The HOG pathway in the halophilic black yeast Hortaea werneckii: isolation of the HOG1 homolog gene and activation of HwHog1p.

The mitogen-activated protein kinase (MAPK) Hog1p plays an essential role in the yeast hyperosmotic response. A homolog of the HOG1 gene was isolated from the halophilic black yeast Hortaea werneckii encoding a putative 359 amino acid protein, HwHog1p, with high homology to Saccharomyces cerevisiae Hog1p and to other eukaryotic Hog1p homologs. HwHog1p contains a TGY motif within a protein kinase catalytic domain and a C-terminal common docking (CD) motif. Its activation by increased salinity is regulated at the posttranscriptional level. HwHog1p is located on the plasma membrane under nonstress conditions. Upon increased external salinity it is translocated from the membrane, presumably to the nucleus.