title: RNA interference (RNAi)-induced suppression of nicotine demethylase activity reduces levels of a key carcinogen in cured tobacco leaves.
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.
authors.affiliation: Department of Crop Science, North Carolina State University, Raleigh, NC 27695, USA. ramsey_lewis@ncsu.edu
authors.forename: Ramsey S
authors.initials: RS
authors.lastname: Lewis
authors.forename: Anne M
authors.initials: AM
authors.lastname: Jack
authors.forename: Jerry W
authors.initials: JW
authors.lastname: Morris
authors.forename: Vincent J M
authors.initials: VJ
authors.lastname: Robert
authors.forename: Lily B
authors.initials: LB
authors.lastname: Gavilano
authors.forename: Balazs
authors.initials: B
authors.lastname: Siminszky
authors.forename: Lowell P
authors.initials: LP
authors.lastname: Bush
authors.forename: Alec J
authors.initials: AJ
authors.lastname: Hayes
authors.forename: Ralph E
authors.initials: RE
authors.lastname: Dewey
mesh_terms: D002273:Carcinogens / Q000032:analysis / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D009602:Nitrosamines / Q000032:analysis / Q000378:metabolism*; D018515:Plant Leaves / Q000737:chemistry* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism*; D034622:RNA Interference; D018749:RNA, Plant / Q000235:genetics; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D002273:Carcinogens; D009602:Nitrosamines; D010940:Plant Proteins; D018749:RNA, Plant; D003577:Cytochrome P-450 Enzyme System; C516919:nicotine demethylase, tobacco; C008655:N'-nitrosonornicotine