A GENETIC, MORPHOLOGICAL AND BIOCHEMICAL ANALYSIS OF AN EGGSHELL MUTATION IN DROSOPHILA MELANOGASTER (CHORION, VITELLINE MEMBRANE)
The purpose of this study was to use genetics as an approach to identify loci involved in the follicle cell eggshell program of Drosophila melanogaster. To do this, seven non-complementing female sterile mutants which showed an altered eggshell morphology were analyzed using genetic, morphological, and biochemical criteria. The female sterility and eggshell mutations were mapped genetically to 20.6 cM, and cytogenetically to 7C1-3 on the X-chromosome. This was a region distinct from previously characterized eggshell loci. Electron microscope analysis of the mature mutant eggshell showed a lack of assembly in the outer, electron dense eggshell layer (the chorion), and an accumulation of electron dense particles within the inner, electron opaque eggshell layer (vitelline membrane). This electron dense material was found to consist of chorion proteins. Analysis of radiolabeled eggshell proteins of wild type and mutant flies showed the mutant flies failed to accumulate two eggshell proteins in the mature eggshell, with molecular weights of 67 Kd and 85 Kd. In wild type flies s85 was found to be produced during stage 10 and processed s67 during stages 13 and 14 of oogenesis. Analysis of protein accumulation during stage 10 of wild type and mutant eggchambers showed that in addition to s85, there was at least on other protein of 130 Kd consistently missing in six of the seven mutants. Short term labeling experiments, in conjunction with in vitro translation of poly A('+) mRNA isolated from wild type stage 10 eggchambers suggested that s85 was not a primary translation product. Use of a geographic strain of wild type flies which showed electrophoretic variations of s130 and s85 suggested that s130 is a primary translation product emanating from the 7C locus and a likely precursor to s85. Although major biochemical differences appear in stage 10, mutant and wild type eggshells are morphologically indistinguishable until stages 13-14. These results suggest that follicle cell proteins synthesized during the time of vitelline membrane deposition (stage 10) are important for proper assembly of the chorion layers during stages 13 and 14.
Beverly Jean Bauer,
"A GENETIC, MORPHOLOGICAL AND BIOCHEMICAL ANALYSIS OF AN EGGSHELL MUTATION IN DROSOPHILA MELANOGASTER (CHORION, VITELLINE MEMBRANE)"
(January 1, 1986).
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