Effects of cyclopropenoid fatty acids on fungal growth and lipid composition

Cyclopropenoid fatty acids (CPE) isolated from Sterculia foetida oil by urea clathration and reverse phase high performance liquid chromatography (HPLC) were introduced into fungal cultures. Stearate levels in phospholipids and triacylglycerols from Ustilago maydis sporidia rose considerably in response to 30 microM CPE. In addition, CPE themselves were incorporated into glycerolipid fractions. Sterol composition was unaffected. Changes in lipid composition were accompanied by inhibition of dry weight accumulation and sporidial number. Treated sporidia showed irregular wall deposition and a branched morphology. Oleate alleviated CPE effects on growth and morphology. Hyphal extension by Rhizoctonia solani was inhibited somewhat by 30 microM sterculate, while Fusarium oxysporum showed no appreciable response. Although CPE appeared to inhibit fatty acid desaturation by F. oxysporum, gross increases in the proportion of stearate were limited to the triacylglycerol fraction during 30 microM treatments. The possibility that the CPE synthesized by plants serve as antifungal agents is discussed.