RNA interference (RNAi)-induced suppression of nicotine demethylase activity reduces levels of a key carcinogen in cured tobacco leaves.
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.
Lewis
Ramsey S
RS
Department of Crop Science, North Carolina State University, Raleigh, NC 27695, USA. ramsey_lewis@ncsu.edu
Jack
Anne M
AM
Morris
Jerry W
JW
Robert
Vincent J M
VJ
Gavilano
Lily B
LB
Siminszky
Balazs
B
Bush
Lowell P
LP
Hayes
Alec J
AJ
Dewey
Ralph E
RE
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
D002273:Carcinogens; D009602:Nitrosamines; D010940:Plant Proteins; D018749:RNA, Plant; D003577:Cytochrome P-450 Enzyme System; C516919:nicotine demethylase, tobacco; C008655:N'-nitrosonornicotine