Canadian Forest Service Publications
New Insights into the Evolution of Entomopoxvirinae from the Complete Genome Sequences of Four Entomopoxviruses Infecting Adoxophyes honmai, Choristoneura biennis, Choristoneura rosaceana, and Mythimna separata. 2013. Thézé, J.; Takatsuka, J.; Li, Z.; Gallais, J.; Doucet, D. Arif, B.; Nakai,M.; Herniou, E.A. Journal of Virology 87:7992-8003.
Issued by: Great Lakes Forestry Centre
Catalog ID: 35154
CFS Availability: PDF (request by e-mail)
Poxviruses are nucleocytoplasmic large DNA viruses encompassing two subfamilies, the Chordopoxvirinae and the Entomopoxvirinae, infecting vertebrates and insects, respectively. While chordopoxvirus genomics have been widely studied, only two entomopoxvirus (EPV) genomes have been entirely sequenced. We report the genome sequences of four EPVs of the Betaentomopoxvirus genus infecting the Lepidoptera: Adoxophyes honmai EPV (AHEV), Choristoneura biennis EPV (CBEV), Choristoneura rosaceana EPV (CREV), and Mythimna separata EPV (MySEV). The genomes are 80% AT rich, are 228 to 307 kbp long, and contain 247 to 334 open reading frames (ORFs). Most genes are homologous to those of Amsacta moorei entomopoxvirus and encode several protein families repeated in tandem in terminal regions. Some genomes also encode proteins of unknown functions with similarity to those of other insect viruses. Comparative genomic analyses highlight a high colinearity among the lepidopteran EPV genomes and little gene order conservation with other poxvirus genomes. As with previously sequenced EPVs, the genomes include a relatively conserved central region flanked by inverted terminal repeats. Protein clustering identified 104 core EPV genes. Among betaentomopoxviruses, 148 core genes were found in relatively high synteny, pointing to low genomic diversity. Whole-genome and spheroidin gene phylogenetic analyses showed that the lepidopteran EPVs group closely in a monophyletic lineage, corroborating their affiliation with the Betaentomopoxvirus genus as well as a clear division of the EPVs according to the orders of insect hosts (Lepidoptera, Coleoptera, and Orthoptera). This suggests an ancient coevolution of EPVs with their insect hosts and the need to revise the current EPV taxonomy to separate orthopteran EPVs from the lepidopteran-specific betaentomopoxviruses so as to form a new genus.
Plain Language Summary
Entompoxviruses are a diverse, under-studied group of viruses that have potential as microbial biocontrol agents in forestry and agriculture. Only two entomopoxvirus genomes had previously been entirely sequenced. We report the complete genome sequences of four other entomopoxviruses and provide new insights into their genomic organization and evolution. The four viruses are of interest because they infect important Asian and North American lepidopteran pests: Adoxophyes honmai (smaller tea tortrix -a pest of tea in Japan), (two-year-cycle Budworm moth - a pest of spruce and fir in interior B.C.), Choristeurana rosaceana (oblique banded leaf roller - a pest of the rose family) and Mythimna separate (Oriental armyworm - an agricultural pest). Our comparative genomic analyses suggest that the viruses coevolved with their insect hosts and that there may be a need to revise the current taxonomy of entompoxviruses.