The complete genome sequence of a second distinct betabaculovirus from the true armyworm, Mythimna unipuncta
Citation
Harrison, R.L., Rowley, D.L., Mowery, J., Bauchan, G.R., Theilmann, D.A., Rohrmann, G.F., Erlandson, M.A. (2017). The complete genome sequence of a second distinct betabaculovirus from the true armyworm, Mythimna unipuncta. PLoS ONE, [online] 12(1), http://dx.doi.org/10.1371/journal.pone.0170510
Plain language summary
A novel betabaculovirus was isolated from the true armyworm, Mythimna unipuncta (Lepidoptera: Noctuidae) and named MyunGV#8. The complete genome of MyunGV#8 was sequenced, de novo assembled and found to be 144,673 bp in size. As a result of an extensive analysis of the MyunGV#8 and a comparison of concatenated baculovirus core gene amino acid sequence alignments demonstrated that within the genus Betabaculovirus two distinct phylogenetic clades existed. A set of 33 genes were identified that appears only in other clade a betabaculovirus isolates. This clade a-specific set includes an gene that encodes a polypeptide sequence containing a CIDE_N domain, which is found in caspase-activated DNAse/DNA fragmentation factor (CAD/DFF) proteins. CAD/DFF proteins are involved in digesting DNA during apoptosis.
Abstract
The betabaculovirus originally called 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) and therefore was renamed MyunGV#8. The MyunGV#8 genome was found to be 144,673 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 MyunGV#8 in clade a of genus Betabaculovirus. Kimura-2-parameter nucleotide distances suggested that MyunGV#8 represents a virus species different and distinct from other species of Betabaculovirus. Among the 153 ORFs annotated in the MyunGV#8 genome, four ORFs appeared to have been obtained from or donated to the alphabaculovirus lineage represented by Leucania separata nucleopolyhedrovirus AH1 (LeseNPV-AH1) during co-infection 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. CAD/DFF proteins are involved in digesting DNA during apoptosis.