Characterization and temporal expression of a omega-6 fatty acid desaturase cDNA from sesame (Sesamum indicum L.) seeds

A cDNA (SeFAD2) encoding a microsomal omega -6 desaturase was characterized in association with its temporal expression and changes in linoleic acid l evels in sesame (Sesamum indicum L.) oilseeds. Much higher sequence identit ies of the SeFAD2 protein were found with microsomal omega -6 (71-81%) than with plastidial omega -6 desaturases (22-24%) and the sequences within the conserved histidine boxes were some different from those of other plant hi stidine boxes examined. Phylogenetic analysis revealed that the SeFAD2 gene might have independently diverged as a different subfamily or family membe r. At least 1-2 copies of the SeFAD2 gene existed in sesame genome and its expression was seed-specific. The SeFAD2 gene vigorously expressed between 18 and 27 days after flowering (DAF). Changes in linoleic acid levels occur red coincidently with changes in the SeFAD2 transcript levels according to the development of sesame oilseeds. It was assumed that the SeFAD2 gene is responsible for production of storage linoleic acid in sesame seeds. (C) 20 01 Elsevier Science Ireland Ltd. All rights reserved.