Safety Evaluation of Bt Plants

Abstract

Bt plants are insect-resistant plants engineered to carry the gene coding the insecticidal protein of a soil bacterium, Bacillus thuringiensis. These transgenic plants provide a highly effective method of insect control and reduce dependence on pesticide chemicals. In consequence, they have provided higher yields, reduced crop mycotoxin levels because of the effective lowering of the insect damage, and have decreased the pesticide spraying work and cost. However, there are public concerns about the safety of Bt plants for humans, animals and the environment. This review describes recent research on the safety evaluation of Bt plants, focusing on our results in the toxicological studies of Bt11 corn.

Nutritional evaluation of transgenic cottonseed in the ration of lactating dairy cows

“…Mean intake of Cry1C through Bt cottonseed was 4.5 mg/d, which appeared to be degraded during the course of its rumen fermentation as per the fate of dietary proteins (Alexander et al 2007, Shimada et al 2008). Kumar and Singhal (2004) reported that presence of Cry1Ac protein did not affect the rumen fermentation and hence the protein digestibility in cows.…”

“…So, single or multiple genes from a naturally occurring soil bacterium, Bacillus thuringiensis (cry1C, cry1Ab, cry1Ac, cry1F etc) that produces insecticidal Cry proteins in cotton plant, have been inserted into the cotton plant's DNA (Hofte and Whiteley 1989). When ingested, these Cry proteins bind to specific receptors in the midgut of susceptible pests forming ion-selective channels in the membrane killing the insects, but do not affect mammals or non-target insects that lack these receptors (Shimada et al 2008). The transgenic crops are found safe and nutritionally equivalent to their non-transgenic counterparts fed to animals (Alexander et al 2007;Flachowsky et al 2007;Shimada et al 2008;Stein et al 2009).…”

A recombinant immunosuppressive protein from Pimpla hypochondriaca (rVPr1) increases the susceptibility of Lacanobia oleracea and Mamestra brassicae larvae to Bacillus thuringiensis

“…In addition, in certain Lepidoptera, it has been proposed that death by septicaemia is caused by the endogenous gut bacteria that migrate through the (Bt endotoxin-damaged) gut wall into the insect haemocoel (Broderick et al, 2006(Broderick et al, , 2009. The ability of Bt to kill insects, together with a lack of negative effects on the environment (including lack of toxicity to humans), means that this bacterium is widely used in biological control programs (Shelton et al, 2002;Bravo et al, 2005Bravo et al, , 2006Roh et al, 2007;Sanchis and Bourguet, 2008;Shimada et al, 2008). For instance, the expression of Bt endotoxin genes in crop plants has successfully provided protection against a number of major insect pests, including the cotton bollworms, Helicoverpa zea and Helicoverpa armigera (Sanchis and Bourguet, 2008;Deguine et al, 2008).…”