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Eukaryotic Cell, July 2006, p. 1065-1080, Vol. 5, No. 7
1535-9778/06/$08.00+0     doi:10.1128/EC.00009-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Transcription Factor STE12 Has Distinct Roles in Morphogenesis, Virulence, and Ecological Fitness of the Primary Pathogenic Yeast Cryptococcus gattii

Ping Ren,¹ Deborah J. Springer,^1,4 Melissa J. Behr,² William A. Samsonoff,³ Sudha Chaturvedi,^1,4 and Vishnu Chaturvedi^1,4*

Mycology,¹ Anatomic Pathology Laboratories,² Electron Microscopy Core, Wadsworth Center, New York State Department of Health,³ Department of Biomedical Sciences, School of Public Health, State University of New York, Albany, New York⁴

Received 5 January 2006/ Accepted 23 March 2006

Cryptococcus gattii is a primary pathogenic yeast, increasingly important in public health, but factors responsible for its host predilection and geographical distribution remain largely unknown. We have characterized C. gattii STE12 to probe its role in biology and pathogenesis because this transcription factor has been linked to virulence in many human and plant pathogenic fungi. A full-length STE12 gene was cloned by colony hybridization and sequenced using primer walk and 3' rapid amplification of cDNA ends strategies, and a ste12 gene knockout mutant was created by URA5 insertion at the homologous site. A semiquantitative analysis revealed delayed and poor mating in ste12 mutant; this defect was not reversed by exogenous cyclic AMP. C. gattii parent and mutant strains showed robust haploid fruiting. Among putative virulence factors tested, the laccase transcript and enzymatic activity were down regulated in the ste12 mutant, with diminished production of melanin. However, capsule, superoxide dismutase, phospholipase, and urease were unaffected. Similarly, Ste12 deficiency did not cause any auxotrophy, assimilation defects, or sensitivity to a large panel of chemicals and antifungals. The ste12 mutant was markedly attenuated in virulence in both BALB/c and A/Jcr mice models of meningoencephalitis, and it also exhibited significant in vivo growth reduction and was highly susceptible to in vitro killing by human neutrophils (polymorphonuclear leukocytes). In tests designed to simulate the C. gattii natural habitat, the ste12 mutant was poorly pigmented on wood agar prepared from two tree species and showed poor survival and multiplication in wood blocks. Thus, STE12 plays distinct roles in C. gattii morphogenesis, virulence, and ecological fitness.

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* Corresponding author. Mailing address: Mycology Lab, Wadsworth Center, New York State Dept. of Health, 120 New Scotland Ave., Albany, NY 12201-2002. Phone: (518) 474-4177. Fax: (518) 486-7811. E-mail: vishnu{at}wadsworth.org.

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

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Eukaryotic Cell, July 2006, p. 1065-1080, Vol. 5, No. 7
1535-9778/06/$08.00+0     doi:10.1128/EC.00009-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

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