Different light-response patterns of coloration and related gene expression in red pears ( Pyrus L.)

The coloration of fruit peel in red pear is influenced by light. However, the various responses to light among different varieties are still unstudied. In this study, the different light-response patterns of 27 pear cultivars under artificial light conditions were observed. The results revealed three types of coloration patterns: type-I cultivars showed no coloration; type-II cultivars showed significant coloration; and type-III cultivars showed faint coloration. Cultivars ‘Mantianhong’, ‘Fojianxi’, ‘Yunhongli 1′, and ‘Starkrimson’ were chosen as representative for further analysis of anthocyanin content and components as well as gene expression related to color. Four anthocyanin components were detected in different cultivars when exposed to artificial light and natural light, and the difference in anthocyanin content led to different colored phenotypes, with a similar response under different light conditions. The expression patterns of genes encoding enzymes indicated that ANS and UFGT were decisive genes involved in anthocyanin biosynthesis for red-skinned pears, and the varying expression of these genes led to coloration differences observed between light-response patterns. The expression patterns of transcription factors indicated that the MYB10, bHLH33, and WD40 genes are involved in differential regulatory mechanisms of anthocyanin biosynthesis and coloration patterns between light-response patterns. The expression of light-responsive genes indicated that the expressions of HY5, PhyA, COP1, DET1, and PIF3 genes are involved in the differential regulatory mechanisms of anthocyanin biosynthesis and coloration patterns between light-response patterns. The results provide an important reference for studying the molecular mechanism of light response and coloration in red pear and lay the foundation for future studies on red pear coloration research.