Metabolic and transcriptional reprogramming during cavity formation and gum accumulation in plum flesh

Abstract Internal cavity formation followed by gum-like substance (GM) accumulation is a frequent quality disorder in mature ‘Fengtangli’ plum fruits, but the underlying physiological and molecular processes remain unclear. Here, we integrated widely targeted metabolomics, transcriptomics, and hormone profiling of GM, cavity-adjacent flesh (CF), and normal flesh (NF). Both GM and CF predominantly accumulated a range of secondary metabolites involved in stress response, including flavonoids, phenolic acids, and terpenoids. Compared with NF, CF exhibited significant reduction of glucose and fructose, along with increased L-malic acid, tartaric acid, and maslinic acid, and decreased cis -aconitic acid and neochlorogenic acid. These changes suggest substantial carbon redistribution that may also influence flavor. Hormone measurements further revealed a coordinated shift of signaling pathways in CF, marked by reduced auxin (IAA), cytokinins (CKs), and gibberellins and by increased jasmonic acid, salicylic acid, and abscisic acid. Consistently, CF exhibited enhanced oxidative- and defense-associated responses, including higher peroxidase activity, increased lignin deposition, and accumulation of phenylpropanoid-derived compounds. Transcriptome analysis showed that differentially expressed genes in CF were implicated in hormone signal transduction, sugar metabolism, and phenylpropanoid/flavonoid pathways. Collectively, these results demonstrate that cavity formation in plum flesh triggers carbon reallocation, secondary metabolite enrichment, and activation of defense-related pathways, providing new insight into tissue adaptation following internal cracking and gum development.