Shading in fruit changes the polyphenol accumulation of pellicle by regulating activity of key enzymes and expression of their gene related polyphenol anabolism of Juglans sigillata Dode

• Published in: Scientia horticulturae 2024-04, Vol.329, p.113017, Article 113017
• Main Authors: Jiang, Yi, Chen, Jing, Zhang, Wen'e, Pan, Xuejun
• Format: Article
• Language: English
• Subjects: Enzyme related to polyphenol; Juglans sigillata Dode; Light; Pellicle; Polyphenol; Polyphenol synthesis gene
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/j.scienta.2024.113017

•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 hig