Search results for "Exigua"
showing 10 items of 49 documents
Lyophilization of lepidopteran midguts: a preserving method for Bacillus thuringiensis toxin binding studies
2004
Binding assays with brush border membrane vesicles (BBMV) from insect midguts are commonly used in the study of the interactions between Bacillus thuringiensis Cry toxins and their receptors. Collaboration between laboratories often require that frozen insect samples are sent in dry ice. Because of customs restrictions and delays, sample thawing is always a risk and often the biological material becomes ruined during shipping. We have tested lyophilization as an alternative method for preserving insect midguts for binding studies with B. thuringiensis Cry toxins. For this purpose, BBMV were prepared from both frozen and lyophilized midguts from three lepidopteran species: Spodoptera exigua,…
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…
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 …
Susceptibility of Spodoptera frugiperda and S. exigua to Bacillus thuringiensis Vip3Aa insecticidal protein
2011
The Vip3Aa protein is an insecticidal protein secreted by Bacillus thuringiensis during the vegetative stage of growth. The activity of this protein has been tested after different steps/protocols of purification using Spodoptera frugiperda as a control insect. The results showed that the Vip3Aa protoxin was stable and retained full toxicity after being subjected to common biochemical steps used in protein purification. Bioassays with the protoxin in S. frugiperda and S. exigua showed pronounced differences in LC(50) values when mortality was measured at 7 vs. 10d. At 7d most live larvae were arrested in their development. LC(50) values of "functional mortality" (dead larvae plus larvae rem…
Proteolytic processing of Bacillus thuringiensis Vip3A proteins by two Spodoptera species
2014
Abstract Vip3 proteins have been described to be secreted by Bacillus thuringiensis during the vegetative growth phase and to display a broad insecticidal spectrum against lepidopteran larvae. Vip3Aa protoxin has been reported to be significantly more toxic to Spodoptera frugiperda than to Spodoptera exigua and differences in the midgut processing have been proposed to be responsible. In contrast, we have found that Vip3Ae is essentially equally toxic against these two species. Proteolysis experiments were performed to study the stability of Vip3A proteins to peptidase digestion and to see whether the differences found could explain differences in toxicity against these two Spodoptera speci…
Can herbivore-induced volatiles protect plants by increasing the herbivores’ susceptibility to natural pathogens?
2018
In response to insect herbivory, plants mobilize various defenses. Defense responses include the release of herbivore-induced plant volatiles (HIPVs) that can serve as signals to alert undamaged tissues and to attract natural enemies of the herbivores. Some HIPVs can have a direct negative impact on herbivore survival, but it is not well understood by what mechanisms. Here, we tested the hypothesis that exposure to HIPVs renders insects more susceptible to natural pathogens. Exposure of the caterpillars of the noctuid Spodoptera exigua to indole and linalool, but not exposure to (Z)-3-hexenyl acetate, increased the susceptibility to Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV). …
Broad-spectrum cross-resistance in Spodoptera exigua from selection with a marginally toxic Cry protein.
2009
BACKGROUND:Spodoptera exigua (Hubner) has developed resistance to a wide range of chemical insecticides. Products based on Bacillus thuringiensis Cry toxins are used in integrated pest management as an ecologically friendly alternative for pest control. Since there are few B. thuringiensis Cry proteins highly active against S. exigua, it is desirable to apply appropriate resistance management strategies to prevent the evolution of resistance to these proteins. RESULTS:Spodoptera exigua larvae were selected with Cry1Ab, a protein with low activity against this pest. Selected larvae developed > 30-fold resistance to Cry1Ab in 13 generations, relative to an unselected strain. The estimated rea…
High Bacterial Agglutination Activity in a Single-CRD C-Type Lectin from <em>Spodoptera exigua</em> (Lepidoptera: Noctuidae)
2017
Lectins are carbohydrate-interacting proteins that play a pivotal role in multiple physiological and developmental aspects of all organisms. They can specifically interact with different bacterial and viral pathogens through carbohydrate-recognition domains (CRD). In addition, lectins are also of biotechnological interest because of their potential use as biosensors for capturing and identifying bacterial species. In this work, three C-type lectins from the Lepidoptera Spodoptera exigua were produced as recombinant proteins and their bacterial agglutination properties were characterized. The lowest protein concentration producing bacterial agglutination against a panel of different Gram+ an…
Effects of ajugarins and related neoclerodane diterpenoids on feeding behaviour of Leptinotarsa decemlineata and Spodoptera exigua larvae
2001
Three naturally occurring ajugarins and seven semisynthetic derivatives of them, possessing different functionalities in the decalin part, together with two natural furoneoclerodane diterpenes, have been assessed as feeding behavior modifying agents of larvae of the generalist Spodoptera exigua and a specialist like Leptinotarsa decemlineata. Ajugarin I and some of its derivatives exhibited a significant antifeedant activity against larvae of S. exigua in both choice and no-choice assays. Conversely, the furoneoclerodane diterpenes only presented antifeedant activity against larvae of L. decemlineata. These results indicate that the biological action of the tested substances is strongly mod…
Natural populations of Spodoptera exigua are infected by multiple viruses that are transmitted to their offspring
2014
Sublethal infections by baculoviruses (Baculoviridae) are believed to be common in Lepidoptera, including Spodoptera exigua. In addition, novel RNA viruses of the family Iflaviridae have been recently identified in a laboratory population of S. exigua (S. exigua iflavirus-1: SeIV-1; S. exigua iflavirus-2: SeIV-2) that showed no overt signs of disease. We determined the prevalence of these viruses in wild populations and the prevalence of co-infection by the different viruses in shared hosts. Infection by S. exigua multiple nucleopolyhedrovirus (SeMNPV) and iflaviruses in S. exigua adults (N= 130) from horticultural greenhouses in southern Spain was determined using qPCR and RT-PCR based tec…