Deletion of
the redox regulated GPD2 gene in Saccharomyces cerevisiae strongly alters Tdh1p
expression during anaerobic growth.
Äsa Valadi,
Hadi Valadi, Ricky Ansell, Lena Gustafsson, Joakim Norbeck, Lennart Adler,
Anders Blomberg
CMB-microbiology, Göteborg University, Medicinaregatan 9C, Göteborg, 41390,
Sweden (asa.valadi@gmm.gu.se)
When yeast cells are cultured under anaerobic conditions they produce glycerol to maintain their cytosolic redox balance. This production is dependent on the anaerobically induced GPD2 gene, encoding an iso-form of the NAD+ dependent glycerol-3-phosphate dehydrogenase. A strain lacking the GPD2 gene exhibits poor anaerobic growth. This growth inhibition appears due to NADH accumulation since wild type growth is restored after addition of acetoin, which serves an artificial acceptor of NADH. To explore how protein expression is affected by anoxic redox stress we investigated the anaerobic protein expression profile of the gpd2 strain by 2D gel electrophoresis. Some of the proteins that are specifically induced in a gpd2 strain under anaerobic conditions are down-regulated following addition of acetoin, suggesting that the enhanced levels are related to the elevated NADH/NAD+ ratio. The protein that displayed the most obvious response in this respect was identified as Tdh1p, an iso-form of glyceraldehyde-3-phosphate dehydrogenase. To investigate the physiological importance of the observed Tdh1p response, TDH1 was deleted in the gpd2 background. Interestingly, this additional deletion of TDH1 improved the anaerobic growth of the strain. We propose that Tdh1p may be used as a sensor of the anaerobic redox state.