Aquaporins and hexose transporters in a wine strain of Saccharomyces cerevisiae

Proteins are important components of the plasma membrane in the yeast Saccharomyces cerevisiae. In this research two classes of membrane proteins were studied in a wine yeast strain: Aquaporins (AQY1 and AQY2) and the Hexose Transporters (HXTI-HXT17 ). These proteins play different roles in the membrane of this organism. Although several functions have been attributed to Aqy1p in laboratory yeast strains, no clear role for Aqy1p in the wine yeast UCD 932 could be defined. The AQY1 gene form UCD 932 was found to be functional in a heterologous expression system but deletion of this gene showed no effect on the ability of the strain to ferment synthetic grape juice media, to resist ethanol challenges, or on the formation/germination of spores. AQY 2 was found to be nonfunctional in UCD 932, as expected.; The hexose transporters play very important roles in the utilization of sugars over a wide concentration range. The first seven hexose transporter genes have been described as the major sugar transporters during fermentation. Of these major hexose transporters during fermentation, HXT1, HXT3 , and HXTS were found to be the most abundant hexose transporters in UCD 932 using Green Fluorescent Protein tagging. Deletion of HXT1, HXT3, or HXT5 in UCD 932 did not affect the ability of the strain to ferment synthetic media. When these deletion strains were grown in media containing ethanol, the strain lacking HXT3 was not able to complete the fermentation to the same extent as the other deletion strains. The role of HXT3 in this ethanol sensitivity was not clearly defined, but the insertion of a functional HXT3 into the HXT5 locus was not able to overcome this defect and restore wild-type growth.