IMMUNOGOLD LOCALIZATION OF LIGHT-HARVESTING AND PHOTOSYSTEM-I COMPLEXES IN THE THYLAKOIDS OF FUCUS-SERRATUS (PHAEOPHYCEAE)

The repartition of light-harvesting complex (LHC) and photosystem I (PS I) complex has been examined in isolated plastids of Fucus serratus by immunocytochemical labelling. LHC is distributed equally all along the length of thylakoid membranes, without any special repartition in the appressed membranes of the three associated thylakoids of Fucus. PS I is present on all the thylakoid membranes, but the external membranes of the three associated thylakoids are largely enriched relatively to the inner ones. This specific repartition of PS I on non-appressed membranes can be compared to the localization of PS I on stroma thylakoid membranes of higher plants and green algae. Consequently, although they share some common features with those of higher plants and green algae, the appressions of thylakoids in brown algae has neither the same structure nor the same functional role as typical grana stacked membranes in the repartition of the harvested energy.