Reaction-Diffusion Pattern in Shoot Apical Meristem of Plants

A fundamental question in developmental biology is how spatial patterns are self-organized from homogeneous structures. In 1952, Turing proposed the reaction-diffusion model in order to explain this issue. Experimental evidence of reaction-diffusion patterns in living organisms was first provided by the pigmentation pattern on the skin of fishes in 1995. However, whether or not this mechanism plays an essential role in developmental events of living organisms remains elusive. Here we show that a reaction-diffusion model can successfully explain the shoot apical meristem (SAM) development of plants. SAM of plants resides in the top of each shoot and consists of a central zone (CZ) and a surrounding peripheral zone (PZ). SAM contains stem cells and continuously produces new organs throughout the lifespan. Molecular genetic studies using Arabidopsis thaliana revealed that the formation and maintenance of the SAM are essentially regulated by the feedback interaction between WUSHCEL (WUS) and CLAVATA (CLV). We developed a mathematical model of the SAM based on a reaction-diffusion dynamics of the WUS-CLV interaction, incorporating cell division and the spatial restriction of the dynamics. Our model explains the various SAM patterns observed in plants, for example, homeostatic control of SAM size in the wild type, enlarged or fasciated SAM in clv mutants, and initiation of ectopic secondary meristems from an initial flattened SAM in wus mutant. In addition, the model is supported by comparing its prediction with the expression pattern of WUS in the wus mutant. Furthermore, the model can account for many experimental results including reorganization processes caused by the CZ ablation and by incision through the meristem center. We thus conclude that the reaction-diffusion dynamics is probably indispensable for the SAM development of plants

水素添加油中でのトリグラセライドの結晶成長

植物油および動物油に水素添加して,結晶性トリグリセライドの量を増加させて試料とし,それらの結晶形態が電子顕微鏡によって観察され,また,多形現象の相転移がX線回折によって測定された。これらの実験によって得られた結晶形態および多形現象の相転移について結晶成長機構を探る観点から検討するのがこの研究の目的である。 実験の結果は植物性油脂,動物性油脂のそれぞれの結晶変態がβ'型,β型であり,これらの変態に対応する結晶形態が前者の場合比較的大きく,後者の場合小さい単結晶に成長することが見出された。 脂肪酸組成は植物性油脂が動物性油脂よりも脂肪酸の種類が少ない。その点から,植物性油脂変態の転移速度が早く,動物性油脂は遅いとされている。しかし実験結果は逆の傾向を示している。これは油脂を構成している液体トリグラセライドと結晶性トリグラセライドの重量比が,動物性油脂の方が植物性油脂よりも大きいために結晶性トリグラセライド分子が液体トリグラセライド分子を媒介にして容易に移動することができて単位格子を作り,また単位格子のパッキングを密にするため転移速度が早くなったと考えられる。 さらに結晶の形態において,β型よりβ'型の方が大きい単結晶に成長する機構は,液体トリグリセライド分子が多いため,結晶性トリグリセライド分子の移転が容易で,多くの結晶核ができやすくなり,単結晶は小さくなる。反対に結晶核が少ないと,核に吸着される結晶性トリグリセライド分子は多くなるので大きい単結晶が成長することになると思われる

Effect of Impurity in Phase Transition on Triglyceride Crystals

The allotropic transition of polymorphsum in tristearin is followed by X-ray diffraction. Four modifications; α-, β’-, intermediate and β- form of tristearin had been identified. The transition rate of modification is depended on a quantity of impurity (liquid paraffin) mixed in tristearin. In the much quantity of impurity, the transition rate of modification become the rapid transition of α-form to β-form. The intensity of X-ray diffraction on (001) and (100) plane in a unit cell of β-form is the same phenomenon for impurity effect

MAA3 (MAGATAMA3) Helicase Gene is Required for Female Gametophyte Development and Pollen Tube Guidance in Arabidopsis thaliana

The female gametophyte plays a central role in the sexual reproduction of angiosperms. We previously isolated the maa3 (magatama3) mutant of Arabidopsis thaliana, defective in development of the female gametophyte, micropylar pollen tube guidance, and preventing the attraction of multiple pollen tubes. We here observed that the nucleolus of polar nuclei is small, and that the fusion of polar nuclei often did not occur at the time of pollination. The MAA3 gene encodes a homolog of yeast Sen1 helicase, required for RNA metabolism. It is suggested that MAA3 may regulate RNA molecules responsible for nucleolar organization and pollen tube guidanc

Crystal Growth of Fatty Acids : I. Stearic Acid

ステアリン酸単結晶をベンゼン溶液中から育成し,結晶成長表面を光学顕微鏡と電子顕微鏡で観察し,らせん成長理論を裏付ける成長らせんを確認した。 結晶成長らせんステップはいずれも異方性を示し,単結晶外形と一致する角度をもっている。光学的に観察された成長らせんには,単一らせん,複数のらせん,反対の符号を持つ2つの転位から出発した成長らせんのつくるループなどが識別されたが,これらはいずれも,らせん成長理論の予測と一致するものであった。不純物によると思われるらせんステップの局部的な曲りが観察されたが,これは不純物効果として説明されるだろう。レプリカ法による,電子顕微鏡を用いて,成長らせん中心付近の徴視的な観察を行ったが,その結果,光学的に確認された成長らせんは,10本以上の単一らせんが束になってできたmacro-spiralに対応することがわかった。The growth patterns on the as-grown surfaces of stearic acid single crystals obtained from benzene solution were observed by optical and electron microscope. Optically, many kinds of growth spiral steps were detected, providing the validity of the spiral growth theory in the case of this solution growth of stearic acid. The modulation of growth steps were observed and explained by the effect of the impurities, which had been included in the solution. Further observations by an electron microscope of replica method have clarified that the growth spirals detected by an optical microscope are the macro spiral consisted of more than ten single steps and that there are many single spirals around the center of the macrospiral.この論文の一部は,国際結晶成長学会議(ICCG-5,Boston,1977.7)にて行われる2つの講演(Growth of Large Single Crystals of Stearic Acid from SolutionとGrowth Mechanism of Stearic Acid Single Crystals)に含まれている

Optical Studies of Lyotropic Liquid Crystaline Phases in Lipids : II. Potassium Caprate -Water System

光学顕微鏡によって，カプリン酸カリウムと水の系の示す，リオトロピック液晶の性質を調べた。 観測された相として，ミドル相，ニート相，粘性等方相の3相があった。カプリン酸カリウムと水の系の相図は，一般の石けんと水の系とよく似た形をしていることがわかった。 リオトロピック液晶の成長の機構を，乾燥法によって観察した。その結果，ニート相の成長パターンは，我々が前回モノグリセライドと水の系の研究で報告したような，球晶ニートと「あわ」の回りのニー卜層が，その成長の初期段階の特徴的パターンであることが確かめられた。ミドル相成長の様相は，ニー卜相とは異なり，むしろ固体結晶の成長パターンに類似している。The lyotropic liquid crystalline phases of the potassium caprate-water system have been investigated by means of a polarizing microscope. Three typical phases of lyotropic liquid crystal were observed in the binary mixture of potassium caprate and water，as being respectively a neat phase，a viscous isotropic phase and a middle phase. The phase diagram of the potassium caprate-water system shows the same form as the other soap-water systems qualitatively， for example the potassium palmitate-water system. The liquid crystal growth experiments for both the neat phase and the middle phase were performed by the drying method. As for the neat phase，it was confirmed that the spherulytic neat and the neat layer around the bubble are the characteristic patterns of the earlier stage of the growth. This was reported by us in the study of the monoglyceride-water system. The growth patterns of the middle phase grown from the isotropic solution differ from those of the neat phase but resemble those of the "solid" crystal

Optical Studies of Lyotropic Mesophases in Lipids : I. Monoglyceride-Water System

モノグリセライドとH2Oの2成分系がつくるリオトロピック液晶を,偏光顕微鏡を使って観察した。その結果,ニート相,粘性等方相そして逆ミドル相の3相が安定相として確認され,相転移は粘性等方相と他の2相とのあいだで可逆であることがわかった。リオトロピック液晶成長の様子も観察された。The lyotropic liquid crystalline phases of the monopalmitin-H2O system have been investigated by means of a polarizing microscope. As a result, the three stable phases of the monoglyceried-H2O system were observed, as being respectively the neat phase, the reversed middle phase and the viscous isotropic phase. It is concluded that the phase transitions both from the viscous isotropic phase to the neat phase and from the viscous isotropic phase to the reversed middle phase are reversible processes. This is contrary to Wilton et al's result for the phase diagram of the monostearin-H2O system. The patterns of the lyotropic liquid crystal growth were observed in relation to those of the smectic liquid crystal. Their growth mechanism is discussed too.本論文の一部は,日本物理学会第30会年会(京都,1975)で著者らによって発表されたものである

Comparison of Impressions of COVID-19 Vaccination and Influenza Vaccination in Japan by Analyzing Social Media Using Text Mining

The aim of this study was to compare impressions of COVID-19 vaccination and influenza vaccination in Japan by analyzing social media (Twitter®) using a text-mining method. We obtained 10,000 tweets using the keywords “corona vaccine” and “influenza vaccine” on 15 December 2022 and 19 February 2023. We then counted the number of times the words were used and listed frequency of these words by a text-mining method called KH Coder. We also investigated concepts in the data using groups of words that often appeared together or groups of documents that contained the same words using multi-dimensional scaling (MDS). “Death” in relation to corona vaccine and “severe disease” for influenza vaccine were frequently used on 15 December 2022. The number of times the word “death” was used decreased, “after effect” was newly recognized for corona vaccine, and “severe disease” was not used in relation to influenza vaccine. Through this comprehensive analysis of social media data, we observed distinct variations in public perceptions of corona vaccination and influenza vaccination in Japan. These findings provide valuable insights for public health authorities and policymakers to better understand public sentiment and tailor their communication strategies accordingly

Expression in E. coli of finger-domain lacking tissue-type plasminogen activator with high fibrin affinity

AbstractTissue-type plasminogen activator (t-PA) has a high affinity for fibrin and induces lysis of fibrin (fibrinolysis) on the surface of fibrin without degrading circulating fibrinogen. cDNA for t-PA which lacks the ‘fingerdomain’ (the site for fibrin affinity) was isolated from Detroit 562 cells. Analysis of the nucleotide sequence revealed a lack of the sequences which code for the finger-domain. A plasmid (pDPAT 1) containing the Escherichia coli tac promoter/operator and the cDNA sequence coding for ‘finger-domain lacking t-PA’ was constructed for expression in E. Coli. The polypeptide so produced was a new type of t-PA lacking finger-domain, but revealed plasminogen activator activity with the function of fibrin affinity.Tissue-type plasminogen activatorFinger-domainFibrin affinityPlasmid E. coli tac promoter/operatorDetroit 562 cel

Regulated motion of glycoproteins revealed by direct visualization of a single cargo in the endoplasmic reticulum

The quality of cargo proteins in the endoplasmic reticulum (ER) is affected by their motion during folding. To understand how the diffusion of secretory cargo proteins is regulated in the ER, we directly analyze the motion of a single cargo molecule using fluorescence imaging/fluctuation analyses. We find that the addition of two N-glycans onto the cargo dramatically alters their diffusion by transient binding to membrane components that are confined by hyperosmolarity. Via simultaneous observation of a single cargo and ER exit sites (ERESs), we could exclude ERESs as the binding sites. Remarkably, actin cytoskeleton was required for the transient binding. These results provide a molecular basis for hypertonicity-induced immobilization of cargo, which is dependent on glycosylation at multiple sites but not the completion of proper folding. We propose that diffusion of secretory glycoproteins in the ER lumen is controlled from the cytoplasm to reduce the chances of aggregation