How transposons drive evolution of virulence in a fungal pathogen

Abstract

Genomic plasticity enables adaptation to changing environments, which is especially relevant for pathogens that engage in arms races with their hosts. In many pathogens, genes mediating aggressiveness cluster in highly variable, transposon-rich, physically distinct genomic compartments. However, understanding of the evolution of these compartments, and the role of transposons therein, remains limited. We now show that transposons are the major driving force for adaptive genome evolution in the fungal plant pathogen Verticillium dahliae. Highly variable genomic regions evolved by frequent segmental duplications mediated by erroneous homologous recombination, often utilizing transposons, leading to genetic material that is free to diverge. Intriguingly, the duplicated regions are enriched in active transposons that further contribute to local genome plasticity. Thus, we provide evidence for genome shaping by transposons, both in an active and passive manner, which impacts the evolution of pathogen aggressiveness.