Fungal genome and mating system transitions facilitated by chromosomal translocations involving intercentromeric recombination

In this study, we sequenced, assembled, and annotated the genomes of 2C.amylolentus isolates, CBS6039 and CBS6273, which are sexual and interfertile. Genome comparison between the 2C.amylolentus isolates identified the boundaries and the complete gene contents of theP/R andHD MAT loci. Bioinformatic and chromatin immunoprecipitation sequencing (ChIP-seq) analyses revealed that, similar to those of the pathogenicCryptococcus species,C.amylolentus has regional centromeres (CENs) that are enriched with species-specific transposable and repetitive DNA elements. Additionally, we found that while neither theP/R nor theHD locus is physically closely linked to its centromere inC.amylolentus, and the regions between theMAT loci and their respective centromeres show overall synteny between the 2 genomes, bothMAT loci exhibit genetic linkage to their respective centromere during meiosis, suggesting the presence of recombinational suppressors and/or epistatic gene interactions in theMAT-CEN intervening regions. Furthermore, genomic comparisons betweenC.amylolentus and related pathogenicCryptococcus species provide evidence that multiple chromosomal rearrangements mediated by intercentromeric recombination have occurred during descent of the 2 lineages from their common ancestor. Taken together, our findings support a model in which the evolution of the bipolar mating system was initiated by an ectopic recombination event mediated by similar repetitive centromeric DNA elements shared betw...
Source: PLoS Biology: Archived Table of Contents - Category: Biology Authors: Source Type: research