Functional analyses of secretory phospholipases A2 in Neurospora crassa

Secretory phospholipases A2 (sPLA2) is a group of enzymes that cleave the sn-2 ester linkage of phospholipids, thereby releasing fatty acids and 1-acyl lysophospholipids. In this study we investigated the physiological roles two sPLA2s in the filamentous fungus Neurospora crassa. We found that the single and double gene deletion strains displayed higher sensitivity to oxidative and heat stresses compared to the wild-type strain. Complementation analysis demonstrated that the enzyme activity of sPLA2s is required for stress tolerance. The expression of both genes was upregulated by the stresses, and in the single gene deletion strain the expression of the other gene was attenuated. RNA-seq analysis of wild-type and double deletion strains revealed that the expression of genes involved in fatty acid biosynthesis was downregulated in the double deletion strain, which was further decreased by the stresses. Supplementation of fatty acids to the culture medium restored the tolerance of the double deletion strain to stresses, suggesting that sPLA2s are involved in stress tolerance through the regulation of fatty acid metabolism.