Analysis of global changes in gene expression during activity-dormancy cycle in hybrid aspen apex

Perennial plants such as the long-lived trees of boreal forest cycle between periods of active growth and dormancy. Transition from active growth to dormancy is induced by short day (SD) signal. Once dormancy is established, prolonged exposure to low temperature is required for breaking dormancy before warm temperatures can induce growth. We have studied global changes in gene expression in the apex of model plant hybrid aspen during the distinct stages of activity-dormancy cycle. Our data shows that all stages of activity-dormancy cycle in the apex are associated with substantial modulation of the transcriptome. Detailed analysis of core cell cycle genes indicates that with the exception of plant specific B-type CDKs, all of the other CDKs are regulated post-transcriptionally during growth cessation. SD signal appears to target the expression of cyclin genes that are down regulated during growth arrest. Several of the cold hardiness related genes e. g. dehydrins are induced during transition to dormancy although temperature is not reduced and the up-regulation of the expression of these genes does not appear to rely on SD mediated induction of classical CBF transcription factors. Our results suggest that transcriptional control plays a key role in modulation of hormones such as ABA and GA that are known to play a central role in various processes during activity-dormancy cycle. Analysis of histone and DNA modification genes indicates that chromatin remodeling could be involved in coordinating global changes in gene expression during activity-dormancy cycle.