@article{RamachandranHamannOskinovaetal.2019, author = {Ramachandran, Varsha and Hamann, Wolf-Rainer and Oskinova, Lidia M. and Gallagher, J. S. and Hainich, Rainer and Shenar, Tomer and Sander, Andreas Alexander Christoph and Todt, Helge Tobias and Fulmer, Leah M.}, title = {Testing massive star evolution, star formation history, and feedback at low metallicity}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {625}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201935365}, pages = {20}, year = {2019}, abstract = {Stars that start their lives with spectral types O and early B are the progenitors of core-collapse supernovae, long gamma-ray bursts, neutron stars, and black holes. These massive stars are the primary sources of stellar feedback in star-forming galaxies. At low metallicities, the properties of massive stars and their evolution are not yet fully explored. Here we report a spectroscopic study of 320 massive stars of spectral types O (23 stars) and B (297 stars) in the Wing of the Small Magellanic Cloud (SMC). The spectra, which we obtained with the ESO Very Large Telescope, were analyzed using state-of-the-art stellar atmosphere models, and the stellar parameters were determined. We find that the stellar winds of our sample stars are generally much weaker than theoretically expected. The stellar rotation rates show broad, tentatively bimodal distributions. The upper Hertzsprung-Russell diagram (HRD) is well populated by the stars of our sample from a specific field in the SMC Wing. A few very luminous O stars are found close to the main sequence, while all other, slightly evolved stars obey a strict luminosity limit. Considering additional massive stars in evolved stages, with published parameters and located all over the SMC, essentially confirms this picture. The comparison with single-star evolutionary tracks suggests a dichotomy in the fate of massive stars in the SMC. Only stars with an initial mass below similar to 30 M-circle dot seem to evolve from the main sequence to the cool side of the HRD to become a red supergiant and to explode as type II-P supernova. In contrast, stars with initially more than similar to 30 M-circle dot appear to stay always hot and might evolve quasi chemically homogeneously, finally collapsing to relatively massive black holes. However, we find no indication that chemical mixing is correlated with rapid rotation. We measured the key parameters of stellar feedback and established the links between the rates of star formation and supernovae. Our study demonstrates that in metal-poor environments stellar feedback is dominated by core-collapse supernovae in combination with winds and ionizing radiation supplied by a few of the most massive stars. We found indications of the stochastic mode of massive star formation, where the resulting stellar population is fully capable of producing large-scale structures such as the supergiant shell SMC-SGS 1 in the Wing. The low level of feedback in metal-poor stellar populations allows star formation episodes to persist over long timescales.}, language = {en} } @article{SanderHamannTodtetal.2019, author = {Sander, Andreas Alexander Christoph and Hamann, Wolf-Rainer and Todt, Helge Tobias and Hainich, Rainer and Shenar, Tomer and Ramachandran, Varsha and Oskinova, Lidia M.}, title = {The Galactic WC and WO stars}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {621}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201833712}, pages = {19}, year = {2019}, abstract = {Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds. Thus, the determination of the WC star parameters is of major importance for several astrophysical fields. With Gaia DR2, for the first time parallaxes for a large sample of Galactic WC stars are available, removing major uncertainties inherent to earlier studies. In this work, we re-examine a previously studied sample of WC stars to derive key properties of the Galactic WC population. All quantities depending on the distance are updated, while the underlying spectral analyzes remain untouched. Contrasting earlier assumptions, our study yields that WC stars of the same subtype can significantly vary in absolute magnitude. With Gaia DR2, the picture of the Galactic WC population becomes more complex: We obtain luminosities ranging from log L/L-circle dot = 4.9-6.0 with one outlier (WR 119) having log L/L-circle dot = 4.7. This indicates that the WC stars are likely formed from a broader initial mass range than previously assumed. We obtain mass-loss rates ranging between log(M) over dot = -5.1 and -4.1, with (M) over dot proportional to L-0.68 and a linear scaling of the modified wind momentum with luminosity. We discuss the implications for stellar evolution, including unsolved issues regarding the need of envelope inflation to address the WR radius problem, and the open questions in regard to the connection of WR stars with Gamma-ray bursts. WC and WO stars are progenitors of massive black holes, collapsing either silently or in a supernova that most-likely has to be preceded by a WO stage.}, language = {en} } @article{HainichRamachandranShenaretal.2019, author = {Hainich, Rainer and Ramachandran, Varsha and Shenar, Tomer and Sander, Andreas Alexander Christoph and Todt, Helge Tobias and Gruner, David and Oskinova, Lidia M. and Hamann, Wolf-Rainer}, title = {PoWR grids of non-LTE model atmospheres for OB-type stars of various metallicities}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {621}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201833787}, pages = {12}, year = {2019}, abstract = {The study of massive stars in different metallicity environments is a central topic of current stellar research. The spectral analysis of massive stars requires adequate model atmospheres. The computation of such models is difficult and time-consuming. Therefore, spectral analyses are greatly facilitated if they can refer to existing grids of models. Here we provide grids of model atmospheres for OB-type stars at metallicities corresponding to the Small and Large Magellanic Clouds, as well as to solar metallicity. In total, the grids comprise 785 individual models. The models were calculated using the state-of-the-art Potsdam Wolf-Rayet (PoWR) model atmosphere code. The parameter domain of the grids was set up using stellar evolution tracks. For all these models, we provide normalized and flux-calibrated spectra, spectral energy distributions, feedback parameters such as ionizing photons, Zanstra temperatures, and photometric magnitudes. The atmospheric structures (the density and temperature stratification) are available as well. All these data are publicly accessible through the PoWR website.}, language = {en} } @article{DimopoulosGebserLuehneetal.2019, author = {Dimopoulos, Yannis and Gebser, Martin and L{\"u}hne, Patrick and Romero Davila, Javier and Schaub, Torsten}, title = {plasp 3}, series = {Theory and practice of logic programming}, volume = {19}, journal = {Theory and practice of logic programming}, number = {3}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {1471-0684}, doi = {10.1017/S1471068418000583}, pages = {477 -- 504}, year = {2019}, abstract = {We describe the new version of the Planning Domain Definition Language (PDDL)-to-Answer Set Programming (ASP) translator plasp. First, it widens the range of accepted PDDL features. Second, it contains novel planning encodings, some inspired by Satisfiability Testing (SAT) planning and others exploiting ASP features such as well-foundedness. All of them are designed for handling multivalued fluents in order to capture both PDDL as well as SAS planning formats. Third, enabled by multishot ASP solving, it offers advanced planning algorithms also borrowed from SAT planning. As a result, plasp provides us with an ASP-based framework for studying a variety of planning techniques in a uniform setting. Finally, we demonstrate in an empirical analysis that these techniques have a significant impact on the performance of ASP planning.}, language = {en} } @article{HamannGraefenerLiermannetal.2019, author = {Hamann, Wolf-Rainer and Gr{\"a}fener, G. and Liermann, A. and Hainich, Rainer and Sander, Andreas Alexander Christoph and Shenar, Tomer and Ramachandran, Varsha and Todt, Helge Tobias and Oskinova, Lidia M.}, title = {The Galactic WN stars revisited}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {625}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201834850}, pages = {11}, year = {2019}, abstract = {Comprehensive spectral analyses of the Galactic Wolf-Rayet stars of the nitrogen sequence (i.e. the WN subclass) have been performed in a previous paper. However, the distances of these objects were poorly known. Distances have a direct impact on the "absolute" parameters, such as luminosities and mass-loss rates. The recent Gaia Data Release (DR2) of trigonometric parallaxes includes nearly all WN stars of our Galactic sample. In the present paper, we apply the new distances to the previously analyzed Galactic WN stars and rescale the results accordingly. On this basis, we present a revised catalog of 55 Galactic WN stars with their stellar and wind parameters. The correlations between mass-loss rate and luminosity show a large scatter, for the hydrogen-free WN stars as well as for those with detectable hydrogen. The slopes of the log L - log M correlations are shallower than found previously. The empirical Hertzsprung-Russell diagram (HRD) still shows the previously established dichotomy between the hydrogen-free early WN subtypes that are located on the hot side of the zero-age main sequence (ZAMS), and the late WN subtypes, which show hydrogen and reside mostly at cooler temperatures than the ZAMS (with few exceptions). However, with the new distances, the distribution of stellar luminosities became more continuous than obtained previously. The hydrogen-showing stars of late WN subtype are still found to be typically more luminous than the hydrogen-free early subtypes, but there is a range of luminosities where both subclasses overlap. The empirical HRD of the Galactic single WN stars is compared with recent evolutionary tracks. Neither these single-star evolutionary models nor binary scenarios can provide a fully satisfactory explanation for the parameters of these objects and their location in the HRD.}, language = {en} } @article{MassaOskinovaPrinjaetal.2019, author = {Massa, Derck and Oskinova, Lidia M. and Prinja, Raman and Ignace, Richard}, title = {Coordinated UV and X-Ray Spectroscopic Observations of the O-type Giant xi Per}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {873}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/1538-4357/ab0283}, pages = {12}, year = {2019}, abstract = {We present new, contemporaneous Hubble Space Telescope STIS and XMM-Newton observations of the O7. III(n) ((f)) star xi Per. We supplement the new data with archival IUE spectra, to analyze the variability of the wind lines and X-ray flux of xi Per. The variable wind of this star is known to have a 2.086-day periodicity. We use a simple, heuristic spot model that fits the low-velocity (near-surface) IUE wind line variability very well, to demonstrate that the low-velocity absorption in the new STIS spectra of N IV lambda 1718 and Si IV lambda 1402 vary with the same 2.086-day period. It is remarkable that the period and amplitude of the STIS data agree with those of the IUE spectra obtained 22 yr earlier. We also show that the time variability of the new XMM-Newton fluxes is also consistent with the 2.086-day period. Thus, our new, multiwavelength coordinated observations demonstrate that the mechanism that causes the UV wind line variability is also responsible for a significant fraction of the X-rays in single O stars. The sequence of events for the multiwavelength light-curve minima is Si IV lambda 1402, N IV lambda 1718, and X-ray flux, each separated by a phase of about 0.06 relative to the 2.086-day period. Analysis of the X-ray fluxes shows that they become softer as they weaken. This is contrary to expectations if the variability is caused by periodic excess absorption. Furthermore, the high-resolution X-ray spectra suggest that the individual emission lines at maximum are more strongly blueshifted. If we interpret the low-velocity wind line light curves in terms of our model, it implies that there are two bright regions, i.e., regions with less absorption, separated by 180 degrees, on the surface of the star. We note that the presence and persistence of two spots separated by 180 degrees suggest that a weak dipole magnetic field is responsible for the variability of the UV wind line absorption and X-ray flux in xi Per.}, language = {en} } @article{OskinovaBikMasHesseetal.2019, author = {Oskinova, Lidia M. and Bik, A. and Mas-Hesse, J. M. and Hayes, M. and Adamo, A. and {\"O}stlin, G{\"o}ran and F{\"u}rst, F. and Ot{\´i}-Floranes, H.}, title = {ULX contribution to stellar feedback}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {627}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201935414}, pages = {7}, year = {2019}, abstract = {Context. X-ray radiation from accreting compact objects is an important part of stellar feedback. The metal-poor galaxy ESO 338-4 has experienced vigorous starburst during the last <40 Myr and contains some of the most massive super star clusters in the nearby Universe. Given its starburst age and its star-formation rate, ESO 338-4 is one of the most efficient nearby manufactures of neutron stars and black holes, hence providing an excellent laboratory for feedback studies. Aims. We aim to use X-ray observations with the largest modern X-ray telescopes XMM-Newton and Chandra to unveil the most luminous accreting neutron stars and black holes in ESO 338-4. Methods. We compared X-ray images and spectra with integral field spectroscopic observations in the optical to constrain the nature of strong X-ray emitters. Results. X-ray observations uncover three ultraluminous X-ray sources (ULXs) in ESO 338-4. The brightest among them, ESO 338 X-1, has X-ray luminosity in excess of 10(40) erg s(-1). We speculate that ESO 338-4 X-1 is powered by accretion on an intermediate-mass (greater than or similar to 300 M-circle dot)black hole. We show that X-ray radiation from ULXs and hot superbubbles strongly contributes to He II ionization and general stellar feedback in this template starburst galaxy.}, language = {en} } @article{GvaramadzeKniazevOskinova2019, author = {Gvaramadze, V. V. and Kniazev, Alexei Y. and Oskinova, Lidia M.}, title = {Discovery of a putative supernova remnant around the long-period X-ray pulsar SXP 1323 in the Small Magellanic Cloud}, series = {Monthly notices of the Royal Astronomical Society}, volume = {485}, journal = {Monthly notices of the Royal Astronomical Society}, number = {1}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnrasl/slz018}, pages = {L6 -- L10}, year = {2019}, abstract = {We report the discovery of a circular shell centred on the Be X-ray binary (BeXB) SXP 1323 in the Small Magellanic Cloud. The shell was detected in an H α image obtained with the Very Large Telescope. Follow-up spectroscopy with the Southern African Large Telescope showed that the shell expands with a velocity of ≈100kms-1 and that its emission is due to shock excitation. We suggest that this shell is a remnant of the supernova explosion that led to the formation of SXP 1323's neutron star ≈40000 yr ago. SXP 1323 represents the second known case of a BeXB associated with a supernova remnant (the first one is SXP 1062). Interestingly, both of these BeXBs harbour long-period pulsars and are located in a low-metallicity galaxy.}, language = {en} } @article{NunesNesiAlseekhdeOliveiraSilvaetal.2019, author = {Nunes-Nesi, Adriano and Alseekh, Saleh and de Oliveira Silva, Franklin Magnum and Omranian, Nooshin and Lichtenstein, Gabriel and Mirnezhad, Mohammad and Romero Gonzalez, Roman R. and Sabio y Garcia, Julia and Conte, Mariana and Leiss, Kirsten A. and Klinkhamer, Peter Gerardus Leonardus and Nikoloski, Zoran and Carrari, Fernando and Fernie, Alisdair}, title = {Identification and characterization of metabolite quantitative trait loci in tomato leaves and comparison with those reported for fruits and seeds}, series = {Metabolomics}, volume = {15}, journal = {Metabolomics}, number = {46}, publisher = {Springer}, address = {New York}, issn = {1573-3882}, doi = {10.1007/s11306-019-1503-8}, pages = {13}, year = {2019}, abstract = {IntroductionTo date, most studies of natural variation and metabolite quantitative trait loci (mQTL) in tomato have focused on fruit metabolism, leaving aside the identification of genomic regions involved in the regulation of leaf metabolism.ObjectiveThis study was conducted to identify leaf mQTL in tomato and to assess the association of leaf metabolites and physiological traits with the metabolite levels from other tissues.MethodsThe analysis of components of leaf metabolism was performed by phenotypying 76 tomato ILs with chromosome segments of the wild species Solanum pennellii in the genetic background of a cultivated tomato (S. lycopersicum) variety M82. The plants were cultivated in two different environments in independent years and samples were harvested from mature leaves of non-flowering plants at the middle of the light period. The non-targeted metabolite profiling was obtained by gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). With the data set obtained in this study and already published metabolomics data from seed and fruit, we performed QTL mapping, heritability and correlation analyses.ResultsChanges in metabolite contents were evident in the ILs that are potentially important with respect to stress responses and plant physiology. By analyzing the obtained data, we identified 42 positive and 76 negative mQTL involved in carbon and nitrogen metabolism.ConclusionsOverall, these findings allowed the identification of S. lycopersicum genome regions involved in the regulation of leaf primary carbon and nitrogen metabolism, as well as the association of leaf metabolites with metabolites from seeds and fruits.}, language = {en} } @article{JoseClementeMorenoOmranianSaezetal.2019, author = {Jose Clemente-Moreno, Maria and Omranian, Nooshin and Saez, Patricia and Maria Figueroa, Carlos and Del-Saz, Nestor and Elso, Mhartyn and Poblete, Leticia and Orf, Isabel and Cuadros-Inostroza, Alvaro and Cavieres, Lohengrin and Bravo, Leon and Fernie, Alisdair and Ribas-Carbo, Miquel and Flexas, Jaume and Nikoloski, Zoran and Brotman, Yariv and Gago, Jorge}, title = {Cytochrome respiration pathway and sulphur metabolism sustain stress tolerance to low temperature in the Antarctic species Colobanthus quitensis}, series = {New phytologist : international journal of plant science}, volume = {225}, journal = {New phytologist : international journal of plant science}, number = {2}, publisher = {Wiley}, address = {Hoboken}, issn = {0028-646X}, doi = {10.1111/nph.16167}, pages = {754 -- 768}, year = {2019}, abstract = {Understanding the strategies employed by plant species that live in extreme environments offers the possibility to discover stress tolerance mechanisms. We studied the physiological, antioxidant and metabolic responses to three temperature conditions (4, 15, and 23 degrees C) of Colobanthus quitensis (CQ), one of the only two native vascular species in Antarctica. We also employed Dianthus chinensis (DC), to assess the effects of the treatments in a non-Antarctic species from the same family. Using fused LASSO modelling, we associated physiological and biochemical antioxidant responses with primary metabolism. This approach allowed us to highlight the metabolic pathways driving the response specific to CQ. Low temperature imposed dramatic reductions in photosynthesis (up to 88\%) but not in respiration (sustaining rates of 3.0-4.2 mu mol CO2 m(-2) s(-1)) in CQ, and no change in the physiological stress parameters was found. Its notable antioxidant capacity and mitochondrial cytochrome respiratory activity (20 and two times higher than DC, respectively), which ensure ATP production even at low temperature, was significantly associated with sulphur-containing metabolites and polyamines. Our findings potentially open new biotechnological opportunities regarding the role of antioxidant compounds and respiratory mechanisms associated with sulphur metabolism in stress tolerance strategies to low temperature.}, language = {en} } @article{DevkarThirumalaikumarXueetal.2019, author = {Devkar, Vikas and Thirumalaikumar, Venkatesh P. and Xue, Gang-Ping and Vallarino, Jose G. and Tureckova, Veronika and Strnad, Miroslav and Fernie, Alisdair and Hoefgen, Rainer and Mueller-Roeber, Bernd and Balazadeh, Salma}, title = {Multifaceted regulatory function of tomato SlTAF1 in the response to salinity stress}, series = {New phytologist : international journal of plant science}, volume = {225}, journal = {New phytologist : international journal of plant science}, number = {4}, publisher = {Wiley}, address = {Hoboken}, issn = {0028-646X}, doi = {10.1111/nph.16247}, pages = {1681 -- 1698}, year = {2019}, abstract = {Salinity stress limits plant growth and has a major impact on agricultural productivity. Here, we identify NAC transcription factor SlTAF1 as a regulator of salt tolerance in cultivated tomato (Solanum lycopersicum). While overexpression of SlTAF1 improves salinity tolerance compared with wild-type, lowering SlTAF1 expression causes stronger salinity-induced damage. Under salt stress, shoots of SlTAF1 knockdown plants accumulate more toxic Na+ ions, while SlTAF1 overexpressors accumulate less ions, in accordance with an altered expression of the Na+ transporter genes SlHKT1;1 and SlHKT1;2. Furthermore, stomatal conductance and pore area are increased in SlTAF1 knockdown plants during salinity stress, but decreased in SlTAF1 overexpressors. We identified stress-related transcription factor, abscisic acid metabolism and defence-related genes as potential direct targets of SlTAF1, correlating it with reactive oxygen species scavenging capacity and changes in hormonal response. Salinity-induced changes in tricarboxylic acid cycle intermediates and amino acids are more pronounced in SlTAF1 knockdown than wild-type plants, but less so in SlTAF1 overexpressors. The osmoprotectant proline accumulates more in SlTAF1 overexpressors than knockdown plants. In summary, SlTAF1 controls the tomato's response to salinity stress by combating both osmotic stress and ion toxicity, highlighting this gene as a promising candidate for the future breeding of stress-tolerant crops.}, language = {en} } @article{FriouxSchaubSchellhornetal.2019, author = {Frioux, Cl{\´e}mence and Schaub, Torsten and Schellhorn, Sebastian and Siegel, Anne and Wanko, Philipp}, title = {Hybrid metabolic network completion}, series = {Theory and practice of logic programming}, volume = {19}, journal = {Theory and practice of logic programming}, number = {1}, publisher = {Cambridge University Press}, address = {New York}, issn = {1471-0684}, doi = {10.1017/S1471068418000455}, pages = {83 -- 108}, year = {2019}, abstract = {Metabolic networks play a crucial role in biology since they capture all chemical reactions in an organism. While there are networks of high quality for many model organisms, networks for less studied organisms are often of poor quality and suffer from incompleteness. To this end, we introduced in previous work an answer set programming (ASP)-based approach to metabolic network completion. Although this qualitative approach allows for restoring moderately degraded networks, it fails to restore highly degraded ones. This is because it ignores quantitative constraints capturing reaction rates. To address this problem, we propose a hybrid approach to metabolic network completion that integrates our qualitative ASP approach with quantitative means for capturing reaction rates. We begin by formally reconciling existing stoichiometric and topological approaches to network completion in a unified formalism. With it, we develop a hybrid ASP encoding and rely upon the theory reasoning capacities of the ASP system dingo for solving the resulting logic program with linear constraints over reals. We empirically evaluate our approach by means of the metabolic network of Escherichia coli. Our analysis shows that our novel approach yields greatly superior results than obtainable from purely qualitative or quantitative approaches.}, language = {en} } @article{ProellerAdam2019, author = {Proeller, Isabella and Adam, Jan P.}, title = {Organisationsreformen}, series = {Handbuch zur Verwaltungsreform}, journal = {Handbuch zur Verwaltungsreform}, edition = {5., vollst{\"a}ndig {\"u}berarb. Aufl.}, publisher = {Springer}, address = {Wiesbaden}, isbn = {978-3-658-21562-0}, pages = {305 -- 317}, year = {2019}, language = {de} } @article{SmithDupontMcCarthyetal.2019, author = {Smith, Sarah R. and Dupont, Chris L. and McCarthy, James K. and Broddrick, Jared T. and Obornik, Miroslav and Horak, Ales and F{\"u}ssy, Zolt{\´a}n and Cihlar, Jaromir and Kleessen, Sabrina and Zheng, Hong and McCrow, John P. and Hixson, Kim K. and Araujo, Wagner L. and Nunes-Nesi, Adriano and Fernie, Alisdair and Nikoloski, Zoran and Palsson, Bernhard O. and Allen, Andrew E.}, title = {Evolution and regulation of nitrogen flux through compartmentalized metabolic networks in a marine diatom}, series = {Nature Communications}, volume = {10}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/s41467-019-12407-y}, pages = {14}, year = {2019}, abstract = {Diatoms outcompete other phytoplankton for nitrate, yet little is known about the mechanisms underpinning this ability. Genomes and genome-enabled studies have shown that diatoms possess unique features of nitrogen metabolism however, the implications for nutrient utilization and growth are poorly understood. Using a combination of transcriptomics, proteomics, metabolomics, fluxomics, and flux balance analysis to examine short-term shifts in nitrogen utilization in the model pennate diatom in Phaeodactylum tricornutum, we obtained a systems-level understanding of assimilation and intracellular distribution of nitrogen. Chloroplasts and mitochondria are energetically integrated at the critical intersection of carbon and nitrogen metabolism in diatoms. Pathways involved in this integration are organelle-localized GS-GOGAT cycles, aspartate and alanine systems for amino moiety exchange, and a split-organelle arginine biosynthesis pathway that clarifies the role of the diatom urea cycle. This unique configuration allows diatoms to efficiently adjust to changing nitrogen status, conferring an ecological advantage over other phytoplankton taxa.}, language = {en} } @article{FerrariProostJanowskietal.2019, author = {Ferrari, Camilla and Proost, Sebastian and Janowski, Marcin Andrzej and Becker, J{\"o}rg and Nikoloski, Zoran and Bhattacharya, Debashish and Price, Dana and Tohge, Takayuki and Bar-Even, Arren and Fernie, Alisdair and Stitt, Mark and Mutwil, Marek}, title = {Kingdom-wide comparison reveals the evolution of diurnal gene expression in Archaeplastida}, series = {Nature Communications}, volume = {10}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/s41467-019-08703-2}, pages = {13}, year = {2019}, abstract = {Plants have adapted to the diurnal light-dark cycle by establishing elaborate transcriptional programs that coordinate many metabolic, physiological, and developmental responses to the external environment. These transcriptional programs have been studied in only a few species, and their function and conservation across algae and plants is currently unknown. We performed a comparative transcriptome analysis of the diurnal cycle of nine members of Archaeplastida, and we observed that, despite large phylogenetic distances and dramatic differences in morphology and lifestyle, diurnal transcriptional programs of these organisms are similar. Expression of genes related to cell division and the majority of biological pathways depends on the time of day in unicellular algae but we did not observe such patterns at the tissue level in multicellular land plants. Hence, our study provides evidence for the universality of diurnal gene expression and elucidates its evolutionary history among different photosynthetic eukaryotes.}, language = {en} } @article{PandeyYuOmranianetal.2019, author = {Pandey, Prashant K. and Yu, Jing and Omranian, Nooshin and Alseekh, Saleh and Vaid, Neha and Fernie, Alisdair and Nikoloski, Zoran and Laitinen, Roosa A. E.}, title = {Plasticity in metabolism underpins local responses to nitrogen in Arabidopsis thaliana populations}, series = {Plant Direct}, volume = {3}, journal = {Plant Direct}, number = {11}, publisher = {John Wiley \& sonst LTD}, address = {Chichester}, issn = {2475-4455}, doi = {10.1002/pld3.186}, pages = {6}, year = {2019}, abstract = {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.}, language = {en} } @article{GongZhengToenjesetal.2019, author = {Gong, Chen Chris and Zheng, Chunming and T{\"o}njes, Ralf and Pikovskij, Arkadij}, title = {Repulsively coupled Kuramoto-Sakaguchi phase oscillators ensemble subject to common noise}, series = {Chaos : an interdisciplinary journal of nonlinear science}, volume = {29}, journal = {Chaos : an interdisciplinary journal of nonlinear science}, number = {3}, publisher = {American Institute of Physics}, address = {Melville}, issn = {1054-1500}, doi = {10.1063/1.5084144}, pages = {11}, year = {2019}, abstract = {We consider the Kuramoto-Sakaguchi model of identical coupled phase oscillators with a common noisy forcing. While common noise always tends to synchronize the oscillators, a strong repulsive coupling prevents the fully synchronous state and leads to a nontrivial distribution of oscillator phases. In previous numerical simulations, the formation of stable multicluster states has been observed in this regime. However, we argue here that because identical phase oscillators in the Kuramoto-Sakaguchi model form a partially integrable system according to the Watanabe-Strogatz theory, the formation of clusters is impossible. Integrating with various time steps reveals that clustering is a numerical artifact, explained by the existence of higher order Fourier terms in the errors of the employed numerical integration schemes. By monitoring the induced change in certain integrals of motion, we quantify these errors. We support these observations by showing, on the basis of the analysis of the corresponding Fokker-Planck equation, that two-cluster states are non-attractive. On the other hand, in ensembles of general limit cycle oscillators, such as Van der Pol oscillators, due to an anharmonic phase response function as well as additional amplitude dynamics, multiclusters can occur naturally. Published under license by AIP Publishing.}, language = {en} }