Transcriptional control of phenylpropanoid metabolism

Transcriptional regulation of phenylpropanoid biosynthetic genes is brought about by the interaction of 2 classes of transcription factors. The Myb class, of which are at least 70 genes in Arabidopsis, are being studied, and early results suggest that the diversity of phenylpropanoid gene expression may be due to differences in tissue specific gene expression and/or gene activation potential of Myb proteins. The mapping and sequencing of Myb genes in Arabidopsis will allow a systematic analysis of their function, and this work will be associated with a detailed functional analysis of Myb action on the phenylalanine ammonia lyase (PAL) and chalcone synthase CHS promoters, where a Myb protein has been found to bind and activate transcription. Gene activation requires the binding of a second class of factors, belonging to the b-ZIP protein family. A major goal is to clarify the function of these, whose activities are defined biochemically, with respect to the function of the bHLH class of transcription factors (akin to Myc proteins) which bind to the same cis sequences as b-ZIPS, and which have a genetically defined role in activating CHS and other tenes. The analysis of bHLH proteins belonging to the maize R gene family reveals mechanisms of light activation of different members of the gene family. This is intriguing in relation to the demonstrated role of parsley bZIP proteins in the light activation of CHS genes.