Progressive redistribution of alcohol dehydrogenase during vitellogenesis in Drosophila melanogaster: characterization of ADH-positive bodies in mature oocytes.

The use of monoclonal antibodies against Drosophila alcohol dehydrogenase (ADH) provides a powerful tool in the analysis of the tissue and temporal patterns of Adh gene expression. Immunocytochemical techniques at the light- and electron-microscopic levels have been used to determine the distribution of ADH in the ovarian follicles of D. melanogaster during oogenesis. In the early stages of oogenesis, small amounts of ADH are detectable in the cystocytes. At the beginning of vitellogenesis (S7), ADH appears to be located mainly in the nurse cells. From stage S9 onwards, the ADH protein is evenly distributed in the ooplasm until the later stages of oogenesis (S13-14), when multiple ADH-positive bodies of varying size appear in the ooplasm. This change in distribution is a result of the compartmentalization of the ADH protein within the glycogen yolk or beta-spheres. Yolk becomes enclosed within the lumen of the primitive gut during embryonic development, and thus our results suggest a mechanism for the transfer of maternally-inherited enzymes to the gut lumen via yolk spheres.