Transcriptomic Analysis of Sweet Cherry Floral Buds During the Development of Cold-Hardiness, Endodormancy and Bud Break

A change in climate has the very real potential of affecting our ability to grow crops due to spring frosts, drought, or reduced chilling accumulation.  It is necessary to have detailed information on the processes involved in order to effectively model these changes.  The effect of temperature on dormancy/phenology models is missing a clear understanding of the induction and completion of dormancy.  Sweet cherry floral buds are initiated in the summer of the year prior to flowering and over-winter in a dormant state and require a prolonged exposure to moderate temperatures (chilling units) to induce bud-break in the spring.  We have examined cold-hardiness of buds using low temperature exotherms (LTE) associated with intra-cellular freezing as well as greenhouse forcing of buds to determine state of endodormancy.  We have sampled dissected floral buds from the same source throughout winter to correlate these physiological processes with anatomical and gene expression changes.  We have constructed 23 RNA-Seq libraries to follow the changes in gene expression throughout the entire late fall to early spring bud-break period.  Genes showing significant transitions in expression preceding or associated with physiological changes have been confirmed with quantitative PCR over three years with significant differences in seasonal weather patterns.