P-301 - Starship giant transposons dominate plastic genomic regions in a plant pathogenic fungus and drive virulence evolution

Starships are giant transposons found in ascomycete fungi and carry a wide diversity of cargo genes. Intriguingly, they can move horizontally between closely related fungal species and confer novel traits, including plant pathogenicity, on recipient strains through their cargo genes. Despite their potential significance, Starships have long remained undiscovered and are still frequently overlooked, leaving their abundance, dynamics, and impact on genome evolution largely unknown. Here, we report an unprecedented abundance and diversity of Starships in the plant pathogenic fungus Verticillium dahliae through the analysis of 56 Verticillium genomes. Many filamentous pathogens, including V. dahliae, harbor plastic genomic regions enriched in virulence effector genes that drive evolutionary arms races with their hosts. Starships are the major constituent of plastic genomic regions in V. dahliae and exhibit genetic and epigenetic characteristics typically associated with these regions. Furthermore, Starships have mediated the horizontal transfer of virulence genes both within Verticillium spp. and between V. dahliae and distantly related Fusarium fungi. Finally, we demonstrate that Starship activity contributed to the formation of a novel virulence gene by fusing a non-coding cargo sequence with a section of a conserved effector gene. Altogether, our study highlights the profound influence of Starship dynamics on fungal genome evolution and virulence development.