CLONING AND CHARACTERIZATION OF A NEUROSPORA-CRASSA GENE REQUIRED FOR(1,3)BETA-GLUCAN SYNTHASE ACTIVITY AND CELL-WALL FORMATION

The glucan synthase 1 gene (gs-1) is required for (1,3)beta-glucan syn thase activity [E.C. 2.4.1.34; UDP glucose:1,3-beta-D-glucan 3-beta-D- glucosyltransferase] and for cell wall formation. The gs-1 gene was cl oned by functional complementation of the cell-wall-less defect of the (1,3)beta-glucan synthase-deficient mutant, TM1, by using a genomic N eurospora crassa cosmid library. A 2568-nucleotide gs-1 cDNA sequence revealed a 532-amino acid open reading frame encoding a polypeptide of 59 kDa. The predicted gs-1 gene product has no obvious signal peptide cleavage sites or transmembrane domains. A gs-1 null mutant is defect ive for cell wall formation and (1,3)beta-glucan synthase activity. Th e predicted GS-1 protein is weakly homologous to a putative Saccharomy ces cerevisiae transcriptional regulatory protein.