Thesis (Ph.D.) -- University of Texas at Arlington, 2009.

<p> <i>Myo-inositol</i> is a six-carbon sugar alcohol. It is essential as a precursor of the phospholipid membrane component phosphatidylinositol (PI) and the phosphoinositide signaling pathway in all eukaryotes. It aids in cellular metabolism, osmoregulation, and plays an important role in fertilization and diseases such as diabetes, bipolar disorder, and Alzheimer&rsquo;s disease. <i> Myo</i>-inositol metabolism is comprised of synthesis, transport, catabolism, and recycling. <i>Myo</i>-inositol synthesis is catalyzed by myo-inositol-3-phosphate synthase (MIPS). Surprisingly, synthesis of <i>myo</i>-inositol and its role in fertilization has not yet been studied in the model organism <span style="text-decoration:overline"> Drosophila melanogaster</span> (fruit fly). We hypothesize that MIPS expression is essential for growth and development of <i>D. melanogaster.</i> In this study, a precise deletion of the entire MIPS gene was generated and confirmed through PCR amplification and sequencing of the resultant DNA fragments. The lack of the MIPS transcript in homozygous MIPS deletion flies was confirmed by RT-PCR. During that experiment, two additional isoforms of MIPS were identified in wild-type flies (CS). Supplementation of chemically defined food with 0.5mM inositol was required to sustain all homozygous MIPS deletion fly strains. Fully-grown homozygous deletion flies could live without additional inositol in the food, but newly emerged larvae only survived to the first instar larval stage. However, even while on rich media supplemented with 170mM inositol, a homozygous MIPS deletion stock was unable to produce viable offspring. Homozygous MIPS deletion strains were identified as male-sterile, incapable of producing offspring when mated to any strain of females (including wild-type). Homozygous female MIPS deletion flies were fertile and maintained a high fecundity rate when mated to any strain (with an exception of homozygous male MIPS deletion flies). The male-sterility was complemented with the addition of a wild-type MIPS gene to chromosome 3. Testes dissections of homozygous male MIPS deletion flies revealed improper progression of spermatogenesis, specifically during sperm individualization. These studies contribute to the understanding of the role of inositol synthesis in growth, development, and fertilization.</p>

Convergent evolution is a central theme in biology. Birds are an ideal system to examine the mechanisms underlying convergent evolution. Although bird patterning is diverse, within-feather patterns have repeatedly converged on the same four types: mottled patterns, scales, bars and spots. Other avian patterns occur, e.g. stripes, but are rare. In my thesis I examine the four main mechanisms underlying convergent evolution in plumage patterns: evolutionary genetics, evolutionary development, natural selection for signaling and camouflage. Japanese quail (Coturnix japonica) is a model system in developmental biology. Examining the developmental basis of pattern formation using molecular techniques, the dorsal patterning of embryonic quail is likely due to activation of the melanocortin-1 receptor, which is a highly conserved pathway in vertebrates. I examined whether a reaction-diffusion based theoretical model of pattern formation may predict developmental constraint in two groups that have different lifestyles and spectacular patterns: waterfowl (Anseriformes) and gamebirds (Galliformes). Tracing the evolutionary trajectory of pattern evolution with Bayesian comparative modeling there was evidence for developmental constraint in pattern evolution. Adaptive explanations may also result in convergence. Cuckoo-hawk mimicry has been demonstrated in the common cuckoo (Cuculus canorus) and the Eurasian sparrowhawk (Accipiter nisus), but may be prevalent in Old World cuckoos. Randomly selecting a parasitic cuckoo from each genera of Old World cuckoos and <8 sympatric raptors, I quantified their barred patterns using digital image analysis and found that parasitism can explain convergent evolution in the patterns of parasitic cuckoos and raptors. Patterns may have evolved due to ecological selection. Examining the patterns of 80% of all avian species worldwide, I found that habitat does not predict patterning, and that all four patterns are found in all habitats. These results demonstrate that the mechanisms of convergent evolution are diverse, and that development and natural selection have contributed to pattern evolution.