Endogenized hypervirulence-associated DNA virus BdDV-1 is primarily restricted to enzootic lineages of the amphibian pathogen Batrachochytrium dendrobatidis

The Global Panzootic Lineage (GPL) of the pathogenic fungus Batrachochytrium dendrobatidis (Bd) has caused severe amphibian population declines, yet the drivers underlying the high frequency of GPL in regions of amphibian decline are unclear. Using publicly available Bd genome sequences, we identified multiple non-GPL Bd isolates that contain a circular Rep-encoding single stranded DNA-like virus which we named BdDV-1. We further sequenced and constructed genome assemblies with long read sequences to find that the virus is integrated into the nuclear genome in some strains. Attempts to cure virus positive isolates were unsuccessful, however, phenotypic differences between naturally virus positive and virus negative Bd isolates suggested that BdDV-1 decreases the growth of its host in vitro but increases the virulence of its host in vivo. BdDV-1 is the first described CRESS DNA mycovirus associated with hypervirulence with a distribution inversely associated with the emergence of the panzootic lineage. Overall design: To identify differentially expressed genes (DEGs) between v+ and v- Bd-BRAZIL we extracted and sequenced mRNA from three samples of the virus positive strain, CLFT067 and the virus negative strain, CLFT071. These strains were selected due to their close phylogenetic relationship and their shared geographic location