Meeting Abstract
Despite having complex mirror eyes and showing mantle shadow response, the molecular details of scallop light perception have been poorly studied. To unravel the molecular components responsible for light perception in scallop, our lab has assembled a transcriptome from the eyes of the scallop Placopecten magellanicus. Among other components of the phototransduction pathway, we have identified scallop opsins that are phylogenetically similar to rhabdomeric opsins and homologous to melanopsin in vertebrates. We present a detailed molecular and functional characterization of two melanopsin-like Gq-opsins (Pma-OPSGq2 and Pma-OPSGq3) from the scallop Placopecten magellanicus. While we could not express Pma-OPSGq3 in vitro, spectral analysis of Pma-OPSGq2 demonstrates that it is light sensitive and it is a bistable pigment that can convert its retinal chromophore from the 11-cis to the all trans conformation multiple times. Semi-quantitative RT-PCR data show that the two opsins are differentially expressed in eye and mantle with Pma-OPSGq2 being expressed at higher level compared to Pma-OPSGq3. Our data suggest that the two opsins are light absorbing Gq-opsins expressed in photosensitive tissues in P. magellanicus. We speculate that Pma-OPSGq2 and Pma-OPSGq3 contribute to the shadow response of the mantle and eye-mediated vision. Differential expression of the two opsins may indicate instances of neofunctionalization and/or neocompartimentalization of light perception in scallop. Future work will elucidate the temporal expression of the two opsins at different life stages and expand the spatial resolution by probing their expression in single eyes and subregions of the mantle.
