New Insights in the Epigenetic Regulation of Floral Bud Dormancy and Cold Accumulation in Sweet Cherry (Prunus avium)

Floral bud dormancy release and flowering in temperate fruit species such as sweet cherry depends on the fulfillment of chilling requirement during winter and heat accumulation at beginning of spring. The uncertainty associated with the climate change on a global level presents a series of new challenges on the management of agricultural systems. Especially in Chile the warmer winters of the last decade have been negatively affecting the sweet cherry industry.

Recent findings highlight the epigenetic control of dormancy events in fruit species such as peach, pear and chestnut. In order to understand the molecular bases of floral bud dormancy and cold accumulation in sweet cherry and to develop molecular markers for the trait, we explored different aspects of epigenetic regulation.

To search for DNA methylation patterns that would be related to cold accumulation we have been using bisulfite sequencing, methylation-sensitive amplified polymorphism (MSAP) and methylated DNA immunoprecipitation (MeDIP). DNA from floral buds with different chilling hour accumulation was obtained from sweet cherry varieties with contrasting chilling requirement. To complement these assays, we also performed small RNA deep sequencing, miRNA identification and validation by stem-loop PCR in one of the varieties.

We could identify some differentially methylated regions that could be correlated to cold accumulation and may be used as epi-alleles for the trait. We also observed that in some cases small RNA directed DNA Methylation (RdDM) seemed to be involved. All together these results suggest that epigenetic regulation plays a pivotal role in the environmental control of dormancy.

Funding: FONDEF G09I1008, CORFO 13CTI21520-SP05, FONDECYT 1130197