Isolation and characterisation of legumin promoter sequence from chickpea (Cicer arietinum L.).

Seed specific promoters are useful for expression of foreign genes in the seeds. We have isolated a Cicer arietinum legumin promoter from lambda EMBL genomic library and subcloned in pBluescript II KS (-) in Eco RV and Pst I site. The 2.762 kb Hind II Pst I fragment was sequenced completely by dideoxy chain termination method by creating a set of unidirectional deletions of the inserts in pAKKIII. The insert contains mainly upstream sequence (2240 bps) and only a part of structural gene (522 bps) sequence. The 522 bps of the structural gene shows approximately 80% homology with pea legumin A and this is almost the same as chickpea legumin in its sequence. The amino acid sequence derived from the part of the structural gene was similar to the chickpea 5' part of the legumin structural gene with a few variations. A 21 amino acid signal peptide was also deduced like many other legumes. Transcription start site (CAT) was located at 55 bp upstream of the initiation codon ATG. One codon downstream to ATG codon Hind III site was present. TATA box was observed at -30 position, with a consensus of CCTATAAATAACC. The consensus CATGCAAG, a part of legumin box was noticed at -110 bp position. At -295 to -265 bp upstream AGGA box like sequences were observed and a 56 bp perfect repeat was located between -913 bp and -972 bp. Strong homology with pea promoter sequence near the CAT sequence was noticed which gradually decreased towards the upstream region. Thus the cloned fragment contains a full length promoter which can be utilised for expression of foreign genes in seeds of chickpea.