scholarly journals Cyt1A of Bacillus thuringiensis Delays Evolution of Resistance to Cry11A in the Mosquito Culex quinquefasciatus

2005 ◽  
Vol 71 (1) ◽  
pp. 185-189 ◽  
Author(s):  
Margaret C. Wirth ◽  
Hyun-Woo Park ◽  
William E. Walton ◽  
Brian A. Federici
Keyword(s):  
Bacillus Thuringiensis ◽  
Culex Quinquefasciatus ◽  
Laboratory Experiments ◽  
Principal Factor ◽  
Resistance Ratio ◽  
Cry Proteins ◽  
Lepidopteran Larvae ◽  
Evolution Of Resistance ◽  
Low Levels ◽  
Selection Of

ABSTRACT Insecticides based on Bacillus thuringiensis subsp. israelensis have been used for mosquito and blackfly control for more than 20 years, yet no resistance to this bacterium has been reported. Moreover, in contrast to B. thuringiensis subspecies toxic to coleopteran or lepidopteran larvae, only low levels of resistance to B. thuringiensis subsp. israelensis have been obtained in laboratory experiments where mosquito larvae were placed under heavy selection pressure for more than 30 generations. Selection of Culex quinquefasciatus with mutants of B. thuringiensis subsp. israelensis that contained different combinations of its Cry proteins and Cyt1Aa suggested that the latter protein delayed resistance. This hypothesis, however, has not been tested experimentally. Here we report experiments in which separate C. quinquefasciatus populations were selected for 20 generations to recombinant strains of B. thuringiensis that produced either Cyt1Aa, Cry11Aa, or a 1:3 mixture of these strains. At the end of selection, the resistance ratio was 1,237 in the Cry11Aa-selected population and 242 in the Cyt1Aa-selected population. The resistance ratio, however, was only 8 in the population selected with the 1:3 ratio of Cyt1Aa and Cry11Aa strains. When the resistant mosquito strain developed by selection to the Cyt1Aa-Cry11Aa combination was assayed against Cry11Aa after 48 generations, resistance to this protein was 9.3-fold. This indicates that in the presence of Cyt1Aa, resistance to Cry11Aa evolved, but at a much lower rate than when Cyt1Aa was absent. These results indicate that Cyt1Aa is the principal factor responsible for delaying the evolution and expression of resistance to mosquitocidal Cry proteins.

Characterization of cry Genes in a Mexican Bacillus thuringiensis Strain Collection

1998 ◽  
Vol 64 (12) ◽  
pp. 4965-4972 ◽  
Author(s):  
Alejandra Bravo ◽  
Sergio Sarabia ◽  
Lorena Lopez ◽  
Hernesto Ontiveros ◽  
Carolina Abarca ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Specific Primers ◽  
Cry Proteins ◽  
Pcr Product ◽  
Strain Collection ◽  
Lepidopteran Insects ◽  
Ecological Patterns ◽  
Biogeographical Regions ◽  
Selection Of

ABSTRACT Mexico is located in a transition zone between the Nearctic and Neotropical biogeographical regions and contains a rich and unique biodiversity. A total of 496 Bacillus thuringiensis strains were isolated from 503 soil samples collected from the five macroregions of the country. The characterization of the strain collection provided useful information on the ecological patterns of distribution of B. thuringiensis and opportunities for the selection of strains to develop novel bioinsecticidal products. The analysis of the strains was based on multiplex PCR with novel general and specific primers that could detect the cry1,cry3, cry5, cry7, cry8,cry9, cry11, cry12,cry13, cry14, cry21, andcyt genes. The proteins belonging to the Cry1 and Cry9 groups are toxic for lepidopteran insects. The Cry3, Cry7, and Cry8 proteins are active against coleopteran insects. The Cry5, Cry12, Cry13, and Cry14 proteins are nematocidal. The Cry11, Cry21, and Cyt proteins are toxic for dipteran insects. Six pairs of general primers are used in this method. Strains for which unique PCR product profiles were obtained with the general primers were further characterized by additional PCRs with specific primers. Strains containingcry1 genes were the most abundant in our collection (49.5%). Thirty-three different cry1-type profiles were identified. B. thuringiensis strains harboringcry3 genes represented 21.5% of the strains, and 7.9% of the strains contained cry11 and cyt genes.cry7, cry8, and cry9 genes were found in 0.6, 2.4, and 2.6% of the strains, respectively. No strains carrying cry5, cry12, cry13,cry14, or cry21 genes were found. Finally, 14% of the strains did not give any PCR product and did not react with any polyclonal antisera. Our results indicate the presence of strains that may harbor potentially novel Cry proteins as well as strains with combinations of less frequently observed cry genes.

scholarly journals Current Insights on Vegetative Insecticidal Proteins (Vip) as Next Generation Pest Killers

Toxins ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 522
Author(s):  
Tahira Syed ◽  
Muhammad Askari ◽  
Zhigang Meng ◽  
Yanyan Li ◽  
Muhammad Ali Abid ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Mechanism Of Action ◽  
Insecticidal Activity ◽  
Binding Sites ◽  
Growth Phases ◽  
Cry Proteins ◽  
Insecticidal Proteins ◽  
Gram Negative ◽  
Vip Proteins ◽  
Evolution Of Resistance

Bacillus thuringiensis (Bt) is a Gram negative soil bacterium. This bacterium secretes various proteins during different growth phases with an insecticidal potential against many economically important crop pests. One of the important families of Bt proteins is vegetative insecticidal proteins (Vip), which are secreted into the growth medium during vegetative growth. There are three subfamilies of Vip proteins. Vip1 and Vip2 heterodimer toxins have an insecticidal activity against many Coleopteran and Hemipteran pests. Vip3, the most extensively studied family of Vip toxins, is effective against Lepidopteron. Vip proteins do not share homology in sequence and binding sites with Cry proteins, but share similarities at some points in their mechanism of action. Vip3 proteins are expressed as pyramids alongside Cry proteins in crops like maize and cotton, so as to control resistant pests and delay the evolution of resistance. Biotechnological- and in silico-based analyses are promising for the generation of mutant Vip proteins with an enhanced insecticidal activity and broader spectrum of target insects.

Evidence for Positive Darwinian Selection of Vip Gene in Bacillus thuringiensis

2007 ◽  
Vol 34 (7) ◽  
pp. 649-660 ◽  
Author(s):  
Jinyu Wu ◽  
Fangqing Zhao ◽  
Jie Bai ◽  
Gang Deng ◽  
Song Qin ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Positive Darwinian Selection ◽  
Darwinian Selection ◽  
Selection Of

scholarly journals SELECTION OF HERBICIDES TARGETING THE USE IN CROP SYSTEMS CULTIVATED WITH SHOWY CROTALARIA

2015 ◽  
Vol 33 (3) ◽  
pp. 521-534 ◽  
Author(s):  
G. B. P BRAZ ◽  
R. S OLIVEIRA JR ◽  
J. CONSTANTIN ◽  
H. K. TAKANO ◽  
C. A. CHASE ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Chemical Control ◽  
Clayey Soil ◽  
Chlorimuron Ethyl ◽  
High Production ◽  
Low Levels ◽  
Postemergence Herbicides ◽  
Potential Use ◽  
Selection Of

ABSTRACT The increase in the area planted with Crotalaria spectabilishas occurred by several factors, highlighting the potential to reduce the nematodes, nitrogen fixation and the high production of biomass. By becoming a species sown as a crop, it is necessary to control the weeds that coexist with showy crotalaria. This change in the use of this crop creates the possibility of this specie becoming a weed. The aim of this study was to assess the potential use of herbicides applied in preemergence and postemergence of C.spectabilisfor different purposes (control of volunteer and selectivity plants). Three experiments were installed in a greenhouse (two with herbicides applied in preemergence - in soils with distinct textural categories; and one experiment with herbicides applied in postemergence). The results of the experiments with herbicides applied in preemergence showed that: amicarbazone, atrazine, diuron, metribuzin, prometryn, fomesafen and sulfentrazone showed effectiveness for control of C.spectabilis in clayey soil. Besides these, flumioxazin and isoxaflutole also showed potential to be used in the control of showy crotalaria in soils with loam texture. In relation to the postemergence herbicides, atrazine, diuron, prometryn, flumioxazin, fomesafen, lactofen, saflufenacil, amonio-glufosinate and glyphosate can be used aiming the chemical control of C.spectabilis. Herbicides chlorimuron-ethyl, diclosulan, imazethapyr, pyrithiobac-sodium, trifloxysulfuron-sodium, clomazone, pendimethalin, S-metolachlor and trifluralin applied in preemergence, and imazethapyr, pyrithiobac-sodium, flumiclorac, bentazon and clethodim applied in postemergence caused low levels of injury to C.spectabilis plants, making necessary the development of new searches to ensure the selectivity of these products.

scholarly journals New Strategy for Identification of Novel cry-Type Genes from Bacillus thuringiensis Strains

2005 ◽  
Vol 71 (2) ◽  
pp. 761-765 ◽  
Author(s):  
Corina M. Berón ◽  
Leonardo Curatti ◽  
Graciela L. Salerno
Keyword(s):  
Bacillus Thuringiensis ◽  
Phylogenetic Distance ◽  
Cloning And Sequencing ◽  
Degenerate Primers ◽  
Dna Templates ◽  
Cry Proteins ◽  
New Strategy ◽  
Genes Encoding ◽  
Encoding Protein

ABSTRACT We designed five degenerate primers for detection of novel cry genes from Bacillus thuringiensis strains. An efficient strategy was developed based on a two-step PCR approach with these primers in five pair combinations. In the first step, only one of the primer pairs is used in the PCR, which allows amplification of DNA fragments encoding protein regions that include consensus domains of representative proteins belonging to different Cry groups. A second PCR is performed by using the first-step amplification products as DNA templates and the set of five primer combinations. Cloning and sequencing of the last-step amplicons allow both the identification of known cry genes encoding Cry proteins covering a wide phylogenetic distance and the detection and characterization of cry-related sequences from novel B. thuringiensis isolates.

Comparative study of selfsteem and social skills in addicts inpatients in a Therapeutic Community / Estudio comparativo de autoestima y habilidades sociales en pacientes adictos de una comunidad terapéutica

2005 ◽  
Vol 5 (1) ◽  
Author(s):  
Alejandra Cattan
Keyword(s):  
Social Skills ◽  
Descriptive Study ◽  
Self Esteem ◽  
The Self ◽  
Community Center ◽  
Drug Addicts ◽  
The Social ◽  
Low Levels ◽  
Admission Group ◽  
Selection Of

La presente investigación tiene como objetivo describir, analizar y comparar la autoestima y las habilidades sociales de un grupo de jóvenes, entre 17 y 24 años de edad, consumidores de drogas que se encuentran realizando tratamiento en la comunidad terapéutica Aylén (Argentina). Es una investigación de tipo descriptiva comparativa, con un diseño de diferencias entre grupos (G1, grupo de admisión) y (G2, grupo de reinserción social). La muestra estuvo conformada por 54 sujetos (25 para grupo de admisión y 29 para el grupo de reinserción social). Los instrumentos utilizados fueron el inventario de Autoestima de Barksdale y la Escala de Habilidades sociales de Goldstein, las cuales fueron adaptadas y validadas para ser aplicadas a la población de estudio. Asimismo, a partir de los procedimientos de validación de estos instrumentos se propusieron para cada uno, nuevos agrupamientos de factores. Los resultados mostraron, bajos niveles de autoestima para ambos grupos y entre niveles bajos y normales de habilidades sociales en cada una de las categorías componentes y el total. Finalmente, no se confirmaron las hipótesis de diferencias significativas en los niveles de autoestima y los niveles de habilidades sociales entre los jóvenes en etapa de admisión y los jóvenes en etapa de reinserción social. AbstractThe objective of the present investigation is to analyze and compare the socials skills and the self-esteem of a group of juveniles between the ages of 17 and 24 years, drug addicts, both under medical treatment in a Community center in Argentina. This is a comparative-descriptive study, with the design of two groups: G1 for admission group and G2 for the reinsertion group. The sample was made of a group of 56 people, 25 for the admission group and 29 for the social reinsertion group. The instruments used were the Goldstein Social Skills Scale and the Self-Esteem Inventory from Barksdale, that were adapted for the use in such case. Also for the use of such instruments, new validation measures were implemented in the selection of the variables. The results showed low levels of self esteem for both groups and between low and normal levels of social skills in each category. Finally, no important differences were founded in the levels of self esteem between the admission group and the social reinsertion period for the juveniles.

scholarly journals Occurrence and Ear Damage of Helicoverpa zea on Transgenic Bacillus thuringiensis Maize in the Field in Texas, U.S. and Its Susceptibility to Vip3A Protein

Toxins ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 102 ◽  
Author(s):  
Fei Yang ◽  
José C. Santiago González ◽  
Jayme Williams ◽  
Donald C. Cook ◽  
Ryan T. Gilreath ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Helicoverpa Zea ◽  
Sustainable Use ◽  
Leaf Tissue ◽  
Corn Earworm ◽  
Laboratory Population ◽  
Bt Maize ◽  
Cry Proteins ◽  
Damage Area ◽  
The U.S

The corn earworm, Helicoverpa zea (Boddie), is a major pest of Bacillus thuringiensis (Bt) maize and cotton in the U.S.. Reduced efficacy of Bt plants expressing Cry1 and Cry2 against H. zea has been reported in some areas of the U.S.. In this study, we evaluated the occurrence and ear damage of H. zea on transgenic Bt maize expressing Cry proteins or a combination of Vip3A and Cry proteins in the field in Texas in 2018. We found that the occurrence of H. zea larvae and the viable kernel damage area on the ear were not different between non-Bt maize and Bt maize expressing Cry1A.105+Cry2Ab2 and Cry1Ab+Cry1F proteins. A total of 67.5% of the pyramided Bt maize expressing Cry1Ab+Cry1F+Vip3A was damaged by 2nd–4th instar larvae of H. zea. Diet bioassays showed that the resistance ratio against Vip3Aa51 for H. zea obtained from Cry1Ab+Cry1F+Vip3A maize was 20.4 compared to a field population collected from Cry1F+Cry1A.105+Cry2Ab2 maize. Leaf tissue bioassays showed that 7-day survivorship on WideStrike3 (Cry1F+Cry1Ac+Vip3A) cotton leaves was significantly higher for the H. zea population collected from Cry1Ab+Cry1F+Vip3A maize than for a Bt-susceptible laboratory population. The results generated from this study suggest that H. zea has evolved practical resistance to Cry1 and Cry2 proteins. Therefore, it is crucial to ensure the sustainable use of the Vip3A technology in Bt maize and cotton.

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