Divergence, hybridization, and recombination in the mitochondrial genome of the human pathogenic yeast Cryptococcus gattii

Abstract

The inheritance of mitochondrial genes and genomes are uniparental in most sexual eukaryotes. This pattern of inheritance makes mitochondrial genomes in natural populations effectively clonal. Here, we examined the mitochondrial population genetics of the emerging human pathogenic fungus Cryptococcus gattii. The DNA sequences for five mitochondrial DNA fragments were obtained from each of 50 isolates belonging to two evolutionary divergent lineages, VGI and VGII. Our analyses revealed a greater sequence diversity within VGI than that within VGII, consistent with observations of the nuclear genes. The combined analyses of all five gene fragments indicated significant divergence between VGI and VGII. However, the five individual genealogies showed different relationships among the isolates, consistent with recent hybridization and mitochondrial gene transfer between the two lineages. Population genetic analyses of the multilocus data identified evidence for predominantly clonal mitochondrial population structures within both lineages. Interestingly, there were clear signatures of recombination among mitochondrial genes within the VGII lineage. Our analyses suggest historical mitochondrial genome divergence within C. gattii, but there is evidence for recent hybridization and recombination in the mitochondrial genome of this important human yeast pathogen.

The fatal fungal outbreak on Vancouver Island is characterized by enhanced intracellular parasitism driven by mitochondrial regulation

“…grubii] (26), indicating that they are under intense selection. This is further supported by recent evidence of mitochondrial recombination in C. gattii (27,28), along with the fact that most of the mitochondrial genetic variation between WM276 (an AFLP4/VGI strain with a low IPR value) and A1M-R265 (a VIO strain with high IPR) lies in coding regions, whilst the intergenic regions are highly conserved.…”

Congenic Strains for Genetic Analysis of Virulence Traits in Cryptococcus gattii

“…When the strains are identical other than the MAT alleles, the effects of the MAT locus predominate, leading to uniparental inheritance controlled by the MAT locus. Additional evidence for biparental inheritance in Cryptococcus species is shown by examples of mitochondrial recombination (48)(49)(50). The observation of uniparental transmission of mitochondria in C. neoformans has been made using crosses between congenic strains or across varieties.…”

Mitochondrial inheritance in basidiomycete fungi

“…For populations with the two other life cycles, abundant signatures of recombination were found for the heterothallic population in desert California while limited or no mtDNA recombination was found for the secondarily homothallic populations from coastal California, Alberta (Canada), or France . However, even in the predominantly clonally reproducing basidiomycete such as C. gattii, signatures of mtDNA recombination have also been found (Bovers et al 2009;Xu et al 2009). In the case of C. gattii, evidence of horizontal gene transfer of an intron between divergent lineages in nature was observed, consistent with their high mobility seen in laboratory crosses in C. cinerea by Economou et al (1987).…”