Date of Award
Fall 2000
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Biological Sciences
First Advisor
Waring, Gail L.
Second Advisor
Courtright, James B.
Third Advisor
Fredricks, Walter W.
Abstract
Eggshell gene expression in Drosophila melanogaster (Dm ) exhibits a tightly regulated developmental program during the late stages of oogenesis. Intriguingly, many of these genes reside in clusters within the genome. Although individual eggshell genes within a cluster are expressed in a discrete qualitative and quantitative manner, their overall expression patterns are quite similar indicating the presence of both local and global regulatory control mechanisms. As an initial step in the investigation of the components of this regulatory program, a functional and comparative search for important regulatory sequences was initiated in the sV23 vitelline membrane (VM) eggshell gene. The Drosophila virilis (Dv ) sV23 gene was used in an evolutionary approach to identify functionally relevant regulatory regions. Functional data indicates that in both Dm and Dv sV23 genes, minimal 5 ' flanking sequences are sufficient to restore normal qualitative expression to an sV23 null mutant. Normal quantitative expression in the Dm gene requires distal 3' sequences that reside between two additional genes in the VM gene cluster. This region contains a highly conserved Ecdysone Response Element identified in several ecdysone responsive genes. Sequence comparisons between the 5' regions of the Dm and Dv sV23 genes revealed a high degree of sequence divergence surrounding several highly conserved core and proximal promoter elements. One of these elements bear striking similarity to the chorion hexamer element that binds the eltraspiracle gene product, and is essential for chorion gene regulation. The sequence and spatial arrangement of the conserved sequences in the sV23 gene regulatory regions are consistent with a role as potential binding sites for a hormonal control mechanism, and experiments are currently underway to determine their functional significance.