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1.
Nucleic Acids Res ; 49(15): 8900-8922, 2021 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-34370034

RESUMO

In eukaryotes, the major nuclear export pathway for mature mRNAs uses the dimeric receptor TAP/p15, which is recruited to mRNAs via the multisubunit TREX complex, comprising the THO core and different export adaptors. Viruses that replicate in the nucleus adopt different strategies to hijack cellular export factors and achieve cytoplasmic translation of their mRNAs. No export receptors are known in plants, but Arabidopsis TREX resembles the mammalian complex, with a conserved hexameric THO core associated with ALY and UIEF proteins, as well as UAP56 and MOS11. The latter protein is an orthologue of mammalian CIP29. The nuclear export mechanism for viral mRNAs has not been described in plants. To understand this process, we investigated the export of mRNAs of the pararetrovirus CaMV in Arabidopsis and demonstrated that it is inhibited in plants deficient in ALY, MOS11 and/or TEX1. Deficiency for these factors renders plants partially resistant to CaMV infection. Two CaMV proteins, the coat protein P4 and reverse transcriptase P5, are important for nuclear export. P4 and P5 interact and co-localise in the nucleus with the cellular export factor MOS11. The highly structured 5' leader region of 35S RNAs was identified as an export enhancing element that interacts with ALY1, ALY3 and MOS11 in vitro.


Assuntos
Regiões 5' não Traduzidas , Proteínas de Arabidopsis/metabolismo , Núcleo Celular/virologia , RNA Mensageiro/metabolismo , RNA Viral/metabolismo , Proteínas Virais/metabolismo , Transporte Ativo do Núcleo Celular , Arabidopsis/virologia , Proteínas de Arabidopsis/fisiologia , Proteínas do Capsídeo/metabolismo , Caulimovirus/genética , Caulimovirus/metabolismo , Núcleo Celular/metabolismo , Doenças das Plantas/virologia , RNA Viral/química , DNA Polimerase Dirigida por RNA/metabolismo
2.
J Exp Bot ; 72(8): 3044-3060, 2021 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-33543244

RESUMO

Shoot branching is a pivotal process during plant growth and development, and is antagonistically orchestrated by auxin and sugars. In contrast to extensive investigations on hormonal regulatory networks, our current knowledge on the role of sugar signalling pathways in bud outgrowth is scarce. Based on a comprehensive stepwise strategy, we investigated the role of glycolysis/the tricarboxylic acid (TCA) cycle and the oxidative pentose phosphate pathway (OPPP) in the control of bud outgrowth. We demonstrated that these pathways are necessary for bud outgrowth promotion upon plant decapitation and in response to sugar availability. They are also targets of the antagonistic crosstalk between auxin and sugar availability. The two pathways act synergistically to down-regulate the expression of BRC1, a conserved inhibitor of shoot branching. Using Rosa calluses stably transformed with GFP-fused promoter sequences of RhBRC1 (pRhBRC1), glycolysis/TCA cycle and the OPPP were found to repress the transcriptional activity of pRhBRC1 cooperatively. Glycolysis/TCA cycle- and OPPP-dependent regulations involve the -1973/-1611 bp and -1206/-709 bp regions of pRhBRC1, respectively. Our findings indicate that glycolysis/TCA cycle and the OPPP are integrative parts of shoot branching control and can link endogenous factors to the developmental programme of bud outgrowth, likely through two distinct mechanisms.


Assuntos
Rosa , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos , Brotos de Planta , Açúcares
4.
New Phytol ; 227(5): 1376-1391, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32343843

RESUMO

The mTERF gene family encodes for nucleic acid binding proteins that are predicted to regulate organellar gene expression in eukaryotes. Despite the implication of this gene family in plant development and response to abiotic stresses, a precise molecular function was assigned to only a handful number of its c. 30 members in plants. Using a reverse genetics approach in Arabidopsis thaliana and combining molecular and biochemical techniques, we revealed new functions for the chloroplast mTERF protein, MDA1. We demonstrated that MDA1 associates in vivo with components of the plastid-encoded RNA polymerase and transcriptional active chromosome complexes. MDA1 protein binds in vivo and in vitro with specificity to 27-bp DNA sequences near the 5'-end of psbE and ndhA chloroplast genes to stimulate their transcription, and additionally promotes the stabilization of the 5'-ends of processed psbE and ndhA messenger (m)RNAs. Finally, we provided evidence that MDA1 function in gene transcription likely coordinates RNA folding and the action of chloroplast RNA-binding proteins on mRNA stabilization. Our results provide examples for the unexpected implication of DNA binding proteins and gene transcription in the regulation of mRNA stability in chloroplasts, blurring the boundaries between DNA and RNA metabolism in this organelle.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Cloroplastos/genética , Proteínas de Cloroplastos/metabolismo , Cloroplastos/genética , Cloroplastos/metabolismo , Regulação da Expressão Gênica de Plantas , Mutação , Óperon , Fatores de Transcrição
5.
Development ; 145(23)2018 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-30389856

RESUMO

The thickening of plant organs is supported by secondary growth, a process by which new vascular tissues (xylem and phloem) are produced. Xylem is composed of several cell types, including xylary fibers, parenchyma and vessel elements. In Arabidopsis, it has been shown that fibers are promoted by the class-I KNOX gene KNAT1 and the plant hormones gibberellins, and are repressed by a small set of receptor-like kinases; however, we lack a mechanistic framework to integrate their relative contributions. Here, we show that DELLAs, negative elements of the gibberellin signaling pathway, physically interact with KNAT1 and impair its binding to KNAT1-binding sites. Our analysis also indicates that at least 37% of the transcriptome mobilized by KNAT1 is potentially dependent on this interaction, and includes genes involved in secondary cell wall modifications and phenylpropanoid biosynthesis. Moreover, the promotion by constitutive overexpression of KNAT1 of fiber formation and the expression of genes required for fiber differentiation were still reverted by DELLA accumulation, in agreement with post-translational regulation of KNAT1 by DELLA proteins. These results suggest that gibberellins enhance fiber development by promoting KNAT1 activity.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citologia , Arabidopsis/metabolismo , Diferenciação Celular , Giberelinas/farmacologia , Proteínas de Homeodomínio/metabolismo , Xilema/citologia , Xilema/metabolismo , Arabidopsis/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Mutação com Ganho de Função/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Fenótipo , Feixe Vascular de Plantas/efeitos dos fármacos , Feixe Vascular de Plantas/metabolismo , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , Transcriptoma/efeitos dos fármacos , Transcriptoma/genética , Xilema/efeitos dos fármacos
6.
Plant Cell ; 30(6): 1353-1374, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29848768

RESUMO

In Arabidopsis thaliana, ARGONAUTE1 (AGO1) plays a central role in microRNA (miRNA) and small interfering RNA (siRNA)-mediated silencing and is a key component in antiviral responses. The polerovirus F-box P0 protein triggers AGO1 degradation as a viral counterdefense. Here, we identified a motif in AGO1 that is required for its interaction with the S phase kinase-associated protein1-cullin 1-F-box protein (SCF) P0 (SCFP0) complex and subsequent degradation. The AGO1 P0 degron is conserved and confers P0-mediated degradation to other AGO proteins. Interestingly, the degron motif is localized in the DUF1785 domain of AGO1, in which a single point mutation (ago1-57, obtained by forward genetic screening) compromises recognition by SCFP0 Recapitulating formation of the RNA-induced silencing complex in a cell-free system revealed that this mutation impairs RNA unwinding, leading to stalled forms of AGO1 still bound to double-stranded RNAs. In vivo, the DUF1785 is required for unwinding perfectly matched siRNA duplexes, but is mostly dispensable for unwinding imperfectly matched miRNA duplexes. Consequently, its mutation nearly abolishes phased siRNA production and sense transgene posttranscriptional gene silencing. Overall, our work sheds new light on the mode of AGO1 recognition by P0 and the in vivo function of DUF1785 in RNA silencing.


Assuntos
Arabidopsis/metabolismo , RNA de Cadeia Dupla/genética , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas Argonauta/genética , Proteínas Argonauta/metabolismo , Proteínas F-Box/genética , Proteínas F-Box/metabolismo , Mutação Puntual/genética , Interferência de RNA
7.
Plant Physiol ; 176(4): 2834-2850, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29472278

RESUMO

The plant cell cycle is tightly regulated by factors that integrate endogenous cues and environmental signals to adapt plant growth to changing conditions. Under drought, cell division in young leaves is blocked by an active mechanism, reducing the evaporative surface and conserving energy resources. The molecular function of cyclin-dependent kinase-inhibitory proteins (CKIs) in regulating the cell cycle has already been well studied, but little is known about their involvement in cell cycle regulation under adverse growth conditions. In this study, we show that the transcript of the CKI gene SIAMESE-RELATED1 (SMR1) is quickly induced under moderate drought in young Arabidopsis (Arabidopsis thaliana) leaves. Functional characterization further revealed that SMR1 inhibits cell division and affects meristem activity, thereby restricting the growth of leaves and roots. Moreover, we demonstrate that SMR1 is a short-lived protein that is degraded by the 26S proteasome after being ubiquitinated by a Cullin-RING E3 ubiquitin ligase. Consequently, overexpression of a more stable variant of the SMR1 protein leads to a much stronger phenotype than overexpression of the native SMR1. Under moderate drought, both the SMR1 transcript and SMR1 protein accumulate. Despite this induction, smr1 mutants do not show overall tolerance to drought stress but do show less growth inhibition of young leaves under drought. Surprisingly, the growth-repressive hormone ethylene promotes SMR1 induction, but the classical drought hormone abscisic acid does not.


Assuntos
Proteínas de Arabidopsis/genética , Secas , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Proteínas Nucleares/genética , Folhas de Planta/genética , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Ciclo Celular/genética , Meristema/genética , Meristema/crescimento & desenvolvimento , Meristema/metabolismo , Mutação , Proteínas Nucleares/metabolismo , Fenótipo , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Plantas Geneticamente Modificadas
8.
Plant Cell ; 28(9): 2043-2059, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27531226

RESUMO

In eukaryotes, DNA repair pathways help to maintain genome integrity and epigenomic patterns. However, the factors at the nexus of DNA repair and chromatin modification/remodeling remain poorly characterized. Here, we uncover a previously unrecognized interplay between the DNA repair factor DNA DAMAGE BINDING PROTEIN2 (DDB2) and the DNA methylation machinery in Arabidopsis thaliana Loss-of-function mutation in DDB2 leads to genome-wide DNA methylation alterations. Genetic and biochemical evidence indicate that at many repeat loci, DDB2 influences de novo DNA methylation by interacting with ARGONAUTE4 and by controlling the local abundance of 24-nucleotide short interfering RNAs (siRNAs). We also show that DDB2 regulates active DNA demethylation mediated by REPRESSOR OF SILENCING1 and DEMETER LIKE3. Together, these findings reveal a role for the DNA repair factor DDB2 in shaping the Arabidopsis DNA methylation landscape in the absence of applied genotoxic stress.

9.
Curr Biol ; 24(16): 1923-8, 2014 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-25127215

RESUMO

Regulation of plant height, one of the most important agronomic traits, is the focus of intensive research for improving crop performance. Stem elongation takes place as a result of repeated cell divisions and subsequent elongation of cells produced by apical and intercalary meristems. The gibberellin (GA) phytohormones have long been known to control stem and internodal elongation by stimulating the degradation of nuclear growth-repressing DELLA proteins; however, the mechanism allowing GA-responsive growth is only slowly emerging. Here, we show that DELLAs directly regulate the activity of the plant-specific class I TCP transcription factor family, key regulators of cell proliferation. Our results demonstrate that class I TCP factors directly bind the promoters of core cell-cycle genes in Arabidopsis inflorescence shoot apices while DELLAs block TCP function by binding to their DNA-recognition domain. GAs antagonize such repression by promoting DELLA destruction and therefore cause a concomitant accumulation of TCP factors on promoters of cell-cycle genes. Consistent with this model, the quadruple mutant tcp8 tcp14 tcp15 tcp22 exhibits severe dwarfism and reduced responsiveness to GA action. Altogether, we conclude that GA-regulated DELLA-TCP interactions in inflorescence shoot apex provide a novel mechanism to control plant height.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Giberelinas/metabolismo , Inflorescência/genética , Inflorescência/crescimento & desenvolvimento , Inflorescência/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Brotos de Planta/genética , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
10.
Front Plant Sci ; 4: 480, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24348487

RESUMO

During interphase, the microtubular cytoskeleton of cycling plant cells is organized in both cortical and perinuclear arrays. Perinuclear microtubules (MTs) are nucleated from γ-Tubulin Complexes (γ-TuCs) located at the surface of the nucleus. The molecular mechanisms of γ-TuC association to the nuclear envelope (NE) are currently unknown. The γ-TuC Protein 3 (GCP3)-Interacting Protein 1 (GIP1) is the smallest γ-TuC component identified so far. AtGIP1 and its homologous protein AtGIP2 participate in the localization of active γ-TuCs at interphasic and mitotic MT nucleation sites. Arabidopsis gip1gip2 mutants are impaired in establishing a fully functional mitotic spindle and exhibit severe developmental defects. In this study, gip1gip2 knock down mutants were further characterized at the cellular level. In addition to defects in both the localization of γ-TuC core proteins and MT fiber robustness, gip1gip2 mutants exhibited a severe alteration of the nuclear shape associated with an abnormal distribution of the nuclear pore complexes. Simultaneously, they showed a misorganization of the inner nuclear membrane protein AtSUN1. Furthermore, AtGIP1 was identified as an interacting partner of AtTSA1 which was detected, like the AtGIP proteins, at the NE. These results provide the first evidence for the involvement of a γ-TuC component in both nuclear shaping and NE organization. Functional hypotheses are discussed in order to propose a model for a GIP-dependent nucleo-cytoplasmic continuum.

11.
Proc Natl Acad Sci U S A ; 109(39): 15942-6, 2012 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-23019378

RESUMO

Posttranscriptional gene silencing (PTGS) mediated by siRNAs is an evolutionarily conserved antiviral defense mechanism in higher plants and invertebrates. In this mechanism, viral-derived siRNAs are incorporated into the RNA-induced silencing complex (RISC) to guide degradation of the corresponding viral RNAs. In Arabidopsis, a key component of RISC is ARGONAUTE1 (AGO1), which not only binds to siRNAs but also carries the RNA slicer activity. At present little is known about posttranslational mechanisms regulating AGO1 turnover. Here we report that the viral suppressor of RNA silencing protein P0 triggers AGO1 degradation by the autophagy pathway. Using a P0-inducible transgenic line, we observed that AGO1 degradation is blocked by inhibition of autophagy. The engineering of a functional AGO1 fluorescent reporter protein further indicated that AGO1 colocalizes with autophagy-related (ATG) protein 8a (ATG8a) positive bodies when degradation is impaired. Moreover, this pathway also degrades AGO1 in a nonviral context, especially when the production of miRNAs is impaired. Our results demonstrate that a selective process such as ubiquitylation can lead to the degradation of a key regulatory protein such as AGO1 by a degradation process generally believed to be unspecific. We anticipate that this mechanism will not only lead to degradation of AGO1 but also of its associated proteins and eventually small RNAs.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Proteínas Argonauta/metabolismo , Autofagia , Proteólise , Arabidopsis/genética , Arabidopsis/virologia , Proteínas de Arabidopsis/genética , Proteínas Argonauta/genética , Inativação Gênica , MicroRNAs/genética , MicroRNAs/metabolismo , Vírus de Plantas/genética , Vírus de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/virologia , RNA de Plantas/genética , RNA de Plantas/metabolismo , RNA Viral/genética , RNA Viral/metabolismo , Complexo de Inativação Induzido por RNA/genética , Complexo de Inativação Induzido por RNA/metabolismo , Ubiquitinação/genética
12.
Plant Cell ; 24(8): 3307-19, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22892320

RESUMO

Gibberellins (GAs) are plant hormones involved in the regulation of plant growth in response to endogenous and environmental signals. GA promotes growth by stimulating the degradation of nuclear growth-repressing DELLA proteins. In Arabidopsis thaliana, DELLAs consist of a small family of five proteins that display distinct but also overlapping functions in repressing GA responses. This study reveals that DELLA RGA-LIKE3 (RGL3) protein is essential to fully enhance the jasmonate (JA)-mediated responses. We show that JA rapidly induces RGL3 expression in a CORONATINE INSENSITIVE1 (COI1)- and JASMONATE INSENSITIVE1 (JIN1/MYC2)-dependent manner. In addition, we demonstrate that MYC2 binds directly to RGL3 promoter. Furthermore, we show that RGL3 (like the other DELLAs) interacts with JA ZIM-domain (JAZ) proteins, key repressors of JA signaling. These findings suggest that JA/MYC2-dependent accumulation of RGL3 represses JAZ activity, which in turn enhances the expression of JA-responsive genes. Accordingly, we show that induction of primary JA-responsive genes is reduced in the rgl3-5 mutant and enhanced in transgenic lines overexpressing RGL3. Hence, RGL3 positively regulates JA-mediated resistance to the necrotroph Botrytis cinerea and susceptibility to the hemibiotroph Pseudomonas syringae. We propose that JA-mediated induction of RGL3 expression is of adaptive significance and might represent a recent functional diversification of the DELLAs.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Ciclopentanos/farmacologia , Oxilipinas/farmacologia , Transdução de Sinais , Adaptação Biológica , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Arabidopsis/microbiologia , Proteínas de Arabidopsis/genética , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Botrytis/patogenicidade , Ciclopentanos/metabolismo , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Giberelinas/farmacologia , Imunoprecipitação , Oxilipinas/metabolismo , Doenças das Plantas/microbiologia , Plantas Geneticamente Modificadas/efeitos dos fármacos , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/microbiologia , Regiões Promotoras Genéticas , Ligação Proteica , Mapeamento de Interação de Proteínas , Pseudomonas syringae/patogenicidade , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Técnicas do Sistema de Duplo-Híbrido
13.
PLoS One ; 4(3): e4780, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19277118

RESUMO

In fungi and metazoans, the SCF-type Ubiquitin protein ligases (E3s) play a critical role in cell cycle regulation by degrading negative regulators, such as cell cycle-dependent kinase inhibitors (CKIs) at the G1-to-S-phase checkpoint. Here we report that FBL17, an Arabidopsis thaliana F-box protein, is involved in cell cycle regulation during male gametogenesis. FBL17 expression is strongly enhanced in plants co-expressing E2Fa and DPa, transcription factors that promote S-phase entry. FBL17 loss-of-function mutants fail to undergo pollen mitosis II, which generates the two sperm cells in mature A. thaliana pollen. Nonetheless, the single sperm cell-like cell in fbl17 mutants is functional but will exclusively fertilize the egg cell of the female gametophyte, giving rise to an embryo that will later abort, most likely due to the lack of functional endosperm. Seed abortion can, however, be overcome by mutations in FIE, a component of the Polycomb group complex, overall resembling loss-of-function mutations in the A. thaliana cyclin-dependent kinase CDKA;1. Finally we identified ASK11, as an SKP1-like partner protein of FBL17 and discuss a possible mechanism how SCF(FBL17) may regulate cell division during male gametogenesis.


Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/fisiologia , Proteínas F-Box/fisiologia , Pólen/crescimento & desenvolvimento , Arabidopsis/embriologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/fisiologia , Motivos F-Box , Fertilização , Germinação , Humanos , Mitose/fisiologia , Peptídeo Hidrolases/metabolismo , Pólen/citologia , Processamento de Proteína Pós-Traducional , Proteínas Repressoras/fisiologia , Sementes , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/fisiologia , Ubiquitinação
14.
Curr Biol ; 17(18): 1609-14, 2007 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-17869110

RESUMO

Plant and animal viruses encode suppressor proteins of an adaptive immunity mechanism in which viral double-stranded RNA is processed into 21-25 nt short interfering (si)RNAs. The siRNAs guide ARGONAUTE (AGO) proteins so that they target viral RNA. Most viral suppressors bind long dsRNA or siRNAs and thereby prevent production of siRNA or binding of siRNA to AGO. The one exception is the 2b suppressor of Cucumoviruses that binds to and inhibits AGO1. Here we describe a novel suppressor mechanism in which a Polerovirus-encoded F box protein (P0) targets the PAZ motif and its adjacent upstream sequence in AGO1 and mediates its degradation. F box proteins are components of E3 ubiquitin ligase complexes that add polyubiquitin tracts on selected lysine residues and thereby mark a protein for proteasome-mediated degradation. With P0, however, the targeted degradation of AGO is insensitive to inhibition of the proteasome, indicating that the proteasome is not involved. We also show that P0 does not block a mobile signal of silencing, indicating that the signal molecule does not have AGO protein components. The ability of P0 to block silencing without affecting signal movement may contribute to the phloem restriction of viruses in the Polerovirus group.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/virologia , Proteínas F-Box/metabolismo , Luteoviridae/fisiologia , Interferência de RNA , Proteínas Virais/metabolismo , Motivos de Aminoácidos , Arabidopsis/metabolismo , Proteínas Argonauta , Proteínas F-Box/genética , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/virologia , Complexo de Endopeptidases do Proteassoma/genética , Complexo de Endopeptidases do Proteassoma/metabolismo , RNA Interferente Pequeno/metabolismo , Transdução de Sinais , Tabaco/genética , Proteínas Virais/genética
15.
Plant Cell Physiol ; 46(7): 1046-53, 2005 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15863435

RESUMO

Root hairs are an excellent model system to study cell developmental processes as they are easily accessible, single-celled, long tubular extensions of root epidermal cells. In a genetic approach to identify loci important for root hair development, we have isolated eight der (deformed root hairs) mutants from an ethylmethanesulfonate (EMS)-mutagenized Arabidopsis population. The der lines represent five new loci involved in root hair development and show a variety of abnormalities in root hair morphology, indicating that different root hair developmental stages are affected. A double mutant analysis with the short root hair actin2 mutant der1-2 confirmed that the der mutants are disturbed at different time points of root hair formation. Auxin and ethylene are known to be important for trichoblast cell fate determination and root hair elongation. Here, we show that they are able to suppress the phenotype of two der mutants. As the auxin- and ethylene-responsive der mutants are affected at different stages of root hair formation, our results demonstrate that the function of auxin and ethylene is not limited to cell differentiation and root hair elongation but that the two hormones are effective throughout the whole root hair developmental process.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/genética , Mutação/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/genética , Alelos , Arabidopsis/anatomia & histologia , Arabidopsis/efeitos dos fármacos , Mapeamento Cromossômico , Segregação de Cromossomos , Cruzamentos Genéticos , Etilenos/farmacologia , Genes de Plantas/genética , Ácidos Indolacéticos/farmacologia , Fenótipo , Raízes de Plantas/citologia , Raízes de Plantas/efeitos dos fármacos
16.
Plant Physiol ; 131(3): 1313-26, 2003 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-12644681

RESUMO

We have searched the Arabidopsis and rice (Oryza sativa) genomes for homologs of LRX1, an Arabidopsis gene encoding a novel type of cell wall protein containing a leucine-rich repeat (LRR) and an extensin domain. Eleven and eight LRX (LRR/EXTENSIN) genes have been identified in these two plant species, respectively. The LRX gene family encodes proteins characterized by a short N-terminal domain, a domain with 10 LRRs, a cysteine-rich motif, and a variable C-terminal extensin-like domain. Phylogenetic analysis performed on the conserved domains indicates the existence of two major clades of LRX proteins that arose before the eudicot/monocot divergence and then diversified independently in each lineage. In Arabidopsis, gene expression studies by northern hybridization and promoter::uidA fusions showed that the two phylogenetic clades represent a specialization into "reproductive" and "vegetative" LRXs. The four Arabidopsis genes of the "reproductive" clade are specifically expressed in pollen, whereas the seven "vegetative" genes are predominantly expressed in various sporophytic tissues. This separation into two expression classes is also supported by previous studies on maize (Zea mays) and tomato (Lycopersicon esculentum) LRX homologs and by information on available rice ESTs. The strong conservation of the amino acids responsible for the putative recognition specificity of the LRR domain throughout the family suggests that the LRX proteins interact with similar ligands.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Parede Celular/metabolismo , Genoma de Planta , Oryza/genética , Sequência de Aminoácidos , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Sequência Conservada/genética , Regulação da Expressão Gênica de Plantas , Glicoproteínas/genética , Glicoproteínas/metabolismo , Magnoliopsida/genética , Magnoliopsida/metabolismo , Dados de Sequência Molecular , Família Multigênica/genética , Oryza/crescimento & desenvolvimento , Oryza/metabolismo , Filogenia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Proteínas/genética , Proteínas/metabolismo , Reprodução/genética , Homologia de Sequência de Aminoácidos , Especificidade por Substrato
17.
Plant Physiol ; 129(4): 1464-72, 2002 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12177460

RESUMO

Root hairs develop as long extensions from root epidermal cells. After the formation of an initial bulge at the distal end of the epidermal cell, the root hair structure elongates by tip growth. Because root hairs are not surrounded by other cells, root hair formation provides an excellent system for studying the highly complex process of plant cell growth. Pharmacological experiments with actin filament-interfering drugs have provided evidence that the actin cytoskeleton is an important factor in the establishment of cell polarity and in the maintenance of the tip growth machinery at the apex of the growing root hair. However, there has been no genetic evidence to directly support this assumption. We have isolated an Arabidopsis mutant, deformed root hairs 1 (der1), that is impaired in root hair development. The DER1 locus was cloned by map-based cloning and encodes ACTIN2 (ACT2), a major actin of the vegetative tissue. The three der1 alleles develop the mutant phenotype to different degrees and are all missense mutations, thus providing the means to study the effect of partially functional ACT2. The detailed characterization of the der1 phenotypes revealed that ACT2 is not only involved in root hair tip growth, but is also required for correct selection of the bulge site on the epidermal cell. Thus, the der1 mutants are useful tools to better understand the function of the actin cytoskeleton in the process of root hair formation.


Assuntos
Actinas/genética , Arabidopsis/genética , Raízes de Plantas/crescimento & desenvolvimento , Actinas/química , Alelos , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Diferenciação Celular/genética , Extensões da Superfície Celular/genética , Teste de Complementação Genética , Microscopia Eletrônica de Varredura , Mutação , Fenótipo , Epiderme Vegetal/genética , Epiderme Vegetal/crescimento & desenvolvimento , Raízes de Plantas/genética , Raízes de Plantas/ultraestrutura , Plantas Geneticamente Modificadas , Conformação Proteica
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