Metabolomic-transcriptomic analysis unravels flavonoids accumulation mechanism in ‘Tainong 1’ mango pulp under enhanced UV-B radiation

Mango ( Mangifera indica L.) is one of the main economic crops in Hainan, China, prized for its distinctive flavor and high nutritional value. It is also rich in health-promoting antioxidants such as vitamin C and flavonoids. Enhanced ultraviolet-B (UV-B) radiation, a growing global environmental concern, alters plant antioxidant systems, with increased flavonoid accumulation as a common adaptive response. However, its effects on mango fruit remain largely unexplored. To investigate the antioxidant responses of mango to enhanced UV-B radiation and identify key responsive flavonoid compounds and regulatory genes, we exposed ‘Tainong 1’ mango fruits growing under natural light to 96 kJ · m -2 · d -1 of UV-B radiation to simulate high UV-B conditions. Treated fruits were smaller in size and had a pulp of a more intense yellow colour. Further, malondialdehyde content in treated fruits was higher during the phase of rapid fruit enlargement. Additionally, treated fruits showed increased sugar-acid ratios, total phenol, total flavonoid, carotenoid, and ascorbic acid contents. Furthermore, they showed significantly enhanced antioxidant activity, as measured by the FRAP, ABTS, and DPPH assays. Extensive targeted metabolomic-analysis identified flavonoids as the largest category of compounds differentially expressed in treated and control groups. Quantitative metabolomics of flavonoids identified Hyperoside, Quercimeritrin, and (-)-Catechin gallate as the key flavonoid metabolites responsive to UV-B treatment. Transcriptome analysis revealed an enrichment of the flavonoid biosynthesis pathway, with most associated differentially expressed genes showing upregulation. Furthermore, qRT-PCR analysis confirmed that the expression of the genes MiCHS7 , MiCHI1 , MiCHI2 , MiFLS , MiF3H2 , and MiF3H3 correlated with changes in key flavonoid metabolites. Indeed, correlation analysis indicated that MiCHS7 , MiCHI1 , MiFLS , and MiF3H3 are potential key genes involved in flavonoid accumulation under UV-B treatment. Thus, our study provides a theoretical basis for breeding for new resilient varieties and developing UV-B-resistant mango cultivation techniques.