A rhodopsin-like protein in the plasma membrane of Silvetia compressa eggs.

Unidirectional blue light directs the rhizoid-thallus axis in the apolar zygote of the brown alga, Silvetia compressa. This effect is mediated by an increase in the intracellular concentration of guanosine 3', 5' - cyclic monophosphate. In this study we show the identification of a rhodopsin-like protein, by means of antibody reaction, in the palsma membrane of Silvetia eggs. This new result suggests a role for opsins in Silvetia photopolarity.