Starship giant transposons dominate plastic genomic regions in a fungal plant pathogen and drive virulence evolution.

Starships form a recently discovered superfamily of giant transposons in Pezizomycotina fungi, implicated in mediating horizontal transfer of diverse cargo genes between fungal genomes. Their elusive nature has long obscured their significance, and their impact on genome evolution remains poorly understood. Here, we reveal a surprising abundance and diversity of Starships in the phytopathogenic fungus Verticillium dahliae. Remarkably, Starships dominate the plastic genomic compartments involved in host colonization, carry multiple virulence-associated genes, and exhibit genetic and epigenetic characteristics associated with adaptive genome evolution. Phylogenetic analyses suggest extensive horizontal transfer of Starships between Verticillium species and, strikingly, from distantly related Fusarium fungi. Finally, homology searches and phylogenetic analyses suggest that a Starship contributed to de novo virulence gene formation. Our findings illuminate the profound influence of Starship dynamics on fungal genome evolution and the development of virulence.