Cloning and characterization of legumin storage protein gene of chickpea (Cicer arietinum L)

Genomic DNA clones coding for legumin storage protein were isolated from chickpea (Cicer arietinum L.) subgenomic library using pea legumin cDNAs as a probe. The complete nucleotide sequence of the legumin gene (leg3) was determined. Sequence analysis indicated that leg3 contains 2022 bp long structural gene interrupted by three small introns. The gene encodes a polypeptide of 496 amino acids including a signal peptide of 21 amino acid residues and a-b subunit cleavage site. Leg3 polypeptide is rich in amide amino acids and contains 5 methionine and 6 cysteine amino acids. DNA sequence comparison showed about 70-80% identity with legumin genes from pea, soybean and broad bean. The 5' flanking region contains regulatory elements such as TATA and legumin box and 3' region contains a stop codon and two polyadenylation signals. Southern hybridisation indicated the presence of multiple copies of leg3 in chickpea and estimated about 10-12 copies per haploid genome. Northern blot hybridisation showed that leg3 expresses in developing seed and not in other tissues of chickpea indicating temporal and tissue-specific expression of this gene.