Functional Analysis Of A Type2Metallothionein Gene Of Suaeda Salsa

Suaeda salsa is one of110species in the Suaeda genus and is highly tolerant to carbonate stress in the alkaline soils in the Northeast China. We constructed a cDNA library from seedlings and isolated a type2metallothionein (MT) gene (GenBank access number8996172, designated as SsMT). The gene amino acid sequence was homologous to those of type2MT-like proteins. Southern blot analysis revealed that this gene exists multiple copies in the S. salsa genome. At the RNA level research SsMT gene expression in different organizations, Northern blot results showed SsMT genes in seeds of the Suaeda salsa expressed quantity highest, secondly, in turn, the leaf, stem, root, flower. The SsMT gene in transgenic yeast and Arabidopsis plants was over-expressed and significantly increased the resistance to metal (CdCl2), salts (NaCl, NaHCO3) and oxidative stresses (H2O2). The comparison of ions transgenic and wild type (WT) genotypes showed that transgenic Arabidopsis accumulated less Na+in the shoots and roots. SsMT increased the resistance to CdCl2and NaCl, NaHCO3, but are not directly linked to Cd2+and Na+accumulation in the transgenic Arabidopsis. In addition, SsMT transgenic Arabidopsis accumulated less reactive oxygen species (H2O2) than WT plants under the stress of CdCl2, NaCl, NaHCO3and H2O2. Transgenic yeast and Arabidopsis expressing synthetic GFP fused to SsMT subcellular localization showed SsMT gene was expressed in the cytoplasm. Further analysis showed that the SsMT was also expressed in the cytoplasm in transgenic cells when stress environment applied. Taken together, the gene SsMT plays an important role in stress tolerance and could function as an effective ROS scavenge. These results increased our understanding of the tolerance mechanisms in the halophyte plants to the metal, salt and oxidative stresses.