The yeast MAPK Hog1 is not essential for immediate survival under osmostress.

The yeast HOG pathway is activated in response to increased osmolarity and affects many cellular activities. As cells lacking Hog1 are osmo-sensitive it is believed that Hog1 is essential for survival under osmostress. We show, however, that hog1Delta cells survive and even proliferate to some degree under high osmostress for many hours. If forced to enter G1/G0 prior the exposure to osmostress, hog1Delta cells survive for at least 6days. We suggest that the primary role of Hog1 is not to preserve viability upon exposure to stress. We discuss the possibility that Hog1 is needed for proliferation under osmostress.