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Takahashi, N.,Kajihara, T.,Okamura, C.,Kim, Y.,Katagiri, Y.,Okushima, Y.,Matsunaga, S.,Hwang, I.,Umeda, M. Current Biology Ltd ; Elsevier Science Ltd 2013 Current biology Vol.23 No.18
Plant roots respond to various internal and external signals and adjust themselves to changes of environmental conditions. In the root meristem, stem cells produce daughter cells that continue to divide several times. When these latter cells reach the transition zone, they stop dividing and enter the endocycle, a modified cell cycle in which DNA replication is repeated without mitosis or cytokinesis. The resultant DNA polyploidization, named endoreduplication, is usually associated with an increase of nuclear and cell volume and with cell differentiation [1-4]. At the transition zone, cytokinin signaling activates two transcription factors, type-B ARABIDOPSIS RESPONSE REGULATOR 1 (ARR1) and ARR12, and induces SHY2/IAA3, a member of the Aux/IAA family of auxin signaling repressors. This inhibits auxin signaling and reduces the expression of auxin efflux carriers, resulting in cell division arrest [5]. Such counteracting actions of two hormones are assumed to determine meristem size. However, it remains unknown whether cytokinins additionally control meristem size through an auxin-independent pathway. Here we show that, in Arabidopsis, the cytokinin-activated ARR2 directly upregulates the expression of CCS52A1, which encodes an activator of an E3 ubiquitin ligase, anaphase-promoting complex/cyclosome (APC/C) [6], thereby promoting the onset of the endocycle and restricting meristem size. Our genetic data revealed that CCS52A1 function is independent of SHY2-mediated control of auxin signaling, indicating that downregulation of auxin signaling and APC/C-mediated degradation of cell-cycle regulators cooperatively promote endocycle onset, and thus fine tune root growth.
Takahashi, A.,Yasuda, A.,Kaneda, H.,Kawada, M.,Kiriyama, Y.,Mouri, A.,Mori, T.,Okada, Y.,Takahashi, H. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
We present the results of far-infrared spectroscopic observations of the Large Magellanic Cloud (LMC) with FIS-FTS. We covered a large area across the LMC, including 30 Doradus (30 Dor) and N44 star-forming regions, by 191 pointings in total. As a result, we detect the [OIII] and [CII] line emission as well as far-infrared dust continuum emission throughout the LMC. We find that the [OIII] emission is widely distributed around 30 Dor. The observed size of the distribution is too large to be explained by massive stars in 30 Dor, which are assumed to be enshrouded by clouds with the constant gas density estimated from the [OIII] line intensities. Therefore the surrounding structure is likely to be highly clumpy. We also find a global correlation between the [OIII] and the far-infrared continuum emission, suggesting that the gas and dust are well mixed in the highly-ionized region where the dust survives in clumpy dense clouds shielded from energetic photons. Furthermore we find that the ratios of [CII]/CO are as high as 110,000 in 30 Dor, and 45,000 even on average, while they are typically 6,000 for star-forming regions in our Galaxy. The unusually high [CII]/CO is also consistent with the picture of clumpy small dense clouds.
Application of Matrix Thinking Method to Introduction Program in Engineering Education
Y. Satoh,K. Takahashi,Y. Takahata,김윤해,S. Kubota 한국공학교육학회 2010 공학교육연구 Vol.13 No.2
From a lot of survey, it is obvious that most students in universities lose their desire for learning just after enteringtheir universities. In order to solve this problem, we developed a novel educational tool for the students, named “Thethinking method based on matrix diagram”. If they try hard with the help of this tool, they will be able to learn how todesign and manage their splendid university lives in addition to get the basic knowledge and to improvetheir basic abilities.It is also found that they can earn the shared knowledge mutually after learning a common method, which supports to makethem to improve their communication abilities drastically.
New Assay Method for Surveying Anti-Emetic Compounds from Natural Sources
Y. Akita,Y. Yang,T. Kawai,K. Kinoshita,K. Koyama,K. Takahashi,K. Watanabe 한국생약학회 1998 Natural Product Sciences Vol.4 No.2
The new assay method was developed by using young chicks instead of frogs for screening of anti-emetic compounds from natural sources. Comparing with our previous method using leopard and rapid frogs, the advantages of the new method were not only completely parallel results but also decreasing standard errors. Hinesol and eudesmol were isolated from MeOH extract of Atractylodes lancea rhizome as the anti-emetic principles.