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Journal of Bacteriology, December 1999, p. 7439-7448, Vol. 181, No. 24
Center for Cancer Research, Massachusetts
Institute of Technology, Cambridge, Massachusetts 02139
Received 30 June 1999/Accepted 29 September 1999
The fungal cell wall has generated interest as a potential target
for developing antifungal drugs, and the genes encoding glucan and
chitin in fungal pathogens have been studied to this end.
Mannoproteins, the third major component of the cell wall, contain
mannose in either O- or N-glycosidic linkages. Here we describe the
molecular analysis of the Candida albicans homolog of
Saccharomyces cerevisiae MNN9, a gene required for the
synthesis of N-linked outer-chain mannan in yeast, and the phenotypes
associated with its disruption. CaMNN9 has significant
homology with S. cerevisiae MNN9, including a putative
N-terminal transmembrane domain, and represents a member of a similar
gene family in Candida. CaMNN9 resides on chromosome 3 and
is expressed at similar levels in both yeast and hyphal cells.
Disruption of both copies of CaMNN9 leads to phenotypic
effects characteristic of cell wall defects including poor growth in
liquid media and on solid media, formation of aggregates in liquid
culture, osmotic sensitivity, aberrant hyphal formation, and increased
sensitivity to lysis after treatment with
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Molecular Analysis of the Candida
albicans Homolog of Saccharomyces cerevisiae MNN9,
Required for Glycosylation of Cell Wall Mannoproteins

-1,3-glucanase. Like all
members of the S. cerevisiae MNN9 gene family the
Camnn9
strain is resistant to sodium orthovanadate and
sensitive to hygromycin B. Analysis of cell wall-associated carbohydrates showed the Camnn9
strain to contain half
the amount of mannan present in cell walls derived from the wild-type
parent strain. Reverse transcription-PCR and Northern analysis of the expression of MNN9 gene family members CaVAN1
and CaANP1 in the Camnn9
strain showed that
transcription of those genes is not affected in the absence of
CaMNN9 transcription. Our results suggest that, while the
role MNN9 plays in glycosylation in both
Candida and Saccharomyces is conserved, loss of
MNN9 function in C. albicans leads to
phenotypes that are inconsistent with the pathogenicity of the organism
and thus identify CaMnn9p as a potential drug target.
*
Corresponding author. Present address: Department of
Molecular and Cellular Biology, Boston University, Goldman School of Dental Medicine, 700 Albany St., Boston, MA 02118-2392. Phone: (617)
414-1047. Fax: (617) 414-1041. E-mail: robbinsp{at}bu.edu.
Present address: Department of Molecular and Cellular Biology,
Boston University, Goldman School of Dental Medicine, Boston, MA
02118-2392.
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