Meeting Abstract
All modes of animal vision depend on opsin proteins of the G protein coupled receptor (GPCR) class. Opsins are present across animals and cnidarian opsins were first described more than a decade ago. After much progress, fundamental questions stemming from the paucity of opsin data representing the major lineages of Cnidaria persist. Recent phylogenomic analyses have clarified cnidarian relationships and provide a comprehensive set of genome-scale datasets that could ameliorate these issues. Here we describe a new bioinformatic approach called Phylogenetic Focusing that progressively circumscribes complete orthologous clades of interest within their larger gene families. We applied phylogenetic focusing to a selection of 60 cnidarian and 25 outgroup genome-scale datasets and find that the GPCR neighborhood within which opsins reside is populated by several, previously undescribed clades of non-bilaterian GPCRs including major radiations in sponges, ctenophores and cnidarians. This finding challenges the view that melatonin receptors are the close evolutionary sister to opsins and highlights a hidden diversity of GPCRs in the close vicinity of opsins. In addition, cnidarians are inferred to have inherited the full complement of opsin types but have lost several of them in a lineage specific manner, leaving anthozoans as the cnidarian clade that best represents the ancestral cnidarian opsin palate. Finally, the rate of opsin gene duplication and loss is significantly higher for many cnidarian taxa as compared to other animal lineages, indicating a tumultuous evolutionary history for cnidarian opsins.
