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Berlin Brandenburg

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  • 1
    Language: English
    In: Plant physiology, November 2012, Vol.160(3), pp.1515-29
    Description: Understanding seasonality and longevity is a major challenge in tree biology. In woody species, growth phases and dormancy follow one another consecutively. In the oldest living individuals, the annual cycle may run for more than 1,000 years. So far, however, not much is known about the processes triggering reactivation from dormancy. In this study, we focused on wood rays, which are known to play an important role in tree development. The transition phase from dormancy to flowering in early spring was compared with the phase of active growth in summer. Rays from wood samples of poplar (Populus × canescens) were enriched by laser microdissection, and transcripts were monitored by poplar whole-genome microarrays. The resulting seasonally varying complex expression and metabolite patterns were subjected to pathway analyses. In February, the metabolic pathways related to flower induction were high, indicating that reactivation from dormancy was already taking place at this time of the year. In July, the pathways related to active growth, like lignin biosynthesis, nitrogen assimilation, and defense, were enriched. Based on "marker" genes identified in our pathway analyses, we were able to validate periodical changes in wood samples by quantitative polymerase chain reaction. These studies, and the resulting ray database, provide new insights into the steps underlying the seasonality of poplar trees.
    Keywords: Seasons ; Populus -- Cytology ; Trees -- Physiology ; Wood -- Cytology
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 09 June 2015, Vol.112(23), pp.7309-14
    Description: The Darwin plant Dionaea muscipula is able to grow on mineral-poor soil, because it gains essential nutrients from captured animal prey. Given that no nutrients remain in the trap when it opens after the consumption of an animal meal, we here asked the question of how Dionaea sequesters prey-derived potassium. We show that prey capture triggers expression of a K(+) uptake system in the Venus flytrap. In search of K(+) transporters endowed with adequate properties for this role, we screened a Dionaea expressed sequence tag (EST) database and identified DmKT1 and DmHAK5 as candidates. On insect and touch hormone stimulation, the number of transcripts of these transporters increased in flytraps. After cRNA injection of K(+)-transporter genes into Xenopus oocytes, however, both putative K(+) transporters remained silent. Assuming that calcium sensor kinases are regulating Arabidopsis K(+) transporter 1 (AKT1), we coexpressed the putative K(+) transporters with a large set of kinases and identified the CBL9-CIPK23 pair as the major activating complex for both transporters in Dionaea K(+) uptake. DmKT1 was found to be a K(+)-selective channel of voltage-dependent high capacity and low affinity, whereas DmHAK5 was identified as the first, to our knowledge, proton-driven, high-affinity potassium transporter with weak selectivity. When the Venus flytrap is processing its prey, the gland cell membrane potential is maintained around -120 mV, and the apoplast is acidified to pH 3. These conditions in the green stomach formed by the closed flytrap allow DmKT1 and DmHAK5 to acquire prey-derived K(+), reducing its concentration from millimolar levels down to trace levels.
    Keywords: Akt ; Cipk ; Dionaea Muscipula ; Hak5 ; Transporter ; Calcium -- Metabolism ; Droseraceae -- Metabolism ; Potassium -- Metabolism ; Protein Kinases -- Metabolism
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 3
    In: Journal of Bacteriology, August, 2000, Vol.182(15-16), p.4443(10)
    Description: Results demonstrate that the membrane-bound subunit IICB(sup)Glc of the glucose transporter system of Escherichia coli K-12 modulates IIC domain leading to ptsG gene expression. Data further indicate that the subunit IICB(sup)Glc facilitates glucose transport as well as glucose sensing and response.
    Keywords: Escherichia Coli -- Genetic Aspects ; Glucose Metabolism -- Physiological Aspects ; Gene Expression -- Analysis ; Active Biological Transport ; Physiological Regulation
    ISSN: 0021-9193
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: The Plant cell, July 2011, Vol.23(7), pp.2696-707
    Description: Cytosolic calcium homeostasis is pivotal for intracellular signaling and requires sensing of calcium concentrations in the cytosol and accessible stores. Numerous Ca²⁺ binding sites have been characterized in cytosolic proteins. However, little is known about Ca²⁺ binding inside organelles, like the vacuole. The slow vacuolar (SV) channel, encoded by Arabidopsis thaliana TPC1, is regulated by luminal Ca²⁺. However, the D454/fou2 mutation in TPC1 eliminates vacuolar calcium sensitivity and increases store calcium content. In a search for the luminal calcium binding site, structure modeling indicated a possible coordination site formed by residues Glu-450, Asp-454, Glu-456, and Glu-457 on the luminal side of TPC1. Each Glu residue was replaced by Gln, the modified genes were transiently expressed in loss-of-TPC1-function protoplasts, and SV channel responses to luminal calcium were recorded by patch clamp. SV channels lacking any of the four negatively charged residues appeared altered in calcium sensitivity of channel gating. Our results indicate that Glu-450 and Asp-454 are directly involved in Ca²⁺ binding, whereas Glu-456 and Glu-457 are probably involved in connecting the luminal Ca²⁺ binding site to the channel gate. This novel vacuolar calcium binding site represents a potential tool to address calcium storage in plants.
    Keywords: Arabidopsis Proteins -- Chemistry ; Calcium -- Metabolism ; Calcium Channels -- Chemistry
    ISSN: 10404651
    E-ISSN: 1532-298X
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  • 5
    In: The Journal of Bacteriology, 2000, Vol. 182(16), p.4443
    Description: In Escherichia coli K-12, the major glucose transporter with a central role in carbon catabolite repression and in inducer exclusion is the phosphoenolpyruvate-dependent glucose:phosphotransferase system (PTS). Its membrane-bound subunit, IICB super(Glc), is encoded by the gene ptsG; its soluble domain, IIA super(Glc), is encoded by crr, which is a member of the pts operon. The system is inducible by D-glucose and, to a lesser degree, by L-sorbose. The regulation of ptsG transcription was analyzed by testing the induction of IICB super(Glc) transporter activity and of a single-copy Phi (ptsGop-lacZ) fusion. Among mutations found to affect directly ptsG expression were those altering the activity of adenylate cyclase (cyaA), the repressor DgsA (dgsA; also called Mlc), the general PTS proteins enzyme I (ptsI) and histidine carrier protein HPr (ptsH), and the IIA super(Glc) and IIB super(Glc) domains, as well as several authentic and newly isolated UmgC mutations. The latter, originally thought to map in the repressor gene umgC outside the ptsG locus, were found to represent ptsG alleles. These affected invariably the substrate specificity of the IICB super(Glc) domain, thus allowing efficient transport and phosphorylation of substrates normally transported very poorly or not at all by this PTS. Simultaneously, all of these substrates became inducers for ptsG. From the analysis of the mutants, from cis-trans dominance tests, and from the identification of the amino acid residues mutated in the UmgC mutants, a new regulatory mechanism involved in ptsG induction is postulated. According to this model, the phosphorylation state of IIB super(Glc) modulates IIC super(Glc) which, directly or indirectly, controls the repressor DgsA and hence ptsG expression. By the same mechanism, glucose uptake and phosphorylation also control the expression of the pts operon and probably of all operons controlled by the repressor DgsA.
    Keywords: Escherichia Coli ; Escherichia Coli ; Carbon ; Gene Fusion ; Operons ; Catabolite Repression ; Gene Regulation ; Carbon ; Gene Fusion ; Operons ; Catabolite Repression ; Gene Regulation ; Lacz Gene ; Ptsg Gene ; Dgsa Protein ; Glucose Transporters ; Lacz Gene ; Ptsg Gene ; Dgsa Protein ; Glucose Transport ; Mutagenesis Techniques ; Enzymes ; Dgsa Protein ; Glucose Transport ; Glucose Transporters ; Lacz Gene ; Ptsg Gene;
    ISSN: 0021-9193
    ISSN: 00219193
    E-ISSN: 10985530
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  • 6
    Language: English
    In: Genome research, June 2016, Vol.26(6), pp.812-25
    Description: Although the concept of botanical carnivory has been known since Darwin's time, the molecular mechanisms that allow animal feeding remain unknown, primarily due to a complete lack of genomic information. Here, we show that the transcriptomic landscape of the Dionaea trap is dramatically shifted toward signal transduction and nutrient transport upon insect feeding, with touch hormone signaling and protein secretion prevailing. At the same time, a massive induction of general defense responses is accompanied by the repression of cell death-related genes/processes. We hypothesize that the carnivory syndrome of Dionaea evolved by exaptation of ancient defense pathways, replacing cell death with nutrient acquisition.
    Keywords: Droseraceae -- Genetics
    ISSN: 10889051
    E-ISSN: 1549-5469
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  • 7
    In: Traffic, July 2012, Vol.13(7), pp.1012-1022
    Description: Two‐pore channels (TPCs) constitute a family of endolysosomal cation channels with functions in Ca2+ signaling. We used a mutational analysis to investigate the role of channel domains for the trafficking of the Arabidopsis TPC1 to the tonoplast, a process that is generally not well understood in plants. The results show that the soluble C‐terminus was not essential for targeting but for channel function, while further C‐terminal truncations of two or more transmembrane domains impaired protein trafficking. An N‐terminal dileucine motif (EDPLI) proved to be critical for vacuolar targeting of TPC1, which was independent of the adaptor protein AP‐3. Deletion or mutation of this sorting motif, which is conserved among TPCs caused redirection of the protein transport to the plasma membrane. An N‐terminal region with a predicted α‐helical structure was shown to support efficient vacuolar trafficking and was essential for TPC1 function. Similar to their localization in mammalian endosomes and lysosomes, MmTPC1 and MmTPC2 were targeted to small organelles and the membrane of the lytic vacuole, respectively, when expressed in plant cells. These results shed new light on the largely uncharacterized sorting signals of plant tonoplast proteins and reveal similarities between the targeting machinery of plants and mammals.
    Keywords: Arabidopsis ; Dileucine Motif ; Protein Sorting ; Tonoplast ; Tpc1 ; Two‐Pore Channel ; Vacuole
    ISSN: 1398-9219
    E-ISSN: 1600-0854
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  • 8
    Language: English
    In: Reviews in the neurosciences, 2011, Vol.22(6), pp.625-45
    Description: Disturbances of dopaminergic neurotransmission may be caused by changes in concentrations of synaptic dopamine (DA) and/or availabilities of pre- and post-synaptic transporter and receptor binding sites. We present a series of experiments which focus on the regulatory mechanisms of the dopamin(DA)ergic synapse in the rat striatum. In these studies, DA transporter (DAT) and/or D(2) receptor binding were assessed with either small animal single-photon emission computed tomography (SPECT) or positron emission tomography (PET) after pharmacological challenge with haloperidol, L-DOPA and methylphenidate, and after nigrostriatal 6-hydroxydopamine lesion. Investigations of DAT binding were performed with [(123)I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane ([(123)I]FP-CIT). D(2) receptor bindingd was assessed with either [(123)I](S)-2-hydroxy-3-iodo-6-methoxy-N-[(1-ethyl-2-pyrrolidinyl)methyl]benzamide ([(123)I]IBZM) or [(18)F]1[3-(4'fluorobenzoyl)propyl]-4-(2-keto-3-methyl-1-benzimidazolinyl)piperidine ([(18)F]FMB). Findings demonstrate that in vivo investigations of transporter and/or receptor binding are feasible with small animal SPECT and PET. Therefore, tracers that are radiolabeled with isotopes of comparatively long half-lives such as (123)I may be employed. Our approach to quantify DAT and/or D(2) receptor binding at baseline and after pharmacological interventions inducing DAT blockade, D(2) receptor blockade, and increases or decreases of endogenous DA concentrations holds promise for the in vivo assessment of synaptic function. This pertains to animal models of diseases associated with pre- or postsynaptic DAergic deficiencies such as Parkinson's disease, Huntington's disease, attention-deficit/hyperactivity disorder, schizophrenia or drug abuse.
    Keywords: Corpus Striatum ; Positron-Emission Tomography ; Tomography, Emission-Computed, Single-Photon ; Dopamine -- Metabolism ; Dopamine Plasma Membrane Transport Proteins -- Metabolism ; Synapses -- Diagnostic Imaging
    ISSN: 0334-1763
    E-ISSN: 21910200
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  • 9
    In: Nuclear Medicine Communications, 2007, Vol.28(3), pp.207-213
    Description: OBJECTIVE: This study investigated dopamine transporter blockade in the rat striatum after treatment with various doses of methylphenidate using a high-resolution small animal SPECT (‘TierSPECT’) and I-FP-CIT. METHODS: I-FP-CIT was administered intravenously 1 h after intraperitoneal injection of methylphenidate (3 mg·kg, 10 mg·kg) or vehicle. Rats underwent scanning 2 h after radioligand application. From the spatial resolution of the imaging system and the size of the rat striatum followed that ‘true’ radioactivity concentrations were underestimated by ∼50%. From cerebellar and partial volume corrected striatal radioactivity concentrations, striatal equilibrium ratios (V3″) were computed as estimations of the binding potential. RESULTS: Vehicle-treated animals yielded striatal V3″ values of 3.5±0.9 (mean±SD). After pre-treatment with 3 mg·kg and 10 mg·kg methylphenidate, striatal V3″ values were reduced to 2.4±0.8 (independent t-test, two-tailed, P=0.026) and 1.7±0.6 (P〈0.001), respectively. CONCLUSIONS: This first in-vivo study of rat dopamine transporter binding after pre-treatment with various doses of methylphenidate showed a dose-dependent reduction of striatal dopamine transporter binding. Results indicate that in-vivo quantification of dopamine transporter binding is feasible with I-FP-CIT and the TierSPECT method. This may be of future relevance for investigating in-vivo binding properties as well as pharmacological profiles of novel agents acting at the dopamine transporter binding site. Moreover, alterations of striatal transporter densities may be investigated in animal models of neurological and psychiatric diseases such as attention-deficit/hyperactivity disorder and Parkinsonʼs disease.
    Keywords: Dopamine Plasma Membrane Transport Proteins -- Antagonists & Inhibitors ; Neostriatum -- Diagnostic Imaging ; Tomography, Emission-Computed, Single-Photon -- Methods;
    ISSN: 0143-3636
    E-ISSN: 14735628
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  • 10
    In: Nuclear Medicine Communications, 2006, Vol.27(3), pp.267-270
    Description: BACKGROUND AND AIM: Dopamine transporters are the target of psychostimulants used for treatment of attention-deficit/hyperactivity disorder (ADHD). Therefore, the present study aimed to evaluate striatal dopamine transporter density in adult patients with ADHD. METHODS: Twenty patients (11 female, nine male; mean age 35±7 years) and 20 control subjects (11 female, nine male, mean age 32±8 years) were examined with SPECT using the specific radiotracer I-FP-CIT. The ratio of striatal to cortical radioactivity concentration was used for semiquantitative evaluation of dopamine transporter binding potential (V3″). There was a significant influence of age (P〈0.001) and a trend towards an influence of gender (P=0.053) on V3″. An ANCOVA with these covariates showed a slightly higher V3″ in the patients than in the control subjects (4.24±0.48 vs. 4.03±0.56; P=0.02). CONCLUSION: This study provides further in-vivo evidence for an involvement of the dopamine transporter in ADHD. However, compared to previous studies, the increase of dopamine transporter density in the patient group is less pronounced here.
    Keywords: Attention Deficit Disorder With Hyperactivity -- Diagnostic Imaging ; Brain -- Diagnostic Imaging ; Corpus Striatum -- Diagnostic Imaging ; Dopamine Plasma Membrane Transport Proteins -- Metabolism;
    ISSN: 0143-3636
    E-ISSN: 14735628
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