EFFECT OF FENPICLONIL ON MACROMOLECULE BIOSYNTHESIS IN FUSARIUM-SULPHUREUM

Fenpiclonil is a phenylpyrrole fungicide used for control of Fusarium sulphureum. Under growth-limiting glucose concentrations, the fungicid e (0.4 muM) specifically inhibited incorporation of glucose and mannos e into fungal macromolecules. This was not observed with a less fenpic lonil-sensitive laboratory isolate of F. sulphureum. Toxicity of pheny lpyrrole analogues ranked with their inhibitory effect on mannose inco rporation. The highest inhibitory effect was found for incorporation o f glucose into hyphal wall glycans. Biosynthesis of these glycans is m ediated by glycan synthetases in the plasma membrane. However, these e nzymes are probably not the target site of fenpiclonil, since fenpiclo nil neither inhibited glycan synthetase activity in cell-free extracts nor caused accumulation of uridinediphosphoglucose in mycelium. Fenpi clonil also inhibited incorporation of C-14-labeled glucose into other fungal macromolecules such as proteins. These results suggest that fe npiclonil does not interfere with various polymerization steps in the biosynthesis of macromolecules, but with an initial metabolization ste p of glucose such as glucose phosphorylation. This hypothesis would al so explain the inhibitory effect of fenpiclonil on incorporation of [C -14]uracil into uridine and UDP-activated sugars. (C) 1994 Academic Pr ess, Inc.