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Berlin Brandenburg

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  • 1
    Language: English
    In: Pl o S Genetics, Dec, 2008, Vol.4(12)
    Description: Shikimate kinase (SK; EC 2.7.1.71) catalyzes the fifth reaction of the shikimate pathway, which directs carbon from the central metabolism pool to a broad range of secondary metabolites involved in plant development, growth, and stress responses. In this study, we demonstrate the role of plant SK gene duplicate evolution in the diversification of metabolic regulation and the acquisition of novel and physiologically essential function. Phylogenetic analysis of plant SK homologs resolves an orthologous cluster of plant SKs and two functionally distinct orthologous clusters. These previously undescribed genes, shikimate kinase-like 1 (SKL1) and -2 (SKL2), do not encode SK activity, are present in all major plant lineages, and apparently evolved under positive selection following SK gene duplication over 400 MYA. This is supported by functional assays using recombinant SK, SKL1, and SKL2 from Arabidopsis thaliana (At) and evolutionary analyses of the diversification of SK-catalytic and -substrate binding sites based on theoretical structure models. AtSKL1 mutants yield albino and novel variegated phenotypes, which indicate SKL1 is required for chloroplast biogenesis. Extant SKL2 sequences show a strong genetic signature of positive selection, which is enriched in a protein-protein interaction module not found in other SK homologs. We also report the first kinetic characterization of plant SKs and show that gene expression diversification among the AtSK inparalogs is correlated with developmental processes and stress responses. This study examines the functional diversification of ancient and recent plant SK gene duplicates and highlights the utility of SKs as scaffolds for functional innovation.
    ISSN: 1553-7390
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  • 2
    In: Plant Journal, November 2013, Vol.76(4), pp.615-626
    Description: The rabidopsis protein t3 belongs to the superfamily named after its two founding members, the ya adenylate cyclase from and the mammalian thiamine triphosphatase. In this study we report the three‐dimensional structure of a plant domain protein, t3, determined at 1.9 Å resolution. The crystal structure revealed the characteristic tunnel architecture of proteins, which specialize in the binding of nucleotides and other organic phosphates and in phosphoryl transfer reactions. The β barrel is composed of eight antiparallel β strands with a cluster of conserved inwardly facing acidic and basic amino acid residues. Mutagenesis of these residues in the catalytic core led to an almost complete loss of enzymatic activity. We established that t3 is not an adenylate cyclase. Instead, the enzyme displayed weak phosphatase as well as strong tripolyphosphatase activities similar to the triphosphate tunnel metalloenzyme proteins from (th) and (eu). is most highly expressed in the proximal meristematic zone of the plant root. Furthermore, an ‐ insertion knockout line displayed a delay in root growth as well as reduced length and number of lateral roots, suggesting a role for t3 in root development.
    Keywords: Arabidopsis Thaliana ; Domain ; Tripolyphosphatase ; Root ; Triphosphate Tunnel Metalloenzyme ; Adenylate Cyclase ; Triphosphatase
    ISSN: 0960-7412
    E-ISSN: 1365-313X
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  • 3
    Language: English
    In: Plant Physiology, 2016, Vol.171(1), p.82(11)
    Keywords: Photosynthesis – Research ; Protein Kinases – Physiological Aspects ; Cytochromes – Physiological Aspects
    ISSN: 0032-0889
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Plant physiology, May 2016, Vol.171(1), pp.82-92
    Description: Photosynthetic organisms have the ability to adapt to changes in light quality by readjusting the cross sections of the light-harvesting systems of photosystem II (PSII) and photosystem I (PSI). This process, called state transitions, maintains the redox poise of the photosynthetic electron transfer chain and ensures a high photosynthetic yield when light is limiting. It is mediated by the Stt7/STN7 protein kinase, which is activated through the cytochrome b6f complex upon reduction of the plastoquinone pool. Its probable major substrate, the light-harvesting complex of PSII, once phosphorylated, dissociates from PSII and docks to PSI, thereby restoring the balance of absorbed light excitation energy between the two photosystems. Although the kinase is known to be inactivated under high-light intensities, the molecular mechanisms governing its regulation remain unknown. In this study we monitored the redox state of a conserved and essential Cys pair of the Stt7/STN7 kinase and show that it forms a disulfide bridge. We could not detect any change in the redox state of these Cys during state transitions and high-light treatment. It is only after prolonged anaerobiosis that this disulfide bridge is reduced. It is likely to be mainly intramolecular, although kinase activation may involve a transient covalently linked kinase dimer with two intermolecular disulfide bonds. Using the yeast two-hybrid system, we have mapped one interaction site of the kinase on the Rieske protein of the cytochrome b6f complex.
    Keywords: Chlamydomonas -- Metabolism ; Cytochrome B6f Complex -- Metabolism ; Protein Kinases -- Metabolism
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 5
    Language: English
    In: Plant physiology, December 2015, Vol.169(4), pp.2874-83
    Description: Light-harvesting complex II (LHCII) is a crucial component of the photosynthetic machinery, with central roles in light capture and acclimation to changing light. The association of an LHCII trimer with PSI in the PSI-LHCII supercomplex is strictly dependent on LHCII phosphorylation mediated by the kinase STATE TRANSITION7, and is directly related to the light acclimation process called state transitions. In Arabidopsis (Arabidopsis thaliana), the LHCII trimers contain isoforms that belong to three classes: Lhcb1, Lhcb2, and Lhcb3. Only Lhcb1 and Lhcb2 can be phosphorylated in the N-terminal region. Here, we present an improved Phos-tag-based method to determine the absolute extent of phosphorylation of Lhcb1 and Lhcb2. Both classes show very similar phosphorylation kinetics during state transition. Nevertheless, only Lhcb2 is extensively phosphorylated (〉98%) in PSI-LHCII, whereas phosphorylated Lhcb1 is largely excluded from this supercomplex. Both isoforms are phosphorylated to different extents in other photosystem supercomplexes and in different domains of the thylakoid membranes. The data imply that, despite their high sequence similarity, differential phosphorylation of Lhcb1 and Lhcb2 plays contrasting roles in light acclimation of photosynthesis.
    Keywords: Arabidopsis -- Metabolism ; Arabidopsis Proteins -- Metabolism ; Light-Harvesting Protein Complexes -- Metabolism ; Photosystem I Protein Complex -- Metabolism
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 6
    Language: English
    In: Plant physiology, June 2015, Vol.168(2), pp.615-34
    Description: In plants and algae, the serine/threonine kinase STN7/STT7, orthologous protein kinases in Chlamydomonas reinhardtii and Arabidopsis (Arabidopsis thaliana), respectively, is an important regulator in acclimation to changing light environments. In this work, we assessed STT7-dependent protein phosphorylation under high light in C. reinhardtii, known to fully induce the expression of light-harvesting complex stress-related protein3 (LHCSR3) and a nonphotochemical quenching mechanism, in relationship to anoxia where the activity of cyclic electron flow is stimulated. Our quantitative proteomics data revealed numerous unique STT7 protein substrates and STT7-dependent protein phosphorylation variations that were reliant on the environmental condition. These results indicate that STT7-dependent phosphorylation is modulated by the environment and point to an intricate chloroplast phosphorylation network responding in a highly sensitive and dynamic manner to environmental cues and alterations in kinase function. Functionally, the absence of the STT7 kinase triggered changes in protein expression and photoinhibition of photosystem I (PSI) and resulted in the remodeling of photosynthetic complexes. This remodeling initiated a pronounced association of LHCSR3 with PSI-light harvesting complex I (LHCI)-ferredoxin-NADPH oxidoreductase supercomplexes. Lack of STT7 kinase strongly diminished PSII-LHCII supercomplexes, while PSII core complex phosphorylation and accumulation were significantly enhanced. In conclusion, our study provides strong evidence that the regulation of protein phosphorylation is critical for driving successful acclimation to high light and anoxic growth environments and gives new insights into acclimation strategies to these environmental conditions.
    Keywords: Environment ; Photosynthesis ; Chlamydomonas Reinhardtii -- Metabolism ; Multiprotein Complexes -- Metabolism ; Plant Proteins -- Metabolism
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 7
    Language: English
    In: PLoS ONE, 2011, Vol.6(1), p.e15237
    Description: Visualization tools for biological data are often limited in their ability to interactively integrate data at multiple scales. These computational tools are also typically limited by two-dimensional displays and programmatic implementations that require separate configurations for each of the user's computing devices and recompilation for functional expansion. Towards overcoming these limitations we have developed “ePlant” ( http://bar.utoronto.ca/eplant ) – a suite of open-source world wide web-based tools for the visualization of large-scale data sets from the model organism Arabidopsis thaliana . These tools display data spanning multiple biological scales on interactive three-dimensional models. Currently, ePlant consists of the following modules: a sequence conservation explorer that includes homology relationships and single nucleotide polymorphism data, a protein structure model explorer, a molecular interaction network explorer, a gene product subcellular localization explorer, and a gene expression pattern explorer. The ePlant's protein structure explorer module represents experimentally determined and theoretical structures covering 〉70% of the Arabidopsis proteome. The ePlant framework is accessed entirely through a web browser, and is therefore platform-independent. It can be applied to any model organism. To facilitate the development of three-dimensional displays of biological data on the world wide web we have established the “3D Data Display Initiative” ( http://3ddi.org ).
    Keywords: Research Article ; Biology ; Genetics And Genomics ; Plant Biology ; Computational Biology
    E-ISSN: 1932-6203
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  • 8
    Language: English
    In: Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 19 April 2014, Vol.369(1640), pp.20130223
    Description: Photosynthetic eukaryotes house two photosystems with distinct light absorption spectra. Natural fluctuations in light quality and quantity can lead to unbalanced or excess excitation, compromising photosynthetic efficiency and causing photodamage. Consequently, these organisms have acquired several distinct adaptive mechanisms, collectively referred to as non-photochemical quenching (NPQ) of chlorophyll fluorescence, which modulates the organization and function of the photosynthetic apparatus. The ability to monitor NPQ processes fluorometrically has led to substantial progress in elucidating the underlying molecular mechanisms. However, the relative contribution of distinct NPQ mechanisms to variable light conditions in different photosynthetic eukaryotes remains unclear. Here, we present a mathematical model of the dynamic regulation of eukaryotic photosynthesis using ordinary differential equations. We demonstrate that, for Chlamydomonas, our model recapitulates the basic fluorescence features of short-term light acclimation known as state transitions and discuss how the model can be iteratively refined by comparison with physiological experiments to further our understanding of light acclimation in different species.
    Keywords: Chlamydomonas Reinhardtii ; Light Acclimation ; Mathematical Modelling ; Non-Photochemical Quenching ; Photosynthesis ; State Transitions ; Light ; Models, Biological ; Acclimatization -- Physiology ; Chlamydomonas Reinhardtii -- Physiology ; Photosynthesis -- Physiology ; Photosynthetic Reaction Center Complex Proteins -- Metabolism
    ISSN: 09628436
    E-ISSN: 1471-2970
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  • 9
    In: Philosophical Transactions of the Royal Society B, 2012, Vol.367(1608), pp.3466-3474
    Description: Photosynthetic organisms are subjected to frequent changes in light quality and quantity and need to respond accordingly. These acclimatory processes are mediated to a large extent through thylakoid protein phosphorylation. Recently, two major thylakoid protein kinases have been identified and characterized. The Stt7/STN7 kinase is mainly involved in the phosphorylation of the LHCII antenna proteins and is required for state transitions. It is firmly associated with the cytochrome b 6 f complex, and its activity is regulated by the redox state of the plastoquinone pool. The other kinase, Stl1/STN8, is responsible for the phosphorylation of the PSII core proteins. Using a reverse genetics approach, we have recently identified the chloroplast PPH1/TAP38 and PBPC protein phosphatases, which counteract the activity of STN7 and STN8 kinases, respectively. They belong to the PP2C-type phosphatase family and are conserved in land plants and algae. The picture that emerges from these studies is that of a complex regulatory network of chloroplast protein kinases and phosphatases that is involved in light acclimation, in maintenance of the plastoquinone redox poise under fluctuating light and in the adjustment to metabolic needs.
    Keywords: Articles
    ISSN: 0962-8436
    E-ISSN: 1471-2970
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  • 10
    Language: English
    In: The Plant Cell, 2012, Vol.24(6), pp.2596-2609
    Description: Reversible protein phosphorylation plays a major role in the rapid acclimation of the photosynthetic apparatus to changes in light. Two paralogous kinases phosphorylate subsets of thylakoid membrane proteins. STN7 phosphorylates LHCII, the light harvesting antenna of photosystem II (PSII), to balance...
    Keywords: Natural Sciences ; Naturvetenskap
    ISSN: 1040-4651
    E-ISSN: 1532298X
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