Reducing tobacco specific nitrosamines through alteration of the nitrate assimilation pathway

A tobacco product having reduced tobacco specific nitrosamine (TSNA) levels, wherein the tobacco product comprises cured plant tissue from a from a tobacco plant of the species Nicotiana tabacum, said tobacco plant being modified to comprise:

• (i) a polynucleotide comprising, consisting or consisting essentially of a sequence encoding a deregulated nitrate reductase enzyme;
• (ii) a polypeptide encoded by the polynucleotide set forth in (i);
• (iii) a polypeptide comprising, consisting or consisting essentially of a deregulated nitrate reductase enzyme;
• or
• (iv) a construct, vector or expression vector comprising the polynucleotide set forth in (i),
• wherein the expression or activity of said nitrate reductase is deregulated as compared to a control unmodified tobacco plant;
• and wherein the deregulated nitrate reductase enzyme comprises:
• (a) a nitrate reductase polypeptide having the sequence of SEQ ID NO:4 and comprising an amino acid substitution at position 523;
• or
• (b) a nitrate reductase polypeptide having the sequence of SEQ ID NO:4 and comprising an amino acid substitution at position 523, wherein the amino acid at position 523 of SEQ ID NO:
• 4 is substituted to an aspartic acid,
• wherein said tobacco product has reduced tobacco specific nitrosamine (TSNA) levels compared to a tobacco product derived from a control tobacco plant in which the nitrate reductase enzyme has not been deregulated, wherein total levels of TSNA are reduced by at least 50%.