Cloning of a cDNA encoding tobacco omega-3 fatty acid desaturase.

A cDNA was isolated from a tobacco (Nicotiana tabacum cv. SR1) leaf cDNA library using, as a hybridization probe, a cDNA fragment from the gene (fad7) encoding Arabidopsis thaliana chloroplast omega-3 fatty acid (FA) desaturase. The deduced 379-amino-acid (aa) sequence has 67-71% identity to those deduced from the previously described genes encoding the omega-3 FA desaturases of A. thaliana. The absence of an N-terminal extension transit peptide in the deduced aa sequence of the cDNA clone and the accumulation pattern of the mRNA corresponding to this cDNA in leaf and root tissues indicate that the isolated cDNA encodes a tobacco microsomal omega-3 FA desaturase.