Coronatine promotes post-harvest softening in ‘Gui Qi’ mango (Mangifera indica L.) through regulation of β-galactosidase and ethylene biosynthesis-related genes

Fruit softening is a key physiological event during ripening that directly influences texture, consumer acceptance, and early market supply. In ‘Gui Qi’ mango (Mangifera indica L.), timely and uniform softening is essential for commercial value and shelf-life management. While ethylene is well established as the primary regulator of ripening and softening in climacteric fruits, the role of coronatine (COR) in this process has not yet been investigated in ‘Gui Qi’ mango. In this study we investigated the effect of exogenous COR on mango fruit ripening and softening. It was observed that COR treatment had no effect on sugar and acid metabolism, but significantly reduced the fruit firmness and malondialdehyde (MDA) content, and increased peroxidase (POD) and catalase (CAT) activities. In addition, we have identified 24 mango β-galactosidase (Miβ-GAL)-encoding genes by transcriptome analysis. The results of relative gene expression showed that COR postharvest-treatment induced the expression of Miβ-GAL2, which exhibits a significant correlation with the ethylene level and its biosynthetic encoding genes such as S-adenosylmethionine synthetase (SAMS), 1-aminocyclopropane-1-carboxylate synthase (ACS), and aminocyclopropanecarboxylate oxidase (ACO) and synergically promote fruit softening. Therefore, treatment with COR modulates the expression of several Miβ-GAL genes, leading to increased β-GAL activity and a faster postharvest softening process in ‘Gui Qi’ mango.