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Eukaryotic Cell, May 2007, p. 844-854, Vol. 6, No. 5
1535-9778/07/$08.00+0     doi:10.1128/EC.00201-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Candida albicans Rho-Type GTPase-Encoding Genes Required for Polarized Cell Growth and Cell Separation{triangledown} ,{dagger}

Alexander Dünkler1 and Jürgen Wendland1,2*

Department of Microbiology, Friedrich Schiller University, Jena, and Junior Research Group, Fungal Pathogens, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute, Jena, Beutenbergstr 11a, D-07745 Jena, Germany,1 Carlsberg Laboratory, Yeast Biology, Gamle Carlsberg Vej 10, DK-2500 Valby, Copenhagen, Denmark2

Received 26 June 2006/ Accepted 20 February 2007

Rho proteins are essential regulators of morphogenesis in eukaryotic cells. In this report, we investigate the role of two previously uncharacterized Rho proteins, encoded by the Candida albicans RHO3 (CaRHO3) and CaCRL1/CaRHO4 genes. The CaRHO3 gene was found to contain one intron. Promoter shutdown experiments using a MET3 promoter-controlled RHO3 revealed a strong cell polarity defect and a partially depolarized actin cytoskeleton. Hyphal growth after promoter shutdown was abolished in rho3 mutants even in the presence of a constitutively active ras1(G13V) allele, and existing germ tubes became swollen. Deletion of C. albicans RHO4 indicated that it is a nonessential gene and that rho4 mutants were phenotypically different from rho3. Two distinct phenotypes of rho4 cells were elongated cell morphology and an unexpected cell separation defect generating chains of cells. Colony morphology of crl1/rho4 resulted in a growth-dependent smooth (long cell cycle length) or wrinkled (short cell cycle length) phenotype. This phenotype was additionally dependent on the rho4 cell separation defect and was also found in a Cacht3 chitinase mutant that shows a strong cytokinesis defect. The overexpression of the endoglucanase encoding the ENG1 gene, but not CHT3, suppressed the cell separation defect of crl1/rho4 but could not suppress the cell elongation phenotype. C. albicans Crl1/Rho4 and Bnr1 both localize to septal sites in yeast and hyphal cells but not to the hyphal tip. Deletion of RHO4 and BNR1 produced similar morphological phenotypes. Based on the localization of Rho4 and on the rho4 mutant phenotype, we propose a model in which Rho4p may function as a regulator of cell polarity, breaking the initial axis of polarity found during early bud growth to promote the construction of a septum.

* Corresponding author. Mailing address: Carlsberg Laboratory, Yeast Biology, Gamle Carlsberg Vej 10, DK-2500 Valby, Copenhagen, Denmark. Phone: 45 3327-5230. Fax: 45 3327-4708. E-mail: jww{at}crc.dk

{triangledown} Published ahead of print on 9 March 2007.

{dagger} Supplemental material for this article may be found at http://ec.asm.org/.

Eukaryotic Cell, May 2007, p. 844-854, Vol. 6, No. 5
1535-9778/07/$08.00+0     doi:10.1128/EC.00201-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Chaffin, W. L. (2008). Candida albicans Cell Wall Proteins. Microbiol. Mol. Biol. Rev. 72: 495-544 [Abstract] [Full Text]  
  • Zheng, W., Chen, J., Liu, W., Zheng, S., Zhou, J., Lu, G., Wang, Z. (2007). A Rho3 Homolog Is Essential for Appressorium Development and Pathogenicity of Magnaporthe grisea. Eukaryot Cell 6: 2240-2250 [Abstract] [Full Text]  
  • Bauer, J., Wendland, J. (2007). Candida albicans Sfl1 Suppresses Flocculation and Filamentation. Eukaryot Cell 6: 1736-1744 [Abstract] [Full Text]  


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