LAUSR

BACKGROUND Oxathiapiprolin, an oxysterol-binding protein inhibitor (OSBPI), shows unexceptionable inhibitory activity against plant pathogenic oomycetes. FRAC classifies it into the mode of action group F9 (lipid homeostasis and transfer/storage), but very little is known about lipid metabolism of oomycete pathogens when subjected to oxathiapiprolin. RESULTS In this study, seven lipid categories and 1435 lipid molecules were identified in Phytophthora sojae, among which glycerolipids, glycerophospholipids, and sphingolipids account for 30.10%, 50.59% and 7.28%, respectively. These lipids were categorized into 31 sub-classes, which varied to different extents when treated with oxathiapiprolin. A total of 11 lipid sub-classes showed significant changes. Among them, 10 lipid sub-classes including lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE), phosphatidylcholine (PC), phosphatidylserine (PS), ceramide (Cer), triglyceride (TG), (o-acyl)-1-hydroxy fatty acid (OAHFA), diglycosylceramide (CerG2), sphingoshine (So), and sitosterol ester (SiE) were significantly up-regulated, while digalactosyldiacylglycerol (DGDG) was the only lipid that was significantly down-regulated by a factor of almost three. These lipid molecules were further analyzed at the lipid species level. A total of 542 species were significantly altered when treated with oxathiapiprolin, including 212 glycerolipids (186 TG and 26 diglycerides (DG)), 167 glycerophospholipids (38 PC, 15 LPC, 19 LPE, 7 PS, etc.), 156 sphingolipids (146 Cer, 4 So, etc.), and some other lipid molecules. Finally, from the orthogonal partial least-squares discrimination analysis (OPLS-DA) model, variable importance for the projection (VIP) score analysis showed that Cer, TG and some glycerophospholipids contribute to the metabolic disorder when subjected to oxathiapiprolin. CONCLUSION Glycerolipids, glycerophospholipids, and sphingolipids in P. sojae undergo significant changes with oxathiapiprolin treatment. These results provided valuable information for further understanding the function of the target protein and the mode of action of OSBPIs in oomycetes.