Postharvest application of methyl jasmonate inhibited ethylene biosynthesis and signaling in peach through activating the negative feedback of JA-signaling pathway

Peach undergoes a rapid ripening and senescence, resulting in quality deterioration after harvest. Ethylene is essential for ripening and senescence in climacteric fruit. Although methyl jasmonate (MeJA) has been found to suppress ethylene biosynthesis, the underlying mechanism is unknown. We investigated the regulation of MeJA treatment (10 mu M, 24 h) on the quality, ethylene biosynthesis and signaling, and jasmonic acid (JA) metabolism and signaling in 'Xiahui 8' peach stored at 20 degrees C. MeJA treatment maintained better fruit quality and reduced ethylene production (the reduction of peak value reached 24 %) during storage. The activities of 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO) decreased by 15-28 % and 15-19 % in MeJA treated fruit during storage. Additionally, the expressions of genes involved in ethylene signaling were downregulated in MeJA treated fruit. MeJA treatment enhanced JA biosynthesis through increasing the activities of allene oxide synthase (AOS), allene oxide cyclase (AOC) and JA-amino synthetase (JAR) during early storage. However, the JA-inducible catabolic pathways and self-repression of myelocytomatosis proteins2 (MYC2) were activated in MeJA treated fruit thereafter. This resulted in the decrease of PpMYC2 transcription and JA-Ile accumulation, which reduced by at most 56 % and 73 % when compared with CK, respectively, on day 0 and day 5. These results suggested that negative feedback regulation terminated and repressed the JA signaling, therefore diminishing its enhancement effect on ethylene biosynthesis in peach during storage.