Search results for "Brush border"

Critical Domains in the Specific Binding of Radiolabeled Vip3Af Insecticidal Protein to Brush Border Membrane Vesicles from Spodoptera spp. and Cultu…

2021

Vegetative insecticidal proteins (Vip3) from Bacillus thuringiensis have been used, in combination with Cry proteins, to better control insect pests and as a strategy to delay the evolution of resistance to Cry proteins in Bt crops (crops protected from insect attack by the expression of proteins from B. thuringiensis). In this study, we have set up the conditions to analyze the specific binding of 125I-Vip3Af to Spodoptera frugiperda and Spodoptera exigua brush border membrane vesicles (BBMV). Heterologous competition binding experiments revealed that Vip3Aa shares the same binding sites with Vip3Af, but Vip3Ca does not recognize all of them. As expected, Cry1Ac and Cry1F did not compete f…

Reduced levels of membrane-bound alkaline phosphatase in Vip3Aa-resistant Heliothis virescens

2020

ABSTRACTThe Vip3Aa insecticidal protein fromBacillus thuringiensis(Bt) is produced by specific transgenic corn and cotton varieties for efficient control of target lepidopteran pests. The main threat to this technology is the evolution of resistance in targeted insect pests, thus understanding the mechanistic basis of resistance is crucial to deploy the most appropriate strategies for resistance management. In this work, a laboratory-selected colony ofHeliothis virescens(Vip-Sel) highly resistant to the Vip3Aa protein was used to test whether an alteration of membrane receptors in the insect midgut might explain the resistance phenotype. Binding of125I-labeled Vip3Aa to brush border membran…

Dual effect of 1-deoxymannojirimycin on the mannose uptake and on the N-glycan processing of the human colon cancer cell line HT-29.

1990

International audience; 1-Deoxymannojirimycin (dMM), a specific alpha-mannosidase I inhibitor, completely blocks the conversion of Man9-8GlcNAc2 into Man7-5-GlcNAc2 in both differentiated and undifferentiated human adenocarcinoma HT-29 cells. Besides this well known effect on N-glycan trimming, we describe here a novel effect of this inhibitor on the D-[2-3H]mannose uptake that is exclusively observed in differentiated intestinal cells, i.e. cells that display a functional apical brush border membrane. This inhibition of D-[2-3H]mannose uptake was shown to be dose-dependent and reversible. Moreover, using microsomal fractions we showed that this effect depends only on the integrity of the b…

Reduced membrane-bound alkaline phosphatase does not affect binding of Vip3Aa in a Heliothis virescens resistant colony

2020

The Vip3Aa insecticidal protein from Bacillus thuringiensis (Bt) is produced by specific transgenic corn and cotton varieties for efficient control of target lepidopteran pests. The main threat to this technology is the evolution of resistance in targeted insect pests and understanding the mechanistic basis of resistance is crucial to deploy the most appropriate strategies for resistance management. In this work, we tested whether alteration of membrane receptors in the insect midgut might explain the &gt

The pronephros of the early ammocoete larva of lampreys (Cyclostomata, Petromyzontes): Fine structure of the renal tubules

1991

The renal tubules of the paired pronephros in early larvae (ammocoetes) of two lamprey species, Lampetra fluviatilis and Petromyzon marinus, were studied by use of light-, scanning- and transmission electron microscopy. They consist of (1) a variable number of pronephric tubules (3 to 6), and (2) an excretory duct. By fine-structural criteria, the renal tubules can be divided into 6 segments. Each pronephric tubule is divided into (1) the nephrostome and (2) the proximal tubule, the excretory duct consisting of (3) a common proximal tubule followed by (4) a short intermediate segment, and then by a pronephric duct composed of (5) a cranial and (6) a caudal section. The epithelium of the nep…

Binding analyses of Cry1Ab and Cry1Ac with membrane vesicles from Bacillus thuringiensis-resistant and -susceptible Ostrinia nubilalis.

2004

The binding properties of Bacillus thuringiensis toxins to brush border membrane vesicles of Dipel-resistant and -susceptible Ostrinia nubilalis larvae were compared using ligand-toxin immunoblot analysis, surface plasmon resonance (SPR), and radiolabeled toxin binding assays. In ligand-toxin immunoblot analysis, the number of Cry1Ab or Cry1Ac toxin binding proteins and the relative toxin binding intensity were similar in vesicles from resistant and susceptible larvae. Surface plasmon resonance with immobilized activated Cry1Ab toxin indicated that there were no significant differences in binding with fluid-phase vesicles from resistant and susceptible larvae. Homologous competition assays …

Screening for Bacillus thuringiensis Crystal Proteins Active against the Cabbage Looper, Trichoplusia ni

2000

Abstract Toxicity tests were performed to find among Cry1 and Cry2 Bacillus thuringiensis crystal proteins those with high activity against the cabbage looper. Tests were performed with neonate larvae on surface-contaminated artificial diet. The crystal proteins found to be toxic were, from higher to lower toxicity: Cry1Ac, Cry1Ab, Cry1C, Cry2Aa, Cry1J, and Cry1F (LC50 of 1.1–4.1, 3.4–4.4, 12, 34, 87, and 250 ng/cm2, respectively). Cry1B, Cry1D, and Cry1E can be considered nontoxic (LC50 higher than 2500 ng/cm2). Cry1Aa was moderately toxic to nontoxic, depending on the source (LC50 of 420 ng/cm2 from PGS and 8100 ng/cm2 from Ecogen). In vitro binding assays with trypsin-activated 125I-labe…

Overproduction of the Bacillus thuringiensis Vip3Aa16 toxin and study of its insecticidal activity against the carob moth Ectomyelois ceratoniae

2015

Abstract The vip3Aa16 gene of Bacillus thuringiensis strain BUPM95 was cloned and expressed in Escherichia coli . Optimization of Vip3A16 protein expression was conducted using Plackett–Burman design and response surface methodology. Accordingly, the optimum Vip3A16 toxin production was 170 μg/ml at 18 h post-induction time and 39 °C post-induction temperature. This corresponds to an improvement of 21 times compared to the starting conditions. The insecticidal activity, evaluated against Ectomyelois ceratoniae , displayed an LC 50 value of 40 ng/cm 2 and the midgut histopathology of Vip3Aa16 fed larvae showed vacuolization of the cytoplasm, brush border membrane destruction, vesicle formati…

Monitoring of Bacillus Thuringiensis Cry3Aa Toxin Pore Formation using Artificial Bilayer Array with Fused Brush Border Membrane Vesicles from Colora…

2017

Study of the bacillus thuringiensis Cry1Ia protein oligomerization promoted by midgut brush border membrane vesicles of lepidopteran and coleopteran …

2020

Bacillus thuringiensis (Bt) produces insecticidal proteins that are either secreted during the vegetative growth phase or accumulated in the crystal inclusions (Cry proteins) in the stationary phase. Cry1I proteins share the three domain (3D) structure typical of crystal proteins but are secreted to the media early in the stationary growth phase. In the generally accepted mode of action of 3D Cry proteins (sequential binding model), the formation of an oligomer (tetramer) has been described as a major step, necessary for pore formation and subsequent toxicity. To know if this could be extended to Cry1I proteins, the formation of Cry1Ia oligomers was studied by Western blot, after the incuba…