Abstract

SummaryWhether or not βglucosidase is active in fleshy fruit remains unknown. We investigated levels of gene expression, enzyme activities, and the physiological functions of βglucosidase 1 (FaBG1) in strawberry (Fragaria ananassa Duch.) fruit flesh. Real-time RT-PCR analysis showed that concomitant with the onset of fruit colour development in strawberry, levels of expression of the βglucosidase 1 gene (FaBG1) increased rapidly. Furthermore, 15 mM histamine, an inhibitor of βglucosidase, significantly inhibited red-colour development in strawberry fruit. These results suggest that FaBG1 might play a role in strawberry fruit ripening. A combination of enzyme incubation assays with receptacle tissue and GC-MS analysis demonstrated that the red-colour in strawberry fruit was rich in abscisic acid (ABA)-glucosyl ester (ABA-GE) and that FaBG1 had high glycosyl hydrolase activity, which could promote the accumulation of free ABA via hydrolysis of ABA-GE. Using tobacco rattle virus (TRV)-induced gene silencing (VIGS), down-regulation of FaBG1 gene expression not only inhibited strawberry fruit ripening, but also led to a significant decline in ABA concentration in VIGS-treated fruit. In conclusion, these results provide physiological, biochemical, and molecular evidence to validate the hypothesis that strawberry βglucosidase 1 (FaBG1) has high glycosyl hydrolase activity and plays a role in fruit ripening via the rapid production of free ABA.

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