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Pazmiño-Ibarra V, Herrero S, Sanjuan R. Spatially Segregated Transmission of Co-Occluded Baculoviruses Limits Virus-Virus Interactions Mediated by Cellular Coinfection during Primary Infection. Viruses 2022; 14:v14081697. [PMID: 36016318 PMCID: PMC9413315 DOI: 10.3390/v14081697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 07/26/2022] [Accepted: 07/27/2022] [Indexed: 11/16/2022] Open
Abstract
The occlusion bodies (OBs) of certain alphabaculoviruses are polyhedrin-rich structures that mediate the collective transmission of tens of viral particles to the same insect host. In addition, in multiple nucleopolyhedroviruses, occlusion-derived virions (ODVs) form nucleocapsid aggregates that are delivered to the same host cell. It has been suggested that, by favoring coinfection, this transmission mode promotes evolutionarily stable interactions between different baculovirus variants. To quantify the joint transmission of different variants, we obtained OBs from cells coinfected with two viral constructs, each encoding a different fluorescent reporter, and used them for inoculating Spodoptera exigua larvae. The microscopy analysis of midguts revealed that the two reporter genes were typically segregated into different infection foci, suggesting that ODVs show limited ability to promote the co-transmission of different virus variants to the same host cell. However, a polyhedrin-deficient mutant underwent inter-host transmission by exploiting the OBs of a fully functional virus and re-acquired the lost gene through recombination, demonstrating cellular coinfection. Our results suggest that viral spatial segregation during transmission and primary infection limits interactions between different baculovirus variants, but that these interactions still occur within the cells of infected insects later in infection.
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Affiliation(s)
- Verónica Pazmiño-Ibarra
- Institute for Integrative Systems Biology (I2SysBio), Consejo Superior de Investigaciones Científicas-Universitat de València, C/Catedrático Agustín Escardino 9, 46980 Paterna, Spain;
| | - Salvador Herrero
- Department of Genetics and Institute BIOTECMED, Universitat de València, 46100 Burjassot, Spain;
| | - Rafael Sanjuan
- Institute for Integrative Systems Biology (I2SysBio), Consejo Superior de Investigaciones Científicas-Universitat de València, C/Catedrático Agustín Escardino 9, 46980 Paterna, Spain;
- Correspondence:
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Boezen D, Ali G, Wang M, Wang X, van der Werf W, Vlak JM, Zwart MP. Empirical estimates of the mutation rate for an alphabaculovirus. PLoS Genet 2022; 18:e1009806. [PMID: 35666722 PMCID: PMC9203023 DOI: 10.1371/journal.pgen.1009806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 06/16/2022] [Accepted: 04/27/2022] [Indexed: 01/02/2023] Open
Abstract
Mutation rates are of key importance for understanding evolutionary processes and predicting their outcomes. Empirical mutation rate estimates are available for a number of RNA viruses, but few are available for DNA viruses, which tend to have larger genomes. Whilst some viruses have very high mutation rates, lower mutation rates are expected for viruses with large genomes to ensure genome integrity. Alphabaculoviruses are insect viruses with large genomes and often have high levels of polymorphism, suggesting high mutation rates despite evidence of proofreading activity by the replication machinery. Here, we report an empirical estimate of the mutation rate per base per strand copying (s/n/r) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV). To avoid biases due to selection, we analyzed mutations that occurred in a stable, non-functional genomic insert after five serial passages in Spodoptera exigua larvae. Our results highlight that viral demography and the stringency of mutation calling affect mutation rate estimates, and that using a population genetic simulation model to make inferences can mitigate the impact of these processes on estimates of mutation rate. We estimated a mutation rate of μ = 1×10−7 s/n/r when applying the most stringent criteria for mutation calling, and estimates of up to μ = 5×10−7 s/n/r when relaxing these criteria. The rates at which different classes of mutations accumulate provide good evidence for neutrality of mutations occurring within the inserted region. We therefore present a robust approach for mutation rate estimation for viruses with stable genomes, and strong evidence of a much lower alphabaculovirus mutation rate than supposed based on the high levels of polymorphism observed. Virus populations can evolve rapidly, driven by the large number of mutations that occur during virus replication. It is challenging to measure mutation rates because selection will affect which mutations are observed: beneficial mutations are overrepresented in virus populations, while deleterious mutations are selected against and therefore underrepresented. Few mutation rates have been estimated for viruses with large DNA genomes, and there are no estimates for any insect virus. Here, we estimate the mutation rate for an alphabaculovirus, a virus that infects caterpillars and has a large, 134 kilobase pair DNA genome. To ensure that selection did not bias our estimate of mutation rate, we studied which mutations occurred in a large artificial region inserted into the virus genome, where mutations did not affect viral fitness. We deep sequenced evolved virus populations, and compared the distribution of observed mutants to predictions from a simulation model to estimate mutation rate. We found evidence for a relatively low mutation rate, of one mutation in every 10 million bases replicated. This estimate is in line with expectations for a DNA virus with self-correcting replication machinery and a large genome.
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Affiliation(s)
- Dieke Boezen
- Department of Microbial Ecology, The Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands
| | - Ghulam Ali
- Laboratory of Virology, Wageningen University and Research, Wageningen, The Netherlands
| | - Manli Wang
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Xi Wang
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Wopke van der Werf
- Centre for Crop Systems Analysis, Wageningen University and Research, Wageningen, The Netherlands
| | - Just M. Vlak
- Laboratory of Virology, Wageningen University and Research, Wageningen, The Netherlands
| | - Mark P. Zwart
- Department of Microbial Ecology, The Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands
- * E-mail:
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Genomic diversity in a population of Spodoptera frugiperda nucleopolyhedrovirus. INFECTION GENETICS AND EVOLUTION 2021; 90:104749. [PMID: 33540087 DOI: 10.1016/j.meegid.2021.104749] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 01/10/2021] [Accepted: 01/29/2021] [Indexed: 01/05/2023]
Abstract
Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) represents a strong candidate to develop environmental-friendly pesticides against the fall armyworm (Spodoptera frugiperda), a widespread pest that poses a severe threat to different crops around the world. To date, SfMNPV genomic diversity of different isolates has been mainly studied by means of restriction pattern analyses and by sequencing of the egt region. Here, the genomic diversity present inside an isolate of SfMNPV was explored using high-throughput sequencing for the first time. We identified 704 intrahost single nucleotide variants, from which 184 are nonsynonymous mutations distributed among 82 different coding sequences. We detected several structural variants affecting SfMNPV genome, including two previously reported deletions inside the egt region. A comparative analysis between polymorphisms present in different SfMNPV isolates and our intraisolate diversity data suggests that coding regions with higher genetic diversity are associated with oral infectivity or unknown functions. In this context, through molecular evolution studies we provide evidence of diversifying selection acting on sf29, a putative collagenase which could contribute to the oral infectivity of SfMNPV. Overall, our results contribute to deepen our understanding of the coevolution between SfMNPV and the fall armyworm and will be useful to improve the applicability of this virus as a biological control agent.
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Mixtures of Insect-Pathogenic Viruses in a Single Virion: towards the Development of Custom-Designed Insecticides. Appl Environ Microbiol 2021; 87:AEM.02180-20. [PMID: 33187994 DOI: 10.1128/aem.02180-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 11/03/2020] [Indexed: 12/19/2022] Open
Abstract
Alphabaculoviruses (Baculoviridae) are pathogenic DNA viruses of Lepidoptera that have applications as the basis for biological insecticides and expression vectors in biotechnological processes. These viruses have a characteristic physical structure that facilitates the transmission of groups of genomes. We demonstrate that coinfection of a susceptible insect by two different alphabaculovirus species results in the production of mixed-virus occlusion bodies containing the parental viruses. This occurred between closely related and phylogenetically more distant alphabaculoviruses. Approximately half the virions present in proteinaceous viral occlusion bodies produced following coinfection of insects with a mixture of two alphabaculoviruses contained both viruses, indicating that the viruses coinfected and replicated in a single cell and were coenveloped within the same virion. This observation was confirmed by endpoint dilution assay. Moreover, both viruses persisted in the mixed-virus population by coinfection of insects during several rounds of insect-to-insect transmission. Coinfection by viruses that differed in genome size had unexpected results on the length of viral nucleocapsids, which differed from those of both parental viruses. These results have unique implications for the development of alphabaculoviruses as biological control agents of insect pests.IMPORTANCE Alphabaculoviruses are used as biological insecticides and expression vectors in biotechnology and medical applications. We demonstrate that in caterpillars infected with particular mixtures of viruses, the genomes of different baculovirus species can be enveloped together within individual virions and occluded within proteinaceous occlusion bodies. This results in the transmission of mixed-virus populations to the caterpillar stages of moth species. Once established, mixed-virus populations persist by coinfection of insect cells during several rounds of insect-to-insect transmission. Mixed-virus production technology opens the way to the development of custom-designed insecticides for control of different combinations of caterpillar pest species.
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Graillot B, Blachere-López C, Besse S, Siegwart M, López-Ferber M. Importance of the Host Phenotype on the Preservation of the Genetic Diversity in Codling Moth Granulovirus. Viruses 2019; 11:v11070621. [PMID: 31284495 PMCID: PMC6669585 DOI: 10.3390/v11070621] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 06/24/2019] [Accepted: 07/02/2019] [Indexed: 01/27/2023] Open
Abstract
To test the importance of the host genotype in maintaining virus genetic diversity, five experimental populations were constructed by mixing two Cydia pomonella granulovirus isolates, the Mexican isolate CpGV-M and the CpGV-R5, in ratios of 99% M + 1% R, 95% M + 5% R, 90% M + 10% R, 50% M + 50% R, and 10% M + 90% R. CpGV-M and CpGV-R5 differ in their ability to replicate in codling moth larvae carrying the type I resistance. This ability is associated with a genetic marker located in the virus pe38 gene. Six successive cycles of replication were carried out with each virus population on a fully-permissive codling moth colony (CpNPP), as well as on a host colony (RGV) that carries the type I resistance, and thus blocks CpGV-M replication. The infectivity of offspring viruses was tested on both hosts. Replication on the CpNPP leads to virus lineages preserving the pe38 markers characteristic of both isolates, while replication on the RGV colony drastically reduces the frequency of the CpGV-M pe38 marker. Virus progeny obtained after replication on CpNPP show consistently higher pathogenicity than that of progeny viruses obtained by replication on RGV, independently of the host used for testing.
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Affiliation(s)
- Benoit Graillot
- LGEI, Ecole des Mines d'Alès, Institut Mines-Telecom et Université de Montpellier Sud de France, 6 Avenue de Clavières, 30319 Alès, France
- Natural Plant Protection, Arysta LifeScience group, Avenue Léon Blum, 64000 Pau, France
| | - Christine Blachere-López
- LGEI, Ecole des Mines d'Alès, Institut Mines-Telecom et Université de Montpellier Sud de France, 6 Avenue de Clavières, 30319 Alès, France
- INRA, 6, Avenue de Clavières, 30319 Alès, France
| | - Samantha Besse
- Natural Plant Protection, Arysta LifeScience group, Avenue Léon Blum, 64000 Pau, France
| | | | - Miguel López-Ferber
- LGEI, Ecole des Mines d'Alès, Institut Mines-Telecom et Université de Montpellier Sud de France, 6 Avenue de Clavières, 30319 Alès, France.
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6
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Population bottlenecks in multicomponent viruses: first forays into the uncharted territory of genome-formula drift. Curr Opin Virol 2018; 33:184-190. [DOI: 10.1016/j.coviro.2018.09.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 08/28/2018] [Accepted: 09/07/2018] [Indexed: 11/23/2022]
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7
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Kitchin D, Bouwer G. Significant differences in the intra-host genetic diversity of Helicoverpa armigera nucleopolyhedrovirus dnapol after serial in vivo passages in the same insect population. Arch Virol 2017; 163:713-718. [PMID: 29181624 DOI: 10.1007/s00705-017-3621-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 09/27/2017] [Indexed: 11/29/2022]
Abstract
A denaturing gradient gel electrophoresis assay was used to assess the genetic diversity within a region of the DNA polymerase gene (dnapol) in Helicoverpa armigera nucleopolyhedrovirus (HearNPV) populations over serial in vivo passages. There was no evidence of movement towards a consensus dnapol variant composition in the different host larvae after multiple per os passages. The study showed that the HearNPV variant structure after in vivo passages in the same host population is not necessarily convergent, and that it may be reasonable to expect significant differences in intra-host HearNPV genetic diversity after inoculation of larvae with a genotypically-diverse HearNPV inoculum.
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Affiliation(s)
- Dale Kitchin
- School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, Wits, Johannesburg, 2050, South Africa
| | - Gustav Bouwer
- School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, Wits, Johannesburg, 2050, South Africa.
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Harrison RL, Rowley DL, Mowery JD, Bauchan GR, Burand JP. The Operophtera brumata Nucleopolyhedrovirus (OpbuNPV) Represents an Early, Divergent Lineage within Genus Alphabaculovirus. Viruses 2017; 9:v9100307. [PMID: 29065456 PMCID: PMC5691658 DOI: 10.3390/v9100307] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 10/12/2017] [Accepted: 10/17/2017] [Indexed: 12/16/2022] Open
Abstract
Operophtera brumata nucleopolyhedrovirus (OpbuNPV) infects the larvae of the winter moth, Operophtera brumata. As part of an effort to explore the pesticidal potential of OpbuNPV, an isolate of this virus from Massachusetts (USA)-OpbuNPV-MA-was characterized by electron microscopy of OpbuNPV occlusion bodies (OBs) and by sequencing of the viral genome. The OBs of OpbuNPV-MA consisted of irregular polyhedra and contained virions consisting of a single rod-shaped nucleocapsid within each envelope. Presumptive cypovirus OBs were also detected in sections of the OB preparation. The OpbuNPV-MA genome assembly yielded a circular contig of 119,054 bp and was found to contain little genetic variation, with most polymorphisms occurring at a frequency of < 6%. A total of 130 open reading frames (ORFs) were annotated, including the 38 core genes of Baculoviridae, along with five homologous repeat (hr) regions. The results of BLASTp and phylogenetic analysis with selected ORFs indicated that OpbuNPV-MA is not closely related to other alphabaculoviruses. Phylogenies based on concatenated core gene amino acid sequence alignments placed OpbuNPV-MA on a basal branch lying outside other alphabaculovirus clades. These results indicate that OpbuNPV-MA represents a divergent baculovirus lineage that appeared early during the diversification of genus Alphabaculovirus.
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Affiliation(s)
- Robert L Harrison
- Invasive Insect Biocontrol and Behavior Laboratory, Beltsville Agricultural Research Center, USDA Agricultural Research Service, Beltsville, MD 20705, USA.
| | - Daniel L Rowley
- Invasive Insect Biocontrol and Behavior Laboratory, Beltsville Agricultural Research Center, USDA Agricultural Research Service, Beltsville, MD 20705, USA.
| | - Joseph D Mowery
- Electron and Confocal Microscopy Unit, Beltsville Agricultural Research Center, USDA Agricultural Research Service, Beltsville, MD 20705, USA.
| | - Gary R Bauchan
- Electron and Confocal Microscopy Unit, Beltsville Agricultural Research Center, USDA Agricultural Research Service, Beltsville, MD 20705, USA.
| | - John P Burand
- Department of Microbiology, University of Massachusetts-Amherst, Amherst, MA 01003, USA.
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9
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Chan KN, Akepratumchai S, Mekvichitsaeng P, Poomputsa K. In vitro production of Spodoptera exigua multiple nucleopolyhedrovirus with enhanced insecticidal activity using a genotypically defined virus inoculum. J Biotechnol 2017; 259:19-25. [PMID: 28780162 DOI: 10.1016/j.jbiotec.2017.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Revised: 07/10/2017] [Accepted: 08/01/2017] [Indexed: 11/26/2022]
Abstract
Defective virus accumulations during baculovirus passages in insect cell culture are impediments to large scale baculovirus production. A genotypically defined virus inoculum comprises of stable genotypes was proposed for production of a Thailand isolated SeMNPV in Se-UCR1 insect cells. Targeted genotypes were from wild-type SeMNPV containing naturally mixed genotypes. Plaque assays, PCR screening and XbaI restriction analysis were employed for genotype purification, genotype selection and genome analysis, respectively. A selective marker was pif2 encoded per os infection factor which predominantly deleted, along with the adjacent pif1, in defective viruses. A purified, genetically stable pif2+ (and pif1+) genotype, namely SeThpif2+, was the first tryout. SeThpif2+ occlusion bodies (OBs) possessed insecticidal activity but at lower level than the wild-type. When the SeThpif2+ was co-infected with another purified, genetically stable pif1- (and pif2-) genotype, SeThpif2-, at ratio of 3:1, respectively, mixed genotypes OBs had 2.8 times greater insecticidal activity than the SeThpif2+ alone. Dilution of deleterious PIF1 of SeThpif2+ by the pif1 deletion genotypes, SeThpif2-, was the key for this enhanced activity. A promising approach was described for SeMNPV production in vitro using the virus inoculum whose genotypes compositions were designed to mimic virus interactions in the wild-type, to generate per oral infective baculovirus.
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Affiliation(s)
- Khin Nyein Chan
- Biotechnology Program, School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bang Khun Thian, Bangkok 10150, Thailand
| | - Saengchai Akepratumchai
- Biotechnology Program, School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bang Khun Thian, Bangkok 10150, Thailand
| | - Phenjun Mekvichitsaeng
- Pilot Plant Development and Training Institute, King Mongkut's University of Technology Thonburi, Bang Khun Thian, Bangkok 10150, Thailand
| | - Kanokwan Poomputsa
- Biotechnology Program, School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bang Khun Thian, Bangkok 10150, Thailand.
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Williams T, Virto C, Murillo R, Caballero P. Covert Infection of Insects by Baculoviruses. Front Microbiol 2017; 8:1337. [PMID: 28769903 PMCID: PMC5511839 DOI: 10.3389/fmicb.2017.01337] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 07/03/2017] [Indexed: 12/19/2022] Open
Abstract
Baculoviruses (Baculoviridae) are occluded DNA viruses that are lethal pathogens of the larval stages of some lepidopterans, mosquitoes, and sawflies (phytophagous Hymenoptera). These viruses have been developed as biological insecticides for control of insect pests and as expression vectors in biotechnological applications. Natural and laboratory populations frequently harbor covert infections by baculoviruses, often at a prevalence exceeding 50%. Covert infection can comprise either non-productive latency or sublethal infection involving low level production of virus progeny. Latency in cell culture systems involves the expression of a small subset of viral genes. In contrast, covert infection in lepidopterans is associated with differential infection of cell types, modulation of virus gene expression and avoidance of immune system clearance. The molecular basis for covert infection may reside in the regulation of host-virus interactions through the action of microRNAs (miRNA). Initial findings suggest that insect nudiviruses and vertebrate herpesviruses may provide useful analogous models for exploring the mechanisms of covert infection by baculoviruses. These pathogens adopt mixed-mode transmission strategies that depend on the relative fitness gains that accrue through vertical and horizontal transmission. This facilitates virus persistence when opportunities for horizontal transmission are limited and ensures virus dispersal in migratory host species. However, when host survival is threatened by environmental or physiological stressors, latent or persistent infections can be activated to produce lethal disease, followed by horizontal transmission. Covert infection has also been implicated in population level effects on host-pathogen dynamics due to the reduced reproductive capacity of infected females. We conclude that covert infections provide many opportunities to examine the complexity of insect-virus pathosystems at the organismal level and to explore the evolutionary and ecological relationships of these pathogens with major crop and forest pests.
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Affiliation(s)
| | - Cristina Virto
- Bioinsecticidas Microbianos, Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas, Universidad Pública de NavarraMutilva, Spain
- Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de NavarraPamplona, Spain
| | - Rosa Murillo
- Bioinsecticidas Microbianos, Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas, Universidad Pública de NavarraMutilva, Spain
- Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de NavarraPamplona, Spain
| | - Primitivo Caballero
- Bioinsecticidas Microbianos, Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas, Universidad Pública de NavarraMutilva, Spain
- Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de NavarraPamplona, Spain
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Graillot B, Bayle S, Blachere-Lopez C, Besse S, Siegwart M, Lopez-Ferber M. Biological Characteristics of Experimental Genotype Mixtures of Cydia Pomonella Granulovirus (CpGV): Ability to Control Susceptible and Resistant Pest Populations. Viruses 2016; 8:v8050147. [PMID: 27213431 PMCID: PMC4885102 DOI: 10.3390/v8050147] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 05/09/2016] [Accepted: 05/11/2016] [Indexed: 12/14/2022] Open
Abstract
The detection of resistance in codling moth (Cydia pomonella) populations against the Mexican isolate of its granulovirus (CpGV-M), raised questions on the sustainability of the use of this biological insecticide. In resistant host cells, CpGV-M is not able to complete its replication cycle because replication is blocked at an early step. Virus isolates able to overcome this resistance have been characterized-among them, the CpGV-R5 isolate. In mixed infections on resistant insects, both CpGV-M and CpGV-R5 viruses replicate, while CpGV-M alone does not induce mortality. Genetically heterogeneous virus populations, containing 50% of each CpGV-M and CpGV-R5 appear to control resistant host populations as well as CpGV-R5 alone at the same final concentration, even if the concentration of CpGV-R5 is only half in the former. The use of mixed genotype virus preparations instead of genotypically homogeneous populations may constitute a better approach than traditional methods for the development of baculovirus-based biological insecticides.
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Affiliation(s)
- Benoit Graillot
- LGEI, Ecole des Mines d'Alès, Institut Mines-Telecom et Université de Montpellier Sud de France, 6 Avenue de Clavières, 30319 Alès, France.
- Natural Plant Protection, Arysta LifeScience Group, Avenue Léon Blum, 64000 Pau, France.
| | - Sandrine Bayle
- LGEI, Ecole des Mines d'Alès, Institut Mines-Telecom et Université de Montpellier Sud de France, 6 Avenue de Clavières, 30319 Alès, France.
| | - Christine Blachere-Lopez
- LGEI, Ecole des Mines d'Alès, Institut Mines-Telecom et Université de Montpellier Sud de France, 6 Avenue de Clavières, 30319 Alès, France.
- INRA, 6, Avenue de Clavières, 30319 Alès, France.
| | - Samantha Besse
- Natural Plant Protection, Arysta LifeScience Group, Avenue Léon Blum, 64000 Pau, France.
| | | | - Miguel Lopez-Ferber
- LGEI, Ecole des Mines d'Alès, Institut Mines-Telecom et Université de Montpellier Sud de France, 6 Avenue de Clavières, 30319 Alès, France.
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12
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Haase S, Sciocco-Cap A, Romanowski V. Baculovirus insecticides in Latin America: historical overview, current status and future perspectives. Viruses 2015; 7:2230-67. [PMID: 25941826 PMCID: PMC4452904 DOI: 10.3390/v7052230] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 03/25/2015] [Accepted: 04/23/2015] [Indexed: 11/16/2022] Open
Abstract
Baculoviruses are known to regulate many insect populations in nature. Their host-specificity is very high, usually restricted to a single or a few closely related insect species. They are amongst the safest pesticides, with no or negligible effects on non-target organisms, including beneficial insects, vertebrates and plants. Baculovirus-based pesticides are compatible with integrated pest management strategies and the expansion of their application will significantly reduce the risks associated with the use of synthetic chemical insecticides. Several successful baculovirus-based pest control programs have taken place in Latin American countries. Sustainable agriculture (a trend promoted by state authorities in most Latin American countries) will benefit from the wider use of registered viral pesticides and new viral products that are in the process of registration and others in the applied research pipeline. The success of baculovirus-based control programs depends upon collaborative efforts among government and research institutions, growers associations, and private companies, which realize the importance of using strategies that protect human health and the environment at large. Initiatives to develop new regulations that promote the use of this type of ecological alternatives tailored to different local conditions and farming systems are underway.
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Affiliation(s)
- Santiago Haase
- Instituto de Biotecnología y Biología Molecular (IBBM), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CONICET, La Plata 1900, Argentina.
| | - Alicia Sciocco-Cap
- Instituto de Microbiología y Zoología Agrícola (IMYZA), Instituto Nacional de Tecnología Agropecuaria (INTA), Castelar 1712, Argentina.
| | - Víctor Romanowski
- Instituto de Biotecnología y Biología Molecular (IBBM), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CONICET, La Plata 1900, Argentina.
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A Novel Binary Mixture of Helicoverpa armigera Single Nucleopolyhedrovirus Genotypic Variants Has Improved Insecticidal Characteristics for Control of Cotton Bollworms. Appl Environ Microbiol 2015; 81:3984-93. [PMID: 25841011 DOI: 10.1128/aem.00339-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Accepted: 03/28/2015] [Indexed: 12/15/2022] Open
Abstract
The genotypic diversity of two Spanish isolates of Helicoverpa armigera single nucleopolyhedrovirus (HearSNPV) was evaluated with the aim of identifying mixtures of genotypes with improved insecticidal characteristics for control of the cotton bollworm. Two genotypic variants, HearSP1A and HearSP1B, were cloned in vitro from the most pathogenic wild-type isolate of the Iberian Peninsula, HearSNPV-SP1 (HearSP1-wt). Similarly, six genotypic variants (HearLB1 to -6) were obtained by endpoint dilution from larvae collected from cotton crops in southern Spain that died from virus disease during laboratory rearing. Variants differed significantly in their insecticidal properties, pathogenicity, speed of kill, and occlusion body (OB) production (OBs/larva). HearSP1B was ∼3-fold more pathogenic than HearSP1-wt and the other variants. HearLB1, HearLB2, HeaLB5, and HearLB6 were the fastest-killing variants. Moreover, although highly virulent, HearLB1, HearLB4, and HearLB5 produced more OBs/larva than did the other variants. The co-occluded HearSP1B:LB6 mixture at a 1:1 proportion was 1.7- to 2.8-fold more pathogenic than any single variant and other mixtures tested and also killed larvae as fast as the most virulent genotypes. Serial passage resulted in modified proportions of the component variants of the HearSP1B:LB6 co-occluded mixture, suggesting that transmissibility could be further improved by this process. We conclude that the improved insecticidal phenotype of the HearSP1B:LB6 co-occluded mixture underlines the utility of the genotypic variant dissection and reassociation approach for the development of effective virus-based insecticides.
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Ferreira BC, Melo FL, Souza ML, Moscardi F, Báo SN, Ribeiro BM. High genetic stability of peroral infection factors from Anticarsia gemmatalis MNPV over 20years of sampling. J Invertebr Pathol 2014; 118:66-70. [PMID: 24590109 DOI: 10.1016/j.jip.2014.02.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Revised: 02/15/2014] [Accepted: 02/19/2014] [Indexed: 10/25/2022]
Abstract
The Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) has been used as a biopesticide since the early 1980s in Brazil to control the major pest of soybean crops, the velvetbean caterpillar, Anticarsia gemmatalis. To monitor the genetic diversity over space and time we sequenced four pif genes (pif1, pif2, pif3 and pif4) from AgMNPV isolates collected from different regions of South America, as well as of seasonal isolates, sampled during a two-decade field experiment. Although all genes presented low levels of polymorphism, the pif-2 carries a slightly higher number of polymorphic sites. Overall, this study reveals that pif genes have remained stable after 20 years of repeated field application.
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Affiliation(s)
- Briana C Ferreira
- Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Campus Darcy Ribeiro, Universidade de Brasília (UnB), Asa Norte, 70910-900 Brasília, DF, Brazil; Embrapa Recursos Genéticos e Biotecnologia (Cenargen), Parque Estação Biológica, W5 Norte Final, 70770-917 Brasília, DF, Brazil
| | - Fernando L Melo
- Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Campus Darcy Ribeiro, Universidade de Brasília (UnB), Asa Norte, 70910-900 Brasília, DF, Brazil
| | - Marlinda L Souza
- Embrapa Recursos Genéticos e Biotecnologia (Cenargen), Parque Estação Biológica, W5 Norte Final, 70770-917 Brasília, DF, Brazil
| | - Flávio Moscardi
- Centro de Ciências Agrárias, Universidade Estadual de Londrina (UEL), 86051-990 Londrina, PR, Brazil
| | - Sônia N Báo
- Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Campus Darcy Ribeiro, Universidade de Brasília (UnB), Asa Norte, 70910-900 Brasília, DF, Brazil
| | - Bergmann M Ribeiro
- Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Campus Darcy Ribeiro, Universidade de Brasília (UnB), Asa Norte, 70910-900 Brasília, DF, Brazil.
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Bombyx mori nucleopolyhedrovirus ORF79 is a per os infectivity factor associated with the PIF complex. Virus Res 2014; 184:62-70. [PMID: 24583368 DOI: 10.1016/j.virusres.2014.02.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 02/13/2014] [Accepted: 02/13/2014] [Indexed: 11/23/2022]
Abstract
Bombyx mori nucleopolyhedrovirus (BmNPV) ORF79 (Bm79) encodes an occlusion-derived virus (ODV)-specific envelope protein, which is a homologue of the per os infectivity factor 4 (PIF4) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV). To investigate the role of ORF79 in the BmNPV life cycle, a Bm79 knockout virus (vBm(Bm79KO)) was constructed through homologous recombination in Escherichia coli. Viral DNA replication, budded virus (BV) production and polyhedra formation were unaffected by the absence of BM79. However, results of the larval bioassay demonstrated that the Bm79 deletion resulted in a complete loss of per os infection. Immunofluorescence analysis showed that BM79 localized at the innernuclear membrane of infected cells through its N-terminal sorting motif (SM). Further bimolecular fluorescence protein complementation and co-immunoprecipitation assays demonstrated the interaction of BM79 with PIF1, PIF2, PIF3 and ODV-E66. Thus, BM79 plays an important role in per os infection and is associated with the viral PIF complex of BmNPV.
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Simón O, Williams T, Cerutti M, Caballero P, López-Ferber M. Expression of a peroral infection factor determines pathogenicity and population structure in an insect virus. PLoS One 2013; 8:e78834. [PMID: 24223853 PMCID: PMC3818493 DOI: 10.1371/journal.pone.0078834] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 09/16/2013] [Indexed: 12/02/2022] Open
Abstract
A Nicaraguan isolate of Spodoptera frugiperda multiple nucleopolyhedrovirus is being studied as a possible biological insecticide. This virus exists as a mixture of complete and deletion genotypes; the latter depend on the former for the production of an essential per os transmission factor (pif1) in coinfected cells. We hypothesized that the virus population was structured to account for the prevalence of pif1 defector genotypes, so that increasing the abundance of pif1 produced by a cooperator genotype in infected cells would favor an increased prevalence of the defector genotype. We tested this hypothesis using recombinant viruses with pif1 expression reprogrammed at its native locus using two exogenous promoters (egt, p10) in the pif2/pif1 intergenic region. Reprogrammed viruses killed their hosts markedly faster than the wild-type and rescue viruses, possibly due to an earlier onset of systemic infection. Group success (transmission) depended on expression of pif1, but overexpression was prejudicial to group-specific transmissibility, both in terms of reduced pathogenicity and reduced production of virus progeny from each infected insect. The presence of pif1-overproducing genotypes in the population was predicted to favor a shift in the prevalence of defector genotypes lacking pif1-expressing capabilities, to compensate for the modification in pif1 availability at the population level. As a result, defectors increased the overall pathogenicity of the virus population by diluting pif1 produced by overexpressing genotypes. These results offer a new and unexpected perspective on cooperative behavior between viral genomes in response to the abundance of an essential public good that is detrimental in excess.
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Affiliation(s)
- Oihane Simón
- Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas-Gobierno de Navarra, Mutilva Baja, Navarra, Spain
| | | | - Martine Cerutti
- Laboratoire Baculovirus et Thérapie, Centre national de la recherche scientifique, Saint Christol-Les-Alés, France
| | - Primitivo Caballero
- Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas-Gobierno de Navarra, Mutilva Baja, Navarra, Spain
- Departamento de Producción Agraria, Universidad Pública de Navarra, Pamplona, Spain
| | - Miguel López-Ferber
- Laboratoire de Génie de l'Environnement Industriel, Ecole des mines d'Alès, Alès, France
- * E-mail:
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A Chrysodeixis chalcites single-nucleocapsid nucleopolyhedrovirus population from the Canary Islands is genotypically structured to maximize survival. Appl Environ Microbiol 2013; 79:7709-18. [PMID: 24096419 DOI: 10.1128/aem.02409-13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A Chrysodeixis chalcites single-nucleocapsid nucleopolyhedrovirus wild-type isolate from the Canary Islands, Spain, named ChchSNPV-TF1 (ChchTF1-wt), appears to have great potential as the basis for a biological insecticide for control of the pest. An improved understanding of the genotypic structure of this wild-type strain population should facilitate the selection of genotypes for inclusion in a bioinsecticidal product. Eight genetically distinct genotypes were cloned in vitro: ChchTF1-A to ChchTF1-H. Quantitative real-time PCR (qPCR) analysis confirmed that ChchTF1-A accounted for 36% of the genotypes in the wild-type population. In bioassays, ChchTF1-wt occlusion bodies (OBs) were significantly more pathogenic than any of the component single-genotype OBs, indicating that genotype interactions were likely responsible for the pathogenicity phenotype of wild-type OBs. However, the wild-type population was slower killing and produced higher OB yields than any of the single genotypes alone. These results strongly suggested that the ChchTF1-wt population is structured to maximize its transmission efficiency. Experimental OB mixtures and cooccluded genotype mixtures containing the most abundant and the rarest genotypes, at frequencies similar to those at which they were isolated, revealed a mutualistic interaction that restored the pathogenicity of OBs. In OB and cooccluded mixtures containing only the most abundant genotypes, ChchTF1-ABC, OB pathogenicity was even greater than that of wild-type OBs. The ChchTF1-ABC cooccluded mixture killed larvae 33 h faster than the wild-type population and remained genotypically and biologically stable throughout five successive passages in vivo. In conclusion, the ChchTF1-ABC mixture shows great potential as the active ingredient of a bioinsecticide to control C. chalcites in the Canary Islands.
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Baillie VL, Bouwer G. The effect of inoculum dose on the genetic diversity detected within Helicoverpa armigera nucleopolyhedrovirus populations. J Gen Virol 2013; 94:2524-2529. [PMID: 23929831 DOI: 10.1099/vir.0.052803-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Environmental and infection variables may affect the genetic diversity of baculovirus populations. In this study, Helicoverpa armigera nucleopolyhedrovirus (HearNPV) was used as a model system for studying the effects of a key infection variable, inoculum dose, on the genetic diversity within nucleopolyhedrovirus populations. Diversity and equitability indices were calculated from DNA polymerase-specific denaturing gradient gel electrophoresis profiles obtained from individual H. armigera neonate larvae inoculated with either an LD5 or LD95 of HearNPV. Although the genetic diversity detected in larvae treated with an LD95 was not statistically different from the diversity detected in the HearNPV inoculum samples, there was a statistically significant difference in the genetic diversity detected in the LD5-inoculated larvae compared with the genetic diversity detected in the HearNPV samples used for the inoculations. The study suggests that inoculum dose needs to be considered carefully in experiments that evaluate HearNPV genetic diversity or in studies where differences in genetic diversity may have phenotypic consequences.
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Affiliation(s)
- Vicky Lynne Baillie
- School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
| | - Gustav Bouwer
- School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
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Serrano A, Williams T, Simón O, López-Ferber M, Caballero P, Muñoz D. Analagous population structures for two alphabaculoviruses highlight a functional role for deletion mutants. Appl Environ Microbiol 2013; 79:1118-25. [PMID: 23204420 PMCID: PMC3568584 DOI: 10.1128/aem.03021-12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 11/29/2012] [Indexed: 12/13/2022] Open
Abstract
A natural Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) isolate from Florida shares a strikingly similar genotypic composition to that of a natural Spodoptera frugiperda MNPV (SfMNPV) isolate from Nicaragua. Both isolates comprise a high proportion of large-deletion genotypes that lack genes that are essential for viral replication or transmission. To determine the likely origins of such genotypically similar population structures, we performed genomic and functional analyses of these genotypes. The homology of nucleotides in the deleted regions was as high as 79%, similar to those of other colinear genomic regions, although some SfMNPV genes were not present in SeMNPV. In addition, no potential consensus sequences were shared between the deletion flanking sequences. These results indicate an evolutionary mechanism that independently generates and sustains deletion mutants within each virus population. Functional analyses using different proportions of complete and deletion genotypes were performed with the two viruses in mixtures of occlusion bodies (OBs) or co-occluded virions. Ratios greater than 3:1 of complete/deletion genotypes resulted in reduced pathogenicity (expressed as median lethal dose), but there were no significant changes in the speed of kill. In contrast, OB yields increased only in the 1:1 mixture. The three phenotypic traits analyzed provide a broader picture of the functional significance of the most extensively deleted SeMNPV genotype and contribute toward the elucidation of the role of such mutants in baculovirus populations.
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Affiliation(s)
- Amaya Serrano
- Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Cientifícas–Universidad Pública de Navarra (CSIC-UPNA), Mutilva, Spain
| | | | - Oihane Simón
- Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Cientifícas–Universidad Pública de Navarra (CSIC-UPNA), Mutilva, Spain
| | - Miguel López-Ferber
- Ecole Nationale Supérieure des Techniques Industrielles et des Mines d'Alès, Alès, France
| | - Primitivo Caballero
- Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Cientifícas–Universidad Pública de Navarra (CSIC-UPNA), Mutilva, Spain
- Departmento de Producción Agraria, Universidad Pública de Navarra, Pamplona, Spain
| | - Delia Muñoz
- Departmento de Producción Agraria, Universidad Pública de Navarra, Pamplona, Spain
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Clavijo G, Williams T, Muñoz D, Caballero P, López-Ferber M. Mixed genotype transmission bodies and virions contribute to the maintenance of diversity in an insect virus. Proc Biol Sci 2009; 277:943-51. [PMID: 19939845 DOI: 10.1098/rspb.2009.1838] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
An insect nucleopolyhedrovirus naturally survives as a mixture of at least nine genotypes. Infection by multiple genotypes results in the production of virus occlusion bodies (OBs) with greater pathogenicity than those of any genotype alone. We tested the hypothesis that each OB contains a genotypically diverse population of virions. Few insects died following inoculation with an experimental two-genotype mixture at a dose of one OB per insect, but a high proportion of multiple infections were observed (50%), which differed significantly from the frequencies predicted by a non-associated transmission model in which genotypes are segregated into distinct OBs. By contrast, insects that consumed multiple OBs experienced higher mortality and infection frequencies did not differ significantly from those of the non-associated model. Inoculation with genotypically complex wild-type OBs indicated that genotypes tend to be transmitted in association, rather than as independent entities, irrespective of dose. To examine the hypothesis that virions may themselves be genotypically heterogeneous, cell culture plaques derived from individual virions were analysed to reveal that one-third of virions was of mixed genotype, irrespective of the genotypic composition of the OBs. We conclude that co-occlusion of genotypically distinct virions in each OB is an adaptive mechanism that favours the maintenance of virus diversity during insect-to-insect transmission.
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Affiliation(s)
- Gabriel Clavijo
- Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de Navarra, Pamplona, Spain
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Clavijo G, Williams T, Muñoz D, López-Ferber M, Caballero P. Entry into midgut epithelial cells is a key step in the selection of genotypes in a nucleopolyhedrovirus. Virol Sin 2009. [DOI: 10.1007/s12250-009-3048-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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