Integrated metabolomics and transcriptomics characterize anthocyanin accumulation in purple-leaved guava (Psidium guajava L.)

Guava ( Psidium guajava L.) leaves occur in purple and green phenotypes, but the mechanisms underlying leaf coloration remain unclear. Here, targeted metabolomics and transcriptomics were used to compare the purple-leaved cultivar “Ziguo” (PL) with the green-leaved cultivar “Zhenzhu” (ZL). Targeted metabolomic analysis showed that PAs accounted for a greater proportion of the quantified flavonoid-related metabolite pool in ZL, whereas anthocyanins predominated in PL, with cyanidin derivatives as the major pigments. Transcriptomic analysis revealed significant downregulation of key proanthocyanidin-branch genes, including LAR and ANR , in PL. In addition, the candidate anthocyanin transport-related gene PgGSTF9 was expressed at higher levels in PL, whereas the candidate PA transport-related gene PgDTX41 was expressed at lower levels. Among candidate regulators, PgMYBA1 showed higher expression in PL, whereas PgMYB3 and PgTT2 were expressed at lower levels. Together, these results show that anthocyanin accumulation in PL is associated with lower expression of PA-branch genes and contrasting expression patterns of candidate transport- and MYB-related genes. These patterns are consistent with possible differences in anthocyanin–PA metabolic partitioning between the two cultivars. This study improves our understanding of anthocyanin accumulation in guava leaves and provides candidate targets for future functional studies.