Exogenous γ-glutamic acid (GABA) induces proline and glutathione synthesis in alleviating Cd-induced photosynthetic inhibition and oxidative damage in tobacco leaves

Abstract

ABSTRACT The effects of exogenous γ-glutamic acid (GABA) on photosynthetic gas exchange capacity, PSII function, proline (Pro) synthesis and ROS metabolism of tobacco leaves under cadmium (Cd) stress were studied. The results showed that both stomatal and non-stomatal factors were the important factors to limit the photosynthetic capacity of tobacco leaves under Cd stress. Pro accumulation and glutathione (GSH) content increase are the important ways for tobacco leaves to adapt to Cd stress. Exogenous GABA significantly increased the stability of oxygen-evolving complex (OEC) and the electron transfer rate of PSII in tobacco leaves under Cd stress, and increased Gs and Pn in varying degrees. Exogenous GABA also increased the expression of P5CS and P5CR genes in tobacco leaves under Cd stress, thus promoting Pro accumulation. In conclusion, 0.5 mmol·L−1 exogenous GABA can not only improve the carbon assimilation ability by increasing the Gs , but also alleviate the oxidative damage by promoting the synthesis and accumulation of Pro and GSH, and improve the stability of photosynthetic function of tobacco leaves under Cd stress.