Meeting Abstract
Learning how complex traits like eyes and other sensory systems originate is fundamental for understanding evolution. One way to study trait origins is to trace the evolutionary history of their component parts. In this way, we can learn when the parts of complex traits came together during evolution and perhaps understand why and how they stayed together. To inform how eyes originated, our lab is reconstructing the evolutionary history of phototransduction, the cascade of protein interactions leading to sensing photons. We find that opsin – the keystone protein of phototransduction – has a dynamic and ancient evolutionary history. Already in the first Bilaterian animals, there were at least nine different opsins, even though no modern group retains all of these. Despite similar genes and light sensitivity in some fungi, we do not find this opsin family outside of animals, indicating opsins arose from other GPCR genes within animals. We studied phototransduction in Cnidaria and discovered it to be used in sensory cells adjacent to cnidocytes (‘stinging cells’). To previously known functions of chemo- and mechanosensation, we added photo-sensation to the repertoire of factors that influence cnidocyte firing. We find modulation of cnidocyte firing by light in a diversity of cnidaria, indicating the function could be ancestral and predate many separate eye origins in Cnidaria. While searching for animal-type opsins in fungi, we discovered certain zoospores to have multi-modal sensory systems, although using different molecular mechanisms compared to Cnidaria. In general, we learn that the history of the senses is ancient and intertwined, often using similar or homologous mechanisms, and often co-opting existing genes for new uses.
