Two viruses that cause salivary gland hypertrophy in Glossina pallidipes and Musca domestica are related and form a distinct phylogenetic clade

Abstract

Glossina pallidipes and Musca domestica salivary gland hypertrophy viruses (GpSGHV and MdSGHV) replicate in the nucleus of salivary gland cells causing distinct tissue hypertrophy and reduction of host fertility. They share general characteristics with the non-occluded insect nudiviruses, such as being insect-pathogenic, having enveloped, rod-shaped virions, and large circular double-stranded DNA genomes. MdSGHV measures 65¾550 nm and contains a 124 279 bp genome (~44 mol% G+C content) that codes for 108 putative open reading frames (ORFs). GpSGHV, measuring 50¾1000 nm, contains a 190 032 bp genome (28 mol% G+C content) with 160 putative ORFs. Comparative genomic analysis demonstrates that 37 MdSGHV ORFs have homology to 42 GpSGHV ORFs, as some MdSGHV ORFs have homology to two different GpSGHV ORFs. Nine genes with known functions (dnapol, ts, pif-1, pif-2, pif-3, mmp, p74, odv-e66 and helicase-2), a homologue of the conserved baculovirus gene Ac81 and at least 13 virion proteins are present in both SGHVs. The amino acid identity ranged from 19 to 39 % among ORFs. An (A/T/G)TAAG motif, similar to the baculovirus late promoter motif, was enriched 100 bp upstream of the ORF transcription initiation sites of both viruses. Six and seven putative microRNA sequences were found in MdSGHV and GpSGHV genomes, respectively. There was genome. Collinearity between the two SGHVs, but not between the SGHVs and the nudiviruses. Phylogenetic analysis of conserved genes clustered both SGHVs in a single clade separated from the nudiviruses and baculoviruses. Although MdSGHV and GpSGHV are different viruses, their pathology, host range and genome composition indicate that they are related.

Nudivirus Genomics and Phylogeny

“…GpSGHV and MdSGHV share 37 homologous ORFs and are phylogenetically closely related (Garcia-Maruniak et al 2009). Surprisingly, several core gene homologues of baculoviruses was identified in the marine WSSV as well (Wang et al 2011), suggesting that WSSV, as suspected since it was observed, is evolutionarily related, albeit distantly, to baculoviruses.…”

Musca domestica Salivary Gland Hypertrophy Virus, a Globally Distributed Insect Virus That Infects and Sterilizes Female Houseflies

“…MdSGHVspecific primer pairs were designed using Primer3 software, and a series of PCR assays was conducted to amplify five genes, including ORFs MdSGHV001 (forward primer 5Ј-ATTTCCGCCACACCATACAT-3Ј and reverse primer 3Ј-GTCACGCATAACATCCGTTG-5Ј; 630 bp), MdSGHV039 (forward primer 5Ј-CCGGATTCCATTATGTGGAC-3Ј and reverse primer 3ЈTTTGACGCGC TTGCATATAG-5Ј; 669 bp), MdSGHV029 (forward primer 5Ј-TCTTTCCGG TGTTCGTATCC-3Ј and reverse primer 3Ј-GCAAATTGGAACGGTTGACT-5Ј; 666 bp), MdSGHV089 (forward primer 5Ј-CCTTTTCCTGTTCGTTCAG C-3Ј and reverse primer 3Ј-CCGAATGAGGCAAATTGTTT-5Ј; 627 bp), and MdSGHV106 (forward primer 5Ј-CGGCAGCAACCTTATTCATT-3Ј and reverse primer 3Ј-CGTCGTCTCCTCCTCTTCAG-5Ј; 608 bp). These five genes were selected because of sequence homology to the DNA polymerase, p74, pif-1, pif-2, and pif-3 genes, respectively, found in other dsDNA insect viruses (5). The 25-l reaction mixtures used for PCR amplification consisted of 2.5 l of 10ϫ Taq buffer with 25 mM MgCl 2 , 0.5 l of 10 mM solutions of deoxynucleoside triphosphates, 1 l of a 10 M forward primer solution, 1 l of a 10 M reverse primer solution, 1 l of salivary gland DNA, and 0.25 l of Taq DNA polymerase.…”

Baculovirus Per Os Infectivity Factors Form a Complex on the Surface of Occlusion-Derived Virus

“…Recent work further revealed that these proteins have homologues in other large invertebrate DNA viruses which replicate in the nucleus, such as salivary gland hypertrophy viruses (SGHVs) (9), nudiviruses (30) and white spot syndrome virus (WSSV) (Nimaviridae) (J. A. Jehle, personal communication).…”