Novel Partitivirus Infection of Bat White-nose Syndrome(WNS) Fungal Pathogen Pseudogymnoascus destructansLinks Eurasian and North American Isolates

Bat White-nose Syndrome (WNS) fungus Pseudogymnoascus destructans had caused mass mortality in the North American bats. A single clone of the pathogen (Hap_1) was likely introduced in the United States while Eurasian population comprised of several haplotypes. The origin and spread of P. destructans remain enigmatic due in part to a lack of precise population markers. We searched for P. destructans mycoviruses as they are highly host-specific, and their spread could provide a window on the origin of the host fungus. We discovered a P. destructans bipartite virus PdPV-1 with two double-stranded RNA (dsRNA) segments - LS (1,683 bp) and SS (1,524 bp) with motifs similar to viral RNA-dependent RNA polymerase (RdRp) and putative capsid proteins (CPs), respectively. Both LS and SS ORFs were embedded only in the positive strand of each dsRNA segment. Sequence alignments and phylogenetic analysis suggested that both segments constitute the genome of a new virus similar to the mycoviruses in the family Partitiviridae genus Gammapartitivirus. Purified viral particles appeared as isometric virions with approximately 33 nm diameters typical of partitiviruses. A newly developed RT-PCR assay revealed that all US isolates and only a few Eurasian isolates were infected with PdPV-1. PdPV-1 was P. destructans - specific as closely related non-pathogenic fungi P. appendiculatus and P. roses tested negative. Thus, PdPV-1 establishes a link between the Eurasian and North American P. destructans. PdPV-1 could be used as an experimental tool to further investigate fungal biogeography, and the host — pathogen interactions.