Vertebrate ancient opsin photopigment spectra and the avian photoperiodic response.
In mammals, photoreception is restricted to cones, rods and a subset of retinal ganglion cells. By contrast, non-mammalian vertebrates possess many extraocular photoreceptors but in many cases the role of these photoreceptors and their underlying photopigments is unknown. In birds, deep brain photoreceptors have been shown to sense photic changes in daylength (photoperiod) and mediate seasonal reproduction. Nonetheless, the specific identity of the opsin photopigment 'sensor' involved has remained elusive. Previously, we showed that vertebrate ancient (VA) opsin is expressed in avian hypothalamic neurons and forms a photosensitive molecule. However, a direct functional link between VA opsin and the regulation of seasonal biology was absent. Here, we report the in vivo and in vitro absorption spectra (λ(max) = ~490 nm) for chicken VA photopigments. Furthermore, the spectral sensitivity of these photopigments match the peak absorbance of the avian photoperiodic response (λ(max) = 492 nm) and permits maximum photon capture within the restricted light environment of the hypothalamus. Such a correspondence argues strongly that VA opsin plays a key role in regulating seasonal reproduction in birds.
Nuffield Laboratory of Ophthalmology, Oxford University, Oxford, UK.
Wayne I L
WI
Davies
Michael
M
Turton
Stuart N
SN
Peirson
Brian K
BK
Follett
Stephanie
S
Halford
Jose M
JM
Garcia-Fernandez
Peter J
PJ
Sharp
Mark W
MW
Hankins
Russell G
RG
Foster
D000818:Animals; D015153:Blotting, Western; D002645:Chickens / Q000502:physiology*; D002846:Chromatography, Affinity; D057809:HEK293 Cells; D006454:Hemoglobins / Q000502:physiology / Q000528:radiation effects; D006801:Humans; D007031:Hypothalamus / Q000166:cytology / Q000502:physiology*; D055355:Opsins / Q000502:physiology* / Q000528:radiation effects; D010775:Photic Stimulation; D017440:Photoperiod; D020419:Photoreceptor Cells, Vertebrate / Q000737:chemistry / Q000502:physiology*; D020033:Protein Isoforms / Q000502:physiology / Q000528:radiation effects; D011994:Recombinant Proteins / Q000378:metabolism / Q000528:radiation effects; D012098:Reproduction; D012172:Retinaldehyde; D012621:Seasons; D013053:Spectrophotometry
D006454:Hemoglobins; D055355:Opsins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D012172:Retinaldehyde