A Hypovirulence-Associated Partitivirus and Re-Examination of Horizontal Gene Transfer Between Partitiviruses and Cellular Organisms

Previous research has unearthed the integration of the coat protein (<i>CP</i>) gene from alphapartitivirus into plant genomes. Nevertheless, the prevalence of this horizontal gene transfer (HGT) between partitiviruses and cellular organisms remains an enigma. In our investigation, we discovered a novel partitivirus, designated Sclerotinia sclerotiorum alphapartitivirus 1 (SsAPV1), from a hypovirulent strain of <i>Sclerotinia sclerotiorum</i>. Intriguingly, we traced homologs of the SsAPV1 CP to plant genomes, including <i>Helianthus annuus</i>. To delve deeper, we employed the CP and RNA-dependent RNA polymerase (RdRP) sequences of partitiviruses as "bait" to search the NCBI database for similar sequences. Our search unveiled a widespread occurrence of HGT between viruses from all five genera within the family <i>Partitiviridae</i> and other cellular organisms. Notably, numerous <i>CP</i>-like and <i>RdRP</i>-like genes were identified in the genomes of plants, protozoa, animals, fungi, and even, for the first time, in an archaeon. The majority of <i>CP</i> and <i>RdRP</i> genes were integrated into plant and insect genomes, respectively. Furthermore, we detected DNA fragments originating from the SsAPV1 RNA genome in some subcultures of virus-infected strains. It suggested that SsAPV1 RdRP may possesses reverse transcriptase activity, facilitating the integration of viral genes into cellular organism genomes, and this function requires further confirmation. Our study not only offers a hypovirulence-associated partitivirus with implications for fungal disease control but also sheds light on the extensive integration events between partitiviruses and cellular organisms and enhances our comprehension of the origins, evolution, and ecology of partitiviruses, as well as the genome evolution of cellular organisms.