Cotton gene modified

It is also to be taken into account that pests, in response to genetically modified crops that bear genetic resistance, may rapidly become adapted, so that new genetically modified crops are needed to maintain high productivity. A gene associated with Bt resistance has been identified in the cotton pest, Heliothis virescens (Gahan 2001). The life span of a genetically modified crop is calculated to be a few years only (Plucknett 1986). 

Fig. 7. Diagrams of the schemes for modifying levels of A, alcohol dehydrogenase and B, pyruvate decarboxylase activity and testing for survival of anoxia. In A, constructs contain the 35S promoter of the cauliflower mosaic virus (35S) driving expression of the cotton Adh cDNA in either the sense (Adh) or antisense (hdA) orientation, linked to the 3 termination signal of the nopaline synthase gene (Nos). Alternatively, the expression of cotton Adh cDNA is under control of the pea Adh promoter sequence (pea Adh). In B, either the 35S promoter or the pea Adh promoter is used to drive expression of the maize pyruvate decarboxylase cDNA (Pdc), linked to a Nos 3 termination sequence. Constructs are introduced into cotton via Agrobacterium tumefaciens-mediated infection of cotton. Transformed cotton callus is then assayed for its ability to survive anoxia.

The use of genetically modified corn and cotton has increased over 10-fold from 1992 to 1999 and as of 2002, 50 crop species have been evaluated for uses by the US Food and Drug Administration (FDA). In the development of transgenic crops, genes isolated from several varieties of the bacterium. Bacillus thuringienses (Bt) are probably the best known and most often cited example of GMO development. 

Even though the genetically modified cotton such as Bt cotton has attracted farmers, it has not been much preferred by environmentalists. Although it reduces the use of pesticides and other pollutants, the release of genes may be harmful to the ecosystem and this is objectionable due to the uncertainty of the risk (Jan, 2009). 

By genetic engineering, a soil bacterium Bacillus thuringienis or BT) has been modified to produce pesticides that are more toxic than natural ones. The modified genes have then been inserted into crop plants to create crops that synthesize their own pesticides. There is Bt corn with a toxin that destroys the European corn borer and other pests, and there is Bt cotton protected against the cotton bollworm and the budworm. 

PHB synthesis has also been demonstrated in the cytoplasm of cells of cotton fiber cells (John 1997 John and Keller 1996). In this approach, PHA is not produced as a source of polyester to be extracted and nsed in the plastic industries, but rather as an intracellular agent that modifies the heat-exchange properties of the fiber. The phaA, phaB, and phaC genes from R. eutropha were expressed in transgenic cotton under the control of a fiber-specific promoter (John 1997 John and Keller 1996). PHB accumulated in the cytoplasm to 0.3% dwt of the mature fiber, a level similar to that for PHB production in A. thaliana cell cytoplasm, yet high enough to change the heat retention dynamic of the fiber, but no deleterious effect on fiber development was reported. 

Another popular GM plant is Bt -cotton and others. Bt stands for Bacillus thuringiensis which is known to produce several toxins to kill some insects. A toxin is modified in its DNA sequence by introducing introns, polyA signals, promoters, and enhancers. The modified DNA is then incorporated into the gene of... 

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