Distribution of blue-sensitive photoreceptors in amphibian retinas

Previously, we reported that an opsin (Rc-MS) belonging to the SWS2 group o psins is expressed in bullfrog green rods [Hisatomi, O. et al., FEBS Lett., 1999, 447, 44-48]. An anti-Rc-MS antiserum recognized the cones of the Jap anese common newt, Cynops pyrrhogaster, which has no green rods. We isolate d a cDNA encoding an SWS2 group opsin (Cp-SWS2) from this newt and found th at Cp-SWS2 is expressed in a small population of the cones. Our results sug gest that SWS2 opsins can be expressed in either green rods or cones of cau data. It seems reasonable to suppose that green rods arose before amphibia were divided into caudata and anura. (C) 2001 Federation of European Bioche mical Societies. Published by Elsevier Science B.V. All rights reserved.