A comparison of the adaptations of strains of Lymantria dispar multiple nucleopolyhedrovirus to hosts from spatially isolated populations

Abstract

The adaptation of pathogens to either their hosts or to environmental conditions is the focus of many current ecological studies. In this work we compared the ability of six spatially-distant Lymantria dispar (gypsy moth) multiple nucleopolyhedrovirus (LdMNPV) strains (three from eastern North America and three from central Asia) to induce acute infection in gypsy moth larvae. We also sequenced the complete genome of one Asian (LdMNPV-27/0) and one North American (LdMNPV-45/0) strain which were used for bioassay. We found that all of the North American virus strains, with the exception of one, demonstrated higher potency than the Asian virus strains, either in North American (Lymantria dispar) larvae or, in Asian (Lymantria dispar asiatica) larvae. Complete genome sequencing revealed two gene deletions in the LdMNPV-27/0 strain: the virus enhancin factor gene (vef-1) and the baculovirus repeated orf gene (bro-p). These deletions were not seen in the LdMNPV-45/0 strain nor in other American strains available in archiving systems. We also found deletions of the bro-e and bro-o genes in LdMNPV-45/0 strain but not in the LdMNPV-27/0 strain. The phylogenetic inference with an alignment of the 37 core gene nucleotide sequences revealed the close relationship of the LdMNPV-45/0 strain with other American strains accessed in GenBank (Ab-a624 and 5-6) while the LdMNPV-27/0 strain was clustered together with the LdMNPV-3054 strain (isolated in Spain) instead of predicted clustering with LdMNPV- 3029 (isolated in Asia). Our study demonstrated that first, different LdMNPV isolates from the same metapopulations of L. dispar exhibit little or no difference in the degree of virulence towards host larvae and second, that locality of host population is not an important driver of LdMNPV virulence. Virulence of LdMNPV is determined only by viral genetics. The genetic differences between North American and Central Asian virus strains are discussed.

Insect parasites in multicomponent systems and development of new bioinsecticides

“…Population differences of viral entomopathogens in terms of virulence are partially determined by their genetic differences. In particular, the strains of Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV, Baculoviridae) isolated in North America possess higher virulence than the Asian strain because of vef-1 gene deletion [9][10]. However, the phenotypic expression of these genetic differences does not depend on the host population [10]; conversely, it is ruled by the environmental conditions.…”

“…In particular, the strains of Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV, Baculoviridae) isolated in North America possess higher virulence than the Asian strain because of vef-1 gene deletion [9][10]. However, the phenotypic expression of these genetic differences does not depend on the host population [10]; conversely, it is ruled by the environmental conditions. In particular, sunlight easily decreases the potency of the American strain by UV even after 15 min of exposure, while the Asian strain possesses higher UV tolerance [11].…”

Comparative genome analysis of related Lymantria dispar nucleopolyhedrovirus isolates differing in virulence

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Motivation and Aim: Nucleopolyhedroviruses (NPVs, Baculoviridae) are specific viruses of insects that are used for pest control. High variation in virus virulence depends upon genetic factors [1]. Here we compare genomes of closely related genetic variants of Lymantria dispar multiple NPV (LdMNPV) that differ in virulence.

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Diversity and biological activity of nucleopolyhedroviruses of the leafworm Spodoptera litura

“…Mutational analysis of ORF122, ORF7 or hr17 using SpltNPV bacmids to be constructed or via CRISPR-CAS9 mutagenesis would be required to substantiate this claim. It is interesting to note that differences in biological activity were found between spatially separated isolates of Lymantria dispar MNPV in conjunction with differences in whole genome sequence information (Harrison et al, 2016;Martemyanov et al, 2017). By applying dN/dS analysis it is possible that other virulence genes come to light, an approach that has worked well when comparing different baculovirus species (Harrison and Bonning 2003).…”

“…However, the fast acting SpltNPV isolates emerged from genogroups A and B and the genetic variability may have contributed towards fast biological activity as the small variation within genome can result in significant changes in biological activity (Cory et al, 2005). A further study demonstrated that the virulence of LdMNPV is determined only by viral genetics and not by the locality of host population (Martemyanov et al, 2017).…”