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Guo Q, Li W, Niu Y, Dai X, Chen L. Culex quinquefasciatus membrane-bound alkaline phosphatase is a putative receptor for Lysinibacillus sphaericus Tpp49Aa1 toxin. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2024; 164:104044. [PMID: 38036275 DOI: 10.1016/j.ibmb.2023.104044] [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: 07/23/2023] [Revised: 11/22/2023] [Accepted: 11/23/2023] [Indexed: 12/02/2023]
Abstract
The binary toxin Cry48Aa1/Tpp49Aa1 produced by Lysinibacillus sphaericus exhibits potent toxicity against Culicidae larvae. Both Cry48Aa1 and Tpp49Aa1 toxins are crucial for binding to the toxin receptor in Culex quinquefasciatus larvae, albeit with different binding sites. Previous studies have identified Glu71, a membrane-bound α-glucosidase, as a putative binding protein for the Cry48Aa1 toxin, involved in the Cry48Aa1/Tpp49Aa1 toxicity. In this study, we employed pulldown assays to identify a group of Tpp49Aa1-binding proteins from C. quinquefasciatus solubilized midgut brush-border membrane proteins (BBMFs). RNA interference assays revealed that the silencing of an alkaline phosphatase gene (referred to as ALP1263) in C. quinquefasciatus resulted in a significant reduction in larval mortality upon exposure to Cry48Aa1/Tpp49Aa1 toxin in vivo. Furthermore, the ALP1263 protein exhibited specific and high-affinity binding to the Tpp49Aa1 toxin, with a dissociation constant (Kd) of approximately 57.3 nM. The dot blot analysis demonstrated that Tpp49Aa1 C-terminal region was essential for its interaction with the ALP1263 protein. In summary, our findings establish ALP1263 as a functional receptor for Tpp49Aa1 and emphasize its role in the toxicity of Cry48Aa1/Tpp49Aa1.
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Affiliation(s)
- Qingyun Guo
- College of Life Sciences, Gannan Normal University, Ganzhou City, Jiangxi Province, 341000, PR China.
| | - Wei Li
- College of Life Sciences, Gannan Normal University, Ganzhou City, Jiangxi Province, 341000, PR China
| | - Yingchao Niu
- College of Life Sciences, Gannan Normal University, Ganzhou City, Jiangxi Province, 341000, PR China
| | - Xiaohua Dai
- College of Life Sciences, Gannan Normal University, Ganzhou City, Jiangxi Province, 341000, PR China
| | - Lin Chen
- College of Life Sciences, Gannan Normal University, Ganzhou City, Jiangxi Province, 341000, PR China
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Guo Q, Gao Y, Xing C, Niu Y, Ding L, Dai X. Culex quinquefasciatus alpha-glucosidase serves as a putative receptor of the Cry48Aa toxin from Lysinibacillus sphaericus. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2022; 147:103799. [PMID: 35662624 DOI: 10.1016/j.ibmb.2022.103799] [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: 12/21/2021] [Revised: 05/20/2022] [Accepted: 05/27/2022] [Indexed: 06/15/2023]
Abstract
The Cry48Aa/Cry49Aa toxin of Lysinibacillus sphaericus shows specific toxicity towards larvae of Culex spp. Individual Cry48Aa and Cry49Aa subunits interact with distinct target sites in the larval midgut and overcome the resistance of Culex to the Bin toxin. However, the toxin-binding proteins have not yet been identified. The present study aimed to identify Cry48Aa-binding proteins in Culex quinquefasciatus. Pulldown assays using C. quinquefasciatus midgut brush-border membrane fractions (BBMFs) identified a class of proteins, including aminopeptidases (APNs), protease m1 zinc metalloproteases, alkaline phosphatases (ALPs), and maltases, that could be potentially involved in the mode of action of this toxin. RNA interference analysis showed that silenced larvae treated with dsRNA of the alpha-glucosidase (named Glu71) gene were more tolerant of the Cry48Aa/Cry49Aa toxin, which induced less than 20% mortality. The amino acid sequence of Glu71 exhibited 42% identity with Cqm1/Cpm1, which acted as a Bin toxin receptor. Toxin binding assays showed that Cry48Aa had a high specific binding capacity for the Glu71 protein, whereas Cry49Aa exhibited no specific binding. Overall, our results showed that Glu71 is a Cry48-binding protein involved in Cry48Aa/Cry49Aa toxicity.
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Affiliation(s)
- Qingyun Guo
- College of Life Sciences, Gannan Normal University, Ganzhou City of Jiangxi Province, 341000, PR China.
| | - Yuan Gao
- College of Life Sciences, Gannan Normal University, Ganzhou City of Jiangxi Province, 341000, PR China
| | - Chong Xing
- School of Information Engineering, Gannan Medical University, Ganzhou City of Jiangxi Province, 341000, PR China
| | - Yingchao Niu
- College of Life Sciences, Gannan Normal University, Ganzhou City of Jiangxi Province, 341000, PR China
| | - Lu Ding
- College of Life Sciences, Gannan Normal University, Ganzhou City of Jiangxi Province, 341000, PR China
| | - Xiaohua Dai
- College of Life Sciences, Gannan Normal University, Ganzhou City of Jiangxi Province, 341000, PR China
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Bacterial Toxins Active against Mosquitoes: Mode of Action and Resistance. Toxins (Basel) 2021; 13:toxins13080523. [PMID: 34437394 PMCID: PMC8402332 DOI: 10.3390/toxins13080523] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/18/2021] [Accepted: 06/19/2021] [Indexed: 12/25/2022] Open
Abstract
Larvicides based on the bacteria Bacillus thuringiensis svar. israelensis (Bti) and Lysinibacillus sphaericus are effective and environmentally safe compounds for the control of dipteran insects of medical importance. They produce crystals that display specific and potent insecticidal activity against larvae. Bti crystals are composed of multiple protoxins: three from the three-domain Cry type family, which bind to different cell receptors in the midgut, and one cytolytic (Cyt1Aa) protoxin that can insert itself into the cell membrane and act as surrogate receptor of the Cry toxins. Together, those toxins display a complex mode of action that shows a low risk of resistance selection. L. sphaericus crystals contain one major binary toxin that display an outstanding persistence in field conditions, which is superior to Bti. However, the action of the Bin toxin based on its interaction with a single receptor is vulnerable for resistance selection in insects. In this review we present the most recent data on the mode of action and synergism of these toxins, resistance issues, and examples of their use worldwide. Data reported in recent years improved our understanding of the mechanism of action of these toxins, showed that their combined use can enhance their activity and counteract resistance, and reinforced their relevance for mosquito control programs in the future years.
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Menezes HSG, Nascimento NA, Paiva-Cavalcanti M, da Costa-Latgé SG, Genta FA, Oliveira CM, Romão TP, Silva-Filha MHN. Molecular and biological features of Culex quinquefasciatus homozygous larvae for two cqm1 alleles that confer resistance to Lysinibacillus sphaericus larvicides. PEST MANAGEMENT SCIENCE 2021; 77:3135-3144. [PMID: 33644981 DOI: 10.1002/ps.6349] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 01/26/2021] [Accepted: 02/28/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND Culex quinquefasciatus resistance to the binary toxin from Lysinibacillus sphaericus larvicides can occur because of mutations in the cqm1 gene that prevents the expression of the toxin receptor, Cqm1 α-glucosidase. In a resistant laboratory-selected colony maintained for more than 250 generations, cqm1REC and cqm1REC-2 resistance alleles were identified. The major allele initially found, cqm1REC , became minor and was replaced by cqm1REC-2 . This study aimed to investigate the features associated with homozygous larvae for each allele to understand the reasons for the allele replacement and to generate knowledge on resistance to microbial larvicides. RESULTS Homozygous larvae for each allele were compared. Both larvae displayed the same level of resistance to the binary toxin (3500-fold); therefore, a change in phenotype was not the reason for the replacement observed. The lack of Cqm1 expression did not reduce the total specific α-glucosidase activity for homozygous cqm1REC and cqm1REC-2 larvae, which were statistically similar to the susceptible strain, using artificial or natural substrates. The expression of eight Cqm1 paralog α-glucosidases was demonstrated in resistant and susceptible larvae. Bioassays in which cqm1REC or cqm1REC-2 homozygous larvae were reared under stressful conditions showed that most adults produced were cqm1REC-2 homozygous (69%). Comparatively, in the offspring of a heterozygous sub-colony reared under optimal conditions for 20 generations, the cqm1REC allele assumed a higher frequency (0.72). CONCLUSION Homozygous larvae for each allele exhibited a similar resistant phenotype. However, they presented specific advantages that might favor their selection and can be used in designing resistance management practices. © 2021 Society of Chemical Industry.
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Affiliation(s)
| | | | | | - Samara G da Costa-Latgé
- Laboratory of Insect Biochemistry and Physiology, Instituto Oswaldo Cruz-FIOCRUZ, Rio de Janeiro, Brazil
| | - Fernando A Genta
- Laboratory of Insect Biochemistry and Physiology, Instituto Oswaldo Cruz-FIOCRUZ, Rio de Janeiro, Brazil
| | | | - Tatiany P Romão
- Department of Entomology, Instituto Aggeu Magalhães-FIOCRUZ, Recife, Brazil
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Lopes RP, Lima JBP, Martins AJ. Insecticide resistance in Culex quinquefasciatus Say, 1823 in Brazil: a review. Parasit Vectors 2019; 12:591. [PMID: 31852489 PMCID: PMC6921570 DOI: 10.1186/s13071-019-3850-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 12/10/2019] [Indexed: 11/10/2022] Open
Abstract
Culex quinquefasciatus is a successful invasive species broadly distributed in subtropical regions, including Brazil. It is an extremely annoying mosquito due to its nocturnal biting behavior, in high-density populations and it is a potential bridge between sylvatic arbovirus from birds to man in urban territories. Herein, we present a review concerning the methods of chemical control employed against Cx. quinquefasciatus in Brazil since the 1950's and insecticide resistance data registered in the literature. As there is no specific national programme for Cx. quinquefasciatus control in Brazil, the selection of insecticide resistance is likely due in part to the well-designed chemical campaigns against Aedes aegypti and the elevated employment of insecticides by households and private companies. There are very few publications about insecticide resistance in Cx. quinquefasciatus from Brazil when compared to Ae. aegypti. Nevertheless, resistance to organophosphates, carbamate, DDT, pyrethroids and biolarvicides has been registered in Cx. quinquefasciatus populations from distinct localities of the country. Concerning physiological mechanisms selected for resistance, distinct patterns of esterases, as well as mutations in the acetylcholinesterase (ace-1) and voltage-gated sodium channel (NaV) genes, have been identified in natural populations. Given environmental changes and socioeconomical issues in the cities, in recent years we have been experiencing an increase in the number of disease cases caused by arboviruses, which may involve Cx. quinquefasciatus participation as a key vector. It is urgent to better understand the efficiency and susceptibility status to insecticides, as well as the genetic background of known resistant mechanisms already present in Cx. quinquefasciatus populations for an effective and rapid chemical control when eventually required.
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Affiliation(s)
- Ramon Pereira Lopes
- Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | - José Bento Pereira Lima
- Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | - Ademir Jesus Martins
- Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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Sharma M, Kumar V. Crystal structure of BinAB toxin receptor (Cqm1) protein and molecular dynamics simulations reveal the role of unique Ca(II) ion. Int J Biol Macromol 2019; 140:1315-1325. [PMID: 31449868 DOI: 10.1016/j.ijbiomac.2019.08.126] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 08/14/2019] [Accepted: 08/14/2019] [Indexed: 10/26/2022]
Abstract
Glycoside hydrolase 13 (GH13) family represents a large and diverse enzyme family. Cqm1, an amylomaltase of Culex mosquito, belongs to the GH13 family and subfamily 17 (GH13_17). The protein acts as the receptor for mosquito-larvicidal BinAB toxin that is used world-wide for control of the mosquito population. The protein was crystallized in the presence of a mixture of divalent metal ions. Cqm1 crystal structure was solved using the MRSAD method using Cd(II) anomalous at 1.9 Å wavelength and the structure was refined against 1.8 Å synchrotron data. One tightly bound Ca(II) ion in each of the monomer was observed and this site is suggested here to be unique to the GH13_17 family. Molecular dynamics simulations provide clues for the functional role of Ca(II) ion shown earlier to be essential for enzymatic activity. An optimized substrate (maltotriose) bound structure of the complex was constructed based on which 'retaining-type' mechanism can be predicted reliably. It reveals large conformational change in aromatic residues situated at active-site entrance. A Cd(II) ion was observed overlapping with the substrate-binding site. Kinetics data suggests non-competitive inhibition of Cqm1 by Cd(II). This is the first structure from the GH13_17 family and provides template for constructing reliable models for other members.
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Affiliation(s)
- Mahima Sharma
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - Vinay Kumar
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400085, India; Homi Bhabha National Institute, Anushaktinagar, Mumbai 400085, India.
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