1
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Lin JJ, Wang FY, Chung WY, Wang TY. The genomic evolution of visual opsin genes in amphibians. Vision Res 2024; 222:108447. [PMID: 38906036 DOI: 10.1016/j.visres.2024.108447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 05/15/2024] [Accepted: 05/16/2024] [Indexed: 06/23/2024]
Abstract
Among tetrapod (terrestrial) vertebrates, amphibians remain more closely tied to an amphibious lifestyle than amniotes, and their visual opsin genes may be adapted to this lifestyle. Previous studies have discussed physiological, morphological, and molecular changes in the evolution of amphibian vision. We predicted the locations of the visual opsin genes, their neighboring genes, and the tuning sites of the visual opsins, in 39 amphibian genomes. We found that all of the examined genomes lacked the Rh2 gene. The caecilian genomes have further lost the SWS1 and SWS2 genes; only the Rh1 and LWS genes were retained. The loss of the SWS1 and SWS2 genes in caecilians may be correlated with their cryptic lifestyles. The opsin gene syntenies were predicted to be highly similar to those of other bony vertebrates. Moreover, dual syntenies were identified in allotetraploid Xenopus laevis and X. borealis. Tuning site analysis showed that only some Caudata species might have UV vision. In addition, the S164A that occurred several times in LWS evolution might either functionally compensate for the Rh2 gene loss or fine-tuning visual adaptation. Our study provides the first genomic evidence for a caecilian LWS gene and a genomic viewpoint of visual opsin genes by reviewing the gains and losses of visual opsin genes, the rearrangement of syntenies, and the alteration of spectral tuning in the course of amphibians' evolution.
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Affiliation(s)
- Jinn-Jy Lin
- National Center for High-performance Computing, National Applied Research Laboratories, Hsinchu, Taiwan
| | - Feng-Yu Wang
- Taiwan Ocean Research Institute, National Applied Research Laboratories, Kaohsiung, Taiwan
| | - Wen-Yu Chung
- Department of Computer Science and Information Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan
| | - Tzi-Yuan Wang
- Biodiversity Research Center, Academia Sinica, Taipei, Taiwan.
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2
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Schott RK, Fujita MK, Streicher JW, Gower DJ, Thomas KN, Loew ER, Bamba Kaya AG, Bittencourt-Silva GB, Guillherme Becker C, Cisneros-Heredia D, Clulow S, Davila M, Firneno TJ, Haddad CFB, Janssenswillen S, Labisko J, Maddock ST, Mahony M, Martins RA, Michaels CJ, Mitchell NJ, Portik DM, Prates I, Roelants K, Roelke C, Tobi E, Woolfolk M, Bell RC. Diversity and Evolution of Frog Visual Opsins: Spectral Tuning and Adaptation to Distinct Light Environments. Mol Biol Evol 2024; 41:msae049. [PMID: 38573520 PMCID: PMC10994157 DOI: 10.1093/molbev/msae049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 02/07/2024] [Accepted: 02/26/2024] [Indexed: 04/05/2024] Open
Abstract
Visual systems adapt to different light environments through several avenues including optical changes to the eye and neurological changes in how light signals are processed and interpreted. Spectral sensitivity can evolve via changes to visual pigments housed in the retinal photoreceptors through gene duplication and loss, differential and coexpression, and sequence evolution. Frogs provide an excellent, yet understudied, system for visual evolution research due to their diversity of ecologies (including biphasic aquatic-terrestrial life cycles) that we hypothesize imposed different selective pressures leading to adaptive evolution of the visual system, notably the opsins that encode the protein component of the visual pigments responsible for the first step in visual perception. Here, we analyze the diversity and evolution of visual opsin genes from 93 new eye transcriptomes plus published data for a combined dataset spanning 122 frog species and 34 families. We find that most species express the four visual opsins previously identified in frogs but show evidence for gene loss in two lineages. Further, we present evidence of positive selection in three opsins and shifts in selective pressures associated with differences in habitat and life history, but not activity pattern. We identify substantial novel variation in the visual opsins and, using microspectrophotometry, find highly variable spectral sensitivities, expanding known ranges for all frog visual pigments. Mutations at spectral-tuning sites only partially account for this variation, suggesting that frogs have used tuning pathways that are unique among vertebrates. These results support the hypothesis of adaptive evolution in photoreceptor physiology across the frog tree of life in response to varying environmental and ecological factors and further our growing understanding of vertebrate visual evolution.
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Affiliation(s)
- Ryan K Schott
- Department of Biology and Centre for Vision Research, York University, Toronto, Ontario, Canada
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - Matthew K Fujita
- Department of Biology, Amphibian and Reptile Diversity Research Center, The University of Texas at Arlington, Arlington, TX, USA
| | | | | | - Kate N Thomas
- Department of Biology, Amphibian and Reptile Diversity Research Center, The University of Texas at Arlington, Arlington, TX, USA
- Natural History Museum, London, UK
| | - Ellis R Loew
- Department of Biomedical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA
| | | | | | - C Guillherme Becker
- Department of Biology and One Health Microbiome Center, Center for Infectious Disease Dynamics, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, USA
| | - Diego Cisneros-Heredia
- Laboratorio de Zoología Terrestre, Instituto de Biodiversidad Tropical IBIOTROP, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito USFQ, Quito, Ecuador
| | - Simon Clulow
- Centre for Conservation Ecology and Genomics, Institute for Applied Ecology, University of Canberra, Bruce, ACT, Australia
| | - Mateo Davila
- Laboratorio de Zoología Terrestre, Instituto de Biodiversidad Tropical IBIOTROP, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito USFQ, Quito, Ecuador
| | - Thomas J Firneno
- Department of Biological Sciences, University of Denver, Denver, USA
| | - Célio F B Haddad
- Department of Biodiversity and Center of Aquaculture—CAUNESP, I.B., São Paulo State University, Rio Claro, São Paulo, Brazil
| | - Sunita Janssenswillen
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel, Brussels, Belgium
| | - Jim Labisko
- Natural History Museum, London, UK
- Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, London, UK
- Island Biodiversity and Conservation Centre, University of Seychelles, Mahé, Seychelles
| | - Simon T Maddock
- Natural History Museum, London, UK
- Island Biodiversity and Conservation Centre, University of Seychelles, Mahé, Seychelles
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Michael Mahony
- Department of Biological Sciences, The University of Newcastle, Newcastle 2308, Australia
| | - Renato A Martins
- Programa de Pós-graduação em Conservação da Fauna, Universidade Federal de São Carlos, São Carlos, Brazil
| | | | - Nicola J Mitchell
- School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia
| | - Daniel M Portik
- Department of Herpetology, California Academy of Sciences, San Francisco, CA, USA
| | - Ivan Prates
- Department of Biology, Lund University, Lund, Sweden
| | - Kim Roelants
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel, Brussels, Belgium
| | - Corey Roelke
- Department of Biology, Amphibian and Reptile Diversity Research Center, The University of Texas at Arlington, Arlington, TX, USA
| | - Elie Tobi
- Gabon Biodiversity Program, Center for Conservation and Sustainability, Smithsonian National Zoo and Conservation Biology Institute, Gamba, Gabon
| | - Maya Woolfolk
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
- Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA
| | - Rayna C Bell
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
- Department of Herpetology, California Academy of Sciences, San Francisco, CA, USA
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3
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Schott RK, Bell RC, Loew ER, Thomas KN, Gower DJ, Streicher JW, Fujita MK. Transcriptomic evidence for visual adaptation during the aquatic to terrestrial metamorphosis in leopard frogs. BMC Biol 2022; 20:138. [PMID: 35761245 PMCID: PMC9238225 DOI: 10.1186/s12915-022-01341-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 05/30/2022] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Differences in morphology, ecology, and behavior through ontogeny can result in opposing selective pressures at different life stages. Most animals, however, transition through two or more distinct phenotypic phases, which is hypothesized to allow each life stage to adapt more freely to its ecological niche. How this applies to sensory systems, and in particular how sensory systems adapt across life stages at the molecular level, is not well understood. Here, we used whole-eye transcriptomes to investigate differences in gene expression between tadpole and juvenile southern leopard frogs (Lithobates sphenocephalus), which rely on vision in aquatic and terrestrial light environments, respectively. Because visual physiology changes with light levels, we also tested the effect of light and dark exposure. RESULTS We found 42% of genes were differentially expressed in the eyes of tadpoles versus juveniles and 5% for light/dark exposure. Analyses targeting a curated subset of visual genes revealed significant differential expression of genes that control aspects of visual function and development, including spectral sensitivity and lens composition. Finally, microspectrophotometry of photoreceptors confirmed shifts in spectral sensitivity predicted by the expression results, consistent with adaptation to distinct light environments. CONCLUSIONS Overall, we identified extensive expression-level differences in the eyes of tadpoles and juveniles related to observed morphological and physiological changes through metamorphosis and corresponding adaptive shifts to improve vision in the distinct aquatic and terrestrial light environments these frogs inhabit during their life cycle. More broadly, these results suggest that decoupling of gene expression can mediate the opposing selection pressures experienced by organisms with complex life cycles that inhabit different environmental conditions throughout ontogeny.
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Affiliation(s)
- Ryan K Schott
- Department of Biology, York University, Toronto, Ontario, Canada. .,Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington DC, USA.
| | - Rayna C Bell
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington DC, USA.,Department of Herpetology, California Academy of Sciences, San Francisco, CA, USA
| | - Ellis R Loew
- Department of Biomedical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA
| | - Kate N Thomas
- Department of Life Sciences, The Natural History Museum, London, UK
| | - David J Gower
- Department of Life Sciences, The Natural History Museum, London, UK
| | | | - Matthew K Fujita
- Department of Biology, Amphibian and Reptile Diversity Research Center, The University of Texas at Arlington, Arlington, TX, USA
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4
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Schott RK, Perez L, Kwiatkowski MA, Imhoff V, Gumm JM. Evolutionary analyses of visual opsin genes in frogs and toads: Diversity, duplication, and positive selection. Ecol Evol 2022; 12:e8595. [PMID: 35154658 PMCID: PMC8820127 DOI: 10.1002/ece3.8595] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 01/07/2022] [Accepted: 01/08/2022] [Indexed: 01/12/2023] Open
Abstract
Among major vertebrate groups, anurans (frogs and toads) are understudied with regard to their visual systems, and little is known about variation among species that differ in ecology. We sampled North American anurans representing diverse evolutionary and life histories that likely possess visual systems adapted to meet different ecological needs. Using standard molecular techniques, visual opsin genes, which encode the protein component of visual pigments, were obtained from anuran retinas. Additionally, we extracted the visual opsins from publicly available genome and transcriptome assemblies, further increasing the phylogenetic and ecological diversity of our dataset to 33 species in total. We found that anurans consistently express four visual opsin genes (RH1, LWS, SWS1, and SWS2, but not RH2) even though reported photoreceptor complements vary widely among species. The proteins encoded by these genes showed considerable sequence variation among species, including at sites known to shift the spectral sensitivity of visual pigments in other vertebrates and had conserved substitutions that may be related to dim-light adaptation. Using molecular evolutionary analyses of selection (dN/dS) we found significant evidence for positive selection at a subset of sites in the dim-light rod opsin gene RH1 and the long wavelength sensitive cone opsin LWS. The function of sites inferred to be under positive selection are largely unknown, but a few are likely to affect spectral sensitivity and other visual pigment functions based on proximity to previously identified sites in other vertebrates. We also found the first evidence of visual opsin duplication in an amphibian with the duplication of the LWS gene in the African bullfrog, which had distinct LWS copies on the sex chromosomes suggesting the possibility of sex-specific visual adaptation. Taken together, our results indicate that ecological factors, such as habitat and life history, as well as behavior, may be driving changes to anuran visual systems.
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Affiliation(s)
- Ryan K. Schott
- Department of BiologyYork UniversityTorontoOntarioCanada
- Department of Vertebrate ZoologyNational Museum of Natural HistorySmithsonian InstitutionWashingtonDistrict of ColumbiaUSA
| | - Leah Perez
- Department of BiologyStephen F. Austin State UniversityNacogdochesTexasUSA
| | | | - Vance Imhoff
- Southern Nevada Fish and Wildlife OfficeUS Fish and Wildlife ServiceLas VegasNevadaUSA
| | - Jennifer M. Gumm
- Department of BiologyStephen F. Austin State UniversityNacogdochesTexasUSA
- Ash Meadows Fish Conservation FacilityUS Fish and Wildlife ServiceAmargosa ValleyNevadaUSA
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5
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Gower DJ, Fleming JF, Pisani D, Vonk FJ, Kerkkamp HMI, Peichl L, Meimann S, Casewell NR, Henkel CV, Richardson MK, Sanders KL, Simões BF. Eye-Transcriptome and Genome-Wide Sequencing for Scolecophidia: Implications for Inferring the Visual System of the Ancestral Snake. Genome Biol Evol 2021; 13:6430116. [PMID: 34791190 PMCID: PMC8643396 DOI: 10.1093/gbe/evab253] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2021] [Indexed: 12/28/2022] Open
Abstract
Molecular genetic data have recently been incorporated in attempts to reconstruct the ecology of the ancestral snake, though this has been limited by a paucity of data for one of the two main extant snake taxa, the highly fossorial Scolecophidia. Here we present and analyze vision genes from the first eye-transcriptomic and genome-wide data for Scolecophidia, for Anilios bicolor, and A. bituberculatus, respectively. We also present immunohistochemistry data for retinal anatomy and visual opsin-gene expression in Anilios. Analyzed in the context of 19 lepidosaurian genomes and 12 eye transcriptomes, the new genome-wide and transcriptomic data provide evidence for a much more reduced visual system in Anilios than in non-scolecophidian (=alethinophidian) snakes and in lizards. In Anilios, there is no evidence of the presence of 7 of the 12 genes associated with alethinophidian photopic (cone) phototransduction. This indicates extensive gene loss and many of these candidate gene losses occur also in highly fossorial mammals with reduced vision. Although recent phylogenetic studies have found evidence for scolecophidian paraphyly, the loss in Anilios of visual genes that are present in alethinophidians implies that the ancestral snake had a better-developed visual system than is known for any extant scolecophidian.
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Affiliation(s)
- David J Gower
- Life Sciences, The Natural History Museum, London, United Kingdom
| | - James F Fleming
- School of Life Sciences, University of Bristol, Bristol, United Kingdom.,Institute for Advanced Biosciences, Keio University, Yamagata, Japan
| | - Davide Pisani
- School of Life Sciences, University of Bristol, Bristol, United Kingdom.,School of Earth Sciences, University of Bristol, Bristol, United Kingdom
| | - Freek J Vonk
- Naturalis Biodiversity Center, Leiden, The Netherlands
| | | | - Leo Peichl
- Institute of Cellular and Molecular Anatomy, Dr. Senckenberg Anatomy, Goethe University Frankfurt, Frankfurt am Main, Germany.,Institute of Clinical Neuroanatomy, Dr. Senckenberg Anatomy, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Sonja Meimann
- Institute of Cellular and Molecular Anatomy, Dr. Senckenberg Anatomy, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Nicholas R Casewell
- Centre for Snakebite Research & Interventions, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Christiaan V Henkel
- Institute of Biology, University of Leiden, Leiden, The Netherlands.,Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | | | - Kate L Sanders
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Bruno F Simões
- School of Life Sciences, University of Bristol, Bristol, United Kingdom.,School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia.,School of Biological and Marine Sciences, University of Plymouth, Plymouth, United Kingdom
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6
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Falcón J, Torriglia A, Attia D, Viénot F, Gronfier C, Behar-Cohen F, Martinsons C, Hicks D. Exposure to Artificial Light at Night and the Consequences for Flora, Fauna, and Ecosystems. Front Neurosci 2020; 14:602796. [PMID: 33304237 PMCID: PMC7701298 DOI: 10.3389/fnins.2020.602796] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 10/22/2020] [Indexed: 12/22/2022] Open
Abstract
The present review draws together wide-ranging studies performed over the last decades that catalogue the effects of artificial-light-at-night (ALAN) upon living species and their environment. We provide an overview of the tremendous variety of light-detection strategies which have evolved in living organisms - unicellular, plants and animals, covering chloroplasts (plants), and the plethora of ocular and extra-ocular organs (animals). We describe the visual pigments which permit photo-detection, paying attention to their spectral characteristics, which extend from the ultraviolet into infrared. We discuss how organisms use light information in a way crucial for their development, growth and survival: phototropism, phototaxis, photoperiodism, and synchronization of circadian clocks. These aspects are treated in depth, as their perturbation underlies much of the disruptive effects of ALAN. The review goes into detail on circadian networks in living organisms, since these fundamental features are of critical importance in regulating the interface between environment and body. Especially, hormonal synthesis and secretion are often under circadian and circannual control, hence perturbation of the clock will lead to hormonal imbalance. The review addresses how the ubiquitous introduction of light-emitting diode technology may exacerbate, or in some cases reduce, the generalized ever-increasing light pollution. Numerous examples are given of how widespread exposure to ALAN is perturbing many aspects of plant and animal behaviour and survival: foraging, orientation, migration, seasonal reproduction, colonization and more. We examine the potential problems at the level of individual species and populations and extend the debate to the consequences for ecosystems. We stress, through a few examples, the synergistic harmful effects resulting from the impacts of ALAN combined with other anthropogenic pressures, which often impact the neuroendocrine loops in vertebrates. The article concludes by debating how these anthropogenic changes could be mitigated by more reasonable use of available technology - for example by restricting illumination to more essential areas and hours, directing lighting to avoid wasteful radiation and selecting spectral emissions, to reduce impact on circadian clocks. We end by discussing how society should take into account the potentially major consequences that ALAN has on the natural world and the repercussions for ongoing human health and welfare.
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Affiliation(s)
- Jack Falcón
- Laboratoire Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), MNHN, CNRS FRE 2030, SU, IRD 207, UCN, UA, Paris, France
| | - Alicia Torriglia
- Centre de Recherche des Cordeliers, INSERM U 1138, Ophtalmopole Hôpital Cochin, Assistance Publique - Hôpitaux de Paris, Université de Paris - SU, Paris, France
| | - Dina Attia
- ANSES, French Agency for Food, Environmental and Occupational Health & Safety, Maisons-Alfort, France
| | | | - Claude Gronfier
- Lyon Neuroscience Research Center (CRNL), Waking Team, Inserm UMRS 1028, CNRS UMR 5292, Université Claude Bernard Lyon 1, Lyon, France
| | - Francine Behar-Cohen
- Centre de Recherche des Cordeliers, INSERM U 1138, Ophtalmopole Hôpital Cochin, Assistance Publique - Hôpitaux de Paris, Université de Paris - SU, Paris, France
| | | | - David Hicks
- Inserm, CNRS, Institut des Neurosciences Cellulaires et Intégratives, Université de Strasbourg, Strasbourg, France
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7
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Oel AP, Neil GJ, Dong EM, Balay SD, Collett K, Allison WT. Nrl Is Dispensable for Specification of Rod Photoreceptors in Adult Zebrafish Despite Its Deeply Conserved Requirement Earlier in Ontogeny. iScience 2020; 23:101805. [PMID: 33299975 PMCID: PMC7702016 DOI: 10.1016/j.isci.2020.101805] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 10/06/2020] [Accepted: 11/10/2020] [Indexed: 12/11/2022] Open
Abstract
The transcription factor NRL (neural retina leucine zipper) has been canonized as the master regulator of photoreceptor cell fate in the retina. NRL is necessary and sufficient to specify rod cell fate and to preclude cone cell fate in mice. By engineering zebrafish, we tested if NRL function has conserved roles beyond mammals or beyond nocturnal species, i.e., in a vertebrate possessing a greater and more typical diversity of cone sub-types. Transgenic expression of Nrl from zebrafish or mouse was sufficient to induce rod photoreceptor cells. Zebrafish nrl−/− mutants lacked rods (and had excess UV-sensitive cones) as young larvae; thus, the conservation of Nrl function between mice and zebrafish appears sound. Strikingly, however, rods were abundant in adult nrl−/− null mutant zebrafish. Rods developed in adults despite Nrl protein being undetectable. Therefore, a yet-to-be-revealed non-canonical pathway independent of Nrl is able to specify the fate of some rod photoreceptors. Nrl is conserved and sufficient to specify rod photoreceptors in the zebrafish retina Nrl is necessary for rod photoreceptors in early ontogeny of zebrafish larvae Zebrafish Nrl is functionally conserved with mouse and human NRL Remarkably, Nrl is dispensable for rod specification in adult zebrafish
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Affiliation(s)
- A Phillip Oel
- Department of Biological Sciences, University of Alberta, Edmonton AB, T7Y 1C4, Canada
| | - Gavin J Neil
- Department of Biological Sciences, University of Alberta, Edmonton AB, T7Y 1C4, Canada
| | - Emily M Dong
- Department of Biological Sciences, University of Alberta, Edmonton AB, T7Y 1C4, Canada
| | - Spencer D Balay
- Department of Biological Sciences, University of Alberta, Edmonton AB, T7Y 1C4, Canada
| | - Keon Collett
- Department of Biological Sciences, University of Alberta, Edmonton AB, T7Y 1C4, Canada
| | - W Ted Allison
- Department of Biological Sciences, University of Alberta, Edmonton AB, T7Y 1C4, Canada.,Department of Medical Genetics, University of Alberta, Edmonton AB, T6G 2R3, Canada
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8
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Rozenblit F, Gollisch T. What the salamander eye has been telling the vision scientist's brain. Semin Cell Dev Biol 2020; 106:61-71. [PMID: 32359891 PMCID: PMC7493835 DOI: 10.1016/j.semcdb.2020.04.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/16/2020] [Accepted: 04/16/2020] [Indexed: 12/30/2022]
Abstract
Salamanders have been habitual residents of research laboratories for more than a century, and their history in science is tightly interwoven with vision research. Nevertheless, many vision scientists - even those working with salamanders - may be unaware of how much our knowledge about vision, and particularly the retina, has been shaped by studying salamanders. In this review, we take a tour through the salamander history in vision science, highlighting the main contributions of salamanders to our understanding of the vertebrate retina. We further point out specificities of the salamander visual system and discuss the perspectives of this animal system for future vision research.
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Affiliation(s)
- Fernando Rozenblit
- Department of Ophthalmology, University Medical Center Göttingen, 37073, Göttingen, Germany; Bernstein Center for Computational Neuroscience Göttingen, 37077, Göttingen, Germany
| | - Tim Gollisch
- Department of Ophthalmology, University Medical Center Göttingen, 37073, Göttingen, Germany; Bernstein Center for Computational Neuroscience Göttingen, 37077, Göttingen, Germany.
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9
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Döring CC, Kumar S, Tumu SC, Kourtesis I, Hausen H. The visual pigment xenopsin is widespread in protostome eyes and impacts the view on eye evolution. eLife 2020; 9:55193. [PMID: 32880369 PMCID: PMC7529461 DOI: 10.7554/elife.55193] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 09/01/2020] [Indexed: 12/31/2022] Open
Abstract
Photoreceptor cells in the eyes of Bilateria are often classified into microvillar cells with rhabdomeric opsin and ciliary cells with ciliary opsin, each type having specialized molecular components and physiology. First data on the recently discovered xenopsin point towards a more complex situation in protostomes. In this study, we provide clear evidence that xenopsin enters cilia in the eye of the larval bryozoan Tricellaria inopinata and triggers phototaxis. As reported from a mollusc, we find xenopsin coexpressed with rhabdomeric-opsin in eye photoreceptor cells bearing both microvilli and cilia in larva of the annelid Malacoceros fuliginosus. This is the first organism known to have both xenopsin and ciliary opsin, showing that these opsins are not necessarily mutually exclusive. Compiling existing data, we propose that xenopsin may play an important role in many protostome eyes and provides new insights into the function, evolution, and possible plasticity of animal eye photoreceptor cells.
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Affiliation(s)
| | - Suman Kumar
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Sharat Chandra Tumu
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Ioannis Kourtesis
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Harald Hausen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
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10
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Heyward JL, Reynolds BD, Foster ML, Archibald KE, Stoskopf MK, Mowat FM. Retinal cone photoreceptor distribution in the American black bear (Ursus americanus). Anat Rec (Hoboken) 2020; 304:662-672. [PMID: 32510783 DOI: 10.1002/ar.24472] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 04/16/2020] [Accepted: 04/23/2020] [Indexed: 11/06/2022]
Abstract
The distribution of cone photoreceptor subtypes (important for color vision and vision quality) varies widely in different carnivore species, but there have been limited studies on bear (ursid) cone distribution. A previous behavioral study suggests that American black bears (Ursus americanus) are dichromatic, indicating that they possess two cone subtypes, although the retinal distribution of cones is unknown. The purpose of this study was to examine the subtype and topography of cones in American black bear retinas to further predict the nature of their color vision and image resolution. We studied 10 eyes from seven individual legally hunted black bears in northeastern North Carolina. Cryosections and retinal wholemounts were labeled using antibodies targeting two cone opsin subtypes: long/medium (L/M) wavelength sensitive and short (S) wavelength sensitive. Cones in fluorescent microscopy images were counted and density maps were created for retinal wholemounts. The black bear retina contains both cone subtypes and L/M cones outnumber S cones by at least 3:1, a finding confirmed in retinal frozen sections. There are higher concentrations of S cones present than typically seen in other carnivores with some evidence for co-expression of L/M and S cones. A cone-dense area centralis is present dorsotemporal to the optic nerve, similar to other carnivores. These results confirm that American black bears are predicted to have a dichromatic vision with high acuity indicated by the presence of a dorsotemporally located area centralis.
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Affiliation(s)
- Jennifer L Heyward
- Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA
| | | | - Melanie L Foster
- Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA
| | - Kate E Archibald
- Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA.,Environmental Medicine Consortium, North Carolina State University, Raleigh, North Carolina, USA.,The Maryland Zoo in Baltimore, Baltimore, Maryland, USA
| | - Michael K Stoskopf
- Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA.,Environmental Medicine Consortium, North Carolina State University, Raleigh, North Carolina, USA
| | - Freya M Mowat
- Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA.,Environmental Medicine Consortium, North Carolina State University, Raleigh, North Carolina, USA.,Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Surgical Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA
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11
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Escobar-Camacho D, Carleton KL, Narain DW, Pierotti MER. Visual pigment evolution in Characiformes: The dynamic interplay of teleost whole-genome duplication, surviving opsins and spectral tuning. Mol Ecol 2020; 29:2234-2253. [PMID: 32421918 DOI: 10.1111/mec.15474] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 05/09/2020] [Accepted: 05/11/2020] [Indexed: 01/06/2023]
Abstract
Vision represents an excellent model for studying adaptation, given the genotype-to-phenotype map that has been characterized in a number of taxa. Fish possess a diverse range of visual sensitivities and adaptations to underwater light, making them an excellent group to study visual system evolution. In particular, some speciose but understudied lineages can provide a unique opportunity to better understand aspects of visual system evolution such as opsin gene duplication and neofunctionalization. In this study, we showcase the visual system evolution of neotropical Characiformes and the spectral tuning mechanisms they exhibit to modulate their visual sensitivities. Such mechanisms include gene duplications and losses, gene conversion, opsin amino acid sequence and expression variation, and A1 /A2 -chromophore shifts. The Characiforms we studied utilize three cone opsin classes (SWS2, RH2, LWS) and a rod opsin (RH1). However, the characiform's entire opsin gene repertoire is a product of dynamic evolution by opsin gene loss (SWS1, RH2) and duplication (LWS, RH1). The LWS- and RH1-duplicates originated from a teleost specific whole-genome duplication as well as characiform-specific duplication events. Both LWS-opsins exhibit gene conversion and, through substitutions in key tuning sites, one of the LWS-paralogues has acquired spectral sensitivity to green light. These sequence changes suggest reversion and parallel evolution of key tuning sites. Furthermore, characiforms' colour vision is based on the expression of both LWS-paralogues and SWS2. Finally, we found interspecific and intraspecific variation in A1 /A2 -chromophores proportions, correlating with the light environment. These multiple mechanisms may be a result of the diverse visual environments where Characiformes have evolved.
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Affiliation(s)
| | - Karen L Carleton
- Department of Biology, University of Maryland, College Park, MD, USA
| | - Devika W Narain
- Environmental Sciences, Anton de Kom University of Suriname, Paramaribo, Suriname
| | - Michele E R Pierotti
- Naos Marine Laboratories, Smithsonian Tropical Research Institute, Panama, Republic of Panama
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12
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Donner K, Yovanovich CAM. A frog's eye view: Foundational revelations and future promises. Semin Cell Dev Biol 2020; 106:72-85. [PMID: 32466970 DOI: 10.1016/j.semcdb.2020.05.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 05/13/2020] [Accepted: 05/13/2020] [Indexed: 12/16/2022]
Abstract
From the mid-19th century until the 1980's, frogs and toads provided important research models for many fundamental questions in visual neuroscience. In the present century, they have been largely neglected. Yet they are animals with highly developed vision, a complex retina built on the basic vertebrate plan, an accessible brain, and an experimentally useful behavioural repertoire. They also offer a rich diversity of species and life histories on a reasonably restricted physiological and evolutionary background. We suggest that important insights may be gained from revisiting classical questions in anurans with state-of-the-art methods. At the input to the system, this especially concerns the molecular evolution of visual pigments and photoreceptors, at the output, the relation between retinal signals, brain processing and behavioural decision-making.
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Affiliation(s)
- Kristian Donner
- Molecular and Integrative Biosciences Research Program, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland; PB 65 (Viikinkaari 1), 00014, University of Helsinki, Finland.
| | - Carola A M Yovanovich
- Department of Zoology, Institute of Biosciences, University of São Paulo, Brazil; Rua do Matão, Trav. 14, N°101, São Paulo, SP, 05508-090, Brazil.
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13
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Liebgold EB, Carleton KL. The Right Light: Tiger Salamander Capture Rates and Spectral Sensitivity. WILDLIFE SOC B 2020. [DOI: 10.1002/wsb.1058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Eric B. Liebgold
- Department of Biological SciencesSalisbury University Salisbury MD 21801 USA
| | - Karen L. Carleton
- Department of BiologyUniversity of Maryland College Park MD 20742 USA
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14
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Lamb JY, Davis MP. Salamanders and other amphibians are aglow with biofluorescence. Sci Rep 2020; 10:2821. [PMID: 32108141 PMCID: PMC7046780 DOI: 10.1038/s41598-020-59528-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 01/30/2020] [Indexed: 02/04/2023] Open
Abstract
Biofluorescence is the absorption of electromagnetic radiation (light) at one wavelength followed by its reemission at a lower energy and longer wavelength by a living organism. Previous studies have documented the widespread presence of biofluorescence in some animals, including cnidarians, arthropods, and cartilaginous and ray-finned fishes. Many studies on biofluorescence have focused on marine animals (cnidarians, cartilaginous and ray-finned fishes) but we know comparatively little about the presence of biofluorescence in tetrapods. We show for the first time that biofluorescence is widespread across Amphibia, with a focus on salamanders (Caudata), which are a diverse group with a primarily Holarctic distribution. We find that biofluorescence is not restricted to any particular family of salamanders, there is striking variation in their fluorescent patterning, and the primary wavelengths emitted in response to blue excitation light are within the spectrum of green light. Widespread biofluorescence across the amphibian radiation is a previously undocumented phenomenon that could have significant ramifications for the ecology and evolution of these diverse and declining vertebrates. Our results provide a roadmap for future studies on the characterization of molecular mechanisms of biofluorescence in amphibians, as well as directions for investigations into the potential impact of biofluorescence on the visual ecology and behavior of biofluorescent amphibians.
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Affiliation(s)
- Jennifer Y Lamb
- St. Cloud State University, Department of Biology, St. Cloud, Minnesota, 56301, USA.
| | - Matthew P Davis
- St. Cloud State University, Department of Biology, St. Cloud, Minnesota, 56301, USA.
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15
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Novales Flamarique I, Sayed Ahmed A, Cheng CL, Molday RS, Devlin RH. Growth hormone regulates opsin expression in the retina of a salmonid fish. J Neuroendocrinol 2019; 31:e12804. [PMID: 31630448 DOI: 10.1111/jne.12804] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 09/07/2019] [Accepted: 10/18/2019] [Indexed: 01/18/2023]
Abstract
Colour vision relies on retinal photoreceptors that express a different predominant visual pigment protein (opsin). In several vertebrates, the primary opsin expressed by a photoreceptor can change throughout ontogeny, although the molecular factors that influence such regulation are poorly understood. One of these factors is thyroid hormone which, together with its receptors, modulates opsin expression in the retinas of multiple vertebrates including rodents and salmonid fishes. In the latter, thyroid hormone induces a switch in opsin expression from SWS1 (ultraviolet light sensitive) to SWS2 (short wavelength or blue light sensitive) in the single cone photoreceptors of the retina. The actions of other hormones on opsin expression have not been investigated. In the present study, we used a transgenic strain of coho salmon (Oncorhynchus kitsutch) with enhanced levels of circulating growth hormone compared to that of wild siblings to assess the effects of this hormone on the SWS1 to SWS2 opsin switch. Transgenic fish showed a developmentally accelerated opsin switch compared to size-matched controls as assessed by immunohistological and in situ hybridisation labelling of photoreceptors and by quantification of transcripts using quantitative polymerase chain reaction. This accelerated switch led to a different spectral sensitivity maximum, under a middle to long wavelength adapting background, from ultraviolet (λmax ~ 380 nm) in controls to short wavelengths (λmax ~ 430 nm) in transgenics, demonstrating altered colour vision. The effects of growth hormone over-expression were independent of circulating levels of thyroid hormone (triiodothyronine), the hormone typically associated with opsin switches in vertebrates.
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Affiliation(s)
- Inigo Novales Flamarique
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
- Department of Biology, University of Victoria, Victoria, BC, Canada
| | - Ahmed Sayed Ahmed
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Christiana L Cheng
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Robert S Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
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16
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Modes of Accessing Bicarbonate for the Regulation of Membrane Guanylate Cyclase (ROS-GC) in Retinal Rods and Cones. eNeuro 2019; 6:eN-NWR-0393-18. [PMID: 30783616 PMCID: PMC6378327 DOI: 10.1523/eneuro.0393-18.2019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/20/2018] [Accepted: 01/15/2019] [Indexed: 11/21/2022] Open
Abstract
The membrane guanylate cyclase, ROS-GC, that synthesizes cyclic GMP for use as a second messenger for visual transduction in retinal rods and cones, is stimulated by bicarbonate. Bicarbonate acts directly on ROS-GC1, because it enhanced the enzymatic activity of a purified, recombinant fragment of bovine ROS-GC1 consisting solely of the core catalytic domain. Moreover, recombinant ROS-GC1 proved to be a true sensor of bicarbonate, rather than a sensor for CO2. Access to bicarbonate differed in rods and cones of larval salamander, Ambystoma tigrinum, of unknown sex. In rods, bicarbonate entered at the synapse and diffused to the outer segment, where it was removed by Cl--dependent exchange. In contrast, cones generated bicarbonate internally from endogenous CO2 or from exogenous CO2 that was present in extracellular solutions of bicarbonate. Bicarbonate production from both sources of CO2 was blocked by the carbonic anhydrase inhibitor, acetazolamide. Carbonic anhydrase II expression was verified immunohistochemically in cones but not in rods. In addition, cones acquired bicarbonate at their outer segments as well as at their inner segments. The multiple pathways for access in cones may support greater uptake of bicarbonate than in rods and buffer changes in its intracellular concentration.
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17
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Kranz AM, Forgan LG, Cole GL, Endler JA. Light environment change induces differential expression of guppy opsins in a multi-generational evolution experiment. Evolution 2018; 72:1656-1676. [PMID: 29920667 DOI: 10.1111/evo.13519] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 05/29/2018] [Accepted: 06/02/2018] [Indexed: 11/30/2022]
Abstract
Light environments critically impact species that rely on vision to survive and reproduce. Animal visual systems must accommodate changes in light that occur from minutes to years, yet the mechanistic basis of their response to spectral (color) changes is largely unknown. Here, we used a laboratory experiment where replicate guppy populations were kept under three different light environments for up to 8-12 generations to explore possible differences in the expression levels of nine guppy opsin genes. Previous evidence for opsin expression-light environment "tuning" has been either correlative or focused exclusively on the relationship between the light environment and opsin expression over one or two generations. In our multigeneration experiment, the relative expression levels of nine different guppy opsin genes responded differently to light environment changes: some did not respond, while others differed due to phenotypic plasticity. Moreover, for the LWS-1 opsin we found that, while we observed a wide range of plastic responses under different light conditions, common plastic responses (where the population replicates all followed the same trajectory) occurred only after multigenerational exposure to different light environments. Taken together this suggests that opsin expression plasticity plays an important role in light environment "tuning" in different light environments on different time scales, and, in turn, has important implications for both visual system function and evolution.
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Affiliation(s)
- Alexandrea M Kranz
- School of Life and Environmental Sciences, Centre for Integrative Ecology, Deakin University, Geelong, Australia
| | - Leonard G Forgan
- School of Life and Environmental Sciences, Deakin University, Geelong, Australia
| | - Gemma L Cole
- School of Life and Environmental Sciences, Centre for Integrative Ecology, Deakin University, Geelong, Australia
| | - John A Endler
- School of Life and Environmental Sciences, Centre for Integrative Ecology, Deakin University, Geelong, Australia
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18
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Variation in opsin transcript expression explains intraretinal differences in spectral sensitivity of the northern anchovy. Vis Neurosci 2018; 35:E005. [DOI: 10.1017/s0952523818000019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractVertebrate retinal photoreceptors house visual pigments that absorb light to begin the process of vision. The light absorbed by a visual pigment depends on its two molecular components: protein (opsin) and chromophore (a vitamin A derivative). Although an increasing number of studies show intraretinal variability in visual pigment content, it is only for two mammals (human and mouse) and two birds (chicken and pigeon) that such variability has been demonstrated to underlie differences in spectral sensitivity of the animal. Here, we show that the spectral sensitivity of the northern anchovy varies with retinal quadrant and that this variability can be explained by differences in the expression of opsin transcripts. Retinal (vitamin A1) was the only chromophore detected in the retina, ruling out this molecular component as a source of variation in spectral sensitivity. Chromatic adaptation experiments further showed that the dorsal retina had the capacity to mediate color vision. Together with published results for the ventral retina, this study is the first to demonstrate that intraretinal opsin variability in a fish drives corresponding variation in the animal’s spectral sensitivity.
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19
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Jacobs GH. Photopigments and the dimensionality of animal color vision. Neurosci Biobehav Rev 2017; 86:108-130. [PMID: 29224775 DOI: 10.1016/j.neubiorev.2017.12.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/04/2017] [Accepted: 12/05/2017] [Indexed: 12/31/2022]
Abstract
Early color-matching studies established that normal human color vision is trichromatic. Subsequent research revealed a causal link between trichromacy and the presence in the retina of three classes of cone photopigments. Over the years, measurements of the photopigment complements of other species have expanded greatly and these are frequently used to predict the dimensionality of an animal's color vision. This review provides an account of how the linkage between the number of active photopigments and the dimensions of human color vision developed, summarizes the various mechanisms that can impact photopigment spectra and number, and provides an across-species survey to examine cases where the photopigment link to the dimensionality of color vision has been claimed. The literature reveals numerous instances where the human model fails to account for the ways in which the visual systems of other animals exploit information obtained from the presence of multiple photopigments in support of their behavior.
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Affiliation(s)
- Gerald H Jacobs
- Department of Psychological and Brain Science, University of California, Santa Barbara, CA 93106, USA.
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20
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Musser JM, Arendt D. Loss and gain of cone types in vertebrate ciliary photoreceptor evolution. Dev Biol 2017; 431:26-35. [DOI: 10.1016/j.ydbio.2017.08.038] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 08/28/2017] [Accepted: 08/30/2017] [Indexed: 01/09/2023]
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21
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Vöcking O, Kourtesis I, Tumu SC, Hausen H. Co-expression of xenopsin and rhabdomeric opsin in photoreceptors bearing microvilli and cilia. eLife 2017; 6:23435. [PMID: 28876222 PMCID: PMC5648526 DOI: 10.7554/elife.23435] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 09/01/2017] [Indexed: 12/22/2022] Open
Abstract
Ciliary and rhabdomeric opsins are employed by different kinds of photoreceptor cells, such as ciliary vertebrate rods and cones or protostome microvillar eye photoreceptors, that have specialized structures and molecular physiologies. We report unprecedented cellular co-expression of rhabdomeric opsin and a visual pigment of the recently described xenopsins in larval eyes of a mollusk. The photoreceptors bear both microvilli and cilia and express proteins that are orthologous to transporters in microvillar and ciliary opsin trafficking. Highly conserved but distinct gene structures suggest that xenopsins and ciliary opsins are of independent origin, irrespective of their mutually exclusive distribution in animals. Furthermore, we propose that frequent opsin gene loss had a large influence on the evolution, organization and function of brain and eye photoreceptor cells in bilaterian animals. The presence of xenopsin in eyes of even different design might be due to a common origin and initial employment of this protein in a highly plastic photoreceptor cell type of mixed microvillar/ciliary organization. Animal eyes have photoreceptor cells that contain light-sensitive molecules called opsins. Although all animal photoreceptor cells of this kind share a common origin, the cells found in different organisms can differ considerably. The photoreceptor cells in flies, squids and other invertebrates store a type of opsin called r-opsin in thin projections on the surface known as microvilli. On the other hand, the visual photoreceptor cells in human and other vertebrate eyes transport another type of opsin (known as c-opsin) into more prominent extensions called cilia. It has been suggested that the fly and vertebrate photoreceptor cells represent clearly distinct evolutionary lineages of cells, which diverged early in animal evolution. However, several organisms that are more closely related to flies than to vertebrates have eye photoreceptor cells with cilia. Do all eye photoreceptors with cilia have a common origin in evolution or did they emerge independently in vertebrates and certain invertebrates? The photoreceptor cells of a marine mollusc called Leptochiton asellus, are unusual because they bear both microvilli and cilia, suggesting they have intermediate characteristics between the two well-known types of photoreceptor cells. Previous studies have shown that these photoreceptor cells use r-opsin, but Vöcking et al. have now detected the presence of an additional opsin in the cells. This opsin is a member of the recently discovered xenopsin family of molecules. Further analyses support the findings of previous studies that suggested this type of opsin emerged early on in animal evolution, independently from c-opsin. Other invertebrates that have cilia on their eye photoreceptors also use xenopsin and not c-opsin. The findings of Vöcking et al. suggest that, in addition to c-opsin and r-opsin, xenopsin has also driven the evolution of photoreceptor cells in animals. Eye photoreceptor cells in invertebrates with cilia probably share a common origin with the microvilli photoreceptor cells that is distinct from that of vertebrate visual cells. The observation that two very different types of opsin can be produced within a single cell suggests that the molecular processes that respond to light in photoreceptor cells may be much more complex than previously anticipated. Further work on these processes may help us to understand how animal eyes work and how they are affected by disease.
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Affiliation(s)
- Oliver Vöcking
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway.,Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States
| | - Ioannis Kourtesis
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Sharat Chandra Tumu
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Harald Hausen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
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22
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Stieb SM, Carleton KL, Cortesi F, Marshall NJ, Salzburger W. Depth-dependent plasticity in opsin gene expression varies between damselfish (Pomacentridae) species. Mol Ecol 2016; 25:3645-61. [DOI: 10.1111/mec.13712] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 05/10/2016] [Accepted: 05/31/2016] [Indexed: 01/02/2023]
Affiliation(s)
- Sara M. Stieb
- Zoological Institute; University of Basel; Basel 4051 Switzerland
- Queensland Brain Institute; The University of Queensland; Brisbane QLD 4072 Australia
| | - Karen L. Carleton
- Department of Biology; University of Maryland; College Park MD 20742 USA
| | - Fabio Cortesi
- Zoological Institute; University of Basel; Basel 4051 Switzerland
- Queensland Brain Institute; The University of Queensland; Brisbane QLD 4072 Australia
| | - N. Justin Marshall
- Queensland Brain Institute; The University of Queensland; Brisbane QLD 4072 Australia
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23
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Valen R, Eilertsen M, Edvardsen RB, Furmanek T, Rønnestad I, van der Meeren T, Karlsen Ø, Nilsen TO, Helvik JV. The two-step development of a duplex retina involves distinct events of cone and rod neurogenesis and differentiation. Dev Biol 2016; 416:389-401. [PMID: 27374844 DOI: 10.1016/j.ydbio.2016.06.041] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 06/23/2016] [Accepted: 06/27/2016] [Indexed: 11/15/2022]
Abstract
Unlike in mammals, persistent postembryonic retinal growth is a characteristic feature of fish, which includes major remodeling events that affect all cell types including photoreceptors. Consequently, visual capabilities change during development, where retinal sensitivity to different wavelengths of light (photopic vision), -and to limited photons (scotopic vision) are central capabilities for survival. Differently from well-established model fish, Atlantic cod has a prolonged larval stage where only cone photoreceptors are present. Rods do not appear until juvenile transition (metamorphosis), a hallmark of indirect developing species. Previously we showed that whole gene families of lws (red-sensitive) and sws1 (UV-sensitive) opsins have been lost in cod, while rh2a (green-sensitive) and sws2 (blue-sensitive) genes have tandem duplicated. Here, we provide a comprehensive characterization of a two-step developing duplex retina in Atlantic cod. The study focuses on cone subtype dynamics and delayed rod neurogenesis and differentiation in all cod life stages. Using transcriptomic and histological approaches we show that different opsins disappear in a topographic manner during development where central to peripheral retina is a key axis of expressional change. Early cone differentiation was initiated in dorso-temporal retina different from previously described in fish. Rods first appeared during initiation of metamorphosis and expression of the nuclear receptor transcription factor nr2e3-1, suggest involvement in rod specification. The indirect developmental strategy thus allows for separate studies of cones and rods development, which in nature correlates with visual changes linked to habitat shifts. The clustering of key retinal genes according to life stage, suggests that Atlantic cod with its sequenced genome may be an important resource for identification of underlying factors required for development and function of photopic and scotopic vision.
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Affiliation(s)
- Ragnhild Valen
- Department of Biology, University of Bergen, NO-5020 Bergen, Norway
| | | | | | - Tomasz Furmanek
- Institute of Marine Research, Nordnes, NO-5005 Bergen, Norway
| | - Ivar Rønnestad
- Department of Biology, University of Bergen, NO-5020 Bergen, Norway
| | - Terje van der Meeren
- Institute of Marine Research, Austevoll Research station and Hjort Centre for Marine Ecosystem Dynamics, NO-5392 Storebø, Norway
| | - Ørjan Karlsen
- Institute of Marine Research, Austevoll Research station and Hjort Centre for Marine Ecosystem Dynamics, NO-5392 Storebø, Norway
| | | | - Jon Vidar Helvik
- Department of Biology, University of Bergen, NO-5020 Bergen, Norway
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24
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Evolutionary transformation of rod photoreceptors in the all-cone retina of a diurnal garter snake. Proc Natl Acad Sci U S A 2015; 113:356-61. [PMID: 26715746 DOI: 10.1073/pnas.1513284113] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Vertebrate retinas are generally composed of rod (dim-light) and cone (bright-light) photoreceptors with distinct morphologies that evolved as adaptations to nocturnal/crepuscular and diurnal light environments. Over 70 years ago, the "transmutation" theory was proposed to explain some of the rare exceptions in which a photoreceptor type is missing, suggesting that photoreceptors could evolutionarily transition between cell types. Although studies have shown support for this theory in nocturnal geckos, the origins of all-cone retinas, such as those found in diurnal colubrid snakes, remain a mystery. Here we investigate the evolutionary fate of the rods in a diurnal garter snake and test two competing hypotheses: (i) that the rods, and their corresponding molecular machinery, were lost or (ii) that the rods were evolutionarily modified to resemble, and function, as cones. Using multiple approaches, we find evidence for a functional and unusually blue-shifted rhodopsin that is expressed in small single "cones." Moreover, these cones express rod transducin and have rod ultrastructural features, providing strong support for the hypothesis that they are not true cones, as previously thought, but rather are modified rods. Several intriguing features of garter snake rhodopsin are suggestive of a more cone-like function. We propose that these cone-like rods may have evolved to regain spectral sensitivity and chromatic discrimination as a result of ancestral losses of middle-wavelength cone opsins in early snake evolution. This study illustrates how sensory evolution can be shaped not only by environmental constraints but also by historical contingency in forming new cell types with convergent functionality.
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25
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Dalton BE, Loew ER, Cronin TW, Carleton KL. Spectral tuning by opsin coexpression in retinal regions that view different parts of the visual field. Proc Biol Sci 2015; 281:rspb.2014.1980. [PMID: 25377457 DOI: 10.1098/rspb.2014.1980] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Vision frequently mediates critical behaviours, and photoreceptors must respond to the light available to accomplish these tasks. Most photoreceptors are thought to contain a single visual pigment, an opsin protein bound to a chromophore, which together determine spectral sensitivity. Mechanisms of spectral tuning include altering the opsin, changing the chromophore and incorporating pre-receptor filtering. A few exceptions to the use of a single visual pigment have been documented in which a single mature photoreceptor coexpresses opsins that form spectrally distinct visual pigments, and in these exceptions the functional significance of coexpression is unclear. Here we document for the first time photoreceptors coexpressing spectrally distinct opsin genes in a manner that tunes sensitivity to the light environment. Photoreceptors of the cichlid fish, Metriaclima zebra, mix different pairs of opsins in retinal regions that view distinct backgrounds. The mixing of visual pigments increases absorbance of the corresponding background, potentially aiding the detection of dark objects. Thus, opsin coexpression may be a novel mechanism of spectral tuning that could be useful for detecting prey, predators and mates. However, our calculations show that coexpression of some opsins can hinder colour discrimination, creating a trade-off between visual functions.
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Affiliation(s)
- Brian E Dalton
- Department of Biology, University of Maryland, Baltimore County, MD 21250, USA Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Ellis R Loew
- Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Thomas W Cronin
- Department of Biology, University of Maryland, Baltimore County, MD 21250, USA
| | - Karen L Carleton
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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26
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Farkas JE, Monaghan JR. Housing and maintenance of Ambystoma mexicanum, the Mexican axolotl. Methods Mol Biol 2015; 1290:27-46. [PMID: 25740475 DOI: 10.1007/978-1-4939-2495-0_3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
The aim of this paper is to assemble a significant amount of information on Ambystoma mexicanum, the axolotl salamander, to assist in the basic knowledge needed to raise, breed, and study most aspects of axolotl biology. It is important to understand the basic biology of the axolotl in order to make informed decisions on their proper care and use in experiments. Therefore, we will provide necessary information to the non-herpetologist that will assist in their study of this unique and fascinating animal. We also aim to provide a resource on the general anatomy, behavior, and experimental tips specific to the Mexican axolotl that will be of use to most axolotl laboratories. Axolotls have been actively researched since the 1860s, giving testament to their relatively straightforward maintenance and their versatility as an animal model for development and regeneration. Interest in using the axolotl in laboratory research has grown tremendously over the past decade, so dedicated resources to support the study of this species are needed and encouraged.
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Affiliation(s)
- Johanna E Farkas
- Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA, 02115-5000, USA
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Wen XH, Dizhoor AM, Makino CL. Membrane guanylyl cyclase complexes shape the photoresponses of retinal rods and cones. Front Mol Neurosci 2014; 7:45. [PMID: 24917784 PMCID: PMC4040495 DOI: 10.3389/fnmol.2014.00045] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 05/01/2014] [Indexed: 12/02/2022] Open
Abstract
In vertebrate rods and cones, photon capture by rhodopsin leads to the destruction of cyclic GMP (cGMP) and the subsequent closure of cyclic nucleotide gated ion channels in the outer segment plasma membrane. Replenishment of cGMP and reopening of the channels limit the growth of the photon response and are requisite for its recovery. In different vertebrate retinas, there may be as many as four types of membrane guanylyl cyclases (GCs) for cGMP synthesis. Ten neuronal Ca2+ sensor proteins could potentially modulate their activities. The mouse is proving to be an effective model for characterizing the roles of individual components because its relative simplicity can be reduced further by genetic engineering. There are two types of GC activating proteins (GCAPs) and two types of GCs in mouse rods, whereas cones express one type of GCAP and one type of GC. Mutant mouse rods and cones bereft of both GCAPs have large, long lasting photon responses. Thus, GCAPs normally mediate negative feedback tied to the light-induced decline in intracellular Ca2+ that accelerates GC activity to curtail the growth and duration of the photon response. Rods from other mutant mice that express a single GCAP type reveal how the two GCAPs normally work together as a team. Because of its lower Ca2+ affinity, GCAP1 is the first responder that senses the initial decrease in Ca2+ following photon absorption and acts to limit response amplitude. GCAP2, with a higher Ca2+ affinity, is recruited later during the course of the photon response as Ca2+ levels continue to decline further. The main role of GCAP2 is to provide for a timely response recovery and it is particularly important after exposure to very bright light. The multiplicity of GC isozymes and GCAP homologs in the retinas of other vertebrates confers greater flexibility in shaping the photon responses in order to tune visual sensitivity, dynamic range and frequency response.
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Affiliation(s)
- Xiao-Hong Wen
- Department of Ophthalmology, Massachusetts Eye and Ear Infirmary and Harvard Medical School Boston, MA, USA
| | - Alexander M Dizhoor
- Department of Basic Sciences Research and Pennsylvania College of Optometry, Salus University Elkins Park, PA, USA
| | - Clint L Makino
- Department of Ophthalmology, Massachusetts Eye and Ear Infirmary and Harvard Medical School Boston, MA, USA
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