A GSHS-like gene from Lycium chinense maybe regulated by cadmium-induced endogenous salicylic acid and overexpression of this gene enhances tolerance to cadmium stress in Arabidopsis

A GSHS gene, LcGSHS , was cloned from L. chinense for the first time. Evidence is presented here that endogenous SA accumulation maybe important for the regulation of LcGSHS expression level. Glutathione (GSH) plays a pivotal role in heavy metal detoxification. GSH synthetase (GSHS) catalyzes the rate-limiting step of GSH synthesis in plants. Salicylic acid (SA) is one of the important plant hormones, which plays a critical role in triggering plant responses to different stresses such as cadmium (Cd) stress. Until now, little has been done to explore the relationship among the accumulation of endogenous SA, GSHS transcript levels and the GSH content in plants under Cd treatment and we will investigate this link in this study. The chlorophyll content, transcripts level of LcGSHS gene, endogenous SA accumulation, GSH accumulation and Cd concentration in the leaves of Lycium chinense were studied under different treatment conditions. Endogenous SA, LcGSHS transcript expression and GSH content can be induced by Cd treatment in L. chinense, however, reduced by co-treatment with 2-aminoindan-2-phosphonic acid (AIP), an inhibitor of SA biosynthesis. Strong staining was observed in the leaves of Arabidopsis expressing ProLcGSHS::GUS under Cd stress and the staining was reduced by co-treatment with AIP. The transgenic Arabidopsis expressing ProLcGSHS::LcGSHS also showed greater tolerance to Cd stress than wild types. Evidence was presented here that under Cd stress, GSH accumulation occurred via enhanced LcGSHS gene expression and the SA signaling cascade was involved in this accumulation. Furthermore, the overexpression of LcGSHS in transgenic Arabidopsis resulted in greater tolerance to Cd stress than wild-type lines.