Epigenome and Transcriptome Studies during Dormancy in Sweet Cherry Flower Buds

In perennial species, dormancy is a period of repressed growth that acts to protect sensitive tissues during unfavorable climatic conditions. Dormancy and bud burst are strongly affected by temperature. The mean surface temperature of the earth is increasing and this climatic change may have serious negative consequences on the dormancy release, potentially resulting in lower cherry production. Despite this strong effect of temperature on dormancy, the molecular events regulating dormancy and the effect of temperature on dormancy are still not very well understood. It has been shown that DORMANCY-ASSOCIATED MADS-box (DAM)-related genes are up-regulated in dormant buds in a certain number of plants (peach, raspberry, leafy spurge, poplar). Recent studies also highlighted the presence of epigenetic mechanisms in the regulation of bud dormancy. To better understand the mechanisms underlying the effect of temperature on dormancy we are assessing genome-wide dynamics of several chromatin marks and expression during dormancy in floral buds of sweet cherry (Prunus avium L.) varieties with contrasted bud burst dates. To validate the role of epigenetic mechanisms in dormancy and the dormancy release in cherry floral buds, we are also studying the effect of epigenetic drugs on the dormancy cycle of floral buds. We observed a distinct change in histone methylation in floral buds during the dormancy cycle. We could also detect transcriptional dynamics of dormancy-related genes and we are currently analysing their interplay. The results of floral bud treatment with epigenetic drugs also confirmed the crucial role of chromatin dynamics in bud burst. Ongoing and future studies will help to identify mechanisms and gene markers involved in dormancy in sweet cherry with a view to draw parallels with the process of vernalisation in annual species as Arabidopsis thaliana, which were already known.