Dimorphism in Yarrowia lipolytica: filament formation is suppressed by nitrogen starvation and inhibition of respiration.

In contrast to Saccharomyces cerevisiae, nitrogen starvation inhibited formation of hyphae in liquid cultures of Y. lipolytica, while carbon source did not seem to be important for filament formation. Inhibitors of mitochondrial respiration strongly suppressed the development of hyphae, indicating that energy conversion processes, and thus carbon metabolism, may be involved. pH of the medium also strongly affected the morphology, but only in the presence of a complex nitrogen source, implying that the cells respond to altered nutrition in media with different pH rather than to pH itself. The results suggest that the XPR2 gene encoding Y. lipolytica alkaline extracellular proteinase is involved in the regulation of dimorphism in this species.