PL-02 Vernalization – Cold-mediated epigenetic regulation of a developmental switch

At a certain stage in their life-cycle plants flower, that is they undergo the transition from vegetative to reproductive development. The correct timing of this transition is crucial for reproductive success, so the plant integrates multiple environmental and endogenous signals to judge when to flower. The Dean laboratory is studying the importance of prolonged cold for flowering, a process known as vernalization. Our current view of the vernalization pathway has been built up though identification of Arabidopsis mutants and analysis of the corresponding genes, complemented by chromatin biochemistry. The vernalization pathway in Arabidopsis mediates the silencing of a target – FLC, by a conserved Polycomb mechanism. The talk will describe our understanding of the triggering of FLC repression by prolonged cold; the nucleation of chromatin silencing at a specific site in FLC; and the spreading of the silencing yet spatial restriction to FLC. We are aiming to describe this epigenetic silencing in a quantitative model and our efforts to date will be presented. Arabidopsis accessions have adapted to a wide range of latitudes and climates. We are studying whether variation in vernalization has contributed to this adaptation and have found that molecular variation at FLC is an important component. Our current understanding of this variation, its evolutionary origins and ecological significance will be discussed.