In Saccharomyces cerevisiae, chitin forms the primary division septum and the bud scar in the walls of vegetative cells. Three chitin synthetic activities have been detected. Two of them, chitin synthase I and chitin synthase II, are not required for synthesis of most of the chitin present in vivo. Using a novel screen, I have identified three mutations, designated csd2, csd3, and csd4, that reduce levels of chitin in vivo by as much as 10-fold without causing any obvious perturbation of cell division. The csd2 and csd4 mutants lack chitin synthase III activity in vitro, while csd3 mutants have wild-type levels of this enzyme. In certain genetic backgrounds, these mutations cause temperature-sensitive growth on rich medium; inclusion of salts or sorbitol bypasses this phenotype. Gene disruption experiments show that CSD2 is nonessential; a small amount of chitin, about 5% of the wild-type level, is detected in the disruptants. DNA sequencing indicates that the CSD2 protein has limited, but statistically significant, similarity to chitin synthase I and chitin synthase II. Other significant similarities are to two developmental proteins: the nodC protein from Rhizobium species and the DG42 protein of Xenopus laevis. The relationship between the nodC and CSD2 proteins suggests that nodC may encode an N-acetylglucosaminyltransferase that synthesizes the oligosaccharide backbone of the nodulation factor NodRm-1.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|