Meeting Abstract

S10-2.3  Monday, Jan. 7  Uncovering gene family expansion and molecular convergence of the photoreceptive protein opsin in scallop (Bivalvia: Pectinidae) SERB, J.M.*; KRAUSE, A.J.; Iowa State University; Iowa State University serb@iastate.edu

Gene duplication is one of the key factors driving genetic diversification and innovation, and may play an important role in phenotypic novelty. We investigated how small-scale, gene-specific duplications in invertebrate visual systems affect function and how diametrically opposed processes of divergence and constraint act on the underlying molecular system by studying the diversity of visual pigments in the mirror-type eyes of the scallop. These bivalves inhabit an array of photic environments and exhibit a diverse set of species-specific behaviors ranging from sessile attachers to mobile long-distance swimmers. Using a comparative transcriptomic and gene-targeting approaches, we identified an expansion of the photoreceptive protein opsin, a member of the G-protein coupled receptor family. Focusing on the Gq-coupled (rhabdomeric or “r-“) opsins, we generated a gene phylogeny from 530 sequences of 33 species across the Pectinidae. Scallop opsins segregated into two major clades, A and B, that differ by 45% in amino acid sequence, yet retain the functional motifs required for chromophore binding. Within each major clade, there was evidence for additional gene duplication events, but the number of duplication events, degree of divergence, and gene loss varied. We then tested the hypothesis that gene duplication events are associated with the spectrum of visible light available in the species’ habitat or with particular behaviors. We found multiple gene loss associated with sedentary lineages, while more mobile species had a suite of opsin copies. Interestingly, we identified molecular convergence in opsin within long-distance swimming lineages, which presumably rely more heavily on visual information. Our results suggest that both the retention and diversification of opsin copies in scallops are correlated with visual-mediated behaviors.