Speaker
Description
Using protein structure modeling-based methods, we recently identified very distant insect Or/Gr homologs, to define a protein superfamily we named 7-Transmembrane domain Ion Channels (7TMICs). 7TMICs are present across the tree of life and likely originated in the Last Universal Common Ancestor (~4 billion years ago). 7TMICs can be classified into two families: Class-A, which includes the insect Ors/Grs and a large family of plant receptors, among many others, and Class-B, functionally mysterious proteins present in invertebrates and vertebrates, including humans, whose common ancestor with Ors/Grs existed ~2 billion years ago. Comparative genomic, phylogenetic and in silico structural analyses of animal Class-B 7TMICs reveal high sequence, structure and copy number conservation, suggesting that they are under substantial evolutionary constraint. Single cell/bulk RNA sequencing data and in vivo expression analyses suggest that Class-B 7TMICs are—in contrast to Ors/Grs—expressed in a wide variety of tissues. Loss of the D. melanogaster homolog does not lead to overt developmental or anatomical phenotypes, but has physiological consequences, including reduced desiccation tolerance, decreased ability to recover from thermal shocks, and lower reproductive output. These ongoing studies raise the possibility that extant 7TMICs are descended from a broadly-expressed, critical ancestral protein, and that the neurosensory role of Ors/Grs is a comparatively recent evolutionary specialization.
