Arabidopsis MYB30 is a direct target of BES1 and cooperates with BES1 to regulate brassinosteroid‐induced gene expression

Abstract

SummaryA paradox of plant hormone biology is how a single small molecule can affect a diverse array of growth and developmental processes. For instance, brassinosteroids (BRs) regulate cell elongation, vascular differentiation, senescence and stress responses. BRs signal through the BES1/BZR1 (bri1-Ethylmethane Sulphonate suppressor 1/brassinazole-resistant 1) family of transcription factors, which regulate hundreds of target genes involved in this pathway, yet little is known of this transcriptional network. Through microarray and chromatin immunoprecipitation (ChIP) experiments, we identified a direct target gene of BES1, AtMYB30, which encodes an MYB family transcription factor. AtMYB30 null mutants display decreased BR responses and enhance the dwarf phenotype of a weak allele of the BR receptor mutant bri1. Many BR-regulated genes have reduced expression and/or hormone-induction in AtMYB30 mutants, indicating that AtMYB30 functions to promote expression of a subset of BR target genes. AtMYB30 and BES1 bind to a conserved MYB-binding site and E-box sequences, respectively, in the promoters of genes that are regulated by both BRs and AtMYB30. Finally, AtMYB30 and BES1 interact with each other both in vitro and in vivo. These results demonstrate that BES1 and AtMYB30 function cooperatively to promote BR target gene expression. Our results therefore establish a new mechanism by which AtMYB30, a direct target of BES1, functions to amplify BR signaling by helping BES1 activate downstream target genes.

Brassinosteroids control male fertility by regulating the expression of key genes involved in Arabidopsis anther and pollen development

“…For instance, BES1 and BIM1 can directly bind to the promoter regions of SAUR-AC1 and regulate its expression (37). A recent study found that AtMYB30, encoding a MYB family transcription factor, is a direct target gene of BES1, which may play an important role in the early stage of plant development (44). It was reported that BRs may play an important role in directing root epidermal cells to differentiate into hair cells or mature hairless cells in Arabidopsis (45).…”

Bipartite Promoter Element Required for Auxin Response

“…Each hormone could influence binding of the other pathway's transcription factor through regulation of cofactors. For example, MYB77 has been shown to interact with ARF7 (Shin et al, 2007) and MYB30 has been shown to directly interact with BES1 (Li et al, 2009). An alternative explanation is that each hormone is affecting the level of the other.…”

“…HUD elements were previously reported as overrepresented in the promoters of cycling genes related to diverse hormone pathways (Michael et al, 2008). Previous studies have shown that MYB30 can directly interact with BES1, bind to a site immediately adjacent to E4, and increase induction of SAUR15 expression (Li et al, 2009). For auxin, there are 10 TGTC/GACA core elements (Fig.…”

MYB transcription factor genes as regulators for plant responses: an overview

“…AtMYB5 regulated the outer seed coat differentiation (Gonzalez et al 2009) while AtMYB66 controlled root hair patterning. AtMYB23 regulated trichome extension and branching in combination with AtMYB5 (Li et al 2009). AtMYB16/MIXTA, is proposed to control the shape of petal epidermal cells (Baumann et al 2007), and AtMYB17 is reported to be a putative regulator of early inflorescence development and seed germination ).…”

“…In seedlings, AtMYB30 has also been shown to act in the brassinosteroid pathway controlling hypocotyls cell elongation (Li et al 2009). AtMYB62 is reported to be induced in response to phosphate starvation (Devaiah et al 2009) while AtMYB108 in both biotic and abiotic stress responses (Mengiste et al 2003).…”