Exogenous arginine enhances the chilling tolerance in postharvest papaya fruit by regulating arginine and proline metabolism

Papaya fruit is easily affected by low temperature, causing chilling injury (CI). In this study, the exogenous arginine was applied in the storage of postharvest papaya fruit and it was found that 0.8 mM arginine treatment significantly alleviated CI of papaya fruit. Arginine treatment promoted the accumulation of polyamines (PAs), which might be ascribed to the increased activities of arginase, arginine decarboxylase (ADC), ornithine decarboxylase (ODC), and S-adenosylmethionine decarboxylase (SAMDC). A higher accumulation of proline was found in arginine-treated papaya fruit, which may be due to increased activity of ornithine-δ-aminotransferase (OAT) and Δ 1 -pyrroline-5-carboxylate acid synthase (P5CS) and inhibited activity of proline dehydrogenase (PDH). In addition, arginine treatment increased higher nitric oxide synthase (NOS) activity and promoted the generation of nitric oxide (NO). The results of this study indicate that exogenous arginine may improve the chilling tolerance of postharvest papaya fruit by regulating arginine and proline metabolism. Practical applications In recent years, chilling injury of tropical fruits is a significant problem, including papaya. Many studies on polyamine, proline, nitric oxide, and chilling injury of fruits, but arginine, as a common precursor of polyamine, proline, and nitric oxide, are rarely studied, especially in papaya fruit. Our findings demonstrated that the exogenous arginine can regulate endogenous arginine metabolism, induce polyamine, putrescine, and nitric oxide accumulation, and coordinate to alleviate chilling injury of papaya fruit.