A CHH Methylation-Ubiquitination Cascade Links Light-Induced Anthocyanin Accumulation in Pear Fruit
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Updated: Nov 3, 2026

Annotation of Plant Gene Function via Combined Genomics, Metabolomics and Informatics
Published on: June 17, 2012
Yansong Zhu1, Xinyu Li1, Chen Yang1
1College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, China.
Abstract:
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.
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