Alterations in the biosynthesis of chitin and glucan in the slime mutant of Neurospora crassa

Abstract

The slime mutant of Neurospora crassa lacks both chitin and insolubleβ(1 → 3)glucans either cellbound or secreted to the medium. Failure to synthesize both polymers is not due to deficiencies in the precursor sugar nucleotides, UDP-GlcNAc and UDP-Glc, since these are present in higher amounts in the mutant than in the wild type. The slime mutant also contains higher levels of chitin synthetase than the wild type, but lacks detectable glucan synthetase activity. an os-1 mutant grown in hypertonic medium contained reduced amounts of chitin and glucan, but its glucan and chitin synthetase activities were nearly normal. It is concluded that the absence of a cell wall in the slime mutant is due to a mutational event(s) which affects the mechanism of activation or delivery of chitin synthetase to the cell surface and the formation of a functionalβ(1 → 3)glucan synthetase. This mutational event must be different in the os-1 strain.