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Torres J, Surya W, Boonserm P. Channel Formation in Cry Toxins: An Alphafold-2 Perspective. Int J Mol Sci 2023; 24:16809. [PMID: 38069132 PMCID: PMC10705909 DOI: 10.3390/ijms242316809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 11/23/2023] [Accepted: 11/24/2023] [Indexed: 12/18/2023] Open
Abstract
Bacillus thuringiensis (Bt) strains produce pore-forming toxins (PFTs) that attack insect pests. Information for pre-pore and pore structures of some of these Bt toxins is available. However, for the three-domain (I-III) crystal (Cry) toxins, the most used Bt toxins in pest control, this crucial information is still missing. In these Cry toxins, biochemical data have shown that 7-helix domain I is involved in insertion in membranes, oligomerization and formation of a channel lined mainly by helix α4, whereas helices α1 to α3 seem to have a dynamic role during insertion. In the case of Cry1Aa, toxic against Manduca sexta larvae, a tetrameric oligomer seems to precede membrane insertion. Given the experimental difficulty in the elucidation of the membrane insertion steps, we used Alphafold-2 (AF2) to shed light on possible oligomeric structural intermediates in the membrane insertion of this toxin. AF2 very accurately (<1 Å RMSD) predicted the crystal monomeric and trimeric structures of Cry1Aa and Cry4Ba. The prediction of a tetramer of Cry1Aa, but not Cry4Ba, produced an 'extended model' where domain I helices α3 and α2b form a continuous helix and where hydrophobic helices α1 and α2 cluster at the tip of the bundle. We hypothesize that this represents an intermediate that binds the membrane and precedes α4/α5 hairpin insertion, together with helices α6 and α7. Another Cry1Aa tetrameric model was predicted after deleting helices α1 to α3, where domain I produced a central cavity consistent with an ion channel, lined by polar and charged residues in helix α4. We propose that this second model corresponds to the 'membrane-inserted' structure. AF2 also predicted larger α4/α5 hairpin n-mers (14 ≤n ≤ 17) with high confidence, which formed even larger (~5 nm) pores. The plausibility of these models is discussed in the context of available experimental data and current paradigms.
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Affiliation(s)
- Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Panadda Boonserm
- Institute of Molecular Biosciences, Mahidol University, Salaya, Phuttamonthon, Nakhon Pathom 73170, Thailand;
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2
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Suárez-Barrera MO, Herrera-Pineda DF, Rondón-Villarreal P, Pinzón-Reyes EH, Ochoa R, Visser L, Rueda-Forero NJ. Toxic Determination of Cry11 Mutated Proteins Obtained Using Rational Design and Its Computational Analysis. Int J Mol Sci 2023; 24:9079. [PMID: 37240424 PMCID: PMC10219489 DOI: 10.3390/ijms24109079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 05/08/2023] [Accepted: 05/16/2023] [Indexed: 05/28/2023] Open
Abstract
Cry11 proteins are toxic to Aedes aegypti, the vector of dengue, chikungunya, and Zika viruses. Cry11Aa and Cry11Bb are protoxins, which when activated present their active-toxin form in two fragments between 30 and 35 kDa respectively. Previous studies conducted with Cry11Aa and Cry11Bb genes using DNA shuffling generated variant 8, which presented a deletion in the first 73 amino acids and one at position 572 and 9 substitutions including L553F and L556W. In this study, variant 8 mutants were constructed using site-directed mutagenesis, resulting in conversion of phenylalanine (F) and tryptophan (W) to leucine (L) at positions 553 and 556, respectively, producing the mutants 8F553L, 8W556L, and 8F553L/8W556L. Additionally, two mutants, A92D and C157R, derived from Cry11Bb were also generated. The proteins were expressed in the non-crystal strain BMB171 of Bacillus thuringiensis and subjected to median-lethal concentration (LC50) tests on first-instar larvae of A. aegypti. LC50 analysis showed that the 8F553L, 8W556L, 8F553L/8W556L, and C157R variants lost their toxic activity (>500 ng·mL-1), whereas the A92D protein presented a loss of toxicity of 11.4 times that of Cry11Bb. Cytotoxicity assays performed using variant 8, 8W556L and the controls Cry11Aa, Cry11Bb, and Cry-negative BMB171 on the colorectal cancer cell line SW480 reported 30-50% of cellular viability except for BMB171. Molecular dynamic simulations performed to identify whether the mutations at positions 553 and 556 were related to the stability and rigidity of the functional tertiary structure (domain III) of the Cry11Aa protein and variant 8 showed the importance of these mutations in specific regions for the toxic activity of Cry11 against A. aegypti. This generates pertinent knowledge for the design of Cry11 proteins and their biotechnological applications in vector-borne disease control and cancer cell lines.
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Affiliation(s)
- Miguel O. Suárez-Barrera
- Facultad de Ciencias Médicas y de la Salud, Instituto de Investigación Masira, Universidad de Santander, Bucaramanga 680003, Colombia; (M.O.S.-B.); (D.F.H.-P.); (P.R.-V.); (E.H.P.-R.)
- Max Planck Tandem Group in Nanobioengineering, Institute of Chemistry, Faculty of Natural and Exacts Sciences, University of Antioquia, Medellin 050010, Colombia
| | - Diego F. Herrera-Pineda
- Facultad de Ciencias Médicas y de la Salud, Instituto de Investigación Masira, Universidad de Santander, Bucaramanga 680003, Colombia; (M.O.S.-B.); (D.F.H.-P.); (P.R.-V.); (E.H.P.-R.)
| | - Paola Rondón-Villarreal
- Facultad de Ciencias Médicas y de la Salud, Instituto de Investigación Masira, Universidad de Santander, Bucaramanga 680003, Colombia; (M.O.S.-B.); (D.F.H.-P.); (P.R.-V.); (E.H.P.-R.)
| | - Efraín Hernando Pinzón-Reyes
- Facultad de Ciencias Médicas y de la Salud, Instituto de Investigación Masira, Universidad de Santander, Bucaramanga 680003, Colombia; (M.O.S.-B.); (D.F.H.-P.); (P.R.-V.); (E.H.P.-R.)
- Centro de Bioinformática, Simulación y Modelado (CBSM), School of Bioinformatic, Universidad de Talca, Talca 3465548, Chile
| | - Rodrigo Ochoa
- Biophysics of Tropical Diseases, Max Planck Tandem Group, University of Antioquia, Medellin 050010, Colombia;
| | - Lydia Visser
- Department of Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, 9701 Groningen, The Netherlands;
| | - Nohora Juliana Rueda-Forero
- Facultad de Ciencias Médicas y de la Salud, Instituto de Investigación Masira, Universidad de Santander, Bucaramanga 680003, Colombia; (M.O.S.-B.); (D.F.H.-P.); (P.R.-V.); (E.H.P.-R.)
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3
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eCry1Gb.1Ig, A Novel Chimeric Cry Protein with High Efficacy against Multiple Fall Armyworm ( Spodoptera frugiperda) Strains Resistant to Different GM Traits. Toxins (Basel) 2022; 14:toxins14120852. [PMID: 36548749 PMCID: PMC9785401 DOI: 10.3390/toxins14120852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 11/24/2022] [Accepted: 11/26/2022] [Indexed: 12/12/2022] Open
Abstract
Spodoptera frugiperda (fall armyworm, FAW) is one of the most devastating insect pests to corn and soybean production in the Americas and is rapidly expanding its range worldwide. It is known to be hard to control either by chemical insecticide applications or by GM. Although the use of GM traits can be an effective way to control this pest, it is very rare to find native insecticidal proteins that provide the necessary level of FAW control in crop fields where FAW pressure and damage are high. Insecticidal Cry proteins sourced from Bacillus thuringiensis have been heavily utilized in the development of crops with GM traits; however, it is increasingly difficult to identify Cry proteins with unique modes of action. Protein engineering via a phylogenetically guided Cry protein domain swapping approach enabled us to discover novel chimeric Cry proteins engineered from inactive parent sequences. Some of these chimeras show excellent efficacy against key biotypes of FAW from Brazil and North America. In this study, we characterized a Cry-based chimera eCry1Gb.1Ig that is a very potent FAW toxin. eCry1Gb.1Ig showed high efficacy against multiple FAW strains that are resistant to various traits, including Cry1Fa, Vip3Aa and Cry1A.105/Cry2Ab. These results clearly indicate that the FAW strains resistant to Cry1Fa, Vip3Aa or Cry1A.105/Cry2Ab demonstrate no cross-resistance to eCry1Gb.1Ig and strongly suggest that eCry1Gb.1Ig acts through a novel mode of action compared to the existing traits. In addition to its FAW activity, eCry1Gb.1Ig has also been shown to control Chrysodeixis includens (soybean looper, SBL) and Anticarsia gemmatalis (velvetbean caterpillar, VBC), which are significant pests of soybean. When eCry1Gb.1Ig was introduced into corn and soybean crops, transgenic events showed strong efficacy against FAW, SBL and VBC, but no adverse plant phenotypes. This suggests that the in planta expression of the eCry1Gb.1Ig protein does not compromise plant growth or reproduction and can protect plants from FAW-related damage. Therefore, this valuable discovery will provide a differentiating FAW control trait that will give growers another tool to help them reduce yield loss due to FAW.
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Kouadio JL, Zheng M, Aikins M, Duda D, Duff S, Chen D, Zhang J, Milligan J, Taylor C, Mamanella P, Rydel T, Kessenich C, Panosian T, Yin Y, Moar W, Giddings K, Park Y, Jerga A, Haas J. Structural and functional insights into the first Bacillus thuringiensis vegetative insecticidal protein of the Vpb4 fold, active against western corn rootworm. PLoS One 2021; 16:e0260532. [PMID: 34928980 PMCID: PMC8687597 DOI: 10.1371/journal.pone.0260532] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 11/11/2021] [Indexed: 01/09/2023] Open
Abstract
The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is a major maize pest in the United States causing significant economic loss. The emergence of field-evolved resistant WCR to Bacillus thuringiensis (Bt) traits has prompted the need to discover and deploy new insecticidal proteins in transgenic maize. In the current study we determined the crystal structure and mode of action (MOA) of the Vpb4Da2 protein (formerly known as Vip4Da2) from Bt, the first identified insecticidal Vpb4 protein with commercial level control against WCR. The Vpb4Da2 structure exhibits a six-domain architecture mainly comprised of antiparallel β-sheets organized into β-sandwich layers. The amino-terminal domains 1-3 of the protein share structural homology with the protective antigen (PA) PA14 domain and encompass a long β-pore forming loop as in the clostridial binary-toxB module. Domains 5 and 6 at the carboxyl-terminal half of Vpb4Da2 are unique as this extension is not observed in PA or any other structurally-related protein other than Vpb4 homologs. These unique Vpb4 domains adopt the topologies of carbohydrate-binding modules known to participate in receptor-recognition. Functional assessment of Vpb4Da2 suggests that domains 4-6 comprise the WCR receptor binding region and are key in conferring the observed insecticidal activity against WCR. The current structural analysis was complemented by in vitro and in vivo characterizations, including immuno-histochemistry, demonstrating that Vpb4Da2 follows a MOA that is consistent with well-characterized 3-domain Bt insecticidal proteins despite significant structural differences.
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Affiliation(s)
| | - Meiying Zheng
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Michael Aikins
- Department of Entomology, Kansas State University, Manhattan, Kansas, United States of America
| | - David Duda
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Stephen Duff
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Danqi Chen
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Jun Zhang
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Jason Milligan
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Christina Taylor
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | | | - Timothy Rydel
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Colton Kessenich
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Timothy Panosian
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Yong Yin
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - William Moar
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Kara Giddings
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Yoonseong Park
- Department of Entomology, Kansas State University, Manhattan, Kansas, United States of America
| | - Agoston Jerga
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Jeffrey Haas
- Bayer Crop Science, Chesterfield, Missouri, United States of America
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5
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Tetreau G, Andreeva EA, Banneville AS, De Zitter E, Colletier JP. Can (We Make) Bacillus thuringiensis Crystallize More Than Its Toxins? Toxins (Basel) 2021; 13:toxins13070441. [PMID: 34206749 PMCID: PMC8309801 DOI: 10.3390/toxins13070441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 06/22/2021] [Accepted: 06/24/2021] [Indexed: 11/16/2022] Open
Abstract
The development of finely tuned and reliable crystallization processes to obtain crystalline formulations of proteins has received growing interest from different scientific fields, including toxinology and structural biology, as well as from industry, notably for biotechnological and medical applications. As a natural crystal-making bacterium, Bacillus thuringiensis (Bt) has evolved through millions of years to produce hundreds of highly structurally diverse pesticidal proteins as micrometer-sized crystals. The long-term stability of Bt protein crystals in aqueous environments and their specific and controlled dissolution are characteristics that are particularly sought after. In this article, we explore whether the crystallization machinery of Bt can be hijacked as a means to produce (micro)crystalline formulations of proteins for three different applications: (i) to develop new bioinsecticidal formulations based on rationally improved crystalline toxins, (ii) to functionalize crystals with specific characteristics for biotechnological and medical applications, and (iii) to produce microcrystals of custom proteins for structural biology. By developing the needs of these different fields to figure out if and how Bt could meet each specific requirement, we discuss the already published and/or patented attempts and provide guidelines for future investigations in some underexplored yet promising domains.
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6
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Chen D, Moar WJ, Jerga A, Gowda A, Milligan JS, Bretsynder EC, Rydel TJ, Baum JA, Semeao A, Fu X, Guzov V, Gabbert K, Head GP, Haas JA. Bacillus thuringiensis chimeric proteins Cry1A.2 and Cry1B.2 to control soybean lepidopteran pests: New domain combinations enhance insecticidal spectrum of activity and novel receptor contributions. PLoS One 2021; 16:e0249150. [PMID: 34138865 PMCID: PMC8211277 DOI: 10.1371/journal.pone.0249150] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 02/07/2021] [Indexed: 01/08/2023] Open
Abstract
Two new chimeric Bacillus thuringiensis (Bt) proteins, Cry1A.2 and Cry1B.2, were constructed using specific domains, which provide insecticidal activity against key lepidopteran soybean pests while minimizing receptor overlaps between themselves, current, and soon to be commercialized plant incorporated protectants (PIP's) in soybean. Results from insect diet bioassays demonstrate that the recombinant Cry1A.2 and Cry1B.2 are toxic to soybean looper (SBL) Chrysodeixis includens Walker, velvetbean caterpillar (VBC) Anticarsia gemmatalis Hubner, southern armyworm (SAW) Spodoptera eridania, and black armyworm (BLAW) Spodoptera cosmioides with LC50 values < 3,448 ng/cm2. Cry1B.2 is of moderate activity with significant mortality and stunting at > 3,448 ng/cm2, while Cry1A.2 lacks toxicity against old-world bollworm (OWB) Helicoverpa armigera. Results from disabled insecticidal protein (DIP) bioassays suggest that receptor utilization of Cry1A.2 and Cry1B.2 proteins are distinct from each other and from current, and yet to be commercially available, Bt proteins in soy such as Cry1Ac, Cry1A.105, Cry1F.842, Cry2Ab2 and Vip3A. However, as Cry1A.2 contains a domain common to at least one commercial soybean Bt protein, resistance to this common domain in a current commercial soybean Bt protein could possibly confer at least partial cross resistance to Cry1A2. Therefore, Cry1A.2 and Cry1B.2 should provide two new tools for controlling many of the major soybean insect pests described above.
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Affiliation(s)
- Danqi Chen
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - William J. Moar
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Agoston Jerga
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Anilkumar Gowda
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Jason S. Milligan
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | | | - Timothy J. Rydel
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - James A. Baum
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Altair Semeao
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Xiaoran Fu
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Victor Guzov
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Karen Gabbert
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Graham P. Head
- Bayer Crop Science, Chesterfield, Missouri, United States of America
| | - Jeffrey A. Haas
- Bayer Crop Science, Chesterfield, Missouri, United States of America
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7
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Vílchez S. Making 3D-Cry Toxin Mutants: Much More Than a Tool of Understanding Toxins Mechanism of Action. Toxins (Basel) 2020; 12:toxins12090600. [PMID: 32948025 PMCID: PMC7551160 DOI: 10.3390/toxins12090600] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 08/15/2020] [Accepted: 08/20/2020] [Indexed: 12/21/2022] Open
Abstract
3D-Cry toxins, produced by the entomopathogenic bacterium Bacillus thuringiensis, have been extensively mutated in order to elucidate their elegant and complex mechanism of action necessary to kill susceptible insects. Together with the study of the resistant insects, 3D-Cry toxin mutants represent one of the pillars to understanding how these toxins exert their activity on their host. The principle is simple, if an amino acid is involved and essential in the mechanism of action, when substituted, the activity of the toxin will be diminished. However, some of the constructed 3D-Cry toxin mutants have shown an enhanced activity against their target insects compared to the parental toxins, suggesting that it is possible to produce novel versions of the natural toxins with an improved performance in the laboratory. In this report, all mutants with an enhanced activity obtained by accident in mutagenesis studies, together with all the variants obtained by rational design or by directed mutagenesis, were compiled. A description of the improved mutants was made considering their historical context and the parallel development of the protein engineering techniques that have been used to obtain them. This report demonstrates that artificial 3D-Cry toxins made in laboratories are a real alternative to natural toxins.
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Affiliation(s)
- Susana Vílchez
- Institute of Biotechnology, Department of Biochemistry and Molecular Biology I, Faculty of Science, University of Granada, 18071 Granada, Spain
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8
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Insecticidal Activity of Bacillus thuringiensis Proteins Against Coleopteran Pests. Toxins (Basel) 2020; 12:toxins12070430. [PMID: 32610662 PMCID: PMC7404982 DOI: 10.3390/toxins12070430] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 06/25/2020] [Accepted: 06/25/2020] [Indexed: 12/17/2022] Open
Abstract
Bacillus thuringiensis is the most successful microbial insecticide agent and its proteins have been studied for many years due to its toxicity against insects mainly belonging to the orders Lepidoptera, Diptera and Coleoptera, which are pests of agro-forestry and medical-veterinary interest. However, studies on the interactions between this bacterium and the insect species classified in the order Coleoptera are more limited when compared to other insect orders. To date, 45 Cry proteins, 2 Cyt proteins, 11 Vip proteins, and 2 Sip proteins have been reported with activity against coleopteran species. A number of these proteins have been successfully used in some insecticidal formulations and in the construction of transgenic crops to provide protection against main beetle pests. In this review, we provide an update on the activity of Bt toxins against coleopteran insects, as well as specific information about the structure and mode of action of coleopteran Bt proteins.
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Liu Y, Zhou Z, Wang Z, Zhong B, Shu C, Zhang J. Replacement of loop2 and 3 of Cry1Ai in domain II affects specificity to the economically important insect Bombyx mori. J Invertebr Pathol 2019; 169:107296. [PMID: 31778713 DOI: 10.1016/j.jip.2019.107296] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 11/22/2019] [Accepted: 11/24/2019] [Indexed: 11/28/2022]
Abstract
Bacillus thuringiensis Cry1Ai belongs to three-domain Cry toxins and only shows growth inhibition effects against the agricultural pest Helicoverpa armigera, although it exhibits high toxicity against the non-target insect Bombyx mori. In previous studies, loop2 and loop3 on domain II from Cry1Ah were found to be related to binding and high toxicity against H. armigera. However, toxicity for B. mori of Cry1Ai-h-loop2, obtained by replacing loop 2 from Cry1Ah into Cry1Ai, was not modified. In this study, to further characterize the role of loop2 and loop3 in Cry1Ai, all of the amino acids in these two loops were substituted with the same amount of alanine residues. The Cry1Ai-loop3 mutant exhibited significantly lower toxicity against B. mori, but the toxicity of the loop2 mutant was not significantly changed. Furthermore, the double-exchange mutant Cry1Ai-h-loop2&3, replacing loop2 and loop3 from Cry1Ah into Cry1Ai, showed decreased toxicity against B. mori related to Cry1Ai. In addition, we found that the binding affinity of Cry1Ai-h-loop2&3 with brush border membrane vesicles (BBMVs) from the midgut of B. mori was lower than that of Cry1Ai, which correlates with the reduced toxicity.
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Affiliation(s)
- Yuxiao Liu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Zishan Zhou
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Zeyu Wang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Boxiong Zhong
- College of Animal Sciences, Zhejiang University, Hangzhou 310058, China
| | - Changlong Shu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
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10
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BenFarhat-Touzri D, Jemli S, Driss F, Tounsi S. Molecular and structural characterization of a novel Cry1D toxin from Bacillus thuringiensis with high toxicity to Spodoptera littoralis (Lepidoptera: Noctuidae). Int J Biol Macromol 2019; 126:969-976. [PMID: 30593807 DOI: 10.1016/j.ijbiomac.2018.12.175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 12/08/2018] [Accepted: 12/19/2018] [Indexed: 10/27/2022]
Abstract
The investigation of new Bacillus thuringiensis (Bt) insecticidal proteins (Cry) with specific toxicity is one of the alternative measures used for Lepidopteran pest control. In the present study, a new Cry toxin was identified from a promising Bt strain BLB250 which was previously selected for its high toxicity against Spodoptera littoralis. The corresponding gene, designated cry1D-250, was cloned. It showed an ORF of 3498bp, encoding a protein of 1165 amino acid residues with a putative molecular mass of 132kDa which was confirmed by SDS-PAGE and Western blot analyses. The corresponding toxin named Cry1D-250 showed a higher insecticidal activity towards S. littoralis than Cry1D-133 (LC50 of 224.4ngcm-2) with an LC50 of only 166ngcm-2. Besides to the 65kDa active toxin, proteolysis activation of Cry1D-133 protein with S. littoralis midgut juice generated an extra form of 56kDa, which was the result of a second cleavage. Via activation study and 3D structure analysis, novel substitutions found in the Cry1D-250 protein compared to Cry1D-133 toxin were shown to be involved in the protein stability and toxicity. Therefore, the Cry1D-250 toxin can be considered to be an effective alternative for the control of S. littoralis.
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Affiliation(s)
- Dalel BenFarhat-Touzri
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box. "1177", 3018 Sfax, Tunisia
| | - Sonia Jemli
- Laboratory of Microbial Biotechnology and Enzyme Engineering, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box. "1177", 3018 Sfax, Tunisia
| | - Fatma Driss
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box. "1177", 3018 Sfax, Tunisia.
| | - Slim Tounsi
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box. "1177", 3018 Sfax, Tunisia
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11
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Peña-Cardeña A, Grande R, Sánchez J, Tabashnik BE, Bravo A, Soberón M, Gómez I. The C-terminal protoxin region of Bacillus thuringiensis Cry1Ab toxin has a functional role in binding to GPI-anchored receptors in the insect midgut. J Biol Chem 2018; 293:20263-20272. [PMID: 30385510 PMCID: PMC6311509 DOI: 10.1074/jbc.ra118.005101] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 10/15/2018] [Indexed: 12/20/2022] Open
Abstract
Bacillus thuringiensis Cry toxins are used worldwide for controlling insects. Cry1Ab is produced as a 130-kDa protoxin that is activated by proteolytic removal of an inert 500 amino-acid-long C-terminal region, enabling the activated toxin to bind to insect midgut receptor proteins, leading to its membrane insertion and pore formation. It has been proposed that the C-terminal region is only involved in toxin crystallization, but its role in receptor binding is undefined. Here we show that the C-terminal region of Cry1Ab protoxin provides additional binding sites for alkaline phosphatase (ALP) and aminopeptidase N (APN) insect receptors. ELISA, ligand blot, surface plasmon resonance, and pulldown assays revealed that the Cry1Ab C-terminal region binds to both ALP and APN but not to cadherin. Thus, the C-terminal region provided a higher binding affinity of the protoxin to the gut membrane that correlated with higher toxicity of protoxin than activated toxin. Moreover, Cry1Ab domain II loop 2 or 3 mutations reduced binding of the protoxin to cadherin but not to ALP or APN, supporting the idea that protoxins have additional binding sites. These results imply that two different regions mediate the binding of Cry1Ab protoxin to membrane receptors, one located in domain II-III of the toxin and another in its C-terminal region, suggesting an active role of the C-terminal protoxin fragment in the mode of action of Cry toxins. These results suggest that future manipulations of the C-terminal protoxin region could alter the specificity and increase the toxicity of B. thuringiensis proteins.
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Affiliation(s)
| | - Ricardo Grande
- Unidad de Secuenciación Masiva y Bioinformática, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad 2001, Colonia Chamilpa, Cuernavaca, Morelos 62210, México and
| | - Jorge Sánchez
- From the Departamento de Microbiología Molecular and
| | - Bruce E Tabashnik
- the Department of Entomology, University of Arizona, Tucson, Arizona 85721
| | | | - Mario Soberón
- From the Departamento de Microbiología Molecular and
| | - Isabel Gómez
- From the Departamento de Microbiología Molecular and.
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Enhancement of Bacillus thuringiensis Cry1Ab and Cry1Fa Toxicity to Spodoptera frugiperda by Domain III Mutations Indicates There Are Two Limiting Steps in Toxicity as Defined by Receptor Binding and Protein Stability. Appl Environ Microbiol 2018; 84:AEM.01393-18. [PMID: 30097439 DOI: 10.1128/aem.01393-18] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 08/01/2018] [Indexed: 11/20/2022] Open
Abstract
Bacillus thuringiensis Cry1Ab and Cry1Fa toxins are environmentally safe insecticides that control important insect pests. Spodoptera frugiperda is an important maize pest that shows low susceptibility to Cry1A toxins, in contrast to Cry1Fa, which is highly active against this pest and is used in transgenic maize for S. frugiperda control. The β16 region from domain III of Cry1Ab has been shown to be involved in interactions with receptors such as alkaline phosphatase (ALP) or aminopeptidase (APN) in different lepidopteran insects. Alanine-scanning mutagenesis of amino acids of Cry1Ab β16 (509STLRVN514) revealed that certain β16 mutations, such as N514A, resulted in increased toxicity of Cry1Ab for S. frugiperda without affecting the toxicity for other lepidopteran larvae, such as Manduca sexta larvae. Exhaustive mutagenesis of N514 was performed, showing that the Cry1Ab N514F, N514H, N514K, N514L, N514Q, and N514S mutations increased the toxicity toward S. frugiperda A corresponding mutation was constructed in Cry1Fa (N507A). Toxicity assays of wild-type and mutant toxins (Cry1Ab, Cry1AbN514A, Cry1AbN514F, Cry1Fa, and Cry1FaN507A) against four S. frugiperda populations from Mexico and one from Brazil revealed that Cry1AbN514A and Cry1FaN507A consistently showed 3- to 18-fold increased toxicity against four of five S. frugiperda populations. In contrast, Cry1AbN514F showed increased toxicity in only two of the S. frugiperda populations analyzed. The mutants Cry1AbN514A and Cry1AbN514F showed greater stability to midgut protease treatment. In addition, binding analysis of the Cry1Ab mutants showed that the increased toxicity correlated with increased binding to brush border membrane vesicles and increased binding affinity for S. frugiperda ALP, APN, and cadherin receptors.IMPORTANCE Spodoptera frugiperda is the main maize pest in South and North America and also is an invasive pest in different African countries. However, it is poorly controlled by Bacillus thuringiensis Cry1A toxins expressed in transgenic crops, which effectively control other lepidopteran pests. In contrast, maize expressing Cry1Fa is effective in the control of S. frugiperda, although its effectiveness is being lost due to resistance evolution. Some of the Cry1Ab domain III mutants characterized here show enhanced toxicity for S. frugiperda without loss of toxicity to Manduca sexta Thus, these Cry1Ab mutants could provide useful engineered toxins that, along with other Cry toxins, would be useful for developing transgenic maize expressing stacked proteins for the effective control of S. frugiperda and other lepidopteran pests in the field.
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Martínez-Solís M, Pinos D, Endo H, Portugal L, Sato R, Ferré J, Herrero S, Hernández-Martínez P. Role of Bacillus thuringiensis Cry1A toxins domains in the binding to the ABCC2 receptor from Spodoptera exigua. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2018; 101:47-56. [PMID: 30077769 DOI: 10.1016/j.ibmb.2018.07.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 07/24/2018] [Accepted: 07/29/2018] [Indexed: 06/08/2023]
Abstract
Cry proteins from Bacillus thuringiensis (Bt) have been used to control insect pests either as formulated sprays or as in Bt-crops. However, field-evolved resistance to Bt proteins is threatening the long-term use of Bt products. The SeABCC2 locus has been genetically linked to resistance to a Bt bioinsecticide (Xentari™) in Spodoptera exigua (a mutation producing a truncated form of the transporter lacking an ATP binding domain was found in the resistant insects). Here, we investigated the role of SeABCC2 in the mode of action of Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ca, and two Cry1A-1Ca hybrids by expressing the receptor in Sf21 and HEK293T cell lines. Cell toxicity assays showed that Sf21 cells expressing SeABCC2 become susceptible to Cry1A proteins. HEK293T cells expressing the transporter were found susceptible to Cry1A proteins but not to Cry1Ca. The results with the Cry1A-1Ca hybrids suggest that domain II from Cry1Ab/c is crucial for the toxicity to Sf21 cells, whereas domain III from Cry1Aa/b is crucial for the toxicity to HEK293T cells. Binding assays showed that the Cry1Ac binding is of high affinity and specific to cells expressing the SeABCC2 transporter. Heterologous competition experiments support a model in which domain II of Cry1Ab/c has a common binding site in the SeABCC2 protein, whereas domain III of Cry1Aa/b binds to a different binding site in the SeABCC2 protein.
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Affiliation(s)
- María Martínez-Solís
- ERI de Biotecnología y Biomedicina (BIOTECMED), Department of Genetics, Universitat de València, 46100 Burjassot, Spain
| | - Daniel Pinos
- ERI de Biotecnología y Biomedicina (BIOTECMED), Department of Genetics, Universitat de València, 46100 Burjassot, Spain
| | - Haruka Endo
- Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Leivi Portugal
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Ryoichi Sato
- Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Juan Ferré
- ERI de Biotecnología y Biomedicina (BIOTECMED), Department of Genetics, Universitat de València, 46100 Burjassot, Spain
| | - Salvador Herrero
- ERI de Biotecnología y Biomedicina (BIOTECMED), Department of Genetics, Universitat de València, 46100 Burjassot, Spain
| | - Patricia Hernández-Martínez
- ERI de Biotecnología y Biomedicina (BIOTECMED), Department of Genetics, Universitat de València, 46100 Burjassot, Spain.
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Expression of hybrid fusion protein (Cry1Ac::ASAL) in transgenic rice plants imparts resistance against multiple insect pests. Sci Rep 2018; 8:8458. [PMID: 29855556 PMCID: PMC5981619 DOI: 10.1038/s41598-018-26881-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 05/21/2018] [Indexed: 12/18/2022] Open
Abstract
To evolve rice varieties resistant to different groups of insect pests a fusion gene, comprising DI and DII domains of Bt Cry1Ac and carbohydrate binding domain of garlic lectin (ASAL), was constructed. Transgenic rice lines were generated and evaluated to assess the efficacy of Cry1Ac::ASAL fusion protein against three major pests, viz., yellow stem borer (YSB), leaf folder (LF) and brown planthopper (BPH). Molecular analyses of transgenic plants revealed stable integration and expression of the fusion gene. In planta insect bioassays on transgenics disclosed enhanced levels of resistance compared to the control plants. High insect mortality of YSB, LF and BPH was observed on transgenics compared to that of control plants. Furthermore, honeydew assays revealed significant decreases in the feeding ability of BPH on transgenic plants as compared to the controls. Ligand blot analysis, using BPH insects fed on cry1Ac::asal transgenic rice plants, revealed a modified receptor protein-binding pattern owing to its ability to bind to additional receptors in insects. The overall results authenticate that Cry1Ac::ASAL protein is endowed with remarkable entomotoxic effects against major lepidopteran and hemipteran insects. As such, the fusion gene appears promising and can be introduced into various other crops to control multiple insect pests.
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Sellami S, Jemli S, Abdelmalek N, Cherif M, Abdelkefi-Mesrati L, Tounsi S, Jamoussi K. A novel Vip3Aa16-Cry1Ac chimera toxin: Enhancement of toxicity against Ephestia kuehniella, structural study and molecular docking. Int J Biol Macromol 2018; 117:752-761. [PMID: 29800666 DOI: 10.1016/j.ijbiomac.2018.05.161] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 05/14/2018] [Accepted: 05/22/2018] [Indexed: 10/16/2022]
Abstract
Bacillus thuringiensis Vip3A protein has been widely used for crop protection and for delay resistance to existing insecticidal Cry toxins. During current study, a fusion between vip3Aa16 and the toxic core sequence of cry1Ac was constructed in pHT Blue plasmid. Vip3Aa16-Cry1Ac protein was expressed in the supernatant of B. thuringiensis with a size of about 150 kDa. Bioassays tested on Ephestia kuehniella showed that the use of the chimera toxin as biopesticide improved the toxicity to reach 90% ± 2 with an enhancement of 20% compared to the single Vip3Aa16 protein. The findings indicated that the fusion protein design opens new ways to enhance Vip3A toxicity against lepidopteran species and could avoiding insect tolerance of B. thuringiensis delta-endotoxins. Through computational study, we have predicted for the first time the whole 3D structure of a Vip3A toxin. We showed that Vip3Aa16 structure is composed by three domains like Cry toxins: an N-terminal domain containing hemolysin like fold as well as two others Carbohydrate Binding Module (CBM)-like domains. Molecular docking analysis of the chimera toxin and the single Vip3Aa16 protein against specific insect receptors revealed that residues of CBM like domains are clearly involved in the binding of the toxin to receptors.
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Affiliation(s)
- Sameh Sellami
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
| | - Sonia Jemli
- Laboratory of Microbial Biotechnology and Enzymes Engineering, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Nouha Abdelmalek
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Marwa Cherif
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Lobna Abdelkefi-Mesrati
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Slim Tounsi
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Kais Jamoussi
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
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Domain III of Cry1Ac Is Critical to Binding and Toxicity against Soybean Looper (Chrysodeixis includens) but Not to Velvetbean Caterpillar (Anticarsia gemmatalis). Toxins (Basel) 2018; 10:toxins10030095. [PMID: 29495466 PMCID: PMC5869383 DOI: 10.3390/toxins10030095] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Revised: 02/13/2018] [Accepted: 02/22/2018] [Indexed: 01/10/2023] Open
Abstract
Insecticidal proteins Cry1Ac and Cry2Ac7 from the bacterium Bacillus thuringiensis (Bt) belong to the three-domain family of Bt toxins. Commercial transgenic soybean hybrids produce Cry1Ac to control the larvae of the soybean looper (Chrysodeixis includens) and the velvet bean caterpillar (Anticarsia gemmatalis). The specificity of Cry1Ac is determined by loops extending from domain II and regions of domain III in the three-dimensional structure of the toxin. In this study, we constructed a hybrid toxin (H1.2Ac) containing domains I and II of Cry1Ac and domain III of Cry2Ac7, in an attempt to obtain a protein with enhanced toxicity compared to parental toxins. Bioassays with H1.2Ac revealed toxicity against the larvae of A. gemmatalis but not against C. includens. Saturation binding assays with radiolabeled toxins and midgut brush border membrane vesicles demonstrated no specific H1.2Ac binding to C. includens, while binding in A. gemmatalis was specific and saturable. Results from competition binding assays supported the finding that Cry1Ac specificity against A. gemmatalis is mainly dictated by domain II. Taken together, these distinct interactions with binding sites may help explain the differential susceptibility to Cry1Ac in C. includens and A. gemmatalis, and guide the design of improved toxins against soybean pests.
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17
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Using phage display technology to obtain Crybodies active against non-target insects. Sci Rep 2017; 7:14922. [PMID: 29097681 PMCID: PMC5668233 DOI: 10.1038/s41598-017-09384-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 07/26/2017] [Indexed: 11/09/2022] Open
Abstract
The insecticidal Cry toxins produced by Bacillus thuringiensis (Bt) are increasingly important in the biological control of insect pests and vectors of human disease. Markets for Bt products and transgenic plants expressing their toxins are driven by their specificity, safety and the move away from chemical control agents. However, the high specificity of Cry toxins can also prove to be a limitation when there is no known Cry toxin active against a particular target. Novel activities can be discovered by screening natural Bt isolates or through modifications of the Cry proteins. Here we demonstrate the use of λ-phage displaying Cry1Aa13 toxin variants modified in domain II loop 2 (Crybodies) to select retargeted toxins. Through biopanning using gut tissue from larvae of the non-target insect Aedes aegypti, we isolated a number of phage for further testing. Two of the overexpressed Cry toxin variants showed significant activity against A. aegypti larvae while another induced mortality at the pupal stage. We present the first report of the use of phage display to identify novel activities toward insects from distant taxonomic Orders and establish this technology based on the use of Crybodies as a powerful tool for developing tailor-made insecticides against new target insects.
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18
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Shah JV, Yadav R, Ingle SS. Engineered Cry1Ac-Cry9Aa hybrid Bacillus thuringiensis delta-endotoxin with improved insecticidal activity against Helicoverpa armigera. Arch Microbiol 2017; 199:1069-1075. [PMID: 28685236 DOI: 10.1007/s00203-017-1407-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Revised: 04/14/2017] [Accepted: 06/28/2017] [Indexed: 10/19/2022]
Abstract
Recombinant Bt construct was prepared by exchange of pore forming domain I with cry1Ac to cry9Aa gene by overlap extension PCR (OE-PCR) technique. Construction of cry1Ac-cry9Aa was accomplished by six base pair homology at 3' ends of PCR products of domain I of cry1Ac and domain II and III of cry9Aa. The recombinant toxin was also modified by deletion of N-terminal alpha helix-1 of recombinant toxin. Both Cry toxins were expressed in E. coli BL21(DE3) plysS and purified by His-tag purification. Upon insect bioassay analysis against devastating crop pest Helicoverpa armigera, toxicity of recombinant toxin was found around fivefold higher than native Cry1Ac while alpha helix-1 deleted N-terminal modified toxin did not resulted in significant increase in toxicity. The recombinant Cry toxins such as Cry1Ac-Cry9Aa and Cry1Ac-Cry9AaMod may be used for insect pest control.
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Affiliation(s)
- Jigar V Shah
- Ground Floor Lab, Department of Microbiology and Biotechnology Centre, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, India
| | - Rakeshkumar Yadav
- Ground Floor Lab, Department of Microbiology and Biotechnology Centre, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, India
| | - Sanjay S Ingle
- Ground Floor Lab, Department of Microbiology and Biotechnology Centre, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, India.
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Jurat-Fuentes JL, Crickmore N. Specificity determinants for Cry insecticidal proteins: Insights from their mode of action. J Invertebr Pathol 2017; 142:5-10. [DOI: 10.1016/j.jip.2016.07.018] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 06/02/2016] [Accepted: 07/28/2016] [Indexed: 12/17/2022]
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20
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Radosavljevic J, Naimov S. Toxicity of Bacillus thuringiensis (L.) Cry proteins against summer fruit tortrix (Adoxophyes orana - Fischer von Rösslerstamm). J Invertebr Pathol 2016; 138:63-5. [PMID: 27311897 DOI: 10.1016/j.jip.2016.06.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 06/10/2016] [Accepted: 06/13/2016] [Indexed: 10/21/2022]
Abstract
The activity of seven Cry1, one Cry9 and one hybrid Cry1 protoxins against neonate larvae of summer fruit tortrix (Adoxophyes orana - Fischer von Rösslerstamm) has been investigated. Cry1Ia is identified as the most toxic protein, followed by Cry1Aa and Cry1Ac. Cry1Ca, Cry1Cb, Cry1Da and Cry1Fa were less active, while SN19 (Cry1 hybrid protein with domain composition 1Ba/1Ia/1Ba) and Cry9Aa exhibited negligible toxicity against A. orana. In vitro trypsin-activated Cry1Ac is still less active than Cry1Ia protoxin, suggesting that toxicity of Cry1Ia is most probably due to more complex differences in further downstream processing, toxin-receptor interactions and pore formation in A. orana's midgut epithelium.
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Affiliation(s)
- Jelena Radosavljevic
- Department of Biochemistry, Faculty of Chemistry, Studentski trg 12, 11000 Belgrade, Serbia; Department of Plant Physiology and Molecular Biology, Faculty of Biology, University of Plovdiv "Paisii Hilendarski", Tzar Asen 24, 4000 Plovdiv, Bulgaria.
| | - Samir Naimov
- Department of Plant Physiology and Molecular Biology, Faculty of Biology, University of Plovdiv "Paisii Hilendarski", Tzar Asen 24, 4000 Plovdiv, Bulgaria
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Pitschmann V, Hon Z. Military Importance of Natural Toxins and Their Analogs. Molecules 2016; 21:molecules21050556. [PMID: 27136512 PMCID: PMC6273326 DOI: 10.3390/molecules21050556] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 04/10/2016] [Accepted: 04/18/2016] [Indexed: 11/24/2022] Open
Abstract
Toxin weapon research, development, production and the ban on its uses is an integral part of international law, with particular attention paid to the protection against these weapons. In spite of this, hazards associated with toxins cannot be completely excluded. Some of these hazards are also pointed out in the present review. The article deals with the characteristics and properties of natural toxins and synthetic analogs potentially constituting the basis of toxin weapons. It briefly describes the history of military research and the use of toxins from distant history up to the present age. With respect to effective disarmament conventions, it mentions certain contemporary concepts of possible toxin applications for military purposes and the protection of public order (suppression of riots); it also briefly refers to the question of terrorism. In addition, it deals with certain traditional as well as modern technologies of the research, synthesis, and use of toxins, which can affect the continuing development of toxin weapons. These are, for example, cases of new toxins from natural sources, their chemical synthesis, production of synthetic analogs, the possibility of using methods of genetic engineering and modern biotechnologies or the possible applications of nanotechnology and certain pharmaceutical methods for the effective transfer of toxins into the organism. The authors evaluate the military importance of toxins based on their comparison with traditional chemical warfare agents. They appeal to the ethics of the scientific work as a principal condition for the prevention of toxin abuse in wars, military conflicts, as well as in non-military attacks.
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Affiliation(s)
- Vladimír Pitschmann
- Faculty of Biomedical Engineering, Czech Technical University in Prague, Sítná sq. 3105, 272 01 Kladno, Czech Republic.
- Oritest spol. s r.o., Staropramenná 17, 156 00 Prague, Czech Republic.
| | - Zdeněk Hon
- Faculty of Biomedical Engineering, Czech Technical University in Prague, Sítná sq. 3105, 272 01 Kladno, Czech Republic.
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Nouha A, Sameh S, Fakher F, Slim T, Souad R. Impact of Q139R substitution of MEB4-Cry2Aa toxin on its stability, accessibility and toxicity against Ephestia kuehniella. Int J Biol Macromol 2015; 81:701-9. [PMID: 26321422 DOI: 10.1016/j.ijbiomac.2015.08.058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/24/2015] [Accepted: 08/25/2015] [Indexed: 10/23/2022]
Abstract
The Bacillus thuringiensis subsp. kurstaki strain MEB4 was previously found to be highly toxic to Ephestia kuehniella. SDS-PAGE analysis of the recombinant strain DH5α (pBS-cry2Aa-MEB4) showed that Cry2Aa-MEB4 delta-endotoxins were forming inclusion bodies, and were 2.75 fold more toxic towards E. kuehniella than those of Cry2Aa-BNS3. Besides to the 65kDa active toxin, proteolysis activation of Cry2Aa-BNS3 protein with E. kuehniella midgut juice generated an extra proteolysis form of 49kDa, which was the result of another chymotrypsin cleavage located in Leu144. The amino acid sequences alignment of Cry2Aa-MEB4 and Cry2Aa-BNS3 showed that among the different 15 amino acids, the Q139R substitution was found to be interesting. In fact, due to its presence within the loop α3-α4, the chymotrypsin-like protease was unable to access to its site in Cry2Aa-MEB4, resulting to the production of only the 65kDa form. The accessible surface and the stability studies of the structure model of the Cry2Aa-BNS3-49 form showed a lower hydrophobicity surface due to the omission of 144 amino acids from the N-terminal comparing with the active Cry2Aa-MEB4 protein. All these features caused the diminishing of Cry2Aa-BNS3 toxicity towards E. kuehniella.
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Affiliation(s)
- Abdelmalek Nouha
- Laboratory of Plant Protection and Improvement (Biopesticides Team), Center of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Sellami Sameh
- Laboratory of Plant Protection and Improvement (Biopesticides Team), Center of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Frikha Fakher
- Faculté des Sciences de Sfax, B.P. n̊ 1171, 3000 Sfax, Tunisia
| | - Tounsi Slim
- Laboratory of Plant Protection and Improvement (Biopesticides Team), Center of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Rouis Souad
- Laboratory of Plant Protection and Improvement (Biopesticides Team), Center of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
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Bt toxin modification for enhanced efficacy. Toxins (Basel) 2014; 6:3005-27. [PMID: 25340556 PMCID: PMC4210883 DOI: 10.3390/toxins6103005] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 09/28/2014] [Accepted: 09/29/2014] [Indexed: 11/23/2022] Open
Abstract
Insect-specific toxins derived from Bacillus thuringiensis (Bt) provide a valuable resource for pest suppression. Here we review the different strategies that have been employed to enhance toxicity against specific target species including those that have evolved resistance to Bt, or to modify the host range of Bt crystal (Cry) and cytolytic (Cyt) toxins. These strategies include toxin truncation, modification of protease cleavage sites, domain swapping, site-directed mutagenesis, peptide addition, and phage display screens for mutated toxins with enhanced activity. Toxin optimization provides a useful approach to extend the utility of these proteins for suppression of pests that exhibit low susceptibility to native Bt toxins, and to overcome field resistance.
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Xu C, Wang BC, Yu Z, Sun M. Structural insights into Bacillus thuringiensis Cry, Cyt and parasporin toxins. Toxins (Basel) 2014; 6:2732-70. [PMID: 25229189 PMCID: PMC4179158 DOI: 10.3390/toxins6092732] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 08/26/2014] [Accepted: 08/28/2014] [Indexed: 11/30/2022] Open
Abstract
Since the first X-ray structure of Cry3Aa was revealed in 1991, numerous structures of B. thuringiensis toxins have been determined and published. In recent years, functional studies on the mode of action and resistance mechanism have been proposed, which notably promoted the developments of biological insecticides and insect-resistant transgenic crops. With the exploration of known pore-forming toxins (PFTs) structures, similarities between PFTs and B. thuringiensis toxins have provided great insights into receptor binding interactions and conformational changes from water-soluble to membrane pore-forming state of B. thuringiensis toxins. This review mainly focuses on the latest discoveries of the toxin working mechanism, with the emphasis on structural related progress. Based on the structural features, B. thuringiensis Cry, Cyt and parasporin toxins could be divided into three categories: three-domain type α-PFTs, Cyt toxin type β-PFTs and aerolysin type β-PFTs. Structures from each group are elucidated and discussed in relation to the latest data, respectively.
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Affiliation(s)
- Chengchen Xu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
| | - Bi-Cheng Wang
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.
| | - Ziniu Yu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
| | - Ming Sun
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
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Lin X, Parthasarathy K, Surya W, Zhang T, Mu Y, Torres J. A conserved tetrameric interaction of cry toxin helix α3 suggests a functional role for toxin oligomerization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1777-84. [PMID: 24657394 DOI: 10.1016/j.bbamem.2014.03.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 03/10/2014] [Accepted: 03/14/2014] [Indexed: 12/16/2022]
Abstract
Crystal (Cry) toxins are widely used for insect control, but their mechanism of toxicity is still uncertain. These toxins can form lytic pores in vitro, and water soluble tetrameric pre-pore intermediates have been reported. Even the precise oligomeric state of the toxin in membranes, trimeric or tetrameric, is still a debated issue. Based on previous reports, we have assumed that interactions between toxin monomers in solution are at least partly mediated by domain I, and we have analyzed in silico the homo-oligomerization tendencies of the domain I α-helices individually. Using many homologous sequences for each α-helix, our strategy allows selection of evolutionarily conserved interactions. These interactions appeared only in helices α3 and α5, but only α3 produced a suitably oriented or α-helical sample in lipid bilayers, forming homotetramers in C14-betaine, and allowing determination of its rotational orientation in lipid bilayers using site-specific infrared dichroism (SSID). The determined orientation in the tetrameric model is in agreement with only one of the evolutionarily conserved models. In addition mutation R99E, which was found to inhibit oligomerization experimentally, greatly destabilized the tetramer in molecular dynamic simulations. In this model, helix 3 is able to form inter-monomer interactions without significant rearrangements of domain I, which is compatible with the available crystal structure of Cry toxins in solution. The model presented here at least partially explains the reported tetrameric oligomerization of Cry toxins in solution and the inhibition of this oligomerization by a synthetic α3 peptide.
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Affiliation(s)
- Xin Lin
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Krupakar Parthasarathy
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Tong Zhang
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore.
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Tajne S, Boddupally D, Sadumpati V, Vudem DR, Khareedu VR. Synthetic fusion-protein containing domains of Bt Cry1Ac and Allium sativum lectin (ASAL) conferred enhanced insecticidal activity against major lepidopteran pests. J Biotechnol 2014; 171:71-5. [DOI: 10.1016/j.jbiotec.2013.11.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 11/26/2013] [Accepted: 11/30/2013] [Indexed: 12/23/2022]
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Sengupta A, Sarkar A, Priya P, Ghosh Dastidar S, Das S. New insight to structure-function relationship of GalNAc mediated primary interaction between insecticidal Cry1Ac toxin and HaALP receptor of Helicoverpa armigera. PLoS One 2013; 8:e78249. [PMID: 24205171 PMCID: PMC3813429 DOI: 10.1371/journal.pone.0078249] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 09/11/2013] [Indexed: 11/30/2022] Open
Abstract
Over the last few decades Cry1Ac toxin has been widely used in controlling the insect attack due to its high specificity towards target insects. The pore-forming toxin undergoes a complex mechanism in the insect midgut involving sequential interaction with specific glycosylated receptors in which terminal GalNAc molecule plays a vital role. Recent studies on Cry toxins interactions with specific receptors revealed the importance of several amino acid residues in domain III of Cry1Ac, namely Q509, N510, R511, Y513 and W545, serve as potential binding sites that surround the putative GalNAc binding pocket and mediate the toxin-receptor interaction. In the present study, alanine substitution mutations were generated in the Cry1Ac domain III region and functional significance of those key residues was monitored by insect bioassay on Helicoverpa armigera larvae. In addition, ligand blot analysis and SPR binding assay was performed to monitor the binding characteristics of Cry1Ac wild type and mutant toxins towards HaALP receptor isolated from Helicoverpa armigera. Mutagenesis data revealed that, alanine substitutions in R511, Y513 and W545 substantially impacted the relative affinity towards HaALP receptor and toxicity toward target insect. Furthermore, in silico study of GalNAc-mediated interaction also confirmed the important roles of these residues. This structural analysis will provide a detail insight for evaluating and engineering new generation Cry toxins to address the problem of change in insect behavioral patterns.
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Affiliation(s)
- Anindita Sengupta
- Division of Plant Biology, Bose Institute, Kolkata, West Bengal, India
| | - Anindya Sarkar
- Division of Plant Biology, Bose Institute, Kolkata, West Bengal, India
| | - Prerna Priya
- Bioinformatics Centre, Bose Institute, Kolkata, West Bengal, India
| | | | - Sampa Das
- Division of Plant Biology, Bose Institute, Kolkata, West Bengal, India
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Hernández-Rodríguez CS, Hernández-Martínez P, Van Rie J, Escriche B, Ferré J. Shared midgut binding sites for Cry1A.105, Cry1Aa, Cry1Ab, Cry1Ac and Cry1Fa proteins from Bacillus thuringiensis in two important corn pests, Ostrinia nubilalis and Spodoptera frugiperda. PLoS One 2013; 8:e68164. [PMID: 23861865 PMCID: PMC3702569 DOI: 10.1371/journal.pone.0068164] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 05/27/2013] [Indexed: 12/29/2022] Open
Abstract
First generation of insect-protected transgenic corn (Bt-corn) was based on the expression of Cry1Ab or Cry1Fa proteins. Currently, the trend is the combination of two or more genes expressing proteins that bind to different targets. In addition to broadening the spectrum of action, this strategy helps to delay the evolution of resistance in exposed insect populations. One of such examples is the combination of Cry1A.105 with Cry1Fa and Cry2Ab to control O. nubilalis and S. frugiperda. Cry1A.105 is a chimeric protein with domains I and II and the C-terminal half of the protein from Cry1Ac, and domain III almost identical to Cry1Fa. The aim of the present study was to determine whether the chimeric Cry1A.105 has shared binding sites either with Cry1A proteins, with Cry1Fa, or with both, in O. nubilalis and in S. frugiperda. Brush-border membrane vesicles (BBMV) from last instar larval midguts were used in competition binding assays with (125)I-labeled Cry1A.105, Cry1Ab, and Cry1Fa, and unlabeled Cry1A.105, Cry1Aa, Cry1Ab, Cry1Ac, Cry1Fa, Cry2Ab and Cry2Ae. The results showed that Cry1A.105, Cry1Ab, Cry1Ac and Cry1Fa competed with high affinity for the same binding sites in both insect species. However, Cry2Ab and Cry2Ae did not compete for the binding sites of Cry1 proteins. Therefore, according to our results, the development of cross-resistance among Cry1Ab/Ac, Cry1A.105, and Cry1Fa proteins is possible in these two insect species if the alteration of shared binding sites occurs. Conversely, cross-resistance between these proteins and Cry2A proteins is very unlikely in such case.
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Affiliation(s)
| | | | | | | | - Juan Ferré
- Departamento de Genética, Universitat de València, Burjassot, Spain
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Transgenic approaches to western corn rootworm control. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2013; 136:135-62. [PMID: 23604211 DOI: 10.1007/10_2013_195] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) is a significant corn pest throughout the United States corn belt. Rootworm larvae feed on corn roots causing yield losses and control expenditures that are estimated to exceed US$1 billion annually. Traditional management practices to control rootworms such as chemical insecticides or crop rotation have suffered reduced effectiveness due to the development of physiological and behavioral resistance. Transgenic maize expressing insecticidal proteins are very successful in protecting against rootworm damage and preserving corn yield potential. However, the high rate of grower adoption and early reliance on hybrids expressing a single mode of action and low-dose traits threatens the durability of commercialized transgenic rootworm technology for rootworm control. A summary of current transgenic approaches for rootworm control and the corresponding insect resistance management practices is included. An overview of potential new modes of action based on insecticidal proteins, and especially RNAi targeting mRNA coding for essential insect proteins is provided.
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García-Robles I, Ochoa-Campuzano C, Sánchez J, Contreras E, Real MD, Rausell C. Functional significance of membrane associated proteolysis in the toxicity of Bacillus thuringiensis Cry3Aa toxin against Colorado potato beetle. Toxicon 2012; 60:1063-71. [DOI: 10.1016/j.toxicon.2012.07.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 07/20/2012] [Accepted: 07/25/2012] [Indexed: 10/28/2022]
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31
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Yang W, He K, Zhang J, Guo S. pH-controlled Bacillus thuringiensis Cry1Ac protoxin loading and release from polyelectrolyte microcapsules. PLoS One 2012; 7:e45233. [PMID: 23024810 PMCID: PMC3443234 DOI: 10.1371/journal.pone.0045233] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 08/17/2012] [Indexed: 11/18/2022] Open
Abstract
Crystal proteins synthesized by Bacillus thuringiensis (Bt) have been used as biopesticides because of their toxicity to the insect larval hosts. To protect the proteins from environmental stress to extend their activity, we have developed a new microcapsule formulation. Poly (acrylic acid) (PAH) and poly (styrene sulfonate) (PSS) were fabricated through layer-by-layer self-assembly based on a CaCO3 core. Cry1Ac protoxins were loaded into microcapsules through layer-by-layer self-assembly at low pH, and the encapsulated product was stored in water at 4°C. Scanning electron microscopy (SEM) was used to observe the morphology of the capsules. To confirm the successful encapsulation, the loading results were observed with a confocal laser scattering microscope (CLSM), using fluorescein-labeled Cry1Ac protoxin (FITC-Cry1Ac). The protoxins were released from the capsule under the alkaline condition corresponding to the midgut of certain insects, a condition which seldom exists elsewhere in the environment. The following bioassay experiment demonstrated that the microcapsules with Cry1Ac protoxins displayed approximately equivalent insecticidal activity to the Asian corn borer compared with free Cry1Ac protoxins, and empty capsules proved to have no effect on insects. Further result also indicated that the formulation could keep stable under the condition of heat and desiccation. These results suggest that this formulation provides a promising methodology that protects protoxins from the environment and releases them specifically in the target insects’ midgut, which has shown potential as biopesticide in the field.
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Affiliation(s)
- Wenhui Yang
- School of Life Science, Beijing Institute of Technology, Beijing, China
| | - Kanglai He
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Shuyuan Guo
- School of Life Science, Beijing Institute of Technology, Beijing, China
- * E-mail:
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Multimodal protein constructs for herbivore insect control. Toxins (Basel) 2012; 4:455-75. [PMID: 22822457 PMCID: PMC3398420 DOI: 10.3390/toxins4060455] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 06/01/2012] [Accepted: 06/05/2012] [Indexed: 01/09/2023] Open
Abstract
Transgenic plants expressing combinations of microbial or plant pesticidal proteins represent a promising tool for the efficient, durable control of herbivorous insects. In this review we describe current strategies devised for the heterologous co-expression of pesticidal proteins in planta, some of which have already shown usefulness in plant protection. Emphasis is placed on protein engineering strategies involving the insertion of single DNA constructs within the host plant genome. Multimodal fusion proteins integrating complementary pesticidal functions along a unique polypeptide are first considered, taking into account the structural constraints associated with protein or protein domain grafting to biologically active proteins. Strategies that allow for the co- or post-translational release of two or more pesticidal proteins are then considered, including polyprotein precursors releasing free proteins upon proteolytic cleavage, and multicistronic transcripts for the parallel translation of single protein-encoding mRNA sequences.
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Tajne S, Sanam R, Gundla R, Gandhi NS, Mancera RL, Boddupally D, Vudem DR, Khareedu VR. Molecular modeling of Bt Cry1Ac (DI–DII)–ASAL (Allium sativum lectin)–fusion protein and its interaction with aminopeptidase N (APN) receptor of Manduca sexta. J Mol Graph Model 2012; 33:61-76. [DOI: 10.1016/j.jmgm.2011.11.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 11/03/2011] [Accepted: 11/04/2011] [Indexed: 01/01/2023]
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34
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Naimov S, Valkova R, Dukiandjiev S, Minkov I, de Maagd RA. Carboxy-terminal extension effects on crystal formation and insecticidal properties of Cry15Aa. J Invertebr Pathol 2011; 108:56-8. [DOI: 10.1016/j.jip.2011.05.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 05/19/2011] [Accepted: 05/19/2011] [Indexed: 11/29/2022]
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Influence of Mutagenesis of Bacillus thuringiensis Cry1Aa Toxin on Larvicidal Activity. Curr Microbiol 2010; 62:968-73. [DOI: 10.1007/s00284-010-9791-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Accepted: 09/02/2010] [Indexed: 10/18/2022]
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36
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Walters FS, deFontes CM, Hart H, Warren GW, Chen JS. Lepidopteran-active variable-region sequence imparts coleopteran activity in eCry3.1Ab, an engineered Bacillus thuringiensis hybrid insecticidal protein. Appl Environ Microbiol 2010; 76:3082-8. [PMID: 20305020 PMCID: PMC2869115 DOI: 10.1128/aem.00155-10] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Accepted: 03/10/2010] [Indexed: 11/20/2022] Open
Abstract
A unique, coleopteran-active protein, termed eCry3.1Ab, was generated following variable-region exchange of a Bacillus thuringiensis lepidopteran-active protein, Cry1Ab, with a Cry3A region. Our results support the hypothesis that this variable-region exchange is responsible for imparting strong bioactivity against the larvae of western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte), a pest species which is not susceptible to either parent protein sequence. This study demonstrates the potential of successfully engineering a portion(s) of a lepidopteran-active B. thuringiensis sequence so that it has activity against coleopterans. Further elucidation of the eCry3.1Ab activity indicated the importance of variable regions 4 to 6 that were derived from Cry1Ab instead of Cry1Ac. There was some flexibility in making domain III of engineered hybrid insecticidal proteins even more Cry1Ab-like and retaining activity, while there was less flexibility in making domain III more Cry3A-like and retaining activity. In vitro binding studies with brush border membrane vesicles demonstrated that there was specific binding of chymotrypsin-processed modified Cry3A (mCry3A), which was not diminished by addition of a 100-fold molar excess of chymotrypsin-processed eCry3.1Ab or unprocessed eCry3.1Ab. In addition, in the converse experiment, specific binding of chymotrypsin-processed eCry3.1Ab was not diminished by the presence of a 75-fold molar excess of chymotrypsin-processed mCry3A. These data support the hypothesis that eCry3.1Ab can interact with different binding sites than the activated form of mCry3A in the WCR brush border and may provide a different mode of action from the standpoint of resistance management.
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Variant Cry1Ia toxins generated by DNA shuffling are active against sugarcane giant borer. J Biotechnol 2009; 145:215-21. [PMID: 19931577 DOI: 10.1016/j.jbiotec.2009.11.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Revised: 11/03/2009] [Accepted: 11/12/2009] [Indexed: 11/22/2022]
Abstract
Sugarcane giant borer (Telchin licus licus) is a serious sugarcane pest in Americas whose endophytic lifestyle hampers effective chemical and biological controls. Therefore, development of alternative control methods is extremely important. Envisaging development of transgenic plants resistant to this pest, we investigated the effect of the Bacillus thuringiensis Cry protein Cry1Ia12synth (truncated protein lacking C-terminus with plant codon usage) and variants against T. l. licus. cry1Ia12synth gene was used to generate mutated variants, which were screened for toxicity toward T. l. licus. For that purpose, an innovative technique combining cry gene shuffling with phage-display was used to build a combinatorial library comprising 1.97x10(5) Cry1Ia12synth variants. Screening of this library for variants binding to T. l. licus Brush Border Midgut Vesicles led to the identification of hundreds of clones, out of which 30 were randomly chosen for toxicity testing. Bioassays revealed four variants exhibiting activity against T. l. licus as compared to the non-toxic Cry1Ia12synth. Eight single substitutions sites were found in these active variants. Based on theoretical molecular modelling, the probable implications of these mutations are discussed. Therefore, we have four genes encoding Cry1Ia12synth variants active against T. l. licus promising for future development of resistant transgenic sugarcane lines.
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Nguyen HT, Jehle JA. Stability of Cry1Ab protein during long-term storage for standardization of insect bioassays. ACTA ACUST UNITED AC 2009; 8:113-9. [DOI: 10.1051/ebr/2009015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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39
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Sujatha M, Lakshminarayana M, Tarakeswari M, Singh PK, Tuli R. Expression of the cry1EC gene in castor (Ricinus communis L.) confers field resistance to tobacco caterpillar (Spodoptera litura Fabr) and castor semilooper (Achoea janata L.). PLANT CELL REPORTS 2009; 28:935-46. [PMID: 19337736 DOI: 10.1007/s00299-009-0699-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Revised: 03/01/2009] [Accepted: 03/16/2009] [Indexed: 05/27/2023]
Abstract
Castor (cv. DCS-9) has been transformed through Agrobacterium-mediated and particle gun bombardment methods using appropriate vectors containing the Bt chimeric gene cry1EC driven by enhanced 35S promoter. About 81 and 12 putative transformants were regenerated following selection on hygromycin and kanamycin, respectively. Southern analysis of DNA extracted from T(0) plants confirmed integration of the introduced gene in castor genome. The integration and inheritance of the introduced genes was demonstrated up to T(4) generation by PCR and Southern analysis. Southern analysis of two events having single and two copies showed the same pattern of integration in the subsequent generations. Insect feeding experiments conducted in the laboratory by releasing neonate larvae of castor semilooper and S. litura on leaf tissues excised from transgenic and control plants showed varying degrees of larval mortality and slow growth in larvae fed on transgenic leaf tissue. Field bioassays against Spodoptera litura and castor semilooper conducted for eight events in T(1)-T(4) generations under net confinement were more informative and events conferring resistance to the two major defoliators were identified.
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Affiliation(s)
- M Sujatha
- Directorate of Oilseeds Research, Rajendranagar, Hyderabad, 500 030, India.
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40
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Loop residues of the receptor binding domain of Bacillus thuringiensis Cry11Ba toxin are important for mosquitocidal activity. FEBS Lett 2009; 583:2021-30. [PMID: 19450583 DOI: 10.1016/j.febslet.2009.05.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 05/05/2009] [Accepted: 05/06/2009] [Indexed: 02/01/2023]
Abstract
Using a Cry11Ba toxin model, predicted loops in domain II were analyzed for their role in receptor binding and toxicity. Peptides corresponding to loops alpha8, 1 and 3, but not loop 2, competed with toxin binding to Aedes midgut membranes. Mutagenesis data reveal loops alpha8, 1 and 3 are involved in toxicity. Loops 1 and 3 are of greater significance in toxicity to Aedes and Culex larvae than to Anopheles. Cry11Ba binds the apical membrane of larval caecae and posterior midgut, and binding can be competed by loop 1 but not by loop 2 peptides. Cry11Ba binds the same regions to which anti-cadherin antibody binds, and this antibody competes with Cry11Ba binding suggesting a possible role of cadherin in toxication.
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41
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Biological characteristics of Bacillus thuringiensis strain Bt11 and identification of its cry-type genes. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/s11703-009-0040-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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42
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Pardo-López L, Muñoz-Garay C, Porta H, Rodríguez-Almazán C, Soberón M, Bravo A. Strategies to improve the insecticidal activity of Cry toxins from Bacillus thuringiensis. Peptides 2009; 30:589-95. [PMID: 18773932 PMCID: PMC2692940 DOI: 10.1016/j.peptides.2008.07.027] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Revised: 07/30/2008] [Accepted: 07/30/2008] [Indexed: 01/28/2023]
Abstract
Bacillus thuringiensis Cry toxins have been widely used in the control of insect pests either as spray products or expressed in transgenic crops. These proteins are pore-forming toxins with a complex mechanism of action that involves the sequential interaction with several toxin-receptors. Cry toxins are specific against susceptible larvae and although they are often highly effective, some insect pests are not affected by them or show low susceptibility. In addition, the development of resistance threatens their effectiveness, so strategies to cope with all these problems are necessary. In this review we will discuss and compare the different strategies that have been used to improve insecticidal activity of Cry toxins. The activity of Cry toxins can be enhanced by using additional proteins in the bioassay like serine protease inhibitors, chitinases, Cyt toxins, or a fragment of cadherin receptor containing a toxin-binding site. On the other hand, different modifications performed in the toxin gene such as site-directed mutagenesis, introduction of cleavage sites in specific regions of the protein, and deletion of small fragments from the amino-terminal region lead to improved toxicity or overcome resistance, representing interesting alternatives for insect pest control.
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Affiliation(s)
| | | | | | | | | | - A. Bravo
- Corresponding author. , Phone 52 777 3291635, Fax 52 777 3291624
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43
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Frutos R, Rang C, Royer M. Managing Insect Resistance to Plants ProducingBacillus thuringiensisToxins. Crit Rev Biotechnol 2008. [DOI: 10.1080/0738-859991229251] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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44
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Yamaguchi T, Sahara K, Bando H, Asano SI. Discovery of a novel Bacillus thuringiensis Cry8D protein and the unique toxicity of the Cry8D-class proteins against scarab beetles. J Invertebr Pathol 2008; 99:257-62. [PMID: 18614174 DOI: 10.1016/j.jip.2008.05.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2008] [Revised: 05/15/2008] [Accepted: 05/25/2008] [Indexed: 11/25/2022]
Abstract
A novel cry gene, cry8Db, highly toxic to scarab beetles such as the Japanese beetle, Popillia japonica Newman, was cloned from an isolate of Bacillus thuringiensis(Bt), BBT2-5. The cry8Db gene has 3525bp nucleotides and codes for a protein of 1174 amino acid residues. The protein, Cry8Db, has typical Bt characteristics such as the 8-block, conserved sequences and the three-domain 3D toxin structure as defined with Cry3Aa. When the amino acid sequence of Cry8Db was compared with that of Cry8Da whose gene was cloned and characterized in our laboratory earlier, substantial sequence diversities were found in their Domain III. The cry8Db gene was expressed in an acrystalliferous B. thuringiensis strain, BT51. BT51 expressing cry8Db formed a spherical crystal like the natural crystal of BBT2-5. The Cry8Db protein was assayed along with the other scarab active Cry8Da and Cry8Ca against the Japanese beetle. While Cry8Da and Cry8Db had toxicity against both adults and larvae of the Japanese beetle, Cry8Ca was toxic to only larvae. Cry8Ca showed no toxicity against the adult beetle up to 30 microg per 1 cm(2) of leaf discs on which the protein was applied. The activation process of Cry8Db by adult and larval gut juice was compared in vitro with the processes of Cry8Da and Cry8Ca. All three proteins, Cry8Db, Cry8Da and Cry8Ca, produced a toxic core of approximately 70kDa equally indicating that the activation process does not inactivate the adult activity of Cry8Ca. We concluded that the adult activity of Cry8D proteins is encoded in Domain II. Further tests against other beetle species showed a significant difference between Cry8D's and Cry8Ca but no difference between Cry8Da and Cry8Db. Comparison of 3D structural models of Cry8Ca, Cry8Da and Cry8Db, which were constructed by using Cry3Bb as the structural template, indicated significant structural differences, especially between Cry8Ca and Cry8D proteins, in three major surface-exposed loops of Domain II that may be involved in determining the adult beetle activity.
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Affiliation(s)
- Takuya Yamaguchi
- Department of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, N9 W9, Sapporo 060-8589, Japan
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Höss S, Arndt M, Baumgarte S, Tebbe CC, Nguyen HT, Jehle JA. Effects of transgenic corn and Cry1Ab protein on the nematode, Caenorhabditis elegans. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2008; 70:334-340. [PMID: 18068780 DOI: 10.1016/j.ecoenv.2007.10.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 10/11/2007] [Accepted: 10/21/2007] [Indexed: 05/25/2023]
Abstract
The effects of the insecticidal Cry1Ab protein from Bacillus thuringiensis (Bt) on the nematode, Caenorhabditis elegans, were studied with soil from experimental fields cultivated with transgenic Bt corn (MON810) and with trypsinized Cry1Ab protein expressed in Escherichia coli. The content of Cry1Ab protein was above the detection limit of an ELISA test in only half of the soil samples obtained from transgenic plots, ranging from 0.19 to 1.31 ng g(-1) dry weight. In a laboratory bioassay, C. elegans was exposed to rhizosphere and bulk soil from fields with isogenic or transgenic corn or to solutions of Cry1Ab protein (0, 24, 41, 63, 118, and 200 mg l(-1)) over a period of 96 h, with growth and reproduction serving as the test parameters. Nematode reproduction and growth were significantly reduced in rhizosphere and bulk soil of Bt corn compared with soil from isogenic corn and were significantly correlated with concentrations of the Cry1Ab protein in the soil samples. Moreover, the toxicity of pure Cry1Ab protein to the reproduction and growth of C. elegans was concentration-dependent. As significant inhibition occurred at relatively high concentrations of the Cry1Ab protein (41 mg l(-1)), the effects of the soil samples from Bt corn could not be assigned directly to the toxicity of the Cry1Ab protein. The results demonstrate that bioassays with the nematode, C. elegans, provide a promising tool for monitoring the potential effects of Bt toxins in aqueous medium and soils.
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Affiliation(s)
- S Höss
- Ecossa (Ecological Sediment and Soil Assessment), Giselastr. 6, 82319 Starnberg, Germany.
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Investigating the properties of Bacillus thuringiensis Cry proteins with novel loop replacements created using combinatorial molecular biology. Appl Environ Microbiol 2008; 74:3497-511. [PMID: 18408065 DOI: 10.1128/aem.02844-07] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cry proteins are a large family of crystalline toxins produced by Bacillus thuringiensis. Individually, the family members are highly specific, but collectively, they target a diverse range of insects and nematodes. Domain II of the toxins is important for target specificity, and three loops at its apex have been studied extensively. There is considerable interest in determining whether modifications in this region may lead to toxins with novel specificity or potency. In this work, we studied the effect of loop substitution on toxin stability and specificity. For this purpose, sequences derived from antibody complementarity-determining regions (CDR) were used to replace native domain II apical loops to create "Crybodies." Each apical loop was substituted either individually or in combination with a library of third heavy-chain CDR (CDR-H3) sequences to create seven distinct Crybody types. An analysis of variants from each library indicated that the Cry1Aa framework can tolerate considerable sequence diversity at all loop positions but that some sequence combinations negatively affect structural stability and protease sensitivity. CDR-H3 substitution showed that loop position was an important determinant of insect toxicity: loop 2 was essential for activity, whereas the effects of substitutions at loop 1 and loop 3 were sequence dependent. Unexpectedly, differences in toxicity did not correlate with binding to cadherins--a major class of toxin receptors--since all Crybodies retained binding specificity. Collectively, these results serve to better define the role of the domain II apical loops as determinants of specificity and establish guidelines for their modification.
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Susceptibility of Spodoptera exigua to 9 toxins from Bacillus thuringiensis. J Invertebr Pathol 2008; 97:245-50. [DOI: 10.1016/j.jip.2007.11.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 10/10/2007] [Accepted: 11/05/2007] [Indexed: 11/30/2022]
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You TH, Lee MK, Jenkins JL, Alzate O, Dean DH. Blocking binding of Bacillus thuringiensis Cry1Aa to Bombyx mori cadherin receptor results in only a minor reduction of toxicity. BMC BIOCHEMISTRY 2008; 9:3. [PMID: 18218126 PMCID: PMC2245940 DOI: 10.1186/1471-2091-9-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Accepted: 01/24/2008] [Indexed: 11/24/2022]
Abstract
Background Bacillus thuringiensis Cry1Aa insecticidal protein is the most active known B. thuringiensis toxin against the forest insect pest Lymantria dispar (gypsy moth), unfortunately it is also highly toxic against the non-target insect Bombyx mori (silk worm). Results Surface exposed hydrophobic residues over domains II and III were targeted for site-directed mutagenesis. Substitution of a phenylalanine residue (F328) by alanine reduced binding to the Bombyx mori cadherin by 23-fold, reduced biological activity against B. mori by 4-fold, while retaining activity against Lymantria dispar. Conclusion The results identify a novel receptor-binding epitope and demonstrate that virtual elimination of binding to cadherin BR-175 does not completely remove toxicity in the case of B. mori.
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Affiliation(s)
- Taek H You
- Department of Biochemistry, The Ohio State University, Columbus, OH 43210, USA.
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Torres J, Lin X, Boonserm P. A trimeric building block model for Cry toxins in vitro ion channel formation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:392-7. [PMID: 18047829 DOI: 10.1016/j.bbamem.2007.10.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Revised: 10/29/2007] [Accepted: 10/29/2007] [Indexed: 12/14/2022]
Abstract
The crystal (Cry) insecticidal toxins, or delta-endotoxins, are lethal to a wide variety of insect larvae, and are therefore very important in insect control. Toxicity has been explained by formation of transmembrane oligomeric pores or ion channels and, more recently, by the ability of the monomeric toxin to subvert cellular signaling pathways. The structure, topology, and precise role of the putative pore in toxicity are not known. However, in vitro biophysical studies suggest that helices alpha4 and alpha5 in domain I insert into the lipid bilayer as an alpha-helical hairpin. Mutagenesis studies have assigned an important role to alpha5 in maintaining oligomerization, and to alpha4 in channel formation. To detect the possible homo-oligomerizing tendencies of these two helices, we have used the evolutionary conservation data contained in sixteen Cry homologs in order to filter non-native interactions found during a global conformational search. No conserved homo-oligomer was found for alpha4, but a right handed trimeric alpha5 model was present in the simulations of all Cry sequences. We propose a model for Cry toxin oligomerization based on sequence analysis and available mutagenesis data.
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Affiliation(s)
- Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, Singapore 637551, Singapore.
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Zheng SJ, Henken B, de Maagd RA, Purwito A, Krens FA, Kik C. Two different Bacillus thuringiensis toxin genes confer resistance to beet armyworm (Spodoptera exigua Hübner) in transgenic Bt-shallots (Allium cepa L.). Transgenic Res 2007; 14:261-72. [PMID: 16145834 DOI: 10.1007/s11248-005-0109-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Agrobacterium-mediated genetic transformation was applied to produce beet armyworm (Spodoptera exigua Hübner) resistant tropical shallots (Allium cepa L. group Aggregatum). A cry1Ca or a H04 hybrid gene from Bacillus thuringiensis, driven by the chrysanthemum ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit (Rubisco SSU) promoter, along with the hygromycin phosphotransferase gene (hpt) driven by the CaMV 35S promoter, was employed for genetic transformation. An average transformation frequency of 3.68% was obtained from two shallot cultivars, Tropix and Kuning. After transfer of the in vitro plants to the greenhouse 69% of the cry1Ca and 39% of the H04 transgenic shallots survived the first half year. After one year of cultivation in the greenhouse the remaining cry1Ca and H04 transgenic plants grew vigorously and had a normal bulb formation, although the cry1Ca transgenic plants (and controls) had darker green leaves compared to their H04 counterparts. Standard PCR, adaptor ligation PCR and Southern analyses confirmed the integration of T-DNA into the shallot genome. Northern blot and ELISA analyses revealed expression of the cry1Ca or H04 gene in the transgenic plants. The amount of Cry1Ca expressed in transgenic plants was higher than the expression levels of H04 (0.39 vs. 0.16% of the total soluble leaf proteins, respectively). There was a good correlation between protein expression and beet armyworm resistance. Cry1Ca or H04 gene expression of at least 0.22 or 0.08% of the total soluble protein in shallot leaves was sufficient to give a complete resistance against beet armyworm. This confirms earlier observations that the H04 toxin is more toxic to S. exigua than the Cry1Ca toxin. The results from this study suggest that the cry1Ca and H04 transgenic shallots developed could be used for introducing resistance to beet armyworm in (sub) tropical shallot.
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Affiliation(s)
- Si-Jun Zheng
- Plant Research International, Wageningen University and Research Center, P O Box 16, 6700 AA Wageningen, The Netherlands
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