Abstract: Soybean PM2 protein belongs to the family of group 3 LEA (late embryogenesis abundant) proteins. In the present paper, yeast expression vectors encoding full-length PM2 protein and deleted polypeptides containing 22-mer motif were constructed. The yeast recombinants were obtained after transformation. Expression of PM2 and the deleted polypeptides of PM2A, PM2B and PM2C were identified in yeast lysis by SDS-PAGE and ESI-MS/MS or MALAI-TOF/TOF analysis. The growth performances of yeast recombinants and their control with empty vector were tested under normal, high salinity（1.5 mol·L^-1 NaCl）or high osmotic（2 mol·L^-1 sorbitol）conditions. The results showed that: 1) the expressions of PM2 protein and its 22-mer motif are not deleterious to the growth behavior of yeast recombinants under normal condition; 2) the recoveries of 4 recombinants are better than that of control with the empty vector under high salinity conditions, indicating that PM2 protein and its 22-mer motif could improve salt tolerance of yeast directly. The high salt tolerance of yeast conferred by 4 polypeptides are PM2C>PM2B≈PM2A≈PM2; 3) no growth difference was observed between the 4 recombinants and the control under high sorbitol stress. These results showed that 22-mer motif is a functional domain in PM2 protein and it is consist with the results described as in E. coli. All these results provide directly experimental support for the hypothesis that “LEA proteins may represent analogous protection to the high salinity stress in prokaryotes and eukaryotes” for the first time.

Key words: LEA3 proteins, PM2 protein, salt tolerance, yeast, 22-mer motif