European rice cultivars were transformed with synthetic Cry1Aa or synthetic Cry1B toxin genes under a constitutive ubiquitin promoter, which turns on the gene in all the tissues all of the time, or synthetic Cry1B gene under a wound inducible maize promoter, which responds to stresses such as insect predation. The constitutive promoter-driven toxin genes produced high toxin levels that prevented striped stem borer predation but left toxin in all the rice tissues and seeds, while the wound inducible strain produced toxin mainly at the site of insect attack.
Research has established that Bt toxin was introduced into soil by root exudates of transgenic rice. The toxin released into the soil affected the enzymes of soil microbes, increasing soil acid phosphatase and decreasing soil urease.
The benefit of insect protection from Bt rice is offset by the potential harmful effects of high levels of toxin protein in the rice grain. As rice is such an important food crop, the safety of Bt rice must be concretely established. It has been found that food irradiation improved the "quality" of GM rice modified with the Cry1Ab toxin, by selectively removing the toxin protein. However, study of the radiation products and adducts created during destruction of the toxin is essential. Furthermore, it is clear that food irradiation may be used to disguise GM rice.
A number of projects have studied the use of snowdrop lectin, Galanthus nivalis agglutinin (GNA) alone or in conjunction with other genes to control rice pests. Lectins are proteins that interact with human blood cells (agglutinin) and also act as anti-predator chemicals in plants or microbes. A GNA gene was driven by a phloem specific promoter accompanied by a hygromycin antibiotic resistance gene and was used to transform japonica rice strains. The modified rice controlled sap-sucking insects that spread rice viruses. However, Ewen and Pusztai showed that potatoes modified with GNA affected different parts of the rat digestive system. Similar research on the in vivo effects of rice genetically engineered with GNA has not been reported.
Rice plants containing both the GNA gene and the unlinked Cry1Ac gene were reported to be resistant to the major rice insect pests, striped stem borer and brown leaf hopper (rice with only Cry1Ac resisted striped stem borer while rice with GNA resisted brown leaf hopper). Rice transformed with a single vector containing Cry1Ab along with GNA and the bar gene for herbicide tolerance was intended to be resistant to yellow stem borer and three sap sucking insects, and also tolerant to the herbicide glufosinate. This huge package of genes was integrated at a single chromosomal site. No account has been taken of the interaction of the various toxins in the human food supply and in the environment.
http://www.i-sis.org.uk/PPGMR.phpNo way to know how much. The estimate was 1/5th of US rice was contaminated but no crystal clear picture of how that was distributed.