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Insect toxin

Sajjad Ali, Muhammad Irfan Ullah, Muhammad Farhan Saeed, Samina Khalid, Muhammad Saqib, Muhammad Arshad, Muhammad Afzal, Christos A Damalas
Insect physiology is affected by the presence of toxins in the surrounding environment of insects as well as their food sources. The objective of this study was to determine the effect of heavy metal exposure to two low concentrations (50 μg/g and 150 μg/g) of lead (Pb) and zinc (Zn) through artificial diet to the larvae on biological parameters of Asian armyworm (Spodoptera litura Fabricius) (Lepidoptera: Noctuidae). Both Pb and Zn, even at low concentrations, had relatively high toxic effects on S. litura larvae (P < 0...
March 13, 2019: Environmental Science and Pollution Research International
Nathan S Little, Blake H Elkins, R Michelle Mullen, Omaththage P Perera, Katherine A Parys, K Clint Allen, Deborah L Boykin
Interpreting variable laboratory measurements of Helicoverpa zea Boddie susceptibility to toxins from Bacillus thuringiensis Berliner (Bt) has been challenging due to a lack of clear evidence to document declining field control. Research that links laboratory measurements of susceptibility to survival on Bt crops is vital for accurate characterization and any subsequent response to the occurrence of an implied H. zea resistance event. In this study, H. zea survival and the resultant damage to plant fruiting structures of non-Bt, Bollgard II, and Bollgard III cottons from two insect colonies with differing levels of laboratory susceptibility to Bt toxins were evaluated in large field cages...
2019: PloS One
Shan Yueming, Changlong Shu, Kanglai He, Xue Cheng, Lili Geng, Wensheng Xiang, Jie Zhang
In the recent decades, there have been increasing reports of insect resistance in Bacillus thuringiensis (Bt) crops. Alternative use of Cry toxins, with high insecticidal activity and different mechanisms of action, may be an important strategy to manage this resistance. Cry9 protein, with high toxicity to the lepidopteran pests and no cross-resistance with commercial Cry1 proteins, is a valuable relevant resource. A novel insecticidal protein MP1489, subsequently named as Cry9Cb1, with 88% amino acid sequence identity with Cry9Ca1, was identified from Bt strain SP663; it exhibited high insecticidal activity against Plutella xylostella, Ostrinia furnacalis, and Chilo suppressalis, and no cross-resistance with Cry1Fa in Ostrinia furnacalis...
March 13, 2019: Journal of Agricultural and Food Chemistry
Jizhen Wei, Yaling Zhang, Shiheng An
Bt crop pyramids produce two or more Bt proteins active to broaden the spectrum of action and to delay the development of resistance in exposed insect populations. The cross-resistance between Bt toxins is a vital restriction factor for Bt crop pyramids, which may reduce the effect of pyramid strategy. In this review, the status of the cross-resistance among more than 20 Bt toxins that are most commonly used against 13 insect pests was analyzed. The potential mechanisms of cross-resistance are discussed. The corresponding measures, including pyramid RNA interference and Bt toxin, "high dose/refuge," and so on are advised to be taken for adopting the pyramided strategy to delay the Bt evolution of resistance and control the target pest insect...
March 12, 2019: Archives of Insect Biochemistry and Physiology
Kelly Niermans, Jan Woyzichovski, Nina Kröncke, Rainer Benning, Ronald Maul
Edible insects as additional food and/or feed source may represent one important component to solve the problem of food security for a growing human population. Especially for covering the rising demand for protein of animal origin, seven insect species currently allowed as feed constituents in the European Union are gaining more interest. However, before considering insects such as yellow mealworm larvae (Tenebrio molitor) as suitable for, e.g. human consumption, the possible presence and accumulation of contaminants must be elucidated...
March 13, 2019: Mycotoxin Research
Kesorn Boonmee, Sutticha Na-Ranong Thammasittirong, Anon Thammasittirong
A total of 511 local isolates of Bacillus thuringiensis from different geographical regions of Thailand were analyzed for the presence of the cry1A, cry1B, cry2A, cry9 , and vip3A genes encoding for lepidopteran-specific toxins. PCR results revealed that 94.32% (482/511) of B. thuringiensis isolates harbored at least one of the detected genes, of which the cry1A, cry1B, cry2A, cry9 , and vip3A genes were detected at frequencies of 90.61%, 89.63%, 76.32%, 40.70%, and 48.18%, respectively. Nineteen gene-combination profiles were discovered among 482 B...
April 2019: 3 Biotech
Eric Yu Yu, Aaron J Gassmann, Thomas W Sappington
The western corn rootworm, Diabrotica virgifera virgifera (LeConte) (Coleoptera: Chrysomelidae), is an economically important pest of corn in the northern United States. Some populations have developed resistance to management strategies including transgenic corn that produces insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt). Knowledge of insect dispersal is of critical importance for models of resistance evolution. Larval density affects survival in the field, and stress from crowding often affects facultative long-distance dispersal of adult insects...
2019: PloS One
Kai Liu, Meichi Wang, Liping Jiang, Xing Tang, Zhen Liu, Zefei Zhou, Weijun Hu, Zhigui Duan, Songping Liang
Spider venoms are insecticidal mixtures with diverse biological activities, and acylpolyamines are their small molecular active components. However, the mechanism for the insecticidal activity of acylpolyamines remains to be elucidated. Here, the structure and function of two acylpolyamine toxins, AVTX-622 and AVTX-636, from Araneus ventricosus were investigated. Nuclear magnetic resonance (NMR) analysis illustrated that the structure of two toxins was very similar, and compared to AVTX-636, AVTX-622 only missed a methylene group in the linker region between the polyamine head and tail...
February 27, 2019: Chemical Research in Toxicology
Chuan Zhang, Ju Luo, Geng Chen, Lanzhi Han, Yufa Peng
Cost-effective Bt resistance monitoring programmes exist to manage insect resistance to Bt crops. F2 screening is widely used in detecting rare resistant alleles. One way to establish numerous isofemale lines for F2 bioassays is acquiring many field-trapped copulated females. However, it is difficult to obtain sufficient Chilo suppressalis isofemale lines because females have low mating rates and fecundity. We developed a new method to establish C. suppressalis isofemale lines with field-collected egg masses...
February 23, 2019: Journal of Invertebrate Pathology
Narender K Dhania, Vinod K Chauhan, R K Chaitanya, Aparna Dutta-Gupta
India is the major producer and exporter of castor oil in the world. Castor semilooper, Achaea janata is one of the main castor crop pests, which causes serious economic loss of crop, hence management and control of the pest are important. Currently, Bacillus thuringiensis (Bt) based biopesticides are being used for their control. However, the insects are known to develop resistance not only against chemical pesticides but also to Bt based biopesticides. In the present study, de novo transcriptome analysis was conducted to monitor the expression pattern of larval midgut genes in Achaea janata exposed to sublethal dose of Bt formulation...
February 15, 2019: Comparative Biochemistry and Physiology. Part D, Genomics & Proteomics
Sudarat Tharad, Boonhiang Promdonkoy, José L Toca-Herrera
Bacillus thuringiensis is a bacterium that produces many insecticidal proteins including cytolytic proteins or Cyt toxins. Although the Cyt toxin shows specific toxicity against Dipteran insect species, the toxin binds directly to the lipid membrane without a specific protein receptor requirement. In this work, we have investigated the interaction of Cyt2Aa2 toxin with lipid bilayers composed of different lipid phases. By means of atomic force microscopy (AFM), lipid phase separation was observed for 1:1 and 4:1 M mixtures of DPPC/POPC bilayers...
February 21, 2019: Biochemical and Biophysical Research Communications
Claudia Rodríguez-de la Noval, Lianet Rodríguez-Cabrera, Laurent Izquierdo, Luis A Espinosa, Daily Hernandez, Milagro Ponce, Ivis Moran-Bertot, Pilar Tellez-Rodríguez, Orlando Borras-Hidalgo, Siliang Huang, Yunchao Kan, Denis J Wright, Camilo Ayra-Pardo
Peritrophins are associated with structural and functional integrity of peritrophic membranes (PM), structures composed of chitin and proteins. PM lines the insect midgut and has roles in digestion and protection from toxins. We report the full-length cDNA cloning, molecular characterization and functional analysis of SfPER, a novel PM peritrophin A protein, in Spodoptera frugiperda. The predicted amino acid sequence indicated SfPER's domain structure as a CMCMC-type, consisting of a signal peptide and three chitin-binding (C) domains with two intervening mucin-like (M) domains...
February 22, 2019: Scientific Reports
Ryoichi Sato, Satomi Adegawa, Xiaoyi Li, Shiho Tanaka, Haruka Endo
When ABC transporter family C2 (ABCC2) and ABC transporter family B1 (ABCB1) were heterologously expressed in non-susceptible cultured cells, the cells swelled in response to Cry1A and Cry3 toxins, respectively. Consistent with the notion that 3D-Cry toxins form cation-permeable pores, Bombyx mori ABCC2 (BmABCC2) facilitated cation-permeable pore formation by Cry1A when expressed in Xenopus oocytes. Furthermore, BmABCC2 had a high binding affinity ( KD ) to Cry1Aa of 3.1 × 10-10 M. These findings suggest that ABC transporters, including ABCC2 and ABCB1, are functional receptors for 3D-Cry toxins...
February 19, 2019: Toxins
Shakeel Ahmad, Hafiza Masooma Naseer Cheema, Asif Ali Khan, Rao Sohail Ahmad Khan, Jam Nazeer Ahmad
Transgenic cotton expressing the toxin Cry1Ac from Bacillus thuringiensis L. (Bt) is widely cultivated in Pakistan after its formal approval in 2010. The exposure of the local target pests to the Cry1Ac endotoxin for this duration might have changed the baseline susceptibility. To probe the status of resistance in one of the main target pests, Helicoverpa armigera, field-collected larvae were reared in the lab for conducting leaf fed bioassays. Twenty-six cotton accessions collected from farmers, including 25 Bt-cotton and one non-Bt, were tested to quantify the level of Cry1Ac, an insecticidal crystalline protein (ICP), in leaves of lower, middle and upper canopies of plants...
February 21, 2019: Transgenic Research
Wenfeng Xiong, Shanshan Gao, Jinjuan Mao, Luting Wei, Jia Xie, Juanjuan Liu, Jingxiu Bi, Xiaowen Song, Bin Li
BACKGROUND: Many insect cytochrome P450 proteins (CYPs) are involved in the metabolic detoxification of exogenous compounds such as plant toxins and insecticides. Tribolium castaneum, the red flour beetle, is a major agricultural pest that damages stored grains and cereal products. With the completion of the sequencing of its genome, two T. castaneum species-specific CYP genes, CYP4BN6 and CYP6BQ11, were identified. However, it is unknown whether the functions of most CYPs are shared by TcCYP4BN6 and TcCYP6BQ11, and the upstream regulatory mechanism of these two CYPs remains elusive...
February 20, 2019: Pest Management Science
Mario Gonzalo Garcia-Arraez, Florent Masson, Juan Camilo Paredes Escobar, Bruno Lemaitre
BACKGROUND: Insects frequently live in close relationship with symbiotic bacteria that carry out beneficial functions for their host, like protection against parasites and viruses. However, in some cases, the mutualistic nature of such associations is put into question because of detrimental phenotypes caused by the symbiont. One example is the association between the vertically transmitted facultative endosymbiont Spiroplasma poulsonii and its natural host Drosophila melanogaster. Whereas S...
February 20, 2019: BMC Microbiology
Matthias Erb, Philippe Reymond
Diverse molecular processes regulate the interactions between plants and insect herbivores. Here, we review genes and proteins that are involved in plant-herbivore interactions and discuss how their discovery has structured the current standard model of plant-herbivore interactions. Plants perceive damage-associated and, possibly, herbivore-associated molecular patterns via receptors that activate early signaling components such as Ca2+ , reactive oxygen species, and MAP kinases. Specific defense reprogramming proceeds via signaling networks that include phytohormones, secondary metabolites, and transcription factors...
February 20, 2019: Annual Review of Plant Biology
Milton T Drott, Tracy Debenport, Steven A Higgins, Daniel H Buckley, Michael G Milgroom
Selective forces that maintain the polymorphism for aflatoxigenic and nonaflatoxigenic individuals of Aspergillus flavus are largely unknown. As soils are widely considered the natural habitat of A. flavus , we hypothesized that aflatoxin production would confer a fitness advantage in the soil environment. To test this hypothesis, we used A. flavus DNA quantified by quantitative PCR (qPCR) as a proxy for fitness of aflatoxigenic and nonaflatoxigenic field isolates grown in soil microcosms. Contrary to predictions, aflatoxigenic isolates had significantly lower fitness than did nonaflatoxigenic isolates in natural soils across three temperatures (25, 37, and 42°C)...
February 19, 2019: MBio
Jing Wang, Ya-Yun Zuo, Ng-Li Li, Hui Wang, Shao-Yan Liu, Yi-Hua Yang, Yi-Dong Wu
Bacillus thuringiensis (Bt) insecticidal toxins have been globally utilized for control of agricultural insects through spraying or transgenic crops. Binding of Bt toxins to special receptors on midgut epithelial cells of target insects is a key step in the mode of action. Previous studies suggested aminopeptidase N1 (APN1) as a receptor or putative receptor in several lepidopteran insects including Helicoverpa armigera through evidence from RNAi-based gene silencing approaches. In the current study we tested the role of APNs in the mode of action of Bt toxins using CRISPR/Cas9-mediated gene knockout...
February 14, 2019: Insect Science
Heba M Abdelgaffar, Cris Oppert, Xiaocun Sun, Jessica Monserrate, Juan Luis Jurat-Fuentes
The Cry1Ac protein is the most active insecticidal toxin from the bacterium Bacillus thuringiensis (Bt) to members of the heliothinae subfamily in Lepidoptera, which includes some of the most devastating pests of corn and cotton worldwide. However, there are wide discrepancies in susceptibility among members of this subfamily in the US. Specifically, susceptibility to Cry1Ac in Helicoverpa zea (Hz) is >100-fold lower when compared to Heliothis virescens (Hv) larvae. The biochemical properties and Cry1Ac protoxin processing activity of gut digestive fluids from larvae of Hz and Hv were compared to test their role in differential susceptibility to Cry1Ac...
January 2019: Pesticide Biochemistry and Physiology
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