Abstract
BackgroundPenaeus monodon nudivirus (PmNV) is the causative agent of spherical baculovirosis in shrimp (Penaeus monodon). This disease causes significant mortalities at the larval stage and early postlarval (PL) stage and may suppress growth and reduce survival and production in aquaculture. The nomenclature and classification status of PmNV has been changed several times due to morphological observation and phylogenetic analysis of its partial genome sequence. In this study, we therefore completed the genome sequence and constructed phylogenetic trees to clarify PmNV’s taxonomic position. To better understand the characteristics of the occlusion bodies formed by this marine occluded virus, we also compared the chemical properties of the polyhedrin produced by PmNV and the baculovirus AcMNPV (Autographa californica nucleopolyhedrovirus).ResultsWe used next generation sequencing and traditional PCR methods to obtain the complete PmNV genome sequence of 119,638 bp encoding 115 putative ORFs. Phylogenetic tree analysis showed that several PmNV genes and sequences clustered with the non-occluded nudiviruses and not with the baculoviruses. We also investigated the characteristics of PmNV polyhedrin, which is a functionally important protein and the major component of the viral OBs (occlusion bodies). We found that both recombinant PmNV polyhedrin and wild-type PmNV OBs were sensitive to acid conditions, but unlike the baculoviral OBs, they were not susceptible to alkali treatment.ConclusionsFrom the viral genome features and phylogenetic analysis we conclude that PmNV is not a baculovirus, and that it should be assigned to the proposed Nudiviridae family with the other nudiviruses, but into a distinct new genus (Gammanudivirus).Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-628) contains supplementary material, which is available to authorized users.
Highlights
Penaeus monodon nudivirus (PmNV) is the causative agent of spherical baculovirosis in shrimp (Penaeus monodon)
Our results suggest that PmNV is not a baculovirus, and we propose that it should be assigned to a third genus, Gammanudivirus, within the newly proposed Nudiviridae family [5]
In the phylogenetic tree based on the helicase protein sequences of baculoviruses and nudiviruses, which had a high bootstrap support percentage at each node, PmNV again formed a cluster with Heliothis zea nudivirus 1 (HzNV-1) and Helicoverpa zea nudivirus 2 (HzNV-2) (Figure 2B)
Summary
We used generation sequencing and traditional PCR methods to obtain the complete PmNV genome sequence of 119,638 bp encoding 115 putative ORFs. We found that both recombinant PmNV polyhedrin and wild-type PmNV OBs were sensitive to acid conditions, but unlike the baculoviral OBs, they were not susceptible to alkali treatment
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