This Article Full Text (PDF) Other Versions of this Article: EC.00080-08v1 7/9/1530    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Google Scholar Articles by Fortwendel, J. R. Articles by Rhodes, J. C. PubMed PubMed Citation Articles by Fortwendel, J. R. Articles by Rhodes, J. C.

 Previous Article  |  Next Article 

Eukaryotic Cell doi:10.1128/EC.00080-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Aspergillus fumigatus RasA regulates asexual development and cell wall integrity

Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, 231 Albert Way, Cincinnati, OH 45267-0529 USA

^* To whom correspondence should be addressed. Email: Judith.rhodes{at}uc.edu.

	Abstract

The Ras family of proteins is a large group of monomeric GTPases. Members of the fungal Ras family act as molecular switches that transduce signals from the outside of the cell to signaling cascades inside the cell. A. fumigatus RasA is 94% identical to the essential RasA gene of Aspergillus nidulans and is the Ras family member sharing the highest identity to Ras homologs studied in many other fungi. In this study, we report that rasA is not essential in A. fumigatus, but its absence is associated with slowed germination and a severe defect in radial growth. The rasA hyphae were over two times the diameter of wild type hyphae, and they displayed repeated changes in the axis of polarity during hyphal growth. The deformed hyphae accumulated numerous nuclei within each hyphal compartment. The rasA mutant conidiated poorly, but this phenotype could be ameliorated by growth on osmotically stabilized media. The rasA mutant also showed increased susceptibility to cell wall stressors, stained more intensely with calcofluor white, and was refractory to lysing enymes used to make protoplasts, suggesting an alteration of the cell wall. All phenotypes associated with deletion of rasA could be corrected by reinsertion of the wild type gene. These data demonstrate a crucial role for RasA in both hyphal growth and asexual development in A. fumigatus and provide evidence that RasA function is linked to cell wall integrity.