AchMYC2 promotes JA-mediated suberin polyphenolic accumulation via the activation of phenylpropanoid metabolism-related genes in the wound healing of kiwifruit (Actinidia chinensis)

Suberin polyphenolic (SPP), a kind of agronomically significant biopolymer, is composed primarily of phenolic acids generally synthesized by phenylpropanoid metabolism. In this study, the transcriptional activation of suberin polyphenolic biosynthesis by jasmonic acid (JA) inducible-transcription factor AchMYC2 was confirmed in wound tissues of kiwifruit (Actinidia chinensis). Three general phenylpropanoid metabolism-related genes, AchPAL, AchC4H and Ach4CL respectively encoding phenylalanine ammonia-lyase (PAL), cinnamic acid-4-hydroxylase (C4H) and 4-coumaric-CoA ligase were determined in the kiwifruit core tissues overexpressing these genes. Besides, the positive regulation of AchMYC2 on AchPAL, AchC4H and Ach4CL was observed. JA-induced AchMYC2 locating in the nucleus activated the transcriptional expression of AchPAL, AchC4H and Ach4CL through binding to their promoters. The results were further evidenced in the kiwifruit core tissues overexpressing of AchMYC2, in which AchMYC2 enhanced the expression levels of AchPAL, AchC4H and Ach4CL and increased the accumulation of phenolic acids including cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid and sinapic acid. Meanwhile, the contents of five phenolic acids in the kiwifruit wound tissues were increased by methyl jasmonate (MeJA), but reduced by diethyldithiocarbamic acid (DIECA, an inhibitor of JA biosynthesis). Together results indicated that AchMYC2 activated AchPAL, AchC4H and Ach4CL transcription to promote JA-mediated suberin polyphenolic accumulation in the wound healing of kiwifruit.