THERMOLUMINESCENCE STUDY OF PHOTOSYSTEM-II IN A GREENING MUTANT OF CHLORELLA-KESSLERI .2. BIOGENESIS OF PHOTOSYSTEM-II COMPLEXES IN YELLOW

Thermoluminescence was used to study the functional properties of a tr ace fraction of dark-synthesized complexes of photosystem II (PS II) a nd to explore their light-dependent biogenesis in greening yellow muta nts of Chlorella kessleri Ys/Sc. The data suggest that in dark-grown h eterotrophic cells the complexes of Ps II are composed of subnuclear u nits, apparently CP47/D1/D2 with a latent water oxidizing system, whic h can be activated with a train of similar to 100 short (3 mu sec) lig ht flashes delivered at the rate of 1 Hz. In continuously illuminated greening cells, the newly synthesized subnuclear units of PSII are bou nd to CP43 and then to the light-harvesting complexes of chlorophyll a lb. The latter step generates the major fraction of water-oxidizing PS II units, probably resulting from association with the external 33 kD Mn-stabilizing protein encoded by the nuclear genome.