RNAi to Reduce Levels of a Key Carcinogen in Tobacco

Certain compounds produced by tobacco, like nitrosonornicotine and other nitrosamines, have been shown to be carcinogenic to laboratory animals, and possibly to humans. Nitrosonornicotine (NNN), a Grade 2B carcinogen, is produced by nitrosation of nornicotine (a nicotine by-product) during curing, aging, processing and smoking of tobacco. Nornicotine, on the other hand, has been implicated in increased risks for hypertension, lung cancer, and other respiratory and gastrointestinal pathologies. The recent identification of the major nicotine demethylase (key enzyme that converts nornicotine to NNN) gene has allowed the reduction of NNN content of cultivated tobacco using biotechnological approaches.

Using RNA interference, scientists from the University of Kentucky and North Carolina State University have developed tobacco lines exhibiting up to six-fold decrease in nornicotine and NNN content. Results of large-scale field trials showed that the GM lines are comparable to non-transgenic tobacco in terms of agronomic properties. Since nicotine demethylase is also essential in the synthesis of other nitrosamines, inhibition of its expression is an effective means of significantly reducing the level of other carcinogens present in tobacco products.

The same technology has been employed to reduce the levels of caffeine in coffee, gossypol in cotton, and linolenic acid in soybean.

The abstract of the paper published by Plant Biotechnology Journal, including links to the full article, is available at http://www.blackwell-synergy.com/doi/abs/10.1111/j.1467-7652.2008.00324.x