RNA interference (RNAi)-induced suppression of nicotine demethylase activity reduces levels of a key carcinogen in cured tobacco leaves

Plant Biotechnol J. 2008 May;6(4):346-54. doi: 10.1111/j.1467-7652.2008.00324.x. Epub 2008 Feb 14.

Abstract

Technologies for reducing the levels of tobacco product constituents that may contribute to unwanted health effects are desired. Target compounds include tobacco-specific nitrosamines (TSNAs), a class of compounds generated through the nitrosation of pyridine alkaloids during the curing and processing of tobacco. Studies have reported the TSNA N'-nitrosonornicotine (NNN) to be carcinogenic in laboratory animals. NNN is formed via the nitrosation of nornicotine, a secondary alkaloid produced through enzymatic N-demethylation of nicotine. Strategies to lower nornicotine levels in tobacco (Nicotiana tabacum L.) could lead to a corresponding decrease in NNN accumulation in cured leaves. The major nicotine demethylase gene of tobacco has recently been isolated. In this study, a large-scale field trial was conducted to evaluate transgenic lines of burley tobacco carrying an RNA interference (RNAi) construct designed to inhibit the expression of this gene. Selected transgenic lines exhibited a six-fold decrease in nornicotine content relative to untransformed controls. Analysis of cured leaves revealed a commensurate decrease in NNN and total TSNAs. The inhibition of nicotine demethylase activity is an effective means of decreasing significantly the level of a key defined animal carcinogen present in tobacco products.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carcinogens / analysis
  • Carcinogens / metabolism*
  • Cytochrome P-450 Enzyme System / genetics*
  • Cytochrome P-450 Enzyme System / metabolism*
  • Gene Expression Regulation, Plant
  • Nitrosamines / analysis
  • Nitrosamines / metabolism*
  • Plant Leaves / chemistry*
  • Plant Leaves / metabolism
  • Plant Proteins / genetics*
  • Plant Proteins / metabolism*
  • RNA Interference*
  • RNA, Plant / genetics
  • Tobacco / enzymology*
  • Tobacco / genetics
  • Tobacco / metabolism

Substances

  • Carcinogens
  • Nitrosamines
  • Plant Proteins
  • RNA, Plant
  • Cytochrome P-450 Enzyme System
  • nicotine demethylase, tobacco
  • N'-nitrosonornicotine