Three Arabidopsis MBF1 homologs with distinct expression profiles play roles as transcriptional co-activators (original) (raw)
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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
Transcriptional coactivator MBF1s from Arabidopsis predominantly localize in nucleolus
Journal of Plant Research, 2005
Multiprotein bridging factor 1 (MBF1) is a transcriptional coactivator. It has been reported that MBF1 changed its subcellular localization from cytoplasm into nuclei with a transcriptional activator for activation of a target gene expression in animals. We found that Arabidopsis MBF1s (AtMBF1s) predominantly localize in nucleolus. We previously reported that plant MBF1s were rapidly induced by several stresses, whereas animal MBF1s were not induced. Therefore, we suggest that MBF1-function in plants is controlled on the level of transcriptional induction but not by nuclear translocation, dissimilar from the case of MBF1s from animals.
Journal of biochemistry and molecular biology, 2006
To gain a better understanding on the function of the potato Solanum tuberosum Multiprotein Bridging Factor 1 protein (StMBF1) its interaction with the TATA box binding protein (TBP) was demonstrated. In addition we reported that StMBF1 rescues the yeast mbf1 mutant phenotype, indicating its role as a plant co-activator. These data reinforce the hypothesis that MBF1 function is also conserved among non closely related plant species. In addition, measurement of StMBF1 protein level by Western blot using anti-StMBF1 antibodies indicated that the protein level increased upon H(2)O(2) and heat shock treatments. However, the potato beta-1,3-glucanase protein level was not changed under the same experimental conditions. These data indicate that StMBF1 participates in the cell stress response against oxidative stress allowing us to suggest that MBF1 genes from different plant groups may share similar functions.
Plant Science, 2008
Transcriptional co-activators of the Multiprotein Bridging Factor1 (MBF1) type belong to a multigenic family that encode key components of the machinery controlling gene expression by communicating between transcription factors and the basal transcription machinery. Knocking-down the expression of one member of the family has proved difficult probably due to functional redundancy. We show here that a fusion of SlER24, an MBF1 type gene of tomato, to the Ethylene-responsive element-binding associated Amphiphilic Repression (EAR) motif is capable of slowing down significantly the expression of the GFP protein driven by a synthetic ethylene-responsive GCC-rich promoter in a single cell transient expression system. A fusion of AtMBF1c of Arabidopsis to EAR, driven by the 35S promoter, caused a reduction of the percentage of seed germination and dwarfism of the plant. Similar fusion with the SlER24 of tomato in the MicroTom cultivar induced a delay of seed germination and no obvious effect on plant growth. Besides giving information on the role of the MBF1 genes in plant development, this study demonstrates that the EAR strategy is efficient not only for regular transcription factors as demonstrated so far, but also in the case of co-activators known to not bind directly to DNA.
The plant MBF1 protein family: a bridge between stress and transcription
Journal of Experimental Botany
The Multiprotein Bridging Factor 1 (MBF1) proteins are transcription co-factors whose molecular function is to form a bridge between transcription factors and the basal machinery of transcription. MBF1s are present in most archaea and all eukaryotes, and numerous reports show that they are involved in developmental processes and in stress responses. In this review we summarize almost three decades of research on the plant MBF1 family, which has mainly focused on their role in abiotic stress responses, in particular the heat stress response. However, despite the amount of information available, there are still many questions that remain about how plant MBF1 genes, transcripts, and proteins respond to stress, and how they in turn modulate stress response transcriptional pathways.
Plant Cell, 2002
Numerous studies have shown that transcription factors are important in regulating plant responses to environmental stress. However, specific functions for most of the genes encoding transcription factors are unclear. In this study, we used mRNA profiles generated from microarray experiments to deduce the functions of genes encoding known and putative Arabidopsis transcription factors. The mRNA levels of 402 distinct transcription factor genes were examined at different developmental stages and under various stress conditions. Transcription factors potentially controlling downstream gene expression in stress signal transduction pathways were identified by observed activation and repression of the genes after certain stress treatments. The mRNA levels of a number of previously characterized transcription factor genes were changed significantly in connection with other regulatory pathways, suggesting their multifunctional nature. The expression of 74 transcription factor genes responsive to bacterial pathogen infection was reduced or abolished in mutants that have defects in salicylic acid, jasmonic acid, or ethylene signaling. This observation indicates that the regulation of these genes is mediated at least partly by these plant hormones and suggests that the transcription factor genes are involved in the regulation of additional downstream responses mediated by these hormones. Among the 43 transcription factor genes that are induced during senescence, 28 of them also are induced by stress treatment, suggesting extensive overlap responses to these stresses. Statistical analysis of the promoter regions of the genes responsive to cold stress indicated unambiguous enrichment of known conserved transcription factor binding sites for the responses. A highly conserved novel promoter motif was identified in genes responding to a broad set of pathogen infection treatments. This observation strongly suggests that the corresponding transcription factors play general and crucial roles in the coordinated regulation of these specific regulons. Although further validation is needed, these correlative results provide a vast amount of information that can guide hypothesis-driven research to elucidate the molecular mechanisms involved in transcriptional regulation and signaling networks in plants.
Journal of Plant Physiology, 2010
Transcriptional co-activators of the multiprotein bridging factor 1 (MBF1) type belong to a small multigenic family that controls gene expression by connecting transcription factors and the basal transcription machinery. In this report, a triple knock-down mutant (abc À ) for the Arabidopsis thaliana MBF1 genes AtMBF1a, AtMBF1b and AtMBF1c was generated. The phenotypic characterization using oxidative agents such as hydrogen peroxide and methyl viologen revealed that the abc À mutant was more sensitive to oxidative stress. The triple knock-down mutant, abc À was also sensitive to osmotic stress mediated by high concentrations of sorbitol. Furthermore, the abc À phenotype was partially or completely rescued by AtMBF1c cDNA over-expression (abc À + c) depending on physiological and developmental conditions. AtMBF1s regulate the expression of ABR1, which is a member of the ethyleneresponse factor family and acts as ABA repressor. Thus, we conclude that AtMBF1 gene family may function as a regulatory component of the cross-talk node between ethylene, ABA and stress signal pathways. Furthermore, higher levels of a HSP70 mRNA and an immunoreactive HSP70 protein were detected in the abc À mutant. The participation of MBF1c as a possible negative regulator of HSP genes was discussed.
Journal of Plant Physiology, 2010
Transcriptional co-activators of the multiprotein bridging factor 1 (MBF1) type belong to a small multigenic family that controls gene expression by connecting transcription factors and the basal transcription machinery. In this report, a triple knock-down mutant (abc À ) for the Arabidopsis thaliana MBF1 genes AtMBF1a, AtMBF1b and AtMBF1c was generated. The phenotypic characterization using oxidative agents such as hydrogen peroxide and methyl viologen revealed that the abc À mutant was more sensitive to oxidative stress. The triple knock-down mutant, abc À was also sensitive to osmotic stress mediated by high concentrations of sorbitol. Furthermore, the abc À phenotype was partially or completely rescued by AtMBF1c cDNA over-expression (abc À + c) depending on physiological and developmental conditions. AtMBF1s regulate the expression of ABR1, which is a member of the ethyleneresponse factor family and acts as ABA repressor. Thus, we conclude that AtMBF1 gene family may function as a regulatory component of the cross-talk node between ethylene, ABA and stress signal pathways. Furthermore, higher levels of a HSP70 mRNA and an immunoreactive HSP70 protein were detected in the abc À mutant. The participation of MBF1c as a possible negative regulator of HSP genes was discussed.
The EMBO journal, 1992
The G-box is a cis-acting element found within the promoters of many plant genes where it mediates expression in response to a variety of different stimuli. This palindromic DNA motif (CCACGTGG) is composed of two identical half sites, the base pairs of which we have numbered -4 to +4 (numbering from 5' to 3'). Both half sites are involved in the binding of the bZIP protein GBF1, a member of the GBF family of Arabidopsis thaliana. Here we demonstrate using the random binding site selection method that GBF1 interacts with, in addition to the palindromic G-box, other DNA motifs that fall into seven distinct groups. All groups share the ACGT core sequence, common to most DNA motifs bound by plant bZIP proteins so far characterized. Our studies demonstrate that a high affinity GBF1 binding site is further defined by the following two parameters: first, all sites contain a G residue at position +3 (as in ACGTG) and secondly, only certain base pair combinations are allowed at posi...