Effects of disruption of the peritrophic membrane on larval susceptibility to Bt toxin Cry1Ac in cabbage loopers

AbstractTransgenic Bt maize expressing the Cry1Ab toxin is poorly effective for suppressing populations of two non-target Lepidoptera,Mythimna unipunctaandHelicoverpa armigera. In order to determine the mechanisms that may be involved in this poor effectiveness, last instar larvae of the two Lepidoptera were fed with a diet containing lyophilized leaves with Bt vs non-Bt toxin for different periods; additionally, some larvae fed on Bt diet were transferred to non-Bt diet for an additional period. In the experimental larvae, we measured the growth (weight) gain from just before treatment to after the end of the treatment, and the Cry1Ab contents in the hemolymph, the peritrophic membrane and its contents and midgut epithelium. Effects of the treatments on the midgut epithelium were observed by light and transmission electron microscopy. It was seen that multiple mechanisms can be involved in the low susceptibility of the two Lepidoptera. The low content of the toxin within the peritrophic membrane 48h after ingestion indicates a high rate of toxin elimination in this space. Moreover,M. unipunctalarvae fed on the Bt diet displayed a similar growth gain index to those fed on the non-Bt diet, and showed an increasing elimination rate during the experiment. Little toxin reached the midgut epithelium, indicating a low permeability of the peritrophic membrane or a low affinity at the binding sites. Larvae fed on the Bt toxin showed rapid recovery in weight gain and in the midgut epithelium, and also showed overcompensation mechanisms.

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Genetic basis of resistance to Bt toxin Cry2Ab in pink bollworm, Pectinophora gossypiella

10.1603/ice.2016.115187 ◽

2016 ◽

Author(s):

Lolita G. Mathew

Keyword(s):

Genetic Basis ◽

Pink Bollworm ◽

Pectinophora Gossypiella ◽

Bt Toxin

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Resistance to Bt Maize by Western Corn Rootworm: Effects of Pest Biology, the Pest–Crop Interaction and the Agricultural Landscape on Resistance

Insects ◽

10.3390/insects12020136 ◽

2021 ◽

Vol 12 (2) ◽

pp. 136

Author(s):

Aaron Gassmann

Keyword(s):

Agricultural Landscape ◽

Continuous Cultivation ◽

Diabrotica Virgifera Virgifera ◽

The United States ◽

Western Corn Rootworm ◽

Corn Rootworm ◽

Agricultural Crop ◽

Bt Maize ◽

Bt Toxin ◽

Resistance Evolution

The western corn rootworm, Diabrotica virgifera virgifera LeConte, is among the most serious pests of maize in the United States. Since 2003, transgenic maize that produces insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) has been used to manage western corn rootworm by killing rootworm larvae, which feed on maize roots. In 2009, the first cases of field-evolved resistance to Bt maize were documented. These cases occurred in Iowa and involved maize that produced Bt toxin Cry3Bb1. Since then, resistance has expanded to include other geographies and additional Bt toxins, with some rootworm populations displaying resistance to all commercially available Bt traits. Factors that contributed to field-evolved resistance likely included non-recessive inheritance of resistance, minimal fitness costs of resistance and limited adult dispersal. Additionally, because maize is the primary agricultural crop on which rootworm larvae can survive, continuous maize cultivation, in particular continuous cultivation of Bt maize, appears to be another key factor facilitating resistance evolution. More diversified management of rootworm larvae, including rotating fields out of maize production and using soil-applied insecticide with non-Bt maize, in addition to planting refuges of non-Bt maize, should help to delay the evolution of resistance to current and future transgenic traits.

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Identifying and Characterizing a Novel Peritrophic Matrix Protein (MdPM-17) Associated With Antibacterial Response From the Housefly, Musca domestica (Diptera: Muscidae)

Journal of Insect Science ◽

10.1093/jisesa/ieaa135 ◽

2020 ◽

Vol 20 (6) ◽

Author(s):

Yu Wang ◽

Jinzhi Cheng ◽

Man Luo ◽

Jianwei Wu ◽

Guo Guo

Keyword(s):

Amino Acid ◽

Antimicrobial Peptide ◽

Musca Domestica ◽

Matrix Protein ◽

Binding Capacity ◽

Malpighian Tubule ◽

Peritrophic Membrane ◽

Distribution Analysis ◽

Peritrophic Matrix ◽

Amino Acid Residues

Abstract Peritrophic matrix/membrane (PM) critically prevents the midgut of insects from external invasion by microbes. The proteins in the peritrophic membrane are its major structural components. Additionally, they determine the formation and function of this membrane. However, the role of PM proteins in immune regulation is unclear. Herein, we isolated a novel PM protein (MdPM-17) from Musca domestica larvae. Further, the function of MdPM-17 in regulating host innate immunity was identified. Results showed that the cDNA of MdPM-17 full is 635 bp in length. Moreover, it consists of a 477-bp open reading frame encoding 158 amino acid residues. These amino acid residues are composed of two Chitin-binding type-2 domain (ChtBD2) and 19 amino acids as a signal peptide. Moreover, tissue distribution analysis indicates that MdPM-17 was enriched expressed in midgut, and moderate levels in the fat body, foregut, and malpighian tubule. Notably, MdPM-17 recombinant protein showed high chitin-binding capacity, thus belongs to the Class III PM protein group. MdPM-17 protein silencing via RNA interference resulted in the expression of antimicrobial peptide (defensin, cecropins, and diptericin) genes, and this occurred after oral inoculation with exogenous microbes Escherichia coli (Enterobacteriales:Enterobacteriaceae), Staphylococcus aureus (Bacillales:Staphylococcaceae), and Candida albicans (Endomycetales:Saccharomycetaceae)). Therefore, all the antimicrobial peptide (AMP) gene expression levels are high in MdPM-17-depleted larvae during microbial infection compared to controls. Consequently, these findings indicate that MdPM-17 protein is associated with the antibacterial response from the housefly.

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Electron-Microscope Study of the Peritrophic Membrane in Dixippus morosus

Nature ◽

10.1038/165397b0 ◽

1950 ◽

Vol 165 (4193) ◽

pp. 397-397 ◽

Cited By ~ 6

Author(s):

WALTER HUBER ◽

CHARLES HAASSER

Keyword(s):

Electron Microscope ◽

Microscope Study ◽

Electron Microscope Study ◽

Peritrophic Membrane

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Cryo-EM structures of an insecticidal Bt toxin reveal its mechanism of action on the membrane

Nature Communications ◽

10.1038/s41467-021-23146-4 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Matthew J. Byrne ◽

Matthew G. Iadanza ◽

Marcos Arribas Perez ◽

Daniel P. Maskell ◽

Rachel M. George ◽

...

Keyword(s):

Functional Data ◽

Insect Pests ◽

Economic Cost ◽

Commercial Agriculture ◽

Efficient Manner ◽

Bt Toxin ◽

Genes Encoding ◽

Potential Applications ◽

Chemical Pesticides ◽

Wide Potential

AbstractInsect pests are a major cause of crop losses worldwide, with an estimated economic cost of $470 billion annually. Biotechnological tools have been introduced to control such insects without the need for chemical pesticides; for instance, the development of transgenic plants harbouring genes encoding insecticidal proteins. The Vip3 (vegetative insecticidal protein 3) family proteins from Bacillus thuringiensis convey toxicity to species within the Lepidoptera, and have wide potential applications in commercial agriculture. Vip3 proteins are proposed to exert their insecticidal activity through pore formation, though to date there is no mechanistic description of how this occurs on the membrane. Here we present cryo-EM structures of a Vip3 family toxin in both inactive and activated forms in conjunction with structural and functional data on toxin–membrane interactions. Together these data demonstrate that activated Vip3Bc1 complex is able to insert into membranes in a highly efficient manner, indicating that receptor binding is the likely driver of Vip3 specificity.

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Plant Resistance in Some Modern Soybean Varieties May Favor Population Growth and Modify the Stylet Penetration of Bemisia tabaci (Hemiptera: Aleyrodidae)

Journal of Economic Entomology ◽

10.1093/jee/toab008 ◽

2021 ◽

Author(s):

Mauricélia F Almeida ◽

Clébson S Tavares ◽

Euires O Araújo ◽

Marcelo C Picanço ◽

Eugênio E Oliveira ◽

...

Keyword(s):

Population Growth ◽

Bemisia Tabaci ◽

Intrinsic Rate ◽

Reproductive Rate ◽

Genetically Engineered ◽

Population Increase ◽

Net Reproductive Rate ◽

Bt Toxin ◽

Demographic Performance

Abstract Complaints of severe damage by whiteflies in soybean fields containing genetically engineered (GE) varieties led us to investigate the role of transgenic soybean varieties expressing resistance to some insects (Cry1Ac Bt toxin) and to herbicide (glyphosate) on the population growth and feeding behavior of Bemisia tabaci (Gennadius) MEAM1 (Hemiptera: Aleyrodidae). In the laboratory, the whiteflies reared on the GE Bt soybeans had a net reproductive rate (R0) 100% higher and intrinsic rate of population increase (rm) 15% higher than those reared on non-GE soybeans. The increased demographic performance was associated with a higher lifetime fecundity. In electrical penetration graphs, the whiteflies reared on the GE soybeans had fewer probes and spent 50% less time before reaching the phloem phase from the beginning of the first successful probe, indicating a higher risk of transmission of whitefly-borne viruses. Data from Neotropical fields showed a higher population density of B. tabaci on two soybean varieties expressing glyphosate resistance and Cry1Ac Bt toxin. These results indicate that some GE soybean varieties expressing insect and herbicide resistances can be more susceptible to whiteflies than non-GE ones or those only expressing herbicide resistance. Most likely, these differences are related to varietal features that increase host-plant susceptibility to whiteflies. Appropriate pest management may be needed to deal with whiteflies in soybean fields, especially in warm regions, and breeders may want to consider the issue when developing new soybean varieties.

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Permeability of the peritrophic membrane in the larvae of Aedes aegypti

Journal of Insect Physiology ◽

10.1016/0022-1910(70)90209-x ◽

1970 ◽

Vol 16 (6) ◽

pp. 1193-1202 ◽

Cited By ~ 28

Author(s):

D.P. Zhuzhikov

Keyword(s):

Aedes Aegypti ◽

Peritrophic Membrane

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An unusual cell surface modification: a double plasma membrane

Journal of Cell Science ◽

10.1242/jcs.39.1.355 ◽

1979 ◽

Vol 39 (1) ◽

pp. 355-372

Author(s):

N.J. Lane ◽

J.B. Harrison

Keyword(s):

Plasma Membrane ◽

Membrane Structure ◽

Cell Layer ◽

Peritrophic Membrane ◽

Thin Sections ◽

Double Membrane ◽

Freeze Fracturing ◽

Blood Sucking ◽

Great Pressure ◽

Insertion Sites

The occurrence of an unusual double plasma membrane structure is reported; it has been studied in conventional thin sections, after lanthanum-impregnation and with freeze-fracturing. This modification of the plasmalemma is found where the luminal cell membrane (I membrane) of gut microvilli in the haematophagous insect, Rhodnius prolixus, is surrounded by a second, outer membrane (O membrane), the 2 separated from one another by a highly regular I-O space of about 10 nm. Lanthanum impregnation reveals the presence of columns inclined at an angle, within this I-O space; as in the continuous junctions which link the lateral borders of these cells, these columns may maintain the very precise I-O distance. From the outer microvillar membranes radiate short spoke-like fibrils or sheets which encounter another more extensive system of myelin-like sheets. Freeze-fracturing reveals that the spoke-like sheets and the other ones which lie like a tube, around and parallel to the microvilli, contain linear ridges composed of particles, lying at random within layers of the myelin-like material which also extends into the lumen of the gut. The microvillar membanes, both O and I, fracture into faces containing rows of either PF particles or EF pits arranged as spiral ridges or grooves around the sides and across the tip of each microbillus. These could be the insertion sites of one or both of the I-O columns and spoke-like sheets while the sheets could represent a variant of peritrophic membrane. The double membrane may be a cellular device to increase the strength of the microvillar layer in these blood-sucking animals, since the cell layer must withstand great pressure owing to a sudden massive extension of the gut during a blood meal.

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