| Popis: |
Among some of the most interesting phenotypes are produced are those that allow a species invasion into a new niche. Approximately 280 million years ago, a new niche was filled by the larva of the newly emerged holometabolous (complete metamorphosis) insects, and among the many novel phenotypes they produced, their eyes are some of the most diverse throughout nature. Although a bountiful amount of work has focused on the adult eye development of D. melanogaster compound eyes, little molecular work has focused on the larval eyes of other holometabolous insects. These studies are aimed at identifying potential genetic mechanisms that may contribute to the evolution of holometabolous larval eyes (stemmata). To address this, we aimed at generating an evolutionary frame work for comparative purposes between the T. marmoratus larval eyes and D. melanogaster compound eyes. To investigate this evolutionary question, we used an integrative approach to study the proteomic architecture, and identify the role of prospective candidate genes that may contribute to the formation of these novel eyes. The camera-type larval eyes of T. marmoratus present an intriguing novel eye phenotype with the ability to simultaneously focus two images. It is through this bifocal lens that T. marmoratus larvae have become very successful visually guided predators. The first key to discover how T. marmoratus could generate such a phenotype is to identify their potential evolutionary origins from their compound eyed ancestors. This is one of the first analyses to investigate the molecular origins and function of cells within the stemma that are not photoreceptors. We utilized this approach to identify the lens secreting cells within the stemma of T. marmoratus and to identify the proteins responsible for the formation of the biofocal lens. Furthermore, a comparative analysis was carried out on the facets of D. melanogaster to identify similarities and differences between the two lens types. Although the proteins constituting the two lenses are not the same, they do appear to share similar evolutionary origins. Currently, what is unknown within the formation of stemma is the molecular origins of their non-neuronal cell types. A candidate gene analysis from D. melanogaster leads to many interesting questions surrounding the origins and potential molecular similarities of many stemma cell types. It was within this analysis two genes that could play a role in the differentiation of lens secreting cell types arose. Moreover, the findings from this study could illustrate how many different stemmata types have independently derived from their compound eyed ancestors. This dissertation suggests many of the characteristics that produce the larval bifocal eye of T. marmoratus are shared with their ancestral compound eyed counterparts. Moreover, these findings may help to understand which genes played a key role in guiding the evolution of derived eye phenotypes. Broadly, this research builds the framework to investigate many more interesting genetic mechanisms governing the eye evolution within holometabolous insects, and may one day lay the ground work for bioengineers to begin craft components that constitute the naturally occurring bifocal lens. |
