The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Michael R Strand - One of the best experts on this subject based on the ideXlab platform.
-
The Encapsidated Genome of Microplitis demolitor Bracovirus Integrates into the Host Pseudoplusia includens
Journal of virology, 2011Co-Authors: Markus H. Beck, Shu Zhang, Kavita Bitra, Gaelen R. Burke, Michael R StrandAbstract:Polydnaviruses (PDVs) are symbionts of parasitoid wasps that function as gene delivery vehicles in the insects (hosts) that the wasps parasitize. PDVs persist in wasps as integrated proviruses but are packaged as circularized and segmented double-stranded DNAs into the virions that wasps inject into hosts. In contrast, little is known about how PDV genomic DNAs persist in host cells. Microplitis demolitor carries Microplitis demolitor bracovirus (MdBV) and parasitizes the host Pseudoplusia includens. MdBV infects primarily host hemocytes and also infects a hemocyte-derived cell line from P. includens called CiE1 cells. Here we report that all 15 genomic segments of the MdBV encapsidated genome exhibited long-term persistence in CiE1 cells. Most MdBV genes expressed in hemocytes were persistently expressed in CiE1 cells, including members of the glc gene family whose products transformed CiE1 cells into a suspension culture. PCR-based integration assays combined with cloning and sequencing of host-virus junctions confirmed that genomic segments J and C persisted in CiE1 cells by integration. These genomic DNAs also rapidly integrated into parasitized P. includens. Sequence analysis of wasp-viral junction clones showed that the integration of proviral segments in M. demolitor was associated with a wasp excision/integration motif (WIM) known from other bracoviruses. However, integration into host cells occurred in association with a previously unknown domain that we named the host integration motif (HIM). The presence of HIMs in most MdBV genomic DNAs suggests that the integration of each genomic segment into host cells occurs through a shared mechanism.
-
The protein P23 identifies capsule-forming plasmatocytes in the moth Pseudoplusia includens.
Developmental and comparative immunology, 2010Co-Authors: Shu Zhang, Kevin D. Clark, Michael R StrandAbstract:The moth Pseudoplusia includens produces four types of hemocytes named granulocytes, plasmatocytes, spherule cells and oenocytoids. Prior studies established that the main function of plasmatocytes in P. includens is encapsulation of parasitoids and other foreign entitites. P. includens plasmatocytes are also recognized by several monoclonal antibodies that bind unknown antigens. Of particular interest is the antibody 43E9A10 whose binding properties indicate that plasmatocytes consist of two subpopulations: cells that can spread on foreign surfaces and cells that cannot. Here we report 43E9A10 recognizes P23, which is a member of the aegerolysin protein family. Expression analyses confirmed that p23 is specifically expressed in plasmatocytes. Functional studies indicated that only P23-expressing plasmatocytes form capsules and spread in response to the cytokine plasmatocyte spreading peptide. In contrast, P23 showed no antibacterial or cytolytic activity toward bacteria and mammalian erythrocytes. Overall, our results suggest that P23 is a maturation marker that identifies capsule-forming plasmatocytes.
-
Regulation of melanization by glutathione in the moth Pseudoplusia includens.
Insect biochemistry and molecular biology, 2010Co-Authors: Kevin D. Clark, Michael R StrandAbstract:Abstract The phenoloxidase (PO) cascade regulates the melanization of hemolymph, which serves as a conserved humoral immune response in insects and other arthropods. The reductant glutathione (GSH) has long been used to inhibit melanization of hemolymph from insects but whether GSH levels in hemolymph are sufficient to play a physiological role in regulating melanization is unknown. Here, we characterized the abundance and effects of GSH on the melanization of plasma from larval stage Pseudoplusia includens (Lepidoptera: Noctuidae). GSH concentration in newly collected plasma from day two fifth instars ranged from 50 to 115 μM, while the titer of tyrosine, a substrate for the PO cascade, was 141 μM. GSH titers rapidly declined in plasma after collection from larvae, but no melanin formation occurred until GSH levels fell below 20 μM. Added GSH dose-dependently blocked melanization while PO substrates overrode GSH inhibition. Experiments conducted in the absence of oxygen and presence of PO cascade inhibitors further suggested that depletion of GSH from plasma was primarily due to formation of reactive intermediates produced by activated PO. Additional studies identified hemocytes as a potential source of plasma GSH. Hemocyte lysates recycled oxidized glutathione (GSSG) into GSH using NADPH, while intact hemocytes released GSH into the medium. These results suggest that in addition to protease cascade-releated mechanisms that regulate phenoloxidase, GSH exerts another level of control on melanization of insect hemolymph.
-
Infection by a symbiotic polydnavirus induces wasting and inhibits metamorphosis of the moth Pseudoplusia includens
The Journal of experimental biology, 2009Co-Authors: Andrea J. Pruijssers, Patrizia Falabella, Jai-hoon Eum, Francesco Pennacchio, Mark R. Brown, Michael R StrandAbstract:Insect pathogens and parasites often affect the growth and development of their hosts, but understanding of these processes is fragmentary. Among the most species-rich and important mortality agents of insects are parasitoid wasps that carry symbiotic polydnaviruses (PDVs). Like many PDV-carrying wasps, Microplitis demolitor inhibits growth and pupation of its lepidopteran host, Pseudoplusia includens, by causing host hemolymph juvenile hormone (JH) titers to remain elevated and preventing ecdysteroid titers from rising. Here we report these alterations only occurred if P. includens was parasitized prior to achieving critical weight, and were fully mimicked by infection with only M. demolitor bracovirus (MdBV). Metabolic assays revealed that MdBV infection of pre-critical weight larvae caused a rapid and persistent state of hyperglycemia and reduced nutrient stores. In vitro ecdysteroid assays further indicated that prothoracic glands from larvae infected prior to achieving critical weight remained in a refractory state of ecdysteroid release, whereas infection of post-critical weight larvae had little or no effect on ecdysteroid release by prothoracic glands. Taken together, our results suggest MdBV causes alterations in metabolic physiology, which prevent the host from achieving critical weight. This in turn inhibits the endocrine events that normally trigger metamorphosis.
-
Microplitis demolitor bracovirus inhibits phagocytosis by hemocytes from Pseudoplusia includens.
Archives of insect biochemistry and physiology, 2006Co-Authors: Michael R Strand, Markus H. Beck, Mark D. Lavine, Kevin D. ClarkAbstract:The braconid wasp Microplitis demolitor carries Microplitis demolitor bracovirus (MdBV) and parasitizes the larval stage of several noctuid moths. A key function of MdBV in parasitism is suppression of the host's cellular immune response. Prior studies in the host Pseudoplusia includens indicated that MdBV blocks encapsulation by preventing two types of hemocytes, plasmatocytes and granulocytes, from adhering to foreign targets. The other main immune response mediated by insect hemocytes is phagocytosis. The goal of this study was to determine which hemocyte types were phagocytic in P. includens and to assess whether MdBV infection affects this defense response. Using the bacterium Escherichia coli and inert polystyrene beads as targets, our results indicated that the professional phagocyte in P. includens is granulocytes. The phagocytic responses of granulocytes were very similar to those of High Five cells that prior studies have suggested are a granulocyte-like cell line. MdBV infection dose-dependently disrupted phagocytosis in both cell types by inhibiting adhesion of targets to the cell surface. The MdBV glc1.8 gene encodes a cell surface glycoprotein that had previously been implicated in disruption of adhesion and encapsulation responses by immune cells. Knockdown of glc1.8 expression by RNA interference (RNAi) during the current study rescued the ability of MdBV-infected High Five cells to phagocytize targets. Collectively, these results indicate that glc1.8 is a key virulence determinant in disruption of both adhesion and phagocytosis by insect immune cells.
Maria Elita B. Castro - One of the best experts on this subject based on the ideXlab platform.
-
Pseudoplusia includens single nucleopolyhedrovirus: genetic diversity, phylogeny and hypervariability of the pif-2 gene.
Journal of invertebrate pathology, 2013Co-Authors: S. R. Craveiro, Peter W. Inglis, Zilda Maria A. Ribeiro, Fernando L. Melo, Sônia Nair Báo, Maria Elita B. CastroAbstract:The soybean looper (Pseudoplusia includens Walker, 1857) has become a major pest of soybean crops in Brazil. In order to determine the genetic diversity and phylogeny of variants of Pseudoplusia includens single nucleopolyhedrovirus (PsinSNPV-IA to -IG), partial sequences of the genes lef-8, lef-9, pif-2, phr and polh were obtained following degenerate PCR and phylogenetic trees constructed using maximum parsimony and Bayesian methods. The aligned sequences showed polymorphisms among the isolates, where the pif-2 gene was by far the most variable and is predicted to be under positive selection. Furthermore, some of the pif-2 DNA sequence mutations are predicted to result in significant amino acid substitutions, possibly leading to changes in oral infectivity of this baculovirus. Cladistic analysis revealed two closely related monophyletic groups, one containing PsinNPV isolates IB, IC and ID and another containing isolates IA, IE, IF and IG. The phylogeny of PsinSNPV in relation to 56 other baculoviruses was also determined from the concatenated partial LEF-8, LEF-9, PIF-2 and POLH/GRAN deduced amino acid sequences, using maximum-parsimony and Bayesian methods. This analysis clearly places PsinSNPV with the Group II Alphabaculovirus, where PsinSNPV is most closely related to Chrysodeixis chalcites NPV and Trichoplusia ni SNPV.
-
Evaluation of seven viral isolates as potential biocontrol agents against Pseudoplusia includens (Lepidoptera: Noctuidae) caterpillars
Journal of invertebrate pathology, 2010Co-Authors: Talita M. Alexandre, S. R. Craveiro, Zilda Maria A. Ribeiro, Flávio Moscardi, Fabiane Cunha, Inês Cristina De Batista Fonseca, Maria Elita B. CastroAbstract:The caterpillar Pseudoplusia includens (Walker, 1857) (Lepidoptera, Noctuidae), known as soybean looper, is a pest that has recently assumed greater importance in soybean in Brazil. Isolates of nucleopolyhedroviruses (NPVs) of this pest have been identified from cotton in Guatemala and soybean farms in Brazil, providing an interesting perspective of potential use of viral insecticide against the insect in lieu to chemical insecticides. With the objective to contribute to the characterization studies of this virus, morphological and molecular analyses and biological activity were carried out with seven P. includens viral isolates (I-A to I-G). Electron microscopy of viral samples, purified from macerated infected larvae, showed particles with typical morphology of the Baculoviridae family, genus Alphabaculovirus (Nucleopolyhedrovirus – NPV) presenting virions with only a single nucleocapsid per envelope (SNPV) occluded in a protein matrix, forming occlusion bodies (OB). This virus was then classified as P. includens single nucleopolyhedrovirus (PsinSNPV). OB particles analyzed in SDS–polyacrylamide gel showed an intense band corresponding in size to NPV polyhedrin protein. DNA restriction profiles of the PsinSNPV isolates showed differences in the fragment size and number suggesting the existence of genotypic variants, except between I-E and I-F profiles that were similar. Among the isolates tested for infectivity against P. includens, I-A, I-E and I-F were the most virulent. Survival times (ST50) varied according to viral concentration, with significant differences among isolates for the three higher concentrations.
James D. Thomas - One of the best experts on this subject based on the ideXlab platform.
-
Factors Influencing Pyrethroid Resistance in a Permethrin-Selected Strain of the Soybean Looper, Pseudoplusia includens (Walker)
Pesticide biochemistry and physiology, 1996Co-Authors: James D. Thomas, David J. Boethel, James A. Ottea, Sanaa A. IbrahimAbstract:Abstract Cytochrome P450 monooxgenase activity towardp-nitroanisole was measured in larvae of three strains of soybean looper,Pseudoplusia includens(Walker), including a laboratory susceptible (S) strain, a resistant (R) strain selected for several generations with permethrin, and a nonselected (NS) strain from the same field collections as the R strain. Activity was significantly higher in R strain larvae than in the S and NS strains (1.8- and 1.4-fold, respectively), and there was no significant difference between activity in the S and NS strains. Resistance to the α-cyano pyrethroids deltamethrin and cypermethrin was similar to or higher than that observed with permethrin (RR = 70.0, 62.4, 145.3 and 12.1, 32.3, and 27.0 for permethrin, deltamethrin, and cypermethrin in R and NS strains, respectively). The R strain was less resistant (RR = 4.3) to tefluthrin, a pyrethroid with a fluorinated-phenyl alcohol moiety, and a nonester (ether) pyrethroid, BRC 429 (RR = 17.7). Piperonyl butoxide (PB) significantly increased the toxicity of each insecticide tested in the R and NS strains. In addition, penetration of14C-cypermethrin was decreased significantly at 24 hr after treatment when R strain larvae were pretreated with PB, with 21.1% of the applied dose unpenetrated in PB-treated larvae and 7.6% unpenetrated in larvae not treated with PB.
-
activity of two novel insecticides against permethrin resistant Pseudoplusia includens
Pesticide Science, 1994Co-Authors: James D. Thomas, Jeffrey S. Mink, D. J. Boethel, A T Wier, Roger B LeonardAbstract:Two experimental insecticides, AC 303,630 and MK 244, were tested against a laboratory colony and three field strains of Pseudoplusia includens (Walker). Topical application bioassays indicated that permethrin resistance in the field strains ranged from 3.9 to 489.0-fold. In leaf dip bioassays, LC50 and LC90 values for AC 303,630 ranged from 6.7 to 15.1 mg litre −1 and 8.7 to 28.2 mg litre −1, respectively, for third-instar larvae. The Louisiana 1991 field strain was significantly more susceptible to AC 303,630 than the laboratory and other field strains. The LC50 (but not LC90) for the Louisiana 1992 field strain was significantly higher than that of the laboratory strain. However, there was no difference in toxicity of AC 303,630 between the field strain with the highest level of permethrin resistance and the laboratory strain. LC50 and LC90 values for MK 244 in leaf dip bioassays ranged from 0.014 to 0.023 mg litre −1 and 0.079 to 0.174 mg litre −1, respectively. There were no significant differences in LC 50 or LC 90 among any of the strains for MK 244. Field trials in soybean were also conducted in 1991 and 1992 in an area of Louisiana where permethrin efficacy against P. includens has declined. In both years, AC 303,630 at 0.11–0.22 kg ha −1, and MK 244 at 0.0042–0.0084 kg ha −1, provided significantly better control than permethrin at 0.11 kg ha −1, and control equal to the recommended standard, thiodicarb. These studies indicate no cross-resistance exists between the experimental insecticides and permethrin.
-
Activity of two novel insecticides against permethrin‐resistant Pseudoplusia includens
Pesticide Science, 1994Co-Authors: James D. Thomas, David J. Boethel, Jeffrey S. Mink, Alan T. Wier, B. Roger LeonardAbstract:Two experimental insecticides, AC 303,630 and MK 244, were tested against a laboratory colony and three field strains of Pseudoplusia includens (Walker). Topical application bioassays indicated that permethrin resistance in the field strains ranged from 3.9 to 489.0-fold. In leaf dip bioassays, LC50 and LC90 values for AC 303,630 ranged from 6.7 to 15.1 mg litre −1 and 8.7 to 28.2 mg litre −1, respectively, for third-instar larvae. The Louisiana 1991 field strain was significantly more susceptible to AC 303,630 than the laboratory and other field strains. The LC50 (but not LC90) for the Louisiana 1992 field strain was significantly higher than that of the laboratory strain. However, there was no difference in toxicity of AC 303,630 between the field strain with the highest level of permethrin resistance and the laboratory strain. LC50 and LC90 values for MK 244 in leaf dip bioassays ranged from 0.014 to 0.023 mg litre −1 and 0.079 to 0.174 mg litre −1, respectively. There were no significant differences in LC 50 or LC 90 among any of the strains for MK 244. Field trials in soybean were also conducted in 1991 and 1992 in an area of Louisiana where permethrin efficacy against P. includens has declined. In both years, AC 303,630 at 0.11–0.22 kg ha −1, and MK 244 at 0.0042–0.0084 kg ha −1, provided significantly better control than permethrin at 0.11 kg ha −1, and control equal to the recommended standard, thiodicarb. These studies indicate no cross-resistance exists between the experimental insecticides and permethrin.
-
Management of Insecticide Resistant Soybean Loopers (Pseudoplusia includens) in the Southern United States
Pest Management in Soybean, 1992Co-Authors: David J. Boernel, Jeffrey S. Mink, Alan T. Wier, James D. Thomas, B. Roger Leonard, Fernando GallardoAbstract:The soybean looper, Pseudoplusia includens (Walker), ranks among the most important of the multitude of pests that threaten soybean annually in the southern United States. With the documentation of resistance to permethrin in 1987, this insect pest has developed resistance to virtually all classes of insecticides to include DDT, cyclodienes, organophosphates, carbamates, and most recently, the pyrethroids. This development is alarming in view of the infrequent use of insecticides on soybean and the rapidity with which resistance has appeared after adoption of an insecticide. The factors responsible relate to the insect’s biology and ecology, which challenge assumptions frequently made when attempting to model development of insecticide resistance in insects. Research progress has been made toward formulation of an insecticide resistance management plan. However, it is evident that expertise and cooperation beyond the soybean community and quite possibly beyond the boundaries of the United States will be necessary to develop and implement a viable strategy.
Sanaa A. Ibrahim - One of the best experts on this subject based on the ideXlab platform.
-
Factors Influencing Pyrethroid Resistance in a Permethrin-Selected Strain of the Soybean Looper, Pseudoplusia includens (Walker)
Pesticide biochemistry and physiology, 1996Co-Authors: James D. Thomas, David J. Boethel, James A. Ottea, Sanaa A. IbrahimAbstract:Abstract Cytochrome P450 monooxgenase activity towardp-nitroanisole was measured in larvae of three strains of soybean looper,Pseudoplusia includens(Walker), including a laboratory susceptible (S) strain, a resistant (R) strain selected for several generations with permethrin, and a nonselected (NS) strain from the same field collections as the R strain. Activity was significantly higher in R strain larvae than in the S and NS strains (1.8- and 1.4-fold, respectively), and there was no significant difference between activity in the S and NS strains. Resistance to the α-cyano pyrethroids deltamethrin and cypermethrin was similar to or higher than that observed with permethrin (RR = 70.0, 62.4, 145.3 and 12.1, 32.3, and 27.0 for permethrin, deltamethrin, and cypermethrin in R and NS strains, respectively). The R strain was less resistant (RR = 4.3) to tefluthrin, a pyrethroid with a fluorinated-phenyl alcohol moiety, and a nonester (ether) pyrethroid, BRC 429 (RR = 17.7). Piperonyl butoxide (PB) significantly increased the toxicity of each insecticide tested in the R and NS strains. In addition, penetration of14C-cypermethrin was decreased significantly at 24 hr after treatment when R strain larvae were pretreated with PB, with 21.1% of the applied dose unpenetrated in PB-treated larvae and 7.6% unpenetrated in larvae not treated with PB.
Dale M Norris - One of the best experts on this subject based on the ideXlab platform.
-
volatiles mediating plant herbivore natural enemy interactions electroantennogram responses of soybean looper Pseudoplusia includens and a parasitoid microplitis demolitor to green leaf volatiles
Journal of Chemical Ecology, 1991Co-Authors: R Ramachandran, Dale M NorrisAbstract:Electroantennograms were recorded from an herbivore,Pseudoplusia includens (Walker) (Lepidoptera: Noctuidae), and a parasitoid,Microplitis demolitor (Wilkinson) (Hymenoptera: Braconidae), exposed to 5-through 12-carbon aliphatic compounds of several chemical classes. The response of the herbivore was higher for the 6- and/or 7-carbon hydrocarbons, alcohols, aldehydes, esters, and ketones. The response of the parasitoid was higher for the 7- and 8-carbon hydrocarbons, aldehydes, and ketones. Responses of the herbivore and the parasitoid to alcohols were similar. Both the herbivore and the parasitoid were most sensitive to aldehydes and ketones, and least sensitive to alcohols and hydrocarbons. Responses of the parasitoid to hydrocarbons, aldehydes, and ketones were numerically higher than those of the herbivore. The adaptive significance of differential olfactory sensitivity between the herbivore and the natural enemy is discussed in relation to tri-trophic interactions among plants, herbivores, and natural enemies.
-
Volatiles mediating plant-herbivore-natural enemy interactions: Electroantennogram responses of soybean looper,Pseudoplusia includens, and a parasitoid,Microplitis demolitor, to green leaf volatiles
Journal of Chemical Ecology, 1991Co-Authors: R Ramachandran, Dale M NorrisAbstract:Electroantennograms were recorded from an herbivore, Pseudoplusia includens (Walker) (Lepidoptera: Noctuidae), and a parasitoid, Microplitis demolitor (Wilkinson) (Hymenoptera: Braconidae), exposed to 5-through 12-carbon aliphatic compounds of several chemical classes. The response of the herbivore was higher for the 6- and/or 7-carbon hydrocarbons, alcohols, aldehydes, esters, and ketones. The response of the parasitoid was higher for the 7- and 8-carbon hydrocarbons, aldehydes, and ketones. Responses of the herbivore and the parasitoid to alcohols were similar. Both the herbivore and the parasitoid were most sensitive to aldehydes and ketones, and least sensitive to alcohols and hydrocarbons. Responses of the parasitoid to hydrocarbons, aldehydes, and ketones were numerically higher than those of the herbivore. The adaptive significance of differential olfactory sensitivity between the herbivore and the natural enemy is discussed in relation to tri-trophic interactions among plants, herbivores, and natural enemies.
