scholarly journals The role of respiration in the activation of photosynthesis upon illumination of dark adapted Chlamydomonas reinhardtii

2008 ◽  
Vol 1777 (11) ◽  
pp. 1449-1454 ◽  
Author(s):  
Giorgio Forti
Author(s):  
Franco V. A. Camargo ◽  
Federico Perozeni ◽  
Gabriel de la Cruz Valbuena ◽  
Luca Zuliani ◽  
Samim Sardar ◽  
...  

2002 ◽  
Vol 29 (10) ◽  
pp. 1141 ◽  
Author(s):  
Govindjee ◽  
Manfredo J. Seufferheld

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.


2001 ◽  
Vol 359 (1) ◽  
pp. 65-75 ◽  
Author(s):  
Valeria MENCHISE ◽  
Catherine CORBIER ◽  
Claude DIDIERJEAN ◽  
Michele SAVIANO ◽  
Ettore BENEDETTI ◽  
...  

Thioredoxins are ubiquitous proteins which catalyse the reduction of disulphide bridges on target proteins. The catalytic mechanism proceeds via a mixed disulphide intermediate whose breakdown should be enhanced by the involvement of a conserved buried residue, Asp-30, as a base catalyst towards residue Cys-39. We report here the crystal structure of wild-type and D30A mutant thioredoxin h from Chlamydomonas reinhardtii, which constitutes the first crystal structure of a cytosolic thioredoxin isolated from a eukaryotic plant organism. The role of residue Asp-30 in catalysis has been revisited since the distance between the carboxylate OD1 of Asp-30 and the sulphur SG of Cys-39 is too great to support the hypothesis of direct proton transfer. A careful analysis of all available crystal structures reveals that the relative positioning of residues Asp-30 and Cys-39 as well as hydrophobic contacts in the vicinity of residue Asp-30 do not allow a conformational change sufficient to bring the two residues close enough for a direct proton transfer. This suggests that protonation/deprotonation of Cys-39 should be mediated by a water molecule. Molecular-dynamics simulations, carried out either in vacuo or in water, as well as proton-inventory experiments, support this hypothesis. The results are discussed with respect to biochemical and structural data.


2022 ◽  
Author(s):  
Xin Liu ◽  
Wojciech J Nawrocki ◽  
Roberta Croce

Non-photochemical quenching (NPQ) is the process that protects photosynthetic organisms from photodamage by dissipating the energy absorbed in excess as heat. In the model green alga Chlamydomonas reinhardtii, NPQ was abolished in the knock-out mutants of the pigment-protein complexes LHCSR3 and LHCBM1. However, while LHCSR3 was shown to be a pH sensor and switching to a quenched conformation at low pH, the role of LHCBM1 in NPQ has not been elucidated yet. In this work, we combine biochemical and physiological measurements to study short-term high light acclimation of npq5, the mutant lacking LHCBM1. We show that while in low light in the absence of this complex, the antenna size of PSII is smaller than in its presence, this effect is marginal in high light, implying that a reduction of the antenna is not responsible for the low NPQ. We also show that the mutant expresses LHCSR3 at the WT level in high light, indicating that the absence of this complex is also not the reason. Finally, NPQ remains low in the mutant even when the pH is artificially lowered to values that can switch LHCSR3 to the quenched conformation. It is concluded that both LHCSR3 and LHCBM1 need to be present for the induction of NPQ and that LHCBM1 is the interacting partner of LHCSR3. This interaction can either enhance the quenching capacity of LHCSR3 or connect this complex with the PSII supercomplex.


2012 ◽  
Vol 1817 (8) ◽  
pp. 1248-1255 ◽  
Author(s):  
Maria A. Sinetova ◽  
Elena V. Kupriyanova ◽  
Alexandra G. Markelova ◽  
Suleyman I. Allakhverdiev ◽  
Natalia A. Pronina

1987 ◽  
Vol 126 (4-5) ◽  
pp. 467-473 ◽  
Author(s):  
Reiner Dolle ◽  
Jürgen Pfau ◽  
Wilhelm Nultsch

PLoS Genetics ◽  
2020 ◽  
Vol 16 (6) ◽  
pp. e1008814 ◽  
Author(s):  
Takuya Matsuo ◽  
Takahiro Iida ◽  
Ayumi Ohmura ◽  
Malavika Gururaj ◽  
Daisaku Kato ◽  
...  

Cells ◽  
2018 ◽  
Vol 7 (7) ◽  
pp. 79 ◽  
Author(s):  
Jenna Wingfield ◽  
Karl-Ferdinand Lechtreck

During ciliogenesis, centrioles convert to membrane-docked basal bodies, which initiate the formation of cilia/flagella and template the nine doublet microtubules of the flagellar axoneme. The discovery that many human diseases and developmental disorders result from defects in flagella has fueled a strong interest in the analysis of flagellar assembly. Here, we will review the structure, function, and development of basal bodies in the unicellular green alga Chlamydomonas reinhardtii, a widely used model for the analysis of basal bodies and flagella. Intraflagellar transport (IFT), a flagella-specific protein shuttle critical for ciliogenesis, was first described in C. reinhardtii. A focus of this review will be on the role of the basal bodies in organizing the IFT machinery.


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