Faculty Opinions recommendation of Evidence of recombination in mixed-mating-type and alpha-only populations of Cryptococcus gattii sourced from single eucalyptus tree hollows.

ABSTRACT Disease caused by the pathogenic yeast Cryptococcus gattii begins with the inhalation of an infectious propagule. As C. gattii is heavily encapsulated, this propagule is most likely to be a basidiospore. However, most C. gattii strains are infertile in laboratory crosses, and population studies indicate that recombination and dispersal are very restricted. In addition, strains of the α mating type predominate, which would not be expected in a mating population. C. gattii comprises four genetically distinct molecular genotypes, designated VGI to VGIV. C. gattii molecular type VGI has a strong association with Eucalyptus camaldulensis and can be found in high numbers in E. camaldulensis hollows. Previous work on isolates obtained from E. camaldulensis suggested that environmental populations of C. gattii are highly fragmented, have limited ability to disperse, and are confined to individual tree hollows. In the current study, we examined large numbers of isolates from three separate hollows for evidence of recombination. In two hollows, the α and a mating types were present in approximately equal numbers. The third hollow had α cells only and was from a region where a isolates have never been found. Statistical analysis of multilocus genotypes revealed recombining subpopulations in the three Eucalyptus hollows. Recombination was equally present in the α-a and α-only populations. This is consistent with recent studies that have found evidence suggestive of α-α mating in C. gattii and Cryptococcus neoformans and raises the possibility this may be a widespread phenomenon, allowing these fungi to recombine despite a paucity of a mating partners.

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Emergence and populations genomics of the highly invasive chestnut blight pathogen

10.35662/unine-thesis-2868 ◽

2020 ◽

Author(s):

◽

Lea Stauber

Keyword(s):

Mating Type ◽

Fungal Genome ◽

Chestnut Blight ◽

Mixed Mating ◽

Large Set ◽

Pathogen Evolution ◽

Invasive Pathogens ◽

Invasive Pathogen ◽

Genome Wide

Invasive pathogens are a threat to forest and agroecosystems, as well as animal and human health. Identifying genomic determinants of pathogen evolution, as well as investigations into the genetic structure of invasive pathogen populations provide fundamental insights to why species can emerge as invasive pathogens. In this PhD project I investigated the emergence and population genomics of the invasive chestnut blight fungus Cryphonectria parasitica, using comparative and population genomic approaches. C. parasitica recently emerged as an invasive bark pathogen on non-Asian Castanea species in North America and Europe. In the first chapter, I investigated genomic determinants of lifestyle transitions in the genus Cryphonectria, by genome comparisons of C. parasitica and its sister species. The study uncovered a striking loss of genes associated with carbohydrate metabolism in the invasive pathogen C. parasitica, which may have promoted its pathogenicity on Castanea species. The second chapter explores the emergence and diversification of a highly invasive chestnut blight lineage across south-eastern Europe. By analyzing the genome-wide diversity of a large set of C. parasitica isolates of predominantly European origin, the study showed that a highly successful clonal pathogen lineage can emerge from a recombinant bridgehead population within Europe. Interestingly, the emergence of this clonal lineage was accompanied by an evolutionary transition from mixed mating type populations to single mating type outbreak populations. Lastly, in the third chapter I investigated temporal changes in genetic diversity of established C. parasitica populations in southern Switzerland, as well as potential links between the presence of the deleterious hyperparasitic mycovirus Cryphonectria hypovirus 1 (CHV1) and fungal genome-wide diversity. The results indicate increased mating among related fungal individuals, resulting in high genetic similarity of genotypes and facilitated CHV1 transmission. There were no substantial changes in fungal population structure and after ˜30 years and no detectable impact of CHV1 presence on fungal genome-wide diversity. Although our results show stable CHV1 incidence in fungal populations over three decades, the short-term interaction dynamics are likely highly volatile. The overall findings of this PhD thesis highlight the relevance of genomic determinants facilitating pathogen emergence and invasions. C. parasitica is a useful model to study fundamental questions of pathogen evolution and invasive processes, as well as antagonistic pathogen-hyperparasite interactions.

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Cryptococcus gattii sero-mating type allelic pattern determined by multiplex PCR

Clinical Microbiology and Infection ◽

10.1016/j.cmi.2014.09.003 ◽

2015 ◽

Vol 21 (2) ◽

pp. 190.e1-190.e4 ◽

Cited By ~ 5

Author(s):

M. Cogliati ◽

R. D'Amicis ◽

A.M. Tortorano

Keyword(s):

Multiplex Pcr ◽

Mating Type ◽

Cryptococcus Gattii

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Clonal Dispersal of Cryptococcus gattii VGII in an Endemic Region of Cryptococcosis in Colombia

Journal of Fungi ◽

10.3390/jof5020032 ◽

2019 ◽

Vol 5 (2) ◽

pp. 32 ◽

Cited By ~ 2

Author(s):

Carolina Firacative ◽

Germán Torres ◽

Wieland Meyer ◽

Patricia Escandón

Keyword(s):

Mating Type ◽

Extracellular Enzymes ◽

Large Cell ◽

Cryptococcus Gattii ◽

Phenotypic Switching ◽

Phenotypic Traits ◽

Endemic Region ◽

Mlst Analysis ◽

Microscopic Morphology

This study characterized the genotype and phenotype of Cryptococcus gattii VGII isolates from Cucuta, an endemic region of cryptococcal disease in Colombia, and compared these traits with those from representative isolates from the Vancouver Island outbreak (VGIIa and VGIIb). Genetic diversity was assessed by multilocus sequence typing (MLST) analysis. Phenotypic characteristics, including growth capacity under different temperature and humidity conditions, macroscopic and microscopic morphology, phenotypic switching, mating type, and activity of extracellular enzymes were studied. Virulence was studied in vivo in a mouse model. MLST analysis showed that the isolates from Cucuta were highly clonal, with ST25 being the most common genotype. Phenotypically, isolates from Cucuta showed large cell and capsular sizes, and shared phenotypic traits and enzymatic activities among them. The mating type a prevailed among the isolates, which were fertile and of considerable virulence in the animal model. This study highlights the need for a continuous surveillance of C. gattii in Colombia, especially in endemic areas like Cucuta, where the highest number of cryptococcosis cases due to this species is reported. This will allow the early detection of potentially highly virulent strains that spread clonally, and can help prevent the occurrence of outbreaks in Colombia and elsewhere.

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The mycobiome of Australian tree hollows in relation to the Cryptococcus gattii and C. neoformans species complexes

Ecology and Evolution ◽

10.1002/ece3.5498 ◽

2019 ◽

Vol 9 (17) ◽

pp. 9684-9700 ◽

Cited By ~ 1

Author(s):

Laura J. Schmertmann ◽

Laszlo Irinyi ◽

Richard Malik ◽

Jeff R. Powell ◽

Wieland Meyer ◽

...

Keyword(s):

Cryptococcus Gattii ◽

Tree Hollows ◽

Species Complexes

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A NEUROSPORA MUTATION THAT ARRESTS PERITHECIAL DEVELOPMENT AS EITHER MALE OR FEMALE PARENT

Genetics ◽

10.1093/genetics/92.4.1107 ◽

1979 ◽

Vol 92 (4) ◽

pp. 1107-1120

Author(s):

Thomas E Johnson

Keyword(s):

Gene Product ◽

Mating Type ◽

Sexual Development ◽

Female Parent ◽

Male Parent ◽

Mixed Mating ◽

Single Mutation ◽

Mating Types ◽

Female Component ◽

Ascospore Formation

ABSTRACT A mutant of Neurospora crassa fails to produce perithecia when crossed as either the male (fertilizing) parent or the female (protoperithecial) parent. This mutant is unique in that it appears to be due to a single mutation that blocks sexual development when crossed as either parent. As either a male or female parent, the mutant, fmf-1, produces perithecia blocked at a diameter of 120 microns and containing no meiotic figures; normal perithecia are over 4.00 microns in diameter. The mutant maps to linkage group IL near arg-1. Forced heterokaryons have been made between fmf-1 and fmf-1 + nuclei. These heterokaryons are fertile when crossed, and fmf-1 can participate as either the male or female component; the mutation is thus heterokaryon recessive and nuclear nonautonomous. Homokaryotic fmf-1 conidia were purified from a mixed conidial population derived from such a heterokaryon; these conidia failed to function as the male parent, suggesting that the fmf-1 + gene product is not contained in the conidium. In mixed mating-type heterokaryons, formed using tol, fmf-1 participates in ascospore formation and triggers perithecial development. Moreover, to1 suppreses the action of fmf-1 if present in both components of a cross.——These data suggest that (1) fmf-1 acts in the perithecium at some time between fusion of the conidium with the trichogyne and the onset of meiosis; (2) the fmf-1 gene product is not contained in conidia; and (3) both mating types may enter the protoperithecium when a mixed mating-type heterokaryon is used as the male parent.

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Pronuclear migration, swelling, and fusion during sexual development in Dictyostelium discoideum

Canadian Journal of Microbiology ◽

10.1139/m87-183 ◽

1987 ◽

Vol 33 (12) ◽

pp. 1046-1049 ◽

Cited By ~ 8

Author(s):

David R. McConachie ◽

Danton H. O'Day

Keyword(s):

Dictyostelium Discoideum ◽

Mating Type ◽

Sexual Development ◽

Significant Relationship ◽

Giant Cells ◽

Mixed Mating ◽

Binucleate Cells ◽

Ultrastructural Studies

In mixed mating type cultures (strains NC4 × V12) of Dictyostelium discoideum, gametes fuse to produce binucleate cells which differentiate into zygote giant cells. As pronuclei move together their volumes increase dramatically. Measurements of pronuclear volumes revealed that there is a direct, linear, and statistically significant relationship between pronuclear size and proximity. Juxtaposition of the swollen pronuclei is followed by their fusion. Ultrastructural studies indicate that pronuclear fusion involves intact pronuclear envelopes.

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