The role of jasmonic acid and lipoxygenase in propylene-induced chilling tolerance on banana fruit

Banana fruit are sensitive to chilling stress. This study investigated the possible mechanism of propylene-reducing chilling injury (CI) to postharvest banana fruit. Firmness, chromaticity, ethylene production, CI index, electrolyte leakage, lipoxygenases (LOX) activity, contents of jasmonic acid (JA) and salicylic acid (SA) and the expression of genes MaLOX1, MaACS1 and MaACO1 in fruit were examined. The study shows that the propylene treatment delayed CI symptom development and chromaticity change by 2 days. Meantime, the treatment reduced electrolyte leakage, induced LOX activity in the early stage of cold storage and increased JA content in banana peel. SA immersion after propylene treatment improved the SA content in banana peel, but inhibited the LOX activity and JA content increasing, resulting in CI symptom as serious as that of untreated controls. Expression of genes MaLOX1, MaACS1 and MaACO1 in banana fruit was enhanced by propylene treatment. But no significant differences were observed in firmness, ethylene production, MaLOX1, MaACS1 and MaACO1 expression levels between propylene and propylene SA-treated fruit. These results indicated that the LOX activity increasing and JA burst in the early stage of cold storage may play a key role in tolerance the chilling stress in banana fruit.