Mutation in yl-HOG1 represses the filament-to-yeast transition in the dimorphic yeast Yarrowia lipolytica

Background: Yarrowia lipolytica is a dimorphic fungus, which switches from yeast to yeast-to-filament form in response to environmental conditions. For industrial purposes it is important to lock cells in the yeast or filamentous form depending on the fermentation process. yl-Hog1 kinase is a key component of the HOG signaling pathway, responsible for activating the osmotic stress response. Additionally, deletion of yl-Hog1 leads to increased filamentation in Yarrowia lipolytica , but causes significant sensitivity to osmotic stress induced by a high concentration of a carbon source. Results In this study, we tested the effect of point mutations on the function of yl-Hog1 protein kinase. The targets of modification were the phosphorylation sites (T171A-Y173A) and the active center (K49R). Introduction of the variant HOG1-49 into the hog1∆ strain partially improved growth under osmotic stress, but did not recover the yeast-like shape of the cells. The HOG1-171/173 variant was completely inactive, and its introduction further weakened the hog1∆ strains. To verify a genetic modification in filament form, we developed a new system based on green fluorescent protein (GFP) for easier screening of proper mutants. Conclusions These results provide new insights into the functions of yl-Hog1 protein in dimorphic transition and constitute a good starting point for further genetic modification of Y. lipolytica in filament form.