Heterologous expression of the osmotolerant yeast Candida glycerolgenesis glycerol-3-phosphate dehydrogenase gene (CgGPD) in Saccharomyces cerevisiae lacking the HOG pathway

Abstract

The cytoplasmic glycerol-3-phosphate dehydrogenase of Candida glycerinogenes encoded by CgGPD is a critical enzyme in overproducing glycerol. The function of CgGPD has been characterized, however little information is known about the participation of CgGPD in the high osmolarity glycerol (HOG) pathway. In this study, expression and the function of CgGPD were investigated in Saccharomyces cerevisiae strains lacking a HOG component (hog1, pbs2 and gpd1/gpd2 mutants). Expression of CgGPD in gpd1/gpd2 mutants not only increased viability but also enhanced the salt tolerance and growth capability in a high osmotic medium. Functional comparison of CgGPD, GPD1 and GPD2 showed that expression of either gene significantly improved growth properties of both hog1 and pbs2 mutants under high osmolarity conditions except that the expression of GPD1 had little effect on the growth of hog1 mutants. Expression of CgGPD and GPD1 led to a similar growth pattern in gpd1/gpd2 mutants however, GPD2 had a perceptible impact on its growth properties. Further analysis showed that intracellular glycerol accumulated increasingly in response to high osmolarity conditions in all mutants expressing CgGPD, GPD1 or GPD2. Furthermore, expression of CgGPD was induced by osmo-stress in hog1 and pbs2 mutants however, the transcriptional strength was correspondingly lower when it was expressed in gpd1/gpd2 mutants.