The occurrence of chromosomal rearrangements in the fungal genus Verticillium

Based on a recent comparative population genomics study, extensive chromosomal rearrangements between strains of the plant pathogenic species V. dahliae have been found (de Jonge et al., 2013). The rearrangements result in the occurrence of lineage-specific genomic regions that appear to be greatly enriched for in planta-expressed genes that encode virulence factors that enable host colonization. Thus, it is speculated that genomic rearrangements foster evolution of aggressiveness in the asexual pathogen V. dahliae (de Jonge et al., 2013). In this project, we aim to investigate the occurrence and regulation of chromosomal rearrangements in the genus Verticillium that comprises plant pathogenic (V. dahliae, V. longisporum, V. albo-atrum, V. alfafae, V. nonalfalfae), and saprophytic and weakly pathogenic (V. tricorpus, V. zagamsianum, V. nubilum, V. isaacii and V. klebahnii) species. We hypothesize that chromosomal rearrangements occur in the virulent plant pathogens and are not observed in the weak pathogens and saprophytes. To investigate this hypothesis, the genomes of multiple strains of each of the species within the Verticillium genus were sequenced and assembled to investigate chromosomal structures within and between each of the species. Furthermore, we investigated chromosomal size polymorphisms based on karyotyping. Collectively, our data show that inter-chromosomal rearrangements are not confined to pathogenic Verticillium spp.