Comparative analysis of organ size, shape, and patterning in diverse species

Abstract

For a long time, the scientific community was concerned with the question how different tissues grow and differentiate. Much work in this respect has been done on complex 3-Dimentional vertebrate model limb systems such as chick and mouse limb buds. Establishing of an alternative model, a Drosophila wing imaginal disc, reduced the complexity of the growth regulation to 2D analysis due to the wing primordia being represented by flat epithelia. Several models have been proposed to describe and explain growth in Drosophila wing discs. I tested whether other non-standard flies can be used to validate these models. For that, I estimated similarity and robustness of the wing development in the Mediterranean fruit fly, Ceratitis capitata, and the common house fly, Musca domestica. I compared the three dipteran species at the organismal and genetic level. I studied size changes and sexual dimorphism of pupae and adult traits and their response to different environmental factors. I showed that size of adult traits may differ among species and the use of a single trait may result in a wrong estimation of the absolute body size, which significantly influences many aspects of insects’ life such as fecundity, life span, and mating success. In addition to the size estimation, I drew my attention to the variation in wing shape between D. melanogaster, C. capitata, and M. domestica. I applied geometric morphometrics and studied inter- and intraspecific shape differences. I revealed shape changes that occurred in consequence of different rearing conditions applied during larval growth, temperature and density, and demonstrated that these changes were sex specific. I discussed the obtained results in the light of different mating behaviors in these flies and proposed a possible explanation of the found wing shape variation. Finally, I analyzed gene expression patterns in wing imaginal discs and found that expression in the wing pouch region was similar among the three species, while expression of the analyzed genes varied in other tissue of the wing imaginal disc. This observation suggests that there are certain differences in development and patterning of structures that grow from these tissues, hinge and thorax. Since I found that development of wings was rather conserved between Drosophila, Ceratitis, and Musca, I developed an approach that can be applied in order to generate transgenic flies. These flies can be used to estimate kinetic parameters of the Dpp morphogen gradient, which is the key player involved in regulation of growth and patterning in developing Drosophila wings.