FENPROPIMORPH AFFECTS UPTAKE OF URACIL AND CYTOSINE IN SACCHAROMYCES-CEREVISIAE

Fenpropimorph was shown to inhibit the accumulation of the pyrimidine bases uracil and cytosine from the growth media in Saccharomyces cerev isiae. Uracil prototrophs of S. cerevisiae were more resistant to the growth-inhibitory effects of fenpropimorph than were uracil auxotrophs . High concentrations of uracil rescued fenpropimorph-treated uracil a uxotrophs, and cytosine, which is accumulated by a separate mechanism, could also support growth of treated uracil auxotrophs. Fenpropimorph caused a significant decrease in the uptake of radiolabeled uracil, w hich was not due to accumulation of ergosta-8,14 dienol (ignosterol) i n the treated cultures. Radiolabeled cytosine uptake was unaffected by drug treatment in a wild-type strain but was inhibited in a sterol mu tant, in which ergosterol,vas absent from the cell. The role of fenpro pimorph in causing membrane dysfunction through a mechanism other than altered sterol metabolism is discussed.