Advances on BmNPV Functional Genomics

¹Zhejiang Provincial Center for Disease Control and Prevention, 310051 Hangzhou, China

²Institute of Insect Science, Zhejiang University, 310058, Hangzhou, China

Corresponding Author:

Chuan-Xi Zhang
Institute of Insect Science, Zhejiang University
310058, Hangzho, China
E-mail: chxzhang@zju.edu.cn

Received date: April 10, 2012; Accepted date: May 10, 2012; Published date: May 12, 2012

Citation: Yang ZN, Zhang CX (2012) Advances on BmNPV Functional Genomics. J Biotechnol Biomaterial S9:006. doi:10.4172/2155-952X.S9-006

Copyright: © 2012 Yang ZN, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Keywords

Bombyx mori nucleopolyhedrovirus; BmNPV; Functional genomics

Introduction

The baculovirus was originally described when silkworm cultures were threatened by a disease indicated as jaundice [1], and the isolation and chemical composition research of the virus resulted in the new era of the baculovirus research [2].

Baculoviruses are arthropod-specific viruses containing large double- stranded circular DNA genomes of 80-180k bp. The Baculoviridae family can be divided into four genera according to common biological and structural characteristics: Alphabaculovirus, which includes lepidopteran specific baculoviruses and is subdivided into Group I or Group II based on the type of fusogenic protein, Betabaculovirus, comprising lepidopteran-specific granuloviruses, Gammabaculovirus, which includes hymenopteran-specific baculoviruses, and Deltabaculovirus, which, to date, comprises only CuniNPV and possibly still undescribed dipteran-specific baculoviruses [3-6].

There are currently 54 complete baculovirus genomes deposited in GenBank before this paper was published (http://www.ncbi.nlm.nih.gov/genomes/GenomesGroup.cgi?taxid=10442). These include 37 Alphabaculoviruses, 13 Betabaculoviruses, 3 Gammabaculoviruses, and 1 Deltabaculovirus. Despite the diversity in gene content present in different baculovirus genomes, there are now 31 core genes conserved in all sequenced baculovirus genomes, the function of these genes can be divided into replication, transcription, packaging and assembly, cell cycle arrest, and oral infectivity (Table 1) [5]. Most of the data comes from the Autographa californica nucleopolyhedrovirus (AcMNPV), as it is the model type for baculovirus and has been extensively studied. Four core genes have been identified as essential players in viral DNA replication: DNApol, Helicase, Lef-1 and Lef-2. Nearly half of the core genes involved in the packaging and assembly.

Table 1: Functions of 31 core genes in 54 baculoviruses

In the most well characterized baculoviruses, the life cycle is biphasic with two different phenotypes during virus infection: Occluded Virions (ODV) and Budded Virions (BV) [7]. The ODV transmits infection from insect to insect by infecting midgut columnar epithelial cells, whereas the BV is responsible for causing systemic infection within the host [8]. The two viral forms are efficient for the natural propagation of the occluded baculoviruses.

Over the years, Baculoviruses are extensively being studied for potential use in bioinsecticides around the world and as expression vectors for heterologous genes expression in insect-derived cells as well as in the host caterpillars. Bombyx mori nucleopolyherovirus (BmNPV), the type member of baculovirus, has been successfully developed for surface display [9]. Additionally, baculoviruses are regarded as potentially useful gene therapy vectors [10,11], and has been applied for veterinary and medical applications, including the development of vaccines and diagnostics, putative nonhuman viral vectors for gene delivery, and biological control agents against insect pests [5,6,12]. These applications further trigger the study of molecular basis of baculovirus infection.

BmNPV Functional Genomics

The history of BmNPV is intimately related to the development of the silk industry. Silk production has been of major cultural significance in China and some other Asian Countries. Though BmNPV was the first described NPV, the genome of the BmNPV was completely sequenced and analyzed in 1999. The BmNPV (T3 strain) genome has a size of 12, 843 bp with a G+C content of 40% and encoding 142 predicated open reading frames (136 of the ORFs encoding predicted proteins of over 60 amino acids) [13,14]. Recently, a BmNPV strain (S1) isolated from the wild silkworm (Bombyx mandarina) was also sequenced [15]. The complete nucleotide sequence of the S1 strain was compared with the T3 strain. The S1 strain was 126,770 nucleotides long, with a G+C content of 40.23%. The genome contained 133 potential ORFs encoding predicted proteins of over 60 amino acids. Most of the putative proteins were more than 96% identical to homologs in the T3 strain, except for bro-a, lef-12, bro-c, and bro-d. The S1 genome did not encode the bro-b and bro-e genes. The BmNPV genome was closely related to that of AcMNPV, sharing over 90% similarity to about threequarters of the genome of AcMNPV. And the relatedness of predicted amino acid sequences of corresponding ORFs between BmNPV and AcMNPV was about 90% identical.

As Bombyx mori is well-studied physiologically, biochemically, and molecular biologically, contributed to the genome sequenced through international collaboration between China and Japan [16]. The genome data stimulated the analysis on the BmNPV-silkworm infection system. However, at least two third of the BmNPV viral gene functions are still remain unknown. BmNPV has potential usage not only for expression vector, but also for the display system, thus the fundamental investigation on gene function is important.

Many researchers have made effort on characterization of the BmNPV genes. And the development of the BmNPV bacmid system and the modification of this technology using a lambda red recombinant system allowed for the efficient production of knockouts, make the single gene function analysis more convenient. By using the knockout technology, Ono et al. [16] generated KOVs (knockout viruses) for 141 BmNPV genes and subdivided the KOVs into four phenotypic groups, types A to D [16].

Rohrmann [6] has included pertinent information on the function of all the ORFs present in the AcMNPV genome. Though AcMNPV and BmNPV share high similarities in the genome, some of the homologous genes in the two viruses function quite differently in the regulation of viral life cycle due to adaptation to different hosts. Here, we listed all the genes characterized in BmNPV up to date in Table 2 and marked by the phenotypic groups established by Ono et al. [16].

Table 2: Characterized genes in BmNPV.

Type-A KOVs showed the ability to expand infections almost equivalent to the wild type virus. The type A genes are likely to be nonessential, as the genes interrupted by insertion/deletion mutagenesis in BmNPV, the virus appeared to be normal, though the deletion may have slight affection on BV/ODV production, virulent, or DNA replication. For instance, it was previously reported that the deletion of Bm56 in BmNPV affected the occlusion body’s morphogenesis [17]. Bm5 is not a structural protein associated with BV or ODV, the Bm5 likely to be nonessential as the KO virus appeared to be viable [18]. And knock out of Bm9 led to a slight reduced production of BV without affect the DNA replication [19]. Bioassays showed that the Bm9-deleted bacmid took approximately 14-22 h longer to kill fifth instar B. mori larvae than wt bacmid, and the LD (50) was about 15 times higher than that of the wt bacmid, indicating that Bm9 is an important but not essential factor in virus production and infectivity in vivo and in vitro. For the core genes of all the baculovirus (Table 1), Oral infectivity genes are type A except Bm79 (OEV-E28/19K/Pif4). Bm79 is an ODV envelope associated protein [20] and in BmNPV and lately was also found associated with the envelope of BV in AcMNPV, and was concluded that Ac96 is a per os infecitivity factor in AcMNPV [6].

Type-B KOVs were characterized by a markedly slow spreading of the infection probably because of the low production of infectious viruses and/or low infectivity of the progeny viruses. As genes have been characterized in BmNPV, only Bm131 (BRO-D) belonged to type B. Bm131 (BRO-D) has been observed as a nucleocytoplasmic shuttling protein, and the KOV of Bm131 was due to a reduction in RNA synthesis [21].

Type-C KOVs expressed report egfp in transfected-BmN cells but the production of infectious viruses was not observed while Type-D showed no ability to express egfp even in the transfection experiments. The core genes of baculovirus involved in replication and transcription are all belonged to type C and type D (Table 1). And most of the type C genes may play important roles in the morphogenesis of BmNPV as most of the genes knocked out in type-C code for virion structural proteins (Table 1). The Bm54-deleted virus produced non-infectious budded virus (BV) and normal nucleocapsids but defect in polyhedra. And disruption of Bmvp80 [22] resulted in single cell infection phenotype. Bmvp80 is essential for normal budded virus production and nucleocapsid maturation, and is functionally divergent between baculovirus species. Also, Bm118 is essential for BV production and nucelocapsid maturation [23].

In the cells transfected with type-D bacmid DNAs, neither egfp expression nor the BV production was detected. Two viral genes of BmNPV have been characterized in type-D KOVs were essential not only for viral replication, but also for polhedrin expression [24].

Take the advantage of silkworm genomic data, researchers analyzed the host-derived protein of the BmNPV [25], the BmNPV resistance in the hemolymph and the fat body in the genomic and proteomic level [26-30]. A dynamic protein-protein interaction network between BmNPV and its host cells was predicted by making comparisons to other insect interactomes recently [31]. This is a comprehensive indepth study analyzing host gene response to baculovirus infection and perhaps the most comprehensive and best described transcriptional analysis available using baculoviruses. Gene enhancements are grouped in functional categories (cell cycle, energy metabolism, etc.) and their potential role during baculovirus infection is well discussed [31]. The protein-protein interaction network prediction provides an excellent resource for others in the community to evaluate certain pathways and to provide more in depth analysis.

Conclusion

In conclusion, two strain genomes of BmNPV have been sequenced and compared. Forty eight genes in a total of 136 BmNPV ORFs have been functionally characterized. As development of new genome sequencing techniques, more and more genomes of baculoviruses have been sequenced, and phylogenetic evolution history of baculoviruses becomes increasingly clear. We have tried to comparatively analyze six various strains from a host at genome level that will enrich our knowledge of evolution of the baculoviruses (data not published). However, many gene functions remain unclear yet. To elucidate the interaction between BmNPV and its host, more works on ORF functions are needed.

References

1. Steinhaus EA (1954) Duration of infectivity of the virus of silkworm jaundice. Science 120: 186-187.
2. Bergold GH, Wellington EF (1954) Isolation and chemical composition of the membranes of an insect virus and their relation to the virus and polyhedral bodies. J Bacteriol 67: 210–216.
3. Herniou EA, Jehle JA (2007) Baculovirus phylogeny and evolution. Current Drug Targets 8: 1043-1050.
4. Jehle JA, Lange M, Wang H, Hu Z, Wang Y, et al. (2006) Molecular identification and phylogenetic analysis of baculoviruses from Lepidoptera. Virology 346: 180-193.
5. Miele SA, Garavaglia MJ, Belaich MN, Ghiringhelli PD (2011) Baculovirus:molecular insights on their diversity and conservation. Int J Evol Biol 2011: 379424.
6. Rohrmann GF (2011) Baculovirus Molecular Biology. (2ndedn), Bethesda (MD): National Center for Biotechnology Information (US), USA.
7. Lu A, Miller LK (1997) Regulation of baculovirus late and very late gene expression. New York: Plenum.
8. Keddie BA, Aponte GW, Volkman LE (1989) The pathway of infection of Autographa californica nuclear polyhedrosis virus in an insect host. Science 243: 1728-1730.
9. Rahman MM, Gopinathan KP (2003) Bombyx mori nucleopolyhedrovirus-based surface display system for recombinant proteins. J Gen Virol 84: 2023-2031.
10. Hüser A, Hofmann C (2003) Baculovirus vectors: novel mammalian cell gene-delivery vehicles and their applications. Am J Pharmacogenomics 3: 53-63.
11. Tani H, Limn CK, Yap CC, Onishi M, Nozaki M, et al. (2003) In vitro and in vivo gene delivery by recombinant baculoviruses. J Virol 77: 9799-9808.
12. Kost TA, Condreay JP, Jarvis DL (2005) Baculovirus as versatile vectors for protein expression in insect and mammalian cells. Nat Biotechnol 23: 567–575.
13. Gomi S, Majima K, Maeda S (1999) Sequence analysis of the genome of Bombyx mori nucleopolyhedrovirus. J Gen Virol 80:1323-1337.
14. Katsuma S, Kang W, Shin-i T, Ohishi K, Kadota K, et al. (2011) Mass identification of transcriptional units expressed from the Bombyx mori 402 nucleopolyhedrovirus genome. J gen virol 92: 200–203.
15. Xu YP, Ye ZP, Niu CY, Bao YY, Wang WB, et al. (2010) Comparative analysis of the genomes of Bombyx mandarina and Bombyx mori nucleopolyhedroviruses . J Microbiol 48: 102-110.
16. Ono C, Kamagata T, Taka H, Sahara K, Asano S, et al. (2012) Phenotypic grouping of 141 BmNPVs lacking viral gene sequences.virus research. Virus Res 165: 197-206.
17. Xu HJ, Yang ZN, Zhao JF, Tian CH, Ge JQ, et al. (2008) Bombyx mori nucleopolyhedrovirus ORF56 encodes an occlusion-derivedvirus protein and is not essential for budded virus production. J Gen Virol 89:1212–1219.
18. Zhou Y, Chen K, Yao Q, Shen H, Liang G, et al. (2010) Characterization of a late expression gene of Bombyx mori nucleopolyhedrovirus. Z Naturforsch C 65: 508-518.
19. Yang ZN, Xu HJ, Thiem SM, Xu YP, Ge JQ, et al. (2009) Bombyx mori nucleopolyhedrovirus ORF9 is a gene involved in the budded virus production and infectivity. J Gen Virol 90: 162-169.
20. Xu HJ, Yang ZN, Wang F, Zhang CX (2006) Bombyx mori nucleopolyhedrovirus ORF79 encodes a 28-kDa structural protein of the ODV envelope. Arch virol 151: 681-695.
21. Kang W, Suzuki M, Zemskov E, Okano K, Maeda S (1999) Characterization of baculovirus repeated open reading frames (bro) in Bombyx mori nucleopolyhedrovirus. J virol 73: 10339-10345.
22. Tang XD, Xu YP, Yu LL, Lang GJ, Tian CH, et al. (2008) Characterization of a Bombyx mori nucleopolyhedrovirus with Bmvp80 disruption. Virus Res 138: 81-88.
23. Yang ZN, Xu HJ, Park EY, Zhang CX (2008) Characterization of Bombyx mori nucleopolyhedrovirus with a deletion of bm118. Virus Res 135: 220-229.
24. Acharya A, Gopinathan KP (2002) Characterization of late gene expression factors lef-9 and lef-8 from Bombyx mori nucleopolyhedrovirus. J Gen Virol 83: 2015-2023.
25. Li G, Wang J, Deng R, Wang X (2008) Characterization of AcMNPV with a deletion of ac68 gene.Virus Genes 37:119–127.
26. Bao YY, Tang XD, Lv ZY, Wang XY, Tian CH, et al. (2009) Gene expression profiling of resistant and susceptible Bombyx mori strains reveals nucleopolyhedrovirus-associated variations in host gene transcript levels. Genomics 94: 138–145.
27. Bao YY, Lv ZY, Liu ZB, Xue J, Xu YP, et al. (2010) Comparative analysis of BmNPV responsive genes in fat body and haemocyte of Bombyx mori resistant and susceptible strains. Insect Molecular Biology 19: 347–358.
28. Cai K, Chen K, Liu X, Yao Q, Li J (2008) Differential expression of haemolymph proteome of resistant strain and susceptible strain for BmNPV in Bombyx mori L. Sheng Wu Gong Cheng Xue Bao 24: 285-290.
29. Liu X, Chen K, Yao Q, Xia H (2010) Proteomic analysis of differentially expressed proteins involved in BmNPV resistance in the fat body of silkworm, Bombyx mori Z Naturforsch C 65: 713-718.
30. Liu X, Yao Q, Wang Y, Chen K (2010) Proteomic analysis of nucleopolyhedrovirus infection resistance in the silkworm, Bombyx mori (Lepidoptera: Bombycidae). J Invertebr Pathol 105: 84-90.
31. Xue J, Qiao N, Zhang W, Cheng RL, Zhang XQ, et al. (2012) Dynamic interactions between Bombyx mori nucleopolyhedrovirus and its host cells revealed by transcriptome analysis. J Virol.
32. Evans JT, Leisy DJ, Rohrmann GF (1997) Characterization of the interaction between the baculovirus replication factors LEF-1 and LEF-2.J Virol 71: 3114–3119.
33. Vanarsdall AL, Okano K, Rohrmann GF (2006) Characterization of the role of very late expression factor 1 in baculovirus capsid structure and DNA processing. J Virol 80: 1724–1733.
34. Huang J, Levin DB (2001) Expression, purification and characterization of the Spodoptera littoralis nucleopolyhedrovirus (SpliNPV) DNA polymerase and interaction with the SpliNPV non-hr origin of DNA replication. J Gen Virol 82:1767-1776.
35. Maeda S, Kamita SG, Kondo A (1993) Host range expansion of Autographa californica nuclear polyhedrosis virus (NPV) following recombination of a 0.6-kilobase-pair DNA fragment originating from Bombyx mori NPV. J Virol 67: 6234–6238.
36. Hang X, Guarino LA (1999) Purification of Autographa californica nucleopolyhedrovirus DNA polymerase from infected insect cells. J Gen Virol 80: 2519-2526.
37. Heldens JG, Kester HA, Zuidema D, Vlak JM (1997) Generation of a p10-based baculovirus expression vector in yeast with infectivity for insect larvae and insect cells. J Virol Methods 68: 57-63.
38. Ito E, Sahri D, Knippers R, Carstens EB (2004) Baculovirus proteins IE-1, LEF-3, and P143 interact with DNA in vivo: a formaldehyde cross-linking study. Virology 329: 337–347.
39. Mcdougal VV, Guarino LA (2000) The Autographa californica nuclear polyhedrosis virus p143 gene encodes a DNA helicase. J Virol 74: 5273–5279.
40. Evans JT, Rosenblatt GS, Leisy DJ, Rohrmann GF (1999) Characterization of the interaction between the baculovirus ssDNA-binding protein (LEF 3) and putative helicase (P143). J Gen Virol 80: 493–500.
41. Guarino LA, Xu B, Jin J, Dong W (1998) A virus-encoded RNA polymerase purified from baculovirus-infected cells. J Virol 72: 7985–7991.
42. McLachlin JR, Miller LK (1994) Identification and characterization of vlf-1, a baculovirus gene involved in very late gene expression. J Virol 68: 7746–7756.
43. Titterington JS, Nun TK, Passarelli AL (2003) Functional dissection of the baculovirus late expression factor-8 gene: sequence requirements for late gene promoter activation. J Gen Virol 84: 1817–1826.
44. Iorio C, Vialard JE, McCracken S, Lagacé M, Richardson CD (1998) The late expression factors 8 and 9 and possibly the phosphoprotein p78/83 of Autographa californica multicapsid nucleopolyhedrovirus are components of the virusinduced RNA polymerase. Intervirology 41: 35–46.
45. Guarino LA, Jin J, Dong W (1998) Guanylyltransferase activity of the LEF-4 subunit of baculovirus RNA polymerase. J Virol 72: 10003–10010.
46. Gross CH, Shuman S (1998) RNA 5’-triphosphatase, nucleoside triphosphatase, and guanylyltransferase activities of baculovirus LEF-4 protein. J Virol 72: 10020–10028.
47. Jin J, Dong W, Guarino LA (1998) The LEF-4 subunit of baculovirus RNA polymerase has RNA 5’- triphosphatase and ATPase activities. J Virol 72: 10011–10019.
48. Gross CH, Shuman S (1998) Characterization of a baculovirus-encoded RNA 5’-triphosphatase. J Virol 72: 7057–7063.
49. Guarino LA, Mistretta TA, Dong W (2002) Baculovirus lef-12 is not required for viral replication. J Virol 76: 12032-12043.
50. Olszewski J, Miller LK (1997) Identification and characterization of a baculovirus structural protein, VP1054, required for nucleocapsid formation. J Virol 71: 5040–5050.
51. Todd JW, Passarelli AL, Lu A, Miller LK (1996) Factors regulating baculovirus late and very late gene expression in transient-expression assays. J Virol 70: 2307–2317.
52. Yang S, Miller LK (1998) Control of baculovirus polyhedrin gene expression by very late factor 1. Virology 248 :131–138.
53. Mikhailov VS, Rohrmann GF (2002)Binding of the baculovirus very late expression factor 1 (VLF-1) to different DNA structures. BMC Mol Biol 3: 14.
54. Whitford M, Faulkner P (1992) A structural polypeptide of the baculovirus Autographa californica nuclear polyhedrosis virus contains O-linked N-acetylglucosamine. J Virol 66: 3324–3329.
55. Olszewski J, Miller LK (1997) A role for baculovirus GP41 in budded virus production. Virology 233: 292–301.
56. Lin X, Chen Y, Yi Y, Yan J, Zhang Z (2008) Promoter analysis of Bombyx mori nucleopolyhedrovirus ubiquitin gene. J Microbiol 46: 429-435.
57. Russell RL, Rohrmann GF (1997) Characterization of P91, a protein associated with virions of an Orgyia pseudotsugata baculovirus.Virology 233: 210–223.
58. Thiem SM, Miller LK (1989) Identification, sequence, and transcriptional mapping of the major capsid protein gene of the baculovirus Autographa californica nuclear polyhedrosis virus. J Virol 63: 2008–2018.
59. Pearson MN, Russell RL, Rohrmann GF, Beaudreau GS (1988) p39, a major baculovirus structural protein: immunocytochemicalcharacterization and genetic location. Virology 167: 407–413.
60. Blissard GW, Quant-Russell RL, Rohrmann GF, Beaudreau GS (1989) Nucleotide sequence, transcriptional mapping, and temporal expression of the gene encoding p39, a major structural protein of the multicapsid nuclear polyhedrosis virus of Orgyia pseudotsugata. Virology 168: 354–362.
61. Lu S, Ge G, Qi Y (2004) Ha-VP39 binding to actin and the influence of F-actin on assembly of progeny virions. Arch Virol 149: 2187–2198.
62. Long CM, Rohrmann GF, Merrill GF (2009) The conserved baculovirus protein p33 (Ac92) is a flavin adenine dinucleotide-linked sulfhydryl oxidase. Virology 388: 231–235.
63. Wu W, Passarelli AL (2010) Autographa californica multiple nucleopolyhedrovirus Ac92 (ORF92, P33) is required for budded virus production and multiply enveloped occlusionderived virus formation. J Virol 84: 12351–12361.
64. Nie Y, Fang M, Theilmann DA (2011) Autographa californica multiple nucleopolyhedrovirus core gene ac92 (p33) is required for efficient budded virus production.Virology 409: 38–45.
65. Wu W, Liang H, Kan J, Liu C, Yuan M, et al. (2008) Autographa californica multiple nucleopolyhedrovirus 38K is a novel nucleocapsid protein that interacts with VP1054, VP39, VP80, and itself. J Virol 82: 12356–12364.
66. Bao YY, Xue J, Wu WJ, Wang Y, Lv ZY, et al. (2011) An immune-induced reeler protein is involved in the Bombyx mori melanization cascade. Insect Biochem Mol Biol 41: 696-706.
67. Wilson ME, Miller LK (1986) Changes in the nucleoprotein complexes of a baculovirus DNA during infection. Virology 151: 315–328.
68. Wilson ME, Mainprize TH, Friesen PD, Miller LK (1987) Location, transcription, and sequence of a baculovirus gene encoding a small arginine-rich polypeptide. J Virol 61: 661–666.
69. Wang M, Tuladhar E, Shen S, Wang H, van Oers MM, et al. (2010) Specificity of baculovirus P6.9 basic DNA-binding proteins and critical role of the C terminus in virion formation. J Virol 84: 8821–8828.
70. Fang M, Wang H, Wang H, Yuan L, Chen X, et al. (2003) Open reading frame 94 of Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus encodes a novel conserved occlusion-derived virion protein, ODV-EC43. J Gen Virol 84: 3021–3027.
71. Deng F, Wang R, Fang M, Jiang Y, Xu X, et al. (2007) Proteomics analysis of Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus identified two new occlusion-derived virusassociated proteins, HA44 and HA100. J Virol 81: 9377–9385.
72. Peng K, Wu M, Deng F, Song J, Dong C, et al. (2010) Identification of protein-protein interactions of the occlusion-derived virusassociated proteins of Helicoverpa armigera nucleopolyhedrovirus. J Gen Virol 91: 659–670.
73. Mikhailov VS, Okano K, Rohrmann GF (2003) Baculovirus alkaline nuclease possesses a 5’-->3’ exonuclease activity and associates with the DNA-binding protein LEF-3. J Virol 77: 2436-2444.
74. Mikhailov VS, Okano K, Rohrmann GF (2004) Specificity of the endonuclease activity of the baculovirus alkaline nuclease for single-stranded DNA. J Biol Chem 279: 14734-14745.
75. Okano K, Vanarsdall AL, Rohrmann GF (2004) Characterization of a baculovirus lacking the alkaline nuclease gene. J Virol 78: 10650-10656.
76. Vanarsdall AL, Pearson MN, Rohrmann GF (2007) Characterization of baculovirus constructs lacking either the Ac 101, Ac 142, or the Ac 144 open reading frame. Virology 367: 187-195.
77. McCarthy CB, Theilmann DA (2008) AcMNPV ac143 (odve18) is essential for mediating budded virus production and is the 30th baculovirus core gene. Virology 375: 277-291.
78. Ke J, Wang J, Deng R, Wang X (2008) Autographa californica multiple nucleopolyhedrovirus ac66 is required for the efficient egress of nucleocapsids from the nucleus, general synthesis of preoccluded virions and occlusion body formation. Virology 374: 421-431.
79. Chen HQ, Chen KP, Yao Q, Guo ZJ, Wang LL (2007) Characterization of a late gene, ORF67 from Bombyx mori nucleopolyhedrovirus. FEBS Letters 581: 5836-5842.
80. Belyavskyi M, Braunagel SC, Summers MD (1998) The structural protein ODV-EC27 of Autographa californica nucleopolyhedrovirus is a multifunctional viral cyclin. Proc Natl Acad Sci U S A 95:11205–11210.
81. Braunagel SC, He H, Ramamurthy P, Summers MD (1996) Transcription, translation, and cellular localization of three Autographa californica nuclear polyhedrosis virus structural proteins: ODV-E18, ODV-E35, and ODV-EC27. Virology 222: 100-114.
82. Pijlman GP, Pruijssers AJ, Vlak JM (2003) Identification of pif-2, a third conserved baculovirus gene required for per os infection of insects. J Gen Virol 84: 2041-2049.
83. Braunagel SC, Russell WK, Rosas-Acosta G, Russell DH, Summers MD (2003) Determination of the protein composition of the occlusion-derived virus of Autographa californica nucleopolyhedrovirus. Proc Natl Acad Sci U S A 100: 9797-9802.
84. Fang M, Nie Y, Harris S, Erlandson MA, Theilmann DA (2009) Autographa californica multiple nucleopolyhedrovirus core gene ac96 encodes a per os infectivity factor (pif-4). J Virol 83: 12569-12578.
85. Kikhno I, Gutiérrez S, Croizier L, Croizier G, Ferber ML (2002) Characterization of pif, a gene required for the per os infectivity of Spodoptera littoralis nucleopolyhedrovirus. J Gen Virol 83: 3013-3022.
86. Ohkawa T, Washburn JO, Sitapara R, Sid E, Volkman LE (2005) Specific binding of Autographa californica M nucleopolyhedrovirus occlusion-derived virus to midgut cells of heliothis virescens larvae is mediated by products of pif genes Ac119 and Ac022 but not by Ac115. J Virol 79: 15258-15264.
87. Faulkner P, Kuzio J, Williams GV, Wilson JA (1997) Analysis of p74, a PDV envelope protein of Autographa californica nucleopolyhedrovirus required for occlusion body infectivity in vivo. J Gen Virol 78: 3091–3100.
88. Zhou W, Yao L, Xu H, Yan F, Qi Y (2005) The function of envelope protein p74 from Autographa californica multi ple nucleopolyhedrovirus in primary infection to host. Virus Genes 30:139–150.
89. Haas-Stapleton EJ, Washburn JO, Volkman LE (2004) P74 mediates specific binding of Autographa californica M nucleopolyhedrovirus occlusion-derived virus to primary cellular targets in the midgut epithelia of Heliothis virescens larvae. J Virol 78: 6786–6791.
90. Yao L, Zhou W, Xu H, Zheng Y, Qi Y (2004) The Heliothis armigera single nucleocapsid nucleopolyhedrovirus envelope protein P74 is required for infection of the host midgut. Virus Res 104: 111–121.
91. Sparks WO, Harrison RL, Bonning BC (2011) Autographa californica multiple nucleopolyhedrovirus ODV-E56 is a per os infectivity factor, but is not essential for binding and fusion of occlusion-derived virus to the host midgut. Virology 409: 69–76.
92. Katsuma S, Horie S, Daimon T, Iwanaga M, Shimada T (2006) In vivo and in vitro analyses of a Bombyx mori nucleopolyhedrovirus mutant lacking functional vfgf. Virology 355: 62-70.
93. Katsuma S, Horie S, Shimada T (2008) The fibroblast growth factor homolog of Bombyx mori nucleopolyhedrovirus enhances systemic virus propagation in B. mori larvae. Virus Res 137: 80-85.
94. Yang S, Miller LK (1998) Expression and mutational analysis of the baculovirus very late factor 1 (vlf-1) gene. Virology 245: 99–109.
95. Gomi S, Zhou CE, Yih W, Majima K, Maeda S (1997) Deletion analysis of four of eighteen late gene expression factor gene homologues of the baculovirus, BmNPV. Virology 230: 35-47.
96. Katsuma S, Fujii T, Kawaoka S, Shimada T (2008) Bombyx mori nucleopolyhedrovirus SNF2 global transactivator homologue (Bm33) enhances viral pathogenicity in B. mori larvae. J Gen Virol 89: 3039-3046.
97. Katsuma S, Shimada T (2009) Bombyx mori nucleopolyhedrovirus ORF34 is required for efficient transcription of late and very late genes. Virology 392: 230-237.
98. Tian CH, Tang XD, Xu HJ, Ge JQ, Miao YG, et al. (2009) Bombyx mori nucleopolyhedrovirus ORF51 encodes a budded virus envelope associated protein. Virus Genes 38: 171-177.
99. Katsuma S, Noguchi Y, Zhou CL, Kobayashi M, Maeda S (1999) Characterization of the 25K FP gene of the baculovirus Bombyx mori nucleopolyhedrovirus: implications for post-mortem host degradation. J Gen Virol 80: 783-791.
100. Katsuma S, Nakanishi T, Shimada T (2009) Bombyx mori nucleopolyhedrovirus FP25K is essential for maintaining a steady-state level of v-cath expression throughout the infection. Virus Res 140: 155-160.
101. Nakanishi T, Shimada T, Katsuma S (2010) Characterization of a Bombyx mori nucleopolyhedrovirus mutant lacking both fp25K and p35. Virus genes 41: 144-148.
102. Tian CH, Zhao JF, Xu YP, Xue J, Zhang BQ, et al. (2009) Involvement of Bombyx mori nucleopolyhedrovirus ORF41 (Bm41) in BV production and ODV envelopment. Virology 387: 184-192.
103. Du MF, Yin XM, Guo ZJ, Zhu LJ (2006) Characterization of a late gene, ORF60 from Bombyx mori nucleopolyhedrovirus. J Biochem Mol Biol 39: 737-742.
104. Wang Y, Li Z, Long Q, Nong G, Wang X (2000) The identification of BmNPV gp64 envelope gene. Wei Sheng Wu Xue Bao 40: 38-43.
105. Iwanaga M, Kurihara M, Kobayashi M, Kang W (2002) Characterization of Bombyx mori nucleopolyhedrovirus orf68 gene that encodes a novel structural protein of budded virus. Virology 297: 39-47.
106. Lu M, Iatrou K (1996) The genes encoding the P39 and CG30 proteins of Bombyx mori nuclear polyhedrosis virus. J Gen Virol 77: 3135-3143.
107. Zhang MJ, Tian CH, Fan XY, Lou YH, Cheng RL, et al. (2012) Bombyx mori nucleopolyhedrovirus ORF54, a viral desmoplakin gene, is associated with infectivity of budded virions. Arch Virol.
108. Shen H, Chen K, Yao Q, Yu W, Pan Y, et al. (2009) Characterization of Bombyx mori nucleopolyhedrovirus orf74, a novel gene involved in virulence of virus. Virus genes 38: 487-494.
109. Liang G, Li G, Chen K, Yao Q, Chen H, et al. (2010) Bombyx mori nucleopolyhedrovirus ORF94, a novel late protein is identified to be a component of ODV structural protein. Curr Microbiol 61:190-196.
110. Wang F, Yang LR, Tang XD, Mo JC, Yang WJ, et al. (2006) The translational and transcriptional initiation sites of BmNPV lef-7 gene. Virus genes 33 : 351-357.
111. Wang F, Zhang CX, Shyam Kumar V, Wu XF (2005) Influences of chitinase gene deletion from BmNPV on the cell lysis and host liquefaction. Arch Virol 150: 981-990.
112. Hu NT, Lu YF, Hashimoto Y, Maeda S, Hou RF (1994) The p10 gene of natural isolates of Bombyx mori nuclear polyhedrosis virus encodes a truncated protein with an M(r) of 7700. J General Virol 75: 2085-2088.
113. Heldens JG, Liu Y, Zuidema D, Goldbach RW, Vlak JM (1997) Characterization of a putative Spodoptera exigua multicapsid nucleopolyhedrovirus helicase gene. J Gen Virol 78: 3101–3114.
114. Zhang CX, Hu C, Wu XF (1998) Studies on the nucleotide sequence, transcription and deletion analysis of the BmNPV protein kinase gene. Sheng Wu Hua Xue Yu Sheng Wu Wu Li Xue Bao (Shanghai) 30: 184-190.
115. Acharya A, Gopinathan K (2002) Transcriptional analysis and preliminary characterization of ORF Bm42 from Bombyx mori nucleopolyhedrovirus. Virology 299: 213-224.
116. Zhang MJ, Cheng RL, Lou YH, Ye WL, Fan XY, et al. (2012) Bombyx mori Nucleopolyhedrovirus ORF71 (Bm71) is not an essential gene but is important for viral replication. Virus Genes.
117. Shen H, Chen K, Yao Q, Zhou Y (2009) Characterization of the Bm61 of the Bombyx mori nucleopolyhedrovirus. Curr Microbiol 59: 65-70.
118. Ge JQ, Yang ZN, Tang XD, Xu HJ, Hong J, et al. (2008) Characterization of a nucleopolyhedrovirus with a deletion of the baculovirus core gene Bm67. J General Virol 89: 766-774.
119. Lu M, Swevers L, Iatrou K (1998) The p95 gene of Bombyx mori nuclear polyhedrosis virus: temporal expression and functional properties. J Virol 72: 4789-4797.
120. Ge JQ, Gao GH, Xu YP, Zhang CX (2011) Characterization of a late gene, ORF75 from Bombyx mori nucleopolyhedrovirus. Mol Biol Rep 38: 2141-2149.
121. Su WJ, Wu Y, Wu HL, Zhu SY, Wang WB (2008) Expression of Bombyx mori nucleopolyhedrovirus ORF76 in permissive and non-permissive cell lines by a novel Bac-to-Bac/BmNPV baculovirus expression system. Pol J Microbiol 57: 271-274.
122. Zhou Y, Yao Q, Shen H, Xia H, Lin F, et al. (2010) Characterization of Bombyx mori nucleopolyhedrovirus ORF109 that encodes a 25-kDa structural protein of the occlusion-derived virion. Current microbiology 61: 451-457.
123. Ge JQ, Zhao JF, Shao YM, Tian CH, Zhang CX (2009) Characterization of an early gene orf122 from Bombyx mori nucleopolyhedrovirus. Mol Biol Rep 36: 543-548.