title: Genetic Factors for Enhancement of Nicotine Levels in Cultivated Tobacco.
abstract: Nicotine has practical applications relating to smoking cessation devices and alternative nicotine products. Genetic manipulation for increasing nicotine content in cultivated tobacco (Nicotiana tabacum L.) may be of value for industrial purposes, including the possibility of enhancing the efficiency of nicotine extraction. Biotechnological approaches have been evaluated in connection with this objective, but field-based results are few. Here, we report characterization of two genes encoding basic-helix-loop-helix (bHLH) transcription factors (TFs), NtMYC2a and NtMYC2b from tobacco. Overexpression of NtMYC2a increased leaf nicotine levels in T1 transgenic lines approximately 2.3-fold in greenhouse-grown plants of tobacco cultivar 'NC 95'. Subsequent field testing of T2 and T3 generations of transgenic NtMYC2a overexpression lines showed nicotine concentrations were 76% and 58% higher than control lines, respectively. These results demonstrated that the increased nicotine trait was stably inherited to the T2 and T3 generations, indicating the important role that NtMYC2a plays in regulating nicotine accumulation in N. tabacum and the great potential of NtMYC2a overexpression in tobacco plants for industrial nicotine production. Collected data in this study also indicated a negative feedback inhibition of nicotine biosynthesis. Further enhancement of nicotine accumulation in tobacco leaf may require modification of the processes of nicotine transport and deposition.
authors.affiliation: Tobacco Breeding Center, Yunnan Academy of Tobacco Agricultural Sciences, Kunming, Yunnan 650021, China.|Crop Science Department, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Bingwu
authors.initials: B
authors.lastname: Wang
authors.affiliation: Crop Science Department, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Ramsey S
authors.initials: RS
authors.lastname: Lewis
authors.affiliation: Tobacco Breeding Center, Yunnan Academy of Tobacco Agricultural Sciences, Kunming, Yunnan 650021, China.
authors.forename: Junli
authors.initials: J
authors.lastname: Shi
authors.affiliation: Tobacco Breeding Center, Yunnan Academy of Tobacco Agricultural Sciences, Kunming, Yunnan 650021, China.
authors.forename: Zhongbang
authors.initials: Z
authors.lastname: Song
authors.affiliation: Tobacco Breeding Center, Yunnan Academy of Tobacco Agricultural Sciences, Kunming, Yunnan 650021, China.
authors.forename: Yulong
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Tobacco Breeding Center, Yunnan Academy of Tobacco Agricultural Sciences, Kunming, Yunnan 650021, China.
authors.forename: Wenzheng
authors.initials: W
authors.lastname: Li
authors.affiliation: Crop Science Department, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Hongxia
authors.initials: H
authors.lastname: Chen
authors.affiliation: Crop Science Department, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Rongda
authors.initials: R
authors.lastname: Qu
mesh_terms: D009538:Nicotine / Q000096:biosynthesis* / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors; D009538:Nicotine