Identification of regulatory elements in the Saccharomyces cerevisiae GPD1 promoter with distinct function during adaptation to or steady-state growth in NaCl.
Homan Alipour, Peter Eriksson, Anders Blomberg
Microbiology, Cell and Molecular Biology, Medicinaregatan 9C, Göteborg, SE-405 30, Sweden (homan.alipour@gmm.gu.se)

The yeast GPD1 gene encodes a NADH-dependent glycerol-3-phosphate dehydrogenase, a key enzyme in the glycerol production pathway, which is important for adaptation and growth during salt stress. Rap1p is an important factor for the GPD1 induction during steady-state growth on medium containing NaCl. However, Rap1p is not involved in the GPD1 regulation during adaptation to NaCl. The GPD1 promoter contains four putative STREs. In this study we demonstrate that a 672bp promoter fragment, that does not contain the most distal C₄T (789) motif, displayed identical responsiveness to both low and high salt compared to the full-length native promoter. In addition, extensive mutations of the three most proximal C₄T motifs did not influence the level of GPD1 induction upon salt stress or heat-shock. These results indicate that none of the four C₄T motifs located in the GPD1 promoter are functionally important during its stress regulation. Furthermore, we have identified a 50bp fragment of the promoter that contains the important sequences for GPD1 osmotic regulation during adaptation. This 50bp fragment is dependent on the transcription factor Hot1p for mediating the salt stress response.

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