Molecular characterization and comparative genomic analysis of two triamitovirus isolates hosted by the hypogean fungus Tuber excavatum Vittad.

The connections between viruses and their hosts are complex and can arise from any combination of different evolutionary events including “codivergence”, “switching”, and “duplication” of the pathogen. Mycoviruses, a diverse virus group whose members specifically infect fungal hosts, are subject to similar evolutionary processes. In this study, we present the identification and complete genome characterization of the second isolate of a mitovirus, commonly known as Tuber excavatum mitovirus, officially named Triamitovirus tuex1. This mycovirus infects the hypogean, ectomyrrhizal fungus Tuber excavatum Vittad.. Both Triamitovirus tuex1 isolates, Tekirdağ (identified by us) and Lammspringe, were found in the fruiting bodies of T. excavatum isolates collected from Türkiye and Germany, respectively. Comparative genomic analyses revealed that the two virus isolates share 85.33% sequence similarity in their whole genomes, with their protein encompassing RNA-dependent RNA polymerase (RdRp) domain showing an identity rate of 94.60%. The most diverse part of the viral genomes was found to be the 5’ untranslated regions (UTRs), with a sequence similarity of 78.53%, while the 3’ UTRs were the most conserved, with 91.53% sequence similarity. Considering the shared host species, the emergence of these Triamitovirus tuex1 isolates appears to reflect a duplication pattern (intra-host divergence) resulting from adaptive radiation.