Search results for "INSECT"
showing 10 items of 2033 documents
Shared Binding Sites in Lepidoptera for Bacillus thuringiensis Cry1Ja and Cry1A Toxins
2001
ABSTRACT Bacillus thuringiensis toxins act by binding to specific target sites in the insect midgut epithelial membrane. The best-known mechanism of resistance to B. thuringiensis toxins is reduced binding to target sites. Because alteration of a binding site shared by several toxins may cause resistance to all of them, knowledge of which toxins share binding sites is useful for predicting cross-resistance. Conversely, cross-resistance among toxins suggests that the toxins share a binding site. At least two strains of diamondback moth ( Plutella xylostella ) with resistance to Cry1A toxins and reduced binding of Cry1A toxins have strong cross-resistance to Cry1Ja. Thus, we hypothesized that…
Variation in Susceptibility to Bacillus thuringiensis Toxins among Unselected Strains of Plutella xylostella
2001
ABSTRACT So far, the only insect that has evolved resistance in the field to Bacillus thuringiensis toxins is the diamondback moth ( Plutella xylostella ). Documentation and analysis of resistant strains rely on comparisons with laboratory strains that have not been exposed to B. thuringiensis toxins. Previously published reports show considerable variation among laboratories in responses of unselected laboratory strains to B. thuringiensis toxins. Because different laboratories have used different unselected strains, such variation could be caused by differences in bioassay methods among laboratories, genetic differences among unselected strains, or both. Here we tested three unselected st…
High Genetic Variability for Resistance to Bacillus thuringiensis Toxins in a Single Population of Diamondback Moth
2001
ABSTRACT The long-term benefit of insecticidal products based on Cry toxins, either in sprays or as transgenic crops, is threatened by the development of resistance by target pests. The models used to predict evolution of resistance to Cry toxins most often are monogenic models in which two alleles are used. Moreover, the high-dose/refuge strategy recommended for implementation with transgenic crops relies on the assumption that the resistance allele is recessive. Using selection experiments, we demonstrated the occurrence in a laboratory colony of diamondback moth of two different genes (either allelic or nonallelic) that confer resistance to Cry1Ab. At the concentration tested, resistance…
Genetic and Biochemical Approach for Characterization of Resistance to Bacillus thuringiensis Toxin Cry1Ac in a Field Population of the Diamondback M…
2000
ABSTRACT Four subpopulations of a Plutella xylostella (L.) strain from Malaysia (F 4 to F 8 ) were selected with Bacillus thuringiensis subsp. kurstaki HD-1, Bacillus thuringiensis subsp. aizawai , Cry1Ab, and Cry1Ac, respectively, while a fifth subpopulation was left as unselected (UNSEL-MEL). Bioassays at F 9 found that selection with Cry1Ac, Cry1Ab, B. thuringiensis subsp. kurstaki , and B. thuringiensis subsp. aizawai gave resistance ratios of >95, 10, 7, and 3, respectively, compared with UNSEL-MEL (>10,500, 500, >100, and 26, respectively, compared with a susceptible population, ROTH). Resistance to Cry1Ac, Cry1Ab, B. thuringiensis subsp. kurstaki , and B. thuringiensis subsp…
Shifts in size, genetic structure and activity of the soil denitrifier community by nematode grazing
2010
International audience; Bacterial-feeding nematodes represent an important driver of the soil microbial activity and diversity. This study aimed at characterizing the impact of nematode grazing on a model functional bacterial guild involved in N-cycling, the denitrifiers. Bacterial-feeding nematodes (Cephalobus pseudoparvus) were inoculated into soil microcosms whose indigenous nematofauna had previously been removed. The size, genetic structure and activity of the soil denitrifier community were characterized 15 and 45 days after nematodes inoculation using quantitative PCR of the nirK, nirS and nosZ denitrification genes, fingerprinting of the nirK and nirS genes and denitrification enzym…
Baculovirus entry into human hepatoma cells.
2005
ABSTRACT Autographa californica multiple nucleopolyhedrovirus (AcMNPV), a prototype member of the Baculoviridae family, has gained increasing interest as a potential vector candidate for mammalian gene delivery applications. AcMNPV is known to enter both dividing and nondividing mammalian cell lines in vitro, but the mode and kinetics of entry as well as the intracellular transport of the virus in mammalian cells is poorly understood. The general objective of this study was to characterize the entry steps of AcMNPV- and green fluorescent protein-displaying recombinant baculoviruses in human hepatoma cells. The viruses were found to bind and transduce the cell line efficiently, and electron …
Downregulation of a Chitin Deacetylase-Like Protein in Response to Baculovirus Infection and Its Application for Improving Baculovirus Infectivity
2009
ABSTRACT Several expressed sequence tags (ESTs) with homology to chitin deacetylase-like protein (CDA) were selected from a group of Helicoverpa armigera genes whose expression changed after infection with H. armigera single nucleopolyhedrovirus (HearNPV). Some of these ESTs coded for a midgut protein containing a chitin deacetylase domain (CDAD). The expressed protein, HaCDA5a, did not show chitin deacetylase activity, but it showed a strong affinity for binding to chitin. Sequence analysis showed the lack of any chitin binding domain, described for all currently known peritrophic membrane (PM) proteins. HaCDA5a has previously been detected in the H. armigera PM. Such localization, togethe…
Purification and analysis of polyhistidine-tagged human parvovirus B19 VP1 and VP2 expressed in insect cells
2008
Human parvovirus B19 is an autonomously replicating human pathogen with a specific tropism for human erythroid progenitor cells. There is an interest in producing empty nucleocapsids of B19 as they can be used as tools in molecular biology and diagnostics. Native B19 virus particles are formed from two structural viral proteins, VP1 and VP2. The VP2 protein alone is able to self assemble and consequently form virus-like particles (VLPs) in heterologous expression systems. Purification of recombinant VLPs has been conducted using various traditional methods. These include laborious and time-consuming, e.g. cesium chloride or sucrose gradient ultracentrifugation steps, allowing limited workin…
6- O - and N -Sulfated Syndecan-1 Promotes Baculovirus Binding and Entry into Mammalian Cells
2013
ABSTRACT Baculoviruses are insect-specific viruses commonly found in nature. They are not able to replicate in mammalian cells but can transduce them when equipped with an appropriate mammalian cell active expression cassette. Although the viruses have been studied in several types of mammalian cells from different origins, the receptor that baculovirus uses to enter or interact with mammalian cells has not yet been identified. Due to the wide tropism of the virus, the receptor has been suggested to be a generally found cell surface molecule. In this article, we investigated the interaction of baculovirus and mammalian cell surface heparan sulfate proteoglycans (HSPG) in more detail. Our da…
Enhancing the multiplication of nucleopolyhedrovirus in vitro by manipulation of the pH
2009
Insect nucleopolyhedroviruses (NPVs) are studied widely as agents for biological control, as expression vectors for the production of heterologous proteins, and as transduction vectors for gene therapy applications. Most of these applications rely on the existence of cell lines that allow in vitro multiplication of the virus. The influence of pH in the medium culture on the multiplication of SeMNPV, HearSNPV and AcMNPV in different cell culture lines was investigated. The study showed a strong influence of the medium pH on the virus multiplication with the best results at pH 6.5, about half pH unit above the pH of insect culture media used most commonly. Additional experiments using a recom…