Development of Photosystem II Complex during Greening of Chlamydomonas reinhardi y-1

Abstract

The relative content of organized pigment, active centers, and acceptor pools of photosystem II and their interconnection dunng the development of the photosynthetic membranes of Chlamydomonas reinhardi y-1 have been measured using the fluorescence induction technique. The degree of connectivity and efficiency of the developing system has been assessed also from measurements of maximal rates, quantum yield, and flash yield of 2,6-dichlorophenolindophenol photoreduction using H20 as the electron donor. The results obtained indicate that the process of membrane development in this organism consists of two phases: an initial phase of reorganization and connection between pre-existing components, and a second phase of actual accumulation of newly formed, complete, and active units. The ratio of active centers to Chl remains practically constant throughout the process while the degree of connectivity between the active center and the plastoquinone pool was doubled during the early phase of the greening. In addition the degree of connectivity between the plastoquinone pool and the rest of the electron transport chain increases as demonstrated by a 10-to 20-fold rise in the quantum yield and a 10-fold rise in the maximal rate and the flash yield. The ratio of light harvesting Chl to active centers remains apparently constant during the second phase of the greening as indicated by light saturation experiments and by the constancy of the apparent photosynthetic unit size. Electron donation from H20 seems to develop slower than the activity of the rest of the complex as demonstrated by measurements of 2,6-dichlorophenolindophenol photoreduction using 1,5-diphenylcarbazide as the electron donor. The value of all the above parameters which remain constant during the second phase of the greening are comparable to those obtained with membranes of light-grown cells.The process of chloroplast membrane biogenesis has been the subject of extensive work carried out in many laboratories. The results obtained so far have been reviewed recently (5,18,28). The process of assembly of components and membrane development can be summarized as follows. The chloroplast membranes grow by progressive insertion of newly formed components within pre-existing membranes. The addition of the new components can occur simultaneously or stepwise, and in the second case can result in continuous rearrangements and organizational changes within the membrane, detected at the ultrastructural level (17) and accompanied by drastic changes in photosynthetic activity (12,27,37 (10).The development of 02 evolution activity during greening of a dark-grown Chlorella mutant has been described by Herron and Mauzerall (15) and measurements of both activation of 02 evolution and variable fluorescence during greening of another Chlorella mutant have been reported by Dubertret and Joliot (7). The data obtained by both groups indicate that in these mutants active centers connected to the electron transport chain are present in the membrane at the very beginning...

Modulation of PSI and PSII Organization During Loss and Repair of Photosynthetic Activity in a Temperature Sensitive Mutant of Chlorella pyrenoidosa

“…Increase in the values of Fv/Chl is interpreted to indicate formation of new PSII reaction centers or assembly of previously formed components into active units (5). The first situation is exemplified by the cells repaired in the light in which additional Chl was synthesized.…”

“…The results are shown in Figure 9. Right, pattern of membrane polypeptides obtained from M cells grown for 0, 5,12,24 and 48 h (slots 1, 2, 3, 4, and 5, respectively) at 33 C. The SDS solubilized membranes were heat denatured prior to electrophoresis, and electrophoresis was carried out in a 10 to 15% polyacrylamide gradient gel instead of a 7.5 to 15% gradient gel which was used in Fig. 10 with addition of CAP including the LHC polypeptides (Fig.…”

Origin of Thylakoid Membranes in Chlamydomonas reinhardtii y-1 at 38°C

“…and National Institute of Child Health and Human Development grant HD-1730 1 to L.G.P. 2 Abbreviations: LHC, light-harvesting complex of photosystem II; DCI, 2,6-dichlorophenolindophenol; LHCP, light-harvesting Chl a/ b-binding apoprotein; F, fluorescence intensity; Fm, maximal fluorescence intensity of intact membranes; Fa, fluorescence intensity of Chl a after dissociation of LHCs with detergent. 1321 We took advantage ofthis system to consider two questions regarding thylakoid membrane biogenesis.…”

Preparation of Antibodies against Specific Chloroplast Membrane Polypeptides Associated with the Formation of Photosystems I and II in Chlamydomonas reinhardi y-1

“…As shown in this work, the effect of aIV depends on the donor used, implying that binding of this antiserum might prevent the access of the donor. Possibly, the effect is more evident when DPC is used as an donor, since its oxidation is a rate limiting reaction of PSII in C. reinhardi (5).…”