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Engineered chimeric insecticidal crystalline protein improves resistance to lepidopteran insects in rice (Oryza sativa L.) and maize (Zea mays L.). Sci Rep 2022; 12:12529. [PMID: 35869123 PMCID: PMC9307649 DOI: 10.1038/s41598-022-16426-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 07/11/2022] [Indexed: 11/08/2022] Open
Abstract
AbstractThe insecticidal crystalline proteins (Crys) are a family of insect endotoxin functioning in crop protection. As insects keep evolving into tolerance to the existing Crys, it is necessary to discover new Cry proteins to overcome potential threatens. Crys possess three functional domains at their N-termini, and the most active region throughout evolution was found at the domain-III. We swapped domain-IIIs from various Cry proteins and generated seven chimeric proteins. All recombinants were expressed in Escherichia coli and their toxicity was assessed by dietary exposure assays. Three of the seven Crys exhibited a high toxicity to Asian corn borer over the controls. One of them, Cry1Ab-Gc, a chimeric Cry1Ab being replaced with the domain-III of Cry1Gc, showed the highest toxicity to rice stem borer when it was over-expressed in Oryza sativa. Furthermore, it was also transformed into maize, backcrossed into commercial maize inbred lines and then produced hybrid to evaluate their commercial value. Transgenic maize performed significant resistance to the Asian corn borer without affecting the yield. We further showed that this new protein did not have adverse effects on the environment. Our results indicated that domain III swapped of Crys could be used as an efficient method for developing new engineered insecticidal protein.
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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: 2.5] [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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Liu L, Chen Z, Yang Y, Xiao Y, Liu C, Ma Y, Soberón M, Bravo A, Yang Y, Liu K. A single amino acid polymorphism in ABCC2 loop 1 is responsible for differential toxicity of Bacillus thuringiensis Cry1Ac toxin in different Spodoptera (Noctuidae) species. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2018; 100:59-65. [PMID: 29964167 DOI: 10.1016/j.ibmb.2018.06.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 06/13/2018] [Accepted: 06/22/2018] [Indexed: 06/08/2023]
Abstract
Bacillus thuringiensis Cry toxins exert their toxicity by forming membrane pores after binding with larval midgut membrane proteins known as receptors. Spodoptera litura and Spodoptera frugiperda belong to the same genus, but S. litura is tolerant to Cry1Ac, while S. frugiperda is susceptible. The mechanism involved in the differential toxicity of Cry1Ac to these insect species is not understood. Amino acid sequences analysis of ABCC2, a well-recognized Cry1Ac receptor, from both species showed high sequence identity. Hi5 insect cells expressing SfABCC2 from S. frugiperda were 65-fold more susceptible than those expressing the SlABCC2 from S. litura. Substitution of fragments, point mutations and deletions between the ABCC2 of the two species revealed that ABCC2 amino acid Q125 from SfABCC2 or E125 from SlABCC2 was key factor for the differential Cry1Ac toxicity to Hi5 cells expressing these receptors. Consistently with this, cells expressing Helicoverpa armigera HaABCC2Q122-GFP, were more susceptible to Cry1Ac than cells expressing HaABCC2E122-GFP mutant. Q125 or E125 is located in a predicted exposed loop 1 region of ABCC2 indicating that this region could be important for Cry1Ac binding. These findings identified a single amino acid residue located in loop 1 of ABCC2 transporter as responsible for the different levels of susceptibility to Cry1Ac among various lepidopteran species.
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Affiliation(s)
- Leilei Liu
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Zuwen Chen
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Yanchao Yang
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Yutao Xiao
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, 518120, China
| | - Chenxi Liu
- State Key Laboratory for Biology of Plant Disease and Insect Pests, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing, 100193, China
| | - Yuemin Ma
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Mario Soberón
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, 62250, Morelos, Mexico
| | - Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, 62250, Morelos, Mexico.
| | - Yongbo Yang
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China.
| | - Kaiyu Liu
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China.
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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: 1.0] [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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US132 Cyclodextrin Glucanotransferase Engineering by Random Mutagenesis for an Anti-Staling Purpose. Mol Biotechnol 2016; 58:551-7. [PMID: 27271016 DOI: 10.1007/s12033-016-9952-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The use of the cyclodextrin glucanotransferase (CGTase) of the US132 strain, which is an effective anti-staling agent, has been hampered by its high cyclization activity. Since that random mutagenesis using error-prone PCR is nowadays a method of choice for enzymes engineering, we have optimized this method by adjusting manganese concentration in order to obtain a high percentage of active CGTase mutants. Therefore, the amplification of the gene encoding the US132 CGTase was performed using a MnCl2 concentration ranging between 0 and 0.5 mM. The finding showed that a manganese concentration of 0.04 mM allowed for 90 % of active mutants. A simple method to rapidly screen the obtained mutants was also developed. After the examination of a small library (of less than 1000 clones), the active mutant named MJ13 was selected for a significant decrease in the cyclization activity, thereby showing a remarkable change in the enzyme specificity towards starch dextrinizing. Sequence analysis showed that MJ13 is a triple mutant with two mutations in the catalytic domain (K47E and S382P) and one substitution in the starch binding domain (N655S).
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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: 9.3] [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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Lucena WA, Pelegrini PB, Martins-de-Sa D, Fonseca FCA, Gomes JE, de Macedo LLP, da Silva MCM, Oliveira RS, Grossi-de-Sa MF. Molecular approaches to improve the insecticidal activity of Bacillus thuringiensis Cry toxins. Toxins (Basel) 2014; 6:2393-423. [PMID: 25123558 PMCID: PMC4147589 DOI: 10.3390/toxins6082393] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 06/23/2014] [Accepted: 06/27/2014] [Indexed: 02/01/2023] Open
Abstract
Bacillus thuringiensis (Bt) is a gram-positive spore-forming soil bacterium that is distributed worldwide. Originally recognized as a pathogen of the silkworm, several strains were found on epizootic events in insect pests. In the 1960s, Bt began to be successfully used to control insect pests in agriculture, particularly because of its specificity, which reflects directly on their lack of cytotoxicity to human health, non-target organisms and the environment. Since the introduction of transgenic plants expressing Bt genes in the mid-1980s, numerous methodologies have been used to search for and improve toxins derived from native Bt strains. These improvements directly influence the increase in productivity and the decreased use of chemical insecticides on Bt-crops. Recently, DNA shuffling and in silico evaluations are emerging as promising tools for the development and exploration of mutant Bt toxins with enhanced activity against target insect pests. In this report, we describe natural and in vitro evolution of Cry toxins, as well as their relevance in the mechanism of action for insect control. Moreover, the use of DNA shuffling to improve two Bt toxins will be discussed together with in silico analyses of the generated mutations to evaluate their potential effect on protein structure and cytotoxicity.
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Affiliation(s)
- Wagner A. Lucena
- Embrapa Cotton, Campina Grande, 58428-095, PB, Brazil; E-Mail:
- Graduate Program in Cellular and Molecular Biology, Federal University of Rio Grande do Sul, Porto Alegre, 91501-970, RS, Brazil
- Embrapa Genetic Resources and Biotechnology, Brasília, 70779-917, DF, Brazil; E-Mails: (P.B.P.); (D.M.-S.); (F.C.A.F.); (J.E.G.); (L.L.P.M.); (M.C.M.S.); (R.S.)
| | - Patrícia B. Pelegrini
- Embrapa Genetic Resources and Biotechnology, Brasília, 70779-917, DF, Brazil; E-Mails: (P.B.P.); (D.M.-S.); (F.C.A.F.); (J.E.G.); (L.L.P.M.); (M.C.M.S.); (R.S.)
| | - Diogo Martins-de-Sa
- Embrapa Genetic Resources and Biotechnology, Brasília, 70779-917, DF, Brazil; E-Mails: (P.B.P.); (D.M.-S.); (F.C.A.F.); (J.E.G.); (L.L.P.M.); (M.C.M.S.); (R.S.)
- Department of Molecular Biology, Federal University of Brasília, Brasília, 70910-900, DF, Brazil
| | - Fernando C. A. Fonseca
- Embrapa Genetic Resources and Biotechnology, Brasília, 70779-917, DF, Brazil; E-Mails: (P.B.P.); (D.M.-S.); (F.C.A.F.); (J.E.G.); (L.L.P.M.); (M.C.M.S.); (R.S.)
- Department of Molecular Biology, Federal University of Brasília, Brasília, 70910-900, DF, Brazil
| | - Jose E. Gomes
- Embrapa Genetic Resources and Biotechnology, Brasília, 70779-917, DF, Brazil; E-Mails: (P.B.P.); (D.M.-S.); (F.C.A.F.); (J.E.G.); (L.L.P.M.); (M.C.M.S.); (R.S.)
- Department of Molecular Biology, Federal University of Brasília, Brasília, 70910-900, DF, Brazil
| | - Leonardo L. P. de Macedo
- Embrapa Genetic Resources and Biotechnology, Brasília, 70779-917, DF, Brazil; E-Mails: (P.B.P.); (D.M.-S.); (F.C.A.F.); (J.E.G.); (L.L.P.M.); (M.C.M.S.); (R.S.)
- Post-Graduation of Genomic Sciences and Biotechnology, Catholic University of Brasilia, Brasília, 70790-160, DF, Brazil
| | - Maria Cristina M. da Silva
- Embrapa Genetic Resources and Biotechnology, Brasília, 70779-917, DF, Brazil; E-Mails: (P.B.P.); (D.M.-S.); (F.C.A.F.); (J.E.G.); (L.L.P.M.); (M.C.M.S.); (R.S.)
| | - Raquel S. Oliveira
- Embrapa Genetic Resources and Biotechnology, Brasília, 70779-917, DF, Brazil; E-Mails: (P.B.P.); (D.M.-S.); (F.C.A.F.); (J.E.G.); (L.L.P.M.); (M.C.M.S.); (R.S.)
- Post-Graduation of Genomic Sciences and Biotechnology, Catholic University of Brasilia, Brasília, 70790-160, DF, Brazil
| | - Maria F. Grossi-de-Sa
- Embrapa Genetic Resources and Biotechnology, Brasília, 70779-917, DF, Brazil; E-Mails: (P.B.P.); (D.M.-S.); (F.C.A.F.); (J.E.G.); (L.L.P.M.); (M.C.M.S.); (R.S.)
- Post-Graduation of Genomic Sciences and Biotechnology, Catholic University of Brasilia, Brasília, 70790-160, DF, Brazil
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Bravo A, Gómez I, Porta H, García-Gómez BI, Rodriguez-Almazan C, Pardo L, Soberón M. Evolution of Bacillus thuringiensis Cry toxins insecticidal activity. Microb Biotechnol 2012; 6:17-26. [PMID: 22463726 PMCID: PMC3815381 DOI: 10.1111/j.1751-7915.2012.00342.x] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Insecticidal Cry proteins produced by Bacillus thuringiensis are use worldwide in transgenic crops for efficient pest control. Among the family of Cry toxins, the three domain Cry family is the better characterized regarding their natural evolution leading to a large number of Cry proteins with similar structure, mode of action but different insect specificity. Also, this group is the better characterized regarding the study of their mode of action and the molecular basis of insect specificity. In this review we discuss how Cry toxins have evolved insect specificity in nature and analyse several cases of improvement of Cry toxin action by genetic engineering, some of these examples are currently used in transgenic crops. We believe that the success in the improvement of insecticidal activity by genetic evolution of Cry toxins will depend on the knowledge of the rate-limiting steps of Cry toxicity in different insect pests, the mapping of the specificity binding regions in the Cry toxins, as well as the improvement of mutagenesis strategies and selection procedures.
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Affiliation(s)
- Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico
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