The mechanism and network of BES1 mediated transcriptional regulation in Brassinosteroids (BR) pathway in Arabidopsis

Li, Lei
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Brassinosteroids (BRs) are a family of steroid hormones present ubiquitously in plant

kingdoms and play important roles throughout plant growth and development. BRs signal to

regulate BES1 and BZR1 family transcription factors, which regulate target genes for various

BR responses. However, our knowledge about the transcriptional network and mechanisms

through which BES1 regulates gene expression is still limited. Background information about

BR signaling and transcriptional regulation is presented in Chapter 1.

The goal of my research is to understand the mechanism and network for BES1

mediated transcription regulation using both forward and reverse genetics, as well as

genomic approaches. Specifically, my thesis includes three main projects I have been

worked on. Chapter 2 is about the transcription factor AtMYB30 that was identified as BR-

induced transcription factor. I found that AtMYB30 is a BES1 direct target and meanwhile its

protein helps BES1 to activate downstream target genes. Chapter 3 describes the discovery

of a novel transcription elongation factor AtIWS1 required for BES1-regulated gene

expression, which was identified by a forward genetics screen. In chapter 4, I describe a

collaborative project in which we used chromatin immunoprecipitation coupled with tiling

arrays (ChIP-chip), global gene profiling, as well as computational modeling to construct and

validate a BR-transcriptional network. Finally, conclusions and future directions are

summarized in chapter 5.

Arabidopsis, BES1, Brassinosteroids, Transcription