Effects of GABA on the polyphenol accumulation and antioxidant activities in tea plants (Camellia sinensis L.) under heat-stress conditions.

Polyphenols are important active components in tea plants, which have strong biological activity and antioxidant activity. A certain degree of stress or exogenous substances can significantly increase the content of polyphenols in plants. γ-Aminobutyric acid (GABA), a natural functional amino acid, was used to study whether exogenous GABA can increase the content of polyphenols and enhance antioxidant activity in tea plants under heat-stress conditions. The results showed that the content of GABA was positively correlated with the content of polyphenols (r = 0.649), especially with the content of total catechins (r = 0.837). Most of the related genes encoding flavonoid metabolism (PAL, C4H, 4CL , CHS, CHI, F3H, F3′H, F3′5′H, DFR, LAR, ANS , ANR and FLS) as well as enzyme activities (PAL, C4H and 4CL) were upregulated. In addition, the activities of antioxidant enzymes were induced under heat-stress conditions. However, 3-mercaptopropionic acid (3-MPA), an inhibitor of GABA synthesis, exhibited opposite results under heat-stress conditions compared with GABA treatment. These results indicated that GABA plays a key role in the accumulation of polyphenols and the upregulation of the antioxidant system in tea plants under heat-stress conditions. • Exogenous GABA greatly contributed to catechin accumulation in tea. • Exogenous GABA actively induced increased POD, CAT and APX activities. • The catechin biosynthesis related genes were upregulated induced by GABA. [ABSTRACT FROM AUTHOR]