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The postharvest deterioration of mango fruits is a critical issue limiting mango storage and preservation due to its climacteric nature. This study evaluated the storage behavior of two mango cultivars and their response to exogenous melatonin (MT, 1000 μmol L−1) treatment in attenuating fruit decay and enhancing fruits' physiological and metabolic processes and gene relative expression subjected to cold storage. MT treatment in both mango cultivars significantly delayed weight loss, firmness, respiration rate, and decay incidence. However, MT did not influence the TSS, TA, and TSS:TA ratio regardless of the cultivar. Moreover, MT inhibited the decrease in total phenol and flavonoid content and AsA content while delaying the increase in the MDA content of mango during storage in both cultivars. In addition, MT dramatically inhibited the enzyme activity of PPO. In contrast, an increase in the activities of antioxidant enzymes (SOD and APX) and PAL and their genes' relative expression was noticed in MT-treated fruits versus control in both cultivars. However, MT treatment was cultivar dependent in most parameters under study. These results demonstrated that MT treatment could be an essential postharvest treatment in minimizing decay, maintaining fruit quality, and extending mango fruits' postharvest shelf life by enhancing the physiological and metabolic processes during cold storage. [ABSTRACT FROM AUTHOR]

• Proper shading could reduce the content of TPC and TFC in in Juglans sigillata Dode pellicle, and promote the accumulation of total flavonoids in extreme darkness. • Shading could reduce the accumulation of flavonoids in Juglans sigillata Dode pellicle. • Shading could increase of PAL enzyme activity and JsPAL expression level indicated that it played an important role in the accumulation of TPC and TFC. • Shading decreased activity of key enzymes (C4H, 4CL, CHS, CHI, F3H, FLS) in the phenylpropane-flavonoid pathway and the down-regulated expression of key structural genes (JsC4H, Js4CL, JsCHS, JsCHI, JsF3H, JsFLS) after shading. Polyphenols, abundant in the pellicle of walnuts, confer health benefits to the human body. The intricate relationship between light and phenolic compounds underscores the impact of shading, which can effectively diminish phenolic content and enhance the palatability of food. In this study, we delved into the connection between polyphenol accumulation, related enzyme activities, and gene expression in the pellicle of Juglans sigillata Dode under varying degrees of shading. The results show that different shade intensities can change polyphenols' content and affect the activity of key polyphenols anabolism enzymes and their gene expression. With the increase of the shading intensity, the total phenolics content (TPC) and total flavonoids content (TFC) were lower than the nomal light. In the mature stage, shading 60 % was lowest. 7 individual phenolics were identified in the pellicle, and the content of each varied significantly with the decrease of light intensity. Except for p -coumaric acid and ferulic acid, which were higher than the control at mature stage, all phenolics were lower than the control, but the overall trend was the same as that of the control. The activity of key enzymes in the anabolism of polyphenols was significantly affected after shading. In complete darkness phenylalanine ammonia lyase (PAL) was highest at the kernel-filling stage, shading 20 % of chalcone synthase (CHS) and shading 60 % of flavonol synthase (FLS) responded most strongly at the hard-core stage, while flavanone 3-hydroxylase (F3H) was most active at shading 60 % of kernel-filling stage, which was 2.03, 1.38, 4.67, and 2.08 times that of the control, respectively. The expression levels of key genes showed that the expression level of JsPAL was significantly increased at hard-core stage and mature stage, and the expression of JsPAL was 3.85 times higher than that of the control at the mature stage with 60 % shading. Correlation analysis showed that PAL enzyme activity was highly correlated with TPC, TFC and various individual phenolics with the increase of shading intensity. The content of p -coumaric acid was positively correlated with the activities of 4-coumarate coenzyme A ligase (4CL), F3H and FLS. The increase of shading intensity enhanced the correlation between total phenolics content, total flavonoids content, individual phenolics substances and JsPAL, JsC4H, JsCHS, JsCHI and JsFLS. Overall, PAL was a key enzyme affecting polyphenol accumulation under different shading levels, while at the genetic level, JsPAL, JsC4H, JsCHS, JsCHI and JsFLS were the key genes affecting them. This study will potentially provide more information for light management and polyphenol regulation in walnut cultivation. [ABSTRACT FROM AUTHOR]

[Display omitted] • TRV-VIGS was successfully used on Juglans sigillata aseptic seedlings. • TRV-VIGS was successfully used on Juglans sigillata fruits. • The functional differences of homologous genes in green husk were evaluated. Juglans sigillata Dode is one of the important tree species in southwest China, and it has significant economic and ecological value. However, there is still a lack of effective methods to identify the functional genes of J. sigillata. By verifying the model plant tobacco, the pTRV2::JsPDS vector was able to cause photobleaching. This study showed that photobleaching occurred 24 and 30 d after the silencing vector was infected with aseptic seedlings and fruits of J. sigillata , respectively. When the OD 600 was 0.6, and the injection dose was 500 μL, the gene silencing efficiency of aseptic seedlings was the highest at 16.7 %, significantly better than other treatments. Moreover, when the OD 600 was 0.8, and the injection dose was 500 μL, the gene silencing efficiency in the walnut fruit was the highest (20 %). In addition, the VIGS system was successfully used to silence JsFLS2 and JsFLS4 genes in J. sigillata. This study also showed that the flavonol content and gene expression in the treatment group were decreased compared to the control group. In addition, the proteins transcribed and translated from the JsFLS4 gene may have higher catalytic activity for dihydroquercetin. The above results indicate that the TRV-mediated VIGS system can be an ideal tool for studying J. sigillata gene function. [ABSTRACT FROM AUTHOR]