A CORM-SPECIFIC GENE ENCODES TARIN, A MAJOR GLOBULIN OF TARO (COLOCASIA-ESCULENTA L SCHOTT)

A gene encoding a globulin from a major tare (Colocasia esculenta L. S chott) corm protein family, tarin (G1, ca. 28 kDa) was isolated from a lambda Charon 35 library, using a cDNA derived from a highly abundant corm-specific mRNA, as probe. The gene, named tar1, and the correspon ding cDNA were characterized and compared. No introns were found. The major transcription start site was determined by primer extension anal ysis. The gene has an open reading frame (ORF) of 765 bp, and the dedu ced amino acid sequence indicated a precursor polypeptide of 255 resid ues that is post-translationally processed into two subunits of about 12.5 kDa each. The deduced protein is 45% homologous to curculin, a sw eet-tasting protein found in the fruit pulp of Curculigo latifolia and 40% homologous to a mannose-binding lectin from Galanthus nivalis. Si gnificant similarity was also found at the nucleic acid sequence level with genes encoding lectins from plant species of the Amaryllidaceae and Lilliaceae families.