Deletion of genes encoding fatty acid desaturases leads to alterations in stress sensitivity in Pichia pastoris

Unsaturated fatty acids (UFAs) are key compounds which have important roles in maintaining cell membrane physiological functions and the adaption to tough conditions. Defects of fatty acid desaturases will change cellular UFA constitution. Pichia pastoris GS115 has four fatty acid desaturase genes, namely FAD9A , FAD9B , FAD12 and FAD15 . Their products catalyze the synthesis of three kinds of UFAs, oleic acid (catalyzed by Fad9A and Fad9B), linoleic acid (catalyzed by Fad12) and α-linolenic acid (catalyzed by Fad15), respectively. In this study, we found that deletion of FAD12 led to increased resistance to oxidative stress. Cellular lipid peroxidation levels declined in the fad12 Δ mutant upon H2O2 treatment. Cellular fatty acids compositions were changed with the increased expression of FAD9A . On the other hand, deletion of FAD9A resulted in increased tolerance to the plasma membrane (PM) damage agent SDS, and PM deformation was not detected in the fad9A Δ mutant under this stress. Our results showed that UFAs are related to cell adaption to adverse environmental changes.