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Sequence, Structure, and Expression of Opsins in the Monochromatic Stomatopod Squilla empusa.
Integr Comp Biol. 2018 09 01; 58(3):386-397.IC

Abstract

Most stomatopod crustaceans have complex retinas in their compound eyes, with up to 16 spectral types of photoreceptors, but members of the superfamily Squilloidea have much simpler retinas, thought to contain a single photoreceptor spectral class. In the Atlantic stomatopod Squilla empusa, microspectrophotometry shows that all photoreceptors absorb light maximally at 517 nm, indicating that a single visual pigment is present in all photoreceptors in the retina. However, six distinct, but partial, long wavelength sensitive (LWS) opsin transcripts, which encode the protein component of the visual pigment, have been previously isolated through RT-PCR. In order to investigate the spectral and functional differences among S. empusa's opsins, we used RT-PCR to complete the 3' end of sequences for five of the six expressed opsins. The extended sequences spanned from the first transmembrane (TM1) helix to the 3' end of the coding region. Using homology-based modeling, we predicted the three-dimensional structure of the amino acid translation of the S. empusa opsins. Based on these analyses, S. empusa LWS opsins share a high sequence identity in TM regions and in amino acids within 15 Å of the chromophore-binding lysine on TM helix 7 (TM7), suggesting that these opsins produce spectrally similar visual pigments in agreement with previous results. However, we propose that these spectrally similar opsins differ functionally, as there are non-conservative amino acid substitutions found in intracellular loop 2 (ICL2) and TM5/ICL3, which are critical regions for G-protein binding, and substitutions in extracellular regions suggest different chromophore attachment affinities. In situ hybridization of two of the opsins (Se5 and Se6) revealed strong co-expression in all photoreceptors in both midband and peripheral regions of the retina as well as in selected ocular and cerebral ganglion neuropils. These data suggest the expression of multiple opsins-likely spectrally identical, but functionally different-in multiple types of neuronal cells in S. empusa. This suggests that the multiple opsins characteristic of other stomatopod species may have similar functional specialization.

Authors+Show Affiliations

Department of Biological Sciences, University of Maryland-Baltimore County, Baltimore, MD 21250, USA.Department of Biological Sciences, University of Maryland-Baltimore County, Baltimore, MD 21250, USA.School of Biological Sciences, University of Bristol, Bristol, UK.Department of Biological Sciences, University of Maryland-Baltimore County, Baltimore, MD 21250, USA.Department of Biological Sciences, University of Maryland-Baltimore County, Baltimore, MD 21250, USA.Department of Biology, University of Hawaii at Manoa, Honolulu, HI 96822, USA.

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

29697793

Citation

Valdez-Lopez, Juan C., et al. "Sequence, Structure, and Expression of Opsins in the Monochromatic Stomatopod Squilla Empusa." Integrative and Comparative Biology, vol. 58, no. 3, 2018, pp. 386-397.
Valdez-Lopez JC, Donohue MW, Bok MJ, et al. Sequence, Structure, and Expression of Opsins in the Monochromatic Stomatopod Squilla empusa. Integr Comp Biol. 2018;58(3):386-397.
Valdez-Lopez, J. C., Donohue, M. W., Bok, M. J., Wolf, J., Cronin, T. W., & Porter, M. L. (2018). Sequence, Structure, and Expression of Opsins in the Monochromatic Stomatopod Squilla empusa. Integrative and Comparative Biology, 58(3), 386-397. https://doi.org/10.1093/icb/icy007
Valdez-Lopez JC, et al. Sequence, Structure, and Expression of Opsins in the Monochromatic Stomatopod Squilla Empusa. Integr Comp Biol. 2018 09 1;58(3):386-397. PubMed PMID: 29697793.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Sequence, Structure, and Expression of Opsins in the Monochromatic Stomatopod Squilla empusa. AU - Valdez-Lopez,Juan C, AU - Donohue,Mary W, AU - Bok,Michael J, AU - Wolf,Julia, AU - Cronin,Thomas W, AU - Porter,Megan L, PY - 2018/4/27/pubmed PY - 2019/3/12/medline PY - 2018/4/27/entrez SP - 386 EP - 397 JF - Integrative and comparative biology JO - Integr Comp Biol VL - 58 IS - 3 N2 - Most stomatopod crustaceans have complex retinas in their compound eyes, with up to 16 spectral types of photoreceptors, but members of the superfamily Squilloidea have much simpler retinas, thought to contain a single photoreceptor spectral class. In the Atlantic stomatopod Squilla empusa, microspectrophotometry shows that all photoreceptors absorb light maximally at 517 nm, indicating that a single visual pigment is present in all photoreceptors in the retina. However, six distinct, but partial, long wavelength sensitive (LWS) opsin transcripts, which encode the protein component of the visual pigment, have been previously isolated through RT-PCR. In order to investigate the spectral and functional differences among S. empusa's opsins, we used RT-PCR to complete the 3' end of sequences for five of the six expressed opsins. The extended sequences spanned from the first transmembrane (TM1) helix to the 3' end of the coding region. Using homology-based modeling, we predicted the three-dimensional structure of the amino acid translation of the S. empusa opsins. Based on these analyses, S. empusa LWS opsins share a high sequence identity in TM regions and in amino acids within 15 Å of the chromophore-binding lysine on TM helix 7 (TM7), suggesting that these opsins produce spectrally similar visual pigments in agreement with previous results. However, we propose that these spectrally similar opsins differ functionally, as there are non-conservative amino acid substitutions found in intracellular loop 2 (ICL2) and TM5/ICL3, which are critical regions for G-protein binding, and substitutions in extracellular regions suggest different chromophore attachment affinities. In situ hybridization of two of the opsins (Se5 and Se6) revealed strong co-expression in all photoreceptors in both midband and peripheral regions of the retina as well as in selected ocular and cerebral ganglion neuropils. These data suggest the expression of multiple opsins-likely spectrally identical, but functionally different-in multiple types of neuronal cells in S. empusa. This suggests that the multiple opsins characteristic of other stomatopod species may have similar functional specialization. SN - 1557-7023 UR - https://www.unboundmedicine.com/medline/citation/29697793/Sequence_Structure_and_Expression_of_Opsins_in_the_Monochromatic_Stomatopod_Squilla_empusa_ L2 - https://academic.oup.com/icb/article-lookup/doi/10.1093/icb/icy007 DB - PRIME DP - Unbound Medicine ER -