Molecular analysis of growth cessation and dormancy in hybrid aspen

Abstract: Perennial plants such as trees living in temperate zones experience extreme changes in temperature during summers and winters. In order to survive, shoot apical and cambial meristem undergo a transition from active growth to dormant state, well in advance of winter onset. The transition between an active growth and dormancy involves physiological and developmental processes such as bud formation, acquisition of cold hardiness that are underpinned by massive changes transcriptional and metabolic programs. The studies of this thesis provide an insight into the molecular regulation underlying the photoperiodic control of growth cessation, adaptive response and acquisition of dormancy in model tree hybrid aspen. Our data show that components of flowering pathway i.e. LAP1 and FDL1 have evolved new functions to mediate in SD-control of growth cessation and adaptive response. Furthermore, we found that FIE, a component of evolutionary conserved PRC2 complex, in concert with Abscisic Acid (ABA) are key regulators of dormancy in Populus. We demonstrate that an interplay between these two components and yet another chromatin remodelling factor PICKLE is necessary for the development of dormancy. In summary, this thesis sheds new light on molecular regulation of activity-dormancy cycle in hybrid aspen. Our better understanding of how trees regulate growth cessation, adaptive response and dormancy may be useful to devise strategies to engineer trees with altered activity-dormancy traits in order to improve their productivity under the impending climate change.