Group II nucleopolyhedrovirus subgroups revealed by phylogenetic analysis of polyhedrin and DNA polymerase gene sequences

Abstract

Two major clades, designated Groups I and II, of nucleopolyhedroviruses (NPVs) from lepidopteran hosts have been previously identified. To reveal more detailed relationships, a series of DNA polymerase nucleotide sequences from the taxa MbMNPV, SeMNPV, HzSNPV, HearNPV, SpltNPV, BusuNPV, and OranNPV have been determined using a polymerase chain reaction (PCR)-based approach. This technique enabled gene sequence determination using microliter samples of NPV-infected insect cadavers. Polyhedrin genes from HearNPV, OranNPV, SeMNPV, and SpltNPV were also isolated and sequenced using a similar approach. These sequences, together with other database entries, were aligned for positional homology of peptide sequences. Phylogenetic analysis of DNA polymerase molecular sequence alignments supports LdMNPV as a taxon of Group II and three Group II subclades, designated A, B, and C. Comparison of DNA polymerase trees with those estimated from occlusion protein molecular sequences enabled identification of three subclades of Group II. These are Subgroup II-A [MbMNPV, LeseNPV, MacoNPV, PaflNPV, SeMNPV, SpltNPV (India isolate), SfMNPV]; Subgroup II-B [SpliNPV, SpltNPV (Japan isolate), SpltNPV (Queensland isolate), and possibly HzSNPV, HearNPV, and ManeNPV], and Subgroup II-C [OpSNPV, OranNPV (S-type), BusuNPV (S-type), and possibly EcobNPV (S-type)]. Notably, all Subgroup II-A taxa are from noctuid hosts. Correlations of virus and host evolution within Group II taxa are discussed. The methods and data developed in this study will allow rapid sequencing of NPV DNA polymerase genes.