The present invention discloses the polynucleotide sequences of genes encoding aspartate transaminase (AAT) from Nicotiana tabacum and the modulation of their expression. There is described a plant cell comprising: (i) a polynucleotide comprising, consisting or consisting essentially of a sequence having at least 80% sequence identity to SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 5, SEQ ID NO: 7, SEQ ID NO: 9, SEQ ID NO: 11, SEQ ID NO: 13 or SEQ ID NO: 15; (ii) a polypeptide encoded by the polynucleotide set forth in (i); (iii) a polypeptide comprising, consisting or consisting essentially of a sequence having at least 95% sequence identity to SEQ ID NO: 6 or SEQ ID No: 8, at least 93% sequence identity to SEQ ID NO: 2 or SEQ ID NO: 10 or SEQ ID No: 12, or at least 94% sequence identity to SEQ ID NO: 4 or SEQ ID NO: 14 or SEQ ID NO: 16; or (iv) a construct, vector or expression vector comprising the isolated polynucleotide set forth in (i), wherein said plant cell comprises at least one modification which modulates the expression or activity of the polynucleotide or the polypeptide as compared to a control plant cell in which the expression or activity of the polynucleotide or polypeptide has not been modified.

The present disclosure provides the identification of tobacco Nic1 locus. Also provided are tobacco plants with altered total alkaloid and nicotine levels and commercially acceptable leaf grade, their development via breeding or transgenic approaches, and production of tobacco products from these tobacco plants. Also provided are compositions and methods for producing tobacco plants having novel Nic1 mutations or alleles to reduce nicotine levels. Further provided are sequence polymorphisms and molecular markers for breeding tobacco with reduced nicotine or nicotine free while maintaining tobacco leaf grade and tobacco product quality.

The present invention relates to a method of reducing the content of at least one tobacco specific nitrosamine (TSNA) or a precursor of a TSNA in tobacco comprising expressing a deregulated cation efflux protein in a tobacco plant, or plant part thereof, or plant cell.

The present disclosure provides tobacco Nic1b locus and associated genes (e.g., a group of ERF genes). Also provided are tobacco plants with altered total alkaloid and nicotine levels and commercially acceptable leaf grade, their development via breeding or transgenic approaches, and production of tobacco products from these tobacco plants. Further provided are compositions and methods for producing tobacco plants having novel mutations or alleles to reduce nicotine levels. Further provided are sequence polymorphisms and molecular markers for breeding tobacco with reduced nicotine or alkaloids while maintaining tobacco leaf grade and tobacco product quality.

The present disclosure provides compositions and methods related to tobacco plants. In particular, the present disclosure provides novel methods for producing tobacco plants, and any related tobacco products, having low nicotinic alkaloid content. Tobacco plants produced according to the methods of the present disclosure exhibit reduced levels of nicotinic alkaloids (e.g., nicotine) compared to both naturally-occurring and transgenic tobacco plants, and thus represent a commercially valuable alternative to currently available tobacco varieties.