Inhibition of autophagy by hydroxychloroquine enhances antioxidant nutrients and delays postharvest fruit senescence of Ziziphus jujuba.

Autophagy, a mechanism of recycling intracellular constituents, favors plant growth, especially under nutrient starvation. However, autophagy's role in regulating postharvest fruit senescence is unclear. Here, effects of the autophagy inhibitor hydroxychloroquine (HCQ) and activator LiCl on postharvest jujube fruit senescence were investigated. HCQ significantly reduced weight loss and decay incidence, and enhanced firmness compared with those of the control. LiCl had the opposite effects. Protein oxidation and H2O2 increased significantly in LiCl-treated compared with HCQ-treated fruit. The contents of vitamin C, total thiol, and phenolics, and total antioxidant capacity and DPPH-radical scavenging capacity, followed the order: HCQ > control > LiCl. The HCQ-mediated reduction in fruit respiration was significantly enhanced by ATP and partly reversed by 2,4-dinitrophenol, a mitochondrial uncoupler. Thus, jujube fruit senescence may be regulated by autophagy and the antioxidant capacity. A mechanism of autophagy-mediated postharvest fruit senescence involving mitochondrial biogenesis and respiration was proposed.