Development of photosystem ii activity in chlamydomonas reinhardi mutants insertion of photosystem ii units into inactive preexisting membranes vs continuous formation of new photosynthetic membranes
Cahen, D.; Malkin, S.; Ohad, I.
Plant Physiology (Rockville) 60(6): 845-849
In a previous work the development of photosystem II activity during the greening process of the y-1 mutant of C. reinhardi was studied. Measurements of quantum yield, maximal rate of electron transfer, flash yield and fluorescence induction indicated that photosystem II development consists of 2 partially overlapping phases: reorganization and integration of preexisting units; and addition of newly formed units to the growing membranes. These two processes were studied independently. This was achieved using 2 experimental systems: cells of the y-1 mutant, greened in the presence of chloramphenicol (CAP), whose activity is repaired under conditions which prevent further chlorophyll synthesis and membrane growth (dark or light with addition of cycloheximide [CHI]); greening cells of a pale mutant derived from y-1 in which chloroplasts membranes was formed gradually during several cell divisions. In both systems different parameters of 2,6-dichlorophenolindophenol reduction and fluorescence, were measured. The results are interpreted using a kinetic model reported previously. Apparently during repair of photosynthetic activity in inactive membranes which were formed previously in the presence of chloramphenicol, photosystem II reaction centers are formed and integrated in preexisting membranes. In the pale green mutant there is complete de novo synthesis of units of constant composition which are added during formation of new chloroplast membranes.