The effects of environmental and genetic factors on the germination of basidiospores in the Cryptococcus gattii species complex

Jianping Xu,Man You

doi:10.1038/s41598-018-33679-2

Abstract

Natural and artificial hybridization has been frequently reported among divergent lineages within and between the two closely related human pathogenic fungi Cryptococcus gattii species complex and Cryptococcus neoformans species complex. However, the biological effects of such hybridization are not well known. Here we used five strains of the C. neoformans species complex and twelve strains of the C. gattii species complex to investigate the potential effects of selected environmental and genetic factors on the germination of their basidiospores from 29 crosses. We found that the germination rates varied widely among crosses and environmental conditions, ranging from 0% to 98%. Overall, the two examined media showed relatively little difference on spore germination while temperature effects were notable, with the high temperature (37 °C) having an overall deleterious effect on spore germination. Within the C. gattii species complex, one intra-lineage VGIII × VGIII cross had the highest germination rates among all crosses at all six tested environmental conditions. Our analyses indicate significant genetic, environmental, and genotype-environment interaction effects on the germination of basidiospores within the C. gattii species complex.

Highlights

C. neoformans × C. deneoformans hybrid C. gattii C. deuterogattii C. bacillisporus C. tetragattii C. decagattii C. deneoformans × C. gattii hybrid C. neoformans × C. gattii hybrid C. neoformans × C. deuterogattii hybrid
We used a total of twelve strains of the C. gattii species complex and five strains of the C. neoformans species complex, including three VGI strains, three VGII strains, six VGIII strains, three VNI strains and two VNIV strains (Table 2)
This study described the potential environmental and genetic factors influencing the germination of basidiospores from among twenty-nine crosses within the C. gattii species complex and between the C. gattii species complex and the C. neoformans species complex

Summary

Introduction

C. neoformans × C. deneoformans hybrid C. gattii C. deuterogattii C. bacillisporus C. tetragattii C. decagattii C. deneoformans × C. gattii hybrid C. neoformans × C. gattii hybrid C. neoformans × C. deuterogattii hybrid. Most studies of hybridization have focused on animals and plants, natural and artificial hybridization has been frequently reported in many microbial groups, including the human pathogenic Cryptococcus Both the C. neoformans species complex and the C. gattii species complex have a bipolar mating system with two different mating types, MATa and MATα. These results suggest that hybridization is common in the human pathogenic Cryptococcus species complexes and that they represent great model organisms for understanding the effects of hybridization on fungal evolution. A previous study described that spores from the C. neoformans species complex were much more infectious than yeast cells in mice[32] Both the C. neoformans species complex and the C. gattii species complex have defined sexual cycles that can produce abundant basidiospores capable of infecting patients[31]. Based on the low spore germination rate at 37 °C, several studies suggested that basidiospores might not be the only nor most important infectious propagule in Cryptococcus[33,34,35]

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