Cambrian origin of the CYP27C1-mediated vitamin A-to-A switch, a key mechanism of vertebrate sensory plasticity.

The spectral composition of ambient light varies across both space and time. Many species of jawed vertebrates adapt to this variation by tuning the sensitivity of their photoreceptors via the expression of CYP27C1, an enzyme that converts vitamin A into vitamin A, thereby shifting the ratio of vitamin A-based rhodopsin to red-shifted vitamin A-based porphyropsin in the eye. Here, we show that the sea lamprey (), a jawless vertebrate that diverged from jawed vertebrates during the Cambrian period (approx.

Voltage-sensitive conductances increase the sensitivity of rod photoresponses following pigment bleaching.

Key Points: Following substantial bleaching of the visual pigment, the desensitization of the rod photovoltage is not as substantial as the desensitization of the rod outer segment photocurrent. The block of cation conductances during the internal dialysis of Cs further desensitizes the photovoltage thereby eliminating its difference in desensitization with the rod outer segment photocurrent. Bleached visual pigment produced an acceleration of the rod photovoltage with respect to the outer segment photocurrent, which is eliminated upon internal dialysis of Cs .