CHS8 - a fourth chitin synthase gene of Candida albicans contributes to in vitro chitin synthase activity, but is dispensable for growth

In silico analysis of the genome sequence of the human pathogenic fungus Candida albicans identified an open reading frame encoding a putative fourth member of the chitin synthase gene family. This gene, named CaCHS8, encodes an 1105 amino acid open reading frame with the conserved motifs characteristic of class I zymogenic chitin synthases with closest sequence similarity to the non-essential C albicans class I CHS2 gene. Although the CaCHS8 gene was expressed in both yeast and hyphal cells, homozygous chs8Delta null mutants had normal growth rates, cellular morphologies and chitin contents. The null mutant strains had a 25% reduction in chitin synthase activity and were hypersensitive to Calcofluor White. A chs2Delta chs8Delta double mutant had less than 3% of normal chitin synthase activity and had increased wall glucan and decreased mannan but was unaffected in growth or cell morphology. The C. albicans class I double mutant did not exhibit a bud-lysis phenotype as found in the class I chs1Delta mutant of Saccharomyces cerevisiae. Therefore, C albicans has four chitin synthases with two non-essential class I Chs isoenzymes that contribute collectively to more than 97% of the in vitro chitin synthase activity. (C) 2003 Elsevier Science (USA). All rights reserved.