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Saroussi S, Redekop P, Karns DAJ, Thomas DC, Wittkopp TM, Posewitz MC, Grossman AR. Restricting electron flow at cytochrome b6f when downstream electron acceptors are severely limited. PLANT PHYSIOLOGY 2023; 192:789-804. [PMID: 36960590 PMCID: PMC10231464 DOI: 10.1093/plphys/kiad185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 06/01/2023]
Abstract
Photosynthetic organisms frequently experience abiotic stress that restricts their growth and development. Under such circumstances, most absorbed solar energy cannot be used for CO2 fixation and can cause the photoproduction of reactive oxygen species (ROS) that can damage the photosynthetic reaction centers of PSI and PSII, resulting in a decline in primary productivity. This work describes a biological "switch" in the green alga Chlamydomonas reinhardtii that reversibly restricts photosynthetic electron transport (PET) at the cytochrome b6f (Cyt b6f) complex when the capacity for accepting electrons downstream of PSI is severely limited. We specifically show this restriction in STARCHLESS6 (sta6) mutant cells, which cannot synthesize starch when they are limited for nitrogen (growth inhibition) and subjected to a dark-to-light transition. This restriction represents a form of photosynthetic control that causes diminished electron flow to PSI and thereby prevents PSI photodamage but does not appear to rely on a ΔpH. Furthermore, when electron flow is restricted, the plastid alternative oxidase (PTOX) becomes active, functioning as an electron valve that dissipates some excitation energy absorbed by PSII and allows the formation of a proton motive force (PMF) that would drive some ATP production (potentially sustaining PSII repair and nonphotochemical quenching [NPQ]). The restriction at the Cyt b6f complex can be gradually relieved with continued illumination. This study provides insights into how PET responds to a marked reduction in availability of downstream electron acceptors and the protective mechanisms involved.
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Affiliation(s)
- Shai Saroussi
- Department of Plant Biology, The Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Petra Redekop
- Department of Plant Biology, The Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Devin A J Karns
- Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401, USA
| | - Dylan C Thomas
- Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401, USA
| | - Tyler M Wittkopp
- Department of Plant Biology, The Carnegie Institution for Science, Stanford, CA 94305, USA
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Matthew C Posewitz
- Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401, USA
| | - Arthur R Grossman
- Department of Plant Biology, The Carnegie Institution for Science, Stanford, CA 94305, USA
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2
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Degen GE. A tale of two CETs: Untangling cyclic electron transfer. PLANT PHYSIOLOGY 2023; 192:7-9. [PMID: 36787230 PMCID: PMC10152672 DOI: 10.1093/plphys/kiad088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/17/2023] [Accepted: 01/17/2023] [Indexed: 05/03/2023]
Affiliation(s)
- Gustaf E Degen
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK
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3
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Zhou Q, Yamamoto H, Shikanai T. Distinct contribution of two cyclic electron transport pathways to P700 oxidation. PLANT PHYSIOLOGY 2023; 192:326-341. [PMID: 36477622 PMCID: PMC10152692 DOI: 10.1093/plphys/kiac557] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 11/09/2022] [Accepted: 11/10/2022] [Indexed: 05/03/2023]
Abstract
Cyclic electron transport (CET) around Photosystem I (PSI) acidifies the thylakoid lumen and downregulates electron transport at the cytochrome b6f complex. This photosynthetic control is essential for oxidizing special pair chlorophylls (P700) of PSI for PSI photoprotection. In addition, CET depending on the PROTON GRADIENT REGULATION 5 (PGR5) protein oxidizes P700 by moving a pool of electrons from the acceptor side of PSI to the plastoquinone pool. This model of the acceptor-side regulation was proposed on the basis of the phenotype of the Arabidopsis (Arabidopsis thaliana) pgr5-1 mutant expressing Chlamydomonas (Chlamydomonas reinhardtii) plastid terminal oxidase (CrPTOX2). In this study, we extended the research including the Arabidopsis chlororespiratory reduction 2-2 (crr2-2) mutant defective in another CET pathway depending on the chloroplast NADH dehydrogenase-like (NDH) complex. Although the introduction of CrPTOX2 did not complement the defect in the acceptor-side regulation by PGR5, the function of the NDH complex was complemented except for its reverse reaction during the induction of photosynthesis. We evaluated the impact of CrPTOX2 under fluctuating light intensity in the wild-type, pgr5-1 and crr2-2 backgrounds. In the high-light period, both PGR5- and NDH-dependent CET were involved in the induction of photosynthetic control, whereas PGR5-dependent CET preferentially contributed to the acceptor-side regulation. On the contrary, the NDH complex probably contributed to the acceptor-side regulation in the low-light period but not in the high-light period. We evaluated the sensitivity of PSI to fluctuating light and clarified that acceptor-side regulation was necessary for PSI photoprotection by oxidizing P700 under high light.
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Affiliation(s)
- Qi Zhou
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Hiroshi Yamamoto
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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4
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Meng X, Bai S, Wang S, Pan Y, Chen K, Xie K, Wang M, Guo S. The sensitivity of photosynthesis to magnesium deficiency differs between rice ( Oryza sativa L.) and cucumber ( Cucumis sativus L.). FRONTIERS IN PLANT SCIENCE 2023; 14:1164866. [PMID: 37123833 PMCID: PMC10141327 DOI: 10.3389/fpls.2023.1164866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 03/27/2023] [Indexed: 05/03/2023]
Abstract
Magnesium is an essential macronutrient for plant photosynthesis, and in response to Mg deficiency, dicots appear more sensitive than monocots. Under Mg deficiency, we investigated the causes of differing photosynthetic sensitivities in a dicot and a monocot species. Rice (Oryza sativa L.) and cucumber (Cucumis sativus L.) were grown in hydroponic culture to explore their physiological responses to Mg deficiency stress. Both Mg-deficient rice and cucumber plants exhibited lower biomass, leaf area, Mg concentration, and chlorophyll content (Chl) compared with Mg-sufficient plants. However, a more marked decline in Chl and carotenoid content (Car) occurred in cucumber. A lower CO2 concentration in chloroplasts (C c) was accompanied by a decrease in the maximum rate of electron transport (J max) and the maximum rate of ribulose 1,5-bisphosphate carboxylation (V cmax), restricting CO2 utilization in Mg-deficient plants. Rice and cucumber photorespiration rate (P r) increased under Mg deficiency. Additionally, for cucumber, Car and non-photochemical quenching (NPQ) were reduced under lower Mg supply. Meanwhile, cucumber Mg deficiency significantly increased the fraction of absorbed light energy dissipated by an additional quenching mechanism (Φf,D). Under Mg deficiency, suppressed photosynthesis was attributed to comprehensive restrictions of mesophyll conductance (g m), J max, and V cmax. Cucumber was more sensitive to Mg deficiency than rice due to lower NPQ, higher rates of electron transport to alternative pathways, and subsequently, photooxidation damage.
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Affiliation(s)
- Xusheng Meng
- Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, The Key Laboratory of Plant Immunity, Nanjing Agricultural University, Nanjing, China
| | - Song Bai
- Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, China
| | - Shiyu Wang
- Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, The Key Laboratory of Plant Immunity, Nanjing Agricultural University, Nanjing, China
| | - Yonghui Pan
- Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, The Key Laboratory of Plant Immunity, Nanjing Agricultural University, Nanjing, China
| | - Kehao Chen
- Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, The Key Laboratory of Plant Immunity, Nanjing Agricultural University, Nanjing, China
| | - Kailiu Xie
- Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, The Key Laboratory of Plant Immunity, Nanjing Agricultural University, Nanjing, China
- School of Land Resources and Environment, Jiangxi Agricultural University, Nanchang, China
| | - Min Wang
- Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, The Key Laboratory of Plant Immunity, Nanjing Agricultural University, Nanjing, China
| | - Shiwei Guo
- Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, The Key Laboratory of Plant Immunity, Nanjing Agricultural University, Nanjing, China
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Perera-Castro AV, Flexas J. The ratio of electron transport to assimilation (ETR/A N): underutilized but essential for assessing both equipment's proper performance and plant status. PLANTA 2023; 257:29. [PMID: 36592261 DOI: 10.1007/s00425-022-04063-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Accepted: 12/27/2022] [Indexed: 06/17/2023]
Abstract
ETR/AN ratios should be in the range 7.5-10.5 for non-stressed C3 plants. Ratios extremely out of this range can be reflecting both uncontrolled plant status and technical mistakes during measurements. We urge users to explicitly refer to this ratio in future studies as a proof for internal data quality control. For the last few decades, the use of infra-red gas-exchange analysers (IRGAs) coupled with chlorophyll fluorometers that allow for measurements of net CO2 assimilation rate and estimates of electron transport rate over the same leaf area has been popularized. The evaluation of data from both instruments in an integrative manner can result in additional valuable information, such as the estimation of the light respiration, mesophyll conductance and the partitioning of the flux of electrons into carboxylation, oxygenation and alternative processes, among others. In this review, an additional and more 'straight' use of the combination of chlorophyll fluorescence and gas exchange-derived parameters is presented, namely using the direct ratio between two fully independently estimated parameters, electron transport rate (ETR)-determined by the fluorometer-and net CO2 assimilation rate (AN)-determined by the IRGA, i.e., the ETR/AN ratio, as a tool for fast detection of incongruencies in the data and potential technical problems associated with them, while checking for the study plant's status. To illustrate this application, a compilation of 75 studies that reported both parameters for a total of 178 species under varying physiological status is presented. Values of ETR/AN between 7.5 and 10.5 were most frequently found for non-stressed C3 plants. C4 species showed an average ETR/AN ratio of 4.7. The observed ratios were larger for species with high leaf mass per area and for plants subjected to stressful factors like drought or nutritional deficit. Knowing the expected ETR/AN ratio projects this ratio as a routinary and rapid check point for guaranteeing both the correct performance of equipment and the optimal/stress status of studied plants. All known errors associated with the under- or overestimation of ETR or AN are summarized in a checklist that aims to be routinely used by any IRGA/fluorometer user to strength the validity of their data.
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Affiliation(s)
- Alicia V Perera-Castro
- Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna, Av. Astrofísico Francisco Sánchez, S/N, 38200, La Laguna, Canary Islands, Spain.
| | - Jaume Flexas
- Department of Biology, Agro-Environmental and Water Economics Institute (INAGEA), Universitat de LES Illes Balears, Carretera de Valldemossa Km 7.5, 07122, Palma, Illes Balears, Spain
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Yang Y, Jia Y, Zhao Y, Wang Y, Zhou T. Comparative chloroplast genomics provides insights into the genealogical relationships of endangered Tetraena mongolica and the chloroplast genome evolution of related Zygophyllaceae species. Front Genet 2022; 13:1026919. [PMID: 36568371 PMCID: PMC9773207 DOI: 10.3389/fgene.2022.1026919] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 11/18/2022] [Indexed: 12/13/2022] Open
Abstract
A comprehensive understanding of genetic background for rare species will provide an important theoretical basis for the future species management, monitoring and conservation. Tetraena mongolica is restrictedly distributed in the western Ordos plateau of China and has been listed as a national protected plant. We generated 13 chloroplast (cp) genomes of T. mongolica (size range of 106,062-106,230 bp) and conducted a series of comparative analyses of six Zygophyllaceae cp genomes. T. mongolica cp genome exhibited a quadripartite structure with drastically reduced inverted repeats (IRs, 4,315 bp) and undergone the loss of a suit of ndh genes and a copy of rRNAs. Furthermore, all the T. mongolica populations were divided into two genetic groups based on complete cp phylogenomics. In addition, notably variable genome size, gene order and structural changes had been observed among the six Zygophyllaceae cp genomes. Overall, our findings provide insights into the cp genome evolution mode and intraspecific relationships of T. mongolica, and provide a molecular basis for scientific conservation of this endangered plant.
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Affiliation(s)
- Yanci Yang
- School of Biological Science and Technology, Baotou Teachers’ College, Baotou, China
| | - Yun Jia
- Xi’an Botanical Garden of Shaanxi Province, Institute of Botany of Shaanxi Province, Xi’an, Shaanxi, China
| | - Yanling Zhao
- School of Biological Science and Technology, Baotou Teachers’ College, Baotou, China
| | - Yonglong Wang
- School of Biological Science and Technology, Baotou Teachers’ College, Baotou, China,*Correspondence: Yonglong Wang, ; Tao Zhou,
| | - Tao Zhou
- School of Pharmacy, Xi’an Jiaotong University, Xi’an, Shaanxi, China,*Correspondence: Yonglong Wang, ; Tao Zhou,
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Krawczyk K, Myszczyński K, Nobis M, Sawicki J. Insights into adaptive evolution of plastomes in Stipa L. (Poaceae). BMC PLANT BIOLOGY 2022; 22:525. [PMID: 36372890 PMCID: PMC9661759 DOI: 10.1186/s12870-022-03923-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 11/01/2022] [Indexed: 06/03/2023]
Abstract
BACKGROUND The study presents results of research on the evolution of plastid genomes in Stipa L. which is a large genus of the Poaceae family, comprising species diverse in terms of geographic distribution, growing under highly variated habitat conditions. Complete plastome sequences of 43 taxa from Stipeae and Ampelodesmae tribes were analyzed for the variability of the coding regions against the background of phylogenetic relationships within the genus Stipa. The research hypothesis put forward in our research was that some of coding regions are affected by a selection pressure differentiated between individual phylogenetic lines of Stipa, potentially reducing the phylogenetic informativeness of these CDS. The study aimed to answer the question, which genes evolve in Stipa most rapidly and what kind of changes in the properties of encoded amino acids this entails. Another goal of this research was to find out whether individual genes are affected by positive selection and finally, whether selective pressure is uniform within the genus or does it vary between particular evolutionary lines within the genus. RESULTS Results of our study proved the presence of selective pressure in 11 genes: ccsA, matK, ndhC, ndhF, ndhK, rbcL, rpoA rpoC1, rpoC2, rps8 and rps11. For the first time the effect of positive selection on the rps8, rps11, and ndhK genes was documented in grasses. The varied pace of evolution, different intensity and effects of selective pressure have been demonstrated between particular phylogenetic lines of the genus tested. CONCLUSIONS Positive selection in plastid genome in Stipa mostly affects photosynthetic genes. The potential strongest adaptive pressure was observed in the rbcL gene, especially in the oldest evolutionary group comprising Central Asian high-mountain species: S. basiplumosa, S. klimesii, S. penicillata and S. purpurea, where adaptive pressure probably affected the amino acids directly related to the efficiency of CO2 assimilation.
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Affiliation(s)
- Katarzyna Krawczyk
- Department of Botany and Nature Protection, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Plac Łódzki 1, 10-727, Olsztyn, Poland.
| | - Kamil Myszczyński
- Laboratory of Translational Oncology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Dębinki 1, 80-211, Gdańsk, Poland
| | - Marcin Nobis
- Institute of Botany, Faculty of Biology, Jagiellonian University, Gronostajowa 3, 30-387, Kraków, Poland
| | - Jakub Sawicki
- Department of Botany and Nature Protection, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Plac Łódzki 1, 10-727, Olsztyn, Poland
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Popova AV, Stefanov M, Ivanov AG, Velitchkova M. The Role of Alternative Electron Pathways for Effectiveness of Photosynthetic Performance of Arabidopsis thaliana, Wt and Lut2, under Low Temperature and High Light Intensity. PLANTS 2022; 11:plants11172318. [PMID: 36079699 PMCID: PMC9460638 DOI: 10.3390/plants11172318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/22/2022] [Accepted: 09/01/2022] [Indexed: 12/02/2022]
Abstract
A recent investigation has suggested that the enhanced capacity for PSI-dependent cyclic electron flow (CEF) and PSI-dependent energy quenching that is related to chloroplast structural changes may explain the lower susceptibility of lut2 to combined stresses—a low temperature and a high light intensity. The possible involvement of alternative electron transport pathways, proton gradient regulator 5 (PGR5)-dependent CEF and plastid terminal oxidase (PTOX)-mediated electron transfer to oxygen in the response of Arabidopsis plants—wild type (wt) and lut2—to treatment with these two stressors was assessed by using specific electron transport inhibitors. Re-reduction kinetics of P700+ indicated that the capacity for CEF was higher in lut2 when this was compared to wt. Exposure of wt plants to the stress conditions caused increased CEF and was accompanied by a substantial raise in PGR5 and PTOX quantities. In contrast, both PGR5 and PTOX levels decreased under the same stress conditions in lut2, and inhibiting PGR5-dependent pathway by AntA did not exhibit any significant effects on CEF during the stress treatment and recovery period. Electron microscopy observations demonstrated that under control conditions the degree of grana stacking was much lower in lut2, and it almost disappeared under the combined stresses, compared to wt. The role of differential responses of alternative electron transport pathways in the acclimation to the stress conditions that are studied is discussed.
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Affiliation(s)
- Antoaneta V. Popova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
- Correspondence:
| | - Martin Stefanov
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
| | - Alexander G. Ivanov
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
- Department of Biology, University of Western Ontario, 1151 Richmond Str. N., London, ON N6A 5B7, Canada
| | - Maya Velitchkova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
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Suslichenko IS, Trubitsin BV, Vershubskii AV, Tikhonov AN. The noninvasive monitoring of the redox status of photosynthetic electron transport chains in Hibiscus rosa-sinensis and Tradescantia leaves. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2022; 185:233-243. [PMID: 35716433 DOI: 10.1016/j.plaphy.2022.06.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 05/13/2022] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
Abstract
We present an approach to the noninvasive determination of the electron capacity of the intersystem pool of electron carriers in chloroplasts in situ. As apt experimental models, we used the leaves of Hibiscus rosa-sinensis and Tradescantia species. Electron paramagnetic resonance and optical response of P700 (the primary electron donor in Photosystem I) were applied to measuring electron transport in chloroplasts. Electron capacities of the intersystem electron transport chain (ETC) were determined from redox transients of P700 upon chromatic transitions (white light → far-red light). During the induction period, we observed the nonmonotonic changes in the number of electron equivalents in the intersystem ETC per P700 (parameter Q). In Hibiscus rosa-sinensis, the light-induced rise of Q from ≈2.5 (in the dark) to Q ≈ 12 was followed by its decrease to Q ≈ 6. The data obtained are discussed in the context of pH-dependent regulation of electron transport in chloroplasts, which provides the well-balanced operation of the intersystem ETC. The decay of Q is explained by the attenuation of Photosystem II activity due to the lumen acidification and the acceleration of plastoquinol re-oxidation as a result of the Calvin-Benson cycle activation. Our computer model of electron and proton transport coupled to ATP synthesis in chloroplasts was used to analyze the up and down feedbacks responsible for pH-dependent regulation of electron transport in chloroplasts. The procedures introduced here may be important for subsequent works aimed at defining the plastoquinone participation in regulation of photosynthetic processes in chloroplasts in situ.
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Affiliation(s)
- Igor S Suslichenko
- Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Boris V Trubitsin
- Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia
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10
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Zhao J, Jiang Y, Tian Y, Mao J, Wei L, Ma W. New insights into the effect of NdhO levels on cyanobacterial cell death triggered by high temperature. FUNCTIONAL PLANT BIOLOGY : FPB 2022; 49:533-541. [PMID: 34428393 DOI: 10.1071/fp21097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 08/05/2021] [Indexed: 06/13/2023]
Abstract
NdhO, a regulatory oxygenic photosynthesis-specific subunit, is close to the ferredoxin-binding site of cyanobacterial NDH-1, and its levels are negatively associated with the rates of cyclic electron transfer around PSI mediated by NDH-1 (NDH-CET). However, the effect of NdhO levels on cyanobacterial cell death triggered by high temperature remains elusive. Here, our results uncovered a synergistic effect of NdhO levels on the cell death and reactive oxygen species (ROS) accumulation when cyanobacterial cells grown at 30°C for 1 day were transferred to 45°C for 2 days. Such synergistic effect was found to be closely associated with the activities of NDH-CET and CO2 assimilation during high temperature. Collectively, we propose that the effect of NdhO levels on the cyanobacterial cell bleaching and cell death triggered by high temperature is a result of influencing production of ROS by NDH-CET, which is considered to be vital to balance the ATP/NADPH ratio and improve the Calvin-Benson cycle.
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Affiliation(s)
- Jiaohong Zhao
- Shanghai Key laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, 100 Guilin Road, Shanghai 200234, China
| | - Yuanyuan Jiang
- Shanghai Key laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, 100 Guilin Road, Shanghai 200234, China
| | - Yuhao Tian
- Shanghai Key laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, 100 Guilin Road, Shanghai 200234, China
| | - Jun Mao
- Shanghai Key laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, 100 Guilin Road, Shanghai 200234, China
| | - Lanzhen Wei
- Shanghai Key laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, 100 Guilin Road, Shanghai 200234, China; and Corresponding author
| | - Weimin Ma
- Shanghai Key laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, 100 Guilin Road, Shanghai 200234, China; and Corresponding author
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11
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Zhou Q, Wang C, Yamamoto H, Shikanai T. PTOX-dependent safety valve does not oxidize P700 during photosynthetic induction in the Arabidopsis pgr5 mutant. PLANT PHYSIOLOGY 2022; 188:1264-1276. [PMID: 34792607 PMCID: PMC8825263 DOI: 10.1093/plphys/kiab541] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 10/15/2021] [Indexed: 05/19/2023]
Abstract
Plastid terminal oxidase (PTOX) accepts electrons from plastoquinol to reduce molecular oxygen to water. We introduced the gene encoding Chlamydomonas reinhardtii (Cr)PTOX2 into the Arabidopsis (Arabidopsis thaliana) wild-type (WT) and proton gradient regulation5 (pgr5) mutant defective in cyclic electron transport around photosystem I (PSI). The accumulation of CrPTOX2 only mildly affected photosynthetic electron transport in the WT background during steady-state photosynthesis but partly complemented the induction of nonphotochemical quenching (NPQ) in the pgr5 background. During the induction of photosynthesis by actinic light (AL) of 130 µmol photons m-2 s-1, the high level of PSII yield (Y(II)) was induced immediately after the onset of AL in WT plants accumulating CrPTOX2. NPQ was more rapidly induced in the transgenic plants than in WT plants. P700 was also oxidized immediately after the onset of AL. Although CrPTOX2 does not directly induce a proton concentration gradient (ΔpH) across the thylakoid membrane, the coupled reaction of PSII generated ΔpH to induce NPQ and the downregulation of the cytochrome b6f complex. Rapid induction of Y(II) and NPQ was also observed in the pgr5 plants accumulating CrPTOX2. In contrast to the WT background, P700 was not oxidized in the pgr5 background. Although the thylakoid lumen was acidified by CrPTOX2, PGR5 was essential for oxidizing P700. In addition to acidification of the thylakoid lumen to downregulate the cytochrome b6f complex (donor-side regulation), PGR5 may be required for draining electrons from PSI by transferring them to the plastoquinone pool. We propose a reevaluation of the contribution of this acceptor-side regulation by PGR5 in the photoprotection of PSI.
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Affiliation(s)
- Qi Zhou
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Caijuan Wang
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Hiroshi Yamamoto
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
- Author for communication:
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12
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Choi BY, Kim H, Shim D, Jang S, Yamaoka Y, Shin S, Yamano T, Kajikawa M, Jin E, Fukuzawa H, Lee Y. The Chlamydomonas bZIP transcription factor BLZ8 confers oxidative stress tolerance by inducing the carbon-concentrating mechanism. THE PLANT CELL 2022; 34:910-926. [PMID: 34893905 PMCID: PMC8824676 DOI: 10.1093/plcell/koab293] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 11/28/2021] [Indexed: 05/19/2023]
Abstract
Photosynthetic organisms are exposed to various environmental sources of oxidative stress. Land plants have diverse mechanisms to withstand oxidative stress, but how microalgae do so remains unclear. Here, we characterized the Chlamydomonas reinhardtii basic leucine zipper (bZIP) transcription factor BLZ8, which is highly induced by oxidative stress. Oxidative stress tolerance increased with increasing BLZ8 expression levels. BLZ8 regulated the expression of genes likely involved in the carbon-concentrating mechanism (CCM): HIGH-LIGHT ACTIVATED 3 (HLA3), CARBONIC ANHYDRASE 7 (CAH7), and CARBONIC ANHYDRASE 8 (CAH8). BLZ8 expression increased the photosynthetic affinity for inorganic carbon under alkaline stress conditions, suggesting that BLZ8 induces the CCM. BLZ8 expression also increased the photosynthetic linear electron transfer rate, reducing the excitation pressure of the photosynthetic electron transport chain and in turn suppressing reactive oxygen species (ROS) production under oxidative stress conditions. A carbonic anhydrase inhibitor, ethoxzolamide, abolished the enhanced tolerance to alkaline stress conferred by BLZ8 overexpression. BLZ8 directly regulated the expression of the three target genes and required bZIP2 as a dimerization partner in activating CAH8 and HLA3. Our results suggest that a CCM-mediated increase in the CO2 supply for photosynthesis is critical to minimize oxidative damage in microalgae, since slow gas diffusion in aqueous environments limits CO2 availability for photosynthesis, which can trigger ROS formation.
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Affiliation(s)
| | | | - Donghwan Shim
- Department of Biological Sciences, Chungnam National University, Daejeon 34134 Korea
| | - Sunghoon Jang
- Department of Life Science, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | | | - Seungjun Shin
- Department of Life Science, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Takashi Yamano
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | | | - EonSeon Jin
- Department of Life Science, Hanyang University, Seoul 133-791, South Korea
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13
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Rog I, Chaturvedi AK, Tiwari V, Danon A. Low light-regulated intramolecular disulfide fine-tunes the role of PTOX in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 109:585-597. [PMID: 34767654 DOI: 10.1111/tpj.15579] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 11/01/2021] [Accepted: 11/08/2021] [Indexed: 06/13/2023]
Abstract
Disulfide-based regulation links the activity of numerous chloroplast proteins with photosynthesis-derived redox signals. The plastid terminal oxidase (PTOX) is a thylakoid-bound plastoquinol oxidase that has been implicated in multiple roles in the light and in the dark, which could require different levels of PTOX activity. Here we show that Arabidopsis PTOX contains a conserved C-terminus domain (CTD) with cysteines that evolved progressively following the colonization of the land by plants. Furthermore, the CTD contains a regulatory disulfide that is in the oxidized state in the dark and is rapidly reduced, within 5 min, in low light intensity (1-5 µE m-2 sec-1 ). The reduced PTOX form in the light was reoxidized within 15 min after transition to the dark. Mutation of the cysteines in the CTD prevented the formation of the oxidized form. This resulted in higher levels of reduced plastoquinone when measured at transition to the onset of low light. This is consistent with the reduced state of PTOX exhibiting diminished PTOX oxidase activity under conditions of limiting PQH2 substrate. Our findings suggest that AtPTOX-CTD evolved to provide light-dependent regulation of PTOX activity for the adaptation of plants to terrestrial conditions.
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Affiliation(s)
- Ido Rog
- Department of Plant & Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Amit Kumar Chaturvedi
- Department of Plant & Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Vivekanand Tiwari
- Department of Plant & Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Avihai Danon
- Department of Plant & Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
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14
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Ivanov AG, Krol M, Savitch LV, Szyszka-Mroz B, Roche J, Sprott DP, Selstam E, Wilson KW, Gardiner R, Öquist G, Hurry VM, Hüner NPA. The decreased PG content of pgp1 inhibits PSI photochemistry and limits reaction center and light-harvesting polypeptide accumulation in response to cold acclimation. PLANTA 2022; 255:36. [PMID: 35015152 DOI: 10.1007/s00425-022-03819-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 12/27/2021] [Indexed: 06/14/2023]
Abstract
Decreased PG constrains PSI activity due to inhibition of transcript and polypeptide abundance of light-harvesting and reaction center polypeptides generating a reversible, yellow phenotype during cold acclimation of pgp1. Cold acclimation of the Arabidopsis pgp1 mutant at 5 °C resulted in a pale-yellow phenotype with abnormal chloroplast ultrastructure compared to its green phenotype upon growth at 20 °C despite a normal cold-acclimation response at the transcript level. In contrast, wild type maintained its normal green phenotype and chloroplast ultrastructure irrespective of growth temperature. In contrast to cold acclimation of WT, growth of pgp1 at 5 °C limited the accumulation of Lhcbs and Lhcas assessed by immunoblotting. However, a novel 43 kD polypeptide of Lhcb1 as well as a 29 kD polypeptide of Lhcb3 accumulated in the soluble fraction which was absent in the thylakoid membrane fraction of cold-acclimated pgp1 which was not observed in WT. Cold acclimation of pgp1 destabilized the Chl-protein complexes associated with PSI and predisposed energy distribution in favor of PSII rather than PSI compared to the WT. Functionally, in vivo PSI versus PSII photochemistry was inhibited in cold-acclimated pgp1 to a greater extent than in WT relative to controls. Greening of the pale-yellow pgp1 was induced when cold-acclimated pgp1 was shifted from 5 to 20 °C which resulted in a marked decrease in excitation pressure to a level comparable to WT. Concomitantly, Lhcbs and Lhcas accumulated with a simultaneous decrease in the novel 43 and 29kD polypeptides. We conclude that the reduced levels of phosphatidyldiacylglycerol in the pgp1 limit the capacity of the mutant to maintain the structure and function of its photosynthetic apparatus during cold acclimation. Thus, maintenance of normal thylakoid phosphatidyldiacylglycerol levels is essential to stabilize the photosynthetic apparatus during cold acclimation.
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Affiliation(s)
- Alexander G Ivanov
- Department of Biology and the Biotron Centre for Experimental Climate Change Research, University of Western Ontario, London, ON, N6A 5B7, Canada
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. bl. 21, 1113, Sofia, Bulgaria
| | - Marianna Krol
- Department of Biology and the Biotron Centre for Experimental Climate Change Research, University of Western Ontario, London, ON, N6A 5B7, Canada
| | - Leonid V Savitch
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, ON, K1A OC6, Canada
| | - Beth Szyszka-Mroz
- Department of Biology and the Biotron Centre for Experimental Climate Change Research, University of Western Ontario, London, ON, N6A 5B7, Canada
| | - Jessica Roche
- Department of Biology and the Biotron Centre for Experimental Climate Change Research, University of Western Ontario, London, ON, N6A 5B7, Canada
- , 6/136 Austin St, Mt. Victoria, Wellington, 6011, New Zealand
| | - D P Sprott
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, ON, K1A OC6, Canada
| | - Eva Selstam
- Department of Plant Physiology, Umeå Plant Science Centre, University of Umeå, 90187, Umeå, Sweden
| | - Kenneth W Wilson
- Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Richard Gardiner
- Department of Biology and the Biotron Centre for Experimental Climate Change Research, University of Western Ontario, London, ON, N6A 5B7, Canada
| | - Gunnar Öquist
- Department of Plant Physiology, Umeå Plant Science Centre, University of Umeå, 90187, Umeå, Sweden
| | - Vaughan M Hurry
- Department of Plant Physiology, Umeå Plant Science Centre, University of Umeå, 90187, Umeå, Sweden
| | - Norman P A Hüner
- Department of Biology and the Biotron Centre for Experimental Climate Change Research, University of Western Ontario, London, ON, N6A 5B7, Canada.
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15
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Bonnanfant M, Marec H, Jesus B, Mouget JL, Pruvost J. Investigation of the photosynthetic response of Chlorella vulgaris to light changes in a torus-shape photobioreactor. Appl Microbiol Biotechnol 2021; 105:8689-8701. [PMID: 34724082 DOI: 10.1007/s00253-021-11636-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 09/14/2021] [Accepted: 10/05/2021] [Indexed: 10/20/2022]
Abstract
An efficient use of light is essential to achieve good performances in microalgae cultivation systems. This can be challenging particularly under solar conditions where light is highly dynamic (e.g., day/night cycles, rapid changes in wind and weather conditions). Microalgae display different mechanisms to optimize light use efficiency. In the short term, when high light is encountered, several processes of photoprotection can be involved to avoid cell damages (e.g., xanthophyll cycle). In the long term, when cells are exposed to a different light intensity, pigment content changes, i.e., photoacclimation. The purpose of this study is to investigate the photosynthetic response of Chlorella vulgaris cultures grown in closed lab-scale, torus-shape photobioreactor under well-controlled light conditions, namely, constant and dynamic light transitions. Experiments were conducted in continuous mode with detailed characterization of the light attenuation conditions for each condition, as represented by the mean rate of photon absorption (MRPA), so as to characterize the time responses of the photosynthetic cells toward light changes. This enables to observe short-term and long-term responses with their own characteristic times. The mechanisms involved were found to be different between increasing and decreasing light transitions. Furthermore the MRPA was found a valuable parameter to relate the effect of light to biological responses (i.e., pigment changes) under constant light and dynamic light conditions.Key points• MRPA proved valuable to relate C. vulgaris responses to light changes.• A linear evolution was found between pigment content and MRPA in continuous light.• A rising PFD step induced fast protection and acclimation mechanisms.
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Affiliation(s)
- M Bonnanfant
- GEPEA, UMR 6144, Oniris, CNRS, Université de Nantes, 44600, Saint-Nazaire, France.,Mer-Molécules-Santé (MMS), EA 2160, Le Mans Université, Le Mans Cedex 9, France
| | - H Marec
- GEPEA, UMR 6144, Oniris, CNRS, Université de Nantes, 44600, Saint-Nazaire, France
| | - B Jesus
- Mer-Molécules-Santé (MMS), EA2160, Faculté Des Sciences, Université de Nantes, Nantes, France
| | - J-L Mouget
- Mer-Molécules-Santé (MMS), EA 2160, Le Mans Université, Le Mans Cedex 9, France
| | - J Pruvost
- GEPEA, UMR 6144, Oniris, CNRS, Université de Nantes, 44600, Saint-Nazaire, France.
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16
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Brown M, Milligan A, Behrenfeld M. Photoacclimation State of Thalassiosira weissflogii is not Affected by Changes in Optical Depth Under A Fluctuating Light Regime Simulating Deep Mixing 1. JOURNAL OF PHYCOLOGY 2021; 57:1212-1222. [PMID: 33590492 DOI: 10.1111/jpy.13149] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 01/26/2021] [Accepted: 01/28/2021] [Indexed: 05/25/2023]
Abstract
Satellite-based remote sensing allows for global estimates of phytoplankton primary productivity by converting measurements of ocean color or photon absorption into units of carbon fixation. Models which perform this conversion often require an estimate of phytoplankton photoacclimation state such as the carbon to chlorophyll a ratio (C:Chl). Recently, our group developed a new photoacclimation model that can be applied to models of primary production. The model assumes that the phytoplankton photoacclimation state is not affected by periods of darkness during deep mixing beneath the photic zone, due to reduction in the plastoquinone pool in darkness and the subsequent deactivation of the signal for chlorophyll synthesis. In this study, we tested these assumptions by culturing the marine diatom Thalassiosira weissflogii under fluctuating light conditions simulating three different optical depths with progressively increasing deep mixing periods. The photoacclimation state, measured by the ratio of C:Chl, in T. weissflogii was not affected by changes in the length of simulated deep mixing periods. In addition, analysis of photosynthesis vs. irradiance (PE) curves showed that increases in optical depth caused decreases in both the maximum Chl-normalized rate of photosynthesis (Pbmax ) and in the slope of light-limited photosynthesis (αb ), but had no effect on the half-saturation irradiance (Ek , another metric of photoacclimation). However, measurements of chlorophyll fluorescence during simulated deep mixing did not support the hypothesis that the PQ pool was reduced during dark periods. Thus, our findings support the use of the photoacclimation model for estimating primary production while suggesting the need for further research into the mechanisms controlling photoacclimation in the upper mixed layer environment of the ocean.
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Affiliation(s)
- Matthew Brown
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, 97331, USA
| | - Allen Milligan
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, 97331, USA
| | - Michael Behrenfeld
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, 97331, USA
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17
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Sagun JV, Badger MR, Chow WS, Ghannoum O. Mehler reaction plays a role in C 3 and C 4 photosynthesis under shade and low CO 2. PHOTOSYNTHESIS RESEARCH 2021; 149:171-185. [PMID: 33534052 DOI: 10.1007/s11120-021-00819-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 01/09/2021] [Indexed: 06/12/2023]
Abstract
Alternative electron fluxes such as the cyclic electron flux (CEF) around photosystem I (PSI) and Mehler reaction (Me) are essential for efficient photosynthesis because they generate additional ATP and protect both photosystems against photoinhibition. The capacity for Me can be estimated by measuring O2 exchange rate under varying irradiance and CO2 concentration. In this study, mass spectrometric measurements of O2 exchange were made using leaves of representative species of C3 and C4 grasses grown under natural light (control; PAR ~ 800 µmol quanta m-2 s-1) and shade (~ 300 µmol quanta m-2 s-1), and in representative species of gymnosperm, liverwort and fern grown under natural light. For all control grown plants measured at high CO2, O2 uptake rates were similar between the light and dark, and the ratio of Rubisco oxygenation to carboxylation (Vo/Vc) was low, which suggests little potential for Me, and that O2 uptake was mainly due to photorespiration or mitochondrial respiration under these conditions. Low CO2 stimulated O2 uptake in the light, Vo/Vc and Me in all species. The C3 species had similar Vo/Vc, but Me was highest in the grass and lowest in the fern. Among the C4 grasses, shade increased O2 uptake in the light, Vo/Vc and the assimilation quotient (AQ), particularly at low CO2, whilst Me was only substantial at low CO2 where it may contribute 20-50% of maximum electron flow under high light.
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Affiliation(s)
- Julius Ver Sagun
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Murray R Badger
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, ACT, 2601, Australia
| | - Wah Soon Chow
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, ACT, 2601, Australia
| | - Oula Ghannoum
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW, 2751, Australia.
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18
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Zhao J, Yu W, Zhang L, Liu J. Chlororespiration protects the photosynthetic apparatus against photoinhibition by alleviating inhibition of photodamaged-PSII repair in Haematococcus pluvialis at the green motile stage. ALGAL RES 2021. [DOI: 10.1016/j.algal.2020.102140] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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19
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Genome-scale metabolic model of the diatom Thalassiosira pseudonana highlights the importance of nitrogen and sulfur metabolism in redox balance. PLoS One 2021; 16:e0241960. [PMID: 33760840 PMCID: PMC7990286 DOI: 10.1371/journal.pone.0241960] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 03/03/2021] [Indexed: 12/22/2022] Open
Abstract
Diatoms are unicellular photosynthetic algae known to secrete organic matter that fuels secondary production in the ocean, though our knowledge of how their physiology impacts the composition of dissolved organic matter remains limited. Like all photosynthetic organisms, their use of light for energy and reducing power creates the challenge of avoiding cellular damage. To better understand the interplay between redox balance and organic matter secretion, we reconstructed a genome-scale metabolic model of Thalassiosira pseudonana strain CCMP 1335, a model for diatom molecular biology and physiology, with a 60-year history of studies. The model simulates the metabolic activities of 1,432 genes via a network of 2,792 metabolites produced through 6,079 reactions distributed across six subcellular compartments. Growth was simulated under different steady-state light conditions (5–200 μmol photons m-2 s-1) and in a batch culture progressing from exponential growth to nitrate-limitation and nitrogen-starvation. We used the model to examine the dissipation of reductants generated through light-dependent processes and found that when available, nitrate assimilation is an important means of dissipating reductants in the plastid; under nitrate-limiting conditions, sulfate assimilation plays a similar role. The use of either nitrate or sulfate uptake to balance redox reactions leads to the secretion of distinct organic nitrogen and sulfur compounds. Such compounds can be accessed by bacteria in the surface ocean. The model of the diatom Thalassiosira pseudonana provides a mechanistic explanation for the production of ecologically and climatologically relevant compounds that may serve as the basis for intricate, cross-kingdom microbial networks. Diatom metabolism has an important influence on global biogeochemistry; metabolic models of marine microorganisms link genes to ecosystems and may be key to integrating molecular data with models of ocean biogeochemistry.
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20
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Yang S, Overlander M, Fiedler J. Genetic analysis of the barley variegation mutant, grandpa1.a. BMC PLANT BIOLOGY 2021; 21:134. [PMID: 33711931 PMCID: PMC7955646 DOI: 10.1186/s12870-021-02915-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 03/04/2021] [Indexed: 05/30/2023]
Abstract
BACKGROUND Providing the photosynthesis factory for plants, chloroplasts are critical for crop biomass and economic yield. However, chloroplast development is a complicated process, coordinated by the cross-communication between the nucleus and plastids, and the underlying biogenesis mechanism has not been fully revealed. Variegation mutants have provided ideal models to identify genes or factors involved in chloroplast development. Well-developed chloroplasts are present in the green tissue areas, while the white areas contain undifferentiated plastids that are deficient in chlorophyll. Unlike albino plants, variegation mutants survive to maturity and enable investigation into the signaling pathways underlying chloroplast biogenesis. The allelic variegated mutants in barley, grandpa 1 (gpa1), have long been identified but have not been genetically characterized. RESULTS We characterized and genetically analyzed the grandpa1.a (gpa1.a) mutant. The chloroplast ultrastructure was evaluated using transmission electron microscopy (TEM), and it was confirmed that chloroplast biogenesis was disrupted in the white sections of gpa1.a. To determine the precise position of Gpa1, a high-resolution genetic map was constructed. Segregating individuals were genotyped with the barley 50 k iSelect SNP Array, and the linked SNPs were converted to PCR-based markers for genetic mapping. The Gpa1 gene was mapped to chromosome 2H within a gene cluster functionally related to photosynthesis or chloroplast differentiation. In the variegated gpa1.a mutant, we identified a large deletion in this gene cluster that eliminates a putative plastid terminal oxidase (PTOX). CONCLUSIONS Here we characterized and genetically mapped the gpa1.a mutation causing a variegation phenotype in barley. The PTOX-encoding gene in the delimited region is a promising candidate for Gpa1. Therefore, the present study provides a foundation for the cloning of Gpa1, which will elevate our understanding of the molecular mechanisms underlying chloroplast biogenesis, particularly in monocot plants.
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Affiliation(s)
- Shengming Yang
- USDA-ARS Cereals Research Unit, Edward T. Schafer Agriculture Research Center, Fargo, ND, 58102, USA.
- Department of Plant Sciences, North Dakota State University, Fargo, ND, 58102, USA.
- Department of Plant Pathology, North Dakota State University, Fargo, ND, 58102, USA.
| | - Megan Overlander
- USDA-ARS Cereals Research Unit, Edward T. Schafer Agriculture Research Center, Fargo, ND, 58102, USA
| | - Jason Fiedler
- USDA-ARS Cereals Research Unit, Edward T. Schafer Agriculture Research Center, Fargo, ND, 58102, USA
- Department of Plant Sciences, North Dakota State University, Fargo, ND, 58102, USA
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21
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Ortega JM, Roncel M. The afterglow photosynthetic luminescence. PHYSIOLOGIA PLANTARUM 2021; 171:268-276. [PMID: 33231323 DOI: 10.1111/ppl.13288] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/12/2020] [Accepted: 11/19/2020] [Indexed: 06/11/2023]
Abstract
The afterglow (AG) photosynthetic luminescence is a long-lived chlorophyll fluorescence emitted from PSII after the illumination of photosynthetic materials by FR or white light and placed in darkness. The AG emission corresponds to the fraction of PSII centers in the S2/3 QB non-radiative state immediately after pre-illumination, in which the arrival of an electron transferred from stroma along cyclic/chlororespiratory pathway(s) produces the S2/3 QB - radiative state that emits luminescence. This emission can be optimally recorded by a linear temperature gradient as sharp thermoluminescence (TL) band peaking at about 45°C. The AG emission recorded by TL technique has been proposed as a simple non-invasive tool to investigate the chloroplast energetic state and some of its metabolism processes as cyclic transport of electrons around PSI, chlororespiration or photorespiration. On the other hand, this emission has demonstrated to be a useful probe to study the effect of various stress conditions in photosynthetic materials.
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Affiliation(s)
- José M Ortega
- Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla-CSIC, Seville, Spain
| | - Mercedes Roncel
- Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla-CSIC, Seville, Spain
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22
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Kalmatskaya OA, Trubitsin BV, Suslichenko IS, Karavaev VA, Tikhonov AN. Electron transport in Tradescantia leaves acclimated to high and low light: thermoluminescence, PAM-fluorometry, and EPR studies. PHOTOSYNTHESIS RESEARCH 2020; 146:123-141. [PMID: 32594291 DOI: 10.1007/s11120-020-00767-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 06/10/2020] [Indexed: 06/11/2023]
Abstract
Using thermoluminescence, PAM-fluorometry, and electron paramagnetic resonance (EPR) for assaying electron transport processes in chloroplasts in situ, we have compared photosynthetic characteristics in Tradescantia fluminensis leaves grown under low light (LL, 50-125 µmol photons m-2 s-1) or high light (HL, 875-1000 µmol photons m-2 s-1) condition. We found differences in the thermoluminescence (TL) spectra of LL- and HL-acclimated leaves. The LL and HL leaves show different proportions of the Q (~ 0 °C) and B (~ 25-30 °C) bands in their TL spectra; the ratios of the "light sums" of the Q and B bands being SQ/SB ≈ 1/1 (LL) and SQ/SB ≈ 1/3 (HL). This suggests the existence of different redox states of electron carriers on the acceptor side of PSII in LL and HL leaves, which may be affected, in particular, by different capacities of their photo-reducible PQ pools. Enhanced content of PQ in chloroplasts of LL leaves may be the reason for an efficient performance of photosynthesis at low irradiance. Kinetic studies of slow induction of Chl a fluorescence and measurements of P700 photooxidation by EPR demonstrate that HL leaves have faster (about 2 times) response to switching on actinic light as compared to LL leaves grown at moderate irradiation. HL leaves also show higher non-photochemical quenching (NPQ) of Chl a fluorescence. These properties of HL leaves (faster response to light and generation of enhanced NPQ) reflect the flexibility of their photosynthetic apparatus, providing sustainability and rapid response to fluctuations of environmental light intensity and solar stress resistance. Analysis of time-courses of the EPR signals of [Formula: see text] induced by far-red (λmax = 707 nm), exciting predominantly PSI, and white light, exciting both PSI and PSII, suggests that there is a contribution of cyclic electron flow around PSI to electron flow through PSI in HL leaves. The data obtained are discussed in terms of photosynthetic apparatus sustainability of HL and LL leaves under variable irradiation conditions.
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Affiliation(s)
| | - Boris V Trubitsin
- Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Igor S Suslichenko
- Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia
| | | | - Alexander N Tikhonov
- Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia.
- N.M. Emanuel Institute of Biochemical Physics of Russian Academy of Sciences, Moscow, Russia.
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23
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Transient depletion of transported metabolites in the streaming cytoplasm of Chara upon shading the long-distance transmission pathway. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148257. [PMID: 32621805 DOI: 10.1016/j.bbabio.2020.148257] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 06/11/2020] [Accepted: 06/18/2020] [Indexed: 01/27/2023]
Abstract
Export of reducing power from chloroplasts to cytoplasm serves to balance the NADPH/ATP ratio that is optimal for CO2 assimilation. Rapid cytoplasmic streaming in characean algae conveys the exported metabolites downstream towards the shaded plastids where envelope transporters may operate for the import of reducing power in accordance with the direction of concentration gradients. Import of reducing equivalents by chloroplasts in the analyzed area transiently enhances the pulse-modulated chlorophyll fluorescence F' controlled by the redox state of photosystem II acceptor QA. When the microfluidic pathway was transferred to darkness while the analyzed cell area remained in dim background light, the amplitude of cyclosis-mediated F' changes dropped sharply and then recovered within 5-10 min. The suppression of long-distance signaling indicates temporal depletion of transmitted metabolites in the streaming cytoplasm. The return to overall background illumination induced an exceptionally large F' response to the first local light pulse admitted to a remote cell region. This indicates the appearance of excess reductants in the streaming cytoplasm at a certain stage of photosynthetic induction. The results suggest highly dynamic exchange of metabolites between stationary chloroplasts lining the microfluidic pathway and the streaming cytoplasm upon light-dark and dark-light transitions. Evidence is obtained that slow stages of chlorophyll fluorescence induction in algae with rapid cytoplasmic streaming directly depend on cyclosis-mediated long-distance delivery of metabolites produced far beyond the analyzed cell area.
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Messant M, Shimakawa G, Perreau F, Miyake C, Krieger-Liszkay A. Evolutive differentiation between alga- and plant-type plastid terminal oxidase: Study of plastid terminal oxidase PTOX isoforms in Marchantia polymorpha. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148309. [PMID: 32956677 DOI: 10.1016/j.bbabio.2020.148309] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 09/02/2020] [Accepted: 09/14/2020] [Indexed: 10/23/2022]
Abstract
The liverwort Marchantia polymorpha contains two isoforms of the plastid terminal oxidase (PTOX), an enzyme that catalyzes the reduction of oxygen to water using plastoquinol as substrate. Phylogenetic analyses showed that one isoform, here called MpPTOXa, is closely related to isoforms occurring in plants and some algae, while the other isoform, here called MpPTOXb, is closely related to the two isoforms occurring in Chlamydomonas reinhardtii. Mutants of each isoform were created in Marchantia polymorpha using CRISPR/Cas9 technology. While no obvious phenotype was found for these mutants, chlorophyll fluorescence analyses demonstrated that the plastoquinone pool was in a higher reduction state in both mutants. This was visible at the level of fluorescence measured in dark-adapted material and by post illumination fluorescence rise. These results suggest that both isoforms have a redundant function. However, when P700 oxidation and re-reduction was studied, differences between these two isoforms were observed. Furthermore, the mutant affected in MpPTOXb showed a slight alteration in the pigment composition, a higher non-photochemical quenching and a slightly lower electron transport rate through photosystem II. These differences may be explained either by differences in the enzymatic activities or by different activities attributed to preferential involvement of the two PTOX isoforms to either linear or cyclic electron flow.
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Affiliation(s)
- Marine Messant
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Ginga Shimakawa
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - François Perreau
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000 Versailles, France
| | - Chikahiro Miyake
- Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Anja Krieger-Liszkay
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France.
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Kayama M, Chen JF, Nakada T, Nishimura Y, Shikanai T, Azuma T, Miyashita H, Takaichi S, Kashiyama Y, Kamikawa R. A non-photosynthetic green alga illuminates the reductive evolution of plastid electron transport systems. BMC Biol 2020; 18:126. [PMID: 32938439 PMCID: PMC7495860 DOI: 10.1186/s12915-020-00853-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 08/21/2020] [Indexed: 11/12/2022] Open
Abstract
Background Plastid electron transport systems are essential not only for photosynthesis but also for dissipating excess reducing power and sinking excess electrons generated by various redox reactions. Although numerous organisms with plastids have lost their photoautotrophic lifestyles, there is a spectrum of known functions of remnant plastids in non-photosynthetic algal/plant lineages; some of non-photosynthetic plastids still retain diverse metabolic pathways involving redox reactions while others, such as apicoplasts of apicomplexan parasites, possess highly reduced sets of functions. However, little is known about underlying mechanisms for redox homeostasis in functionally versatile non-photosynthetic plastids and thus about the reductive evolution of plastid electron transport systems. Results Here we demonstrated that the central component for plastid electron transport systems, plastoquinone/plastoquinol pool, is still retained in a novel strain of an obligate heterotrophic green alga lacking the photosynthesis-related thylakoid membrane complexes. Microscopic and genome analyses revealed that the Volvocales green alga, chlamydomonad sp. strain NrCl902, has non-photosynthetic plastids and a plastid DNA that carries no genes for the photosynthetic electron transport system. Transcriptome-based in silico prediction of the metabolic map followed by liquid chromatography analyses demonstrated carotenoid and plastoquinol synthesis, but no trace of chlorophyll pigments in the non-photosynthetic green alga. Transient RNA interference knockdown leads to suppression of plastoquinone/plastoquinol synthesis. The alga appears to possess genes for an electron sink system mediated by plastid terminal oxidase, plastoquinone/plastoquinol, and type II NADH dehydrogenase. Other non-photosynthetic algae/land plants also possess key genes for this system, suggesting a broad distribution of an electron sink system in non-photosynthetic plastids. Conclusion The plastoquinone/plastoquinol pool and thus the involved electron transport systems reported herein might be retained for redox homeostasis and might represent an intermediate step towards a more reduced set of the electron transport system in many non-photosynthetic plastids. Our findings illuminate a broadly distributed but previously hidden step of reductive evolution of plastid electron transport systems after the loss of photosynthesis.
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Affiliation(s)
- Motoki Kayama
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida nihonmatsu cho, Sakyo ku, Kyoto, Kyoto, 606-8501, Japan
| | - Jun-Feng Chen
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida nihonmatsu cho, Sakyo ku, Kyoto, Kyoto, 606-8501, Japan
| | - Takashi Nakada
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
| | | | | | - Tomonori Azuma
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida nihonmatsu cho, Sakyo ku, Kyoto, Kyoto, 606-8501, Japan
| | - Hideaki Miyashita
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida nihonmatsu cho, Sakyo ku, Kyoto, Kyoto, 606-8501, Japan
| | - Shinichi Takaichi
- Department of Molecular Microbiology, Tokyo University of Agriculture, Tokyo, Japan
| | - Yuichiro Kashiyama
- Graduate School of Engineering, Fukui University of Technology, Fukui, Japan
| | - Ryoma Kamikawa
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida nihonmatsu cho, Sakyo ku, Kyoto, Kyoto, 606-8501, Japan. .,Graduate School of Agriculture, Kyoto University, Kitashirakawa oiwake cho, Sakyo ku, Kyoto, Kyoto, 606-8502, Japan.
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Tan Y, Zhang QS, Zhao W, Liu Z, Ma MY, Zhong MY, Wang MX, Xu B. Chlororespiration Serves as Photoprotection for the Photo-Inactivated Oxygen-Evolving Complex in Zostera marina, a Marine Angiosperm. PLANT & CELL PHYSIOLOGY 2020; 61:1517-1529. [PMID: 32492141 DOI: 10.1093/pcp/pcaa075] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Accepted: 05/28/2020] [Indexed: 06/11/2023]
Abstract
As an alternative electron sink, chlororespiration, comprising the NAD(P)H dehydrogenase complex and plastid terminal plastoquinone oxidase, may play a significant role in sustaining the redox equilibrium between stroma and thylakoid membrane. This study identified a distinct role for chlororespiration in the marine angiosperm Zostera marina, whose oxygen-evolving complex (OEC) is prone to photo-inactivation as a result of its inherent susceptibility to excess irradiation. The strong connectivity between OEC peripheral proteins and key chlororespiratory enzymes, as demonstrated in the interaction network of differentially expressed genes, suggested that the recovery of photo-inactivated OEC was connected with chlororespiration. Chlorophyll fluorescence, transcriptome and Western blot data verified a new physiological role for chlororespiration to function as photoprotection and generate a proton gradient across the thylakoid membrane for the recovery of photo-inactivated OEC. Chlororespiration was only activated in darkness following excess irradiation exposure, which might be related to electron deficiency in the electron transport chain because of the continuous impairment of the OEC. The activation of chlororespiration in Z. marina was prone to proactivity, which was also supported by the further activation of the oxidative pentose-phosphate pathway synthesizing NADPH to meet the demand of chlororespiration during darkness. This phenomenon is distinct from the common assumption that chlororespiration is prone to consuming redundant reducing power during the short transition phase from light to dark.
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Affiliation(s)
- Ying Tan
- Phycology Laboratory, Ocean School, Yantai University, Yantai 264005, PR China
| | - Quan Sheng Zhang
- Phycology Laboratory, Ocean School, Yantai University, Yantai 264005, PR China
| | - Wei Zhao
- Phycology Laboratory, Ocean School, Yantai University, Yantai 264005, PR China
| | - Zhe Liu
- Phycology Laboratory, Ocean School, Yantai University, Yantai 264005, PR China
| | - Ming Yu Ma
- Phycology Laboratory, Ocean School, Yantai University, Yantai 264005, PR China
| | - Ming Yu Zhong
- Phycology Laboratory, Ocean School, Yantai University, Yantai 264005, PR China
| | - Meng Xin Wang
- Phycology Laboratory, Ocean School, Yantai University, Yantai 264005, PR China
| | - Bin Xu
- Phycology Laboratory, Ocean School, Yantai University, Yantai 264005, PR China
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Ciou HS, Tsai YL, Chiu CC. Arabidopsis chloroplast J protein DJC75/CRRJ mediates nitrate-promoted seed germination in the dark. ANNALS OF BOTANY 2020; 125:1091-1099. [PMID: 32157271 PMCID: PMC7262469 DOI: 10.1093/aob/mcaa040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Accepted: 03/06/2020] [Indexed: 06/10/2023]
Abstract
BACKGROUND AND AIMS Nitrate can stimulate seed germination of many plant species in the absence of light; however, the molecular mechanism of nitrate-promoted seed germination in the dark remains largely unclear and no component of this pathway has been identified yet. Here, we show that a plastid J-domain protein, DJC75/CRRJ, in arabidopsis (Arabidopsis thaliana) is important for nitrate-promoted seed germination in the dark. METHODS The expression of DJC75 during imbibition in the dark was investigated. The seed germination rate of mutants defective in DJC75 was determined in the presence of nitrate when light cues for seed germination were eliminated by the treatment of imbibed seeds with a pulse of far-red light to inactivate phytochrome B (phyB), or by assaying germination in the dark with seeds harbouring the phyB mutation. The germination rates of mutants defective in CRRL, a J-like protein related to DJC75, and in two chloroplast Hsp70s were also measured in the presence of nitrate in darkness. KEY RESULTS DJC75 was expressed during seed imbibition in the absence of light. Mutants defective in DJC75 showed seed germination defects in the presence of nitrate when light cues for seed germination were eliminated. Mutants defective in CRRL and in two chloroplast Hsp70s also exhibited similar seed germination defects. Upregulation of gibberellin biosynthetic gene GA3ox1 expression by nitrate in imbibed phyB mutant seeds was diminished when DJC75 was knocked out. CONCLUSIONS Our data suggest that plastid J-domain protein DJC75 regulates nitrate-promoted seed germination in the dark by upregulation of expression of the gibberellin biosynthetic gene GA3ox1 through an unknown mechanism and that DJC75 may work in concert with chloroplast Hsp70s to regulate nitrate-promoted seed germination. DJC75 is the first pathway component identified for nitrate-promoted seed germination in the dark.
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Affiliation(s)
- Huai-Syuan Ciou
- Institute of Tropical Plant Sciences and Microbiology, National Cheng Kung University, Tainan, Taiwan
| | - Yu-Lun Tsai
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Chi-Chou Chiu
- Institute of Tropical Plant Sciences and Microbiology, National Cheng Kung University, Tainan, Taiwan
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28
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Tan Y, Zhang QS, Zhao W, Liu Z, Ma MY, Zhong MY, Wang MX. The highly efficient NDH-dependent photosystem I cyclic electron flow pathway in the marine angiosperm Zostera marina. PHOTOSYNTHESIS RESEARCH 2020; 144:49-62. [PMID: 32152819 DOI: 10.1007/s11120-020-00732-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 03/03/2020] [Indexed: 05/13/2023]
Abstract
Zostera marina, a fully submerged marine angiosperm with a unique evolutionary history associated with its terrestrial origin, has distinct photochemical characteristics caused by its oxygen-evolving complex (OEC) being prone to deactivation in visible light. Based on the present phylogenetic analysis, the chloroplast NADPH dehydrogenase-like (NDH) complex was found to be completed in of Z. marina, unlike other marine plants, suggesting its crucial role. Thus, the responses of electron transport to irradiation were investigated through multiple chlorophyll fluorescence techniques and Western blot analysis. Moreover, the respective contribution of the two photosystem I cyclic electron flow (PSI-CEF) pathways to the generation of trans-thylakoid proton gradient (∆pH) was also examined using inhibitors. The contributions of the two PSI-CEF pathways to ∆pH were similar; furthermore, there was a trade-off between the two pathways under excess irradiation: the PGR5/L1-dependent PSI-CEF decreased gradually following its activation during the initial illumination, while NDH-dependent PSI-CEF was activated gradually with exposure duration. OEC inactivation was continuously under excess irradiation, which exhibits a positive linear correlation with the activation of NDH-dependent PSI-CEF. We suggest that PGR5/L1-dependent PSI-CEF was preferentially activated to handle the excess electron caused by the operation of OEC during the initial illumination. Subsequently, the increasing OEC inactivation with exposure duration resulted in a deficit of electrons. Limited electrons from PSI might preferentially synthesize NADPH, which could support the function of NDH-dependent PSI-CEF to generate ∆pH and ATP via reducing ferredoxin, thereby maintaining OEC stability.
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Affiliation(s)
- Ying Tan
- Ocean School, Yantai University, Yantai, 264005, People's Republic of China
| | - Quan Sheng Zhang
- Ocean School, Yantai University, Yantai, 264005, People's Republic of China.
| | - Wei Zhao
- Ocean School, Yantai University, Yantai, 264005, People's Republic of China
| | - Zhe Liu
- Ocean School, Yantai University, Yantai, 264005, People's Republic of China
| | - Ming Yu Ma
- Ocean School, Yantai University, Yantai, 264005, People's Republic of China
| | - Ming Yu Zhong
- Ocean School, Yantai University, Yantai, 264005, People's Republic of China
| | - Meng Xin Wang
- Ocean School, Yantai University, Yantai, 264005, People's Republic of China
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Nowicka B. Practical aspects of the measurements of non-photochemical chlorophyll fluorescence quenching in green microalgae Chlamydomonas reinhardtii using Open FluorCam. PHYSIOLOGIA PLANTARUM 2020; 168:617-629. [PMID: 31264713 DOI: 10.1111/ppl.13003] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Accepted: 06/19/2019] [Indexed: 06/09/2023]
Abstract
Methods of chlorophyll fluorescence measurements are widely used in the research on photosynthesis and ecophysiology of plants and algae. Among them, a very popular technique is pulse-amplitude-modulation (PAM) flourometry, which is simple to carry out, fast and non-invasive. However, this method is also prone to generate artifacts if the experiments were not planned and executed properly. Application of this technique to algae brings additional complications, which need to be taken into consideration. Some of them are connected with sample preparation and setting of the protocols used, while another origin from the differences in the photosynthetic apparatus and regulation of photosynthesis in various algal groups when compared to vascular plants. In the present paper, some important practical aspects concerning PAM fluorometry measurements in the green microalga Chlamydomonas reinhardtii have been described, including the equipment settings and sample preparation. The impact of growth conditions, such as light, temperature and medium type on the induction of non-photochemical quenching of chlorophyll fluorescence have been also tackled, as well as the question of state transitions occurring in darkness.
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Affiliation(s)
- Beatrycze Nowicka
- Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, 30-387, Poland
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30
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Fernández-Marín B, Gulías J, Figueroa CM, Iñiguez C, Clemente-Moreno MJ, Nunes-Nesi A, Fernie AR, Cavieres LA, Bravo LA, García-Plazaola JI, Gago J. How do vascular plants perform photosynthesis in extreme environments? An integrative ecophysiological and biochemical story. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:979-1000. [PMID: 31953876 DOI: 10.1111/tpj.14694] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 12/14/2019] [Accepted: 01/07/2020] [Indexed: 05/24/2023]
Abstract
In this work, we review the physiological and molecular mechanisms that allow vascular plants to perform photosynthesis in extreme environments, such as deserts, polar and alpine ecosystems. Specifically, we discuss the morpho/anatomical, photochemical and metabolic adaptive processes that enable a positive carbon balance in photosynthetic tissues under extreme temperatures and/or severe water-limiting conditions in C3 species. Nevertheless, only a few studies have described the in situ functioning of photoprotection in plants from extreme environments, given the intrinsic difficulties of fieldwork in remote places. However, they cover a substantial geographical and functional range, which allowed us to describe some general trends. In general, photoprotection relies on the same mechanisms as those operating in the remaining plant species, ranging from enhanced morphological photoprotection to increased scavenging of oxidative products such as reactive oxygen species. Much less information is available about the main physiological and biochemical drivers of photosynthesis: stomatal conductance (gs ), mesophyll conductance (gm ) and carbon fixation, mostly driven by RuBisCO carboxylation. Extreme environments shape adaptations in structures, such as cell wall and membrane composition, the concentration and activation state of Calvin-Benson cycle enzymes, and RuBisCO evolution, optimizing kinetic traits to ensure functionality. Altogether, these species display a combination of rearrangements, from the whole-plant level to the molecular scale, to sustain a positive carbon balance in some of the most hostile environments on Earth.
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Affiliation(s)
- Beatriz Fernández-Marín
- Department of Botany, Ecology and Plant Physiology, University of La Laguna, Tenerife, 38200, Spain
- Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Barrio Sarriena s/n, 48940, Leioa, Spain
| | - Javier Gulías
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears (UIB), Instituto de Investigaciones Agroambientales y de Economía del Agua (INAGEA), Ctra. Valldemossa km 7.5, 07122, Palma, Spain
| | - Carlos M Figueroa
- UNL, CONICET, FBCB, Instituto de Agrobiotecnología del Litoral, 3000, Santa Fe, Argentina
| | - Concepción Iñiguez
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears (UIB), Instituto de Investigaciones Agroambientales y de Economía del Agua (INAGEA), Ctra. Valldemossa km 7.5, 07122, Palma, Spain
| | - María J Clemente-Moreno
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears (UIB), Instituto de Investigaciones Agroambientales y de Economía del Agua (INAGEA), Ctra. Valldemossa km 7.5, 07122, Palma, Spain
| | - Adriano Nunes-Nesi
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil
| | - Alisdair R Fernie
- Central Metabolism Group, Molecular Physiology Department, Max-Planck-Institut für Molekulare Pflanzenphysiologie, Golm, Germany
| | - Lohengrin A Cavieres
- ECOBIOSIS, Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile
| | - León A Bravo
- Lab. de Fisiología y Biología Molecular Vegetal, Dpt. de Cs. Agronómicas y Recursos Naturales, Facultad de Cs. Agropecuarias y Forestales, Instituto de Agroindustria, Universidad de La Frontera, Temuco, Chile
- Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Technological Bioresource Nucleus, Universidad de La Frontera, Temuco, Chile
| | - José I García-Plazaola
- Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Barrio Sarriena s/n, 48940, Leioa, Spain
| | - Jorge Gago
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears (UIB), Instituto de Investigaciones Agroambientales y de Economía del Agua (INAGEA), Ctra. Valldemossa km 7.5, 07122, Palma, Spain
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Krishna PS, Morello G, Mamedov F. Characterization of the transient fluorescence wave phenomenon that occurs during H2 production in Chlamydomonas reinhardtii. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:6321-6336. [PMID: 31504725 PMCID: PMC6859737 DOI: 10.1093/jxb/erz380] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 08/14/2019] [Indexed: 05/10/2023]
Abstract
The redox state of the plastoquinone (PQ) pool in sulfur-deprived, H2-producing Chlamydomonas reinhardtii cells was studied using single flash-induced variable fluorescence decay kinetics. During H2 production, the fluorescence decay kinetics exhibited an unusual post-illumination rise of variable fluorescence, giving a wave-like appearance. The wave showed the transient fluorescence minimum at ~60 ms after the flash, followed by a rise, reaching the transient fluorescence maximum at ~1 s after the flash, before decaying back to the initial fluorescence level. Similar wave-like fluorescence decay kinetics have been reported previously in anaerobically incubated cyanobacteria but not in green algae. From several different electron and proton transfer inhibitors used, polymyxin B, an inhibitor of type II NAD(P)H dehydrogenase (NDA2), had the effect of eliminating the fluorescence wave feature, indicating involvement of NDA2 in this phenomenon. This was further confirmed by the absence of the fluorescence wave in the Δnda2 mutant lacking NDA2. Additionally, Δnda2 mutants have also shown delayed and diminished H2 production (only 23% if compared with the wild type). Our results show that the fluorescence wave phenomenon in C. reinhardtii is observed under highly reducing conditions and is induced by the NDA2-mediated electron flow from the reduced stromal components to the PQ pool. Therefore, the fluorescence wave phenomenon is a sensitive probe for the complex network of redox reactions at the PQ pool level in the thylakoid membrane. It could be used in further characterization and improvement of the electron transfer pathways leading to H2 production in C. reinhardtii.
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Affiliation(s)
- Pilla Sankara Krishna
- Molecular Biomimetics, Department of Chemistry – Ångström Laboratory, Uppsala University, Uppsala, Sweden
| | - Giorgio Morello
- Molecular Biomimetics, Department of Chemistry – Ångström Laboratory, Uppsala University, Uppsala, Sweden
| | - Fikret Mamedov
- Molecular Biomimetics, Department of Chemistry – Ångström Laboratory, Uppsala University, Uppsala, Sweden
- Correspondence:
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32
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Burlacot A, Peltier G, Li-Beisson Y. Subcellular Energetics and Carbon Storage in Chlamydomonas. Cells 2019; 8:E1154. [PMID: 31561610 PMCID: PMC6830334 DOI: 10.3390/cells8101154] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 09/19/2019] [Accepted: 09/24/2019] [Indexed: 01/09/2023] Open
Abstract
Microalgae have emerged as a promising platform for production of carbon- and energy- rich molecules, notably starch and oil. Establishing an economically viable algal biotechnology sector requires a holistic understanding of algal photosynthesis, physiology, cell cycle and metabolism. Starch/oil productivity is a combined effect of their cellular content and cell division activities. Cell growth, starch and fatty acid synthesis all require carbon building blocks and a source of energy in the form of ATP and NADPH, but with a different requirement in ATP/NADPH ratio. Thus, several cellular mechanisms have been developed by microalgae to balance ATP and NADPH supply which are essentially produced by photosynthesis. Major energy management mechanisms include ATP production by the chloroplast-based cyclic electron flow and NADPH removal by water-water cycles. Furthermore, energetic coupling between chloroplast and other cellular compartments, mitochondria and peroxisome, is increasingly recognized as an important process involved in the chloroplast redox poise. Emerging literature suggests that alterations of energy management pathways affect not only cell fitness and survival, but also influence biomass content and composition. These emerging discoveries are important steps towards diverting algal photosynthetic energy to useful products for biotechnological applications.
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Affiliation(s)
- Adrien Burlacot
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache CEDEX, 13108 Saint Paul-Lez-Durance, France.
| | - Gilles Peltier
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache CEDEX, 13108 Saint Paul-Lez-Durance, France.
| | - Yonghua Li-Beisson
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache CEDEX, 13108 Saint Paul-Lez-Durance, France.
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Gasulla F, Casano L, Guéra A. Chlororespiration induces non-photochemical quenching of chlorophyll fluorescence during darkness in lichen chlorobionts. PHYSIOLOGIA PLANTARUM 2019; 166:538-552. [PMID: 29952012 DOI: 10.1111/ppl.12792] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 06/15/2018] [Accepted: 06/19/2018] [Indexed: 06/08/2023]
Affiliation(s)
- Francisco Gasulla
- Departamento de Ciencias de la Vida, Universidad de Alcalá, Edificio de Ciencias, Campus Científico-Tecnológico (Externo), 28802, Alcalá de Henares (Madrid), Spain
| | - Leonardo Casano
- Departamento de Ciencias de la Vida, Universidad de Alcalá, Edificio de Ciencias, Campus Científico-Tecnológico (Externo), 28802, Alcalá de Henares (Madrid), Spain
| | - Alfredo Guéra
- Departamento de Ciencias de la Vida, Universidad de Alcalá, Edificio de Ciencias, Campus Científico-Tecnológico (Externo), 28802, Alcalá de Henares (Madrid), Spain
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Alternative outlets for sustaining photosynthetic electron transport during dark-to-light transitions. Proc Natl Acad Sci U S A 2019; 116:11518-11527. [PMID: 31101712 PMCID: PMC6561286 DOI: 10.1073/pnas.1903185116] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Most forms of life on Earth cannot exist without photosynthesis. Our food and atmosphere depend on it. To obtain high photosynthetic yields, light energy must be efficiently coupled to the fixation of CO2 into organic molecules. Suboptimal environmental conditions can severely impact the conversion of light energy to biomass and lead to reactive oxygen production, which in turn can cause cellular damage and loss of productivity. Hence, plants, algae, and photosynthetic bacteria have evolved a network of alternative outlets to sustain the flow of photosynthetically derived electrons. Our work is focused on the nature and integration of these outlets, which will inform a rational engineering of crop plants and algae to optimize photosynthesis and meet the increased global demand for food. Environmental stresses dramatically impact the balance between the production of photosynthetically derived energetic electrons and Calvin–Benson–Bassham cycle (CBBC) activity; an imbalance promotes accumulation of reactive oxygen species and causes cell damage. Hence, photosynthetic organisms have developed several strategies to route electrons toward alternative outlets that allow for storage or harmless dissipation of their energy. In this work, we explore the activities of three essential outlets associated with Chlamydomonas reinhardtii photosynthetic electron transport: (i) reduction of O2 to H2O through flavodiiron proteins (FLVs) and (ii) plastid terminal oxidases (PTOX) and (iii) the synthesis of starch. Real-time measurements of O2 exchange have demonstrated that FLVs immediately engage during dark-to-light transitions, allowing electron transport when the CBBC is not fully activated. Under these conditions, we quantified maximal FLV activity and its overall capacity to direct photosynthetic electrons toward O2 reduction. However, when starch synthesis is compromised, a greater proportion of the electrons is directed toward O2 reduction through both the FLVs and PTOX, suggesting an important role for starch synthesis in priming/regulating CBBC and electron transport. Moreover, partitioning energized electrons between sustainable (starch; energetic electrons are recaptured) and nonsustainable (H2O; energetic electrons are not recaptured) outlets is part of the energy management strategy of photosynthetic organisms that allows them to cope with the fluctuating conditions encountered in nature. Finally, unmasking the repertoire and control of such energetic reactions offers new directions for rational redesign and optimization of photosynthesis to satisfy global demands for food and other resources.
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Suslichenko IS, Tikhonov AN. Photo-reducible plastoquinone pools in chloroplasts of Tradescentia plants acclimated to high and low light. FEBS Lett 2019; 593:788-798. [PMID: 30896038 DOI: 10.1002/1873-3468.13366] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 02/28/2019] [Accepted: 03/19/2019] [Indexed: 11/09/2022]
Abstract
In photosynthetic systems of oxygenic type, plastoquinone (PQ) molecules are reduced by photosystem II (PSII). The turnover of PQ determines the rate of PSII operation. PQ molecules are present in surplus with respect to PSII. In this work, using the pulse amplitude modulation-fluorometry technique, we quantified photo-reducible PQ pools in chloroplasts of two contrasting ecotypes of Tradescantia, acclimated either to low light (~ 100 μmol photons·m-2 ·s-1 , LL) or to high light (~ 1000 μmol photons·m-2 ·s-1 , HL). The LL-grown plants are characterized by higher capacity of rapidly reducible PQ pool ([PQ]0 /[PSII] ≈ 8) as compared to HL-grown plants of both species ([PQ]0 /[PSII] ≈ 4). The elevated content of PQ in LL plants favours photosynthetic electron flow at low-solar irradiance.
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Affiliation(s)
| | - Alexander N Tikhonov
- Faculty of Physics, M.V.Lomonosov Moscow State University, Russia.,N.M.Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia
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Zlobin IE, Ivanov YV, Kartashov AV, Sarvin BA, Stavrianidi AN, Kreslavski VD, Kuznetsov VV. Impact of weak water deficit on growth, photosynthetic primary processes and storage processes in pine and spruce seedlings. PHOTOSYNTHESIS RESEARCH 2019; 139:307-323. [PMID: 29779192 DOI: 10.1007/s11120-018-0520-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 05/15/2018] [Indexed: 06/08/2023]
Abstract
We investigated the influence of 40 days of drought on growth, storage processes and primary photosynthetic processes in 3-month-old Scots pine and Norway spruce seedlings growing in perlite culture. Water stress significantly affected seedling water status, whereas absolute dry biomass growth was not substantially influenced. Water stress induced an increase in non-structural carbohydrate content (sugars, sugar alcohols, starch) in the aboveground part of pine seedlings in contrast to spruce seedlings. Due to the relatively low content of sugars and sugar alcohols in seedling organs, their expected contribution to osmotic potential changes was quite low. In contrast to biomass accumulation and storage, photosynthetic primary processes were substantially influenced by water shortage. In spruce seedlings, PSII was more sensitive to water stress than PSI. In particular, electron transport in PSI was stable under water stress despite the substantial decrease of electron transport in PSII. The increase in thermal energy dissipation due to enhancement of non-photochemical quenching (NPQ) was evident in both species under water stress. Simultaneously, the yields of non-regulated energy dissipation in PSII were decreased in pine seedlings under drought. A relationship between growth, photosynthetic activities and storage processes is analysed under weak water deficit.
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Affiliation(s)
- Ilya E Zlobin
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia
| | - Yury V Ivanov
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia.
| | - Alexander V Kartashov
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia
| | | | | | - Vladimir D Kreslavski
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Russia
| | - Vladimir V Kuznetsov
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia
- Tomsk State University, Tomsk, Russia
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Oxygenic photosynthesis: EPR study of photosynthetic electron transport and oxygen-exchange, an overview. Cell Biochem Biophys 2018; 77:47-59. [PMID: 30460441 DOI: 10.1007/s12013-018-0861-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Accepted: 11/01/2018] [Indexed: 12/28/2022]
Abstract
In this review, we consider the applications of electron paramagnetic resonance (EPR) methods to the study of the relationships between the electron transport and oxygen-exchange processes in photosynthetic systems of oxygenic type. One of the purposes of this article is to encourage scientists to use the advantageous EPR oximetry approaches to study oxygen-related electron transport processes in photosynthetic systems. The structural organization of the photosynthetic electron transfer chain and the EPR approaches to the measurements of molecular oxygen (O2) with O2-sensitive species (nitroxide spin labels and solid paramagnetic particles) are briefly reviewed. In solution, the collision of O2 with spin probes causes the broadening of their EPR spectra and the reduction of their spin-lattice relaxation times. Based on these effects, tools for measuring O2 concentration and O2 diffusion in biological systems have been developed. These methods, named "spin-label oximetry," include not only nitroxide spin labels, but also other stable-free radicals with narrow EPR lines, as well as particulate probes with EPR spectra sensitive to molecular oxygen (lithium phthalocyanine, coals, and India ink). Applications of EPR approaches for measuring O2 evolution and consumption are illustrated using examples of photosynthetic systems of oxygenic type, chloroplasts in situ (green leaves), and cyanobacteria.
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Ryu KH, Sung M, Kim B, Heo S, Chang YK, Lee JH. A mathematical model of intracellular behavior of microalgae for predicting growth and intracellular components syntheses under nutrient‐replete and ‐deplete conditions. Biotechnol Bioeng 2018; 115:2441-2455. [DOI: 10.1002/bit.26744] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Revised: 05/13/2018] [Accepted: 06/05/2018] [Indexed: 11/09/2022]
Affiliation(s)
- Kyung Hwan Ryu
- Department of Chemical and Biomolecular EngineeringKorea Advanced Institute of Science and TechnologyDeajeon Republic of Korea
| | - Min‐Gyu Sung
- Department of Chemical and Biomolecular EngineeringKorea Advanced Institute of Science and TechnologyDeajeon Republic of Korea
| | - Boeun Kim
- Department of Chemical and Biomolecular EngineeringKorea Advanced Institute of Science and TechnologyDeajeon Republic of Korea
| | - Seongmin Heo
- Department of Chemical and Biomolecular EngineeringKorea Advanced Institute of Science and TechnologyDeajeon Republic of Korea
| | - Yong Keun Chang
- Department of Chemical and Biomolecular EngineeringKorea Advanced Institute of Science and TechnologyDeajeon Republic of Korea
- Advanced Biomass R&D Center, Korea Advanced Institute of Science and TechnologyDeajeon Republic of Korea
| | - Jay H. Lee
- Department of Chemical and Biomolecular EngineeringKorea Advanced Institute of Science and TechnologyDeajeon Republic of Korea
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Mullineaux PM, Exposito-Rodriguez M, Laissue PP, Smirnoff N. ROS-dependent signalling pathways in plants and algae exposed to high light: Comparisons with other eukaryotes. Free Radic Biol Med 2018; 122:52-64. [PMID: 29410363 DOI: 10.1016/j.freeradbiomed.2018.01.033] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 01/27/2018] [Accepted: 01/31/2018] [Indexed: 01/09/2023]
Abstract
Like all aerobic organisms, plants and algae co-opt reactive oxygen species (ROS) as signalling molecules to drive cellular responses to changes in their environment. In this respect, there is considerable commonality between all eukaryotes imposed by the constraints of ROS chemistry, similar metabolism in many subcellular compartments, the requirement for a high degree of signal specificity and the deployment of thiol peroxidases as transducers of oxidising equivalents to regulatory proteins. Nevertheless, plants and algae carry out specialised signalling arising from oxygenic photosynthesis in chloroplasts and photoautotropism, which often induce an imbalance between absorption of light energy and the capacity to use it productively. A key means of responding to this imbalance is through communication of chloroplasts with the nucleus to adjust cellular metabolism. Two ROS, singlet oxygen (1O2) and hydrogen peroxide (H2O2), initiate distinct signalling pathways when photosynthesis is perturbed. 1O2, because of its potent reactivity means that it initiates but does not transduce signalling. In contrast, the lower reactivity of H2O2 means that it can also be a mobile messenger in a spatially-defined signalling pathway. How plants translate a H2O2 message to bring about changes in gene expression is unknown and therefore, we draw on information from other eukaryotes to propose a working hypothesis. The role of these ROS generated in other subcellular compartments of plant cells in response to HL is critically considered alongside other eukaryotes. Finally, the responses of animal cells to oxidative stress upon high irradiance exposure is considered for new comparisons between plant and animal cells.
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Affiliation(s)
- Philip M Mullineaux
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK.
| | | | | | - Nicholas Smirnoff
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
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Kamies R, Farrant JM, Tadele Z, Cannarozzi G, Rafudeen MS. A Proteomic Approach to Investigate the Drought Response in the Orphan Crop Eragrostis tef. Proteomes 2017; 5:E32. [PMID: 29140297 PMCID: PMC5748567 DOI: 10.3390/proteomes5040032] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/20/2017] [Accepted: 11/10/2017] [Indexed: 01/13/2023] Open
Abstract
The orphan crop, Eragrostis tef, was subjected to controlled drought conditions to observe the physiological parameters and proteins changing in response to dehydration stress. Physiological measurements involving electrolyte leakage, chlorophyll fluorescence and ultra-structural analysis showed tef plants tolerated water loss to 50% relative water content (RWC) before adverse effects in leaf tissues were observed. Proteomic analysis using isobaric tag for relative and absolute quantification (iTRAQ) mass spectrometry and appropriate database searching enabled the detection of 5727 proteins, of which 211 proteins, including a number of spliced variants, were found to be differentially regulated with the imposed stress conditions. Validation of the iTRAQ dataset was done with selected stress-related proteins, fructose-bisphosphate aldolase (FBA) and the protective antioxidant proteins, monodehydroascorbate reductase (MDHAR) and peroxidase (POX). Western blot analyses confirmed protein presence and showed increased protein abundance levels during water deficit while enzymatic activity for FBA, MDHAR and POX increased at selected RWC points. Gene ontology (GO)-term enrichment and analysis revealed terms involved in biotic and abiotic stress response, signaling, transport, cellular homeostasis and pentose metabolic processes, to be enriched in tef upregulated proteins, while terms linked to reactive oxygen species (ROS)-producing processes under water-deficit, such as photosynthesis and associated light harvesting reactions, manganese transport and homeostasis, the synthesis of sugars and cell wall catabolism and modification, to be enriched in tef downregulated proteins.
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Affiliation(s)
- Rizqah Kamies
- Department of Molecular and Cell Biology, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
| | - Jill M Farrant
- Department of Molecular and Cell Biology, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
| | - Zerihun Tadele
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
| | - Gina Cannarozzi
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
| | - Mohammed Suhail Rafudeen
- Department of Molecular and Cell Biology, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
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41
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Wu CS, Wang TJ, Wu CW, Wang YN, Chaw SM. Plastome Evolution in the Sole Hemiparasitic Genus Laurel Dodder (Cassytha) and Insights into the Plastid Phylogenomics of Lauraceae. Genome Biol Evol 2017; 9:2604-2614. [PMID: 28985306 PMCID: PMC5737380 DOI: 10.1093/gbe/evx177] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/06/2017] [Indexed: 12/29/2022] Open
Abstract
To date, little is known about the evolution of plastid genomes (plastomes) in Lauraceae. As one of the top five largest families in tropical forests, the Lauraceae contain many species that are important ecologically and economically. Lauraceous species also provide wonderful materials to study the evolutionary trajectory in response to parasitism because they contain both nonparasitic and parasitic species. This study compared the plastomes of nine Lauraceous species, including the sole hemiparasitic and herbaceous genus Cassytha (laurel dodder; here represented by Cassytha filiformis). We found differential contractions of the canonical inverted repeat (IR), resulting in two IR types present in Lauraceae. These two IR types reinforce Cryptocaryeae and Neocinnamomum-Perseeae-Laureae as two separate clades. Our data reveal several traits unique to Cas. filiformis, including loss of IRs, loss or pseudogenization of 11 ndh and rpl23 genes, richness of repeats, and accelerated rates of nucleotide substitutions in protein-coding genes. Although Cas. filiformis is low in chlorophyll content, our analysis based on dN/dS ratios suggests that both its plastid house-keeping and photosynthetic genes are under strong selective constraints. Hence, we propose that short generation time and herbaceous lifestyle rather than reduced photosynthetic ability drive the accelerated rates of nucleotide substitutions in Cas. filiformis.
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Affiliation(s)
- Chung-Shien Wu
- Biodiversity Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Ting-Jen Wang
- Biodiversity Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Chia-Wen Wu
- Biodiversity Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Ya-Nan Wang
- School of Forestry and Resource Conservation, Nation Taiwan University, Taipei 10617, Taiwan
| | - Shu-Miaw Chaw
- Biodiversity Research Center, Academia Sinica, Taipei 11529, Taiwan
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Saroussi S, Sanz-Luque E, Kim RG, Grossman AR. Nutrient scavenging and energy management: acclimation responses in nitrogen and sulfur deprived Chlamydomonas. CURRENT OPINION IN PLANT BIOLOGY 2017; 39:114-122. [PMID: 28692856 DOI: 10.1016/j.pbi.2017.06.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 06/08/2017] [Indexed: 05/10/2023]
Abstract
Photosynthetic organisms have evolved to modulate their metabolism to accommodate the highly dynamic light and nutrient conditions in nature. In this review we discuss ways in which the green alga Chlamydomonas reinhardtii acclimates to nitrogen and sulfur deprivation, conditions that would limit the anabolic use of excitation energy because of a markedly reduced capacity for cell growth and division. Major aspects of this acclimation process are stringently regulated and involve scavenging the limited nutrient from internal and external sources, and the redirection of fixed carbon toward energy storage (e.g. starch, oil). However, photosynthetic organisms have also evolved mechanisms to dissipate excess absorbed light energy, and to eliminate potentially dangerous energetic electrons through the reduction of O2 and H+ to H2O; this reduction can occur both through photosynthetic electron transport (e.g. Mehler reaction, chlororespiration) and mitochondrial respiration. Furthermore, algal cells likely exploit other energy management pathways that are currently not linked to nutrient limitation responses or that remain to be identified.
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Affiliation(s)
- Shai Saroussi
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, United States
| | - Emanuel Sanz-Luque
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, United States
| | - Rick G Kim
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, United States; Department of Biology, Stanford University, Stanford, CA 94305-5020, United States
| | - Arthur R Grossman
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, United States.
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Hanawa H, Ishizaki K, Nohira K, Takagi D, Shimakawa G, Sejima T, Shaku K, Makino A, Miyake C. Land plants drive photorespiration as higher electron-sink: comparative study of post-illumination transient O 2 -uptake rates from liverworts to angiosperms through ferns and gymnosperms. PHYSIOLOGIA PLANTARUM 2017; 161:138-149. [PMID: 28419460 DOI: 10.1111/ppl.12580] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 03/09/2017] [Accepted: 03/19/2017] [Indexed: 06/07/2023]
Abstract
In higher plants, the electron-sink capacity of photorespiration contributes to alleviation of photoinhibition by dissipating excess energy under conditions when photosynthesis is limited. We addressed the question at which point in the evolution of photosynthetic organisms photorespiration began to function as electron sink and replaced the flavodiiron proteins which catalyze the reduction of O2 at photosystem I in cyanobacteria. Algae do not have a higher activity of photorespiration when CO2 assimilation is limited, and it can therefore not act as an electron sink. Using land plants (liverworts, ferns, gymnosperms, and angiosperms) we compared photorespiration activity and estimated the electron flux driven by photorespiration to evaluate its electron-sink capacity at CO2 -compensation point. In vivo photorespiration activity was estimated by the simultaneous measurement of O2 -exchange rate and chlorophyll fluorescence yield. All C3-plants leaves showed transient O2 -uptake after actinic light illumination (post-illumination transient O2 -uptake), which reflects photorespiration activity. Post-illumination transient O2 -uptake rates increased in the order from liverworts to angiosperms through ferns and gymnosperms. Furthermore, photorespiration-dependent electron flux in photosynthetic linear electron flow was estimated from post-illumination transient O2 -uptake rate and compared with the electron flux in photosynthetic linear electron flow in order to evaluate the electron-sink capacity of photorespiration. The electron-sink capacity at the CO2 -compensation point also increased in the above order. In gymnosperms photorespiration was determined to be the main electron-sink. C3-C4 intermediate species of Flaveria plants showed photorespiration activity, which intermediate between that of C3- and C4-flaveria species. These results indicate that in the first land plants, liverworts, photorespiration started to function as electron sink. According to our hypothesis, the dramatic increase in partial pressure of O2 in the atmosphere about 0.4 billion years ago made it possible to drive photorespiration with higher activity in liverworts.
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Affiliation(s)
- Hitomi Hanawa
- Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan
| | - Kimitsune Ishizaki
- Department of Biology, Faculty of Science, Graduate School of Science, Kobe University, Kobe, 657-8501, Japan
| | - Kana Nohira
- Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan
| | - Daisuke Takagi
- Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan
| | - Ginga Shimakawa
- Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan
| | - Takehiro Sejima
- Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan
| | - Keiichiro Shaku
- Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan
| | - Amane Makino
- Department of Agriculture, Graduate School of Agricultural Science, Tohoku University, Sendai, 981-8555, Japan
| | - Chikahiro Miyake
- Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan
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Complete Chloroplast Genome Sequence of Coptis chinensis Franch. and Its Evolutionary History. BIOMED RESEARCH INTERNATIONAL 2017; 2017:8201836. [PMID: 28698879 PMCID: PMC5494076 DOI: 10.1155/2017/8201836] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 05/23/2017] [Indexed: 11/17/2022]
Abstract
The Coptis chinensis Franch. is an important medicinal plant from the Ranunculales. We used next generation sequencing technology to determine the complete chloroplast genome of C. chinensis. This genome is 155,484 bp long with 38.17% GC content. Two 26,758 bp long inverted repeats separated the genome into a typical quadripartite structure. The C. chinensis chloroplast genome consists of 128 gene loci, including eight rRNA gene loci, 28 tRNA gene loci, and 92 protein-coding gene loci. Most of the SSRs in C. chinensis are poly-A/T. The numbers of mononucleotide SSRs in C. chinensis and other Ranunculaceae species are fewer than those in Berberidaceae species, while the number of dinucleotide SSRs is greater than that in the Berberidaceae. C. chinensis diverged from other Ranunculaceae species an estimated 81 million years ago (Mya). The divergence between Ranunculaceae and Berberidaceae was ~111 Mya, while the Ranunculales and Magnoliaceae shared a common ancestor during the Jurassic, ~153 Mya. Position 104 of the C. chinensis ndhG protein was identified as a positively selected site, indicating possible selection for the photosystem-chlororespiration system in C. chinensis. In summary, the complete sequencing and annotation of the C. chinensis chloroplast genome will facilitate future studies on this important medicinal species.
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Strand DD, Fisher N, Kramer DM. The higher plant plastid NAD(P)H dehydrogenase-like complex (NDH) is a high efficiency proton pump that increases ATP production by cyclic electron flow. J Biol Chem 2017; 292:11850-11860. [PMID: 28559282 DOI: 10.1074/jbc.m116.770792] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 05/26/2017] [Indexed: 12/31/2022] Open
Abstract
Cyclic electron flow around photosystem I (CEF) is critical for balancing the photosynthetic energy budget of the chloroplast by generating ATP without net production of NADPH. We demonstrate that the chloroplast NADPH dehydrogenase complex, a homolog to respiratory Complex I, pumps approximately two protons from the chloroplast stroma to the lumen per electron transferred from ferredoxin to plastoquinone, effectively increasing the efficiency of ATP production via CEF by 2-fold compared with CEF pathways involving non-proton-pumping plastoquinone reductases. By virtue of this proton-pumping stoichiometry, we hypothesize that NADPH dehydrogenase not only efficiently contributes to ATP production but operates near thermodynamic reversibility, with potentially important consequences for remediating mismatches in the thylakoid energy budget.
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Affiliation(s)
- Deserah D Strand
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48823
| | - Nicholas Fisher
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48823
| | - David M Kramer
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48823; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48823.
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Røkke G, Melø TB, Hohmann-Marriott MF. The plastoquinone pool of Nannochloropsis oceanica is not completely reduced during bright light pulses. PLoS One 2017; 12:e0175184. [PMID: 28403199 PMCID: PMC5389811 DOI: 10.1371/journal.pone.0175184] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 03/21/2017] [Indexed: 11/18/2022] Open
Abstract
The lipid-producing model alga Nannochloropsis oceanica has a distinct photosynthetic machinery. This organism possesses chlorophyll a as its only chlorophyll species, and has a high ratio of PSI to PSII. This high ratio of PSI to PSII may affect the redox state of the plastoquinone pool during exposure to light, and consequently may play a role in activating photoprotection mechanisms. We utilized pulse-amplitude modulated fluorometry to investigate the redox state of the plastoquinone pool during and after bright light pulses. Our data indicate that even very intense (5910 μmol photons s-1m-2 of blue light having a wavelength of 440 nm) light pulses of 0.8 second duration are not sufficient to completely reduce the plastoquinone pool in Nannochloropsis. In order to achieve extensive reduction of the plastoquinone pool by bright light pulses, anaerobic conditions or an inhibitor of the photosynthetic electron transport chain has to be utilized. The implication of this finding for the application of the widely used saturating pulse method in algae is discussed.
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Affiliation(s)
- Gunvor Røkke
- Department of Biotechnology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Thor Bernt Melø
- Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway
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Characterization of the influence of chlororespiration on the regulation of photosynthesis in the glaucophyte Cyanophora paradoxa. Sci Rep 2017; 7:46100. [PMID: 28387347 PMCID: PMC5384210 DOI: 10.1038/srep46100] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 03/10/2017] [Indexed: 01/19/2023] Open
Abstract
Glaucophytes are primary symbiotic algae with unique plastids called cyanelles, whose structure is most similar to ancestral cyanobacteria among plastids in photosynthetic organisms. Here we compare the regulation of photosynthesis in glaucophyte with that in cyanobacteria in the aim of elucidating the changes caused by the symbiosis in the interaction between photosynthetic electron transfer and other metabolic pathways. Chlorophyll fluorescence measurements of the glaucophyte Cyanophora paradoxa NIES-547 indicated that plastoquinone (PQ) pool in photosynthetic electron transfer was reduced in the dark by chlororespiration. The levels of nonphotochemical quenching of chlorophyll fluorescence was high in the dark but decreased under low light, and increased again under high light. This type of concave light dependence was quite similar to that observed in cyanobacteria. Moreover, the addition of ionophore hardly affected nonphotochemical quenching, suggesting state transition as a main component of the regulatory system in C. paradoxa. These results suggest that cyanelles of C. paradoxa retain many of the characteristics observed in their ancestral cyanobacteria. From the viewpoint of metabolic interactions, C. paradoxa is the primary symbiotic algae most similar to cyanobacteria than other lineages of photosynthetic organisms.
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Paredes M, Quiles MJ. Chilling stress and hydrogen peroxide accumulation in Chrysanthemum morifolium and Spathiphyllum lanceifolium. Involvement of chlororespiration. JOURNAL OF PLANT PHYSIOLOGY 2017; 211:36-41. [PMID: 28142095 DOI: 10.1016/j.jplph.2016.11.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 11/28/2016] [Accepted: 11/29/2016] [Indexed: 05/11/2023]
Abstract
Plants of Chrysanthemum morifolium (sun species) and Spathiphyllum lanceifolium (shade species) were used to study the effects of chilling stems under high illumination. The stress conditions resulted in a greater accumulation of H2O2 in C. morifolium than in S. lanceifolium, and in the down-regulation of photosynthetic linear electron transport in both species. However, only a slight decrease in the maximal quantum yield of PSII was observed under unfavorable conditions in both species, suggesting that mechanisms exist in the chloroplasts that dissipate excess excitation energy and prevent damage to the photosynthetic apparatus. Additionally, changes were observed in the PGR5 polypeptide involved in cyclic electron flow around PSI and in chlororespiratory enzymes (plastidial NDH complex and PTOX). The level of PGR5 increased significantly only in chilled plants of C. morifolium, whereas the levels of the PTOX and NDH-H polypeptide of the plastidial NDH complex and the NDH activity increased significantly only in chilled plants of S. lanceifolium. These findings suggest that the cyclic electron flow involving PGR5 is more active in C. morifolium, while in S. lanceifolium, other mechanisms involving chlororespiratory enzymes are stimulated in response to chilling and high light, resulting in less H2O2 being accumulated in leaves.
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Affiliation(s)
- Miriam Paredes
- Departamento de Biología Vegetal, Facultad de Biología, Universidad de Murcia, Campus de Espinardo, E-30100 Murcia, Spain
| | - María José Quiles
- Departamento de Biología Vegetal, Facultad de Biología, Universidad de Murcia, Campus de Espinardo, E-30100 Murcia, Spain.
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Figueroa FL, Álvarez-Gómez F, del Rosal Y, Celis-Plá PS, González G, Hernández M, Korbee N. In situ photosynthetic yields of cave photoautotrophic biofilms using two different Pulse Amplitude Modulated fluorometers. ALGAL RES 2017. [DOI: 10.1016/j.algal.2016.12.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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50
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Huang W, Yang YJ, Zhang SB. Specific roles of cyclic electron flow around photosystem I in photosynthetic regulation in immature and mature leaves. JOURNAL OF PLANT PHYSIOLOGY 2017; 209:76-83. [PMID: 28013173 DOI: 10.1016/j.jplph.2016.11.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 11/07/2016] [Accepted: 11/16/2016] [Indexed: 05/07/2023]
Abstract
Cyclic electron flow (CEF) around photosystem I (PSI) is essential for photosynthesis in mature leaves. However, the physiological roles of CEF in immature leaves are little known. Here, we measured the PSI and PSII activities, light response changes in PSI and PSII energy quenching for immature and mature leaves of Erythrophleum guineense grown under full sunlight. Comparing with the maximum quantum yield of PSII (Fv/Fm), the immature leaves had much lower values of the maximum photo-oxidizable P700 (Pm) than the mature leaves, suggesting the unsynchronized development of PSI and PSII activities. Furthermore, the immature leaves displayed significantly lower capacities for the photosynthetic electron flow through PSII (ETRII) and CEF. However, when exposed to high light, the immature leaves displayed higher levels of non-photochemical quenching (NPQ) and P700 oxidation ration [Y(ND)] than mature leaves. Under high light, the similar NPQ values were accompanied with much lower CEF activity in the immature leaves. These results suggest that, in immature leaves, CEF primarily contributes to photoprotection for PSI and PSII via acidification of thylakoid lumen. By comparison, in mature leaves, a large fraction of CEF-dependent generation of ΔpH contributes to ATP synthesis and a relative small proportion favors photoprotection via lumen acidification. These findings highlight the specific roles of CEF in photosynthetic regulation in immature and mature leaves.
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Affiliation(s)
- Wei Huang
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China; Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China
| | - Ying-Jie Yang
- Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China
| | - Shi-Bao Zhang
- Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China.
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