Key genes involved in the synthesis of nicotine and nornicotine alkaloids in Nicotiana leaves. The berberine bridge enzyme-like protein converts nicotinic acid and N-methylpyrrolinium cation into nicotine, and nicotine N-deaminase converts it further to nornicotine. AO, L-aspartate oxidase; BBL, berberine bridge enzyme-like protein; MPO, methyleputrescine oxidase; NND, nicotine N-demethylase; PMT, putrecine N-methyltransferase; QPT, quinolinate phosphoribosyltransferase; QS, quinolinate synthase.
Sierro et al. Genome Biology 2013 14:R60 doi:10.1186/gb-2013-14-6-r60