Isolation and Characterization of Candidate Genes Involved in Nornicotine Biosynthesis

The term "conversion" refers to the genetic process by which tobacco plants that produce nicotine as their predominant alkaloid give rise to a progeny that accumulate up to 90% of their alkaloid content in the fOlm ofnomicotine. Nomicotine is an undesired, demethylated derivative of nicotine and a precursor of nitrosonornicotine, a compound that has carcinogenic properties in laboratory animals. To better understand the regulation of nomicotine production, we devised several strategies for elucidating the molecular basis of the conversion phenomenon with the ultimate goal of reducing the nOrnlcotine content of tobacco by eliminating the conversion process. Based on experimental evidence collected at North Carolina State University, two models have been proposed to describe the molecular mechanism of nicotine demethylation (For a detailed description, see the proposal entitled "Elucidating the Mechanism of Nomicotine Biosynthesis in Nicotiana tabacum" by R. E. Dewey). The first model describes a scenario where nicotine demethylation by converter tobacco is a direct result of a factor that is present at higher concentrations in converter tobacco than in