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Insect toxin

Isabel Gómez, Josue Ocelotl, Jorge Sánchez, Christina Lima, Erica Martins, Anayeli Rosales-Juárez, Sotero Aguilar-Medel, André Abad, Hua Dong, Rose Monnerat, Guadalupe Peña, Jie Zhang, Mark Nelson, Gusui Wu, Alejandra Bravo, Mario Soberón
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 that is highly active against this pest and is used in transgenic maize for S. frugiperda control. The region of β16 from domain III of Cry1Ab has been shown to be involved in interaction with receptors such as alkaline phosphatase (ALP) or aminopeptidase (APN) in different lepidopteran insects...
August 10, 2018: Applied and Environmental Microbiology
Gerson Adriano Silva, Izailda Barbosa Santos, Silvério Oliveira Campos, Tarcísio Visintin Silva Galdino, Elisângela Gomes Fidelis Morais, Júlio Claudio Martins, Lino Roberto Ferreira, Raul Narciso Carvalho Guedes, Marcelo Coutinho Picanço
Insect pests are one of the factors that most impact plant yield. The magnitude of the losses and the spatiotemporal pest distribution in crops is a result of their interactions with the environment. Therefore, the understanding of the causes of production losses and the pest spatial patterns is important for the development of suitable sampling plans and pest management programs. Thus, this study aimed to quantify grain losses caused by insects and to determine the spatial distribution pattern of arthropod pest species in Bt and non-Bt corn...
2018: PloS One
Ivan Hiltpold, Bruce E Hibbard
Plants genetically modified to produce insecticidal toxins from the bacterium Bacillus thuringiensis Berliner (Bt) have been extensively used to manage the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) in the United States. Evolution of WCR resistance to Bt toxins has forced the consideration of alternative pest management and improved insect resistance management. Entomopathogenic nematodes (EPNs), obligate insect parasites, are attracted toward volatile organic compounds (VOCs) emitted by maize roots after WCR herbivory...
August 2, 2018: Journal of Economic Entomology
María Martínez-Solís, Daniel Pinos, Haruka Endo, Leivi Portugal, Ryoichi Sato, Juan Ferré, Salvador Herrero, Patricia Hernández-Martínez
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...
August 2, 2018: Insect Biochemistry and Molecular Biology
C V Haridas, Brigitte Tenhumberg
Widespread use of pesticides has resulted in the evolution of of resistance in many insect pests worldwide limiting their use in pest control. Effective pest and resistance management practices require understanding of the genetics of resistance and of the life history of the pest. Most models for pesticide resistance assume that resistance is monogenic, conferred by a single gene. However, resistance could evolve as a polygenic quantitative trait resulting from the action of several genes, especially when pesticide dose is low...
July 31, 2018: Journal of Theoretical Biology
Yong Wang, Dabo Li, Hao Zhou, Hui Liu, Lin Niu, Lihua Wang, Weihua Ma
Transgenic crops expressing Cry toxins are effective and considered environmentally friendly alternatives to synthetic pesticides, but assessment of environmental risks of their application on non-target organisms is ongoing. The main risk is the transfer of Cry toxins to natural enemies through the food chain. There is reported evidence supporting that Cry toxins can be detected in the body and gut of some natural enemy insects. Considering that binding of Cry toxins to insect proteins is an essential step in the intoxication process, this work was conducted to evaluate interactions between Cry1Ac and Cry2Aa toxins with proteins from larvae/nymphs and adults of two important predatory natural enemies in cotton fields, Harmonia axyridis and Orius similis...
July 30, 2018: Journal of Agricultural and Food Chemistry
Carlos Pascacio-Villafán, Larissa Guillén, Trevor Williams, Martín Aluja
The larval developmental environment can affect the quality of artificially reared insects used in pest control programs that apply the sterile insect technique. We used a liquid larval diet lacking corncob fractions (an ingredient which may be contaminated by toxins that inhibit larval development and drastically reduce insect production in mass-rearing facilities) to examine quality indicators of Anastrepha ludens (Loew) (Diptera: Tephritidae) as a function of larval density (1-5 larvae per ml of diet) and on two types of supporting materials (synthetic sponge and carpet felt) compared with a standard solid diet with corncob fractions inoculated with a fixed quantity of A...
July 25, 2018: Journal of Economic Entomology
Huaizong Shen, Zhangqiang Li, Yan Jiang, Xiaojing Pan, Jianping Wu, Ben Cristofori-Armstrong, Jennifer J Smith, Yanni K Y Chin, Jianlin Lei, Qiang Zhou, Glenn F King, Nieng Yan
Animal toxins that modulate the activity of Nav channels are broadly divided into two categories-pore blockers and gating modifiers. The pore blockers tetrodotoxin (TTX) and saxitoxin (STX) are responsible for pufferfish and shellfish poisoning in humans, respectively. Here we present structures of the insect Nav channel Nav PaS bound to a gating modifier toxin Dc1a at 2.8 Å and in the presence of TTX or STX at 2.6 Å and 3.2 Å resolution, respectively. Dc1a inserts into the cleft between VSDII and the pore of Nav PaS, making key contacts with both domains...
July 26, 2018: Science
Yun Yang, Jufang Gao, Yang Zhang, Wenping Xu, Youwu Hao, Zhiping Xu, Liming Tao
Natural pyrethrins, one kind of insects' neural toxin, have been used worldwide for the control of pests of crops, livestock, and human beings. However, their specific mechanisms of action are incompletely understood and hence further investigation is required. Here we used a series of experiments including colony formation, fluorescent staining, western blotting, enzyme activity detection, immunofluorescence analysis, and real-time quantitative PCR (QPCR) to investigate whether natural pyrethrins (0-40 μg/mL) are able to modulate autophagy process through AMPK/mTOR signaling pathway, in order to reveal their cytotoxic mechanisms...
October 2018: Environmental Pollution
Tatsuya Kawasaki, Takuya Matsumoto, Yuma Iwai, Mamiyo Kawakami, Narinobu Juge, Hiroshi Omote, Tomohiro Nabekura, Yoshinori Moriyama
Human MATE1 (multidrug and toxin extrusion 1, hMATE1) is a H+ /organic cation (OC) exchanger responsible for the final step of toxic organic cation excretion in the kidney and liver. To investigate the mechanism of transport, we have established an in vitro assay procedure that includes its expression in insect cells, solubilization with octyl glucoside, purification, and reconstitution into liposomes. The resultant proteoliposomes containing hMATE1 as the sole protein component took up radiolabeled tetraethylammonium (TEA) in a ∆pH-dependent and electroneutral fashion...
July 17, 2018: Biochimica et Biophysica Acta
Yinglong Wang, Yonglei Liu, Jie Zhang, Neil Crickmore, Fuping Song, Jiguo Gao, Changlong Shu
Transgenic plants expressing insecticidal proteins originating from Bacillus thuringiensis (Bt) have successfully been used to control lepidopteran and coleopteran pests with chewing mouthparts. However, only a handful of Bt proteins have been identified that have bioactivity against sap sucking pests (Hemiptera), including aphids, whiteflies, plant bugs and planthoppers. A novel Bt insecticidal protein with significant toxicity against a hemipteran insect pest is described here. The gene encoding the 359 amino acid, 40...
July 11, 2018: Journal of Invertebrate Pathology
Nikita A Kuldyushev, Konstantin S Mineev, Antonina A Berkut, Steve Peigneur, Alexander S Arseniev, Jan Tytgat, Eugene V Grishin, Alexander A Vassilevski
Sodium channel alpha-toxins from scorpion venom (α-NaTx) inhibit the inactivation of voltage-gated sodium channels. We used solution NMR to investigate the structure of BeM9 toxin from Mesobuthus eupeus scorpion, a prototype α-NaTx classified as an "α-like" toxin due to its wide spectrum of activity on insect and mammalian channels. We identified a new motif that we named "arginine hand", whereby arginine side chain forms several hydrogen bonds with main chain atoms. The arginine hand was found in the "specificity module", a part of the molecule that dictates toxin selectivity; and just single arginine-to-lysine point mutation drastically changed BeM9 selectivity profile...
July 14, 2018: Proteins
Mahima Sharma, Gagan D Gupta, Vinay Kumar
Lysinibacillus sphaericus parasporal BinAB toxin displays mosquito larvicidal activity against Culex and Anopheles, but several Aedes species are refractory. Recently reported crystal structure of BinAB revealed the presence of N-terminal lectin-like domain in BinA. Hemagglutination and hemolytic activities were not observed for BinA in the present studies. We attempted to characterize carbohydrate specificity of BinA by high-throughput approaches using extrinsic fluorescence and thermofluor shift assay. A total of 34 saccharides (mono-, di- and polysaccharides, and glycoproteins) were used for initial high-throughput screening...
July 2018: Journal of Invertebrate Pathology
Zhuo Li, Megha N Parajulee, Fajun Chen
Background: Bt crops will face a new ecological risk of reduced effectiveness against target-insect pests owing to the general decrease in exogenous-toxin content in Bt crops grown under elevated carbon dioxide (CO2 ). The method chosen to deal with this issue may affect the sustainability of transgenic crops as an effective pest management tool, especially under future atmospheric CO2 level raising. Methods: In this study, rhizobacterias, as being one potential biological regulator to enhance nitrogen utilization efficiency of crops, was selected and the effects of Bt maize (Line IE09S034 with Cry1Ie vs...
2018: PeerJ
Daniela Zanga, Georgina Sanahuja, Matilde Eizaguirre, Ramon Albajes, Paul Christou, Teresa Capell, Paul Fraser, Chris Gerrisch, Carmen López
We assessed the effectiveness of a biofortified maize line (4BtxHC) which accumulates high levels of antioxidant carotenoids that also expressed the insecticidal Cry1Ac Bacillus thuringiensis (Bt) gene against the European corn borer Ostrinia nubilalis. This line had been previously engineered to accumulate carotenoids specifically in the seed endosperm, whereas the Bt gene was expressed constitutively. The concentrations of Bt toxin (Cry 1Ac) in the leaves of the 4Bt and 4BtxHC lines were not significantly different at 47±6 μg/g of fresh weight (FW); neither were they in the kernels of both lines (35±3 μg/g FW)...
2018: PloS One
Guillaume Tetreau
Toxins are a major virulence factor produced by many pathogenic bacteria. In vertebrates, the response of hosts to the bacteria is inseparable from the response to the toxins, allowing a comprehensive understanding of this tripartite host-pathogen-toxin interaction. However, in invertebrates, this interaction has been investigated by two complementary but historically distinct fields of research: toxinology and immunology. In this article, I highlight how such dichotomy between these two fields led to a biased, or even erroneous view of the ecology and evolution of the interaction between insects, toxins, and bacteria...
July 6, 2018: Toxins
Tom R Bilbo, Francis P F Reay-Jones, Dominic D Reisig, Fred R Musser, Jeremy K Greene
The corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), is only moderately susceptible to most toxins from the bacterium Bacillus thuringiensis (Bt) expressed in transgenic corn. To better understand the impact of Bt corn on the life cycle of H. zea, we collected pupae of H. zea during 2014-2016 in North Carolina, South Carolina, and Mississippi from corn hybrids expressing Cry1Ab, Cry1F, Cry1F + Cry1Ab, Cry1F + Cry1Ab + Vip3Aa20, Cry1A.105 + Cry2Ab2, and Cry1A.105 + Cry2Ab2 + Cry1F, as well as from non-Bt near-isolines...
July 9, 2018: Journal of Economic Entomology
Lin Chen, Jizhen Wei, Chen Liu, Wanna Zhang, Bingjie Wang, LinLin Niu, Gemei Liang
A pyramid strategy combining the crystal (Cry) 1A and 2A toxins in Bacillus thuringiensis (Bt) crops are active against many species of insects and nematode larvae. It has been widely used to delay pest adaption to genetically modified plants and broaden the insecticidal spectrum in many countries. Unfortunately, Cry2A can also bind with the specific receptor proteins of Cry1A. ATP-binding cassette (ABC) transporters can interact with Cry1A toxins as receptors in the insect midgut, and ABC transporter mutations result in resistance to Bt proteins...
2018: Frontiers in Physiology
Leilei Liu, Zuwen Chen, Yanchao Yang, Yutao Xiao, Chenxi Liu, Yuemin Ma, Mario Soberón, Alejandra Bravo, Yongbo Yang, Kaiyu Liu
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...
June 29, 2018: Insect Biochemistry and Molecular Biology
Christopher Graf, Antonia B Kesel, Elena V Gorb, Stanislav N Gorb, Jan-Henning Dirks
Most insects with smooth or hairy adhesive pads have very little problems in attaching to smooth substrates. A careful selection of surface roughness, however, can effectively limit the contact area of the adhesive organs with the surface. In comparison to conventional toxin-based insect repelling methods, biologically inspired micro- and nanostructured insect repellent surface structures, thus, offer a great potential to effective and environmentally-friendly control insect pests. We here present a simple experimental approach to qualitatively and quantitatively analyse the efficiency of a micro- and nanorough surface structure...
July 31, 2018: Bioinspiration & Biomimetics
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