RESUMO

In a comparative analysis of genome sequences from isolates of the baculovirus Chrysodeixis includens nucleopolyhedrovirus (ChinNPV) from Brazil and Guatemala, we identified a subset of isolates possessing chimeric genomes. We identified six distinct phylogenetically incongruous regions (PIRs) dispersed in the genomes, of between 279 and 3345 bp in length. The individual PIRs possessed high sequence similarity among the affected ChinNPV isolates but varied in coverage in some instances. The donor for four of the PIRs implicated in horizontal gene transfer (HGT) was identified as Trichoplusia ni single nucleopolyhedrovirus (TnSNPV), an alphabaculovirus closely related to ChinNPV, or another unknown but closely related virus. BLAST searches of the other two PIRs returned only ChinNPV sequences, but HGT from an unknown donor baculovirus cannot be excluded. Although Chrysodeixis includens and Trichoplusia ni are frequently co-collected from soybean fields in Brazil, pathogenicity data suggest that natural coinfection of C. includens larvae with ChinNPV and TnSNPV is probably uncommon. Additionally, since the chimeric ChinNPV genomes with tracts of TnSNPV sequence were restricted to a single monophyletic lineage of closely related isolates, a model of progressive restoration of the native DNA sequence by recombination with ChinNPV possessing a fully or partially non-chimeric genome is reasonable. However, multiple independent HGT from TnSNPV to ChinNPV during the evolution of these isolates cannot be excluded. Mortality data suggest that the ChinNPV isolates with chimeric genomes are not significantly different in pathogenicity towards C. includens when compared to most other ChinNPV isolates. Exclusion of the PIRs prior to phylogenetic analysis had a large impact on the topology of part of the maximum-likelihood tree, revealing a homogenous clade of three isolates (IB, IC and ID) from Paraná state in Brazil collected in 2006, together with an isolate from Guatemala collected in 1972 (IA), comprising the lineage uniquely affected by HGT from TnSNPV. The other 10 Brazilian ChinNPV isolates from Paraná, Mato Grosso, and Minas Gerais states showed higher variability, where only three isolates from Paraná state formed a monophyletic group correlating with geographical origin.

Assuntos

Genoma Viral/genética , Nucleopoliedrovírus/genética , Virulência/genética , Animais , Baculoviridae/genética , Sequência de Bases , Brasil , Evolução Molecular , Larva/virologia , Mariposas/virologia , Controle Biológico de Vetores , Filogenia , Glycine max/virologia

RESUMO

We report the complete genomic sequences of seven viral isolates from the soybean looper (Chrysodeixis includens) from midwestern and southeastern Brazil. The genomes range from 138,760 to 139,637 bp in length with a G+C content of 39.2% and 140 open reading frames (ORFs).

RESUMO

The baculovirus, Chrysodeixis (formerly Pseudoplusia) includens nucleopolyhedrovirus (ChinNPV), is a new Alphabaculovirus pathogenic to Chrysodeixis includens Here, we report the complete genome sequences of six ChinNPV isolates. The availability of these genome sequences will provide information on ChinNPV molecular genetics, promoting understanding of its pathogenicity, diversity, and evolution.