Effect of Paper-Bagging on Apple Skin Patterning Associated with MdMYB10 Promoter Methylation

Paper-bagging is an efficient method to maximize apple skin color, but a relationship between this technique and fruit skin patterning has not been demonstrated. Here, the 'Fuji' fruit with red-striped skin changed to red-blushed skin under re-exposure to light after bag treatment. Higher expression of MdMYB10, a transcription factor that regulates anthocyanin biosynthesis in apples, correlated with increased anthocyanin concentration in bag removal fruit. At the mature stage, a comparison of methylation status in the MdMYB10 promoter revealed that the methylation level in the region from -2585 to -2117 bp was reduced in bag removal fruit, especially for CHG context. It can be regulated by the downregulated expression of DNA methyltransferases such as MdMET, MdCMT, and MdDRM. Our results suggest that the bag removal treatment in this cultivar causes a change in skin patterning from striped to blushed pigmentation by inducing DNA demethylation of MdMYB10.