Origins, Evolution, and Integration of GPCR Photosensitivity
- Author(s): Swafford, Andrew
- Advisor(s): Oakley, Todd H
- et al.
Complex sensory systems such as vision shape the way organisms perceive, interact, and adapt to the environment. Of these systems, sight is a unique sense that has arisen multiple times from a deceptively small cadre of genes given the complex coordination of molecular machinery it requires. In animals, almost every instance of vision relies on a single gene family, opsin, which is widely regarded as the evolutionary lynchpin that triggered the evolution of complex eyes. However, our understanding of when opsins first originated and how the gene family has diversified throughout time remains largely unexplored. I develop new methods to reveal opsins as an ancient gene family that first appeared in early, unicellular animals. My broad synthesis of existing literature reveals that the genes crucial to vision and eye development share the common theme of mitigating UV specific stressors both in and out of eyes. Opsins’ function as a sensory protein in UV-mitigation pathways highlights the multitude of effects that light cues have on organismal biology. In opposition to current hypothesis that opsins represent the only photosensitive clade of G-protein coupled receptors (GPCRs), I find evidence of photosensitive non-opsin GPCRs. Additionally, I discover a staggering amount of convergent evolution in GPCRs on specific amino acids at positions known to enable light sensitivity. Lastly, I develop the Allomyces fungi as a system which can be used to further study sensory system remodeling and integration after the gain and loss of sensory modalities. As a whole, my research suggests that the origins of complex traits may be rooted in the elaboration of stress mitigation followed by developmental capture, that integration of light sensitivity into organismal physiology and behavior is likely more common than currently expected, and I present a system in which we can test these hypotheses.