Glaucocystophyte Cyanophora Paradoxa Research Articles

Phycobilisome model with novel skeleton-like structures in a glaucocystophyte Cyanophora paradoxa

Phycobilisome (PBS) is a photosynthetic antenna supercomplex consisting of a central core subcomplex with several peripheral rods radiating from the core. Subunit structure of PBS was studied in a glaucocystophyte Cyanophora paradoxa strain NIES 547. Subunit composition of PBS was identified by N-terminal sequencing and genes for the subunits were determined by homology search of databases. They included rod linker proteins CpcK1 and CpcK2, rod-core linker proteins CpcG1 and CpcG2, and core linker proteins ApcC1 and ApcC2. Subfractionation by native polyacrylamide gel electrophoresis provided evidence for novel subcomplexes (ApcE/CpcK1/CpcG2/ApcA/ApcB/CpcD and ApcE/CpcK2/CpcG1/ApcA/ApcB), which connect rod and core subcomplexes. These skeleton-like structures may serve as a scaffold of the whole PBS assembly. Different roles of ApcC1 and ApcC2 were also suggested. Based on these findings, structural models for PBS were proposed. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.

Novel Supercomplex Organization of Photosystem I in Anabaena and Cyanophora paradoxa

The supercomplex organization of photosystem complexes was studied in various cyanobacteria, a glaucocystophyte and a primitive rhodophyte by blue-native PAGE with a wide range of detergent concentrations. In contrast to known cyanobacteria that produced the PSI trimer, a filamentous N(2)-fixing cyanobacterium Anabaena sp. PCC 7120 and a glaucocystophyte Cyanophora paradoxa NIES 547 had a PSI tetramer and dimer but no trimer at all. This was confirmed by sucrose density gradient centrifugation. A primitive rhodophyte Cyanidioschyzon merolae had two species of PSI monomeric complex with a light-harvesting Chl complex of a different composition. These results are discussed with regard to the evolution of the PSI supercomplex.

Transketolase from Cyanophora paradoxa: in vitro import into cyanelles and pea chloroplasts and a complex history of a gene often, but not always, transferred in the context of secondary endosymbiosis.

The glaucocystophyte Cyanophora paradoxa is an obligatorily photoautotrophic biflagellated protist containing cyanelles, peculiar plastids surrounded by a peptidoglycan layer between their inner and outer envelope membranes. Although the 136-kb cyanelle genome surpasses higher plant chloroplast genomes in coding capacity by about 50 protein genes, these primitive plastids still have to import >2,000 polypeptides across their unique organelle wall. One such protein is transketolase, an essential enzyme of the Calvin cycle. We report the sequence of the pre-transketolase cDNA from C. paradoxa and in vitro import experiments of precursor polypeptides into cyanelles and into pea chloroplasts. The transit sequence clearly indicates the localization of the gene product to cyanelles and is more similar to the transit sequences of the plant homologues than to transit sequences of other cyanelle precursor polypeptides with the exception of a cyanelle consensus sequence at the N-terminus. The mature sequence reveals conservation of the thiamine pyrophosphate binding site. A neighbor-net planar graph suggests that Cyanophora, higher plants, and the photosynthetic protist Euglena gracilis acquired their nuclear-encoded transketolase genes via endosymbiotic gene transfer from the cyanobacterial ancestor of plastids; in the case of Euglena probably entailing two transfers, once from the plastid in the green algal lineage and once again in the secondary endosymbiosis underlying the origin of Euglena's plastids. By contrast, transketolase genes in some eukaryotes with secondary plastids of red algal origin, such as Thalassiosira pseudonana, have retained the pre-existing transketolase gene germane to their secondary host.

Acclimation to low [CO2] by an inorganic carbon‐concentrating mechanism in Cyanophora paradoxa

The glaucocystophyte Cyanophora paradoxa contains cyanelles, plastids with prokaroytic features such as a peptidoglycan wall and a central proteinaceous inclusion body. While this central body includes the majority of the enzyme ribulose 1,5-bisphosphate carboxylase/oxgenase Rubisco), the presence of a carbon-concentrating mechanism (CCM) in C. paradoxa has only been hypothesized. Here, we present physiological data in support of a CCM: CO(2) exchange activity as well as apparent affinity against inorganic carbon were found to increase under CO(2)-limiting stress. Further, expressed sequence tags (ESTs) of C. paradoxa were obtained from two cDNA libraries, one from cells grown in high [CO(2)] conditions and one from cells grown under low [CO(2)] conditions. A cDNA microarray platform assembled from 2378 cDNA sequences revealed that 142 genes significantly responded to a shift from high to low [CO(2)]. Trends in gene expression were comparable to those reported for Chlamydomonas reinhardtii and the cyanobacterium Synechocystis 6803, both possessing a CCM. Among genes regulated by [CO(2)], transcripts were identified encoding carbonic anhydrases (CAs), Rubisco activase and a putative bicarbonate transporter in C. paradoxa, likely functionally involved in the CCM. These results and the polyhedric appearance of the central body further support the hypothesis of a unique 'eukaryotic carboxysome' in Cyanophora.

The central body of the cyanelles of Cyanophora paradoxa: a eukaryotic carboxysome?

The cyanelles of the glaucocystophyte Cyanophora paradoxa combine two prokaryotic features not found in other phototrophic eukaryotes: a peptidoglycan wall and a putative carboxysome. Both of them would be indispensable when a inorganic carbon concentrating mechanism involving high accumulation of bicarbonate in the cyanelle stroma is assumed. Two approaches were used. (i) An expressed sequence tag library was generated allowing access to interesting genes and microarray technology. Hybridization of the microarrays to RNA from cells grown at high and low CO2 yielded 97 genes that were upregulated under CO2 stress whereas 87 genes were found to be downregulated. (ii) Cyanelle central bodies were isolated and protein components other than Rubisco were investigated by mass spectrometry. So far, mass spectrometric analysis of putative carboxysomal proteins yielded only sequences with no match in the databases. Rubisco activase could be shown via in vitro import and Western blotting to be copackaged with Rubisco in isolated purified central bodies. While our data support the presence of an inorganic carbon concentrating mechanism in cyanelles, they do not allow us to distinguish the microcompartment as a carboxysome or pyrenoid.Key words: Cyanophora paradoxa, cyanelles, carboxysome, Rubisco activase, carbon-concentrating mechanism, microarrays.

Diverse Eukaryotes have Retained Mitochondrial Homologues of the Bacterial Division Protein FtsZ

Mitochondrial fission requires the division of both the inner and outer mitochondrial membranes. Dynamin-related proteins operate in division of the outer membrane of probably all mitochondria, and also that of chloroplasts--organelles that have a bacterial origin like mitochondria. How the inner mitochondrial membrane divides is less well established. Homologues of the major bacterial division protein, FtsZ, are known to reside inside mitochondria of the chromophyte alga Mallomonas, a red alga, and the slime mould Dictyostelium discoideum, where these proteins are likely to act in division of the organelle. Mitochondrial FtsZ is, however, absent from the genomes of higher eukaryotes (animals, fungi, and plants), even though FtsZs are known to be essential for the division of probably all chloroplasts. To begin to understand why higher eukaryotes have lost mitochondrial FtsZ, we have sampled various diverse protists to determine which groups have retained the gene. Database searches and degenerate PCR uncovered genes for likely mitochondrial FtsZs from the glaucocystophyte Cyanophora paradoxa, the oomycete Phytophthora infestans, two haptophyte algae, and two diatoms--one being Thalassiosira pseudonana, the draft genome of which is now available. From Thalassiosira we also identified two chloroplast FtsZs, one of which appears to be undergoing a C-terminal shortening that may be common to many organellar FtsZs. Our data indicate that many protists still employ the FtsZ-based ancestral mitochondrial division mechanism, and that mitochondrial FtsZ has been lost numerous times in the evolution of eukaryotes.

11] Cyanelle ribonuclease P: Isolation and structure-function studies of an organellar ribonucleoprotein enzyme

Although all photosynthetic organelles are phylogenetically related to cyanobacteria, RNase P from different types of plastids shows striking diversity: whereas no RNA subunit can be detected in the chloroplast enzyme from green algae or higher plants, the plastids of some primitive algae encode an RNase P RNA of the cyanobacterial type. The photosynthetic organelle (cyanelle) of the glaucocystophyte Cyanophora paradoxa combines properties of free-living cyanobacteria and true chloroplasts, which makes it an ideal model system to study the evolution, structure, and function of RNase P from plastids. This chapter describes the methods used to grow this organism in amounts sufficient for enzyme preparation; the isolation of the organellar RNase P holoenzyme, detection of its activity, and analysis of the RNase P RNA structure; and the preparation of RNA and protein components from this and related organisms for use in homologous and heterologous reconstitution experiments. The unusual variability of RNase P in the phylogenefic lineage leading to and including modern chloroplasts necessitates the analysis of different members of this group of organisms and requires different approaches and methodologies.

Molecular phylogeny of the stress-70 protein family with reference to algal relationships

The stress-70 protein family has previously been shown to be a useful tool for molecular phylogeny at the kingdom to family levels. Although sequences of many members of the stress-70 family are available, few genes from the Protoctista have been sequenced to date. Phylogenetic analyses of algae based on various molecules have not, as yet, provided clear results concerning relationships between major divisions. We cloned and sequenced several algal stress-70 genes in order to provide additional data and to further analyse phylogenetic relationships among algal divisions. New nuclear sequences were obtained from Guillardia theta (Cryptophyta), Ascophyllum nodosum (Heterokontophyta) and Cyanophora paradoxa (Glaucocystophyta). Phylogenetic trees of the stress-70 protein family calculated using different methods are presented. In our trees, the heterokont alga Ascophyllum nodosum is closely related to the slime mould Dictyostelium discoideum, while the nucleomorph (eukaryotic endosymbiont) of the cryptophyte Rhodomonas salina seems to be related to the chlorobiont lineage. The glaucocystophyte Cyanophora paradoxa and the nuclear sequence (host) of the cryptomonad alga Guillardia theta also seem to be closely related. The Cryptophyta and the heterokont algae have evolved from different secondary endosymbiotic events involving different hosts and probably different endosymbionts. However, until more stress-70 sequences of algal divisions become available no definitive conclusions can be drawn concerning branching of the major divisions.

Molecular phylogeny of the stress-70 protein family with reference to algal relationships

The stress-70 protein family has previously been shown to be a useful tool for molecular phylogeny at the kingdom to family levels. Although sequences of many members of the stress-70 family are available, few genes from the Protoctista have been sequenced to date. Phylogenetic analyses of algae based on various molecules have not, as yet, provided clear results concerning relationships between major divisions. We cloned and sequenced several algal stress-70 genes in order to provide additional data and to further analyse phylogenetic relationships among algal divisions. New nuclear sequences were obtained from Guillardia theta (Cryptophyta), Ascophyllum nodosum (Heterokontophyta) and Cyanophora paradoxa (Glaucocystophyta). Phylogenetic trees of the stress-70 protein family calculated using different methods are presented. In our trees, the heterokont alga Ascophyllum nodosum is closely related to the slime mould Dictyostelium discoideum, while the nucleomorph (eukaryotic endosymbiont) of the cryptophyte Rhodomonas salina seems to be related to the chlorobiont lineage. The glaucocystophyte Cyanophora paradoxa and the nuclear sequence (host) of the cryptomonad alga Guillardia theta also seem to be closely related. The Cryptophyta and the heterokont algae have evolved from different secondary endosymbiotic events involving different hosts and probably different endosymbionts. However, until more stress-70 sequences of algal divisions become available no definitive conclusions can be drawn concerning branching of the major divisions.

The actin gene of the glaucocystophyte Cyanophora paradoxa: analysis of the coding region and introns, and an actin phylogeny of eukaryotes.

We isolated the actin gene of the glaucocystophyte alga Cyanophora paradoxa and analyzed the coding region and its introns. Phylogenetic analyses of the actin coding region and the inferred protein sequence in data sets containing 47 other actin sequences show Cyanophora to be a member of the eukaryotic crown-group radiation in agreement with ribosomal DNA sequence analyses. Four of the five Cyanophora actin introns are relatively short (55-59 nt) and occupy novel positions in a catalogue of actin introns containing 56 distinct sites. The fifth intron has a length of 171 nt and occurs also in actin genes from green algae and the crustacean Artemia.