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Mechanism of Atomic Force Microscopy and its Application to Photosynthetic Membranes
No full text光合成膜で起こるエネルギー移動や電子伝達反応の理解には，膜内におけるタンパク質の配置に関する情報を得ることは必要不可欠である．原子間力顕微鏡(AFM)は，溶液環境を保ったまま光合成膜内のタンパク質を一分子レベルで観察できる手法であり，紅色細菌から高等植物に至るまで，様々な生物の光合成膜におけるタンパク質分布を明らかにしてきた．本稿では，AFMの測定原理と空間分解能について解説するとともに，近年開発されたAFMの高速化技術についても取り上げる．また，実際に光合成膜を観察する際のサンプル処理方法と，AFMを用いて光合成膜を観察した代表的な研究例について紹介する．To understand the well-organized photosynthetic reaction, it is important to obtain information on the distribution and orientation of proteins in the membrane. Atomic force microscopy (AFM) is one of the most powerful tools for visualizing the protein structure at the molecular level under physiological conditions. AFM has been applied to various photosynthetic membranes from photosynthetic bacteria, cyanobacteria, and higher plants. In this CHAPTER, we first explain working principle, spatial resolution of AFM, and data interpretation. Next, several representative imaging research of photosynthetic membranes using conventional AFM and high-speed AFM are introduced
Principles of electrophoresis and comparison of buffer systems : from SDS-PAGE to Native-PAGE
No full textゲル電気泳動法はタンパク質やタンパク質複合体の分離に広く用いられてきた手法である．本稿ではまず，ゲル電気泳動において考慮すべき三つの要点について説明する．すなわち，1） 負電荷の付与方法，2） ゲルマトリックス，3） 界面活性剤の選択である．次に，SDS-PAGE，blue-native（ BN）-PAGE，clear-ative（ CN）-PAGEの各電気泳動法について，そのbuffer系の歴史と原理を解説する．特に，SDS-PAGEとCN-PAGEについては，標準的なbuffer系に加え，改変buffer系についても紹介する．Gel electrophoresis is a widely used technique for the separation of proteins and protein complexes. This paper discusses three critical considerations in gel electrophoresis: 1) selection of the chemical that gives negative charge to the protein, 2) selection of the gel matrix, and 3) selection of the detergent. In addition, I review the historical development and underlying principles of buffer systems used in SDS-PAGE, blue-native (BN) PAGE, and clearnative (CN) PAGE. Special attention is given to the standard buffer systems used in SDS-PAGE and CN-PAGE, as well as modified buffer systems, two of which have been developed by the author
Freezing Resistance of Overwintering Plants
No full text植物は夏から秋にかけて成長が停止し，休眠を始める．さらに秋から冬にかけて低温馴化過程を経て凍結抵抗性が高まり，越冬が可能となる．また，冬から春にかけて気温が上昇するにつれて脱馴化過程を経ることで凍結抵抗性が低下すると共に，開芽・開葉など成長が始まる．越冬する植物にとって必要な低温馴化や凍結抵抗性の上昇などの現象は休眠過程と並行して起こるもので，多くの生理反応が関与する．本章では，越冬する植物にとって必要な低温馴化や凍結抵抗性などの生理機構や凍結に対する細胞の応答 (凍結挙動) について概説する．Plants gradually stop growing in late summer and enter dormancy. From autumn to winter, plants undergo a cold acclimation process, which increases their freezing resistance, enabling them to survive the winter. As the temperature rises from winter to spring, plants undergo a deacclimation process, which reduces their freezing resistance, and they also begin to grow, with buds opening and leaves expanding. Cold acclimation and increase in freezing resistance, which are necessary for overwintering plants, occur in parallel with the dormancy process and involve a number of physiological responses. This chapter outlines the physiological mechanisms including cold acclimation and freezing resistance that are necessary for overwintering plants and the cellular response of plants to freezing
30 years of partner switching systems : From the perspective of a cyanobacterial researcher
No full textパートナースイッチングシステム（PSS）は，セリンキナーゼ（アンチシグマ因子），アンタゴニスト，およびPP2C型ホスファターゼの3者から成る調節系であり，様々な細菌が，ストレス応答，細胞分化，運動性，病原性の獲得など，多様な細胞機能の制御に利用している．本稿では，筆者の博士論文における推定セリンキナーゼPmgAの同定と，当時，枯草菌で進められていたPSSの分子機構の解明に始まり，多様なPSSの発見を経て，シアノバクテリアのPSSが光合成や炭素同化，糖異化などの代謝制御に重要な役割を果たしていることが明らかになりつつある現在までの研究史を，シアノバクテリア研究者の観点から概説する．The partner switching system (PSS) is a tripartite regulatory system consisting of a serine kinase (an antisigma factor), an antagonist and a PP2C-type phosphatase. PSS has been widespread among bacterial species to regulate diverse cellular functions such as stress response, cell differentiation, motility and pathogenesis. In this paper, the research history of PSS is described from the perspective of a cyanobacterial researcher, starting with the identification of the putative serine kinase PmgA in cyanobacteria during the author's PhD study, together with the early PSS studies in Bacillus subtilis, and continuing through to the notion that PSSs play an important role in metabolic control to balance photosynthetic electron transport, carbon assimilation and sugar catabolism in cyanobacteria
Overwintering of evergreen plants, and effects of snow cover on photosynthesis and distribution of evergreen plants
No full text中高緯度地域に分布する常緑植物は，越冬時に低温や乾燥にさらされる．まず，越冬時に，土壌や通導組織の水が凍結し引き起こされる障害と，常緑広葉樹・常緑針葉樹の分布との関係について述べる．次に積雪が日本海側と太平洋側での近縁種の分布のような，植物種の分布に与える影響について述べる．さらに，積雪の有無による光合成能力や生存の違いを調べた研究例を紹介する．積雪下の植物の光合成，特に光化学系のタンパク質や色素に関しては研究が進んでいないため，今後の研究が期待される．最後に，温暖化による積雪深や雪解け時期の変化が，常緑植物の生存や植生の変化に与えうることを示した研究を紹介する．Evergreen plants distributed in mid- to high-latitude regions are exposed to low temperatures and drought during overwintering. I will explain the damage caused by freezing water in soil and xylem tissues during overwintering and discuss its relationship to the distribution of evergreen broadleaf and evergreen conifer species. Next, the effects of snow cover on the distribution of plant species, such as the distribution of closely related species on the Sea of Japan and Pacific Ocean sides, will be discussed. Snow cover can alter not only plant water use but also light utilization. Studies examining changes in photosynthetic capacity and survival with and without snow cover will be presented. Future research on photosynthesis in plants under snow cover, especially with regard to photosystem proteins and pigments, is expected to be conducted, since such research has not progressed to date. Finally, I will present studies which show that changes in snow depth and snowmelt timing due to global warming can affect the survival of evergreen plants and vegetation
Mechanisms and roles of autumn coloring
No full text紅葉はクロロフィルの分解と同時に赤い色素であるアントシアニンが集積することによって生じる．アントシアニンの働きとしては，１）遮光効果と抗酸化作用によって低温下での光ストレスから葉を守り，窒素回収に貢献するという「光防御仮説」と，２）植食性昆虫に対して防御物質が多く窒素栄養が少ないことを知らせるシグナルとして働くという「共進化仮説」が主流であった．本稿では，ハウチワカエデの季節変化を調べた研究を例に取り，アントシアニンがデンプンの代替として光合成産物の消費先となることで糖濃度の上昇と光阻害を抑え，窒素回収に貢献するという新しい説を紹介する．Two major hypotheses regarding the role of anthocyanins are the 'photoprotection hypothesis' and the 'coevolution hypothesis.' The former suggests that anthocyanins function as a sunscreen and antioxidants, while the latter proposes that anthocyanins serve as a signal indicating a higher amount of defensive substances and poor nutrient conditions. Based on the seasonal changes in physiological traits of a typical anthocyanic tree species, Acer japonicum, we propose a novel hypothesis: anthocyanins act as alternative sinks for carbon and energy in response to a decline in starch synthesis, contributing to nitrogen resorption by circumventing photoinhibition
Oxygen-reducing reactions in chloroplasts
No full text植物や藻類，シアノバクテリアが行う酸素発生型光合成では光エネルギーを利用して水と二酸化炭素から糖と酸素が生じる．一般的に酸素は光合成において「生成」されるものだが，実際は光合成を行う葉緑体やシアノバクテリア細胞では光照射下において酸素の還元，すなわち「消費」も起こっており，そこに係る分子メカニズムの中には，細胞レベルにおいて光合成に引けをとらない活性をもつものも存在する．本稿では，光合成において明反応でも暗反応でもない「ナニカ」である葉緑体の酸素還元について解説する．Oxygenic photosynthesis in plants, algae, and cyanobacteria produces sugar and O2 with light energy. Generally, O2 is recognized as what produced, and actually it is also what consumed in illuminated chloroplasts and cyanobacterial cells through the molecular mechanisms, some of which have comparable capacity to photosynthesis at cellular levels. Here, I review the O2-reducing reactions in chloroplasts that are neither light nor dark reactions of photosynthesis
北海道における災害後の植生動態と地形特性の理解に向けたマルチソースリモートセンシングとマルチモデルアプローチのシナジー
No full textIn recent years, the frequency and severity of natural disasters, such as typhoons and earthquakes, have significantly impacted ecosystems and the environment. This research addresses the urgent need for efficient post-disaster environmental monitoring and assessment by presenting five case studies, particularly in the context of the increasing frequency and intensity of natural disasters in Japanese mountain ecosystems. By advancing remote sensing applications, this work highlights innovative methods for post-disaster damage assessment, with a focus on Hokkaido, Japan.
The first case study investigates forest damage from three typhoons in Hokkaido in 2016.
This study compared existing forest damage estimation techniques with the goal of identifying their respective advantages and suitable use cases. Using Landsat 8 imagery, vegetation indices, machine learning classifiers, and the CLASlite software, various approaches to damage estimation were compared. Machine learning classifiers, especially Random Forest (RF) and Support Vector Machines (SVM), demonstrated high accuracy (80.36% overall accuracy) when using Fractional Vegetation Cover as a predictor. Among vegetation damage indices, Difference Normalized Difference Vegetation Index (DNDVI) showed better performance to identify forest damage areas.
This analysis revealed that forest damage was more severe on windward slopes and at higher elevations, emphasizing the role of landscape features in damage distribution.
The second case study examines topographic changes and vegetation dynamics in areas affected by the 2018 Mw 6.6 Hokkaido Eastern Iburi earthquake. High-resolution digital elevation models (DEMs) and multi-temporal satellite imagery from Sentinel-2 and Planet were used to map landslide activity and vegetation regrowth as an indicator of stability. Results showed significant topographic steepening due to the earthquake, with slow vegetation recovery, indicating ongoing vulnerability to debris flows and gully erosion. These findings highlight the need for long-term monitoring to assess landscape stability after seismic events.
In the third and fourth case studies, high-resolution topographic changes in landslide-affected areas following the 2018 earthquake were analyzed using LiDAR-derived DEMs.
Changes in slope, relief, and texture were examined, and comprehensive volume estimates of shallow landslides were compared with global area-volume relationships, highlighting uncertainties in scaling earthquake-induced landslides. By compiling an inventory of 1,719 landslides for the 2018 Mw 6.6 Hokkaido-Iburi earthquake epicentral region, this study estimates that the volume of soil landslides can be estimated by γ = 1.15. The total volume of eroded debris from Hokkaido-Iburi catchments based on this new scaling relationship is estimated as 64-72 million m3. Findings suggest that the earthquake not only steepened the topography but also generated debris volumes exceeding typical uplift rates, providing valuable insights to co-seismic uplift and erosion processes.
The final case study utilizes UAV-LiDAR data to capture microtopographic changes in the Iburi region, focusing on rill erosion dynamics in areas with minimal vegetation regrowth. This case study presents a UAV-LiDAR based data collection and processing workflow to capture the microtopography of a post-landslide area. A flow-accumulation based method for automated detection of rills is proposed and evaluated. Multi-year acquisitions were analyzed to assess changes in rill-density, width and depth dimensions, and sediment volume loss. A Zenmuse L1 LiDAR sensor was used for data acquisition. DEMs with a spatial resolution of 1 cm were generated from the LiDAR point cloud processing. A flow-accumulation algorithm with a threshold value of 5,000 could detect the rill network accurately (Producer & User accuracies >86%). Vertical cross-sections of the individual rills showed an increase in the depth and width of rills over one-year. This study demonstrates that a UAV-LiDAR system can effectively capture microtopography in a post-landslide landscape and facilitate analysis of small-scale rill-characteristics and the progression of rill erosion over time.
Collectively, the methodologies and findings presented in this thesis demonstrate the effectiveness of integrating multi-source remote sensing data and advanced processing techniques to enhance post-disaster damage assessment. These insights can guide future monitoring and risk assessment efforts in disaster-prone regions, supporting more resilient environmental management strategies