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Original Article |
Regulates Virulence but Is Not Essential for Mating
June_Kwon-Chung{at}nih.gov
The Cryptococcus neoformans STE12
gene, a homologue of Saccharomyces cerevisiae STE12, exists only in mating type (MAT)
cells. In S. cerevisiae, STE12 was required for mating and filament formation. In C. neoformans, haploid fruiting on filament agar required STE12
. The ability to form hyphae, however, was not affected by deletion of STE12
when convergently growing MATa strains were present. Furthermore, ste12
disruptants were fertile when mated with MATa strains, albeit with reduced mating frequency. Most importantly, the virulence of a ste12
disruptant of serotype D strain was significantly reduced in a mouse model. When the ste12
locus was reconstituted with the wild-type allele by cotransformation, virulence was restored. Histopathological analysis demonstrated a reduction in capsular size of yeast cells, less severe cystic lesions, and stronger immune responses in meninges of mice infected with ste12
cells than those of mice infected with STE12
cells. Using reporter gene constructs, we found that STE12
controls the expression of several phenotypes known to be involved in virulence, such as capsule and melanin production. These results demonstrate a clear molecular link between mating type and virulence in C. neoformans.
Key Words: haploid fruiting mating assay STE12 cotransformation virulence factor
© 2000 government
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