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Unisexual reproduction of Cryptococcus gattii.

Phadke SS, Feretzaki M, Clancey SA, Mueller O, Heitman J - PLoS ONE (2014)

Bottom Line: Cryptococcus gattii is a basidiomycetous human fungal pathogen that typically causes infection in tropical and subtropical regions and is responsible for an ongoing outbreak in immunocompetent individuals on Vancouver Island and in the Pacific Northwest of the US.A marked predominance of only one mating type (α) in clinical and environmental isolates suggests that a-α opposite-sex reproduction may be infrequent or geographically restricted, raising the possibility of an alternative unisexual cycle involving cells of only α mating type, as discovered previously in the related pathogenic species Cryptococcus neoformans.Our results are consistent with population genetic evidence of recombination in the largely unisexual populations of C. gattii and provide a useful genetic model for understanding how novel modes of sexual reproduction may contribute to evolution and virulence in this species.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, United States of America.

ABSTRACT
Cryptococcus gattii is a basidiomycetous human fungal pathogen that typically causes infection in tropical and subtropical regions and is responsible for an ongoing outbreak in immunocompetent individuals on Vancouver Island and in the Pacific Northwest of the US. Pathogenesis of this species may be linked to its sexual cycle that generates infectious propagules called basidiospores. A marked predominance of only one mating type (α) in clinical and environmental isolates suggests that a-α opposite-sex reproduction may be infrequent or geographically restricted, raising the possibility of an alternative unisexual cycle involving cells of only α mating type, as discovered previously in the related pathogenic species Cryptococcus neoformans. Here we report observation of hallmark features of unisexual reproduction in a clinical isolate of C. gattii (isolate 97/433) and describe genetic and environmental factors conducive to this sexual cycle. Our results are consistent with population genetic evidence of recombination in the largely unisexual populations of C. gattii and provide a useful genetic model for understanding how novel modes of sexual reproduction may contribute to evolution and virulence in this species.

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MAPK pathway is involved in unisexual reproduction of 97/433.gpa3Δ and crg1Δ mutations, and overexpression of MAT2, ZNF2, or CPR2 all enhanced self-fertility of 97/433. (A) Two independent gpa3Δ and crg1Δ mutants were analyzed (see also Figure S2). Solo-cultures or (B) confrontation assays with a partner of the a mating type (YL4a on the left side of each panel) were incubated on MS agar for 3 weeks at room temperature (24°C) in the dark and photographed. Scale bar = 50 µm. (C) Mutants were analyzed for elevated expression of the MFα pheromone gene as compared to the wildtype after 48 hours incubation on MS medium (C).
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pone-0111089-g003: MAPK pathway is involved in unisexual reproduction of 97/433.gpa3Δ and crg1Δ mutations, and overexpression of MAT2, ZNF2, or CPR2 all enhanced self-fertility of 97/433. (A) Two independent gpa3Δ and crg1Δ mutants were analyzed (see also Figure S2). Solo-cultures or (B) confrontation assays with a partner of the a mating type (YL4a on the left side of each panel) were incubated on MS agar for 3 weeks at room temperature (24°C) in the dark and photographed. Scale bar = 50 µm. (C) Mutants were analyzed for elevated expression of the MFα pheromone gene as compared to the wildtype after 48 hours incubation on MS medium (C).

Mentions: We targeted two negative regulators of the MAPK pathway including the CRG1 gene, which encodes a regulator of G-protein signaling (RGS) that attenuates the pheromone response [20], [53] and GPA3, which encodes one of the three Gα subunits that interact to regulate Cpk1-dependent hyphal formation during mating in C. neoformans[54], [55], [56]. Deletion of either gene resulted in significantly higher pheromone expression than wild-type and led to enhanced and accelerated hyphal growth in solo-culture and confrontation assays of these 97/433 mutants on MS agar (21 days for gpa3Δ or crg1Δ vs ∼60 days for wild-type in solo-cultures) (Figure 3A and 3B, Figure S1). These observations show that activation of the pheromone response pathway enhances monokaryotic fruiting of C. gattii (Figure 3C), consistent with unisexual reproduction as the underlying mechanism.


Unisexual reproduction of Cryptococcus gattii.

Phadke SS, Feretzaki M, Clancey SA, Mueller O, Heitman J - PLoS ONE (2014)

MAPK pathway is involved in unisexual reproduction of 97/433.gpa3Δ and crg1Δ mutations, and overexpression of MAT2, ZNF2, or CPR2 all enhanced self-fertility of 97/433. (A) Two independent gpa3Δ and crg1Δ mutants were analyzed (see also Figure S2). Solo-cultures or (B) confrontation assays with a partner of the a mating type (YL4a on the left side of each panel) were incubated on MS agar for 3 weeks at room temperature (24°C) in the dark and photographed. Scale bar = 50 µm. (C) Mutants were analyzed for elevated expression of the MFα pheromone gene as compared to the wildtype after 48 hours incubation on MS medium (C).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4206507&req=5

pone-0111089-g003: MAPK pathway is involved in unisexual reproduction of 97/433.gpa3Δ and crg1Δ mutations, and overexpression of MAT2, ZNF2, or CPR2 all enhanced self-fertility of 97/433. (A) Two independent gpa3Δ and crg1Δ mutants were analyzed (see also Figure S2). Solo-cultures or (B) confrontation assays with a partner of the a mating type (YL4a on the left side of each panel) were incubated on MS agar for 3 weeks at room temperature (24°C) in the dark and photographed. Scale bar = 50 µm. (C) Mutants were analyzed for elevated expression of the MFα pheromone gene as compared to the wildtype after 48 hours incubation on MS medium (C).
Mentions: We targeted two negative regulators of the MAPK pathway including the CRG1 gene, which encodes a regulator of G-protein signaling (RGS) that attenuates the pheromone response [20], [53] and GPA3, which encodes one of the three Gα subunits that interact to regulate Cpk1-dependent hyphal formation during mating in C. neoformans[54], [55], [56]. Deletion of either gene resulted in significantly higher pheromone expression than wild-type and led to enhanced and accelerated hyphal growth in solo-culture and confrontation assays of these 97/433 mutants on MS agar (21 days for gpa3Δ or crg1Δ vs ∼60 days for wild-type in solo-cultures) (Figure 3A and 3B, Figure S1). These observations show that activation of the pheromone response pathway enhances monokaryotic fruiting of C. gattii (Figure 3C), consistent with unisexual reproduction as the underlying mechanism.

Bottom Line: Cryptococcus gattii is a basidiomycetous human fungal pathogen that typically causes infection in tropical and subtropical regions and is responsible for an ongoing outbreak in immunocompetent individuals on Vancouver Island and in the Pacific Northwest of the US.A marked predominance of only one mating type (α) in clinical and environmental isolates suggests that a-α opposite-sex reproduction may be infrequent or geographically restricted, raising the possibility of an alternative unisexual cycle involving cells of only α mating type, as discovered previously in the related pathogenic species Cryptococcus neoformans.Our results are consistent with population genetic evidence of recombination in the largely unisexual populations of C. gattii and provide a useful genetic model for understanding how novel modes of sexual reproduction may contribute to evolution and virulence in this species.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, United States of America.

ABSTRACT
Cryptococcus gattii is a basidiomycetous human fungal pathogen that typically causes infection in tropical and subtropical regions and is responsible for an ongoing outbreak in immunocompetent individuals on Vancouver Island and in the Pacific Northwest of the US. Pathogenesis of this species may be linked to its sexual cycle that generates infectious propagules called basidiospores. A marked predominance of only one mating type (α) in clinical and environmental isolates suggests that a-α opposite-sex reproduction may be infrequent or geographically restricted, raising the possibility of an alternative unisexual cycle involving cells of only α mating type, as discovered previously in the related pathogenic species Cryptococcus neoformans. Here we report observation of hallmark features of unisexual reproduction in a clinical isolate of C. gattii (isolate 97/433) and describe genetic and environmental factors conducive to this sexual cycle. Our results are consistent with population genetic evidence of recombination in the largely unisexual populations of C. gattii and provide a useful genetic model for understanding how novel modes of sexual reproduction may contribute to evolution and virulence in this species.

Show MeSH
Related in: MedlinePlus