CHARACTERIZATION AND SPATIAL LOCALIZATION OF THE MAJOR GLOBULIN FAMILIES OF TARO (COLOCASIA-ESCULENTA L SCHOTT) TUBERS

The globulins from tubers of tare (Colocasia esculenta L. Schott) were characterized. They account for similar to 80% of total soluble tuber proteins. Western blot analysis and microsequencing indicated the pre sence of two non-related globulin families, denoted G1 and G2. The G1 family is composed of a large number of isoforms of 12.5 kD with isoel ectric points (pIs) ranging from 5.5 to 9.5. The G2 family is composed of two sets of proteins of 24 kD (G2a) and 22 kD (G2b), with pIs near 7.5. Both protein families are highly abundant and specifically found in tare tubers. G1 and G2 are found very early and throughout all sta ges of tuber development. They are partially degraded in tubers during sprouting, suggesting that they may be storage proteins. Antisera rai sed against these globulins did not cross-react with proteins from tub ers of sweet potato, carrot, cassava, yam and Arracacia xanthorrizha B ancr. Immunocytochemical studies indicated that they are found in vacu oles of storage parenchyma, mainly in the cells that store starch gran ules.