Meeting Abstract
The evolution of cephalopod neural and morphological novelties has been attributed at a genomic level to independent gene family expansions. In the Octopus bimaculoides genome, one such expansion occurred in the G-protein coupled receptors (GPCRs) repertoire, a family of transmembrane proteins involved in a variety of functions in eukaryotes. In animals, one of the predominant functions of GPCRs is mediating signal transduction in various sensory systems. Here we assessed the relationship between this GPCRs repertoire expansion and the cephalopods’ remarkable sensory abilities which make use of highly developed organs that resemble vertebrate sense organs in complexity. To study the evolutionary mechanisms that drove this expansion we first constructed a Bayesian phylogenetic tree using the O. bimaculoides GPCR repertoire. Diversification rates and positive selection (Ka/ Ks) analyses suggested that three clades within the tree suffered an accelerated diversification process, two of them associated with positive selection. Functional predictions of the proteins of one of the positively selected clades, represented by rhodopsin-like GPCRs, indicated a possible role as somatostatin receptors. Somatostatin is a neurotransmitter concentrated in the optic lobe of cephalopods and localized to an area analogous to the vertebrate retina. Despite the need for further investigation, our result suggests an important role of GPCRs during the convergent evolution of the cephalopod and vertebrate visual systems.
