Phe265 of the D1 protein is required to stabilize plastoquinone binding in the Q-binding site of photosystem II in Synechocystis sp. PCC 6803.

In Photosystem II electrons from water splitting pass through a primary quinone electron acceptor (Q) to the secondary plastoquinone (Q). The D2 protein forms the Q-binding site and the D1 protein forms the Q-binding site. A non-heme iron sits between Q and Q resulting in a quinone-Fe-acceptor complex that must be activated before assembly of the oxygen-evolving complex can occur.

Investigation of singlet-oxygen-responsive genes in the cyanobacterium Synechocystis PCC 6803.

Singlet oxygen (O) is an important reactive oxygen species whose formation by the type-II, light-dependent, photodynamic reaction is inevitable during photosynthetic processes. In the last decades, the recognition that O is not only a damaging agent, but can also affect gene expression and participates in signal transduction pathways has received increasing attention. However, contrary to several other taxa, O-responsive genes have not been identified in the important cyanobacterial model organism Synechocystis PCC 6803.

Characterization of the Flash-Induced Fluorescence Wave Phenomenon in the Coral Endosymbiont Algae, Symbiodiniaceae.

The dinoflagellate algae, Symbiodiniaceae, are significant symbiotic partners of corals due to their photosynthetic capacity. The photosynthetic processes of the microalgae consist of linear electron transport, which provides the energetic balance of ATP and NADPH production for CO fixation, and alternative electron transport pathways, including cyclic electron flow, which ensures the elevated ATP requirements under stress conditions. Flash-induced chlorophyll fluorescence relaxation is a non-invasive tool to assess the various electron transport pathways.

Tyr244 of the D2 Protein Is Required for Correct Assembly and Operation of the Quinone-Iron-Bicarbonate Acceptor Complex of Photosystem II.

Two plastoquinone electron acceptors, Q and Q, are present in Photosystem II (PS II) with their binding sites formed by the D2 and D1 proteins, respectively. A hexacoordinate non-heme iron is bound between Q and Q by D2 and D1, each providing two histidine ligands, and a bicarbonate that is stabilized via hydrogen bonds with D2-Tyr244 and D1-Tyr246. Both tyrosines and bicarbonate are conserved in oxygenic photosynthetic organisms but absent from the corresponding quinone-iron electron acceptor complex of anoxygenic photosynthetic bacteria.

Viable protoplast formation of the coral endosymbiont alga spp. in a microfluidics platform.

Symbiodiniaceae is an important dinoflagellate family which lives in endosymbiosis with reef invertebrates, including coral polyps, making them central to the holobiont. With coral reefs currently under extreme threat from climate change, there is a pressing need to improve our understanding on the stress tolerance and stress avoidance mechanisms of spp. Reactive oxygen species (ROS) such as singlet oxygen are central players in mediating various stress responses; however, the detection of ROS using specific dyes is still far from definitive in intact cells due to the hindrance of uptake of certain fluorescent dyes because of the presence of the cell wall.

Characterization of the Wave Phenomenon in Flash-Induced Fluorescence Relaxation and Its Application to Study Cyclic Electron Pathways in Microalgae.

Photosynthesis is a series of redox reactions, in which several electron transport processes operate to provide the energetic balance of light harvesting. In addition to linear electron flow, which ensures the basic functions of photosynthetic productivity and carbon fixation, alternative electron transport pathways operate, such as the cyclic electron flow (CEF), which play a role in the fine tuning of photosynthesis and balancing the ATP/NADPH ratio under stress conditions. In this work, we characterized the electron transport processes in microalgae species that have high relevance in applied research and industry (e.

Characterization of the wave phenomenon of flash-induced chlorophyll fluorescence in Chlamydomonas reinhardtii.

Flash-induced chlorophyll fluorescence relaxation is a powerful tool to monitor the reoxidation reactions of the reduced primary quinone acceptor, Q by Q and the plastoquinone (PQ) pool, as well as the charge recombination reactions between the donor and acceptor side components of Photosystem II (PSII). Under certain conditions, when the PQ pool is highly reduced (e.g.

Increased sensitivity of heavy metal bioreporters in transporter deficient Synechocystis PCC6803 mutants.

The detection and identification of heavy metal contaminants are becoming increasingly important as environmental pollution causes an ever-increasing health hazard in the last decades. Bacterial heavy metal reporters, which constitute an environmentally friendly and cheap approach, offer great help in this process. Although their application has great potential in the detection of heavy metal contamination, their sensitivity still needs to be improved.

Singlet oxygen damages the function of Photosystem II in isolated thylakoids and in the green alga Chlorella sorokiniana.

Singlet oxygen (O) is an important damaging agent, which is produced during illumination by the interaction of the triplet excited state pigment molecules with molecular oxygen. In cells of photosynthetic organisms O is formed primarily in chlorophyll containing complexes, and damages pigments, lipids, proteins and other cellular constituents in their environment. A useful approach to study the physiological role of O is the utilization of external photosensitizers.

Identification of the AG afterglow thermoluminescence band in the cyanobacterium Synechocystis PCC 6803.

The so-called afterglow, AG, thermoluminescence (TL) band is a useful indicator of the presence of cyclic electron flow (CEF), which is mediated by the NADH dehydrogenase-like (NDH) complex in higher plants. Although NDH-dependent CEF occurs also in cyanobacteria, the AG band has previously not been found in these organisms. In the present study, we tested various experimental conditions and could identify a TL component with ca.

Proline is a quencher of singlet oxygen and superoxide both in in vitro systems and isolated thylakoids.

Proline is a versatile plant metabolite, which is produced in large amounts in plants exposed to osmotic and oxidative stress. Proline has been shown to provide protection against various reactive oxygen species (ROS), such as hydrogen peroxide and hydroxyl radicals. On the other hand, its protective effect against singlet oxygen has been debated, and it is considered ineffective against superoxide.

Chloramphenicol enhances Photosystem II photodamage in intact cells of the cyanobacterium Synechocystis PCC 6803.

The effect of chloramphenicol, an often used protein synthesis inhibitor, in photosynthetic systems was studied on the rate of Photosystem II (PSII) photodamage in the cyanobacterium Synechocystis PCC 6803. Light-induced loss of PSII activity was compared in the presence of chloramphenicol and another protein synthesis inhibitor, lincomycin, by measuring the rate of oxygen evolution in Synechocystis 6803 cells. Our data show that the rate of PSII photodamage was significantly enhanced by chloramphenicol, at the usually applied 200 μg mL concentration, relative to that obtained in the presence of lincomycin.

A simple method to produce Synechocystis PCC6803 biofilm under laboratory conditions for electron microscopic and functional studies.

Cyanobacteria can form biofilms in nature, which have ecological roles and high potential for practical applications. In order to study them we need biofilm models that contain healthy cells and can withstand physical manipulations needed for structural studies. At present, combined studies on the structural and physiological features of axenic cyanobacterial biofilms are limited, mostly due to the shortage of suitable model systems.

A multi-parametric screening platform for photosynthetic trait characterization of microalgae and cyanobacteria under inorganic carbon limitation.

Microalgae and cyanobacteria are considered as important model organisms to investigate the biology of photosynthesis; moreover, they are valuable sources of biomolecules for several biotechnological applications. Understanding the species-specific traits of photosynthetic electron transport is extremely important, because it contributes to the regulation of ATP/NADPH ratio, which has direct/indirect links to carbon fixation and other metabolic pathways and thus overall growth and biomass production. In the present work, a cuvette-based setup is developed, in which a combination of measurements of dissolved oxygen, pH, chlorophyll fluorescence and NADPH kinetics can be performed without disturbing the physiological status of the sample.

Stabilization of Photosystem II by the PsbT protein impacts photodamage, repair and biogenesis.

Photosystem II (PS II) catalyzes the light-driven process of water splitting in oxygenic photosynthesis. Four core membrane-spanning proteins, including D1 that binds the majority of the redox-active co-factors, are surrounded by 13 low-molecular-weight (LMW) proteins. We previously observed that deletion of the LMW PsbT protein in the cyanobacterium Synechocystis sp.

A single plasmid based CRISPR interference in Synechocystis 6803 - A proof of concept.

We developed a simple method to apply CRISPR interference by modifying an existing plasmid pCRISPathBrick containing the native S. pyogenes CRISPR assembly for Synechocystis PCC6803 and named it pCRPB1010. The technique presented here using deadCas9 is easier to implement for gene silencing in Synechocystis PCC6803 than other existing techniques as it circumvents the genome integration and segregation steps thereby significantly shortens the construction of the mutant strains.

D1:Glu244 and D1:Tyr246 of the bicarbonate-binding environment of Photosystem II moderate high light susceptibility and electron transfer through the quinone-Fe-acceptor complex.

In cyanobacteria, Glu-244 and Tyr-246 of the Photosystem II (PS II) D1 protein are hydrogen bonded to two water molecules that are part of a hydrogen-bond network between the bicarbonate ligand to a non-heme iron and the cytosol. Ala substitutions were introduced in Synechocystis sp. PCC 6803 to investigate the roles of these residues and the hydrogen-bond network on electron transfer between the primary plastoquinone acceptor, Q, and the secondary plastoquinone acceptor, Q, of the quinone-Fe-acceptor complex.

Co-occurrence of Mild Salinity and Drought Synergistically Enhances Biomass and Grain Retardation in Wheat.

In the present study we analyzed the responses of wheat to mild salinity and drought with special emphasis on the so far unclarified interaction of these important stress factors by using high-throughput phenotyping approaches. Measurements were performed on 14 genotypes of different geographic origin (Austria, Azerbaijan, and Serbia). The data obtained by non-invasive digital RGB imaging of leaf/shoot area reflect well the differences in total biomass measured at the end of the cultivation period demonstrating that leaf/shoot imaging can be reliably used to predict biomass differences among different cultivars and stress conditions.

Differential gene expression and physiological changes during acute or persistent plant virus interactions may contribute to viral symptom differences.

Viruses have different strategies for infecting their hosts. Fast and acute infections result in the development of severe symptoms and may cause the death of the plant. By contrast, in a persistent interaction, the virus can survive within its host for a long time, inducing only mild symptoms.

Environmental pH and a Glu364 to Gln mutation in the chlorophyll-binding CP47 protein affect redox-active TyrD and charge recombination in Photosystem II.

In Photosystem II, loop E of the chlorophyll-binding CP47 protein is located near a redox-active tyrosine, Y , forming a symmetrical analog to loop E in CP43, which provides a ligand to the oxygen-evolving complex (OEC). A Glu364 to Gln substitution in CP47, near Y , does not affect growth in the cyanobacterium Synechocystis sp. PCC 6803; however, deletion of the extrinsic protein PsbV in this mutant leads to a strain displaying a pH-sensitive phenotype.

Maximum fluorescence and electron transport kinetics determined by light-induced fluorescence transients (LIFT) for photosynthesis phenotyping.

Photosynthetic phenotyping requires quick characterization of dynamic traits when measuring large plant numbers in a fluctuating environment. Here, we evaluated the light-induced fluorescence transient (LIFT) method for its capacity to yield rapidly fluorometric parameters from 0.6 m distance.

Functional Analysis of the CDPK-Related Kinase Family: At Regulates Responses to Continuous Light.

The Calcium-Dependent Protein Kinase (CDPK)-Related Kinase family (CRKs) consists of eight members in . Recently, At was shown to play a direct role in the regulation of root gravitropic response involving polar auxin transport (PAT). However, limited information is available about the function of the other At genes.

Detection of Singlet Oxygen Formation inside Photoactive Biohybrid Composite Material.

Photosynthetic reaction center proteins (RCs) are the most efficient light energy converter systems in nature. The first steps of the primary charge separation in photosynthesis take place in these proteins. Due to their unique properties, combining RCs with nano-structures promising applications can be predicted in optoelectronic systems.

The stress-induced SCP/HLIP family of small light-harvesting-like proteins (ScpABCDE) protects Photosystem II from photoinhibitory damages in the cyanobacterium Synechocystis sp. PCC 6803.

Small CAB-like proteins (SCPs) are single-helix light-harvesting-like proteins found in all organisms performing oxygenic photosynthesis. We investigated the effect of growth in moderate salt stress on these stress-induced proteins in the cyanobacterium Synechocystis sp. PCC 6803 depleted of Photosystem I (PSI), which expresses SCPs constitutively, and compared these cells with a PSI-less/ScpABCDE mutant.