conditions; and (3 consequently, adventitious sprouting would be better enabled in favorable than unfavorable conditions. We found strong support for the first hypothesis, only limited support for the second, and none for the third. Our results imply that whereas soil nutrients and competition marginally influence plant tolerance to damage, potential bud banks enable plants to overcome meristem limitation from severe damage, and therefore better tolerate it. All the significant effects were found in intraspecific comparisons, whereas interspecific differences were not found. Monocarpic plants with potential bud banks therefore represent a distinct strategy occupying a narrow environmental niche. The disturbance regime typical for this niche remains to be examined, as do the costs associated with the banks of adventitious and axillary reserve meristems.

Regulation of Arabidopsis root development by nitrate availability.

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Zhang, H; Forde, B G

2000-01-01

When the root systems of many plant species are exposed to a localized source of nitrate (NO3- they respond by proliferating their lateral roots to colonize the nutrient-rich zone. This study reviews recent work with Arabidopsis thaliana in which molecular genetic approaches are being used to try to understand the physiological and genetic basis for this response. These studies have led to the conclusion that there are two distinct pathways by which NO3- modulates root branching in Arabidopsis. On the one hand, meristematic activity in lateral root tips is stimulated by direct contact with an enriched source of NO3- (the localized stimulatory effect). On the other, a critical stage in the development of the lateral root (just after its emergence from the primary root) is highly susceptible to inhibition by a systemic signal that is related to the amount of NO3- absorbed by the plant (the systemic inhibitory effect). Evidence has been obtained that the localized stimulatory effect is a direct effect of the NO3- ion itself rather than a nutritional effect. A NO3(-)-inducible MADS-box gene (ANR1) has been identified which encodes a component of the signal transduction pathway linking the external NO3- supply to the increased rate of lateral root elongation. Experiments using auxin-resistant mutants have provided evidence for an overlap between the auxin and NO3- response pathways in the control of lateral root elongation. The systemic inhibitory effect, which does not affect lateral root initiation but delays the activation of the lateral root meristem, appears to be positively correlated with the N status of the plant and is postulated to involve a phloem-mediated signal from the shoot.

Belowground neighbor perception in Arabidopsis thaliana studied by transcriptome analysis: roots of Hieracium pilosella cause biotic stress

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Christoph eSchmid

2013-08-01

Full Text Available Root-root interactions are much more sophisticated than previously thought, yet the mechanisms of belowground neighbor perception remain largely obscure. Genome-wide transcriptome analyses allow detailed insight into plant reactions to environmental cues.A root interaction trial was set up to explore both morphological and whole genome transcriptional responses in roots of Arabidopsis thaliana in the presence or absence of an inferior competitor, Hieracium pilosella.Neighbor perception was indicated by Arabidopsis roots predominantly growing away from the neighbor (segregation, while solitary plants placed more roots towards the middle of the pot. Total biomass remained unaffected. Database comparisons in transcriptome analysis revealed considerable similarity between Arabidopsis root reactions to neighbors and reactions to pathogens. Detailed analyses of the functional category ‘biotic stress’ using MapMan tools found the sub-category ‘pathogenesis-related proteins’ highly significantly induced. A comparison to a study on intraspecific competition brought forward a core of genes consistently involved in reactions to neighbor roots.We conclude that beyond resource depletion roots perceive neighboring roots or their associated microorganisms by a relatively uniform mechanism that involves the strong induction of pathogenesis-related proteins. In an ecological context the findings reveal that belowground neighbor detection may occur independently of resource depletion, allowing for a time advantage for the root to prepare for potential interactions.

Qualitative and quantitative modifications of root mitochondria during senescence of above-ground parts of Arabidopis thaliana.

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Fanello, Diego Darío; Bartoli, Carlos Guillermo; Guiamet, Juan José

2017-05-01

This work studied modifications experienced by root mitochondria during whole plant senescence or under light deprivation, using Arabidopsis thaliana plants with YFP tagged to mitochondria. During post-bolting development, root respiratory activity started to decline after aboveground organs (i.e., rosette leaves) had senesced. This suggests that carbohydrate starvation may induce root senescence. Similarly, darkening the whole plant induced a decrease in respiration of roots. This was partially due to a decrease in the number of total mitochondria (YFP-labelled mitochondria) and most probably to a decrease in the quantity of mitochondria with a developed inner membrane potential (ΔΨm, i.e., Mitotracker red- labelled mitochondria). Also, the lower amount of mitochondria with ΔΨm compared to YFP-labelled mitochondria at 10d of whole darkened plant, suggests the presence of mitochondria in a "standby state". The experiments also suggest that small mitochondria made the main contribution to the respiratory activity that was lost during root senescence. Sugar supplementation partially restored the respiration of mitochondria after 10d of whole plant dark treatment. These results suggest that root senescence is triggered by carbohydrate starvation, with loss of ΔΨm mitochondria and changes in mitochondrial size distribution. Copyright © 2017 Elsevier B.V. All rights reserved.

Multi-omics analysis identifies genes mediating the extension of cell walls in the Arabidopsis thaliana root elongation zone

DEFF Research Database (Denmark)

Wilson, Michael H; Holman, Tara J; Sørensen, Iben

2015-01-01

Plant cell wall composition is important for regulating growth rates, especially in roots. However, neither analyses of cell wall composition nor transcriptomes on their own can comprehensively reveal which genes and processes are mediating growth and cell elongation rates. This study reveals...... the benefits of carrying out multiple analyses in combination. Sections of roots from five anatomically and functionally defined zones in Arabidopsis thaliana were prepared and divided into three biological replicates. We used glycan microarrays and antibodies to identify the major classes of glycans......)cellular localization of many epitopes. Extensins were localized in epidermal and cortex cell walls, while AGP glycans were specific to different tissues from root-hair cells to the stele. The transcriptome analysis found several gene families peaking in the REZ. These included a large family of peroxidases (which...

Clastogenic adaption of Vicia faba root tip meristem cells after consecutive treatments with S-phase dependent and S-phase independent agents

International Nuclear Information System (INIS)

Heindorff, K.; Schubert, I.; Rieger, R.; Michaelis, A.

1987-01-01

Pretreatment of Vicia faba root tip meristems with low doses of S-phase independent clastogens, such as X-rays or bleomycin, prior to a high (challenge) dose of S-phase dependent clastogens, such as alkylating agents (TEM, Trenimon) or the pyridazine derivative MH, led to decreased challenge treatment-induced aberration frequencies, i.e., clastogenic adaptation. Using the inverse treatment sequence bleomycin and MH proved to be able to substitute for each other in provoking clastogenic (cross) adaptation while bleomycin and alkylating agents were unable to do so. The data support the assumption of inducible cellular functions that become triggered by low clastogen doses and additionally describe some particular properties of bleomycin when used for conditioning. Bleomycin proved to be capable to exert protection independent of the agent used for challenge treatment. (author)

MAIL1 is essential for development of the primary root but not of anchor roots

OpenAIRE

Ühlken, Christine; Hoth, Stefan; Weingartner, Magdalena

2014-01-01

MAIN-LIKE1 (MAIL1) is a ubiquitously expressed nuclear protein, which has a crucial function during root development. We have recently described loss of function mutants for MAIL1, in which the organization and function of the primary root meristem is lost soon after germination. Moreover cell differentiation is impaired resulting in primary root growth arrest soon after emergence. Here we show that mail1 mutants form several anchor roots from the hypocotyl to root junction. These anchor root...

Iron- and ferritin-dependent reactive oxygen species distribution: impact on Arabidopsis root system architecture.

Science.gov (United States)

Reyt, Guilhem; Boudouf, Soukaina; Boucherez, Jossia; Gaymard, Frédéric; Briat, Jean-Francois

2015-03-01

Iron (Fe) homeostasis is integrated with the production of reactive oxygen species (ROS), and distribution at the root tip participates in the control of root growth. Excess Fe increases ferritin abundance, enabling the storage of Fe, which contributes to protection of plants against Fe-induced oxidative stress. AtFer1 and AtFer3 are the two ferritin genes expressed in the meristematic zone, pericycle and endodermis of the Arabidopsis thaliana root, and it is in these regions that we observe Fe stained dots. This staining disappears in the triple fer1-3-4 ferritin mutant. Fe excess decreases primary root length in the same way in wild-type and in fer1-3-4 mutant. In contrast, the Fe-mediated decrease of lateral root (LR) length and density is enhanced in fer1-3-4 plants due to a defect in LR emergence. We observe that this interaction between excess Fe, ferritin, and root system architecture (RSA) is in part mediated by the H2O2/O2·- balance between the root cell proliferation and differentiation zones regulated by the UPB1 transcription factor. Meristem size is also decreased in response to Fe excess in ferritin mutant plants, implicating cell cycle arrest mediated by the ROS-activated SMR5/SMR7 cyclin-dependent kinase inhibitors pathway in the interaction between Fe and RSA. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

Transition zone cells reach G2 phase before initiating elongation in maize root apex

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M. Victoria Alarcón

2017-06-01

Full Text Available Root elongation requires cell divisions in the meristematic zone and cell elongation in the elongation zone. The boundary between dividing and elongating cells is called the transition zone. In the meristem zone, initial cells are continuously dividing, but on the basal side of the meristem cells exit the meristem through the transition zone and enter in the elongation zone, where they stop division and rapidly elongate. Throughout this journey cells are accompanied by changes in cell cycle progression. Flow cytometry analysis showed that meristematic cells are in cycle, but exit when they enter the elongation zone. In addition, the percentage of cells in G2 phase (4C strongly increased from the meristem to the elongation zone. However, we did not observe remarkable changes in the percentage of cells in cell cycle phases along the entire elongation zone. These results suggest that meristematic cells in maize root apex stop the cell cycle in G2 phase after leaving the meristem.

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.

Iron and ferritin dependent ROS distribution impact Arabidopsis root system architecture.

Science.gov (United States)

Reyt, Guilhem; Boudouf, Soukaina; Boucherez, Jossia; Gaymard, Frédéric; Briat, Jean-Franois

2014-11-09

Iron (Fe) homeostasis is integrated with the production of Reactive Oxygen Species (ROS) whose distribution at the root tip participates in the control of root growth. Excess Fe increases ferritin abundance, enabling the storage of Fe which contributes to protection of plants against Fe-induced oxidative stress. AtFer1 and AtFer3 are the two ferritin genes expressed in the meristematic zone, pericycle and endodermis of the Arabidopsis thaliana (Arabidopsis) root, and it is in these regions that we observe Fe stained dots. This staining disappears in the triple fer1-3-4 ferritin mutant. Fe excess decreases primary root length in the same way in wild-type and in fer1-3-4 mutant. In contrast, the Fe mediated decrease of lateral root (LR) length and density is enhanced in fer1-3-4 plants due to a defect in LR emergence. We observe that this interaction between excess Fe, ferritin and RSA is in part mediated by the H 2 O 2 /O 2 .- balance between the root cell proliferation and differentiation zones regulated by the UPB1 transcription factor. Further, meristem size is also decreased in response to Fe excess in ferritin mutant plants, implicating cell cycle arrest mediated by the ROS-activated SMR5/SMR7 cyclin-dependent kinase inhibitors pathway in the interaction between Fe and RSA. © The Author 2014. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.

Analyzing Arabidopsis thaliana root proteome provides insights into the molecular bases of enantioselective imazethapyr toxicity

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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.

lAA and BAP affect protein phosphorylation-dependent processes during sucrose-mediated G1 to S and G2 to M transitions in root meristem cells of Vicia faba

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Justyna Teresa Polit

2011-01-01

Full Text Available In carbohydrate-starved root meristems of Vicia faba subsp. minor, the expression of two Principal Control Points located at the final stages of the G1 (PCP1 and G2 (PCP2 phases has been found to be correlated with a marked decrease of protein phosphorylation within cell nuclei, nucleoli and cytoplasm. Adopting the same experimental model in our present studies, monoclonal FITC conjugated antibodies that recognize phosphorylated form of threonine (αTPab-FITC were used to obtain an insight about how the indole-3-acetic acid (IAA, benzyl-6-aminopurine (BAP, and the mixture of both phytohormones influence the time-course changes in an overall protein phosphorylation during sucrose-mediated PCP1→S and PCP2→M transitions. Unsuspectedly, neither IAA, BAP, nor the mixture of both phytohormones supplied in combination with sucrose did up-regulate protein phosphorylation. However using the block-and-release method, it was shown that root meristems of Vicia provided with sucrose alone indicated higher levels of αTPab-FITC. Contrarily, phytohormones supplied in combination with sucrose induced apparent decline in phosphorylation of cell proteins, which - when compared with the influence of sucrose alone - became increasingly evident in time. Thus, it seems probable, that a general decline in the amount of αTPab-FITC labeled epitopes may overlay specific phosphorylations and dephosphorylations governed by the main cell cycle kinases and phosphatases.

N,N-dimethyl hexadecylamine and related amines regulate root morphogenesis via jasmonic acid signaling in Arabidopsis thaliana.

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Raya-González, Javier; Velázquez-Becerra, Crisanto; Barrera-Ortiz, Salvador; López-Bucio, José; Valencia-Cantero, Eduardo

2017-05-01

Plant growth-promoting rhizobacteria are natural inhabitants of roots, colonize diverse monocot and dicot species, and affect several functional traits such as root architecture, adaptation to adverse environments, and protect plants from pathogens. N,N-dimethyl-hexadecylamine (C16-DMA) is a rhizobacterial amino lipid that modulates the postembryonic development of several plants, likely as part of volatile blends. In this work, we evaluated the bioactivity of C16-DMA and other related N,N-dimethyl-amines with varied length and found that inhibition of primary root growth was related to the length of the acyl chain. C16-DMA inhibited primary root growth affecting cell division and elongation, while promoting lateral root formation and root hair growth and density in Arabidopsis thaliana (Arabidopsis) wild-type (WT) seedlings. Interestingly, C16-DMA induced the expression of the jasmonic acid (JA)-responsive gene marker pLOX2:uidA, while JA-related mutants jar1, coi1-1, and myc2 affected on JA biosynthesis and perception, respectively, are compromised in C16-DMA responses. Comparison of auxin-regulated gene expression, root architectural changes in WT, and auxin-related mutants aux1-7, tir1/afb2/afb3, and arf7-1/arf19-1 to C16-DMA shows that the C16-DMA effects occur independently of auxin signaling. Together, these results reveal a novel class of aminolipids modulating root organogenesis via crosstalk with the JA signaling pathway.

Phenolics from Ageratina adenophora roots and their phytotoxic effects on Arabidopsis thaliana seed germination and seedling growth.

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Zhou, Zhong-Yu; Liu, Wan-Xue; Pei, Gang; Ren, Hui; Wang, Jing; Xu, Qiao-Lin; Xie, Hai-Hui; Wan, Fang-Hao; Tan, Jian-Wen

2013-12-04

A bioassay-directed phytochemical study was conducted to investigate potential allelochemicals in the roots of the invasive plant Ageratina adenophora. Eleven phenolic compounds, including seven new ones, 7-hydroxy-8,9-dehydrothymol 9-O-trans-ferulate (1), 7-hydroxythymol 9-O-trans-ferulate (2), 7,8-dihydroxythymol 9-O-trans-ferulate (3), 7,8-dihydroxythymol 9-O-cis-ferulate (4), methyl (7R)-3-deoxy-4,5-epoxy-D-manno-2-octulosonate 8-O-trans-p-coumarate (5), methyl (7R)-3-deoxy-4,5-epoxy-D-manno-2-octulosonate 8-O-cis-p-coumarate (6), and 3-(2-hydroxyphenyl)propyl methyl malonate (7), were isolated from a bioactive subfraction of the ethanol extract of the roots of A. adenophora. The new structures were established on the basis of detailed spectroscopic analysis. The potential phytotoxic effects of these compounds on the germination of Arabidopsis thaliana seeds were tested by a filter paper assay. Compound 7 and known compounds 3-(2-hydroxyphenyl)-1-propanol (8) and o-coumaric acid (9) remarkably showed inhibition activity against Arabidopsis seed germination at a concentration of 1.0 mM. Compounds 1, 2, 5, 6, and 10 showed slight inhibitory activity at the test concentration after treatment for 3 days, while the other compounds showed no obvious inhibitory effects. Moreover, 7-9 were further found to show obvious inhibitory activity on retarding the seedling growth of Ar. thaliana cultured in soil medium.

Mutations in Arabidopsis thaliana genes involved in the tryptophan biosynthesis pathway affect root waving on tilted agar surfaces

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Rutherford, R.; Gallois, P.; Masson, P. H.

1998-01-01

Arabidopsis thaliana roots grow in a wavy pattern upon a slanted surface. A novel mutation in the anthranilate synthase alpha 1 (ASA1) gene, named trp5-2wvc1, and mutations in the tryptophan synthase alpha and beta 1 genes (trp3-1 and trp2-1, respectively) confer a compressed root wave phenotype on tilted agar surfaces. When trp5-2wvc1 seedlings are grown on media supplemented with anthranilate metabolites, their roots wave like wild type. Genetic and pharmacological experiments argue that the compressed root wave phenotypes of trp5-2wvc1, trp2-1 and trp3-1 seedlings are not due to reduced IAA biosynthetic potential, but rather to a deficiency in L-tryptophan (L-Trp), or in a L-Trp derivative. Although the roots of 7-day-old seedlings possess higher concentrations of free L-Trp than the shoot as a whole, trp5-2wvc1 mutants show no detectable alteration in L-Trp levels in either tissue type, suggesting that a very localized shortage of L-Trp, or of a L-Trp-derived compound, is responsible for the observed phenotype.

Reactivation of meristem activity and sprout growth in potato tubers require both cytokinin and gibberellin.

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Hartmann, Anja; Senning, Melanie; Hedden, Peter; Sonnewald, Uwe; Sonnewald, Sophia

2011-02-01

Reactivation of dormant meristems is of central importance for plant fitness and survival. Due to their large meristem size, potato (Solanum tuberosum) tubers serve as a model system to study the underlying molecular processes. The phytohormones cytokinins (CK) and gibberellins (GA) play important roles in releasing potato tuber dormancy and promoting sprouting, but their mode of action in these processes is still obscure. Here, we established an in vitro assay using excised tuber buds to study the dormancy-releasing capacity of GA and CK and show that application of gibberellic acid (GA(3)) is sufficient to induce sprouting. In contrast, treatment with 6-benzylaminopurine induced bud break but did not support further sprout growth unless GA(3) was administered additionally. Transgenic potato plants expressing Arabidopsis (Arabidopsis thaliana) GA 20-oxidase or GA 2-oxidase to modify endogenous GA levels showed the expected phenotypical changes as well as slight effects on tuber sprouting. The isopentenyltransferase (IPT) from Agrobacterium tumefaciens and the Arabidopsis cytokinin oxidase/dehydrogenase1 (CKX) were exploited to modify the amounts of CK in transgenic potato plants. IPT expression promoted earlier sprouting in vitro. Strikingly, CKX-expressing tubers exhibited a prolonged dormancy period and did not respond to GA(3). This supports an essential role of CK in terminating tuber dormancy and indicates that GA is not sufficient to break dormancy in the absence of CK. GA(3)-treated wild-type and CKX-expressing tuber buds were subjected to a transcriptome analysis that revealed transcriptional changes in several functional groups, including cell wall metabolism, cell cycle, and auxin and ethylene signaling, denoting events associated with the reactivation of dormant meristems.

Identifying the transition to the maturation zone in three ecotypes of Arabidopsis thaliana roots.

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Cajero Sánchez, Wendy; García-Ponce, Berenice; Sánchez, María de la Paz; Álvarez-Buylla, Elena R; Garay-Arroyo, Adriana

2018-01-01

The Arabidopsis thaliana (hereafter Arabidopsis) root has become a useful model for studying how organ morphogenesis emerge from the coordination and balance of cell proliferation and differentiation, as both processes may be observed and quantified in the root at different stages of development. Hence, being able to objectively identify and delimit the different stages of root development has been very important. Up to now, three different zones along the longitudinal axis of the primary root of Arabidopsis, have been identified: the root apical meristematic zone (RAM) with two domains [the proliferative (PD) and the transition domain (TD)], the elongation zone (EZ) and the maturation zone (MZ). We previously reported a method to quantify the length of the cells of the meristematic and the elongation zone, as well as the boundaries or transitions between the root domains along the growing part of the Arabidopsis root. In this study, we provide a more accurate criterion to identify the MZ. Traditionally, the transition between the EZ to the MZ has been established by the emergence of the first root-hair bulge in the epidermis, because this emergence coincides with cell maturation in this cell type. But we have found here that after the emergence of the first root-hair bulge some cells continue to elongate and we have confirmed this in three different Arabidopsis ecotypes. We established the limit between the EZ and the MZ by looking for the closest cortical cell with a longer length than the average cell length of 10 cells after the cortical cell closest to the epidermal cell with the first root-hair bulge in these three ecotypes. In Col-0 and Ws this cell is four cells above the one with the root hair bulge and, in the Ler ecotype, this cell is five cells above. To unambiguously identifying the site at which cells stop elongating and attain their final length and fate at the MZ, we propose to calculate the length of completely elongated cortical cells counting 10

Primary root protophloem differentiation requires balanced phosphatidylinositol-4,5-biphosphate levels and systemically affects root branching.

OpenAIRE

Rodriguez-Villalon Antia; Gujas Bojan; van Wijk Ringo; Munnik Teun; Hardtke Christian S

2015-01-01

Protophloem is a specialized vascular tissue in growing plant organs, such as root meristems. In Arabidopsis mutants with impaired primary root protophloem differentiation, brevis radix (brx) and octopus (ops), meristematic activity and consequently overall root growth are strongly reduced. Second site mutation in the protophloem-specific presumed phosphoinositide 5-phosphatase cotyledon vascular pattern 2 (CVP2), but not in its homolog CVP2-like 1 (CVL1), partially rescues brx defects. Consi...

Cell fate regulation in the shoot meristem.

Science.gov (United States)

Laux, T; Mayer, K F

1998-04-01

The shoot meristem is a proliferative centre containing pluripotent stem cells that are the ultimate source of all cells and organs continuously added to the growing shoot. The progeny of the stem cells have two developmental options, either to renew the stem cell population or to leave the meristem and to differentiate, possibly according to signals from more mature tissue. The destiny of each cell depends on its position within the dynamic shoot meristem. Genetic data suggest a simple model in which graded positional information is provided by antagonistic gene functions and is interpreted by genes which regulate cell fate.

N-MYC down-regulated-like proteins regulate meristem initiation by modulating auxin transport and MAX2 expression.

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Mudgil, Yashwanti; Ghawana, Sanjay; Jones, Alan M

2013-01-01

N-MYC down-regulated-like (NDL) proteins interact with the Gβ subunit (AGB1) of the heterotrimeric G protein complex and play an important role in AGB1-dependent regulation of lateral root formation by affecting root auxin transport, auxin gradients and the steady-state levels of mRNA encoding the PIN-FORMED 2 and AUXIN 1 auxin transport facilitators. Auxin transport in aerial tissue follows different paths and utilizes different transporters than in roots; therefore, in the present study, we analyzed whether NDL proteins play an important role in AGB1-dependent, auxin-mediated meristem development. Expression levels of NDL gene family members need to be tightly regulated, and altered expression (both over-expression and down-regulation) confers ectopic growth. Over-expression of NDL1 disrupts vegetative and reproductive organ development. Reduced expression of the NDL gene family members results in asymmetric leaf emergence, twinning of rosette leaves, defects in leaf formation, and abnormal silique distribution. Reduced expression of the NDL genes in the agb1-2 (null allele) mutant rescues some of the abnormal phenotypes, such as silique morphology, silique distribution, and peduncle angle, suggesting that proper levels of NDL proteins are maintained by AGB1. We found that all of these abnormal aerial phenotypes due to altered NDL expression were associated with increases in basipetal auxin transport, altered auxin maxima and altered MAX2 expression within the inflorescence stem. NDL proteins, together with AGB1, act as positive regulators of meristem initiation and branching. AGB1 and NDL1 positively regulate basipetal inflorescence auxin transport and modulate MAX2 expression in shoots, which in turn regulates organ and lateral meristem formation by the establishment and maintenance of auxin gradients.

N-MYC down-regulated-like proteins regulate meristem initiation by modulating auxin transport and MAX2 expression.

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Yashwanti Mudgil

Full Text Available N-MYC down-regulated-like (NDL proteins interact with the Gβ subunit (AGB1 of the heterotrimeric G protein complex and play an important role in AGB1-dependent regulation of lateral root formation by affecting root auxin transport, auxin gradients and the steady-state levels of mRNA encoding the PIN-FORMED 2 and AUXIN 1 auxin transport facilitators. Auxin transport in aerial tissue follows different paths and utilizes different transporters than in roots; therefore, in the present study, we analyzed whether NDL proteins play an important role in AGB1-dependent, auxin-mediated meristem development.Expression levels of NDL gene family members need to be tightly regulated, and altered expression (both over-expression and down-regulation confers ectopic growth. Over-expression of NDL1 disrupts vegetative and reproductive organ development. Reduced expression of the NDL gene family members results in asymmetric leaf emergence, twinning of rosette leaves, defects in leaf formation, and abnormal silique distribution. Reduced expression of the NDL genes in the agb1-2 (null allele mutant rescues some of the abnormal phenotypes, such as silique morphology, silique distribution, and peduncle angle, suggesting that proper levels of NDL proteins are maintained by AGB1. We found that all of these abnormal aerial phenotypes due to altered NDL expression were associated with increases in basipetal auxin transport, altered auxin maxima and altered MAX2 expression within the inflorescence stem.NDL proteins, together with AGB1, act as positive regulators of meristem initiation and branching. AGB1 and NDL1 positively regulate basipetal inflorescence auxin transport and modulate MAX2 expression in shoots, which in turn regulates organ and lateral meristem formation by the establishment and maintenance of auxin gradients.

Relationship between plant growth and cytological effect in root apical meristem after exposure of wheat dry seeds to carbon ion beams

Energy Technology Data Exchange (ETDEWEB)

Liu, Qingfang [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Zhuanzi; Zhou, Libin; Qu, Ying; Lu, Dong [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China); Yu, Lixia; Du, Yan [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Jin, Wenjie [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China); Li, Wenjian, E-mail: wjli@impcas.ac.cn [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China)

2013-06-15

In order to analyze the relationship between plant growth and cytological effects, wheat dry seeds were exposed to various doses of {sup 12}C{sup 6+} beams and the biological endpoints reflecting plant growth and root apical meristem (RAM) activities were investigated. The results showed that most of the seeds were able to germinate normally within all dose range, while the plant survival rate descended at higher doses. The seedling growth including root length and seedling height also decreased significantly at higher doses. Mitotic index (MI) in RAM had no changes at 10 and 20 Gy and decreased obviously at higher doses and the proportion of prophase cells had the same trend with MI. These data suggested that RAM cells experienced cell cycle arrest, which should be responsible for the inhibition of root growth after exposure to higher doses irradiation. Moreover, various types of chromosome aberrations (CAs) were observed in the mitotic cells. The frequencies of mitotic cells with lagging chromosomes and these with anaphase bridges peaked around 60 Gy, while the frequencies of these with fragments increased as the irradiation doses increased up to 200 Gy. The total frequencies of mitotic cells with CAs induced by irradiation increased significantly with the increasing doses. The serious damage of mitotic chromosomes maybe caused cell cycle arrest or cell death. These findings suggested that the influences of {sup 12}C{sup 6+} beams irradiation on plant growth were related to the alternation of mitotic activities and the chromosomal damages in RAM.

Root nodule structure in Chamaecytisus podolicus

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Monika Skawińska

2017-06-01

Full Text Available By means of microscopic analyses, it was shown that root nodules formed by Chamaecytisus podolicus exhibited all structural features typical for indeterminate nodules of temperate genistean shrubs: (i apical nodule meristem composed of infected and non-infected domains, (ii parenchymatous bacteroid-containing tissue with infected cells only resulting from mitotic activity of infected meristematic cells, (iii absence of infection threads, and (iv convoluted bacteroids singly enclosed in a symbiosome membrane. For the first time, it was shown that the nodule meristem is organized into longitudinal files of sister cells.

Composite Cucurbita pepo plants with transgenic roots as a tool to study root development.

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Ilina, Elena L; Logachov, Anton A; Laplaze, Laurent; Demchenko, Nikolay P; Pawlowski, Katharina; Demchenko, Kirill N

2012-07-01

In most plant species, initiation of lateral root primordia occurs above the elongation zone. However, in cucurbits and some other species, lateral root primordia initiation and development takes place in the apical meristem of the parental root. Composite transgenic plants obtained by Agrobacterium rhizogenes-mediated transformation are known as a suitable model to study root development. The aim of the present study was to establish this transformation technique for squash. The auxin-responsive promoter DR5 was cloned into the binary vectors pKGW-RR-MGW and pMDC162-GFP. Incorporation of 5-ethynyl-2'-deoxyuridine (EdU) was used to evaluate the presence of DNA-synthesizing cells in the hypocotyl of squash seedlings to find out whether they were suitable for infection. Two A. rhizogenes strains, R1000 and MSU440, were used. Roots containing the respective constructs were selected based on DsRED1 or green fluorescent protein (GFP) fluorescence, and DR5::Egfp-gusA or DR5::gusA insertion, respectively, was verified by PCR. Distribution of the response to auxin was visualized by GFP fluorescence or β-glucuronidase (GUS) activity staining and confirmed by immunolocalization of GFP and GUS proteins, respectively. Based on the distribution of EdU-labelled cells, it was determined that 6-day-old squash seedlings were suited for inoculation by A. rhizogenes since their root pericycle and the adjacent layers contain enough proliferating cells. Agrobacterium rhizogenes R1000 proved to be the most virulent strain on squash seedlings. Squash roots containing the respective constructs did not exhibit the hairy root phenotype and were morphologically and structurally similar to wild-type roots. The auxin response pattern in the root apex of squash resembled that in arabidopsis roots. Composite squash plants obtained by A. rhizogenes-mediated transformation are a good tool for the investigation of root apical meristem development and root branching.

Study of genes induced by ionizing radiations at Arabidopsis thaliana: identification and molecular characterization of the ATGR1 gene, a new gene encoding a protein involved in plant cell division

International Nuclear Information System (INIS)

Deveaux, Yves

1999-01-01

DNA damage, that can be experimentally introduced by ionizing radiation (IR), induces complex signal transduction pathways leading to cell recovery or, alternatively to programmed cell death if damages are too severe. To identify the inducible components of the response to genotoxic stress in plants, we have screened by Differential Display for mRNAs that rapidly and strongly accumulate after IR treatment in A. thaliana cells. We have characterized ATGR1, a new single copy Arabidopsis gene encoding a PEST-box protein of unknown function. In unstressed plant organs the ATGR1 mRNA is hardly detectable, whereas the protein is present in extracts prepared from roots, shoot meristems and inflorescences, that all contain large amounts of actively dividing cells. This pattern is confirmed by immuno localisation on tissue sections that shows constitutive ATGR1 protein expression covering the root elongation zone, the shoot meristem, leaf primordial and the ovules of developing flowers. Histochemical analysis of transgenic plants expressing the GUS reporter gene under the control of the ATGR1 promoter, demonstrate that the developmental and tissue-specific profile of ATGR1 protein expression is conferred by the gene promoter. The massive, transient and dose-dependent accumulation of ATGR1 transcripts after IR treatment observed in all plant organs does not lead to significant changes in ATGR1 protein pattern. Stable ATGR1 protein overexpression, as exemplified by transgenic A. thaliana plants that contain a 35S promoter-ATGR1 gene fusion, does not induce notable changes of the overall ATGR1 protein level, but leads to male and female sterility. The cause of sterility is a lack of correct chromosome assembly and distribution at the stage metaphase II of meiosis. Taken together our results show that i) ATGR1 gene expression is associated to cell division during plant development ii) the ATGR1 protein level is regulated at the transcriptional and post-transcriptional level iii

Sugar-Mediated Acclimation: The Importance of Sucrose Metabolism in Meristems

NARCIS (Netherlands)

Carpentier, S.C.; Vertommen, A.; Swennen, R.; Witters, E.; Fortes, C.; Souza, M.T.; Panis, B.

2010-01-01

We have designed an in vitro experimental setup to study the role of sucrose in sugar-mediated acclimation of banana meristems using established highly proliferating meristem cultures. It is a first step toward the systems biology of a meristem and the understanding of how it can survive severe

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

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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.

Enhancement of Chlorogenic Acid Production in Hairy Roots of Platycodon grandiflorum by Over-Expression of An Arabidopsis thaliana Transcription Factor AtPAP1

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Pham Anh Tuan

2014-08-01

Full Text Available To improve the production of chlorogenic acid (CGA in hairy roots of Platycodon grandiflorum, we induced over-expression of Arabidopsis thaliana transcription factor production of anthocyanin pigment (AtPAP1 using an Agrobacterium rhizogenes-mediated transformation system. Twelve hairy root lines showing over-expression of AtPAP1 were generated. In order to investigate the regulation of AtPAP1 on the activities of CGA biosynthetic genes, the expression levels of seven P. grandiflorum CGA biosynthetic genes were analyzed in the hairy root line that had the greatest accumulation of AtPAP1 transcript, OxPAP1-1. The introduction of AtPAP1 increased the mRNA levels of all examined CGA biosynthetic genes and resulted in a 900% up-regulation of CGA accumulation in OxPAP1-1 hairy roots relative to controls. This suggests that P. grandiflorum hairy roots that over-express the AtPAP1 gene are a potential alternative source of roots for the production of CGA.

Meristem identity and phyllotaxis in inflorescence development

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Madelaine Elisabeth Bartlett

2014-10-01

Full Text Available Inflorescence morphology is incredibly diverse. This diversity of form has been a fruitful source of inquiry for plant morphologists for more than a century. Work in the grasses (Poaceae, the tomato family (Solanaceae, and Arabidopsis (Brassicaceae has led to a richer understanding of the molecular genetics underlying this diversity. The character of individual meristems, a combination of the number (determinacy and nature (identity of the products a meristem produces, is key in the development of plant form. A framework that describes inflorescence development in terms of shifting meristem identities has emerged and garnered empirical support in a number of model systems. We discuss this framework and highlight one important aspect of meristem identity that is often considered in isolation, phyllotaxis. Phyllotaxis refers to the arrangement of lateral organs around a central axis. The development and evolution of phyllotaxis in the inflorescence remains underexplored, but recent work analyzing early inflorescence development in the grasses identified an evolutionary shift in primary branch phyllotaxis in the Pooideae. We discuss the evidence for an intimate connection between meristem identity and phyllotaxis in both the inflorescence and vegetative shoot, and touch on what is known about the establishment of phyllotactic patterns in the meristem. Localized auxin maxima are instrumental in determining the position of lateral primordia. Upstream factors that regulate the position of these maxima remain unclear, and how phyllotactic patterns change over the course of a plant’s lifetime and evolutionary time, is largely unknown. A more complete understanding of the molecular underpinnings of phyllotaxis and architectural diversity in inflorescences will require capitalizing on the extensive resources available in existing genetic systems, and developing new model systems that more fully represent the diversity of plant morphology.

DELLA genes restrict inflorescence meristem function independently of plant height.

Science.gov (United States)

Serrano-Mislata, Antonio; Bencivenga, Stefano; Bush, Max; Schiessl, Katharina; Boden, Scott; Sablowski, Robert

2017-09-01

DELLA proteins associate with transcription factors to control plant growth in response to gibberellin 1 . Semi-dwarf DELLA mutants with improved harvest index and decreased lodging greatly improved global food security during the 'green revolution' in the 1960-1970s 2 . However, DELLA mutants are pleiotropic and the developmental basis for their effects on plant architecture remains poorly understood. Here, we show that DELLA proteins have genetically separable roles in controlling stem growth and the size of the inflorescence meristem, where flowers initiate. Quantitative three-dimensional image analysis, combined with a genome-wide screen for DELLA-bound loci in the inflorescence tip, revealed that DELLAs limit meristem size in Arabidopsis by directly upregulating the cell-cycle inhibitor KRP2 in the underlying rib meristem, without affecting the canonical WUSCHEL-CLAVATA meristem size regulators 3 . Mutation of KRP2 in a DELLA semi-dwarf background restored meristem size, but not stem growth, and accelerated flower production. In barley, secondary mutations in the DELLA gain-of-function mutant Sln1d 4 also uncoupled meristem and inflorescence size from plant height. Our work reveals an unexpected and conserved role for DELLA genes in controlling shoot meristem function and suggests how dissection of pleiotropic DELLA functions could unlock further yield gains in semi-dwarf mutants.

NSP-Dependent Simple Nitrile Formation Dominates upon Breakdown of Major Aliphatic Glucosinolates in Roots, Seeds, and Seedlings of Arabidopsis thaliana Columbia-0.

Science.gov (United States)

Wittstock, Ute; Meier, Kathrin; Dörr, Friederike; Ravindran, Beena M

2016-01-01

One of the best-studied plant defense systems, the glucosinolate-myrosinase system of the Brassicales, is composed of thioglucosides known as glucosinolates and their hydrolytic enzymes, the myrosinases. Tissue disruption brings these components together, and bioactive products are formed as a consequence of myrosinase-catalyzed glucosinolate hydrolysis. Among these products, isothiocyanates have attracted most interest as chemical plant defenses against herbivores and pathogens and health-promoting compounds in the human diet. Previous research has identified specifier proteins whose presence results in the formation of alternative product types, e.g., nitriles, at the expense of isothiocyanates. The biological roles of specifier proteins and alternative breakdown products are poorly understood. Here, we assessed glucosinolate breakdown product profiles obtained upon maceration of roots, seedlings and seeds of Arabidopsis thaliana Columbia-0. We identified simple nitriles as the predominant breakdown products of the major endogenous aliphatic glucosinolates in root, seed, and seedling homogenates. In agreement with this finding, genes encoding nitrile-specifier proteins (NSPs) are expressed in roots, seeds, and seedlings. Analysis of glucosinolate breakdown in mutants with T-DNA insertions in any of the five NSP genes demonstrated, that simple nitrile formation upon tissue disruption depended almost entirely on NSP2 in seeds and mainly on NSP1 in seedlings. In roots, about 70-80% of the nitrile-forming activity was due to NSP1 and NSP3 . Thus, glucosinolate breakdown product profiles are organ-specifically regulated in A. thaliana Col-0, and high proportions of simple nitriles are formed in some parts of the plant. This should be considered in future studies on biological roles of the glucosinolate-myrosinase system.

NSP-dependent simple nitrile formation dominates upon breakdown of major aliphatic glucosinolates in roots, seeds, and seedlings of Arabidopsis thaliana Columbia-0

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Ute Wittstock

2016-12-01

Full Text Available One of the best-studied plant defense systems, the glucosinolate-myrosinase system of the Brassicales, is composed of thioglucosides known as glucosinolates and their hydrolytic enzymes, the myrosinases. Tissue disruption brings these components together, and bioactive products are formed as a consequence of myrosinase-catalyzed glucosinolate hydrolysis. Among these products, isothiocyanates have attracted most interest as chemical plant defenses against herbivores and pathogens and health-promoting compounds in the human diet. Previous research has identified specifier proteins whose presence results in the formation of alternative product types, e.g. nitriles, at the expense of isothiocyanates. The biological roles of specifier proteins and alternative breakdown products are poorly understood. Here, we assessed glucosinolate breakdown product profiles obtained upon maceration of roots, seedlings and seeds of Arabidopsis thaliana Columbia-0. We identified simple nitriles as the predominant breakdown products of the major endogenous aliphatic glucosinolates in root, seed, and seedling homogenates. In agreement with this finding, genes encoding nitrile-specifier proteins (NSPs are expressed in roots, seeds, and seedlings. Analysis of glucosinolate breakdown in mutants with T-DNA insertions in any of the five NSP genes demonstrated, that simple nitrile formation upon tissue disruption depended almost entirely on NSP2 in seeds and mainly on NSP1 in seedlings. In roots, about 70-80 % of the nitrile-forming activity was due to NSP1 and NSP3. Thus, glucosinolate breakdown product profiles are organ-specifically regulated in A. thaliana Col 0, and high proportions of simple nitriles are formed in some parts of the plant. This should be considered in future studies on biological roles of the glucosinolate-myrosinase system.

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

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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.

Auxin and cytokinin metabolism and root morphological modifications in Arabidopsis thaliana seedlings infected with Cucumber mosaic virus (CMV) or exposed to cadmium.

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Vitti, Antonella; Nuzzaci, Maria; Scopa, Antonio; Tataranni, Giuseppe; Remans, Tony; Vangronsveld, Jaco; Sofo, Adriano

2013-03-26

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.

Distinctive features and differential regulation of the DRTS genes of Arabidopsis thaliana.

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Maniga, Antonio; Ghisaura, Stefania; Perrotta, Lara; Marche, Maria Giovanna; Cella, Rino; Albani, Diego

2017-01-01

In plants and protists, dihydrofolate reductase (DHFR) and thymidylate synthase (TS) are part of a bifunctional enzyme (DRTS) that allows efficient recycling of the dihydrofolate resulting from TS activity. Arabidopsis thaliana possesses three DRTS genes, called AtDRTS1, AtDRTS2 and AtDRTS3, that are located downstream of three members of the sec14-like SFH gene family. In this study, a characterization of the AtDRTS genes identified alternatively spliced transcripts coding for AtDRTS isoforms which may account for monofunctional DHFR enzymes supporting pathways unrelated to DNA synthesis. Moreover, we discovered a complex differential regulation of the AtDRTS genes that confirms the expected involvement of the AtDRTS genes in cell proliferation and endoreduplication, but indicates also functions related to other cellular activities. AtDRTS1 is widely expressed in both meristematic and differentiated tissues, whereas AtDRTS2 expression is almost exclusively limited to the apical meristems and AtDRTS3 is preferentially expressed in the shoot apex, in stipules and in root cap cells. The differential regulation of the AtDRTS genes is associated to distinctive promoter architectures and the expression of AtDRTS1 in the apical meristems is strictly dependent on the presence of an intragenic region that includes the second intron of the gene. Upon activation of cell proliferation in germinating seeds, the activity of the AtDRTS1 and AtDRTS2 promoters in meristematic cells appears to be maximal at the G1/S phase of the cell cycle. In addition, the promoters of AtDRTS2 and AtDRTS3 are negatively regulated through E2F cis-acting elements and both genes, but not AtDRTS1, are downregulated in plants overexpressing the AtE2Fa factor. Our study provides new information concerning the function and the regulation of plant DRTS genes and opens the way to further investigations addressing the importance of folate synthesis with respect to specific cellular activities.

The effects of redox controls mediated by glutathione peroxidases on root architecture in Arabidopsis thaliana.

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Passaia, Gisele; Queval, Guillaume; Bai, Juan; Margis-Pinheiro, Marcia; Foyer, Christine H

2014-03-01

Glutathione peroxidases (GPXs) fulfil important functions in oxidative signalling and protect against the adverse effects of excessive oxidation. However, there has been no systematic characterization of the functions of the different GPX isoforms in plants. The roles of the different members of the Arabidopsis thaliana GPX gene (AtGPX) family were therefore investigated using gpx1, gpx2, gpx3, gpx4, gpx6, gpx7, and gpx8 T-DNA insertion mutant lines. The shoot phenotypes were largely similar in all genotypes, with small differences from the wild type observed only in the gpx2, gpx3, gpx7, and gpx8 mutants. In contrast, all the mutants showed altered root phenotypes compared with the wild type. The gpx1, gpx4, gpx6, gpx7, and gpx8 mutants had a significantly greater lateral root density (LRD) than the wild type. Conversely, the gpx2 and gpx3 mutants had significantly lower LRD values than the wild type. Auxin increased the LRD in all genotypes, but the effect of auxin was significantly greater in the gpx1, gpx4, and gpx7 mutants than in the wild type. The application of auxin increased GPX4 and GPX7 transcripts, but not GPX1 mRNAs in the roots of wild-type plants. The synthetic strigolactone GR24 and abscisic acid (ABA) decreased LRD to a similar extent in all genotypes, except gpx6, which showed increased sensitivity to ABA. These data not only demonstrate the importance of redox controls mediated by AtGPXs in the control of root architecture but they also show that the plastid-localized GPX1 and GPX7 isoforms are required for the hormone-mediated control of lateral root development.

MAIL1 is essential for development of the primary root but not of anchor roots.

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Ühlken, Christine; Hoth, Stefan; Weingartner, Magdalena

2014-01-01

MAIN-LIKE1 (MAIL1) is a ubiquitously expressed nuclear protein, which has a crucial function during root development. We have recently described loss of function mutants for MAIL1, in which the organization and function of the primary root meristem is lost soon after germination. Moreover cell differentiation is impaired resulting in primary root growth arrest soon after emergence. Here we show that mail1 mutants form several anchor roots from the hypocotyl to root junction. These anchor roots show similar defects in the organization of the stem cell niche as the primary root. In contrast, differentiation processes are not impaired and thus anchor roots seem to be able to compensate for the loss of primary root function. Our data show that MAIL1 is essential for specification of cell fate in the primary root but not in anchor roots.

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

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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.

Exogenous glucosinolate produced by Arabidopsis thaliana has an impact on microbes in the rhizosphere and plant roots.

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Bressan, Mélanie; Roncato, Marie-Anne; Bellvert, Floriant; Comte, Gilles; Haichar, Feth Zahar; Achouak, Wafa; Berge, Odile

2009-11-01

A specificity of Brassicaceous plants is the production of sulphur secondary metabolites called glucosinolates that can be hydrolysed into glucose and biocidal products. Among them, isothiocyanates are toxic to a wide range of microorganisms and particularly soil-borne pathogens. The aim of this study was to investigate the role of glucosinolates and their breakdown products as a factor of selection on rhizosphere microbial community associated with living Brassicaceae. We used a DNA-stable isotope probing approach to focus on the active microbial populations involved in root exudates degradation in rhizosphere. A transgenic Arabidopsis thaliana line producing an exogenous glucosinolate and the associated wild-type plant associated were grown under an enriched (13)CO(2) atmosphere in natural soil. DNA from the rhizospheric soil was separated by density gradient centrifugation. Bacterial (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Acidobacteria), Archaea and fungal community structures were analysed by DGGE fingerprints of amplified 16S and 18S rRNA gene sequences. Specific populations were characterized by sequencing DGGE fragments. Roots of the transgenic plant line presented an altered profile of glucosinolates and other minor additional modifications. These modifications significantly influenced microbial community on roots and active populations in the rhizosphere. Alphaproteobacteria, particularly Rhizobiaceae, and fungal communities were mainly impacted by these Brassicaceous metabolites, in both structure and composition. Our results showed that even a minor modification in plant root could have important repercussions for soil microbial communities.

Effect of growth regulators in meristem culture of potato (solanum tuberosmum l.)

International Nuclear Information System (INIS)

Batool, A.; Zaidi, S.S.H.

2014-01-01

Two growth regulators, viz., Gibberellic acid (GA3) and Naphthalene acetic acid (NAA) and a combination of both (GA3 and NAA) were evaluated at three different levels (200, 300 and 400 meul) to check the growth rate of root, shoot, number of leaves and nodes of potato plantlets in two potato varieties, namely cardinal and SH-5, grown by meristem culture. Analysis of variance revealed highly significant differences between varieties, hormones and their interaction for all the studied traits. Mean values revealed that among two varieties Cardinal produced root length (0.70 cm), shoot length (2.50 cm), number of leaves (6.96) and number of nodes (8) are better than the SH-5 which produced root length (0.54 cm), shoot length (1.38 cm), number of leaves (4.29) and number of nodes (5.3). The variety cardinal and GA3 at 300 meul followed by 200 meul produced most suitable results. By using the concentration of 300 meul maximum root length of (1.40 cm), shoot length of (3.43 cm), number of leaves (10) and no of nodes (11) was obtained. At 200 meul, though root and shoot length obtained was very similar at 300 meul but produced less number of leaves and nodes. (author)

Phytoremediation of the organic Xenobiotic simazine by p450-1a2 transgenic Arabidopsis thaliana plants.

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Azab, Ehab; Hegazy, Ahmad K; El-Sharnouby, Mohamed E; Abd Elsalam, Hassan E

2016-01-01

The potential use of human P450-transgenic plants for phytoremediation of pesticide contaminated soils was tested in laboratory and greenhouse experiments. The transgenic P450 CYP1A2 gene Arabidopsis thaliana plants metabolize number of herbicides, insecticides and industrial chemicals. The P450 isozymes CYP1A2 expressed in A. thaliana were examined regarding the herbicide simazine (SIM). Transgenic A. thaliana plants expressing CYP1A2 gene showed significant resistance to SIM supplemented either in plant growth medium or sprayed on foliar parts. The results showed that SIM produces harmful effect on both rosette diameter and primary root length of the wild type (WT) plants. In transgenic A. thaliana lines, the rosette diameter and primary root length were not affected by SIM concentrations used in this experiment. The results indicate that CYP1A2 can be used as a selectable marker for plant transformation, allowing efficient selection of transgenic lines in growth medium and/or in soil-grown plants. The transgenic A. thaliana plants exhibited a healthy growth using doses of up to 250 μmol SIM treatments, while the non-transgenic A. thaliana plants were severely damaged with doses above 50 μmol SIM treatments. The transgenic A. thaliana plants can be used as phytoremediator of environmental SIM contaminants.

Effects of PEG-Induced Water Deficit in Solanum nigrum on Zn and Ni Uptake and Translocation in Split Root Systems

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Urs Feller

2015-06-01

Full Text Available Drought strongly influences root activities in crop plants and weeds. This paper is focused on the performance of the heavy metal accumulator Solanum nigrum, a plant which might be helpful for phytoremediation. The water potential in a split root system was decreased by the addition of polyethylene glycol (PEG 6000. Rubidium, strontium and radionuclides of heavy metals were used as markers to investigate the uptake into roots, the release to the shoot via the xylem, and finally the basipetal transport via the phloem to unlabeled roots. The uptake into the roots (total contents in the plant was for most makers more severely decreased than the transport to the shoot or the export from the shoot to the unlabeled roots via the phloem. Regardless of the water potential in the labeling solution, 63Ni and 65Zn were selectively redistributed within the plant. From autoradiographs, it became evident that 65Zn accumulated in root tips, in the apical shoot meristem and in axillary buds, while 63Ni accumulated in young expanded leaves and roots but not in the meristems. Since both radionuclides are mobile in the phloem and are, therefore, well redistributed within the plant, the unequal transfer to shoot and root apical meristems is most likely caused by differences in the cell-to-cell transport in differentiation zones without functional phloem (immature sieve tubes.

Effects of gamma radiation on potato meristems

International Nuclear Information System (INIS)

Fernandez Gonzalez, J.; Garcia Collantes, M.A.

1976-01-01

The development of buds in potato tubers subjected to gamma radiation at doses of 3, 6, 8 and 12 Krad is studied at histological level. The irradiation was supplied at the beguining and end of the resting period, and the irradiated buds were observed at different stages of their development. Meristem's sensitivity depends on the state of activity involved at the moment of irradiation. Different parts of the meristem present different radiosensitivity, being the most radioresistant. (author) [es

Phytoremediation potential of Arabidopsis thaliana, expressing ectopically a vacuolar proton pump, for the industrial waste phosphogypsum.

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Khoudi, Habib; Maatar, Yafa; Brini, Faïçal; Fourati, Amine; Ammar, Najoua; Masmoudi, Khaled

2013-01-01

Phosphogypsum (PG) is a by-product of the phosphorus-fertiliser industry and represents an environmental concern since it contains pollutants such as cadmium (Cd). We have recently shown that the overexpression of a proton pump gene (TaVP1) in transgenic tobacco (Nicotiana tabacum) led to an enhanced Cd tolerance and accumulation. The aim of this study was to evaluate the potential of transgenic Arabidopsis thaliana plants harbouring the TaVP1 gene to phytoremediate phosphogypsum. A pot experiment was carried out under greenhouse conditions. Transgenic A. thaliana plants harbouring the TaVP1 gene were grown on various substrates containing phosphogypsum (0, 25, 50 and 100 %) for 40 days. At the end of the growth period, we examined the growth (germination, root length, fresh weight) and physiological parameters (chlorophyll and protein contents, catalase activity and proteolysis) as well as the cadmium, Mg, Ca, and P contents of the A. thaliana plants. In order to evaluate Cd tolerance of the A. thaliana lines harbouring the TaVP1 gene, an in vitro experiment was also carried out. One week-old seedlings were transferred to Murashige and Skoog agar plates containing various concentrations of cadmium; the germination, total leaf area and root length were determined. The growth and physiological parameters of all A. thaliana plants were significantly altered by PG. The germination capacity, root growth and biomass production of wild-type (WT) plants were more severely inhibited by PG compared with the TaVP1 transgenic A. thaliana lines. In addition, TaVP1 transgenic A. thaliana plants maintained a higher antioxidant capacity than the WT. Interestingly, elemental analysis of leaf material derived from plants grown on PG revealed that the transgenic A. thaliana line accumulated up to ten times more Cd than WT. Despite its higher Cd content, the transgenic A. thaliana line performed better than the WT counterpart. In vitro evaluation of Cd tolerance showed that TaVP1

PLATINUM SENSITIVE 2 LIKE impacts growth, root morphology, seed set, and stress responses.

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Amr R A Kataya

Full Text Available Eukaryotic protein phosphatase 4 (PP4 is a PP2A-type protein phosphatase that is part of a conserved complex with regulatory factors PSY2 and PP4R2. Various lines of Arabidopsis thaliana with mutated PP4 subunit genes were constructed to study the so far completely unknown functions of PP4 in plants. Mutants with knocked out putative functional homolog of the PSY2 LIKE (PSY2L gene were dwarf and bushy, while plants with knocked out PP4R2 LIKE (PP4R2L looked very similar to WT. The psy2l seedlings had short roots with disorganized morphology and impaired meristem. Seedling growth was sensitive to the genotoxin cisplatin. Global transcript analysis (RNA-seq of seedlings and rosette leaves revealed several groups of genes, shared between both types of tissues, strongly influenced by knocked out PSY2L. Receptor kinases, CRINKLY3 and WAG1, important for growth and development, were down-regulated 3-7 times. EUKARYOTIC ELONGATION FACTOR5A1 was down-regulated 4-6 fold. Analysis of hormone sensitive genes indicated that abscisic acid levels were high, while auxin, cytokinin and gibberellic acid levels were low in psy2l. Expression of specific transcription factors involved in regulation of anthocyanin synthesis were strongly elevated, e.g. the master regulator PAP1, and intriguingly TT8, which is otherwise mainly expressed in seeds. The psy2l mutants accumulated anthocyanins under conditions where WT did not, pointing to PSY2L as a possible upstream negative regulator of PAP1 and TT8. Expression of the sugar-phosphate transporter GPT2, important for cellular sugar and phosphate homeostasis, was enhanced 7-8 times. Several DNA damage response genes, including the cell cycle inhibitor gene WEE1, were up-regulated in psy2l. The activation of DNA repair signaling genes, in combination with phenotypic traits showing aberrant root meristem and sensitivity to the genotoxic cisplatin, substantiate the involvement of Arabidopsis PSY2L in maintenance of genome

Phytoplasmal infection derails genetically preprogrammed meristem fate and alters plant architecture

OpenAIRE

Wei, Wei; Davis, Robert Edward; Nuss, Donald L.; Zhao, Yan

2013-01-01

In higher plants, the destiny of apical meristems (stem cells) is specific organogenesis, which determines the pattern of plant growth, and therefore morphotype and fertility. We found that bacterial infection can derail the meristems from their genetically preprogrammed destiny, altering plant morphogenesis. We identified four abnormal growth patterns, symptoms, in tomato infected with a cell wall-less bacterium, and found that each symptom corresponds to a distinct phase in meristem fate de...

T-DNA transfer and T-DNA integration efficiencies upon Arabidopsis thaliana root explant cocultivation and floral dip transformation.

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Ghedira, Rim; De Buck, Sylvie; Van Ex, Frédéric; Angenon, Geert; Depicker, Ann

2013-12-01

T-DNA transfer and integration frequencies during Agrobacterium-mediated root explant cocultivation and floral dip transformations of Arabidopsis thaliana were analyzed with and without selection for transformation-competent cells. Based on the presence or absence of CRE recombinase activity without or with the CRE T-DNA being integrated, transient expression versus stable transformation was differentiated. During root explant cocultivation, continuous light enhanced the number of plant cells competent for interaction with Agrobacterium and thus the number of transient gene expression events. However, in transformation competent plant cells, continuous light did not further enhance cotransfer or cointegration frequencies. Upon selection for root transformants expressing a first T-DNA, 43-69 % of these transformants showed cotransfer of another non-selected T-DNA in two different light regimes. However, integration of the non-selected cotransferred T-DNA occurred only in 19-46 % of these transformants, indicating that T-DNA integration in regenerating root cells limits the transformation frequencies. After floral dip transformation, transient T-DNA expression without integration could not be detected, while stable T-DNA transformation occurred in 0.5-1.3 % of the T1 seedlings. Upon selection for floral dip transformants with a first T-DNA, 8-34 % of the transformants showed cotransfer of the other non-selected T-DNA and in 93-100 % of them, the T-DNA was also integrated. Therefore, a productive interaction between the agrobacteria and the female gametophyte, rather than the T-DNA integration process, restricts the floral dip transformation frequencies.

The Root Transition Zone: A Hot Spot for Signal Crosstalk.

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Kong, Xiangpei; Liu, Guangchao; Liu, Jiajia; Ding, Zhaojun

2018-05-01

The root transition zone (TZ), located between the apical meristem and basal elongation region, has a unique role in root growth and development. The root TZ is not only the active site for hormone crosstalk, but also the perception site for various environmental cues, such as aluminum (Al) stress and low phosphate (Pi) stress. We propose that the root TZ is a hot spot for the integration of diverse inputs from endogenous (hormonal) and exogenous (sensorial) stimuli to control root growth. Copyright © 2018 Elsevier Ltd. All rights reserved.

Cytokinin signaling during root development.

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Bishopp, Anthony; Help, Hanna; Helariutta, Ykä

2009-01-01

The cytokinin class of phytohormones regulates division and differentiation of plant cells. They are perceived and signaled by a phosphorelay mechanism similar to those observed in prokaryotes. Research into the components of phosphorelay had previously been marred by genetic redundancy. However, recent studies have addressed this with the creation of high-order mutants. In addition, several new elements regulating cytokinin signaling have been identified. This has uncovered many roles in diverse developmental and physiological processes. In this review, we look at these processes specifically in the context of root development. We focus on the formation and maintenance of the root apical meristem, primary and secondary vascular development, lateral root emergence and development, and root nodulation. We believe that the root is an ideal organ with which to investigate cytokinin signaling in a wider context.

AtMRP6/AtABCC6, an ATP-Binding Cassette transporter gene expressed during early steps of seedling development and up-regulated by cadmium in Arabidopsis thaliana

Science.gov (United States)

Gaillard, Stéphane; Jacquet, Hélène; Vavasseur, Alain; Leonhardt, Nathalie; Forestier, Cyrille

2008-01-01

Background ABC proteins constitute one of the largest families of transporters found in all living organisms. In Arabidopsis thaliana, 120 genes encoding ABC transporters have been identified. Here, the characterization of one member of the MRP subclass, AtMRP6, is described. Results This gene, located on chromosome 3, is bordered by AtMRP3 and AtMRP7. Using real-time quantitative PCR (RT-Q-PCR) and the GUS reporter gene, we found that this gene is essentially expressed during early seedling development, in the apical meristem and at initiation point of secondary roots, especially in xylem-opposite pericycle cells where lateral roots initiate. The level of expression of AtMRP6 in response to various stresses was explored and a significant up-regulation after cadmium (Cd) treatment was detected. Among the three T-DNA insertion lines available from the Salk Institute library, two knock-out mutants, Atmrp6.1 and Atmrp6.2 were invalidated for the AtMRP6 gene. In the presence of Cd, development of leaves was more affected in the mutants than wild-type plants, whereas root elongation and ramification was comparable. Conclusion The position of AtMRP6 on chromosome 3, flanked by two other MRP genes, (all of which being induced by Cd) suggests that AtMRP6 is part of a cluster involved in metal tolerance, although additional functions in planta cannot be discarded. PMID:18307782

AtMMS21, an SMC5/6 complex subunit, is involved in stem cell niche maintenance and DNA damage responses in Arabidopsis roots.

Science.gov (United States)

Xu, Panglian; Yuan, Dongke; Liu, Ming; Li, Chunxin; Liu, Yiyang; Zhang, Shengchun; Yao, Nan; Yang, Chengwei

2013-04-01

Plants maintain stem cells in meristems to sustain lifelong growth; these stem cells must have effective DNA damage responses to prevent mutations that can propagate to large parts of the plant. However, the molecular links between stem cell functions and DNA damage responses remain largely unexplored. Here, we report that the small ubiquitin-related modifier E3 ligase AtMMS21 (for methyl methanesulfonate sensitivity gene21) acts to maintain the root stem cell niche by mediating DNA damage responses in Arabidopsis (Arabidopsis thaliana). Mutation of AtMMS21 causes defects in the root stem cell niche during embryogenesis and postembryonic stages. AtMMS21 is essential for the proper expression of stem cell niche-defining transcription factors. Moreover, mms21-1 mutants are hypersensitive to DNA-damaging agents, have a constitutively increased DNA damage response, and have more DNA double-strand breaks (DSBs) in the roots. Also, mms21-1 mutants exhibit spontaneous cell death within the root stem cell niche, and treatment with DSB-inducing agents increases this cell death, suggesting that AtMMS21 is required to prevent DSB-induced stem cell death. We further show that AtMMS21 functions as a subunit of the STRUCTURAL MAINTENANCE OF CHROMOSOMES5/6 complex, an evolutionarily conserved chromosomal ATPase required for DNA repair. These data reveal that AtMMS21 acts in DSB amelioration and stem cell niche maintenance during Arabidopsis root development.

Elimination of PPV and PNRSV through thermotherapy and meristem-tip culture in nectarine.

Science.gov (United States)

Manganaris, G A; Economou, A S; Boubourakas, I N; Katis, N I

2003-10-01

The plum pox virus (PPV) and prunus necrotic ringspot virus (PNRSV) cause serious disease problems in stone-fruit trees. In this work, the possibility of obtaining plant material free from these viruses through thermotherapy and meristem-tip culture from infected nectarine shoots (Prunus persica var. nectarina Max, cv. 'Arm King') was studied. In addition, the detection of these viruses in in vitro cultures and young acclimatized plantlets with double antibody sandwich-enzyme-linked immunosorbent assay (DAS-ELISA) and multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) was studied. Meristem-tip explants (0.8-1.3 mm) derived from sprouted buds of winter wood and spring shoots from field grown plants had a 2-5% regeneration response. However, application of thermotherapy to potted nectarine trees (3 weeks at a maximum temperature of 35 degrees C) facilitated excision of longer meristem tips (1.3-2.0 mm) that resulted in a significantly higher regeneration response (38%) in woody plant medium (WPM) without plant growth regulators. Such explants formed multiple shoots with the addition of 8 microM benzylaminopurine and 0.8 microM indoleacetic acid. When they were tested for the presence of PPV and PNRSV, 86% and 81% were found to be virus-free as detected by DAS-ELISA and multiplex RT-PCR, respectively. Individual shoots excised from virus-free cultures readily rooted in vitro (half-strength WPM plus 2 microM indolebutyric acid) and grew to plantlets. The combination of an efficient protocol for virus elimination and the establishment of highly sensitive diagnostics resulted in the production of nectarine plants free from PPV and PNRSV.

Lateral root formation and the multiple roles of auxin

NARCIS (Netherlands)

Du, Yujuan; Scheres, Ben

2018-01-01

Root systems can display variable architectures that contribute to survival strategies of plants. The model plant Arabidopsis thaliana possesses a tap root system, in which the primary root and lateral roots (LRs) are major architectural determinants. The phytohormone auxin fulfils multiple roles

Establishment of an Indirect Genetic Transformation Method for Arabidopsis thaliana ecotype Bangladesh

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Bulbul AHMED

2011-11-01

Full Text Available Arabidopsis thaliana is a small flowering plant belonging to the Brassicaceae family, which is adopted as a model plant for genetic research. Agrobacterium tumifaciensmediated transformation method for A. thaliana ecotype Bangladesh was established. Leaf discs of A. thaliana were incubated with A. tumefaciens strain LBA4404 containing chimeric nos. nptII. nos and intron-GUS genes. Following inoculation and co-cultivation, leaf discs were cultured on selection medium containing 50 mg/l kanamycin + 50 mg/l cefotaxime + 1.5 mg/l NAA and kanamycin resistant shoots were induced from the leaf discs after two weeks. Shoot regeneration was achieved after transferring the tissues onto fresh medium of the same combination. Finally, the shoots were rooted on MS medium containing 50 mg/l kanamycin. Incorporation and expression of the transgenes were confirmed by PCR analysis. Using this protocol, transgenic A. thaliana plants can be obtained and indicates that genomic transformation in higher plants is possible through insertion of desired gene. Although Agrobacterium mediated genetic transformation is established for A. thaliana, this study was the conducted to transform A. thaliana ecotype Bangladesh.

Root–Root Interactions:Towards A Rhizosphere Framework

NARCIS (Netherlands)

Mommer, L.; Kirkegaard, John; Ruijven, van J.

2016-01-01

Plant scientists have made great progress in understanding molecular mechanisms controlling root responses to nutrients of arabidopsis (Arabidopsis thaliana) plants under controlled conditions. Simultaneously, ecologists and agronomists have demonstrated that root–root interactions involve more than

An auxin responsive CLE gene regulates shoot apical meristem development in Arabidopsis

Directory of Open Access Journals (Sweden)

Hongyan eGuo

2015-05-01

Full Text Available Plant hormone auxin regulates most, if not all aspects of plant growth and development, including lateral root formation, organ pattering, apical dominance and tropisms. Peptide hormones are peptides with hormone activities. Some of the functions of peptide hormones in regulating plant growth and development are similar to that of auxin, however, the relationship between auxin and peptide hormones remains largely unknown. Here we report the identification of OsCLE48, a rice (Oryza sativa CLE (CLAVATA3/ENDOSPERM SURROUNDING REGION gene, as an auxin response gene, and the functional characterization of OsCLE48 in Arabidopsis and rice. OsCLE48 encodes a CLE peptide hormone that is similar to Arabidopsis CLEs. RT-PCR analysis showed that OsCLE48 was induced by exogenously application of IAA (indole-3-acetic acid, a naturally occurred auxin. Expression of integrated OsCLE48p:GUS reporter gene in transgenic Arabidopsis plants was also induced by exogenously IAA treatment. These results indicate that OsCLE48 is an auxin responsive gene. Histochemical staining showed that GUS activity was detected in all the tissue and organs of the OsCLE48p:GUS transgenic Arabidopsis plants. Expression of OsCLE48 under the control of the 35S promoter in Arabidopsis inhibited shoot apical meristem development. Expression of OsCLE48 under the control of the CLV3 native regulatory elements almost completely complemented clv3-2 mutant phenotypes, suggesting that OsCLE48 is functionally similar to CLV3. On the other hand, expression of OsCLE48 under the control of the 35S promoter in Arabidopsis has little, if any effects on root apical meristem development, and transgenic rice plants overexpressing OsCLE48 are morphologically indistinguishable from wild type plants, suggesting that the functions of some CLE peptides may not be fully conserved in Arabidopsis and rice.

PHABULOSA Controls the Quiescent Center-Independent Root Meristem Activities in Arabidopsis thaliana

Czech Academy of Sciences Publication Activity Database

Sebastian, J.; Ryu, K.H.; Zhou, J.; Tarkowská, Danuše; Tarkowski, P.; Cho, Y.H.; Yoo, S.D.; Kim, E.S.; Lee, J.Y.

2015-01-01

Roč. 11, č. 3 (2015) ISSN 1553-7390 Grant - others:GA MŠk(CZ) ED0007/01/01 Program:ED Institutional support: RVO:61389030 Keywords : STEM-CELL NICHE * POSTTRANSCRIPTIONAL REGULATION * GENE-EXPRESSION Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 7.528, year: 2014

Arabidopsis pdr2 reveals a phosphate-sensitive checkpoint in root development.

Science.gov (United States)

Ticconi, Carla A; Delatorre, Carla A; Lahner, Brett; Salt, David E; Abel, Steffen

2004-03-01

Plants have evolved complex strategies to maintain phosphate (Pi) homeostasis and to maximize Pi acquisition when the macronutrient is limiting. Adjustment of root system architecture via changes in meristem initiation and activity is integral to the acclimation process. However, the mechanisms that monitor external Pi status and interpret the nutritional signal remain to be elucidated. Here, we present evidence that the Pi deficiency response, pdr2, mutation disrupts local Pi sensing. The sensitivity and amplitude of metabolic Pi-starvation responses, such as Pi-responsive gene expression or accumulation of anthocyanins and starch, are enhanced in pdr2 seedlings. However, the most conspicuous alteration of pdr2 is a conditional short-root phenotype that is specific for Pi deficiency and caused by selective inhibition of root cell division followed by cell death below a threshold concentration of about 0.1 mm external Pi. Measurements of general Pi uptake and of total phosphorus (P) in root tips exclude a defect in high-affinity Pi acquisition. Rescue of root meristem activity in Pi-starved pdr2 by phosphite (Phi), a non-metabolizable Pi analog, and divided-root experiments suggest that pdr2 disrupts sensing of low external Pi availability. Thus, PDR2 is proposed to function at a Pi-sensitive checkpoint in root development, which monitors environmental Pi status, maintains and fine-tunes meristematic activity, and finally adjusts root system architecture to maximize Pi acquisition.

Hypocotyl adventitious root organogenesis differs from lateral root development.

Science.gov (United States)

Verstraeten, Inge; Schotte, Sébastien; Geelen, Danny

2014-01-01

Wound-induced adventitious root (AR) formation is a requirement for plant survival upon root damage inflicted by pathogen attack, but also during the regeneration of plant stem cuttings for clonal propagation of elite plant varieties. Yet, adventitious rooting also takes place without wounding. This happens for example in etiolated Arabidopsis thaliana hypocotyls, in which AR initiate upon de-etiolation or in tomato seedlings, in which AR initiate upon flooding or high water availability. In the hypocotyl AR originate from a cell layer reminiscent to the pericycle in the primary root (PR) and the initiated AR share histological and developmental characteristics with lateral roots (LRs). In contrast to the PR however, the hypocotyl is a determinate structure with an established final number of cells. This points to differences between the induction of hypocotyl AR and LR on the PR, as the latter grows indeterminately. The induction of AR on the hypocotyl takes place in environmental conditions that differ from those that control LR formation. Hence, AR formation depends on differentially regulated gene products. Similarly to AR induction in stem cuttings, the capacity to induce hypocotyl AR is genotype-dependent and the plant growth regulator auxin is a key regulator controlling the rooting response. The hormones cytokinins, ethylene, jasmonic acid, and strigolactones in general reduce the root-inducing capacity. The involvement of this many regulators indicates that a tight control and fine-tuning of the initiation and emergence of AR exists. Recently, several genetic factors, specific to hypocotyl adventitious rooting in A. thaliana, have been uncovered. These factors reveal a dedicated signaling network that drives AR formation in the Arabidopsis hypocotyl. Here we provide an overview of the environmental and genetic factors controlling hypocotyl-born AR and we summarize how AR formation and the regulating factors of this organogenesis are distinct from LR

Hypocotyl adventitious root organogenesis differs from lateral root development

Directory of Open Access Journals (Sweden)

Inge eVerstraeten

2014-09-01

Full Text Available Wound-induced adventitious root (AR formation is a requirement for plant survival upon root damage inflicted by pathogen attack, but also during the regeneration of plant stem cuttings for clonal propagation of elite plant varieties. Yet, adventitious rooting also takes place without wounding. This happens for example in etiolated Arabidopsis thaliana hypocotyls, in which AR initiate upon de-etiolation or in tomato seedlings, in which AR initiate upon flooding or high water availability. In the hypocotyl AR originate from a cell layer reminiscent to the pericycle in the primary root (PR and the initiated AR share histological and developmental characteristics with lateral roots (LR. In contrast to the PR however, the hypocotyl is a determinate structure with an established final number of cells. This points to differences between the induction of hypocotyl AR and LR on the PR, as the latter grows indeterminately. The induction of AR on the hypocotyl takes place in environmental conditions that differ from those that control LR formation. Hence, AR formation depends on differentially regulated gene products. Similarly to AR induction in stem cuttings, the capacity to induce hypocotyl AR is genotype-dependent and the plant growth regulator auxin is a key regulator controlling the rooting response. The hormones cytokinins, ethylene, jasmonic acid and strigolactones in general reduce the root-inducing capacity. The involvement of this many regulators indicates that a tight control and fine-tuning of the initiation and emergence of AR exists. Recently, several genetic factors, specific to hypocotyl adventitious rooting in Arabidopsis thaliana, have been uncovered. These factors reveal a dedicated signaling network that drives AR formation in the Arabidopsis hypocotyl. Here we provide an overview of the environmental and genetic factors controlling hypocotyl-born AR and we summarize how AR formation and the regulating factors of this organogenesis are

Regeneration of three sweet potato (Ipomea batatas (L.)) accessions via meristem, Nodal and callus induction

International Nuclear Information System (INIS)

Addae-Frimpomaah, F.

2012-11-01

In vitro regeneration of three sweet potato accessions UE007, UK-BNARI and SA-BNARI using meristem, nodal cuttings or callus induction was studied. Meristematic explants cultured on Murashige and Skoog (1962) basal medium supplemented with low concentration of benzylaminopurine (BAP) or kinetin resulted in callus with or without shoot development which delayed shoot emergence. The degree of callus development increased as the concentration of the cytokinin in the culture medium increased. Although, callus development was comparatively lower on kinetin amended medium than BAP amended medium, Murashige and Skoog medium supplemented with 0.25mg/1BAP had the highest shoot induction (80%). For further differentiation of callus or shoots into distinct stem and leaves, the culture were transferred into fresh MS medium supplemented with 0.25mg/1 BAP, 0.1 mg/1 NAA and 0.1 mg/1 Gibberellic acid (GA 3 . To overcome the delay in shoot initiation using meristem culture, nodal cuttings of sweet potato were used as explants and cultured on MS medium amended with 0.3 - 0.9mg/1 BAP. All explants cultured on 0.3 or 0.6mg/1 BAP developed shoots. Furthermore, liquid MS medium amended with 0.25mg/1 BAP, 0.1mg/I NAA, and 0.1mg/1 GA 3 also enhanced early shoot development from nodal cutting explants compared to solid culture. Post flask acclimatisation of meristem or nodal cutting-derived plantlets showed that meristem derived plantlets were better acclimatised than nodal cutting plants due to vigorous root development leading to higher percentage survival in pots and subsequent tuber production. Callusogenesis was achieved when leaf lobe explants were cultured on CLC/ Ipomoea medium supplemented with 1.0 - 4.0mg/1 2,4-D with 4.0mg/1 2,4-D being the optimal concentration. However, the calli were non-embryogenic and therefore could not produce embryos when transferred to 0.1mg/1 BAP amended medium but rather produced either single or multiple shoots. The highest percentage shoot (83

Edaphic history over seedling characters predicts integration and plasticity of integration across geologically variable populations of Arabidopsis thaliana.

Science.gov (United States)

Cousins, Elsa A; Murren, Courtney J

2017-12-01

Studies on phenotypic plasticity and plasticity of integration have uncovered functionally linked modules of aboveground traits and seedlings of Arabidopsis thaliana , but we lack details about belowground variation in adult plants. Functional modules can be comprised of additional suites of traits that respond to environmental variation. We assessed whether shoot and root responses to nutrient environments in adult A. thaliana were predictable from seedling traits or population-specific geologic soil characteristics at the site of origin. We compared 17 natural accessions from across the native range of A. thaliana using 14-day-old seedlings grown on agar or sand and plants grown to maturity across nutrient treatments in sand. We measured aboveground size, reproduction, timing traits, root length, and root diameter. Edaphic characteristics were obtained from a global-scale dataset and related to field data. We detected significant among-population variation in root traits of seedlings and adults and in plasticity in aboveground and belowground traits of adult plants. Phenotypic integration of roots and shoots varied by population and environment. Relative integration was greater in roots than in shoots, and integration was predicted by edaphic soil history, particularly organic carbon content, whereas seedling traits did not predict later ontogenetic stages. Soil environment of origin has significant effects on phenotypic plasticity in response to nutrients, and on phenotypic integration of root modules and shoot modules. Root traits varied among populations in reproductively mature individuals, indicating potential for adaptive and integrated functional responses of root systems in annuals. © 2017 Botanical Society of America.

Root - shoot - signaling in Chenopodium rubrum L. as studied by 15O labeled water uptake

International Nuclear Information System (INIS)

Ohya, T.; Hayashi, Y.; Tanoi, K.; Rai, H.; Nakanishi, T.M.; Suzuki, K.; Albrechtova, J.T.P.; Wagner, E.

2005-01-01

Full text: It has been demonstrated with C. rubrum that the different organ systems are transmitting surface action potentials which might be the basis for systemic signal transduction. Shoot tip respectively root generated action potentials travel along the stem axis. Shoot tip generated action potentials arriving at the basis can be reflected and travel upwards. The radioactive labeling technique was established at the NIRS in Inage, Japan. About 2 GBq of 15 O labeled Hoagland's solution was supplied to the plant root or cut stem in a phytotron at 25 o C with 45 % of relative humidity and continuous light. By cutting the shoot apical bud and the apices of main side branches the uptake of 15 O labeled water was inhibited in plants with intact roots but not in plants with roots cut. Because of the short half-life of 15 O (2 min), experiments could be repeated in hourly intervals. Cutting the apex probably limits root water uptake via a hydraulic-electrochemical signal. The results are discussed with respect to the significance of a continuous communication between the root system and the shoot apical meristem(s) in the adaptation of plants to their environment. (author)

Recruitment of glutathione into the nucleus during cell proliferation adjusts whole-cell redox homeostasis in Arabidopsis thaliana and lowers the oxidative defence shield.

Science.gov (United States)

Vivancos, Pedro Diaz; Dong, Yingping; Ziegler, Kerstin; Markovic, Jelena; Pallardó, Federico V; Pellny, Till K; Verrier, Paul J; Foyer, Christine H

2010-12-01

Cellular redox homeostasis and signalling are important in progression of the eukaryotic cell cycle. In animals, the low-molecular-weight thiol tripeptide glutathione (GSH) is recruited into the nucleus early in the cell proliferation cycle. To determine whether a similar process occurs in plants, we studied cell proliferation in Arabidopsis thaliana. We show that GSH co-localizes with nuclear DNA during the proliferation of A. thaliana cells in culture. Moreover, GSH localization in the nucleus was observed in dividing pericycle cells of the lateral root meristem. There was pronounced accumulation of GSH in the nucleus at points in the growth cycle at which a high percentage of the cells were in G(1) phase, as identified by flow cytometry and marker transcripts. Recruitment of GSH into the nucleus led to a high abundance of GSH in the nucleus (GSHn) and severe depletion of the cytoplasmic GSH pool (GSHc). Sequestration of GSH in the nucleus was accompanied by significant decreases in transcripts associated with oxidative signalling and stress tolerance, and an increase in the abundance of hydrogen peroxide, an effect that was enhanced when the dividing cells were treated with salicylic acid. Total cellular GSH and the abundance of GSH1 and GSH2 transcripts increased after the initial recruitment of GSH into the nucleus. We conclude that GSH recruitment into the nucleus during cell proliferation has a profound effect on the whole-cell redox state. High GSHn levels trigger redox adjustments in the cytoplasm, favouring decreased oxidative signalling and enhanced GSH synthesis. © 2010 The Authors. The Plant Journal © 2010 Blackwell Publishing Ltd.

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

KAUST Repository

Muraro, D.; Voss, U.; Wilson, M.; Bennett, M.; Byrne, H.; De Smet, I.; Hodgman, C.; King, J.

2013-01-01

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

A molecular framework for the inhibition of Arabidopsis root growth in response to boron toxicity.

Science.gov (United States)

Aquea, Felipe; Federici, Fernan; Moscoso, Cristian; Vega, Andrea; Jullian, Pastor; Haseloff, Jim; Arce-Johnson, Patricio

2012-04-01

Boron is an essential micronutrient for plants and is taken up in the form of boric acid (BA). Despite this, a high BA concentration is toxic for the plants, inhibiting root growth and is thus a significant problem in semi-arid areas in the world. In this work, we report the molecular basis for the inhibition of root growth caused by boron. We show that application of BA reduces the size of root meristems, correlating with the inhibition of root growth. The decrease in meristem size is caused by a reduction of cell division. Mitotic cell number significantly decreases and the expression level of key core cell cycle regulators is modulated. The modulation of the cell cycle does not appear to act through cytokinin and auxin signalling. A global expression analysis reveals that boron toxicity induces the expression of genes related with abscisic acid (ABA) signalling, ABA response and cell wall modifications, and represses genes that code for water transporters. These results suggest that boron toxicity produces a reduction of water and BA uptake, triggering a hydric stress response that produces root growth inhibition. © 2011 Blackwell Publishing Ltd.

Toxicity and transfer of CuO Nanoparticles on Arabidopsis thaliana

Science.gov (United States)

Zhao, Shilin; Dai, Yanhui; Xu, Lina

2018-02-01

CuO engineered nanoparticles (ENPs) are widely used in commercial applications. With increasing CuO ENPs production, CuO ENPs are likely to present in the environment and cause a potential threaten to ecosystem. In this work, Arabidopsis thaliana (Bay-0) was chosen to take the toxic experiment after exposed to CuO ENPs (0, 20, and 50 mg/L) and Cu2+ (0.15 mg/L). And the copper content of shoots at 50 mg/L CuO ENPs was about 20 times of control, indicating that CuO ENPs could be absorbed into Arabidopsis thaliana seedlings and transfered from root to shoot in a certain way.

Effect of 2 MHz ultrasound irradiation on Pisum sativum roots

International Nuclear Information System (INIS)

Miller, M.W.; Voorhees, S.M.; Carstensen, E.L.; Kaufman, G.E.

1976-01-01

The effect of 2 MHz ultrasound at intensity levels from 2.5 to 22 W/cm 2 on the growth rate and mitotic index of Pisum sativum roots was studied. The ultrasound produced an immediate reduction in the growth rate on the first postexposure day, followed by a gradual recovery to the control value. Ultrasound reduced the root meristem mitotic index. Intensity- and time-dependent relations were found for the growth rate and mitotic index reductions

A seed treatment to prevent shoot apical meristem arrest in Brassica oleracea

NARCIS (Netherlands)

Jonge, de J.; Goffman, Fernando D.; Kodde, J.; Angenent, G.C.; Groot, S.P.C.

2018-01-01

Brassica oleracea plants can suffer from shoot apical meristem arrest, when sown at cold temperatures, giving rise to so-called blind seedlings that stop development and the formation of new leaves. We developed a seed treatment that strongly reduces the occurrence of this meristem arrest in

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

The Arabidopsis thaliana homolog of the helicase RTEL1 plays multiple roles in preserving genome stability.

Science.gov (United States)

Recker, Julia; Knoll, Alexander; Puchta, Holger

2014-12-01

In humans, mutations in the DNA helicase Regulator of Telomere Elongation Helicase1 (RTEL1) lead to Hoyeraal-Hreidarsson syndrome, a severe, multisystem disorder. Here, we demonstrate that the RTEL1 homolog in Arabidopsis thaliana plays multiple roles in preserving genome stability. RTEL1 suppresses homologous recombination in a pathway parallel to that of the DNA translocase FANCM. Cytological analyses of root meristems indicate that RTEL1 is involved in processing DNA replication intermediates independently from FANCM and the nuclease MUS81. Moreover, RTEL1 is involved in interstrand and intrastrand DNA cross-link repair independently from FANCM and (in intrastrand cross-link repair) parallel to MUS81. RTEL1 contributes to telomere homeostasis; the concurrent loss of RTEL1 and the telomerase TERT leads to rapid, severe telomere shortening, which occurs much more rapidly than it does in the single-mutant line tert, resulting in developmental arrest after four generations. The double mutant rtel1-1 recq4A-4 exhibits massive growth defects, indicating that this RecQ family helicase, which is also involved in the suppression of homologous recombination and the repair of DNA lesions, can partially replace RTEL1 in the processing of DNA intermediates. The requirement for RTEL1 in multiple pathways to preserve genome stability in plants can be explained by its putative role in the destabilization of DNA loop structures, such as D-loops and T-loops. © 2014 American Society of Plant Biologists. All rights reserved.

Comparative study of the sensitivities of onion and broad bean root ...

African Journals Online (AJOL)

Chemicals which cause chromosomal aberration (CA) in plant cells frequently produce identical CA in cultured animal cells. Plant species however, differ in sensitivities. Onion and broad bean (BB) root meristem cells were compared for sensitivity to chlorpyrifos (CPF), mercury chloride (HgCl2), ethyl methanesulphonate ...

Induced mutations in ornamental plants by 'in vitro' irradiation of Petunia hybrida meristems

International Nuclear Information System (INIS)

Gonzalez-Jimenez, J.

1993-01-01

In recent decades it has been observed that for the induction of mutation in ornamental plants we can obtain better results when the plants are irradiated in vegetative state and even better 'in vitro' that when its are irradiated 'in vivo'. In this work the possibilities are showed to avoid the best use of a new biotechnology: the gamma irradiations on the meristem 'in vitro'. A tissue culture method was described for the best vegetative propagation of Petunia hybrid hort through morphogenesis induction of meristem. These were planted in the Murashige and Skoog's basic medium added with BAP and ANA. The pH was adjusted to 6.5 prior autoclaving at 121 Centigrade degree and 1.1 Kg/ cm 2 for 15 minutes. Latter the meristem of plantules in immature and mature physiology stated were irradiated with gamma ray doses ranging from 1.0 at 10.0 Gy. The meristem were then subcultived aseptically with the following results: 1) The immature stage was higher radio sensibilities. 2) The LD 50 for the matured plants was to ranged from 1.0 at 9.0 Gy. and immature 1.0 at 8.0 Gy. 3) The better doses was at 7.5 Gy. 4) The meristem gamma irradiation at 7.5 Gy. showed in the first culture: the adventitious bud induced and the multi meristem formation. 5) In the second cultured the results reveals the 'variegadas' plants formations and the new purples flowers. (Author)

Expression of pH-sensitive green fluorescent protein in Arabidopsis thaliana

Science.gov (United States)

Moseyko, N.; Feldman, L. J.

2001-01-01

This is the first report on using green fluorescent protein (GFP) as a pH reporter in plants. Proton fluxes and pH regulation play important roles in plant cellular activity and therefore, it would be extremely helpful to have a plant gene reporter system for rapid, non-invasive visualization of intracellular pH changes. In order to develop such a system, we constructed three vectors for transient and stable transformation of plant cells with a pH-sensitive derivative of green fluorescent protein. Using these vectors, transgenic Arabidopsis thaliana and tobacco plants were produced. Here the application of pH-sensitive GFP technology in plants is described and, for the first time, the visualization of pH gradients between different developmental compartments in intact whole-root tissues of A. thaliana is reported. The utility of pH-sensitive GFP in revealing rapid, environmentally induced changes in cytoplasmic pH in roots is also demonstrated.

Potential Bud Bank Responses to Apical Meristem Damage and Environmental Variables: Matching or Complementing Axillary Meristems?

Czech Academy of Sciences Publication Activity Database

Klimešová, Jitka; Malíková, Lenka; Rosenthal, J.; Šmilauer, P.

2014-01-01

Roč. 9, č. 2 (2014), e88093 E-ISSN 1932-6203 R&D Projects: GA ČR GPP504/12/P540; GA ČR GA526/09/0963 Institutional support: RVO:67985939 Keywords : bud bank * axillary meristem * disturbance Subject RIV: EH - Ecology, Behaviour Impact factor: 3.234, year: 2014

Developmental Functions of miR156-Regulated SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) Genes in Arabidopsis thaliana.

Science.gov (United States)

Xu, Mingli; Hu, Tieqiang; Zhao, Jianfei; Park, Mee-Yeon; Earley, Keith W; Wu, Gang; Yang, Li; Poethig, R Scott

2016-08-01

Correct developmental timing is essential for plant fitness and reproductive success. Two important transitions in shoot development-the juvenile-to-adult vegetative transition and the vegetative-to-reproductive transition-are mediated by a group of genes targeted by miR156, SQUAMOSA PROMOTER BINDING PROTEIN (SBP) genes. To determine the developmental functions of these genes in Arabidopsis thaliana, we characterized their expression patterns, and their gain-of-function and loss-of-function phenotypes. Our results reveal that SBP-LIKE (SPL) genes in Arabidopsis can be divided into three functionally distinct groups: 1) SPL2, SPL9, SPL10, SPL11, SPL13 and SPL15 contribute to both the juvenile-to-adult vegetative transition and the vegetative-to-reproductive transition, with SPL9, SP13 and SPL15 being more important for these processes than SPL2, SPL10 and SPL11; 2) SPL3, SPL4 and SPL5 do not play a major role in vegetative phase change or floral induction, but promote the floral meristem identity transition; 3) SPL6 does not have a major function in shoot morphogenesis, but may be important for certain physiological processes. We also found that miR156-regulated SPL genes repress adventitious root development, providing an explanation for the observation that the capacity for adventitious root production declines as the shoot ages. miR156 is expressed at very high levels in young seedlings, and declines in abundance as the shoot develops. It completely blocks the expression of its SPL targets in the first two leaves of the rosette, and represses these genes to different degrees at later stages of development, primarily by promoting their translational repression. These results provide a framework for future studies of this multifunctional family of transcription factors, and offer new insights into the role of miR156 in Arabidopsis development.

Apple latent spherical virus vectors for reliable and effective virus-induced gene silencing among a broad range of plants including tobacco, tomato, Arabidopsis thaliana, cucurbits, and legumes

International Nuclear Information System (INIS)

Igarashi, Aki; Yamagata, Kousuke; Sugai, Tomokazu; Takahashi, Yukari; Sugawara, Emiko; Tamura, Akihiro; Yaegashi, Hajime; Yamagishi, Noriko; Takahashi, Tsubasa; Isogai, Masamichi; Takahashi, Hideki; Yoshikawa, Nobuyuki

2009-01-01

Apple latent spherical virus (ALSV) vectors were evaluated for virus-induced gene silencing (VIGS) of endogenous genes among a broad range of plant species. ALSV vectors carrying partial sequences of a subunit of magnesium chelatase (SU) and phytoene desaturase (PDS) genes induced highly uniform knockout phenotypes typical of SU and PDS inhibition on model plants such as tobacco and Arabidopsis thaliana, and economically important crops such as tomato, legume, and cucurbit species. The silencing phenotypes persisted throughout plant growth in these plants. In addition, ALSV vectors could be successfully used to silence a meristem gene, proliferating cell nuclear antigen and disease resistant N gene in tobacco and RCY1 gene in A. thaliana. As ALSV infects most host plants symptomlessly and effectively induces stable VIGS for long periods, the ALSV vector is a valuable tool to determine the functions of interested genes among a broad range of plant species.

Meristem micropropagation of cassava (Manihot esculenta) evokes genome-wide changes in DNA methylation.

Science.gov (United States)

Kitimu, Shedrack R; Taylor, Julian; March, Timothy J; Tairo, Fred; Wilkinson, Mike J; Rodríguez López, Carlos M

2015-01-01

There is great interest in the phenotypic, genetic and epigenetic changes associated with plant in vitro culture known as somaclonal variation. In vitro propagation systems that are based on the use of microcuttings or meristem cultures are considered analogous to clonal cuttings and so widely viewed to be largely free from such somaclonal effects. In this study, we surveyed for epigenetic changes during propagation by meristem culture and by field cuttings in five cassava (Manihot esculenta) cultivars. Principal Co-ordinate Analysis of profiles generated by methylation-sensitive amplified polymorphism revealed clear divergence between samples taken from field-grown cuttings and those recovered from meristem culture. There was also good separation between the tissues of field samples but this effect was less distinct among the meristem culture materials. Application of methylation-sensitive Genotype by sequencing identified 105 candidate epimarks that distinguish between field cutting and meristem culture samples. Cross referencing the sequences of these epimarks to the draft cassava genome revealed 102 sites associated with genes whose homologs have been implicated in a range of fundamental biological processes including cell differentiation, development, sugar metabolism, DNA methylation, stress response, photosynthesis, and transposon activation. We explore the relevance of these findings for the selection of micropropagation systems for use on this and other crops.

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

Science.gov (United States)

Vanhoudt, Nathalie; Vandenhove, Hildegarde; Horemans, Nele; Remans, Tony; Opdenakker, Kelly; Smeets, Karen; Bello, Daniel Martinez; Wannijn, Jean; Van Hees, May; Vangronsveld, Jaco; Cuypers, Ann

2011-06-01

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 μM 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 μM. 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(2)O(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. Copyright © 2011 Elsevier Ltd. All rights reserved.

Coordination of growth in root and shoot apices by AIL/PLT transcription factors

NARCIS (Netherlands)

Scheres, Ben; Krizek, Beth A.

2018-01-01

Growth at the root tip and organ generation at the shoot tip depend on the proper functioning of apical meristems and the transitioning of meristematic cell descendants from a proliferating state to cell elongation and differentiation. Members of the AINTEGUMENTA-LIKE/PLETHORA (AIL/PLT)

How and why does the areole meristem move in Echinocereus (Cactaceae)?

Science.gov (United States)

Sánchez, Daniel; Grego-Valencia, Dalia; Terrazas, Teresa; Arias, Salvador

2015-01-01

In Cactaceae, the areole is the organ that forms the leaves, spines and buds. Apparently, the genus Echinocereus develops enclosed buds that break through the epidermis of the stem adjacent to the areole; this trait most likely represents a synapomorphy of Echinocereus. The development of the areole is investigated here in order to understand the anatomical modifications that lead to internal bud development and to supplement anatomical knowledge of plants that do not behave according to classical shoot theory. The external morphology of the areole was documented and the anatomy was studied using tissue clearing, scanning electron microscopy and light microscopy for 50 species that represent the recognized clades and sections of the traditional classification of the genus, including Morangaya pensilis (Echinocereus pensilis). In Echinocereus, the areole is sealed by the periderm, and the areole meristem is moved and enclosed by the differential growth of the epidermis and surrounding cortex. The enclosed areole meristem is differentiated in a vegetative or floral bud, which develops internally and breaks through the epidermis of the stem. In Morangaya pensilis, the areole is not sealed by the periderm and the areole meristem is not enclosed. The enclosed areole meristem and internal bud development are understood to be an adaptation to protect the meristem and the bud from low temperatures. The anatomical evidence supports the hypothesis that the enclosed bud represents one synapomorphy for Echinocereus and also supports the exclusion of Morangaya from Echinocereus. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

High CO2 triggers preferential root growth of Arabidopsis thaliana via two distinct systems under low pH and low N stresses.

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Hachiya, Takushi; Sugiura, Daisuke; Kojima, Mikiko; Sato, Shigeru; Yanagisawa, Shuichi; Sakakibara, Hitoshi; Terashima, Ichiro; Noguchi, Ko

2014-02-01

Biomass allocation between shoots and roots is an important strategy used by plants to optimize growth in various environments. Root to shoot mass ratios typically increase in response to high CO2, a trend particularly evident under abiotic stress. We investigated this preferential root growth (PRG) in Arabidopsis thaliana plants cultivated under low pH/high CO2 or low nitrogen (N)/high CO2 conditions. Previous studies have suggested that changes in plant hormone, carbon (C) and N status may be related to PRG. We therefore examined the mechanisms underlying PRG by genetically modifying cytokinin (CK) levels, C and N status, and sugar signaling, performing sugar application experiments and determining primary metabolites, plant hormones and expression of related genes. Both low pH/high CO2 and low N/high CO2 stresses induced increases in lateral root (LR) number and led to high C/N ratios; however, under low pH/high CO2 conditions, large quantities of C were accumulated, whereas under low N/high CO2 conditions, N was severely depleted. Analyses of a CK-deficient mutant and a starchless mutant, in conjunction with sugar application experiments, revealed that these stresses induce PRG via different mechanisms. Metabolite and hormone profile analysis indicated that under low pH/high CO2 conditions, excess C accumulation may enhance LR number through the dual actions of increased auxin and decreased CKs.

In roots of Arabidopsis thaliana, the damage-associated molecular pattern AtPep1 is a stronger elicitor of immune signalling than flg22 or the chitin heptamer.

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Lorenzo Poncini

Full Text Available Plants interpret their immediate environment through perception of small molecules. Microbe-associated molecular patterns (MAMPs such as flagellin and chitin are likely to be more abundant in the rhizosphere than plant-derived damage-associated molecular patterns (DAMPs. We investigated how the Arabidopsis thaliana root interprets MAMPs and DAMPs as danger signals. We monitored root development during exposure to increasing concentrations of the MAMPs flg22 and the chitin heptamer as well as of the DAMP AtPep1. The tissue-specific expression of defence-related genes in roots was analysed using a toolkit of promoter::YFPN lines reporting jasmonic acid (JA-, salicylic acid (SA-, ethylene (ET- and reactive oxygen species (ROS- dependent signalling. Finally, marker responses were analysed during invasion by the root pathogen Fusarium oxysporum. The DAMP AtPep1 triggered a stronger activation of the defence markers compared to flg22 and the chitin heptamer. In contrast to the tested MAMPs, AtPep1 induced SA- and JA-signalling markers in the root and caused a severe inhibition of root growth. Fungal attack resulted in a strong activation of defence genes in tissues close to the invading fungal hyphae. The results collectively suggest that AtPep1 presents a stronger danger signal to the Arabidopsis root than the MAMPs flg22 and chitin heptamer.

Natural Arabidopsis brx loss-of-function alleles confer root adaptation to acidic soil.

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Gujas, Bojan; Alonso-Blanco, Carlos; Hardtke, Christian S

2012-10-23

Soil acidification is a major agricultural problem that negatively affects crop yield. Root systems counteract detrimental passive proton influx from acidic soil through increased proton pumping into the apoplast, which is presumably also required for cell elongation and stimulated by auxin. Here, we found an unexpected impact of extracellular pH on auxin activity and cell proliferation rate in the root meristem of two Arabidopsis mutants with impaired auxin perception, axr3 and brx. Surprisingly, neutral to slightly alkaline media rescued their severely reduced root (meristem) growth by stimulating auxin signaling, independent of auxin uptake. The finding that proton pumps are hyperactive in brx roots could explain this phenomenon and is consistent with more robust growth and increased fitness of brx mutants on overly acidic media or soil. Interestingly, the original brx allele was isolated from a natural stock center accession collected from acidic soil. Our discovery of a novel brx allele in accessions recently collected from another acidic sampling site demonstrates the existence of independently maintained brx loss-of-function alleles in nature and supports the notion that they are advantageous in acidic soil pH conditions, a finding that might be exploited for crop breeding. Copyright © 2012 Elsevier Ltd. All rights reserved.

Piriformospora indica root colonization triggers local and systemic root responses and inhibits secondary colonization of distal roots.

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Pedrotti, Lorenzo; Mueller, Martin J; Waller, Frank

2013-01-01

Piriformosporaindica is a basidiomycete fungus colonizing roots of a wide range of higher plants, including crop plants and the model plant Arabidopsis thaliana. Previous studies have shown that P. indica improves growth, and enhances systemic pathogen resistance in leaves of host plants. To investigate systemic effects within the root system, we established a hydroponic split-root cultivation system for Arabidopsis. Using quantitative real-time PCR, we show that initial P. indica colonization triggers a local, transient response of several defense-related transcripts, of which some were also induced in shoots and in distal, non-colonized roots of the same plant. Systemic effects on distal roots included the inhibition of secondary P. indica colonization. Faster and stronger induction of defense-related transcripts during secondary inoculation revealed that a P. indica pretreatment triggers root-wide priming of defense responses, which could cause the observed reduction of secondary colonization levels. Secondary P. indica colonization also induced defense responses in distant, already colonized parts of the root. Endophytic fungi therefore trigger a spatially specific response in directly colonized and in systemic root tissues of host plants.

Simulation of organ patterning on the floral meristem using a polar auxin transport model.

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Simon van Mourik

Full Text Available An intriguing phenomenon in plant development is the timing and positioning of lateral organ initiation, which is a fundamental aspect of plant architecture. Although important progress has been made in elucidating the role of auxin transport in the vegetative shoot to explain the phyllotaxis of leaf formation in a spiral fashion, a model study of the role of auxin transport in whorled organ patterning in the expanding floral meristem is not available yet. We present an initial simulation approach to study the mechanisms that are expected to play an important role. Starting point is a confocal imaging study of Arabidopsis floral meristems at consecutive time points during flower development. These images reveal auxin accumulation patterns at the positions of the organs, which strongly suggests that the role of auxin in the floral meristem is similar to the role it plays in the shoot apical meristem. This is the basis for a simulation study of auxin transport through a growing floral meristem, which may answer the question whether auxin transport can in itself be responsible for the typical whorled floral pattern. We combined a cellular growth model for the meristem with a polar auxin transport model. The model predicts that sepals are initiated by auxin maxima arising early during meristem outgrowth. These form a pre-pattern relative to which a series of smaller auxin maxima are positioned, which partially overlap with the anlagen of petals, stamens, and carpels. We adjusted the model parameters corresponding to properties of floral mutants and found that the model predictions agree with the observed mutant patterns. The predicted timing of the primordia outgrowth and the timing and positioning of the sepal primordia show remarkable similarities with a developing flower in nature.

The Arabidopsis thaliana Homolog of the Helicase RTEL1 Plays Multiple Roles in Preserving Genome Stability[C][W

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Recker, Julia; Knoll, Alexander; Puchta, Holger

2014-01-01

In humans, mutations in the DNA helicase Regulator of Telomere Elongation Helicase1 (RTEL1) lead to Hoyeraal-Hreidarsson syndrome, a severe, multisystem disorder. Here, we demonstrate that the RTEL1 homolog in Arabidopsis thaliana plays multiple roles in preserving genome stability. RTEL1 suppresses homologous recombination in a pathway parallel to that of the DNA translocase FANCM. Cytological analyses of root meristems indicate that RTEL1 is involved in processing DNA replication intermediates independently from FANCM and the nuclease MUS81. Moreover, RTEL1 is involved in interstrand and intrastrand DNA cross-link repair independently from FANCM and (in intrastrand cross-link repair) parallel to MUS81. RTEL1 contributes to telomere homeostasis; the concurrent loss of RTEL1 and the telomerase TERT leads to rapid, severe telomere shortening, which occurs much more rapidly than it does in the single-mutant line tert, resulting in developmental arrest after four generations. The double mutant rtel1-1 recq4A-4 exhibits massive growth defects, indicating that this RecQ family helicase, which is also involved in the suppression of homologous recombination and the repair of DNA lesions, can partially replace RTEL1 in the processing of DNA intermediates. The requirement for RTEL1 in multiple pathways to preserve genome stability in plants can be explained by its putative role in the destabilization of DNA loop structures, such as D-loops and T-loops. PMID:25516598

Meristem micropropagation of cassava (Manihot esculenta evokes genome-wide changes in DNA methylation

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Shedrack Reuben Kitimu

2015-08-01

Full Text Available There is great interest in the phenotypic, genetic and epigenetic changes associated with plant in vitro culture known as somaclonal variation. In vitro propagation systems that are based on the use of microcuttings or meristem cultures are considered analogous to clonal cuttings and so widely viewed to be largely free from such somaclonal effects. In this study, we surveyed for epigenetic changes during propagation by meristem culture and by field cuttings in five cassava (Manihot esculenta cultivars. Principal Co-ordinate Analysis of profiles generated by Methylation Sensitive Amplified Polymorphism (MSAP revealed clear divergence between samples taken from field-grown cuttings and those recovered from meristem culture. There was also good separation between the tissues of field samples but this effect was less distinct among the meristem culture materials. Application of methylation-sensitive Genotype By Sequencing (msGBS identified 105 candidate epimarks that distinguish between field cutting and meristem culture samples. Cross referencing the sequences of these epimarks to the draft cassava genome revealed 102 sites associated with genes whose homologues have been implicated in a range of fundamental biological processes including cell differentiation, development, sugar metabolism, DNA methylation, stress response, photosynthesis, and transposon activation. We explore the relevance of these findings for the selection of micropropagation systems for use on this and other crops.

The garlic allelochemical diallyl disulfide affects tomato root growth by influencing cell division, phytohormone balance and expansin gene expression

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Fang Cheng

2016-08-01

Full Text Available Diallyl disulfide (DADS is a volatile organosulfur compound derived from garlic (Allium sativum L., and it is known as an allelochemical responsible for the strong allelopathic potential of garlic. The anticancer properties of DADS have been studied in experimental animals and various types of cancer cells, but to date, little is known about its mode of action as an allelochemical at the cytological level. The current research presents further studies on the effects of DADS on tomato (Solanum lycopersicum L. seed germination, root growth, mitotic index and cell size in root meristem, as well as the phytohormone levels and expression profile of auxin biosynthesis genes (FZYs, auxin transport genes (SlPINs and expansin genes (EXPs in tomato root. The results showed a biphasic, dose-dependent effect on tomato seed germination and root growth under different DADS concentrations. Lower concentrations (0.01-0.62 mM of DADS significantly promoted root growth, whereas higher levels (6.20-20.67 mM showed inhibitory effects. Cytological observations showed that the cell length of root meristem was increased and that the mitotic activity of meristematic cells in seedling root tips was enhanced at lower concentrations of DADS. In contrast, DADS at higher concentrations inhibited root growth by affecting both the length and division activity of meristematic cells. However, the cell width of the root meristem was not affected. Additionally, DADS increased the IAA and ZR contents of seedling roots in a dose-dependent manner. The influence on IAA content may be mediated by the up-regulation of FZYs and PINs. Further investigation into the underlying mechanism revealed that the expression levels of tomato EXPs were significantly affected by DADS. The expression levels of EXPB2 and beta-expansin precursor were increased after 3 d, and those of EXP1, EXPB3 and EXLB1 were increased after 5 d of DADS treatment (0.41 mM. This result suggests that tomato root growth

Characterization of a Cytokinin Response Factor in Arabidopsis thaliana

OpenAIRE

Ketelsen, Bernd

2012-01-01

The papers of this thesis are not available in Munin: 1. Bernd Ketelsen, Rainer Schwacke, Kirsten Krause and Karsten Fischer: 'Transcriptional activation by Cytokinin Response Factor 5 is governed by an acidic Cterminus containing two conserved domains' (manuscript) 2. Bernd Ketelsen, Stian Olsen, Kirsten Krause and Karsten Fischer: 'Cytokinin responsive factor 5 (CRF5) is involved in root development, hormonal crosstalk and sugar metabolism in Arabidopsis thaliana' (manuscript) 3. Bernd K...

CsSCL1 is differentially regulated upon maturation in chestnut microshoots and is specifically expressed in rooting-competent cells.

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Vielba, Jesús M; Díaz-Sala, Carmen; Ferro, Enrique; Rico, Saleta; Lamprecht, María; Abarca, Dolores; Ballester, Antonio; Sánchez, Conchi

2011-10-01

The Castanea sativa SCL1 gene (CsSCL1) has previously been shown to be induced by auxin during adventitious root (AR) formation in rooting-competent microshoots. However, its expression has not previously been analyzed in rooting-incompetent shoots. This study focuses on the regulation of CsSCL1 during maturation and the role of the gene in the formation of AR. The expression of CsSCL1 in rooting-incompetent microshoots and other tissues was investigated by quantitative reverse transcriptase--polymerase chain reaction. The analysis was complemented by in situ hybridization of the basal segments of rooting-competent and --incompetent microshoots during AR induction, as well as in AR and lateral roots. It was found that CsSCL1 is upregulated by auxin in a cell-type- and phase-dependent manner during the induction of AR. In root-forming shoots, CsSCL1 mRNA was specifically located in the cambial zone and derivative cells, which are rooting-competent cells, whereas in rooting-incompetent shoots the hybridization signal was more diffuse and evenly distributed through the phloem and parenchyma. CsSCL1 expression was also detected in lateral roots and axillary buds. The different CsSCL1 expression patterns in rooting-competent and -incompetent microshoots, together with the specific location of transcripts in cell types involved in root meristem initiation and in the root primordia of AR and lateral roots, indicate an important role for the gene in determining whether certain cells will enter the root differentiation pathway and its involvement in meristem maintenance.

Lateral root development in the maize (Zea mays) lateral rootless1 mutant.

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Husakova, Eva; Hochholdinger, Frank; Soukup, Ales

2013-07-01

The maize lrt1 (lateral rootless1) mutant is impaired in its development of lateral roots during early post-embryonic development. The aim of this study was to characterize, in detail, the influences that the mutation exerts on lateral root initiation and the subsequent developments, as well as to describe the behaviour of the entire plant under variable environmental conditions. Mutant lrt1 plants were cultivated under different conditions of hydroponics, and in between sheets of moist paper. Cleared whole mounts and anatomical sections were used in combination with both selected staining procedures and histochemical tests to follow root development. Root surface permeability tests and the biochemical quantification of lignin were performed to complement the structural data. The data presented suggest a redefinition of lrt1 function in lateral roots as a promoter of later development; however, neither the complete absence of lateral roots nor the frequency of their initiation is linked to lrt1 function. The developmental effects of lrt1 are under strong environmental influences. Mutant primordia are affected in structure, growth and emergence; and the majority of primordia terminate their growth during this last step, or shortly thereafter. The lateral roots are impaired in the maintenance of the root apical meristem. The primary root shows disturbances in the organization of both epidermal and subepidermal layers. The lrt1-related cell-wall modifications include: lignification in peripheral layers, the deposition of polyphenolic substances and a higher activity of peroxidase. The present study provides novel insights into the function of the lrt1 gene in root system development. The lrt1 gene participates in the spatial distribution of initiation, but not in its frequency. Later, the development of lateral roots is strongly affected. The effect of the lrt1 mutation is not as obvious in the primary root, with no influences observed on the root apical meristem

Lateral root development in the maize (Zea mays) lateral rootless1 mutant

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Husakova, Eva; Hochholdinger, Frank; Soukup, Ales

2013-01-01

Background and Aims The maize lrt1 (lateral rootless1) mutant is impaired in its development of lateral roots during early post-embryonic development. The aim of this study was to characterize, in detail, the influences that the mutation exerts on lateral root initiation and the subsequent developments, as well as to describe the behaviour of the entire plant under variable environmental conditions. Methods Mutant lrt1 plants were cultivated under different conditions of hydroponics, and in between sheets of moist paper. Cleared whole mounts and anatomical sections were used in combination with both selected staining procedures and histochemical tests to follow root development. Root surface permeability tests and the biochemical quantification of lignin were performed to complement the structural data. Key Results The data presented suggest a redefinition of lrt1 function in lateral roots as a promoter of later development; however, neither the complete absence of lateral roots nor the frequency of their initiation is linked to lrt1 function. The developmental effects of lrt1 are under strong environmental influences. Mutant primordia are affected in structure, growth and emergence; and the majority of primordia terminate their growth during this last step, or shortly thereafter. The lateral roots are impaired in the maintenance of the root apical meristem. The primary root shows disturbances in the organization of both epidermal and subepidermal layers. The lrt1-related cell-wall modifications include: lignification in peripheral layers, the deposition of polyphenolic substances and a higher activity of peroxidase. Conclusions The present study provides novel insights into the function of the lrt1 gene in root system development. The lrt1 gene participates in the spatial distribution of initiation, but not in its frequency. Later, the development of lateral roots is strongly affected. The effect of the lrt1 mutation is not as obvious in the primary root, with no

Europium Uptake and Partitioning in Oat (Avena sativa) Roots as studied By Laser-Induced Fluorescence Spectroscopy and Confocal Microscopy Profiling Technique

International Nuclear Information System (INIS)

Fellows, Robert J.; Wang, Zheming; Ainsworth, Calvin C.

2003-01-01

The uptake of Eu3+ by elongating oat plant roots was studied by fluorescence spectroscopy, fluorescence lifetime measurement, as well as laser excitation time-resolved confocal fluorescence profiling technique. The results of this work indicated that the initial uptake of Eu(III) by oat root was most evident within the apical meristem of the root just proximal to the root cap. Distribution of assimilated Eu(III) within the roots differentiation and elongation zone was non-uniform. Higher concentrations were observed within the vascular cylinder, specifically in the phloem and developing xylem parenchyma. Elevated levels of the metal were also observed in the root hairs of the mature root. The concentration of assimilated Eu3+ dropped sharply from the apical meristem to the differentiation and elongation zone and then gradually decreased as the distance from the root cap increased. Fluorescence spectroscopic characteristics of the assimilated Eu3+ suggested that the Eu3+ exists a s inner-sphere mononuclear complexes inside the root. This work has also demonstrated the effectiveness of a time-resolved Eu3+ fluorescence spectroscopy and confocal fluorescence profiling techniques for the in vivo, real-time study of metal[Eu3+] accumulation by a functioning intact plant root. This approach can prove valuable for basic and applied studies in plant nutrition and environmental uptake of actinide radionuclides

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

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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. 

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

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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

Root morphology of Ni-treated plants

International Nuclear Information System (INIS)

Leskova, A.; Fargasova, A.; Giehl, R. F. H.; Wiren, N. von

2015-01-01

Plant roots are very important organs in terms of nutrient and water acquisition but they also serve as anchorages for the aboveground parts of the plants. The roots display extraordinary plasticity towards stress conditions as a result of integration of environmental cues into the developmental processes of the roots. Our aim was to investigate the root morphology of Arabidopsis thaliana plants exposed to a particular stress condition, excess Ni supply. We aimed to find out which cellular processes - cell division, elongation and differentiation are affected by Ni, thereby explaining the seen root phenotype. Our results reveal that a distinct sensitivity exists between roots of different order and interference with various cellular processes is responsible for the effects of Ni on roots. We also show that Ni-treated roots have several auxin-related phenotypes. (authors)

An activated form of UFO alters leaf development and produces ectopic floral and inflorescence meristems.

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Eddy Risseeuw

Full Text Available Plants are unique in their ability to continuously produce new meristems and organ primordia. In Arabidopsis, the transcription factor LEAFY (LFY functions as a master regulator of a gene network that is important for floral meristem and organ specification. UNUSUAL FLORAL ORGANS (UFO is a co-activator of LEAFY and is required for proper activation of APETALA3 in the floral meristem during the specification of stamens and petals. The ufo mutants display defects in other parts of the flower and the inflorescence, suggestive of additional roles. Here we show that the normal determinacy of the developing Arabidopsis leaves is affected by the expression of a gain-of-function UFO fusion protein with the VP16 transcriptional activator domain. In these lines, the rosette and cauline leaf primordia exhibit reiterated serration, and upon flowering produce ectopic meristems that develop into flowers, bract leaves and inflorescences. These striking phenotypes reveal that developing leaves maintain the competency to initiate flower and inflorescence programs. Furthermore, the gain-of-function phenotypes are dependent on LFY and the SEPALLATA (SEP MADS-box transcription factors, indicative of their functional interactions with UFO. The findings of this study also suggest that UFO promotes the establishment of the lateral meristems and primordia in the peripheral zone of the apical and floral meristems by enhancing the activity of LFY. These novel phenotypes along with the mutant phenotypes of UFO orthologs in other plant species suggest a broader function for UFO in plants.

An activated form of UFO alters leaf development and produces ectopic floral and inflorescence meristems.

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Risseeuw, Eddy; Venglat, Prakash; Xiang, Daoquan; Komendant, Kristina; Daskalchuk, Tim; Babic, Vivijan; Crosby, William; Datla, Raju

2013-01-01

Plants are unique in their ability to continuously produce new meristems and organ primordia. In Arabidopsis, the transcription factor LEAFY (LFY) functions as a master regulator of a gene network that is important for floral meristem and organ specification. UNUSUAL FLORAL ORGANS (UFO) is a co-activator of LEAFY and is required for proper activation of APETALA3 in the floral meristem during the specification of stamens and petals. The ufo mutants display defects in other parts of the flower and the inflorescence, suggestive of additional roles. Here we show that the normal determinacy of the developing Arabidopsis leaves is affected by the expression of a gain-of-function UFO fusion protein with the VP16 transcriptional activator domain. In these lines, the rosette and cauline leaf primordia exhibit reiterated serration, and upon flowering produce ectopic meristems that develop into flowers, bract leaves and inflorescences. These striking phenotypes reveal that developing leaves maintain the competency to initiate flower and inflorescence programs. Furthermore, the gain-of-function phenotypes are dependent on LFY and the SEPALLATA (SEP) MADS-box transcription factors, indicative of their functional interactions with UFO. The findings of this study also suggest that UFO promotes the establishment of the lateral meristems and primordia in the peripheral zone of the apical and floral meristems by enhancing the activity of LFY. These novel phenotypes along with the mutant phenotypes of UFO orthologs in other plant species suggest a broader function for UFO in plants.

Early development and gravitropic response of lateral roots in Arabidopsis thaliana.

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Guyomarc'h, S; Léran, S; Auzon-Cape, M; Perrine-Walker, F; Lucas, M; Laplaze, L

2012-06-05

Root system architecture plays an important role in determining nutrient and water acquisition and is modulated by endogenous and environmental factors, resulting in considerable developmental plasticity. The orientation of primary root growth in response to gravity (gravitropism) has been studied extensively, but little is known about the behaviour of lateral roots in response to this signal. Here, we analysed the response of lateral roots to gravity and, consistently with previous observations, we showed that gravitropism was acquired slowly after emergence. Using a lateral root induction system, we studied the kinetics for the appearance of statoliths, phloem connections and auxin transporter gene expression patterns. We found that statoliths could not be detected until 1 day after emergence, whereas the gravitropic curvature of the lateral root started earlier. Auxin transporters modulate auxin distribution in primary root gravitropism. We found differences regarding PIN3 and AUX1 expression patterns between the lateral root and the primary root apices. Especially PIN3, which is involved in primary root gravitropism, was not expressed in the lateral root columella. Our work revealed new developmental transitions occurring in lateral roots after emergence, and auxin transporter expression patterns that might explain the specific response of lateral roots to gravity.

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.

Exogenous auxin alleviates cadmium toxicity in Arabidopsis thaliana by stimulating synthesis of hemicellulose 1 and increasing the cadmium fixation capacity of root cell walls

International Nuclear Information System (INIS)

Zhu, Xiao Fang; Wang, Zhi Wei; Dong, Fang; Lei, Gui Jie; Shi, Yuan Zhi; Li, Gui Xin; Zheng, Shao Jian

2013-01-01

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 2+ ) stress decreased the endogenous auxin level, whereas exogenous auxin (α-naphthaleneacetic acid, NAA, a permeable auxin analog) reduced shoot Cd 2+ concentration and rescued Cd 2+ -induced chlorosis in Arabidopsis thaliana. Under Cd 2+ stress conditions, NAA increased Cd 2+ retention in the roots and most Cd 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 2+ , whereas it significantly increased the content of hemicellulose 1 and the amount of Cd 2+ retained in it. There were highly significant correlations between Cd 2+ concentrations in the root, cell wall and hemicellulose 1 when the plants were subjected to Cd 2+ or NAA + Cd 2+ treatment for 1 to 7 d, suggesting that the increase in hemicellulose 1 contributes greatly to the fixation of Cd 2+ in the cell wall. Taken together, these results demonstrate that auxin-induced alleviation of Cd 2+ toxicity in Arabidopsis is mediated through increasing hemicellulose 1 content and Cd 2+ fixation in the root, thus reducing the translocation of Cd 2+ from roots to shoots

Comparative evaluation of total RNA extraction methods in Theobroma cacao using shoot apical meristems.

Science.gov (United States)

Silva, D V; Branco, S M J; Holanda, I S A; Royaert, S; Motamayor, J C; Marelli, J P; Corrêa, R X

2016-03-04

Theobroma cacao is a species of great economic importance with its beans used for chocolate production. The tree has been a target of various molecular studies. It contains many polyphenols, which complicate the extraction of nucleic acids with the extraction protocols requiring a large amount of plant material. These issues, therefore, necessitate the optimization of the protocols. The aim of the present study was to evaluate different methods for extraction of total RNA from shoot apical meristems of T. cacao 'CCN 51' and to assess the influence of storage conditions for the meristems on the extraction. The study also aimed to identify the most efficient protocol for RNA extraction using a small amount of plant material. Four different protocols were evaluated for RNA extraction using one shoot apical meristem per sample. Among these protocols, one that was more efficient was then tested to extract RNA using four different numbers of shoot apical meristems, subjected to three different storage conditions. The best protocol was tested for cDNA amplification using reverse transcription-polymerase chain reaction; the cDNA quality was determined to be satisfactory for molecular analyses. The study revealed that with the best RNA extraction protocol, one shoot apical meristem was sufficient for extraction of high-quality total RNA. The results obtained might enable advances in genetic analyses and molecular studies using reduced amount of plant material.

Cryopreservation of in vitro grown shoot tips and apical meristems of the forage legume Arachis pintoi.

Science.gov (United States)

Rey, Hebe Y; Faloci, Mirta; Medina, Ricardo; Dolce, Natalia; Mroginski, Luis; Engelmann, Florent

2009-01-01

A cryopreservation protocol using the encapsulation-dehydration procedure was established for shoot tips (2-3 mm in length) and meristems (0.3-0.5 mm) sampled from in vitro plantlets of diploid and triploid cytotypes of Arachis pintoi. The optimal protocol was the following: after dissection, explants were precultured for 24 h on establishment medium (EM), encapsulated in calcium alginate beads and pretreated in liquid EM medium with daily increasing sucrose concentration (0.5, 0.75, 1.0 M) and desiccated to 22-23 percent moisture content (fresh weight basis). Explants were frozen using slow cooling (1 C per min from 25C to -30C followed by direct immersion in liquid nitrogen), thawed rapidly and post-cultured in liquid EM medium enriched with daily decreasing sucrose concentrations (0.75, 0.50, 0.1 M). Explants were then transferred to solid EM medium in order to achieve shoot regeneration, then on Murashige and Skoog medium supplemented with 0.05 microM naphthalene acetic acid to induce rooting of shoots. With this procedure, 53 percent and 56 percent of cryopreserved shoot tips of the diploid and triploid cytotypes, respectively, survived and formed plants. However, only 16 percent of cryopreserved meristems of both cytotypes regenerated plants. Using ten isozyme systems and seven RAPD profiles, no modification induced by cryopreservation could be detected in plantlets regenerated from cryopreserved material.

Talking through walls: mechanisms of lateral root emergence in Arabidopsis thaliana.

Science.gov (United States)

Vilches-Barro, Amaya; Maizel, Alexis

2015-02-01

Lateral roots are formed postembryonically and determine the final shape of the root system, a determinant of the plants ability to uptake nutrients and water. The lateral root primordia are initiated deep into the main root and to protrude out the primary root they have to grow through three cell layers. Recent findings have revealed that these layers are not merely a passive physical obstacle to the emergence of the lateral root but have an active role in its formation. Here, we review examples of communication between the lateral root primordium and the surrounding tissues, highlighting the importance of auxin-mediated growth coordination as well as cell and tissue mechanics for the morphogenesis of lateral roots. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Differential TOR activation and cell proliferation in Arabidopsis root and shoot apexes.

Science.gov (United States)

Li, Xiaojuan; Cai, Wenguo; Liu, Yanlin; Li, Hui; Fu, Liwen; Liu, Zengyu; Xu, Lin; Liu, Hongtao; Xu, Tongda; Xiong, Yan

2017-03-07

The developmental plasticity of plants relies on the remarkable ability of the meristems to integrate nutrient and energy availability with environmental signals. Meristems in root and shoot apexes share highly similar molecular players but are spatially separated by soil. Whether and how these two meristematic tissues have differential activation requirements for local nutrient, hormone, and environmental cues (e.g., light) remain enigmatic in photosynthetic plants. Here, we report that the activation of root and shoot apexes relies on distinct glucose and light signals. Glucose energy signaling is sufficient to activate target of rapamycin (TOR) kinase in root apexes. In contrast, both the glucose and light signals are required for TOR activation in shoot apexes. Strikingly, exogenously applied auxin is able to replace light to activate TOR in shoot apexes and promote true leaf development. A relatively low concentration of auxin in the shoot and high concentration of auxin in the root might be responsible for this distinctive light requirement in root and shoot apexes, because light is required to promote auxin biosynthesis in the shoot. Furthermore, we reveal that the small GTPase Rho-related protein 2 (ROP2) transduces light-auxin signal to activate TOR by direct interaction, which, in turn, promotes transcription factors E2Fa,b for activating cell cycle genes in shoot apexes. Consistently, constitutively activated ROP2 plants stimulate TOR in the shoot apex and cause true leaf development even without light. Together, our findings establish a pivotal hub role of TOR signaling in integrating different environmental signals to regulate distinct developmental transition and growth in the shoot and root.

The Arabidopsis thaliana NAC transcription factor family: structure-function relationships and determinants of ANAC019 stress signalling

DEFF Research Database (Denmark)

Jensen, Michael K; Kjaersgaard, Trine; Nielsen, Michael M.

2010-01-01

-termini. Nine of the ten NAC domains analysed bind a previously identified conserved DNA target sequence with a CGT[GA] core, although with different affinities. Likewise, all but one of the NAC proteins analysed is dependent on the C-terminal region for transactivational activity. In silico analyses show......TFs (transcription factors) are modular proteins minimally containing a DBD (DNA-binding domain) and a TRD (transcription regulatory domain). NAC [for NAM (no apical meristem), ATAF, CUC (cup-shaped cotyledon)] proteins comprise one of the largest plant TF families. They are key regulators...... of stress perception and developmental programmes, and most share an N-terminal NAC domain. On the basis of analyses of gene expression data and the phylogeny of Arabidopsis thaliana NAC TFs we systematically decipher structural and functional specificities of the conserved NAC domains and the divergent C...

ARABIDOPSIS HOMOLOG of TRITHORAX1 (ATX1) is required for cell production, patterning, and morphogenesis in root development

OpenAIRE

Napsucialy-Mendivil, Selene; Alvarez-Venegas, Raúl; Shishkova, Svetlana; Dubrovsky, Joseph G.

2014-01-01

ARABIDOPSIS HOMOLOG of TRITHORAX1 (ATX1/SDG27), a known regulator of flower development, encodes a H3K4histone methyltransferase that maintains a number of genes in an active state. In this study, the role of ATX1 in root development was evaluated. The loss-of-function mutant atx1-1 was impaired in primary root growth. The data suggest that ATX1 controls root growth by regulating cell cycle duration, cell production, and the transition from cell proliferation in the root apical meristem (RAM)...

Consequences of a Deficit in Vitamin B6 Biosynthesis de Novo for Hormone Homeostasis and Root Development in Arabidopsis1[OPEN

Science.gov (United States)

Boycheva, Svetlana; Dominguez, Ana; Rolcik, Jakub; Boller, Thomas; Fitzpatrick, Teresa B.

2015-01-01

Vitamin B6 (pyridoxal 5′-phosphate) is an essential cofactor of many metabolic enzymes. Plants biosynthesize the vitamin de novo employing two enzymes, pyridoxine synthase1 (PDX1) and PDX2. In Arabidopsis (Arabidopsis thaliana), there are two catalytically active paralogs of PDX1 (PDX1.1 and PDX1.3) producing the vitamin at comparable rates. Since single mutants are viable but the pdx1.1 pdx1.3 double mutant is lethal, the corresponding enzymes seem redundant. However, the single mutants exhibit substantial phenotypic differences, particularly at the level of root development, with pdx1.3 being more impaired than pdx1.1. Here, we investigate the differential regulation of PDX1.1 and PDX1.3 by identifying factors involved in their disparate phenotypes. Swapped-promoter experiments clarify the presence of distinct regulatory elements in the upstream regions of both genes. Exogenous sucrose (Suc) triggers impaired ethylene production in both mutants but is more severe in pdx1.3 than in pdx1.1. Interestingly, Suc specifically represses PDX1.1 expression, accounting for the stronger vitamin B6 deficit in pdx1.3 compared with pdx1.1. Surprisingly, Suc enhances auxin levels in pdx1.1, whereas the levels are diminished in pdx1.3. In the case of pdx1.3, the previously reported reduced meristem activity combined with the impaired ethylene and auxin levels manifest the specific root developmental defects. Moreover, it is the deficit in ethylene production and/or signaling that triggers this outcome. On the other hand, we hypothesize that it is the increased auxin content of pdx1.1 that is responsible for the root developmental defects observed therein. We conclude that PDX1.1 and PDX1.3 play partially nonredundant roles and are differentially regulated as manifested in disparate root growth impairment morphologies. PMID:25475669

Linking salinity stress tolerance with tissue-specific Na+ sequestration in wheat roots

Directory of Open Access Journals (Sweden)

Honghong eWu

2015-02-01

Full Text Available Salinity stress tolerance is a physiologically complex trait that is conferred by the large array of interacting mechanisms. Among these, vacuolar Na+ sequestration has always been considered as one of the key components differentiating between sensitive and tolerant species and genotypes. However, vacuolar Na+ sequestration has been rarely considered in the context of the tissue-specific expression and regulation of appropriate transporters contributing to Na+ removal from the cytosol. In this work, six bread wheat varieties contrasting in their salinity tolerance (three tolerant and three sensitive were used to understand the essentiality of vacuolar Na+ sequestration between functionally different root tissues, and link it with the overall salinity stress tolerance in this species. Roots of 4-d old wheat seedlings were treated with 100 mM NaCl for 3 days, and then Na+ distribution between cytosol and vacuole was quantified by CoroNa Green fluorescent dye imaging. Our major observations were as follows: 1 salinity stress tolerance correlated positively with vacuolar Na+ sequestration ability in the mature root zone but not in the root apex; 2 Contrary to expectations, cytosolic Na+ levels in root meristem were significantly higher in salt tolerant than sensitive group, while vacuolar Na+ levels showed an opposite trend. These results are interpreted as meristem cells playing a role of the salt sensor; 3 No significant difference in the vacuolar Na+ sequestration ability was found between sensitive and tolerant group in either transition or elongation zones; 4 The overall Na+ accumulation was highest in the elongation zone, suggesting its role in osmotic adjustment and turgor maintenance required to drive root expansion growth. Overall, the reported results suggest high tissue-specificity of Na+ uptake, signalling, and sequestration in wheat root. The implications of these findings for plant breeding for salinity stress tolerance are discussed.

The founder-cell transcriptome in the Arabidopsis apetala1 cauliflower inflorescence meristem.

Science.gov (United States)

Frerichs, Anneke; Thoma, Rahere; Abdallah, Ali Taleb; Frommolt, Peter; Werr, Wolfgang; Chandler, John William

2016-11-03

Although the pattern of lateral organ formation from apical meristems establishes species-specific plant architecture, the positional information that confers cell fate to cells as they transit to the meristem flanks where they differentiate, remains largely unknown. We have combined fluorescence-activated cell sorting and RNA-seq to characterise the cell-type-specific transcriptome at the earliest developmental time-point of lateral organ formation using DORNRÖSCHEN-LIKE::GFP to mark founder-cell populations at the periphery of the inflorescence meristem (IM) in apetala1 cauliflower double mutants, which overproliferate IMs. Within the lateral organ founder-cell population at the inflorescence meristem, floral primordium identity genes are upregulated and stem-cell identity markers are downregulated. Additional differentially expressed transcripts are involved in polarity generation and boundary formation, and in epigenetic and post-translational changes. However, only subtle transcriptional reprogramming within the global auxin network was observed. The transcriptional network of differentially expressed genes supports the hypothesis that lateral organ founder-cell specification involves the creation of polarity from the centre to the periphery of the IM and the establishment of a boundary from surrounding cells, consistent with bract initiation. However, contrary to the established paradigm that sites of auxin response maxima pre-pattern lateral organ initiation in the IM, auxin response might play a minor role in the earliest stages of lateral floral initiation.

Physiological and Molecular Effects of the Cyclic Nucleotides cAMP and cGMP on Arabidopsis thaliana

KAUST Repository

Herrera, Natalia M.

2012-01-01

transport in Arabidopsis thaliana leaves and, that these changes at the molecular level can have functional biological consequences. For this reason we tested if CNs modulate the photosynthetic rate, responses to high light and root ion transport. Real time

Non-linear character of dose dependences of chromosome aberration frequency in radiation-damaged root

International Nuclear Information System (INIS)

Kravets, E.A.; Berezhnaya, V.V.; Sakada, V.I.; Rashidov, N.M.; Grodzinskij, D.M.; Kravets, E.A.; Berezhnaya, V.V.; Sakada, V.I.; Rashidov, N.M.; Grodzinskij, D.M.

2012-01-01

The dose dependences of the aberrant anaphases in the root meristem in 48 hours after the irradiation have non-linear character and a plateau in the region about 6-8 Gy. The plateau indicates the activation of recovery processes. In the plateau range, the level of damages for this genotype is 33% for aberrant anaphases (FAA), 2.3 aberrations per aberrant anaphase (A/AC), and 0.74 aberrations for the total number of anaphases. At 10 Gy, the dose curve forms the exponential region caused by the involvement of the large number of new cells with unrepaired damages in the mutation process. The increase of A/AC to 1.1 indicate the ''criticality'' of the meristem radiation damage.

Flavonols Mediate Root Phototropism and Growth through Regulation of Proliferation-to-Differentiation Transition

OpenAIRE

Silva, Javier; Moreno Risueño, Miguel Ángel; Manzano, Concepción; Téllez Robledo, Bárbara; Navarro Neila, Sara; Carrasco Loba, Víctor; Pollmann, Stephan; Gallego, Javier; Pozo Benito, Juan Carlos del

2016-01-01

Roots normally grow in darkness, but they may be exposed to light. After perceiving light, roots bend to escape from light (root light avoidance) and reduce their growth. How root light avoidance responses are regulated is not well understood. Here, we show that illumination induces the accumulation of flavonols in Arabidopsis thaliana roots. During root illumination, flavonols rapidly accumulate at the side closer to light in the transition zone. This accumulation promotes asymmetrical cell ...

Live Imaging of Shoot Meristems on an Inverted Confocal Microscope Using an Objective Lens Inverter Attachment

Science.gov (United States)

Nimchuk, Zachary L.; Perdue, Tony D.

2017-01-01

Live imaging of above ground meristems can lead to new insights in plant development not possible from static imaging of fixed tissue. The use of an upright confocal microscope offers several technical and biological advantages for live imaging floral or shoot meristems. However, many departments and core facilities possess only inverted confocal microscopes and lack the funding for an additional upright confocal microscope. Here we show that imaging of living apical meristems can be performed on existing inverted confocal microscopes with the use of an affordable and detachable InverterScope accessory. PMID:28579995

Live Imaging of Shoot Meristems on an Inverted Confocal Microscope Using an Objective Lens Inverter Attachment.

Science.gov (United States)

Nimchuk, Zachary L; Perdue, Tony D

2017-01-01

Live imaging of above ground meristems can lead to new insights in plant development not possible from static imaging of fixed tissue. The use of an upright confocal microscope offers several technical and biological advantages for live imaging floral or shoot meristems. However, many departments and core facilities possess only inverted confocal microscopes and lack the funding for an additional upright confocal microscope. Here we show that imaging of living apical meristems can be performed on existing inverted confocal microscopes with the use of an affordable and detachable InverterScope accessory.

Fusarium oxysporum Triggers Tissue-Specific Transcriptional Reprogramming in Arabidopsis thaliana

Science.gov (United States)

Lyons, Rebecca; Stiller, Jiri; Powell, Jonathan; Rusu, Anca; Manners, John M.; Kazan, Kemal

2015-01-01

Some of the most devastating agricultural diseases are caused by root-infecting pathogens, yet the majority of studies on these interactions to date have focused on the host responses of aerial tissues rather than those belowground. Fusarium oxysporum is a root-infecting pathogen that causes wilt disease on several plant species including Arabidopsis thaliana. To investigate and compare transcriptional changes triggered by F. oxysporum in different Arabidopsis tissues, we infected soil-grown plants with F. oxysporum and subjected root and leaf tissue harvested at early and late timepoints to RNA-seq analyses. At least half of the genes induced or repressed by F. oxysporum showed tissue-specific regulation. Regulators of auxin and ABA signalling, mannose binding lectins and peroxidases showed strong differential expression in root tissue. We demonstrate that ARF2 and PRX33, two genes regulated in the roots, promote susceptibility to F. oxysporum. In the leaves, defensins and genes associated with the response to auxin, cold and senescence were strongly regulated while jasmonate biosynthesis and signalling genes were induced throughout the plant. PMID:25849296

Fusarium oxysporum triggers tissue-specific transcriptional reprogramming in Arabidopsis thaliana.

Directory of Open Access Journals (Sweden)

Rebecca Lyons

Full Text Available Some of the most devastating agricultural diseases are caused by root-infecting pathogens, yet the majority of studies on these interactions to date have focused on the host responses of aerial tissues rather than those belowground. Fusarium oxysporum is a root-infecting pathogen that causes wilt disease on several plant species including Arabidopsis thaliana. To investigate and compare transcriptional changes triggered by F. oxysporum in different Arabidopsis tissues, we infected soil-grown plants with F. oxysporum and subjected root and leaf tissue harvested at early and late timepoints to RNA-seq analyses. At least half of the genes induced or repressed by F. oxysporum showed tissue-specific regulation. Regulators of auxin and ABA signalling, mannose binding lectins and peroxidases showed strong differential expression in root tissue. We demonstrate that ARF2 and PRX33, two genes regulated in the roots, promote susceptibility to F. oxysporum. In the leaves, defensins and genes associated with the response to auxin, cold and senescence were strongly regulated while jasmonate biosynthesis and signalling genes were induced throughout the plant.

Onion root tip cell system for biodosimetry?

International Nuclear Information System (INIS)

Paradiz, J; Druskovic, B.; Lovka, M.; Skrk, J.

1996-01-01

Methodology for radiation dose assessment based on chromosomal damage to plant cells has no yet been established, although root meristems have been the pioneer cytogenetic materials and profound analyses of irradiated meristematic cells of horse bean (Viciafaba L.) had been performed. Onion (Allium cepa L.) root tips frequently used for radiation cytogenetic studies, are recently considered to be one of the most promising plant test system for the detection of genotoxic environmental pollutants. We studied the possibility of using cytogenetic analyses of irradiated onion cells to determine the effective biological dose of ionizing radiation. The dose-effect relationships for chromosomal damages to onion meristematic cells were established after plants had been irradiated and subsequently grown in both laboratory and field conditions

Isolation and characterization of CNGC17 gene from Arabidopsis thaliana

International Nuclear Information System (INIS)

Yamagami, Mutsumi; Kobayashi, Daisuke; Hisamatsu, Shun'ichi

2007-01-01

Phytoremediation is a possible countermeasure for cleaning up soil contaminated by 137 Cs, and development of plants which can effectively absorb 137 Cs is important for it. It is expected that capability of Cs extraction from soil can be strengthened by genetic alteration of the Cs + root-uptake mechanism of plants. This study aimed at elucidating the uptake mechanism of Cs + for future genetic engineering. Plant roots take up Cs + from the soil solution via transport proteins at the plasma membrane of root cells. Voltage-insensitive cation channels (VICCs) are a possible transfer route of Cs + , and they are encoded by cyclic-nucleotide gated channel (CNGC) and glutamate receptor (GLR) gene families. The genome of Arabidopsis thaliana contains 20 CNGC genes. We have cloned a putative AtCNGC17 gene from cDNAs which were generated with total-RNA obtained from leaves of Arabidopsis thaliana by RT-PCR. The cDNA contained 2163 bp with an ORF that encoded a protein consisting of 721 amino acids residues. The plasmid prepared by the insertion of the gene under a Taq promoter was used to transform an E. coli deficient in the three major K + uptake systems (Kdp, Trk, and Kup). Only the E. coli with AtCNGC17 gene grew in low K + concentration minimal medium. This result suggested that the AtCNGC17 protein has a function of K + uptake. Growth rates of the E. coli cells expressing the gene were strongly inhibited by CsCl in low K + concentration minimal medium, suggesting that the AtCNGC17 transporter also carries Cs + . (author)

Final Scientific/Technical report for "ABI8: Prototype of a novel signaling factor"

Energy Technology Data Exchange (ETDEWEB)

Finkelstein, Ruth R. [Univ. of California, Santa Barbara, CA (United States)

2013-02-21

The Arabidopsis thaliana ABSCISIC ACID-INSENSITIVE8 locus encodes a highly conserved plant-specific protein that mediates abscisic acid (ABA) and sugar responses essential for growth. Although initial database comparisons revealed no domains of predictable function, it has recently been re-annotated as a member of the Glycosyltransferase family A. However, this function has not been demonstrated experimentally and no specific substrates have been identified. Mutations affecting ABI8 are near-lethal due to pleiotropic yet specific effects including altered ABA signaling, sugar transport, cell wall synthesis, root meristem maintenance, vascular patterning, and male sterility. Because the predicted sequence initially provided no clues, we used a guilt by association strategy to address function of this protein by determining its subcellular localization and identifying interacting proteins. Our studies showed that ABI8 is localized to the endomembrane system and may interact with proteins implicated in Golgi trafficking, lignification, and stress signaling. We found that the root meristem arrest reflects decreased auxin accumulation and resulting decreases in regulators required for meristem identity, all of which can be rescued by added glucose. Further studies showed that this glucose-dependence reflects reduced glucose uptake as well as the decreased expression of sugar-mobilizing enzymes. This work suggests that ABI8 may regulate trafficking of membrane proteins such as auxin transporters and cellulose synthase, but this hypothesis has not yet been tested. The altered gene expression is likely to be a secondary or later effect of this pleiotropic mutation.

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

DEFF Research Database (Denmark)

Hebelstrup, Kim Henrik; Jensen, Erik Østergaard

2008-01-01

-symbiotic hemoglobin gene, GLB2, in Arabidopsis thaliana. Lines with GLB1 silencing had a significant delay of bolting and after bolting, shoots reverted to the rosette vegetative phase by formation of aerial rosettes at lateral meristems. Lines with overexpression of GLB1 or GLB2 bolted earlier than wild type plants....... By germinating the lines in a medium containing the nitric oxide (NO) donor, sodium nitroprusside (SNP), it was demonstrated that both GLB1 and GLB2 promote bolting by antagonizing the effect of NO, suggesting that non-symbiotic plant hemoglobin controls bolting by scavenging the floral transition signal...... molecule, NO. So far, NO scavenging has only been demonstrated for class 1 non-symbiotic hemoglobins. A direct assay in Arabidopsis leaf cells shows that GLB1 as well as the class 2 non-symbiotic hemoglobin, GLB2, scavenge NO in vivo. NO has also been demonstrated to be a growth stimulating signal...

Molecular cloning, phylogenetic analysis, and expression patterns of LATERAL SUPPRESSOR-LIKE and REGULATOR OF AXILLARY MERISTEM FORMATION-LIKE genes in sunflower (Helianthus annuus L.).

Science.gov (United States)

Fambrini, Marco; Salvini, Mariangela; Pugliesi, Claudio

2017-03-01

The wild sunflower (Helianthus annuus) plants develop a highly branched form with numerous small flowering heads. The origin of a no branched sunflower, producing a single large head, has been a key event in the domestication process of this species. The interaction between hormonal factors and several genes organizes the initiation and outgrowth of axillary meristems (AMs). From sunflower, we have isolated two genes putatively involved in this process, LATERAL SUPPRESSOR (LS)-LIKE (Ha-LSL) and REGULATOR OF AXILLARY MERISTEM FORMATION (ROX)-LIKE (Ha-ROXL), encoding for a GRAS and a bHLH transcription factor (TF), respectively. Typical amino acid residues and phylogenetic analyses suggest that Ha-LSL and Ha-ROXL are the orthologs of the branching regulator LS and ROX/LAX1, involved in the growth habit of both dicot and monocot species. qRT-PCR analyses revealed a high accumulation of Ha-LSL transcripts in roots, vegetative shoots, and inflorescence shoots. By contrast, in internodal stems and young leaves, a lower amount of Ha-LSL transcripts was observed. A comparison of transcription patterns between Ha-LSL and Ha-ROXL revealed some analogies but also remarkable differences; in fact, the gene Ha-ROXL displayed a low expression level in all organs analyzed. In situ hybridization (ISH) analysis showed that Ha-ROXL transcription was strongly restricted to a small domain within the boundary zone separating the shoot apical meristem (SAM) and the leaf primordia and in restricted regions of the inflorescence meristem, beforehand the separation of floral bracts from disc flower primordia. These results suggested that Ha-ROXL may be involved to establish a cell niche for the initiation of AMs as well as flower primordia. The accumulation of Ha-LSL transcripts was not restricted to the boundary zones in vegetative and inflorescence shoots, but the mRNA activity was expanded in other cellular domains of primary shoot apical meristem as well as AMs. In addition, Ha

Early development and gravitropic response of lateral roots in Arabidopsis thaliana

OpenAIRE

Guyomarc'h, S.; Leran, S.; Auzon-Cape, M.; Perrine-Walker, F.; Lucas, Mikaël; Laplaze, Laurent

2012-01-01

Root system architecture plays an important role in determining nutrient and water acquisition and is modulated by endogenous and environmental factors, resulting in considerable developmental plasticity. The orientation of primary root growth in response to gravity (gravitropism) has been studied extensively, but little is known about the behaviour of lateral roots in response to this signal. Here, we analysed the response of lateral roots to gravity and, consistently with previous observati...

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...

Meristem micropropagation of cassava (Manihot esculenta) evokes genome-wide changes in DNA methylation

OpenAIRE

Shedrack Reuben Kitimu; Shedrack Reuben Kitimu; Julian eTaylor; Timothy J March; Fred eTairo; Mike J Wilkinson; Carlos Marcelino Rodriguez Lopez

2015-01-01

There is great interest in the phenotypic, genetic and epigenetic changes associated with plant in vitro culture known as somaclonal variation. In vitro propagation systems that are based on the use of microcuttings or meristem cultures are considered analogous to clonal cuttings and so widely viewed to be largely free from such somaclonal effects. In this study, we surveyed for epigenetic changes during propagation by meristem culture and by field cuttings in five cassava (Manihot esculenta...

Comparative radioresistance of chronically irradiated populations of Arabidopsis thaliana (L.) Heynh

International Nuclear Information System (INIS)

Dineva, S.B.; Abramov, V.I.; Shevchenko, V.A.

1994-01-01

The radioresistance of seeds of populations of Arabidopsis thaliana (L.) Heynh. growing for 5 years in the regions with different levels of radioactive contamination within 30 km zone of Chernobyl NPP was studied. The analysis of comparative radiosensitivity by root test was performed. It has been shown that plants from arabidopsis population growing under chronic irradiation did not gain an increased radioresistance. The data obtained shown that they are more radiosensitive

Genetic Control of Plant Root Colonization by the Biocontrol agent, Pseudomonas fluorescens

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Cole, Benjamin J.; Fletcher, Meghan; Waters, Jordan; Wetmore, Kelly; Blow, Matthew J.; Deutschbauer, Adam M.; Dangl, Jeffry L.; Visel, Axel

2015-03-19

Plant growth promoting rhizobacteria (PGPR) are a critical component of plant root ecosystems. PGPR promote plant growth by solubilizing inaccessible minerals, suppressing pathogenic microorganisms in the soil, and directly stimulating growth through hormone synthesis. Pseudomonas fluorescens is a well-established PGPR isolated from wheat roots that can also colonize the root system of the model plant, Arabidopsis thaliana. We have created barcoded transposon insertion mutant libraries suitable for genome-wide transposon-mediated mutagenesis followed by sequencing (TnSeq). These libraries consist of over 105 independent insertions, collectively providing loss-of-function mutants for nearly all genes in the P.fluorescens genome. Each insertion mutant can be unambiguously identified by a randomized 20 nucleotide sequence (barcode) engineered into the transposon sequence. We used these libraries in a gnotobiotic assay to examine the colonization ability of P.fluorescens on A.thaliana roots. Taking advantage of the ability to distinguish individual colonization events using barcode sequences, we assessed the timing and microbial concentration dependence of colonization of the rhizoplane niche. These data provide direct insight into the dynamics of plant root colonization in an in vivo system and define baseline parameters for the systematic identification of the bacterial genes and molecular pathways using TnSeq assays. Having determined parameters that facilitate potential colonization of roots by thousands of independent insertion mutants in a single assay, we are currently establishing a genome-wide functional map of genes required for root colonization in P.fluorescens. Importantly, the approach developed and optimized here for P.fluorescens>A.thaliana colonization will be applicable to a wide range of plant-microbe interactions, including biofuel feedstock plants and microbes known or hypothesized to impact on biofuel-relevant traits including biomass productivity

Primary root protophloem differentiation requires balanced phosphatidylinositol-4,5-biphosphate levels and systemically affects root branching.

Science.gov (United States)

Rodriguez-Villalon, Antia; Gujas, Bojan; van Wijk, Ringo; Munnik, Teun; Hardtke, Christian S

2015-04-15

Protophloem is a specialized vascular tissue in growing plant organs, such as root meristems. In Arabidopsis mutants with impaired primary root protophloem differentiation, brevis radix (brx) and octopus (ops), meristematic activity and consequently overall root growth are strongly reduced. Second site mutation in the protophloem-specific presumed phosphoinositide 5-phosphatase cotyledon vascular pattern 2 (CVP2), but not in its homolog CVP2-like 1 (CVL1), partially rescues brx defects. Consistent with this finding, CVP2 hyperactivity in a wild-type background recreates a brx phenotype. Paradoxically, however, while cvp2 or cvl1 single mutants display no apparent root defects, the root phenotype of cvp2 cvl1 double mutants is similar to brx or ops, although, as expected, cvp2 cvl1 seedlings contain more phosphatidylinositol-4,5-biphosphate. Thus, tightly balanced phosphatidylinositol-4,5-biphosphate levels appear essential for proper protophloem differentiation. Genetically, OPS acts downstream of phosphatidylinositol-4,5-biphosphate levels, as cvp2 mutation cannot rescue ops defects, whereas increased OPS dose rescues cvp2 cvl1 defects. Finally, all three mutants display higher density and accelerated emergence of lateral roots, which correlates with increased auxin response in the root differentiation zone. This phenotype is also created by application of peptides that suppress protophloem differentiation, clavata3/embryo surrounding region 26 (CLE26) and CLE45. Thus, local changes in the primary root protophloem systemically shape overall root system architecture. © 2015. Published by The Company of Biologists Ltd.

IAA-producing rhizobacteria from chickpea (Cicer arietinum L.) induce changes in root architecture and increase root biomass.

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Fierro-Coronado, Rosario Alicia; Quiroz-Figueroa, Francisco Roberto; García-Pérez, Luz María; Ramírez-Chávez, Enrique; Molina-Torres, Jorge; Maldonado-Mendoza, Ignacio Eduardo

2014-10-01

Rhizobacteria promote and have beneficial effects on plant growth, making them useful to agriculture. Nevertheless, the rhizosphere of the chickpea plant has not been extensively examined. The aim of the present study was to select indole-3-acetic acid (IAA) producing rhizobacteria from the rhizosphere of chickpea plants for their potential use as biofertilizers. After obtaining a collection of 864 bacterial isolates, we performed a screen using the Salkowski reaction for the presence of auxin compounds (such as IAA) in bacterial Luria-Bertani supernatant (BLBS). Our results demonstrate that the Salkowski reaction has a greater specificity for detecting IAA than other tested auxins. Ten bacterial isolates displaying a wide range of auxin accumulation were selected, producing IAA levels of 5 to 90 μmol/L (according to the Salkowski reaction). Bacterial isolates were identified on the basis of 16S rDNA partial sequences: 9 isolates belonged to Enterobacter, and 1 isolate was classified as Serratia. The effect of BLBS on root morphology was evaluated in Arabidopsis thaliana. IAA production by rhizobacteria was confirmed by means of a DR5::GFP construct that is responsive to IAA, and also by HPLC-GC/MS. Finally, we observed that IAA secreted by rhizobacteria (i) modified the root architecture of A. thaliana, (ii) caused an increase in chickpea root biomass, and (iii) activated the green fluorescent protein (GFP) reporter gene driven by the DR5 promoter. These findings provide evidence that these novel bacterial isolates may be considered as putative plant-growth-promoting rhizobacteria modifying root architecture and increasing root biomass.

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

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Zoltán Kevei

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

Mutations in a plastid-localized elongation factor G alter early stages of plastid development in Arabidopsis thaliana

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Hangarter Roger P

2007-07-01

Full Text Available Abstract Background Proper development of plastids in embryo and seedling tissues is critical for plant development. During germination, plastids develop to perform many critical functions that are necessary to establish the seedling for further growth. A growing body of work has demonstrated that components of the plastid transcription and translation machinery must be present and functional to establish the organelle upon germination. Results We have identified Arabidopsis thaliana mutants in a gene that encodes a plastid-targeted elongation factor G (SCO1 that is essential for plastid development during embryogenesis since two T-DNA insertion mutations in the coding sequence (sco1-2 and sco1-3 result in an embryo-lethal phenotype. In addition, a point mutation allele (sco1-1 and an allele with a T-DNA insertion in the promoter (sco1-4 of SCO1 display conditional seedling-lethal phenotypes. Seedlings of these alleles exhibit cotyledon and hypocotyl albinism due to improper chloroplast development, and normally die shortly after germination. However, when germinated on media supplemented with sucrose, the mutant plants can produce photosynthetically-active green leaves from the apical meristem. Conclusion The developmental stage-specific phenotype of the conditional-lethal sco1 alleles reveals differences in chloroplast formation during seedling germination compared to chloroplast differentiation in cells derived from the shoot apical meristem. Our identification of embryo-lethal mutant alleles in the Arabidopsis elongation factor G indicates that SCO1 is essential for plant growth, consistent with its predicted role in chloroplast protein translation.

Mechanically, the shoot apical meristem of Arabidopsis behaves like a shell inflated by a pressure of about 1 MPa

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Léna eBeauzamy

2015-11-01

Full Text Available In plants, the shoot apical meristem contains the stem cells and is responsible for the generation of all aerial organs. Mechanistically, organogenesis is associated with an auxin-dependent local softening of the epidermis. This has been proposed to be sufficient to trigger outgrowth, because the epidermis is thought to be under tension and stiffer than internal tissues in all the aerial part of the plant. However, this has not been directly demonstrated in the shoot apical meristem. Here we tested this hypothesis in Arabidopsis using indentation methods and modeling. We considered two possible scenarios: either the epidermis does not have unique properties and the meristem behaves as a homogeneous linearly-elastic tissue, or the epidermis is under tension and the meristem exhibits the response of a shell under pressure. Large indentation depths measurements with a large tip (~size of the meristem were consistent with a shell-like behavior. This also allowed us to deduce a value of turgor pressure, estimated at 0.82 ± 0.16 MPa. Indentation with atomic force microscopy provided local measurements of pressure in the epidermis, further confirming the values obtained from large deformations. Altogether, our data demonstrate that the Arabidopsis shoot apical meristem behaves like a shell under a MPa range pressure and support a key role for the epidermis in shaping the shoot apex.

ORF Sequence: NC_003070 [GENIUS II[Archive

Lifescience Database Archive (English)

Full Text Available NC_003070 gi|18407972 >gi|18407972|ref|NP_564823.1| no apical meristem (NAM) famil...y protein [Arabidopsis thaliana] MQAEEIICRVSDEEIIENYLRPKINGETSSIPRYVVELAEELYTVEPWLLPRQTAPILNPGEWFYFGKRNRKYSN

Consequences of a deficit in vitamin B6 biosynthesis de novo for hormone homeostasis and root development in Arabidopsis.

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Boycheva, Svetlana; Dominguez, Ana; Rolcik, Jakub; Boller, Thomas; Fitzpatrick, Teresa B

2015-01-01

Vitamin B(6) (pyridoxal 5'-phosphate) is an essential cofactor of many metabolic enzymes. Plants biosynthesize the vitamin de novo employing two enzymes, pyridoxine synthase1 (PDX1) and PDX2. In Arabidopsis (Arabidopsis thaliana), there are two catalytically active paralogs of PDX1 (PDX1.1 and PDX1.3) producing the vitamin at comparable rates. Since single mutants are viable but the pdx1.1 pdx1.3 double mutant is lethal, the corresponding enzymes seem redundant. However, the single mutants exhibit substantial phenotypic differences, particularly at the level of root development, with pdx1.3 being more impaired than pdx1.1. Here, we investigate the differential regulation of PDX1.1 and PDX1.3 by identifying factors involved in their disparate phenotypes. Swapped-promoter experiments clarify the presence of distinct regulatory elements in the upstream regions of both genes. Exogenous sucrose (Suc) triggers impaired ethylene production in both mutants but is more severe in pdx1.3 than in pdx1.1. Interestingly, Suc specifically represses PDX1.1 expression, accounting for the stronger vitamin B6 deficit in pdx1.3 compared with pdx1.1. Surprisingly, Suc enhances auxin levels in pdx1.1, whereas the levels are diminished in pdx1.3. In the case of pdx1.3, the previously reported reduced meristem activity combined with the impaired ethylene and auxin levels manifest the specific root developmental defects. Moreover, it is the deficit in ethylene production and/or signaling that triggers this outcome. On the other hand, we hypothesize that it is the increased auxin content of pdx1.1 that is responsible for the root developmental defects observed therein. We conclude that PDX1.1 and PDX1.3 play partially nonredundant roles and are differentially regulated as manifested in disparate root growth impairment morphologies. © 2015 American Society of Plant Biologists. All Rights Reserved.

The NADPH-oxidase AtRbohI plays a positive role in drought-stress response in Arabidopsis thaliana

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He, Huan [Nanjing Agricultural Univ. (China); Yan, Jingwei [Nanjing Agricultural Univ. (China); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Yu, Xiaoyun [Nanjing Agricultural Univ. (China); Liang, Yan [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Fang, Lin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Scheller, Henrik Vibe [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Zhang, Aying [Nanjing Agricultural Univ. (China)

2017-05-27

As the major resource of reactive oxygen species (ROS), the NADPH oxidases (Rbohs) have been shown to play important roles in plant cells under normal growth and stress conditions. Although many family members of Rbohs were studied, little is known about the function of RbohI in Arabidopsis thaliana. Here, we report that exogenous ABA application decreases RbohI expression and mannitol significantly increases RbohI expression at transcript level. The RbohI transcripts were strongly detected in dry seeds and roots. The loss-of-function mutant rbohI exhibited sensitivity to ABA and mannitol stress during germination. Furthermore, the lateral root growth of rbohI was severely inhibited after treatment with mannitol stress. Overexpression of RbohI in Arabidopsis significantly improves the drought tolerance. Moreover, more H₂O₂ accumulated in RbohI overexpressors than in wild type plants in response to mannitol stress. Our conclusion is that AtRbohI functions in drought-stress response in Arabidopsis thaliana.

Phytotoxic flavonoids from roots of Stellera chamaejasme L. (Thymelaeaceae).

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Yan, Zhiqiang; Guo, Hongru; Yang, Jiayue; Liu, Quan; Jin, Hui; Xu, Rui; Cui, Haiyan; Qin, Bo

2014-10-01

Allelopathy, the negative effect on plants of chemicals released to the surroundings by a neighboring plant, is an important factor which contributes to the spread of some weeds in plant communities. In this field, Stellera chamaejasme L. (Thymelaeaceae) is one of the most toxic and ecologically-threatening weeds in some of the grasslands of north and west China. Bioassay-guided fractionation of root extracts of this plant led to the isolation of eight flavonoids 1-8, whose structures were elucidated by spectroscopic analysis. All compounds obtained, except 7-methoxylneochaejasmin A (4) and (+)-epiafzelechin (5), showed strong phytotoxic activity against Arabidopsis thaliana seedlings. Seedling growth was reduced by neochamaejasmin B (1), mesoneochamaejasmin A (2), chamaejasmenin C (3), genkwanol A (6), daphnodorin B (7) and dihydrodaphnodorin B (8) with IC50 values of 6.9, 12.1, 43.2, 74.8, 7.1 and 27.3μg/mL, respectively, and all of these compounds disrupted root development. Endogenous auxin levels at the root tips of the A. thaliana DR5::GUS transgenic line were largely reduced by compounds 1, 2 and 6-8, and were increased by compound 4. Moreover, the inhibition rate of A. thaliana auxin transport mutants pin2 and aux1-7 by compounds 1-8 were all lower than the wild type (Col-0). The influence of these compounds on endogenous auxin distribution is thus proposed as a critical factor for the phytotoxic effect. Compounds 1, 2, 4 and 8 were found in soils associated with S. chamaejasme, and these flavonoids also showed phytotoxicity to Clinelymus nutans L., an associated weed of S. chamaejasme. These results indicated that some phytotoxic compounds from roots of S. chamaejasme may be involved in the potential allelopathic behavior of this widespread weed. Copyright © 2014 Elsevier Ltd. All rights reserved.

An Undergraduate Study of Two Transcription Factors that Promote Lateral Root Formation

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Bargmann, Bastiaan O. R.; Birnbaum, Kenneth D.; Brenner, Eric D.

2014-01-01

We present a lab that enables students to test the role of genes involved in the regulation of lateral roots growth in the model plant "Arabidopsis thaliana." Here, students design an experiment that follows the effects of the hormone auxin on the stimulation of genes involved in the formation of lateral root initials. These genes, known…

Inheritance and gene expression of a root-growth inhibiting mutant in rice (Oryza sativa L.)

International Nuclear Information System (INIS)

Kitano, H.; Futsuhara, Y.

1990-01-01

Full text: A root-growth inhibiting mutant was induced in the dwarf mutant line, 'Fukei 71', through ethylene-imine. The mutant is characterised by the excessive inhibition of both seminal and crown roots elongation just after germination, although its shoots grow nearly normal. To study the genetics, the mutant was crossed with its original line 'Fukei 71' and some other normal cultivars. Results show that the root-growth inhibition is controlled by a recessive gene (rt), independent of the dwarf gene, d-50(t) locus in Fukei 71. For elucidating the gene action on root morphogenesis, histological and cytological experiments were carried out using a longitudinal and transverse thin section of seminal and/or crown root tips. Observations suggest that the rt gene affects the normal formation of the epidermal system which is differentiated from the protoderm of the root apical meristem. (author)

Effects of ionizing radiation on the hypocotyl-root axis of three species of gossypium

International Nuclear Information System (INIS)

Reed, J.P.

1977-01-01

The hypocotyl-root axis of cotton seedlings grown from irradiated and non-irradiated seeds was investigated using light microscopy and histological techniques. Special emphasis was placed on the pattern of vascular transition. Two patterns of vascular transition in non-irradiated seedlings were found. In Gossypium hirsutum and G. barbadense there are prominent metaxylem bands between the vascular bundles in the hypocotyl. In G. gossypioides there are no bands. The presence or absence of the bands was easily detected using polarized light. The most outstanding effects of radiation were inhibition of lateral root development and alteration of the pattern of vascular transition in seedlings grown from irradiated seeds. The findings suggest that the root apical meristem determines the vascular pattern

UFO in the Arabidopsis inflorescence apex is required for floral-meristem identity and bract suppression.

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Hepworth, Shelley R; Klenz, Jennifer E; Haughn, George W

2006-03-01

The UNUSUAL FLORAL ORGANS (UFO) gene of Arabidopsis encodes an F-box protein required for the determination of floral-organ and floral-meristem identity. Mutation of UFO leads to dramatic changes in floral-organ type which are well-characterized whereas inflorescence defects are more subtle and less understood. These defects include an increase in the number of secondary inflorescences, nodes that alternate between forming flowers and secondary inflorescences, and nodes in which a single flower is subtended by a bract. Here, we show how inflorescence defects correlate with the abnormal development of floral primordia and establish a temporal requirement for UFO in this process. At the inflorescence apex of ufo mutants, newly formed primordia are initially bract-like. Expression of the floral-meristem identity genes LFY and AP1 are confined to a relatively small adaxial region of these primordia with expression of the bract-identity marker FIL observed in cells that comprise the balance of the primordia. Proliferation of cells in the adaxial region of these early primordia is delayed by several nodes such that primordia appear "chimeric" at several nodes, having visible floral and bract components. However, by late stage 2 of floral development, growth of the bract generally ceases and is overtaken by development of the floral primordium. This abnormal pattern of floral meristem development is not rescued by expression of UFO from the AP1 promoter, indicating that UFO is required prior to AP1 activation for normal development of floral primordia. We propose that UFO and LFY are jointly required in the inflorescence meristem to both promote floral meristem development and inhibit, in a non-cell autonomous manner, growth of the bract.

Lateral root organogenesis - from cell to organ.

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Benková, Eva; Bielach, Agnieszka

2010-12-01

Unlike locomotive organisms capable of actively approaching essential resources, sessile plants must efficiently exploit their habitat for water and nutrients. This involves root-mediated underground interactions allowing plants to adapt to soils of diverse qualities. The root system of plants is a dynamic structure that modulates primary root growth and root branching by continuous integration of environmental inputs, such as nutrition availability, soil aeration, humidity, or salinity. Root branching is an extremely flexible means to rapidly adjust the overall surface of the root system and plants have evolved efficient control mechanisms, including, firstly initiation, when and where to start lateral root formation; secondly lateral root primordia organogenesis, during which the development of primordia can be arrested for a certain time; and thirdly lateral root emergence. Our review will focus on the most recent advances in understanding the molecular mechanisms involved in the regulation of lateral root initiation and organogenesis with the main focus on root system of the model plant Arabidopsis thaliana. Copyright © 2010 Elsevier Ltd. All rights reserved.

Evolutionary Co-Option of Floral Meristem Identity Genes for Patterning of the Flower-Like Asteraceae Inflorescence.

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Zhao, Yafei; Zhang, Teng; Broholm, Suvi K; Tähtiharju, Sari; Mouhu, Katriina; Albert, Victor A; Teeri, Teemu H; Elomaa, Paula

2016-09-01

The evolutionary success of Asteraceae, the largest family of flowering plants, has been attributed to the unique inflorescence architecture of the family, which superficially resembles an individual flower. Here, we show that Asteraceae inflorescences (flower heads, or capitula) resemble solitary flowers not only morphologically but also at the molecular level. By conducting functional analyses for orthologs of the flower meristem identity genes LEAFY (LFY) and UNUSUAL FLORAL ORGANS (UFO) in Gerbera hybrida, we show that GhUFO is the master regulator of flower meristem identity, while GhLFY has evolved a novel, homeotic function during the evolution of head-like inflorescences. Resembling LFY expression in a single flower meristem, uniform expression of GhLFY in the inflorescence meristem defines the capitulum as a determinate structure that can assume floral fate upon ectopic GhUFO expression. We also show that GhLFY uniquely regulates the ontogeny of outer, expanded ray flowers but not inner, compact disc flowers, indicating that the distinction of different flower types in Asteraceae is connected with their independent evolutionary origins from separate branching systems. © 2016 American Society of Plant Biologists. All rights reserved.

ROTUNDA3 function in plant development by phosphatase 2A-mediated regulation of auxin transporter recycling.

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Karampelias, Michael; Neyt, Pia; De Groeve, Steven; Aesaert, Stijn; Coussens, Griet; Rolčík, Jakub; Bruno, Leonardo; De Winne, Nancy; Van Minnebruggen, Annemie; Van Montagu, Marc; Ponce, María Rosa; Micol, José Luis; Friml, Jiří; De Jaeger, Geert; Van Lijsebettens, Mieke

2016-03-08

The shaping of organs in plants depends on the intercellular flow of the phytohormone auxin, of which the directional signaling is determined by the polar subcellular localization of PIN-FORMED (PIN) auxin transport proteins. Phosphorylation dynamics of PIN proteins are affected by the protein phosphatase 2A (PP2A) and the PINOID kinase, which act antagonistically to mediate their apical-basal polar delivery. Here, we identified the ROTUNDA3 (RON3) protein as a regulator of the PP2A phosphatase activity in Arabidopsis thaliana. The RON3 gene was map-based cloned starting from the ron3-1 leaf mutant and found to be a unique, plant-specific gene coding for a protein with high and dispersed proline content. The ron3-1 and ron3-2 mutant phenotypes [i.e., reduced apical dominance, primary root length, lateral root emergence, and growth; increased ectopic stages II, IV, and V lateral root primordia; decreased auxin maxima in indole-3-acetic acid (IAA)-treated root apical meristems; hypergravitropic root growth and response; increased IAA levels in shoot apices; and reduced auxin accumulation in root meristems] support a role for RON3 in auxin biology. The affinity-purified PP2A complex with RON3 as bait suggested that RON3 might act in PIN transporter trafficking. Indeed, pharmacological interference with vesicle trafficking processes revealed that single ron3-2 and double ron3-2 rcn1 mutants have altered PIN polarity and endocytosis in specific cells. Our data indicate that RON3 contributes to auxin-mediated development by playing a role in PIN recycling and polarity establishment through regulation of the PP2A complex activity.

Evolutionary Co-Option of Floral Meristem Identity Genes for Patterning of the Flower-Like Asteraceae Inflorescence1

Science.gov (United States)

Broholm, Suvi K.; Tähtiharju, Sari

2016-01-01

The evolutionary success of Asteraceae, the largest family of flowering plants, has been attributed to the unique inflorescence architecture of the family, which superficially resembles an individual flower. Here, we show that Asteraceae inflorescences (flower heads, or capitula) resemble solitary flowers not only morphologically but also at the molecular level. By conducting functional analyses for orthologs of the flower meristem identity genes LEAFY (LFY) and UNUSUAL FLORAL ORGANS (UFO) in Gerbera hybrida, we show that GhUFO is the master regulator of flower meristem identity, while GhLFY has evolved a novel, homeotic function during the evolution of head-like inflorescences. Resembling LFY expression in a single flower meristem, uniform expression of GhLFY in the inflorescence meristem defines the capitulum as a determinate structure that can assume floral fate upon ectopic GhUFO expression. We also show that GhLFY uniquely regulates the ontogeny of outer, expanded ray flowers but not inner, compact disc flowers, indicating that the distinction of different flower types in Asteraceae is connected with their independent evolutionary origins from separate branching systems. PMID:27382139

Flux-based transport enhancement as a plausible unifying mechanism for auxin transport in meristem development.

Directory of Open Access Journals (Sweden)

Szymon Stoma

2008-10-01

Full Text Available Plants continuously generate new organs through the activity of populations of stem cells called meristems. The shoot apical meristem initiates leaves, flowers, and lateral meristems in highly ordered, spiralled, or whorled patterns via a process called phyllotaxis. It is commonly accepted that the active transport of the plant hormone auxin plays a major role in this process. Current hypotheses propose that cellular hormone transporters of the PIN family would create local auxin maxima at precise positions, which in turn would lead to organ initiation. To explain how auxin transporters could create hormone fluxes to distinct regions within the plant, different concepts have been proposed. A major hypothesis, canalization, proposes that the auxin transporters act by amplifying and stabilizing existing fluxes, which could be initiated, for example, by local diffusion. This convincingly explains the organised auxin fluxes during vein formation, but for the shoot apical meristem a second hypothesis was proposed, where the hormone would be systematically transported towards the areas with the highest concentrations. This implies the coexistence of two radically different mechanisms for PIN allocation in the membrane, one based on flux sensing and the other on local concentration sensing. Because these patterning processes require the interaction of hundreds of cells, it is impossible to estimate on a purely intuitive basis if a particular scenario is plausible or not. Therefore, computational modelling provides a powerful means to test this type of complex hypothesis. Here, using a dedicated computer simulation tool, we show that a flux-based polarization hypothesis is able to explain auxin transport at the shoot meristem as well, thus providing a unifying concept for the control of auxin distribution in the plant. Further experiments are now required to distinguish between flux-based polarization and other hypotheses.

Influence of root-bed size on the response of tobacco to elevated CO2 as mediated by cytokinins

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Schaz, Ulrike; Düll, Barbara; Reinbothe, Christiane; Beck, Erwin

2014-01-01

The extent of growth stimulation of C3 plants by elevated CO2 is modulated by environmental factors. Under optimized environmental conditions (high light, continuous water and nutrient supply, and others), we analysed the effect of an elevated CO2 atmosphere (700 ppm, EC) and the importance of root-bed size on the growth of tobacco. Biomass production was consistently higher under EC. However, the stimulation was overridden by root-bed volumes that restricted root growth. Maximum growth and biomass production were obtained at a root bed of 15 L at ambient and elevated CO2 concentrations. Starting with seed germination, the plants were strictly maintained under ambient or elevated CO2 until flowering. Thus, the well-known acclimation effect of growth to enhanced CO2 did not occur. The relative growth rates of EC plants exceeded those of ambient-CO2 plants only during the initial phases of germination and seedling establishment. This was sufficient for a persistently higher absolute biomass production by EC plants in non-limiting root-bed volumes. Both the size of the root bed and the CO2 concentration influenced the quantitative cytokinin patterns, particularly in the meristematic tissues of shoots, but to a smaller extent in stems, leaves and roots. In spite of the generally low cytokinin concentrations in roots, the amounts of cytokinins moving from the root to the shoot were substantially higher in high-CO2 plants. Because the cytokinin patterns of the (xylem) fluid in the stems did not match those of the shoot meristems, it is assumed that cytokinins as long-distance signals from the roots stimulate meristematic activity in the shoot apex and the sink leaves. Subsequently, the meristems are able to synthesize those phytohormones that are required for the cell cycle. Root-borne cytokinins entering the shoot appear to be one of the major control points for the integration of various environmental cues into one signal for optimized growth. PMID:24790131

Abnormal mitosis in root meristem cells of Allium cepa L. induced by ...

African Journals Online (AJOL)

This investigation was aimed to find mitotic abnormalities as cytological evidence induced by the dye in root tip cells of onion (Allium cepa L.) grown in different concentrations: 0.01, 0.05, 0.1, 0.5 and 1.0% (weight per volume) prepared in distilled water in separate treatment schedules for 24 and 48 h. Mitotic aberrations ...

Quantitative trait loci and candidate genes underlying genotype by environment interaction in the response of Arabidopsis thaliana to drought

NARCIS (Netherlands)

El-Soda, M.; Kruijer, Willem; Malosetti, M.; Koornneef, M.; Aarts, M.G.M.

2015-01-01

Drought stress was imposed on two sets of Arabidopsis thaliana genotypes grown in sand under short-day conditions and analysed for several shoot and root growth traits. The response to drought was assessed for quantitative trait locus (QTL) mapping in a genetically diverse set of Arabidopsis

Comparison of Meristem Culture and Heat Therapy to Clean Garlic ...

African Journals Online (AJOL)

(meristem culture) እንዱሁም ከሶስቱም ዝርያዎች በቫይረስ የተበከለ ኮረቶችን በሙቀት ... Eastern and Central Africa-International Livestock Research Institute Hub ...

The NADPH-oxidase AtRbohI plays a positive role in drought-stress response in Arabidopsis thaliana.

Science.gov (United States)

He, Huan; Yan, Jingwei; Yu, Xiaoyun; Liang, Yan; Fang, Lin; Scheller, Henrik Vibe; Zhang, Aying

2017-09-23

As the major resource of reactive oxygen species (ROS), the NADPH oxidases (Rbohs) have been shown to play important roles in plant cells under normal growth and stress conditions. Although many family members of Rbohs were studied, little is known about the function of RbohI in Arabidopsis thaliana. Here, we report that exogenous ABA application decreases RbohI expression and mannitol significantly increases RbohI expression at transcript level. The RbohI transcripts were strongly detected in dry seeds and roots. The loss-of-function mutant rbohI exhibited sensitivity to ABA and mannitol stress during germination. Furthermore, the lateral root growth of rbohI was severely inhibited after treatment with mannitol stress. Overexpression of RbohI in Arabidopsis significantly improves the drought tolerance. Moreover, more H 2 O 2 accumulated in RbohI overexpressors than in wild type plants in response to mannitol stress. Our conclusion is that AtRbohI functions in drought-stress response in Arabidopsis thaliana. Copyright © 2017. Published by Elsevier Inc.

Induction of Oxidative Stress and Antioxidative Mechanisms in Arabidopsis thaliana after Uranium Exposure at pH 7.5

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Eline Saenen

2015-06-01

Full Text Available To evaluate the environmental impact of uranium (U contamination, it is important to investigate the effects of U at ecologically relevant conditions. Since U speciation, and hence its toxicity, strongly depends on environmental pH, the present study aimed to investigate dose-dependent effects of U at pH 7.5. Arabidopsis thaliana plants (Mouse-ear Cress were exposed for three days to different U concentrations at pH 7.5. In the roots, the increased capacities of ascorbate peroxidase and glutathione reductase indicate an important role for the ascorbate-glutathione cycle during U-induced stress. However, a significant decrease in the ascorbate redox state was observed after exposure to 75 and 100 µM U, indicating that those roots are severely stressed. In accordance with the roots, the ascorbate-glutathione cycle plays an important role in the antioxidative defence systems in A. thaliana leaves exposed to U at pH 7.5 as the ascorbate and glutathione biosynthesis were upregulated. In addition, small inductions of enzymes of the antioxidative defence system were observed at lower U concentrations to counteract the U-induced stress. However, at higher U concentrations it seems that the antioxidative defence system of the leaves collapses as reductions in enzyme activities and gene expression levels were observed.

Gene expression polymorphisms and ESTs associated with gravitropic response of subterranean branch meristems and growth habit in Leymus wildryes

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Parminder Kaur; Ivan W. Mott; Steven R. Larson; B. Shaun Bushman; Alvaro G. Hernandez; W. Ryan Kim; Lei Liu; Mark A. Mikel

2008-01-01

Negatively orthogeotropic (NOGT) tiller and diageotropic (DGT) rhizome meristems develop from the same type of lateral axillary meristems and phytomer structure. Although subterranean NOGT and DGT buds appear similar, they display different responses to gravity and perhaps other cues governing branch angle and overall growth habit (GH). Leymus wildryes show remarkable...

Strictly NO3- Nutrition Alleviates Iron Deficiency Chlorosis in Arabidopsis thaliana Plants

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Najoua Msilini

2014-03-01

Full Text Available The effects of NO3- nutrition on iron deficiency responses were investigated in Arabidopsis thaliana. Plants were grown with or without 5 µM Fe, and with NO3- alone or a mixture of NO3- and NH4+. The results indicated that, NO3- nutrition induced higher dry matter production, regardless the Fe concentration. Fe deficiency reduced growth activity, photosynthetic pigment concentration and Fe content of plants, whatever the N forms. This decrease was more pronounced in plants grown with mixed N source; those plants presented the highest EL and MDA and anthocyanin contents compared to plants grown under Fe sufficient conditions. In iron free-solutions, with NO3- as the sole nitrogen source, enhanced FC-R activity in the roots was observed. However, in the presence of NH4+, plants displayed some decrease in in FC-R and PEPC activities. The presence of NH4+ modified typical Fe stress responses in Arabidopsis thaliana plants.

The RTR Complex Partner RMI2 and the DNA Helicase RTEL1 Are Both Independently Involved in Preserving the Stability of 45S rDNA Repeats in Arabidopsis thaliana.

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Sarah Röhrig

2016-10-01

Full Text Available The stability of repetitive sequences in complex eukaryotic genomes is safeguarded by factors suppressing homologues recombination. Prominent in this is the role of the RTR complex. In plants, it consists of the RecQ helicase RECQ4A, the topoisomerase TOP3α and RMI1. Like mammals, but not yeast, plants harbor an additional complex partner, RMI2. Here, we demonstrate that, in Arabidopsis thaliana, RMI2 is involved in the repair of aberrant replication intermediates in root meristems as well as in intrastrand crosslink repair. In both instances, RMI2 is involved independently of the DNA helicase RTEL1. Surprisingly, simultaneous loss of RMI2 and RTEL1 leads to loss of male fertility. As both the RTR complex and RTEL1 are involved in suppression of homologous recombination (HR, we tested the efficiency of HR in the double mutant rmi2-2 rtel1-1 and found a synergistic enhancement (80-fold. Searching for natural target sequences we found that RTEL1 is required for stabilizing 45S rDNA repeats. In the double mutant with rmi2-2 the number of 45S rDNA repeats is further decreased sustaining independent roles of both factors in this process. Thus, loss of suppression of HR does not only lead to a destabilization of rDNA repeats but might be especially deleterious for tissues undergoing multiple cell divisions such as the male germline.

The RTR Complex Partner RMI2 and the DNA Helicase RTEL1 Are Both Independently Involved in Preserving the Stability of 45S rDNA Repeats in Arabidopsis thaliana.

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Röhrig, Sarah; Schröpfer, Susan; Knoll, Alexander; Puchta, Holger

2016-10-01

The stability of repetitive sequences in complex eukaryotic genomes is safeguarded by factors suppressing homologues recombination. Prominent in this is the role of the RTR complex. In plants, it consists of the RecQ helicase RECQ4A, the topoisomerase TOP3α and RMI1. Like mammals, but not yeast, plants harbor an additional complex partner, RMI2. Here, we demonstrate that, in Arabidopsis thaliana, RMI2 is involved in the repair of aberrant replication intermediates in root meristems as well as in intrastrand crosslink repair. In both instances, RMI2 is involved independently of the DNA helicase RTEL1. Surprisingly, simultaneous loss of RMI2 and RTEL1 leads to loss of male fertility. As both the RTR complex and RTEL1 are involved in suppression of homologous recombination (HR), we tested the efficiency of HR in the double mutant rmi2-2 rtel1-1 and found a synergistic enhancement (80-fold). Searching for natural target sequences we found that RTEL1 is required for stabilizing 45S rDNA repeats. In the double mutant with rmi2-2 the number of 45S rDNA repeats is further decreased sustaining independent roles of both factors in this process. Thus, loss of suppression of HR does not only lead to a destabilization of rDNA repeats but might be especially deleterious for tissues undergoing multiple cell divisions such as the male germline.

Optimization of a protocol for direct organogenesis of red clover (Trifolium pratense L. meristems for breeding purposes

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JUAN C CARRILLO

2004-01-01

Full Text Available A series of experiments were carried out in order to optimize a protocol for the direct organogenesis of Chilean red clover germplasm. A range of cultivars were used to analyze the effect of explant source (crown or stem meristems of vegetative plants, culture media and plant growth regulators. Our findings showed that stem meristems were easier to obtain, presented lower levels of contamination and a better development than crown meristems. The L2 medium showed better results than B5 and MS media for the cultivars and experimental lines studied. L2 medium supplemented with 0.003 mg/l of 4-amino-3,5,6-trichloropicolinic acid and 1.0 mg/l of 6-benzylaminopurine gave consistently better results and will be applied in our breeding program to propagate, maintain and eliminate viruses from elite red clover clones.

Stochastic gene expression in Arabidopsis thaliana.

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Araújo, Ilka Schultheiß; Pietsch, Jessica Magdalena; Keizer, Emma Mathilde; Greese, Bettina; Balkunde, Rachappa; Fleck, Christian; Hülskamp, Martin

2017-12-14

Although plant development is highly reproducible, some stochasticity exists. This developmental stochasticity may be caused by noisy gene expression. Here we analyze the fluctuation of protein expression in Arabidopsis thaliana. Using the photoconvertible KikGR marker, we show that the protein expressions of individual cells fluctuate over time. A dual reporter system was used to study extrinsic and intrinsic noise of marker gene expression. We report that extrinsic noise is higher than intrinsic noise and that extrinsic noise in stomata is clearly lower in comparison to several other tissues/cell types. Finally, we show that cells are coupled with respect to stochastic protein expression in young leaves, hypocotyls and roots but not in mature leaves. Our data indicate that stochasticity of gene expression can vary between tissues/cell types and that it can be coupled in a non-cell-autonomous manner.

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

Strigolactones suppress adventitious rooting in Arabidopsis and pea.

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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.

The QTL GNP1 Encodes GA20ox1, Which Increases Grain Number and Yield by Increasing Cytokinin Activity in Rice Panicle Meristems.

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Wu, Yuan; Wang, Yun; Mi, Xue-Fei; Shan, Jun-Xiang; Li, Xin-Min; Xu, Jian-Long; Lin, Hong-Xuan

2016-10-01

Cytokinins and gibberellins (GAs) play antagonistic roles in regulating reproductive meristem activity. Cytokinins have positive effects on meristem activity and maintenance. During inflorescence meristem development, cytokinin biosynthesis is activated via a KNOX-mediated pathway. Increased cytokinin activity leads to higher grain number, whereas GAs negatively affect meristem activity. The GA biosynthesis genes GA20oxs are negatively regulated by KNOX proteins. KNOX proteins function as modulators, balancing cytokinin and GA activity in the meristem. However, little is known about the crosstalk among cytokinin and GA regulators together with KNOX proteins and how KNOX-mediated dynamic balancing of hormonal activity functions. Through map-based cloning of QTLs, we cloned a GA biosynthesis gene, Grain Number per Panicle1 (GNP1), which encodes rice GA20ox1. The grain number and yield of NIL-GNP1TQ were significantly higher than those of isogenic control (Lemont). Sequence variations in its promoter region increased the levels of GNP1 transcripts, which were enriched in the apical regions of inflorescence meristems in NIL-GNP1TQ. We propose that cytokinin activity increased due to a KNOX-mediated transcriptional feedback loop resulting from the higher GNP1 transcript levels, in turn leading to increased expression of the GA catabolism genes GA2oxs and reduced GA1 and GA3 accumulation. This rebalancing process increased cytokinin activity, thereby increasing grain number and grain yield in rice. These findings uncover important, novel roles of GAs in rice florescence meristem development and provide new insights into the crosstalk between cytokinin and GA underlying development process.

Plantlet regeneration potential from seedling explants of vitegnus (Vitex agnus castus).

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Chamandoosti, F

2007-11-15

In this research a simple and repeatable method for regeneration of a important medicinal plant (Vitex agnus castus) described. Different seedling explants such as hypocotyl, cotyledon, root and apical meristem were cultured in MS basal media with different kinds and concentrations of PGRs. Root and apical meristem explants were the only explants that have regeneration whole plantlets potential. It was interesting that regeneration whole plantlets from root and apical meristem explants have different developmental pathways. Whole plantlets from apical meristem explants regenerated by passing phase callusing whereas regeneration whole plantlets from root was direct and without phase callusing. This subject implies that we can have many manipulation possibilities in order to different objects of tissue culture by selecting different explants in vitegnus.

Thorium impact on tobacco root transcriptome

Czech Academy of Sciences Publication Activity Database

Mazari, Kateřina; Landa, Přemysl; Přerostová, Sylva; Müller, Karel; Vaňková, Radomíra; Soudek, Petr; Vaněk, Tomáš

2017-01-01

Roč. 325, MAR 5 (2017), s. 163-169 ISSN 0304-3894 R&D Projects: GA MŠk(CZ) LD11073; GA MŠk(CZ) LD13029 Institutional support: RVO:61389030 Keywords : arabidopsis-thaliana roots * juncea var. foliosa * cadmium accumulation * deficiency responses * mineral- nutrition * gene-expression * plant transfer * iron uptake * uranium * soil * Microarray * Thorium * Gene expression * Toxicity * Nicotiana tabacum Subject RIV: ED - Physiology OBOR OECD: Plant sciences, botany Impact factor: 6.065, year: 2016

Propagación in vitro de Carica papaya var. PTM-331 a partir de meristemos apicales In vitro propagation of Carica papaya var. PTM-331 from apical meristem

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Reynaldo Solis L.

2012-02-01

Full Text Available El trabajo consistió en desarrollar un protocolo de propagación in vitro de la variedad de papaya PTM-331 a partir de meristemos apicales, con la finalidad de obtener plántulas vigorosas y libres de enfermedades, empleando la técnica del cultivo de tejidos. Las yemas apicales empleadas fueron obtenidas de plantas cultivadas en invernadero, los cuales fueron usados como explantes para la extracción de meristemos. La mejor diferenciación de meristemos se logró en el medio basal MS suplementado con 0,5 mg.L-1 de BAP, 0,5 mg.L-1 de AIA y 10 mg.L-1 de adenina. La mejor multiplicación se logró con el medio MS suplementado con 0,5 mg.L-1 de BAP, 0,5 mg.L-1 de AIA y 0,3 mg.L-1 de AG3, con un coeficiente de multiplicación de 3,42; mientras que el mejor medio para el enraizamiento fue la combinación del medio MS, 3 mg.L-1 de AIB y 5 mg.L-1 de adenina, donde se obtuvo 83,33% de plantas enraizadas.An in vitro protocol was develop to propagate variety of papaya PTM-331 from apical meristems, with the objective of obtaining vigorous and disease-free seedlings, using tissue culture techniques. Apical buds were obtained from seedlings cultivated in greenhouse and used as explants for meristem dissection. Meristems were cultured on MS basal medium supplemented with 0,5 mg.L-1 of BAP, 0,5 mg.L-1 of AIA and 10 mg.L-1 of adenine for their differentiation. The best multiplication of explants was achieved with the combination of MS medium supplemented with 0,5 mg.L-1 of BAP, 0,5 mg.L-1 of AIA and 0,3 mg.L-1 of AG3, where largest seedlings, with more shoots were obtained. The best medium for rooting was the combination of MS, 3 mg.L-1 of AIB and 5 mg.L-1 of adenine, where 83,33% of rooted plants were obtained.

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.

The early inflorescence of Arabidopsis thaliana demonstrates positional effects in floral organ growth and meristem patterning.

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Plackett, Andrew R G; Powers, Stephen J; Phillips, Andy L; Wilson, Zoe A; Hedden, Peter; Thomas, Stephen G

2018-06-01

Linear modelling approaches detected significant gradients in organ growth and patterning across early flowers of the Arabidopsis inflorescence and uncovered evidence of new roles for gibberellin in floral development. Most flowering plants, including the genetic model Arabidopsis thaliana, produce multiple flowers in sequence from a reproductive shoot apex to form a flower spike (inflorescence). The development of individual flowers on an Arabidopsis inflorescence has typically been considered as highly stereotypical and uniform, but this assumption is contradicted by the existence of mutants with phenotypes visible in early flowers only. This phenomenon is demonstrated by mutants partially impaired in the biosynthesis of the phytohormone gibberellin (GA), in which floral organ growth is retarded in the first flowers to be produced but has recovered spontaneously by the 10th flower. We presently lack systematic data from multiple flowers across the Arabidopsis inflorescence to explain such changes. Using mutants of the GA 20-OXIDASE (GA20ox) GA biosynthesis gene family to manipulate endogenous GA levels, we investigated the dynamics of changing floral organ growth across the early Arabidopsis inflorescence (flowers 1-10). Modelling of floral organ lengths identified a significant, GA-independent gradient of increasing stamen length relative to the pistil in the wild-type inflorescence that was separable from other, GA-dependent effects. It was also found that the first flowers exhibited unstable organ patterning in contrast to later flowers and that this instability was prolonged by exogenous GA treatment. These findings indicate that the development of individual flowers is influenced by hitherto unknown factors acting across the inflorescence and also suggest novel functions for GA in floral patterning.

A pivotal role of the jasmonic acid signal pathway in mediating radiation-induced bystander effects in Arabidopsis thaliana

Energy Technology Data Exchange (ETDEWEB)

Wang, Ting; Xu, Wei; Deng, Chenguang; Xu, Shaoxin; Li, Fanghua; Wu, Yuejin; Wu, Lijun [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei 230031 (China); Bian, Po, E-mail: bianpo@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei 230031 (China)

2016-09-15

Highlights: • The JA signal pathway plays a pivotal role in mediating radiation-induced bystander effects in Arabidopsis thaliana. • The JA signal pathway is involved in both the generation of bystander signals in irradiated roots and radiation responses in bystander aerial plants. • Over-accumulation of endogenous JA enhances the radiosensitivity of plants in terms of RIBE. - Abstract: Although radiation-induced bystander effects (RIBE) in Arabidopsis thaliana have been well demonstrated in vivo, little is known about their underlying mechanisms, particularly with regard to the participating signaling molecules and signaling pathways. In higher plants, jasmonic acid (JA) and its bioactive derivatives are well accepted as systemic signal transducers that are produced in response to various environmental stresses. It is therefore speculated that the JA signal pathway might play a potential role in mediating radiation-induced bystander signaling of root-to-shoot. In the present study, pretreatment of seedlings with Salicylhydroxamic acid, an inhibitor of lipoxigenase (LOX) in JA biosynthesis, significantly suppressed RIBE-mediated expression of the AtRAD54 gene. After root irradiation, the aerial parts of A. thaliana mutants deficient in JA biosynthesis (aos) and signaling cascades (jar1-1) showed suppressed induction of the AtRAD54 and AtRAD51 genes and TSI and 180-bp repeats, which have been extensively used as endpoints of bystander genetic and epigenetic effects in plants. These results suggest an involvement of the JA signal pathway in the RIBE of plants. Using the root micro-grafting technique, the JA signal pathway was shown to participate in both the generation of bystander signals in irradiated root cells and radiation responses in the bystander aerial parts of plants. The over-accumulation of endogenous JA in mutant fatty acid oxygenation up-regulated 2 (fou2), in which mutation of the Two Pore Channel 1 (TPC1) gene up-regulates expression of the LOX

Evaluation of the plant growth-promoting activity of Pseudomonas nitroreducens in Arabidopsis thaliana and Lactuca sativa.

Science.gov (United States)

Trinh, Cao Son; Lee, Hyeri; Lee, Won Je; Lee, Seok Jin; Chung, Namhyun; Han, Juhyeong; Kim, Jongyun; Hong, Suk-Whan; Lee, Hojoung

2018-06-01

Pseudomonas nitroreducens: strain IHB B 13561 (PnIHB) enhances the growth of Arabidopsis thaliana and Lactuca sativa via the stimulation of cell development and nitrate absorption. Plant growth-promoting rhizobacteria (PGPR) enhance plant development through various mechanisms; they improve the uptake of soil resources by plants to greatly promote plant growth. Here, we used Arabidopsis thaliana seedlings and Lactuca sativa to screen the growth enhancement activities of a purified PGPR, Pseudomonas nitroreducens strain IHB B 13561 (PnIHB). When cocultivated with PnIHB, both species of plants exhibited notably improved growth, particularly in regard to biomass. Quantitative reverse transcription polymerase chain reaction analysis indicated high expression levels of the nitrate transporter genes, especially NRT2.1, which plays a major role in the high-affinity nitrate transport system in roots. Moreover, enhanced activity of the cyclin-B1 promoter was observed when wild-type 'Columbia-0' Arabidopsis seedlings were exposed to PnIHB, whereas upregulation of cyclin-B also occurred in the inoculated lettuce seedlings. Overall, these results suggest that PnIHB improves A. thaliana and L. sativa growth via specific pathways involved in the promotion of cell development and enhancement of nitrate uptake.

In silico comparison of transcript abundances during Arabidopsis thaliana and Glycine max resistance to Fusarium virguliforme

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Iqbal M Javed

2008-09-01

Full Text Available Abstract Background Sudden death syndrome (SDS of soybean (Glycine max L. Merr. is an economically important disease, caused by the semi-biotrophic fungus Fusarium solani f. sp. glycines, recently renamed Fusarium virguliforme (Fv. Due to the complexity and length of the soybean-Fusarium interaction, the molecular mechanisms underlying plant resistance and susceptibility to the pathogen are not fully understood. F. virguliforme has a very wide host range for the ability to cause root rot and a very narrow host range for the ability to cause a leaf scorch. Arabidopsis thaliana is a host for many types of phytopathogens including bacteria, fungi, viruses and nematodes. Deciphering the variations among transcript abundances (TAs of functional orthologous genes of soybean and A. thaliana involved in the interaction will provide insights into plant resistance to F. viguliforme. Results In this study, we reported the analyses of microarrays measuring TA in whole plants after A. thaliana cv 'Columbia' was challenged with fungal pathogen F. virguliforme. Infection caused significant variations in TAs. The total number of increased transcripts was nearly four times more than that of decreased transcripts in abundance. A putative resistance pathway involved in responding to the pathogen infection in A. thaliana was identified and compared to that reported in soybean. Conclusion Microarray experiments allow the interrogation of tens of thousands of transcripts simultaneously and thus, the identification of plant pathways is likely to be involved in plant resistance to Fusarial pathogens. Dissection of the set functional orthologous genes between soybean and A. thaliana enabled a broad view of the functional relationships and molecular interactions among plant genes involved in F. virguliforme resistance.

Effects of polyamines and polyamine biosynthetic inhibitors on mitotic activity of Allium cepa root tips.

Science.gov (United States)

Unal, Meral; Palavan-Unsal, Narcin; Tufekci, M A

2008-03-01

The genotoxic and cytotoxic effects of exogenous polyamines (PAs), putrescine (Put), spermidine (Spd), spermine (Spm) and PA biosynthetic inhibitors, alpha-difluoromethylornithine (DFMO), cyclohexilamine (CHA), methylglioxal bis-(guanylhydrazone) (MGBG) were investigated in the root meristems of Allium cepa L. The reduction of mitotic index and the induction of chromosomal aberrations such as bridges, stickiness, c-mitotic anaphases, micronuclei, endoredupliction by PAs and PA biosynthetic inhibitors were observed and these were used as evidence of genotoxicity and cytotoxicity.

TOPOISOMERASE1α Acts through Two Distinct Mechanisms to Regulate Stele and Columella Stem Cell Maintenance.

Science.gov (United States)

Zhang, Yonghong; Zheng, Lanlan; Hong, Jing Han; Gong, Ximing; Zhou, Chun; Pérez-Pérez, José Manuel; Xu, Jian

2016-05-01

TOPOISOMERASE1 (TOP1), which releases DNA torsional stress generated during replication through its DNA relaxation activity, plays vital roles in animal and plant development. In Arabidopsis (Arabidopsis thaliana), TOP1 is encoded by two paralogous genes (TOP1α and TOP1β), of which TOP1α displays specific developmental functions that are critical for the maintenance of shoot and floral stem cells. Here, we show that maintenance of two different populations of root stem cells is also dependent on TOP1α-specific developmental functions, which are exerted through two distinct novel mechanisms. In the proximal root meristem, the DNA relaxation activity of TOP1α is critical to ensure genome integrity and survival of stele stem cells (SSCs). Loss of TOP1α function triggers DNA double-strand breaks in S-phase SSCs and results in their death, which can be partially reversed by the replenishment of SSCs mediated by ETHYLENE RESPONSE FACTOR115 In the quiescent center and root cap meristem, TOP1α is epistatic to RETINOBLASTOMA-RELATED (RBR) in the maintenance of undifferentiated state and the number of columella stem cells (CSCs). Loss of TOP1α function in either wild-type or RBR RNAi plants leads to differentiation of CSCs, whereas overexpression of TOP1α mimics and further enhances the effect of RBR reduction that increases the number of CSCs Taken together, these findings provide important mechanistic insights into understanding stem cell maintenance in plants. © 2016 American Society of Plant Biologists. All Rights Reserved.

Biochemical and genetic characterization of three molybdenum cofactor hydroxylases in Arabidopsis thaliana

DEFF Research Database (Denmark)

Hoff, Tine; Frandsen, Gitte Inselmann; Rocher, Anne

1998-01-01

Aldehyde oxidases and xanthine dehydrogenases/oxidases belong to the molybdenum cofactor dependent hydroxylase class of enzymes. Zymograms show that Arabidopsis thaliana has at least three different aldehyde oxidases and one xanthine oxidase. Three different cDNA clones encoding putative aldehyde...... oxidases (AtAO1, 2, 3) were isolated. An aldehyde oxidase is the last step in abscisic acid (ABA) biosynthesis. AtAO1 is mainly expressed in seeds and roots which might reflect that it is involved in ABA biosynthesis....

BoALMT1, an Al-Induced Malate Transporter in Cabbage, Enhances Aluminum Tolerance in Arabidopsis thaliana

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Lei Zhang

2018-01-01

Full Text Available Aluminum (Al is present in approximately 50% of the arable land worldwide and is regarded as the main limiting factor of crop yield on acidic soil. Al-induced root malate efflux plays an important role in the Al tolerance of plants. Here, the aluminum induced malate transporter BoALMT1 (KF322104 was cloned from cabbage (Brassica oleracea. BoALMT1 showed higher expression in roots than in shoots. The expression of BoALMT1 was specifically induced by Al treatment, but not the trivalent cations lanthanum (La, cadmium (Cd, zinc (Zn, or copper (Cu. Subcellular localization studies were performed in onion epidermal cells and revealed that BoALMT1 was localized at the plasma membrane. Scanning Ion-selective Electrode Technique was used to analyze H+ flux. Xenopus oocytes and Arabidopsis thaliana expressing BoALMT1 excreted more H+ under Al treatment. Overexpressing BoALMT1 in transgenic Arabidopsis resulted in enhanced Al tolerance and increased malate secretion. The results suggested that BoALMT1 functions as an Al-resistant gene and encodes a malate transporter. Expressing BoALMT1 in Xenopus oocytes or A. thaliana indicated that BoALMT1 could increase malate secretion and H+ efflux to resist Al tolerance.

Ds tagging of BRANCHED FLORETLESS 1 (BFL1 that mediates the transition from spikelet to floret meristem in rice (Oryza sativa L

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Hoque Mohammad

2003-09-01

Full Text Available Abstract Background The genetics of spikelet formation, a feature unique to grasses such as rice and maize, is yet to be fully understood, although a number of meristem and organ identity mutants have been isolated and investigated in Arabidopsis and maize. Using a two-element Ac/Ds transposon tagging system we have isolated a rice mutant, designated branched floretless 1 (bfl1 which is defective in the transition from spikelet meristem to floret meristem. Results The bfl1 mutant shows normal differentiation of the primary rachis-branches leading to initial spikelet meristem (bract-like structure equivalent to rudimentary glumes formation but fails to develop empty glumes and florets. Instead, axillary meristems in the bract-like structure produce sequential alternate branching, thus resulting in a coral shaped morphology of the branches in the developing panicle. The bfl1 mutant harbours a single Ds insertion in the upstream region of the BFL1 gene on chromosome 7 corresponding to PAC clone P0625E02 (GenBank Acc No. message URL http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=nucleotide&list_uids=34395191&dopt=GenBank&term=ap004570AP004570. RT-PCR analyses revealed a drastic reduction of BFL1 transcript levels in the bfl1 mutant compared to that in the wild-type. In each of the normal panicle-bearing progeny plants, from occasional revertant seeds of the vegetatively-propagated mutant plant, Ds was shown to be excised from the bfl1 locus. BFL1 contains an EREBP/AP2 domain and is most likely an ortholog of the maize transcription factor gene BRANCHED SILKLESS1 (BD1. Conclusions bfl1 is a Ds-tagged rice mutant defective in the transition from spikelet meristem (SM to floret meristem (FM. BFL1 is most probably a rice ortholog of the maize ERF (EREBP/AP2 transcription factor gene BD1. Based on the similarities in mutant phenotypes bfl1 is likely to be an allele of the previously reported frizzy panicle locus.

Environmental regulation of lateral root emergence in Medicago truncatula requires the HD-Zip I transcription factor HB1.

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Ariel, Federico; Diet, Anouck; Verdenaud, Marion; Gruber, Véronique; Frugier, Florian; Chan, Raquel; Crespi, Martin

2010-07-01

The adaptation of root architecture to environmental constraints is a major agricultural trait, notably in legumes, the third main crop worldwide. This root developmental plasticity depends on the formation of lateral roots (LRs) emerging from primary roots. In the model legume Medicago truncatula, the HD-Zip I transcription factor HB1 is expressed in primary and lateral root meristems and induced by salt stress. Constitutive expression of HB1 in M. truncatula roots alters their architecture, whereas hb1 TILLING mutants showed increased lateral root emergence. Electrophoretic mobility shift assay, promoter mutagenesis, and chromatin immunoprecipitation-PCR assays revealed that HB1 directly recognizes a CAATAATTG cis-element present in the promoter of a LOB-like (for Lateral Organ Boundaries) gene, LBD1, transcriptionally regulated by auxin. Expression of these genes in response to abscisic acid and auxin and their behavior in hb1 mutants revealed an HB1-mediated repression of LBD1 acting during LR emergence. M. truncatula HB1 regulates an adaptive developmental response to minimize the root surface exposed to adverse environmental stresses.

Investigating uptake of water-dispersible CdSe/ZnS quantum dot nanoparticles by Arabidopsis thaliana plants

International Nuclear Information System (INIS)

Navarro, Divina A.; Bisson, Mary A.; Aga, Diana S.

2012-01-01

Graphical abstract: This study highlights the importance of quantum dot (QD) structural stability in preventing phytotoxicity. Overall, there is no evidence that Arabidopsis thaliana plants can internalize intact QDs within 1–7 days of exposure, with or without humic acids. Highlights: ► Potential uptake of water-dispersible CdSe/ZnS QDs by Arabidopsis was demonstrated. ► QDs were not internalized by Arabidopsis as intact particles. ► Plants exposed to Cd-, Se-, and QD + HA suspensions experienced oxidative stress. ► An effective LC–MS method proves detection of low levels of glutathione in plants. ► Uptake of Cd and/or Se leached from QDs is of major concern. - Abstract: Interest on the environmental impacts of engineered nanomaterials has rapidly increased over the past years because it is expected that these materials will eventually be released into the environment. The present work investigates the potential root uptake of water-dispersible CdSe/ZnS quantum dots (QDs) by the model plant species, Arabidopsis thaliana. Experiments revealed that Arabidopsis exposed to QDs that are dispersed in Hoagland's solution for 1–7 days did not internalize intact QDs. Analysis of Cd and Se concentrations in roots and leaves by inductively-coupled plasma mass spectrometry indicated that Cd and Se from QD-treated plants were not translocated into the leaves, and remained in the root system of Arabidopsis. Furthermore, fluorescence microscopy showed strong evidence that the QDs were generally on the outside surfaces of the roots, where the amount of QDs adsorbed is dependent on the stability of the QDs in suspension. Despite no evidence of nanoparticle internalization, the ratio of reduced glutathione levels (GSH) relative to the oxidized glutathione (GSSG) in plants decreased when plants were exposed to QD dispersions containing humic acids, suggesting that QDs caused oxidative stress on the plant at this condition.

Dark exposure of petunia cuttings strongly improves adventitious root formation and enhances carbohydrate availability during rooting in the light.

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Klopotek, Yvonne; Haensch, Klaus-Thomas; Hause, Bettina; Hajirezaei, Mohammad-Reza; Druege, Uwe

2010-05-01

The effect of temporary dark exposure on adventitious root formation (ARF) in Petuniaxhybrida 'Mitchell' cuttings was investigated. Histological and metabolic changes in the cuttings during the dark treatment and subsequent rooting in the light were recorded. Excised cuttings were exposed to the dark for seven days at 10 degrees C followed by a nine-day rooting period in perlite or were rooted immediately for 16 days in a climate chamber at 22/20 degrees C (day/night) and a photosynthetic photon flux density (PPFD) of 100micromolm(-2)s(-1). Dark exposure prior to rooting increased, accelerated and synchronized ARF. The rooting period was reduced from 16 days (non-treated cuttings) to 9 days (treated cuttings). Under optimum conditions, despite the reduced rooting period, dark-exposed cuttings produced a higher number and length of roots than non-treated cuttings. An increase in temperature to 20 degrees C during the dark treatment or extending the cold dark exposure to 14 days caused a similar enhancement of root development compared to non-treated cuttings. Root meristem formation had already started during the dark treatment and was enhanced during the subsequent rooting period. Levels of soluble sugars (glucose, fructose and sucrose) and starch in leaf and basal stem tissues significantly decreased during the seven days of dark exposure. This depletion was, however, compensated during rooting after 6 and 24h for soluble sugars in leaves and the basal stem, respectively, whereas the sucrose level in the basal stem was already increased at 6h. The association of higher carbohydrate levels with improved rooting in previously dark-exposed versus non-treated cuttings indicates that increased post-darkness carbohydrate availability and allocation towards the stem base contribute to ARF under the influence of dark treatment and provide energy for cell growth subject to a rising sink intensity in the base of the cutting. Copyright 2009 Elsevier GmbH. All rights reserved.

The chromoplasts of Or mutants of cauliflower (Brassica oleracea L. var. botrytis).

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Paolillo, D J; Garvin, D F; Parthasarathy, M V

2004-12-01

The Or mutation in cauliflower (Brassica oleracea L. var. botrytis) leads to abnormal accumulations of beta-carotene in orange chromoplasts, in tissues in which leucoplasts are characteristic of wild-type plants. Or chromoplasts were investigated by light microscopy of fresh materials and electron microscopy of glutaraldehyde- and potassium permanganate-fixed materials. Carotenoid inclusions in Or chromoplasts resemble those found in carrot root chromoplasts in their optical activity and angular shape. Electron microscopy revealed that the inclusions are made up of parallel, membrane-bound compartments. These stacks of membranes are variously rolled and folded into three-dimensional objects. We classify Or chromoplasts as "membranous" chromoplasts. The Or mutation also limits plastid replication so that a single chromoplast constitutes the plastidome in most of the affected cells. There are one to two chromoplasts in each cell of a shoot apex. The ability of differentiated chromoplasts to divide in the apical meristems of Or mutant plants resembles the ability of proplastids to maintain plastid continuity from cell to cell in meristems of Arabidopsis thaliana mutants in which plastid replication is drastically limited. The findings are used to discuss the number of levels of regulation involved in plastid replication.

Cell lineage patterns in the shoot meristem of the sunflower embryo in the dry seed

International Nuclear Information System (INIS)

Jegla, D.E.; Sussex, I.M.

1989-01-01

We mapped the fate of cells in the shoot meristem of the dry-seed embryo of sunflower, Helianthus annuus L. cv. Peredovic, using irradiation-induced somatic sectors. We analyzed 249 chlorophyll-deficient or glabrous (hairless) sectors generated in 236 plants. Most sectors observed in the inflorescence extended into vegetative nodes. Thus cell lineages that ultimately gave rise to reproductive structures also contributed to vegetative structures. No single sector extended the entire length of the shoot. Thus the shoot is not derived from one or a few apical initials. Rather, the position, vertical extent, and width of the sectors at different levels of the shoot suggest that the shoot is derived from three to four circumferential populations of cells in each of three cell layers of the embryo meristem. Sectors had no common boundaries even in plants with two or three independent sectors, but varied in extent and overlapped along the length of the shoot. Thus individual cells in a single circumferential population behaved independently to contribute lineages of different vertical extents to the growing shoot. The predicted number of circumferential populations of cells as well as the apparent cell number in each population was consistent with the actual number of cells in the embryo meristem observed in histological sections

The structurally related auxin and melatonin tryptophan-derivatives and their roles in Arabidopsis thaliana and in the human malaria parasite Plasmodium falciparum.

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Koyama, Fernanda C; Carvalho, Thais L G; Alves, Eduardo; da Silva, Henrique B; de Azevedo, Mauro F; Hemerly, Adriana S; Garcia, Célia R S

2013-01-01

Indole compounds are involved in a range of functions in many organisms. In the human malaria parasite Plasmodium falciparum, melatonin and other tryptophan derivatives are able to modulate its intraerythrocytic cycle, increasing the schizont population as well as parasitemia, likely through ubiquitin-proteasome system (UPS) gene regulation. In plants, melatonin regulates root development, in a similar way to that described for indoleacetic acid, suggesting that melatonin and indoleacetic acid could co-participate in some physiological processes due to structural similarities. In the present work, we evaluate whether the chemical structure similarity found in indoleacetic acid and melatonin can lead to similar effects in Arabidopsis thaliana lateral root formation and P. falciparum cell cycle modulation, as well as in the UPS of gene regulation, by qRT-PCR. Our data show that P. falciparum is not able to respond to indoleacetic acid either in the modulation of the intraerythrocytic cycle or in the gene regulation mediated by the UPS as observed for melatonin. The similarities of these indole compounds are not sufficient to confer synergistic functions in P. falciparum cell cycle modulation, but could interplay in A. thaliana lateral root formation. © 2013 The Author(s) Journal of Eukaryotic Microbiology © 2013 International Society of Protistologists.

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

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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.

Trichoderma-Induced Acidification Is an Early Trigger for Changes in Arabidopsis Root Growth and Determines Fungal Phytostimulation

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Pelagio-Flores, Ramón; Esparza-Reynoso, Saraí; Garnica-Vergara, Amira; López-Bucio, José; Herrera-Estrella, Alfredo

2017-01-01

Trichoderma spp. are common rhizosphere inhabitants widely used as biological control agents and their role as plant growth promoting fungi has been established. Although soil pH influences several fungal and plant functional traits such as growth and nutrition, little is known about its influence in rhizospheric or mutualistic interactions. The role of pH in the Trichoderma–Arabidopsis interaction was studied by determining primary root growth and lateral root formation, root meristem status and cell viability, quiescent center (QC) integrity, and auxin inducible gene expression. Primary root growth phenotypes in wild type seedlings and STOP1 mutants allowed identification of a putative root pH sensing pathway likely operating in plant–fungus recognition. Acidification by Trichoderma induced auxin redistribution within Arabidopsis columella root cap cells, causing root tip bending and growth inhibition. Root growth stoppage correlated with decreased cell division and with the loss of QC integrity and cell viability, which were reversed by buffering the medium. In addition, stop1, an Arabidopsis mutant sensitive to low pH, was oversensitive to T. atroviride primary root growth repression, providing genetic evidence that a pH root sensing mechanism reprograms root architecture during the interaction. Our results indicate that root sensing of pH mediates the interaction of Trichoderma with plants. PMID:28567051

Bioavailability of nanoparticulate hematite to Arabidopsis thaliana

International Nuclear Information System (INIS)

Marusenko, Yevgeniy; Shipp, Jessie; Hamilton, George A.; Morgan, Jennifer L.L.; Keebaugh, Michael; Hill, Hansina; Dutta, Arnab; Zhuo, Xiaoding; Upadhyay, Nabin; Hutchings, James; Herckes, Pierre; Anbar, Ariel D.; Shock, Everett; Hartnett, Hilairy E.

2013-01-01

The environmental effects and bioavailability of nanoparticulate iron (Fe) to plants are currently unknown. Here, plant bioavailability of synthesized hematite Fe nanoparticles was evaluated using Arabidopsis thaliana (A. thaliana) as a model. Over 56-days of growing wild-type A. thaliana, the nanoparticle-Fe and no-Fe treatments had lower plant biomass, lower chlorophyll concentrations, and lower internal Fe concentrations than the Fe-treatment. Results for the no-Fe and nanoparticle-Fe treatments were consistently similar throughout the experiment. These results suggest that nanoparticles (mean diameter 40.9 nm, range 22.3–67.0 nm) were not taken up and therefore not bioavailable to A. thaliana. Over 14-days growing wild-type and transgenic (Type I/II proton pump overexpression) A. thaliana, the Type I plant grew more than the wild-type in the nanoparticle-Fe treatment, suggesting Type I plants cope better with Fe limitation; however, the nanoparticle-Fe and no-Fe treatments had similar growth for all plant types. -- Highlights: ► Iron nanoparticles were synthesized and assessed for bioavailability to Arabidopsis. ► Arabidopsis grew better in the presence of EDTA-bound iron than nanoparticulate iron. ► Arabidopsis grew the same in the presence of nanoparticulate iron compared to no iron. -- Synthesized iron nanoparticles were not bioavailable to Arabidopsis thaliana in agar nutrient media

An Intergenic Region Shared by At4g35985 and At4g35987 in Arabidopsis thaliana Is a Tissue Specific and Stress Inducible Bidirectional Promoter Analyzed in Transgenic Arabidopsis and Tobacco Plants

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Banerjee, Joydeep; Sahoo, Dipak Kumar; Dey, Nrisingha; Houtz, Robert L.; Maiti, Indu Bhushan

2013-01-01

On chromosome 4 in the Arabidopsis genome, two neighboring genes (calmodulin methyl transferase At4g35987 and senescence associated gene At4g35985) are located in a head-to-head divergent orientation sharing a putative bidirectional promoter. This 1258 bp intergenic region contains a number of environmental stress responsive and tissue specific cis-regulatory elements. Transcript analysis of At4g35985 and At4g35987 genes by quantitative real time PCR showed tissue specific and stress inducible expression profiles. We tested the bidirectional promoter-function of the intergenic region shared by the divergent genes At4g35985 and At4g35987 using two reporter genes (GFP and GUS) in both orientations in transient tobacco protoplast and Agro-infiltration assays, as well as in stably transformed transgenic Arabidopsis and tobacco plants. In transient assays with GFP and GUS reporter genes the At4g35985 promoter (P85) showed stronger expression (about 3.5 fold) compared to the At4g35987 promoter (P87). The tissue specific as well as stress responsive functional nature of the bidirectional promoter was evaluated in independent transgenic Arabidopsis and tobacco lines. Expression of P85 activity was detected in the midrib of leaves, leaf trichomes, apical meristemic regions, throughout the root, lateral roots and flowers. The expression of P87 was observed in leaf-tip, hydathodes, apical meristem, root tips, emerging lateral root tips, root stele region and in floral tissues. The bidirectional promoter in both orientations shows differential up-regulation (2.5 to 3 fold) under salt stress. Use of such regulatory elements of bidirectional promoters showing spatial and stress inducible promoter-functions in heterologous system might be an important tool for plant biotechnology and gene stacking applications. PMID:24260266

An intergenic region shared by At4g35985 and At4g35987 in Arabidopsis thaliana is a tissue specific and stress inducible bidirectional promoter analyzed in transgenic arabidopsis and tobacco plants.

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Joydeep Banerjee

Full Text Available On chromosome 4 in the Arabidopsis genome, two neighboring genes (calmodulin methyl transferase At4g35987 and senescence associated gene At4g35985 are located in a head-to-head divergent orientation sharing a putative bidirectional promoter. This 1258 bp intergenic region contains a number of environmental stress responsive and tissue specific cis-regulatory elements. Transcript analysis of At4g35985 and At4g35987 genes by quantitative real time PCR showed tissue specific and stress inducible expression profiles. We tested the bidirectional promoter-function of the intergenic region shared by the divergent genes At4g35985 and At4g35987 using two reporter genes (GFP and GUS in both orientations in transient tobacco protoplast and Agro-infiltration assays, as well as in stably transformed transgenic Arabidopsis and tobacco plants. In transient assays with GFP and GUS reporter genes the At4g35985 promoter (P85 showed stronger expression (about 3.5 fold compared to the At4g35987 promoter (P87. The tissue specific as well as stress responsive functional nature of the bidirectional promoter was evaluated in independent transgenic Arabidopsis and tobacco lines. Expression of P85 activity was detected in the midrib of leaves, leaf trichomes, apical meristemic regions, throughout the root, lateral roots and flowers. The expression of P87 was observed in leaf-tip, hydathodes, apical meristem, root tips, emerging lateral root tips, root stele region and in floral tissues. The bidirectional promoter in both orientations shows differential up-regulation (2.5 to 3 fold under salt stress. Use of such regulatory elements of bidirectional promoters showing spatial and stress inducible promoter-functions in heterologous system might be an important tool for plant biotechnology and gene stacking applications.

Dichlorophen and Dichlorovos mediated genotoxic and cytotoxic assessment on root meristem cells of Allium cepa

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Sibhghatulla Shaikh

2012-06-01

Full Text Available Plants are direct recipients of agro – toxics and therefore important materials for assessing environmental chemicals for genotoxicity. The meristematic mitotic cell of Allium cepa is an efficient cytogenetic material for chromosome aberration assay on environmental pollutants. Onion root tips were grown on moistened filter paper in petri dish at room temperature. Germinated root tips were then exposed to three concentrations of each pesticide for 24 h. About 1 – 2 mm length of root tip was cut, fixed in cornoy’s fixative, hydrolyzed in warm 1 N HCL, stained with acetocarmine and squashed on glass slide. About 3000 cells were scored and classified into interphase and normal or aberrant division stage. Cytotoxicity was determined by comparing the mitotic index (MI of treated cells with that of the negative control. The MI of cells treated with Dichlorophen and Dichlorovos at one or more concentration was half or less than that of control are said to be cytotoxic. Genotoxicity was measured by comparing the number of cells/1000 in aberrant division stages at each dose with the negative control using Mann – Whitney U test. Both Dichlorophen and Dichlorovos are genotoxic at higher concentrations i.e. 0.001%, 0.002% and 0.028%, 0.056% inducing chromosome fragment, chromosome lagging and bridges, stick chromosome and multipolar anaphase.

Expression differences for genes involved in lignin, glutathione and sulphate metabolism in response to cadmium in Arabidopsis thaliana and the related Zn/Cd-hyperaccumulator Thlaspi caerulescens

NARCIS (Netherlands)

van de Mortel, Judith E.; Schat, Henk; Moerland, Perry D.; Ver Loren van Themaat, Emiel; van der Ent, Sjoerd; Blankestijn, Hetty; Ghandilyan, Artak; Tsiatsiani, Styliani; Aarts, Mark G. M.

2008-01-01

Cadmium (Cd) is a widespread, naturally occurring element present in soil, rock, water, plants and animals. Cd is a non-essential element for plants and is toxic at higher concentrations. Transcript profiles of roots of Arabidopsis thaliana (Arabidopsis) and Thlaspi caerulescens plants exposed to Cd

Exudation of fluorescent beta-carbolines from Oxalis tuberosa L roots.

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Bais, Harsh Pal; Park, Sang-Wook; Stermitz, Frank R; Halligan, Kathleen M; Vivanco, Jorge M

2002-11-01

Root fluorescence is a phenomenon in which roots of seedlings fluoresce when irradiated with ultraviolet (UV) light. Soybean (Glycine max) and rye grass (Elymus glaucus) are the only plant species that have been reported to exhibit this occurrence in germinating seedling roots. The trait has been useful as a marker in genetic, tissue culture and diversity studies, and has facilitated selection of plants for breeding purposes. However, the biological significance of this occurrence in plants and other organisms is unknown. Here we report that the Andean tuber crop species Oxalis tuberosa, known as oca in the highlands of South America, secretes a fluorescent compound as part of its root exudates. The main fluorescent compounds were characterized as harmine (7-methoxy-1-methyl-beta-carboline) and harmaline (3, 4-dihydroharmine). We also detected endogenous root fluorescence in other plant species, including Arabidopsis thaliana and Phytolacca americana, a possible indication that this phenomenon is widespread within the plant kingdom.

RIMA-dependent nuclear accumulation of IYO triggers auxin-irreversible cell differentiation in arabidopsis

NARCIS (Netherlands)

Muñoz, Alfonso; Mangano, Silvina; González-García, Mary Paz; Contreras, Ramón; Sauer, Michael; Rybel, De Bert; Weijers, Dolf; Sánchez-Serrano, José Juan; Sanmartín, Maite; Rojo, Enrique

2017-01-01

The transcriptional regulator MINIYO (IYO) is essential and rate-limiting for initiating cell differentiation in Arabidopsis thaliana. Moreover, IYO moves from the cytosol into the nucleus in cells at the meristem periphery, possibly triggering their differentiation. However, the genetic mechanisms

Cell walls as a stage for intercellular communication regulating shoot meristem development

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Toshiaki eTameshige

2015-05-01

Full Text Available Aboveground organs of plants are ultimately derived/generated from the shoot apical meristem (SAM, which is the proliferative tissue located at the apex of the stem. The SAM contains a population of stem cells that provide new cells for organ/tissue formation. The SAM is composed of distinct cell layers and zones with different properties. Primordia of lateral organs develop at the periphery of the SAM. The shoot apex is a dynamic and complex tissue, and as such intercellular communications among cells, layers and zones play significant roles in the coordination of cell proliferation, growth and differentiation to achieve elaborate morphogenesis. Recent findings have highlighted the importance of a number of singling molecules acting in the cell wall space for the intercellular communication, including classic phytohormones and secretory peptides. Moreover, accumulating evidences reveal that cell wall properties and their modifying enzymes modulate hormone actions. In this review, we overview how behaviors of singling molecules and changes of cell wall properties are integrated for the shoot meristem regulation.

UFO: an Arabidopsis gene involved in both floral meristem and floral organ development.

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Levin, J Z; Meyerowitz, E M

1995-05-01

We describe the role of the UNUSUAL FLORAL ORGANS (UFO) gene in Arabidopsis floral development based on a genetic and molecular characterization of the phenotypes of nine ufo alleles. UFO is required for the proper identity of the floral meristem and acts in three different aspects of the process that distinguishes flowers from shoots. UFO is involved in establishing the whorled pattern of floral organs, controlling the determinacy of the floral meristem, and activating the APETALA3 and PISTILLATA genes required for petal and stamen identity. In many respects, UFO acts in a manner similar to LEAFY, but the ufo mutant phenotype also suggests an additional role for UFO in defining boundaries within the floral primordia or controlling cell proliferation during floral organ growth. Finally, genetic interactions that prevent flower formation and lead to the generation of filamentous structures implicate UFO as a member of a new, large, and diverse class of genes in Arabidopsis necessary for flower formation.

Phytoremediation of arsenic from the contaminated soil using transgenic tobacco plants expressing ACR2 gene of Arabidopsis thaliana.

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Nahar, Noor; Rahman, Aminur; Nawani, Neelu N; Ghosh, Sibdas; Mandal, Abul

2017-11-01

We have cloned, characterized and transformed the AtACR2 gene (arsenic reductase 2) of Arabidopsis thaliana into the genome of tobacco (Nicotiana tabacum, var Sumsun). Our results revealed that the transgenic tobacco plants are more tolerant to arsenic than the wild type ones. These plants can grow on culture medium containing 200μM arsenate, whereas the wild type can barely survive under this condition. Furthermore, when exposed to 100μM arsenate for 35days the amount of arsenic accumulated in the shoots of transgenic plants was significantly lower (28μg/g d wt.) than that found in the shoots of non-transgenic controls (40μg/g d wt.). However, the arsenic content in the roots of transgenic plants was significantly higher (2400μg/g d. wt.) than that (2100μg/g d. wt.) observed in roots of wild type plants. We have demonstrated that Arabidopsis thaliana AtACR2 gene is a potential candidate for genetic engineering of plants to develop new crop cultivars that can be grown on arsenic contaminated fields to reduce arsenic content of the soil and can become a source of food containing no arsenic or exhibiting substantially reduced amount of this metalloid. Copyright © 2017 Elsevier GmbH. All rights reserved.

Adaptation response of Arabidopsis thaliana to random positioning

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Kittang, A.-I.; Winge, P.; van Loon, J. J. W. A.; Bones, A. M.; Iversen, T.-H.

2013-10-01

Arabidopsis thaliana seedlings were exposed on a Random Positioning Machine (RPM) under light conditions for 16 h and the samples were analysed using microarray techniques as part of a preparation for a space experiment on the International Space Station (ISS). The results demonstrated a moderate to low regulation of 55 genes (genes). Genes encoding proteins associated with the chaperone system (e.g. heat shock proteins, HSPs) and enzymes in the flavonoid biosynthesis were induced. Most of the repressed genes were associated with light and sugar responses. Significant up-regulation of selected HSP genes was found by quantitative Real-Time PCR in 1 week old plants after the RPM exposure both in light and darkness. Higher quantity of DPBA (diphenylboric acid 2-amino-ethyl ester) staining was observed in the whole root and in the root elongation zone of the seedlings exposed on the RPM by use of fluorescent microscopy, indicating higher flavonoid content. The regulated genes and an increase of flavonoids are related to several stresses, but increased occurrence of HSPs and flavonoids are also representative for normal growth (e.g. gravitropism). The response could be a direct stress response or an integrated response of the two signal pathways of light and gravity resulting in an overall light response.

Two alleles of the AtCesA3 gene in Arabidopsis thaliana display intragenic complementation.

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Pysh, Leonard D

2015-09-01

Cellulose is the most abundant biomolecule on the planet, yet the mechanism by which it is synthesized by higher plants remains largely unknown. In Arabidopsis thaliana (L.) Heynh, synthesis of cellulose in the primary cell wall requires three different cellulose synthase genes (AtCesA1, AtCesA3, and AtCesA6-related genes [AtCesA2, AtCesA5, and AtCesA6]). The multiple response expansion1 (mre1) mutant contains a hypomorphic AtCesA3 allele that results in significantly shorter, expanded roots. Crosses between mre1 and another allele of AtCesA3 (constitutive expression of VSP1, cev1) yielded an F1 with roots considerably longer and thinner than either parent, suggesting intragenic complementation. The F2 generation resulting from self-crossing these F1 showed three different root phenotypes: roots like mre1, roots like cev1, and roots like the F1. The segregation patterns of the three root phenotypes in multiple F2 and F3 generations were determined. Multiple characteristics of the roots and shoots were analyzed both qualitatively and quantitatively at different developmental stages, both on plates and on soil. The trans-heterozygous plants differed significantly from the parental mre1 and cev1 lines. The two alleles display intragenic complementation. A classic genetic interpretation of these results would suggest that cellulose synthesis requires homo-multimerization of cellulose synthase monomers. © 2015 Botanical Society of America.

The jasmonate receptor COI1 plays a role in jasmonate-induced lateral root formation and lateral root positioning in Arabidopsis thaliana.

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Raya-González, Javier; Pelagio-Flores, Ramón; López-Bucio, José

2012-09-15

Jasmonic acid (JA) regulates a broad range of plant defense and developmental responses. COI1 has been recently found to act as JA receptor. In this report, we show that low micromolar concentrations of JA inhibited primary root (PR) growth and promoted lateral root (LR) formation in Arabidopsis wild-type (WT) seedlings. It was observed that the coi1-1 mutant was less sensitive to JA on pericycle cell activation to induce lateral root primordia (LRP) formation and presented alterations in lateral root positioning and lateral root emergence on bends. To investigate JA-auxin interactions important for remodeling of root system (RS) architecture, we tested the expression of auxin-inducible markers DR5:uidA and BA3:uidA in WT and coi1-1 seedlings in response to indole-3-acetic acid (IAA) and JA and analyzed the RS architecture of a suite of auxin-related mutants under JA treatments. We found that JA did not affect DR5:uidA and BA3:uidA expression in WT and coi1-1 seedlings. Our data also showed that PR growth inhibition in response to JA was likely independent of auxin signaling and that the induction of LRP required ARF7, ARF19, SLR, TIR1, AFB2, AFB3 and AXR1 loci. We conclude that JA regulation of postembryonic root development involves both auxin-dependent and independent mechanisms. Copyright © 2012 Elsevier GmbH. All rights reserved.

Carbon source-sink relationship in Arabidopsis thaliana: the role of sucrose transporters.

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Durand, Mickaël; Mainson, Dany; Porcheron, Benoît; Maurousset, Laurence; Lemoine, Rémi; Pourtau, Nathalie

2018-03-01

The regulation of source-to-sink sucrose transport is associated with AtSUC and AtSWEET sucrose transporters' gene expression changes in plants grown hydroponically under different physiological conditions. Source-to-sink transport of sucrose is one of the major determinants of plant growth. Whole-plant carbohydrates' partitioning requires the specific activity of membrane sugar transporters. In Arabidopsis thaliana plants, two families of transporters are involved in sucrose transport: AtSUCs and AtSWEETs. This study is focused on the comparison of sucrose transporter gene expression, soluble sugar and starch levels and long distance sucrose transport, in leaves and sink organs (mainly roots) in different physiological conditions (along the plant life cycle, during a diel cycle, and during an osmotic stress) in plants grown hydroponically. In leaves, the AtSUC2, AtSWEET11, and 12 genes known to be involved in phloem loading were highly expressed when sucrose export was high and reduced during osmotic stress. In roots, AtSUC1 was highly expressed and its expression profile in the different conditions tested suggests that it may play a role in sucrose unloading in roots and in root growth. The SWEET transporter genes AtSWEET12, 13, and 15 were found expressed in all organs at all stages studied, while differential expression was noticed for AtSWEET14 in roots, stems, and siliques and AtSWEET9, 10 expressions were only detected in stems and siliques. A role for these transporters in carbohydrate partitioning in different source-sink status is proposed, with a specific attention on carbon demand in roots. During development, despite trophic competition with others sinks, roots remained a significant sink, but during osmotic stress, the amount of translocated [U- 14 C]-sucrose decreased for rosettes and roots. Altogether, these results suggest that source-sink relationship may be linked with the regulation of sucrose transporter gene expression.

Root developmental adaptation to phosphate starvation: better safe than sorry.

Science.gov (United States)

Péret, Benjamin; Clément, Mathilde; Nussaume, Laurent; Desnos, Thierry

2011-08-01

Phosphorus is a crucial component of major organic molecules such as nucleic acids, ATP and membrane phospholipids. It is present in soils in the form of inorganic phosphate (Pi), which has low availability and poor mobility. To cope with Pi limitations, plants have evolved complex adaptive responses that include morphological and physiological modifications. This review describes how the model plant Arabidopsis thaliana adapts its root system architecture to phosphate deficiency through inhibition of primary root growth, increase in lateral root formation and growth and production of root hairs, which all promote topsoil foraging. A better understanding of plant adaptation to low phosphate will open the way to increased phosphorus use efficiency by crops. Such an improvement is needed in order to adjust how we manage limited phosphorus stocks and to reduce the disastrous environmental effects of phosphate fertilizers overuse. Copyright © 2011 Elsevier Ltd. All rights reserved.

Patterning of Inflorescences and Flowers by the F-Box Protein DOUBLE TOP and the LEAFY Homolog ABERRANT LEAF AND FLOWER of Petunia.

NARCIS (Netherlands)

Souer, E.J.; Bliek, M.; Koes, R.E.; Kusters, E.; Bruin de, R.A.

2008-01-01

Angiosperms display a wide variety of inflorescence architectures differing in the positions where flowers or branches arise. The expression of floral meristem identity (FMI) genes determines when and where flowers are formed. In Arabidopsis thaliana, this is regulated via transcription of LEAFY

Protists are an integral part of the Arabidopsis thaliana microbiome.

Science.gov (United States)

Sapp, Melanie; Ploch, Sebastian; Fiore-Donno, Anna M; Bonkowski, Michael; Rose, Laura E

2018-01-01

Although protists occupy a vast range of habitats and are known to interact with plants among other things via disease suppression, competition or growth stimulation, their contributions to the 'phytobiome' are not well described. To contribute to a more comprehensive picture of the plant holobiont, we examined cercozoan and oomycete taxa living in association with the model plant Arabidopsis thaliana grown in two different soils. Soil, roots, leaves and wooden toothpicks were analysed before and after surface sterilization. Cercozoa were identified using 18S rRNA gene metabarcoding, whereas the Internal Transcribed Spacer 1 was used to determine oomycetes. Subsequent analyses revealed strong spatial structuring of protist communities between compartments, although oomycetes appeared more specialized than Cercozoa. With regards to oomycetes, only members of the Peronosporales and taxa belonging to the genus Globisporangium were identified as shared members of the A. thaliana microbiome. This also applied to cercozoan taxa belonging to the Glissomonadida and Cercomonadida. We identified a strong influence by edaphic factors on the rhizosphere, but not for the phyllosphere. Distinct differences of Cercozoa found preferably in wood or fresh plant material imply specific niche adaptations. Our results highlight the importance of micro-eukaryotes for the plant holobiont. © 2017 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Diversification of Root Hair Development Genes in Vascular Plants.

Science.gov (United States)

Huang, Ling; Shi, Xinhui; Wang, Wenjia; Ryu, Kook Hui; Schiefelbein, John

2017-07-01

The molecular genetic program for root hair development has been studied intensively in Arabidopsis ( Arabidopsis thaliana ). To understand the extent to which this program might operate in other plants, we conducted a large-scale comparative analysis of root hair development genes from diverse vascular plants, including eudicots, monocots, and a lycophyte. Combining phylogenetics and transcriptomics, we discovered conservation of a core set of root hair genes across all vascular plants, which may derive from an ancient program for unidirectional cell growth coopted for root hair development during vascular plant evolution. Interestingly, we also discovered preferential diversification in the structure and expression of root hair development genes, relative to other root hair- and root-expressed genes, among these species. These differences enabled the definition of sets of genes and gene functions that were acquired or lost in specific lineages during vascular plant evolution. In particular, we found substantial divergence in the structure and expression of genes used for root hair patterning, suggesting that the Arabidopsis transcriptional regulatory mechanism is not shared by other species. To our knowledge, this study provides the first comprehensive view of gene expression in a single plant cell type across multiple species. © 2017 American Society of Plant Biologists. All Rights Reserved.

Strigolactones Suppress Adventitious Rooting in Arabidopsis and Pea1[C][W][OA

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

2012-01-01

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

Heterologous expression of the wheat aquaporin gene TaTIP2;2 compromises the abiotic stress tolerance of Arabidopsis thaliana.

Directory of Open Access Journals (Sweden)

Chunhui Xu

Full Text Available Aquaporins are channel proteins which transport water across cell membranes. We show that the bread wheat aquaporin gene TaTIP2;2 maps to the long arm of chromosome 7b and that its product localizes to the endomembrane system. The gene is expressed constitutively in both the root and the leaf, and is down-regulated by salinity and drought stress. Salinity stress induced an increased level of C-methylation within the CNG trinucleotides in the TaTIP2;2 promoter region. The heterologous expression of TaTIP2;2 in Arabidopsis thaliana compromised its drought and salinity tolerance, suggesting that TaTIP2;2 may be a negative regulator of abiotic stress. The proline content of transgenic A. thaliana plants fell, consistent with the down-regulation of P5CS1, while the expression of SOS1, SOS2, SOS3, CBF3 and DREB2A, which are all stress tolerance-related genes acting in an ABA-independent fashion, was also down-regulated. The supply of exogenous ABA had little effect either on TaTIP2;2 expression in wheat or on the phenotype of transgenic A. thaliana. The expression level of the ABA signalling genes ABI1, ABI2 and ABF3 remained unaltered in the transgenic A. thaliana plants. Thus TaTIP2;2 probably regulates the response to stress via an ABA-independent pathway(s.

A role for IAA in the infection of Arabidopsis thaliana by Orobanche aegyptiaca.

Science.gov (United States)

Bar-Nun, Nurit; Sachs, Tsvi; Mayer, Alfred M

2008-01-01

Vascular continuity is established between a host plant and the root parasite broomrape. It is generally accepted that the direction of vascular continuity results from polar flow of auxin. Our hypothesis was that chemical disruptions of auxin transport and activity could influence the infection of the host by the parasite. A sterile system for the routine infection of Arabidopsis thaliana seedlings in Nunc cell culture plates by germinated seeds of Orobanche aegyptiaca was developed. This method permitted a quantitative assay of the rate of host infection. The three-dimensional structure of the vascular contacts was followed in cleared tissue. IAA (indole acetic acid) or substances that influence its activity and transport were applied locally to the host root. The orientation of the xylem contacts showed that broomrape grafts itself upon the host by acting hormonally as a root rather than a shoot. Local applications of IAA, PCIB (p-chlorophenoxyisobutyric acid) or NPA (naphthylphthalamic acid) all resulted in drastic reductions of Orobanche infection Broomrape manipulates the host by acting as a sink for auxin. Disruption of auxin action or auxin flow at the contact site could be a novel basis for controlling infection by Orobanche.

Epigenetic control of root and nodule development : the role of plant-specific histone deacetylases and LHP1 in root cell reprogramming

NARCIS (Netherlands)

Schilderink, S.

2012-01-01

In plants, unlike in animals, most organs develop post embryonically. These organs originate from clusters of undifferentiated dividing cells that form so-called meristems. Differentiated cells can be re-activated to enter the cell cycle and to ultimately give rise to new meristems. These

The Emerging Role of Reactive Oxygen Species Signaling during Lateral Root Development.

Science.gov (United States)

Manzano, Concepción; Pallero-Baena, Mercedes; Casimiro, Ilda; De Rybel, Bert; Orman-Ligeza, Beata; Van Isterdael, Gert; Beeckman, Tom; Draye, Xavier; Casero, Pedro; Del Pozo, Juan C

2014-07-01

Overall root architecture is the combined result of primary and lateral root growth and is influenced by both intrinsic genetic programs and external signals. One of the main questions for root biologists is how plants control the number of lateral root primordia and their emergence through the main root. We recently identified S-phase kinase-associated protein2 (SKP2B) as a new early marker for lateral root development. Here, we took advantage of its specific expression pattern in Arabidopsis (Arabidopsis thaliana) in a cell-sorting and transcriptomic approach to generate a lateral root-specific cell sorting SKP2B data set that represents the endogenous genetic developmental program. We first validated this data set by showing that many of the identified genes have a function during root growth or lateral root development. Importantly, genes encoding peroxidases were highly represented in our data set. Thus, we next focused on this class of enzymes and showed, using genetic and chemical inhibitor studies, that peroxidase activity and reactive oxygen species signaling are specifically required during lateral root emergence but, intriguingly, not for primordium specification itself. © 2014 American Society of Plant Biologists. All Rights Reserved.

Haemoglobin modulates NO emission and hyponasty under hypoxia-related stress in Arabidopsis thaliana

DEFF Research Database (Denmark)

Hebelstrup, Kim; van Zanten, Martijn; Mandon, Julien

2012-01-01

Nitric oxide (NO) and ethylene are signalling molecules that are synthesized in response to oxygen depletion. Non-symbiotic plant haemoglobins (Hbs) have been demonstrated to act in roots under oxygen depletion to scavenge NO. Using Arabidopsis thaliana plants, the online emission of NO or ethylene...... was directly quantified under normoxia, hypoxia (0.1–1.0% O2), or full anoxia. The production of both gases was increased with reduced expression of either of the Hb genes GLB1 or GLB2, whereas NO emission decreased in plants overexpressing these genes. NO emission in plants with reduced Hb gene expression......-nitrosylated compounds, and it is demonstrated that hypoxia substantially increased the content of S-nitrosylated compounds. A parallel up-regulation of Hb gene expression in the normoxic shoots of the flooded plants may reflect signal transmission from root to shoot via ethylene and a role for Hb in the shoots. Hb gene...

The interaction between glucose and cytokinin signaling in controlling Arabidopsis thaliana seedling root growth and development.

Science.gov (United States)

Kushwah, Sunita; Laxmi, Ashverya

2017-05-04

Cytokinin (CK) and glucose (GLC) control several common responses in plants. There is an extensive overlap between CK and GLC signal transduction pathways in Arabidopsis. Physiologically, both GLC and CK could regulate root length in light. CK interacts with GLC via HXK1 dependent pathway for root length control. Wild-type (WT) roots cannot elongate in the GLC free medium while CK-receptor mutant ARABIDOPSIS HISTIDINE KINASE4 (ahk4) and type B ARR triple mutant ARABIDOPSIS RESPONSE REGULATOR1, 10,11 (arr1, 10,11) roots could elongate even in the absence of GLC as compared with the WT. The root hair initiation was also found defective in CK signaling mutants ahk4, arr1,10,11 and arr3,4,5,6,8,9 on increasing GLC concentration (up to 3%); and lesser number of root hairs were visible even at 5% GLC as compared with the WT. Out of 941 BAP regulated genes, 103 (11%) genes were involved in root growth and development. Out of these 103 genes, 60 (58%) genes were also regulated by GLC. GLC could regulate 5736 genes, which include 327 (6%) genes involved in root growth and development. Out of these 327 genes, 60 (18%) genes were also regulated by BAP. Both GLC and CK signaling cannot alter root length in light in auxin signaling mutant AUXIN RESPONSE3/INDOLE-3-ACETIC ACID17 (axr3/iaa17) suggesting that they may involve auxin signaling component as a nodal point. Therefore CK- and GLC- signaling are involved in controlling different aspects of root growth and development such as root length, with auxin signaling components working as downstream target.

Modulation of modeled microgravity on radiation-induced bystander effects in Arabidopsis thaliana

Energy Technology Data Exchange (ETDEWEB)

Wang, Ting [Key Laboratory of Ion Beam Bio-engineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Sun, Qiao [Space Molecular Biological Lab, China Academy of Space Technology, Beijing 100086 (China); Xu, Wei; Li, Fanghua [Key Laboratory of Ion Beam Bio-engineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Li, Huasheng; Lu, Jinying [Space Molecular Biological Lab, China Academy of Space Technology, Beijing 100086 (China); Wu, Lijun; Wu, Yuejin [Key Laboratory of Ion Beam Bio-engineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Liu, Min [Space Molecular Biological Lab, China Academy of Space Technology, Beijing 100086 (China); Bian, Po [Key Laboratory of Ion Beam Bio-engineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China)

2015-03-15

Highlights: • The effects of microgravity on the radiation-induced bystander effects (RIBE) were definitely demonstrated. • The effects of microgravity on RIBE might be divergent for different biological events. • The microgravity mainly modified the generation or transport of bystander signals at early stage. - Abstract: Both space radiation and microgravity have been demonstrated to have inevitable impact on living organisms during space flights and should be considered as important factors for estimating the potential health risk for astronauts. Therefore, the question whether radiation effects could be modulated by microgravity is an important aspect in such risk evaluation. Space particles at low dose and fluence rate, directly affect only a fraction of cells in the whole organism, which implement radiation-induced bystander effects (RIBE) in cellular response to space radiation exposure. The fact that all of the RIBE experiments are carried out in a normal gravity condition bring forward the need for evidence regarding the effect of microgravity on RIBE. In the present study, a two-dimensional rotation clinostat was adopted to demonstrate RIBE in microgravity conditions, in which the RIBE was assayed using an experimental system of root-localized irradiation of Arabidopsis thaliana (A. thaliana) plants. The results showed that the modeled microgravity inhibited significantly the RIBE-mediated up-regulation of expression of the AtRAD54 and AtRAD51 genes, generation of reactive oxygen species (ROS) and transcriptional activation of multicopy P35S:GUS, but made no difference to the induction of homologous recombination by RIBE, showing divergent responses of RIBE to the microgravity conditions. The time course of interaction between the modeled microgravity and RIBE was further investigated, and the results showed that the microgravity mainly modulated the processes of the generation or translocation of the bystander signal(s) in roots.

Main: 1UT7 [RPSD[Archive

Lifescience Database Archive (English)

Full Text Available 1UT7 シロイヌナズナ Arabidopsis Arabidopsis thaliana (L.) Heynh. Nac-Domain Containing Pro... Meristem Protein; Synonym: Nam, Anac, Abscisic Acid Responsive Nac, Dicyanoaurate Derivative; Chain: A, B; ...Fragment: Dna-Binding Nac Domain, Residues 1-168; Engineered: Yes; Other_details:...A.Ernst, A.N.Olsen, K.Skriver, S.Larsen, L.Lo Leggio Structure Of The Conserved Domain Of Anac, A Member Of ... Transcription Factor, Dna Binding, Abscisic Acid Response, Arabidopsis Thaliana, Crystal Structure, Nac Domai

AtNPF2.5 Modulates Chloride (Cl−) Efflux from Roots of Arabidopsis thaliana

KAUST Repository

Li, Bo

2017-01-05

The accumulation of high concentrations of chloride (Cl) in leaves can adversely affect plant growth. When comparing different varieties of the same Cl sensitive plant species those that exclude relatively more Cl from their shoots tend to perform better under saline conditions; however, the molecular mechanisms involved in maintaining low shoot Cl remain largely undefined. Recently, it was shown that the NRT1/PTR Family 2.4 protein (NPF2.4) loads Cl into the root xylem, which affects the accumulation of Cl in Arabidopsis shoots. Here we characterize NPF2.5, which is the closest homolog to NPF2.4 sharing 83.2% identity at the amino acid level. NPF2.5 is predominantly expressed in root cortical cells and its transcription is induced by salt. Functional characterisation of NPF2.5 via its heterologous expression in yeast (Saccharomyces cerevisiae) and Xenopus laevis oocytes indicated that NPF2.5 is likely to encode a Cl permeable transporter. Arabidopsis npf2.5 T-DNA knockout mutant plants exhibited a significantly lower Cl efflux from roots, and a greater Cl accumulation in shoots compared to salt-treated Col-0 wild-type plants. At the same time, NO- content in 3 the shoot remained unaffected. Accumulation of Cl in the shoot increased following (1) amiRNA-induced knockdown of NPF2.5 transcript abundance in the root, and (2) constitutive over-expression of NPF2.5. We suggest that both these findings are consistent with a role for NPF2.5 in modulating Cl transport. Based on these results, we propose that NPF2.5 functions as a pathway for Cl efflux from the root, contributing to exclusion of Cl from the shoot of Arabidopsis.

Effects of GhWUS from upland cotton (Gossypium hirsutum L.) on somatic embryogenesis and shoot regeneration.

Science.gov (United States)

Xiao, Yanqing; Chen, Yanli; Ding, Yanpeng; Wu, Jie; Wang, Peng; Yu, Ya; Wei, Xi; Wang, Ye; Zhang, Chaojun; Li, Fuguang; Ge, Xiaoyang

2018-05-01

The WUSCHEL (WUS) gene encodes a plant-specific homeodomain-containing transcriptional regulator, which plays important roles during embryogenesis, as well as in the formation of shoot and flower meristems. Here, we isolated two homologues of Arabidopsis thaliana WUS (AtWUS), GhWUS1a_At and GhWUS1b_At, from upland cotton (Gossypium hirsutum). Domain analysis suggested that the two putative GhWUS proteins contained a highly conserved DNA-binding HOX domain and a WUS-box. Expression profile analysis showed that GhWUSs were predominantly expressed during the embryoid stage. Ectopic expression of GhWUSs in Arabidopsis could induce somatic embryo and shoot formation from seedling root tips. Furthermore, in the absence of exogenous hormone, overexpression of GhWUSs in Arabidopsis could promote shoot regeneration from excised roots, and in the presence of exogenous auxin, excised roots expressing GhWUS could be induced to produce somatic embryo. In addition, expression of the chimeric GhWUS repressor in cotton callus inhibited embryogenic callus formation. Our results show that GhWUS is an important regulator of somatic embryogenesis and shoot regeneration. Copyright © 2018 Elsevier B.V. All rights reserved.

Alteration of plant meristem function by manipulation of the Retinoblastoma-like plant RRB gene

Science.gov (United States)

Durfee, Tim [Madison, WI; Feiler, Heidi [Albany, CA; Gruissem, Wilhelm [Forch, CH; Jenkins, Susan [Martinez, CA; Roe, Judith [Manhattan, KS; Zambryski, Patricia [Berkeley, CA

2007-01-16

This invention provides methods and compositions for altering the growth, organization, and differentiation of plant tissues. The invention is based on the discovery that, in plants, genetically altering the levels of Retinoblastoma-related gene (RRB) activity produces dramatic effects on the growth, proliferation, organization, and differentiation of plant meristem.

Effects of long-term pruning, meristem origin, and branch order on the rooting of Douglas-fir stem cuttings.

Science.gov (United States)

D.L. Copes

1992-01-01

The rooting percentages of 14 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) clones were examined annually from 1974 to 1988. The trees were 10 and 13 years old in 1974 and were pruned to 2.0 m in 1978 and 1979 and then recut annually to 0.5, 1.0, or 1.5 m, starting in 1983. The pruned trees showed no evidence of decreased rooting percentage...

Genetic Components of Root Architecture Remodeling in Response to Salt Stress

KAUST Repository

Julkowska, Magdalena; Koevoets, Iko Tamar; Mol, Selena; Hoefsloot, Huub CJ; Feron, Richard; Tester, Mark A.; Keurentjes, Joost J.B.; Korte, Arthur; Haring, Michel A; de Boer, Gert-Jan; Testerink, Christa

2017-01-01

Salinity of the soil is highly detrimental to plant growth. Plants respond by a redistribution of root mass between main and lateral roots, yet the genetic machinery underlying this process is still largely unknown. Here, we describe the natural variation among 347 Arabidopsis thaliana accessions in root system architecture (RSA) and identify the traits with highest natural variation in their response to salt. Salt-induced changes in RSA were associated with 100 genetic loci using genome-wide association studies (GWAS). Two candidate loci associated with lateral root development were validated and further investigated. Changes in CYP79B2 expression in salt stress positively correlated with lateral root development in accessions, and cyp79b2 cyp79b3 double mutants developed fewer and shorter lateral roots under salt stress, but not in control conditions. By contrast, high HKT1 expression in the root repressed lateral root development, which could be partially rescued by addition of potassium. The collected data and Multi-Variate analysis of multiple RSA traits, available through the Salt_NV_Root App, capture root responses to salinity. Together, our results provide a better understanding of effective RSA remodeling responses, and the genetic components involved, for plant performance in stress conditions.

Genetic Components of Root Architecture Remodeling in Response to Salt Stress

KAUST Repository

Julkowska, Magdalena

2017-11-07

Salinity of the soil is highly detrimental to plant growth. Plants respond by a redistribution of root mass between main and lateral roots, yet the genetic machinery underlying this process is still largely unknown. Here, we describe the natural variation among 347 Arabidopsis thaliana accessions in root system architecture (RSA) and identify the traits with highest natural variation in their response to salt. Salt-induced changes in RSA were associated with 100 genetic loci using genome-wide association studies (GWAS). Two candidate loci associated with lateral root development were validated and further investigated. Changes in CYP79B2 expression in salt stress positively correlated with lateral root development in accessions, and cyp79b2 cyp79b3 double mutants developed fewer and shorter lateral roots under salt stress, but not in control conditions. By contrast, high HKT1 expression in the root repressed lateral root development, which could be partially rescued by addition of potassium. The collected data and Multi-Variate analysis of multiple RSA traits, available through the Salt_NV_Root App, capture root responses to salinity. Together, our results provide a better understanding of effective RSA remodeling responses, and the genetic components involved, for plant performance in stress conditions.

Complex Regulation of Prolyl-4-Hydroxylases Impacts Root Hair Expansion

DEFF Research Database (Denmark)

Velasquez, Silvia M; Ricardi, Martiniano M; Poulsen, Christian Peter

2015-01-01

Root hairs are single cells that develop by tip growth, a process shared with pollen tubes, axons, and fungal hyphae. However, structural plant cell walls impose constraints to accomplish tip growth. In addition to polysaccharides, plant cell walls are composed of hydroxyproline-rich glycoproteins......5, and to a lesser extent P4H2 and P4H13, are pivotal for root hair tip growth. Second, we demonstrate that P4H5 has in vitro preferred specificity for EXT substrates rather than for other HRGPs. Third, by P4H promoter and protein swapping approaches, we show that P4H2 and P4H13 have interchangeable...... peptidyl-proline hydroxylation on EXTs, and possibly in other HRGPs, is required for proper cell wall self-assembly and hence root hair elongation in Arabidopsis thaliana....

Arabidopsis Root-Type Ferredoxin:NADP(H) Oxidoreductase 2 is Involved in Detoxification of Nitrite in Roots.

Science.gov (United States)

Hachiya, Takushi; Ueda, Nanae; Kitagawa, Munenori; Hanke, Guy; Suzuki, Akira; Hase, Toshiharu; Sakakibara, Hitoshi

2016-11-01

Ferredoxin:NADP(H) oxidoreductase (FNR) plays a key role in redox metabolism in plastids. Whereas leaf FNR (LFNR) is required for photosynthesis, root FNR (RFNR) is believed to provide electrons to ferredoxin (Fd)-dependent enzymes, including nitrite reductase (NiR) and Fd-glutamine-oxoglutarate aminotransferase (Fd-GOGAT) in non-photosynthetic conditions. In some herbal species, however, most nitrate reductase activity is located in photosynthetic organs, and ammonium in roots is assimilated mainly by Fd-independent NADH-GOGAT. Therefore, RFNR might have a limited impact on N assimilation in roots grown with nitrate or ammonium nitrogen sources. AtRFNR genes are rapidly induced by application of toxic nitrite. Thus, we tested the hypothesis that RFNR could contribute to nitrite reduction in roots by comparing Arabidopsis thaliana seedlings of the wild type with loss-of-function mutants of RFNR2 When these seedlings were grown under nitrate, nitrite or ammonium, only nitrite nutrition caused impaired growth and nitrite accumulation in roots of rfnr2 Supplementation of nitrite with nitrate or ammonium as N sources did not restore the root growth in rfnr2 Also, a scavenger for nitric oxide (NO) could not effectively rescue the growth impairment. Thus, nitrite toxicity, rather than N depletion or nitrite-dependent NO production, probably causes the rfnr2 root growth defect. Our results strongly suggest that RFNR2 has a major role in reduction of toxic nitrite in roots. A specific set of genes related to nitrite reduction and the supply of reducing power responded to nitrite concomitantly, suggesting that the products of these genes act co-operatively with RFNR2 to reduce nitrite in roots. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Nitrate modulates stem cell dynamics in Arabidopsis shoot meristems through cytokinins

OpenAIRE

Jonsson, Sten Henrik; Meyerowitz,; Landrein, Benoit Pierre; Formosa-Jordan,; Malivert,; Schuster, C; Melnyk, CW; Yang, W; Turnbull,; Locke, James Charles

2018-01-01

The shoot apical meristem (SAM) is responsible for the generation of all of the aerial parts of plants. Given its critical role, dynamical changes in SAM activity should play a central role in the adaptation of plant architecture to the environment. Using quantitative microscopy, grafting experiments and genetic perturbations, we connect the plant environment to the SAM, by describing the molecular mechanism by which cytokinins signal the level of nutrient availability to the SAM. We show tha...

Sincronização do ciclo celular em meristema radicular de baru (Dipteryx alata Vog. Sinchronization of cell cycle in root meristem of baru (Dipteryx alata Vog.

Directory of Open Access Journals (Sweden)

Giovana Augusta Torres

2003-04-01

Full Text Available Uma das dificuldades de se conduzir estudos citogenéticos em espécies vegetais nativas do cerrado é a ocorrência de baixos índices metafásicos no meristema radicular. O incremento dos índices mitótico e metafásico em células de pontas de raiz tem sido obtido em várias espécies com a sincronização do ciclo celular por meio de hidroxiuréia (HU. Neste trabalho foram determinadas as condições ótimas para a sincronização eficiente do ciclo em células meristemáticas de raízes de baru (Dipteryx alata Vog.. Foram testadas quatro concentrações de HU (0,00; 1,25; 2,50; 5,00 e 10,00 mM, três tempos de exposição das raízes (10, 15 e 20 h e dois tempos de recuperação do ciclo (5 e 10 h. As melhores respostas foram obtidas com exposição das raízes, de cerca de 1 cm, à solução de HU 3,5 mM, por 20 horas, com posterior recuperação do ciclo em água destilada por 5 horas. O índice de 45% de células em divisão representou um incremento de cerca de 5 vezes em relação à testemunha, ao passo que para células em metáfases, o índice de 22,6% foi cerca de 10 vezes superior. Portanto, o uso dessa estratégia mostrou-se bastante eficiente para a obtenção de grande quantidade de cromossomos para análise citogenética do baru.A major difficulty in cytogenetic studies of plant species from "cerrado" is the low metaphasic index in root tip cells. Cell cycle synchronization, by using hydroxyurea (HU, has been successfully used in order to obtain high mitotic and metaphasic index in several species. The goal of this work was to optimize conditions for efficient synchronization of Dipteryx alata root tip meristematic cells. Different levels of hydroxyurea (0, 1.25, 2.50, 5.00, and 10.00 mM, periods of treatment (10, 15, and 20 h and periods of cell cycle recovery (5 and 10 h were tested. Best results were achieved by treating 10-mm long roots with 3.5 mM hydroxyurea, for 20 h and incubating for 5 h in distilled water. The

Heuristic Aspect of the Lateral Root Initiation Index: A Case Study of the Role of Nitric Oxide in Root Branching

Directory of Open Access Journals (Sweden)

Veronica Lira-Ruan

2013-10-01

Full Text Available Premise of the study: Lateral root (LR initiation (LRI is a central process in root branching. Based on LR and/or LR primordium densities, it has been shown that nitric oxide (NO promotes LRI. However, because NO inhibits primary root growth, we hypothesized that NO may have an opposite effect if the analysis is performed on a cellular basis. Using a previously proposed parameter, the LRI index (which measures how many LRI events take place along a root portion equivalent to the length of a single file of 100 cortical cells of average length, we addressed this hypothesis and illustrate here that the LRI index provides a researcher with a tool to uncover hidden but important information about root initiation. Methods and Results: Arabidopsis thaliana roots were treated with an NO donor (sodium nitroprusside [SNP] and/or an NO scavenger (2-(4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide [cPTIO]. LRI was analyzed separately in the root portions formed before and during the treatment. In the latter, SNP caused root growth inhibition and an increase in the LR density accompanied by a decrease in LRI index, indicating overall inhibitory outcome of the NO donor on branching. The inhibitory effect of SNP was reversed by cPTIO, showing the NO-specific action of SNP on LRI. Conclusions: Analysis of the LRI index permits the discovery of otherwise unknown modes of action of a substance on the root system formation. NO has a dual action on root branching, slightly promoting it in the root portion formed before the treatment and strongly inhibiting it in the root portion formed during the treatment.

Spatial Regulation of Root Growth: Placing the Plant TOR Pathway in a Developmental Perspective

Science.gov (United States)

Barrada, Adam; Montané, Marie-Hélène; Robaglia, Christophe; Menand, Benoît

2015-01-01

Plant cells contain specialized structures, such as a cell wall and a large vacuole, which play a major role in cell growth. Roots follow an organized pattern of development, making them the organs of choice for studying the spatio-temporal regulation of cell proliferation and growth in plants. During root growth, cells originate from the initials surrounding the quiescent center, proliferate in the division zone of the meristem, and then increase in length in the elongation zone, reaching their final size and differentiation stage in the mature zone. Phytohormones, especially auxins and cytokinins, control the dynamic balance between cell division and differentiation and therefore organ size. Plant growth is also regulated by metabolites and nutrients, such as the sugars produced by photosynthesis or nitrate assimilated from the soil. Recent literature has shown that the conserved eukaryotic TOR (target of rapamycin) kinase pathway plays an important role in orchestrating plant growth. We will summarize how the regulation of cell proliferation and cell expansion by phytohormones are at the heart of root growth and then discuss recent data indicating that the TOR pathway integrates hormonal and nutritive signals to orchestrate root growth. PMID:26295391

Accumulation of the coumarin scopolin under abiotic stress conditions is mediated by the Arabidopsis thaliana THO/TREX complex

KAUST Repository

Döll, Stefanie

2017-12-09

Secondary metabolites are involved in the plant stress response. Among these are scopolin and its active form scopoletin, which are coumarin derivatives associated with reactive oxygen species scavenging and pathogen defence. Here we show that scopolin accumulation can be induced in the root by osmotic stress and in the leaf by low-temperature stress in Arabidopsis thaliana. A genetic screen for altered scopolin levels in A. thaliana revealed a mutant compromised in scopolin accumulation in response to stress; the lesion was present in a homologue of THO1 coding for a subunit of the THO/TREX complex. The THO/TREX complex contributes to RNA silencing, supposedly by trafficking precursors of small RNAs. Mutants defective in THO, AGO1, SDS3 and RDR6 were impaired with respect to scopolin accumulation in response to stress, suggesting a mechanism based on RNA silencing such as the trans-acting small interfering RNA pathway, which requires THO/TREX function.

Effects of locally targeted heavy-ion and laser microbeam on root hydrotropism in Arabidopsis thaliana

International Nuclear Information System (INIS)

Miyazawa, Yutaka; Sakashita, Tetsuya; Funayama, Tomoo

2008-01-01

Classical studies on root hydrotropism have hypothesized the importance of columella cells as well as the de novo gene expression, such as auxin-inducible gene, at the elongation zone in hydrotropism; however, there has been no confirmation that columella cells or auxin-mediated signaling in the elongation zone are necessary for hydrotropism. We examined the role of root cap and elongation zone cells in root hydrotropism using heavy-ion and laser microbeam. Heavy-ion microbeam irradiation of the elongation zone, but not that of the columella cells, significantly and temporarily suppressed the development of hydrotropic curvature. However, laser ablation confirmed that columella cells are indispensable for hydrotropism. Systemic heavy-ion broad-beam irradiation suppressed de novo expression of INDOLE ACETIC ACID 5 gene, but not MIZU-KUSSEI1 gene. Our results indicate that both the root cap and elongation zone have indispensable and functionally distinct roles in root hydrotropism, and that de novo gene expression might be required for hydrotropism in the elongation zone, but not in columella cells. (author)

Identification of new adventitious rooting mutants amongst suppressors of the Arabidopsis thaliana superroot2 mutation.

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Pacurar, Daniel Ioan; Pacurar, Monica Lacramioara; Bussell, John Desmond; Schwambach, Joseli; Pop, Tiberia Ioana; Kowalczyk, Mariusz; Gutierrez, Laurent; Cavel, Emilie; Chaabouni, Salma; Ljung, Karin; Fett-Neto, Arthur Germano; Pamfil, Doru; Bellini, Catherine

2014-04-01

The plant hormone auxin plays a central role in adventitious rooting and is routinely used with many economically important, vegetatively propagated plant species to promote adventitious root initiation and development on cuttings. Nevertheless the molecular mechanisms through which it acts are only starting to emerge. The Arabidopsis superroot2-1 (sur2-1) mutant overproduces auxin and, as a consequence, develops excessive adventitious roots in the hypocotyl. In order to increase the knowledge of adventitious rooting and of auxin signalling pathways and crosstalk, this study performed a screen for suppressors of superroot2-1 phenotype. These suppressors provide a new resource for discovery of genetic players involved in auxin signalling pathways or at the crosstalk of auxin and other hormones or environmental signals. This study reports the identification and characterization of 26 sur2-1 suppressor mutants, several of which were identified as mutations in candidate genes involved in either auxin biosynthesis or signalling. In addition to confirming the role of auxin as a central regulator of adventitious rooting, superroot2 suppressors indicated possible crosstalk with ethylene signalling in this process.

Analysis of the Arabidopsis superman allelic series and the interactions with other genes demonstrate developmental robustness and joint specification of male-female boundary, flower meristem termination and carpel compartmentalization.

Science.gov (United States)

Breuil-Broyer, Stéphanie; Trehin, Christophe; Morel, Patrice; Boltz, Véronique; Sun, Bo; Chambrier, Pierre; Ito, Toshiro; Negrutiu, Ioan

2016-04-01

SUPERMAN is a cadastral gene controlling the sexual boundary in the flower. The gene's functions and role in flower development and evolution have remained elusive. The analysis of a contrasting SUP allelic series (for which the names superman, superwoman and supersex have been coined) makes it possible to distinguish early vs. late regulatory processes at the flower meristem centre to which SUP is an important contributor. Their understanding is essential in further addressing evolutionary questions linking bisexuality and flower meristem homeostasis. Inter-allelic comparisons were carried out and SUP interactions with other boundary factors and flower meristem patterning and homeostasis regulators (such as CLV, WUS, PAN, CUC, KNU, AG, AP3/PI, CRC and SPT) have been evaluated at genetic, molecular, morphological and histological levels. Early SUP functions include mechanisms of male-female (sexual) boundary specification, flower mersitem termination and control of stamen number. A SUP-dependent flower meristem termination pathway is identified and analysed. Late SUP functions play a role in organ morphogenesis by controlling intra-whorl organ separation and carpel medial region formation. By integrating early and late SUP functions, and by analyzing in one single experiment a series of SUP genetic interactions, the concept of meristematic 'transference' (cascade) - a regulatory bridging process redundantly and sequentially co-ordinating the triggering and completion of flower meristem termination, and carpel margin meristem and placenta patterning - is proposed. Taken together, the results strongly support the view that SUP(-type) function(s) have been instrumental in resolving male/female gradients into sharp male and female identities (whorls, organs) and in enforcing flower homeostasis during evolution. This has probably been achieved by incorporating the meristem patterning system of the floral axis into the female/carpel programme. © The Author 2016

Ectopic phytocystatin expression leads to enhanced drought stress tolerance in soybean (Glycine max) and Arabidopsis thaliana through effects on strigolactone pathways and can also result in improved seed traits.

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Quain, Marian D; Makgopa, Matome E; Márquez-García, Belén; Comadira, Gloria; Fernandez-Garcia, Nieves; Olmos, Enrique; Schnaubelt, Daniel; Kunert, Karl J; Foyer, Christine H

2014-09-01

Ectopic cystatin expression has long been used in plant pest management, but the cysteine protease, targets of these inhibitors, might also have important functions in the control of plant lifespan and stress tolerance that remain poorly characterized. We therefore characterized the effects of expression of the rice cystatin, oryzacystatin-I (OCI), on the growth, development and stress tolerance of crop (soybean) and model (Arabidopsis thaliana) plants. Ectopic OCI expression in soybean enhanced shoot branching and leaf chlorophyll accumulation at later stages of vegetative development and enhanced seed protein contents and decreased the abundance of mRNAs encoding strigolactone synthesis enzymes. The OCI-expressing A. thaliana showed a slow-growth phenotype, with increased leaf numbers and enhanced shoot branching at flowering. The OCI-dependent inhibition of cysteine proteases enhanced drought tolerance in soybean and A. thaliana, photosynthetic CO2 assimilation being much less sensitive to drought-induced inhibition in the OCI-expressing soybean lines. Ectopic OCI expression or treatment with the cysteine protease inhibitor E64 increased lateral root densities in A. thaliana. E64 treatment also increased lateral root densities in the max2-1 mutants that are defective in strigolactone signalling, but not in the max3-9 mutants that are defective in strigolactone synthesis. Taken together, these data provide evidence that OCI-inhibited cysteine proteases participate in the control of growth and stress tolerance through effects on strigolactones. We conclude that cysteine proteases are important targets for manipulation of plant growth, development and stress tolerance, and also seed quality traits. © 2014 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

CYCP2;1 integrates genetic and nutritional information to promote meristem cell division in Arabidopsis

Czech Academy of Sciences Publication Activity Database

Peng, L.; Skylar, A.; Chang, P.L.; Bišová, Kateřina; Wu, X.

2014-01-01

Roč. 393, č. 2 (2014), s. 160-170 ISSN 0012-1606 R&D Projects: GA AV ČR M200201205 Grant - others:NSF(US) MCB-1122213 Institutional support: RVO:61388971 Keywords : cell cycle * arabidopsis * meristem Subject RIV: EE - Microbiology, Virology Impact factor: 3.547, year: 2014

Effect of the gamma radiation in the metabolic activity of the apical meristem of asparagus (Asparagus officinalis)

International Nuclear Information System (INIS)

Sanchez E, A.; Orozco A, J.A.; Troncoso R, R.; Ojeda C, A.J.; Mercado R, J.N.; Gardea B, A.; Tiznado H, M.E.; Melendrez A, R.

2007-01-01

The asparagus (Asparagus officinalis) is an agricultural product whose production generates a great quantity of wages as well as foreign currencies for the country because a great part of its production is exported to international markets. In direct reason to the high metabolic activity of the apical meristem, this product it possesses a short shelf life under good conditions of commercialization. Due to the above mentioned, the present work had as objective to evaluate the effect of the gamma radiation in the metabolic activity of the apical meristem of turions of asparagus during the postharvest. Turions of asparagus variety Brock of standard quality was treated with gamma radiation to absorbed dose of 1.0, 1.5, 2.0, 2.5 and 3.0 kGy using an irradiator of 60 Co and stored in one controlled temperature camera maintained at 2 C during 8 days. During the experiment, the camera stayed in darkness and under conditions of high relative humidity by means of the water aspersion. Immediately before the one treatment and after 1, 2, 4 and 8 days of storage, the asparagus were sampled to evaluate the breathing speed (VRCG) by means of gas chromatography and scanning differential calorimetry (VRCDB), ethylene production (PE) by means of gas chromatography and production of metabolic heat of the apical meristem of the asparagus by means of scanning differential calorimetry (Q). Its were not found effects due to the gamma radiation in the variables of VRCG, VRCDB and Q. However, for the PE case, it was found that the doses of 1.5 and 2.5 reduced the PE from the first day of storage, while the 3 kGy dose achievement to eliminate completely the ethylene production from the first day of storage. It was concluded that the gamma radiation at the used levels in the present experiment doesn't reduce the metabolic activity of the apical meristem of the turion of asparagus although it can to improve the postharvest quality from the asparagus when reducing the ethylene production

Gain-of-function mutants of the cytokinin receptors AHK2 and AHK3 regulate plant organ size, flowering time and plant longevity

Czech Academy of Sciences Publication Activity Database

Bartrina, I.; Jensen, H.; Novák, Ondřej; Strnad, Miroslav; Werner, T.; Schmülling, T.

2017-01-01

Roč. 173, č. 3 (2017), s. 1783-1797 ISSN 0032-0889 R&D Projects: GA ČR GA15-22322S Institutional support: RVO:61389030 Keywords : SHOOT APICAL MERISTEM * ARABIDOPSIS-THALIANA * HISTIDINE KINASE Subject RIV: CE - Biochemistry OBOR OECD: Plant sciences, botany Impact factor: 6.456, year: 2016

A simple method suitable to study de novo root organogenesis

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Xiaodong eChen

2014-05-01

Full Text Available De novo root organogenesis is the process in which adventitious roots regenerate from detached or wounded plant tissues or organs. In tissue culture, appropriate types and concentrations of plant hormones in the medium are critical for inducing adventitious roots. However, in natural conditions, regeneration from detached organs is likely to rely on endogenous hormones. To investigate the actions of endogenous hormones and the molecular mechanisms guiding de novo root organogenesis, we developed a simple method to imitate natural conditions for adventitious root formation by culturing Arabidopsis thaliana leaf explants on B5 medium without additive hormones. Here we show that the ability of the leaf explants to regenerate roots depends on the age of the leaf and on certain nutrients in the medium. Based on these observations, we provide examples of how this method can be used in different situations, and how it can be optimized. This simple method could be used to investigate the effects of various physiological and molecular changes on the regeneration of adventitious roots. It is also useful for tracing cell lineage during the regeneration process by differential interference contrast observation of -glucuronidase staining, and by live imaging of proteins labeled with fluorescent tags.

A pivotal role of the jasmonic acid signal pathway in mediating radiation-induced bystander effects in Arabidopsis thaliana.

Science.gov (United States)

Wang, Ting; Xu, Wei; Deng, Chenguang; Xu, Shaoxin; Li, Fanghua; Wu, Yuejin; Wu, Lijun; Bian, Po

Although radiation-induced bystander effects (RIBE) in Arabidopsis thaliana have been well demonstrated in vivo, little is known about their underlying mechanisms, particularly with regard to the participating signaling molecules and signaling pathways. In higher plants, jasmonic acid (JA) and its bioactive derivatives are well accepted as systemic signal transducers that are produced in response to various environmental stresses. It is therefore speculated that the JA signal pathway might play a potential role in mediating radiation-induced bystander signaling of root-to-shoot. In the present study, pretreatment of seedlings with Salicylhydroxamic acid, an inhibitor of lipoxigenase (LOX) in JA biosynthesis, significantly suppressed RIBE-mediated expression of the AtRAD54 gene. After root irradiation, the aerial parts of A. thaliana mutants deficient in JA biosynthesis (aos) and signaling cascades (jar1-1) showed suppressed induction of the AtRAD54 and AtRAD51 genes and TSI and 180-bp repeats, which have been extensively used as endpoints of bystander genetic and epigenetic effects in plants. These results suggest an involvement of the JA signal pathway in the RIBE of plants. Using the root micro-grafting technique, the JA signal pathway was shown to participate in both the generation of bystander signals in irradiated root cells and radiation responses in the bystander aerial parts of plants. The over-accumulation of endogenous JA in mutant fatty acid oxygenation up-regulated 2 (fou2), in which mutation of the Two Pore Channel 1 (TPC1) gene up-regulates expression of the LOX and allene oxide synthase (AOS) genes, inhibited RIBE-mediated expression of the AtRAD54 gene, but up-regulated expression of the AtKU70 and AtLIG4 genes in the non-homologous end joining (NHEJ) pathway. Considering that NHEJ is employed by plants with increased DNA damage, the switch from HR to NHEJ suggests that over-accumulation of endogenous JA might enhance the radiosensitivity of plants

Comparative Cytogenetic Study on the Toxicity of Magnetite and Zinc Ferrite Nanoparticles in Sunflower Root Cells

Science.gov (United States)

Foca-nici, Ecaterina; Capraru, Gabriela; Creanga, Dorina

2010-12-01

In this experimental study the authors present their results regarding the cellular division rate and the percentage of chromosomal aberrations in the root meristematic cells of Helianthus annuus cultivated in the presence of different volume fractions of magnetic nanoparticle suspensions, ranging between 20 and 100 microl/l. The aqueous magnetic colloids were prepared from chemically co-precipitated ferrites coated in sodium oleate. Tissue samples from the root meristeme of 2-3 day old germinated seeds were taken to prepare microscope slides following Squash method combined with Fuelgen techniques. Microscope investigation (cytogenetic tests) has resulted in the evaluation of mitotic index and chromosomal aberration index that appeared diminished and respectively increased following the addition of magnetic nanoparticles in the culture medium of the young seedlings. Zinc ferrite toxic influence appeared to be higher than that of magnetite, according to both cytogenetic parameters.

Domestication-driven Gossypium profilin 1 (GhPRF1) gene transduces early flowering phenotype in tobacco by spatial alteration of apical/floral-meristem related gene expression.

Science.gov (United States)

Pandey, Dhananjay K; Chaudhary, Bhupendra

2016-05-13

Plant profilin genes encode core cell-wall structural proteins and are evidenced for their up-regulation under cotton domestication. Notwithstanding striking discoveries in the genetics of cell-wall organization in plants, little is explicit about the manner in which profilin-mediated molecular interplay and corresponding networks are altered, especially during cellular signalling of apical meristem determinacy and flower development. Here we show that the ectopic expression of GhPRF1 gene in tobacco resulted in the hyperactivation of apical meristem and early flowering phenotype with increased flower number in comparison to the control plants. Spatial expression alteration in CLV1, a key meristem-determinacy gene, is induced by the GhPRF1 overexpression in a WUS-dependent manner and mediates cell signalling to promote flowering. But no such expression alterations are recorded in the GhPRF1-RNAi lines. The GhPRF1 transduces key positive flowering regulator AP1 gene via coordinated expression of FT4, SOC1, FLC1 and FT1 genes involved in the apical-to-floral meristem signalling cascade which is consistent with our in silico profilin interaction data. Remarkably, these positive and negative flowering regulators are spatially controlled by the Actin-Related Protein (ARP) genes, specifically ARP4 and ARP6 in proximate association with profilins. This study provides a novel and systematic link between GhPRF1 gene expression and the flower primordium initiation via up-regulation of the ARP genes, and an insight into the functional characterization of GhPRF1 gene acting upstream to the flowering mechanism. Also, the transgenic plants expressing GhPRF1 gene show an increase in the plant height, internode length, leaf size and plant vigor. Overexpression of GhPRF1 gene induced early and increased flowering in tobacco with enhanced plant vigor. During apical meristem determinacy and flower development, the GhPRF1 gene directly influences key flowering regulators through ARP

The arabidopsis thaliana AGRAVITROPIC 1 gene encodes a component of the polar-auxin-transport efflux carrier

Science.gov (United States)

Chen, R.; Hilson, P.; Sedbrook, J.; Rosen, E.; Caspar, T.; Masson, P. H.

1998-01-01

Auxins are plant hormones that mediate many aspects of plant growth and development. In higher plants, auxins are polarly transported from sites of synthesis in the shoot apex to their sites of action in the basal regions of shoots and in roots. Polar auxin transport is an important aspect of auxin functions and is mediated by cellular influx and efflux carriers. Little is known about the molecular identity of its regulatory component, the efflux carrier [Estelle, M. (1996) Current Biol. 6, 1589-1591]. Here we show that mutations in the Arabidopsis thaliana AGRAVITROPIC 1 (AGR1) gene involved in root gravitropism confer increased root-growth sensitivity to auxin and decreased sensitivity to ethylene and an auxin transport inhibitor, and cause retention of exogenously added auxin in root tip cells. We used positional cloning to show that AGR1 encodes a putative transmembrane protein whose amino acid sequence shares homologies with bacterial transporters. When expressed in Saccharomyces cerevisiae, AGR1 promotes an increased efflux of radiolabeled IAA from the cells and confers increased resistance to fluoro-IAA, a toxic IAA-derived compound. AGR1 transcripts were localized to the root distal elongation zone, a region undergoing a curvature response upon gravistimulation. We have identified several AGR1-related genes in Arabidopsis, suggesting a global role of this gene family in the control of auxin-regulated growth and developmental processes.

Differential expression analysis of boron transporters and some stress-related genes in response to 24-epibrassinolide and boron by semi-quantitative RT-PCR in Arabidopsis thaliana (L. Heynh

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Surgun Yonca

2016-01-01

Full Text Available Plant steroidal hormones, brassinosteroids (BRs, promote plant developmental processes and enhance tolerance to several abiotic stresses including high boron (B stress. To examine the possible role of BR in high B-induced stress at the transcriptional level, we investigated the response of B transporter genes (BOR1-4, high B-induced genes (MATE, Hsp-like, BR-induced genes (Hsp70-4, Hsp90-1 and other stress-related genes (LTI/COR78, LEA4-5 upon exogenous treatments of 24-epibrassinolide (EBL on Arabidopsis thaliana (L. Heynh exposed to high concentrations of boric acid (BA using semi-quantitative RT-PCR. BA treatments led to down regulation of BOR1 and BOR3 genes in leaf and root tissues and higher concentration of EBL further decreased expression of these genes in roots. The expression of high B-induced genes was observed to be upregulated by 1 μM EBL treatment under high B stress in both tissues of the seedlings. The upregulation of BR-induced genes were clearly evident in root tissues co-treated with 1 μM EBL and BA as compared to BA alone. Higher concentration of EBL was found to be more effective in increasing expression of LTI/COR78 gene in root and LEA4-5 gene in shoot tissues. To our knowledge, this is the first report how exogenous application of EBL modulates high B stress responses at molecular level in model plant Arabidopsis thaliana.

Indole-3-butyric acid promotes adventitious rooting in Arabidopsis thaliana thin cell layers by conversion into indole-3-acetic acid and stimulation of anthranilate synthase activity.

Science.gov (United States)

Fattorini, L; Veloccia, A; Della Rovere, F; D'Angeli, S; Falasca, G; Altamura, M M

2017-07-11

Indole-3-acetic acid (IAA), and its precursor indole-3-butyric acid (IBA), control adventitious root (AR) formation in planta. Adventitious roots are also crucial for propagation via cuttings. However, IBA role(s) is/are still far to be elucidated. In Arabidopsis thaliana stem cuttings, 10 μM IBA is more AR-inductive than 10 μM IAA, and, in thin cell layers (TCLs), IBA induces ARs when combined with 0.1 μM kinetin (Kin). It is unknown whether arabidopsis TCLs produce ARs under IBA alone (10 μM) or IAA alone (10 μM), and whether they contain endogenous IAA/IBA at culture onset, possibly interfering with the exogenous IBA/IAA input. Moreover, it is unknown whether an IBA-to-IAA conversion is active in TCLs, and positively affects AR formation, possibly through the activity of the nitric oxide (NO) deriving from the conversion process. Revealed undetectable levels of both auxins at culture onset, showing that arabidopsis TCLs were optimal for investigating AR-formation under the total control of exogenous auxins. The AR-response of TCLs from various ecotypes, transgenic lines and knockout mutants was analyzed under different treatments. It was shown that ARs are better induced by IBA than IAA and IBA + Kin. IBA induced IAA-efflux (PIN1) and IAA-influx (AUX1/LAX3) genes, IAA-influx carriers activities, and expression of ANTHRANILATE SYNTHASE -alpha1 (ASA1), a gene involved in IAA-biosynthesis. ASA1 and ANTHRANILATE SYNTHASE -beta1 (ASB1), the other subunit of the same enzyme, positively affected AR-formation in the presence of exogenous IBA, because the AR-response in the TCLs of their mutant wei2wei7 was highly reduced. The AR-response of IBA-treated TCLs from ech2ibr10 mutant, blocked into IBA-to-IAA-conversion, was also strongly reduced. Nitric oxide, an IAA downstream signal and a by-product of IBA-to-IAA conversion, was early detected in IAA- and IBA-treated TCLs, but at higher levels in the latter explants. Altogether, results showed that IBA induced

Abscisic acid regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin.

Science.gov (United States)

Rowe, James H; Topping, Jennifer F; Liu, Junli; Lindsey, Keith

2016-07-01

Understanding the mechanisms regulating root development under drought conditions is an important question for plant biology and world agriculture. We examine the effect of osmotic stress on abscisic acid (ABA), cytokinin and ethylene responses and how they mediate auxin transport, distribution and root growth through effects on PIN proteins. We integrate experimental data to construct hormonal crosstalk networks to formulate a systems view of root growth regulation by multiple hormones. Experimental analysis shows: that ABA-dependent and ABA-independent stress responses increase under osmotic stress, but cytokinin responses are only slightly reduced; inhibition of root growth under osmotic stress does not require ethylene signalling, but auxin can rescue root growth and meristem size; osmotic stress modulates auxin transporter levels and localization, reducing root auxin concentrations; PIN1 levels are reduced under stress in an ABA-dependent manner, overriding ethylene effects; and the interplay among ABA, ethylene, cytokinin and auxin is tissue-specific, as evidenced by differential responses of PIN1 and PIN2 to osmotic stress. Combining experimental analysis with network construction reveals that ABA regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

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

DOAP1 Promotes Flowering in the Orchid Dendrobium Chao Praya Smile.

Science.gov (United States)

Sawettalake, Nunchanoke; Bunnag, Sumontip; Wang, Yanwen; Shen, Lisha; Yu, Hao

2017-01-01

APETALA1 ( AP1 ) encodes a key MADS-box transcription factor that specifies the floral meristem identity on the flank of the inflorescence meristem, and determines the identity of perianth floral organs in the model plant Arabidopsis thaliana . Orchids are members of the Orchidaceae, one of the largest families of angiosperms. Although the expression patterns of a few AP1 -like genes in orchids have been reported, their actual functions in orchid reproductive development are so far largely unknown. In this study, we isolated and characterized an AP1 ortholog, DOAP1 , from Dendrobium Chao Praya Smile. DOAP1 was highly expressed in reproductive tissues, including inflorescence apices and flowers at various developmental stages. Overexpression of DOAP1 resulted in early flowering in Arabidopsis , and was able to rescue the floral organ defects of Arabidopsis ap1 mutants. Moreover, we successfully created transgenic Dendrobium Chao Praya Smile orchids overexpressing DOAP1 , which displayed earlier flowering and earlier termination of inflorescence meristems into floral meristems than wild-type orchids. Our results demonstrate that DOAP1 plays an evolutionarily conserved role in promoting flowering and floral meristem specification in the Orchidaceae family.

DOAP1 Promotes Flowering in the Orchid Dendrobium Chao Praya Smile

Science.gov (United States)

Sawettalake, Nunchanoke; Bunnag, Sumontip; Wang, Yanwen; Shen, Lisha; Yu, Hao

2017-01-01

APETALA1 (AP1) encodes a key MADS-box transcription factor that specifies the floral meristem identity on the flank of the inflorescence meristem, and determines the identity of perianth floral organs in the model plant Arabidopsis thaliana. Orchids are members of the Orchidaceae, one of the largest families of angiosperms. Although the expression patterns of a few AP1-like genes in orchids have been reported, their actual functions in orchid reproductive development are so far largely unknown. In this study, we isolated and characterized an AP1 ortholog, DOAP1, from Dendrobium Chao Praya Smile. DOAP1 was highly expressed in reproductive tissues, including inflorescence apices and flowers at various developmental stages. Overexpression of DOAP1 resulted in early flowering in Arabidopsis, and was able to rescue the floral organ defects of Arabidopsis ap1 mutants. Moreover, we successfully created transgenic Dendrobium Chao Praya Smile orchids overexpressing DOAP1, which displayed earlier flowering and earlier termination of inflorescence meristems into floral meristems than wild-type orchids. Our results demonstrate that DOAP1 plays an evolutionarily conserved role in promoting flowering and floral meristem specification in the Orchidaceae family. PMID:28386268

Molecular evolutionary analysis of the Alfin-like protein family in Arabidopsis lyrata, Arabidopsis thaliana, and Thellungiella halophila.

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Yu Song

Full Text Available In previous studies, the Alfin1 gene, a transcription factor, enhanced salt tolerance in alfalfa, primarily through altering gene expression levels in the root. Here, we examined the molecular evolution of the Alfin-like (AL proteins in two Arabidopsis species (A. lyrata and A. thaliana and a salt-tolerant close relative Thellungiella halophila. These AL-like proteins could be divided into four groups and the two known DUF3594 and PHD-finger domains had co-evolved within each group of genes, irrespective of species, due to gene duplication events in the common ancestor of all three species while gene loss was observed only in T. halophila. To detect whether natural selection acted in the evolution of AL genes, we calculated synonymous substitution ratios (dn/ds and codon usage statistics, finding positive selection operated on four branches and significant differences in biased codon usage in the AL family between T. halophila and A. lyrata or A. thaliana. Distinctively, only the AL7 branch was under positive selection on the PHD-finger domain and the three members on the branch showed the smallest difference when codon bias was evaluated among the seven clusters. Functional analysis based on transgenic overexpression lines and T-DNA insertion mutants indicated that salt-stress-induced AtAL7 could play a negative role in salt tolerance of A. thaliana, suggesting that adaptive evolution occurred in the members of AL gene family.

Multiwall carbon nanotubes modulate paraquat toxicity in Arabidopsis thaliana.

Science.gov (United States)

Fan, Xiaoji; Xu, Jiahui; Lavoie, Michel; Peijnenburg, W J G M; Zhu, Youchao; Lu, Tao; Fu, Zhengwei; Zhu, Tingheng; Qian, Haifeng

2018-02-01

Carbon nanotubes can be either toxic or beneficial to plant growth and can also modulate toxicity of organic contaminants through surface sorption. The complex interacting toxic effects of carbon nanotubes and organic contaminants in plants have received little attention in the literature to date. In this study, the toxicity of multiwall carbon nanotubes (MWCNT, 50 mg/L) and paraquat (MV, 0.82 mg/L), separately or in combination, were evaluated at the physiological and the proteomic level in Arabidopsis thaliana for 7-14 days. The results revealed that the exposure to MWCNT had no inhibitory effect on the growth of shoots and leaves. Rather, MWCNT stimulated the relative electron transport rate and the effective photochemical quantum yield of PSII value as compared to the control by around 12% and lateral root production up to nearly 4-fold as compared to the control. The protective effect of MWCNT on MV toxicity on the root surface area could be quantitatively explained by the extent of MV adsorption on MWCNT and was related to stimulation of photosynthesis, antioxidant protection and number and area of lateral roots which in turn helped nutrient assimilation. The influence of MWCNT and MV on photosynthesis and oxidative stress at the physiological level was consistent with the proteomics analysis, with various over-expressed photosynthesis-related proteins (by more than 2 folds) and various under-expressed oxidative stress related proteins (by about 2-3 folds). This study brings new insights into the interactive effects of two xenobiotics (MWCNT and MV) on the physiology of a model plant. Copyright © 2017 Elsevier Ltd. All rights reserved.

Natural variation at the FRD3 MATE transporter locus reveals cross-talk between Fe homeostasis and Zn tolerance in Arabidopsis thaliana

OpenAIRE

Pineau, Christophe; Loubet, Stéphanie; Lefoulon, Cécile; Chaliès, Claude; Fizames, Cécile; Lacombe, Benoît; Ferrand, Marina; Loudet, Olivier; Berthomieu, Pierre; Richard, Odile

2012-01-01

Author Summary Plants are adapted to soils in which the amounts of different nutrients vary widely, like Zn-deficient or Zn-contaminated soils. Exploring the molecular bases of plant adaptation to Zn-contaminated soils is important in determining strategies for phytoremediation. Here, we describe the mapping and characterization of a QTL for Zn tolerance in A. thaliana that underlies the natural variation of the root response to excess Zn. This physiological variation is controlled by differe...

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

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Andres Marilou A

2007-09-01

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

Root-secreted allelochemical in the noxious weed Phragmites australis deploys a reactive oxygen species response and microtubule assembly disruption to execute rhizotoxicity.

Science.gov (United States)

Rudrappa, Thimmaraju; Bonsall, Justin; Gallagher, John L; Seliskar, Denise M; Bais, Harsh P

2007-10-01

Phragmites australis is considered the most invasive plant in marsh and wetland communities in the eastern United States. Although allelopathy has been considered as a possible displacing mechanism in P. australis, there has been minimal success in characterizing the responsible allelochemical. We tested the occurrence of root-derived allelopathy in the invasiveness of P. australis. To this end, root exudates of two P. australis genotypes, BB (native) and P38 (an exotic) were tested for phytotoxicity on different plant species. The treatment of the susceptible plants with P. australis root exudates resulted in acute rhizotoxicity. It is interesting to note that the root exudates of P38 were more effective in causing root death in susceptible plants compared to the native BB exudates. The active ingredient in the P. australis exudates was identified as 3,4,5-trihydroxybenzoic acid (gallic acid). We tested the phytotoxic efficacy of gallic acid on various plant systems, including the model plant Arabidopsis thaliana. Most tested plants succumbed to the gallic acid treatment with the exception of P. australis itself. Mechanistically, gallic acid treatment generated elevated levels of reactive oxygen species (ROS) in the treated plant roots. Furthermore, the triggered ROS mediated the disruption of the root architecture of the susceptible plants by damaging the microtubule assembly. The study also highlights the persistence of the exuded gallic acid in P. australis's rhizosphere and its inhibitory effects against A. thaliana in the soil. In addition, gallic acid demonstrated an inhibitory effect on Spartina alterniflora, one of the salt marsh species it successfully invades.

The CUP-SHAPED COTYLEDON3 gene is required for boundary and shoot meristem formation in Arabidopsis

DEFF Research Database (Denmark)

Vroemen, Casper W; Mordhorst, Andreas P; Albrecht, Cathy

2003-01-01

From an enhancer trap screen for genes expressed in Arabidopsis embryos, we identified a gene expressed from the octant stage onward in the boundary between the two presumptive cotyledons and in a variety of postembryonic organ and meristem boundaries. This gene, CUP-SHAPED COTYLEDON3 (CUC3...

Root-Knot and Cyst Nematodes Activate Procambium-Associated Genes in Arabidopsis Roots

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Yasuka L. Yamaguchi

2017-07-01

Full Text Available Developmental plasticity is one of the most striking features of plant morphogenesis, as plants are able to vary their shapes in response to environmental cues. Biotic or abiotic stimuli often promote organogenesis events in plants not observed under normal growth conditions. Root-knot nematodes (RKNs are known to parasitize multiple species of rooting plants and to induce characteristic tissue expansion called galls or root-knots on the roots of their hosts by perturbing the plant cellular machinery. Galls contain giant cells (GCs and neighboring cells, and the GCs are a source of nutrients for the parasitizing nematode. Highly active cell proliferation was observed in galls. However, the underlying mechanisms that regulate the symptoms triggered by the plant-nematode interaction have not yet been elucidated. In this study, we deciphered the molecular mechanism of gall formation with an in vitro infection assay system using RKN Meloidogyne incognita, and the model plant Arabidopsis thaliana. By taking advantages of this system, we performed next-generation sequencing-based transcriptome profiling, and found that the expression of procambium identity-associated genes were enriched during gall formation. Clustering analyses with artificial xylogenic systems, together with the results of expression analyses of the candidate genes, showed a significant correlation between the induction of gall cells and procambium-associated cells. Furthermore, the promoters of several procambial marker genes such as ATHB8, TDR and WOX4 were activated not only in M. incognita-induced galls, but similarly in M. javanica induced-galls and Heterodera schachtii-induced syncytia. Our findings suggest that phytoparasitic nematodes modulate the host’s developmental regulation of the vascular stem cells during gall formation.

Root-Knot and Cyst Nematodes Activate Procambium-Associated Genes in Arabidopsis Roots.

Science.gov (United States)

Yamaguchi, Yasuka L; Suzuki, Reira; Cabrera, Javier; Nakagami, Satoru; Sagara, Tomomi; Ejima, Chika; Sano, Ryosuke; Aoki, Yuichi; Olmo, Rocio; Kurata, Tetsuya; Obayashi, Takeshi; Demura, Taku; Ishida, Takashi; Escobar, Carolina; Sawa, Shinichiro

2017-01-01

Developmental plasticity is one of the most striking features of plant morphogenesis, as plants are able to vary their shapes in response to environmental cues. Biotic or abiotic stimuli often promote organogenesis events in plants not observed under normal growth conditions. Root-knot nematodes (RKNs) are known to parasitize multiple species of rooting plants and to induce characteristic tissue expansion called galls or root-knots on the roots of their hosts by perturbing the plant cellular machinery. Galls contain giant cells (GCs) and neighboring cells, and the GCs are a source of nutrients for the parasitizing nematode. Highly active cell proliferation was observed in galls. However, the underlying mechanisms that regulate the symptoms triggered by the plant-nematode interaction have not yet been elucidated. In this study, we deciphered the molecular mechanism of gall formation with an in vitro infection assay system using RKN Meloidogyne incognita , and the model plant Arabidopsis thaliana. By taking advantages of this system, we performed next-generation sequencing-based transcriptome profiling, and found that the expression of procambium identity-associated genes were enriched during gall formation. Clustering analyses with artificial xylogenic systems, together with the results of expression analyses of the candidate genes, showed a significant correlation between the induction of gall cells and procambium-associated cells. Furthermore, the promoters of several procambial marker genes such as ATHB8 , TDR and WOX4 were activated not only in M. incognita -induced galls, but similarly in M. javanica induced-galls and Heterodera schachtii -induced syncytia. Our findings suggest that phytoparasitic nematodes modulate the host's developmental regulation of the vascular stem cells during gall formation.

Functional interactome of Aquaporin 1 sub-family reveals new physiological functions in Arabidopsis Thaliana

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Mohamed Ragab Abdel Gawwad

2013-09-01

Full Text Available Aquaporins are channel proteins found in plasma membranes and intercellular membranes of different cellular compartments, facilitate the water flux, solutes and gases across the cellular plasma membranes. The present study highlights the sub-family plasma membrane intrinsic protein (PIP predicting the 3-D structure and analyzing the functional interactome of it homologs. PIP1 homologs integrate with many proteins with different plant physiological roles in Arabidopsis thaliana including; PIP1A and PIP1B: facilitate the transport of water, diffusion of amino acids and/or peptides from the vacuolar compartment to the cytoplasm, play a role in the control of cell turgor and cell expansion and involved in root water uptake respectively. In addition we found that PIP1B plays a defensive role against Pseudomonas syringae infection through the interaction with the plasma membrane Rps2 protein. Another substantial function of PIP1C via the interaction with PIP2E is the response to nematode infection. Generally, PIP1 sub-family interactome controlling many physiological processes in plant cell like; osmoregulation in plants under high osmotic stress such as under a high salt, response to nematode, facilitate the transport of water across cell membrane and regulation of floral initiation in Arabidopsis thaliana.

Meristem Plant Cells as a Sustainable Source of Redox Actives for Skin Rejuvenation

Science.gov (United States)

Korkina, Liudmila G.; Mayer, Wolfgang; de Luca, Chiara

2017-01-01

Recently, aggressive advertisement claimed a “magic role” for plant stem cells in human skin rejuvenation. This review aims to shed light on the scientific background suggesting feasibility of using plant cells as a basis of anti-age cosmetics. When meristem cell cultures obtained from medicinal plants are exposed to appropriate elicitors/stressors (ultraviolet, ultrasound ultraviolet (UV), ultrasonic waves, microbial/insect metabolites, heavy metals, organic toxins, nutrient deprivation, etc.), a protective/adaptive response initiates the biosynthesis of secondary metabolites. Highly bioavailable and biocompatible to human cells, low-molecular weight plant secondary metabolites share structural/functional similarities with human non-protein regulatory hormones, neurotransmitters, pigments, polyamines, amino-/fatty acids. Their redox-regulated biosynthesis triggers in turn plant cell antioxidant and detoxification molecular mechanisms resembling human cell pathways. Easily isolated in relatively large quantities from contaminant-free cell cultures, plant metabolites target skin ageing mechanisms, above all redox imbalance. Perfect modulators of cutaneous oxidative state via direct/indirect antioxidant action, free radical scavenging, UV protection, and transition-metal chelation, they are ideal candidates to restore photochemical/redox/immune/metabolic barriers, gradually deteriorating in the ageing skin. The industrial production of plant meristem cell metabolites is toxicologically and ecologically sustainable for fully “biological” anti-age cosmetics. PMID:28498360

Genetic Analysis of Gravity Signal Transduction in Arabidopsis thaliana Seedlings

Science.gov (United States)

Boonsirichai, K.; Harrison, B.; Stanga, J.; Young, L.-S.; Neal, C.; Sabat, G.; Murthy, N.; Harms, A.; Sedbrook, J.; Masson, P.

The primary roots of Arabidopsis thaliana seedlings respond to gravity stimulation by developing a tip curvature that results from differential cellular elongation on opposite flanks of the elongation zone. This curvature appears modulated by a lateral gradient of auxin that originates in the gravity-perceiving cells (statocytes) of the root cap through an apparent lateral repositioning of a component the auxin efflux carrier complex within these cells (Friml et al, 2002, Nature 415: 806-809). Unfortunately, little is known about the molecular mechanisms that govern early phases of gravity perception and signal transduction within the root-cap statocytes. We have used a molecular genetic approach to uncover some of these mechanisms. Mutations in the Arabidopsis ARG1 and ARL2 genes, which encode J-domain proteins, resulted in specific alterations in root and hypocotyl gravitropism, without pleiotropic phenotypes. Interestingly, ARG1 and ARL2 appear to function in the same genetic pathway. A combination of molecular genetic, biochemical and cell-biological approaches were used to demonstrate that ARG1 functions in early phases of gravity signal transduction within the root and hypocotyl statocytes, and is needed for efficient lateral auxin transport within the cap. The ARG1 protein is associated with components of the secretory and/or endosomal pathways, suggesting its role in the recycling of components of the auxin efflux carrier complex between plasma membrane and endosome (Boonsirichai et al, 2003, Plant Cell 15:2612-2625). Genetic modifiers of arg1-2 were isolated and shown to enhance the gravitropic defect of arg1-2, while resulting in little or no gravitropic defects in a wild type ARG1 background. A slight tendency for arg1-2;mar1-1 and arg1-2;mar2-1 double-mutant organs to display an opposite gravitropic response compared to wild type suggests that all three genes contribute to the interpretation of the gravity-vector information by seedling organs. The

The plasma membrane H⁺ -ATPase AHA2 contributes to the root architecture in response to different nitrogen supply

DEFF Research Database (Denmark)

Młodzińska, Ewa; Kłobus, Grażyna; Christensen, Monica Daugbjerg

2015-01-01

of lateral root primordia, root elongation and increase the root biomass. However, the signal transduction mechanisms, which enable roots to sense changes in different mineral environments and match their growth and development patterns to actual conditions in the soil, are still unknown. Most recent...... comments have focused on one of the essential macroelements, namely nitrogen, and its role in the modification of the root architecture of Arabidopsis thaliana. As yet, not all elements of the signal transduction pathway leading to the perception of the nitrate stimulus, and hence to anatomical changes...... of the root, which allow for adaptation to variable ion concentrations in the soil, are known. Our data demonstrate that primary and lateral root length were shorter lower in aha2 mutant lines compared to wild-type plants in response to a variable nitrogen source. This suggests that the plasma membrane proton...

Molecular Characterization of the Plant Growth Promoting Bacterium Enterobacter sp. SA187 upon Contact with Arabidopsis thaliana

KAUST Repository

Alsharif, Wiam

2018-05-01

Salt stress is a severe environmental challenge in agriculture, limiting the quality and productivity of the crops around the globe. Plant growth promoting rhizobacteria (PGPR) is proposed as a friendly solution to overcome those challenges. The desert plant endophytic bacterium, Enterobacter sp. SA187 has shown plant growth promotion and salt stress tolerance beneficial effect on the model plant Arabidopsis thaliana in vitro as well as under the field conditions on different crops. SA187 has a distinguished morphology of yellow colonies (SA187Y) that could be due to carotenoid biosynthesis. However, the bacteria tend to lose the yellow color upon incubation with the plants and the colonies turn to white (SA187W). In comparison to SA187Y, SA187W shows 50% reduction on the beneficial impact on A. thaliana fresh and dry weight of root and shoot system. By counting the CFU/plant, we showed that SA187Y and SA187W both have similar colonization rate in both shoots and roots. Under non-salt conditions, optimal bacterial colonization was observed on day 8 after inocubation, however, under the salt stress condition, the optimal colonization was observed at day 4. Moreover, during the time period of the incubation of the SA187Y with the plants, there was a consistent noticeable loss of the yellow color of the colonies. This change in color is only observed eight days after transfer and the number of white colonies increases with the increase of the incubation time. In addition, SA187W was GFP-tagged by Tn7 transposon system and visualized by confocal laser scanning microscopy. The SA187W-GFP colonies have shown a similar colonization pattern as SA187Y-GFP, bacteria were colonizing the differentiation zone and cell elongation zone in the roots. Finally, the gene expression of the carotenoid biosynthesis pathways genes in SA187Y showed an overall higher gene expression compared to SA187W. In conclusion, the color loss seems to affect the beneficial impact of the bacteria on

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

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Sultana eRasheed

2016-02-01

Full Text Available 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 indicated that the expression of many drought stress-responsive genes and abscisic acid biosynthesis-related genes was differentially regulated in roots and shoots from days 3 to 9. The expression of cellular and metabolic process-related genes was up-regulated at an earlier time-point in roots than in shoots. In this regard, the expression of genes involved in oxidative signaling, chromatin structure, and cell wall modification also increased significantly in roots compared to shoots. Moreover, the increased expression of genes involved in the transport of amino acids and other solutes; including malate, iron, and sulfur, was observed in roots during the early time points following the initiation of the drought stress. These data suggest that plants may utilize these signaling channels and metabolic adjustments as adaptive responses in the early stages of a drought stress. Collectively, the results of the present study increases our understanding of the differences pertaining to the molecular mechanisms occurring in roots versus shoots in response to a drought stress. Furthermore, these findings also aid in the selection of novel genes and promoters that can be used to potentially produce crop plants with increased drought tolerance.

Similar Pathogen Targets in Arabidopsis thaliana and Homo sapiens Protein Networks

Science.gov (United States)

2012-09-21

Similar Pathogen Targets in Arabidopsis thaliana and Homo sapiens Protein Networks Paulo Shakarian1*, J. Kenneth Wickiser2 1 Paulo Shakarian...significantly attacked. Citation: Shakarian P, Wickiser JK (2012) Similar Pathogen Targets in Arabidopsis thaliana and Homo sapiens Protein Networks...to 00-00-2012 4. TITLE AND SUBTITLE Similar Pathogen Targets in Arabidopsis thaliana and Homo sapiens Protein Networks 5a. CONTRACT NUMBER 5b

Plant stem cell niches.

Science.gov (United States)

Aichinger, Ernst; Kornet, Noortje; Friedrich, Thomas; Laux, Thomas

2012-01-01

Multicellular organisms possess pluripotent stem cells to form new organs, replenish the daily loss of cells, or regenerate organs after injury. Stem cells are maintained in specific environments, the stem cell niches, that provide signals to block differentiation. In plants, stem cell niches are situated in the shoot, root, and vascular meristems-self-perpetuating units of organ formation. Plants' lifelong activity-which, as in the case of trees, can extend over more than a thousand years-requires that a robust regulatory network keep the balance between pluripotent stem cells and differentiating descendants. In this review, we focus on current models in plant stem cell research elaborated during the past two decades, mainly in the model plant Arabidopsis thaliana. We address the roles of mobile signals on transcriptional modules involved in balancing cell fates. In addition, we discuss shared features of and differences between the distinct stem cell niches of Arabidopsis.

A late embryogenesis abundant protein HVA1 regulated by an inducible promoter enhances root growth and abiotic stress tolerance in rice without yield penalty.

Science.gov (United States)

Chen, Yi-Shih; Lo, Shuen-Fang; Sun, Peng-Kai; Lu, Chung-An; Ho, Tuan-Hua D; Yu, Su-May

2015-01-01

Regulation of root architecture is essential for maintaining plant growth under adverse environment. A synthetic abscisic acid (ABA)/stress-inducible promoter was designed to control the expression of a late embryogenesis abundant protein (HVA1) in transgenic rice. The background of HVA1 is low but highly inducible by ABA, salt, dehydration and cold. HVA1 was highly accumulated in root apical meristem (RAM) and lateral root primordia (LRP) after ABA/stress treatments, leading to enhanced root system expansion. Water-use efficiency (WUE) and biomass also increased in transgenic rice, likely due to the maintenance of normal cell functions and metabolic activities conferred by HVA1 which is capable of stabilizing proteins, under osmotic stress. HVA1 promotes lateral root (LR) initiation, elongation and emergence and primary root (PR) elongation via an auxin-dependent process, particularly by intensifying asymmetrical accumulation of auxin in LRP founder cells and RAM, even under ABA/stress-suppressive conditions. We demonstrate a successful application of an inducible promoter in regulating the spatial and temporal expression of HVA1 for improving root architecture and multiple stress tolerance without yield penalty. © 2014 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

THE MECHANISM OF 5-AMINOURACIL-INDUCED SYNCHRONY OF CELL DIVISION IN VI CIA FABA ROOT MERISTEMS

Science.gov (United States)

Prensky, Wolf; Smith, Harold H.

1965-01-01

Cessation of mitosis was brought about in Vicia faba roots incubated for 24 hours in the thymine analogue, 5-aminouracil. Recovery of mitotic activity began 8 hours after removal from 5-aminouracil and reached a peak at 15 hours. If colchicine was added 4 hours before the peak of mitoses, up to 80 per cent of all cells accumulated in mitotic division stages. By use of single and double labeling techniques, it was shown that synchrony of cell divisions resulted from depression in the rate of DNA synthesis by 5-aminouracil, which brought about an accumulation of cells in the S phase of the cell cycle. Treatment with 5-aminouracil may have also caused a delay in the rate of exit of cells from the G2 period. It appeared to have no effect on the duration of the G1 period. When roots were removed from 5-aminouracil, DNA synthesis resumed in all cells in the S phase. Although thymidine antagonized the effects of 5-aminouracil, an exogenous supply of it was not necessary for the resumption of DNA synthesis, as shown by incorporation studies with tritiated deoxycytidine. PMID:19866644

The scale of population structure in Arabidopsis thaliana.

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Alexander Platt

2010-02-01

Full Text Available The population structure of an organism reflects its evolutionary history and influences its evolutionary trajectory. It constrains the combination of genetic diversity and reveals patterns of past gene flow. Understanding it is a prerequisite for detecting genomic regions under selection, predicting the effect of population disturbances, or modeling gene flow. This paper examines the detailed global population structure of Arabidopsis thaliana. Using a set of 5,707 plants collected from around the globe and genotyped at 149 SNPs, we show that while A. thaliana as a species self-fertilizes 97% of the time, there is considerable variation among local groups. This level of outcrossing greatly limits observed heterozygosity but is sufficient to generate considerable local haplotypic diversity. We also find that in its native Eurasian range A. thaliana exhibits continuous isolation by distance at every geographic scale without natural breaks corresponding to classical notions of populations. By contrast, in North America, where it exists as an exotic species, A. thaliana exhibits little or no population structure at a continental scale but local isolation by distance that extends hundreds of km. This suggests a pattern for the development of isolation by distance that can establish itself shortly after an organism fills a new habitat range. It also raises questions about the general applicability of many standard population genetics models. Any model based on discrete clusters of interchangeable individuals will be an uneasy fit to organisms like A. thaliana which exhibit continuous isolation by distance on many scales.

Accumulation and phytotoxicity of perfluorooctanoic acid in the model plant species Arabidopsis thaliana

International Nuclear Information System (INIS)

Yang, Xinping; Ye, Chengchen; Liu, Yu; Zhao, Fang-Jie

2015-01-01

Perfluorooctanoic acid (PFOA) is widely used in the manufacture of many industrial and household products. To assess the potential environmental risk of PFOA, its accumulation, translocation and phytotoxic effects were investigated using the model plant species Arabidopsis thaliana. Exposure to 18 μM PFOA-F in agar plates did not affect plant growth, but 181–1811 μM PFOA-F inhibited root and shoot growth. PFOA was more phytotoxic on shoot growth than NaF at the equivalent F concentration, with the latter having 3.9–7.6 times higher EC50 for shoot biomass than PFOA. PFOA was efficiently translocated from roots to shoots, where it existed as intact PFOA molecules without transformation evidenced by the 19 F NMR spectra. PFOA caused a significant increase in the concentration of H 2 O 2 and malondialdehyde (MDA) in shoots, indicating that oxidative stress is a likely cause of PFOA phytotoxicity. - Highlights: • PFOA is more phytotoxic on shoot growth than NaF at the equivalent F concentration. • PFOA is readily taken up and translocated from roots to shoots. • PFOA exists as intact molecules without transformation in Arabidopsis shoots. • PFOA causes oxidative stress in Arabidopsis shoots. - Perfluorooctanoic acid causes oxidative stress and is more phytotoxic on shoot growth than inorganic fluoride at the equivalent F concentration.

Regulation of root morphogenesis in arbuscular mycorrhizae: what role do fungal exudates, phosphate, sugars and hormones play in lateral root formation?

Science.gov (United States)

Fusconi, Anna

2014-01-01

Background Arbuscular mycorrhizae (AMs) form a widespread root–fungus symbiosis that improves plant phosphate (Pi) acquisition and modifies the physiology and development of host plants. Increased branching is recognized as a general feature of AM roots, and has been interpreted as a means of increasing suitable sites for colonization. Fungal exudates, which are involved in the dialogue between AM fungi and their host during the pre-colonization phase, play a well-documented role in lateral root (LR) formation. In addition, the increased Pi content of AM plants, in relation to Pi-starved controls, as well as changes in the delivery of carbohydrates to the roots and modulation of phytohormone concentration, transport and sensitivity, are probably involved in increasing root system branching. Scope This review discusses the possible causes of increased branching in AM plants. The differential root responses to Pi, sugars and hormones of potential AM host species are also highlighted and discussed in comparison with those of the non-host Arabidopsis thaliana. Conclusions Fungal exudates are probably the main compounds regulating AM root morphogenesis during the first colonization steps, while a complex network of interactions governs root development in established AMs. Colonization and high Pi act synergistically to increase root branching, and sugar transport towards the arbusculated cells may contribute to LR formation. In addition, AM colonization and high Pi generally increase auxin and cytokinin and decrease ethylene and strigolactone levels. With the exception of cytokinins, which seem to regulate mainly the root:shoot biomass ratio, these hormones play a leading role in governing root morphogenesis, with strigolactones and ethylene blocking LR formation in the non-colonized, Pi-starved plants, and auxin inducing them in colonized plants, or in plants grown under high Pi conditions. PMID:24227446

Effects of N6-benzylaminopurine and Indole Acetic Acid on In Vitro Shoot Multiplication, Nodule-like Meristem Proliferation and Plant Regeneration of Malaysian Bananas (Musa spp.)

Science.gov (United States)

Sipen, Philip; Davey, Michael R

2012-01-01

Different concentrations of N6-benzylaminopurine (BAP) and indole acetic acid (IAA) in Murashige and Skoog based medium were assessed for their effects on shoot multiplication, nodule-like meristem proliferation and plant regeneration of the Malaysian banana cultivars Pisang Mas, Pisang Nangka, Pisang Berangan and Pisang Awak. BAP at 1–14 mg L−1 with or without 0.2 mg L−1 IAA, or BAP at 7–14 mg L−1 with the same concentration of IAA, was evaluated for shoot multiplication from shoot tips and the proliferation of nodule-like meristems from scalps, respectively. Plant regeneration from scalps was assessed using 1 mg L−1 BAP and 0.2 mg L−1 IAA separately, or a combination of these two growth regulators. Data on shoot multiplication, the proliferation of nodule-like meristems with associated plant regeneration were recorded after 30 days of culture. A maximum of 5 shoots per original shoot tip was achieved on medium supplemented with BAP at 5 mg L−1 (Pisang Nangka), 6 mg L−1 (Pisang Mas and Pisang Berangan), or 7 mg L−1 (Pisang Awak), with 0.2 mg L−1 IAA. BAP at 11 mg L−1 with 0.2 mg L−1 IAA induced the most highly proliferating nodule-like meristems in the four banana cultivars. Plant regeneration from scalps was optimum in all cases on medium containing 1 mg L−1 BAP and 0.2 mg L−1 IAA. This is the first report on the successful induction of highly proliferating nodule-like meristems and plant regeneration from scalps of the Malaysian banana cultivars Pisang Mas, Pisang Nangka, Pisang Berangan and Pisang Awak. PMID:24575235

Innate immune responses activated in Arabidopsis roots by microbe-associated molecular patterns.

Science.gov (United States)

Millet, Yves A; Danna, Cristian H; Clay, Nicole K; Songnuan, Wisuwat; Simon, Matthew D; Werck-Reichhart, Danièle; Ausubel, Frederick M

2010-03-01

Despite the fact that roots are the organs most subject to microbial interactions, very little is known about the response of roots to microbe-associated molecular patterns (MAMPs). By monitoring transcriptional activation of beta-glucuronidase reporters and MAMP-elicited callose deposition, we show that three MAMPs, the flagellar peptide Flg22, peptidoglycan, and chitin, trigger a strong tissue-specific response in Arabidopsis thaliana roots, either at the elongation zone for Flg22 and peptidoglycan or in the mature parts of the roots for chitin. Ethylene signaling, the 4-methoxy-indole-3-ylmethylglucosinolate biosynthetic pathway, and the PEN2 myrosinase, but not salicylic acid or jasmonic acid signaling, play major roles in this MAMP response. We also show that Flg22 induces the cytochrome P450 CYP71A12-dependent exudation of the phytoalexin camalexin by Arabidopsis roots. The phytotoxin coronatine, an Ile-jasmonic acid mimic produced by Pseudomonas syringae pathovars, suppresses MAMP-activated responses in the roots. This suppression requires the E3 ubiquitin ligase COI1 as well as the transcription factor JIN1/MYC2 but does not rely on salicylic acid-jasmonic acid antagonism. These experiments demonstrate the presence of highly orchestrated and tissue-specific MAMP responses in roots and potential pathogen-encoded mechanisms to block these MAMP-elicited signaling pathways.

ANGUSTIFOLIA mediates one of the multiple SCRAMBLED signaling pathways regulating cell growth pattern in Arabidopsis thaliana.

Science.gov (United States)

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

2015-09-25

In Arabidopsis thaliana, an atypical leucine-rich repeat receptor-like kinase, SCRAMBLED (SCM), is required for multiple developmental processes including root epidermal cell fate determination, silique dehiscence, inflorescence growth, ovule morphogenesis, and tissue morphology. Previous work suggested that SCM regulates these multiple pathways using distinct mechanisms via interactions with specific downstream factors. ANGUSTIFOLIA (AN) is known to regulate cell and tissue morphogenesis by influencing cortical microtubule arrangement, and recently, the AN protein was reported to interact with the SCM protein. Therefore, we examined whether AN might be responsible for mediating some of the SCM-dependent phenotypes. We discovered that both scm and an mutant lines cause an abnormal spiral or twisting growth of roots, but only the scm mutant affected root epidermal patterning. The siliques of the an and scm mutants also exhibited spiral growth, as previously reported, but only the scm mutant altered silique dehiscence. Interestingly, we discovered that the spiral growth of roots and siliques of the scm mutant is rescued by a truncated SCM protein that lacks its kinase domain, and that a juxtamembrane domain of SCM was sufficient for AN binding in the yeast two-hybrid analysis. These results suggest that the AN protein is one of the critical downstream factors of SCM pathways specifically responsible for mediating its effects on cell/tissue morphogenesis through cortical microtubule arrangement. Copyright © 2015 Elsevier Inc. All rights reserved.

AtNPF2.5 Modulates Chloride (Cl−) Efflux from Roots of Arabidopsis thaliana

KAUST Repository

Li, Bo; Qiu, Jiaen; Jayakannan, Maheswari; Xu, Bo; Li, Yuan; Mayo, Gwenda M.; Tester, Mark A.; Gilliham, Matthew; Roy, Stuart J.

2017-01-01

better under saline conditions; however, the molecular mechanisms involved in maintaining low shoot Cl remain largely undefined. Recently, it was shown that the NRT1/PTR Family 2.4 protein (NPF2.4) loads Cl into the root xylem, which affects

PARVUS affects aluminium sensitivity by modulating the structure of glucuronoxylan in Arabidopsis thaliana.

Science.gov (United States)

Zhu, Xiao Fang; Wan, Jiang Xue; Wu, Qi; Zhao, Xu Sheng; Zheng, Shao Jian; Shen, Ren Fang

2017-09-01

Glucuronoxylan (GX), an important component of hemicellulose in the cell wall, appears to affect aluminium (Al) sensitivity in plants. To investigate the role of GX in cell-wall-localized xylan, we examined the Arabidopsis thaliana parvus mutant in detail. This mutant lacks α-D-glucuronic acid (GlcA) side chains in GX and has greater resistance to Al stress than wild-type (WT) plants. The parvus mutant accumulated lower levels of Al in its roots and cell walls than WT despite having cell wall pectin content and pectin methylesterase (PME) activity similar to those of WT. Our results suggest that the altered properties of hemicellulose in the mutant contribute to its decreased Al accumulation. Although we observed almost no differences in hemicellulose content between parvus and WT under control conditions, less Al was retained in parvus hemicellulose than in WT. This observation is consistent with the finding that GlcA substitutions in WT GX, but not mutant GX, were increased under Al stress. Taken together, these results suggest that the modulation of GlcA levels in GX affects Al resistance by influencing the Al binding capacity of the root cell wall in Arabidopsis. © 2017 John Wiley & Sons Ltd.

Ecology of Arabidopsis thaliana : local adaptation and interaction with herbivores

NARCIS (Netherlands)

Mosleh Arany, A.

2006-01-01

As first step the impact of herbivory and abiotic factors on population dynamics of Arabidopsis thaliana were studied. Ceutorhynchus atomus and C. contractus were identified as the major insect herbivores on A. thaliana population, reducing seed production by more than 40%. Mortality from February

Identification of cyst nematode B-type CLE peptides and modulation of the vascular stem cell pathway for feeding cell formation

Science.gov (United States)

Stem cells are important in the continuous formation of various tissues during postembryonic organogenesis. Stem cell pools in the SAM (shoot apical meristem), RAM (root apical meristem) and vascular procambium/cambium are regulated by CLE-receptor kinase-WOX signaling modules. Previous data showed ...

The MicroRNA390/TAS3 Pathway Mediates Symbiotic Nodulation and Lateral Root Growth1[OPEN

Science.gov (United States)

Bustos-Sanmamed, Pilar; Mysore, Kirankumar S.

2017-01-01

Legume roots form two types of postembryonic organs, lateral roots and symbiotic nodules. Nodule formation is the result of the interaction of legumes with rhizobia and requires the mitotic activation and differentiation of root cells as well as an independent, but coordinated, program that allows infection by rhizobia. MicroRNA390 (miR390) is an evolutionarily conserved microRNA that targets the Trans-Acting Short Interference RNA3 (TAS3) transcript. Cleavage of TAS3 by ARGONAUTE7 results in the production of trans-acting small interference RNAs, which target mRNAs encoding AUXIN RESPONSE FACTOR2 (ARF2), ARF3, and ARF4. Here, we show that activation of the miR390/TAS3 regulatory module by overexpression of miR390 in Medicago truncatula promotes lateral root growth but prevents nodule organogenesis, rhizobial infection, and the induction of two key nodulation genes, Nodulation Signaling Pathway1 (NSP1) and NSP2. Accordingly, inactivation of the miR390/TAS3 module, either by expression of a miR390 target mimicry construct or mutations in ARGONAUTE7, enhances nodulation and rhizobial infection, alters the spatial distribution of the nodules, and increases the percentage of nodules with multiple meristems. Our results revealed a key role of the miR390/TAS3 pathway in legumes as a modulator of lateral root organs, playing opposite roles in lateral root and nodule development. PMID:28663332

Cadmium induces hypodermal periderm formation in the roots of the monocotyledonous medicinal plant Merwilla plumbea.

Science.gov (United States)

Lux, Alexander; Vaculík, Marek; Martinka, Michal; Lisková, Desana; Kulkarni, Manoj G; Stirk, Wendy A; Van Staden, Johannes

2011-02-01

Merwilla plumbea is an important African medicinal plant. As the plants grow in soils contaminated with metals from mining activities, the danger of human intoxication exists. An experiment with plants exposed to cadmium (Cd) was performed to investigate the response of M. plumbea to this heavy metal, its uptake and translocation to plant organs and reaction of root tissues. Plants grown from seeds were cultivated in controlled conditions. Hydroponic cultivation is not suitable for this species as roots do not tolerate aquatic conditions, and additional stress by Cd treatment results in total root growth inhibition and death. After cultivation in perlite the plants exposed to 1 and 5 mg Cd L(-1) in half-strength Hoagland's solution were compared with control plants. Growth parameters were evaluated, Cd content was determined by inductively coupled plasma mass spectroscopy (ICP-MS) and root structure was investigated using various staining procedures, including the fluorescent stain Fluorol yellow 088 to detect suberin deposition in cell walls. The plants exposed to Cd were significantly reduced in growth. Most of the Cd taken up by plants after 4 weeks cultivation was retained in roots, and only a small amount was translocated to bulbs and leaves. In reaction to higher Cd concentrations, roots developed a hypodermal periderm close to the root tip. Cells produced by cork cambium impregnate their cell walls by suberin. It is suggested that the hypodermal periderm is developed in young root parts in reaction to Cd toxicity to protect the root from radial uptake of Cd ions. Secondary meristems are usually not present in monocotyledonous species. Another interpretation explaining formation of protective suberized layers as a result of periclinal divisions of the hypodermis is discussed. This process may represent an as yet unknown defence reaction of roots when exposed to elemental stress.

Intracellular magnetophoresis of amyloplasts and induction of root curvature

Science.gov (United States)

Kuznetsov, O. A.; Hasenstein, K. H.

1996-01-01

High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, delta(H2/2), was about 10(9) Oe2.cm-1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 +/- 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 +/- 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.

The pattern of polymorphism in Arabidopsis thaliana.

Directory of Open Access Journals (Sweden)

2005-07-01

Full Text Available We resequenced 876 short fragments in a sample of 96 individuals of Arabidopsis thaliana that included stock center accessions as well as a hierarchical sample from natural populations. Although A. thaliana is a selfing weed, the pattern of polymorphism in general agrees with what is expected for a widely distributed, sexually reproducing species. Linkage disequilibrium decays rapidly, within 50 kb. Variation is shared worldwide, although population structure and isolation by distance are evident. The data fail to fit standard neutral models in several ways. There is a genome-wide excess of rare alleles, at least partially due to selection. There is too much variation between genomic regions in the level of polymorphism. The local level of polymorphism is negatively correlated with gene density and positively correlated with segmental duplications. Because the data do not fit theoretical null distributions, attempts to infer natural selection from polymorphism data will require genome-wide surveys of polymorphism in order to identify anomalous regions. Despite this, our data support the utility of A. thaliana as a model for evolutionary functional genomics.

Demographic history of european populations of Arabidopsis thaliana.

Directory of Open Access Journals (Sweden)

Olivier François

2008-05-01

Full Text Available The model plant species Arabidopsis thaliana is successful at colonizing land that has recently undergone human-mediated disturbance. To investigate the prehistoric spread of A. thaliana, we applied approximate Bayesian computation and explicit spatial modeling to 76 European accessions sequenced at 876 nuclear loci. We find evidence that a major migration wave occurred from east to west, affecting most of the sampled individuals. The longitudinal gradient appears to result from the plant having spread in Europe from the east approximately 10,000 years ago, with a rate of westward spread of approximately 0.9 km/year. This wave-of-advance model is consistent with a natural colonization from an eastern glacial refugium that overwhelmed ancient western lineages. However, the speed and time frame of the model also suggest that the migration of A. thaliana into Europe may have accompanied the spread of agriculture during the Neolithic transition.

Arabidopsis BLADE-ON-PETIOLE1 and 2 promote floral meristem fate and determinacy in a previously undefined pathway targeting APETALA1 and AGAMOUS-LIKE24.

Science.gov (United States)

Xu, Mingli; Hu, Tieqiang; McKim, Sarah M; Murmu, Jhadeswar; Haughn, George W; Hepworth, Shelley R

2010-09-01

The transition to flowering is a tightly controlled developmental decision in plants. In Arabidopsis, LEAFY (LFY) and APETALA1 (AP1) are key regulators of this transition and expression of these genes in primordia produced by the inflorescence meristem confers floral fate. Here, we examine the role of architectural regulators BLADE-ON-PETIOLE1 (BOP1) and BOP2 in promotion of floral meristem identity. Loss-of-function bop1 bop2 mutants show subtle defects in inflorescence and floral architecture but in combination with lfy or ap1, synergistic defects in floral meristem fate and determinacy are revealed. The most dramatic changes occur in bop1 bop2 ap1-1 triple mutants where flowers are converted into highly branched inflorescence-like shoots. Our data show that BOP1/2 function distinctly from LFY to upregulate AP1 in floral primordia and that all three activities converge to down-regulate flowering-time regulators including AGAMOUS-LIKE24 in stage 2 floral meristems. Subsequently, BOP1/2 promote A-class floral-organ patterning in parallel with LFY and AP1. Genetic and biochemical evidence support the model that BOP1/2 are recruited to the promoter of AP1 through direct interactions with TGA bZIP transcription factors, including PERIANTHIA. These data reveal an important supporting role for BOP1/2 in remodeling shoot architecture during the floral transition. © 2010 The Authors. Journal compilation © 2010 Blackwell Publishing Ltd.

Control of plant architecture by the TALE homeobox genes ATH1 and PENNYWISE

NARCIS (Netherlands)

Rutjens, B.P.W.

2007-01-01

In plants, pattern formation is an ongoing process that starts during embryogenesis and lasts the entire life span. Most of the plant adult body is formed post-embryonically by continuous organogenic potential of the root and shoot meristems. Proper shoot apical meristem (SAM) function requires

Localized iron supply triggers lateral root elongation in Arabidopsis by altering the AUX1-mediated auxin distribution.

Science.gov (United States)

Giehl, Ricardo F H; Lima, Joni E; von Wirén, Nicolaus

2012-01-01

Root system architecture depends on nutrient availability, which shapes primary and lateral root development in a nutrient-specific manner. To better understand how nutrient signals are integrated into root developmental programs, we investigated the morphological response of Arabidopsis thaliana roots to iron (Fe). Relative to a homogeneous supply, localized Fe supply in horizontally separated agar plates doubled lateral root length without having a differential effect on lateral root number. In the Fe uptake-defective mutant iron-regulated transporter1 (irt1), lateral root development was severely repressed, but a requirement for IRT1 could be circumvented by Fe application to shoots, indicating that symplastic Fe triggered the local elongation of lateral roots. The Fe-stimulated emergence of lateral root primordia and root cell elongation depended on the rootward auxin stream and was accompanied by a higher activity of the auxin reporter DR5-β-glucuronidase in lateral root apices. A crucial role of the auxin transporter AUXIN RESISTANT1 (AUX1) in Fe-triggered lateral root elongation was indicated by Fe-responsive AUX1 promoter activities in lateral root apices and by the failure of the aux1-T mutant to elongate lateral roots into Fe-enriched agar patches. We conclude that a local symplastic Fe gradient in lateral roots upregulates AUX1 to accumulate auxin in lateral root apices as a prerequisite for lateral root elongation.

Effect of arabinogalactan proteins from the root caps of pea and Brassica napus on Aphanomyces euteiches zoospore chemotaxis and germination.

Science.gov (United States)

Cannesan, Marc Antoine; Durand, Caroline; Burel, Carole; Gangneux, Christophe; Lerouge, Patrice; Ishii, Tadashi; Laval, Karine; Follet-Gueye, Marie-Laure; Driouich, Azeddine; Vicré-Gibouin, Maïté

2012-08-01

Root tips of many plant species release a number of border, or border-like, cells that are thought to play a major role in the protection of root meristem. However, little is currently known on the structure and function of the cell wall components of such root cells. Here, we investigate the sugar composition of the cell wall of the root cap in two species: pea (Pisum sativum), which makes border cells, and Brassica napus, which makes border-like cells. We find that the cell walls are highly enriched in arabinose and galactose, two major residues of arabinogalactan proteins. We confirm the presence of arabinogalactan protein epitopes on root cap cell walls using immunofluorescence microscopy. We then focused on these proteoglycans by analyzing their carbohydrate moieties, linkages, and electrophoretic characteristics. The data reveal (1) significant structural differences between B. napus and pea root cap arabinogalactan proteins and (2) a cross-link between these proteoglycans and pectic polysaccharides. Finally, we assessed the impact of root cap arabinogalactan proteins on the behavior of zoospores of Aphanomyces euteiches, an oomycetous pathogen of pea roots. We find that although the arabinogalactan proteins of both species induce encystment and prevent germination, the effects of both species are similar. However, the arabinogalactan protein fraction from pea attracts zoospores far more effectively than that from B. napus. This suggests that root arabinogalactan proteins are involved in the control of early infection of roots and highlights a novel role for these proteoglycans in root-microbe interactions.

Localization of ENHANCER OF TRY AND CPC1 protein in Arabidopsis root epidermis.

Science.gov (United States)

Tominaga-Wada, Rumi; Kurata, Tetsuya; Wada, Takuji

2017-07-01

CAPRICE (CPC) is a R3-type MYB transcription factor, which induces root-hair cell differentiation in Arabidopsis thaliana. The CPC homologous gene ENHANCER TRY AND CPC1 (ETC1) has a similar function to CPC, and acts in concert with CPC. The CPC protein moves between root epidermal cells, from hairless cells to the neighboring cells, and promotes root-hair differentiation. Therefore, ETC1 is predicted to have movement ability similar to that of CPC. In this study, we generated ETC1:ETC1:GFP and CPC:ETC1:GFP transgenic plants to clarify whether ETC1 exhibits cell-to-cell movement. Transgenic plants showed many-root-haired and trichome-less phenotypes, similar to those observed in CPC:CPC:GFP plants, suggesting a similar function of ETC1 and CPC. However, the ETC1:GFP fusion protein located exclusively to the hairless cells in both ETC1:ETC1:GFP and CPC:ETC1:GFP transgenic plants. These results indicate that, unexpectedly, the ETC1 protein cannot move in the root epidermis from hairless cells to the neighboring cells. Copyright © 2017 Elsevier GmbH. All rights reserved.

Evolutionary origins of Brassicaceae specific genes in Arabidopsis thaliana

Science.gov (United States)

2011-01-01

Background All sequenced genomes contain a proportion of lineage-specific genes, which exhibit no sequence similarity to any genes outside the lineage. Despite their prevalence, the origins and functions of most lineage-specific genes remain largely unknown. As more genomes are sequenced opportunities for understanding evolutionary origins and functions of lineage-specific genes are increasing. Results This study provides a comprehensive analysis of the origins of lineage-specific genes (LSGs) in Arabidopsis thaliana that are restricted to the Brassicaceae family. In this study, lineage-specific genes within the nuclear (1761 genes) and mitochondrial (28 genes) genomes are identified. The evolutionary origins of two thirds of the lineage-specific genes within the Arabidopsis thaliana genome are also identified. Almost a quarter of lineage-specific genes originate from non-lineage-specific paralogs, while the origins of ~10% of lineage-specific genes are partly derived from DNA exapted from transposable elements (twice the proportion observed for non-lineage-specific genes). Lineage-specific genes are also enriched in genes that have overlapping CDS, which is consistent with such novel genes arising from overprinting. Over half of the subset of the 958 lineage-specific genes found only in Arabidopsis thaliana have alignments to intergenic regions in Arabidopsis lyrata, consistent with either de novo origination or differential gene loss and retention, with both evolutionary scenarios explaining the lineage-specific status of these genes. A smaller number of lineage-specific genes with an incomplete open reading frame across different Arabidopsis thaliana accessions are further identified as accession-specific genes, most likely of recent origin in Arabidopsis thaliana. Putative de novo origination for two of the Arabidopsis thaliana-only genes is identified via additional sequencing across accessions of Arabidopsis thaliana and closely related sister species

Arabidopsis thaliana peroxidase N

DEFF Research Database (Denmark)

Mirza, Osman Asghar; Henriksen, A; Ostergaard, L

2000-01-01

The structure of the neutral peroxidase from Arabidopsis thaliana (ATP N) has been determined to a resolution of 1.9 A and a free R value of 20.5%. ATP N has the expected characteristic fold of the class III peroxidases, with a C(alpha) r.m.s.d. of 0.82 A when compared with horseradish peroxidase C...

Multiple reference genomes and transcriptomes for Arabidopsis thaliana

KAUST Repository

Gan, Xiangchao

2011-08-28

Genetic differences between Arabidopsis thaliana accessions underlie the plants extensive phenotypic variation, and until now these have been interpreted largely in the context of the annotated reference accession Col-0. Here we report the sequencing, assembly and annotation of the genomes of 18 natural A. thaliana accessions, and their transcriptomes. When assessed on the basis of the reference annotation, one-third of protein-coding genes are predicted to be disrupted in at least one accession. However, re-annotation of each genome revealed that alternative gene models often restore coding potential. Gene expression in seedlings differed for nearly half of expressed genes and was frequently associated with cis variants within 5 kilobases, as were intron retention alternative splicing events. Sequence and expression variation is most pronounced in genes that respond to the biotic environment. Our data further promote evolutionary and functional studies in A. thaliana, especially the MAGIC genetic reference population descended from these accessions. ©2011 Macmillan Publishers Limited. All rights reserved.

Multiple reference genomes and transcriptomes for Arabidopsis thaliana

KAUST Repository

Gan, Xiangchao; Stegle, Oliver; Behr, Jonas; Steffen, Joshua G.; Drewe, Philipp; Hildebrand, Katie L.; Lyngsoe, Rune; Schultheiss, Sebastian J.; Osborne, Edward J.; Sreedharan, Vipin T.; Kahles, André ; Bohnert, Regina; Jean, Gé raldine; Derwent, Paul; Kersey, Paul; Belfield, Eric J.; Harberd, Nicholas P.; Kemen, Eric; Toomajian, Christopher; Kover, Paula X.; Clark, Richard M.; Rä tsch, Gunnar; Mott, Richard

2011-01-01

Genetic differences between Arabidopsis thaliana accessions underlie the plants extensive phenotypic variation, and until now these have been interpreted largely in the context of the annotated reference accession Col-0. Here we report the sequencing, assembly and annotation of the genomes of 18 natural A. thaliana accessions, and their transcriptomes. When assessed on the basis of the reference annotation, one-third of protein-coding genes are predicted to be disrupted in at least one accession. However, re-annotation of each genome revealed that alternative gene models often restore coding potential. Gene expression in seedlings differed for nearly half of expressed genes and was frequently associated with cis variants within 5 kilobases, as were intron retention alternative splicing events. Sequence and expression variation is most pronounced in genes that respond to the biotic environment. Our data further promote evolutionary and functional studies in A. thaliana, especially the MAGIC genetic reference population descended from these accessions. ©2011 Macmillan Publishers Limited. All rights reserved.

WHEN STRESS AND DEVELOPMENT GO HAND IN HAND: MAIN HORMONAL CONTROLS OF ADVENTITIOUS ROOTING IN CUTTINGS

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Cibele Tesser Da Costa

2013-05-01

Full Text Available Adventitious rooting (AR is a multifactorial response leading to new roots at the base of stem cuttings, and the establishment of a complete and autonomous plant. AR has two main phases: a induction, with a requirement for higher auxin concentration; b formation, inhibited by high auxin and in which anatomical changes take place. The first stages of this process in severed organs necessarily include wounding and water stress responses which may trigger hormonal changes that contribute to reprogram target cells that are competent to respond to rooting stimuli. At severance, the roles of jasmonate and abscisic acid are critical for wound response and perhaps sink strength establishment, although their negative roles on the cell cycle may inhibit root induction. Strigolactones may also inhibit AR. A reduced cytokinin concentration in cuttings results from the separation of the root system, whose tips are a relevant source of these root induction inhibitors. The combined increased accumulation of basipetally transported auxins from the shoot apex at the cutting base is often sufficient for AR in easy-to-root species. The role of peroxidases and phenolic compounds in auxin catabolism may be critical at these early stages right after wounding. The events leading to AR strongly depend on mother plant nutritional status, both in terms of minerals and carbohydrates, as well as on sink establishment at cutting bases. Auxins play a central role in AR. Auxin transporters control auxin canalization to target cells. There, auxins act primarily through selective proteolysis and cell wall loosening, via their receptor proteins TIR1 and ABP1. A complex microRNA circuitry is involved in the control of auxin response factors essential for gene expression in AR. After root establishment, new hormonal controls take place, with auxins being required at lower concentrations for root meristem maintenance and cytokinins needed for root tissue differentiation.

Structure and function of homodomain-leucine zipper (HD-Zip) proteins.

Science.gov (United States)

Elhiti, Mohamed; Stasolla, Claudio

2009-02-01

Homeodomain-leucine zipper (HD-Zip) proteins are transcription factors unique to plants and are encoded by more than 25 genes in Arabidopsis thaliana. Based on sequence analyses these proteins have been classified into four distinct groups: HD-Zip I-IV. HD-Zip proteins are characterized by the presence of two functional domains; a homeodomain (HD) responsible for DNA binding and a leucine zipper domain (Zip) located immediately C-terminal to the homeodomain and involved in protein-protein interaction. Despite sequence similarities HD-ZIP proteins participate in a variety of processes during plant growth and development. HD-Zip I proteins are generally involved in responses related to abiotic stress, abscisic acid (ABA), blue light, de-etiolation and embryogenesis. HD-Zip II proteins participate in light response, shade avoidance and auxin signalling. Members of the third group (HD-Zip III) control embryogenesis, leaf polarity, lateral organ initiation and meristem function. HD-Zip IV proteins play significant roles during anthocyanin accumulation, differentiation of epidermal cells, trichome formation and root development.

Genome-scale cold stress response regulatory networks in ten Arabidopsis thaliana ecotypes

DEFF Research Database (Denmark)

Barah, Pankaj; Jayavelu, Naresh Doni; Rasmussen, Simon

2013-01-01

available from Arabidopsis thaliana 1001 genome project, we further investigated sequence polymorphisms in the core cold stress regulon genes. Significant numbers of non-synonymous amino acid changes were observed in the coding region of the CBF regulon genes. Considering the limited knowledge about......BACKGROUND: Low temperature leads to major crop losses every year. Although several studies have been conducted focusing on diversity of cold tolerance level in multiple phenotypically divergent Arabidopsis thaliana (A. thaliana) ecotypes, genome-scale molecular understanding is still lacking....... RESULTS: In this study, we report genome-scale transcript response diversity of 10 A. thaliana ecotypes originating from different geographical locations to non-freezing cold stress (10°C). To analyze the transcriptional response diversity, we initially compared transcriptome changes in all 10 ecotypes...

Arabidopsis homolog of trithorax1 (ATX1) is required for cell production, patterning, and morphogenesis in root development.

Science.gov (United States)

Napsucialy-Mendivil, Selene; Alvarez-Venegas, Raúl; Shishkova, Svetlana; Dubrovsky, Joseph G

2014-12-01

Arabidopsis homolog of trithorax1 (ATX1/SDG27), a known regulator of flower development, encodes a H3K4histone methyltransferase that maintains a number of genes in an active state. In this study, the role of ATX1 in root development was evaluated. The loss-of-function mutant atx1-1 was impaired in primary root growth. The data suggest that ATX1 controls root growth by regulating cell cycle duration, cell production, and the transition from cell proliferation in the root apical meristem (RAM) to cell elongation. In atx1-1, the quiescent centre (QC) cells were irregular in shape and more expanded than those of the wild type. This feature, together with the atypical distribution of T-divisions, the presence of oblique divisions, and the abnormal cell patterning in the RAM, suggests a lack of coordination between cell division and cell growth in the mutant. The expression domain of QC-specific markers was expanded both in the primary RAM and in the developing lateral root primordia of atx1-1 plants. These abnormalities were independent of auxin-response gradients. ATX1 was also found to be required for lateral root initiation, morphogenesis, and emergence. The time from lateral root initiation to emergence was significantly extended in the atx1-1 mutant. Overall, these data suggest that ATX1 is involved in the timing of root development, stem cell niche maintenance, and cell patterning during primary and lateral root development. Thus, ATX1 emerges as an important player in root system architecture. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

The KNOXI Transcription Factor SHOOT MERISTEMLESS Regulates Floral Fate in Arabidopsis.

Science.gov (United States)

Roth, Ohad; Alvarez, John; Levy, Matan; Bowman, John L; Ori, Naomi; Shani, Eilon

2018-05-09

Plants have evolved a unique and conserved developmental program that enables the conversion of leaves into floral organs. Elegant genetic and molecular work has identified key regulators of flower meristem identity. However, further understanding of flower meristem specification has been hampered by redundancy and by pleiotropic effects. The KNOXI transcription factor SHOOT MERISTEMLESS (STM) is a well-characterized regulator of shoot apical meristem maintenance. Arabidopsis thaliana stm loss-of-function mutants arrest shortly after germination, and therefore the knowledge on later roles of STM in later processes, including flower development, is limited. Here, we uncover a role for STM in the specification of flower meristem identity. Silencing STM in the APETALA1 (AP1) expression domain in the ap1-4 mutant background resulted in a leafy-flower phenotype, and an intermediate stm-2 allele enhanced the flower meristem identity phenotype of ap1-4. Transcriptional profiling of STM perturbation suggested that STM activity affects multiple floral fate genes, among them the F-Box protein-encoding gene UNUSUAL FLORAL ORGANS (UFO). In agreement with this notion, stm-2 enhanced the ufo-2 floral fate phenotype, and ectopic UFO expression rescued the leafy flowers in genetic backgrounds with compromised AP1 and STM activities. This work suggests a genetic mechanism that underlies the activity of STM in the specification of flower meristem identity. © 2018 American Society of Plant Biologists. All rights reserved.

A WUSCHEL-Independent Stem Cell Specification Pathway Is Repressed by PHB, PHV and CNA in Arabidopsis

Science.gov (United States)

Lee, Chunghee; Clark, Steven E.

2015-01-01

The homeostatic maintenance of stem cells that carry out continuous organogenesis at the shoot meristem is crucial for plant development. Key known factors act to signal between the stem cells and an underlying group of cells thought to act as the stem cell niche. In Arabidopsis thaliana the homeodomain transcription factor WUSCHEL (WUS) is essential for stem cell initiation and maintenance at shoot and flower meristems. Recent data suggest that the WUS protein may move from the niche cells directly into the stem cells to maintain stem cell identity. Here we provide evidence for a second, previously unknown, pathway for stem cell specification at shoot and flower meristems that bypasses the requirement for WUS. We demonstrate that this novel stem cell specification pathway is normally repressed by the activity of the HD-zip III transcription factors PHABULOSA (PHB), PHAVOLUTA (PHV) and CORONA (CNA). When de-repressed, this second stem cell pathway leads to an accumulation of stem cells and an enlargement of the stem cell niche. When de-repressed in a wus mutant background, this second stem cell pathway leads to functional meristems with largely normal cell layering and meristem morphology, activation of WUS cis regulatory elements, and extensive, but not indeterminate, organogenesis. Thus, WUS is largely dispensable for stem cell specification and meristem function, suggesting a set of key stem cell specification factors, competitively regulated by WUS and PHB/PHV/CNA, remain unidentified. PMID:26011610

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

Directory of Open Access Journals (Sweden)

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.

Investigating the Association between Flowering Time and Defense in the Arabidopsis thaliana-Fusarium oxysporum Interaction

Science.gov (United States)

Lyons, Rebecca; Rusu, Anca; Stiller, Jiri; Powell, Jonathan; Manners, John M.; Kazan, Kemal

2015-01-01

Plants respond to pathogens either by investing more resources into immunity which is costly to development, or by accelerating reproductive processes such as flowering time to ensure reproduction occurs before the plant succumbs to disease. In this study we explored the link between flowering time and pathogen defense using the interaction between Arabidopsis thaliana and the root infecting fungal pathogen Fusarium oxysporum. We report that F. oxysporum infection accelerates flowering time and regulates transcription of a number of floral integrator genes, including FLOWERING LOCUS C (FLC), FLOWERING LOCUS T (FT) and GIGANTEA (GI). Furthermore, we observed a positive correlation between late flowering and resistance to F. oxysporum in A. thaliana natural ecotypes. Late-flowering gi and autonomous pathway mutants also exhibited enhanced resistance to F. oxysporum, supporting the association between flowering time and defense. However, epistasis analysis showed that accelerating flowering time by deletion of FLC in fve-3 or fpa-7 mutants did not alter disease resistance, suggesting that the effect of autonomous pathway on disease resistance occurs independently from flowering time. Indeed, RNA-seq analyses suggest that fve-3 mediated resistance to F. oxysporum is most likely a result of altered defense-associated gene transcription. Together, our results indicate that the association between flowering time and pathogen defense is complex and can involve both pleiotropic and direct effects. PMID:26034991

The Interaction between Auxin and Nitric Oxide Regulates Root Growth in Response to Iron Deficiency in Rice

Directory of Open Access Journals (Sweden)

Huwei Sun

2017-12-01

Full Text Available Fe deficiency (-Fe is a common abiotic stress that affects the root development of plants. Auxin and nitric oxide (NO are key regulator of root growth under -Fe. However, the interactions between auxin and NO regulate root growth in response to Fe deficiency are complex and unclear. In this study, the indole-3-acetic acid (IAA and NO levels in roots, and the responses of root growth in rice to different levels of Fe supply were investigated using wild type (WT, ospin1b and osnia2 mutants. -Fe promoted LR formation but inhibited seminal root elongation. IAA levels, [3H] IAA transport, and expression levels of PIN1a-c genes in roots were reduced under -Fe, suggesting that polar auxin transport from shoots to roots was decreased. Application of IAA to -Fe seedlings restored seminal root length, but not LR density, to levels similar to those under normal Fe (+Fe, and the seminal root length was shorter in two ospin1b mutants relative to WT under +Fe, but not under -Fe, confirming that auxin transport participates in -Fe-inhibited seminal root elongation. Moreover, -Fe-induced LR density and -Fe-inhibited seminal root elongation paralleled NO production in roots. Interestingly, similar NO accumulation and responses of LR density and root elongation were observed in osnia2 mutants compared to WT, and the higher expression of NOA gene under -Fe, suggesting that -Fe-induced NO was generated via the NO synthase-like pathway rather than the nitrate reductase pathway. However, IAA could restore the functions of NO in inhibiting seminal root elongation, but did not replace the role of NO-induced LR formation under -Fe. Overall, our findings suggested that NO functions downstream of auxin in regulating LR formation; NO-inhibited seminal root elongation by decreasing meristem activity in root tips under -Fe, with the involvement of auxin.

Unraveling uranium induced oxidative stress related responses in Arabidopsis thaliana seedlings. Part II: responses in the leaves and general conclusions

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, Environmental Biology, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium); Cuypers, Ann [Hasselt University, Environmental Biology, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium); Horemans, Nele [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Remans, Tony; Opdenakker, Kelly; Smeets, Karen [Hasselt University, Environmental Biology, 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); Havaux, Michel [Commissariat a l' Energie Atomique (CEA)/Cadarache, Direction des Sciences du Vivant, Departement d' Ecophysiologie Vegetale et de Microbiologie, Laboratoire d' Ecophysiologie de la Photosynthese, 13108 Saint-Paul-lez-Durance (France); Wannijn, Jean; Van Hees, May [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Vangronsveld, Jaco [Hasselt University, Environmental Biology, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium); Vandenhove, Hildegarde [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium)

2011-06-15

The cellular redox balance seems an important modulator under heavy metal stress. While for other heavy metals these processes are well studied, oxidative stress related responses are also known to be triggered under uranium stress but information remains limited. This study aimed to further unravel the mechanisms by which plants respond to uranium stress. Seventeen-day-old Arabidopsis thaliana seedlings, grown on a modified Hoagland solution under controlled conditions, were exposed to 0, 0.1, 1, 10 and 100 {mu}M uranium for 1, 3 and 7 days. While in Part I of this study oxidative stress related responses in the roots were discussed, this second Part II discusses oxidative stress related responses in the leaves and general conclusions drawn from the results of the roots and the leaves will be presented. As several responses were already visible following 1 day exposure, when uranium concentrations in the leaves were negligible, a root-to-shoot signaling system was suggested in which plastids could be important sensing sites. While lipid peroxidation, based on the amount of thiobarbituric acid reactive compounds, was observed after exposure to 100 {mu}M uranium, affecting membrane structure and function, a transient concentration dependent response pattern was visible for lipoxygenase initiated lipid peroxidation. This transient character of uranium stress responses in leaves was emphasized by results of lipoxygenase (LOX2) and antioxidative enzyme transcript levels, enzyme capacities and glutathione concentrations both in time as with concentration. The ascorbate redox balance seemed an important modulator of uranium stress responses in the leaves as in addition to the previous transient responses, the total ascorbate concentration and ascorbate/dehydroascorbate redox balance increased in a concentration and time dependent manner. This could represent either a slow transient response or a stable increase with regard to plant acclimation to uranium stress

MPK6 controls H2 O2-induced root elongation by mediating Ca2+ influx across the plasma membrane of root cells in Arabidopsis seedlings.

Science.gov (United States)

Han, Shuan; Fang, Lin; Ren, Xuejian; Wang, Wenle; Jiang, Jing

2015-01-01

Mitogen-activated protein kinases (MPKs) play critical roles in signalling and growth, and Ca(2+) and H2 O2 control plant growth processes associated with abscisic acid (ABA). However, it remains unclear how MPKs are involved in H2 O2 - and Ca(2+) -mediated root elongation. Root elongation in seedlings of the loss-of-function mutant Atmpk6 (Arabidopsis thaliana MPK6) was less sensitive to moderate H2 O2 or ABA than that in wild-type (WT) plants. The enhanced elongation was a result of root cell expansion. This effect disappeared when ABA-induced H2 O2 accumulation or the cytosolic Ca(2+) increase were defective. Molecular and biochemical evidence showed that increased expression of the cell wall peroxidase PRX34 in Atmpk6 root cells enhanced apoplastic H2 O2 generation; this promoted a cytosolic Ca(2+) increase and Ca(2+) influx across the plasma membrane. The plasma membrane damage caused by high levels of H2 O2 was ameliorated in a Ca(2+) -dependent manner. These results suggested that there was intensified PRX34-mediated H2 O2 generation in the apoplast and increased Ca(2+) flux into the cytosol of Atmpk6 root cells; that is, the spatial separation of apoplastic H2 O2 from cytosolic Ca(2+) in root cells prevented H2 O2 -induced inhibition of root elongation in Atmpk6 seedlings. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Synchronisms and correlations of spring phenology between apical and lateral meristems in two boreal conifers.

Science.gov (United States)

Antonucci, Serena; Rossi, Sergio; Deslauriers, Annie; Lombardi, Fabio; Marchetti, Marco; Tognetti, Roberto

2015-10-01

Phenological synchronisms between apical and lateral meristems could clarify some aspects related to the physiological relationships among the different organs of trees. This study correlated the phenological phases of bud development and xylem differentiation during spring 2010-14 in balsam fir (Abies balsamea Mill.) and black spruce [(Picea mariana Mill. (BSP)] of the Monts-Valin National Park (Quebec, Canada) by testing the hypothesis that bud development occurs after the reactivation of xylem growth. From May to September, we conducted weekly monitoring of xylem differentiation using microcores and bud development with direct observations on terminal branches. Synchronism between the beginning of bud development and xylem differentiation was found in both species with significant correlations between the phases of bud and xylem phenology. Degree-day sum was more appropriate in assessing the date of bud growth resumption, while thermal thresholds were more suitable for cambium phenology. Our results provide new knowledge on the dynamics of spring phenology and novel information on the synchronisms between two meristems in coniferous trees. The study demonstrates the importance of precisely defining the phases of bud development in order to correctly analyse the relationships with xylem phenology. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Root defense analysis against Fusarium oxysporum reveals new regulators to confer resistance

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Chen, Yi Chung; Wong, Chin Lin; Muzzi, Frederico; Vlaardingerbroek, Ido; Kidd, Brendan N.; Schenk, Peer M.

2014-01-01

Fusarium oxysporum is a root-infecting fungal pathogen that causes wilt disease on a broad range of plant species, including Arabidopsis thaliana. Investigation of the defense response against this pathogen had primarily been conducted using leaf tissue and little was known about the root defense response. In this study, we profiled the expression of root genes after infection with F. oxysporum by microarray analysis. In contrast to the leaf response, root tissue did not show a strong induction of defense-associated gene expression and instead showed a greater proportion of repressed genes. Screening insertion mutants from differentially expressed genes in the microarray uncovered a role for the transcription factor ETHYLENE RESPONSE FACTOR72 (ERF72) in susceptibility to F. oxysporum. Due to the role of ERF72 in suppressing programmed cell death and detoxifying reactive oxygen species (ROS), we examined the pub22/pub23/pub24 U-box type E3 ubiquitin ligase triple mutant which is known to possess enhanced ROS production in response to pathogen challenge. We found that the pub22/23/24 mutant is more resistant to F. oxysporum infection, suggesting that a heightened innate immune response provides protection against F. oxysporum. We conclude that root-mediated defenses against soil-borne pathogens can be provided at multiple levels. PMID:24998294

Why is intracellular ice lethal? A microscopical study showing evidence of programmed cell death in cryo-exposed embryonic axes of recalcitrant seeds of Acer saccharinum

CSIR Research Space (South Africa)

Wesley-Smith, J

2015-10-01

Full Text Available Walters3,*, N. W. Pammenter1 and Patricia Berjak1,‡ 1Plant Germplasm Conservation Research, School of Life Sciences, University of KwaZulu-Natal (Westville Campus), Durban, 4001 South Africa, 2National Centre for Nanostructured Materials, Council.... In roots, regrowth occurred from the ground meristem and procambium, not the distal meristem, which became lethally damaged. Regrowth of shoots occurred from isolated pockets of surviving cells of peripheral and pith meristems. The size of these pockets...

Aberrant cell divisions in root meristeme of maize following exposure to X-rays low doses compared to similar effects of 50 Hz electromagnetic exposure

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Luchian T.

2012-04-01

Full Text Available The response of maize to radiation exposure was investigated by two cytogenetic methods considering the importance of the geno-toxic effect for environmental and agricultural purposes. Uniform genophond seeds, freshly germinated, were exposed to relatively low radiation doses using a radiotherapy X-ray applicator from a hospital irradiation device and to a 50 Hz electromagnetic field with about 10 mT magnetic induction (generated within laboratory assembled electromagnetic coils. Radicular meristeme tissue aliquots were prevailed for cytogenetic investigation based on microscopic observations and cell counting. Microscope slides were prepared following a specific procedure (squash technique and Feulgen method based on modified Carr reactive coloration. Mitotic index as well as chromosomal aberration percentage were calculated for more than 30,000 cells taken into account. From a qualitative viewpoint, chromosomal aberrations such as interchromatidian bridges, lagging and expelled chromosomes and multipolar divisions were evidenced - no distinct situation for either ionizing radiation or electromagnetic field being identified. The main quantitative difference consisted in the increased mitotic index for electromagnetic exposure increased times compared with the diminished mitotic index in the case of low X-ray doses.

The Aux/IAA gene rum1 involved in seminal and lateral root formation controls vascular patterning in maize (Zea mays L.) primary roots.

Science.gov (United States)

Zhang, Yanxiang; Paschold, Anja; Marcon, Caroline; Liu, Sanzhen; Tai, Huanhuan; Nestler, Josefine; Yeh, Cheng-Ting; Opitz, Nina; Lanz, Christa; Schnable, Patrick S; Hochholdinger, Frank

2014-09-01

The maize (Zea mays L.) Aux/IAA protein RUM1 (ROOTLESS WITH UNDETECTABLE MERISTEMS 1) controls seminal and lateral root initiation. To identify RUM1-dependent gene expression patterns, RNA-Seq of the differentiation zone of primary roots of rum1 mutants and the wild type was performed in four biological replicates. In total, 2 801 high-confidence maize genes displayed differential gene expression with Fc ≥2 and FDR ≤1%. The auxin signalling-related genes rum1, like-auxin1 (lax1), lax2, (nam ataf cuc 1 nac1), the plethora genes plt1 (plethora 1), bbm1 (baby boom 1), and hscf1 (heat shock complementing factor 1) and the auxin response factors arf8 and arf37 were down-regulated in the mutant rum1. All of these genes except nac1 were auxin-inducible. The maize arf8 and arf37 genes are orthologues of Arabidopsis MP/ARF5 (MONOPTEROS/ARF5), which controls the differentiation of vascular cells. Histological analyses of mutant rum1 roots revealed defects in xylem organization and the differentiation of pith cells around the xylem. Moreover, histochemical staining of enlarged pith cells surrounding late metaxylem elements demonstrated that their thickened cell walls displayed excessive lignin deposition. In line with this phenotype, rum1-dependent mis-expression of several lignin biosynthesis genes was observed. In summary, RNA-Seq of RUM1-dependent gene expression in maize primary roots, in combination with histological and histochemical analyses, revealed the specific regulation of auxin signal transduction components by RUM1 and novel functions of RUM1 in vascular development. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Elongation-related functions of LEAFY COTYLEDON1 during the development of Arabidopsis thaliana.

Science.gov (United States)

Junker, Astrid; Mönke, Gudrun; Rutten, Twan; Keilwagen, Jens; Seifert, Michael; Thi, Tuyet Minh Nguyen; Renou, Jean-Pierre; Balzergue, Sandrine; Viehöver, Prisca; Hähnel, Urs; Ludwig-Müller, Jutta; Altschmied, Lothar; Conrad, Udo; Weisshaar, Bernd; Bäumlein, Helmut

2012-08-01

The transcription factor LEAFY COTYLEDON1 (LEC1) controls aspects of early embryogenesis and seed maturation in Arabidopsis thaliana. To identify components of the LEC1 regulon, transgenic plants were derived in which LEC1 expression was inducible by dexamethasone treatment. The cotyledon-like leaves and swollen root tips developed by these plants contained seed-storage compounds and resemble the phenotypes produced by increased auxin levels. In agreement with this, LEC1 was found to mediate up-regulation of the auxin synthesis gene YUCCA10. Auxin accumulated primarily in the elongation zone at the root-hypocotyl junction (collet). This accumulation correlates with hypocotyl growth, which is either inhibited in LEC1-induced embryonic seedlings or stimulated in the LEC1-induced long-hypocotyl phenotype, therefore resembling etiolated seedlings. Chromatin immunoprecipitation analysis revealed a number of phytohormone- and elongation-related genes among the putative LEC1 target genes. LEC1 appears to be an integrator of various regulatory events, involving the transcription factor itself as well as light and hormone signalling, especially during somatic and early zygotic embryogenesis. Furthermore, the data suggest non-embryonic functions for LEC1 during post-germinative etiolation. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.

Biological effects of α-radiation exposure by 241Am in Arabidopsis thaliana seedlings are determined both by dose rate and 241Am distribution

International Nuclear Information System (INIS)

Biermans, Geert; Horemans, Nele; Vanhoudt, Nathalie; Vandenhove, Hildegarde; Saenen, Eline; Van Hees, May; Wannijn, Jean; Vangronsveld, Jaco; Cuypers, Ann

2015-01-01

Human activity has led to an increasing amount of radionuclides in the environment and subsequently to an increased risk of exposure of the biosphere to ionising radiation. Due to their high linear energy transfer, α-emitters form a threat to biota when absorbed or integrated in living tissue. Among these, 241 Am is of major concern due to high affinity for organic matter and high specific activity. This study examines the dose-dependent biological effects of α-radiation delivered by 241 Am at the morphological, physiological and molecular level in 14-day old seedlings of Arabidopsis thaliana after hydroponic exposure for 4 or 7 days. Our results show that 241 Am has high transfer to the roots but low translocation to the shoots. In the roots, we observed a transcriptional response of reactive oxygen species scavenging and DNA repair pathways. At the physiological and morphological level this resulted in a response which evolved from redox balance control and stable biomass at low dose rates to growth reduction, reduced transfer and redox balance decline at higher dose rates. This situation was also reflected in the shoots where, despite the absence of a transcriptional response, the control of photosynthesis performance and redox balance declined with increasing dose rate. The data further suggest that the effects in both organs were initiated in the roots, where the highest dose rates occurred, ultimately affecting photosynthesis performance and carbon assimilation. Though further detailed study of nutrient balance and 241 Am localisation is necessary, it is clear that radionuclide uptake and distribution is a major parameter in the global exposure effects on plant performance and health. - Highlights: • Arabidopsis thaliana was exposed hydroponically to a range of 241 Am concentrations. • Effects at molecular, morphological and physiological level were observed. • Effects were dependent on both dose rate and 241 Am distribution.

Genetic analysis of seed development in Arabidopsis thaliana = [Genetische analyse van de zaadontwikkeling in Arabidopsis thaliana

NARCIS (Netherlands)

Leon - Kloosterziel, K.

1997-01-01

This thesis deals with the genetic aspects of seed development in Arabidopsisthaliana. Mutants affected in several aspects of seed development and, more specifically, in seed maturation have been isolated by various selection

Heterologous Expression of Secreted Bacterial BPP and HAP Phytases in Plants Stimulates Arabidopsis thaliana Growth on Phytate

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Lia R. Valeeva

2018-02-01

Full Text Available Phytases are specialized phosphatases capable of releasing inorganic phosphate from myo-inositol hexakisphosphate (phytate, which is highly abundant in many soils. As inorganic phosphorus reserves decrease over time in many agricultural soils, genetic manipulation of plants to enable secretion of potent phytases into the rhizosphere has been proposed as a promising approach to improve plant phosphorus nutrition. Several families of biotechnologically important phytases have been discovered and characterized, but little data are available on which phytase families can offer the most benefits toward improving plant phosphorus intake. We have developed transgenic Arabidopsis thaliana plants expressing bacterial phytases PaPhyC (HAP family of phytases and 168phyA (BPP family under the control of root-specific inducible promoter Pht1;2. The effects of each phytase expression on growth, morphology and inorganic phosphorus accumulation in plants grown on phytate hydroponically or in perlite as the only source of phosphorus were investigated. The most enzymatic activity for both phytases was detected in cell wall-bound fractions of roots, indicating that these enzymes were efficiently secreted. Expression of both bacterial phytases in roots improved plant growth on phytate and resulted in larger rosette leaf area and diameter, higher phosphorus content and increased shoot dry weight, implying that these plants were indeed capable of utilizing phytate as the source of phosphorus for growth and development. When grown on phytate the HAP-type phytase outperformed its BPP-type counterpart for plant biomass production, though this effect was only observed in hydroponic conditions and not in perlite. Furthermore, we found no evidence of adverse side effects of microbial phytase expression in A. thaliana on plant physiology and seed germination. Our data highlight important functional differences between these members of bacterial phytase families and indicate

Heterologous Expression of Secreted Bacterial BPP and HAP Phytases in Plants Stimulates Arabidopsis thaliana Growth on Phytate.

Science.gov (United States)

Valeeva, Lia R; Nyamsuren, Chuluuntsetseg; Sharipova, Margarita R; Shakirov, Eugene V

2018-01-01

Phytases are specialized phosphatases capable of releasing inorganic phosphate from myo -inositol hexakisphosphate (phytate), which is highly abundant in many soils. As inorganic phosphorus reserves decrease over time in many agricultural soils, genetic manipulation of plants to enable secretion of potent phytases into the rhizosphere has been proposed as a promising approach to improve plant phosphorus nutrition. Several families of biotechnologically important phytases have been discovered and characterized, but little data are available on which phytase families can offer the most benefits toward improving plant phosphorus intake. We have developed transgenic Arabidopsis thaliana plants expressing bacterial phytases PaPhyC (HAP family of phytases) and 168phyA (BPP family) under the control of root-specific inducible promoter Pht1;2 . The effects of each phytase expression on growth, morphology and inorganic phosphorus accumulation in plants grown on phytate hydroponically or in perlite as the only source of phosphorus were investigated. The most enzymatic activity for both phytases was detected in cell wall-bound fractions of roots, indicating that these enzymes were efficiently secreted. Expression of both bacterial phytases in roots improved plant growth on phytate and resulted in larger rosette leaf area and diameter, higher phosphorus content and increased shoot dry weight, implying that these plants were indeed capable of utilizing phytate as the source of phosphorus for growth and development. When grown on phytate the HAP-type phytase outperformed its BPP-type counterpart for plant biomass production, though this effect was only observed in hydroponic conditions and not in perlite. Furthermore, we found no evidence of adverse side effects of microbial phytase expression in A. thaliana on plant physiology and seed germination. Our data highlight important functional differences between these members of bacterial phytase families and indicate that future

Heterologous Expression of Secreted Bacterial BPP and HAP Phytases in Plants Stimulates Arabidopsis thaliana Growth on Phytate

Science.gov (United States)

Valeeva, Lia R.; Nyamsuren, Chuluuntsetseg; Sharipova, Margarita R.; Shakirov, Eugene V.

2018-01-01

Phytases are specialized phosphatases capable of releasing inorganic phosphate from myo-inositol hexakisphosphate (phytate), which is highly abundant in many soils. As inorganic phosphorus reserves decrease over time in many agricultural soils, genetic manipulation of plants to enable secretion of potent phytases into the rhizosphere has been proposed as a promising approach to improve plant phosphorus nutrition. Several families of biotechnologically important phytases have been discovered and characterized, but little data are available on which phytase families can offer the most benefits toward improving plant phosphorus intake. We have developed transgenic Arabidopsis thaliana plants expressing bacterial phytases PaPhyC (HAP family of phytases) and 168phyA (BPP family) under the control of root-specific inducible promoter Pht1;2. The effects of each phytase expression on growth, morphology and inorganic phosphorus accumulation in plants grown on phytate hydroponically or in perlite as the only source of phosphorus were investigated. The most enzymatic activity for both phytases was detected in cell wall-bound fractions of roots, indicating that these enzymes were efficiently secreted. Expression of both bacterial phytases in roots improved plant growth on phytate and resulted in larger rosette leaf area and diameter, higher phosphorus content and increased shoot dry weight, implying that these plants were indeed capable of utilizing phytate as the source of phosphorus for growth and development. When grown on phytate the HAP-type phytase outperformed its BPP-type counterpart for plant biomass production, though this effect was only observed in hydroponic conditions and not in perlite. Furthermore, we found no evidence of adverse side effects of microbial phytase expression in A. thaliana on plant physiology and seed germination. Our data highlight important functional differences between these members of bacterial phytase families and indicate that future crop

The ethylene-inhibitor aminoethoxyvinylglycine restores normal nodulation by Rhizobium leguminosarum biovar. viciae on Vicia sativa subsp. nigra by suppressing the 'Thick and short roots' phenotype.

Science.gov (United States)

Zaat, S A; Van Brussel, A A; Tak, T; Lugtenberg, B J; Kijne, J W

1989-02-01

Nodulation of Vicia sativa subsp. nigra L. by Rhizobium bacteria is coupled to the development of thick and short roots (Tsr). This root phenotype as well as root-hair induction (Hai) and root-hair deformation (Had) are caused by a factor(s) produced by the bacteria in response to plant flavonoids. When very low inoculum concentrations (0.5-5 bacteria·ml(-1)) were used, V. sativa plants did not develop the Tsr phenotype and became nodulated earlier than plants with Tsr roots. Furthermore, the nodules of these plants were located on the primary root in contrast to nodules on Tsr roots, which were all located at sites of lateral-root emergence. The average numbers of nodules per plant were not significantly different for these two types of nodulation. Root-growth inhibition and Hai, but not Had, could be mimicked by ethephon, and inhibited by aminoethoxyvinylglycine (AVG). Addition of AVG to co-cultures of Vicia sativa and the standard inoculum concentration of 5·10(5) bacteria·ml(-1) suppressed the development of the Tsr phenotype and restored nodulation to the pattern that was observed with very low concentrations of bacteria (0.5-5 bacteria·ml(-1)). The delay in nodulation on Tsr roots appeared to be caused by the fact that nodule meristems did not develop on the primary root, but only on the emerging laterals. The relationship between Tsr, Hai, Had, and nodulation is discussed.

Role of Translocted Signals in Regulating Root Development and Nutrient Uptake in Legumes

Energy Technology Data Exchange (ETDEWEB)

Atkins, C. A. [School of Plant Biology, University of Western Australia, Crawley, WA (Australia)

2013-11-15

Uptake of nutrients is achieved through the expression and activity of specific carrier/transporter mechanisms localized in the root system and distributed as a consequence of the development of the architecture of the system. Both root system development and the nutrient transport mechanisms are responsive to environmental factors that include nutrient supply and availability, water supply, salinity, soil acidity and compaction together with a wide range of biotic stresses. The response to each may be regulated at the molecular level by both local and systemic signals. These signals include the classical plant growth regulators but also low molecular weight compounds such as sugars and amino acids as well as macromolecules, including peptides, proteins and nucleic acids. Among the latter, recent research has shown that small RNA species and especially small interfering RNAs (siRNA) and microRNAs (miRNA) are potent and effective regulators of gene expression which, in the context of root development as well as nutrient uptake, have central and critical roles. Systemic (translocated) signals that specifically regulate root development and function are less well defined but analyses of phloem exudate in species of lupin (Lupinus albus and L. angustifolius) and species of Brassica and cucurbits have demonstrated that a wide range of macromolecules, including miRNAs, are present and potentially translocated from source organs (principally leaves) to sinks (shoot apical meristems, developing fruits and seeds, roots and nodules). While specific signaling roles for many of these macromolecules are yet to be discovered there are some that have been documented and their regulatory activity in organ development and functioning, as well as in nutrition, confirmed. The following article provides an up to date review and presents the results of recent research using lupin with emphasis on the analysis of small RNAs and their likely role(s) in regulation of root development and

A root specific induction of carotenoid biosynthesis contributes to ABA production upon salt stress in arabidopsis.

Directory of Open Access Journals (Sweden)

M Águila Ruiz-Sola

Full Text Available Abscisic acid (ABA is a hormone that plays a vital role in mediating abiotic stress responses in plants. Salt exposure induces the synthesis of ABA through the cleavage of carotenoid precursors (xanthophylls, which are found at very low levels in roots. Here we show that de novo ABA biosynthesis in salt-treated Arabidopsis thaliana roots involves an organ-specific induction of the carotenoid biosynthetic pathway. Upregulation of the genes encoding phytoene synthase (PSY and other enzymes of the pathway producing ABA precursors was observed in roots but not in shoots after salt exposure. A pharmacological block of the carotenoid pathway substantially reduced ABA levels in stressed roots, confirming that an increase in carotenoid accumulation contributes to fuel hormone production after salt exposure. Treatment with exogenous ABA was also found to upregulate PSY expression only in roots, suggesting an organ-specific feedback regulation of the carotenoid pathway by ABA. Taken together, our results show that the presence of high concentrations of salt in the growth medium rapidly triggers a root-specific activation of the carotenoid pathway, probably to ensure a proper supply of ABA precursors required for a sustained production of the hormone.

Origin, timing, and gene expression profile of adventitious rooting in Arabidopsis hypocotyls and stems.

Science.gov (United States)

Welander, Margareta; Geier, Thomas; Smolka, Anders; Ahlman, Annelie; Fan, Jing; Zhu, Li-Hua

2014-02-01

Adventitious root (AR) formation is indispensable for vegetative propagation, but difficult to achieve in many crops. Understanding its molecular mechanisms is thus important for such species. Here we aimed at developing a rooting protocol for direct AR formation in stems, locating cellular AR origins in stems and exploring molecular differences underlying adventitious rooting in hypocotyls and stems. In-vitro-grown hypocotyls or stems of wild-type and transgenic ecotype Columbia (Col-0) of Arabidopsis thaliana were rooted on rooting media. Anatomy of AR formation, qRT-PCR of some rooting-related genes and in situ GUS expression were carried out during rooting from hypocotyls and stems. We developed a rooting protocol for AR formation in stems and traced back root origins in stems by anatomical and in situ expression studies. Unlike rooting in hypocotyls, rooting in stems was slower, and AR origins were mainly from lateral parenchyma of vascular bundles and neighboring starch sheath cells as well as, to a lesser extent, from phloem cap and xylem parenchyma. Transcript levels of GH3-3, LBD16, LBD29, and LRP1 in hypocotyls and stems were similar, but transcript accumulation was delayed in stems. In situ expression signals of DR5::GUS, LBD16::GUS, LBD29::GUS, and rolB::GUS reporters in stems mainly occurred at the root initiation sites, suggesting their involvement in AR formation. We have developed an efficient rooting protocol using half-strength Lepoivre medium for studying AR formation in stems, traced back the cellular AR origins in stems, and correlated expression of rooting-related genes with root initiation sites.

Inhibition of phospholipase C disrupts cytoskeletal organization and gravitropic growth in Arabidopsis roots.

Science.gov (United States)

Andreeva, Zornitza; Barton, Deborah; Armour, William J; Li, Min Y; Liao, Li-Fen; McKellar, Heather L; Pethybridge, Kylie A; Marc, Jan

2010-10-01

The phospholipase protein superfamily plays an important role in hormonal signalling and cellular responses to environmental stimuli. There is also growing evidence for interactions between phospholipases and the cytoskeleton. In this report we used a pharmacological approach to investigate whether inhibiting a member of the phospholipase superfamily, phospholipase C (PLC), affects microtubules and actin microfilaments as well as root growth and morphology of Arabidopsis thaliana seedlings. Inhibiting PLC activity using the aminosteroid U73122 significantly inhibited root elongation and disrupted root morphology in a concentration-dependent manner, with the response being saturated at 5 μM, whereas the inactive analogue U73343 was ineffective. The primary root appeared to lose growth directionality accompanied by root waving and formation of curls. Immunolabelling of roots exposed to increasingly higher U73122 concentrations revealed that the normal transverse arrays of cortical microtubules in the elongation zone became progressively more disorganized or depolymerized, with the disorganization appearing within 1 h of incubation. Likewise, actin microfilament arrays also were disrupted. Inhibiting PLC using an alternative inhibitor, neomycin, caused similar disruptions to both cytoskeletal organization and root morphology. In seedlings gravistimulated by rotating the culture plates by 90°, both U73122 and neomycin disrupted the normal gravitropic growth of roots and etiolated hypocotyls. The effects of PLC inhibitors are therefore consistent with the notion that, as with phospholipases A and D, PLC likewise interacts with the cytoskeleton, alters growth morphology, and is involved in gravitropism.

Abscisic acid analogs as chemical probes for dissection of abscisic acid responses in Arabidopsis thaliana.

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Benson, Chantel L; Kepka, Michal; Wunschel, Christian; Rajagopalan, Nandhakishore; Nelson, Ken M; Christmann, Alexander; Abrams, Suzanne R; Grill, Erwin; Loewen, Michele C

2015-05-01

Abscisic acid (ABA) is a phytohormone known to mediate numerous plant developmental processes and responses to environmental stress. In Arabidopsis thaliana, ABA acts, through a genetically redundant family of ABA receptors entitled Regulatory Component of ABA Receptor (RCAR)/Pyrabactin Resistant 1 (PYR1)/Pyrabactin Resistant-Like (PYL) receptors comprised of thirteen homologues acting in concert with a seven-member set of phosphatases. The individual contributions of A. thaliana RCARs and their binding partners with respect to specific physiological functions are as yet poorly understood. Towards developing efficacious plant growth regulators selective for specific ABA functions and tools for elucidating ABA perception, a panel of ABA analogs altered specifically on positions around the ABA ring was assembled. These analogs have been used to probe thirteen RCARs and four type 2C protein phosphatases (PP2Cs) and were also screened against representative physiological assays in the model plant Arabidopsis. The 1'-O methyl ether of (S)-ABA was identified as selective in that, at physiologically relevant levels, it regulates stomatal aperture and improves drought tolerance, but does not inhibit germination or root growth. Analogs with the 7'- and 8'-methyl groups of the ABA ring replaced with bulkier groups generally retained the activity and stereoselectivity of (S)- and (R)-ABA, while alteration of the 9'-methyl group afforded an analog that substituted for ABA in inhibiting germination but neither root growth nor stomatal closure. Further in vitro testing indicated differences in binding of analogs to individual RCARs, as well as differences in the enzyme activity resulting from specific PP2Cs bound to RCAR-analog complexes. Ultimately, these findings highlight the potential of a broader chemical genetics approach for dissection of the complex network mediating ABA-perception, signaling and functionality within a given species and modifications in the future design

A quantitative and dynamic model for plant stem cell regulation.

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Florian Geier

Full Text Available Plants maintain pools of totipotent stem cells throughout their entire life. These stem cells are embedded within specialized tissues called meristems, which form the growing points of the organism. The shoot apical meristem of the reference plant Arabidopsis thaliana is subdivided into several distinct domains, which execute diverse biological functions, such as tissue organization, cell-proliferation and differentiation. The number of cells required for growth and organ formation changes over the course of a plants life, while the structure of the meristem remains remarkably constant. Thus, regulatory systems must be in place, which allow for an adaptation of cell proliferation within the shoot apical meristem, while maintaining the organization at the tissue level. To advance our understanding of this dynamic tissue behavior, we measured domain sizes as well as cell division rates of the shoot apical meristem under various environmental conditions, which cause adaptations in meristem size. Based on our results we developed a mathematical model to explain the observed changes by a cell pool size dependent regulation of cell proliferation and differentiation, which is able to correctly predict CLV3 and WUS over-expression phenotypes. While the model shows stem cell homeostasis under constant growth conditions, it predicts a variation in stem cell number under changing conditions. Consistent with our experimental data this behavior is correlated with variations in cell proliferation. Therefore, we investigate different signaling mechanisms, which could stabilize stem cell number despite variations in cell proliferation. Our results shed light onto the dynamic constraints of stem cell pool maintenance in the shoot apical meristem of Arabidopsis in different environmental conditions and developmental states.

Effect of Arabinogalactan Proteins from the Root Caps of Pea and Brassica napus on Aphanomyces euteiches Zoospore Chemotaxis and Germination12[C][W

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Cannesan, Marc Antoine; Durand, Caroline; Burel, Carole; Gangneux, Christophe; Lerouge, Patrice; Ishii, Tadashi; Laval, Karine; Follet-Gueye, Marie-Laure; Driouich, Azeddine; Vicré-Gibouin, Maïté

2012-01-01

Root tips of many plant species release a number of border, or border-like, cells that are thought to play a major role in the protection of root meristem. However, little is currently known on the structure and function of the cell wall components of such root cells. Here, we investigate the sugar composition of the cell wall of the root cap in two species: pea (Pisum sativum), which makes border cells, and Brassica napus, which makes border-like cells. We find that the cell walls are highly enriched in arabinose and galactose, two major residues of arabinogalactan proteins. We confirm the presence of arabinogalactan protein epitopes on root cap cell walls using immunofluorescence microscopy. We then focused on these proteoglycans by analyzing their carbohydrate moieties, linkages, and electrophoretic characteristics. The data reveal (1) significant structural differences between B. napus and pea root cap arabinogalactan proteins and (2) a cross-link between these proteoglycans and pectic polysaccharides. Finally, we assessed the impact of root cap arabinogalactan proteins on the behavior of zoospores of Aphanomyces euteiches, an oomycetous pathogen of pea roots. We find that although the arabinogalactan proteins of both species induce encystment and prevent germination, the effects of both species are similar. However, the arabinogalactan protein fraction from pea attracts zoospores far more effectively than that from B. napus. This suggests that root arabinogalactan proteins are involved in the control of early infection of roots and highlights a novel role for these proteoglycans in root-microbe interactions. PMID:22645070

Evidence for functional interaction between brassinosteroids and cadmium response in Arabidopsis thaliana.

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Villiers, Florent; Jourdain, Agnès; Bastien, Olivier; Leonhardt, Nathalie; Fujioka, Shozo; Tichtincky, Gabrielle; Parcy, François; Bourguignon, Jacques; Hugouvieux, Véronique

2012-02-01

Plant hormones, in addition to regulating growth and development, are involved in biotic and abiotic stress responses. To investigate whether a hormone signalling pathway plays a role in the plant response to the heavy metal cadmium (Cd), gene expression data in response to eight hormone treatments were retrieved from the Genevestigator Arabidopsis thaliana database and compared with published microarray analysis performed on plants challenged with Cd. Across more than 3000 Cd-regulated genes, statistical approaches and cluster analyses highlighted that gene expression in response to Cd and brassinosteroids (BR) showed a significant similarity. Of note, over 75% of the genes showing consistent (e.g. opposite) regulation upon BR and Brz (BR biosynthesis inhibitor) exposure exhibited a BR-like response upon Cd exposure. This phenomenon was confirmed by qPCR analysis of the expression level of 10 BR-regulated genes in roots of Cd-treated wild-type (WT) plants. Although no change in BR content was observed in response to Cd in our experimental conditions, adding epibrassinolide (eBL, a synthetic brassinosteroid) to WT plants significantly enhanced Cd-induced root growth inhibition, highlighting a synergistic response between eBL and the metal. This effect was specific to this hormone treatment. On the other hand, dwarf1 seedlings, showing a reduced BR level, exhibited decreased root growth inhibition in response to Cd compared with WT, reversed by the addition of eBL. Similar results were obtained on Brz-treated WT plants. These results argue in favour of an interaction between Cd and BR signalling that modulates plant sensitivity, and opens new perspectives to understand the plant response to Cd.

Cytokinins Are Initial Targets of Light in the Control of Bud Outgrowth(1[OPEN])

Czech Academy of Sciences Publication Activity Database

Roman, H.; Girault, T.; Barbier, F.; Peron, T.; Brouard, N.; Pěnčík, Aleš; Novák, Ondřej; Vian, A.; Sakr, S.; Lothier, J.; Le Gourrierec, J.; Leduc, N.

2016-01-01

Roč. 172, č. 1 (2016), s. 489-509 ISSN 0032-0889 R&D Projects: GA MŠk(CZ) LO1204; GA MŠk LK21306 Institutional support: RVO:61389030 Keywords : cell-cycle regulation * pea axillary buds * oryza-sativa l. * apical dominance * rosa sp * arabidopsis-thaliana * lateral buds * meristem activity * plant-responses * acts downstream Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.456, year: 2016

Modification of genetic effect of gamma-irradiation by electric current

International Nuclear Information System (INIS)

Grigor'eva, N.N.; Shakhbazov, V.G.

1983-01-01

The effect of direct current of different polarity on genetic sequels of #betta#-radiation of Vicia faba seedlings is studied. It is established that weak current might modify genetic sequels of #betta#-radiation. Protective current effect on irradiated meristem cells of seedlings manifests at negative polarization of the meristem before radiation and at positive polarization-after radiation. Modifying effect of electric current is brought about at the expense of redistribution of anions and cations between the meristem and other root zones

Azospirillum brasilense ameliorates the response of Arabidopsis thaliana to drought mainly via enhancement of ABA levels.

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Cohen, Ana C; Bottini, Rubén; Pontin, Mariela; Berli, Federico J; Moreno, Daniela; Boccanlandro, Hernán; Travaglia, Claudia N; Piccoli, Patricia N

2015-01-01

Production of phytohormones is one of the main mechanisms to explain the beneficial effects of plant growth-promoting rhizobacteria (PGPR) such as Azospirillum sp. The PGPRs induce plant growth and development, and reduce stress susceptibility. However, little is known regarding the stress-related phytohormone abscisic acid (ABA) produced by bacteria. We investigated the effects of Azospirillum brasilense Sp 245 strain on Arabidopsis thaliana Col-0 and aba2-1 mutant plants, evaluating the morphophysiological and biochemical responses when watered and in drought. We used an in vitro-grown system to study changes in the root volume and architecture after inoculation with Azospirillum in Arabidopsis wild-type Col-0 and on the mutant aba2-1, during early growth. To examine Arabidopsis development and reproductive success as affected by the bacteria, ABA and drought, a pot experiment using Arabidopsis Col-0 plants was also carried out. Azospirillum brasilense augmented plant biomass, altered root architecture by increasing lateral roots number, stimulated photosynthetic and photoprotective pigments and retarded water loss in correlation with incremented ABA levels. As well, inoculation improved plants seed yield, plants survival, proline levels and relative leaf water content; it also decreased stomatal conductance, malondialdehyde and relative soil water content in plants submitted to drought. Arabidopsis inoculation with A. brasilense improved plants performance, especially in drought. © 2014 Scandinavian Plant Physiology Society.

Ectopic expression of AtPAD4 broadens resistance of soybean to soybean cyst and root-knot nematodes.

Science.gov (United States)

Youssef, Reham M; MacDonald, Margaret H; Brewer, Eric P; Bauchan, Gary R; Kim, Kyung-Hwan; Matthews, Benjamin F

2013-04-25

The gene encoding PAD4 (PHYTOALEXIN-DEFICIENT4) is required in Arabidopsis for expression of several genes involved in the defense response to Pseudomonas syringae pv. maculicola. AtPAD4 (Arabidopsis thaliana PAD4) encodes a lipase-like protein that plays a regulatory role mediating salicylic acid signaling. We expressed the gene encoding AtPAD4 in soybean roots of composite plants to test the ability of AtPAD4 to deter plant parasitic nematode development. The transformed roots were challenged with two different plant parasitic nematode genera represented by soybean cyst nematode (SCN; Heterodera glycines) and root-knot nematode (RKN; Meloidogyne incognita). Expression of AtPAD4 in soybean roots decreased the number of mature SCN females 35 days after inoculation by 68 percent. Similarly, soybean roots expressing AtPAD4 exhibited 77 percent fewer galls when challenged with RKN. Our experiments show that AtPAD4 can be used in an economically important crop, soybean, to provide a measure of resistance to two different genera of nematodes.

Innate Immune Responses Activated in Arabidopsis Roots by Microbe-Associated Molecular Patterns[W][OA

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Millet, Yves A.; Danna, Cristian H.; Clay, Nicole K.; Songnuan, Wisuwat; Simon, Matthew D.; Werck-Reichhart, Danièle; Ausubel, Frederick M.

2010-01-01

Despite the fact that roots are the organs most subject to microbial interactions, very little is known about the response of roots to microbe-associated molecular patterns (MAMPs). By monitoring transcriptional activation of β-glucuronidase reporters and MAMP-elicited callose deposition, we show that three MAMPs, the flagellar peptide Flg22, peptidoglycan, and chitin, trigger a strong tissue-specific response in Arabidopsis thaliana roots, either at the elongation zone for Flg22 and peptidoglycan or in the mature parts of the roots for chitin. Ethylene signaling, the 4-methoxy-indole-3-ylmethylglucosinolate biosynthetic pathway, and the PEN2 myrosinase, but not salicylic acid or jasmonic acid signaling, play major roles in this MAMP response. We also show that Flg22 induces the cytochrome P450 CYP71A12-dependent exudation of the phytoalexin camalexin by Arabidopsis roots. The phytotoxin coronatine, an Ile-jasmonic acid mimic produced by Pseudomonas syringae pathovars, suppresses MAMP-activated responses in the roots. This suppression requires the E3 ubiquitin ligase COI1 as well as the transcription factor JIN1/MYC2 but does not rely on salicylic acid–jasmonic acid antagonism. These experiments demonstrate the presence of highly orchestrated and tissue-specific MAMP responses in roots and potential pathogen-encoded mechanisms to block these MAMP-elicited signaling pathways. PMID:20348432

Analysis of Transcriptional Responses of the Inflorescence Meristems in Jatropha curcas Following Gibberellin Treatment

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Wen-Kai Hui

2018-02-01

Full Text Available Jatropha curcas L. seeds an oilseed plant with great potential for biodiesel production. However, low seed yield, which was limited by its lower female flowers, was a major drawback for its utilization. Our previous study found that the flower number and female-to-male ratio were increased by gibberellin treatment. Here, we compared the transcriptomic profiles of inflorescence meristem at different time points after gibberellic acid A3 (GA3 treatment. The present study showed that 951 differentially expressed genes were obtained in response to gibberellin treatment, compared with control samples. The 6-h time point was an important phase in the response to exogenous gibberellin. Furthermore, the plant endogenous gibberellin, auxin, ethylene, abscisic acid, and brassinolide-signaling transduction pathways were repressed, whereas the genes associated with cytokinin and jasmonic acid signaling were upregulated for 24-h time point following GA3 treatment. In addition, the floral meristem determinacy genes (JcLFY, JcSOC1 and floral organ identity genes (JcAP3, JcPI, JcSEP1-3 were significantly upregulated, but their negative regulator (JcSVP was downregulated after GA3 treatment. Moreover, the effects of phytohormone, which was induced by exogenous plant growth regulator, mainly acted on the female floral differentiation process. To the best of our knowledge, this data is the first comprehensive analysis of the underlying transcriptional response mechanism of floral differentiation following GA3 treatment in J. curcas, which helps in engineering high-yielding varieties of Jatropha.

Localized Iron Supply Triggers Lateral Root Elongation in Arabidopsis by Altering the AUX1-Mediated Auxin Distribution[C][W][OA

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Giehl, Ricardo F.H.; Lima, Joni E.; von Wirén, Nicolaus

2012-01-01

Root system architecture depends on nutrient availability, which shapes primary and lateral root development in a nutrient-specific manner. To better understand how nutrient signals are integrated into root developmental programs, we investigated the morphological response of Arabidopsis thaliana roots to iron (Fe). Relative to a homogeneous supply, localized Fe supply in horizontally separated agar plates doubled lateral root length without having a differential effect on lateral root number. In the Fe uptake-defective mutant iron-regulated transporter1 (irt1), lateral root development was severely repressed, but a requirement for IRT1 could be circumvented by Fe application to shoots, indicating that symplastic Fe triggered the local elongation of lateral roots. The Fe-stimulated emergence of lateral root primordia and root cell elongation depended on the rootward auxin stream and was accompanied by a higher activity of the auxin reporter DR5-β-glucuronidase in lateral root apices. A crucial role of the auxin transporter AUXIN RESISTANT1 (AUX1) in Fe-triggered lateral root elongation was indicated by Fe-responsive AUX1 promoter activities in lateral root apices and by the failure of the aux1-T mutant to elongate lateral roots into Fe-enriched agar patches. We conclude that a local symplastic Fe gradient in lateral roots upregulates AUX1 to accumulate auxin in lateral root apices as a prerequisite for lateral root elongation. PMID:22234997

Efficient method of protein extraction from Theobroma cacao L. roots for two-dimensional gel electrophoresis and mass spectrometry analyses.

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Bertolde, F Z; Almeida, A-A F; Silva, F A C; Oliveira, T M; Pirovani, C P

2014-07-04

Theobroma cacao is a woody and recalcitrant plant with a very high level of interfering compounds. Standard protocols for protein extraction were proposed for various types of samples, but the presence of interfering compounds in many samples prevented the isolation of proteins suitable for two-dimensional gel electrophoresis (2-DE). An efficient method to extract root proteins for 2-DE was established to overcome these problems. The main features of this protocol are: i) precipitation with trichloroacetic acid/acetone overnight to prepare the acetone dry powder (ADP), ii) several additional steps of sonication in the ADP preparation and extractions with dense sodium dodecyl sulfate and phenol, and iii) adding two stages of phenol extractions. Proteins were extracted from roots using this new protocol (Method B) and a protocol described in the literature for T. cacao leaves and meristems (Method A). Using these methods, we obtained a protein yield of about 0.7 and 2.5 mg per 1.0 g lyophilized root, and a total of 60 and 400 spots could be separated, respectively. Through Method B, it was possible to isolate high-quality protein and a high yield of roots from T. cacao for high-quality 2-DE gels. To demonstrate the quality of the extracted proteins from roots of T. cacao using Method B, several protein spots were cut from the 2-DE gels, analyzed by tandem mass spectrometry, and identified. Method B was further tested on Citrus roots, with a protein yield of about 2.7 mg per 1.0 g lyophilized root and 800 detected spots.