Publications by authors named "Kiminori Toyooka"

Live imaging of secretory cargoes is a powerful method for understanding the mechanisms of membrane trafficking. Inducing the synchronous release of cargoes from an organelle is key for enhancing microscopic observation. We developed an optical cargo-releasing method, 'retention using dark state of LOV2' (RudLOV), which enables precise spatial, temporal, and quantity control during cargo release.

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  • - The study investigates how SARS-CoV-2 buds and transports its virions from the ERGIC to the cell surface, revealing that the vesicles involved have a protein coat known as coatomer complex I (COPI).
  • - Researchers observed that during infection, the distribution of COPI and the ERGIC changed, suggesting they play a role in the virus's replication process.
  • - Depleting a key COPI component, COPB2, confined the SARS-CoV-2 virions within the ERGIC and significantly reduced viral release, indicating that targeting COPI could be a potential strategy for developing antiviral treatments.
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Chloroplasts are photosynthetic organelles that evolved through the endosymbiosis between cyanobacteria-like symbionts and hosts. Many studies have attempted to isolate intact chloroplasts to analyze their morphological characteristics and photosynthetic activity. Although several studies introduced isolated chloroplasts into the cells of different species, their photosynthetic activities have not been confirmed.

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Land plants have evolved a hydrophobic cuticle on the surface of aerial organs as an adaptation to ensure survival in terrestrial environments. Cuticle is mainly composed of lipids, namely cutin and intracuticular wax, with epicuticular wax deposited on plant surface. The composition and permeability of cuticle have a large influence on its ability to protect plants against drought stress.

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Purpose: Retinitis pigmentosa represents a leading cause of blindness in developed countries, yet effective treatments for the disease remain unestablished. Previous studies have demonstrated the potential of stem cell-derived retinal organoid (SC-RO) sheet transplantation to form host-graft synapses and to improve light responsiveness in animal models of retinal degeneration. However, the detailed microstructures of these de novo synapses and their functional contribution have not been well elucidated.

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  • Chloroplasts in different species, like Chlamydomonas reinhardtii and C. applanata, exhibit complex shapes such as cup-like forms and starfish-like structures, challenging the traditional view that they are merely spheroid.
  • Advanced imaging techniques revealed that C. reinhardtii chloroplasts have features like large and small holes that aid in metabolite transport, along with an increase in volume under certain conditions.
  • The study suggests a need to rethink our understanding of chloroplast morphology and evolution, moving away from the idea that chloroplasts are uniform in shape and closely resembling cyanobacteria.
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A comprehensive study of soluble -ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) in the fly genome by RNAi in photoreceptors indicated that knockdown of any of the COPI-SNAREs, , , and , resulted in the same characteristic phenotypes: Golgi stacks gathering on their -side, laterally expanded Golgi cisternae, and a reduced number of discrete Golgi stacks. These Golgi stacks are reminiscent of mammalian Golgi ribbons and Brefeldin A (BFA)-bodies in S2 cells. As previously reported, BFA suppresses -Golgi network (TGN) fission and Golgi stack separation to form a BFA-body, which is a cluster of Golgi stacks cored by recycling endosomes.

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Arctic (E22G) mutation in amyloid-β (Aβ enhances Aβ40 fibril accumulation in Alzheimer's disease (AD). Unlike sporadic AD, familial AD (FAD) patients with the mutation exhibit more Aβ40 in the plaque core. However, structural details of E22G Aβ40 fibrils remain elusive, hindering therapeutic progress.

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  • Sandwich freezing, a technique that sandwiches specimens between copper disks for rapid freezing, is effective for observing the ultrastructure of living yeast and bacteria.
  • Recent findings indicate its success in preserving cell images from glutaraldehyde-fixed cultured cells and various tissues.
  • This study uniquely applies sandwich freezing to Arabidopsis plant tissues, demonstrating excellent preservation of cellular structure for the first time in plant observation.
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  • The study introduces ELASTomics, a new method for analyzing both the mechanical properties and genetic expression of individual cells using electroporation to introduce labeled macromolecules into cells for sequencing.
  • This technique combines insights into cell surface tension and transcriptional regulation, allowing researchers to investigate how these factors relate to various cell types, including cancer cells and senescent cells.
  • ELASTomics can enhance our understanding of cell mechanics and molecular profiles in diverse biological situations, offering a powerful tool for future cellular research.
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During leaf development, the timing of transition from cell proliferation to expansion is an important factor in determining the final organ size. However, the regulatory system involved in this transition remains less understood. To get an insight into this system, we investigated the compensation phenomenon, in which the cell number decreases while the cell size increases in organs with determinate growth.

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In Catharanthus roseus, monoterpenoid indole alkaloids (MIAs) are produced through the cooperation of four cell types, with final products accumulating in specialized cells known as idioblasts and laticifers. To explore the relationship between cellular differentiation and cell type-specific MIA metabolism, we analyzed the expression of MIA biosynthesis in germinating seeds. Embryos from immature and mature seeds were observed via stereomicroscopy, fluorescence microscopy, and electron microscopy.

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Correlative array tomography, combining light and electron microscopy via serial sections, plays a crucial role in the three-dimensional ultrastructural visualization and molecular distribution analysis in biological structures. To address the challenges of aligning fluorescence and electron microscopy images and aligning serial sections of irregularly shaped biological specimens, we developed a diamond notch knife, a new tool for puncturing holes using a diamond needle. The diamond needle featured a triangular and right-angled tip, enabling the drilling of deep holes upon insertion into the polished block face.

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Tailocins are headless phage tail structures that mediate interbacterial antagonism. Although the prototypical tailocins, R- and F-pyocins, in Pseudomonas aeruginosa, and other predominantly R-type tailocins have been studied, their presence in Alphaproteobacteria remains unexplored. Here, we report the first alphaproteobacterial F-type tailocin, named rhizoviticin, as a determinant of the biocontrol activity of Allorhizobium vitis VAR03-1 against crown gall.

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In angiosperms, the transition from floral-organ maintenance to abscission determines reproductive success and seed dispersion. For petal abscission, cell-fate decisions specifically at the petal-cell base are more important than organ-level senescence or cell death in petals. However, how this transition is regulated remains unclear.

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Serine metabolism is involved in various biological processes. Here we investigate primary functions of the phosphorylated pathway of serine biosynthesis in a non-vascular plant Marchantia polymorpha by analyzing knockout mutants of MpPGDH encoding 3-phosphoglycerate dehydrogenase in this pathway. Growth phenotypes indicate that serine from the phosphorylated pathway in the dark is crucial for thallus growth.

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  • Properly patterned cell walls in plants are crucial for their functions, with protoxylem and metaxylem vessel cells showing distinct wall structures.
  • The scaffold protein MIDD1 is key in regulating microtubule patterns, affecting how cell walls are deposited, and its phase separation helps to adjust spacing in these vessel cells.
  • MIDD1's interaction with ROP GTPases is essential, as disruptions can lead to narrower gaps in protoxylem walls, highlighting phase separation's role in fine-tuning cell wall patterns in Arabidopsis thaliana.
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In the final step of cytokinin biosynthesis, the main pathway is the elimination of a ribose-phosphate moiety from the cytokinin nucleotide precursor by phosphoribohydrolase, an enzyme encoded by a gene named LONELY GUY (LOG). This reaction accounts for most of the cytokinin supply needed for regulating plant growth and development. In contrast, the LOG-independent pathway, in which dephosphorylation and deribosylation sequentially occur, is also thought to play a role in cytokinin biosynthesis, but the gene entity and physiological contribution have been elusive.

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In the family Fagaceae, fertilization is delayed by several weeks to 1 year after pollination, leading to 1- or 2-year fruiting species depending on whether fruiting occurs in the same or the next year after flowering. To investigate physiological responses underlying the regulation of delayed fertilization, we monitored seasonal changes in genome-wide gene expression in tissues including leaves and buds over 2 years under natural conditions in one- (Quercus glauca) and 2-year fruiting species (Lithocarpus edulis). Genes associated with metabolic changes in response to winter cold, photosynthesis and cell proliferation, which are essential for survival and growth, showed highly conserved seasonal expression profiles between species.

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  • - This research uncovers a unique mechanism that allows the plant Vigna riukiuensis to tolerate salt, highlighting its ability to accumulate sodium in its leaves, unlike its relative V. nakashimae which restricts sodium allocation.
  • - While initially suspected to have vacuoles for sodium storage, no differences in vacuole formation were found when compared to a salt-sensitive species, V. angularis; instead, an abundance of starch granules in the chloroplasts was observed in V. riukiuensis.
  • - The study suggests that these starch granules may play a role in trapping sodium near them, providing new insights into how certain plants manage salt stress and adding to previous findings related to other species like
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Mobilisation of seed storage reserves is important for seedling establishment in . In this process, sucrose is synthesised from triacylglycerol via core metabolic processes. Mutants with defects in triacylglycerol-to-sucrose conversion display short etiolated seedlings.

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  • Mutations in Lamin A/C disrupt the structure of cardiomyocytes and contribute to dilated cardiomyopathy (DCM) by trapping the transcription factor TEAD1 at the nuclear membrane.
  • Advanced techniques like single-cell RNA sequencing and ATAC-seq were used to explore the molecular mechanisms behind these mutations, revealing an issue with gene expression regulation.
  • Targeting the Hippo pathway shows promise for correcting the gene dysregulation caused by these mutations, suggesting a potential treatment avenue for patients with DCM linked to this specific mutation.
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Different organelles function coordinately in numerous intracellular processes. Photorespiration incidental to photosynthetic carbon fixation is organized across three subcellular compartments: chloroplasts, peroxisomes, and mitochondria. Under light conditions, these three organelles often form a ternary organellar complex in close proximity, suggesting a connection with metabolism during photorespiration.

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Programmed cell death (PCD) in lateral root caps (LRCs) is crucial for maintaining root cap functionality. Endoplasmic reticulum (ER) bodies play important roles in plant immunity and PCD. However, the distribution of ER bodies and their communication with vacuoles in the LRC remain elusive.

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  • Plants produce lipophilic metabolites that help protect against environmental stresses, but the process of how these compounds are secreted into apoplastic spaces is not well understood.
  • Researchers studied shikonin-producing cells from Lithospermum erythrorhizon to analyze the secretion process, noting that shikonin derivatives accumulate in apoplastic spaces and the root epidermis.
  • The study found that triacylglycerol secreted by the cultured cells helps encapsulate shikonin derivatives with phospholipids, suggesting its role as a matrix lipid in the secretion of these specialized metabolites.
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