Transcriptional Memory in Plants: Dissection of a Mechanism Required for Expression of the FLC/MAF MADS-box Gene Family

Michigan State University, East Lansing MI

Investigators

Abstract

An excellent model to study epigenetic mechanisms in eukaryotes is the Polycomb Group (PcG)-mediated silencing of the Arabidopsis MADS-box floral repressor gene FLOWERING LOCUS C (FLC), and associated initiation of flowering, after extended growth of the plant in the cold. To better understand the dynamics of FLC expression, genetic screens were used identify seven genes designated VIP1-VIP7 required for the maintenance of FLC activity in non-vernalized plants. At least four of these encode proteins related to distinct components of yeast Paf1C, a transcription factor that associates with elongating RNA polymerase II (Pol II) and assists in the establishment and/or maintenance of transcription-promotive chromatin modifications, such as methylation of histone H3 lysine-4 by the trithorax-related histone methylase Set1. It is thought that, in yeast, H3K4 trimethylation within active genes comprises a 'molecular memory' of gene transcription. Potentially the Arabidopsis VIP proteins act as a mediator between transcriptional activity and the maintenance of 'activating' histone modifications. The goal of this project is to build a mechanistic model for the activity of the VIP proteins on their targets FLC and the related MAF1, and for the interaction of this activity with developmental mechanisms of gene silencing. This project will contribute to our knowledge of plant development, transcriptional elongation, and epigenetic mechanisms in eukaryotes. The research will provide training opportunities for postdocs, graduates, undergraduates, and high-school students, including members of minority groups under-represented in science. Training in protein-related techniques such as those described here will be especially valuable to the plant research community, where such techniques have not yet been widely used.