Insecticidal toxins

Saxena, D. Flores, S. Stotzky, G. (1999) Insecticidal toxin in root exudates from Bt com. Nature, 402,480. 

Bt crop A crop plant genetically engineered to produce insecticidal toxins derived from the bacterium Bacillus thuringiensis. Current commercial Bt crops include Bt cotton, Bt corn, and Bt soybeans. 

Figure 4.13 Three-dimensional structures of insecticide toxins produced by Bacillus thuringiensis. DI, II, III, domains I, II, and III. (From Bravo, A.M. et al., in Comprehensive Molecular Insect Science, Gilbert, L.I., Iatrou, K., and Gill, S.S., Eds., Vol. 6, Elsevier, London, 2005, p. 175. With permission.)...

Figure 7.23 Diagrammatic representation of cross section of nicotinic acetylcholine receptor showing various sites that bind acetylcholine, insecticides, toxins, and drugs. ACh, acetylcholine NTX, nereistoxin a-BGT, a-bungarotoxin H12-HTX, pH]perhydrohistrionicotoxin PCP, phencyclidine. (From Eldefrawi, M.E. and Eldefrawi, A.T., in Safe Insecticides Development and Use, Hodgson, E. and Ruhr, R.J., Eds., Marcel Dekker, New York, 1990, p. 155. With permission.)...

The varieties of Bacillus thuringiensis used commercially survive when injected into mice, and at least one of the purified insecticidal toxins is toxic to mice. Infections of humans have been extremely rare (two recognized cases) and no occurrences of human toxicosis have been reported. From studies involving deliberate ingestion by human subjects, it appears possible, but not likely, that the organism can cause gastroenteritis. Bacillus thuringiensis... 

In summary, the complexity of the HD-1 strain can be stated as follows it contains at least four insecticidal toxin genes, three of the PI type (that specify proteins active on lepidopteran insects and are of high molecular weight) and a P2 gene (whose protein is much smaller and has bifunctional activity on both lepidopteran and dipteran insects). These... 

A new class of insecticidal toxins called vegetative insecticidal proteins has recently been isolated from Bt. They are produced during the vegetative growth stage. The proteins are different from other known proteins, and their function and versatility for insect control have yet to be elucidated. 

The natural ecosystem maintains a delicate balance between pests and predators. Pest insects can be controlled by the artificial release of predators. One example is a parasitic wasp, Diadegma insulare. The adult female wasp lays eggs in a Plutella xylostella larva and pupates inside the cocoon of the mature larva. This and other insect predators are available commercially, but the usage is limited. Protozoa and nematodes are also used in insect pest control. One example of a protozoan that effectively infects locusts and controls the population is Nosema locustae. A commercially available nematode insect control agent is Steinemema carpocapsae. This nematode parasitizes scarab larvae with a symbiotic Photorhabdus bacterium that produces insecticidal toxins. 

Vadlamudi, R. K. Ji, T. H. Bulla Jr., L. A. A specific binding protein from Manduca sexta for the insecticidal toxin of Bacillus thuringiensis subsp. berliner. J. Biol Chem. 1993 268, 12334-12340. 

Aronson, A.l. and Y. Shai. 2001. Why Bacillus thuringiensis insecticidal toxins are so effective unique features of their mode of action. FEMS Microbiol. Lett. 195 1-8... 

Burton, S.L., D.J. Ellar, J. Li, and D.J Derbyshire. 1999. N-acetylgalactosamine on the putative insect receptor aminopeptidase N is recognised by a site on the domain III lectin-like fold of a Bacillus thuringiensis insecticidal toxin. JMol. Biol. 287 1011-1022. 

Grochulski, P., L. Masson, S. Borisova, M. Pusztai-Carey, J.L. Schwartz, R. Broussear, and M. Cygler. 1995. Bacillus thuringiensis CrylA(a) insecticidal toxin crystal structure and channel formation. J. Mol. Biol. 

Saxena. D. and G. Stotzky. 2000. Insecticidal toxin from Bacillus thuringiensis is released from roots of transgenic Bt corn in vitro and in situ. FEMS Microbiol. Ecol. 33 35-39. 

Tapp, H. and G. Stotzky. 1995a. Dot blot enzyme-lynked immunosorbent assay for monitoring the fate of insecticidal toxins from Bacillus thuringiensis in soil. Appl. Environ. Microbiol. 61 602-609. 

Von Tersch, M.A., H.L. Robbins, C.S. Jany, and T.B. Johnson. 1991. Insecticidal toxins from Bacillus thuringiensis subsp. kenyae Gene cloning and characterization and comparison with B. thuringiensis subsp. kurstaki CrylA(c) toxins. Appl. Environ. Microbiol. 57 349-358. 

Smedley, D.P. and D.J. Ellar. 1996. Mutagenesis of three surface-exposed loops of a Bacillus thuringiensis insecticidal toxin reveals residues important for toxicity, receptor recognition and possibly membrane insertion. Microbiol. 142 1617-1624. 

Kirouac, M. Vachon, V. Rivest, S. Schwartz, J. L. Laprade, R. Analysis of the properties of Bacillus thuringiensis insecticidal toxins using a potential-sensitive fluorescent probe. J. Membr. Biol. 2003,196, 51-59. 

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