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Light controls growth and development via a conserved pathway in the fungal kingdom.

Idnurm A, Heitman J - PLoS Biol. (2005)

Bottom Line: One UV-sensitive mutant that filaments equally well in the light and the dark was identified and found to have an insertion in the BWC2 gene, whose product is structurally similar to N. crassa WC-2.Deletion of BWC1 or BWC2 reduces the virulence of C. neoformans in a murine model of infection; the Bwc1-Bwc2 system thus represents a novel protein complex that influences both development and virulence in a pathogenic fungus.These results demonstrate that a role for blue/UV light in controlling development is an ancient process that predates the divergence of the fungi into the ascomycete and basidiomycete phyla.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina, USA.

ABSTRACT
Light inhibits mating and haploid fruiting of the human fungal pathogen Cryptococcus neoformans, but the mechanisms involved were unknown. Two genes controlling light responses were discovered through candidate gene and insertional mutagenesis approaches. Deletion of candidate genes encoding a predicted opsin or phytochrome had no effect on mating, while strains mutated in the white collar 1 homolog gene BWC1 mated equally well in the light or the dark. The predicted Bwc1 protein shares identity with Neurospora crassa WC-1, but lacks the zinc finger DNA binding domain. BWC1 regulates cell fusion and repression of hyphal development after fusion in response to blue light. In addition, bwc1 mutant strains are hypersensitive to ultraviolet light. To identify other components required for responses to light, a novel self-fertile haploid strain was created and subjected to Agrobacterium-mediated insertional mutagenesis. One UV-sensitive mutant that filaments equally well in the light and the dark was identified and found to have an insertion in the BWC2 gene, whose product is structurally similar to N. crassa WC-2. The C. neoformans Bwc1 and Bwc2 proteins interact in the yeast two-hybrid assay. Deletion of BWC1 or BWC2 reduces the virulence of C. neoformans in a murine model of infection; the Bwc1-Bwc2 system thus represents a novel protein complex that influences both development and virulence in a pathogenic fungus. These results demonstrate that a role for blue/UV light in controlling development is an ancient process that predates the divergence of the fungi into the ascomycete and basidiomycete phyla.

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Related in: MedlinePlus

Bwc1 Inhibits Filament Formation during C. neoformans Mating or Haploid FruitingFilamentation assays were on V8 medium (pH 7) and conducted in the dark or under white fluorescent light.(A) Filamentation in crosses between wild type (WT), bwc1 mutant, and bwc1 + BWC1 reconstituted strains (48 h). Filament formation develops and is overgrown by yeast cells in wild-type or reconstituted strains crossed in the light.(B) Haploid fruiting filaments and blastospore production from yeast colonies incubated on filament agar (7 d).(C) Filament formation in wild-type (WT) or bwc1/bwc1 mutant diploid strains (24 h).(D) Filamentation in crosses of serotype A strains wild type (WT), bwc1 mutant, and bwc1 + BWC1 reconstituted strains mated with a serotype D bwc1 mutant (48 h).
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pbio-0030095-g001: Bwc1 Inhibits Filament Formation during C. neoformans Mating or Haploid FruitingFilamentation assays were on V8 medium (pH 7) and conducted in the dark or under white fluorescent light.(A) Filamentation in crosses between wild type (WT), bwc1 mutant, and bwc1 + BWC1 reconstituted strains (48 h). Filament formation develops and is overgrown by yeast cells in wild-type or reconstituted strains crossed in the light.(B) Haploid fruiting filaments and blastospore production from yeast colonies incubated on filament agar (7 d).(C) Filament formation in wild-type (WT) or bwc1/bwc1 mutant diploid strains (24 h).(D) Filamentation in crosses of serotype A strains wild type (WT), bwc1 mutant, and bwc1 + BWC1 reconstituted strains mated with a serotype D bwc1 mutant (48 h).

Mentions: Mating and fruiting of C. neoformans can be variable during culturing. Previous work in our laboratory and others has endeavored to find environmental factors that lead to this variation. One factor identified was light; cultures wrapped in aluminum foil exhibited enhanced mating and haploid fruiting compared to cultures in the light [19,21]. Our assays used cardboard containers in which 9-cm2 holes were excised from the lid and overlaid with aluminum foil or clear plastic wrap. Under these conditions, light inhibited both mating and haploid fruiting of C. neoformans, thereby ruling out any effects of plate-sealing on CO2 levels or desiccation (Figure 1A and 1B).


Light controls growth and development via a conserved pathway in the fungal kingdom.

Idnurm A, Heitman J - PLoS Biol. (2005)

Bwc1 Inhibits Filament Formation during C. neoformans Mating or Haploid FruitingFilamentation assays were on V8 medium (pH 7) and conducted in the dark or under white fluorescent light.(A) Filamentation in crosses between wild type (WT), bwc1 mutant, and bwc1 + BWC1 reconstituted strains (48 h). Filament formation develops and is overgrown by yeast cells in wild-type or reconstituted strains crossed in the light.(B) Haploid fruiting filaments and blastospore production from yeast colonies incubated on filament agar (7 d).(C) Filament formation in wild-type (WT) or bwc1/bwc1 mutant diploid strains (24 h).(D) Filamentation in crosses of serotype A strains wild type (WT), bwc1 mutant, and bwc1 + BWC1 reconstituted strains mated with a serotype D bwc1 mutant (48 h).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1064852&req=5

pbio-0030095-g001: Bwc1 Inhibits Filament Formation during C. neoformans Mating or Haploid FruitingFilamentation assays were on V8 medium (pH 7) and conducted in the dark or under white fluorescent light.(A) Filamentation in crosses between wild type (WT), bwc1 mutant, and bwc1 + BWC1 reconstituted strains (48 h). Filament formation develops and is overgrown by yeast cells in wild-type or reconstituted strains crossed in the light.(B) Haploid fruiting filaments and blastospore production from yeast colonies incubated on filament agar (7 d).(C) Filament formation in wild-type (WT) or bwc1/bwc1 mutant diploid strains (24 h).(D) Filamentation in crosses of serotype A strains wild type (WT), bwc1 mutant, and bwc1 + BWC1 reconstituted strains mated with a serotype D bwc1 mutant (48 h).
Mentions: Mating and fruiting of C. neoformans can be variable during culturing. Previous work in our laboratory and others has endeavored to find environmental factors that lead to this variation. One factor identified was light; cultures wrapped in aluminum foil exhibited enhanced mating and haploid fruiting compared to cultures in the light [19,21]. Our assays used cardboard containers in which 9-cm2 holes were excised from the lid and overlaid with aluminum foil or clear plastic wrap. Under these conditions, light inhibited both mating and haploid fruiting of C. neoformans, thereby ruling out any effects of plate-sealing on CO2 levels or desiccation (Figure 1A and 1B).

Bottom Line: One UV-sensitive mutant that filaments equally well in the light and the dark was identified and found to have an insertion in the BWC2 gene, whose product is structurally similar to N. crassa WC-2.Deletion of BWC1 or BWC2 reduces the virulence of C. neoformans in a murine model of infection; the Bwc1-Bwc2 system thus represents a novel protein complex that influences both development and virulence in a pathogenic fungus.These results demonstrate that a role for blue/UV light in controlling development is an ancient process that predates the divergence of the fungi into the ascomycete and basidiomycete phyla.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina, USA.

ABSTRACT
Light inhibits mating and haploid fruiting of the human fungal pathogen Cryptococcus neoformans, but the mechanisms involved were unknown. Two genes controlling light responses were discovered through candidate gene and insertional mutagenesis approaches. Deletion of candidate genes encoding a predicted opsin or phytochrome had no effect on mating, while strains mutated in the white collar 1 homolog gene BWC1 mated equally well in the light or the dark. The predicted Bwc1 protein shares identity with Neurospora crassa WC-1, but lacks the zinc finger DNA binding domain. BWC1 regulates cell fusion and repression of hyphal development after fusion in response to blue light. In addition, bwc1 mutant strains are hypersensitive to ultraviolet light. To identify other components required for responses to light, a novel self-fertile haploid strain was created and subjected to Agrobacterium-mediated insertional mutagenesis. One UV-sensitive mutant that filaments equally well in the light and the dark was identified and found to have an insertion in the BWC2 gene, whose product is structurally similar to N. crassa WC-2. The C. neoformans Bwc1 and Bwc2 proteins interact in the yeast two-hybrid assay. Deletion of BWC1 or BWC2 reduces the virulence of C. neoformans in a murine model of infection; the Bwc1-Bwc2 system thus represents a novel protein complex that influences both development and virulence in a pathogenic fungus. These results demonstrate that a role for blue/UV light in controlling development is an ancient process that predates the divergence of the fungi into the ascomycete and basidiomycete phyla.

Show MeSH
Related in: MedlinePlus