Genetic Analyses of Visual Pigments of the Pigeon (Columba livia)

We isolated five classes of retinal opsin genes rh1Cl, rh2Cl, sws1Cl, sws2Cl, and lwsCl from the pigeon; these encode RH1Cl, RH2Cl, SWS1Cl, SWS2Cl, and LWSCl opsins, respectively. Upon binding to 11-cis-retinal, these opsins regenerate the corresponding photosensitive molecules, visual pigments. The absorbance spectra of visual pigments have a broad bell shape with the peak, being called λmax. Previously, the SWS1Cl opsin cDNA was isolated from the pigeon retinal RNA, expressed in cultured COS1 cells, reconstituted with 11-cis-retinal, and the λmax of the resulting SWS1Cl pigment was shown to be 393 nm. In this article, using the same methods, the λmax values of RH1Cl, RH2Cl, SWS2Cl, and LWSCl pigments were determined to be 502, 503, 448, and 559 nm, respectively. The pigeon is also known for its UV vision, detecting light at 320–380 nm. Being the only pigments that absorb light below 400 nm, the SWS1Cl pigments must mediate its UV vision. We also determined that a nonretinal PCl pigment in the pineal gland of the pigeon has a λmax value at 481 nm.