Date of Award
Doctor of Philosophy (PhD)
Rebecca B. Simmons
Turk E. Rhen
In this dissertation, I present four papers. Three explore different aspects of wing color pattern development in the painted lady butterfly, Vanessa cardui; while the fourth examines the evolution of an epigenetic silencer complex across invertebrate animals. In the first paper, I used transcriptomics to identify patterning genes from the Drosophila wing gene regulatory network (GRN) in larval and pupal wings of V. cardui and to examine how temporal expression dynamics of this gene network correspond to expression of ommochrome and melanin pigment genes. This study identified key developmental periods of gene upregulation and highlights the temporal separation between peak expression of patterning and melanin pigment genes. In the second paper, I present evidence that hind wing eyespots of V. cardui exhibit phenotypic plasticity. Using morphometrics, I quantified how temperature shock and heparin modify eyespot size and pigment ring composition. This information is used to examine whether eyespot plasticity was a function of trait integration or modularity. In the third paper, I used qPCR to explore the role that epigenetic mechanisms may play in phenotypic plasticity of V. cardui eyespots. I examined expression of an epigenetic silencer, the polycomb repressive complex (PRC) in developing wings and in modified eyespots at 6 days post-pupation. I present evidence that the PRC is expressed during butterfly wing development and exhibits a similar pattern of expression to the wing GRN. Polycomb genes were not differentially expressed in eyespots modified by temperature shock and heparin sulfate; however, expression of several patterning genes was altered by these treatments. In the final paper, I present a comprehensive phylogenetic analysis of the PRC2 across non-vertebrate animals. This analysis revealed that the evolutionary history of the PRC2 does not reconstruct the known phylogeny of animals, due to significant sequence divergence in the nematode lineage. Thus, PRC2 has undergone significant evolutionary changes in nematodes that may be a consequence of Hox gene depletion and re-organization in this lineage.
Connahs, Heidi, "Molecular Mechanisms Underlying Wing Color Pattern Development In Vanessa Cardui And Evolution Of The Polycomb Repressive Complex 2" (2015). Theses and Dissertations. 1758.