Endogenous melatonin delays sepal senescence and extends the storage life of broccoli florets by decreasing ethylene biosynthesis

Abstract

Although previous work has revealed that exogenous melatonin (MT) improves the storage life and quality of broccoli, whether endogenous MT has similar effects and the mechanism of MT action remains uncertain. We discovered that during storage of broccoli, endogenous MT was impaired. Supplementation with 100 μmol L-1 MT enhanced endogenous MT production, whereas 10 μmol L-1 luzindole (LD, an MT receptor inhibitor) decreased endogenous MT production. Differences in sepal yellowing, storage life, and chlorophyll degradation were observed, such that the senescence of broccoli was delayed by MT but accelerated by LD. Further results revealed that the decreased storage life and accelerated senescence induced by LD were blocked by MT administration, and endogenous MT homeostasis was re-established. These beneficial roles of MT were verified by the alleviation of senescence-induced ethylene production and the increased activities of ethylene biosynthesis enzymes. Compared with those of LD alone, the expressions of chlorophyll degradation-related and ethylene biosynthesis-related genes were also downregulated when MT was added. Overall, the above results imply that endogenous MT homeostasis prolongs the storage life and delays the senescence of broccoli by decreasing ethylene biosynthesis.