Researchers Investigate Molecular Mechanisms of Duplicated Genes in Tobacco

Gene duplication is a powerful source of phenotypic diversity in plants, however, only few studies have investigated the underlying molecular mechanisms that generate new functions in duplicated genes. This led Nara Institute of Science and Technology scientists Tsubasa Shoji and Takashi Hashimoto to analyze how duplicated genes encoding quinolinate phosphoribosyltransferase (QPT), an enzyme involved in the production of nicotinamide adenine dinucleotide (NAD), are regulated by the jasmonate-responsive transcriptional factor ERF189 that functions critically for nicotine biosynthesis in tobacco.

Tobacco has two QPT genes: QPT1 is expressed at a constitutive basal level, and QPT1 is regulated coordinately with other structural genes involved in nicotine production. Assays revealed that the QPT2 promoter contains three functional ERF189-binding sites, and all of which confer incremental ERF189-mediated activation to the promoter. The QPT1 promoter is not bound and regulated by ERF189. Based on this findings, one copy of the duplicated QPT genes was recruited to a tobacco alkaloid regulon (a group of genes regulated by one protein) by evolving several target cis-regulatory elements of ERF189 in its promoter, to cope with an increased metabolic demand for pyridine precursors during active alkaloid production.

Subscribers of the Plant Journal may download the complete article at http://onlinelibrary.wiley.com/doi/10.1111/j.1365-313X.2011.04647.x/abstract.