The Complete Genome Sequence of a Second Distinct Betabaculovirus from the True Armyworm, Mythimna unipuncta

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.

Genome-wide diversity in temporal and regional populations of the betabaculovirusErinnyis ello granulovirus(ErelGV)

“…As expected, all ErelGV isolates clustered together, having ChocGV as their most closely related taxon, as observed by [11]. The analysis also revealed two main clades of betabaculoviruses ( Figure 6), which showed a slightly different species composition compared to previous studies [30][31][32]. Instead of placing PlxyGV and AgseGV as basal taxa in clade A, the topology of the betabaculovirus subtree shows them in clade B, which includes CpGV and the ErelGV isolates.…”

Genomic analysis of an Argentinean isolate of Spodoptera frugiperda granulovirus reveals that various baculoviruses code for Lef-7 proteins with three F-box domains

“…In an effort to better understand betabaculovirus diversification, Harrison and coworkers detected a group of genes that only occur in clade a —but not clade b —betabaculoviruses, based on the gene content analysis of Pseudaletia (Mythimna) sp. granulovirus #8 (MyunGV#8) genome [ 18 ]. Considering genes from SfGV that meet this criterion, this clade a list rises to 40 genes ( S1 Table ).…”

A Novel Betabaculovirus Isolated from the Monocot Pest Mocis latipes (Lepidoptera: Noctuidae) and the Evolution of Multiple-Copy Genes

“…For instance, a recently described serine protease inhibitor found in the genome of Hemileuca sp. nucleopolyhedrovirus (HespNPV) was introduced into a hot spot for recombination with high content of repeat regions [ 38 ]. On the other hand, when we compared the MolaGV genome with its ancestor-related betabaculovirus species (i.e., SpfrGV), we found the opposite: a shortening of 6 kb on the genome size.…”

“…Highlighted in red, noctuid-isolated betabaculovirus species. Most of these expanded open reading frames (ORFs) correspond to the betabaculovirus clade a specific ORFs identified in XecnGV clusters 1, 2, 3 and 4 described by [ 38 ].…”