ELECTRIC CURRENTS EVOKED BY DOUBLE-FLASH EXCITATION OF THE PHOTOTACTIC ALGA CHLAMYDOMONAS-REINHARDTII

The electric responses that accompany photosensory transduction in Chl amydomonas reinhardtii were measured using a recently developed suspen sion method. Double-laser-flash excitations were applied to acquire mo re information on the nature of the photocycle of the retina containin g protein in the eye spot, and on the nature of the different componen ts of the photoelectric signals ('photoreceptor potential' and 'regene rative response'). It was found that blue light, as a second illuminat ion following the driving flash with a wavelength of 500 nm, did not a ffect the membrane-coupled electric events. A characteristic turnover time of nearly 1 s was established for these processes with a second f lash of wavelength 500 nm. The results are discussed in terms of their relevance to the photocycle of the retinal protein and to the signal transduction mechanism. (C) 1997 Elsevier Science S.A.