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Gan C, Zhang Z, Jin Z, Wang F, Fabrick JA, Wu Y. Helicoverpa armigera ATP-binding cassette transporter ABCA2 is a functional receptor of Bacillus thuringiensis Cry2Ab toxin. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2023; 197:105658. [PMID: 38072533 DOI: 10.1016/j.pestbp.2023.105658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Revised: 10/17/2023] [Accepted: 10/19/2023] [Indexed: 12/18/2023]
Abstract
Crystalline (Cry) proteins from the bacterium Bacillus thuringiensis (Bt) are widely used in transgenic crops to control important insect pests. Bt crops have many benefits compared with traditional broad-spectrum insecticides, including improved pest control with reduced negative impacts on off-target organisms and fewer environmental consequences. Transgenic corn and cotton producing Cry2Ab Bt toxin are used globally to control several major lepidopteran pests, including the cotton bollworm, Helicoverpa armigera. Resistance to the Cry2Ab toxin and to Bt crops producing Cry2Ab is associated with mutations in the midgut ATP-binding cassette transporter ABCA2 gene in several lepidopterans. Gene-editing knockout has further shown that ABCA2 plays an important functional role in Cry2Ab intoxication. However, the precise role of ABCA2 in the mode of action of Cry2Ab has yet to be reported. Here, we used two in vitro expression systems to study the roles of the H. armigera ABCA2 (HaABCA2) protein in Cry2Ab intoxication. Cry2Ab bound to cultured Sf9 insect cells producing HaABCA2, resulting in specific and dose-dependent susceptibility to Cry2Ab. In contrast, Sf9 cells expressing recombinant mutant proteins missing at least one of the extracellular loop regions 1, 3, 4, and 6 or the intracellular loop containing nucleotide-binding domain 1 lost susceptibility to Cry2Ab, indicating these regions are important for receptor function. Consistent with these results, Xenopus laevis oocytes expressing recombinant HaABCA2 showed strong ion membrane flux in the presence of Cry2Ab, suggesting that HaABCA2 is involved in promoting pore formation during Cry2Ab intoxication. Together with previously published data, our results support HaABCA2 being an important receptor of Cry2Ab where it functions to promote intoxication in H. armigera.
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Affiliation(s)
- Chunxia Gan
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Zheng Zhang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Zeng Jin
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Falong Wang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Jeffrey A Fabrick
- USDA ARS, U.S. Arid Land Agricultural Research Center, Maricopa, AZ, USA
| | - Yidong Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
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Naing ZL, Soe ET, Zhang C, Niu L, Tang J, Ding Z, Yu S, Lu J, Fang F, Liang G. Cadherin Is a Binding Protein but Not a Functional Receptor of Bacillus thuringiensis Cry2Ab in Helicoverpa armigera. Appl Environ Microbiol 2023; 89:e0062523. [PMID: 37378519 PMCID: PMC10370303 DOI: 10.1128/aem.00625-23] [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: 04/13/2023] [Accepted: 05/29/2023] [Indexed: 06/29/2023] Open
Abstract
Midgut receptors play a critical role in the specificity of Cry toxins for individual insect species. Cadherin proteins are essential putative receptors of Cry1A toxins in lepidopteran larvae. Cry2A family members share common binding sites in Helicoverpa armigera, and one of them, Cry2Aa, has been widely reported to interact with midgut cadherin. Here, we studied the binding interaction and functional role of H. armigera cadherin in the mechanism of Cry2Ab toxicity. A region spanning from cadherin repeat 6 (CR6) to the membrane-proximal region (MPR) of cadherin protein was produced as six overlapping peptides to identify the specific binding regions of Cry2Ab. Binding assays showed that Cry2Ab binds nonspecifically to peptides containing CR7 and CR11 regions in a denatured state but binds specifically only to CR7-containing peptides in the native state. The peptides CR6-11 and CR6-8 were transiently expressed in Sf9 cells to assess the functional role of cadherin. Cytotoxicity assays showed that Cry2Ab is not toxic to the cells expressing any of the cadherin peptides. However, ABCA2-expressing cells showed high sensitivity to Cry2Ab toxin. Neither increased nor decreased sensitivity to Cry2Ab was observed when the peptide CR6-11 was coexpressed with the ABCA2 gene in Sf9 cells. Instead, treating ABCA2-expressing cells with a mixture of Cry2Ab and CR6-8 peptides resulted in significantly reduced cell death compared with treatment with Cry2Ab alone. Moreover, silencing of the cadherin gene in H. armigera larvae showed no significant effect on Cry2Ab toxicity, in contrast to the reduced mortality in ABCA2-silenced larvae. IMPORTANCE To improve the efficiency of production of a single toxin in crops and to delay the evolution of insect resistance to the toxin, the second generation of Bt cotton, expressing Cry1Ac and Cry2Ab, was introduced. Understanding the mode action of the Cry proteins in the insect midgut and the mechanisms insects use to overcome these toxins plays a crucial role in developing measures to counter them. Extensive studies have been conducted on the receptors of Cry1A toxins, but relatively little has been done about those of Cry2Ab. By showing the nonfunctional binding of cadherin protein with Cry2Ab, we have furthered the understanding of Cry2Ab receptors.
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Affiliation(s)
- Zaw Lin Naing
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
| | - Ei Thinzar Soe
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
| | - Caihong Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
| | - Linlin Niu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
| | - Jinrong Tang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
| | - Zhongwei Ding
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
| | - Siqi Yu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
| | - Jie Lu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
| | - Fengyun Fang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
| | - Gemei Liang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China
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Anees Siddiqui H, Asif M, Zahra Naqvi R, Shehzad A, Sarwar M, Amin I, Mansoor S. Development of modified Cry1Ac for the control of resistant insect pest of cotton, Pectinophora gossypiella. Gene 2023; 856:147113. [PMID: 36543309 DOI: 10.1016/j.gene.2022.147113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 11/19/2022] [Accepted: 12/09/2022] [Indexed: 12/23/2022]
Abstract
Cotton has been one of the most important cash crops in Pakistan, but its production is adversely affected by biotic and abiotic stresses. Insect pests such as pink bollworm present a colossal vulnerability to such a financially important commodity. Bt toxins have been widely used to safeguard agricultural plants against notorious insect pests such as cotton bollworm and pink bollworm, and they have proven to be effective in reducing chewing insect pests. However, its efficacy has been challenged due to the development of resistance in insect pests against Bt toxins such as Cry1Ac and this poses a significant risk to the long-term adoption of these Bt crops. Resistance in insect pests against Bt toxin Cry1Ac is developed due to the mutations in the midgut receptors such as cadherin. In this study first 56 amino acids which also includes helix alpha-1 portion from N-terminus of the Cry1Ac were removed and the gene was commercially synthesized following codon optimization. Modified Cry1Ac was used to develop transgenic plants of Nicotiana tabacum and insect bioassays were conducted to check the efficacy of Cry1Ac through leaf bioassays. Cry1Ac, a modified Bt toxin, was produced pET-28a (+), and diet bioassays were performed using purified protein at various doses against Pectinophora gossypiella. Based on the insect mortality and LC50, the Cry1AcM3 form of the modified toxins was shown to be more potent than the other modified versions (Cry1AcM1, Cry1AcM2), with more than 80 % mortality against resistant pink bollworm at 1.25 g/mL and an LC50 of 0.48. The results suggest that modified toxin cry1Ac may be useful in controlling population of pink bollworm resistant against cry1Ac.
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Affiliation(s)
- Hamid Anees Siddiqui
- Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) College Pakistan Institute of Engineering and Applied Sciences, Faisalabad, Punjab, Pakistan; Department of Biotechnology, University of Sialkot, Sialkot, Pakistan
| | - Muhammad Asif
- Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) College Pakistan Institute of Engineering and Applied Sciences, Faisalabad, Punjab, Pakistan
| | - Rubab Zahra Naqvi
- Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) College Pakistan Institute of Engineering and Applied Sciences, Faisalabad, Punjab, Pakistan
| | - Aamir Shehzad
- Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) College Pakistan Institute of Engineering and Applied Sciences, Faisalabad, Punjab, Pakistan
| | - Muhammad Sarwar
- Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) College Pakistan Institute of Engineering and Applied Sciences, Faisalabad, Punjab, Pakistan
| | - Imran Amin
- Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) College Pakistan Institute of Engineering and Applied Sciences, Faisalabad, Punjab, Pakistan
| | - Shahid Mansoor
- Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE) College Pakistan Institute of Engineering and Applied Sciences, Faisalabad, Punjab, Pakistan.
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Fabrick JA, Li X, Carrière Y, Tabashnik BE. Molecular Genetic Basis of Lab- and Field-Selected Bt Resistance in Pink Bollworm. INSECTS 2023; 14:insects14020201. [PMID: 36835770 PMCID: PMC9959750 DOI: 10.3390/insects14020201] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 02/03/2023] [Accepted: 02/14/2023] [Indexed: 05/17/2023]
Abstract
Transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) control some important insect pests. However, evolution of resistance by pests reduces the efficacy of Bt crops. Here we review resistance to Bt cotton in the pink bollworm, Pectinophora gossypiella, one of the world's most damaging pests of cotton. Field outcomes with Bt cotton and pink bollworm during the past quarter century differ markedly among the world's top three cotton-producing countries: practical resistance in India, sustained susceptibility in China, and eradication of this invasive lepidopteran pest from the United States achieved with Bt cotton and other tactics. We compared the molecular genetic basis of pink bollworm resistance between lab-selected strains from the U.S. and China and field-selected populations from India for two Bt proteins (Cry1Ac and Cry2Ab) produced in widely adopted Bt cotton. Both lab- and field-selected resistance are associated with mutations affecting the cadherin protein PgCad1 for Cry1Ac and the ATP-binding cassette transporter protein PgABCA2 for Cry2Ab. The results imply lab selection is useful for identifying genes important in field-evolved resistance to Bt crops, but not necessarily the specific mutations in those genes. The results also suggest that differences in management practices, rather than genetic constraints, caused the strikingly different outcomes among countries.
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Affiliation(s)
- Jeffrey A. Fabrick
- USDA ARS, U.S. Arid Land Agricultural Research Center, Maricopa, AZ 85138, USA
- Correspondence:
| | - Xianchun Li
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
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Fabrick JA, Heu CC, LeRoy DM, DeGain BA, Yelich AJ, Unnithan GC, Wu Y, Li X, Carrière Y, Tabashnik BE. Knockout of ABC transporter gene ABCA2 confers resistance to Bt toxin Cry2Ab in Helicoverpa zea. Sci Rep 2022; 12:16706. [PMID: 36202979 PMCID: PMC9537329 DOI: 10.1038/s41598-022-21061-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 09/22/2022] [Indexed: 11/08/2022] Open
Abstract
Evolution of pest resistance reduces the benefits of widely cultivated genetically engineered crops that produce insecticidal proteins derived from Bacillus thuringiensis (Bt). Better understanding of the genetic basis of pest resistance to Bt crops is needed to monitor, manage, and counter resistance. Previous work shows that in several lepidopterans, resistance to Bt toxin Cry2Ab is associated with mutations in the gene encoding the ATP-binding cassette protein ABCA2. The results here show that mutations introduced by CRISPR/Cas9 gene editing in the Helicoverpa zea (corn earworm or bollworm) gene encoding ABCA2 (HzABCA2) can cause resistance to Cry2Ab. Disruptive mutations in HzABCA2 facilitated the creation of two Cry2Ab-resistant strains. A multiple concentration bioassay with one of these strains revealed it had > 200-fold resistance to Cry2Ab relative to its parental susceptible strain. All Cry2Ab-resistant individuals tested had disruptive mutations in HzABCA2. We identified five disruptive mutations in HzABCA2 gDNA. The most common mutation was a 4-bp deletion in the expected Cas9 guide RNA target site. The results here indicate that HzABCA2 is a leading candidate for monitoring Cry2Ab resistance in field populations of H. zea.
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Affiliation(s)
- Jeffrey A Fabrick
- USDA ARS, U.S. Arid Land Agricultural Research Center, 21881 N. Cardon Lane, Maricopa, AZ, 85138, USA.
| | - Chan C Heu
- USDA ARS, U.S. Arid Land Agricultural Research Center, 21881 N. Cardon Lane, Maricopa, AZ, 85138, USA
| | - Dannialle M LeRoy
- USDA ARS, U.S. Arid Land Agricultural Research Center, 21881 N. Cardon Lane, Maricopa, AZ, 85138, USA
| | - Ben A DeGain
- Department of Entomology, University of Arizona, Tucson, AZ, 85721, USA
| | - Alex J Yelich
- Department of Entomology, University of Arizona, Tucson, AZ, 85721, USA
| | | | - Yidong Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, 210095, China
| | - Xianchun Li
- Department of Entomology, University of Arizona, Tucson, AZ, 85721, USA
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ, 85721, USA
| | - Bruce E Tabashnik
- Department of Entomology, University of Arizona, Tucson, AZ, 85721, USA
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Tabashnik BE, Unnithan GC, Yelich AJ, Fabrick JA, Dennehy TJ, Carrière Y. Responses to Bt toxin Vip3Aa by pink bollworm larvae resistant or susceptible to Cry toxins. PEST MANAGEMENT SCIENCE 2022; 78:3973-3979. [PMID: 35633103 DOI: 10.1002/ps.7016] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 05/17/2022] [Accepted: 05/28/2022] [Indexed: 05/29/2023]
Abstract
BACKGROUND Transgenic crops that make insecticidal proteins from Bacillus thuringiensis (Bt) have revolutionized management of some pests. However, evolution of resistance to Bt toxins by pests diminishes the efficacy of Bt crops. Resistance to crystalline (Cry) Bt toxins has spurred adoption of crops genetically engineered to produce the Bt vegetative insecticidal protein Vip3Aa. Here we used laboratory diet bioassays to evaluate responses to Vip3Aa by pink bollworm (Pectinophora gossypiella), one of the world's most damaging pests of cotton. RESULTS Against pink bollworm larvae susceptible to Cry toxins, Vip3Aa was less potent than Cry1Ac or Cry2Ab. Conversely, Vip3Aa was more potent than Cry1Ac or Cry2Ab against laboratory strains highly resistant to those Cry toxins. Five Cry-susceptible field populations were less susceptible to Vip3Aa than a Cry-susceptible laboratory strain (APHIS-S). Relative to APHIS-S, significant resistance to Vip3Aa did not occur in strains selected in the laboratory for > 700-fold resistance to Cry1Ac or both Cry1Ac and Cry2Ab. CONCLUSIONS Resistance to Cry1Ac and Cry2Ab did not cause strong cross-resistance to Vip3Aa in pink bollworm, which is consistent with predictions based on the lack of shared midgut receptors between these toxins and previous results from other lepidopterans. Comparison of the Bt toxin concentration in plants relative to the median lethal concentration (LC50 ) from bioassays may be useful for estimating efficacy. The moderate potency of Vip3Aa against Cry1Ac- and Cry2Ab-resistant and susceptible pink bollworm larvae suggests that Bt cotton producing this toxin together with novel Cry toxins might be useful as one component of integrated pest management. © 2022 Society of Chemical Industry.
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Affiliation(s)
| | | | | | - Jeffrey A Fabrick
- USDA ARS, US Arid Land Agricultural Research Center, Maricopa, AZ, USA
| | | | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ, USA
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CRISPR-mediated mutations in the ABC transporter gene ABCA2 confer pink bollworm resistance to Bt toxin Cry2Ab. Sci Rep 2021; 11:10377. [PMID: 34001946 PMCID: PMC8128902 DOI: 10.1038/s41598-021-89771-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 04/28/2021] [Indexed: 11/29/2022] Open
Abstract
Crops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt) have many benefits and are important globally for managing insect pests. However, the evolution of pest resistance to Bt crops reduces their benefits. Understanding the genetic basis of such resistance is needed to better monitor, manage, and counter pest resistance to Bt crops. Previous work shows that resistance to Bt toxin Cry2Ab is associated with mutations in the gene encoding the ATP-binding cassette protein ABCA2 in lab- and field-selected populations of the pink bollworm (Pectinophora gossypiella), one of the world’s most destructive pests of cotton. Here we used CRISPR/Cas9 gene editing to test the hypothesis that mutations in the pink bollworm gene encoding ABCA2 (PgABCA2) can cause resistance to Cry2Ab. Consistent with this hypothesis, introduction of disruptive mutations in PgABCA2 in a susceptible strain of pink bollworm increased the frequency of resistance to Cry2Ab and facilitated creation of a Cry2Ab-resistant strain. All Cry2Ab-resistant individuals tested in this study had disruptive mutations in PgABCA2. Overall, we found 17 different disruptive mutations in PgABCA2 gDNA and 26 in PgABCA2 cDNA, including novel mutations corresponding precisely to single-guide (sgRNA) sites used for CRISPR/Cas9. Together with previous results, these findings provide the first case of practical resistance to Cry2Ab where evidence identifies a specific gene in which disruptive mutations can cause resistance and are associated with resistance in field-selected populations.
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The Essential and Enigmatic Role of ABC Transporters in Bt Resistance of Noctuids and Other Insect Pests of Agriculture. INSECTS 2021; 12:insects12050389. [PMID: 33924857 PMCID: PMC8145640 DOI: 10.3390/insects12050389] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 04/25/2021] [Accepted: 04/26/2021] [Indexed: 11/18/2022]
Abstract
Simple Summary The insect family, Noctuidae, contains some of the most damaging pests of agriculture, including bollworms, budworms, and armyworms. Transgenic cotton and maize expressing Cry-type insecticidal proteins from Bacillus thuringiensis (Bt) are protected from such pests and greatly reduce the need for chemical insecticides. However, evolution of Bt resistance in the insects threatens the sustainability of this environmentally beneficial pest control strategy. Understanding the interaction between Bt toxins and their targets in the insect midgut is necessary to evaluate the risk of resistance evolution. ABC transporters, which in eukaryotes typically expel small molecules from cells, have recently been proposed as a target for the pore-forming Cry toxins. Here we review the literature surrounding this hypothesis in noctuids and other insects. Appreciation of the critical role of ABC transporters will be useful in discovering counterstrategies to resistance, which is already evolving in some field populations of noctuids and other insects. Abstract In the last ten years, ABC transporters have emerged as unexpected yet significant contributors to pest resistance to insecticidal pore-forming proteins from Bacillus thuringiensis (Bt). Evidence includes the presence of mutations in resistant insects, heterologous expression to probe interactions with the three-domain Cry toxins, and CRISPR/Cas9 knockouts. Yet the mechanisms by which ABC transporters facilitate pore formation remain obscure. The three major classes of Cry toxins used in agriculture have been found to target the three major classes of ABC transporters, which requires a mechanistic explanation. Many other families of bacterial pore-forming toxins exhibit conformational changes in their mode of action, which are not yet described for the Cry toxins. Three-dimensional structures of the relevant ABC transporters, the multimeric pore in the membrane, and other proteins that assist in the process are required to test the hypothesis that the ATP-switch mechanism provides a motive force that drives Cry toxins into the membrane. Knowledge of the mechanism of pore insertion will be required to combat the resistance that is now evolving in field populations of insects, including noctuids.
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Mishra R, Guo Y, Kumar P, Cantón PE, Tavares CS, Banerjee R, Kuwar S, Bonning BC. Streamlined phage display library protocols for identification of insect gut binding peptides highlight peptide specificity. CURRENT RESEARCH IN INSECT SCIENCE 2021; 1:100012. [PMID: 36003592 PMCID: PMC9387513 DOI: 10.1016/j.cris.2021.100012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 02/09/2021] [Accepted: 02/14/2021] [Indexed: 05/10/2023]
Abstract
Phage display libraries have been used to isolate insect gut binding peptides for use as pathogen transmission blocking agents, and to provide artificial anchors for increased toxicity of bacteria-derived pesticidal proteins. Previously, phage clones displaying enriched peptides were sequenced by Sanger sequencing. Here we present a streamlined protocol for identification of insect gut binding peptides, using insect-appropriate feeding strategies, with next generation sequencing and tailored bioinformatics analyses. The bioinformatics pipeline is designed to eliminate poorly enriched and false positive peptides, and to identify peptides predicted to be stable and hydrophilic. In addition to developing streamlined protocols, we also sought to address whether candidate gut binding peptides can bind to insects from more than one order, which is an important consideration for safe, practical use of peptide-modified pesticidal proteins. To this end, we screened phage display libraries for peptides that bind to the gut epithelia of two pest insects, the Asian citrus psyllid, Diaphorina citri (Hemiptera) and beet armyworm, Spodoptera exigua (Lepidoptera), and one beneficial insect, the western honey bee, Apis mellifera (Hymenoptera). While unique peptide sequences totaling 13,427 for D. citri, 89,561 for S. exigua and 69,053 for A. mellifera were identified from phage eluted from the surface of the insect guts, final candidate pools were comprised of 53, 107 and 1423 peptides respectively. The benefits of multiple rounds of biopanning, along with peptide binding properties in relation to practical use of peptide-modified pesticidal proteins for insect pest control are discussed.
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