Cry34Ab1

43.8 kDa insecticidal crystal protein
Identifiers
Organism	Bacillus thuringiensis
Symbol	Cry35Ab1
UniProt	Q939S9
Search for
Structures	Swiss-model
Domains	InterPro

Search for
Structures	Swiss-model
Domains	InterPro

13.6 kDa insecticidal crystal protein
Identifiers
Organism	Bacillus thuringiensis
Symbol	Cry34Ab1
UniProt	Q939T0
Search for
Structures	Swiss-model
Domains	InterPro

Last updated September 12, 2019

Cry34Ab1 is one member of a binary Bacillus thuringiensis (Bt) crystal protein set isolated from Bt strain PS149B1.^[1] The protein exists as a 14 kDa aegerolysin that, in presence of Cry35Ab1, exhibits insecticidal activity towards Western Corn Rootworm. ^[1]^[2] The protein has been transformed into maize plants under the commercialized events 4114 (DP-ØØ4114-3) by Pioneer Hi-Bred and 59122 (DAS-59122-7) by Dow AgroSciences. These events have, in turn, been bred into multiple trait stacks in additional products.

<i>Bacillus thuringiensis</i> species of bacterium

Bacillus thuringiensis is a Gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide. B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well on leaf surfaces, aquatic environments, animal feces, insect-rich environments, and flour mills and grain-storage facilities. It has also been observed to parasitize other moths such as Cadra calidella—in laboratory experiments working with C. calidella, many of the moths were diseased due to this parasite.

In molecular biology, transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane(s). For transformation to take place, the recipient bacteria must be in a state of competence, which might occur in nature as a time-limited response to environmental conditions such as starvation and cell density, and may also be induced in a laboratory.

Maize, also known as corn, is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The leafy stalk of the plant produces pollen inflorescences and separate ovuliferous inflorescences called ears that yield kernels or seeds, which are fruits.

Cry34/35Ab1 binary toxins bind to the insect's brush border membrane vesicles (BBMVs) of cells in the epithelial lining of midgut, where they form pores; this leads to necrosis and, eventually, the insect's death.^[3] The Cry35Ab1 (45 kDa) protein does not convey specificity in the absence of Cry34Ab1, indicating that the smaller 14 kDa Cry34Ab1 protein is critical for BBMV binding and recruitment of Cry35Ab1 to induce insecticidal effect.^[2]

Brush border The dense covering of microvilli on the apical surface of a epithelial cells in tissues such as the intestine, kidney, and choroid plexus; the microvilli aid absorption by increasing the surface area of the cell.

A brush border is the microvilli-covered surface of simple cuboidal epithelium and simple columnar epithelium cells found in certain locations of the body. Microvilli are approximately 100 nanometers in diameter and their length varies from approximately 100 to 2,000 nanometers in length. Because individual microvilli are so small and are tightly packed in the brush border, individual microvilli can only be resolved using electron microscopes; with a light microscope they can usually only be seen collectively as a fuzzy fringe at the surface of the epithelium. This fuzzy appearance gave rise to the term brush border, as early anatomists noted that this structure appeared very much like the bristles of a paintbrush.

Necrosis is a form of cell injury which results in the premature death of cells in living tissue by autolysis.

Cry34Ab1 is unrelated to Bt delta-endotoxins. It is an aegerolysin (Pfam PF06355) composed of two beta sheets in a beta-sandwich structure; the total protein is composed of 117 amino acid residues and contains a hydrophobic core.^[4] Its family placement shows that interaction with cell membranes is consistent with its role in the binary Cry34Ab1/Cry35Ab1 toxin complex.^[4] The partner toxin, Cry35Ab1, is a prototypical member of its own group (Pfam PF05431). Its structure is similar to that of aerolysin, Cry45Aa1, and Cry46Aa1.^[4]

Pfam is a database of protein families that includes their annotations and multiple sequence alignments generated using hidden Markov models. The most recent version, Pfam 32.0, was released in September 2018 and contains 17,929 families.

In molecular biology, aerolysin is a cytolytic pore-forming toxin exported by Aeromonas hydrophila, a Gram-negative bacterium associated with diarrhoeal diseases and deep wound infections. The mature toxin binds to eukaryotic cells and aggregates to form holes leading to the destruction of the membrane permeability barrier and osmotic lysis. The structure of proaerolysin has been determined to 2.8A resolution and shows the protoxin to adopt a novel fold. Images of an aerolysin oligomer derived from electron microscopy have helped to construct a model of the protein in its heptameric conformation, and to outline a mechanism by which this assembly might insert into lipid bilayers to form ion channels.

Related Research Articles

Genetically modified maize (corn) is a genetically modified crop. Specific maize strains have been genetically engineered to express agriculturally-desirable traits, including resistance to pests and to herbicides. Maize strains with both traits are now in use in multiple countries. GM maize has also caused controversy with respect to possible health effects, impact on other insects and impact on other plants via gene flow. One strain, called Starlink, was approved only for animal feed in the US, but was found in food, leading to a series of recalls starting in 2000.

Pesticide resistance describes the decreased susceptibility of a pest population to a pesticide that was previously effective at controlling the pest. Pest species evolve pesticide resistance via natural selection: the most resistant specimens survive and pass on their acquired heritable changes traits to their offspring.

<i>Bacillus thuringiensis israelensis</i> subspecies of bacterium

Bacillus thuringiensis serotype israelensis (Bti) is a group of bacteria used as biological control agents for larvae stages of certain dipterans. Bti produces toxins which are effective in killing various species of mosquitoes, fungus gnats, and blackflies, while having almost no effect on other organisms. Indeed, this is one of the major advantages of B. thuringiensis products in general is that they are thought to affect few nontarget species.

The Western corn rootworm, Diabrotica virgifera virgifera, is one of the most devastating corn rootworm species in North America, especially in the midwestern corn-growing areas such as Iowa. A related species, the Northern corn rootworm, D. barberi co-inhabits in much of the range, and is fairly similar in biology.

The cabbage looper is a moth in the family Noctuidae, a family commonly referred to as owlet moths. Its common name comes from its preferred host plants and distinctive crawling behavior. Cruciferous vegetables, such as cabbage, bok choy, and broccoli, are its main host plant; hence, the reference to cabbage in its common name. The larva is called a looper because it arches its back into a loop when it crawls.

Bt cotton is a genetically modified organism (GMO) or genetically modified pest resistant plant cotton variety, which produces an insecticide to combat bollworm.

Pore-forming toxin class of proteins synthesized by one cell and secreted for insertion into the membrane of another cell where they form transmembrane pores

Pore-forming proteins are usually produced by bacteria, and include a number of protein exotoxins but may also be produced by other organisms such as lysenin, produced by earthworms. They are frequently cytotoxic, as they create unregulated pores in the membrane of targeted cells.

MON 863 is a genetically engineered variety of maize produced by Monsanto. It is genetically altered to express a modified version of Cry3Bb1, a delta endotoxin which originates from Bacillus thuringiensis. This protects the plant from corn rootworm. Unlike MON 810, Bt 11, and Bt 176 which each produce a modified Cry1Ab, MON 863 instead produces a modified Cry3Bb1 toxin and contains nptII, a marker gene for antibiotic resistance.

Lysinibacillus sphaericus is a Gram-positive, mesophilic, rod-shaped bacterium commonly found on soil. It can form resistant endospores that are tolerant to high temperatures, chemicals and ultraviolet light and can remain viable for long periods of time. It is of particular interest to the World Health Organization due to the larvicide effect of some strains against two mosquito genera, more effective than Bacillus thuringiensis, frequently used as a biological pest control. It is ineffective against Aedes aegypti, an important vector of yellow fever and dengue viruses.

Delta endotoxins (δ-endotoxins) are pore-forming toxins produced by Bacillus thuringiensis species of bacteria. They are useful for their insecticidal action and are the primary toxin produced by Bt corn. During spore formation the bacteria produce crystals of such proteins that are also known as parasporal bodies, next to the endospores; as a result some members are known as a parasporin. The Cyt (cytolytic) toxin group is a group of delta-endotoxins different from the Cry group.

Bacillus anthracis is the etiologic agent of anthrax—a common disease of livestock and, occasionally, of humans—and the only obligate pathogen within the genus Bacillus. B. anthracis is a Gram-positive, endospore-forming, rod-shaped bacterium, with a width of 1.0–1.2 µm and a length of 3–5 µm. It can be grown in an ordinary nutrient medium under aerobic or anaerobic conditions.

Clostridium enterotoxins are toxins produced by Clostridium species.

The AB toxins are two-component protein complexes secreted by a number of pathogenic bacteria. They can be classified as Type III toxins because they interfere with internal cell function. They are named AB toxins due to their components: the "A" component is usually the "active" portion, and the "B" component is usually the "binding" portion. The "A" subunit possesses enzyme activity, and is transferred to the host cell following a conformational change in the membrane-bound transport "B" subunit. These proteins consist of two independent polypeptides, which correspond to the A/B subunit moieties. The enzyme component (A) enters the cell through endosomes produced by the oligomeric binding/translocation protein (B), and prevents actin polymerisation through ADP-ribosylation of monomeric G-actin.

The MON 810 corn is a genetically modified maize used around the world. It is a Zea mays line known as YieldGard from the company Monsanto. This plant is a genetically modified organism (GMO) designed to combat crop loss due to insects. There is an inserted gene in the DNA of MON810 which allows the plant to make a protein that harms insects that try to eat it. The inserted gene is from the Bacillus thuringiensis which produces the Bt protein that is poisonous to insects in the order Lepidoptera, including the European Corn Borer.

Cry1Ac protoxin is a crystal protein produced by the gram-positive bacterium, Bacillus thuringiensis (Bt) during sporulation. Cry1Ac is one of the delta endotoxins produced by this bacterium which act as insecticides. Because of this, the genes for these have been introduced into commercially important crops by genetic engineering in order to confer pest resistance on those plants.

Bacillus thuringiensis serotype kurstaki (Btk) is a group of bacteria used as biological control agents against lepidopterans. Btk, along with other B. thuringiensis products, is one of the most widely used biological pesticides due to its high specificity; it is effective against lepidopterans, and it has little to no effect on nontarget species. During sporulation, Btk produces a crystal protein that is lethal to lepidopteran larvae. Once ingested by the insect, the dissolution of the crystal allows the protoxin to be released. The toxin is then activated by the insect gut juice, and it begins to break down the gut.

Cry6Aa is a toxic crystal protein generated by the bacterial family Bacillus thuringiensis during sporulation. This protein is a member of the alpha pore forming toxins family, which gives it insecticidal qualities advantageous in agricultural pest control. Each Cry protein has some level of target specificity; Cry6Aa has specific toxic action against coleopteran insects and nematodes. The corresponding B. thuringiensis gene, cry6aa, is located on bacterial plasmids. Along with several other Cry protein genes, cry6aa can be genetically recombined in Bt corn and Bt cotton so the plants produce specific toxins. Insects are developing resistance to the most commonly inserted proteins like Cry1Ac. Since Cry6Aa proteins function differently than other Cry proteins, they are combined with other proteins to decrease the development of pest resistance. Recent studies suggest this protein functions better in combination with other virulence factors such as other Cry proteins and metalloproteinases.

Aparna Dutta Gupta is an Indian scientist and professor. She teaches in the Department of Animal Biology, School of Life Sciences, University of Hyderabad. Her research is on zoology, developmental biology and endocrinology. She has carried out research in the field of insect physiology, focusing on pests and their control. Her novel contribution includes that insect fat body expresses hexamerin genes, and the expressed proteins are sequestered by various tissues including male accessory-glands and play a role in reproduction.

References

1 2 Moellenbeck, Daniel J.; Peters, Melvin L.; Bing, James W.; Rouse, James R.; Higgins, Laura S.; Sims, Lynne; Nevshemal, Tony; Marshall, Lisa; Ellis, R. Tracy (2001-07-01). "Insecticidal proteins from Bacillus thuringiensis protect corn from corn rootworms". Nature Biotechnology. 19 (7): 668–672. doi:10.1038/90282. ISSN 1546-1696. PMID 11433280.
1 2 Li, Huarong; Olson, Monica; Lin, Gaofeng; Hey, Timothy; Tan, Sek Yee; Narva, Kenneth E. (2013-01-04). "Bacillus thuringiensis Cry34Ab1/Cry35Ab1 Interactions with Western Corn Rootworm Midgut Membrane Binding Sites". PLOS ONE. 8 (1): e53079. Bibcode:2013PLoSO...853079L. doi:10.1371/journal.pone.0053079. ISSN 1932-6203. PMC 3537739 . PMID 23308139.
↑ Palma, Leopoldo; Muñoz, Delia; Berry, Colin; Murillo, Jesús; Caballero, Primitivo (2014-12-11). "Bacillus thuringiensis Toxins: An Overview of Their Biocidal Activity". Toxins. 6 (12): 3296–3325. doi:10.3390/toxins6123296. PMC 4280536 . PMID 25514092.
1 2 3 Kelker, Matthew S.; Berry, Colin; Evans, Steven L.; Pai, Reetal; McCaskill, David G.; Wang, Nick X.; Russell, Joshua C.; Baker, Matthew D.; Yang, Cheng (2014-11-12). "Structural and Biophysical Characterization of Bacillus thuringiensis Insecticidal Proteins Cry34Ab1 and Cry35Ab1". PLOS ONE. 9 (11): e112555. Bibcode:2014PLoSO...9k2555K. doi:10.1371/journal.pone.0112555. ISSN 1932-6203. PMC 4229197 . PMID 25390338.

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[Moellenbeck_et_al-1] 1 2 Moellenbeck, Daniel J.; Peters, Melvin L.; Bing, James W.; Rouse, James R.; Higgins, Laura S.; Sims, Lynne; Nevshemal, Tony; Marshall, Lisa; Ellis, R. Tracy (2001-07-01). "Insecticidal proteins from Bacillus thuringiensis protect corn from corn rootworms". Nature Biotechnology. 19 (7): 668–672. doi:10.1038/90282. ISSN 1546-1696. PMID 11433280.

[Li_et_al-2] 1 2 Li, Huarong; Olson, Monica; Lin, Gaofeng; Hey, Timothy; Tan, Sek Yee; Narva, Kenneth E. (2013-01-04). "Bacillus thuringiensis Cry34Ab1/Cry35Ab1 Interactions with Western Corn Rootworm Midgut Membrane Binding Sites". PLOS ONE. 8 (1): e53079. Bibcode:2013PLoSO...853079L. doi:10.1371/journal.pone.0053079. ISSN 1932-6203. PMC 3537739 . PMID 23308139.

[3] Palma, Leopoldo; Muñoz, Delia; Berry, Colin; Murillo, Jesús; Caballero, Primitivo (2014-12-11). "Bacillus thuringiensis Toxins: An Overview of Their Biocidal Activity". Toxins. 6 (12): 3296–3325. doi:10.3390/toxins6123296. PMC 4280536 . PMID 25514092.

[Kelker_et_al-4] 1 2 3 Kelker, Matthew S.; Berry, Colin; Evans, Steven L.; Pai, Reetal; McCaskill, David G.; Wang, Nick X.; Russell, Joshua C.; Baker, Matthew D.; Yang, Cheng (2014-11-12). "Structural and Biophysical Characterization of Bacillus thuringiensis Insecticidal Proteins Cry34Ab1 and Cry35Ab1". PLOS ONE. 9 (11): e112555. Bibcode:2014PLoSO...9k2555K. doi:10.1371/journal.pone.0112555. ISSN 1932-6203. PMC 4229197 . PMID 25390338.