RNAi-mediated down-regulation of ornithine decarboxylase (ODC) leads to reduced nicotine and increased anatabine levels in transgenic Nicotiana tabacum L.

Polyamines delay leaf maturation in low‐alkaloid tobacco varieties

“…LA plants with the highest total polyamine content showed the most severe impairment of leaf maturation, characterized by weak senescence, a higher chlorophyll content, and more leaf mesophyll cells per unit area (Figure 1 2005). ODC is the main enzyme responsible for putrescine biosynthesis in tobacco roots and plays a key role in the production of nicotine and the overall alkaloid profile (Chintapakorn & Hamill, 2007;Dalton et al, 2016;DeBoer et al, 2011DeBoer et al, , 2013. Topping of tobacco plants allows the crop to reach its full yield and quality potential at harvest and leads to increased activity of ODC and several enzymes in the nicotine biosynthesis pathway, including putrescine methyltransferase and quinolinate phosphoribosyltransferase, in tobacco roots 24-48 hr after topping (Mizusaki, Tanabe, Noguchi, & Tamaki, 1973;Saunders & Bush, 1979 where ADC rather than ODC is responsible for putrescine biosynthesis (Figure 4a), DFMO treatment resulted in a significantly higher total polyamine content.…”

“…Previous studies have demonstrated that the ADC route to putrescine has only a minor effect on the alkaloid profile of tobacco whereas the ODC pathway plays the major role in nicotine biosynthesis (Chintapakorn & Hamill, 2007;Dalton et al, 2016;DeBoer, Dalton, Edward, & Hamill, 2011;DeBoer, Dalton, Edward, Ryan, & Hamill, 2013). Putrescine is converted to spermidine and then spermine by the successive addition of aminopropyl groups derived from decarboxylated S-adenosylmethionine (SAM), in reactions catalyzed by the enzymes spermidine synthase and spermine synthase, respectively.…”

“…In most plants, putrescine can be synthesized either directly from ornithine by ornithine decarboxylase (ODC) or from arginine via three enzymatic steps, initiated by arginine decarboxylase (ADC; Illingworth et al, 2003;Michael, Furze, Rhodes, & Burtin, 1996;Piotrowski, Janowitz, & Kneifel, 2003). Previous studies have demonstrated that the ADC route to putrescine has only a minor effect on the alkaloid profile of tobacco whereas the ODC pathway plays the major role in nicotine biosynthesis (Chintapakorn & Hamill, 2007;Dalton et al, 2016;DeBoer, Dalton, Edward, & Hamill, 2011;DeBoer, Dalton, Edward, Ryan, & Hamill, 2013). Putrescine is converted to spermidine and then spermine by the successive addition of aminopropyl groups derived from decarboxylated S-adenosylmethionine (SAM), in reactions catalyzed by the enzymes spermidine synthase and spermine synthase, respectively.…”

Genomic Insights into the Evolution of the Nicotine Biosynthesis Pathway in Tobacco

“…As a defense toxin, nicotine production is drastically increased in response to damage caused by grazing herbivores (Baldwin, 1989), and jasmonates play a central signaling role in the damage-induced nicotine biosynthesis (Baldwin et al, 1994;Shoji et al, 2000. Nicotine has heterocyclic pyridine and pyrrolidine rings (Shoji and Hashimoto, 2011a;Dewey and Xie, 2013); the pyrrolidine ring is formed through consecutive reactions catalyzed by Orn decarboxylase (ODC; Imanishi et al, 1998;DeBoer et al, 2011a), putrescine N-methyltransferase (PMT; Hibi et al, 1994), and N-methylputrescine oxidase (MPO; Heim et al, 2007;Katoh et al, 2007), whereas enzymes involved in early steps of NAD synthesis, Asp oxidase (AO), quinolinate synthase (QS), and quinolinate phosphoribosyl transferase (QPT) are responsible for the formation of the pyridine ring (Sinclair et al, 2000;Katoh et al, 2006;Fig. 1).…”

Use of the wound-inducible NtQPT2 promoter from Nicotiana tabacum for production of a plant-made vaccine

“…When plants were approximately 20 cm in height, wounding was undertaken, if required, by surgical removal of the uppermost *1 cm of stem, comprising young unexpanded leaves and the apical meristem. This simple wounding treatment of N. tabacum results in large increases in QPT transcript, and those of other genes associated with alkaloid synthesis, within a few hours of aerial damage and precedes elevated levels of alkaloid in upper, non-damaged leaves when plants are analysed 5-7 days later (Sinclair et al 2000;Cane et al 2005, De Boer et al 2011b). Tissue samples were taken from roots and upper, non-damaged leaves of control and wounded plants 5 days after apex removal and analysed for the presence of LTB by ELISA.…”