A mandelamide pesticide alters lipid metabolism in Phytophthora infestans

Several pesticide classes have been used for control of the notorious plant pathogen, Phytophthora infestans . Some of these alter lipids, suggesting that lipid metabolism may be a target site. Here, we investigate the action of a new, active, mandelamide compound, SX 623509 (N -2'-(4'-ethoxy-3'-methoxy) phenylethyl-3, 4-dichloromandelamide), on lipid metabolism. Phytophthora infestans cultured in pea-broth or minimal media was exposed to different concentrations of SX 623509. Lipid metabolism was followed with radiolabelled acetate, choline or ethanolamine. Products were analysed following separation by thin-layer chromatography and gas-liquid chromatography. SX 623509 reduced growth and lipid labelling from [C-14]acetate in both media. The inhibition in lipid labelling was not caused merely by a reduction in uptake of the radiolabelled precursor. There were changes in labelling patterns, particularly reductions in phosphatidylcholine and triacylglycerol and increases in phosphatidate and diacylglycerol. The effect of SX 623509 on phosphatidylcholine labelling was followed in more detail. We conclude that the mandelamide pesticide SX 623509 reduces lipid synthesis at concentrations similar to those inhibiting growth. Specific effects on lipid labelling patterns are probably caused by inhibition of cholinephosphotransferase, which may be a future target site for pesticide development.