FaABI4 is involved in strawberry fruit ripening

• FaABI4, as a critical downstream component of ABA signaling in plants, whether it is involved in strawberry ripening remains unclear.
• FaABI4 is expressed ubiquitously in strawberry plants and higher in red-coloring fruits, and induced by ABA, sucrose and glucose.
• Downregulation of FaABI4 transcripts inhibits ABA and sugar contents, also ripening, demonstrating that FaABI4 takes part in the ripening.

Abscisic acid (ABA) is regarded as an important regulator in non-climacteric fruit ripening, especially in strawberry fruit. FaABI4, as a critical downstream component of ABA signaling in plants, whether it is involved in strawberry ripening remains unclear. The octoploid strawberry (Fragaria ananassa, ‘Beinongxiang’) fruits were used here to explore this question. Our results showed that FaABI4 expressed higher in leaves, followed in flowers and fruits, but less in roots and stems, and that coupled with the fruit ripening, its transcripts increased gradually, suggesting that FaABI4 might play a role in the ripening. Using tobacco rattle virus-induced gene silencing (VIGS), downregulation of FaABI4 transcripts significantly delayed fruit ripening in consistent with changes of firmness, sugar and ABA contents, as well as transcripts of several ripening-related genes, including CA4H, CHI, DFR, CHS, GAL6, PE5, and XYL2. Interestingly, ABA, sucrose and glucose all induced FaABI4 expression through fruit-disc incubation in vitro. In conclusion, our results demonstrate that FaABI4 plays an important role in the regulation of strawberry fruit ripening, and its expression is induced by ABA, sucrose and glucose.