TY - JOUR A1 - Omidbakhshfard, Mohammad Amin A1 - Neerakkal, Sujeeth A1 - Gupta, Saurabh A1 - Omranian, Nooshin A1 - Guinan, Kieran J. A1 - Brotman, Yariv A1 - Nikoloski, Zoran A1 - Fernie, Alisdair R. A1 - Mueller-Roeber, Bernd A1 - Gechev, Tsanko S. T1 - A Biostimulant Obtained from the Seaweed Ascophyllum nodosum Protects Arabidopsis thaliana from Severe Oxidative Stress JF - International Journal of Molecular Sciences N2 - Abiotic stresses cause oxidative damage in plants. Here, we demonstrate that foliar application of an extract from the seaweed Ascophyllum nodosum, SuperFifty (SF), largely prevents paraquat (PQ)-induced oxidative stress in Arabidopsis thaliana. While PQ-stressed plants develop necrotic lesions, plants pre-treated with SF (i.e., primed plants) were unaffected by PQ. Transcriptome analysis revealed induction of reactive oxygen species (ROS) marker genes, genes involved in ROS-induced programmed cell death, and autophagy-related genes after PQ treatment. These changes did not occur in PQ-stressed plants primed with SF. In contrast, upregulation of several carbohydrate metabolism genes, growth, and hormone signaling as well as antioxidant-related genes were specific to SF-primed plants. Metabolomic analyses revealed accumulation of the stress-protective metabolite maltose and the tricarboxylic acid cycle intermediates fumarate and malate in SF-primed plants. Lipidome analysis indicated that those lipids associated with oxidative stress-induced cell death and chloroplast degradation, such as triacylglycerols (TAGs), declined upon SF priming. Our study demonstrated that SF confers tolerance to PQ-induced oxidative stress in A. thaliana, an effect achieved by modulating a range of processes at the transcriptomic, metabolic, and lipid levels. KW - Ascophyllum nodosum KW - Arabidopsis thaliana KW - biostimulant KW - paraquat KW - priming KW - oxidative stress tolerance KW - reactive oxygen species Y1 - 2019 U6 - https://doi.org/10.3390/ijms21020474 SN - 1422-0067 VL - 21 IS - 2 PB - Molecular Diversity Preservation International CY - Basel ER - TY - THES A1 - Apriyanto, Ardha T1 - Analysis of starch metabolism in source and sink tissue of plants T1 - Analyse des Stärkestoffwechsels im Source und Sink Gewebe von Pflanzen N2 - Starch is an essential biopolymer produced by plants. Starch can be made inside source tissue (such as leaves) and sink tissue (such as fruits and tubers). Nevertheless, understanding how starch metabolism is regulated in source and sink tissues is fundamental for improving crop production. Despite recent advances in the understanding of starch and its metabolism, there is still a knowledge gap in the source and sink metabolism. Therefore, this study aimed to summarize the state of the art regarding starch structure and metabolism inside plants. In addition, this study aimed to elucidate the regulation of starch metabolism in the source tissue using the leaves of a model organism, Arabidopsis thaliana, and the sink tissue of oil palm (Elaeis guineensis) fruit as a commercial crop. The research regarding the source tissue will focus on the effect of the blockage of starch degradation on the starch parameter in leaves, especially in those of A. thaliana, which lack both disproportionating enzyme 2 (DPE2) and plastidial glucan phosphorylase 1 (PHS1) (dpe2/phs1). The additional elimination of phosphoglucan water dikinase (PWD), starch excess 4 (SEX4), isoamylase 3 (ISA3), and disproportionating enzyme 1 (DPE1) in the dpe2/phs1 mutant background demonstrates the alteration of starch granule number per chloroplast. This study provides insights into the control mechanism of granule number regulation in the chloroplast. The research regarding the sink tissue will emphasize the relationship between starch metabolism and the lipid metabolism pathway in oil palm fruits. This study was conducted to observe the alteration of starch parameters, metabolite abundance, and gene expression during oil palm fruit development with different oil yields. This study shows that starch and sucrose can be used as biomarkers for oil yield in oil palms. In addition, it is revealed that the enzyme isoforms related to starch metabolism influence the oil production in oil palm fruit. Overall, this thesis presents novel information regarding starch metabolism in the source tissue of A.thaliana and the sink tissue of E.guineensis. The results shown in this thesis can be applied to many applications, such as modifying the starch parameter in other plants for specific needs. N2 - Stärke ist ein unverzichtbares Biopolymer, das von Pflanzen sowohl in den Quellgeweben (sources, z. B. Blätter) als auch in den Senkengeweben (sinks, z. B. Früchten und Knollen) gebildet wird. Daher ist ein profundes Wissen über die Regulation des Stärkestoffwechsel in den source und sink Organen von grundlegender Bedeutung für die Verbesserung der Pflanzenproduktion. Trotz der jüngsten Fortschritte im Verständnis des Stärkestoffwechsels bleiben weiterhin viele Fragen über den detaillierten source und sink Metabolismus offen. Ziel dieser Studie war es daher, den aktuellen Forschungsstand über die Struktur und den Stoffwechsel von Stärke in Pflanzen aufzuzeigen. Darüber hinaus sollte in dieser Studie die Regulierung des Stärkestoffwechsels in den Blättern (source) des Modellorganismus Arabidopsis thaliana und in den Ölpalmfrüchten (sink) von Elaeis guineensis, einer Nutzpflanze, aufgeklärt werden. Die Analyse des source Gewebes konzentrierte sich dabei auf die Auswirkungen auf Stärkeparamter wie beispielsweise die Granulazahl durch die Blockierung des Stärkeabbaus in Blättern. Dazu wurde die Arabidopsis Mutante, der das cytosolische Disproportionating Enzym 2 (DPE2) und die plastidiale Glucanphosphorylase 1 (PHS1) fehlen (dpe2/phs1), untersucht. Ebenfalls wurden Dreifachmutanten im Hintergund von dpe2/phs1, denen Starch excess 4 (SEX4), Isoamylase 3, Phosphoglucan-Wasser-Dikinase (PWD) oder das Disproportionating Enzym 1 (DPE1) fehlen, erzeugt. Die Analyse zeigt, dass die Anzahl der Stärkegranula pro Chloroplast nicht festgelegt ist und während des gesamten Wachstums der Pflanze reguliert wird. Diese Daten liefern ein verbessertes Verständnis über die Komplexität der Kontrollmechanismen der Granulazahlregulation in Chloroplasten. Die Untersuchung des sink Gewebes soll die Beziehung zwischen dem Stärkestoffwechsel und dem Lipidstoffwechselweg in Ölpalmenfrüchten verdeutlichen. Diese Studie wurde durchgeführt, um die Veränderung von Stärkeparametern, die Häufigkeit von Metaboliten und die Genexpression während der Entwicklung von Ölpalmenfrüchten mit unterschiedlichen Ölausbeuten zu erforschen. Die Analyse zeigt, dass sowohl Stärke als auch Saccharose als reliable Biomarker für den Ölertrag von Ölpalmen verwendet werden können. Darüber hinaus konnte bewiesen werden, dass die mit dem Stärkestoffwechsel verbundenen Enzymisoformen die Ölproduktion in Ölpalmenfrüchten beeinflussen. Insgesamt liefert diese Arbeit neue Informationen über den Stärkestoffwechsel im source Gewebe von A.thaliana und im sink von E.guineensis. Die in dieser Arbeit gezeigten Ergebnisse können für viele Anwendungen genutzt werden, z. B. für die Veränderung der Stärkeparameter in anderen Pflanzen für spezifische Bedürfnisse. KW - starch KW - oil palm KW - Arabidopsis thaliana KW - source and sink KW - Arabidopsis thaliana KW - Palmöl KW - Source und Sink KW - Stärke Y1 - 2023 ER - TY - JOUR A1 - Bäurle, Isabel A1 - Brzezinka, Krzysztof A1 - Altmann, Simone T1 - BRUSHY1/TONSOKU/MGOUN3 is required for heat stress memory JF - Plant Cell & Environment N2 - Plants encounter biotic and abiotic stresses many times during their life cycle and this limits their productivity. Moderate heat stress (HS) primes a plant to survive higher temperatures that are lethal in the naïve state. Once temperature stress subsides, the memory of the priming event is actively retained for several days preparing the plant to better cope with recurring HS. Recently, chromatin regulation at different levels has been implicated in HS memory. Here, we report that the chromatin protein BRUSHY1 (BRU1)/TONSOKU/MGOUN3 plays a role in the HS memory in Arabidopsis thaliana. BRU1 is also involved in transcriptional gene silencing and DNA damage repair. This corresponds with the functions of its mammalian orthologue TONSOKU‐LIKE/NFΚBIL2. During HS memory, BRU1 is required to maintain sustained induction of HS memory‐associated genes, whereas it is dispensable for the acquisition of thermotolerance. In summary, we report that BRU1 is required for HS memory in A. thaliana, and propose a model where BRU1 mediates the epigenetic inheritance of chromatin states across DNA replication and cell division. KW - Arabidopsis thaliana KW - BRUSHY1 KW - chromatin KW - priming Y1 - 2019 U6 - https://doi.org/10.1111/pce.13365 VL - 42 SP - 771 EP - 781 ER - TY - JOUR A1 - Liu, Hsiang-chin A1 - Lämke, Jörn A1 - Lin, Siou-ying A1 - Hung, Meng-Ju A1 - Liu, Kuan-Ming A1 - Charng, Yee-yung A1 - Bäurle, Isabel T1 - Distinct heat shock factors and chromatin modifications mediate the organ-autonomous transcriptional memory of heat stress JF - The plant journal N2 - Plants can be primed by a stress cue to mount a faster or stronger activation of defense mechanisms upon subsequent stress. A crucial component of such stress priming is the modified reactivation of genes upon recurring stress; however, the underlying mechanisms of this are poorly understood. Here, we report that dozens of Arabidopsis thaliana genes display transcriptional memory, i.e. stronger upregulation after a recurring heat stress, that lasts for at least 3 days. We define a set of transcription factors involved in this memory response and show that the transcriptional memory results in enhanced transcriptional activation within minutes of the onset of a heat stress cue. Further, we show that the transcriptional memory is active in all tissues. It may last for up to a week, and is associated during this time with histone H3 lysine 4 hypermethylation. This transcriptional memory is cis-encoded, as we identify a promoter fragment that confers memory onto a heterologous gene. In summary, heat-induced transcriptional memory is a widespread and sustained response, and our study provides a framework for future mechanistic studies of somatic stress memory in higher plants. KW - epigenetics KW - priming KW - heat stress KW - H3K4 methylation KW - transcriptional memory KW - Arabidopsis thaliana KW - HSF Y1 - 2018 U6 - https://doi.org/10.1111/tpj.13958 SN - 0960-7412 SN - 1365-313X VL - 95 IS - 3 SP - 401 EP - 413 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Malinova, Irina A1 - Mahto, Harendra A1 - Brandt, Felix A1 - AL-Rawi, Shadha A1 - Qasim, Hadeel A1 - Brust, Henrike A1 - Hejazi, Mahdi A1 - Fettke, Jörg T1 - EARLY STARVATION1 specifically affects the phosphorylation action of starch-related dikinases JF - The plant journal N2 - Starch phosphorylation by starch-related dikinases glucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD) is a key step in starch degradation. Little information is known about the precise structure of the glucan substrate utilized by the dikinases and about the mechanisms by which these structures may be influenced. A 50-kDa starch-binding protein named EARLY STARVATION1 (ESV1) was analyzed regarding its impact on starch phosphorylation. In various invitro assays, the influences of the recombinant protein ESV1 on the actions of GWD and PWD on the surfaces of native starch granules were analyzed. In addition, we included starches from various sources as well as truncated forms of GWD. ESV1 preferentially binds to highly ordered, -glucans, such as starch and crystalline maltodextrins. Furthermore, ESV1 specifically influences the action of GWD and PWD at the starch granule surface. Starch phosphorylation by GWD is decreased in the presence of ESV1, whereas the action of PWD increases in the presence of ESV1. The unique alterations observed in starch phosphorylation by the two dikinases are discussed in regard to altered glucan structures at the starch granule surface. KW - Arabidopsis thaliana KW - EARLY STARVATION1 KW - glucan KW - phosphoglucan KW - starch granule surface KW - starch phosphorylation KW - water dikinase Y1 - 2018 U6 - https://doi.org/10.1111/tpj.13937 SN - 0960-7412 SN - 1365-313X VL - 95 IS - 1 SP - 126 EP - 137 PB - Wiley CY - Hoboken ER - TY - THES A1 - Vyse, Kora T1 - Elucidating molecular determinants of the loss of freezing tolerance during deacclimation after cold priming and low temperature memory after triggering N2 - Während ihrer Entwicklung müssen sich Pflanzen an Temperaturschwankungen anpassen. Niedrige Temperaturen über dem Gefrierpunkt induzieren in Pflanzen eine Kälteakklimatisierung und höhere Frosttoleranz, die sich bei wärmeren Temperaturen durch Deakklimatisierung wieder zurückbildet. Der Wechsel zwischen diesen beiden Prozessen ist für Pflanzen unerlässlich, um als Reaktion auf unterschiedliche Temperaturbedingungen eine optimale Fitness zu erreichen. Die Kälteakklimatisierung ist umfassend untersucht worden,über die Regulierung der Deakklimatisierung ist jedoch wenig bekannt. In dieser Arbeit wird der Prozess der Deakklimatisierung auf physiologischer und molekularer Ebene in Arabidopsis thaliana untersucht. Messungen des Elektrolytverlustes während der Kälteakklimatisierung und bis zu vier Tagen nach Deakklimatisierung ermöglichten die Identifizierung von vier Knockout-Mutanten (hra1, lbd41, mbf1c und jub1), die im Vergleich zum Wildtyp eine langsamere Deakklimatisierungsrate aufwiesen. Eine transkriptomische Studie mit Hilfe von RNA-Sequenzierung von A. thaliana Col-0, jub1 und mbf1c zeigte die Bedeutung der Hemmung von stressreaktiven und Jasmonat-ZIM-Domänen-Genen sowie die Regulierung von Zellwandmodifikationen während der Deakklimatisierung. Darüber hinaus zeigten Messungen der Alkoholdehydrogenase Aktivität und der Genexpressionsänderungen von Hypoxiemarkern während der ersten vier Tagen der Deakklimatisierung, dass eine Hypoxie-Reaktion während der Deakklimatisierung aktiviert wird. Es wurde gezeigt, dass die epigenetische Regulierung während der Kälteakklimatisierung und der 24-stündigen Deakklimatisierung in A. thaliana eine große Rolle spielt. Darüber hinaus zeigten beide Deakklimatisierungsstudien, dass die frühere Hypothese, dass Hitzestress eine Rolle bei der frühen Deakklimatisierung spielen könnte, unwahrscheinlich ist. Eine Reihe von DNA- und Histondemethylasen sowie Histonvarianten wurden während der Deakklimatisierung hochreguliert, was auf eine Rolle im pflanzlichen Gedächtnis schließen lässt. In jüngster Zeit haben mehrere Studien gezeigt, dass Pflanzen in der Lage sind, die Erinnerung an einen vorangegangenen Kältestress auch nach einer Woche Deakklimatisierung zu bewahren. In dieser Arbeit ergaben Transkriptom- und Metabolomanalysen von Arabidopsis während 24 Stunden Priming (Kälteakklimatisierung) und Triggering (wiederkehrender Kältestress nach Deakklimatisierung) eine unikale signifikante und vorübergehende Induktion der Transkriptionsfaktoren DREB1D, DREB1E und DREB1F während des Triggerings, die zur Feinabstimmung der zweiten Kältestressreaktion beiträgt. Darüber hinaus wurden Gene, die für Late Embryogenesis Abundant (LEA) und Frostschutzproteine kodieren, sowie Proteine, die reaktive Sauerstoffspezies entgiften, während des späten Triggerings (24 Stunden) stärker induziert als nach dem ersten Kälteimpuls, während Xyloglucan- Endotransglucosylase/Hydrolase Gene, deren Produkte für eine Restrukturierung der Zellwand verantwortlich sind, früh auf das Triggering reagierten. Die starke Induktion dieser Gene, sowohl bei der Deakklimatisierung als auch beim Triggering, lässt vermuten, dass sie eine wesentliche Rolle bei der Stabilisierung der Zellen während des Wachstums und bei der Reaktion auf wiederkehrende Stressbedingungen spielen. Zusammenfassend gibt diese Arbeit neue Einblicke in die Regulierung der Deakklimatisierung und des Kältestress-Gedächtnisses in A. thaliana und eröffnet neue Möglichkeiten für künftige, gezielte Studien von essentiellen Genen in diesem Prozess. N2 - Throughout their lifetime plants need to adapt to temperature changes. Plants adapt to nonfreezing cold temperatures in a process called cold priming (cold acclimation) and lose the acquired freezing tolerance during warmer temperatures through deacclimation. The alternation of both processes is essential for plants to achieve optimal fitness in response to different temperature conditions. Cold acclimation has been extensively studied, however, little is known about the regulation of deacclimation. This thesis elucidates the process of deacclimation on a physiological and molecular level in Arabidopsis thaliana. Electrolyte leakage measurements during cold acclimation and up to four days of deacclimation enabled the identification of four knockout mutants (hra1, lbd41, mbf1c and jub1) with a slower rate of deacclimation compared to the wild type. A transcriptomic study using RNA-Sequencing in A. thaliana Col-0, jub1 and mbf1c identified the importance of the inhibition of stress responsive and Jasmonate-ZIM-domain genes as well as the regulation of cell wall modifications during deacclimation. Moreover, measurements of alcohol dehydrogenase activity and gene expression changes of hypoxia markers during the first four days of deacclimation evidently showed that a hypoxia response is activated during deacclimation. Epigenetic regulation was observed to be extensively involved during cold acclimation and 24 h of deacclimation in A. thaliana. Further, both deacclimation studies showed that the previous hypothesis that heat stress might play a role in early deacclimation, is not likely. A number of DNA- and histone demethylases as well as histone variants were upregulated during deacclimation suggesting a role in plant memory. Recently, multiple studies have shown that plants are able to retain memory of a previous cold stress even after a week of deacclimation. In this work, transcriptomic and metabolomic analyses of Arabidopsis during 24 h of priming (cold acclimation) and triggering (recurring cold stress after deacclimation) revealed a uniquely significant and transient induction of DREB1D, DREB1E and DREB1F transcription factors during triggering contributing to fine-tuning of the second cold stress response. Furthermore, genes encoding Late Embryogenesis Abundant (LEA) and antifreeze proteins and proteins detoxifying reactive oxygen species were higher induced during late triggering (24 h) compared to primed samples, while cell wall remodelers of the class xyloglucan endotransglucosylase/hydrolase were early responders of triggering. The high induction of cell wall remodelers during deacclimation as well as triggering proposes that these proteins play an essential role in the stabilization of the cells during growth as well as the response to recurring stresses. Collectively this work gives new insights on the regulation of deacclimation and cold stress memory in A. thaliana and opens the door to future targeted studies of essential genes in this process. KW - cold stress KW - deacclimation KW - Arabidopsis thaliana KW - epigenetics KW - co-expression network analysis KW - WGCNA KW - RNA-sequencing KW - differential gene expression KW - hypoxia KW - transcription factors KW - Kältestress KW - Deakklimatisierung KW - Epigenetik KW - Koexpression Netzwerk Analysen KW - RNA-Sequenzierung KW - Differenzielle Genexpression KW - Hypoxie KW - Transkriptionsfaktoren Y1 - 2022 ER - TY - JOUR A1 - Hansen, Bjoern Oest A1 - Meyer, Etienne H. A1 - Ferrari, Camilla A1 - Vaid, Neha A1 - Movahedi, Sara A1 - Vandepoele, Klaas A1 - Nikoloski, Zoran A1 - Mutwil, Marek T1 - Ensemble gene function prediction database reveals genes important for complex I formation in Arabidopsis thaliana JF - New phytologist : international journal of plant science N2 - Recent advances in gene function prediction rely on ensemble approaches that integrate results from multiple inference methods to produce superior predictions. Yet, these developments remain largely unexplored in plants. We have explored and compared two methods to integrate 10 gene co-function networks for Arabidopsis thaliana and demonstrate how the integration of these networks produces more accurate gene function predictions for a larger fraction of genes with unknown function. These predictions were used to identify genes involved in mitochondrial complex I formation, and for five of them, we confirmed the predictions experimentally. The ensemble predictions are provided as a user-friendly online database, EnsembleNet. The methods presented here demonstrate that ensemble gene function prediction is a powerful method to boost prediction performance, whereas the EnsembleNet database provides a cutting-edge community tool to guide experimentalists. KW - Arabidopsis thaliana KW - co-function network KW - complex I KW - ensemble prediction KW - gene function prediction Y1 - 2017 U6 - https://doi.org/10.1111/nph.14921 SN - 0028-646X SN - 1469-8137 VL - 217 IS - 4 SP - 1521 EP - 1534 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Malinova, Irina A1 - Kössler, Stella A1 - Orawetz, Tom A1 - Matthes, Ulrike A1 - Orzechowski, Slawomir A1 - Koch, Anke A1 - Fettke, Jörg T1 - Identification of two Arabidopsis thaliana plasma membrane transporters able to transport glucose 1-phosphate JF - Plant & cell physiology N2 - Primary carbohydrate metabolism in plants includes several sugar and sugar-derivative transport processes. Over recent years, evidences have shown that in starch-related transport processes, in addition to glucose 6-phosphate, maltose, glucose and triose-phosphates, glucose 1-phosphate also plays a role and thereby increases the possible fluxes of sugar metabolites in planta. In this study, we report the characterization of two highly similar transporters, At1g34020 and At4g09810, in Arabidopsis thaliana, which allow the import of glucose 1-phosphate through the plasma membrane. Both transporters were expressed in yeast and were biochemically analyzed to reveal an antiport of glucose 1-phosphate/phosphate. Furthermore, we showed that the apoplast of Arabidopsis leaves contained glucose 1-phosphate and that the corresponding mutant of these transporters had higher glucose 1-phosphate amounts in the apoplast and alterations in starch and starch-related metabolism. KW - apoplast KW - Arabidopsis thaliana KW - glucose 1-phosphate transport KW - starch metabolism KW - sugar transport Y1 - 2020 U6 - https://doi.org/10.1093/pcp/pcz206 SN - 0032-0781 SN - 1471-9053 VL - 61 IS - 2 SP - 381 EP - 392 PB - Oxford University Press CY - Oxford ER - TY - THES A1 - Mahto, Harendra T1 - In vitro analysis of Early Starvation 1 (ESV1) and Like Early Starvation 1 (LESV) on starch degradation with focus on glucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD) N2 - Starch is an insoluble polyglucan, comprises of two polymers, namely, the branched α-1,4: α-1,6-D-glucan amylopectin and the almost unbranched α-1,4-D-glucan amylose. The growth of all plants is directly dependent on the accumulation of transitory starch during the daytime when photosynthesis takes place and subsequently starch degradation during the night. Starch phosphorylation takes place by starch-related dikinases called α-glucan, water dikinase (GWD), and phosphoglucan, water dikinase (PWD), and is a very important step in starch degradation. The biochemical mechanisms of phosphorylation of starch are not properly understood. Recent studies have found that there are two starch binding proteins namely, Early Starvation1 (ESV1) and Like Early Starvation1 (LESV), which play an important role in starch metabolism. It has been shown that ESV1 and LESV proteins affect the starch phosphorylation activity of GWD and PWD enzymes, which control the rate of degradation of starch granules. In this thesis, various in vitro assays were performed to identify and understand the mechanism of recombinant proteins; ESV1 and LESV on the starch degradation. The starch degradation was performed by phosphorylation enzymes, GWD and PWD separately. In various enzymatic assays, the influence of the ESV1 and LESV on the actions of GWD and PWD on the surfaces of different native starch granules were analysed. Furthermore, ESV1 and LESV have specifically shown influences on the phosphorylation activities of GWD and PWD on the starch granule surfaces in an antagonistic pattern in such a way that, the GWD mediated phosphorylation were significantly reduced while PWD mediated phosphorylation were significantly increased respectively. In another set of experiments, ISA and BAM hydrolyzing enzymes were used to alter the structure of starch, and then determine the effect of both dikinases mediated phosphorylation in the presence of ESV1 and LESV on the altered starch granules surfaces. In these results, significant decreases in both GWD and PWD mediated phosphorylation were observed in all the treatments containing either ESV1 or LESV proteins only or both ESV1 and LESV. It was also found that LESV preferentially binds to both amylose and amylopectin, while ESV1 binds to highly ordered glucans such as maltodextrins and amylopectin, which are crystalline in structure. Both ESV1 or LESV proteins either individually or in combination have shown influence on the activity of GWD and PWD phosphate incorporation into the starch granules via reduction even though at different percentages depending on the sources of starch, therefore it is difficult to distinguish the specific function between them. The biochemical studies have shown that protein-glucan interaction specifically between ESV1 or LESV or in combination with different species of starch granules has very strong surface binding, or it might be possible that both the proteins not only bind to the surface of the starch granules but also have entered deep inside the glucan structure of the starch granules. However, the results also revealed that ESV1 and LESV did not alter the autophosphorylation of the dikinases. Also, the chain length distribution pattern of the released glucan chains after treatment of starch with ISA enzyme was evaluated with respect to the degree of polymerization (DP) of the different starch granules. Capillary electrophoresis was employed to study the effect of LESV and ESV1 on the chain length distribution. In summary, this study confirms that ESV1 and LESV play an important role in organizing and regulating the starch metabolism process. In the later half, studies were performed to monitor whether the metabolism of carbohydrates and partitioning, contribute to the higher salt tolerance of the facultative halophyte Hordeum marinum when compared to glycophyte Hordeum vulgare. Seedlings with the same size from both species were hydroponically grown at 0, 150, and 300 mM of NaCl for 3 weeks. H. marinum maintained a high relative growth rate, which was found concomitant in higher aptitude plants to maintain efficient shoot tissue hydration and integrity of membrane under salt conditions when compared to H. vulgare. Hence, our data suggested that the change in the starch storage, distribution of soluble sugar concentrations between source and sink organs, and also changes in the level of enzymes involved in the starch metabolism was significant to give insights into the importance of carbohydrate metabolism in barley species with regards to the salt tolerance. Although these results are still in their nascent state, it could be vital for other researchers to formulate future studies. The preliminary results which were studies about the carbohydrate metabolism and partitioning in salt responses in the halophyte H. marinum and the glycophyte H. vulgare revealed that salt tolerance in barley species is not due to osmotic adjustments, but due to other reasons that were not explored in the past studies. However, the activity of DPE2 in H. vulgare was not hampered by the presence of NaCl as observed. While Pho1 and Pho2, activities were highly increased in cultivated barley. These findings could be suggestive of a possible role of these enzymes in the responses of carbohydrate metabolism to salinity. When sea and cultivated barley species were compared, it was discovered that the former had more versatility in carbohydrate metabolism and distribution. N2 - Stärke ist ein unlösliches Polyglucan, das aus zwei Polymeren besteht, nämlich dem verzweigten α-1,4: α-1,6-D-Glucan Amylopektin und dem fast unverzweigten α-1,4-D-Glucan Amylose. Das Wachstum aller Pflanzen hängt direkt von der Akkumulation transitorischer Stärke während des Tages, wenn die Photosynthese stattfindet, und dem anschließenden Stärkeabbau während der Nacht ab. Die Phosphorylierung von Stärke erfolgt durch stärkeverwandte Dikinasen, die α-Glucan-Wasser-Dikinase (GWD) und Phosphoglucan-Wasser-Dikinase (PWD), und ist ein entscheidender Schritt beim Stärkeabbau. Die biochemischen Mechanismen der Phosphorylierung von Stärke sind nicht genau bekannt. Jüngste Studien haben ergeben, dass es zwei stärkebindende Proteine gibt, nämlich Early Starvation1 (ESV1) und Like Early Starvation1 (LESV), die eine wichtige Rolle im Stärkestoffwechsel spielen. Es hat sich gezeigt, dass ESV1- und LESV-Proteine die Stärkephosphorylierungsaktivität der GWD- und PWD-Enzyme beeinflussen, die die Geschwindigkeit des Abbaus von Stärkekörnern steuern. In dieser Arbeit wurden verschiedene In-vitro-Tests durchgeführt, um den Mechanismus der rekombinanten Proteine ESV1 und LESV auf den Stärkeabbau zu identifizieren und zu verstehen.Der Stärkeabbau wurde von den Phosphorylierungsenzymen GWD und PWD getrennt durchgeführt. In verschiedenen enzymatischen Assays wurde der Einfluss von ESV1 und LESV auf die Wirkung von GWD und PWD auf die Oberflächen verschiedener nativer Stärkekörner analysiert. Darüber hinaus haben ESV1 und LESV spezifisch Einflüsse auf die Phosphorylierungsaktivitäten von GWD und PWD auf den Oberflächen der Stärkekörner in einem antagonistischen Muster gezeigt, so dass die GWD-vermittelte Phosphorylierung signifikant reduziert wurde, während die PWD-vermittelte Phosphorylierung signifikant erhöht wurde. In einer anderen Versuchsreihe wurden ISA- und BAM verwendet, um die Struktur der Stärke zu verändern und dann die Auswirkungen der durch beide Dikinasen vermittelten Phosphorylierung in Gegenwart von ESV1 und LESV auf die veränderten Oberflächen der Stärkekörner zu bestimmen. In diesen Ergebnissen wurde ein signifikanter Rückgang der GWD- und PWD-vermittelten Phosphorylierung in allen Behandlungen beobachtet, die entweder nur ESV1- oder LESV-Proteine oder sowohl ESV1 als auch LESV enthielten. Es wurde auch festgestellt, dass LESV vorzugsweise an Amylose und Amylopektin bindet, während ESV1 an hochgeordnete Glucane wie Maltodextrine und Amylopektin bindet, die eine kristalline Struktur aufweisen. Sowohl ESV1- als auch LESV-Proteine haben entweder einzeln oder in Kombination einen Einfluss auf die Aktivität des GWD- und PWD-Phosphateinbaus in die Stärkekörner durch Reduktion gezeigt, jedoch zu unterschiedlichen Prozentsätzen, je nach Stärkequelle, so dass es schwierig ist, ihre spezifische Funktion zu unterscheiden. Die biochemischen Untersuchungen zeigen, dass die Protein-Glucan-Interaktion speziell zwischen ESV1 oder LESV oder in Kombination mit verschiedenen Arten von Stärkekörnern eine sehr starke Oberflächenbindung aufweist, oder es ist möglich, dass beide Proteine nicht nur an die Oberfläche der Stärkekörner binden, sondern auch tief in die Glucanstruktur der Stärkekörner eingedrungen sind. Die Ergebnisse zeigten jedoch auch, dass ESV1 und LESV die Autophosphorylierung der Dikinasen nicht veränderten. Außerdem wurde die Kettenlängenverteilung der freigesetzten Glucanketten nach Behandlung der Stärke mit dem ISA-Enzym im Hinblick auf den Polymerisationsgrad (DP) der verschiedenen Stärkekörner bewertet. Mit Hilfe der Kapillarelektrophorese wurde die Wirkung von LESV und ESV1 auf die Kettenlängenverteilung untersucht. Zusammenfassend bestätigt diese Studie, dass ESV1 und LESV eine wichtige Rolle bei der Organisation und Regulierung des Stärkestoffwechsels spielen. In der zweiten Hälfte wurden Untersuchungen durchgeführt, um zu prüfen, ob der Stoffwechsel von Kohlenhydraten und deren Verteilung zu der höheren Salztoleranz des fakultativen Halophyten Hordeum marinum im Vergleich zum Glykophyten Hordeum vulgare beitragen. Die gleich großen Sämlinge beider Arten wurden 3 Wochen lang bei 0, 150 und 300 mM NaCl hydroponisch gezogen. H. marinum wies eine hohe relative Wachstumsrate auf, die mit einer höheren Fähigkeit der Pflanzen einherging, unter Salzbedingungen eine effiziente Hydratation des Sprossgewebes und die Integrität der Membran aufrechtzuerhalten, als dies bei H. vulgare der Fall war. Unsere Daten deuten also darauf hin, dass die Veränderungen in der Stärkespeicherung, die Verteilung der Konzentrationen löslicher Zucker zwischen Source- und Sinkorganen und auch die Veränderungen in der Menge der am Stärkestoffwechsel beteiligten Enzyme von Bedeutung sind und Einblicke in die Bedeutung des Kohlenhydratstoffwechsels bei Gerstenarten im Hinblick auf die Salztoleranz geben. Obwohl sich diese Ergebnisse noch im Anfangsstadium befinden, könnten sie für andere Forscher bei der Formulierung künftiger Studien von entscheidender Bedeutung sein. Die vorläufigen Ergebnisse der Studien über den Kohlenhydratstoffwechsel und die Verteilung der Kohlenhydrate bei Salzreaktionen im Halophyten H. marinum und im Glykophyten H. vulgare haben gezeigt, dass die Salztoleranz bei Gerstenarten nicht auf osmotische Anpassungen zurückzuführen ist, sondern auf andere Gründe, die in den bisherigen Studien nicht untersucht wurden. Die Aktivität von DPE2 in H. vulgare wurde jedoch nicht wie beobachtet durch die Anwesenheit von NaCl beeinträchtigt. Dagegen waren die Aktivitäten von Pho1 und Pho2 in kultivierter Gerste stark erhöht. Diese Ergebnisse könnten auf eine mögliche Rolle dieser Enzyme bei der Reaktion des Kohlenhydratstoffwechsels auf den Salzgehalt hinweisen. Beim Vergleich von Meeres- und Kulturgerstenarten wurde festgestellt, dass erstere eine größere Vielseitigkeit im Kohlenhydratstoffwechsel und in der Kohlenhydratverteilung aufweisen. KW - Arabidopsis thaliana KW - starch phosphorylation KW - phosphoglucan KW - starch granule surface KW - Early Starvation 1 Y1 - 2022 ER - TY - JOUR A1 - Wang, Meng A1 - Li, Panpan A1 - Ma, Yao A1 - Nie, Xiang A1 - Grebe, Markus A1 - Men, Shuzhen T1 - Membrane sterol composition in Arabidopsis thaliana affects root elongation via auxin biosynthesis JF - International journal of molecular sciences N2 - Plant membrane sterol composition has been reported to affect growth and gravitropism via polar auxin transport and auxin signaling. However, as to whether sterols influence auxin biosynthesis has received little attention. Here, by using the sterol biosynthesis mutant cyclopropylsterol isomerase1-1 (cpi1-1) and sterol application, we reveal that cycloeucalenol, a CPI1 substrate, and sitosterol, an end-product of sterol biosynthesis, antagonistically affect auxin biosynthesis. The short root phenotype of cpi1-1 was associated with a markedly enhanced auxin response in the root tip. Both were neither suppressed by mutations in polar auxin transport (PAT) proteins nor by treatment with a PAT inhibitor and responded to an auxin signaling inhibitor. However, expression of several auxin biosynthesis genes TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1 (TAA1) was upregulated in cpi1-1. Functionally, TAA1 mutation reduced the auxin response in cpi1-1 and partially rescued its short root phenotype. In support of this genetic evidence, application of cycloeucalenol upregulated expression of the auxin responsive reporter DR5:GUS (beta-glucuronidase) and of several auxin biosynthesis genes, while sitosterol repressed their expression. Hence, our combined genetic, pharmacological, and sterol application studies reveal a hitherto unexplored sterol-dependent modulation of auxin biosynthesis during Arabidopsis root elongation. KW - Arabidopsis thaliana KW - auxin KW - auxin biosynthesis KW - cycloeucalenol KW - CPI1 KW - sitosterol KW - sterol Y1 - 2021 U6 - https://doi.org/10.3390/ijms22010437 SN - 1422-0067 VL - 22 IS - 1 PB - MDPI CY - Basel ER - TY - JOUR A1 - Tejos, Ricardo A1 - Rodriguez-Furlan, Cecilia A1 - Adamowski, Maciej A1 - Sauer, Michael A1 - Norambuena, Lorena A1 - Friml, Jiri T1 - PATELLINS are regulators of auxin-mediated PIN1 relocation and plant development in Arabidopsis thaliana JF - Journal of cell science N2 - Coordinated cell polarization in developing tissues is a recurrent theme in multicellular organisms. In plants, a directional distribution of the plant hormone auxin is at the core of many developmental programs. A feedback regulation of auxin on the polarized localization of PIN auxin transporters in individual cells has been proposed as a self-organizing mechanism for coordinated tissue polarization, but the molecular mechanisms linking auxin signalling to PIN-dependent auxin transport remain unknown. We used a microarray-based approach to find regulators of the auxin-induced PIN relocation in Arabidopsis thaliana root, and identified a subset of a family of phosphatidylinositol transfer proteins (PITPs), the PATELLINs (PATLs). Here, we show that PATLs are expressed in partially overlapping cell types in different tissues going through mitosis or initiating differentiation programs. PATLs are plasma membrane-associated proteins accumulated in Arabidopsis embryos, primary roots, lateral root primordia and developing stomata. Higher order patl mutants display reduced PIN1 repolarization in response to auxin, shorter root apical meristem, and drastic defects in embryo and seedling development. This suggests that PATLs play a redundant and crucial role in polarity and patterning in Arabidopsis. KW - PATELLIN KW - Auxin KW - Arabidopsis thaliana KW - Auxin transport KW - Canalization Y1 - 2018 U6 - https://doi.org/10.1242/jcs.204198 SN - 0021-9533 SN - 1477-9137 VL - 131 IS - 2 PB - Company of Biologists Limited CY - Cambridge ER - TY - JOUR A1 - Ralevski, Alexandra A1 - Apelt, Federico A1 - Olas, Justyna Jadwiga A1 - Müller-Röber, Bernd A1 - Rugarli, Elena I. A1 - Kragler, Friedrich A1 - Horvath, Tamas L. T1 - Plant mitochondrial FMT and its mammalian homolog CLUH controls development and behavior in Arabidopsis and locomotion in mice JF - Cellular and molecular life sciences N2 - Mitochondria in animals are associated with development, as well as physiological and pathological behaviors. Several conserved mitochondrial genes exist between plants and higher eukaryotes. Yet, the similarities in mitochondrial function between plant and animal species is poorly understood. Here, we show that FMT (FRIENDLY MITOCHONDRIA) from Arabidopsis thaliana, a highly conserved homolog of the mammalian CLUH (CLUSTERED MITOCHONDRIA) gene family encoding mitochondrial proteins associated with developmental alterations and adult physiological and pathological behaviors, affects whole plant morphology and development under both stressed and normal growth conditions. FMT was found to regulate mitochondrial morphology and dynamics, germination, and flowering time. It also affects leaf expansion growth, salt stress responses and hyponastic behavior, including changes in speed of hyponastic movements. Strikingly, Cluh(+/-) heterozygous knockout mice also displayed altered locomotive movements, traveling for shorter distances and had slower average and maximum speeds in the open field test. These observations indicate that homologous mitochondrial genes may play similar roles and affect homologous functions in both plants and animals. KW - Arabidopsis thaliana KW - Mitochondria KW - FMT KW - Hyponasty KW - Mice KW - CLUH; KW - Locomotion Y1 - 2022 U6 - https://doi.org/10.1007/s00018-022-04382-3 SN - 1420-682X SN - 1420-9071 VL - 79 IS - 6 PB - Springer International Publishing AG CY - Cham (ZG) ER - TY - JOUR A1 - Pandey, Prashant K. A1 - Yu, Jing A1 - Omranian, Nooshin A1 - Alseekh, Saleh A1 - Vaid, Neha A1 - Fernie, Alisdair R. A1 - Nikoloski, Zoran A1 - Laitinen, Roosa A. E. T1 - Plasticity in metabolism underpins local responses to nitrogen in Arabidopsis thaliana populations JF - Plant Direct N2 - Nitrogen (N) is central for plant growth, and metabolic plasticity can provide a strategy to respond to changing N availability. We showed that two local A. thaliana populations exhibited differential plasticity in the compounds of photorespiratory and starch degradation pathways in response to three N conditions. Association of metabolite levels with growth-related and fitness traits indicated that controlled plasticity in these pathways could contribute to local adaptation and play a role in plant evolution. KW - Arabidopsis thaliana KW - natural variation KW - nitrogen availability KW - photorespiration KW - plasticity Y1 - 2019 U6 - https://doi.org/10.1002/pld3.186 SN - 2475-4455 VL - 3 IS - 11 PB - John Wiley & sonst LTD CY - Chichester ER - TY - JOUR A1 - Merida, Angel A1 - Fettke, Jörg T1 - Starch granule initiation in Arabidopsis thaliana chloroplasts JF - The plant journal N2 - The initiation of starch granule formation and the mechanism controlling the number of granules per plastid have been some of the most elusive aspects of starch metabolism. This review covers the advances made in the study of these processes. The analyses presented herein depict a scenario in which starch synthase isoform 4 (SS4) provides the elongating activity necessary for the initiation of starch granule formation. However, this protein does not act alone; other polypeptides are required for the initiation of an appropriate number of starch granules per chloroplast. The functions of this group of polypeptides include providing suitable substrates (maltooligosaccharides) to SS4, the localization of the starch initiation machinery to the thylakoid membranes, and facilitating the correct folding of SS4. The number of starch granules per chloroplast is tightly regulated and depends on the developmental stage of the leaves and their metabolic status. Plastidial phosphorylase (PHS1) and other enzymes play an essential role in this process since they are necessary for the synthesis of the substrates used by the initiation machinery. The mechanism of starch granule formation initiation in Arabidopsis seems to be generalizable to other plants and also to the synthesis of long-term storage starch. The latter, however, shows specific features due to the presence of more isoforms, the absence of constantly recurring starch synthesis and degradation, and the metabolic characteristics of the storage sink organs. KW - starch granules KW - starch metabolism KW - starch granule initiation KW - starch KW - granule number per chloroplast KW - starch morphology KW - Arabidopsis thaliana Y1 - 2021 U6 - https://doi.org/10.1111/tpj.15359 SN - 0960-7412 SN - 1365-313X VL - 107 IS - 3 SP - 688 EP - 697 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Liu, Qingting A1 - Li, Xiaoping A1 - Fettke, Jörg T1 - Starch granules in Arabidopsis thaliana mesophyll and guard cells show similar morphology but differences in size and number JF - International journal of molecular sciences N2 - Transitory starch granules result from complex carbon turnover and display specific situations during starch synthesis and degradation. The fundamental mechanisms that specify starch granule characteristics, such as granule size, morphology, and the number per chloroplast, are largely unknown. However, transitory starch is found in the various cells of the leaves of Arabidopsis thaliana, but comparative analyses are lacking. Here, we adopted a fast method of laser confocal scanning microscopy to analyze the starch granules in a series of Arabidopsis mutants with altered starch metabolism. This allowed us to separately analyze the starch particles in the mesophyll and in guard cells. In all mutants, the guard cells were always found to contain more but smaller plastidial starch granules than mesophyll cells. The morphological properties of the starch granules, however, were indiscernible or identical in both types of leaf cells. KW - starch granules KW - starch granule number per chloroplast KW - starch morphology KW - mesophyll cell KW - guard cell KW - LCSM KW - Arabidopsis thaliana KW - starch granule initiation KW - starch metabolism Y1 - 2021 U6 - https://doi.org/10.3390/ijms22115666 SN - 1422-0067 SN - 1661-6596 VL - 22 IS - 11 PB - Molecular Diversity Preservation International CY - Basel ER - TY - JOUR A1 - Lisso, Janina A1 - Altmann, Thomas A1 - Müssig, Carsten T1 - The AtNFXL1 gene encodes a NF-X1 type zinc finger protein required for growth under salt stress JF - FEBS letters : the journal for rapid publication of short reports in molecular biosciences N2 - The human NF-X1 protein and homologous proteins in eukaryotes represent a class of transcription factors which are characterised. by NF-X1 type zinc finger motifs. The Arabidopsis genome encodes two NF-X1 homologs, which we termed AtNFXL1 and AtNFXL2. Growth and survival was impaired in atnfxl1 knock-out mutants and AtNFXL1-antisense plants under salt stress in comparison to wild-type plants. In contrast, 35S: :AtNFXL1 plants showed higher survival rates. The AtNFXL2 protein potentially plays an antagonistic role. The Arabidopsis NF-X1 type zinc finger proteins likely are part of regulatory mechanisms, which protect major processes such as photosynthesis. KW - Arabidopsis thaliana KW - NF-X1 KW - salt stress Y1 - 2006 U6 - https://doi.org/10.1016/j.febslet.2006.07.079 SN - 0014-5793 VL - 580 IS - 22 SP - 4851 EP - 4856 PB - Elsevier CY - Amsterdam ER - TY - THES A1 - von Bismarck, Thekla T1 - The influence of long-term light acclimation on photosynthesis in dynamic light N2 - Photosynthesis converts light into metabolic energy which fuels plant growth. In nature, many factors influence light availability for photosynthesis on different time scales, from shading by leaves within seconds up to seasonal changes over months. Variability of light energy supply for photosynthesis can limit a plant´s biomass accumulation. Plants have evolved multiple strategies to cope with strongly fluctuation light (FL). These range from long-term optimization of leaf morphology and physiology and levels of pigments and proteins in a process called light acclimation, to rapid changes in protein activity within seconds. Therefore, uncovering how plants deal with FL on different time scales may provide key ideas for improving crop yield. Photosynthesis is not an isolated process but tightly integrates with metabolism through mutual regulatory interactions. We thus require mechanistic understanding of how long-term light acclimation shapes both, dynamic photosynthesis and its interactions with downstream metabolism. To approach this, we analyzed the influence of growth light on i) the function of known rapid photosynthesis regulators KEA3 and VCCN1 in dynamic photosynthesis (Chapter 2-3) and ii) the interconnection of photosynthesis with photorespiration (PR; Chapter 4). We approached topic (i) by quantifying the effect of different growth light regimes on photosynthesis and photoprotection by using kea3 and vccn1 mutants. Firstly, we found that, besides photosynthetic capacity, the activities of VCCN1 and KEA3 during a sudden high light phase also correlated with growth light intensity. This finding suggests regulation of both proteins by the capacity of downstream metabolism. Secondly, we showed that KEA3 accelerated photoprotective non-photochemical quenching (NPQ) kinetics in two ways: Directly via downregulating the lumen proton concentration and thereby de-activating pH-dependent NPQ, and indirectly via suppressing accumulation of the photoprotective pigment zeaxanthin. For topic (ii), we analyzed the role of PR, a process which recycles a toxic byproduct of the carbon fixation reactions, in metabolic flexibility in a dynamically changing light environment. For this we employed the mutants hpr1 and ggt1 with a partial block in PR. We characterized the function of PR during light acclimation by tracking molecular and physiological changes of the two mutants. Our data, in contrast to previous reports, disprove a generally stronger physiological relevance of PR under dynamic light conditions. Additionally, the two different mutants showed pronounced and distinct metabolic changes during acclimation to a condition inducing higher photosynthetic activity. This underlines that PR cannot be regarded purely as a cyclic detoxification pathway for 2PG. Instead, PR is highly interconnected with plant metabolism, with GGT1 and HPR1 representing distinct metabolic modulators. In summary, the presented work provides further insight into how energetic and metabolic flexibility is ensured by short-term regulators and PR during long-term light acclimation. N2 - Photosynthese wandelt Lichtenergie in metabolische Energie um, welche das Pflanzenwachstum antreibt. In der Natur wird die Verfügbarkeit von Licht von vielerlei Faktoren auf unterschiedlichen Zeitskalen beeinflusst, z. B. von der Beschattung durch Blätter innerhalb von Sekunden bis hin zu jahreszeitlichen Veränderungen über Monate. Fluktuationen in der Lichtenergieverfügbarkeit in der Natur kann die Biomasseakkumulation der Pflanzen limitieren. Pflanzen haben verschiedene Strategien entwickelt, um stark fluktuierendes Licht nutzen zu können. Diese reichen von der langfristigen Optimierung der Blattmorphologie und Physiologie und des Gehalts an Pigmenten und Proteinen in dem Prozess der Lichtakklimatisierung bis hin zu schnellen Veränderungen der Proteinaktivität innerhalb von Sekunden. Daher kann die Aufdeckung der Art und Weise, wie Pflanzen mit FL auf verschiedenen Zeitskalen umgehen, wichtige Ideen zur Verbesserung der Ernteerträge liefern. Die Photosynthese ist kein isolierter Prozess, sondern steht in enger Interaktion mit den nachgeschalteten Stoffwechselwegen. Daher benötigen wir mechanistisches Verständnis, wie Lichtakklimatisierung die dynamische Photosynthese als auch deren Interaktion mit Downstream-Metabolismus moduliert. Dafür haben wir den Einfluss von Lichtakklimatisierung auf i) die Funktion der schnellen Photosyntheseregulatoren KEA3 und VCCN1 in der dynamischen Photosynthese und ii) die flexible Interaktion von Photorespiration mit Photosynthese analysiert. Im ersten Themenkomplex (i) wurden die Auswirkungen verschiedener Wachstumslicht-bedingungen auf Photosynthese und Photoprotektion anhand von kea3- und vccn1-Mutanten quantifiziert. Zum einen konnten wir zeigen, dass neben der photosynthetischen Kapazität auch die Aktivitäten von VCCN1 und KEA3 während eines Hochlichtpulses mit der Wachstumslichtintensität korrelierten. Dies deutet auf eine Regulierung beider Proteine durch die Kapazität des Downstream-Metabolismus hin. Zum anderen beschleunigte KEA3 die Kinetik des photoprotektiven nicht-photochemischen Quenchings (NPQ) auf zweifache Weise: Direkt über die Herabregulierung der lumenalen Protonenkonzentration, was den pH-abhängigen NPQ deaktivierte, und indirekt über die Unterdrückung der Akkumulation des photoprotektiven Pigments Zeaxanthin. Für das zweite Thema (ii) untersuchten wir die Rolle des photorespiratorischen Metabolismus (PR), welcher ein toxisches Nebenprodukt der Kohlenstofffixierungsreaktionen recycelt, in der metabolischen Flexibilität in einer sich dynamisch verändernden Lichtumgebung. Dazu verwendeten wir die Mutanten hpr1 und ggt1 mit teilweise blockiertem PR Flux. Unsere Daten widerlegen, im Gegensatz zu früheren Berichten, eine allgemein größere physiologische Bedeutung von PR unter dynamischen Lichtbedingungen. Die beiden Mutanten zeigten ausgeprägte und distinkte metabolische Veränderungen während der Akklimatisierung an eine Bedingung mit höherer photosynthetischer Aktivität. Dies zeigt, dass PR nicht ausschließlich als zyklischer Entgiftungsweg für 2PG angesehen werden kann. Vielmehr ist PR tief in den pflanzlichen Stoffwechsel eingebettet, wobei GGT1 und HPR1 als distinkte Stellschrauben des Downstream-Metabolismus agieren. Zusammenfassend liefert die vorliegende Arbeit weitere Erkenntnisse darüber, wie die energetische und metabolische Flexibilität durch kurzfristige Regulatoren und den photorespiratorischen Metabolismus während der langfristigen Lichtakklimatisierung gewährleistet wird. KW - photosynthesis KW - fluctuating light KW - Arabidopsis thaliana KW - Photosynthese KW - fluktuierendes Licht Y1 - 2023 ER - TY - JOUR A1 - Zhang, Yunming A1 - Ramming, Anna A1 - Heinke, Lisa A1 - Altschmied, Lothar A1 - Slotkin, R. Keith A1 - Becker, Jörg D. A1 - Kappel, Christian A1 - Lenhard, Michael T1 - The poly(A) polymerase PAPS1 interacts with the RNA-directed DNA-methylation pathway in sporophyte and pollen development JF - The plant journal N2 - RNA-based processes play key roles in the regulation of eukaryotic gene expression. This includes both the processing of pre-mRNAs into mature mRNAs ready for translation and RNA-based silencing processes, such as RNA-directed DNA methylation (RdDM). Polyadenylation of pre-mRNAs is one important step in their processing and is carried out by three functionally specialized canonical nuclear poly(A) polymerases in Arabidopsis thaliana. Null mutations in one of these, termed PAPS1, result in a male gametophytic defect. Using a fluorescence-labelling strategy, we have characterized this defect in more detail using RNA and small-RNA sequencing. In addition to global defects in the expression of pollen-differentiation genes, paps1 null-mutant pollen shows a strong overaccumulation of transposable element (TE) transcripts, yet a depletion of 21- and particularly 24-nucleotide-long short interfering RNAs (siRNAs) and microRNAs (miRNAs) targeting the corresponding TEs. Double-mutant analyses support a specific functional interaction between PAPS1 and components of the RdDM pathway, as evident from strong synergistic phenotypes in mutant combinations involving paps1, but not paps2 paps4, mutations. In particular, the double-mutant of paps1 and rna-dependent rna polymerase 6 (rdr6) shows a synergistic developmental phenotype disrupting the formation of the transmitting tract in the female gynoecium. Thus, our findings in A. thaliana uncover a potentially general link between canonical poly(A) polymerases as components of mRNA processing and RdDM, reflecting an analogous interaction in fission yeast. KW - poly(A) polymerase KW - RNA-directed DNA methylation KW - pollen development KW - siRNAs KW - transposable elements KW - gynoecium development KW - Arabidopsis thaliana Y1 - 2019 U6 - https://doi.org/10.1111/tpj.14348 SN - 0960-7412 SN - 1365-313X VL - 99 IS - 4 SP - 655 EP - 672 PB - Wiley CY - Hoboken ER -