Meeting Abstract
Recent transcriptome analysis of scallops eyes and mantle from our lab has shown that scallops have a suite of four melanopsin-like Gq-coupled opsins. These opsins are expressed both in the eye and in the photosensitive mantle of scallops and virtually nothing is known about their spectral properties. Of the four Gq opsins, we have shown that OPSGq2 has the highest level of expression in mantle and eye. We have isolated five OPSGq2 from five different species (Argopecten irradians, Air-OPSGq2, Placopecten magellanicus; Pma-OPSGq2, Mizuhopecten yessoensis; Mye-OPSGq2, Chlamys farreri; Cfa-OPSGq2 and Pecten maximus; Pmax-OPSGq2). The five OPSGq2s differ in the amino acid sequence and present some differences in the chromophore pocket, the region of the opsin that surrounds the chromophore and determines which wavelength of light is maximally absorbed. Of the four opsins that we could express in our system, all were showed to be bleached by light and possess a bistable ability to convert the chromophore from the 11-cis to the all-trans conformation and vice versa. By mutagenesis experiments of Air-OPSGq2 and Pmax-OPSGq2, we identified residue changes in the chromophore pocket affecting the wavelength of maximum absorbance. Our results provide the first in vitro characterization of Gq-opsins in bivalves and provide evidence for the feasibility of mutagenesis experiment of Gq-opsins in scallop. Given the dramatic natural variation of scallop life style between species and the complex suite of opsins that they express, our in vitro research advances our understanding of the evolution of light perception and vision. Finally, the feasibility of mutagenesis of scallop opsins may provide possible material for the design of new optogenetic tools.
