Methylation of Is Associated with Anthocyanin Accumulation in the Kiwifruit Outer Pericarp.

Most red-fleshed kiwifruit cultivars, such as Hongyang, only accumulate anthocyanins in the inner pericarp; the trait of full red flesh becomes the goal pursued by breeders. In this study, we identified a mutant "H-16" showing a red color in both the inner and outer pericarps, and the underlying mechanism was explored. Through transcriptome analysis, a key differentially expressed gene was screened out, which was positively correlated with anthocyanin accumulation in the outer pericarp. The result of McrBC-PCR and bisulfite sequencing revealed that the SG3 region (-292 to -597 bp) of promoter in "H-16" had a significantly lower CHH cytosine methylation level than that in Hongyang, accompanied by low expression of methyltransferase genes ( and ) and high expression of demethylase genes ( and ). Transient calli transformation confirmed that demethylase gene can activate transcription of to enhance its expression. Overexpression of enhanced the anthocyanin accumulation in the fruit flesh and leaves of the transgenic lines. These results suggested that a decrease in the methylation level of the promoter may contribute to accumulation of anthocyanin in the outer pericarp of "H-16".