Characterization of two ferredoxin-dependent sulfite reductases having different substrate specificity in the red alga Cyanidioschyzon merolae.

Assimilatory sulfite reductase (SiR) and nitrite reductase (NiR), which are important determinants in biomass productivity, are homologous enzymes that catalyze the reduction of sulfite to sulfide and nitrite to ammonium, respectively. They have a siroheme and a [4Fe-4S] cluster as prosthetic groups in common. The red alga Cyanidioschyzon merolae encodes two SiR-like enzymes, CmSiRA and CmSiRB, which are likely products of recent gene duplication, but no homologues of NiR.

Characterization of three putative xylulose 5-phosphate/fructose 6-phosphate phosphoketolases in the cyanobacterium Anabaena sp. PCC 7120.

Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp) is a key enzyme in the central carbohydrate metabolism in heterofermentative bacteria, in which enzymatic property of Xfps is well characterized. This is not the case in other microbes. The cyanobacterium Anabaena sp.

Subcellular distribution of central carbohydrate metabolism pathways in the red alga Cyanidioschyzon merolae.

Comprehensive subcellular localization analysis revealed that the subcellular distribution of carbohydrate metabolic pathways in the red alga Cyanidioschyzon is essentially identical with that in Arabidopsis , except the lack of transaldolase. In plants, the glycolysis and oxidative pentose phosphate pathways (oxPPP) are located in both cytosol and plastids. However, in algae, particularly red algae, the subcellular localization of enzymes involved in carbon metabolism is unclear.

Analysis of the complete plastid genome of the unicellular red alga Porphyridium purpureum.

We determined the complete nucleotide sequence of the plastid genome of the unicellular marine red alga Porphyridium purpureum strain NIES 2140, belonging to the unsequenced class Porphyridiophyceae. The genome is a circular DNA composed of 217,694 bp with the GC content of 30.3%.

Localization and phylogenetic analysis of enzymes related to organellar genome replication in the unicellular rhodophyte Cyanidioschyzon merolae.

Plants and algae possess plastids and mitochondria harboring their own genomes, which are replicated by the apparatus consisting of DNA polymerase, DNA primase, DNA helicase, DNA topoisomerase, single-stranded DNA maintenance protein, DNA ligase, and primer removal enzyme. In the higher plant Arabidopsis thaliana, organellar replication-related enzymes (OREs) are similar in plastids and mitochondria because many of them are dually targeted to plastids and mitochondria. In the red algae, there is a report about a DNA replicase, plant/protist organellar DNA polymerase, which is localized to both plastids and mitochondria.

Characterization of cell-cycle-driven and light-driven gene expression in a synchronous culture system in the unicellular rhodophyte Cyanidioschyzon merolae.

The unicellular rhodophyte Cyanidioschyzon merolae, having a single plastid and a single mitochondrion, is suitable for the analysis of the cell cycle involving the division of organelles. In conventional methods of synchronous culture of algae, light/dark cycles have been used as signals for synchronization, and the gene expression promoted by light is not separated from the gene expression related to cell cycle progression. We previously devised a novel synchronous culture system with controlled photosynthesis, which is triggered by 6 h-light/18 h-dark cycles combined with different levels of CO(2).

A novel variant of ferredoxin-dependent sulfite reductase having preferred substrate specificity for nitrite in the unicellular red alga Cyanidioschyzon merolae.

Plant NiR (nitrite reductase) and SiR (sulfite reductase) have common structural and functional features. Both enzymes are generally distinguished in terms of substrate specificity for nitrite and sulfite. The genome of Cyanidioschyzon merolae, a unicellular red alga living in acidic hot springs, encodes two SiR homologues, namely CmSiRA and CmSiRB (C.

Live imaging of chloroplast FtsZ1 filaments, rings, spirals, and motile dot structures in the AtMinE1 mutant and overexpressor of Arabidopsis thaliana.

Chloroplast division involves the tubulin-related GTPase FtsZ that assembles into a ring structure (Z-ring) at the mid-chloroplast division site, which is where invagination and constriction of the envelope membranes occur. Z-ring assembly is usually confined to the mid-chloroplast site by a well balanced counteraction of the stromal proteins MinD and MinE. The in vivo mechanisms by which FtsZ nucleates at specific sites, polymerises into a protofilament and organizes a closed ring of filament bundles remain largely unknown.

DNA binding and partial nucleoid localization of the chloroplast stromal enzyme ferredoxin:sulfite reductase.

Sulfite reductase (SiR) is an important enzyme catalyzing the reduction of sulfite to sulfide during sulfur assimilation in plants. This enzyme is localized in plastids, including chloroplasts, and uses ferredoxin as an electron donor. Ferredoxin-dependent SiR has been found in isolated chloroplast nucleoids, but its localization in vivo or in intact plastids has not been examined.

Reversible DNA compaction by sulfite reductase regulates transcriptional activity of chloroplast nucleoids.

The transcriptional activity of nucleoids changes during plastid development, presumably due to the morphological and molecular differences of the nucleoids. Pea chloroplast nucleoids have an abundant 70-kDa protein identified as sulfite reductase (SiR) that can compact DNA. Using an in vitro transcription assay, we show here that heparin increased the transcriptional activity of chloroplast nucleoids with concomitant release of SiR.