Conservation of DNA photolyase genes in group II nucleopolyhedroviruses infecting plusiine insects.

DNA photolyase genes (phr) encode photoreactive enzymes, which are involved in the repair of UV-damaged DNA. Cyclobutane pyrimidine dimer (CPD) specific photolyase genes are present in nucleopolyhedroviruses isolated from Chrysodeixis chalcites (ChchNPV) and Trichoplusia ni (TnSNPV), insects belonging to the Plusiinae (Noctuidae). To better understand the occurrence and evolution of these genes in baculoviruses, we investigated their possible conservation in other group II NPVs, which infect plusiine insects. A PCR based strategy using degenerate phr-specific primers was designed to detect and analyze possible photolyase genes. Six additional Plusiinae-infecting NPVs were analyzed and all, except Thysanoplusia oricalcea NPV A28-1, which is a group I NPV, contained one or more phr-like sequences. Phylogenetic analysis revealed that all photolyase genes of the tested Plusiinae-infecting baculoviruses group in a single clade, separated into three subgroups. The phylogeny of the polyhedrin sequences of these viruses confirmed that the analyzed viruses also formed a single clade in group II NPVs. We hypothesize that all plusiine group II NPVs contain one or more photolyase genes and that these have a common ancestor.