IMMUNOLOCALIZATION OF THE TEMPORALLY EARLY SECRETED MAJOR STRUCTURAL CHORION PROTEINS, DVS38 AND DVS36, IN THE EGGSHELL LAYERS AND REGIONS OF DROSOPHILA-VIRILIS

We have shown by means of conventional electron microscopy that the eg gshell of Drosophila virilis at the main body of the laid egg consists of the vitelline membrane and the multilayered chorion, which include s the wax layer, the innermost chorionic layer, the endochorion, and t he exochorion, while several specialized regions of the eggshell are s een across the anterior-posterior axis of the egg. Biochemical analysi s revealed the existence of six quantitatively enriched chorion protei ns. Among them, Dvs38 and Dvs36 are synthesized when the innermost cho rionic layer and the endochorion are assembled. Immunogold electron mi croscopy has shown that these two proteins are incorporated in the mor phologically complete vitelline membrane apparently through an interca lation process and represent structural components of the endochorion in all the specialized regions of the eggshell. Additionally, by cytoc hemical means, the enzyme eggshell peroxidase, which is synthesized in parallel with Dvs38 and Dvs36, has been identified as a structural co mponent of the innermost chorionic layer and the endochorion. These fi ndings suggest a complex protein-protein recognition pattern during th e formation of the eggshell since the cosecretion of its components (i .e., Dvs38, Dvs36 chorion proteins and eggshell peroxidase) does not r ecommend their colocalization in the eggshell sublayers and the timing of their synthesis is not related to their final position on the eggs hell (i.e., the identification of Dvs38 and Dvs36 chorion proteins as vitelline membrane components). (C) 1998 Academic Press.