S19 - Session O1 - Spatiotemporal genome-wide DNA methylation changes during blueberry ripening and DNA demethylation-induced cluster ripening

Authors: Taishan Li *, Yamane Hisayo, Ryutaro Tao

Fruit ripening is a complex process in which not only plant hormones and transcription factors, but also epigenetic modifications may play crucial roles. In recent years, DNA methylation has been reported to affect fruit ripening in various horticultural crops, while the relationship between DNA methylation and the ripening of blueberry ( Vaccinium spp. ) remains to be elucidated. We first performed whole-genome methylation sequencing on blueberry 'O'Neal' fruit during fruit ripening. The results showed that the status of CHG- and CHH-type methylated cytosines (mCs) changed differently in the peel and flesh from the green to the mature stages on the global level, while differentially modified mCs analysis suggests similar demethylation changes in peel and flesh, with more than 3500 hypo-differentially methylated regions in both organs. In order to verify the function of demethylation changes on fruit ripening, azacytidine (5-AzaC) was used to reduce the global DNA methylation level of six-year-old 'O'Neal'. We found that 5-AzaC treatment could significantly promote fruit ripening, and the average ripening date of the treated group was two weeks earlier than the control group. In addition, the consistency of cluster ripening was also significantly improved, which indicates the potential value of DNA demethylation as a technique for blueberry cluster harvesting. We also found a significantly higher anthocyanin content in the treated group. A significant increase in sugar content was found in treated groups when compared with the control group although the sugar content in the treated fruit was lower than that of the normally mature (2~3 weeks after treatment) fruits, due to the limited duration of maturation. Taken together, these results indicate the potential utility of DNA demethylation in regulating the ripening of blueberry.