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Sugano S.,Japan National Institute of Agrobiological Science | Hayashi N.,Japan National Institute of Agrobiological Science | Kawagoe Y.,Japan National Institute of Agrobiological Science | Mochizuki S.,Japan National Institute of Agrobiological Science | And 7 more authors.
Plant Molecular Biology | Year: 2016

Membrane trafficking plays pivotal roles in many cellular processes including plant immunity. Here, we report the characterization of OsVAMP714, an intracellular SNARE protein, focusing on its role in resistance to rice blast disease caused by the fungal pathogen Magnaporthe oryzae. Disease resistance tests using OsVAMP714 knockdown and overexpressing rice plants demonstrated the involvement of OsVAMP714 in blast resistance. The overexpression of OsVAMP7111, whose product is highly homologous to OsVAMP714, did not enhance blast resistance to rice, implying a potential specificity of OsVAMP714 to blast resistance. OsVAMP714 was localized to the chloroplast in mesophyll cells and to the cellular periphery in epidermal cells of transgenic rice plant leaves. We showed that chloroplast localization is critical for the normal OsVAMP714 functioning in blast resistance by analyzing the rice plants overexpressing OsVAMP714 mutants whose products did not localize in the chloroplast. We also found that OsVAMP714 was located in the vacuolar membrane surrounding the invasive hyphae of M. oryzae. Furthermore, we showed that OsVAMP714 overexpression promotes leaf sheath elongation and that the first 19 amino acids, which are highly conserved between animal and plant VAMP7 proteins, are crucial for normal rice plant growths. Our studies imply that the OsVAMP714-mediated trafficking pathway plays an important role in rice blast resistance as well as in the vegetative growth of rice. © 2016 Springer Science+Business Media Dordrecht Source

Atarashi K.,RIKEN | Atarashi K.,Keio University | Tanoue T.,RIKEN | Ando M.,Yakult Central Institute | And 34 more authors.
Cell | Year: 2015

Intestinal Th17 cells are induced and accumulate in response to colonization with a subgroup of intestinal microbes such as segmented filamentous bacteria (SFB) and certain extracellular pathogens. Here, we show that adhesion of microbes to intestinal epithelial cells (ECs) is a critical cue for Th17 induction. Upon monocolonization of germ-free mice or rats with SFB indigenous to mice (M-SFB) or rats (R-SFB), M-SFB and R-SFB showed host-specific adhesion to small intestinal ECs, accompanied by host-specific induction of Th17 cells. Citrobacter rodentium and Escherichia coli O157 triggered similar Th17 responses, whereas adhesion-defective mutants of these microbes failed to do so. Moreover, a mixture of 20 bacterial strains, which were selected and isolated from fecal samples of a patient with ulcerative colitis on the basis of their ability to cause a robust induction of Th17 cells in the mouse colon, also exhibited EC-adhesive characteristics. © 2015 Elsevier Inc. Source

Saeki N.,Niigata University | Kawanabe T.,Kobe University | Ying H.,CSIRO | Shimizu M.,Niigata University | And 12 more authors.
BMC Plant Biology | Year: 2016

Background: Heterosis or hybrid vigour is a phenomenon in which hybrid progeny exhibit superior performance compared to their parental inbred lines. Most commercial Chinese cabbage cultivars are F1 hybrids and their level of hybrid vigour is of critical importance and is a key selection criterion in the breeding system. Results: We have characterized the heterotic phenotype of one F1 hybrid cultivar of Chinese cabbage and its parental lines from early- to late-developmental stages of the plants. Hybrid cotyledons are larger than those of the parents at 4 days after sowing and biomass in the hybrid, determined by the fresh weight of leaves, is greater than that of the larger parent line by approximately 20 % at 14 days after sowing. The final yield of the hybrid harvested at 63 days after sowing is 25 % greater than the yield of the better parent. The larger leaves of the hybrid are a consequence of increased cell size and number of the photosynthetic palisade mesophyll cells and other leaf cells. The accumulation of plant hormones in the F1 was within the range of the parental levels at both 2 and 10 days after sowing. Two days after sowing, the expression levels of chloroplast-targeted genes in the cotyledon cells were upregulated in the F1 hybrid relative to their mid parent values. Shutdown of chlorophyll biosynthesis in the cotyledon by norflurazon prevented the increased leaf area in the F1 hybrid. Conclusions: In the cotyledons of F1 hybrids, chloroplast-targeted genes were upregulated at 2 days after sowing. The increased activity levels of this group of genes suggested that their differential transcription levels could be important for establishing early heterosis but the increased transcription levels were transient. Inhibition of the photosynthetic process in the cotyledon reduced heterosis in later seedling stages. These observations suggest early developmental events in the germinating seedling of the hybrid may be important for later developmental vigour and yield advantage. © 2016 Saeki et al. Source

Nakabayashi R.,Center for Sustainable Resource Science | Mori T.,Center for Sustainable Resource Science | Saito K.,Center for Sustainable Resource Science | Saito K.,Chiba University
Plant Signaling and Behavior | Year: 2014

Plants have developed mechanisms to protect themselves against both biotic and abiotic environmental stress. Specialized/secondary metabolism is one of the stress response mechanisms. Recently, we reported that flavonoids, a class of specialized metabolites, including flavonols and anthocyanins with strong radical scavenging activity contributed to the mitigation of oxidative and drought stress in Arabidopsis thaliana (Arabidopsis). However, the behavior of flavonoids during drought stress is still not well-documented. Herein we investigated the time-series alternation of flavonoids in the aerial part of Arabidopsis (wild type, Col-0) during drought stress by LC-QTO F-MS. The drastic alternation of 5 flavonols and 5 anthocyanins was revealed together with changes in marker metabolites of drought stress, e.g., proline, raffinose, and galactinol. These findings indicate that flavonols and anthocyanins can mitigate drought stress. © 2014 Landes Bioscience. Source

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

Researchers at the RIKEN Center for Sustainable Resource Science and the University of Tokyo have demonstrated that the bacterium Acidithiobacillus ferrooxidans can take electrons needed for growth directly from an electrode power source when iron—its already known source of energy—is absent. The study, published in Frontiers in Microbiology, shows that A. ferrooxidans can use direct uptake of electrons from an electrode to fuel the same metabolic pathway that is activated by the oxidation of diffusible iron ions. Just as plants with chlorophyll use photosynthesis to convert energy from light into sugars needed for growth, other organisms—like animals—gain energy for the manufacture of sugars by taking electrons from substances in their surrounding environments—a process called chemosynthesis. Organisms that gain their energy this way are called chemotrophs, and those that get their electrons through oxidation of inorganic substances are called chemolithoautotrophs. Phototrophs and chemotrophs make up two interconnected ecosystems. "We are investigating the possibility of a third type of ecosystem," explains group leader Ryuhei Nakamura. "We call it the electro-ecosystem because microbial activity is sustained primarily by direct electrical current." Recently, his team has discovered geo-electric currents across the walls of black-smoker chimneys formed by hydrothermanl vents, suggesting that some deep-sea microbes might double as a electrolithoautotrophs, organisms that can use electrical potential—meaning that they simply eat electrons—as an energy source instead of light or surrounding inorganic substances. Because access to microbes in this environment is not easy, and to verify their hypothesis that being able to switch energy sources from inorganic substances to electricity is not unique in the microbial world, the team experimented with A. ferrooxidans, a chemolithoautotrophic bacterium known to oxidize iron ions (Fe2+). The team cultured A. ferrooxidans in an Fe2+-free environment and supplied an electrode with an electrical potential of +0.4 V, carbon-dioxide as a carbon source, and oxygen as an electron acceptor. They found that these conditions created a current that originated from the electrode, and that the strength of the current depended on how many cells were attached to the electrode. Killing the cells with UV light immediately suppressed the current. To determine how this current was being generated, they used an artificial photochemical reaction. Normally, carbon monoxide attaches to heme proteins in A. ferrooxidans outer membranes and prevents oxidation. But, when exposed to light, this bond is broken and oxidation continues as usual. When tested, carbon-monoxide also prevented the current formed between the electrode and A. ferrooxidans cells and exposure to light reversed this block and allowed the current to flow. This suggested that a heme protein is needed for the electrosynthesis exhibited by A. ferrooxidans. Further analysis showed that the responsible heme protein is the aa3 complex which is known to play a role in down-hill electron transfer in A. ferrooxidans that generates ATP and the proton-motive-force that allows uphill electron transfer and carbon fixation—the hallmarks of sugar production. Inhibition of a protein complex that is part of the uphill-transfer process suppressed the current, showing that the proton-motive-forces being generated were indeed used for up-hill electron transport. Additionally, the optical density of cells cultured with the electrode for eight days increased over time, indicating growth and that the current generated by electrons flowing from the electrode to the cells was being used for carbon fixation. "Now that we have identified the metabolic pathway for electrolithoautotrophs in A. ferrooxidans, we will be able to apply this knowledge to bacteria we find in the deep sea vent," says Nakamura. "The next step is to prove the existence of electro-ecosystems in on-site deep-sea experiments." Understanding electro-ecosystems and how electrical currents can support life could lead to a blueprint for sustainable human ecosystems, using technology such as fuel cells, batteries, and thermoelectric converters." Explore further: Scientists trick iron-eating bacteria into breathing electrons instead More information: Takumi Ishii et al. From chemolithoautotrophs to electrolithoautotrophs: CO2 fixation by Fe(II)-oxidizing bacteria coupled with direct uptake of electrons from solid electron sources, Frontiers in Microbiology (2015). DOI: 10.3389/fmicb.2015.00994

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