Okayama University

Photosystem I (PSI) converts light energy into chemical energy in photosynthesis, and forms supercomplexes with light-harvesting complexes (LHCI) in eukaryotes to enhance energy capture and transfer. Various numbers and organizations of both PSI core and LHCI subunits are observed in various organisms. A subgroup of haptophytes named coccolithophores play a major role in marine carbon cycle and CaCO3 production, and the light-harvesting antennas of them are named FCPs (fucoxanthin-chlorophyll a/c binding protein) because they bind chlorophyll c and fucoxanthin in addition to chlorophyll a. A structure of a large PSI-FCPI supercomplex containing 38 FCPI subunits has been reported from a coccolithophore Emiliania huxleyi recently (L. Shen et al., Science 389, eadv2132, 2025). Here we solved five cryo-electron microscopy (cryo-EM) structures of PSI-FCPI supercomplexes isolated from another coccolithophore Chrysotila roscoffensis with different detergents at resolutions ranging from 2.3 to 1.7Å. These structures represent discrete PSI-FCPIs containing 1, 4, 6, 8 and 9 FCPI subunits, with FCPIs arranged in a modular fashion. Association of each FCPI module to the PSI core, as well as the arrangement of protein subunits and pigments, are revealed. Contributions of individual antenna modules to excitation energy transfer were calculated and compared with PSI-FCPI supercomplexes from other species of coccolithophores and haptophytes. These results pinpoint the assembly of stable PSI-FCPI supercomplexes in C. roscoffensis and provide insights into how antenna modules contribute to energy transfer in coccolithophores.

A simple and instrument-free colorimetric method for quantitative analysis is reported, in which analyte concentration is determined by measuring the length of a colored adsorption band formed in a packed silica gel column. The proposed method employs a miniature silica gel column that acts as a signal transducer after it adsorbs the colored compound from a solution during its flow in the column. The length of this band increases proportionally with analyte concentration, which enables quantitative detection via simple distance measurement. A theoretical model was developed to describe the relationship between solute concentration, adsorption behavior, and band propagation along the column. The principle was validated via the detection of both iron ions and enzyme-mediated glutamic acid. For Fe2+ analysis, the o-phenanthroline complexation method shows a level of sensitivity comparable to that of conventional spectrophotometry, which enables an almost quantitative recovery of trace iron in tap water. The limit of detection (LOD) and the limit of quantification (LOQ) were estimated to be 0.20μM and 0.60μM for the proposed method and 0.23μM and 0.70μM for spectrophotometry, respectively. The approach was further extended to glutamate detection using a cascade reaction involving glutamate oxidase and horseradish peroxidase with N-benzoyl leucomethylene blue as the chromogenic substrate. The LOD and the LOQ of the proposed method were 0.08 and 0.25μM, and both values are superior to the 0.24μM and 0.73μM obtained using a microplate reader. By integrating preconcentration with a distance-based readout, this method provides a simple yet highly sensitive analytical platform and establishes distance as a quantitative signal for colorimetric detection.

Temperature sensing shapes behavior and cellular functions, yet the molecular basis of thermosensitivity in non-neuronal cells remains poorly defined. Microglia are resident immune cells of the central nervous system that help maintain brain homeostasis via immune surveillance and injury responses. We previously showed that microglial motility is temperature dependent and is largely mediated by the thermosensitive ion channel transient receptor potential vanilloid 4 (TRPV4), a thermosensitive ion channel. However, the contribution of transient receptor potential melastatin 4 (TRPM4) is unclear because suitable Trpm4 mutant mice were not available in our earlier work. Here, we generated functional Trpm4-knockout mice (TRPM4KO) using CRISPR/Cas9 genome editing based on a published strategy. Time-lapse imaging of primary microglia across a range of temperatures revealed that Trpm4 deficiency did not alter temperature-dependent motility in vitro. These results indicate that TRPM4 is dispensable for temperature-dependent microglial motility.

Population growth debates often posit that depopulation would reduce ecological strains. We explore that premise through the case of Japan, where population decline coincides with rising affluence, dietary change, and growing dependence on food imports. Using environmentally-extended multi-regional input-output analysis, we examine changes in Japan’s food-system footprints between 2008-2022 and apply decomposition analysis to identify key drivers. Our findings show that despite a shrinking population, absolute footprints remained stable, while per-capita shares increased by 21-30%, driven primarily by consumption of ultra-processed and animal-based foods, underpinned by affluence and dietary change. Most critically, Japan’s ultra-globalized food system offshores around 90% of its virtual land and water demand, while 54% of embodied GHG emissions are sourced domestically. Hence, Japan’s experience foreshadows a broader structural shift, whereby affluent societies generate disproportionately large per-capita environmental footprints. We emphasize the primacy of consumption and trade in shaping sustainability outcomes in the Anthropocene. • Depopulation in Japan has not reduced food consumption footprints • Rising affluence and caloric intake offset anticipated gains from depopulation • Ultra-processed and animal food products drive most land, water, and GHG footprints • Japan’s consumption footprints are increasingly displaced via international trade • Human depopulation alone is insufficient for sustainable food system transitions

Recent studies have shown that cancer-associated fibroblasts (CAFs), a key component of the tumor microenvironment, are heterogeneous and can be divided into distinct subsets. Although all CAFs were believed to promote tumor progression, recent studies have identified a distinguished subset of tumor-restraining CAFs (rCAFs). It was previously demonstrated that the up-regulation of Meflin (immunoglobulin superfamily containing leucine-rich repeat) expression confers a tumor-restraining role on CAFs in pancreatic, colon, urothelial, and lung cancers. Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer with a poor prognosis. In this study, it was shown that Meflin can be a candidate marker for rCAFs in TNBC. In co-culture experiments with tumor cells and fibroblasts, Meflin overexpression in fibroblasts inhibited tumor cell growth in a three-dimensional culture model and shifted their gene expression profile toward that characteristic of universal or normal fibroblasts. Meflin overexpression in fibroblasts significantly reduced the expression of the chemokine receptor ACKR3 and enhanced that of the prostaglandin synthase PTGDS. This is suggestive of the involvement of these proteins in tumor microenvironment regulation. Furthermore, Meflin deficiency reduced the area of tumor vessels in a TNBC mouse model, highlighting its role in CAF-mediated inhibition of TNBC progression and improvement of drug delivery. Accordingly, Meflin plays a role as a potential functional marker of rCAFs in TNBC.

The emergence of bacteria with both antimicrobial resistance and high virulence has become a global health concern, underscoring the urgent need to elucidate the molecular basis underlying these traits. Here, we employed the silkworm (Bombyx mori) infection model, which is suitable for high-throughput screening, together with an Escherichia coli library containing plasmid clones of all genes from strain W3110, to identify genes whose overexpression enhances virulence. We found that overexpression of the uncharacterized protein YaiX promoted bacterial proliferation in silkworms and increased host lethality. Compared with the empty-vector control, the YaiX-overexpressing strain exhibited resistance to multiple antimicrobial agents with diverse mechanisms of action, including β-lactams, tetracyclines, fluoroquinolones, aminoglycosides, cationic surfactants, and hydrogen peroxide. Sequence analysis revealed that amino acids 18-52 of YaiX contain a transferase hexapeptide domain predicted to form a left-handed parallel β-helix. Overexpression of YaiX mutants lacking regions outside this domain conferred ampicillin resistance, whereas deletion of the hexapeptide domain abolished this phenotype. RNA sequencing and GO enrichment analyses further indicated that YaiX overexpression altered the expression of genes encoding RNA-binding proteins and porins. These findings suggest that YaiX overexpression, through its hexapeptide domain, modulates gene expression and contributes to both multidrug resistance and enhanced virulence in E. coli.