| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
,
,
1 State Key Laboratory of Virology and Joint Laboratory of Invertebrate Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
2 Department of Virology, Wageningen University, Bennenhaven 11, 6709 PD Wageningen, The Netherlands
Correspondence
Zhihong Hu
huzh{at}wh.iov.cn
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
These authors contributed equally to this work. 
Present address: Department of Plant Science, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
). The baculovirus Helicoverpa armigera nucleopolyhedrovirus [HearNPV, also called Helicoverpa armigera single nucleocapsid polyhedrovirus (HaSNPV)] is a naturally occurring pathogen of cotton bollworm and was first isolated from diseased larvae in the Hubei province of China. It has been developed as a successful commercial pesticide for the control of cotton bollworm in China (Zhang, 1994).
To understand the genetic properties of HearNPV and further improve its effectiveness, the complete nucleotide sequence and genetic organization of HearNPV have been elucidated (Chen et al., 2001). The virus was modified genetically by deleting the ecdysteroid UDP-glucosyltransferase (egt) gene from its genome or by inserting an insect-selective scorpion toxin gene that has been shown to improve the viral insecticidal property (Chen et al., 2000; Sun et al., 2004). We are now focusing on studying other genes that may contribute to the insecticidal property of the virus. Per os infectivity factors are among the genes of interest, as they may serve as targets for future genetic engineering to enhance the oral infectivity of baculoviruses.
Recently, Se35 has been identified as encoding a per os infectivity factor (PIF-2) of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) (Pijlman et al., 2003). It has been known that the PIF-2 homologue (Ac22) in Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a structural component of the occlusion-derived virus (ODV) (Braunagel et al., 2003). Although the gene is conserved in baculoviruses, its functionality in viruses other than SeMNPV has not yet been elucidated. NPVs are designated single (S) or multiple (M) NPVs based on whether the ODV that initiates primary midgut infections contains single or multiple nucleocapsids. Washburn et al. (2003) revealed that, in orally inoculated larvae of Heliothis virescens, Helicoverpa zea single nucleopolyhedrovirus (HzSNPV) initiated primary infections quicker and in greater numbers than AcMNPV, implying differences between SNPVs and MNPVs in primary midgut infection.
In this report, we characterized open reading frame (ORF) 132 of HearNPV (Ha132), a homologue of Se35, and studied its function by deleting it from the virus. RT-PCR was performed to detect transcription and Western blot analysis was used to identify whether HA132 was a component of the virus structure. Recombinant viruses HearNPV
132 with deletion of Ha132 were constructed from wild-type (wt) HearNPV. The infectivity of budded virus (BV) and ODV was examined in vivo. The data presented in this manuscript ascertain that Ha132 is functional in HearNPV.
|
METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
; Altschul et al., 1997). HA132 was analysed by using software of the ExPASy server (Appel et al., 1994) to predict domains and motifs (Reinhardt & Hubbard, 1998). Multiple sequence alignments were performed with CLUSTAL_X (Thompson et al., 1997). Alignment editing was performed with GeneDoc software (Nicholas et al., 1997). The following motifs were searched as potential transcription start sites of Ha132: early promoter motifs TATAA, ATCA(G/T)T and CGTGC (Blissard & Rorhmann, 1990), baculovirus late transcription start site DTAAG (Blissard & Rorhmann, 1989) and downstream activating elements (A/T)CACNG (Friesen, 1997).
Insect cells and virus.
The Helicoverpa zea cell line HzAM1 (McIntosh & Ignoffo, 1983) was maintained at 28 °C in Grace's medium supplemented with 10 % fetal bovine serum. HearNPV strain G4, the genome of which has been sequenced entirely (GenBank accession no. AF271059
[GenBank]
; Chen et al., 2001), was deemed as wt and propagated in HzAM1 cells.
RNA isolation and RT-PCR.
HzAM1 cells were infected by wt HearNPV at an m.o.i. of 5 and total RNA was isolated with TRIzol (Gibco-BRL) at 0, 4, 8, 16, 24, 48 and 72 h post-infection (p.i.). RT-PCR was performed with 1 µg total RNA as template per time point. First-strand cDNA synthesis was performed by using AMV (avian myeloblastosis virus) reverse transcriptase (Promega) and a 15mer oligo-dT primer (Takara) according to the manufacturer's instructions. The cDNA mixtures were amplified with PCR by using the 132down primer (5'-GGGAAGCTTTTACGACGGCAAATCCCTACG-3') (the HindIII site is underlined and the italic sequence is complementary to nt 127750–127770 in the HearNPV G4 genome) and a primer internal to Ha132 (132in) containing an EcoRI site (underlined) (5'-GAATTCAAAATATGAGTCAGG-3') (the italic sequence corresponds to nt 127122–127137 in the HearNPV G4 genome).
Western blot analysis.
Monolayers of HzAM1 cells were infected by wt or recombinant HearNPV at an m.o.i. of 5. Infected cells were harvested at 0, 8, 16, 24, 36, 48 and 72 h p.i. BV and ODV were purified according to IJkel et al. (2001). Samples of total cell proteins, BV and ODV were separated by SDS-PAGE and transferred onto a Hybond-N membrane (Amersham Biosciences) for Western blotting. The primary antibody was a polyclonal, HA132-specific antiserum generated from rabbits immunized with purified HA132–glutathione S-transferase expressed in Escherichia coli. Alkaline phosphatase-conjugated goat anti-rabbit immunoglobulin (Gibco-BRL) was used as the secondary antibody. The signal was detected by using a BICP/NBT kit (Sino-America).
Deletion of Ha132 from HearNPV.
To construct an Ha132 deletion mutant, a transfer vector was constructed as follows: the upstream flanking sequence of Ha132 was amplified by PCR with the primers P1 containing a HindIII site (underlined), 5'-GGGAAGCTTTGTTGCGGGGTTACGAAGAGC-3' (the italic sequence corresponds to nt 125131–125151 in the HearNPV G4 genome) and P2 with a PstI site (underlined), 5'-CCCCTGCAGCAATAGCAGCCAGATCAACAT-3' (the italic sequence is complementary to nt 126599–126621 in the HearNPV G4 genome). The downstream flanking sequence of Ha132 was obtained by PCR with the primers P3 containing a KpnI site (underlined), 5'-GGGGGTACCTTCGTAGGGATTTGCCGTCGT-3' (the italic sequence corresponds to nt 127748–127768 in the HearNPV G4 genome) and P4 containing an EcoRI site (underlined): 5'-GGGGAATTCAAACGAAACATTGGATTGAACTT-3' (the italic sequence is complementary to nt 129309–129331 in the HearNPV G4 genome). The two PCR products were first cloned into pUC19 to generate p132LR. The lacZ gene was cloned into p132LR to generate p132LR-LacZ. Co-transfection of wt HearNPV and p132LR-LacZ in HzAM1 was performed as described by King & Possee (1992). Recombinant plaques were identified by blue colour and polyhedron formation. The deletion mutant HearNPV132 was purified by three rounds of plaque purification and identified by restriction-enzyme analysis.
In vivo infectivity assay.
The infectivity of BV was examined by injecting 10 µl supernatant with a titre of 105 TCID50 ml–1 into the third-instar larvae of H. armigera. Grace's medium was used as a negative control. For the oral-infectivity assay, polyhedra of wt HearNPV and HearNPV132 were purified from diseased larvae as described by Sun et al. (1998). The infectivity was assayed in neonate and third-instar H. armigera larvae by diet contamination, using 106 occlusion bodies (OBs) per larva. Infected larvae were reared individually in 24-well plates and monitored daily until all larvae had either pupated or died.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Appropriate searches of protein databases showed that the putative HA132 protein and homologues were highly conserved among all baculoviruses whose genomes have been sequenced so far. Alignment of HA132 homologues from SeMNPV (a group II MNPV), AcMNPV (a group I MNPV), Xestia c-nigrum granulovirus (XcGV), Neodiprion sertifer nucleopolyhedrovirus (NeseNPV; a hymenopteran NPV) and Culex nigripalpus nucleopolyhedrovirus (CuniNPV; a dipteran NPV) revealed that the predicted amino acid sequence of HA132 shared identity ranging from 66 % with SeMNPV ORF35 to 44 % with NeseNPV ORF55 (Fig. 1). As expected, HA132 is related most closely to ORF97 of HzSNPV with 100 % identity, as HzSNPV is a substrain of HearNPV (Chen et al., 2002). The similarity was distributed throughout the sequence and there were several regions where the sequences were more highly conserved. One striking phenomenon was that all 14 cysteine residues of HA132 were completely conserved among this group of proteins (Fig. 1). This indicates that the protein can form multiple disulfide bonds. The N terminus of HA132 was found to be highly hydrophobic, with 13 of the first 19 aa consisting of Leu, Ile and Val. This hydrophobic N-terminal region was conserved in all of the HA132 homologues (Fig. 1). This region was also predicted as a transmembrane domain by TMPRED (Hofmann et al., 1993).
|
). The data demonstrate that Ha132 is a late gene, as the replication of viral DNA in HzAM1 cells started at 7 h p.i. (W. T. Dai, personal communication). Sequence analysis of the upstream and downstream regions indicated that there was a baculovirus late promoter motif TTAAG 13 nt upstream of the start codon ATG. As it has been shown previously by primer extension that the p6.9 gene of HearNPV used ATAAG as its late promoter (Wang et al., 2001), this TAAG motif upstream of Ha132 is likely to be functional.
|
). The size of the 43 kDa protein is close to the predicted 44.5 kDa size of the putative Ha132 translational product, suggesting no major post-translational modifications.
|
), suggesting that HA132 is a structural component of ODV.
Construction of HearNPV132
HearNPV132, an Ha132 deletion mutant, was constructed as described in Methods. HindIII restriction-digestion profiles of HearNPV132 were compared with those of wt HearNPV (Fig. 4a). The data showed that the HindIII–D fragment (12.9 kb) from the wt HearNPV genome had disappeared, with a concomitant appearance of two fragments of 8.1 and 7.2 kb in the HearNPV132 profile. The digestion proved that the correct deletion mutant was produced.
|
132 (Fig. 4b). HA132 was detectable in wt HearNPV-infected cells at 72 h p.i., but was undetectable in HearNPV132-infected cells at different times post-infection. This result confirmed that Ha132 was deleted in HearNPV132.
HearNPV132 lost its oral infectivity, but retained its BV infectivity
To study the infectivity of BV and ODV of HearNPV132, three bioassay experiments were carried out (summarized in Table 1). Firstly, BVs of wt HearNPV and HearNPV132 were injected into the haemolymph of third-instar H. armigera larvae. Mortalities due to HearNPV132 and wt viruses were about 92 and 94 %, respectively (Table 1), whereas larvae injected with Grace's medium (negative control) survived (data not shown). OBs of wt HearNPV and HearNPV132 were fed to neonate or third-instar H. armigera larvae by diet contamination. The results showed that HearNPV132 was not infectious to H. armigera larvae by oral ingestion (Table 1). Therefore, the deletion of Ha132 resulted in the complete lost of per os infectivity, but did not affect BV infectivity.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
The HA132 antiserum identified a 43 kDa polypeptide from HearNPV-infected cell lysates (Fig. 3a). HA132 was first detected at 36 h and continued to be present at 96 h post-infection. This type of temporal expression is consistent with the finding that HA132 is an ODV structural protein. The N terminus of HA132 contains a hydrophobic region that is conserved in its homologues. It has been reported that some ODV proteins contain an N-terminal hydrophobic structure, such as OpMNPV P91 (Russell & Rohrmann, 1997), AcMNPV ODV-E66 and ODV-E25 (Hong et al., 1997). PIF-1 and SE35 also contain a similar structure (Kikhno et al., 2002; Pijlman et al., 2003). The hydrophobic domain of PIF-1, PIF-2, ODV-E66 and ODV-E25 is also rich in isoleucine, leucine and valine (Figs 1, 5; Hong et al., 1997; Kikhno et al., 2002; Pijlman et al., 2003). It has been reported that the N-terminal hydrophobic domains of ODV-E66 and ODV-E25 are uncleaved in the ODV envelope and they were sufficient to direct reporter proteins to the nuclear envelope, intranuclear microvesicles and the ODV envelope within baculovirus-infected cells (Hong et al., 1997). This sequence, called the sorting motif (SM), contains two features, a hydrophobic sequence and associated charged amino acids oriented on the cytoplasmic/nucleoplasmic face. It is proposed that, once inserted into the endoplasmic reticulum (ER), the SM protein interacts with the viral proteins FP25K and/or E26 during trafficking to the nuclear envelope (Braunagel et al., 1999, 2004; Rosas-Acosta et al., 2001). From the comparison (Fig. 5) of N-terminal sequences of PIF-1, PIF-2, PIF-3, ODV-E66 and ODV-E25, all of the PIFs possess the same characteristics of the SM as ODV-E25 and ODV-E66, suggesting that these PIFs are transported to the inner nuclear membrane and intranuclear vesicles by the same pathway as ODV-E25/ODV-E66. Whether the N-terminal hydrophobic domains of PIFs function in a manner similar to those of ODV-E66 and ODV-E25 needs to be investigated further.
|
; Faulkner et al., 1997). Deletion or disruption of the AcMNPV p74 gene results in the complete elimination of the per os infectivity of OBs, while virions purified from mutant OBs were infectious when injected into the haemocoel of Trichoplusia ni and Heliothis virescens larvae (Faulkner et al., 1997; Haas-Stapleton et al., 2004). Competing assays indicated that P74 might function as an ODV attachment protein that binds to a specific receptor on primary target cells within the midgut (Haas-Stapleton et al., 2004). Complementation assays revealed that the defect in oral infectivity of P74-null AcMNPV could be rescued by mixed infection of p74-null virus with wt AcMNPV (Zhou et al., 2005) or purified P74 protein (Yao et al., 2004). PIF-1 was first identified in Spodoptera littoralis nucleopolyhedrovirus (Kikhno et al., 2002). The virus with deletion of pif-1 (Spli7) was shown to be unable to infect S. littoralis larvae per os and the product of pif-1 is an ODV-specific structural protein (Kikhno et al., 2002). PIF-2 was first identified in SeMNPV, where deletion of pif-2 (Se35) resulted in the complete loss of per os infectivity to the host (Pijlman et al., 2003). It was speculated that pif-2 from SeMNPV would encode a structural protein of ODV (Pijlman et al., 2003). Recent research by Ohkawa et al. (2005) revealed that PIF-1 (Ac119), PIF-2 (Ac022) and PIF-3 (Ac115) are essential for oral infection of AcMNPV. The competing assay implicated that PIF-1 and PIF-2 might function as attachment proteins for ODV binding to primary target cells in the midgut, while PIF-3 mediates another unidentified, but critical, early event during primary infection (Ohkawa et al., 2005). In this study, we have ascertained that the homologue of pif-2 in HearNPV, Ha132, encodes a structural component associated with ODVs and that the deletion of Ha132 resulted in the complete elimination of per os infectivity of OBs. Therefore, like MNPVs, PIF-2 is also an essential factor for oral infection in SNPVs. It was speculated that P74, PIF-1 and PIF-2 might interact with each other (Kikhno et al., 2002; Pijlman et al., 2003) and with microvillar binding partners (Ohkawa et al., 2005). Further experiments would allow the determination of possible interactions of these ODV-specific structural proteins and how these proteins enable ODV to set up a successful infection in vivo.
|
ACKNOWLEDGEMENTS |
|---|
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Appel, R. D., Bairoch, A. & Hochstrasser, D. F. (1994). A new generation of information retrieval tools for biologists: the example of the ExPASy WWW server. Trends Biochem Sci 19, 258–260.[CrossRef][Medline]
Blissard, G. W. & Rohrmann, G. F. (1990). Baculovirus diversity and molecular biology. Ann Rev Entomol 35, 127–155.[CrossRef][Medline]
Blissard, G. W., Quant-Rusell, R. L., Rohrmann, G. F. & Beaudreau, G. S. (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.[CrossRef][Medline]
Braunagel, S. C., Burks, J. K., Rosas-Acosta, G., Harrison, R. L., Ma, H. & Summers, M. D. (1999). Mutations within the Autographa californica nucleopolyhedrovirus FP25K gene decrease the accumulation of ODV-E66 and alter its intranuclear transport. J Virol 73, 8559–8570.
Braunagel, S. C., Russell, W. K., Rosas-Acosta, G., Russell, D. H. & Summers, M. D. (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.
Braunagel, S. C., Williamson, S. T., Saksena, S., Zhong, Z., Russell, W. K., Russell, D. H. & Summers, M. D. (2004). Trafficking of ODV-E66 is mediated via a sorting motif and other viral proteins: facilitated trafficking to the inner nuclear membrane. Proc Natl Acad Sci U S A 101, 8372–8377.
Chen, X., Sun, X., Hu, Z. H., Li, M., O'Reilly, D. R., Zuidema, D. & Vlak, J. M. (2000). Genetic engineering of Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus as an improved pesticide. J Invertebr Pathol 76, 140–146.[CrossRef][Medline]
Chen, X., IJkel, W. F. J., Tarchini, R. & 8 other authors (2001). The sequence of the Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus genome. J Gen Virol 82, 241–257.
Chen, X., Zhang, W.-J., Wong, J. & 9 other authors (2002). Comparative analysis of the complete genome sequences of Helicoverpa zea and Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus. J Gen Virol 83, 673–684.
Faulkner, P., Kuzio, J., Williams, G. V. & Wilson, J. A. (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.[Abstract]
Frisen, P. D. (1997). Regulation of baculovirus early gene expression. In The Baculovirus, pp 141–170. Edited by L. K. Miller. New York: Plenum.
Haas-Stapleton, E. J., Washburn, J. O. & Volkman, L. E. (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.
Hofmann, K. & Stoffel, W. (1993). TMbase – a database of membrane spanning protein segments. Biol Chem Hoppe Seyler 374, 166.
Hong, T., Summers, M. D. & Braunagel, S. C. (1997). N-terminal sequences from Autographa californica nuclear polyhedrosis virus envelope proteins ODV-E66 and ODV-E25 are sufficient to direct reporter proteins to the nuclear envelope, intranuclear microvesicles and the envelope of occlusion derived virus. Proc Natl Acad Sci U S A 94, 4050–4055.
IJkel, W. F. J., Lebbink, R.-J., Op den Brouw, M. L., Goldbach, R. W., Vlak, J. M. & Zuidema, D. (2001). Identification of a novel occlusion derived virus-specific protein in Spodoptera exigua multicapsid nucleopolyhedrovirus. Virology 284, 170–181.[CrossRef][Medline]
Kikhno, I., Gutiérrez, S., Croizier, L., Croizier, G. & López Ferber, M. (2002). Characterization of pif, a gene required for the per os infectivity of Spodoptera littoralis nucleopolyhedrovirus. J Gen Virol 83, 3013–3022.
King, L. A. & Possee, R. D. (1992). Production and selection of recombinant virus. In The Baculovirus Expression System: a Laboratory Guide, pp. 127–140. Edited by L. A. King & R. D. Possee. London: Chapman & Hall.
Kuzio, J., Jaques, R. & Faulkner, P. (1989). Identification of p74, a gene essential for virulence of baculovirus occlusion bodies. Virology 173, 759–763.[CrossRef][Medline]
McIntosh, A. H. & Ignoffo, C. M. (1983). Characterization of five cell lines established from species of Heliothis. Appl Entomol Zool 18, 262–269.
Nicholas, K. B., Nicholas, H. B., Jr & Deerfield, D. W., II (1997). GeneDoc: analysis and visualization of genetic variation. EMBNEW News 4, 14.
Ohkawa, T., Washburn, J. O., Sitapara, R., Sid, E. & Volkman, L. E. (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.
Pearson, W. R. (1990). Rapid and sensitive sequence comparison with FASTP and FASTA. Methods Enzymol 183, 63–98.[Medline]
Pijlman, G. P., Pruijssers, A. J. P. & Vlak, J. M. (2003). Identification of pif-2, a third conserved baculovirus gene required for per os infection of insects. J Gen Virol 84, 2041–2049.
Reinhardt, A. & Hubbard, T. (1998). Using neural networks for prediction of the subcellular location of proteins. Nucleic Acids Res 26, 2230–2236.
Rosas-Acosta, G., Braunagel, S. C. & Summers, M. D. (2001). Effects of deletion and overexpression of the Autographa californica nuclear polyhedrosis virus FP25K gene on synthesis of two occlusion-derived virus envelope proteins and their transport into virus-induced intranuclear membranes. J Virol 75, 10829–10842.
Russell, R. L. Q. & Rohrmann, G. F. (1997). Characterization of P91, a protein associated with virions of an Orgyia pseudotsugata baculovirus. Virology 233, 210–223.[CrossRef][Medline]
Sun, X., Zhang, G., Zhang, Z., Hu, Z.-H., Vlak, J. M. & Arif, B. M. (1998). In vivo cloning of Helicoverpa armigera single nucleocapsid nuclear polyhedrosis virus genotypes. Virol Sin 13, 83–88.
Sun, X., Sun, X., van Der Werf, W., Vlak, J. M. & Hu, Z. (2004). Field inactivation of wild-type and genetically modified Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus in cotton. Biocontrol Sci Technol 14, 185–192.[CrossRef]
Thompson, J. D., Gibson, T. J., Plewniak, F., Jeanmougin, F. & Higgins, D. G. (1997). The CLUSTAL_X windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools. Nucleic Acids Res 25, 4876–4882.
Wang, H., Chen, X., Wang, H., Arif, B. M., Vlak, J. M. & Hu, Z. (2001). Nucleotide sequence and transcriptional analysis of a putative basic DNA-binding protein of Helicoverpa armigera nucleopolyhedrovirus. Virus Genes 22, 113–120.[CrossRef][Medline]
Washburn, J. O., Trudeau, D., Wong, J. F. & Volkman, L. E. (2003). Early pathogenesis of Autographa californica multiple nucleopolyhedrovirus and Helicoverpa zea single nucleopolyhedrovirus in Heliothis virescens: a comparison of the ‘M’ and ‘S’ strategies for establishing fatal infection. J Gen Virol 84, 343–351.
Wood, H. A. & Granados, R. R. (1991). Genetically engineered baculoviruses as agents for pest control. Annu Rev Microbiol 45, 69–87.[CrossRef][Medline]
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.[CrossRef][Medline]
Zhang, G. (1994). Research, development and application of Heliothis viral pesticide in China. Resour Environ Yangtze Valley 3, 1–6.
Zhou, W., Yao, L., Xu, H., Yan, F. & Qi, Y. (2005). The function of envelope protein P74 from Autographa californica multiple nucleopolyhedrovirus in primary infection to host. Virus Genes 30, 139–150.[CrossRef][Medline]
Received 22 December 2005;
accepted 2 May 2006.
This article has been cited by other articles:
|
|
 |
|
  M. Fang, Y. Nie, S. Harris, M. A. Erlandson, and D. A. Theilmann Autographa californica Multiple Nucleopolyhedrovirus Core Gene ac96 Encodes a Per Os Infectivity Factor (pif-4) J. Virol., December 1, 2009; 83(23): 12569 - 12578. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. de Jong, B. M. Arif, D. A. Theilmann, and P. J. Krell Autographa californica Multiple Nucleopolyhedrovirus me53 (ac140) Is a Nonessential Gene Required for Efficient Budded-Virus Production J. Virol., August 1, 2009; 83(15): 7440 - 7448. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Clavijo, T. Williams, O. Simon, D. Munoz, M. Cerutti, M. Lopez-Ferber, and P. Caballero Mixtures of Complete and pif1- and pif2-Deficient Genotypes Are Required for Increased Potency of an Insect Nucleopolyhedrovirus J. Virol., May 15, 2009; 83(10): 5127 - 5136. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Song, R. Wang, F. Deng, H. Wang, and Z. Hu Functional studies of per os infectivity factors of Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus J. Gen. Virol., September 1, 2008; 89(9): 2331 - 2338. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Deng, R. Wang, M. Fang, Y. Jiang, X. Xu, H. Wang, X. Chen, B. M. Arif, L. Guo, H. Wang, et al. Proteomics Analysis of Helicoverpa armigera Single Nucleocapsid Nucleopolyhedrovirus Identified Two New Occlusion-Derived Virus-Associated Proteins, HA44 and HA100 J. Virol., September 1, 2007; 81(17): 9377 - 9385. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| INT J SYST EVOL MICROBIOL | MICROBIOLOGY | J GEN VIROL |
| J MED MICROBIOL | ALL SGM JOURNALS | |
