ABA accelerates blackberry (Rubus spp.) fruit ripening by positively affecting ripening-related gene expression and metabolite profiles

BACKGROUND: The softness of blackberry fruits limits their postharvest shelf-life and commercial use, and abscisic acid (ABA) is considered one of the key hormones involved in fruit ripening. OBJECTIVE: This study aimed to explore the underlying physiological and molecular actions of ABA on blackberry fruit ripening and softening. METHODS: Various physiological indices of and plant hormone levels in treated and untreated blackberry fruits were determined simultaneously. The differentially expressed genes (DEGs) were analyzed by RNA-sequencing, and their expression profiles were detected. The ripening mechanism was elucidated by UHPLC-MS using two groups of fruits at 28 d. RESULTS: After 25 d, the ABA concentration and polygalacturonase (PG) and beta-1,4-endoglucanase (EG) activities in ABA-treated fruits were significantly higher than those in untreated fruits. Large differences in the expression profiles were detected at 28 d. The expression of DEGs related to cell wall softening and ABA synthesis was largely triggered after 25 or 28 d. Sixty-nine differentially accumulated metabolites were ultimately annotated as related to fruit ripening. CONCLUSIONS: ABA stimulates blackberry fruit ripening by promoting cell wall enzyme activities, the expression of various ripening-related genes and metabolite accumulation.