A Role of Plasma Membrane K+ Channels in Salt Adaptation of Tabacco Suspension Cells

The fluorescent probe method was applied to determine the membrane potential of tobacco (Nicotiana tabacum L. cv Bright Yellow) cells that were either unadapted (NaCl-unadapted cells) or adapted to 50 mM NaCl (Na50-adapted cells). There were no deffrences in the bahavior of the membrane potential between the NaCl-unadapted cells and the Na50-adapted cells. The patch-cpamp technique was used to study and compare the characterristics of cation channels in the plasma membrance of NaCl-unadapted cells, Na50-adapted and Na100-adapted cells. The steady-state amplitude of the outward whole-cell currents decreased in the following order; NaCl-unadapted cells>Na50-adapted cells>Na100-adapted cells. There were no significant differences between the NaCl-unadapted cells and the Na50-adapted cells in terms of the K+/Na+ selectivity of these channels. These observations suggest that adaptation to salinity in reduced permeability of the K+ channels to both K+ and Na+. K+ channels in the plasma membrane were investigated using the patch-clamp technique. The outward rectifying whole-cell currents were reduced with increasing extracellular Ca2+ and were independent of intracellular Ca2+. The K+/Na+ selectivity were independent of Ca2+ concentration. These observations suggest that extracellular Ca2+ is an important factor in the regulation of ion permeability. The characteristics of Ca2+ binding on the plasma membrane were investigated by the micro-electrophoresis tecniqui. Comparison of the amount of Ca2+ bound in the presence of 30 mM NaCl with that in the presence of 30 mM KCl indicated that Na+ reduced the amount of Ca2+ bound to the plasma membrane of the NaCl-unadapted cells,but did not reduce the amount of Ca2+ bound to the plasma membrane of the Na50-adapted cells. These results suggest that adaptation to salt sterss results in increased resisrtance to the displecement of membrane-associated Ca2+ by Na+.一般に、高等植物は塩に弱く、土壌の塩の集積によって、生育が困難になり、枯死に至る。しかし、塩に強い、あるいは、塩を好む高等植物も存在している。これらの植物の耐塩性あるいは塩ストレス適応機構の解明は、塩ストレス適応植物または耐塩性植物作出のための基礎的知見を与える。高等植物にとって塩ストレスは、ナトリウムによる代謝阻害を意味する。《イオンストレス》と、水分の吸収に関わる《浸透圧ストレス》とに大別される。これまでの研究によって、塩ストレスの主たる原因は、《イオンストレス》であることが知られるようになった。また、塩生植物も含め高等植物は塩に強い酵素を持たないため、細胞質中の高いカリウムイオンとナトリウムイオンとの比（K+/Na+）の維持が塩ストレス適応機構および耐塩性機構にふかく関わっていることも明らかにされつつある。しかし、細胞質中の高K+やNa+の主な流出入の経路と考えられる原形質膜のイオンチャンネルの役割については、ほどんど明らかにされていない。また、塩ストレスの初期の段階でNa+によって原形質膜表面のCa2+が置換されることや細胞外のCa2+の減少によってK+の流出が起きること、細胞外のCa2+によって塩ストレスが軽減されることなど、Ca2+が塩ストレスの初期の段階で重要な動きをしていることが示唆されている。しかし、そのCa2+の制御機構についても、詳細は明らかにされていない。本研究では、高等植物の細胞レベルでの研究に適しているタバコ培養細胞（BY-2）を材料として、また電気生理学的手法（パッチクランプ法、細胞電気泳動法、本研究で確立した蛍光プローブによる定量的膜電位測定法）を用いて、高等植物の塩ストレス適応機構における原形質膜のK+チャンネルの役割の解明、塩ストレス適応機構における細胞内外および表面のCa2+の役割の解明を行なった

Transgenic Petunia for Iron Deficiency in Alkaline Environments

Iron is an essential nutrient for all plants. However, terrestrial plants often suffer from iron deficiency in alkaline soil due to its extremely low solubility. Alkaline soil accounts for about 30% of all cultivated ground in the world. Plants have evolved two distinct strategies, I and II, for iron uptake from the soil. Dicots and non-graminaceous monocots use Strategy I, which is primarily based on the reduction of iron(III) to iron(II) and the uptake of iron(II) by the iron-regulated transporter, IRT1. In contrast, graminaceous plants use Strategy II to efficiently acquire insoluble iron(III). Strategy II comprises the synthesis and secretion of iron-chelating phytosiderophores, such as mugineic acids and the Yellow Stripe 1 transporter proteins of the iron(III)-phytosiderophore complex. Barley, which exhibits the highest tolerance to iron deficiency in alkaline soil among graminaceous plants, utilizes mugineic acids and the specific iron(III)-mugineic acids transporter, HvYS1. In this study, we established the transgenic plant Petunia hybrida, which originally had only Strategy I, by introducing the HvYS1 transporter gene derived from barley. When the transgenic plants were grown hydroponically in media containing the iron(III)-2′-deoxymugineic acid complex, free 2′-deoxymugineic acid and its iron(III) complex were detected in the root extract of the transgenic plant by electrospray ionization-Fourier transform-ion cyclotron resonance mass spectrometry. The growth of the transgenic petunia was significantly better than that of the control host in alkaline conditions. Consequently, the transgenic plant acquired a significantly enhanced tolerance to alkaline hydroponic media in the presence of the iron(III)-2′-deoxymugineic acid complex. Furthermore, the flower color of the transgenic plant deepened. The results showed that iron-phytosiderophore complexes and their transporters can potentially be utilized to overcome the worldwide iron uptake problems to diverse plant species that are found in areas with alkaline conditions

An experimental study of reinforced concrete beamcolumn joint with partially high strengthened longitudinal bar

It is necessary to generate the yield position away from the column face to minimize damage to the beam-column joint during a large earthquake in a reinforced concrete building. The same efficacy can be realized using partially high strengthened rebar. The number of longitudinal bars can be calculated for a bending moment smaller than the column face, reducing their number compared to the conventional bar-arrangement method. This paper describes reinforced concrete an interior beam-column subassemblage tests using this rebar as the longitudinal bars of beams and a column. The beam yield hinge was formed at a position apart from the column face, and the damage to the beam-column joint was less than the conventional bar-arrangement method. Additionally, the good performance was obtained if the bending strength of the column was large, even if the shear capacity margin of the beam-column joint was small. The column-beam flexural strength ratio and shear capacity margin at the beam-column joint need to be set with consideration of their relationship

Compulsory Repetitive Learning to Improve Student Achievement and Performance in Fundamental Subjects

　We employ the methodology of “Compulsory Repetitive Learning” to improve student learning and performance in fundamental subjects. It is a challenge for many universities to intrinsically motivate students and it is a demanding issue that a large part of students do not sufficiently do homework. Here, we let students solve the problems associated with the teaching immediately following each lecture. Through the usage of “Compulsory Repetitive Learning”, each student as well as the subject teacher(s) could monitor and evaluate the quality of student learning and performance

Resistance imparted by vitamin C, vitamin e and vitamin B12 to the acute hepatic glycogen change in rats caused by noise.

The effects of vitamin C, vitamin E and vitamin B12 on the noise-induced acute change in hepatic glycogen content in rats were investigated. The exposure of rats to 95 dB and 110 dB of noise acutely reduced their hepatic glycogens. Vitamin C (ascorbic acid) and vitamin E (alpha -tocopherol) attenuated the noise-inducedacute reduction in the hepatic glycogen contents. This result suggests that antioxidants could reduce the change via reactive oxygen species. Vitamin B12 (cobalamin) delayed the noiseinduced change, a finding that suggests that vitamin B12 could postpone the acute change via compensating for vitamin B12 deficiency

The effect of exogenous dihydroxyacetone and methylglyoxal on growth, anthocyanin accumulation, and the glyoxalase system in Arabidopsis

Dihydroxyacetone (DHA) occurs in wide-ranging organisms, including plants, and can undergo spontaneous conversion to methylglyoxal (MG). While the toxicity of MG to plants is well-known, the toxicity of DHA to plants remains to be elucidated. We investigated the effects of DHA and MG on Arabidopsis. Exogenous DHA at up to 10 mM did not affect the radicle emergence, the expansion of green cotyledons, the seedling growth, or the activity of glyoxalase II, while DHA at 10 mM inhibited the root elongation and increased the activity of glyoxalase I. Exogenous MG at 1.0 mM inhibited these physiological responses and increased both activities. Dihydroxyacetone at 10 mM increased the MG content in the roots. These results indicate that DHA is not so toxic as MG in Arabidopsis seeds and seedlings and suggest that the toxic effect of DHA at high concentrations is attributed to MG accumulation by the conversion to MG

Photochemical Products from Ergosterol in the Plasma Membrane of the Yeast Rhodotorula minuta cells illuminated by Near-UV

When the plasma mumbrane of the yeast Rhodotorula minuta cells was exposed to near-UV at 0℃, three new compounds were formes photochemically with decrease in ergosterol content. When 0.4%-SDS solution containing ergosterol was illuminated with near-UV, the same three compounds as in the membrane were formed. As a result of instruments analysis, one of three photochemical products was identified as previtamine D2 and another two compounds were characterized chemically that they had the structure of ergosta-4, 7, 22-trein-3-on. In addition, these photochemical products did not affect the growth and carotenogenesis of the yeast Rhodotorulaminuta.赤色酵母R.minuta細胞膜に長波長紫外光を照射した時に生じるエルゴステロール由来の光化学反応生成物の単離・精製およびその同定を行った。結果、3種類の物質が単離・精製され、そのうち1つはPrevitamin D2であることが同定され、残りの2つについてはergosta-4,7,22-trien-3-on の何かの炭素にOH基が付いたものであることが分かった。単離した成分を培地に加え、菌体の増殖とカロテノイド生合成に対する影響を調べた結果、これらの物質はそのどちらにも影響を及ぼさなかった

Enhanced O-GlcNAcylation Mediates Cytoprotection under Proteasome Impairment by Promoting Proteasome Turnover in Cancer Cells

The proteasome is a therapeutic target in cancer, but resistance to proteasome inhibitors often develops owing to the induction of compensatory pathways. Through a genome-wide siRNA screen combined with RNA sequencing analysis, we identified hexokinase and downstream O-GlcNAcylation as cell survival factors under proteasome impairment. The inhibition of O-GlcNAcylation synergistically induced massive cell death in combination with proteasome inhibition. We further demonstrated that O-GlcNAcylation was indispensable for maintaining proteasome activity by enhancing biogenesis as well as proteasome degradation in a manner independent of Nrf1, a well-known compensatory transcription factor that upregulates proteasome gene expression. Our results identify a pathway that maintains proteasome function under proteasome impairment, providing potential targets for cancer therapy