Comparative genomics of the Neodiprion sertifer nucleopolyhedrovirus from Turkey with the fewest ORFs among baculoviruses.

Abstract

The complete genome of a European pine sawfly Neodiprion sertifer nucleopolyhedrovirus (NeseNPV-TR) was sequenced and characterized from next-generation sequencing data of N. sertifer larva from Türkiye. This genome was analyzed and compared to previously reported genomes of baculoviruses. The baculovirus phylogeny was reconstructed and the species identity of the NeseNPV-TR was delineated using K2P distance. The length of the genome was 82,052bp, with a G + C content of 33.28%. It contained 83 putative ORFs, including 38 baculovirus core genes, three lepidopteran baculovirus core genes, and three non-conserved genes. It had five hrs with 20.6% overall mean distance on average. The pairwise K2P distances of lef-8, lef-9, and polh genes and combinations of three genes and 38 genes between NeseNPV-TR and NeseNPV were slightly higher than the specified threshold values for species demarcation. The most variable genes were lef-2, helicase, p40, desmoplakin, pif7, p6.9, vp91, and vp39, while the most conserved were lef-8, lef-9, odv-e18, pif2, and lef-5 among baculoviruses. The genome of NeseNPV-TR is smaller and contains the fewest ORFs among baculoviruses. Some of unassigned ORFs had conserved domains and hence, we suggest further investigation to determine their structural and functional roles. Phylogenetic analyses confirmed its position within genus Gammabaculovirus. Taking into account the phylogenetic position, K2P distances, and NJ tree, the NeseNPV-TR can be classified in the same species (Gammabaculovirus nesertiferis) with NeseNPV. The different divergence rates in the baculovirus core genes may be related with different selection pressures acting on the genes. The lower genetic diversity of Group I alphabaculoviruses is most probably due to recent emergence.