Keeping still life away from death: Functions and dynamics of gene expression during dormacy of Saccharomyces cerevisiae spores

While life is present everywhere on earth, each individual species can only grow and proliferate in a specific set of conditions. Moreover due to inherent fluctuation of the environment, individual organisms are often periodically confronted to stressful conditions that prohibit growth, reproduction and increase mortality. One of the most common strategy to cope with these harmful conditions is to shield and quietly wait for the storm to finish. Indeed upon change of the environment, many organisms enter "dormancy", whereby they differentiate into a distinct resting form with additional protection, storage and with greatly reduced internal activity (dormant state). Although relying on widely different molecular basis, specialized dormant stage are found in virtually every group of living organisms, including endospores of bacteria, spores of fungi, seeds of plants, cysts of protists and diapaused eggs of animals. Even after sometimes years of apparent inactivity, dormant organisms can resume growth and reproduction upon sudden improvement of environmental conditions.How such organisms manage to keep the potential to resume growth while having a nearly ceased activity? Over the last 20 years, scientists have uncovered various physiological and molecular mechanisms that control entry and exit of dormancy. However a basic understanding of what exactly happens during dormancy, i.e how to survive while stopping nearly all internal activity, is still missing. Two reasons are likely responsible for that knowledge gap. A first conceptual obstacle is a general view that since by definition nothingmuch happens during dormancy, nothing important happens. A second technical obstacle is the lack of sensitive enough instruments to quantify the "nearly ceased" activity during dormancy. As a result, very few studies have established the concrete link between a vanishing internal activity and the ability to survive during dormancy in a single experimental system.In this thesiswe propose to focus on dormant Saccharomyces cerevisiae yeast spores to specifically investigate the links between gene expression and the ability to survive during week-long dormancy.BN/Greg Bokinsky La