MBF1s regulate ABA-dependent germination of Arabidopsis seeds (original) (raw)
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The Plant Journal, 2016
The seed expressed gene DELAY OF GERMINATION (DOG) 1 is absolutely required for the induction of dormancy. Next to a non-dormant phenotype, the dog1-1 mutant is also characterized by a reduced seed longevity suggesting that DOG1 may affect additional seed processes as well. This aspect however, has been hardly studied and is poorly understood. To uncover additional roles of DOG1 in seeds we performed a detailed analysis of the dog1 mutant using both transcriptomics and metabolomics to investigate the molecular consequences of a dysfunctional DOG1 gene. Further, we used a genetic approach taking advantage of the weak aba insensitive (abi) 3-1 allele as a sensitized genetic background in a cross with dog1-1. DOG1 affects the expression of hundreds of genes including LATE EMBRYOGENESIS ABUNDANT and HEAT SHOCK PROTEIN genes which are affected by DOG1 partly via control of ABI5 expression. Furthermore, the content of a subset of primary metabolites, which normally accumulate during seed maturation, was found to be affected in the dog1-1 mutant. Surprisingly, the abi3-1 dog1-1 double mutant produced green seeds which are highly ABA insensitive, phenocopying severe abi3 mutants, indicating that dog1-1 acts as an enhancer of the weak abi3-1 allele and thus revealing a genetic interaction between both genes. Analysis of the dog1 and dog1 abi3 mutants revealed additional seed phenotypes and therefore we hypothesize that DOG1 function is not limited to dormancy but that it is required for multiple aspects of seed maturation, in part by interfering with ABA signalling components.
The Plant Journal, 2010
Seed dormancy is a very important trait that maximizes the survival of seed in nature, the control of which can have important repercussions on the yield of many crop species. We have used gene expression profiling to identify genes that are involved in dormancy regulation in Arabidopsis thaliana. RNA was isolated from imbibed dormant (D) and after-ripened (AR) ecotype C24 seeds, and then screened by quantitative RT-PCR (qRT-PCR) for differentially expressed transcription factors (TFs) and other regulatory genes. Out of 2207 genes screened, we have identified 39 that were differentially expressed during the first few hours of imbibition. After analyzing T-DNA insertion mutants for 22 of these genes, two displayed altered dormancy compared with the wild type. These mutants are affected in genes that encode a RING finger and an HDZip protein. The first, named DESPIERTO, is involved in ABA sensitivity during seed development, regulates the expression of ABI3, and produces a complete loss of dormancy when mutated. The second, the HDZip (ATHB20), is expressed during seed germination in the micropylar endosperm and in the root cap, and increases ABA sensitivity and seed dormancy when mutated.
Plant Physiology, 2005
The plant hormone abscisic acid (ABA) plays an important role in plant development and stress responses. An important step of ABA action is activation or inactivation of gene expression. Although several transcription factors are identified to function as positive regulators of ABA-induced gene expression, little is known about the negative regulators of ABA-regulated gene expression. Here, we have identified an APETALA2 (AP2) domain transcription factor that serves as a repressor of ABA response during seed germination and ABA-and stress-induced gene expression in Arabidopsis (Arabidopsis thaliana). The expression of the AP2-like ABA repressor 1 (ABR1) gene itself was responsive to ABA and stress conditions including cold, high salt, and drought. Disruption of ABR1 led to hypersensitive response to ABA in seed germination and root growth assays. The mutant plants were also hypersensitive to osmotic stress conditions, such as high salt and high concentrations of mannitol. Further analyses indicated that increased stress sensitivity may result from hypersensitivity to ABA as ABA biosynthesis inhibitor rescued the stress hypersensitivity phenotype. The abr1 mutant plants accumulated significantly higher levels of ABA-and stress-inducible gene transcripts as compared to the wild-type plants, supporting the hypothesis that this AP2 domain protein serves as a repressor of ABA-regulated gene expression.
PLANT PHYSIOLOGY, 2000
We have characterized developmental, environmental, and genetic regulation of abscisic acid-insensitive (ABI)4 gene expression in Arabidopsis. Although expressed most strongly in seeds, ABI4 transcripts are also present at low levels in vegetative tissue; vegetative expression is not induced by abscisic acid (ABA) or stress treatments. Comparison of transcript levels in mature seeds of ABA-insensitive, ABA-hypersensitive, ABA-deficient, or heterochronic mutants indicates that ABI4 expression is altered in only two of the backgrounds, the ABA-insensitive mutants abi1-1 and abi3-1. To determine whether ABI4 is necessary and/or sufficient for ABA response, we assayed the effects of loss of ABI4 function and ectopic ABI4 expression on growth and gene expression. We examined genetic interactions among three ABA response loci, ABI3, ABI4, and ABI5, by comparing phenotypes of mutants, ectopic expression lines, mutants carrying an ectopically expressed transgene, and the corresponding wild-type lines. Our results indicate some cross-regulation of expression among ABI3, ABI4, and ABI5 and suggest that they function in a combinatorial network, rather than a regulatory hierarchy, controlling seed development and ABA response.
Plant Physiology, 2006
Abscisic acid (ABA) is an important phytohormone that plays a critical role in seed development, dormancy, and stress tolerance. 9-cis-Epoxycarotenoid dioxygenase is the key enzyme controlling ABA biosynthesis and stress tolerance. In this study, we investigated the effect of ectopic expression of another ABA biosynthesis gene, ABA2 (or GLUCOSE INSENSITIVE 1 [GIN1]) encoding a short-chain dehydrogenase/reductase in Arabidopsis (Arabidopsis thaliana). We show that ABA2-overexpressing transgenic plants with elevated ABA levels exhibited seed germination delay and more tolerance to salinity than wild type when grown on agar plates and/or in soil. However, the germination delay was abolished in transgenic plants showing ABA levels over 2-fold higher than that of wild type grown on 250 mm NaCl. The data suggest that there are distinct mechanisms underlying ABA-mediated inhibition of seed germination under diverse stress. The ABA-deficient mutant aba2, with a shorter primary root, can be ...
The Plant Cell, 1994
The accumulation kinetics of 18 mRNAs were characterized during Arabidopsis silique development. These marker mRNAs could be grouped in distinct classes according to their coordinate temporal expression in the wild type and provided a basis for further characteriration of the corresponding regulatory pathways. The abscisic acid (ABA)-insensitive abi3-4 mutation modified the expression pattern of several but not all members of each of these wild-type temporal mRNA classes. This indicates that the A613 protein directly participates in the regulation of several developmental programs and that multiple regulatory pathways can lead to the simultaneous expression of distinct mRNA markers. The A613 gene is specifically expressed in seed, but ectopic expression of A613 conferred the ability to accumulate several seed-specific mRNA markers in response to ABA in transgenic plantlets. This suggested that expression of these marker mRNAs might be contmlled by an AB13dependent and AEA-dependent pathway(s) in seed. However, characterization of the ABA-biosynthetic aba mutant revealed that the accumulation of these mRNAs is not correlated to the ABA content of seed. A possible means of regulating gene expression by developmental variations in ABA sensitivity is apparently not attributable to variations in AB13 cellular abundance. The total content of A613 protein per seed markedly increased at certain developmental stages, but this augmentation appears to result primarily from the simultaneous multiplication of embryonic cells. Our current findings are discussed in relation to their general implications for the mechanisms controlling gene expression programs in seed. The Plant Cell Table 1. Marker mRNAs Monitored during Silique Development: Previously Described Arabidopsis Genes
Characterization of green seed, an Enhancer of abi3-1 in Arabidopsis That Affects Seed Longevity
PLANT PHYSIOLOGY, 2003
Seeds are usually stored in physiological conditions in which they gradually lose their viability and vigor depending on storage conditions, storage time, and genotype. Very little is known about the underlying genetics of seed storability and seed deterioration. We analyzed a mutant in Arabidopsis disturbed in seed storability. This mutant was isolated as a grs (green-seeded) mutant in an abi3-1 (abscisic acid 3) mutant background. Genetic and physiological characterization showed that the monogenic grs mutant was not visibly green seeded and mapped on chromosome 4. This enhancer mutation did not affect the ABA sensitivity of seed germination or seed dormancy but was found to affect seed storability and seedling vigor. Seed storability was assessed in a controlled deterioration test, in which the germination capacity of the mutant decreased with the duration of the treatment. The decrease in viability and vigor was confirmed by storing the seeds in two relative humidities (RHs) for a prolonged period. At 60% RH, the mutant lost germinability, but storage at 32% RH showed no decrease of germination although seed vigor decreased. The decrease in viability and vigor could be related to an increase in conductivity, suggesting membrane deterioration. This was not affected by light conditions during imbibition, expected to influence the generation of active oxygen species. During seed maturation, ABI3 regulates several processes: acquiring dormancy and long-term storability and loss of chlorophyll. Our results indicate that GRS is a common regulator in the latter two but not of dormancy/germination. ; fax 31-317-483146.
Plant, cell & environment, 2015
Various Myb proteins have been shown to play crucial roles in plants, including primary and secondary metabolism, determination of cell fate and identity, regulation of development and involvement in responses to biotic and abiotic stresses. The 126 R2R3 Myb proteins (with two Myb repeats) have been found in Arabidopsis; however, the functions of most of these proteins remain to be fully elucidated. In the present study, we characterized the function of AtMyb7 using molecular biological and genetic analyses. We used qRT-PCR to determine the levels of stress-response gene transcripts in wild-type and atmyb7 plants. We showed that Arabidopsis AtMyb7 plays a critical role in seed germination. Under abscisic acid (ABA) and high-salt stress conditions, atmyb7 plants showed a lower germination rate than did wild-type plants. Furthermore, AtMyb7 promoter:GUS seeds exhibited different expression patterns in response to variations in the seed imbibition period. AtMyb7 negatively controls the...
The Plant Journal, 2007
After-ripening (AR) is a time and environment regulated process occurring in the dry seed, which determines the germination potential of seeds. Both metabolism and perception of the phytohormone abscisic acid (ABA) are important in the initiation and maintenance of dormancy. However, molecular mechanisms that regulate the capacity for dormancy or germination through AR are unknown. To understand the relationship between ABA and AR, we analysed genome expression in Arabidopsis thaliana mutants defective in seed ABA synthesis (aba1-1) or perception (abi1-1). Even though imbibed mutant seeds showed no dormancy, they exhibited changes in global gene expression resulting from dry AR that were comparable with changes occurring in wildtype (WT) seeds. Core gene sets were identified that were positively or negatively regulated by dry seed storage. Each set included a gene encoding repression or activation of ABA function (LPP2 and ABA1, respectively), thereby suggesting a mechanism through which dry AR may modulate subsequent germination potential in WT seeds. Application of exogenous ABA to after-ripened WT seeds did not reimpose characteristics of freshly harvested seeds on imbibed seed gene expression patterns. It was shown that secondary dormancy states reinstate AR status-specific gene expression patterns. A model is presented that separates the action of ABA in seed dormancy from AR and dry storage regulated gene expression. These results have major implications for the study of genetic mechanisms altered in seeds as a result of crop domestication into agriculture, and for seed behaviour during dormancy cycling in natural ecosystems.
Structure and expression analysis of three subtypes of< i> Arabidopsis MBF1 genes
Biochimica Et Biophysica Acta-gene Structure and Expression, 2004
Multiprotein bridging factor 1 (MBF1) is a transcriptional co-activator that mediates transcriptional activation by bridging between an activator and a TATA-box binding protein (TBP). Recently, we have reported that three Arabidopsis MBF1s play roles as transcriptional coactivators. This study shows that AtMBF1c is totally different from the other two in its structure and expression pattern, and that MBF1c genes also occur in other plant species, including monocots. We performed histochemical analysis of these genes using h-glucuronidase (GUS) assays to characterize the expression profile of each AtMBF1 gene extensively. In pAtMBF1aDGUS transformants, GUS staining was observed only in anthers and seeds, whereas strong GUS activity in pAtMBF1bDGUS transformants was detected in leaf veins, stems, anthers, and seeds. In mature pAtMBF1cDGUS transformants, GUS staining was observed in almost all tissues. It is noteworthy that intense GUS staining was observed in anthers of all transformants. We also found that AtMBF1c expression was up-regulated upon diverse stress treatments including exposure to heat, hydrogen peroxide, dehydration, and high concentrations of salt. These findings suggest that AtMBF1c may be involved in stress response pathway. D