A CHH Methylation–Ubiquitination Cascade Links Light‐Induced Anthocyanin Accumulation in Pear Fruit
Yansong Zhu, Xinyu Li, Chen Yang, Yunfu Gong, Wenjun Liu, Qi Zou, Lei Yu, Nan Wang, Xuesen Chen, Zongying ZhangABSTRACT
Light is a key environmental cue for anthocyanin biosynthesis in fruit, but the DNA methylation targets and downstream mechanisms remain largely unclear. Using the red‐skinned pear cultivar ‘Aohong No. 1’, we performed whole‐genome bisulfite sequencing (WGBS) and RNA‐seq on peels before and after light exposure following bag removal. Light‐induced genome‐wide CHH hypermethylation, with differentially methylated regions (DMRs) enriched in promoters. Integrative analysis identified the RING‐type E3 ligase RGLG5 as a negative regulator of pigmentation. A 420‐bp promoter fragment of RGLG5 underwent light‐induced CHH hypermethylation, concomitant with RGLG5 transcriptional downregulation. This methylation blocked the binding of the AP2 transcription factor to the fragment, thereby silencing RGLG5. RGLG5 mediated ubiquitin–proteasome‐dependent degradation of the transcription factor WRKY75L. Silencing of RGLG5 allowed WRKY75L to accumulate and directly activate MYB10, promoting pigmentation. Co‐expression assays further confirmed that RGLG5 antagonized WRKY75L‐driven anthocyanin accumulation in pear peel and callus tissues. Collectively, these findings support a model in which light‐triggered CHH methylation of the RGLG5 promoter links epigenetic silencing to protein stability during fruit pigmentation, and identify the RGLG5 promoter as a potential epigenetic target for breeding.