Tokyo University of Science

About: Tokyo University of Science is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Catalysis & Thin film. The organization has 15800 authors who have published 24147 publications receiving 438081 citations. The organization is also known as: Tōkyō Rika Daigaku & Science University of Tokyo.

Plasma membrane protein OsMCA1 is involved in regulation of hypo-osmotic shock-induced Ca2+influx and modulates generation of reactive oxygen species in cultured rice cells

Abstract: Mechanosensing and its downstream responses are speculated to involve sensory complexes containing Ca2+-permeable mechanosensitive channels. On recognizing osmotic signals, plant cells initiate activation of a widespread signal transduction network that induces second messengers and triggers inducible defense responses. Characteristic early signaling events include Ca2+ influx, protein phosphorylation and generation of reactive oxygen species (ROS). Pharmacological analyses show Ca2+ influx mediated by mechanosensitive Ca2+ channels to influence induction of osmotic signals, including ROS generation. However, molecular bases and regulatory mechanisms for early osmotic signaling events remain poorly elucidated. We here identified and investigated OsMCA1, the sole rice homolog of putative Ca2+-permeable mechanosensitive channels in Arabidopsis (MCAs). OsMCA1 was specifically localized at the plasma membrane. A promoter-reporter assay suggested that OsMCA1 mRNA is widely expressed in seed embryos, proximal and apical regions of shoots, and mesophyll cells of leaves and roots in rice. Ca2+ uptake was enhanced in OsMCA1-overexpressing suspension-cultured cells, suggesting that OsMCA1 is involved in Ca2+ influx across the plasma membrane. Hypo-osmotic shock-induced ROS generation mediated by NADPH oxidases was also enhanced in OsMCA1-overexpressing cells. We also generated and characterized OsMCA1-RNAi transgenic plants and cultured cells; OsMCA1-suppressed plants showed retarded growth and shortened rachises, while OsMCA1-suppressed cells carrying Ca2+-sensitive photoprotein aequorin showed partially impaired changes in cytosolic free Ca2+ concentration ([Ca2+]cyt) induced by hypo-osmotic shock and trinitrophenol, an activator of mechanosensitive channels. We have identified a sole MCA ortholog in the rice genome and developed both overexpression and suppression lines. Analyses of cultured cells with altered levels of this putative Ca2+-permeable mechanosensitive channel indicate that OsMCA1 is involved in regulation of plasma membrane Ca2+ influx and ROS generation induced by hypo-osmotic stress in cultured rice cells. These findings shed light on our understanding of mechanical sensing pathways.

Large perpendicular magnetic anisotropy at Fe/MgO interface

Abstract: A large perpendicular magnetic anisotropy (PMA) of 1.4 MJ/m3 was observed from ultrathin Fe/MgO(001) bilayers grown on Cr-buffered MgO(001). The PMA strongly depends on the surface state of Fe prior to the MgO deposition. A large PMA energy density of 1.4 MJ/m3 was achieved for a 0.7 nm thick Fe layer having adsorbate-induced surface reconstruction, which is likely to originate from oxygen atoms floating up from the Cr buffer layer. This large magnitude of PMA satisfies the criterion that is required for thermal stability of magnetization in a few tens nanometer-sized magnetic memory elements.

shk1-D, a dwarf Arabidopsis mutant caused by activation of the CYP72C1 gene, has altered brassinosteroid levels.

Abstract: *Summary Brassinosteroids (BRs) are plant steroidal hormones that regulate plant growth and development. An Arabidopsis dwarf mutant, shrink1-D (shk1-D), was isolated and the phenotype was shown to be caused by activation of the CYP72C1 gene. CYP72C1 is a member of the cytochrome P 450 monooxygenase gene family similar to BAS1/CYP734A1 that regulates BR inactivation. shk1-D has short hypocotyls in both light and dark, and short petioles and siliques. The seeds are also shortened along the longitudinal axis indicating CYP72C1 controls cell elongation. The expression of CPD, TCH4 and BAS1 were altered in CYP72C1 overexpression transgenic lines and endogenous levels of castasterone, 6-deoxocastasterone and 6-deoxotyphasterol were also altered. Unlike BAS1/CYP734A1 the expression of CYP72C1 was not changed by application of exogenous brassinolide. We propose that CYP72C1 controls BR homeostasis by modulating the concentration of BRs.