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Interaction between photosynthesis and respiration in ..

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Interaction Between Flowering Initiation and Photosynthesis

In order to affect expression of photosynthesis genes through AppA, CryB would need to influence AppA–PpsR interaction. To test this possibility electrophoretic mobility shift assays with the upstream region of the pucB gene together with PpsR and different amounts of AppA and CryB were performed (). Addition of CryB under oxidizing conditions had no effect on the interaction between AppAΔN and PpsR (A). Interestingly, a molar excess of CryB led to an increase of free PpsR protein under reducing conditions in the dark (B and ). This is in accordance with our observation that the R. sphaeroides overexpression strain ΔcryB (pRKpufcryB) shows diminished levels of photosynthesis gene expression and lowered absorption spectra ().

NOVA - Official Website | Illuminating Photosynthesis

The minimum length for this assignment is 1,500 words.
Cellular respiration and photosynthesis form a critical cycle of energy and matter that supports the continued existence of life on earth. Describe the stages of cellular respiration and photosynthesis and their interaction and interdependence including raw materials, products, and amount of ATP or glucose produced during each phase. How is each linked to specific organelles within the eukaryotic cell. What has been the importance and significance of these processes and their cyclic interaction to the evolution and diversity of life?

01/01/2011 · Illuminating Photosynthesis

06/01/2018 · Interaction effects of phosphorus and zinc on photosynthesis, growth and yield of dwarf bean grown in two environments

Our recent work demonstrated that the CryB protein of R. sphaeroides influences the expression of photosynthesis genes (); however, the mechanism of this regulation was still elusive. To further elucidate the regulatory function of the CryB protein a yeast two-hybrid interaction analysis was performed against the AppA/PpsR system, which possesses a well understood function in the regulation of photosynthesis genes in R. sphaeroides (). To this end the full-length cryB gene was cloned into the pGBK-T7 vector. The resulting vector pGBK-T7-cryB was then transformed into yeast competent cells together with a plasmid harboring the full-length appA (pGAD-T7-appA) gene. Colonies were first selected for growth on leucine/tryptophan/histidine and later for a more stringent selection additionally for growth on adenine. Cotransformation with pGAD-T7-appA or with pGBK-T7-cryB led to growth on leucine/tryptophan/histidine/adenine () and positive blue/white selection. After the transfer of the plasmids pGBK-T7-cryB and pGAD-T7-appA into Saccharomyces cervisiae Y187 the strain showed ~40% of the β-galactosidase activity of the yeast control strain harboring plasmids pGADT7-T and pGBK-T7-53 (S-40+p53), which encode the SV40 T antigen and the p53 protein (), indicating an interaction between AppA and CryB. Interaction studies in the identical yeast system revealed 35% of the control for the two component system proteins RegA and RegB of Rhodobacter capsulatus and ~15% for RegA and NtrX, which were shown to interact in vitro in a pull-down assay (). Cotransfer of pGBK-T7-cryB and pGAD-T7-ppsR into S. cervisiae Y187 led to no measurable β-galactosidase activity.

It remained however elusive, by which mechanisms CryB affects expression of photosynthesis genes. Since the affinity of CryB to double-stranded DNA was low (), we considered that it may act on gene expression by interaction to other proteins.

013 - Photosynthesis and Respiration — bozemanscience

OCR new spec GCSE interaction of limiting factors and their effect on the rate of photosynthesis. GCSE OCR biology / combined science. Includes inverse …

The expression of photosynthesis genes in the facultatively photosynthetic bacterium Rhodobacter sphaeroides is controlled by the oxygen tension and by light quantity. Two photoreceptor proteins, AppA and CryB, have been identified in the past, which are involved in this regulation. AppA senses light by its N-terminal BLUF domain, its C-terminal part binds heme and is redox-responsive. Through its interaction to the transcriptional repressor PpsR the AppA photoreceptor controls expression of photosynthesis genes. The cryptochrome-like protein CryB was shown to affect regulation of photosynthesis genes, but the underlying signal chain remained unknown. Here we show that CryB interacts with the C-terminal domain of AppA and modulates the binding of AppA to the transcriptional repressor PpsR in a light-dependent manner. Consequently, binding of the transcription factor PpsR to its DNA target is affected by CryB. In agreement with this, all genes of the PpsR regulon showed altered expression levels in a CryB deletion strain after blue-light illumination. These results elucidate for the first time how a bacterial cryptochrome affects gene expression.

In between observations, use this website to explain what happens during photosynthesis. You may choose to project the interactive for whole-class discussion, or students may access it individually on computers during learning centers.

The Discovery of Photosynthesis
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GCSE Physics – unit 1, unit 2 and unit 3. AQA

We could demonstrate a light-dependent interaction of CryB and AppA in vivo in the yeast system. Since we used the yeast strain expressing the C-terminal part of AppA we can exclude that this light effect was due to the BLUF domain of AppA. The in vivo experiments revealed an increase of the interaction after illumination. This would lead to decreased binding of PpsR by AppA and consequently decreased expression of photosynthesis genes in response to blue light. Thus CryB would support the light-dependent effect of AppA on photosynthesis gene expression.

A Tree and Photosynthesis - The Photosynthetic Process

To further verify the interaction indicated by the yeast two-hybrid assay pull-down analyzes were performed. To this end full-length AppA protein tagged with MBP () was bound to amylose resin and a pull-down with cell lysate from R. sphaeroides was performed. Since the levels of CryB protein in the wild-type are low, an R. sphaeroides His-CryB overexpression strain harboring the pRKpufcry plasmid was used for the pull-down (). After incubation with the cell lysate and extensive washing under reducing conditions, high amounts of the CryB protein were eluted together with the full-length AppA protein (A), while no CryB was visible on western blot in the elution fractions without prior binding of AppA to the amylose resin (B). The results from the yeast two-hybrid assays suggested that the C-terminal part and the SCHIC domain of the AppA protein are sufficient for interaction with CryB. To confirm this interaction GST tagged AppAΔN () or the AppA SCHIC domain were bound to gluthathion sepharose and a pull-down with cell lysate from the CryB overexpression was performed. Again CryB protein was detectable on western blot in the elution fractions (C and D). Control experiments without prior binding of the AppA domains showed no signals on western blot. Reconstitution of the purified MBP-AppA, GST-AppAΔN and GST-SCHIC with heme as described before () had no influence on the interaction. To eliminate the possibility of an unspecific binding of the His-tag of CryB to the GST-AppAΔN protein a control experiment was performed using cell lysate from the R. sphaeroides His-LOV overexpression strain harboring the pRKpuflov plasmid (). No LOV protein could be detected on the western blot (E).

Photosynthesis Research Unit, ..

Rhodobacter sphaeroides harbors a set of different photoreceptors including two phytochromes, a LOV domain protein, three BLUF (Blue Light sensing Using FAD) domain proteins and a cryptochrome. Both phytochromes are composed of the PAS–GAF–PHY photosensory module, typically present in phytochromes, but linked to GGDEF–EAL output modules. One of the phytochromes, BphG1, was shown to be involved in the turn-over of c-di-GMP (). The short LOV domain protein of R. sphaeroides lacks an output module and undergoes a photocycle but its biological function remains to be elucidated (). Similarly, two of the BLUF domain proteins of R. sphaeroides lack an output domain () and their biological function is not known. The BLUF domain was first discovered in the AppA protein of R. sphaeroides (,,), which was intensively studied in regard to its biological function, the mechanisms of signal transduction and its photocycle. The AppA protein was initially identified as a redox regulator of photosynthesis genes, which functions as antagonist of the PpsR protein (,). PpsR represses photosynthesis genes at high oxygen tension by binding to target promoters (). Binding to PpsR is mediated by the C-terminal part of AppA (), which was shown to bind heme (,). The novel type of heme-binding domain was named SCHIC (Sensor Containing Heme Instead of Cobalamin) domain (). AppA also functions as photoreceptor through its BLUF domain, which interferes with PpsR binding at intermediate oxygen concentrations in response to blue light (,,,). shows a simplified schematic model for photosynthesis gene regulation by AppA/PpsR. Recently we demonstrated the involvement of the cryptochrome CryB in the regulation of photosynthesis genes in R. sphaeroides (). The promoter of cryB is recognized by the RpoE-dependent alternative sigma factor RpoHII, both sigma factors have a major role in the response of R. sphaeroides to photooxidative stress ().

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