The PpAHL17-PpHYH module is involved in light-independent anthocyanin accumulation in fruit peel of Prunus persica.

Key message: The PpAHL17-PpHYH module is involved in the accumulation of light-independent anthocyanins in peach peel. PpAHL17 activated the expression of PpHYH and positively regulated the synthesis of anthocyanin. The red color of peach peel is derived from the accumulation of anthocyanins, which significantly impacts its market value. While the understanding of the mechanism underlying light-dependent anthocyanin accumulation in peach peel is comprehensive, the process of light-independent anthocyanin accumulation remains elusive. Here, we examined two peach varieties, 'Zhongyou 4' (light-dependent) and 'Luxing' (light-independent), which showed different patterns of anthocyanin accumulation after shading bagging treatments. Analysis of these two peach varieties using RNA sequencing (RNA-seq) and weighted correlation network analysis (WGCNA) revealed that the genes PpAHL17 and PpHYH play a key role in regulating light-independent anthocyanin accumulation in peach peel. Under dark conditions, PpAHL17 and PpHYH have a high expression in the peel of the light-independent varieties, but not in the light-dependent varieties. Results from transient overexpression experiments demonstrated that the upregulation of PpAHL17 and PpHYH genes enhanced the biosynthesis of anthocyanins in peach peel. Furthermore, PpAHL17 can bind to the PpHYH promoter, thereby activating its expression, and PpHYH positively regulated the expression of anthocyanin synthesis-related genes PpF3H, PpUFGT, and PpMYB10.1. Our research provides new perspectives on the mechanisms governing the accumulation of anthocyanins in peach peel in the absence of light.