Tobacco Plants Get Gene Therapy

Source from:  newsobserver.com Wade Rawlins, Staff Writer 03/19/2008

Knocking out a specific gene in burley tobacco plants significantly reduces harmful carcinogens in cured tobacco leaves, scientists at N.C. State University have shown. The findings could lead to less- harmful tobacco products, in particular smokeless forms such as chewing tobacco. The research was sponsored by the tobacco company Philip Morris. In large-scale field trials involving hundreds of genetically altered plants in three states, Ralph Dewey and Ramsey Lewis, crop scientists at NCSU, teamed with colleagues from the University of Kentucky to silence a gene that turns nicotine into nornicotine, which converts to a carcinogen as the tobacco is cured, processed and stored. "As far as modifying the genetics of the tobacco plant itself, it's novel in that sense," Dewey said. "There is a lot of research being done in this area, but it's a fairly new field of research." Dewey and Lewis stressed that the best way for people to avoid the health risks of tobacco is to avoid using tobacco products. Smoking causes 87 percent of lung cancer deaths, according to the National Cancer Institute, and smokeless tobacco is linked to mouth and throat cancers. "We don't want to claim we're making tobacco products safe," Lewis said. "It's having an incremental impact that will have more effect on smokeless tobacco than on cigarettes. This is really for people who are going to use tobacco products anyway. They may be made a little safer." Smokeless products Dewey said the research may have greater potential with smokeless tobacco because the class of carcinogens they studied was more plentiful in those products. Cigarettes have more carcinogens, but the majority of them are products of combustion, he said. The findings show that targeted gene silencing can work in the field. The field tests in Kentucky, Virginia and North Carolina compared cured burley tobacco plants with the troublesome gene silenced and plants that had not been genetically engineered. The researchers reported significant decrease in the carcinogenic chemical N-nitrosonornicotine in the genetically modified tobacco plants, as well as a 50 percent overall reduction in the class of harmful compounds called tobacco-specific nitrosamines. The research results were published online in Plant Biotechnology Journal, a peer-reviewed scientific journal. David Sutton, a spokesman for Philip Morris USA, said the cigarette company had supported the research as part of a commitment to reduce the harmful compounds in tobacco products. "This study is an important part of that ongoing effort," Sutton said. "We'll be reviewing this research to determine future applicability in our products." Under way for about six years, the research started with an effort by Dewey and a Kentucky researcher to identify and isolate which among the 40,000 to 50,000 genes in the tobacco plant causes a nicotine molecule to convert to the compound nornicotine. Once they did that, they then used the techniques of biotechnology to shut that gene down and keep nornicotine from forming. "If you greatly reduce the amount of nornicotine, you by default reduce the amount of NNN," Dewey said. Next: Plant breeding But the intent is not to introduce genetically modified tobacco plants. Dewey said the next phase will be to develop tobacco plants that have the same low nornicotine characteristics without genetic engineering and to develop similar characteristics in other varieties of tobacco. But plant breeding is a slow process. "Once you find a trait of interest, introducing that trait into varieties that a farmer would grow takes numbers of years," Dewey said. Enditem