Relation between the Light-Harvesting Chlorophyll a-Protein Complex LHCPa and Photosystem I in the Alga Chlamydobotrys stellata

Abstract

ABSTRACT

Hydrogen Photoevolution Indicates an Increase in the Antenna Size of Photosystem I in Chlamydobotrys stellata during Transition from Autotrophic to Photoheterotrophic Nutrition

“…Because all of the H2 photoevolution measurements were carried out on the basis of equal Chl content of the samples, an increase in both the number of PSI reaction centers and their antenna size involves a concomitant decrease in the contribution of Chl to PSII units. The changes in the antenna sizes of PSI and PSII are in good correlation with the results of gel electrophoresis analysis (7,8). During transition of the algae from autotrophy to photoheterotrophy, the amounts of lightharvesting Chl protein complexes of PSI, CPI, and LHCPa quickly increased, with a simultaneous decrease in the amount of LHCPb.…”

“…Moreover, a 10-fold acceleration of the oxidation of Cyt b563 (21) in the photoheterotrophic algae also indicates an enhanced rate of cyclic electron transport and phosphorylation in the heterotrophic cells. The increase in the antenna size of PSI (Table I), with a simultaneous decrease in LHCPb and a concomitant de novo synthesis of the light-harvesting system of PSI, CPI, and LHCPa (7,8), the disorganized membrane structure (28), the extremely lowered room temperature fluorescence yield (30), the faster turnover rate of PSI (Table II), and diminished electron transport rate of PSII (29), as well as the smaller Chl (a + b)/P700 ratio (Table II) observed during transition of C.…”

“…Under heterotrophic culture conditions when CO2 is replaced by acetate, 02 evolution is abolished and only PSI activity is necessary for acetate metabolism (26,27). In the photoheterophic cells, the membrane structure of the chloroplasts is almost grana free (28) and the amount of LHCPb2 is diminished (7,8 2 Abbreviations: LHCPb, light-harvesting chlorophyll a/b protein complex related to PSII; LHCPa, light-harvesting chlorophyll a protein complex related to PSI; DCPIP, 2,6-dichlorophenolindophenol; CPI, chlorophyll a protein complex associated with PSI; MV, methylviologen; P700, reaction center chlorophyll of PSI; PA, photoauthe loss of LHCPb, which supplies both PSII and PSI with energy in autotrophically grown C. stellata cells, is greatly overcompensated for by the synthesis of the Chl a protein complex of PSI, CPI, and by de novo formation of LHCPa (7). These changes in the composition of choroplast membranes during transition from autotrophic to photoheterotrophic cultivation should be reflected in the functional characteristics of the photosynthetic apparatus.…”

Induction of the De Novo Formation of the Photosystem I-Related Light-Harvesting Chlorophyll Protein Complex LHCPa by Photoheterotrophic Nutrition

“…Moreover, the CPIa functioning as light-harvesting system for PSI in higher plants is absent in C. stellata (5). Under photoheterotrophic conditions, therefore, the loss of LHCPb, which supplies PSII and PSI with energy (3) in autotrophically grown Chiamydobotrys cells, is compensated by the de novo formation ofthe LHCPa, which is an integrated component of the PSI in C. stellata (6).…”