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.

Identification of Polycistronic Transcriptional Units and Non-canonical Introns in Green Algal Chloroplasts Based on Long-read RNA Sequencing Data

2020 ◽  
Author(s):  
Xiaoxiao Zou ◽  
Heroen Verbruggen ◽  
Tianjingwei Li ◽  
Jun Zhu ◽  
Zuo Chen ◽  
...  
Keyword(s):  
Chloroplast Genome ◽  
Green Algae ◽  
Higher Plants ◽  
Green Algal ◽  
Chloroplast Genomes ◽  
Caulerpa Lentillifera ◽  
Transcriptional Units ◽  
Group Ii ◽  
Distinct Features ◽  
Algal Chloroplast

Abstract Background: Chloroplasts are important semi-autonomous organelles in plants and algae. Unlike higher plants, the chloroplast genomes of green algal linage have distinct features both in organization and expression. Despite the architecture of chloroplast genome have been extensively studied in higher plants and several model species of algae, little is known about transcriptional features in green algal lineages. Results: Based on full-length cDNA (Iso-Seq) sequencing, we identified widely co-transcribed polycistronic transcriptional units (PTUs) in the green alga Caulerpa lentillifera. In addition to clusters of genes from the same pathway, we identified a series of PTUs of up to nine genes whose function in the plastid is not understood. The RNA data further allowed us to confirm widespread expression of fragmented genes and conserved open reading frames, which are both important features in green algal chloroplast genomes. In addition, a newly fragmented gene specific to C. lentillifera was discovered, which may represent a recent gene fragmentation event in chloroplast genome.Taking the accurate exon-intron boundary information, gene structural annotation was greatly improved across the siphonous green algae lineages. Our data also revealed a type of non-canonical Group II introns, with a deviant secondary structure and intronic ORFs lacking known splicing or mobility domains. These widespread introns have conserved positions in their genes and are excised precisely despite lacking clear consensus intron boundaries.Conclusion: Our study fills important knowledge gaps in chloroplast genome organization and transcription in green algae, and providing new insights into expression of polycistronic transcripts, freestanding ORFs and fragmented genes in algal chloroplast genomes. Moreover, we revealed an unusual type of Group II intron with distinct features and conserved positions in Bryopsidales. Our data represents interesting additions to knowledge of chloroplast intron structure and highlights clusters of uncharacterized genes that probably play important roles in plastid.

scholarly journals Midpoint redox potentials of plant and algal ferredoxins

1977 ◽  
Vol 168 (2) ◽  
pp. 205-209 ◽  
Author(s):  
R Cammack ◽  
K K Rao ◽  
C P Bargeron ◽  
K G Hutson ◽  
P W Andrew ◽  
...  
Keyword(s):  
Green Algae ◽  
Higher Plants ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Photosynthetic Electron Transport ◽  
Resonance Spectroscopy ◽  
Redox Potentials ◽  
Higher Plant ◽  
Paramagnetic Resonance ◽  
Blue Green Algae ◽  
Nostoc Strain

Midpoint potentials of plant-type ferredoxins from a range of sources were measured by redox titrations combined with electron-paramagnetic-resonance spectroscopy. For ferredoxins from higher plants, green algae and most red algae, the midpoint potentials (at pH 8.0) were between —390 and —425 mV. Values for the major ferredoxin fractions from blue-green algae were less negative (between —325 and —390 mV). In addition, Spirulina maxima and Nostoc strain MAC contain second minor ferredoxin components with a different potential, —305 mV (the highest so far measured for a plant-algal ferrodoxin) for Spirulina ferrodoxin II, and —455 mV (the lowest so far measured for a plant-algal ferredoxin) for Nostoc strain MAC ferredoxin II. However, two ferredoxins extracted from a variety of the higher plant Pisum sativum (pea) had midpoint potentials that were only slightly different from each other. These values are discussed in terms of possible roles for the ferredoxins in addition to their involvement in photosynthetic electron transport.

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 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 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 Mapping the Algal Secret Genome: The small RNA Locus Map for Chlamydomonas reinhardtii

2020 ◽  
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

AbstractSmall (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. The green alga Chlamydomonas reinhardtii is a well-studied unicellular alga species with sRNA-based mechanisms that are distinct from those of land plants. It is, therefore, a good model to study sRNA evolution but a systematic classification of sRNA mechanisms is lacking in this and 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.

Confocal microscopy of thylakoid autofluorescence in relation to origin of grana and phylogeny in the green algae

1999 ◽  
Vol 26 (7) ◽  
pp. 695 ◽  
Author(s):  
B. E. S. Gunning ◽  
O. M. Schwartz
Keyword(s):  
Electron Microscopy ◽  
Chlorophyll Fluorescence ◽  
Confocal Microscopy ◽  
Green Algae ◽  
Higher Plants ◽  
Higher Plant ◽  
Thylakoid Stacking ◽  
Uniform Background ◽  
High Concentrations ◽  
Thylakoid Appression

Confocal microscopy was used to examine heterogeneity of chlorophyll fluorescence in chloroplasts of selected green algae, in the light of evidence that the technique reveals the distribution of photosystem II (PSII). Three levels of complexity were seen: (1) uniform fluorescence (Codium) or intergrading zones of bright and less bright fluorescence in genera known from electron microscopy to have irregular areas of thylakoid appression (e.g. Chlamydomonas — in which Bertos and Gibbs (J. Phycol., 34, 1009, 1998) have found absence of segregation of photosystem I (PSI) and PSII, Ulothrix, Stigeoclonium, Draparnaldia); (2) a pattern of 1–2 µm patches of fluorescence on a less bright uniform background, in taxa where more organized thylakoid stacking (but not grana sensu higher plants) is seen by electron microscopy (Ulva, Oedogonium); and (3) Discrete 0.5–2 µm spots of fluorescence in a relatively fluorescence-free background, closely resembling higher plant grana (Cladophorophyceae, Zygnematales, Coleochaete, Nitella). Further investigation of these states may illuminate the evolution of higher plant thylakoid systems, where PSII is segregated into grana, and may provide clues concerning the adaptive advantages of grana. Association of putative PSII fluorescence with pyrenoids was found in most taxa, although fluorescence of trans-pyrenoid thylakoids was seen in one case only. The association prevails whether or not there is a starch sheath around the pyrenoids, and is persistent in pyrenoids isolated from Spirogyra. We speculate that this fluorescence may represent a subset of PSII that functions with thylakoid carbonic anhydrase to provide locally high concentrations of CO2 to the Rubisco in the pyrenoid core, as predicted by Raven (Plant, Cell and Environment, 20, 147, 1997).

scholarly journals Identification of polycistronic transcriptional units and non-canonical introns in green algal chloroplasts based on long-read RNA sequencing data

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Xiaoxiao Zou ◽  
Heroen Verbruggen ◽  
Tianjingwei Li ◽  
Jun Zhu ◽  
Zou Chen ◽  
...  
Keyword(s):  
Chloroplast Genome ◽  
Green Algae ◽  
Higher Plants ◽  
Green Algal ◽  
Chloroplast Genomes ◽  
Caulerpa Lentillifera ◽  
Transcriptional Units ◽  
Group Ii ◽  
Distinct Features ◽  
Algal Chloroplast

Abstract Background Chloroplasts are important semi-autonomous organelles in plants and algae. Unlike higher plants, the chloroplast genomes of green algal linage have distinct features both in organization and expression. Despite the architecture of chloroplast genome having been extensively studied in higher plants and several model species of algae, little is known about the transcriptional features of green algal chloroplast-encoded genes. Results Based on full-length cDNA (Iso-Seq) sequencing, we identified widely co-transcribed polycistronic transcriptional units (PTUs) in the green alga Caulerpa lentillifera. In addition to clusters of genes from the same pathway, we identified a series of PTUs of up to nine genes whose function in the plastid is not understood. The RNA data further allowed us to confirm widespread expression of fragmented genes and conserved open reading frames, which are both important features in green algal chloroplast genomes. In addition, a newly fragmented gene specific to C. lentillifera was discovered, which may represent a recent gene fragmentation event in the chloroplast genome. With the newly annotated exon-intron boundary information, gene structural annotation was greatly improved across the siphonous green algae lineages. Our data also revealed a type of non-canonical Group II introns, with a deviant secondary structure and intronic ORFs lacking known splicing or mobility domains. These widespread introns have conserved positions in their genes and are excised precisely despite lacking clear consensus intron boundaries. Conclusion Our study fills important knowledge gaps in chloroplast genome organization and transcription in green algae, and provides new insights into expression of polycistronic transcripts, freestanding ORFs and fragmented genes in algal chloroplast genomes. Moreover, we revealed an unusual type of Group II intron with distinct features and conserved positions in Bryopsidales. Our data represents interesting additions to knowledge of chloroplast intron structure and highlights clusters of uncharacterized genes that probably play important roles in plastids.

A Scanning Electron Microscopic Study of Pro-Vascular Cellular Morphology in Chaetophora Incressata

1985 ◽  
Vol 43 ◽  
pp. 638-639
Author(s):  
A. E. Hotchkiss ◽  
A. T. Hotchkiss ◽  
R. P. Apkarian
Keyword(s):  
Green Algae ◽  
Vascular Plants ◽  
Vascular System ◽  
Higher Plants ◽  
Wall Structure ◽  
Electron Microscopic ◽  
Physiological Processes ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Multicellular green algae may be an ancestral form of the vascular plants. These algae exhibit cell wall structure, chlorophyll pigmentation, and physiological processes similar to those of higher plants. The presence of a vascular system which provides water, minerals, and nutrients to remote tissues in higher plants was believed unnecessary for the algae. Among the green algae, the Chaetophorales are complex highly branched forms that might require some means of nutrient transport. The Chaetophorales do possess apical meristematic groups of cells that have growth orientations suggestive of stem and root positions. Branches of Chaetophora incressata were examined by the scanning electron microscope (SEM) for ultrastructural evidence of pro-vascular transport.

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