Fatty acid metabolism inTaphrina deformans treated with sterol biosynthesis inhibitors

Changes in the unsaturated fatty acid content of the fungusTaphrina deformans as a function of growth, temperature, and sterol content were investigated. It was found that the highest growth rate was accompanied by a relatively high degree of fatty acid unsaturation (18∶1<18∶2+18∶3) and low sterol (brassicasterol) content. Also, a substantial shift in the degree of unsaturation from mainly 18∶2+18∶3 to 18∶1 occurred in the later stages (mid-linear) of culture development. Cells readily adapted from 18°C to 13°C, and exhibited a higher growth rate at the lower temperature after a period of acclimation. Growth was readily inhibited by the sterol biosynthesis inhibitors propiconazole and naftifine, which blocked brassicasterol biosynthesis at C-14 demethylation and squalene epoxidation, respectively. Growth was also inhibited by tunicamycin which did so without affecting sterol content. The shift in degree of fatty acid unsaturation did not occur in cells from cultures at reduced temperature or treated with any of the inhibitors. Since tunicamycin did not affect the sterol content, delay in the shift in the degree of fatty acid unsaturation was attributed to factors other than a reduction in sterol content.