Plant Physiol. Nicotine is a NAD-related secondary alkaloid found in high concentration in the leaves of the tetraploid tobacco plant (Nicotiana tabacum).
The recent sequencing of the N. tabacum genome allowed a comprehensive analysis of genes involved in NAD and nicotine biosynthesis. The analysis revealed the presence of a nicotine regulon, constituted of genes involved in the last steps of the nicotine pathway, under the control of ERF transcription factors. In contrast, genes of early steps in nicotine biosynthesis overlap with NAD biosynthesis and are often duplicated: one gene of each type is part of the nicotine regulon. It usually contains P-box and MYC2-binding G-box elements in the promoter region. The other gene lacks nicotine-related TF binding sites, its expression is not restricted to nicotine-producing tissues and is therefore likely involved in primary metabolism (NAD production) rather than nicotine biosynthesis.
The genome sequencing also allowed the elucidation of the NIC2 locus which contains several transcription factors regulating nicotine biosynthesis and its modifications in a low-nicotine variant.