Penzes, J. J. | Search bioRxiv

bioRxiv2022

Structural and molecular biology of Acheta domesticus segmented densovirus, the first parvovirus to harbor a bipartite genome

Parvoviruses (family Parvoviridae) are defined by their linear monopartite ssDNA genome, T=1 icosahedral capsid, and distinct structural (VP) and non-structural (NS) protein expression cassettes within their genome. Here, we report the first parvovirus with a segmented genome, Acheta domesticus segmented densovirus (AdSDV), a house cricket (Acheta domesticus) pathogen. The AdSDV harbors its NS and VP cassettes on two separate segmented genomes. Its VP segment acquired a phospholipase A2-encoding gene via inter-subfamily recombination, which is absent from its capsid. The AdSDV evolved a transcription profile in response to its multipartite replication strategy that has diverged from its Brevihamaparvovirus ancestors. Furthermore, AdSDV assembles three capsid populations, which package one genome segment per particle. The cryoEM structures of these three capsids (2.3 to 3.3 [A] resolution) reveal a genome packaging mechanism, which differs from other parvoviruses. This study provides a new perspective on ssDNA genome segmentation and on the plasticity of parvovirus biology.

microbiology↗

bioRxiv2022

Identification by cryoEM of a densovirus causing mass mortality in mass-reared larval darkling beetles (Zophobas morio)

A reared colony of larval superworms (Zophobas morio) experienced the swift and unexplained death of about 90% of its population. We isolated a high-abundance virus from dead larvae and, using cryoEM, identified it as a novel densovirus, which we name Zophobas morio black wasting virus (ZmBWV). Densoviruses (DVs) are small, ssDNA viruses of the family Parvoviridae that infect protostome and deuterostome invertebrates. The vast majority of DVs have been associated with severe pathology, especially in larval stage insects. By cryoEM we resolved the high-resolution capsid structure of this new DV at 2.9 [A] resolution for the genome-packaging, infectious particles and at a resolution of 3.3 [A] in case of the empty particles, both purified directly from the infected Z. morio larvae. The capsid structure of ZmBWV provides the first insights into the capsid morphology of a structurally previously-uncharacterized genus, Blattambidensovirus. Consequently, the ZmBWV capsid harbors a unique surface morphology within the family, yet shows the T=1 icosahedral symmetry, the eight-stranded jelly roll core, as well as general features of multimer interactions previously found typical of subfamily Densovirinae. Although we have not inoculated healthy larvae with ZmBWV, on the basis of its prodigious abundance in infected larvae and the prior probability of larval pathology with viruses of this subfamily, ZmBWV is the most probable cause of the observed mass mortality event.

microbiology↗