Functional characterization of a type 2 metallothionein gene, SsMT2, from alkaline-tolerant Suaeda salsa.

A type 2 metallothionein gene, SsMT2, was cloned from Suaeda salsa, a salt- and alkali-tolerant plant, which is dominant species on the saline/alkali soil of northeast China. The SsMT2 gene was expressed in all organs except the flower and its expression was induced by various stresses such as CdCl2, NaCl, NaHCO3, and H2O2 treatments. SsMT2-transgenic yeast (Saccharomyces cerevisiae) and plants (Arabidopsis thaliana) showed significantly increased resistance to metal, salt and oxidant stresses. These transgenics accumulated more Cd2+, but less Na+ than their wild type counterparts. SsMT2 transgenic Arabidopsis maintained lower level of H2O2 than wild type plants did in response to the stress treatments. These results demonstrated that the SsMT2 gene plays an important role in reactive oxygen species scavenging and confers enhanced metal and oxidant tolerance to plants.