scholarly journals Structure of a C2S2M2N2-type PSII–LHCII supercomplex from the green alga Chlamydomonas reinhardtii

2019 ◽  
Vol 116 (42) ◽  
pp. 21246-21255 ◽  
Author(s):  
Liangliang Shen ◽  
Zihui Huang ◽  
Shenghai Chang ◽  
Wenda Wang ◽  
Jingfen Wang ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Chlamydomonas Reinhardtii ◽  
Green Alga ◽  
Higher Plants ◽  
Huge Number ◽  
Higher Plant ◽  
Low Light ◽  
Green Algal ◽  
Light Harvesting Antenna ◽  
Energy Transfer Pathway

Photosystem II (PSII) in the thylakoid membranes of plants, algae, and cyanobacteria catalyzes light-induced oxidation of water by which light energy is converted to chemical energy and molecular oxygen is produced. In higher plants and most eukaryotic algae, the PSII core is surrounded by variable numbers of light-harvesting antenna complex II (LHCII), forming a PSII–LHCII supercomplex. In order to harvest energy efficiently at low–light-intensity conditions under water, a complete PSII–LHCII supercomplex (C2S2M2N2) of the green alga Chlamydomonas reinhardtii (Cr) contains more antenna subunits and pigments than the dominant PSII–LHCII supercomplex (C2S2M2) of plants. The detailed structure and energy transfer pathway of the Cr-PSII–LHCII remain unknown. Here we report a cryoelectron microscopy structure of a complete, C2S2M2N2-type PSII–LHCII supercomplex from C. reinhardtii at 3.37-Å resolution. The results show that the Cr-C2S2M2N2 supercomplex is organized as a dimer, with 3 LHCII trimers, 1 CP26, and 1 CP29 peripheral antenna subunits surrounding each PSII core. The N-LHCII trimer partially occupies the position of CP24, which is present in the higher-plant PSII–LHCII but absent in the green alga. The M trimer is rotated relative to the corresponding M trimer in plant PSII–LHCII. In addition, some unique features were found in the green algal PSII core. The arrangement of a huge number of pigments allowed us to deduce possible energy transfer pathways from the peripheral antennae to the PSII core.

scholarly journals Structure of photosystem I-LHCI-LHCII from the green alga Chlamydomonas reinhardtii in State 2

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zihui Huang ◽  
Liangliang Shen ◽  
Wenda Wang ◽  
Zhiyuan Mao ◽  
Xiaohan Yi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Energy Transfer ◽  
Chlamydomonas Reinhardtii ◽  
Green Alga ◽  
Photosystem I ◽  
State Transition ◽  
Higher Plants ◽  
Photosynthetic Performance ◽  
Light Harvesting Complexes ◽  
Cryo Electron Microscopy

AbstractPhotosystem I (PSI) and II (PSII) balance their light energy distribution absorbed by their light-harvesting complexes (LHCs) through state transition to maintain the maximum photosynthetic performance and to avoid photodamage. In state 2, a part of LHCII moves to PSI, forming a PSI-LHCI-LHCII supercomplex. The green alga Chlamydomonas reinhardtii exhibits state transition to a far larger extent than higher plants. Here we report the cryo-electron microscopy structure of a PSI-LHCI-LHCII supercomplex in state 2 from C. reinhardtii at 3.42 Å resolution. The result reveals that the PSI-LHCI-LHCII of C. reinhardtii binds two LHCII trimers in addition to ten LHCI subunits. The PSI core subunits PsaO and PsaH, which were missed or not well-resolved in previous Cr-PSI-LHCI structures, are observed. The present results reveal the organization and assembly of PSI core subunits, LHCI and LHCII, pigment arrangement, and possible pathways of energy transfer from peripheral antennae to the PSI core.

scholarly journals Condensation of Rubisco into a proto-pyrenoid in higher plant chloroplasts

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Nicky Atkinson ◽  
Yuwei Mao ◽  
Kher Xing Chan ◽  
Alistair J. McCormick
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Recent Work ◽  
Single Phase ◽  
Inorganic Carbon ◽  
Higher Plants ◽  
Initial Step ◽  
Operating Efficiency ◽  
Higher Plant ◽  
Spontaneous Condensation ◽  
Concentrating Mechanism

AbstractPhotosynthetic CO2 fixation in plants is limited by the inefficiency of the CO2-assimilating enzyme Rubisco. In most eukaryotic algae, Rubisco aggregates within a microcompartment known as the pyrenoid, in association with a CO2-concentrating mechanism that improves photosynthetic operating efficiency under conditions of low inorganic carbon. Recent work has shown that the pyrenoid matrix is a phase-separated, liquid-like condensate. In the alga Chlamydomonas reinhardtii, condensation is mediated by two components: Rubisco and the linker protein EPYC1 (Essential Pyrenoid Component 1). Here, we show that expression of mature EPYC1 and a plant-algal hybrid Rubisco leads to spontaneous condensation of Rubisco into a single phase-separated compartment in Arabidopsis chloroplasts, with liquid-like properties similar to a pyrenoid matrix. This work represents a significant initial step towards enhancing photosynthesis in higher plants by introducing an algal CO2-concentrating mechanism, which is predicted to significantly increase the efficiency of photosynthetic CO2 uptake.

scholarly journals The small RNA locus map for Chlamydomonas reinhardtii

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242516
Author(s):  
Sebastian Y. Müller ◽  
Nicholas E. Matthews ◽  
Adrian A. Valli ◽  
David C. Baulcombe
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Genome Stability ◽  
Higher Plants ◽  
Multiple Correspondence Analysis ◽  
Regulation Of Gene Expression ◽  
Transcriptional Gene Silencing ◽  
Evolutionary Divergence ◽  
Learning Approaches ◽  
Higher Plant ◽  
Systematic Classification

Small (s)RNAs play crucial roles in the regulation of gene expression and genome stability across eukaryotes where they direct epigenetic modifications, post-transcriptional gene silencing, and defense against both endogenous and exogenous viruses. It is known that Chlamydomonas reinhardtii, a well-studied unicellular green algae species, possesses sRNA-based mechanisms that are distinct from those of land plants. However, definition of sRNA loci and further systematic classification is not yet available for this or any other algae. Here, using data-driven machine learning approaches including Multiple Correspondence Analysis (MCA) and clustering, we have generated a comprehensively annotated and classified sRNA locus map for C. reinhardtii. This map shows some common characteristics with higher plants and animals, but it also reveals distinct features. These results are consistent with the idea that there was diversification in sRNA mechanisms after the evolutionary divergence of algae from higher plant lineages.

scholarly journals Purification and characterization of high- and low-molecular-mass isoforms of phosphoenolpyruvate carboxylase from Chlamydomonas reinhardtii

1998 ◽  
Vol 331 (1) ◽  
pp. 201-209 ◽  
Author(s):  
Jean RIVOAL ◽  
William C. PLAXTON ◽  
David H. TURPIN
Keyword(s):  
Green Algae ◽  
Phosphoenolpyruvate Carboxylase ◽  
Higher Plants ◽  
Current Model ◽  
Catalytic Subunit ◽  
Dihydroxyacetone Phosphate ◽  
Evolutionary Divergence ◽  
Banana Fruit ◽  
Higher Plant ◽  
Green Algal

Phosphoenolpyruvate carboxylase (PEPC) is a key enzyme in the supply of carbon skeletons for the assimilation of nitrogen by green algae. Two PEPC isoforms with respective native molecular masses of 400 (PEPC1) and 650 (PEPC2) kDa have been purified from Chlamydomonas reinhardtiiCW-15 cc1883 (Chlorophyceae). SDS/PAGE, immunoblot and CNBr peptide-mapping analyses indicate the presence of the same 100 kDa PEPC catalytic subunit in both isoforms. PEPC1 is a homotetramer, whereas PEPC2 seems to be a complex between the PEPC catalytic subunit and other immunologically unrelated polypeptides of 50–70 kDa. Kinetic analyses indicate that these PEPC isoforms are (1) differentially regulated by pH, (2) activated by glutamine and dihydroxyacetone phosphate and (3) inhibited by glutamate, aspartate, 2-oxoglutarate and malate. These results are consistent with the current model for the regulation of anaplerotic carbon fixation in green algae, and demonstrate that green algal PEPCs are uniquely regulated by glutamine. Several techniques were used to assess the structural relationships between C. reinhardtiiPEPC and the higher plant or prokaryotic enzyme. Immunoblot studies using anti-(green algal or higher plant PEPC) IgGs suggested that green algal (C. reinhardtii, Selenastrum minutum), higher plant (maize, banana fruit, tobacco) and prokaryotic (Synechococcus leopoliensis, Escherichia coli)PEPCs have little or no immunological relatedness. Moreover, the N-terminal amino acid sequence of the C. reinhardtiiPEPC subunit did not have significant similarity to the highly conserved corresponding region in enzymes from higher plants, and CNBr cleavage patterns of green algal PEPCs were distinct from those of higher plant and cyanobacterial PEPCs. These results point to significant evolutionary divergence between green algal, higher plant and prokaryotic PEPCs.

scholarly journals Difference in light use strategy in red alga between Griffithsia pacifica and Porphyridium purpureum

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mingyuan Xie ◽  
Wenjun Li ◽  
Hanzhi Lin ◽  
Xiaoxiao Wang ◽  
Jianwen Dong ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Red Algae ◽  
High Efficiency ◽  
Fluorescence Decay ◽  
Light Environment ◽  
Low Light ◽  
Porphyridium Purpureum ◽  
Time Resolved ◽  
Transfer Rates ◽  
Light Harvesting Antenna

AbstractPhycobilisomes (PBSs) are the largest light-harvesting antenna in red algae, and feature high efficiency and rate of energy transfer even in a dim environment. To understand the influence of light on the energy transfer in PBSs, two red algae Griffithsia pacifica and Porphyridium purpureum living in different light environment were selected for this research. The energy transfer dynamics in PBSs of the two red algae were studied in time-resolved fluorescence spectroscopy in sub-picosecond resolution. The energy transfer pathways and the related transfer rates were uncovered by deconvolution of the fluorescence decay curve. Four time-components, i.e., 8 ps, 94 ps, 970 ps, and 2288 ps were recognized in the energy transfer in PBSs of G. pacifica, and 10 ps, 74 ps, 817 ps and 1292 ps in P. purpureum. In addition, comparison in energy transfer dynamics between the two red algae revealed that the energy transfer was clearly affected by lighting environment. The findings help us to understand the energy transfer mechanisms of red algae for adaptation to a natural low light environment.

Only iron-limited cells of the cyanobacterium Anabaena flos-aquae inhibit growth of the green alga Chlamydomonas reinhardtii

2004 ◽  
Vol 82 (4) ◽  
pp. 436-442 ◽  
Author(s):  
Carlyn J Matz ◽  
Michael R Christensen ◽  
Auralee D Bone ◽  
Courtney D Gress ◽  
Scott B Widenmaier ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Green Alga ◽  
Activated Charcoal ◽  
Algal Growth ◽  
Inhibitory Effect ◽  
The Other ◽  
Iron Limitation ◽  
Green Algal ◽  
Cyanobacterium Anabaena ◽  
Cobalt Copper

Cocultivation of iron-limited cells of the cyanobacterium Anabaena flos-aquae (Lyng.) Brèb. and the green alga Chlamydomonas reinhardtii Dangeard resulted in growth of Anabaena but not Chlamydomonas, even in the presence of excess exogenous iron. This effect was also observed during the cultivation of Chlamydomonas in a medium in which iron-limited Anabaena cells had been growing, but were removed prior to culture of Chlamydomonas. Conversely, iron-limited Chlamydomonas cells grew very well in medium from iron (nutrient)-sufficient, phosphate-limited, and nitrogen-limited Anabaena cultures. Iron-limited Anabaena cultures produced siderophores, while the other types of Anabaena cultures did not. Treatment of Anabaena iron-limited medium with activated charcoal completely removed the inhibitory effect on Chlamydomonas growth, and boiling the medium removed most of the inhibitory effect. Both the charcoal and the boiling treatments also removed siderophores from the medium. Partially purified Anabaena siderophore preparations were also inhibitory to Chlamydomonas growth. The inhibitory effect of iron-limited Anabaena medium could be partially overcome by addition of excess micronutrients (especially cobalt copper) but not by addition of iron. We suggest that Anabaena-derived siderophores, present only in iron-limited Anabaena medium, inhibit the growth of Chlamydomonas cells via a previously uncharacterized toxicity. This effect is different from previously described experiments in which cyanobacterial siderophores suppressed green algal growth via competition for limiting amounts of iron.Key words: Anabaena, Chlamydomonas, cocultivation, iron limitation, micronutrients; siderophores.

scholarly journals Catalytic by-product formation and ligand binding by ribulose bisphosphate carboxylases from different phylogenies

2006 ◽  
Vol 399 (3) ◽  
pp. 525-534 ◽  
Author(s):  
F. Grant Pearce
Keyword(s):  
Rhodospirillum Rubrum ◽  
Higher Plants ◽  
Product Formation ◽  
Enzyme Dynamics ◽  
Ribulose Bisphosphate ◽  
Higher Plant ◽  
Bisphosphate Carboxylase ◽  
Green Algal ◽  
Activated State ◽  
By Products

During catalysis, all Rubisco (D-ribulose-1,5-bisphosphate carboxylase/oxygenase) enzymes produce traces of several by-products. Some of these by-products are released slowly from the active site of Rubisco from higher plants, thus progressively inhibiting turnover. Prompted by observations that Form I Rubisco enzymes from cyanobacteria and red algae, and the Form II Rubisco enzyme from bacteria, do not show inhibition over time, the production and binding of catalytic by-products was measured to ascertain the underlying differences. In the present study we show that the Form IB Rubisco from the cyanobacterium Synechococcus PCC6301, the Form ID enzyme from the red alga Galdieria sulfuraria and the low-specificity Form II type from the bacterium Rhodospirillum rubrum all catalyse formation of by-products to varying degrees; however, the by-products are not inhibitory under substrate-saturated conditions. Study of the binding and release of phosphorylated analogues of the substrate or reaction intermediates revealed diverse strategies for avoiding inhibition. Rubisco from Synechococcus and R. rubrum have an increased rate of inhibitor release. G. sulfuraria Rubisco releases inhibitors very slowly, but has an increased binding constant and maintains the enzyme in an activated state. These strategies may provide information about enzyme dynamics, and the degree of enzyme flexibility. Our observations also illustrate the phylogenetic diversity of mechanisms for regulating Rubisco and raise questions about whether an activase-like mechanism should be expected outside the green-algal/higher-plant lineage.

scholarly journals Unique organization of photosystem I–light-harvesting supercomplex revealed by cryo-EM from a red alga

2018 ◽  
Vol 115 (17) ◽  
pp. 4423-4428 ◽  
Author(s):  
Xiong Pi ◽  
Lirong Tian ◽  
Huai-En Dai ◽  
Xiaochun Qin ◽  
Lingpeng Cheng ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Photosystem I ◽  
Light Harvesting ◽  
Higher Plants ◽  
Red Alga ◽  
Cyanidioschyzon Merolae ◽  
Higher Plant ◽  
Light Harvesting Complex ◽  
Red Algal ◽  
Eukaryotic Organisms

Photosystem I (PSI) is one of the two photosystems present in oxygenic photosynthetic organisms and functions to harvest and convert light energy into chemical energy in photosynthesis. In eukaryotic algae and higher plants, PSI consists of a core surrounded by variable species and numbers of light-harvesting complex (LHC)I proteins, forming a PSI-LHCI supercomplex. Here, we report cryo-EM structures of PSI-LHCR from the red alga Cyanidioschyzon merolae in two forms, one with three Lhcr subunits attached to the side, similar to that of higher plants, and the other with two additional Lhcr subunits attached to the opposite side, indicating an ancient form of PSI-LHCI. Furthermore, the red algal PSI core showed features of both cyanobacterial and higher plant PSI, suggesting an intermediate type during evolution from prokaryotes to eukaryotes. The structure of PsaO, existing in eukaryotic organisms, was identified in the PSI core and binds three chlorophylls a and may be important in harvesting energy and in mediating energy transfer from LHCII to the PSI core under state-2 conditions. Individual attaching sites of LHCRs with the core subunits were identified, and each Lhcr was found to contain 11 to 13 chlorophylls a and 5 zeaxanthins, which are apparently different from those of LHCs in plant PSI-LHCI. Together, our results reveal unique energy transfer pathways different from those of higher plant PSI-LHCI, its adaptation to the changing environment, and the possible changes of PSI-LHCI during evolution from prokaryotes to eukaryotes.

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