Search results for "Cry1Ac"
showing 10 items of 45 documents
Lack of Detrimental Effects of Bacillus thuringiensis Cry Toxins on the Insect Predator Chrysoperla carnea : a Toxicological, Histopathological, and …
2006
ABSTRACT The effect of Cry proteins of Bacillus thuringiensis on the green lacewing ( Chrysoperla carnea ) was studied by using a holistic approach which consisted of independent, complementary experimental strategies. Tritrophic experiments were performed, in which lacewing larvae were fed Helicoverpa armigera larvae reared on Cry1Ac, Cry1Ab, or Cry2Ab toxins. In complementary experiments, a predetermined amount of purified Cry1Ac was directly fed to lacewing larvae. In both experiments no effects on prey utilization or fitness parameters were found. Since binding to the midgut is an indispensable step for toxicity of Cry proteins to known target insects, we hypothesized that specific bind…
Screening for Bacillus thuringiensis Crystal Proteins Active against the Cabbage Looper, Trichoplusia ni
2000
Abstract Toxicity tests were performed to find among Cry1 and Cry2 Bacillus thuringiensis crystal proteins those with high activity against the cabbage looper. Tests were performed with neonate larvae on surface-contaminated artificial diet. The crystal proteins found to be toxic were, from higher to lower toxicity: Cry1Ac, Cry1Ab, Cry1C, Cry2Aa, Cry1J, and Cry1F (LC50 of 1.1–4.1, 3.4–4.4, 12, 34, 87, and 250 ng/cm2, respectively). Cry1B, Cry1D, and Cry1E can be considered nontoxic (LC50 higher than 2500 ng/cm2). Cry1Aa was moderately toxic to nontoxic, depending on the source (LC50 of 420 ng/cm2 from PGS and 8100 ng/cm2 from Ecogen). In vitro binding assays with trypsin-activated 125I-labe…
Synergism and Antagonism between Bacillus thuringiensis Vip3A and Cry1 Proteins in Heliothis virescens, Diatraea saccharalis and Spodoptera frugiperda
2014
Made available in DSpace on 2015-03-18T15:56:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-10-02Bitstream added on 2015-03-18T16:28:28Z : No. of bitstreams: 1 WOS000342591500006.pdf: 270331 bytes, checksum: c280e3f5bc5e3bb0b92bf74d046135f0 (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Spanish Ministry of Economy and Competivity FEDER Second generation Bt crops (insect resistant crops carrying Bacillus thuringiensis genes) combine more than one gene that codes for insecticidal proteins in the same plant to provide better control of agricultural pests. Some of the new combinations involve co-expression of cry and vip genes. Because Cry and Vip proteins …
Different mechanisms of resistance to Bacillus thuringiensis toxins in the indianmeal moth.
2001
ABSTRACT Susceptibility to protoxin and toxin forms of Cry1Ab and the binding of 125 I-labeled Cry1Ab and Cry1Ac has been examined in three Plodia interpunctella colonies, one susceptible (688 s ) and two resistant (198 r and Dpl r ) to Bacillus thuringiensis . Toxicological studies showed that the 198 r colony was 11-fold more resistant to Cry1Ab protoxin than to Cry1Ab activated toxin, whereas the Dpl r colony was 4-fold more resistant to protoxin versus toxin. Binding results with 125 I-labeled toxins indicated the occurrence of two different binding sites for Cry1Ab in the susceptible insects, one of them shared with Cry1Ac. Cry1Ab binding was found to be altered in insects from both re…
Susceptibility of Spodoptera exigua to 9 toxins from Bacillus thuringiensis
2007
Nine of the most common lepidopteran active Cry proteins from Bacillus thuringiensis have been tested for activity against Spodoptera exigua. Because of possible intraspecific variability, three laboratory strains (FRA, HOL, and MUR) have been used. Mortality assays were performed with the three strains. LC(50) values for the active toxins were determined to the FRA and the HOL strains, whereas susceptibility of the MUR strain was assessed using only two concentrations. The results showed that Cry1Ca, Cry1Da, and Cry1Fa were the most effective toxins with all strains. Cry1Ab was found effective for the HOL strain, but very little effective against FRA (6.5-fold) and MUR strains. Cry1Aa and …
Mechanism of Resistance to Bacillus thuringiensis Toxin Cry1Ac in a Greenhouse Population of the Cabbage Looper, Trichoplusia ni
2007
ABSTRACT The cabbage looper, Trichoplusia ni , is one of only two insect species that have evolved resistance to Bacillus thuringiensis in agricultural situations. The trait of resistance to B. thuringiensis toxin Cry1Ac from a greenhouse-evolved resistant population of T. ni was introgressed into a highly inbred susceptible laboratory strain. The resulting introgression strain, GLEN-Cry1Ac-BCS, and its nearly isogenic susceptible strain were subjected to comparative genetic and biochemical studies to determine the mechanism of resistance. Results showed that midgut proteases, hemolymph melanization activity, and midgut esterase were not altered in the GLEN-Cry1Ac-BCS strain. The pattern of…
Binding of individual Bacillus thuringiensis Cry proteins to the olive moth Prays oleae (Lepidoptera: Yponomeutidae)
2009
The microlepidopteran Prays oleae is one of the main insect pests causing significant crop losses in the Mediterranean olive groves. Bacillus thuringiensis based insecticides are being successfully used to minimize the impact of the second and third generations of this pest. However, because of its very small size and difficulty of rearing, very few studies have been carried out to determine the potency and mode of action of B. thuringiensis Cry proteins in this insect. In this study, Cry1Ac, Cry1Ca, and Cry1Fa proteins were shown to be toxic to third instar larvae of P. oleae. Furthermore, binding assays with (125)I-Cry1Ac and brush border membrane vesicles from midguts of last-instar larv…
Tribolium castaneum Apolipophorin-III acts as an immune response protein against Bacillus thuringiensis Cry3Ba toxic activity
2013
In this study, a 2.1-fold Apolipophorin-III mRNA up-regulation was found in Tribolium castaneum larvae challenged with Bacillus thuringiensis Cry3Ba spore-crystal mixture. Knockdown of Apolipophorin-III by RNAi resulted in increased T. castaneum larvae susceptibility following Cry3Ba spore-crystal treatment, demonstrating Apolipophorin-III involvement in insect defense against B. thuringiensis. We showed that Apolipophorin-III participates in T. castaneum immune response to B. thuringiensis activating the prophenoloxidase cascade since: (i) phenoloxidase activity significantly increased after Cry3Ba spore-crystal treatment compared to untreated or Cry1Ac spore-crystal treated larvae and (ii…
Common, but Complex, Mode of Resistance of Plutella xylostella to Bacillus thuringiensis Toxins Cry1Ab and Cry1Ac
2005
ABSTRACT A field collected population of Plutella xylostella (SERD4) was selected in the laboratory with Bacillus thuringiensis endotoxins Cry1Ac (Cry1Ac-SEL) and Cry1Ab (Cry1Ab-SEL). Both subpopulations showed similar phenotypes: high resistance to the Cry1A toxins and little cross-resistance to Cry1Ca or Cry1D. A previous analysis of the Cry1Ac-SEL showed incompletely dominant resistance to Cry1Ac with more than one factor, at least one of which was sex influenced. In the present study reciprocal mass crosses between Cry1Ab-SEL and a laboratory susceptible population (ROTH) provided evidence that Cry1Ab resistance was also inherited as incompletely dominant trait with more than one factor…
ABCC transporters mediate insect resistance to multiple Bt toxins revealed by bulk segregant analysis
2014
[EN] Background: Relatively recent evidence indicates that ABCC2 transporters play a main role in the mode of action of Bacillus thuringiensis (Bt) Cry1A-type proteins. Mapping of major Cry1A resistance genes has linked resistance to the ABCC2 locus in Heliothis virescens, Plutella xylostella, Trichoplusia ni and Bombyx mori, and mutations in this gene have been found in three of these Bt-resistant strains. Results: We have used a colony of Spodoptera exigua (Xen-R) highly resistant to a Bt commercial bioinsecticide to identify regions in the S. exigua genome containing loci for major resistance genes by using bulk segregant analysis (BSA). Results reveal a region containing three genes fro…