TY - JOUR A1 - Oliver, Sandra N. A1 - Lunn, John Edward A1 - Urbanczyk-Wochniak, Ewa A1 - Lytovchenko, Anna A1 - van Dongen, Joost T. A1 - Faix, Benjamin A1 - Schmälzlin, Elmar A1 - Fernie, Alisdair R. A1 - Schmäelzlin, E. A1 - Geigenberger, Peter T1 - Decreased expression of cytosolic pyruvate kinase in potato tubers leads to a decline in pyruvate resulting in an in vivo repression of the alternative oxidase N2 - The aim of this work was to investigate the effect of decreased cytosolic pyruvate kinase (PKc) on potato (Solanum tuberosum) tuber metabolism. Transgenic potato plants with strongly reduced levels of PKc were generated by RNA interference gene silencing under the control of a tuber-specific promoter. Metabolite profiling showed that decreased PKc activity led to a decrease in the levels of pyruvate and some other organic acids involved in the tricarboxylic acid cycle. Flux analysis showed that this was accompanied by changes in carbon partitioning, with carbon flux being diverted from glycolysis toward starch synthesis. However, this metabolic shift was relatively small and hence did not result in enhanced starch levels in the tubers. Although total respiration rates and the ATP to ADP ratio were largely unchanged, transgenic tubers showed a strong decrease in the levels of alternative oxidase (AOX) protein and a corresponding decrease in the capacity of the alternative pathway of respiration. External feeding of pyruvate to tuber tissue or isolated mitochondria resulted in activation of the AOX pathway, both in the wild type and the PKc transgenic lines, providing direct evidence for the regulation of AOX by changes in pyruvate levels. Overall, these results provide evidence for a crucial role of PKc in the regulation of pyruvate levels as well as the level of the AOX in heterotrophic plant tissue, and furthermore reveal that these parameters are interlinked in vivo. Y1 - 2008 UR - http://www.plantphysiol.org/content/148/3/1640.full U6 - https://doi.org/10.1104/pp.108.126516 ER - TY - JOUR A1 - Annunziata, Maria Grazia A1 - Apelt, Federico A1 - Carillo, Petronia A1 - Krause, Ursula A1 - Feil, Regina A1 - Mengin, Virginie A1 - Lauxmann, Martin A. A1 - Koehl, Karin A1 - Nikoloski, Zoran A1 - Stitt, Mark A1 - Lunn, John Edward T1 - Getting back to nature: a reality check for experiments in controlled environments JF - Journal of experimental botany N2 - Irradiance from sunlight changes in a sinusoidal manner during the day, with irregular fluctuations due to clouds, and light-dark shifts at dawn and dusk are gradual. Experiments in controlled environments typically expose plants to constant irradiance during the day and abrupt light-dark transitions. To compare the effects on metabolism of sunlight versus artificial light regimes, Arabidopsis thaliana plants were grown in a naturally illuminated greenhouse around the vernal equinox, and in controlled environment chambers with a 12-h photoperiod and either constant or sinusoidal light profiles, using either white fluorescent tubes or light-emitting diodes (LEDs) tuned to a sunlight-like spectrum as the light source. Rosettes were sampled throughout a 24-h diurnal cycle for metabolite analysis. The diurnal metabolite profiles revealed that carbon and nitrogen metabolism differed significantly between sunlight and artificial light conditions. The variability of sunlight within and between days could be a factor underlying these differences. Pairwise comparisons of the artificial light sources (fluorescent versus LED) or the light profiles (constant versus sinusoidal) showed much smaller differences. The data indicate that energy-efficient LED lighting is an acceptable alternative to fluorescent lights, but results obtained from plants grown with either type of artificial lighting might not be representative of natural conditions. KW - Amino acid KW - Arabidopsis thaliana KW - controlled environment KW - LED lighting KW - visible light spectrum KW - organic acid KW - starch KW - sucrose KW - trehalose 6-phosphate Y1 - 2017 U6 - https://doi.org/10.1093/jxb/erx220 SN - 0022-0957 SN - 1460-2431 VL - 68 SP - 4463 EP - 4477 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Malinova, Irina A1 - Alseekh, Saleh A1 - Feil, Regina A1 - Fernie, Alisdair R. A1 - Baumann, Otto A1 - Schoettler, Mark Aurel A1 - Lunn, John Edward A1 - Fettke, Jörg T1 - Starch Synthase 4 and Plastidal Phosphorylase Differentially Affect Starch Granule Number and Morphology JF - Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants N2 - The process of starch granule formation in leaves of Arabidopsis ( Arabidopsis thaliana) is obscure. Besides STARCH SYNTHASE4 (SS4), the PLASTIDIAL PHOSPHORYLASE (PHS1) also seems to be involved, since dpe2-1/phs1a double mutants lacking both PHS1 and the cytosolic DISPROPORTIONATING ENZYME2 (DPE2) displayed only one starch granule per chloroplast under normal growth conditions. For further studies, a dpe2-1/phs1a/ss4 triple mutant and various combinations of double mutants were generated and metabolically analyzed with a focus on starch metabolism. The dpe2-1/phs1a/ ss4 mutant revealed a massive starch excess phenotype. Furthermore, these plants grown under 12 h of light/12 h of dark harbored a single large and spherical starch granule per plastid. The number of starch granules was constant when the light/dark regime was altered, but this was not observed in the parental lines. With regard to growth, photosynthetic parameters, and metabolic analyses, the triple mutant additionally displayed alterations in comparison with ss4 and dpe21/phs1a. The results clearly illustrate that PHS1 and SS4 are differently involved in starch granule formation and do not act in series. However, SS4 appears to exert a stronger influence. In connection with the characterized double mutants, we discuss the generation of starch granules and the observed formation of spherical starch granules. Y1 - 2017 U6 - https://doi.org/10.1104/pp.16.01859 SN - 0032-0889 SN - 1532-2548 VL - 174 SP - 73 EP - 85 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Martins, Marina Camara Mattos A1 - Hejazi, Mahdi A1 - Fettke, Jörg A1 - Steup, Martin A1 - Feil, Regina A1 - Krause, Ursula A1 - Arrivault, Stephanie A1 - Vosloh, Daniel A1 - Figueroa, Carlos Maria A1 - Ivakov, Alexander A1 - Yadav, Umesh Prasad A1 - Piques, Maria A1 - Metzner, Daniela A1 - Stitt, Mark A1 - Lunn, John Edward T1 - Feedback inhibition of starch degradation in arabidopsis leaves mediated by trehalose 6-phosphate JF - Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants N2 - Many plants accumulate substantial starch reserves in their leaves during the day and remobilize them at night to provide carbon and energy for maintenance and growth. In this paper, we explore the role of a sugar-signaling metabolite, trehalose-6-phosphate (Tre6P), in regulating the accumulation and turnover of transitory starch in Arabidopsis (Arabidopsis thaliana) leaves. Ethanol-induced overexpression of trehalose-phosphate synthase during the day increased Tre6P levels up to 11-fold. There was a transient increase in the rate of starch accumulation in the middle of the day, but this was not linked to reductive activation of ADP-glucose pyrophosphorylase. A 2- to 3-fold increase in Tre6P during the night led to significant inhibition of starch degradation. Maltose and maltotriose did not accumulate, suggesting that Tre6P affects an early step in the pathway of starch degradation in the chloroplasts. Starch granules isolated from induced plants had a higher orthophosphate content than granules from noninduced control plants, consistent either with disruption of the phosphorylation-dephosphorylation cycle that is essential for efficient starch breakdown or with inhibition of starch hydrolysis by beta-amylase. Nonaqueous fractionation of leaves showed that Tre6P is predominantly located in the cytosol, with estimated in vivo Tre6P concentrations of 4 to 7 mu M in the cytosol, 0.2 to 0.5 mu M in the chloroplasts, and 0.05 mu M in the vacuole. It is proposed that Tre6P is a component in a signaling pathway that mediates the feedback regulation of starch breakdown by sucrose, potentially linking starch turnover to demand for sucrose by growing sink organs at night. Y1 - 2013 U6 - https://doi.org/10.1104/pp.113.226787 SN - 0032-0889 SN - 1532-2548 VL - 163 IS - 3 SP - 1142 EP - 1163 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Paparelli, Eleonora A1 - Gonzali, Silvia A1 - Parlanti, Sandro A1 - Novi, Giacomo A1 - Giorgi, Federico M. A1 - Licausi, Francesco A1 - Kosmacz, Monika A1 - Feil, Regina A1 - Lunn, John Edward A1 - Brust, Henrike A1 - van Dongen, Joost T. A1 - Steup, Martin A1 - Perata, Pierdomenico T1 - Misexpression of a chloroplast aspartyl protease leads to severe growth defects and alters carbohydrate metabolism in arabidopsis JF - Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants N2 - The crucial role of carbohydrate in plant growth and morphogenesis is widely recognized. In this study, we describe the characterization of nana, a dwarf Arabidopsis (Arabidopsis thaliana) mutant impaired in carbohydrate metabolism. We show that the nana dwarf phenotype was accompanied by altered leaf morphology and a delayed flowering time. Our genetic and molecular data indicate that the mutation in nana is due to a transfer DNA insertion in the promoter region of a gene encoding a chloroplast-located aspartyl protease that alters its pattern of expression. Overexpression of the gene (oxNANA) phenocopies the mutation. Both nana and oxNANA display alterations in carbohydrate content, and the extent of these changes varies depending on growth light intensity. In particular, in low light, soluble sugar levels are lower and do not show the daily fluctuations observed in wild-type plants. Moreover, nana and oxNANA are defective in the expression of some genes implicated in sugar metabolism and photosynthetic light harvesting. Interestingly, some chloroplast-encoded genes as well as genes whose products seem to be involved in retrograde signaling appear to be down-regulated. These findings suggest that the NANA aspartic protease has an important regulatory function in chloroplasts that not only influences photosynthetic carbon metabolism but also plastid and nuclear gene expression. Y1 - 2012 U6 - https://doi.org/10.1104/pp.112.204016 SN - 0032-0889 VL - 160 IS - 3 SP - 1237 EP - 1250 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Garapati, Prashanth A1 - Feil, Regina A1 - Lunn, John Edward A1 - Van Dijck, Patrick A1 - Balazadeh, Salma A1 - Müller-Röber, Bernd T1 - Transcription Factor Arabidopsis Activating Factor1 Integrates Carbon Starvation Responses with Trehalose Metabolism JF - Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants N2 - Plants respond to low carbon supply by massive reprogramming of the transcriptome and metabolome. We show here that the carbon starvation-induced NAC (for NO APICAL MERISTEM/ARABIDOPSIS TRANSCRIPTION ACTIVATION FACTOR/CUP-SHAPED COTYLEDON) transcription factor Arabidopsis (Arabidopsis thaliana) Transcription Activation Factor1 (ATAF1) plays an important role in this physiological process. We identified TREHALASE1, the only trehalase-encoding gene in Arabidopsis, as a direct downstream target of ATAF1. Overexpression of ATAF1 activates TREHALASE1 expression and leads to reduced trehalose-6-phosphate levels and a sugar starvation metabolome. In accordance with changes in expression of starch biosynthesis-and breakdown-related genes, starch levels are generally reduced in ATAF1 overexpressors but elevated in ataf1 knockout plants. At the global transcriptome level, genes affected by ATAF1 are broadly associated with energy and carbon starvation responses. Furthermore, transcriptional responses triggered by ATAF1 largely overlap with expression patterns observed in plants starved for carbon or energy supply. Collectively, our data highlight the existence of a positively acting feedforward loop between ATAF1 expression, which is induced by carbon starvation, and the depletion of cellular carbon/energy pools that is triggered by the transcriptional regulation of downstream gene regulatory networks by ATAF1. Y1 - 2015 U6 - https://doi.org/10.1104/pp.15.00917 SN - 0032-0889 SN - 1532-2548 VL - 169 IS - 1 SP - 379 EP - 390 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Fichtner, Franziska A1 - Barbier, Francois F. A1 - Annunziata, Maria Grazia A1 - Feil, Regina A1 - Olas, Justyna Jadwiga A1 - Müller-Röber, Bernd A1 - Stitt, Mark A1 - Beveridge, Christine A. A1 - Lunn, John Edward T1 - Regulation of shoot branching in arabidopsis by trehalose 6-phosphate JF - New phytologist : international journal of plant science N2 - Trehalose 6-phosphate (Tre6P) is a sucrose signalling metabolite that has been implicated in regulation of shoot branching, but its precise role is not understood. We expressed tagged forms of TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1) to determine where Tre6P is synthesized in arabidopsis (Arabidopsis thaliana), and investigated the impact of localized changes in Tre6P levels, in axillary buds or vascular tissues, on shoot branching in wild-type and branching mutant backgrounds. TPS1 is expressed in axillary buds and the subtending vasculature, as well as in the leaf and stem vasculature. Expression of a heterologous Tre6P phosphatase (TPP) to lower Tre6P in axillary buds strongly delayed bud outgrowth in long days and inhibited branching in short days. TPP expression in the vasculature also delayed lateral bud outgrowth and decreased branching. Increased Tre6P in the vasculature enhanced branching and was accompanied by higher expression of FLOWERING LOCUS T (FT) and upregulation of sucrose transporters. Increased vascular Tre6P levels enhanced branching in branched1 but not in ft mutant backgrounds. These results provide direct genetic evidence of a local role for Tre6P in regulation of axillary bud outgrowth within the buds themselves, and also connect Tre6P with systemic regulation of shoot branching via FT. KW - Arabidopsis thaliana (arabidopsis) KW - axillary bud KW - branching KW - sucrose KW - sugar signalling KW - trehalose 6‐ phosphate (Tre6P) Y1 - 2020 U6 - https://doi.org/10.1111/nph.17006 SN - 0028-646X SN - 1469-8137 VL - 229 IS - 4 SP - 2135 EP - 2151 PB - Wiley CY - Hoboken ER - TY - GEN A1 - Fichtner, Franziska A1 - Barbier, Francois F. A1 - Annunziata, Maria Grazia A1 - Feil, Regina A1 - Olas, Justyna Jadwiga A1 - Müller-Röber, Bernd A1 - Stitt, Mark A1 - Beveridge, Christine A. A1 - Lunn, John Edward T1 - Regulation of shoot branching in arabidopsis by trehalose 6-phosphate T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Trehalose 6-phosphate (Tre6P) is a sucrose signalling metabolite that has been implicated in regulation of shoot branching, but its precise role is not understood. We expressed tagged forms of TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1) to determine where Tre6P is synthesized in arabidopsis (Arabidopsis thaliana), and investigated the impact of localized changes in Tre6P levels, in axillary buds or vascular tissues, on shoot branching in wild-type and branching mutant backgrounds. TPS1 is expressed in axillary buds and the subtending vasculature, as well as in the leaf and stem vasculature. Expression of a heterologous Tre6P phosphatase (TPP) to lower Tre6P in axillary buds strongly delayed bud outgrowth in long days and inhibited branching in short days. TPP expression in the vasculature also delayed lateral bud outgrowth and decreased branching. Increased Tre6P in the vasculature enhanced branching and was accompanied by higher expression of FLOWERING LOCUS T (FT) and upregulation of sucrose transporters. Increased vascular Tre6P levels enhanced branching in branched1 but not in ft mutant backgrounds. These results provide direct genetic evidence of a local role for Tre6P in regulation of axillary bud outgrowth within the buds themselves, and also connect Tre6P with systemic regulation of shoot branching via FT. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1383 KW - Arabidopsis thaliana (arabidopsis) KW - axillary bud KW - branching KW - sucrose KW - sugar signalling KW - trehalose 6‐ phosphate (Tre6P) Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-569564 SN - 1866-8372 IS - 4 ER - TY - JOUR A1 - Fichtner, Franziska A1 - Olas, Justyna Jadwiga A1 - Feil, Regina A1 - Watanabe, Mutsumi A1 - Krause, Ursula A1 - Hoefgen, Rainer A1 - Stitt, Mark A1 - Lunn, John Edward T1 - Functional features of Trehalose-6-Phosphate Synthase 1 BT - an essential enzyme in Arabidopsis JF - The Plant Cell N2 - Tre6P synthesis by TPS1 is essential for embryogenesis and postembryonic growth in Arabidopsis, and appropriate Suc signaling by Tre6P is dependent on the noncatalytic domains of TPS1. In Arabidopsis (Arabidopsis thaliana), TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1) catalyzes the synthesis of the sucrose-signaling metabolite trehalose 6-phosphate (Tre6P) and is essential for embryogenesis and normal postembryonic growth and development. To understand its molecular functions, we transformed the embryo-lethal tps1-1 null mutant with various forms of TPS1 and with a heterologous TPS (OtsA) from Escherichia coli, under the control of the TPS1 promoter, and tested for complementation. TPS1 protein localized predominantly in the phloem-loading zone and guard cells in leaves, root vasculature, and shoot apical meristem, implicating it in both local and systemic signaling of Suc status. The protein is targeted mainly to the nucleus. Restoring Tre6P synthesis was both necessary and sufficient to rescue the tps1-1 mutant through embryogenesis. However, postembryonic growth and the sucrose-Tre6P relationship were disrupted in some complementation lines. A point mutation (A119W) in the catalytic domain or truncating the C-terminal domain of TPS1 severely compromised growth. Despite having high Tre6P levels, these plants never flowered, possibly because Tre6P signaling was disrupted by two unidentified disaccharide-monophosphates that appeared in these plants. The noncatalytic domains of TPS1 ensure its targeting to the correct subcellular compartment and its catalytic fidelity and are required for appropriate signaling of Suc status by Tre6P. KW - cyanobacterial sucrose-phosphatase KW - trehalose 6-phosphate KW - vegetative growth KW - crystal-structure KW - gene-expression KW - thaliana KW - metabolism KW - phosphorylation KW - reveals KW - proteins Y1 - 2020 U6 - https://doi.org/10.1105/tpc.19.00837 SN - 0032-0781 SN - 1471-9053 VL - 32 IS - 6 SP - 1949 EP - 1972 PB - Oxford University Press CY - Oxford ER - TY - GEN A1 - Fichtner, Franziska A1 - Olas, Justyna Jadwiga A1 - Feil, Regina A1 - Watanabe, Mutsumi A1 - Krause, Ursula A1 - Hoefgen, Rainer A1 - Stitt, Mark A1 - Lunn, John Edward T1 - Functional features of Trehalose-6-Phosphate Synthase 1 BT - an essential enzyme in Arabidopsis T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Tre6P synthesis by TPS1 is essential for embryogenesis and postembryonic growth in Arabidopsis, and appropriate Suc signaling by Tre6P is dependent on the noncatalytic domains of TPS1. In Arabidopsis (Arabidopsis thaliana), TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1) catalyzes the synthesis of the sucrose-signaling metabolite trehalose 6-phosphate (Tre6P) and is essential for embryogenesis and normal postembryonic growth and development. To understand its molecular functions, we transformed the embryo-lethal tps1-1 null mutant with various forms of TPS1 and with a heterologous TPS (OtsA) from Escherichia coli, under the control of the TPS1 promoter, and tested for complementation. TPS1 protein localized predominantly in the phloem-loading zone and guard cells in leaves, root vasculature, and shoot apical meristem, implicating it in both local and systemic signaling of Suc status. The protein is targeted mainly to the nucleus. Restoring Tre6P synthesis was both necessary and sufficient to rescue the tps1-1 mutant through embryogenesis. However, postembryonic growth and the sucrose-Tre6P relationship were disrupted in some complementation lines. A point mutation (A119W) in the catalytic domain or truncating the C-terminal domain of TPS1 severely compromised growth. Despite having high Tre6P levels, these plants never flowered, possibly because Tre6P signaling was disrupted by two unidentified disaccharide-monophosphates that appeared in these plants. The noncatalytic domains of TPS1 ensure its targeting to the correct subcellular compartment and its catalytic fidelity and are required for appropriate signaling of Suc status by Tre6P. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1432 KW - cyanobacterial sucrose-phosphatase KW - trehalose 6-phosphate KW - vegetative growth KW - crystal-structure KW - gene-expression KW - thaliana KW - metabolism KW - phosphorylation KW - reveals KW - proteins Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516532 SN - 1866-8372 IS - 6 ER -