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181.
Tanja Strecker Annette Jesch Drte Bachmann Melissa Jüds Kevin Karbstein Janneke Ravenek Christiane Roscher Alexandra Weigelt Nico Eisenhauer Stefan Scheu 《Ecology and evolution》2021,11(9):4295
Although nitrogen (N) deposition is increasing globally, N availability still limits many organisms, such as microorganisms and mesofauna. However, little is known to which extent soil organisms rely on mineral‐derived N and whether plant community composition modifies its incorporation into soil food webs. More diverse plant communities more effectively compete with microorganisms for mineral N likely reducing the incorporation of mineral‐derived N into soil food webs. We set up a field experiment in experimental grasslands with different levels of plant species and functional group richness. We labeled soil with 15NH4 15NO3 and analyzed the incorporation of mineral‐derived 15N into soil microorganisms and mesofauna over 3 months. Mineral‐derived N incorporation decreased over time in all investigated organisms. Plant species richness and presence of legumes reduced the uptake of mineral‐derived N into microorganisms. In parallel, the incorporation of mineral‐derived 15N into mesofauna species declined with time and decreased with increasing plant species richness in the secondary decomposer springtail Ceratophysella sp. Effects of both plant species richness and functional group richness on other mesofauna species varied with time. The presence of grasses increased the 15N incorporation into Ceratophysella sp., but decreased it in the primary decomposer oribatid mite Tectocepheus velatus sarekensis. The results highlight that mineral N is quickly channeled into soil animal food webs via microorganisms irrespective of plant diversity. The amount of mineral‐derived N incorporated into soil animals, and the plant community properties affecting this incorporation, differed markedly between soil animal taxa, reflecting species‐specific use of food resources. Our results highlight that plant diversity and community composition alter the competition for N in soil and change the transfer of N across trophic levels in soil food webs, potentially leading to changes in soil animal population dynamics and community composition. Sustaining high plant diversity may buffer detrimental effects of elevated N deposition on soil biota. 相似文献
182.
183.
Dorothea G. Meldau Stefan Meldau Long H. Hoang Stefanie Underberg Hendrik Wünsche Ian T. Baldwin 《The Plant cell》2013,25(7):2731-2747
Bacillus sp B55, a bacterium naturally associated with Nicotiana attenuata roots, promotes growth and survival of wild-type and, particularly, ethylene (ET)–insensitive 35S-ethylene response1 (etr1) N. attenuata plants, which heterologously express the mutant Arabidopsis thaliana receptor ETR1-1. We found that the volatile organic compound (VOC) blend emitted by B55 promotes seedling growth, which is dominated by the S-containing compound dimethyl disulfide (DMDS). DMDS was depleted from the headspace during cocultivation with seedlings in bipartite Petri dishes, and 35S was assimilated from the bacterial VOC bouquet and incorporated into plant proteins. In wild-type and 35S-etr1 seedlings grown under different sulfate (SO4−2) supply conditions, exposure to synthetic DMDS led to genotype-dependent plant growth promotion effects. For the wild type, only S-starved seedlings benefited from DMDS exposure. By contrast, growth of 35S-etr1 seedlings, which we demonstrate to have an unregulated S metabolism, increased at all SO4−2 supply rates. Exposure to B55 VOCs and DMDS rescued many of the growth phenotypes exhibited by ET-insensitive plants, including the lack of root hairs, poor lateral root growth, and low chlorophyll content. DMDS supplementation significantly reduced the expression of S assimilation genes, as well as Met biosynthesis and recycling. We conclude that DMDS by B55 production is a plant growth promotion mechanism that likely enhances the availability of reduced S, which is particularly beneficial for wild-type plants growing in S-deficient soils and for 35S-etr1 plants due to their impaired S uptake/assimilation/metabolism. 相似文献
184.
Bastien Christ Iris Süssenbacher Simone Moser Nicole Bichsel Aurelie Egert Thomas Müller Bernhard Kr?utler Stefan H?rtensteiner 《The Plant cell》2013,25(5):1868-1880
Nonfluorescent chlorophyll catabolites (NCCs) were described as products of chlorophyll breakdown in Arabidopsis thaliana. NCCs are formyloxobilin-type catabolites derived from chlorophyll by oxygenolytic opening of the chlorin macrocycle. These linear tetrapyrroles are generated from their fluorescent chlorophyll catabolite (FCC) precursors by a nonenzymatic isomerization inside the vacuole of senescing cells. Here, we identified a group of distinct dioxobilin-type chlorophyll catabolites (DCCs) as the major breakdown products in wild-type Arabidopsis, representing more than 90% of the chlorophyll of green leaves. The molecular constitution of the most abundant nonfluorescent DCC (NDCC), At-NDCC-1, was determined. We further identified cytochrome P450 monooxygenase CYP89A9 as being responsible for NDCC accumulation in wild-type Arabidopsis; cyp89a9 mutants that are deficient in CYP89A9 function were devoid of NDCCs but accumulated proportionally higher amounts of NCCs. CYP89A9 localized outside the chloroplasts, implying that FCCs occurring in the cytosol might be its natural substrate. Using recombinant CYP89A9, we confirm FCC specificity and show that fluorescent DCCs are the products of the CYP89A9 reaction. Fluorescent DCCs, formed by this enzyme, isomerize to the respective NDCCs in weakly acidic medium, as found in vacuoles. We conclude that CYP89A9 is involved in the formation of dioxobilin-type catabolites of chlorophyll in Arabidopsis. 相似文献
185.
Erwin P. Meijer Stefan A.J. Coolen Aalt Bast Klaas R. Westerterp 《Free radical research》2013,47(4):435-443
Effects of 12 wk exercise training on oxidative stress were examined in elderly humans. We measured oxidative stress during a 45 min cycling test by using antipyrine hydroxylation products. Antipyrine breakdown is independent of blood flow to the liver, which is important during exercise. Furthermore, antipyrine reacts quickly with hydroxyl radicals to form para- and ortho-hydroxyantipyrine. Ortho-hydroxyantipyrine is not formed in man through the mono-oxygenase pathway of cytochrome P450. Twenty subjects (9 women; 60 ± 3 y) participated in the training program. Thirteen subjects (5 women; 64 ± 7 y) served as inactive controls. Subjects trained, twice a week for 1h, at a fitness center. After 12 wk, maximal oxygen uptake (p < .005) and workload capacity (p < .001) were only significantly elevated in the training group. After 12 wk, both groups observed no change in the ratios of antipyrine hydroxylates, para- and ortho-hydroxy-antipyrine, to native antipyrine. Furthermore, no differences were observed within or between groups in the exercise-induced increase in the plasma level of thiobarbituric acid reactive species. In conclusion, 12-wk training had no effect on exercise-induced oxidative stress in elderly humans as measured by free radical reaction products of antipyrine. Despite the fact that training in elderly humans improves functional capacity, it appears not to compromise antioxidant defense mechanisms. 相似文献
186.
Lena M. Jonsson Daryl D. Rees Thomas Edlund Stefan L. Marklund 《Free radical research》2013,47(7):755-758
Nitric oxide is a major vasorelaxant and regulator of the blood pressure. The blood vessels contain several active sources of the superoxide radical, which reacts avidly with nitric oxide to form noxious peroxynitrite. There are large amounts of extracellular-superoxide dismutase (EC-SOD) in the vascular wall. To evaluate the importance of EC-SOD for the physiology of nitric oxide, here we studied the blood pressure in mice lacking the enzyme. In chronically instrumented non-anaesthetized mice there was no difference in mean arterial blood pressure between wild-type controls and EC-SOD mutants. Extensive inhibition of nitric oxide synthases with N -monomethyl- l -arginine however resulted in a larger increase in blood pressure, and infusion of the nitric oxide donor nitrosoglutathione caused less reduction in blood pressure in the EC-SOD null mice. We interpret the alterations to be caused by a moderately increased consumption of nitric oxide by the superoxide radical in the EC-SOD null mice. One role of EC-SOD may be to preserve nitric oxide, a function that should be particularly important in vascular pathologies, in which large increases in superoxide formation have been documented. 相似文献
187.
Georgios Ioannis Karras Marco Fumasoni Grzegorz Sienski Fabio Vanoli Dana Branzei Stefan Jentsch 《Molecular cell》2013,49(3):536-546
Highlights? 9-1-1 and Exo1 are components of the error-free RAD6 pathway ? 9-1-1 promotes postreplicative template switching ? Polyubiquitylated PCNA and 9-1-1 cooperate in the error-free RAD6 pathway ? 9-1-1’s role in the error-free RAD6 pathway is uncoupled from checkpoint functions 相似文献
188.
Artur Burdzy Bohdan Skalski Ewa Bia? Andrzej Kowalewski Stefan Paszyc Rysard W. Adamiak 《Nucleosides, nucleotides & nucleic acids》2013,32(3-5):979-982
Abstract New route to oligodeoxynucleotides labeled with fluorescent luminarine was explored. Regioselective oxidation of 6-methylthio-purines to 6-methylsulphoxides reactive toward pyridine was achieved. Upon UV irradiation of 6-pyridinium-purines oligonucleotide cleavage instead of phototransformation to luminarine was observed. 相似文献
189.
Gunther Ott Lubos Arnold Jiri Smrt Michal Sobkowski Stefan Limmer Hans-Peter Hofmann 《Nucleosides, nucleotides & nucleic acids》2013,32(5):1069-1085
Abstract Dimethylaminomethylene was applied as the protecting group for the exocyclic amino groups of adenosine and guanosine in the automated chemical synthesis of oligoribonucleotides on a polymer bound support. The dimethyl-aminomethylene protecting group can be removed at room temperature under conditions where the concomitant loss of the 2′-protection group can be excluded. The transformation of 2′-O-(t-butyldimethylsilyl)-5′-O-(4,4′-dimethoxytrityl) protected nucleosides to 3′-H-phosphonates yields synthons, well suited for the automated chemical synthesis of oligoribonucleotides. Using these H-phosphonate monomers, a coupling time of two minute: is sufficient to obtain average coupling yields of more than 98 %. Synthesized RNA is recognized as a substrate in an enzymatic reaction, forms the expected secondary structures and is suitable for NMR structural investigations. 相似文献
190.
Stefan Milton Raunak Esther Yeheskiely Roger Strömberg 《Nucleosides, nucleotides & nucleic acids》2013,32(10-12):1495-1499
In order to obtain higher quality 2 ′-O-carbamoylmethyl oligoribonucleotides we are conducting studies of this modification. Here we present synthesis of 2 ′-O-carbamoylmethyl containing H-phosphonate building blocks as well as synthesis of model dinucleotides needed for these studies. 相似文献