Integrated Transcriptome and Metabolome Analyses Reveal Anthocyanin Biosynthesis in Red and Green Mango Pericarps under Light and Shade Conditions

Anthocyanin is a natural plant pigment whose biosynthesis is intricately linked to light regulation. Here, pericarps of red mango cultivars named 'Xinshiji (XSJ)' and 'Hongmang No.6 (HM6)' directly exposed to sunlight were red while they were green under shade conditions, whereas the pericarps of green mango cultivar known as 'Guiqi (GQ)' maintained green within both light and shade conditions. However, the mechanisms underlying these color changes under different light conditions remain largely unexplored. Therefore, we analyzed the contents, components, and biosynthesis of anthocyanins in the above mango pericarps through metabolome and transcriptome analyses. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis releaved a total of 35 anthocyanin compounds were detected in the mango pericarps. Transcriptome analysis uncovered 44 differentially expressed genes among the comparison of 'XSJ', 'HM6', and 'GQ' samples. Twelve and eight candidate genes were identified in the anthocyanin biosynthesis and chlorophyll breakdown pathways, respectively. A co-expression network of the key anthocyanin biosynthetic genes revealed that twelve transcription factors may govern anthocyanin biosynthesis and chlorophyll breakdown processes under light. These candidate genes were further verified by real-time quantitative PCR (RT-qPCR) for providing a regulatory model for the formation of red-and green-pericarps in mangoes under light and shade conditions. These results deepen our understanding of light-induced anthocyanin biosynthesis in fruits.