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Bunsupa S.,Chiba University | Katayama K.,Chiba University | Ikeura E.,Chiba University | Oikawa A.,RIKEN | And 5 more authors.
Plant Cell | Year: 2012

Lysine decarboxylase (LDC) catalyzes the first-step in the biosynthetic pathway of quinolizidine alkaloids (QAs), which form a distinct, large family of plant alkaloids. A cDNA of lysine/ornithine decarboxylase (L/ODC) was isolated by differential transcript screening in QA-producing and nonproducing cultivars of Lupinus angustifolius. We also obtained L/ODC cDNAs from four other QA-producing plants, Sophora flavescens, Echinosophora koreensis, Thermopsis chinensis, and Baptisia australis. These L/ODCs form a phylogenetically distinct subclade in the family of plant ornithine decarboxylases. Recombinant L/ODCs from QA-producing plants preferentially or equally catalyzed the decarboxylation of L-lysine and L-ornithine. L. angustifolius L/ODC (La-L/ODC) was found to be localized in chloroplasts, as suggested by the transient expression of a fusion protein of La-L/ODC fused to the N terminus of green fluorescent protein in Arabidopsis thaliana. Transgenic tobacco (Nicotiana tabacum) suspension cells and hairy roots produced enhanced levels of cadaverine-derived alkaloids, and transgenic Arabidopsis plants expressing (La-L/ODC) produced enhanced levels of cadaverine, indicating the involvement of this enzyme in lysine decarboxylation to form cadaverine. Site-directed mutagenesis and protein modeling studies revealed a structural basis for preferential LDC activity, suggesting an evolutionary implication of L/ODC in the QAproducing plants. © 2012 American Society of Plant Biologists. All rights reserved. Source

Jung J.-H.,Seoul National University | Jung J.-H.,University of Cambridge | Park J.-H.,Seoul National University | Lee S.,Seoul National University | And 6 more authors.
Plant Cell | Year: 2013

Exposure to short-term cold stress delays flowering by activating the floral repressor FLOWERING LOCUS C (FLC) in Arabidopsis thaliana. The cold signaling attenuator HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE1 (HOS1) negatively regulates cold responses. Notably, HOS1-deficient mutants exhibit early flowering, and FLC expression is suppressed in the mutants. However, it remains unknown how HOS1 regulates FLC expression. Here, we show that HOS1 induces FLC expression by antagonizing the actions of FVE and its interacting partner histone deacetylase 6 (HDA6) under short-term cold stress. HOS1 binds to FLC chromatin in an FVE-dependentmanner, and FVE is essential for the HOS1-mediated activation of FLC transcription. HOS1 also interacts with HDA6 and inhibits the binding of HDA6 to FLC chromatin. Intermittent cold treatments induce FLC expression by activating HOS1, which attenuates the activity of HDA6 in silencing FLC chromatin, and the effects of intermittent cold are diminished in hos1 and fve mutants. These observations indicate that HOS1 acts as a chromatin remodeling factor for FLC regulation under short-term cold stress. © 2013 American Society of Plant Biologists. All rights reserved. Source

Kitao A.,Japan Science and Technology Agency | Kitao A.,Core Research for Evolutional Science and Technology
Journal of Chemical Physics | Year: 2011

Transform and relax sampling (TRS) is proposed as a conformational sampling method to enhance soft fluctuation in highly anisotropic systems using molecular dynamics simulation. This method consists of three stages; transform, relax, and sampling. In the transform stage, molecular dynamics simulation is performed with randomly assigned force bias to enhance the fluctuations along relatively soft collective movements, as expected from the linear response theory. After relaxing the heated system to equilibrium without force bias in the relax stage, Monte Carlo-type determination is made as to whether the generated state is accepted or not. The sampling stage is then conducted for conformational sampling by conventional molecular dynamics simulation. TRS is first applied for the idealized multidimensional double-well Cα model to mimic protein open-close transition. Subsequently, it is applied to three different all-atom protein systems in an explicit solvent model; T4 lysozyme, glutamine binding protein, and a mini-protein chignolin. Investigation of structural variations in the hinge angle of T4 lysozyme in crystals is demonstrated by TRS. The liganded close structure of the glutamine binding protein is sampled starting from the unliganded open form. Chignolin is shown to fold into a native structure multiple times starting from highly extended structures within 100 ns. It is concluded that TRS sampled a reasonable conformational space within a relatively short simulation time in these cases. Possible future extensions of TRS are also discussed. © 2011 American Institute of Physics. Source

News Article
Site: http://phys.org/chemistry-news/

"A global shortage of fresh water is a long-term challenge that mankind faces in this century," said the director of the ROBUST membrane project, Professor Toshinori Tsuru. Professor Tsuru and his team have designed a new kind of ultra-thin layered membrane that acts as a sieve and separates salt from seawater to produce fresh water, a technique known as reverse osmosis. The membrane is partly made from silicon and overcomes several challenges of existing designs by tolerating the harsh conditions inside desalination plant equipment. The research has been published in the Journal of Membrane Science. One practical problem of separation membranes is "biofouling", where biofilms form on the membrane surface. This slows the amount of water that can pass through the membrane. Sodium hypochlorite is commonly used to remove these biofilms; however, the chlorine can also damage the membrane. Professor Tsuru, who is supported by CREST (Core Research for Evolutional Science and Technology) and is a member of the Center for Research on Environmentally Friendly Smart Materials at Hiroshima University's Institute of Engineering, said that the new membranes are more robust, which makes them resistant to chlorine. They are also heat resistant, meaning they can be used in desalination at a temperature of 80°C. "We are developing ROBUST membranes using three materials: silicon-based, hydrocarbon, and chemical vapor deposition. First we have developed silicon-based ROBUST membranes," Professor Tsuru said. "We expect Japan to continue to be one of the leading countries in membrane technologies and membrane-treatment systems," he said. Explore further: New membranes deliver clean water more efficiently

Murashima T.,Kyoto University | Murashima T.,Core Research for Evolutional Science and Technology | Taniguchi T.,Kyoto University | Taniguchi T.,Core Research for Evolutional Science and Technology
Journal of the Physical Society of Japan | Year: 2012

Polymer melts exhibit flow-history-dependent behavior. To clearly show this behavior, we have investigated the flow behavior of an entangled polymer melt around two cylinders placed in tandem along the flow direction in a two-dimensional periodic system. In this system, polymer states around a cylinder on the downstream side differ from those around a cylinder on the upstream side because the former have a memory of the strain they experienced when passing around the cylinder on the upstream side but the latter have no such memory. Therefore, the shear stress distributions around two cylinders are found to differ. Moreover, we have found that the mean flow velocity decreases accordingly with increasing distance between the two cylinders, whereas the applied external force is constant. Although this behavior is consistent with that of the Newtonian fluid, the flow-history-dependent behavior is found to enhance the reduction in the flow resistance. We have also discussed the microscopic states during the flow, observing the mean length of polymer chains, the mean number of entanglements, and the degree of orientation of polymer chains, which represented the flow-history-dependent behavior that reflects each relaxation process. © 2012 The Physical Society of Japan. Source

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