Location: Invasive Insect Biocontrol & Behavior LaboratoryTitle: The complete genome sequence of a second distinct betabaculovirus from the true armyworm, Mythimna unipuncta
|Harrison, Robert - Bob|
|THEILMAN, DAVID - Agriculture And Agri-Food Canada|
|ROHRMANN, GEORGE - Oregon State University|
Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2017
Publication Date: 1/19/2017
Citation: Harrison, R.L., Rowley, D.L., Mowery, J.D., Bauchan, G.R., Theilman, D.A., Rohrmann, G.F. 2017. The complete genome sequence of a second distinct betabaculovirus from the true armyworm, Mythimna unipuncta. PLoS One. 12(1):e0170510.
Interpretive Summary: The true armyworm is a widespread pest of graminaceous crops and pastures. A virus that infects and kills larvae of true armyworm had previously been identified from a USDA Forest Service virus collection. To obtain a more complete understanding of the genetic factors regulating the insecticidal activity of the true armyworm virus, its entire genomic DNA sequence was determined and analyzed. Features of the genome that may contribute to this virus’s insecticidal activity were documented, and along with its relationships to other similar insect viruses. The information in this study contributes to progress towards developing ecologically safe and environmentally friendly virus-based insecticides to control damaging outbreaks of true armyworm, and will be of interest to those in academia, government, and industry who work with this group of insect viruses or with true armyworm and its management.
Technical Abstract: The betabaculovirus Pseudaletia (Mythimna) sp. granulovirus #8 (MyspGV#8) was examined by electron microscopy, host barcoding PCR, and determination of the nucleotide sequence of its genome. Scanning and transmission electron microscopy revealed that the occlusion bodies of MyspGV#8 possessed the characteristic size range and morphology of betabaculovirus granules. Barcoding PCR using cytochrome oxidase I primers with DNA from the MyspGV#8 collection sample confirmed that it had been isolated from the true armyworm, Mythimna unipuncta (Lepidoptera: Noctuidae). The MyspGV#8 genome was found to be 144,510 bp in size with a nucleotide distribution of 49.9% G+C, which was significantly smaller and more GC-rich than the genome of Pseudaletia unipuncta granulovirus H (PsunGV-H), another M. unipuncta betabaculovirus. A phylogeny based on concatenated baculovirus core gene amino acid sequence alignments placed MyspGV#8 in clade a of genus Betabaculovirus. Kimura-2-parameter nucleotide distances suggested that MyspGV#8 represents a virus species different and distinct from other species of Betabaculovirus. Among the 153 ORFs annotated in the MyspGV#8 genome, four ORFs appeared to have been obtained from or donated to Leucania separata nucleopolyhedrovirus AH1 (LeseNPV-AH1) during co-infection by the two viruses of Mythimna sp. larvae. A set of 33 ORFs was identified that appears only in other clade a betabaculovirus isolates. This clade a-specific set includes an ORF that encodes a polypeptide sequence containing a CIDE_N domain, which is found in caspase-activated DNAse/DNA fragmentation factor (CAD/DFF) proteins.