Genome Evolution and Innovation across the Four Major Lineages of Cryptococcus gattii

Area of Science:

• Mycology
• Genomics
• Pathogen Evolution

Background:

• Cryptococcus gattii is a fungal pathogen causing pulmonary infections in healthy hosts.
• Understanding genomic variation is key to identifying virulence factors and potential drug targets.

Purpose of the Study:

• To characterize genomic variation among the four major lineages of Cryptococcus gattii (VGI, -II, -III, and -IV).
• To identify genetic differences associated with pathogenicity and host adaptation.

Main Methods:

• Generated and compared 16 de novo genome assemblies for C. gattii.
• Identified syntenic regions, structural rearrangements, and gene content variations.
• Analyzed population-level data from 37 additional isolates.

Main Results:

• Discovered 15 structural rearrangements primarily in VGI-III-IV lineages.
• Identified 737 lineage-specific genes, enriched for stress response, mitochondrial import, and metal transport.
• Found lineage-specific gene expansions (e.g., iron-binding in VGI, heat shock proteins in VGII) and a unique copper transporter absence in VGIV.
• Detected a new transcontinental clonal group (VGIIx), mitochondrial recombination, and positive selection in multidrug transporters and aconitase.

Conclusions:

• Genomic diversification through gene expansion/contraction and positive selection contributes to C. gattii pathogenicity.
• Specific genetic variations offer insights into virulence mechanisms and potential therapeutic strategies.