Search results for "Larva"
showing 10 items of 632 documents
Phenotypic Heterogeneity of the Insect Pathogen Photorhabdus luminescens: Insights into the Fate of Secondary Cells
2019
Photorhabdus luminescens is a Gram-negative bacterium that lives in symbiosis with soil nematodes and is simultaneously highly pathogenic toward insects. The bacteria exist in two phenotypically different forms, designated primary (1°) and secondary (2°) cells. Yet unknown environmental stimuli as well as global stress conditions induce phenotypic switching of up to 50% of 1° cells to 2° cells. An important difference between the two phenotypic forms is that 2° cells are unable to live in symbiosis with nematodes and are therefore believed to remain in the soil after a successful infection cycle. In this work, we performed a transcriptomic analysis to highlight and better understand the rol…
The respiratory proteins of insects
2007
For a long time, respiratory proteins have been considered unnecessary in most insects because the tracheal system was thought to be sufficient for oxygen supply. Only a few species that survive under hypoxic conditions were known exceptions. However, recently it has become evident that (1) intracellular hemoglobins belong to the standard repertoire of insects and (2) that hemocyanin is present in many "lower" insects. Intracellular hemoglobins have been identified in Drosophila, Anopheles, Apis and many other insects. In all investigated species, hemoglobin is mainly expressed in the fat body and the tracheal system. The major Drosophila hemoglobin binds oxygen with high affinity. This hem…
Quaternary and subunit structure of Calliphora arylphorin as deduced from electron microscopy, electrophoresis, and sequence similarities with arthro…
1992
Arylphorin was purified from larvae of the blowfly Calliphora vicina and studied in its oligomeric form and after dissociation at pH 9.6 into native subunits. In accordance with earlier literature, it was electrophoretically shown to be a 500 kDa hexamer (1 x 6) consisting of 78 kDa polypeptides (= subunits). Electron micrographs of negatively stained hexamers show a characteristic curvilinear, equilateral triangle of 12 nm in diameter (top view) and a rectangle measuring 10 x 12 nm (side view). Alternatively, particles in the top view orientation exhibit a roughly circular shape 12 nm in diameter. Crossed immunoelectrophoresis revealed the presence of a major subunit type; the nature of a …
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…
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 …
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…
Essential oils from three Algerian medicinal plants (Artemisia campestris, Pulicaria arabica, and Saccocalyx satureioides) as new botanical insectici…
2020
Medicinal and aromatic plants represent an outstanding source of green active ingredients for a broad range of real-world applications. In the present study, we investigated the insecticidal potential of the essential oils obtained from three medicinal and aromatic plants of economic importance in Algeria, Artemisia campestris, Pulicaria arabica, and Saccocalyx satureioides. Gas chromatography coupled with mass spectrometry (GC-MS) was used to study the essential oil chemical compositions. The three essential oils were tested against a mosquito vectoring filariasis and arboviruses, i.e., Culex quinquefasciatus, a fly pest acting also as pathogens vector, Musca domestica, and an agricultural…
The Rapid Evolution of Resistance to Vip3Aa Insecticidal Protein in Mythimna separata (Walker) Is Not Related to Altered Binding to Midgut Receptors
2021
Laboratory selection for resistance of field populations is a well-known and useful tool to understand the potential of insect populations to evolve resistance to insecticides. It provides us with estimates of the frequency of resistance alleles and allows us to study the mechanisms by which insects developed resistance to shed light on the mode of action and optimize resistance management strategies. Here, a field population of Mythimna separata was subjected to laboratory selection with either Vip3Aa, Cry1Ab, or Cry1F insecticidal proteins from Bacillus thuringiensis. The population rapidly evolved resistance to Vip3Aa reaching, after eight generations, a level of >3061-fold resistance…