Changes in glycosylation during Drosophila development. The influence of ecdysone on hemomucin isoforms

To explore a possible signal function of glycodeterminants and the tissue s pecificity of glycosylation in Drosophila melanogaster, hemomucin, a surfac e mucin previously isolated from cell lines was studied. It was shown to ex ist in two glycoforms with molecular masses of 100 and 105 kDa, respectivel y. The two forms differ by the presence of O-linked galactose, which was on ly detected in the larger glycoform using the beta -galactose specific pean ut agglutinin (PNA). The 105 form was found in cell lines after addition of the cell cycle inhibitor taxol and after induction with ecdysone. When who le animal tissues were analyzed using PNA, dramatic changes were observed d uring development. We were able to identify a number of proteins, which sho wed strong PNA-staining in stages with a high ecdysone titer, while virtual ly no staining was detected in adults. This pattern was specific for PNA an d was not observed with any of the other lectins employed in this study. Su rprisingly, in contrast to our observation in cell lines, PNA staining of h emomucin was not observed in late third larval and pupal stages, which are known to produce high ecdysone titers. The only organ, in which significant amounts of the 105 form were detected, were the ovaries, where hemomucin i s produced in follicle cells during the late phase of oogenesis and subsequ ently incorporated into the chorion. (C) 2001 Elsevier Science Ltd. All rig hts reserved.