CDNAS ENCODING FOR STORAGE PROTEINS IN THE TUBERS OF TARO (COLOCASIA-ESCULENTA-SCHOTT)

Two major protein groups of taro (Colocasia esculenta) tuber were purified, and their antisera were used for the screening of the cDNA library constructed from poly(A)+RNA of taro tuber. A cDNA clone obtained by screening with an anti-12 kD protein antiserum had an insert 1058 bp-long, and an open reading frame for a peptide of 268 amino acids. The analyses of the N-terminal amino acid sequence and in vitro translation product suggested that the protein was synthesized as a peptide with a molecular weight of 27 kD, and then processed into two mature peptides with a molecular weight of 12.5 and 13.9 kD and an extra peptide with a molecular weight of 0.6 kD. The cDNA clones obtained using the anti-25 kD protein antiserum were highly homologous with each other. One of them had an insert 958 bp-long and an open reading frame for a peptide with 209 amino acids. The amino acid sequence deduced from the nucleotide sequence of this clone indicated that the 25 kD proteins were homologous to the trypsin inhibitors of soybean and winged bean as well as sporamins, the storage proteins of sweet potato.