The Aspergillus nidulans septin encoding gene, aspB, is essential for growth.

Septins are a highly conserved family of presumed cytoskeletal proteins involved in cytokinesis and morphogenesis in Saccharomyces cerevisiae and Drosophila melanogaster. To investigate the role of septins in filamentous fungi, we have identified presumptive septin homologues in Aspergillus nidulans. One of these septins, aspB, is expressed during vegetative growth and asexual sporulation. Based on cDNA and genomic sequences, the predicted aspB protein shares a P-loop motif and coiled coil regions with septins from other organisms. Antibodies generated against an aspB fusion protein recognized an A. nidulans protein of approximately 50 kDa, but could not localize the septin product in cells by immunofluorescence. Hybridization to a chromosome-specific ordered cosmid library placed the aspB gene on the right arm of chromosome I. Disruption of aspB showed that it is an essential gene.