Spectral tuning and deactivation kinetics of marine mammal melanopsins.

In mammals, the photopigment melanopsin (Opn4) is found in a subset of retinal ganglion cells that serve light detection for circadian photoentrainment and pupil constriction (i.e., mydriasis). For a given species, the efficiency of photoentrainment and length of time that mydriasis occurs is determ...

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Autores principales:	Jeffry I Fasick, Haya Algrain, Courtland Samuels, Padmanabhan Mahadevan, Lorian E Schweikert, Zaid J Naffaa, Phyllis R Robinson
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/e02343410e884cf687b1cb28bee5a024
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spelling	oai:doaj.org-article:e02343410e884cf687b1cb28bee5a0242021-12-02T20:16:53ZSpectral tuning and deactivation kinetics of marine mammal melanopsins.1932-620310.1371/journal.pone.0257436https://doaj.org/article/e02343410e884cf687b1cb28bee5a0242021-01-01T00:00:00Zhttps://doi.org/10.1371/journal.pone.0257436https://doaj.org/toc/1932-6203In mammals, the photopigment melanopsin (Opn4) is found in a subset of retinal ganglion cells that serve light detection for circadian photoentrainment and pupil constriction (i.e., mydriasis). For a given species, the efficiency of photoentrainment and length of time that mydriasis occurs is determined by the spectral sensitivity and deactivation kinetics of melanopsin, respectively, and to date, neither of these properties have been described in marine mammals. Previous work has indicated that the absorbance maxima (λmax) of marine mammal rhodopsins (Rh1) have diversified to match the available light spectra at foraging depths. However, similar to the melanopsin λmax of terrestrial mammals (~480 nm), the melanopsins of marine mammals may be conserved, with λmax values tuned to the spectrum of solar irradiance at the water's surface. Here, we investigated the Opn4 pigments of 17 marine mammal species inhabiting diverse photic environments including the Infraorder Cetacea, as well as the Orders Sirenia and Carnivora. Both genomic and cDNA sequences were used to deduce amino acid sequences to identify substitutions most likely involved in spectral tuning and deactivation kinetics of the Opn4 pigments. Our results show that there appears to be no amino acid substitutions in marine mammal Opn4 opsins that would result in any significant change in λmax values relative to their terrestrial counterparts. We also found some marine mammal species to lack several phosphorylation sites in the carboxyl terminal domain of their Opn4 pigments that result in significantly slower deactivation kinetics, and thus longer mydriasis, compared to terrestrial controls. This finding was restricted to cetacean species previously found to lack cone photoreceptor opsins, a condition known as rod monochromacy. These results suggest that the rod monochromat whales rely on extended pupillary constriction to prevent photobleaching of the highly photosensitive all-rod retina when moving between photopic and scotopic conditions.Jeffry I FasickHaya AlgrainCourtland SamuelsPadmanabhan MahadevanLorian E SchweikertZaid J NaffaaPhyllis R RobinsonPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 16, Iss 10, p e0257436 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Jeffry I Fasick Haya Algrain Courtland Samuels Padmanabhan Mahadevan Lorian E Schweikert Zaid J Naffaa Phyllis R Robinson Spectral tuning and deactivation kinetics of marine mammal melanopsins.
description	In mammals, the photopigment melanopsin (Opn4) is found in a subset of retinal ganglion cells that serve light detection for circadian photoentrainment and pupil constriction (i.e., mydriasis). For a given species, the efficiency of photoentrainment and length of time that mydriasis occurs is determined by the spectral sensitivity and deactivation kinetics of melanopsin, respectively, and to date, neither of these properties have been described in marine mammals. Previous work has indicated that the absorbance maxima (λmax) of marine mammal rhodopsins (Rh1) have diversified to match the available light spectra at foraging depths. However, similar to the melanopsin λmax of terrestrial mammals (~480 nm), the melanopsins of marine mammals may be conserved, with λmax values tuned to the spectrum of solar irradiance at the water's surface. Here, we investigated the Opn4 pigments of 17 marine mammal species inhabiting diverse photic environments including the Infraorder Cetacea, as well as the Orders Sirenia and Carnivora. Both genomic and cDNA sequences were used to deduce amino acid sequences to identify substitutions most likely involved in spectral tuning and deactivation kinetics of the Opn4 pigments. Our results show that there appears to be no amino acid substitutions in marine mammal Opn4 opsins that would result in any significant change in λmax values relative to their terrestrial counterparts. We also found some marine mammal species to lack several phosphorylation sites in the carboxyl terminal domain of their Opn4 pigments that result in significantly slower deactivation kinetics, and thus longer mydriasis, compared to terrestrial controls. This finding was restricted to cetacean species previously found to lack cone photoreceptor opsins, a condition known as rod monochromacy. These results suggest that the rod monochromat whales rely on extended pupillary constriction to prevent photobleaching of the highly photosensitive all-rod retina when moving between photopic and scotopic conditions.
format	article
author	Jeffry I Fasick Haya Algrain Courtland Samuels Padmanabhan Mahadevan Lorian E Schweikert Zaid J Naffaa Phyllis R Robinson
author_facet	Jeffry I Fasick Haya Algrain Courtland Samuels Padmanabhan Mahadevan Lorian E Schweikert Zaid J Naffaa Phyllis R Robinson
author_sort	Jeffry I Fasick
title	Spectral tuning and deactivation kinetics of marine mammal melanopsins.
title_short	Spectral tuning and deactivation kinetics of marine mammal melanopsins.
title_full	Spectral tuning and deactivation kinetics of marine mammal melanopsins.
title_fullStr	Spectral tuning and deactivation kinetics of marine mammal melanopsins.
title_full_unstemmed	Spectral tuning and deactivation kinetics of marine mammal melanopsins.
title_sort	spectral tuning and deactivation kinetics of marine mammal melanopsins.
publisher	Public Library of Science (PLoS)
publishDate	2021
url	https://doaj.org/article/e02343410e884cf687b1cb28bee5a024
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Spectral tuning and deactivation kinetics of marine mammal melanopsins.

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