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• 1
Article
Language: English
In: Plant physiology, April 2015, Vol.167(4), pp.1566-78
Description: In Chlamydomonas reinhardtii, the LIGHT-HARVESTING COMPLEX STRESS-RELATED PROTEIN3 (LHCSR3) protein is crucial for efficient energy-dependent thermal dissipation of excess absorbed light energy and functionally associates with photosystem II-light-harvesting complex II (PSII-LHCII) supercomplexes. Currently, it is unknown how LHCSR3 binds to the PSII-LHCII supercomplex. In this study, we investigated the role of PHOTOSYSTEM II SUBUNIT R (PSBR) an intrinsic membrane-spanning PSII subunit, in the binding of LHCSR3 to PSII-LHCII supercomplexes. Down-regulation of PSBR expression diminished the efficiency of oxygen evolution and the extent of nonphotochemical quenching and had an impact on the stability of the oxygen-evolving complex as well as on PSII-LHCII-LHCSR3 supercomplex formation. Its down-regulation destabilized the PSII-LHCII supercomplex and strongly reduced the binding of LHCSR3 to PSII-LHCII supercomplexes, as revealed by quantitative proteomics. PHOTOSYSTEM II SUBUNIT P deletion, on the contrary, destabilized PHOTOSYSTEM II SUBUNIT Q binding but did not affect PSBR and LHCSR3 association with PSII-LHCII. In summary, these data provide clear evidence that PSBR is required for the stable binding of LHCSR3 to PSII-LHCII supercomplexes and is essential for efficient energy-dependent quenching and the integrity of the PSII-LHCII-LHCSR3 supercomplex under continuous high light.
Keywords: Proteomics ; Chlamydomonas Reinhardtii -- Genetics ; Light-Harvesting Protein Complexes -- Metabolism ; Oxygen -- Metabolism ; Photosystem II Protein Complex -- Metabolism
ISSN: 00320889
E-ISSN: 1532-2548
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• 2
Article
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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• 3
Article
Language: English
In: Plant physiology, December 2014, Vol.166(4), pp.1764-76
Description: Rapid responses of chloroplast metabolism and adjustments to photosynthetic machinery are of utmost importance for plants' survival in a fluctuating environment. These changes may be achieved through posttranslational modifications of proteins, which are known to affect the activity, interactions, and localization of proteins. Recent studies have accumulated evidence about the crucial role of a multitude of modifications, including acetylation, methylation, and glycosylation, in the regulation of chloroplast proteins. Both of the Arabidopsis (Arabidopsis thaliana) leaf-type FERREDOXIN-NADP(+) OXIDOREDUCTASE (FNR) isoforms, the key enzymes linking the light reactions of photosynthesis to carbon assimilation, exist as two distinct forms with different isoelectric points. We show that both AtFNR isoforms contain multiple alternative amino termini and undergo light-responsive addition of an acetyl group to the α-amino group of the amino-terminal amino acid of proteins, which causes the change in isoelectric point. Both isoforms were also found to contain acetylation of a conserved lysine residue near the active site, while no evidence for in vivo phosphorylation or glycosylation was detected. The dynamic, multilayer regulation of AtFNR exemplifies the complex regulatory network systems controlling chloroplast proteins by a range of posttranslational modifications, which continues to emerge as a novel area within photosynthesis research.
Keywords: Protein Processing, Post-Translational ; Arabidopsis -- Enzymology ; Ferredoxin-Nadp Reductase -- Metabolism
ISSN: 00320889
E-ISSN: 1532-2548
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• 4
Article
Language: English
In: Plant physiology, November 2012, Vol.160(3), pp.1384-406
Description: Crop plant development is strongly dependent on the availability of nitrogen (N) in the soil and the efficiency of N utilization for biomass production and yield. However, knowledge about molecular responses to N deprivation derives mainly from the study of model species. In this article, the metabolic adaptation of source leaves to low N was analyzed in maize (Zea mays) seedlings by parallel measurements of transcriptome and metabolome profiling. Inbred lines A188 and B73 were cultivated under sufficient (15 mM) or limiting (0.15 mM) nitrate supply for up to 30 d. Limited availability of N caused strong shifts in the metabolite profile of leaves. The transcriptome was less affected by the N stress but showed strong genotype- and age-dependent patterns. N starvation initiated the selective down-regulation of processes involved in nitrate reduction and amino acid assimilation; ammonium assimilation-related transcripts, on the other hand, were not influenced. Carbon assimilation-related transcripts were characterized by high transcriptional coordination and general down-regulation under low-N conditions. N deprivation caused a slight accumulation of starch but also directed increased amounts of carbohydrates into the cell wall and secondary metabolites. The decrease in N availability also resulted in accumulation of phosphate and strong down-regulation of genes usually involved in phosphate starvation response, underlining the great importance of phosphate homeostasis control under stress conditions.
Keywords: Adaptation, Physiological ; Carbon -- Metabolism ; Nitrogen -- Deficiency ; Phosphates -- Metabolism ; Zea Mays -- Physiology
ISSN: 00320889
E-ISSN: 1532-2548
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• 5
Article
Language: English
In: Journal of Marketing Research, 1 August 2010, Vol.47(4), pp.685-698
Description: Conjoint analysis has become a widely accepted tool for preference measurement in marketing research, though its applicability and performance strongly depend on the complexity of the product or service. Therefore, self-explicated approaches are still frequently used because of their simple design, which facilitates preference elicitation when large numbers of attributes need to be considered. However, the direct measurement of preferences, or rather utilities, has been criticized as being imprecise in many cases. Against this background, the authors present a compositional consumer preference measurement approach based on paired comparisons, otherwise known as PCPM. The trade-off character of paired comparisons ensures that the stated judgments are more intuitive than traditional self-explicated preference statements. In contrast to the latter, PCPM accounts for response errors and thus allows for the elicitation of more precise preferences. The authors benchmark PCPM against adaptive conjoint analysis and computer-assisted self-explication of multiattributed preferences to demonstrate its relative validity and predictive accuracy in two empirical studies using complex, high-involvement products. They find that PCPM yields better results than the benchmark approaches with respect to interview length, individual hit rates, and aggregate choice share predictions.
Keywords: Business -- Business administration -- Corporate communications ; Applied sciences -- Computer science -- Computer engineering ; Biological sciences -- Biology -- Cytology ; Behavioral sciences -- Behavioral economics -- Consumer behavior ; Mathematics -- Applied mathematics -- Statistics ; Mathematics -- Mathematical values -- Ratios ; Arts -- Performing arts -- Music ; Applied sciences -- Engineering -- Transportation ; Applied sciences -- Engineering -- Telecommunications ; Applied sciences -- Technology -- Tools
ISSN: 00222437
E-ISSN: 15477193
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• 6
Article
Language: English
In: Proceedings of the National Academy of Sciences of the United States of America, 06 May 2014, Vol.111(18), pp.6768-73
Description: The genus Yersinia has been used as a model system to study pathogen evolution. Using whole-genome sequencing of all Yersinia species, we delineate the gene complement of the whole genus and define patterns of virulence evolution. Multiple distinct ecological specializations appear to have split pathogenic strains from environmental, nonpathogenic lineages. This split demonstrates that contrary to hypotheses that all pathogenic Yersinia species share a recent common pathogenic ancestor, they have evolved independently but followed parallel evolutionary paths in acquiring the same virulence determinants as well as becoming progressively more limited metabolically. Shared virulence determinants are limited to the virulence plasmid pYV and the attachment invasion locus ail. These acquisitions, together with genomic variations in metabolic pathways, have resulted in the parallel emergence of related pathogens displaying an increasingly specialized lifestyle with a spectrum of virulence potential, an emerging theme in the evolution of other important human pathogens.
Keywords: Enterobacteriaceae ; Genomics Metabolic Streamlining ; Pathoadaptation ; Evolution, Molecular ; Virulence -- Genetics ; Yersinia -- Genetics
ISSN: 00278424
E-ISSN: 1091-6490
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• 7
Article
Language: English
In: Proceedings of the National Academy of Sciences of the United States of America, 15 April 2014, Vol.111(15), pp.E1510-8
Description: The Deepwater Horizon disaster released more than 636 million L of crude oil into the northern Gulf of Mexico. The spill oiled upper surface water spawning habitats for many commercially and ecologically important pelagic fish species. Consequently, the developing spawn (embryos and larvae) of tunas, swordfish, and other large predators were potentially exposed to crude oil-derived polycyclic aromatic hydrocarbons (PAHs). Fish embryos are generally very sensitive to PAH-induced cardiotoxicity, and adverse changes in heart physiology and morphology can cause both acute and delayed mortality. Cardiac function is particularly important for fast-swimming pelagic predators with high aerobic demand. Offspring for these species develop rapidly at relatively high temperatures, and their vulnerability to crude oil toxicity is unknown. We assessed the impacts of field-collected Deepwater Horizon (MC252) oil samples on embryos of three pelagic fish: bluefin tuna, yellowfin tuna, and an amberjack. We show that environmentally realistic exposures (1-15 µg/L total PAH) cause specific dose-dependent defects in cardiac function in all three species, with circulatory disruption culminating in pericardial edema and other secondary malformations. Each species displayed an irregular atrial arrhythmia following oil exposure, indicating a highly conserved response to oil toxicity. A considerable portion of Gulf water samples collected during the spill had PAH concentrations exceeding toxicity thresholds observed here, indicating the potential for losses of pelagic fish larvae. Vulnerability assessments in other ocean habitats, including the Arctic, should focus on the developing heart of resident fish species as an exceptionally sensitive and consistent indicator of crude oil impacts.
Keywords: Damage Assessment ; Embryology ; Heart Development ; Oil Spill ; Tuna ; Fish Diseases -- Chemically Induced ; Heart -- Drug Effects ; Heart Diseases -- Veterinary ; Petroleum -- Toxicity ; Petroleum Pollution -- History
ISSN: 00278424
E-ISSN: 1091-6490
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• 8
Article
Language: English
In: Plant physiology, January 2014, Vol.164(1), pp.412-23
Description: Barley (Hordeum vulgare) is an important cereal crop and a model species for Triticeae genomics. To lay the foundation for hierarchical map-based sequencing, a genome-wide physical map of its large and complex 5.1 billion-bp genome was constructed by high-information content fingerprinting of almost 600,000 bacterial artificial chromosomes representing 14-fold haploid genome coverage. The resultant physical map comprises 9,265 contigs with a cumulative size of 4.9 Gb representing 96% of the physical length of the barley genome. The reliability of the map was verified through extensive genetic marker information and the analysis of topological networks of clone overlaps. A minimum tiling path of 66,772 minimally overlapping clones was defined that will serve as a template for hierarchical clone-by-clone map-based shotgun sequencing. We integrated whole-genome shotgun sequence data from the individuals of two mapping populations with published bacterial artificial chromosome survey sequence information to genetically anchor the physical map. This novel approach in combination with the comprehensive whole-genome shotgun sequence data sets allowed us to independently validate and improve a previously reported physical and genetic framework. The resources developed in this study will underpin fine-mapping and cloning of agronomically important genes and the assembly of a draft genome sequence.
Keywords: Physical Chromosome Mapping ; Polymorphism, Single Nucleotide ; Hordeum -- Genetics
ISSN: 00320889
E-ISSN: 1532-2548
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• 9
Article
Language: English
In: Proceedings of the National Academy of Sciences of the United States of America, 02 April 2002, Vol.99(7), pp.4550-5
Description: Lymphoblastoid cell lines, generated by immortalization of normal B cells by Epstein-Barr virus (EBV) in vitro, have strong antigen-presenting capacity, are sensitive to EBV-specific cytotoxic T cells, and are highly allostimulatory in mixed lymphocyte culture. By contrast, EBV-positive Burkitt lymphoma (BL) cells are poor antigen presenters, are not recognized by EBV-specific cytotoxic T cells, and are poorly allostimulatory, which raises the question of whether immunological pressure exerted during BL pathogenesis in vivo has selected for a 'nonimmunogenic' tumor phenotype. The present work addresses this question by examining the immunogenicity/antigenicity of cell lines, generated by conversion of a conditionally immortalized lymphoblastoid cell line to permanent growth independent of EBV-latent proteins by introduction of a constitutively active or tetracycline-regulated c-myc gene (A1 and P493-6 cells, respectively). Compared with its parental lymphoblastoid cell line, A1 cells showed many of the features of the nonimmunogenic BL phenotype, namely poor allostimulatory activity, poor antigen-presenting function associated with impaired proteasomal activity, down-regulation of peptide transporter, reduced HLA class I expression, and an inability to present endogenously expressed EBV-latent proteins to cytotoxic T cells. P493-6 cells, when grown in the presence of estrogen with the exogenous c-myc gene switched off, were strongly immunogenic. The cells had lost their immunogenic potential, however, when grown on a c-myc-driven proliferation program in the absence of estrogen. Deregulation of c-myc, a step central to the development of uncontrolled BL cell growth in vivo, can thus impose a nonimmunogenic phenotype on proliferating human B cells in the absence of any immune pressure.
Keywords: B-Lymphocytes -- Immunology ; Herpesvirus 4, Human -- Immunology ; Proto-Oncogene Proteins C-Myc -- Physiology
ISSN: 0027-8424
E-ISSN: 10916490
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• 10
Article
In: Philosophical Transactions of the Royal Society B: Biological Sciences, 1996, Vol.351(1348), pp.1689-1701
Description: The development, life cycle, ultrastructure and phylogenetic position of an obligate, spore-forming endoparasite of Daphnia magna Straus is described. The microparasite was found in the body cavity of three Daphnia species (D. magna, D. pulex and D. longispina) collected in England and Russia during 1992-1994 and maintained in artificial culture by co-cultivation with D. magna. Transmission of the endoparasite occurred horizontally through waterborne spores released from the remains of dead infected hosts. Progeny of infected hosts were never infected, indicating that vertical transmission does not occur. Egg production by infected mothers ceased soon after infection and death ensued after 46 days (〈latex〉$\pm$〈/latex〉 7 standard error) at 20 degrees C. Phase contrast light microscopy and transmission electron microscopy of the infection process showed the endoparasite to have a polymorphic life cycle beginning with the appearance of branched `cauliflower-like' rosettes and ended with the development of single, oval endospores, nippled at one end and with complex internal structure. Endospore formation resembled that found in endosporeforming bacteria. Morphologically the parasite has strong resemblance to the Pasteuria ramosa that Metchnikoff isolated from D. magna and D. pulex in Ukraine and described in 1888. Identification of this parasite has been an enduring puzzle since Metchnikoff. The previously confused phylogenetic position of P. ramosa (it has been classified as bacterium, yeast and protozoa) was resolved by sequencing the 16S rDNA molecule. Fluorescent in situ hybridizations confirmed that the 16S rDNA sequence obtained from the spores within the D. magna body cavity originated from the endoparasite. Maximum likelihood and maximum parsimony analysis showed that P. ramosa belongs to the low G+C Gram positive branch of the eubacteria and resides within a clade containing Bacillus tusciae, Alicyclobacillus cycloheptanicus and A. acidocaldarius as its nearest neighbours. These results confirm suggestions that this parasite is a bacterium and refute its previous tentative placement based on its morphological complexity among the Actinomycetales.
Keywords: Medicine ; Sciences (General) ; Biology;
ISSN: 0962-8436
E-ISSN: 1471-2970
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