The complete genome sequence of a third distinct baculovirus isolated from the true armyworm, Mythimna unipuncta, contains two copies of the lef-7 gene

• Published in: Virus genes 2018-04, Vol.54 (2), p.297-310
• Main Authors: Harrison, Robert L., Mowery, Joseph D., Rowley, Daniel L., Bauchan, Gary R., Theilmann, David A., Rohrmann, George F., Erlandson, Martin A.
• Format: Article
• Language: English
• Subjects: Amino acid sequence; Animals; Baculoviridae; Base Composition; Biomedical and Life Sciences; Biomedicine; Cluster Analysis; DNA Barcoding, Taxonomic; DNA biosynthesis; Electron microscopy; Genes, Viral; Genome, Viral; Genomes; Inclusion Bodies, Viral - ultrastructure; Lepidoptera - virology; Medical Microbiology; Mythimna unipuncta; Nucleocapsids; Nucleopolyhedrovirus - genetics; Nucleopolyhedrovirus - isolation & purification; Nucleopolyhedrovirus - ultrastructure; Nucleotide sequence; Occlusion bodies; Open Reading Frames; Phylogeny; Plant Sciences; Polymerase Chain Reaction; Repetitive Sequences, Nucleic Acid; Sequence Analysis, DNA; Species; Virion - ultrastructure; Virions; Virology
• ISSN: 0920-8569; 1572-994X
• DOI: 10.1007/s11262-017-1525-0

A baculovirus isolate from a USDA Forest Service collection was characterized by electron microscopy and analysis of its genome sequence. The isolate, formerly referred to as Pseudoletia ( Mythimna ) sp. nucleopolyhedrovirus #7 (MyspNPV#7), was determined by barcoding PCR to derive from the host species Mythimna unipuncta (true armyworm) and was renamed Mythimna unipuncta nucleopolyhedrovirus #7 (MyunNPV#7). The occlusion bodies (OBs) and virions exhibited a size and morphology typical for OBs produced by the species of genus Alphabaculovirus , with occlusion-derived virions consisting of 2–5 nucleocapsids within a single envelope. The MyunNPV#7 genome was determined to be 148,482 bp with a 48.58% G+C nucleotide distribution. A total of 159 ORFs of 150 bp or larger were annotated in the genome sequence, including the 38 core genes of family Baculoviridae . The genome contained six homologous repeat regions ( hr s) consisting of multiple copies of a 34-bp imperfect palindrome. Phylogenetic inference from concatenated baculovirus core gene amino acid sequence alignments placed MyunNPV#7 with group II alphabaculoviruses isolated from other armyworm and cutworm host species of lepidopteran family Noctuidae. MyunNPV#7 could be distinguished from other viruses in this group on the basis of differences in gene content and order. Pairwise nucleotide distances suggested that MyunNPV#7 represents a distinct species in Alphabaculovirus . The MyunNPV#7 genome was found to contain two copies of the late expression factor - 7 ( lef - 7 ) gene, a feature not reported for any other baculovirus genome to date. Both copies of lef - 7 encoded an F-box domain, which is required for the function of LEF-7 in baculovirus DNA replication.