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1.
Plant J ; 108(4): 1020-1036, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34510583

RESUMO

Underdeveloped (small) embryos embedded in abundant endosperm tissue, and thus having morphological dormancy (MD) or morphophysiological dormancy (MPD), are considered to be the ancestral state in seed dormancy evolution. This trait is retained in the Apiaceae family, which provides excellent model systems for investigating the underpinning mechanisms. We investigated Apium graveolens (celery) MD by combined innovative imaging and embryo growth assays with the quantification of hormone metabolism, as well as the analysis of hormone and cell-wall related gene expression. The integrated experimental results demonstrated that embryo growth occurred inside imbibed celery fruits in association with endosperm degradation, and that a critical embryo size was required for radicle emergence. The regulation of these processes depends on gene expression leading to gibberellin and indole-3-acetic acid (IAA) production by the embryo and on crosstalk between the fruit compartments. ABA degradation associated with distinct spatiotemporal patterns in ABA sensitivity control embryo growth, endosperm breakdown and radicle emergence. This complex interaction between gibberellins, IAA and ABA metabolism, and changes in the tissue-specific sensitivities to these hormones is distinct from non-MD seeds. We conclude that the embryo growth to reach the critical size and the associated endosperm breakdown inside MD fruits constitute a unique germination programme.

2.
Cell Rep ; 35(11): 109263, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-34133931

RESUMO

The interplay between the phytohormone abscisic acid (ABA) and the gasotransmitter nitric oxide (NO) regulates seed germination and post-germinative seedling growth. We show that GAP1 (germination in ABA and cPTIO 1) encodes the transcription factor ANAC089 with a critical membrane-bound domain and extranuclear localization. ANAC089 mutants lacking the membrane-tethered domain display insensitivity to ABA, salt, and osmotic and cold stresses, revealing a repressor function. Whole-genome transcriptional profiling and DNA-binding specificity reveals that ANAC089 regulates ABA- and redox-related genes. ANAC089 truncated mutants exhibit higher NO and lower ROS and ABA endogenous levels, alongside an altered thiol and disulfide homeostasis. Consistently, translocation of ANAC089 to the nucleus is directed by changes in cellular redox status after treatments with NO scavengers and redox-related compounds. Our results reveal ANAC089 to be a master regulator modulating redox homeostasis and NO levels, able to repress ABA synthesis and signaling during Arabidopsis seed germination and abiotic stress.

4.
New Phytol ; 229(4): 2179-2191, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-32970853

RESUMO

How the biophysical properties of overlaying tissues control growth, such as the embryonic root (radicle) during seed germination, is a fundamental question. In eudicot seeds the endosperm surrounding the radicle confers coat dormancy and controls germination responses through modulation of its cell wall mechanical properties. Far less is known for grass caryopses that differ in tissue morphology. Here we report that the coleorhiza, a sheath-like organ that surrounds the radicle in grass embryos, performs the same role in the grass weed Avena fatua (common wild oat). We combined innovative biomechanical techniques, tissue ablation, microscopy, tissue-specific gene and enzyme activity expression with the analysis of hormones and oligosaccharides. The combined experimental work demonstrates that in grass caryopses the coleorhiza indeed controls germination for which we provide direct biomechanical evidence. We show that the coleorhiza becomes reinforced during dormancy maintenance and weakened during germination. Xyloglucan endotransglycosylases/hydrolases may have a role in coleorhiza reinforcement through cell wall remodelling to confer coat dormancy. The control of germination by coleorhiza-enforced dormancy in grasses is an example of the convergent evolution of mechanical restraint by overlaying tissues.


Assuntos
Germinação , Dormência de Plantas , Avena , Endosperma , Sementes
5.
Nat Commun ; 8(1): 72, 2017 07 13.
Artigo em Inglês | MEDLINE | ID: mdl-28706187

RESUMO

The time of seed germination is a major decision point in the life of plants determining future growth and development. This timing is controlled by seed dormancy, which prevents germination under favourable conditions. The plant hormone abscisic acid (ABA) and the protein DELAY OF GERMINATION 1 (DOG1) are essential regulators of dormancy. The function of ABA in dormancy is rather well understood, but the role of DOG1 is still unknown. Here, we describe four phosphatases that interact with DOG1 in seeds. Two of them belong to clade A of type 2C protein phosphatases: ABA-HYPERSENSITIVE GERMINATION 1 (AHG1) and AHG3. These phosphatases have redundant but essential roles in the release of seed dormancy epistatic to DOG1. We propose that the ABA and DOG1 dormancy pathways converge at clade A of type 2C protein phosphatases.The DOG1 protein is a major regulator of seed dormancy in Arabidopsis. Here, Née et al. provide evidence that DOG1 can interact with the type 2C protein phosphatases AHG1 and AHG3 and that this represents the convergence point of the DOG1-regulated dormancy pathway and signalling by the plant hormone abscisic acid.


Assuntos
Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Fosfoproteínas Fosfatases/metabolismo , Dormência de Plantas/genética , Sementes/crescimento & desenvolvimento , Arabidopsis , Germinação/genética , Sementes/metabolismo , Transdução de Sinais
6.
PLoS Genet ; 11(12): e1005737, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26684465

RESUMO

The Arabidopsis protein DELAY OF GERMINATION 1 (DOG1) is a key regulator of seed dormancy, which is a life history trait that determines the timing of seedling emergence. The amount of DOG1 protein in freshly harvested seeds determines their dormancy level. DOG1 has been identified as a major dormancy QTL and variation in DOG1 transcript levels between accessions contributes to natural variation for seed dormancy. The DOG1 gene is alternatively spliced. Alternative splicing increases the transcriptome and proteome diversity in higher eukaryotes by producing transcripts that encode for proteins with altered or lost function. It can also generate tissue specific transcripts or affect mRNA stability. Here we suggest a different role for alternative splicing of the DOG1 gene. DOG1 produces five transcript variants encoding three protein isoforms. Transgenic dog1 mutant seeds expressing single DOG1 transcript variants from the endogenous DOG1 promoter did not complement because they were non-dormant and lacked DOG1 protein. However, transgenic plants overexpressing single DOG1 variants from the 35S promoter could accumulate protein and showed complementation. Simultaneous expression of two or more DOG1 transcript variants from the endogenous DOG1 promoter also led to increased dormancy levels and accumulation of DOG1 protein. This suggests that single isoforms are functional, but require the presence of additional isoforms to prevent protein degradation. Subsequently, we found that the DOG1 protein can bind to itself and that this binding is required for DOG1 function but not for protein accumulation. Natural variation for DOG1 binding efficiency was observed among Arabidopsis accessions and contributes to variation in seed dormancy.


Assuntos
Processamento Alternativo/genética , Proteínas de Arabidopsis/genética , Arabidopsis/genética , Dormência de Plantas/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/biossíntese , Regulação da Expressão Gênica de Plantas , Germinação/genética , Mutação , Fenótipo , Plantas Geneticamente Modificadas , Ligação Proteica , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Locos de Características Quantitativas , Sementes/genética , Sementes/crescimento & desenvolvimento
7.
Plant Cell ; 26(11): 4362-75, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25415980

RESUMO

Seed dormancy determines germination timing and contributes to crop production and the adaptation of natural populations to their environment. Our knowledge about its regulation is limited. In a mutagenesis screen of a highly dormant Arabidopsis thaliana line, the reduced dormancy5 (rdo5) mutant was isolated based on its strongly reduced seed dormancy. Cloning of RDO5 showed that it encodes a PP2C phosphatase. Several PP2C phosphatases belonging to clade A are involved in abscisic acid signaling and control seed dormancy. However, RDO5 does not cluster with clade A phosphatases, and abscisic acid levels and sensitivity are unaltered in the rdo5 mutant. RDO5 transcript could only be detected in seeds and was most abundant in dry seeds. RDO5 was found in cells throughout the embryo and is located in the nucleus. A transcriptome analysis revealed that several genes belonging to the conserved PUF family of RNA binding proteins, in particular Arabidopsis PUMILIO9 (APUM9) and APUM11, showed strongly enhanced transcript levels in rdo5 during seed imbibition. Further transgenic analyses indicated that APUM9 reduces seed dormancy. Interestingly, reduction of APUM transcripts by RNA interference complemented the reduced dormancy phenotype of rdo5, indicating that RDO5 functions by suppressing APUM transcript levels.


Assuntos
Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Regulação da Expressão Gênica de Plantas , Fosfoproteínas Fosfatases/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Proteínas de Ligação a RNA/metabolismo , Transdução de Sinais , Arabidopsis/genética , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Perfilação da Expressão Gênica , Germinação , Mutação , Fenótipo , Fosfoproteínas Fosfatases/genética , Dormência de Plantas , Plantas Geneticamente Modificadas , Proteína Fosfatase 2C , Proteínas de Ligação a RNA/genética , Sementes/enzimologia , Sementes/genética , Sementes/fisiologia
8.
Plant Cell ; 24(7): 2826-38, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22829147

RESUMO

Seed dormancy controls the start of a plant's life cycle by preventing germination of a viable seed in an unfavorable season. Freshly harvested seeds usually show a high level of dormancy, which is gradually released during dry storage (after-ripening). Abscisic acid (ABA) has been identified as an essential factor for the induction of dormancy, whereas gibberellins (GAs) are required for germination. The molecular mechanisms controlling seed dormancy are not well understood. DELAY OF GERMINATION1 (DOG1) was recently identified as a major regulator of dormancy in Arabidopsis thaliana. Here, we show that the DOG1 protein accumulates during seed maturation and remains stable throughout seed storage and imbibition. The levels of DOG1 protein in freshly harvested seeds highly correlate with dormancy. The DOG1 protein becomes modified during after-ripening, and its levels in stored seeds do not correlate with germination potential. Although ABA levels in dog1 mutants are reduced and GA levels enhanced, we show that DOG1 does not regulate dormancy primarily via changes in hormone levels. We propose that DOG1 protein abundance in freshly harvested seeds acts as a timer for seed dormancy release, which functions largely independent from ABA.


Assuntos
Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Dormência de Plantas , Reguladores de Crescimento de Plantas/metabolismo , Sementes/fisiologia , Ácido Abscísico/análise , Arabidopsis/citologia , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Germinação , Giberelinas/análise , Giberelinas/metabolismo , Mutação , Reguladores de Crescimento de Plantas/análise , Plantas Geneticamente Modificadas , RNA Mensageiro/genética , RNA de Plantas/genética , Sementes/citologia , Sementes/genética , Sementes/metabolismo , Transdução de Sinais , Temperatura , Fatores de Tempo , Regulação para Cima
9.
Plant Cell Environ ; 35(10): 1769-86, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22620982

RESUMO

Seed dormancy is an important component of plant fitness that causes a delay of germination until the arrival of a favourable growth season. Dormancy is a complex trait that is determined by genetic factors with a substantial environmental influence. Several of the tissues comprising a seed contribute to its final dormancy level. The roles of the plant hormones abscisic acid and gibberellin in the regulation of dormancy and germination have long been recognized. The last decade saw the identification of several additional factors that influence dormancy including dormancy-specific genes, chromatin factors and non-enzymatic processes. This review gives an overview of our present understanding of the mechanisms that control seed dormancy at the molecular level, with an emphasis on new insights. The various regulators that are involved in the induction and release of dormancy, the influence of environmental factors and the conservation of seed dormancy mechanisms between plant species are discussed. Finally, expected future directions in seed dormancy research are considered.


Assuntos
Regulação da Expressão Gênica no Desenvolvimento/genética , Dormência de Plantas/genética , Reguladores de Crescimento de Plantas/metabolismo , Plantas/genética , Sementes/genética , Ácido Abscísico/metabolismo , Ácido Abscísico/fisiologia , Meio Ambiente , Regulação da Expressão Gênica de Plantas/genética , Giberelinas/metabolismo , Giberelinas/fisiologia , Modelos Biológicos , Reguladores de Crescimento de Plantas/fisiologia , Sementes/crescimento & desenvolvimento , Sementes/fisiologia
10.
Methods Mol Biol ; 773: 239-57, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21898260

RESUMO

The chromatin structure determines gene expression and thereby regulates developmental processes in the plant. The molecular mechanisms regulating the induction and release of seed dormancy are still largely unknown and the underlying changes in chromatin organization have hardly been analyzed. Most chromatin studies in plants have been performed on vegetative tissues and have focused on seedlings. The composition of seeds hampers molecular analyses and requires adaptation of the methods that are used for other tissues. Here, we give an overview of the current methods that are used to study different aspects of chromatin organization in seeds. Cytogenetic methods, like fluorescence in situ hybridization and immunolocalization, are used to study chromatin at the microscopic level. Changes in DNA methylation and histone modifications can be studied with molecular methods, like bisulfite sequencing, immunoblotting, and chromatin immunoprecipitation.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Cromatina/metabolismo , Dormência de Plantas/genética , Sementes/crescimento & desenvolvimento , Ácido Abscísico/genética , Ácido Abscísico/metabolismo , Arabidopsis/genética , Cromatina/genética , Montagem e Desmontagem da Cromatina/genética , Imunoprecipitação da Cromatina , Metilação de DNA/genética , Epigênese Genética , Regulação da Expressão Gênica de Plantas , Histonas/genética , Sementes/genética
11.
Mol Ecol ; 20(16): 3336-49, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21740475

RESUMO

Seasonal germination timing of Arabidopsis thaliana strongly influences overall life history expression and is the target of intense natural selection. This seasonal germination timing depends strongly on the interaction between genetics and seasonal environments both before and after seed dispersal. DELAY OF GERMINATION 1 (DOG1) is the first gene that has been identified to be associated with natural variation in primary dormancy in A. thaliana. Here, we report interaccession variation in DOG1 expression and document that DOG1 expression is associated with seed-maturation temperature effects on germination; DOG1 expression increased when seeds were matured at low temperature, and this increased expression was associated with increased dormancy of those seeds. Variation in DOG1 expression suggests a geographical structure such that southern accessions, which are more dormant, tend to initiate DOG1 expression earlier during seed maturation and achieved higher expression levels at the end of silique development than did northern accessions. Although elimination of the synthesis of phytohormone abscisic acid (ABA) results in the elimination of maternal temperature effects on dormancy, DOG1 expression predicted dormancy better than expression of genes involved in ABA metabolism.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/fisiologia , Germinação/fisiologia , Sementes/fisiologia , Ácido Abscísico/biossíntese , Meio Ambiente , Regulação da Expressão Gênica de Plantas , Variação Genética , Genótipo , Dormência de Plantas , Reguladores de Crescimento de Plantas/biossíntese , Polimorfismo Genético , Temperatura
12.
Plant Physiol ; 151(2): 641-54, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19648230

RESUMO

The phytohormones abscisic acid (ABA) and gibberellins (GAs) are the primary signals that regulate seed dormancy and germination. In this study, we investigated the role of a double APETALA2 repeat transcription factor, CHOTTO1 (CHO1), in seed dormancy, germination, and phytohormone metabolism of Arabidopsis (Arabidopsis thaliana). Wild-type seeds were dormant when freshly harvested seeds were sown, and these seeds were released from dormancy after a particular period of dry storage (after-ripening). The cho1 mutant seeds germinated easily even in a shorter period of storage than wild-type seeds. The cho1 mutants showed reduced responsiveness to ABA, whereas transgenic plants constitutively expressing CHO1 (p35SCHO1) showed an opposite phenotype. Notably, after-ripening reduced the ABA responsiveness of the wild type, cho1 mutants, and p35SCHO1 lines. Hormone profiling demonstrated that after-ripening treatment decreased the levels of ABA and salicylic acid and increased GA(4), jasmonic acid, and isopentenyl adenine when wild-type seeds were imbibed. Expression analysis showed that the transcript levels of genes for ABA and GA metabolism were altered in the wild type by after-ripening. Hormone profiling and expression analyses indicate that cho1 seeds, with a short period of storage, resembled fully after-ripened wild-type seeds. Genetic analysis showed that the cho1 mutation partially restored delayed seed germination and reduced GA biosynthesis activity in the ABA-overaccumulating cyp707a2-1 mutant background but did not restore seed germination in the GA-deficient ga1-3 mutant background. These results indicate that CHO1 acts downstream of ABA to repress GA biosynthesis during seed germination.


Assuntos
Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Germinação , Giberelinas/biossíntese , Proteínas de Homeodomínio/química , Proteínas Nucleares/química , Sementes/crescimento & desenvolvimento , Fatores de Transcrição/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Sequência de Bases , Ensaio de Desvio de Mobilidade Eletroforética , Regulação da Expressão Gênica de Plantas , Glucuronidase/metabolismo , Dados de Sequência Molecular , Mutação/genética , Reguladores de Crescimento de Plantas/metabolismo , Estrutura Terciária de Proteína , Sequências Reguladoras de Ácido Nucleico/genética , Sequências Repetitivas de Aminoácidos , Sementes/genética , Sementes/metabolismo , Fatores de Transcrição/genética
13.
Plant Signal Behav ; 4(12): 1166-8, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20514237

RESUMO

We reported a loss-of-function of an Arabidopsis double AP2 transcription factor CHOTTO1 (CHO1) gene results in the altered responses to high concentrations of nitrate (approximately 50 mM). Nitrate up to 10 mM promotes growth of the wildtype seedling, but inhibits it under higher concentrations. The cho1 seedlings responded to nitrate up to 10 mM similarly to the wildtype, but the inhibitory effect of excess nitrate is less prominent in the mutants. This phenotype is restricted to the cotyledons, and growth of the hypocotyl and roots of the cho1 mutants is inhibited by excess nitrate. The cho1 mutations caused the upregulation of two nitrate transporter genes, AtNRT1.4 and At1g52190. Altered nitrate distribution and storage may explain the phenotypes of the cho1 mutants.

14.
Plant J ; 55(3): 526-42, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18419781

RESUMO

We analyzed global gene expression in Arabidopsis in response to various hormones and in related experiments as part of the AtGenExpress project. The experimental agents included seven basic phytohormones (auxin, cytokinin, gibberellin, brassinosteroid, abscisic acid, jasmonate and ethylene) and their inhibitors. In addition, gene expression was investigated in hormone-related mutants and during seed germination and sulfate starvation. Hormone-inducible genes were identified from the hormone response data. The effects of each hormone and the relevance of the gene lists were verified by comparing expression profiles for the hormone treatments and related experiments using Pearson's correlation coefficient. This approach was also used to analyze the relationships among expression profiles for hormone responses and those included in the AtGenExpress stress-response data set. The expected correlations were observed, indicating that this approach is useful to monitor the hormonal status in the stress-related samples. Global interactions among hormones-inducible genes were analyzed in a pairwise fashion, and several known and novel hormone interactions were detected. Genome-wide transcriptional gene-to-gene correlations, analyzed by hierarchical cluster analysis (HCA), indicated that our data set is useful for identification of clusters of co-expressed genes, and to predict the functions of unknown genes, even if a gene's function is not directly related to the experiments included in AtGenExpress. Our data are available online from AtGenExpressJapan; the results of genome-wide HCA are available from PRIMe. The data set presented here will be a versatile resource for future hormone studies, and constitutes a reference for genome-wide gene expression in Arabidopsis.


Assuntos
Arabidopsis/genética , Bases de Dados Genéticas , Expressão Gênica/efeitos dos fármacos , Reguladores de Crescimento de Plantas/farmacologia , Arabidopsis/efeitos dos fármacos , Arabidopsis/crescimento & desenvolvimento , Análise por Conglomerados , Perfilação da Expressão Gênica , Genoma de Planta , Genótipo , Reguladores de Crescimento de Plantas/antagonistas & inibidores , Sementes/efeitos dos fármacos , Sementes/genética , Sementes/crescimento & desenvolvimento
15.
Plant J ; 53(1): 42-52, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17953649

RESUMO

To understand the molecular mechanisms underlying regulation of seed germination, we searched enriched cis elements in the upstream regions of Arabidopsis genes whose transcript levels increased during seed germination. Using available published microarray data, we found that two cis elements, Up1 or Up2, which regulate outgrowth of Arabidopsis axillary shoots, were significantly over-represented. Classification of Up1- and Up2-containing genes by gene ontology revealed that protein synthesis-related genes, especially ribosomal protein genes, were highly over-represented. Expression analysis using a reporter gene driven by a synthetic promoter regulated by these elements showed that the Up1 is necessary and sufficient for germination-associated gene induction, whereas Up2 acts as an enhancer of Up1. Up1-mediated gene expression was suppressed by treatments that blocked germination. Up1 is almost identical to the site II motif, which is the predicted target of TCP transcription factors. Of 24 AtTCP genes, AtTCP14, which showed the highest transcript level just prior to germination, was functionally characterized to test its involvement in the regulation of seed germination. Transposon-tagged lines for AtTCP14 showed delayed germination. In addition, germination of attcp14 mutants exhibited hypersensitivity to exogenously applied abscisic acid and paclobutrazol, an inhibitor of gibberellin biosynthesis. AtTCP14 was predominantly expressed in the vascular tissues of the embryo, and affected gene expression in radicles in a non-cell-autonomous manner. Taken together, these results indicate that AtTCP14 regulates the activation of embryonic growth potential in Arabidopsis seeds.


Assuntos
Arabidopsis/embriologia , Arabidopsis/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Germinação/fisiologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Plantas Geneticamente Modificadas , RNA Mensageiro/genética , Sementes/genética , Sementes/fisiologia , Fatores de Transcrição/química , Transcrição Genética/fisiologia , Ativação Transcricional , Proteínas de Transporte Vesicular/metabolismo
16.
Plant Physiol ; 146(3): 1368-85, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-18162586

RESUMO

Suppression of seed germination at supraoptimal high temperature (thermoinhibiton) during summer is crucial for Arabidopsis (Arabidopsis thaliana) to establish vegetative and reproductive growth in appropriate seasons. Abscisic acid (ABA) and gibberellins (GAs) are well known to be involved in germination control, but it remains unknown how these hormone actions (metabolism and responsiveness) are altered at high temperature. Here, we show that ABA levels in imbibed seeds are elevated at high temperature and that this increase is correlated with up-regulation of the zeaxanthin epoxidase gene ABA1/ZEP and three 9-cis-epoxycarotenoid dioxygenase genes, NCED2, NCED5, and NCED9. Reverse-genetic studies show that NCED9 plays a major and NCED5 and NCED2 play relatively minor roles in high temperature-induced ABA synthesis and germination inhibition. We also show that bioactive GAs stay at low levels at high temperature, presumably through suppression of GA 20-oxidase genes, GA20ox1, GA20ox2, and GA20ox3, and GA 3-oxidase genes, GA3ox1 and GA3ox2. Thermoinhibition-tolerant germination of loss-of-function mutants of GA negative regulators, SPINDLY (SPY) and RGL2, suggests that repression of GA signaling is required for thermoinibition. Interestingly, ABA-deficient aba2-2 mutant seeds show significant expression of GA synthesis genes and repression of SPY expression even at high temperature. In addition, the thermoinhibition-resistant germination phenotype of aba2-1 seeds is suppressed by a GA biosynthesis inhibitor, paclobutrazol. We conclude that high temperature stimulates ABA synthesis and represses GA synthesis and signaling through the action of ABA in Arabidopsis seeds.


Assuntos
Ácido Abscísico/biossíntese , Arabidopsis/metabolismo , Giberelinas/metabolismo , Temperatura Alta , Sementes/metabolismo , Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Sistema Enzimático do Citocromo P-450/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Dioxigenases , Regulação da Expressão Gênica de Plantas , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Oxirredutases/genética , Oxirredutases/metabolismo , Oxigenases/genética , Oxigenases/metabolismo , Proteínas de Plantas , Proteínas Repressoras/metabolismo , Transdução de Sinais/fisiologia , Fatores de Transcrição/metabolismo
17.
Plant J ; 41(5): 697-709, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15703057

RESUMO

To reveal the transcriptomes of Arabidopsis seed, comprehensive expression analysis was performed using ATH1 GeneChips (Affymetrix, Santa Clara, CA, USA). In the dry seed, more than 12 000 stored mRNA species were detected, including all ontological categories. Statistical analysis revealed that promoters of highly expressed genes in wild-type dry seeds overrepresented abscisic acid-responsive elements (ABREs) containing the core motif ACGT. Although the coupling element and seed-specific enhancer RY motif alone were not prominently overrepresented in genes with high expression, the presence of these elements in combination with ABRE was associated with particularly high gene expression. The transcriptome of the imbibed seeds differed from that of the dry seed even at 6 h after seed imbibition. After imbibition many upregulated and downregulated genes were co-regulated in clusters of three to five genes. Genes for which expression was affected by the abi5 mutation tended to be located in clusters, suggesting that transactivation by ABI5 is not restricted to a single gene, but affects other proximal genes. Furthermore, cytosine methylation was observed not only in large silent retrotransposon clusters in centromeric regions, but also in non-centromeric silent gene clusters in the seed. These results suggest that such regions might be transcriptionally silenced by methylation or heterochromatin structures. Our analyses reveal that transcriptomes of Arabidopsis seed are characterized by multiple regulatory mechanisms: epigenetic chromatin structures, chromosomal locations (e.g. co-regulated gene clusters) and cis-acting elements.


Assuntos
Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Genoma de Planta , Germinação/fisiologia , RNA Mensageiro/genética , RNA de Plantas/genética , Sementes/fisiologia , Transcrição Genética , Arabidopsis/genética , Arabidopsis/fisiologia , Metilação de DNA , DNA de Plantas/genética , Germinação/genética , Cinética , Análise de Sequência com Séries de Oligonucleotídeos , Sementes/genética
18.
EMBO J ; 23(7): 1647-56, 2004 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-15044947

RESUMO

The hormonal action of abscisic acid (ABA) in plants is controlled by the precise balance between its biosynthesis and catabolism. In plants, ABA 8'-hydroxylation is thought to play a predominant role in ABA catabolism. ABA 8'-hydroxylase was shown to be a cytochrome P450 (P450); however, its corresponding gene had not been identified. Through phylogenetic and DNA microarray analyses during seed imbibition, the candidate genes for this enzyme were narrowed down from 272 Arabidopsis P450 genes. These candidate genes were functionally expressed in yeast to reveal that members of the CYP707A family, CYP707A1-CYP707A4, encode ABA 8'-hydroxylases. Expression analyses revealed that CYP707A2 is responsible for the rapid decrease in ABA level during seed imbibition. During drought stress conditions, all CYP707A genes were upregulated, and upon rehydration a significant increase in mRNA level was observed. Consistent with the expression analyses, cyp707a2 mutants exhibited hyperdormancy in seeds and accumulated six-fold greater ABA content than wild type. These results demonstrate that CYP707A family genes play a major regulatory role in controlling the level of ABA in plants.


Assuntos
Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Sistema Enzimático do Citocromo P-450/metabolismo , Oxigenases de Função Mista/metabolismo , Ácido Abscísico/química , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Sistema Enzimático do Citocromo P-450/genética , Perfilação da Expressão Gênica , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Oxigenases de Função Mista/genética , Estrutura Molecular , Análise de Sequência com Séries de Oligonucleotídeos , Fenótipo , Proteínas de Plantas , Sementes/enzimologia
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