LED light treatment modulates metabolite accumulation and gene expression to enhance flavor and alter pigmentation in litchi fruits

• LED light increased the ratio of sugars to organic acids in litchi pulp and altered the amino acid profile in litchi pulp. • Exposure to LED light during litchi growth promoted the accumulation of flavor components in litchi pulp. • LED light irradiation increased the total anthocyanin content but decreased procyanidin levels in the litchi pericarp. These changes may be associated with the regulation of genes involved in the flavonoid biosynthesis pathway. Litchi is renowned for its distinctive appearance, flavor, and nutrient composition. This study investigated the potential of nocturnal white LED light exposure, applied from the pre-second physiological fruit drop stage to harvest, to enhance the quality of ‘Feizixiao’ litchi. We focused on understanding its effects on the physical-chemical properties, aromatic profile, and gene activity. Our results showed that LED treatment significantly improved internal fruit quality by increasing the sugar/organic acid ratio in the litchi pulp and delaying the postharvest loss of key aroma compounds like 2,4-nonadienal and rose oxide isomers. Metabolomic analysis of the pulp identified 254 differentially accumulated metabolites (DAMs), primarily associated with amino acid biosynthesis. Additionally, LED treatment altered the anthocyanin profile in the pericarp, significantly elevating the level of cyanidin-3- O -glucoside, a key contributor to red pigmentation, even as it reduced the overall content of procyanidins. Transcriptomic data indicated that this shift may be attributed to LED-induced regulation of flavonoid biosynthesis genes. This work demonstrates LED light profoundly shapes litchi quality, offering valuable insights for balancing flavor and appearance in horticultural practices.