AtMyb7, a subgroup 4 R2R3 Myb, negatively regulates ABA-induced inhibition of seed germination by blocking the expression of the bZIP transcription factor ABI5 (original) (raw)
Related papers
MBF1s regulate ABA-dependent germination of Arabidopsis seeds
Plant Signaling & Behavior, 2012
Abbreviations: ABA, abscisic acid; abc-, Arabidopsis thaliana triple knock-down mutant for MBF1 genes; abc-+c, abcmutant complemented with AtMBF1c gene over-expression; ABR1, absisic acid repressor; ACC, 1-aminocyclopropane-1-carboxylic acid; ERF, ethelyne responsive factor family; H 2 O 2, hydrogen peroxide; MBF1, multiprotein bridging factor 1; MV, methyl viologen Transcriptional co-activators of the multiprotein bridging factor 1 (MBF1) control gene expression by connecting transcription factors and the basal transcription machinery. In Arabidopsis thaliana functions of MBF1 genes have been related to stress tolerance and developmental alterations. Endogenous ABA plays a major role in the regulation of Arabidopsis seed dormancy and germination. Seed dormancy and ABA sensitivity are enhanced in ethylene insensitive mutants suggesting that ethylene signal transduction pathway is necessary to fully develop ABA-dependent germination. In this report we showed that a triple knock-down mutant for Arabidopsis MBF1 genes (abc-) has enhanced seed dormancy and displays hypersensitivity to exogenous ABA. In addition, higher ABA contents were detected in abcseeds after imbibition. These evidences suggest a negative role of MBF1s genes in ABA-dependent inhibition of germination. The participation of MBF1s in ethylene signal transduction pathway is also discussed.
Journal of Biological Chemistry, 2003
The expression of many seed storage protein genes in cereals relies on transcription factors of the bZIP class, belonging to the maize OPAQUE2 family. Here, we describe a survey of such factors in the genome of Arabidopsis thaliana, and the characterization of two of them, AtbZIP10 and AtbZIP25. Expression analysis by in situ hybridization shows that the occurrence of their mRNAs in the seed starts from early stages of development, peaks at maturation, and declines later in seed development, matching temporally and spatially those of the seed storage protein genes encoding 2S albumins and cruciferins. Gel mobility shift assays showed that AtbZIP10 and AtbZIP25 bind the ACGT boxes present in At2S and CRU3 promoters. Moreover, using the yeast two-hybrid system we show that AtbZIP10 and AtbZIP25 can interact in vivo with ABI3, an important regulator of gene expression in the seed of Arabidopsis. Transient expression analyses of a reporter gene under the control of the At2S1 promoter in transgenic plants overexpressing ectopically AtbZIP10, AtbZIP25, and ABI3 reveal that none of these factors could activate significantly the reporter gene when expressed individually. However, co-expression of AtbZIP10/25 with ABI3 resulted in a remarkable increase in the activation capacity over the At2S1 promoter, suggesting that they are part of a regulatory complex involved in seed-specific expression. This study shows a common mechanism of ABI3 in regulating different seed-specific genes through combinatorial interactions with particular bZIP proteins and a conserved role of O2-like bZIPs in monocot and dicot species.
2018
Low temperatures, salinity, and drought cause significant crop losses. These conditions involve osmotic stress, triggering transcriptional remodeling, and consequently, the restitution of cellular homeostasis and growth recovery. Protein transcription factors regulate target genes, thereby mediating plant responses to stress. bZIP17 is a transcription factor involved in cellular responses to salinity and the unfolded protein response. Because salinity can also produce osmotic stress, the role of bZIP17 in response to osmotic stress was assessed. Mannitol treatments induced the transcript accumulation and protein processing of bZIP17. Transcriptomic analyses showed that several genes associated with seed storage and germination showed lower expression in bzip17 mutants than in wild-type plants. Interestingly, bZIP17 transcript was more abundant in seeds, and germination analyses revealed that wild-type plants germinated later than bzip17 mutants in the presence of mannitol, but no effects were observed when the seeds were exposed to ABA. Finally, the transcript levels of bZIP17 target genes that control seed storage and germination were assessed in seeds exposed to mannitol treatments, which showed lower expression levels in bzip17 mutants compared to the wild-type seeds. These results suggest that bZIP17 plays a role in osmotic stress, acting as a negative regulator of germination through the regulation of genes involved in seed storage and germination.
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.
Aob Plants, 2019
An increasing number of candidate genes related to abiotic stress tolerance are being discovered and proposed to improve the existing cultivars of the high oil-bearing crop sesame (Sesamum indicum L.). However, the in planta functional validation of these genes is remarkably lacking. In this study, we cloned a novel sesame R2-R3 MYB gene SiMYB75 which is strongly induced by drought, sodium chloride (NaCl), abscisic acid (ABA) and mannitol. SiMYB75 is expressed in various sesame tissues, especially in root and its protein is predicted to be located in the nucleus. Ectopic over-expression of SiMYB75 in Arabidopsis notably promoted root growth and improved plant tolerance to drought, NaCl and mannitol treatments. Furthermore, SiMYB75 over-expressing lines accumulated higher content of ABA than wild-type plants under stresses and also increased sensitivity to ABA. Physiological analyses revealed that SiMYB75 confers abiotic stress tolerance by promoting stomatal closure to reduce water loss; inducing a strong reactive oxygen species scavenging activity to alleviate cell damage and apoptosis; and also, up-regulating the expression levels of various stress-marker genes in the ABAdependent pathways. Our data suggested that SiMYB75 positively modulates drought, salt and osmotic stresses responses through ABA-mediated pathways. Thus, SiMYB75 could be a promising candidate gene for the improvement of abiotic stress tolerance in crop species including sesame.
MYB transcription factors in Arabidopsis
Trends in plant science, 2010
The MYB family of proteins is large, functionally diverse and represented in all eukaryotes. Most MYB proteins function as transcription factors with varying numbers of MYB domain repeats conferring their ability to bind DNA. In plants, the MYB family has selectively expanded, particularly through the large family of R2R3-MYB. Members of this family function in a variety of plant-specific processes, as evidenced by their extensive functional characterization in Arabidopsis (Arabidopsis thaliana). MYB proteins are key factors in regulatory networks controlling development, metabolism and responses to biotic and abiotic stresses. The elucidation of MYB protein function and regulation that is possible in Arabidopsis will provide the foundation for predicting the contributions of MYB proteins to the biology of plants in general.
Plant and Cell Physiology, 2010
Functional analysis of a putative novel transcription factor Arabidopsis MYB-like protein designated AtMYBL, which contains two predicted DNA-binding domains, was performed. The physiological role of the R-R-type MYB-like transcription factor has not been reported in any plant. Analyses of an AtMYBL promoter-b-glucuronidase (GUS) construct revealed substantial gene expression in old leaves and induction of GUS activity by ABA and salt stress. AtMYBL-overexpressing plants displayed a markedly enhanced leaf senescence phenotype. Moreover, the ectopic expression of the AtMYBL gene was very significantly influential in senescence parameters including Chl content, membrane ion leakage and the expression of senescencerelated genes. Although the seed germination rate was improved under ABA and saline stress conditions in the AtMYBL-overexpressing plants, decreased salt tolerance was evident compared with the wild type and atmybl RNA interference lines during later seedling growth when exposed to long-term salt stress, indicating that AtMYBL protein is able to developmentally regulate stress sensitivity. Furthermore, AtMYBL protein activated the transcription of a reporter gene in yeast. Green fluorescent protein-tagged AtMYBL was localized in the nuclei of transgenic Arabidopsis cells. Taken together, these results suggest that AtMYBL functions in the leaf senescence process, with the abiotic stress response implicated as a putative potential transcription factor.
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.
Journal of Plant Physiology, 2013
Diverse RNA-binding proteins (RBPs) have increasingly been determined to perform crucial roles in posttranscriptional regulation of RNA metabolism during plant response to abscisic acid (ABA) or abiotic stresses, but the functional roles of a variety of ABA-responsive RBPs in ABA and stress response remain poorly understood. Here, we characterized an ABA-regulated putative RBP (At3g54770) in Arabidopsis thaliana, designated ARP1, for its role in response to ABA or abiotic stresses. The expression of ARP1 was markedly downregulated by ABA, and ARP1 is localized to the nucleus. Interestingly, both overexpression and knockout of ARP1 resulted in delayed seed germination under ABA, high salt, or dehydration stress conditions. The identical phenotypes of ARP1-overexpressing plants and the arp1 null mutant indicate that a tight regulation of ARP1 transcript is required for normal function. Transcript levels of several germination-responsive genes were modulated by ARP1 under ABA. Taken together, the results of the present study demonstrate that ARP1 affects ABA-regulated seed germination of Arabidopsis, and indicate that the regulation of posttranscriptional RNA metabolism is critical in plant response to ABA or abiotic stresses.