Gene expression and organization of thylakoid protein complexes in the PSII-less mutant of sp. PCC 6803.

Photosystems I and II (PSI and PSII) are the integral components of the photosynthetic electron transport chain that utilize light to provide chemical energy for CO fixation. In this study, we investigated how the deficiency of PSII affects the gene expression, accumulation, and organization of thylakoid protein complexes as well as physiological characteristics of sp. PCC 6803 by combining biochemical, biophysical, and transcriptomic approaches.

Psb28 is involved in recovery of photosystem II at high temperature in Synechocystis sp. PCC 6803.

Psb28 is an extrinsic protein of photosystem II (PSII), which is conserved among photosynthetic organisms from cyanobacteria to higher plants. A unicellular cyanobacterium, Synechocystis sp. PCC 6803, has two homologs of Psb28, Psb28-1 and Psb28-2.

Positive regulation of psbA gene expression by cis-encoded antisense RNAs in Synechocystis sp. PCC 6803.

The D1 protein of photosystem II in the thylakoid membrane of photosynthetic organisms is encoded by psbA genes, which in cyanobacteria occur in the form of a small gene family. Light-dependent up-regulation of psbA gene expression is crucial to ensure the proper replacement of the D1 protein. To gain a high level of gene expression, psbA transcription can be enhanced by several orders of magnitude.

The antisense RNA As1_flv4 in the Cyanobacterium Synechocystis sp. PCC 6803 prevents premature expression of the flv4-2 operon upon shift in inorganic carbon supply.

The functional relevance of natural cis-antisense transcripts is mostly unknown. Here we have characterized the association of three antisense RNAs and one intergenically encoded noncoding RNA with an operon that plays a crucial role in photoprotection of photosystem II under low carbon conditions in the cyanobacterium Synechocystis sp. PCC 6803.

Strategies for psbA gene expression in cyanobacteria, green algae and higher plants: from transcription to PSII repair.

The Photosystem (PS) II of cyanobacteria, green algae and higher plants is prone to light-induced inactivation, the D1 protein being the primary target of such damage. As a consequence, the D1 protein, encoded by the psbA gene, is degraded and re-synthesized in a multistep process called PSII repair cycle. In cyanobacteria, a small gene family codes for the various, functionally distinct D1 isoforms.

Isolation and characterization of a barley yellow stripe-like gene, HvYSL5.

Yellow stripe-like (YSL) family transporters, belonging to a novel subfamily of oligopeptide transporter (OPT), has been proposed to be involved in metal uptake and long-distance transport, but only a few of them have been functionally characterized so far. In the present study, we isolated an uncharacterized member of the YSL family, HvYSL5, in barley based on expressed sequence tag (EST) information. HvYSL5 shared 50% identity with HvYS1, a transporter for the ferric-mugineic acid complex, at the amino acid level.

Increased expression of peroxisome proliferator-activated receptor (PPAR)-alpha and PPAR-gamma in human atherosclerosis.

To clarify the mechanism of atherosclerosis development in humans, we studied the mRNA and protein expression of PPAR subtypes in various types of atherosclerotic lesions and their correlation with cell proliferation and macrophage invasion. Human aortas were obtained from 35 autopsied cases, and each sample was divided into halves. One half was used for the analysis of mRNA or protein expression with RT-PCR or Western blotting, respectively.

The PsbK subunit is required for the stable assembly and stability of other small subunits in the PSII complex in the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1.

PsbK is a small membrane protein of the PSII core complex and is highly conserved from cyanobacteria to plants. Here, we studied its role in the thermophilic cyanobacterium, Thermosynechococcus elongatus BP-1, by focusing on a psbK disruptant with hexahistidine-tagged CP47. The psbK disruptant showed photoautotrophic growth comparable with that of the wild type under a wide range of light conditions.

Purification and characterization of photosystem I complex from Synechocystis sp. PCC 6803 by expressing histidine-tagged subunits.

We generated Synechocystis sp. PCC 6803 strains, designated F-His and J-His, which express histidine-tagged PsaF and PsaJ subunits, respectively, for simple purification of the photosystem I (PSI) complex. Six histidine residues were genetically added to the C-terminus of the PsaF subunit in F-His cells and the N-terminus of the PsaJ subunit in J-His cells.

Involvement of digalactosyldiacylglycerol in cellular thermotolerance in Synechocystis sp. PCC 6803.

The effects of digalactosyldiacylglycerol (DGDG) deficiency on photosynthesis at high temperatures were examined using a dgdA mutant of Synechocystis sp. PCC 6803 incapable of DGDG biosynthesis. The dgdA mutant cells showed significant growth retardation when the temperature was increased from 30 to 38 degrees C, although wild-type cells grew normally.

Lack of digalactosyldiacylglycerol increases the sensitivity of Synechocystis sp. PCC 6803 to high light stress.

The physiological role of digalactosyldiacylglycerol (DGDG) in photosynthesis was examined using a dgdA mutant of Synechocystis sp. PCC 6803 that is defective in the biosynthesis of DGDG. The dgdA mutant cells showed normal growth under low light (LL) conditions.

Effects of phospholipase and lipase treatments on photosystem II core dimer from a thermophilic cyanobacterium.

Lipids are important components of transmembrane protein complexes. In order to study the roles of lipids in photosystem II (PSII), we treated the PSII core dimer complex from a thermophilic cyanobacterium Thermosynechococcus vulcanus with phospholipase A(2) (PLA(2)) and lipase, and examined their effects on PSII structure and function. PLA(2)-treatment decreased the content of phospholipid, phosphatidylglycerol (PG) by 59%, leading to a decrease of oxygen evolution by 40%.

A method for analyzing lipid-modified proteins with mass spectrometry.

In protein analysis using mass spectrometry, proteins are usually separated by electrophoresis and digested within the gel with proteases such as trypsin. However, analysis of lipid-modified proteins is difficult due to the low recovery of lipid-modified peptide fragments from the gel as well as their low ionization efficiency during mass spectrometry. In this study, we developed a simple extraction method with n-dodecyl-beta-D-maltoside following chloroform/methanol extraction that efficiently elutes lipid-modified fragments from gels.

Digalactosyldiacylglycerol is required for stabilization of the oxygen-evolving complex in photosystem II.

The galactolipid digalactosyldiacylglycerol (DGDG) is present in the thylakoid membranes of oxygenic photosynthetic organisms such as higher plants and cyanobacteria. Recent x-ray crystallographic analysis of protein-cofactor supercomplexes in thylakoid membranes revealed that DGDG molecules are present in the photosystem II (PSII) complex (four molecules per monomer), suggesting that DGDG molecules play important roles in folding and assembly of subunits in the PSII complex. However, the specific role of DGDG in PSII has not been fully clarified.

Effects of the lack of phosphatidylglycerol on the donor side of photosystem II.

Our previous studies with the pgsA mutant of the cyanobacterium Synechocystis sp. PCC6803 (hereafter termed pgsA mutant), which is defective for the biosynthesis of phosphatidylglycerol (PG), revealed an important role for PG in the electron acceptor side of photosystem II (PSII), especially in the electron transport between plastoquinones Q(A) and Q(B). This study now shows that PG also plays an important role in the electron donor side of PSII, namely, the oxygen-evolving system.

Lipids in oxygen-evolving photosystem II complexes of cyanobacteria and higher plants.

Lipids in dimeric photosystem II complexes prepared from two species of cyanobacteria, Thermosynechococcus vulcanus and Synechocystis sp. PCC6803, and two higher plants, spinach and rice, were analyzed to determine how many lipid molecules and what class of lipids are present in the photosystem II complexes. It was estimated that 27, 20, 8, and 7 lipid molecules per monomer are bound to the dimeric photosystem II complexes of T.

Identification of an Arabidopsis thaliana gene for cardiolipin synthase located in mitochondria.

Cardiolipin (CL) is an anionic phospholipid with a dimeric structure. In eukaryotes, it is primarily localized in the inner membranes of mitochondria. Although the biosynthetic pathway of CL is well known, the gene for CL synthase has not been identified in any higher organisms.

Requirement of carotene isomerization for the assembly of photosystem II in Synechocystis sp. PCC 6803.

Carotene isomerase mutant (crtH mutant) cells of Synechocystis sp. PCC 6803 can accumulate beta-carotene under light conditions. However, the mutant cells grown under a light-activated heterotrophic growth condition contained detectable levels of neither beta-carotene nor D1 protein of the photosystem (PS) II reaction center, and no oxygen-evolving activity of PSII was detected.

Phosphatidylglycerol is essential for oligomerization of photosystem I reaction center.

Our earlier studies with the pgsA mutant of Synechocystis PCC6803 demonstrated the important role of phosphatidylglycerol (PG) in PSII dimer formation and in electron transport between the primary and secondary electron-accepting plastoquinones of PSII. Using a long-term depletion of PG from pgsA mutant cells, we could induce a decrease not only in PSII but also in PSI activity. Simultaneously with the decrease in PSI activity, dramatic structural changes of the PSI complex were detected.

Requirement of phosphatidylglycerol for maintenance of photosynthetic machinery.

Phosphatidylglycerol (PG) is a ubiquitous component of thylakoid membranes. Experiments with the pgsA mutant of the cyanobacterium Synechocystis sp. PCC6803 defective in biosynthesis of PG have demonstrated an indispensable role of PG in photosynthesis.

Phosphatidylglycerol is essential for the development of thylakoid membranes in Arabidopsis thaliana.

Phosphatidylglycerol is a ubiquitous phospholipid in the biological membranes of many organisms. In plants, phosphatidylglycerol is mainly present in thylakoid membranes and has been suggested to play specific roles in photosynthesis. Here, we have isolated two T-DNA tagged lines of Arabidopsis thaliana that have a T-DNA insertion in the PGP1 gene encoding a phosphatidylglycerolphosphate synthase involved in the biosynthesis of phosphatidylglycerol.

Significance of apoptosis in morphogenesis of human lung development: light microscopic observation using in situ DNA end-labeling and ultrastructural study.

To clarify the significance of apoptosis in lung morphogenesis, the occurrence and localization of apoptosis were investigated in developing human lungs, using TdT-mediated dUTP-biotin nick end labeling (TUNEL) and ultrastructural observation. Under light microscopic observation, apoptotic cells were demonstrated in the epithelial lining of the developing respiratory tubes and their growth ends (bronchial tips). Small numbers of apoptotic cells were also observed in the mesenchymal cells surrounding the immature respiratory trees.