|Harrison, Robert - Bob|
|THEILMANN, DAVID - Agriculture And Agri-Food Canada|
|ERLANDSON, MARTIN - Agriculture And Agri-Food Canada|
Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2018
Publication Date: 2/1/2019
Citation: Harrison, R.L., Mowery, J.D., Bauchan, G.R., Theilmann, D.A., Erlandson, M.A. 2019. The complete genome sequence of a second alphabaculovirus from the true armyworm, Mythimna unipuncta: Implications for baculovirus phylogeny and host specificity. Virus Genes. 55:104-116.
Interpretive Summary: The true armyworm is a widespread pest of crops and pastures. Three distinct viruses that infect and kill larvae of the true armyworm had previously been identified and characterized. To obtain a more complete understanding of the insecticidal activity of viruses, the entire molecular sequence was determined for a new true armyworm virus isolated from diseased larvae in a Kentucky pasture. Analysis of the molecular sequence revealed that the Kentucky virus was not closely related to other true armyworm viruses. The results highlighted the difficulty of predicting the ability of a virus to infect and kill a specific insect pest based on molecular evidence alone. This information will be of interest to those in academia, government, and industry who are trying to develop environmentally-friendly forms of insect control.
Technical Abstract: The Mythimna unipuncta nucleopolyhedrovirus isolate KY310 (MyunNPV-KY310) is an alphabaculovirus isolated from a true armyworm (Mythimna unipuncta) population in Kentucky, USA. Occlusion bodies of this virus were examined by electron microscopy and the genome sequence was determined by 454 pyrosequencing. MyunNPV-KY310 occlusion bodies consisted of irregular polyhedra measuring 0.8 to 1.8 µm in diameter and containing multiple virions, with one to six nucleocapsids per virion. The genome sequence was determined to be 156,647 bp with a nucleotide distribution of 43.9% G+C. 152 ORFs and six homologous repeat (hr) regions were annotated for the sequence, including the 38 core genes of family Baculoviridae and an additional group of 26 conserved alphabaculovirus genes. BLAST queries and phylogenetic inference confirmed that MyunNPV-KY310 is most closely related to the alphabaculovirus Leucania separata nucleopolyhedrovirus isolate AH1, which infects Mythimna separata. In contrast, MyunNPV-KY310 did not exhibit a close relationship with Mythimna unipuncta nucleopolyhedrovirus isolate #7, an alphabaculovirus from the same host species. MyunNPV-KY310 lacks the gp64 envelope glycoprotein, which is a characteristic of group II alphabaculoviruses. However, this virus and five other alphabaculoviruses lacking gp64 are placed outside the group I and group II clades in core gene phylogenies, further demonstrating that viruses of genus Alphabaculovirus do not occur in two monophyletic clades. Potential instances of MyunNPV-KY310 ORFs arising by horizontal transfer were detected. Although there are now genome sequences of four different baculoviruses from M. unipuncta, comparison of their genome sequences provides little insight into the genetic basis for their host specificity.