Abstract
Sterols were not detected in the mycelium of Phytophthora infestans when grown on a chemically denned sterol-free medium. The incorporation of various exogenously supplied sterols into the mycelium was demonstrated. The amounts of each sterol incorporated did not correlate with the ability of that sterol to stimulate vegetative growth of the fungus on agar medium. Inter-conversions within the mycelium of one sterol to another could not be detected with cholesterol, cholestanol, stigmasterol or β -sitosterol. There was some evidence for the conversion of lanosterol to cholesterol. The fate of exogenously supplied ergosterol was unclear. Radiolabel, supplied as [4- 14 C] cholesterol to the growing mycelium, became associated predominantly with a particulate subcellular fraction. The ability of Triton X-100 to solubilize this radiolabel suggested an association with membranes. A significant proportion of the radio-label was associated with the supernatant/oily fraction of the mycelial contents. Preliminary studies of the metabolism of radiolabelled cholesterol by P. infestans showed that some conversion to metabolites of lower polarity, probably by esterification, had occurred.
Published Version
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