Localization of opsins in the photoreceptor systems of Anolu. carolinensis

Purpose. Four photorecepior organs -the lateral and parietal eyes, the pineal organ, and the deep brain photoreceptor - are ecogmsed in the lizard Anolis carolinensis, mediating visual and circadian responses to light. Other investigators have identified and sequcnced five different opsins in the Anolis genome. We have studied the expression of these genes in the eye, pinral, and brain. Methods Total RNA was used for the synthesis of cDNA by Supeiscnpt II. Primers were designed lor the specific amplification of rhodopsin, L opsin, rhodopsm-likc M opsin, SI opsin, and S2 opsin, as well as 16S rRNA as a positive control, and used for PCR amplification of the different samples. Results. The different opsins were localized to the dillcrenl photoreceptor organs as follows. PCR pr xlucts were subcloned for sequencing in order to determine specificity: Eye Pineal Brain Rhodopsin + + + L opsin + - - Rhodopsin-like M opsin + - - 51 opsin - + - 52 opsin + + - Conclusions. The detection of rhodopsin mRNA in the rod less Anolis retina confirms immunocytochemical data publ shed by other investigators. The finding of four different photopigments in the eye b consistent with its role in colour vision. Among the circadian photoreceptor systems, we find S opsins in the superficially localized pineal, but not in the deep brain photorecepiors which are unlikely to be exposed to light of these wavelength because of the overlaying tissues. Experiments desiened In confirm our results by RNAse nrntertion assays are in progress.