Effect of UV-B radiation on mass fraction of phenolic substances,antioxidant capacity and genes expression in Tetrastigma hemsleyanum
[Objective]This study aims to investigate the effects of UV-B radiation on phenolic components,antioxidant capacity and relation genes expression in Tetrastigma hemsleyanum.[Method]Three-year-old T.hemsleyanum seedlings were subjected to continuous UV-B radiation for 12.0 h and their phenotypes were observed at 0,0.5,1.0,3.0,6.0,and 12.0 h.With those untreated as control(ck),some other T.hemsleyanum were irradiated for 1.0 and 3.0 h(T1 and T3),and supplemented with dark treatment for 24.0 h(T1+23 and T3+21).Mass fractions of phenolic substances(total phenols and total flavonoids),antioxidant capacity,anti-stress enzyme activity,malondialdehyde(MDA)mass molar concentration in leaves were determined and transcriptome analysis was made.[Result]Continuous UV-B radiation had an effect on the phenotype of T.hemsleyanum.The leaves of 3-h group were partially yellowed,while the leaves of 6-h and 12-h groups were significantly yellowed and slightly curled.The mass fractions of total phenols(2.65 and 2.63 mg·g-1)and total flavonoids(7.16 and 7.30 mg·g-1)in leaves and root tubers,as well as the antioxidant capacity(86.56%)in root tubers reached the maximum in T1+23 group.Meanwhile,dark treatment after UV-B radiation promoted a significant increase in activities of catalase(CAT),peroxidase(POD)and superoxide dismutase(SOD),which reached the maximum in T1+23 group.The MDA mass molar concentration was the highest in T3+21 group(7.21 mmol·g-1).UV-B radiation and dark treatment down-regulated the expression of flavonoid synthesis pathway genes(ThF3H,ThANS,ThCHS,ThANR,etc.)and up-regulated the expression of oxidation-related regulators(CAT and SOD).[Conclusion]Darkness treatment after UV-B radiation increases the mass fraction of phenolic substances,antioxidant capacity and anti-stress enzymes activity of T.hemsleyanum,reaching the maximum in T1+23 group.The expression of flavonoid synthase genes is down-regulated and the expression of oxidative stress-related genes is up-regulated.[Ch,7 fig.2 tab.52 ref.]
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