The regulatory MaIAA1-like-MaERF003 module modulates the ripening of "Fenjiao" bananas.

Fruit ripening is a complex process mediated by plant hormones and transcriptional regulation. Ethylene and auxin are key regulators, but little is known about their crosstalk in fruit ripening. This study discovered the synergistic effect of auxin and ethylene during "Fenjiao" banana (Musa ABB Pisang Awak) fruit ripening, which is regulated by transcription factors MaIAA1-like and MaERF003. Both ethylene and auxin enhanced ripening and the expression of MaIAA1-like and MaERF003. However, 1-methylcyclopropene (1-MCP) treatment suppressed ripening and the expression of both genes. MaIAA1-like and MaERF003 activated the transcripts of genes associated with chlorophyll, starch, and cell wall degradation. Transient overexpression of MaIAA1-like and MaERF003 in "Fenjiao" banana enhanced ripening by accelerating softening and de-greening and by stimulating the expression of genes related to chlorophyll, starch, and cell wall degradation, while the transient silencing of MaIAA1-like and MaERF003 delayed softening and de-greening. Ectopic overexpression of MaIAA1-like and MaERF003 in tomato (Solanum lycopersicum) also accelerated fruit ripening. MaIAA1-like regulated MaERF003 transcription by directly interacting with its promoter. Additionally, the exogenous application of IAA mitigated the effect of 1-MCP on ripening in "Fenjiao" banana fruit, alleviating the ripening disorder induced by unsuitable 1-MCP. Our findings show that the MaIAA1-like-MaERF003 regulator module participates in the auxin-ethylene signal crosstalk to mediate ripening in "Fenjiao" banana.