The regulatory module involved in ABA-induced ethylene production and fruit ripening in banana and its implications

The plant hormone abscisic acid (ABA) affects ethylene biosynthesis and postharvest shelf life of fruits. However, the family members encoding the ABA core signaling components that are responsible for ABA-induced ethylene biosynthesis and fruit ripening remain unidentified, with the underlying mechanism elusive. Here, we confirm that exogenous ABA treatment induces ethylene biosynthesis and accelerates postharvest banana ripening. Combining transcriptomic analysis and the information of gene families encoding ABA signaling components and downstream transcription factors, we highlight MaPYL3-MaPP2C17-MaSnRK2.3 as one of the major signaling modules responsible for ABA-induced ethylene production. Downstream of the ABA signaling, the transcription factor MabZIP95 is controlled by ABA treatment and directly binds to the promoters of MbACS7, MbACO2, and MbACO3, key for ethylene biosynthesis during banana fruit ripening. The expression of this ABA regulatory module was significantly elevated at 5 days postharvest after ABA treatment, well associated with the earlier and stronger ethylene production. Besides, the comparison of the ABA-related fruit ripening process has been discussed between horticultural crops, suggesting our strategy as effective in the gene discovery towards ABA-regulated fruit development. Finally, our work reveals the MaPYL3-MaPP2C17-MaSnRK2.3-MabZIP95-MbACS7/MbACO3/MbACO2 regulatory module and indicates its functional involvement in ABA-induced ethylene synthesis and postharvest ripening in banana, providing valuable target genes for the molecular breeding to extend the shelf-life of banana.