CHARACTERIZATION OF THE LIGHT-HARVESTING COMPLEX OF GIRAUDYOPSIS STELLIFER (CHRYSOPHYCEAE) AND EFFECTS OF LIGHT STRESS

The light-harvesting complex (LHC) of Giraudyopsis stellifer Dangeard was isolated on a sucrose density gradient after digitonin treatment, and the pigment composition was analyzed by reverse-phase high-pressur e liquid chromatography. The LHC is a chlorophyll (Chl) a/c/fucoxanthi h/violaxanthin complex, depleted of beta-carotene, comparable to the L HC of Fucophyceae. The excitation transfer from Chl c and fucoxanthin to Chl a is efficient in whole cells. Immunological reactions indicate a close relationship between Chrysophyceae and Fucophyceae. The immun ocytochemical labeling confirms the lack of segregation of the LHC in the appressed membranes of the three associated thylakoids and its loc alization in the intrapyrenoid thylakoid. The violaxanthin-antheraxan- thin-zeaxanthin cycle is operative in the cells and efficiently protec ts photosystem II reaction centers against photoinhibition.