Improvement of salt tolerance in transgenic potato plants by glyceraldehyde-3 phosphate dehydrogenase gene transfer

In the previous experiment, we isolated and characterized glyceraldehyde-3- phosphate dehydrogenase (GPD) gene of the oyster mushroom, Pleurotus sajor- caju. Expression levels of the GPD gene in the mycelia of P sajor-caju was significantly increased by exposing the mycelia to abiotic stresses, such a s salt, cold, heat, and drought. We also showed that GPD confers abiotic st ress resistance when introduced into yeast cells. The survival rate of the transgenic yeast cell that harbored the GPD gene was significantly higher w hen the yeast cells were subjected to salt, cold, heat, and drought stresse s, compared with the yeast that was transformed with the pYES2 vector alone . In order to investigate the functional role of the R sajor-caju GPD gene in higher plant cells, the complete P sajor-caju GPD cDNA was fused into th e CaM35S promoter and then introduced into potato plants. Putative potato t ransformants were screened by using PCR. Twenty-one transformants were furt her analyzed with RT-PCR to confirm the expression of P sajor-caju GPD. A R T-PCR Southern blot analysis revealed that 12 transgenics induced the P. sa jor-caju GPD gene expression. A bioassay of these transformants revealed th at the R sajor-caju GPD gene was enough to confer salt stress resistance in the potato plant cell system. Results showed that P sajor-caju GPD, which was continuously expressed in transgenic potato plants under normal growing conditions, resulted in improved tolerance against salt loading.