MBE Advance Access originally published online on July 26, 2006
Molecular Biology and Evolution 2006 23(10):1879-1890; doi:10.1093/molbev/msl070
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Research Article |
Recent Evolution of the Human Pathogen Cryptococcus neoformans by Intervarietal Transfer of a 14-Gene Fragment
Department of Molecular Genetics and Microbiology, Duke University Medical Center
E-mail: dietr003{at}mc.duke.edu.
The availability of the whole-genome sequence from the 2 known varieties of the human pathogenic fungus Cryptococcus neoformans provides an opportunity to study the relative contribution of divergence and introgression during the process of speciation in a genetically tractable organism. At the genomic level, these varieties are nearly completely syntenic, share 
85–90% nucleotide identity, and are believed to have diverged 18 MYA. Via a comparative genomic approach, we identified a 14-gene region (40 kb) that is nearly identical between the 2 varieties that resulted from a nonreciprocal transfer event from var. grubii to var. neoformans 2 MYA. The majority of clinical and environmental var. neoformans strains from around the world contain this sequence obtained from var. grubii. This introgression event likely occurred via an incomplete intervarietal sexual cycle, creating a hybrid intermediate where mobile elements common to both lineages mediated the exchange. The subsequent duplication in laboratory strains of a fragment of this same genomic region supports evolutionary theories that instabilities in subtelomeric regions promote adaptive evolution through gene amplification and subsequent adaptation. Along with a more ancient predicted transfer event in C. neoformans and a recently reported example from Saccharomyces cerevisiae, these data indicate that DNA exchange between closely related sympatric varieties or species may be a recurrent theme in the evolution of fungal species. It further suggests that although evolutionary divergence is the primary force driving speciation, rare introgression events also play a potentially important role.
Key Words: Cryptococcus neoformans • segmental duplication • parasexual • subtelomeric • introgression • transposons
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  X. Lin, K. Nielsen, S. Patel, and J. Heitman Impact of Mating Type, Serotype, and Ploidy on the Virulence of Cryptococcus neoformans Infect. Immun., July 1, 2008; 76(7): 2923 - 2938. [Abstract] [Full Text] [PDF]
|
|