Abstract
Motivation exists to develop tobacco cultivars with reduced nicotine content for the purpose of facilitating compliance with expected tobacco product regulations that could mandate the lowering of nicotine levels per se, or the reduction of carcinogenic alkaloid-derived tobacco specific nitrosamines (TSNAs). A berberine bridge enzyme-like (BBL) gene family was recently characterized for N. tabacum and found to catalyze one of the final steps in pyridine alkaloid synthesis for this species. Because this gene family acts downstream in the nicotine biosynthetic pathway, it may represent an attractive target for genetic strategies with the objective of reducing alkaloid content in field-grown tobacco. In this research, we produced transgenic doubled haploid lines of tobacco cultivar K326 carrying an RNAi construct designed to reduce expression of the BBL gene family. Field-grown transgenic lines carrying functional RNAi constructs exhibited average cured leaf nicotine levels of 0.684%, in comparison to 2.454% for the untransformed control. Since numerous barriers would need to be overcome to commercialize transgenic tobacco cultivars, we subsequently pursued a mutation breeding approach to identify EMS-induced mutations in the three most highly expressed isoforms of the BBL gene family. Field evaluation of individuals possessing different homozygous combinations of truncation mutations in BBLa, BBLb, and BBLc indicated that a range of alkaloid phenotypes could be produced, with the triple homozygous knockout genotype exhibiting greater than a 13-fold reduction in percent total alkaloids. The novel source of genetic variability described here may be useful in future tobacco breeding for varied alkaloid levels.
Highlights
The pyridine alkaloids of tobacco (Nicotiana tabacum L.) are among the most studied group of plant secondary compounds in plants
To establish whether silencing the berberine bridge enzyme-like (BBL) gene family represents a viable means of obtaining reduced nicotine tobacco plants under conventional field growth conditions, we employed an RNAi approach (S1 Fig.)
Tobacco varieties currently grown in the United States must exhibit nicotine and total alkaloid levels within specific windows defined with reference to certain long-term check varieties [38,39]
Summary
The pyridine alkaloids of tobacco (Nicotiana tabacum L.) are among the most studied group of plant secondary compounds in plants. Nicotine constitutes greater than 90% of the total. Tobacco Alkaloid Reduction grant from the Tobacco Education and Research Council/North Carolina Tobacco Foundation. Any opinion, finding, conclusion or recommendation expressed in this publication are those of the authors and do not necessarily reflect the view and policies of the Tobacco Education and Research Council, Inc. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
