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Journal of Bacteriology, September 2000, p. 4941-4950, Vol. 182, No. 17
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Expression of a Constitutively Active Cdc42 Homologue Promotes Development of Sclerotic Bodies but Represses Hyphal Growth in the Zoopathogenic Fungus Wangiella (Exophiala) dermatitidis

Xiangcang Ye and Paul J. Szaniszlo^*

Section of Molecular Genetics and Microbiology, School of Biological Sciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712

Received 21 March 2000/Accepted 30 May 2000

In contrast to the CDC42 homologues of Saccharomyces cerevisiae and Schizosaccharomyces pombe, the WdCDC42 gene in the human pathogenic fungus Wangiella (Exophiala) dermatitidis was found to be nonessential for cell viability. Expression of the constitutively active allele wdcdc42^G14V at 37°C induced nonpolarized growth that led to cell enlargement and multiple nucleation. The swollen cells subsequently converted into planate divided bicellular forms or multiply septated sclerotic bodies in post-log phase, when the G14V-altered protein was diminished. The wdcdc42^G14V mutation also strongly repressed filamentous growth both in the wild-type strain and in the temperature-sensitive hyphal-form mutant Hf1. In contrast, overexpression of the dominant negative alleles wdcdc42^T19N and wdcdc42^D120A had no obvious effect on fungal-cell polarization. These results suggested that WdCdc42p plays a unique regulatory role in cellular morphogenesis in W. dermatitidis. Activation of this protein in response to extracellular or intracellular signals seems to commit its yeast-like cells to a phenotype transition that produces sclerotic bodies while repressing hyphal development.

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^* Corresponding author. Mailing address: Section of Molecular Genetics and Microbiology, The University of Texas at Austin, Austin, TX 78712. Phone: (512) 471-3384. Fax: (512) 471-7088. E-mail: pjszaniszlo{at}mail.utexas.edu.

Present address: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030.

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Journal of Bacteriology, September 2000, p. 4941-4950, Vol. 182, No. 17
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

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