Hydrogen sulfide alleviates zinc toxicity by reducing zinc uptake and regulating genes expression of antioxidative enzymes and metallothioneins in roots of the cadmium/zinc hyperaccumulator Solanum nigrum L.

Abstract

Zinc (Zn) is a toxic element for plant at high concentrations. As a biologically active gaseous molecule, hydrogen sulfide (H2S) regulates plant growth and development. The aim of this study is to reveal the ameliorative effects of H2S on the physiological and molecular responses of a hyperaccumulator to Zn toxicity. Growth analysis, biochemical and zymological methods, fluorescent microscopic imaging, western-blot and quantitative real-time PCR analysis were performed to investigate the roles of NaHS (a donor of H2S) on the cadmium (Cd)/Zn hyperaccumulator, Solanum nigrum L. H2S ameliorated excess Zn-induced growth inhibition, especially in roots. H2S decreased free cytosolic Zn2+ content in roots which was correlated well with the down-regulation of Zn uptake and homeostasis related genes expression. Besides, H2S further enhanced the expression of the metallothioneins (MTs). Moreover, Zn-induced oxidative stress was also alleviated by H2S. The alleviation of H2S on excess Zn toxicity in S. nigrum is presumably attributed to: (1) the decrease in Zn accumulation via down-regulation of Zn uptake and homeostasis related genes expression; (2) the enhancement in the expression of MTs which chelate excess Zn; (3) the change in the genes expression of antioxidative enzymes, leading to H2O2 reduction.