The Endoplasmic Reticulum Protein Orm2 is Required for Cold Adaptation in Saccharomyces cerevisiae

Despite the fact that wild yeast are known to grow under a wide range of environmental conditions, relatively little is known about mechanisms of cold adaptation. We have found that an endoplasmic reticulum‐resident protein Orm2 is required for cold adaptation in yeast as evidenced by poor growth of the deletion mutant orm2Δ at 10 degrees Celsius. In contrast, the homologous protein Orm1 is not required for cold adaptation. To elucidate the role of Orm2 in cold adaptation, we compared the sensitivity of orm2Δ and wild‐type cells to the anti‐fungal drug amphotericin B and found that orm2Δ cells are more sensitive to the drug at 10 degrees, but not at 30 degrees. orm2Δ mutants also displayed differences in relative amounts of the membrane components ergosterol and squalene as compared to wild‐type at 10 degrees, but not at 30 degrees. Taken together, these results suggest a role for Orm2 as a temperature‐sensitive regulator of the sterol biosynthetic pathway.