Isolation and characterization of a metallothionein-1 protein in Chloris virgata Swartz that enhances stress tolerances to oxidative, salinity and carbonate stress in Saccharomyces cerevisiaei

Chloris virgata Swartz (C. virgata) is a gramineous wild plant that is found in alkaline soil areas in northeast China and is highly tolerant to carbonate stress. We constructed a cDNA library from C. virgata seedlings treated with NaHCO3, and isolated a type1 metallothionein (MT1) gene (ChlMT1: AB294238) from the library. The amino acid sequence of ChlMT1 contained 12 cysteine residues that constituted the Cys-X-Cys (X = amino acid except Cys) motifs in the N- and C-terminal regions. Northern hybridization showed that expression of ChlMT1 was induced by several abiotic stresses, from salts (NaCl and NaHCO3), a ROS inducer (paraquat), and metals (CUSO4, ZnSO4, and COCl2). ChlMT1 expression in leaf was induced by 200 mM NaCl and 100 mM NaHCO3. About 5 mu M Paraquat, 500 mu M Zn2+, and 500 mu M Co2+ also induced expression of ChlMT1 in leaf after 6 h, and 100 mu M CU2+ induced it after 24 h. Saccharomyces cerevisiae when transformed with the ChlMT1 gene had dramatically increased tolerances to salts (NaCl and NaHCO3) and ROS.