RRC ID 65598
Author Wada S, Shen B, Kawano-Yamashita E, Nagata T, Hibi M, Tamotsu S, Koyanagi M, Terakita A.
Title Color opponency with a single kind of bistable opsin in the zebrafish pineal organ.
Journal Proc Natl Acad Sci U S A
Abstract Lower vertebrate pineal organs discriminate UV and visible light. Such color discrimination is typically considered to arise from antagonism between two or more spectrally distinct opsins, as, e.g., human cone-based color vision relies on antagonistic relationships between signals produced by red-, green-, and blue-cone opsins. Photosensitive pineal organs contain a bistable opsin (parapinopsin) that forms a signaling-active photoproduct upon UV exposure that may itself be returned to the signaling-inactive "dark" state by longer-wavelength light. Here we show the spectrally distinct parapinopsin states (with antagonistic impacts on signaling) allow this opsin alone to provide the color sensitivity of this organ. By using calcium imaging, we show that single zebrafish pineal photoreceptors held under a background light show responses of opposite signs to UV and visible light. Both such responses are deficient in zebrafish lacking parapinopsin. Expressing a UV-sensitive cone opsin in place of parapinopsin recovers UV responses but not color opponency. Changes in the spectral composition of white light toward enhanced UV or visible wavelengths respectively increased vs. decreased calcium signal in parapinopsin-sufficient but not parapinopsin-deficient photoreceptors. These data reveal color opponency from a single kind of bistable opsin establishing an equilibrium-like mixture of the two states with different signaling abilities whose fractional concentrations are defined by the spectral composition of incident light. As vertebrate visual color opsins evolved from a bistable opsin, these findings suggest that color opponency involving a single kind of bistable opsin might have been a prototype of vertebrate color opponency.
Volume 115(44)
Pages 11310-11315
Published 2018-10-30
DOI 10.1073/pnas.1802592115
PII 1802592115
PMID 30322939
PMC PMC6217433
MeSH Animals Color Color Vision / physiology* Fish Proteins / metabolism Light Pineal Gland / metabolism Pineal Gland / physiology* Retinal Cone Photoreceptor Cells / metabolism Retinal Cone Photoreceptor Cells / physiology Rod Opsins / metabolism Rod Opsins / physiology* Ultraviolet Rays Zebrafish / metabolism Zebrafish / physiology*
IF 9.412
Zebrafish RIKEN WT