The Neurospora crassa chs3 gene encodes an essential class I chitin synthase

In Neurospora crassa, at least five different DNA fragments related to chitin synthases have been identified. In this study we have cloned, sequenced, mapped and characterized the chitin synthase 3 structural gene (designated chs3) of N. crassa. Based on the amino acid sequence deduced from the cloned chs3 genomic DNA fragments we have desig- nated this gene as a class I chitin synthase. The chs3 gene is transcribed predominantly at the early stages of mycelial growth and is expressed during all stages of asexual growth. The fact that strains with nuclei harboring a disrupted chs3 gene could only be main- tained as heterokaryons indicates that this gene is indispensable in N. crassa.