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Baculovirus-induced tree-top disease: how extended is the role of egt as a gene for the extended phenotype?
Ros, V.I.D. ; Houte, S. van; Hemerik, L. ; Oers, M.M. van - \ 2015
Molecular Ecology 24 (2015)1. - ISSN 0962-1083 - p. 249 - 258.
spodoptera-exigua larvae - udp-glucosyl transferase - escherichia-coli - lepidopteran host - trichoplusia-ni - deletion - nucleopolyhedrovirus - behavior - insect - infection
Many parasites alter host behaviour to enhance their chance of transmission. Recently, the ecdysteroid UDP-glucosyl transferase (egt) gene from the baculovirus Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) was identified to induce tree-top disease in L. dispar larvae. Infected gypsy moth larvae died at elevated positions (hence the term tree-top disease), which is thought to promote dissemination of the virus to lower foliage. It is, however, unknown whether egt has a conserved role among baculoviruses in inducing tree-top disease. Here, we studied tree-top disease induced by the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) in two different host insects, Trichoplusia ni and Spodoptera exigua, and we investigated the role of the viral egt gene therein. AcMNPV induced tree-top disease in both T. ni and S. exigua larvae, although in S. exigua a moulting-dependent effect was seen. Those S. exigua larvae undergoing a larval moult during the infection process died at elevated positions, while larvae that did not moult after infection died at low positions. For both T. ni and S. exigua, infection with a mutant AcMNPV lacking egt did not change the position where the larvae died. We conclude that egt has no highly conserved role in inducing tree-top disease in lepidopteran larvae. The conclusion that egt is a ‘gene for an extended phenotype’ is therefore not generally applicable for all baculovirus–host interactions. We hypothesize that in some baculovirus–host systems (including LdMNPV in L. dispar), an effect of egt on tree-top disease can be observed through indirect effects of egt on moulting-related climbing behaviour.
Population-Related Variation in Plant Defense more Strongly Affects Survival of an Herbivore than Its Solitary Parasitoid Wasp
Harvey, J.A. ; Gols, R. - \ 2011
Journal of Chemical Ecology 37 (2011)10. - ISSN 0098-0331 - p. 1081 - 1090.
hyperparasitoid performance - lepidopteran herbivores - campoletis-sonorensis - specialist herbivore - mortality hypothesis - insect parasitoids - brassica-oleracea - trichoplusia-ni - pieris-rapae - host-plant
The performance of natural enemies, such as parasitoid wasps, is affected by differences in the quality of the host’s diet, frequently mediated by species or population-related differences in plant allelochemistry. Here, we compared survival, development time, and body mass in a generalist herbivore, the cabbage moth, Mamestra brassicae, and its solitary endoparasitoid, Microplitis mediator, when reared on two cultivated (CYR and STH) and three wild (KIM, OH, and WIN) populations of cabbage, Brassica oleracea. Plants either were undamaged or induced by feeding of larvae of the cabbage butterfly, Pieris rapae. Development and biomass of M. brassicae and Mi. mediator were similar on both cultivated and one wild cabbage population (KIM), intermediate on the OH population, and significantly lower on the WIN population. Moreover, development was prolonged and biomass was reduced on herbivore-induced plants. However, only the survival of parasitized hosts (and not that of healthy larvae) was affected by induction. Analysis of glucosinolates in leaves of the cabbages revealed higher levels in the wild populations than cultivars, with the highest concentrations in WIN plants. Multivariate statistics revealed a negative correlation between insect performance and total levels of glucosinolates (GS) and levels of 3-butenyl GS. However, GS chemistry could not explain the reduced performance on induced plants since only indole GS concentrations increased in response to herbivory, which did not affect insect performance based on multivariate statistics. This result suggests that, in addition to aliphatic GS, other non-GS chemicals are responsible for the decline in insect performance, and that these chemicals affect the parasitoid more strongly than the host. Remarkably, when developing on WIN plants, the survival of Mi. mediator to adult eclosion was much higher than in its host, M. brassicae. This may be due to the fact that hosts parasitized by Mi. mediator pass through fewer instars, and host growth is arrested when they are only a fraction of the size of healthy caterpillars. Certain aspects of the biology and life-history of the host and parasitoid may determine their response to chemical challenges imposed by the food plant.
In Situ cleavage of Baculovirus occlusion-derived virus receptor binding protein P74 in the peroral infectivity complex
Peng, K. ; Lent, J.W.M. van; Vlak, J.M. ; Hu, Zhihong ; Oers, M.M. van - \ 2011
Journal of Virology 85 (2011)20. - ISSN 0022-538X - p. 10710 - 10718.
nuclear-polyhedrosis-virus - heliothis-virescens larvae - per-os infectivity - autographa-californica - alkaline protease - proteolytic cleavage - envelope protein - granulosis-virus - trichoplusia-ni - viral entry
Proteolytic processing of viral membrane proteins is common among enveloped viruses to facilitate virus entry. The Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) occlusion derived virus (ODV) protein P74 is part of a complex of essential peroral infectivity factors (PIFs). Here we report that P74 is efficiently cleaved into two fragments of about equal size by an OB endogenous alkaline protease during ODV release when AcMNPV occlusion bodies (OB) are derived from larvae. The cleavage is specific for P74 since the other known peroral infectivity factors in the same complex (PIF1, PIF2 and PIF3) were not cleaved under the same conditions. P74 cleavage was not observed in OBs produced in three different insect cell lines suggesting a larval host origin of the responsible protease. P74 in OBs produced in larvae of two different host species was cleaved into fragments with the same apparent molecular mass indicating that the virus incorporates a similar alkaline protease from different hosts. Co-immunoprecipitation analysis revealed that the two P74 subunit fragments remain associated with the recently discovered PIF complex. We propose that under in vivo ODV infection conditions P74 undergoes two sequential cleavage events, the first one being performed by an ODV-associated host alkaline protease and the second carried out by trypsin in the host midgut
Constitutive Activation of the Midgut Response to Bacillus thuringiensis in Bt-Resistant Spodoptera exigua
Hernandez-Martinez, P. ; Navarro-Cerrillo, G. ; Caccia, S. ; Maagd, R.A. de; Moar, W.J. ; Ferre, J. ; Escriche, B. ; Herrero, S. - \ 2010
PLoS One 5 (2010)9. - ISSN 1932-6203
mediated insect resistance - stem-cell proliferation - heliothis-virescens - manduca-sexta - bacterial-infection - posterior midgut - crystal proteins - aminopeptidase n - kinase pathways - trichoplusia-ni
Bacillus thuringiensis is the most effective microbial control agent for controlling numerous species from different insect orders. The main threat for the long term use of B. thuringiensis in pest control is the ability of insects to develop resistance. Thus, the identification of insect genes involved in conferring resistance is of paramount importance. A colony of Spodoptera exigua (Lepidoptera: Noctuidae) was selected for 15 years in the laboratory for resistance to Xentari (TM), a B. thuringiensis-based insecticide, reaching a final resistance level of greater than 1,000-fold. Around 600 midgut ESTs were analyzed by DNA-macroarray in order to find differences in midgut gene expression between susceptible and resistant insects. Among the differentially expressed genes, repat and arylphorin were identified and their increased expression was correlated with B. thuringiensis resistance. We also found overlap among genes that were constitutively over-expressed in resistant insects with genes that were up-regulated in susceptible insects after exposure to Xentari (TM), suggesting a permanent activation of the response to Xentari (TM) in resistant insects. Increased aminopeptidase activity in the lumen of resistant insects in the absence of exposure to Xentari (TM) corroborated the hypothesis of permanent activation of response genes. Increase in midgut proliferation has been proposed as a mechanism of response to pathogens in the adult from several insect species. Analysis of S. exigua larvae revealed that midgut proliferation was neither increased in resistant insects nor induced by exposure of susceptible larvae to Xentari (TM), suggesting that mechanisms other than midgut proliferation are involved in the response to B. thuringiensis by S. exigua larvae.
Transmission of wild-type and recombinant HaSNPV among larvae of Helicoverpa armigera (Lepidoptera: Noctuidae) on cotton.
Georgievska, L. ; Vries, R.S.M. ; Gao, P. ; Sun, X. ; Cory, J.S. ; Vlak, J.M. ; Werf, W. van der - \ 2010
Environmental Entomology 39 (2010)2. - ISSN 0046-225X - p. 459 - 467.
single-nucleocapsid nucleopolyhedrovirus - nuclear-polyhedrosis-virus - heliothis-armigera - trichoplusia-ni - baculovirus - field - infections - insecticides - persistence - pesticide
Horizontal transmission of insect viruses is a key factor in their cycling in agro-ecosystems. Here we study the transmission of the baculovirus HaSNPV among larvae of Helicoverpa armigera (Hübner) in cotton. Transmission of three HaSNPV genotypes was studied from larvae infected with a single virus genotype and from larvae infected with two different genotypes. Genotypes included a wild-type virus, an ecdysteroid UDP-glucosyltransferase (egt) deletion mutant (HaSNPV-LM2) with slightly enhanced speed of kill, and an egt-negative genotype that expresses a neurotoxin gene derived from the scorpion Androctonus australis Hector (HaSNPV-4A). The latter genotype has a substantially increased speed of kill. In three field experiments, the wild-type and egt deletion virus variants and a mixture of the two had similar rates of transmission. Transmission increased with density of infector insects and decreased with time lapsed since the inoculation of the infector larvae. Transmission of the neurotoxin expressing virus was lower than that of the other two genotypes in a glasshouse experiment. The studied genotypes of HaSNPV have significant differences in time to kill and virus yield, but we found no significant differences in rates of virus transmission at the crop level in the case of the egt deletion variant HaSNPV-LM2. Transmission of the transgenic virus genotype HaSNPV-4A was significantly reduced. Overall, differences in transmission between virus genotypes were subtler, and more difficult to detect with statistical significance, than effects of other factors, such as density of infectors and time delay between release of infectors and recipient caterpillars on the plant.
Dose dependency of time to death in single and mixed infections with a wildtype and egt deletion strain of Helicoverpa armigera nucleopolyhedrovirus
Georgievska, L. ; Hoover, K. ; Werf, W. van der; Muñoz, D. ; Cabalerro, P. ; Cory, J.S. ; Vlak, J.M. - \ 2010
Journal of Invertebrate Pathology 104 (2010)1. - ISSN 0022-2011 - p. 44 - 50.
autographa-californica - heliothis-virescens - trichoplusia-ni - nucleocapsid nucleopolyhedrovirus - baculovirus insecticide - recombinant baculovirus - inclusion-bodies - genotypes - host - gene
Recombinant insect nucleopolyhedroviruses lacking the egt gene generally kill their hosts faster than wild-type strains, but the response of insects to mixtures of virus genotypes is less well known. Here, we compared the survival time, lethal dose and occlusion body yield in third instar larvae of Helicoverpa armigera (Hübner) after challenge with wild-type H. armigera SNPV (HaSNPV-wt), a strain with a deletion of the egt gene, HaSNPV-LM2, and a 1:1 mixture of these two virus strains. A range of doses was used to determine whether the total number of OBs influenced the response to challenge with a mixture of virus strains versus single strains. At high virus doses, HaSNPV-LM2 killed H. armigera larvae significantly faster (ca. 20 h) than HaSNPV-wt, but at low doses, there was no significant difference in survival time between the viruses. The survival time after challenge with mixed virus inoculum was significantly different from and intermediate between that of the single viruses at high doses, and not different from that of the single viruses at low doses. No differences in lethal dose were found between single and mixed infections or between virus genotypes. The number of occlusion bodies produced per larva increased with time to death and decreased with virus dose, but no significant differences among virus types were found.
An experimental test of the independent action hypothesis in virus-insect pathosystems
Zwart, M.P. ; Hemerik, L. ; Cory, J.S. ; Visser, J.A.G.M. de; Bianchi, F.J.J.A. ; Oers, M.M. van; Vlak, J.M. ; Hoekstra, R.F. ; Werf, W. van der - \ 2009
Proceedings of the Royal Society. B: Biological Sciences 276 (2009)1665. - ISSN 0962-8452 - p. 2233 - 2242.
developmental resistance - mamestra-brassicae - spodoptera-exigua - trichoplusia-ni - rna virus - baculovirus - infection - transmission - virulence - genotypes
The `independent action hypothesis¿ (IAH) states that each pathogen individual has a non-zero probability of causing host death and that pathogen individuals act independently. IAH has not been rigorously tested. In this paper, we (i) develop a probabilistic framework for testing IAH and (ii) demonstrate that, in two out of the six virus¿insect pathosystems tested, IAH is supported by the data. We first show that IAH inextricably links host survivorship to the number of infecting pathogen individuals, and develop a model to predict the frequency of single- and dual-genotype infections when a host is challenged with a mixture of two genotypes. Model predictions were tested using genetically marked, near-identical baculovirus genotypes, and insect larvae from three host species differing in susceptibility. Observations in early-instar larvae of two susceptible host species support IAH, but observations in late-instar larvae of susceptible host species and larvae of a less susceptible host species were not in agreement with IAH. Hence the model is experimentally supported only in pathosystems in which the host is highly susceptible. We provide, to our knowledge, the first qualitative experimental evidence that, in such pathosystems, the action of a single virion is sufficient to cause disease
Mixed infections and the competitive fitness of faster-acting genetically modified viruses
Zwart, M.P. ; Werf, W. van der; Oers, M.M. van; Hemerik, L. ; Lent, J.W.M. van; Visser, J.A.G.M. de; Vlak, J.M. ; Cory, J.S. - \ 2009
Evolutionary Applications 2 (2009)2. - ISSN 1752-4563 - p. 209 - 221.
nuclear polyhedrosis-virus - baculovirus insecticide - trichoplusia-ni - recombinant - persistence - evolution - field - nucleopolyhedrovirus - population - host
Faster-acting recombinant baculoviruses have shown potential for improved suppression of insect pests, but their ecological impact on target and nontarget hosts and naturally occurring pathogens needs to be assessed. Previous studies have focused on the fitness of recombinants at the between-hosts level. However, the population structure of the transmission stages will also be decided by within-host selection. Here we have experimentally quantified the within-host competitive fitness of a fast-acting recombinant Autographa californica multicapsid nucleopolyhedrovirus missing the endogenous egt gene (vEGTDEL), by means of direct competition in single- and serial-passage experiments with its parental virus. Quantitative real-time PCR was employed to determine the ratio of these two viruses in passaged mixtures. We found that vEGTDEL had reduced within-host fitness: per passage the ratio of wild type to vEGTDEL was on average enhanced by a factor of 1.53 (single passage) and 1.68 (serial passage). There is also frequency-dependence: the higher the frequency of vEGTDEL, the stronger the selection against it is. Additionally, the virus ratio is a predictor of time to host death and virus yield. Our results show that egt is important to within-host fitness and allow for a more complete assessment of the ecological impact of recombinant baculovirus release.
Low multiplicity of infection in vivo results in purifying selection against baculovirus deletion mutants
Zwart, M.P. ; Erro, E. ; Oers, M.M. van; Visser, J.A.G.M. de; Vlak, J.M. - \ 2008
Journal of General Virology 89 (2008). - ISSN 0022-1317 - p. 1220 - 1224.
trichoplusia-ni - insect cells - recombinant - protein - nucleopolyhedrovirus - lepidoptera - noctuidae - genotypes - system
The in vivo fate of Autographa californica multiple nucleopolyhedrovirus deletion mutants originating from serial passage in cell culture was investigated by passaging a population enriched in these mutants in insect larvae. The infectivity of polyhedra and occlusion-derived virion content per polyhedron were restored within two passages in vivo. The frequency of occurrence of deletion mutants was determined by real-time PCR. The frequency of the non-homologous region origin (non-HR ori) of DNA replication was reduced to wild-type levels within two passages. The frequency of the polyhedrin gene did not increase and remained below wild-type levels. A low m.o.i. during the initial infection in insect larvae, causing strong purifying selection for autonomously replicating viruses, could explain these observations. The same virus population used in vivo was also passaged once at a different m.o.i. in cell culture. A similar effect (i.e. lower non-HR ori frequency) was observed at low m.o.i. only, indicating that m.o.i. was the key selective condition
Development of a quantitative real-time PCR for determination of genotype frequencies for studies in baculovirus population biology
Zwart, M.P. ; Oers, M.M. van; Cory, J.S. ; Lent, J.W.M. van; Werf, W. van der; Vlak, J.M. - \ 2008
Journal of Virological Methods 148 (2008)1-2. - ISSN 0166-0934 - p. 146 - 154.
nuclear polyhedrosis-virus - polymerase-chain-reaction - trichoplusia-ni - sybr-green - mosaic-virus - wild-type - rt-pcr - nucleopolyhedrovirus - mutants - larvae
Two bacmid-derived Autographa californica Multiple-capsid Nucleopolyhedrovirus genotypes ¿ that differ only in a short tag sequence for differential PCR recognition ¿ were generated. By electron microscopy, these genotypes were found to have identical polyhedra morphology. Mixtures of quantified polyhedra were made and used to validate a SYBR Green I-based quantitative real-time PCR (qPCR) to determine genotype frequencies in mixed genotype populations. The PCR could accurately quantify genotype ratios over a range of 8 orders of magnitude. Only a small correction of the genotype ratio was necessary to obtain a valid result. Low levels of aspecific background (a fluorescent signal when the template corresponding with the primer set used is not present) were measured in these validation experiments and in a typical laboratory setup. A small fitness difference between the genotypes generated was observed in a median lethal dose bioassay. The bacmid-derived virus genotypes generated and the qPCR assays are valuable tools for studying the population biology of baculoviruses.
Development of an insect herbivore and its pupal parasitoid reflect differences in direct plant defense
Harvey, J.A. ; Gols, R. ; Wagenaar, R. ; Bezemer, T.M. - \ 2007
Journal of Chemical Ecology 33 (2007)8. - ISSN 0098-0331 - p. 1556 - 1569.
4 trophic levels - host-plant - specialist herbivore - phytophagous insects - plutella-xylostella - brassica-oleracea - wild populations - trichoplusia-ni - manduca-sexta - pieris-rapae
In nature, plants defend themselves by production of allelochemicals that are toxic to herbivores. There may be considerable genetic variation in the expression of chemical defenses because of various selection pressures. In this study, we examined the development of the small cabbage butterfly, Pieris rapae, and its gregarious pupal ectoparasitoid, Pteromalus puparum, when reared on three wild populations (Kimmeridge, Old Harry, Winspit) of cabbage, Brassica oleracea, and a Brussels sprout cultivar. Wild plant populations were obtained from seeds of plants that grow naturally along the south coast of Dorset, England. Significant differences in concentrations of allelochemicals (glucosinolates) were found in leaves of plants damaged by P. rapae. Total glucosinolate concentrations in Winspit plants, the population with the highest total glucosinolate concentration, were approximately four times higher than in the cultivar, the strain with the lowest total glucosinolate concentration. Pupal mass of P. rapae and adult body mass of Pt. puparum were highest when reared on the cultivar and lowest when developing on Kimmeridge plants, the wild strain with the lowest total glucosinolate concentration. Development of male parasitoids was also more negatively affected than female parasitoids. Our results reveal that plant quality, at least for the development of 'adapted' oligophagous herbivores, such as P. rapae, is not based on total glucosinolate content. The only glucosinolate compound that corresponded with the performance of P. rapae was the indole glucosinolate, neoglucobrassicin. Our results show that performance of ectoparasitoids may closely reflect constraints on the development of the host.
Stabilized baculovirus vector expressing a heterologous gene and GP64 from a single bicistronic transcript
Pijlman, G.P. ; Roode, E.C. ; Fan, X.X. ; Roberts, L.O. ; Belsham, G.J. ; Vlak, J.M. ; Oers, M.M. van - \ 2006
Journal of Biotechnology 123 (2006)1. - ISSN 0168-1656 - p. 13 - 21.
nuclear polyhedrosis-virus - ribosome entry site - non-hr origin - autographa-californica - insect cells - spodoptera-frugiperda - dna-replication - recombinant baculovirus - trichoplusia-ni - foreign genes
The efficient scale-up of recombinant protein production in insect-cell bioreactors using baculovirus expression vectors is hampered by reductions in yield with increasing viral passage, the so-called passage effect. This phenomenon is characterized by the generation and subsequent accumulation of defective interfering baculoviruses (DIs), which interfere with the replication of genomically intact virus. A novel baculovirus expression vector is presented equipped with a bicistronic expression cassette that allows the simultaneous expression of the recombinant gene (GFP, first cistron) and an essential baculovirus gene (GP64, second cistron) from a single messenger RNA (mRNA). The translation of GP64 is mediated by an internal ribosome entry site (IRES) element from Rhopalosiphum padi virus (RhPV) while the native GP64 gene is deleted. In this way, a dominant selection pressure is placed on the entire bicistronic mRNA and hence on the maintenance of the foreign gene. The bicistronic expression vector was superior to the control baculovirus vector in that GFP expression remained at much higher levels upon continued virus passage. The versatility of this stabilized vector was demonstrated by its ability to propagate in a number of cell lines including Sf21, Sf9 and High Five cells. This novel baculovirus vector is especially valuable for large-scale recombinant protein production in insect-cell bioreactors where the number of viral passages is high.
Persistence and coexistence of engineered baculoviruses
Bonsall, M.B. ; O'Reilly, D.R. ; Cory, J.S. ; Hails, R.S. - \ 2005
Theoretical Population Biology 67 (2005)4. - ISSN 0040-5809 - p. 217 - 230.
insect-pathogen interactions - nuclear polyhedrosis-virus - udp-glucosyl transferase - recombinant baculovirus - trichoplusia-ni - egt gene - population-dynamics - spodoptera-exigua - gypsy-moth - host
Baculoviruses, and in particular, the nucleopolyhedroviruses infect a wide range of arthropod hosts and have the potential to be used as biopesticides. However, one of the major drawbacks with these pathogens as biocontrol agents is that they have a slow response time. Alterations to the speed of kill and pathogen life history characteristics can influence the competitive outcome and persistence between wildtype and modified strains. Here, we explore, theoretically, how life-history modifications of pathogens can affect the epidemiology and ecology of strain coexistence. In particular, we show how under simple mass action disease transmission, life-history difference between strains are insufficient to allow coexistence. Additional heterogeneities in transmission are shown to be necessary to facilitate coexistence of wildtype and modified pathogen strains. We also illustrate how the patterns of infectivity of wildtype and modified strains can also affect long-term coexistence, and argue that appropriate assessment of genetic modifications must be presented in terms of relevant ecological theory.
Horizontal and vertical transmission of wild-type and recombinant Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus
Zhou, M. ; Sun, X. ; Sun, X.C. ; Vlak, J.M. ; Hu, Z.H. ; Werf, W. van der - \ 2005
Journal of Invertebrate Pathology 89 (2005)2. - ISSN 0022-2011 - p. 165 - 175.
nuclear polyhedrosis-virus - baculovirus insecticide - trichoplusia-ni - cotton - larvae - field - lepidoptera - inactivation - evolution - ecology
Transmission plays a central role in the ecology of baculoviruses and the population dynamics of their hosts. Here, we report on the horizontal and vertical transmission dynamics of wild-type Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (HaSNPV-WT) and a genetically modified variant (HaSNPV-AaIT) with enhanced speed of action through the expression of an insect-selective scorpion toxin (AaIT). In caged field plots, horizontal transmission of both HaSNPV variants was greatest when inoculated 3rd instar larvae were used as infectors, transmission was intermediate with 2nd instar infectors and lowest with 1st instar infectors. Transmission was greater at a higher density of infectors (1 per plant) than at a lower density (1 per 4 plants); however, the transmission coefficient (number of new infections per initial infector) was lower at the higher density of infectors than at the lower density. HaSNPV-AaIT exhibited a significantly lower rate of transmission than HaSNPV-WT in the field cages. This was also the case in open field experiments. In the laboratory, the vertical transmission of HaSNPV-AaIT from infected females to offspring of 16.7 ± 2.1% was significantly lower than that of HaSNPV-WT (30.9 ± 2.9%). Likewise, in the field, vertical transmission of HaSNPV-AaIT (8.4 ± 1.1%) was significantly lower than that of HaSNPV-WT (12.6 ± 2.0%). The results indicate that the recombinant virus will be transmitted at lower rates in H. armigera populations than the wild-type virus. This may potentially affect negatively its long-term efficacy as compared to wild-type virus, but contributing positively to its biosafety
Adaptation in an insect host-plant pathogen interaction
Cory, J.S. ; Myers, J.H. - \ 2004
Ecology Letters 7 (2004)8. - ISSN 1461-023X - p. 632 - 639.
nuclear polyhedrosis viruses - local adaptation - heliothis-virescens - entomopathogenic nematodes - bacillus-thuringiensis - genotypic variation - trichoplusia-ni - food plant - baculovirus - nucleopolyhedrovirus
Selection on parasites to adapt to local host populations may be direct or through other components of the system such as vectors or the food plant on which the parasite is ingested. To test for local adaptation of nucleopolyhedrovirus among island populations of western tent caterpillars, Malacosoma californicum pluviale, we compared virus isolates from three geographically distinct sites with different dominant host plants. Pathogenicity, speed of kill and virus production of each isolate were examined on the three food plants. Virus isolates from the two permanent host populations had the fastest speed of kill on the host plant from which they were isolated. This was not the case for a caterpillar population that goes extinct when populations are regionally low. Virus isolates on some plant species combined rapid speed of kill with high virus yield. Infection of hosts by mixed microparasite populations could facilitate local adaptation in response to differing food plant chemistry.
Microparasite manipulation of an insect: the influence of the egt gene on the interaction between a baculovirus and its lepidopteran host
Cory, J.S. ; Clarke, E.E. ; Brown, M.L. ; Hails, R.S. ; O'Reilly, D.R. - \ 2004
Functional Ecology 18 (2004)3. - ISSN 0269-8463 - p. 443 - 450.
ecdysteroid udp-glucosyltransferase - nuclear polyhedrosis-virus - trichoplusia-ni - glucosyl transferase - gypsy-moth - nucleopolyhedrovirus - deletion - larvae - improvement - heliothis
Parasites and pathogens manipulate their hosts in a variety of ways that are thought to enhance their fitness. However, it is rare to be able to link such phenotypic changes to specific genes. 2. Here the effect of a single pathogen gene is examined. The ecdysteroid UDP-glucosyltransferase (egt) gene of insect baculoviruses produces an enzyme that interferes with host moulting. 3. The effect of the egt gene was examined by comparing two baculoviruses that differed only in the expression of this gene. All three fitness traits examined ¿ pathogenicity, infection duration and pathogen productivity ¿ were affected by deletion of the gene. 4. Trichoplusia ni larvae in all five instars died earlier when infected with the egt-minus virus compared with those infected by the wild-type Autographa californica nucleopolyhedrovirus. 5. Unexpectedly, the egt-minus virus was more pathogenic to final instar larvae than the wild-type virus. Virus genotype and dose both influenced insect development. 6. Wild-type infected insects had a significantly higher yield of virus at death, cadaver weight and yield of virus per unit weight than those infected with the egt-minus virus. 7. The size of the virus challenge had a major influence on the outcome of the interaction. The consequences of these data for pathogen fitness are discussed.
Biological activity and field efficacy of a genetically modified Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus expressing an insect-selective toxin from a chimeric promoter
Sun, X. ; Wang, H. ; Sun, X.C. ; Chen Xinwen, ; Peng, C. ; Pan, D. ; Jehle, J.A. ; Werf, W. van der; Vlak, J.M. ; Hu, Z. - \ 2004
Biological Control 29 (2004)1. - ISSN 1049-9644 - p. 124 - 137.
nuclear polyhedrosis-virus - juvenile-hormone esterase - spodoptera-exigua larvae - recombinant baculovirus - heliothis-virescens - multicapsid nucleopolyhedrovirus - trichoplusia-ni - deletion - gene - lepidoptera
A recombinant baculovirus (HaSNPV-AaIT) with improved insecticidal properties was constructed for the control of the cotton bollworm (Helicoverpa armigera). A chimeric promoter of the p6.9 and polyhedrin gene of H. armigera single-nucleocapsid nucleopolyhedrovirus (HaSNPV) was used to drive the expression of an insect-selective scorpion toxin (AaIT) at the egt gene locus of HaSNPV. This chimeric promoter, denoted ph-p69p, was constructed by directional insertion of the p6.9 promoter downstream of the polyhedrin promoter. Laboratory bioassays indicate that the infectivity (LD(50)s) of this recombinant is unchanged, compared to one wild-type clone of HaSNPV (HaSNPV-WT), and an egt-deletion mutant (HaSNPV-EGTD). The median survival times (ST(50)s) of 1st to 5th instar H. armigera larvae were reduced 17-34% after infection with HaSNPV-AaIT in comparison to HaSNPV-WT. The median times of feeding cessation (FT(50)s) Were 30-43% shorter for HaSNPV-AaIT than for HaSNPV-WT in the 3rd to 5th instar of this species. This virus acts also quicker than HaSNPV-EGTD. Field trials at two research sites in 2000 indicate that the number of larvae and the proportion of damaged squares, flowers, and bolls was significantly lower in cotton plots treated with HaSNPV-AaIT than in plots treated with HaSNPV-WT or HaSNPV-EGTD. When HaSNPV-AaIT was applied to control infestations of bollworm over an entire cotton season, yield of cotton lint in plots treated by this recombinant was 22.1% higher than that in HaSNPV-WT treated plots in 2001 (p <0.05) and 20.7% higher in 2002 (p = 0.251). These results indicate that this novel HaSNPV recombinant HaSNPV-AaIT is a more effective biocontrol agent than its wild-type relative, at least in the short term, and suggest that it offers potential for practical use. (C) 2003 Elsevier Inc. All rights reserved.
comparative pathogenesis of the Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus in noctuid hosts of different susceptibility
Herz, A. ; Kleespies, R.G. ; Huber, J. ; Chen Xinwen, ; Vlak, J.M. - \ 2003
Journal of Invertebrate Pathology 83 (2003). - ISSN 0022-2011 - p. 31 - 36.
nuclear polyhedrosis-virus - heliothis-virescens - trichoplusia-ni - lepidoptera - larvae - baculoviruses - activation - infection - replication - resistance
A new cell line was established from the embryos of the insect Chrysodeixis chalcites (Lepidoptera, Noctuidae, Plusiinae). The cell line contains several morphologically different cell types and was distinguished from three other lepidopteran cell lines propagated in the laboratory by DNA amplification fingerprinting. The cultured cells, which we officially named WU-CcE-1 cells, were permissive for infection by C. chalcites nucleopolyhedrovirus (ChchNPV) and large numbers of occlusion bodies were produced that retained their infectivity for C. chalcites larvae. The CcE-1 cells were also permissive for Trichoplusia ni single nucleopolyhedrovirus (TnSNPV). ChchNPV could be passaged in these cells for at least four passages indicating that budded virus production was supported. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) and Helicoverpa armigera (Hear) NPV both induced apoptosis in these cells. The results obtained indicate that the CcE-1 cell line will be a useful tool in the study of both ChchNPV and TnSNPV.