RETINAL IDENTIFICATION IN PELVETIA-FASTIGIATA

Unidirectional blue light directs the rhizoid-thallus axis in the apol ar zygote of the brown alga Pelvetia fastigiata. This effect is mediat ed by an increase in the intracellular concentration of cGMP, Here, we show the extraction, purification and identification of 1 mu g of all -trans retinal from 1.2 x 10(6) Pelvetia zygotes, The number of retina l molecules per cell was about 410(9). Since retinal, wherever presen t, is exclusively associated with an opsin to form a light sensitive c omplex (rhodopsin-Like proteins), and since the physiological response originated by this protein produces a variation of cGMP concentration , this new finding suggests that a rhodopsin-like protein could be the photoreceptor in this brown alga. (C) 1998 Academic Press.