Recombination of Autographa californica and Rachiplusia ou Nuclear Polyhedrosis Viruses in Galleria mellonella L.

Previous studies have shown that of 15 Artogeia (Pieris) rapae granulosis virus isolates (ArGV1 to ArGV15) only two, ArGV1 and ArGV2, gave a normal dose-mortality response in larvae from an established colony of Pieris brassicae. We report here that at extremely high doses, approaching 10000 times the LDs0 for ArGV1 and ArGV2, three other ArGV isolates caused low and irregular levels of mortality in P. brassicae. At similar doses Agrotis segetum GV caused 43 % mortality in one infection, but no deaths ensued from other inoculations with this virus. Restriction endonuclease analysis of viral DNA recovered from individual larval cadavers revealed that, in most cases, progeny virus differed from the inoculum and consisted either of ArGV1 or of novel genotypes explicable as recombinants between genomes of the inoculum and of ArGV1. Field-collected P. brassicae inoculated with ArGV8 yielded a similar range of progeny genotypes. Physical maps were constructed for two such recombinants, based on comparative restriction analysis with reference to the published map of ArGVl and to those of ArGV5 and ArGV8, which are presented. Replication of the inoculum genotype was observed in only two infections. The origin of ArGV1 DNA appearing among progeny from these infections and the relevance of our results to identifying ArGV DNA sequences that modulate pathogenicity for P. brassicae are discussed.

Section: Discussionsupporting

confidence: 68%

Characterization of new baculovirus genotypes arising from inoculation of Pieris brassicae with granulosis viruses

Smith¹,

Crook²

1993

“…It is well established that recombination between baculoviruses can occur in laboratory experiments in cell culture or in insects (Croizier et al, 1988;Kondo & Maeda, 1991;Crook et al, 1993) and there has been much speculation that such recombination events may take place between baculoviruses in the wild. Our observations emphasize that one should consider the possibility of horizontal gene transfer in the evolution of these viruses.…”

Section: Iiiiiiiiiii!iiiiiiiiiii Iiii Iiii III Iiii Iiiiiiiiiiimentioning

confidence: 99%

Characterization of the ecdysteroid UDP-glucosyltransferase gene from Mamestra brassicae nucleopolyhedrovirus

Clarke

Tristem²,

Cory³

et al. 1996

Interest in insect baculoviruses has been stimulated by their potential as biological control agents and intensive research has focused on the improvement of their pesticidal properties by genetic engineering. Much of this effort has been directed at Autographa californica nucleopolyhedrovirus (AcMNPV). One approach taken has been the deletion of the AcMNPV egt gene. The egt gene product, ecdysteroid UDP-glucosyltransferase (EGT), catalyses the conjugation of insect ecdysteroid hormones with UDP-sugars (O'Reilly et al., I99I,

“…In vitro studies have shown that recombination events, sequence duplication, DNA point mutations, and insertion and deletion events commonly occur during the baculovirus replication cycle (Croizier et al, 1988;Croizier & Ribeiro, 1992;Martin & Weber, 1997).…”

mentioning

confidence: 99%

The effect of inoculum dose on the genetic diversity detected within Helicoverpa armigera nucleopolyhedrovirus populations

Baillie

Bouwer

2013

Environmental and infection variables may affect the genetic diversity of baculovirus populations. In this study, Helicoverpa armigera nucleopolyhedrovirus (HearNPV) was used as a model system for studying the effects of a key infection variable, inoculum dose, on the genetic diversity within nucleopolyhedrovirus populations. Diversity and equitability indices were calculated from DNA polymerase-specific denaturing gradient gel electrophoresis profiles obtained from individual H. armigera neonate larvae inoculated with either an LD 5 or LD 95 of HearNPV. Although the genetic diversity detected in larvae treated with an LD 95 was not statistically different from the diversity detected in the HearNPV inoculum samples, there was a statistically significant difference in the genetic diversity detected in the LD 5 -inoculated larvae compared with the genetic diversity detected in the HearNPV samples used for the inoculations. The study suggests that inoculum dose needs to be considered carefully in experiments that evaluate HearNPV genetic diversity or in studies where differences in genetic diversity may have phenotypic consequences.Baculoviruses are dsDNA viruses that are characterized by proteinaceous occlusion bodies (OBs) that enclose the virions (Funk et al., 1997;Theilmann & Blissard, 2008). The family Baculoviridae is divided into four genera (Alphabaculovirus, Betabaculovirus, Deltabaculovirus and Gammabaculovirus) based on phylogenetics, genome composition, host range, and morphological and pathological traits (Jehle et al., 2006). The alphabaculoviruses include the lepidopteran-specific nucleopolyhedroviruses (NPVs), which have virions that may contain a single nucleocapsid (SNPV) or multiple nucleocapsids (MNPV) (Theilmann & Blissard, 2008).Baculoviruses have been shown to have a high degree of genotypic variation between and within baculovirus isolates (Cory et al., 2005;Crook et al., 1985;Graham et al., 2004; Hitchman et al., 2007; Parnell et al., 2002;van Oers & Vlak, 2007). It has even been shown that baculovirus genetic variation can be detected within an individual host insect (Baillie & Bouwer, 2012b;Cory et al., 2005). Furthermore, Cory et al. (2005) showed that a number of the genetic variants isolated from a single host insect differed in phenotypic traits, including those for pathogenicity and kill time.The maintenance of genetic variation may be affected by host immune response specificity, tradeoffs between virus genotype fitness components, interactions of genotypes within the host, and differential selection of genotypes (Hitchman et al., 2007;Hodgson et al., 2001Hodgson et al., , 2002. Genetic heterogeneity must be important for the survival of baculoviruses as the less dominant (minority) viral variants are not lost from the virus population over time (Simó n et al., 2008). It has been shown that the minority genotypes affect the timing of mortality and the overall pathogenicity of the virus population (Simó n et al., 2005(Simó n et al., , 2008. The mixture of genotypes may consist of c...