Erich Grotewold

Dept. of Plant Biology and Plant Biotechnology Center, The Ohio State University, Columbus, OH 43210

Over the past years we have used flavonoid biosynthesis as a model system to investigate the mechanisms by which plants control gene expression. In maize, two branches of flavonoid biosynthesis are independently regulated by the Myb-domain proteins P and C1, providing one of the best understood regulatory networks in plants. Understanding how Myb-domain transcription factors achieve biological specificity is of central importance, as plants express several hundreds of these proteins. P activates transcription on its own, but C1 does not and requires a Myb-domain mediated physical interaction with an R/B bHLH factor. A central question is how does this protein-protein contact modulates C1 function, and what are the determinants for the specificity of this interaction. Our studies are starting to shed light on a possibly wider role played by Myb domains as protein-protein interaction motifs. Recently, we have started to use transposable elements to dissect promoter function in vivo, and to understand how insertions in cis-acting elements can affect gene expression. Preliminary data will be presented suggesting that this may provide a novel and unique way to understand the structure, function and evolution of DNA regulatory elements.