Biology subjects

Yasuda, J.

Publications and source records attributed to Yasuda, J..

10 recordsLinked to original sources

bioRxiv2026

A CO2-limitation-induced cytosolic repressor enables shutdown of the algal CO2-concentrating mechanism

Aquatic photosynthetic organisms face limited CO2 availability because CO2 diffuses slowly in water and most dissolved inorganic carbon (Ci) exists as HCO3- at physiological pH. To overcome this limitation, aquatic photoautotrophs operate CO2-concentrating mechanisms (CCMs) that elevate CO2 around Rubisco and sustain carbon fixation. Because CCM operation consumes energy, it must be suppressed when CO2 becomes abundant, but how this shutdown occurs remains poorly understood. In Chlamydomonas reinhardtii, the nuclear protein CBP1 was identified as a CCM repressor, but its loss causes only partial derepression under high CO2, indicating that an additional mechanism is required for complete shutdown. Here, we identify High-Affinity CCM Repressor 1 (HCR1), a cytosolic protein related to CBP1, as a second repressor. Under high CO2, hcr1 mutants retained high affinity for Ci and derepressed CCM and photoacclimation genes. Combined disruption of HCR1 and CBP1 further increased Ci affinity, approaching that of wild-type cells with a fully induced CCM under CO2 limitation, and promoted the accumulation of Ci transporters. HCR1 loss also prevented redistribution of the chloroplast regulator CAS away from the pyrenoid and was accompanied by retention of a pyrenoid starch sheath. In contrast, LCIB, a chloroplast CO2-recapture protein, relocated normally. Unexpectedly, HCR1 accumulated during CO2 limitation and declined after transfer to high CO2. These results show that CCM shutdown is an active transition rather than the passive reversal of induction. We propose that CBP1 restrains CCM1-dependent transcription, while HCR1 is preloaded during CO2 limitation to terminate the CAS-associated, starch-sheathed, high-affinity state when CO2 becomes replete.

plant biology↗

bioRxiv2025

A nuclear CobW/WW-domain factor represses the CO2-concentrating mechanism in the green alga Chlamydomonas reinhardtii

Microalgae induce a CO2-concentrating mechanism (CCM) to maintain photosynthesis when dissolved CO2 is limited, but how this energy-intensive system is suppressed when CO2 levels rise has remained unclear. The CCM consumes 15-30% of photosynthetically-generated ATP, making its regulation critical for cellular energy balance. Here, we identify a nuclear repressor of the CCM in the green alga Chlamydomonas reinhardtii. A pull-down screen for interacting partners of the master activator CCM1/CIA5 revealed an uncharacterized protein that co-purifies with CCM1 even after high-salt washes. This protein, designated CCM1-binding protein 1 (CBP1), combines a CobW/CobW_C GTP-binding metallochaperone module with a WW domain characteristic of protein-protein interactions. CBP1 colocalizes with CCM1 in the nucleus regardless of CO2 conditions, and the two proteins interact in vivo. CRISPR/Cas9-based disruption of CBP1 does not affect growth or CCM induction under CO2 limitation but derepresses 27 of 41 CCM1-dependent low-CO2 inducible genes under high-CO2 conditions. These include the periplasmic and intracellular carbonic anhydrases (CAH1, LCIB) and inorganic carbon transporters/channels (LCIA, LCI1, BST1, BST3). Consistently, cbp1 mutants accumulate higher levels of CAH1 and LCIB proteins and exhibit a 40% increase in inorganic carbon affinity under high-CO2 conditions; this phenotype is rescued by CBP1 complementation or by acetazolamide treatment. These results demonstrate that CBP1 prevents unnecessary CCM activity when CO2 is abundant, acting upstream of both transporter/channel and carbonic anhydrase modules. Our findings suggest a regulatory mechanism potentially linking zinc-dependent protein chemistry to CCM gene repression, providing insights into energy-efficient CO2 sensing in aquatic photosynthetic organisms. Significance statementAlgae flourish by activating a CO2-concentrating mechanism (CCM) when dissolved CO2 is limited but must deactivate it when CO2 levels increase to conserve energy. We have identified the nuclear protein that functions as this long sought "off switch" in the model green alga. Deletion of this protein causes cells to overproduce CCM transporters and enzymes, maintaining CCM activity even under high CO2 conditions, demonstrating its essential role in suppressing the system when carbon is abundant. This finding illuminates how algae balance energy consumption with carbon capture and offers a new target for engineering strains that fix CO2 more efficiently for biofuel production or climate-mitigation technologies.

plant biology↗

bioRxiv2023

Characteristics of the rumen virome in Japanese cattle

The rumen microbiome is a highly complex ecosystem that includes bacteria, archaea, protozoa, fungi, and viruses. Viruses have a high potential to modify the rumen digestion of feeds via infection and cell lysis of prokaryotes in the rumen; however, understanding of the rumen virome is substantially less advanced due to limitations of the reference genome database. In this study, we conducted metagenomic sequencing of virus-like particles (VLPs) in the rumens of 22 Japanese cattle to construct a reference viral genome catalog of the rumen and uncover the rumen virome characteristics. We succeeded in construction of 8 232 nonredundant viral genomes ([≥]5 kb length and [≥]50% completeness). Among them, putative hosts of 1 223 virus genomes were predicted, and 1 053 virus genomes were taxonomically classified, mainly Siphoviridae, Myoviridae, and Podoviridae. Additionally, 2 764 putative auxiliary metabolic genes (AMGs) were identified in the viral genomes. Importantly, 22 viral genomes associated with archaea in the rumen were identified. Some archaeal viruses have AMGs related to DNA synthesis, suggesting that archaeal viruses control archaeal populations in the rumen and affect methane production from the rumen. Furthermore, we revealed that most rumen viruses were highly rumen-and individual-specific and related to rumen-specific prokaryotes. Overall, the rumen viral catalog and findings of this study will help future analyses to uncover the roles of rumen viruses in feed digestion, productivity, and methane production.

microbiology↗

bioRxiv2022

Novel orthonairovirus in rodents and shrews, Gabon

Small mammals harbor various zoonotic viruses and are natural reservoirs for emerging viruses. Here, we identified a novel orthonairovirus, which is genetically close to the virus suggested the association with human neural diseases. The virus was found in 24.6% of the small mammals captured in Gabon, Central Africa.

microbiology↗

bioRxiv2021

Potential and action mechanism of favipiravir as an antiviral against Junin virus

Favipiravir is a nucleoside analogue that inhibits the replication and transcription of a broad spectrum of RNA viruses, including pathogenic arenaviruses. In this study, we isolated a favipiravir-resistant mutant of Junin virus (JUNV), which is the causative agent of Argentine hemorrhagic fever, and analyzed the antiviral mechanism of favipiravir against JUNV. Two amino acid substitutions, N462D in the RNA-dependent RNA polymerase (RdRp) and A168T in the glycoprotein precursor GPC, were identified in the mutant. GPC-A168T substitution enhanced the efficiency of JUNV internalization, which explains the robust replication kinetics of the mutant in the virus growth analysis. Although RdRp-N462D substitution did not affect polymerase activity levels in a minigenome system, comparisons of RdRp error frequencies showed that the virus with RdRp-D462 possessed a significantly higher fidelity. We also provided experimental evidence for the first time that favipiravir inhibited JUNV through the accumulation of transition mutations, confirming its role as a purine analogue against arenaviruses. Moreover, we showed that treatment with a combination of favipiravir and either ribavirin or remdesivir inhibited JUNV replication in a synergistic manner, blocking the generation of the drug-resistant mutant. Our findings provide new insights for the clinical management and treatment of Argentine hemorrhagic fever.

microbiology↗

bioRxiv2020

5-amino levulinic acid inhibits SARS-CoV-2 infection in vitro

The current COVID-19 pandemic requires urgent development of effective therapeutics. 5-amino levulinic acid (5-ALA) is a naturally synthesized amino acid and has been used for multiple purposes including as an anticancer therapy and as a dietary supplement due to its high bioavailability. In this study, we demonstrated that 5-ALA treatment potently inhibited infection of SARS-CoV-2, a causative agent of COVID-19. The antiviral effects could be detected in both human and non-human cells, without significant cytotoxicity. Therefore, 5-ALA is a candidate as an oral antiviral drug for COVID-19.

microbiology↗

bioRxiv2020

Japonica Array NEO with increased genome-wide coverage and abundant disease risk SNPs

BackgroundIncreasing the power of genome-wide association studies in diverse populations is important for understanding the genetic determinants of disease risks, and large-scale genotype data are collected by genome cohort and biobank projects all over the world. In particular, ethnic-specific SNP arrays are becoming more important because the use of universal SNP arrays has some limitations in terms of cost-effectiveness and throughput. As part of the Tohoku Medical Megabank Project, which integrates prospective genome cohorts into a biobank, we have been developing a series of Japonica Arrays for genotyping participants based on reference panels constructed from whole-genome sequence data of the Japanese population. ResultsWe designed a novel version of the SNP Array for the Japanese population, called Japonica Array NEO, comprising a total of 666,883 SNPs, including tag SNPs of autosomes and X chromosome with pseudoautosomal regions, SNPs of Y chromosome and mitochondria, and known disease risk SNPs. Among them, 654,246 tag SNPs were selected from an expanded reference panel of 3,552 Japanese using pairwise r2 of linkage disequilibrium measures. Moreover, 28,298 SNPs were included for the evaluation of previously identified disease risk SNPs from the literature and databases, and those present in the Japanese population were extracted using the reference panel. The imputation performance of Japonica Array NEO was assessed by genotyping 286 Japanese samples. We found that the imputation quality r2 and INFO score in the minor allele frequency bin >2.5%-5% were >0.9 and >0.8, respectively, and >12 million markers were imputed with an INFO score >0.8. After verification, Japonica Arrays were used to efficiently genotype cohort participants from the sample selection to perform a quality assessment of the raw data; approximately 130,000 genotyping data of >150,000 participants has already been obtained. ConclusionsJaponica Array NEO is a promising tool for genotyping the Japanese population with genome-wide coverage, contributing to the development of genetic risk scores for this population and further identifying disease risk alleles among individuals of East Asian ancestry.

genomics↗

bioRxiv2020

Novel candidates of pathogenic variants of the BRCA1 and BRCA2 genes in a 3,552 Japanese whole-genome sequence dataset (3.5KJPNv2)

Identification of pathogenic germline variants yet no clinical evidence in BRCA genes has become important in patient care of hereditary breast and ovarian cancer syndrome (HBOC). Computational scoring and prospective cohort studies may help to identify such pathogenic variants. We annotated the variants in the BRCA1 and BRCA2 genes from a dataset of 3,552 whole-genome sequences obtained from members of the genome cohorts by Tohoku Medical Megabank Project (TMM) with the InterVar software. Computational impact scores (CADD_phred and Eigen_raw) and minor allele frequencies (MAF) of pathogenic (P) and likely pathogenic (LP) variants in ClinVar are used for filtration criteria. Familial predispositions in cancers among the 35,000 TMM genome cohort participants are analyzed to verify the pathogenicity. Seven potentially pathogenic variants were newly identified. Carriers of these potential pathogenic variants and definite P and LP variants among participants of the TMM prospective cohort show a statistically significant preponderance in cancer onset in sisters in the self-reported cancer history. Filtering by computational scoring and MAF is useful to identify potential pathogenic variants in BRCA genes for Japanese population. These results will be helpful to follow up the carriers of variants of uncertain significance in the HBOC genes.

genetics↗

bioRxiv2019

Construction and Integration of Three De Novo Japanese Human Genome Assemblies toward a Population-Specific Reference

The complete sequence of the human genome is used as a reference for next-generation sequencing analyses. However, some ethnic ancestries are under-represented in the international human reference genome (e.g., GRCh37), especially Asian populations, due to a strong bias toward European and African ancestries in a single mosaic haploid genome consisting chiefly of a single donor. Here, we performed de novo assembly of the genomes from three Japanese male individuals using >100x PacBio long reads and Bionano optical maps per sample. We integrated the genomes using the major allele for consensus, and anchored the scaffolds using sequence-tagged site markers from conventional genetic and radiation hybrid maps to reconstruct each chromosome sequence. The resulting genome sequence, designated JG1, is highly contiguous, accurate, and carries the major allele in the majority of single nucleotide variant sites for a Japanese population. We adopted JG1 as the reference for confirmatory exome re-analyses of seven Japanese families with rare diseases and found that re-analysis using JG1 reduced false-positive variant calls versus GRCh37 while retaining disease-causing variants. These results suggest that integrating multiple genome assemblies from a single ethnic population can aid next-generation sequencing analyses of individuals originated from the population.

genomics↗

bioRxiv2019

3.5KJPNv2, An allele frequency panel of 3,552 Japanese Individuals

The first step towards realizing personalized healthcare is to catalog the genetic variations in a population. Since the dissemination of individual-level genomic information is strictly controlled, it will be useful to construct population-level allele frequency panels and to provide them through easy-to-use interfaces. In the Tohoku Medical Megabank Project, we have sequenced nearly 4,000 individuals from a Japanese population, and constructed an allele frequency panel of 3,552 individuals after removing related samples. The panel is called the 3.5KJPNv2. It was constructed by using a standard pipeline including the 1KGP and gnomAD algorithms to reduce technical biases and to allow comparisons to other populations. Our database is the first largescale panel providing the frequencies of variants present on the X chromosome and on the mitochondria in the Japanese population. All the data are available on our original database at https://jmorp.megabank.tohoku.ac.jp.

genomics↗