Associate Professor American University Washington, District of Columbia
Body of Abstract: Organ development in multicellular eukaryotes relies on the precise control of gene expression patterns. In angiosperms, floral organs are specified by the combinatorial action of multiple transcriptional activators with clearly defined functional domains. The boundaries of these domains are maintained by transcriptional repression mechanisms which spatially restrict the expression of floral organ identity genes. The transcriptional co-repressor TOPLESS (TPL) is central to cadastral regulation throughout the Arabidopsis flower. Numerous transcription factors have been shown to repress target genes by recruiting TPL, which associates with chromatin modifiers such as histone deacetylases. In this work, we employ genetic and biochemical approaches to investigate novel roles for TPL in the control of Arabidopsis floral gene expression. Similar to established TPL regulatory processes, we show that the ethylene-responsive element binding factor-associated amphiphilic repression (EAR) motif is important for the recruitment of TPL by transcription factors during floral patterning. Mutations of the conserved EAR motif in transcription factors result in misexpression of genes and homeotic conversion of floral organs. Collectively, this work broadens our understanding of the molecular mechanisms that establish gene expression boundaries in the flower.