Action Mechanism of Diethofencarb to a Benzimidazole-Resistant Mutant in Neurospora crassa

Abstract

In the presence of 0.5 g/ml diethofencarb, conidia of a benzimidazole-resistant mutant of Neurospora crassa germinated, with distorted, swollen germ tubes. Diethofencarb induced scattered nucleus and inhibited mitotic nuclear division in the resistant strain. The morphological abnormality was quite similar to the one observed in the wild-type strain treated with carbendazim (MBC). Diethofencarb, however, did not morphologically affect the germ tubes and nuclei of a wild-type strain. Diethofencarb formed a complex in vitro with a protein present in the mycelial extracts of the resistant mutant. The binding protein of the resistant strain was retained on a DEAE-Sephadex A-50 and eluted with 0.5 m kc1. The molecular weight of the binding protein was estimated 105,000 by gel filtration on Sephacryl S-200 chromatography. The data well coincide with those on the MBC-binding protein in the wild-type strain, suggesting that diethofencarb was selectively toxic to the benzimidazole-resistant strain by binding to the tubulin. © 1992, Pesticide Science Society of Japan. All rights reserved.