Abstract

Phytohormones are signaling molecules produced by plants and play pivotal roles in various physiological and developmental processes. Ethylene and abscisic acid (ABA) are usually considered to have separate roles in regulating fruit ripening and co-regulation involving both hormones have rarely been investigated. Here, similar changes in ethylene and ABA were observed underlying postharvest persimmon ripening. High CO 2 (95% CO 2 , 1% O 2 ) and high CO 2 + 1-methylcyclopropene (CO 2 + 1-MCP) are two widely used commercial deastringency treatments for persimmon, which accumulate acetaldehyde by anaerobic metabolism to precipitate astringent soluble tannins . Unexpectedly, CO 2 treatment triggered the accumulation of both ethylene and ABA. This could be inhibited by CO 2 + 1-MCP, which also prevented CO 2 -driven rapid softening. Three differentially expressed genes, DkACS1 , DkNCED1 + 3′ and DkNCED2 + 3′ involved in ethylene and ABA synthesis were identified, but none of the differentially expressed transcription factors tested showed any obvious transactivation effects on their gene promoters. RNA binding protein DkRBM24–1 was shown to regulate the transcription of DkACS1 and DkNCED2 + 3′ by binding to the 3′UTR region of their mRNA. Further analysis indicated that DkbHLH11 was able to activate the expression of DkNCED1 + 3′ after phosphorylation by protein kinase DkMAPKKK1. Overall, the present study indicated the ethylene and ABA production in ripening fruit have both shared (DkRBM24–1) and distinct (DkbHLH11) regulators.