Vector 21-41 tobacco has been genetically engineered to express a
quinolinic acid phosphoribosyltransferase (QPTase) in the reverse,
or antisense position, which disrupts the normal expression of
QPTase, a key enzyme in the biosynthetic pathway leading to the
production of nicotine and related alkaloids. The effect of this
genetic change is to reduce the nicotine levels of nicotine,
nor-nicotine, and total alkaloids in the leaves of Vector 21-41
The tobacco line also contains the nptII marker gene derived from
the bacterium Escherichia coli. The nptII gene encodes the enzyme
neomycin phosphotransferase type II (NPTII) and is used as a
selectable marker in the initial laboratory stages of plant cell
selection. Expression of the added genes is controlled in part by
gene sequences from the plant pathogen Agrobacterium tumefaciens.
The A. tumefaciens method was used to transfer the added genes into
the parental recipient tobacco variety.