Relationship Between Photochemical Quenching and Non-Photochemical Quenching in Six Species of Cyanobacteria Reveals Species Difference in Redox State and Species Commonality in Energy Dissipation
Although the photosynthetic reaction center is well conserved among different cyanobacterial species, the modes of metabolism, e.g. respiratory, nitrogen and carbon metabolism and their mutual interaction, are quite diverse. To explore such uniformity and diversity among cyanobacteria, here we compare the influence of the light environment on the condition of photosynthetic electron transport through Chl fluorescence measurement of six cyanobacterial species grown under the same photon flux densities and at the same temperature. In the dark or under weak light, up to growth light, a large difference in the plastoquinone (P...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Misumi, M., Katoh, H., Tomo, T., Sonoike, K. Tags: Special Focus Issue - Regular Papers Source Type: research
Contribution of PsbS Function and Stomatal Conductance to Foliar Temperature in Higher Plants
Natural capacity has evolved in higher plants to absorb and harness excessive light energy. In basic models, the majority of absorbed photon energy is radiated back as fluorescence and heat. For years the proton sensor protein PsbS was considered to play a critical role in non-photochemical quenching (NPQ) of light absorbed by PSII antennae and in its dissipation as heat. However, the significance of PsbS in regulating heat emission from a whole leaf has never been verified before by direct measurement of foliar temperature under changing light intensity. To test its validity, we here investigated the foliar temperature ch...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Kulasek, M., Bernacki, M. J., Ciszak, K., Witon, D., Karpinski, S. Tags: Special Focus Issue - Regular Papers Source Type: research
Allocation of Absorbed Light Energy in Photosystem II in NPQ Mutants of Arabidopsis
To analyze changes of energy allocation in PSII at non-steady state photosynthesis, the induction and relaxation of non-photochemical quenching of Chl fluorescence was re-evaluated with the use of Arabidopsis thaliana mutants in which the ability to induce non-photochemical quenching was either enhanced (npq2) or suppressed (npq1 and npq4). When dark-treated leaves of the wild type (WT) were illuminated, very high f,D, which represents the loss of excitation energy via non-regulated dissipation, at the beginning of light illumination was gradually decreased to the steady-state level. In contrast, NPQ, representing regulate...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Ikeuchi, M., Sato, F., Endo, T. Tags: Special Focus Issue - Regular Papers Source Type: research
The Flavodiiron Protein Flv3 Functions as a Homo-Oligomer During Stress Acclimation and is Distinct from the Flv1/Flv3 Hetero-Oligomer Specific to the O2 Photoreduction Pathway
The flavodiiron proteins (FDPs) Flv1 and Flv3 in cyanobacteria function in photoreduction of O2 to H2O, without concomitant formation of reactive oxygen species, known as the Mehler-like reaction. Both Flv1 and Flv3 are essential for growth under fluctuating light (FL) intensities, providing protection for PSI. Here we compared the global transcript profiles of the wild type (WT), flv1 and flv1/flv3 grown under constant light (GL) and FL. In the WT, FL induced the largest down-regulation in transcripts involved in carbon-concentrating mechanisms (CCMs), while those of the nitrogen assimilation pathways increased as compare...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Mustila, H., Paananen, P., Battchikova, N., Santana-Sanchez, A., Muth-Pawlak, D., Hagemann, M., Aro, E.-M., Allahverdiyeva, Y. Tags: Special Focus Issue - Regular Papers Source Type: research
Analysis of Photosystem I Donor and Acceptor Sides with a New Type of Online-Deconvoluting Kinetic LED-Array Spectrophotometer
The newly developed Dual/KLAS-NIR spectrophotometer, technical details of which were reported very recently, is used in measuring redox changes of P700, plastocyanin (PC) and ferredoxin (Fd) in intact leaves of Hedera helix, Taxus baccata and Brassica napus. An overview of various light-/dark-induced changes of deconvoluted P700+, PC+ and Fd– signals is presented demonstrating the wealth of novel information and the consistency of the obtained results. Fd– changes are particularly large after dark adaptation. PC oxidation precedes P700 oxidation during dark–light induction and in steady-state light respon...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Schreiber, U., Klughammer, C. Tags: Special Focus Issue - Regular Papers Source Type: research
Reduction-Induced Suppression of Electron Flow (RISE) in the Photosynthetic Electron Transport System of Synechococcus elongatus PCC 7942
This study aims to elucidate the molecular mechanism for the oxidation of reaction center Chl of PSI, P700, after saturated pulse (SP) light illumination of the cyanobacterium Synechococcus elongatus PCC 7942 under steady-state photosynthetic conditions. Both P700 and NADPH were transiently oxidized after SP light illumination under CO2-depleted photosynthesis conditions. In contrast, the Chl fluorescence intensity transiently increased. Compared with the wild type, the increase in Chl fluorescence and the oxidations of P700 and NADPH were greatly enhanced in a mutant (flv1/3) deficient in the genes encoding FLAVODIIRON 1 ...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Shaku, K., Shimakawa, G., Hashiguchi, M., Miyake, C. Tags: Special Focus Issue - Regular Papers Source Type: research
Reactive Carbonyl Species Activate Caspase-3-Like Protease to Initiate Programmed Cell Death in Plants
Reactive oxygen species (ROS)-triggered programmed cell death (PCD) is a typical plant response to biotic and abiotic stressors. We have recently shown that lipid peroxide-derived reactive carbonyl species (RCS), downstream products of ROS, mediate oxidative signal to initiate PCD. Here we investigated the mechanism by which RCS initiate PCD. Tobacco Bright Yellow-2 cultured cells were treated with acrolein, one of the most potent RCS. Acrolein at 0.2 mM caused PCD in 5 h (i.e. lethal), but at 0.1 mM it did not (sublethal). Specifically, these two doses caused critically different effects on the cells. Both lethal and subl...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Biswas, M. S., Mano, J. Tags: Special Focus Issue - Regular Papers Source Type: research
Mitochondrial Alternative Pathway-Associated Photoprotection of Photosystem II is Related to the Photorespiratory Pathway
Respiratory electron transport has two ubiquinol-oxidizing pathways, the cytochrome pathway (CP) and the alternative pathway (AP). The AP, which is catalyzed by the alternative oxidase (AOX), is energetically wasteful but may alleviate PSII photoinhibition under light conditions excessive for photosynthesis. However, its mechanism remains unknown. We used Arabidopsis aox1a mutants lacking AOX activity and studied the mutation’s effects on photoinhibition by measuring the decrease in the maximum quantum yield of PSII (Fv/Fm) after high light exposure. Since the CP compensates for the lack of AOX, we monitored the exte...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Watanabe, C. K. A., Yamori, W., Takahashi, S., Terashima, I., Noguchi, K. Tags: Special Focus Issue - Regular Papers Source Type: research
Redox-Dependent Conformational Dynamics of Decameric 2-Cysteine Peroxiredoxin and its Interaction with Cyclophilin 20-3
2-Cysteine peroxiredoxins (2-CysPrxs) switch between functions as a thiol peroxidase, chaperone, an interaction partner and possibly a proximity-based oxidase in a redox-dependent manner. In photosynthetic eukaryotes, 2-CysPrx localizes to the plastid, functions in the context of photosynthesis and enables an ascorbate peroxidase-independent water–water cycle for detoxifying H2O2. The high degree of evolutionary conservation of 2-CysPrx suggests that the switching is an essential characteristic and needed to transduce redox information to downstream pathways and regulation. The study aimed at exploring the dissociati...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Liebthal, M., Strüve, M., Li, X., Hertle, Y., Maynard, D., Hellweg, T., Viehhauser, A., Dietz, K.-J. Tags: Special Focus Issue - Regular Papers Source Type: research
Elucidation of Photoprotective Mechanisms of PSI Against Fluctuating Light photoinhibition
It has been claimed that the cyclic electron flow around PSI (CEF-PSI) plays an important role in protection of PSI against fluctuating light photoinhibition. However, the photoprotective mechanism of PSI is not fully elucidated. Here, we examined the mechanism, using two CEF-PSI mutants of Arabidopsis thaliana, and antimycin A, an inhibitor of the PGR5 (proton gradient regulation 5)-mediated CEF-PSI. Dark-adapted leaves in these plants were illuminated in fluctuating light alternating between high light at 1,200 µmol m–2 s–1 and low light at 30 µmol m–2 s–1 every 2 min, and PSI and PSII...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Kono, M., Terashima, I. Tags: Special Focus Issue - Regular Papers Source Type: research
The Mechanisms of Oxygen Reduction in the Terminal Reducing Segment of the Chloroplast Photosynthetic Electron Transport Chain
The review is dedicated to ascertainment of the roles of the electron transfer cofactors of the pigment–protein complex of PSI, ferredoxin (Fd) and ferredoxin-NADP reductase in oxygen reduction in the photosynthetic electron transport chain (PETC) in the light. The data regarding oxygen reduction in other segments of the PETC are briefly analyzed, and it is concluded that their participation in the overall process in the PETC under unstressful conditions should be insignificant. Data concerning the contribution of Fd to the oxygen reduction in the PETC are examined. A set of collateral evidence as well as results of ...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Kozuleva, M. A., Ivanov, B. N. Tags: Special Focus Issue - Mini Reviews Source Type: research
Plastid Terminal Oxidase as a Route to Improving Plant Stress Tolerance: Known Knowns and Known Unknowns
A plastid-localized terminal oxidase, PTox, was first described due to its role in chloroplast development, with plants lacking PTox producing white sectors on their leaves. This phenotype is explained as being due to PTox playing a role in carotenoid biosynthesis, as a cofactor of phytoene desaturase. Co-occurrence of PTox with a chloroplast-localized NADPH dehydrogenase (NDH) has suggested the possibility of a functional respiratory pathway in plastids. Evidence has also been found that, in certain stress-tolerant plant species, PTox can act as an electron acceptor from PSII, making it a candidate for engineering stress-...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Johnson, G. N., Stepien, P. Tags: Special Focus Issue - Mini Reviews Source Type: research
Diversity and Evolution of Ascorbate Peroxidase Functions in Chloroplasts: More Than Just a Classical Antioxidant Enzyme?
Reactive oxygen species (ROS) have dual functions in plant cells as cytotoxic molecules and emergency signals. The balance between the production and scavenging of these molecules in chloroplasts, major sites for the production of ROS, is one of the key determinants for plant acclimation to stress conditions. The water–water cycle is a crucial regulator of ROS levels in chloroplasts. In this cycle, the stromal and thylakoid membrane-attached isoforms of ascorbate peroxidase (sAPX and tAPX, respectively) are involved in the metabolism of H2O2. Current genome and phylogenetic analyses suggest that the first monofunctio...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Maruta, T., Sawa, Y., Shigeoka, S., Ishikawa, T. Tags: Special Focus Issue - Mini Reviews Source Type: research
ROS Generation in Peroxisomes and its Role in Cell Signaling
In plant cells, as in most eukaryotic organisms, peroxisomes are probably the major sites of intracellular H2O2 production, as a result of their essentially oxidative type of metabolism. In recent years, it has become increasingly clear that peroxisomes carry out essential functions in eukaryotic cells. The generation of the important messenger molecule hydrogen peroxide (H2O2) by animal and plant peroxisomes and the presence of catalase in these organelles has been known for many years, but the generation of superoxide radicals (O2·–) and the occurrence of the metalloenzyme superoxide dismutase was reported f...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: del Rio, L. A., Lopez-Huertas, E. Tags: Special Focus Issue - Mini Reviews Source Type: research
The Water to Water Cycles in Microalgae
In oxygenic photosynthesis, light produces ATP plus NADPH via linear electron transfer, i.e. the in-series activity of the two photosystems: PSI and PSII. This process, however, is thought not to be sufficient to provide enough ATP per NADPH for carbon assimilation in the Calvin–Benson–Bassham cycle. Thus, it is assumed that additional ATP can be generated by alternative electron pathways. These circuits produce an electrochemical proton gradient without NADPH synthesis, and, although they often represent a small proportion of the linear electron flow, they could have a huge importance in optimizing CO2 assimil...
Source: Plant and Cell Physiology - July 7, 2016 Category: Cytology Authors: Curien, G., Flori, S., Villanova, V., Magneschi, L., Giustini, C., Forti, G., Matringe, M., Petroutsos, D., Kuntz, M., Finazzi, G. Tags: Special Focus Issue - Invited Review Source Type: research
