複数画像の信号処理的統合に基づく焦点画像処理とその応用

University of Tokyo (東京大学

N-ビニル-α-ハロアミドのラジカル環化反応における位置選択性とカルバペネム合成への応用

取得学位：博士(薬学)，学位授与番号：博甲第471号，学位授与年月日：平成14年3月22日,学位授与年：200

Bilirubin is produced nonenzymatically in plants to maintain chloroplast redox status

血液の分解産物ビリルビンが植物で作られることを発見 --植物の効率的な光合成に寄与している可能性--. 京都大学プレスリリース. 2023-06-08.Bilirubin, a potent antioxidant, is a product of heme catabolism in heterotrophs. Heterotrophs mitigate oxidative stress resulting from free heme by catabolism into bilirubin via biliverdin. Although plants also convert heme to biliverdin, they are generally thought to be incapable of producing bilirubin because they lack biliverdin reductase, the enzyme responsible for bilirubin biosynthesis in heterotrophs. Here, we demonstrate that bilirubin is produced in plant chloroplasts. Live-cell imaging using the bilirubin-dependent fluorescent protein UnaG revealed that bilirubin accumulated in chloroplasts. In vitro, bilirubin was produced nonenzymatically through a reaction between biliverdin and reduced form of nicotinamide adenine dinucleotide phosphate at concentrations comparable to those in chloroplasts. In addition, increased bilirubin production led to lower reactive oxygen species levels in chloroplasts. Our data refute the generally accepted pathway of heme degradation in plants and suggest that bilirubin contributes to the maintenance of redox status in chloroplasts

Organellar Glue: A Molecular Tool to Artificially Control Chloroplast–Chloroplast Interactions

細胞小器官を接着する新技術「オルガネラグルー」を開発 --オルガネラ間コミュニケーションの操作に期待--. 京都大学プレスリリース. 2022-09-30.Organelles can physically interact to facilitate various cellular processes such as metabolite exchange. Artificially regulating these interactions represents a promising approach for synthetic biology. Here, we artificially controlled chloroplast–chloroplast interactions in living plant cells with our organelle glue (ORGL) technique, which is based on reconstitution of a split fluorescent protein. We simultaneously targeted N-terminal and C-terminal fragments of a fluorescent protein to the chloroplast outer envelope membrane or cytosol, respectively, which induced chloroplast–chloroplast interactions. The cytosolic C-terminal fragment likely functions as a bridge between two N-terminal fragments, thereby bringing the chloroplasts in close proximity to interact. We modulated the frequency of chloroplast–chloroplast interactions by altering the ratio of N- and C-terminal fragments. We conclude that the ORGL technique can successfully control chloroplast–chloroplast interactions in plants, providing a proof of concept for the artificial regulation of organelle interactions in living cells

Mitochondrial movement during its association with chloroplasts in Arabidopsis thaliana

葉緑体との相互作用におけるミトコンドリア運動を発見 --相互作用の制御による効率的な物質代謝の可能性に期待--. 京都大学プレスリリース. 2021-03-19.Plant mitochondria move dynamically inside cells and this movement is classified into two types: directional movement, in which mitochondria travel long distances, and wiggling, in which mitochondria travel short distances. However, the underlying mechanisms and roles of both types of mitochondrial movement, especially wiggling, remain to be determined. Here, we used confocal laser-scanning microscopy to quantitatively characterize mitochondrial movement (rate and trajectory) in Arabidopsis thaliana mesophyll cells. Directional movement leading to long-distance migration occurred at high speed with a low angle-change rate, whereas wiggling leading to short-distance migration occurred at low speed with a high angle-change rate. The mean square displacement (MSD) analysis could separate these two movements. Directional movement was dependent on filamentous actin (F-actin), whereas mitochondrial wiggling was not, but slightly influenced by F-actin. In mesophyll cells, mitochondria could migrate by wiggling, and most of these mitochondria associated with chloroplasts. Thus, mitochondria migrate via F-actin-independent wiggling under the influence of F-actin during their association with chloroplasts in Arabidopsis

Ferrocenylnaphthalene Diimide-Based Electrochemical Detection of Aberrant Methylation in hTERT Gene

Since aberrant methylation at CpG sites is linked to the silencing of tumor suppressor genes, DNA methylation analysis is important for cancer diagnosis. We developed ferrocenylnaphthalene diimide (FND), which has two ferrocenyl moieties at the substituent termini, as an electrochemical indicator for hybridized DNA duplexes. In this study, we attempted to detect aberrant methylation of human telomerase reverse transcriptase gene (hTERT), an efficient cancer marker, using FND-based hybridization coupled with electrochemical detection via a multi-electrode chip