Structure and Function of the Golgi Complex in Rice Cells: Characterization of Golgi Membrane Glycoproteins

The structure and synthesis of the saccharide chains of Golgimembrane glycoproteins in suspension-cultured rice (Oryza sativaL.) cells were studied. Peanut lectin (PNA) and Ulex europaeuslectin-I (UEA-I) have high affinity for typical O-linked saccharidechains and both recognized the saccharide chains of rice Golgimembrane glycoproteins. These glycoproteins were also sensitiveto alkali and to O-glycanase. These results indicate that theGolgi membrane glycoproteins have O-linked saccharide chains.Brefeldin A, a specific inhibitor of Golgi-mediated secretion,induced morphological changes in Golgi complexes and preventedthe synthesis of the saccharide chains of the membrane glycoproteinsthat could be recognized by PNA and UEA-I. These glycoproteinswere typically localized in all compartments of the Golgi complex.Monensin can arrest the transport of secretory proteins frommedial to trans Golgi compartments but did not affect the formationand localization of the Golgi membrane glycoproteins. Tunicamycin,an inhibitor of the synthesis of N-linked saccharide chains,did not inhibit the synthesis of the saccharide chains of theseGolgi membrane glycoproteins. These results strongly suggestthat the synthesis of O-linked saccharide chains of Golgi membraneglycoproteins is initiated in the cis Golgi compartment. (Received September 24, 1992; Accepted June 4, 1993)