title: Expression of a constitutively active nitrate reductase variant in tobacco reduces tobacco-specific nitrosamine accumulation in cured leaves and cigarette smoke.
abstract: Burley tobaccos (Nicotiana tabacum) display a nitrogen-use-deficiency phenotype that is associated with the accumulation of high levels of nitrate within the leaf, a trait correlated with production of a class of compounds referred to as tobacco-specific nitrosamines (TSNAs). Two TSNA species, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-nitrosonornicotine (NNN), have been shown to be strong carcinogens in numerous animal studies. We investigated the potential of molecular genetic strategies to lower nitrate levels in burley tobaccos by overexpressing genes encoding key enzymes of the nitrogen-assimilation pathway. Of the various constructs tested, only the expression of a constitutively active nitrate reductase (NR) dramatically decreased free nitrate levels in the leaves. Field-grown tobacco plants expressing this NR variant exhibited greatly reduced levels of TSNAs in both cured leaves and mainstream smoke of cigarettes made from these materials. Decreasing leaf nitrate levels via expression of a constitutively active NR enzyme represents an exceptionally promising means for reducing the production of NNN and NNK, two of the most well-documented animal carcinogens found in tobacco products.
authors.affiliation: Department of Crop Science, North Carolina State University, Raleigh, NC, USA.
authors.forename: Jianli
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Crop Science, North Carolina State University, Raleigh, NC, USA.
authors.forename: Leichen
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Crop Science, North Carolina State University, Raleigh, NC, USA.
authors.forename: Ramsey S
authors.initials: RS
authors.lastname: Lewis
authors.affiliation: Philip Morris International R&D, Philip Morris Products SA, Neuchatel, Switzerland.
authors.forename: Lucien
authors.initials: L
authors.lastname: Bovet
authors.affiliation: Philip Morris International R&D, Philip Morris Products SA, Neuchatel, Switzerland.
authors.forename: Simon
authors.initials: S
authors.lastname: Goepfert
authors.affiliation: Kentucky Research and Development Center, University of Kentucky, Lexington, KY, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Jack
authors.affiliation: Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Crutchfield
authors.affiliation: Kentucky Research and Development Center, University of Kentucky, Lexington, KY, USA.
authors.forename: Huihua
authors.initials: H
authors.lastname: Ji
authors.affiliation: Department of Crop Science, North Carolina State University, Raleigh, NC, USA.
authors.forename: Ralph E
authors.initials: RE
authors.lastname: Dewey
mesh_terms: D002273:Carcinogens / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D050901:Nitrate Reductase / Q000235:genetics*; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009602:Nitrosamines / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D062789:Tobacco Products
chemical_list: D002273:Carcinogens; D009566:Nitrates; D009602:Nitrosamines; D050901:Nitrate Reductase; D009584:Nitrogen
keywords: NNK; NNN; burley; nitrate reductase; nitrogen-assimilation pathway; tobacco; tobacco-specific nitrosamines