Gene acquisition by giant transposons primes eukaryotes for rapid evolution via horizontal gene transfer

Horizontal gene transfer (HGT) disseminates genetic information between species. The significance of HGT in eukaryotes is not well established, with evidence currently limited to isolated examples, typically absent of a mechanism. It has been proposed that mobile elements might be active agents of HGT in eukaryotes, as they are in prokaryotes. To test this hypothesis, we examined a gene cluster, which putatively contributes to formaldehyde resistance and is found within some members of the Starship superfamily of giant transposons. Remarkably, we found four instances where ssf has been independently acquired by distantly related Starships , and show that each acquisition event coincided with the element’s horizontal transfer (at least 9 HGT events in total). Our results demonstrate that acquisition of host-beneficial cargo by Starships primes fungi for rapid and repeated adaptation via HGT, revealing and elevating the role of HGT in eukaryotic biology.