Expression strategy of densonucleosis virus from Mythimna loreyi

Development of a Species Diagnostic Molecular Tool for an Invasive Pest, Mythimna loreyi, Using LAMP

The Mythimna loreyi (Duponchel) is one of the well-known invasive noctuid pests in Africa, Australia, and many Asian countries. However, it is difficult to identify the invasive and morphologically similar species, Mythimna separate, which occur at the cornfield in the larvae stage. Currently, the molecular biology method for diagnosing M. loreyi species is only using the mtCO1 universal primer (LCO1490, HCO2198), which requires a lot of time and effort, such as DNA extraction, PCR, electrophoresis, and sequencing. In this study, the LAMP assay was developed for rapid, simple, effective species identification. By analyzing the mitochondrial genome, the species-specific sequence was found at the coding region of the NADH dehydrogenase subunit 5 gene. Based on this unique sequence, four LAMP primers and two loop primers were designed. The F3 and B3 primers were able to diagnose species-specific, in general, and multiplex PCR and specifically reacted within the inner primers in LAMP assay. The optimal incubation condition of the LAMP assay was 61 °C for 60 min with four LAMP primers, though additional loop primers, BF and LF, did not significantly shorten the amplification time. The broad range of DNA concentration was workable in LAMP assay, in which the minimum detectable DNA concentration was 100 pg. DNA releasing method was applied, which took five minutes of incubation at 95 °C without the DNA extraction process. Only some pieces of tissue of larvae and adult samples were needed to extract DNA. The incidence of invasive pests is gradually diversifying. Therefore, this simple and accurate LAMP assay is possibly applied in the intensive field monitoring for invasive pests and integrated management of Mythimna loreyi.

Intracellular Localization of Blattella germanica Densovirus (BgDV1) Capsid Proteins

Densovirus genome replication and capsid assembly take place in the nucleus of the infected cells. However, the mechanisms underlying such processes as the delivery of virus proteins to the nucleus and the export of progeny virus from the nucleus remain elusive. It is evident that nuclear transport signals should be involved in these processes. We performed an in silico search for the putative nuclear localization signal (NLS) and nuclear export signal (NES) motifs in the capsid proteins of the Blattella germanica Densovirus 1 (BgDV1) densovirus. A high probability NLS motif was found in the common C-terminal of capsid proteins together with a NES motif in the unique N-terminal of VP2. We also performed a global search for the nuclear traffic signals in the densoviruses belonging to five Densovirinae genera, which revealed high diversity in the patterns of NLSs and NESs. Using a heterologous system, the HeLa mammalian cell line expressing GFP-fused BgDV1 capsid proteins, we demonstrated that both signals are functionally active. We suggest that the NLS shared by all three BgDV1 capsid proteins drives the trafficking of the newly-synthesized proteins into the nucleus, while the NES may play a role in the export of the newly-assembled BgDV1 particles into the cytoplasm through nuclear pore complexes.

Reprint of: Diversity of small, single-stranded DNA viruses of invertebrates and their chaotic evolutionary past

A wide spectrum of invertebrates is susceptible to various single-stranded DNA viruses. Their relative simplicity of replication and dependence on actively dividing cells makes them highly pathogenic for many invertebrates (Hexapoda, Decapoda, etc.). We present their taxonomical classification and describe the evolutionary relationships between various groups of invertebrate-infecting viruses, their high degree of recombination, and their relationship to viruses infecting mammals or other vertebrates. They share characteristics of the viruses within the various families, including structure of the virus particle, genome properties, and gene expression strategy.

Structure and transcription of the Helicoverpa armigera densovirus (HaDV2) genome and its expression strategy in LD652 cells

Background

Densoviruses (DVs) are highly pathogenic to their hosts. However, we previously reported a mutualistic DV (HaDV2). Very little was known about the characteristics of this virus, so herein we undertook a series of experiments to explore the molecular biology of HaDV2 further.

Results

Phylogenetic analysis showed that HaDV2 was similar to members of the genus Iteradensovirus. However, compared to current members of the genus Iteradensovirus, the sequence identity of HaDV2 is less than 44% at the nucleotide-level, and lower than 36, 28 and 19% at the amino-acid-level of VP, NS1 and NS2 proteins, respectively. Moreover, NS1 and NS2 proteins from HaDV2 were smaller than those from other iteradensoviruses due to their shorter N-terminal sequences. Two transcripts of about 2.2 kb coding for the NS proteins and the VP proteins were identified by Northern Blot and RACE analysis. Using specific anti-NS1 and anti-NS2 antibodies, Western Blot analysis revealed a 78 kDa and a 48 kDa protein, respectively. Finally, the localization of both NS1 and NS2 proteins within the cell nucleus was determined by using Green Fluorescent Protein (GFP) labelling.

Conclusion

The genome organization, terminal hairpin structure, transcription and expression strategies as well as the mutualistic relationship with its host, suggested that HaDV2 was a novel member of the genus Iteradensovirus within the subfamily Densovirinae.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0691-y) contains supplementary material, which is available to authorized users.

Diversity of small, single-stranded DNA viruses of invertebrates and their chaotic evolutionary past

A wide spectrum of invertebrates is susceptible to various single-stranded DNA viruses. Their relative simplicity of replication and dependence on actively dividing cells makes them highly pathogenic for many invertebrates (Hexapoda, Decapoda, etc.). We present their taxonomical classification and describe the evolutionary relationships between various groups of invertebrate-infecting viruses, their high degree of recombination, and their relationship to viruses infecting mammals or other vertebrates. They share characteristics of the viruses within the various families, including structure of the virus particle, genome properties, and gene expression strategy.

Genetic and phylogenetic characterization of novel bocaparvovirus infecting chimpanzee

Primate bocaparvoviruses were first described in 2005, since then further human and gorilla bocaparvoviruses have been identified. To uncover diversity of non-human primates' bocaparvoviruses, their phylogenetic relationship and potential to cross the host species barrier, we tested 153 fecal samples from 17 captive primate species. The only one captive female of central chimpanzee (coded CPZh2) has been identified as bocaparvovirus positive. Based on the full genome phylogenetic analyses, CPZh2 strain shows close relationship to HBoV3 and GBoV. Further recombination analysis confirmed expected mosaic origin of CPZh2 strain. According the phylogenetic position, following the ICTV recommendations, we propose a novel genotype within the Primate bocaparvovirus 1 species infecting chimpanzee.

Gene expression of five different iteradensoviruses: Bombyx mori densovirus, Casphalia extranea densovirus, Papilio polyxenes densovirus, Sibine fusca densovirus, and Danaus plexippus densovirus

Iteradensoviruses are 5-kb parvoviruses with typical J-shaped inverted terminal repeats of about 250 nucleotides and terminal hairpins of about 165 nucleotides. The single-stranded DNA genome contains several open reading frames, but their expression strategy is still unknown. Here the transcription maps and expression of the viruses in this genus were explored. As for brevidensoviruses, the two nonstructural (NS) genes were expressed by overlapping promoters with alternate transcription starts at both sides of the NS1 start codon.

Expression analysis of Bombyx mori bidensovirus structural proteins and assembly of virus-like particles in insect cells

Bombyx mori bidensovirus (BmBDV) is a new designated species of the new genus Bidensovirus in the new family Bidnaviridae, which contains two single-stranded linear DNAs (VD1 and VD2) and causes the chronic densonucleosis disease of silkworm. Previous researches revealed that VD1-ORF3 encodes the major structural proteins VPs. In this work, through western blot, we found that VPs expressed from 48 h post-inoculation and kept increasing until 120 h post-inoculation in midgut of Bombyx mori. In order to further investigate the translation of vp gene, the ORFs (vp1 and vp2) of the VP started just up-stream of the first two candidate initiation codons were expressed in Sf9 cells by a baculovirus expression system. The expression products were purified by gradient density centrifugation and analyzed by Western blot and electron microscopy. The results showed that the expressions of vp1 yielded three proteins (VP1, VP1', and VP2), which are the same with the viral VPs expression in midgut of Bombyx mori, and vp2 generated two VPs with the molecular weights of about 51 kDa (VP2) and 37 kDa. The observation by electron microscopy indicated that these VPs can auto-assemble into virus-like particles that could not be distinguished from virus particles. These findings will provide materials for studying the structure of BmBDV and be helpful in the studies on BmBDV-based disease in silkworms.

A Novel Ambisense Densovirus, Acheta domesticus Mini Ambidensovirus, from Crickets

The genome structure of Acheta domesticus mini ambidensovirus, isolated from crickets, resembled that of ambisense densoviruses from Lepidoptera but was 20% smaller. It had the highest (<25%) protein sequence identity with the nonstructural protein 1 (NS1) of Iteravirus and VP of Densovirus members (both with 25% coverage) and smaller (0.2- versus 0.55-kb) Y-shaped inverted terminal repeats.

Comparative Genomic Analysis of Acheta domesticus Densovirus Isolates from Different Outbreaks in Europe, North America, and Japan

The first densovirus from a cricket, Acheta domesticus densovirus (AdDNV) (Parvoviridae), was isolated in Europe in 1977 and has been studied previously. We compared seven additional AdDNV genomes isolated from 4 other European outbreaks, 2 major North American outbreaks, and a Japanese outbreak. Phylogenetic analysis suggested that the 2009 Japanese and North American outbreaks were not related.

Junonia coenia Densovirus (JcDNV) Genome Structure

The sequence of Junonia coenia densovirus was the first densovirus genome sequence published, but the first published sequence contained incomplete inverted terminal repeats and ambiguous nucleotides or indels leading to an incorrect map of the open reading frames. Our sequencing of clones of the complete genome demonstrated that this virus is closely related to other viruses in the Densovirus genus.

Expression strategy of Aedes albopictus densovirus

The transcription map of the Aedes albopictus densovirus (AalDNV) brevidensovirus was identified by Northern blotting, rapid amplification of cDNA ends (RACE) analysis, and RNase protection assays. AalDNV produced mRNAs of 3,359 (NS1), 3,345 (NS2), and 1,246 (VP) nucleotides. The two overlapping P7/7.4 NS promoters employed closely located alternate transcription initiation sites, positioned at either side of the NS1 initiation codon. All NS mRNAs coterminated with VP mRNA. All promoters, explored using luciferase assays, were functional in insect and human cell lines.

Analysis of the transcription strategy of the Junonia coenia densovirus (JcDNV) genome

The Junonia coenia densovirus (JcDNV) has an ambisense genome with the structural (VP) and nonstructural (NS) genes located in the 5' half on opposite strands. Northern blot analysis of Ld652 cells and Spodoptera littoralis larvae transfected with plasmid pBRJ encompassing an infectious sequence of the JcDNV genome revealed three transcripts, an unspliced 2.5 kb VP mRNA encoding capsid proteins and two NS mRNAs, one unspliced 2.5 kb mRNA encoding NS3, the other of 1.7 kb resulting from the splicing out of the NS3 coding sequence and expressing NS1 and NS2. Mapping of the transcriptional start sites revealed that VP and NS transcripts start both at 32 nt downsream of the P9 and P93 TATA boxes, respectively. The VP mRNA has a very short (3 nt) 5' untranslated region whereas the NS mRNAs have 83 nt (unspliced) and 86nt (Spliced) 5' UTR. The VP and NS transcripts co-terminate in the middle of their respective strand and possess an overlapping sequence of 61 nt at their 3' termini. Analysis of the in vivo and in vitro translation products of VP mRNA clearly showed that the 4 capsid proteins are generated by a leaky scanning mechanism.

Pseudoplusia includens densovirus genome organization and expression strategy

The genome of a densovirus of a major phytophagous pest, Pseudoplusia includens, was analyzed. It contained 5,990 nucleotides (nt) and included inverted terminal repeats of 540 nt with terminal Y-shaped hairpins of 120 nt. Its DNA sequence and ambisense organization with 4 typical open reading frames demonstrated that it belonged to the genus Densovirus in the subfamily Densovirinae of the family Parvoviridae.

Direct interactions between bidensovirus BmDNV-Z proteins and midgut proteins from the virus target Bombyx mori

In this study we aimed to identify the protein-protein interactions between Bombyx mori midgut and the bidensovirus BmDNV-Z via a yeast two-hybrid (Y2H) system. To achieve this we constructed a Gal4 activation domain fusion library that expresses the host genes and Gal4 DNA binding domain fusion bait vectors that express BmDNV-Z genes. Y2H assay revealed 15 potential interactions between host and viral proteins. To verify the interactions, we modified and reconstructed a pair of bimolecular fluorescence complementation (BiFC) vectors and achieved the co-expressions of the candidate host genes and viral genes in insect culture cells. The BiFC assay confirmed the specificity of the interactions including B. mori 35 kDa protease and two BmDNV-Z proteins encoded by VD1-ORF2 and VD2-ORF1; B. mori transgelin and BmDNV-Z protein encoded by VD2-ORF3; and B. mori serine protease precursor and BmDNV-Z encoded by VD2-ORF3 in vitro. Our findings revealed that the specific host midgut proteins are involved in the interactions between B. mori and BmDNV-Z, which will facilitate our understanding of the molecular mechanisms of BmDNV-Z infection.

Characterization of the promoter elements of Bombyx mori bidensovirus nonstructural gene 1

Bombyx mori Bidensovirus (BmBDV), a bipartite virus possesses two single-stranded linear DNAs (VD1 and VD2) and shows high pathogenic ability to Bombyx mori. Previous research found that the genes of nonstructural protein ns1 and ns2 were in the same transcript. To investigate the mechanism of transcriptional regulation of ns1 and ns2 genes, the 5'-flanking sequence (289 nt) of ns1 gene, encompasses the regions of the common terminal sequence (CTS) and the predicted P5 promoter from the 5'-terminus of the viral genome to the transcription initiation site of the ns1 gene was cloned and fused to the upstream of the luciferase reporter gene. The luciferase reporter assay showed that the 53 nt CTS of VD1 and VD2 can downregulate the activity of P5 by 13.3 %. The comparison in different cell lines showed that P5 possessed high promoter activity in BmN and Hi5 cell lines. Interestingly, P5 also had high activity in Hela cells, a kind of cancer cell of human. Subsequent truncated promoter analysis showed that the 31 nt (-236 to -206 nt) sequence is very important to P5 for the activity down to 36.5 % after deletion of it. While the activity also remained 26.5 % after the deletion of the TATA box, suggesting that the promoter is TATA independent. Moreover, in order to further understand the activity intensity of P5, a comparison with other three promoters, B. mori actin3 (Bm-actin3), B. mori nuclear polyhedrosis virus (BmNPV) immediate early 1 gene promoter (BmNPV-ie-1), and a synthetic promoter (3xP3) was carried out, the result indicated that the activity of P5 was weaker than that of anyone of them.

Organization of the ambisense genome of the Helicoverpa armigera Densovirus

A natural densovirus (DNV) of a serious phytophagous pest, Helicoverpa armigera, was isolated. The genome of HaDNV contained 6,039 nucleotides (nt) and included inverted terminal repeats (ITRs) of 545 nt with terminal Y-shaped hairpins of 126 nt. Its DNA sequence and ambisense organization with four typical open reading frames (ORFs) demonstrated that it belonged to the genus Densovirus in the subfamily Densovirinae of the family Parvoviridae.

Expression strategy of densonucleosis virus from the German cockroach, Blattella germanica

Blattella germanica densovirus (BgDNV) is an autonomous parvovirus that infects the German cockroach. BgDNV possesses three mRNAs for NS proteins, two of which are splice variants of the unspliced transcript. The unspliced variant encodes open reading frame 5 (ORF5) (NS3), while NSspl1 encodes ORF3 (NS1) and ORF4 (NS2) and NSspl2 encodes the C-proximal half of NS1. BgDNV possesses three VP transcripts, one of which (VP) is unspliced, while the other two (VPspl1 and VPspl2) are generated by alternative splicing. The unspliced VP transcript contains both ORF1 and ORF2, while in VPspl1, ORF1 and ORF2 are joined in frame. The transcription of NS genes begins at an earlier stage of the virus life cycle than the transcription of VP genes. NS and VP transcripts overlap by 48 nucleotides (nt). BgDNV is characterized by two additional NS transcripts overlapping by more than 1,650 nt with VP-coding transcripts. Four different bands (97, 85, 80, and 57 kDa) corresponding to three BgDNV capsid proteins were detected on SDS-PAGE. Mass spectrometry analysis showed that the amino acid composition of the 85-kDa and 80-kDa proteins is the same. Moreover, both of these proteins are ubiquitinated. The BgDNV PLA(2) domain, which is critical for cellular uptake of the virus, is located in ORF2 and is present only in VP1. In contrast to all of the parvoviruses studied in this respect, VP2 has a unique N terminus that is not contained within VP1 and VP3. In situ recognition with NS1- and VP-specific antibodies revealed an uneven pattern of NS1 expression resembling a halo within the nuclear membrane.

Susceptibility of North-American and European crickets to Acheta domesticus densovirus (AdDNV) and associated epizootics

The European house cricket, Acheta domesticus L., is highly susceptible to A. domesticus densovirus (AdDNV). Commercial rearings of crickets in Europe are frequently decimated by this pathogen. Mortality was predominant in the last larval stage and young adults. Infected A. domesticus were smaller, less active, did not jump as high, and the adult females seldom lived more than 10-14 days. The most obvious pathological change was the completely empty digestive caecae. Infected tissues included adipose tissue, midgut, epidermis, and Malpighian tubules. Sudden AdDNV epizootics have decimated commercial mass rearings in widely separated parts of North America since the autumn of 2009. Facilities that are producing disease-free crickets have avoided the importation of crickets and other non-cricket species (or nonliving material). Five isolates from different areas in North America contained identical sequences as did AdDNV present in non-cricket species collected from these facilities. The North American AdDNVs differed slightly from sequences of European AdDNV isolates obtained in 1977, 2004, 2006, 2007 and 2009 and an American isolate from 1988. The substitution rate of the 1977 AdDNV 5kb genome was about two nucleotides per year, about half of the substitutions being synonymous. The American and European AdDNV strains are estimated to have diverged in 2006. The lepidopterans Spodoptera littoralis and Galleria mellonella could not be infected with AdDNV. The Jamaican cricket, Gryllus assimilis, and the European field cricket, Gryllus bimaculatus, were also found to be resistant to AdDNV.

Pathogenesis of Junonia coenia densovirus in Spodoptera frugiperda: a route of infection that leads to hypoxia

To evaluate densovirus potential against lepidopteran pests and their capacity to invade new hosts, we have characterised in vivo the infection and pathogenesis of the Junonia coenia densovirus (JcDNV) in the noctuid pest Spodoptera frugiperda. Here we show that infection starts with the ingestion of viral particles that cross the midgut epithelium without replicating. By quantitative PCR we established the kinetic and the route of infection, from virus ingestion to replication in visceral tracheae and hemocytes. JcDNV has a high particle-to-infection ratio mostly due to the barrier function of the midgut. Pathology and cytopathology suggested that infection of tracheal cells impairs oxygen delivery to demanding tissues leading to cytopathic effects in all the tissues. Finally, larval death results from several physiological shocks, including molting arrest and anoxia.

Non-structural proteins of Periplaneta fuliginosa densovirus inhibit cellular gene expression and induce necrosis in Sf9 cell cultures

The non-structural protein NS1 of Periplaneta fuliginosa densovirus (PfDNV) is a multifunctional protein that has previously been shown to possess ATP-binding, ATPase, site-specific DNA-binding, helicase, and transcription activation activities. We report here an investigation of the cytopathogenicity of this viral non-structural (NS) protein, as well as other two NSs, NS2, and NS3, in cultured insect cells. The expression of NS1 alone potently inhibited cellular gene expression, whereas NS2 and NS3 did not produce a similar effect. The inhibition of gene expression by NS1 was confirmed to be specific and not a simple manifestation of toxicity. For example, NS1 inhibited expression of several reporter genes under the control of different RNA polymerase II promoters, whereas it did not inhibit expression from a T7 RNA polymerase promoter construct. Mapping analysis identified the carboxy-terminal peptide of this protein as the region important for the inhibition of cellular gene expression, suggesting that this inhibition is independent of its DNA-binding activity. Next, the mutagenesis assay showed that ATP-binding was essential for the unique function of this protein. Furthermore, we found that NS2 and NS3 cooperatively enhanced the NS1-induced transcription inhibition. Co-expression of all the three NS proteins in Sf9 cells also led to necrotic cell death by ATP depletion.

Characterization of the genome structure of Bombyx mori densovirus (China isolate)

The genome of Bombyx mori densovirus (China isolate), termed as BmDNV-3, is composed of two kinds of different single-stranded linear DNA molecules (VD1 and VD2). In this study, the viral DNA molecules were purified and cloned into pUC119 vector, and the complete nucleotide sequence was determined. Sequence analysis showed that VD1 genome consisted of 6,543 nts including inverted terminal repeats (ITRs) of 224 nts, and VD2 genome consisted of 6,022 nts including ITRs of 524 nts. Comparison of the complete genome sequence between BmDNV-3 and BmDNV-2 (Yamanashi isolate) showed an identity of 98.4% in VD1 and 97.7% in VD2, with a total number of 228 bp substitutions, 11 bp deletions and 3 bp insertions found in BmDNV-3. A single nucleotide "A" deletion at nt 1589 in BmDNV-3 caused a frame shift mutation and brought about a premature stop codon, thus dividing VD2 of BmDNV-3 into two ORFs (named VD2 ORF1a and VD2 ORF1b) within that region, while there was only one ORF (named VD2 ORF1) in the corresponding region of BmDNV-2 (Yamanashi isolate). Comparative polymorphisms of ORFs and ITR regions of the two viral genomes showed that highly variable regions were mainly located in VD1 ORF3, VD1 ORF4, VD2 ORF2, and ITRs of BmDNV-3. Northern blots analysis revealed that VD1 had 1.1 kb and 1.5 kb transcripts from the left half of its plus strand, and one transcript about 3.3 kb from the right half of its minus strand. Sequencing of 3' and 5' RACE products showed that the 1.1 kb transcript started at nt 290 and ended at nt 1437, the 1.5 kb transcript started at nt 1423 and ended at nt 2931, and the 3.3 kb transcript started at nt 6287 and ended at nt 2922. These results help us to further understand the variation between different DNV genera and its possible causes, providing clues for studying the evolutionary history of densoviruses.

Characterization of a new densovirus infecting the German cockroach, Blattella germanica

A new DNA virus (Parvoviridae: Densovirinae, Densovirus) was isolated and purified from descendants of field-collected German cockroaches, Blattella germanica. Viral DNA and cockroach tissues infected with B. germanica densovirus (BgDNV) were examined by electron microscopy. Virus particles, about 20 nm in diameter, were observed both in the nucleus and in the cytoplasm of infected cells. Virus DNA proved to be a linear molecule of about 1.2 microm in length. BgDNV isolated from infected cockroaches infected successfully and could be maintained in BGE-2, a B. germanica cell line. The complete BgDNV genome was sequenced and analysed. Five open reading frames (ORFs) were detected in the 5335 nt sequence: two ORFS that were on one DNA strand encoded structural capsid proteins (69.7 and 24.8 kDa) and three ORFs that were on the other strand encoded non-structural proteins (60.2, 30.3 and 25.9 kDa). Three putative promoters and polyadenylation signals were identified. Structural analysis of the inverted terminal repeats revealed the presence of extended palindromes. The genome structure of BgDNV was compared with that of other members of the family Parvoviridae; the predicted amino acid sequences were aligned and subjected to phylogenetic analyses.

SAT: a late NS protein of porcine parvovirus

The genomes of all members of the Parvovirus genus were found to contain a small open reading frame (ORF), designated SAT, with a start codon four or seven nucleotides downstream of the VP2 initiation codon. Green fluorescent protein or FLAG fusion constructs of SAT demonstrated that these ORFs were expressed. Although the SAT proteins of the different parvoviruses are not particularly conserved, they were all predicted to contain a membrane-spanning helix, and mutations in this hydrophobic stretch affected the localization of the SAT protein. SAT colocalized with calreticulin in the membranes of the endoplasmic reticulum and the nucleus. A knockout mutant (SAT(-)), with an unmodified VP sequence, showed a "slow-spreading" phenotype. These knockout mutants could be complemented with VP2(-) SAT(+) mutant. The SAT protein is a late nonstructural (NS) protein, in contrast to previously identified NS proteins, since it is expressed from the same mRNA as VP2.

Nucleotide sequence and genomic organization of a newly isolated densovirus infecting Dendrolimus punctatus

The nucleotide sequence of a novel icosahedral DNA virus infecting Dendrolimus punctatus has been determined. The genome is 5039 nt long and includes inverted terminal repeats of 200 nt containing 131 nt long J-shaped terminal hairpins. The ‘plus' strand of the genome contains three large open reading frames (ORFs), the left and the mid-ORFs (within the left ORF) in the left-half encoding the non-structural proteins and the right ORF in the right-half encoding viral capsid proteins. NS1 protein contains conserved replication initiation and DNA-dependent ATPase/helicase domains. VP1 protein contains a conserved PGY and phospholipase A2 motifs and shows high identities with VPs of Casphalia extranea densovirus and Bombyx mori densovirus-1 belonging to the genus Iteravirus. Phylogenetic analysis also revealed that this virus is most closely related to Casphalia extranea densovirus and Bombyx mori densovirus-1. Consequently, this virus was considered as a new third member of the genus Iteravirus of the subfamily Densovirinae, and designated Dendrolimus punctatus densovirus.