Effect of Phenylpyrroles on Glycerol Accumulation and Protein Kinase Activity ofNeurospora crassa

The effect of phenylpyrroles on glycerol synthesis in Neurospora crassa has been investigated and compared with the mode of action of vinclozolin (a dicarboximide). The results indicated that fenpiclonil, fludioxonil and vinclozolin at concentrations which inhibit growth by 50% induce accumulation of glycerol in the mycelium of N. crassa. Furthermore a protein kinase (PK-III) possibly involved in the regulation of the glycerol synthesis is inhibited by phenylpyrroles, whereas vinclozolin is without effect. This implies that the target sites of phenylpyrroles and dicarboximides in the osmosensing signal transmission pathway are different. Comparative experiments with enzymes from human and animal sources revealed that PK-III could be a protein kinase Cδ. It is suggested that inhibition of PK-III activity may result in an increased concentration of a non-phosphorylated regulatory protein which may activate a MAP-kinase cascade of reactions resulting in increased glycerol synthesis.