ABA and chromatin remodelling regulate the activity-dormancy cycle in hybrid aspen

One of the most important survival strategies plants have evolved is the cessation of growth and development of dormancy in response to the seasonal changes. Apical meristems of deciduous woody plants living in temperate and boreal zones undergo a yearly cycle between an active and a dormant state, which allows them to protect the meristem and avoid damage provoked by extremes of low temperatures during the winter. The transition between an active and a dormant state includes a complex network of physiological and developmental processes such as acquisition of cold hardiness, bud formation and maturation and metabolic changes, which are underlined by a global change in gene expression. The studies described in my thesis provide an overview of the transcriptional control underlying the activity-dormancy cycle and are aimed to dissect the regulation of overlapping short days (SD)-induced processes. We investigated the control of SD-induced bud formation and maturation, acquisition of adaptive responses and of endodormancy and identified novel key molecular players regulating these processes. Our results provide evidence for a composite control of the activity-dormancy cycle by the SD signal that involves plant hormone abscisic acid (ABA) and a component of a chromatin remodelling complex, FERTILISATION INDEPEDENDENT ENDOSPERM (FIE), as key players. Importantly, our work reveals a degree of conservation in the regulatory framework for the control of dormancy in seeds and apical buds.