Effect of dissolved inorganic carbon on oxygen evolution and uptake by Chlamydomonas reinhardtii suspensions adapted to ambient and CO2-enriched air

1987 ◽  
Vol 12 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Dieter F. S�ltemeyer ◽  
Klaus Klug ◽  
Heinrich P. Fock
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Oxygen Evolution ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon

Active uptake of inorganic carbon by Chlamydomonas reinhardtii: evidence for simultaneous transport of HCO3− and CO2 and characterization of active CO2 transport

1991 ◽  
Vol 69 (5) ◽  
pp. 995-1002 ◽  
Author(s):  
Dieter F. Sültemeyer ◽  
Heinrich P. Fock ◽  
David T. Canvin
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Transport Mechanism ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Ambient Air ◽  
Whole Cells ◽  
High Affinity ◽  
Atp Formation ◽  
Cyclic Photophosphorylation

Washed protoplasts of low CO2 grown cells of Chlamydomonas reinhardtii were used to further characterize the ability for active CO2 transport. The CO2 transport mechanism and the high affinity for dissolved inorganic carbon were completely induced within 4 h after transferring 5% CO2 grown cells to ambient air (0.035% CO2). Net O2 evolution and CO2 uptake were saturable processes showing saturation between 100 and 200 μM DIC (1.6–3.2 μM CO2) at pH 8.0. For both O2 evolution in whole cells and CO2 uptake in the protoplasts the concentration of dissolved inorganic carbon required for 50% of the maximal rates was about 12 μM (= 0.20 μM CO2). Studies with 3-(3,4-dichloro-phenyl)-1,1 dimethylurea, dibromo-thymoquinone, tetramethyl phenylenediamine and protoplasts of a cytochrome c oxidase deficient mutant of C. reinhardtii indicated the CO2 transport was driven by cyclic or pseudocyclic ATP formation and oxidative phosphorylation was not involved. These studies also show that CO2 transport and CO2 fixation are distinct mechanisms and that active CO2 uptake may occur in the absence of CO2 fixation. Key words: Chlamydomonas reinhardtii; CO2–HCO3− concentrating mechanism, CO2 transport, cyclic photophosphorylation, pseudocyclic photophosphorylation.

Non-photochemical quenching of chlorophyll a fluorescence: early history and characterization of two xanthophyll-cycle mutants of Chlamydomonas reinhardtii

2002 ◽  
Vol 29 (10) ◽  
pp. 1141 ◽  
Author(s):  
Govindjee ◽  
Manfredo J. Seufferheld
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Oxygen Evolution ◽  
Xanthophyll Cycle ◽  
Photochemical Quenching ◽  
Chl A ◽  
Fluorescence Transient ◽  
Chl A Fluorescence ◽  
Non Photochemical Quenching

This paper deals first with the early, although incomplete, history of photoinhibition, of 'non-QA-related chlorophyll (Chl) a fluorescence changes', and the xanthophyll cycle that preceded the discovery of the correlation between non-photochemical quenching of Chl a fluorescence (NPQ) and conversion of violaxanthin to zeaxanthin. It includes the crucial observation that the fluorescence intensity quenching, when plants are exposed to excess light, is indeed due to a change in the quantum yield of fluorescence. The history ends with a novel turn in the direction of research — isolation and characterization of NPQ xanthophyll-cycle mutants of Chlamydomonas reinhardtii Dangeard and Arabidopsis thaliana (L.) Heynh., blocked in conversion of violaxanthin to zeaxanthin, and zeaxanthin to violaxanthin, respectively. In the second part of the paper, we extend the characterization of two of these mutants (npq1, which accumulates violaxanthin, and npq2, which accumulates zeaxanthin) through parallel measurements on growth, and several assays of PSII function: oxygen evolution, Chl a fluorescence transient (the Kautsky effect), the two-electron gate function of PSII, the back reactions around PSII, and measurements of NPQ by pulse-amplitude modulation (PAM 2000) fluorimeter. We show that, in the npq2 mutant, Chl a fluorescence is quenched both in the absence and presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). However, no differences are observed in functioning of the electron-acceptor side of PSII — both the two-electron gate and the back reactions are unchanged. In addition, the role of protons in fluorescence quenching during the 'P-to-S' fluorescence transient was confirmed by the effect of nigericin in decreasing this quenching effect. Also, the absence of zeaxanthin in the npq1 mutant leads to reduced oxygen evolution at high light intensity, suggesting another protective role of this carotenoid. The available data not only support the current model of NPQ that includes roles for both pH and the xanthophylls, but also are consistent with additional protective roles of zeaxanthin. However, this paper emphasizes that we still lack sufficient understanding of the different parts of NPQ, and that the precise mechanisms of photoprotection in the alga Chlamydomonas may not be the same as those in higher plants.

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