bioRxiv Science⌕ Search

Biology subjects

Ogata, H.

Publications and source records attributed to Ogata, H..

At least 37 records · Page 2Linked to original sources

Allometric multi-scaling of weight-for-height relation in children and adolescents: Revisiting the theoretical basis of body mass index of thinness and obesity assessment

The body mass index (BMI), defined as weight in kilograms divided by height in meters squared, has been widely used to assess thinness and obesity in all age groups, including children and adolescents. However, the validity and utility of BMI as a reliable measure of nutritional health have been questioned. This study discusses the mathematical conditions that support the validity of BMI based on population statistics. Here, we propose a condition defined as allometric uni-scaling to ensure the validity of BMI as an objective height-adjusted measure. Any given centile curve, including the median curve, in a weight-for-height distribution should be approximated using power-law functions with the same scaling exponent. In contrast, when the scaling exponent varies depending on the position of the centile curve, it is called allometric multi-scaling. By introducing a method for testing these scaling properties using quantile regression, we analyzed a large-scale Japanese database that included 7,863,520 children aged 5-17 years. We demonstrated the remarkable multi-scaling properties at ages 5-13 years for males and 5-11 years for females, and the convergence to uni-scaling with a scaling exponent close to 2 as they approached 17 years of age for both sexes. We confirmed that conventional BMI is appropriate as an objective height-adjusted mass measure at least 17 years of age, close to adulthood, for both males and females. However, the validity of BMI could not be confirmed in younger age groups. Our findings indicate that the growth of childrens weight-for-height relation is much more complex than previously assumed. Therefore, a single BMI-type formula cannot be used to assess thinness and obesity in children and adolescents.

biophysics↗

Eukaryotic genomic data uncover an extensive host range of mirusviruses

A recent marine metagenomic study has revealed the existence of a novel group of viruses designated mirusviruses, which are proposed to form an evolutionary link between two realms of double-stranded DNA viruses, Varidnaviria and Duplodnaviria. Metagenomic data suggest that mirusviruses infect microeukaryotes in the photic layer of the ocean, but their host range remains largely unknown. In this study, we investigated the presence of mirusvirus marker genes in publicly available 1,901 eukaryotic genome assemblies, mainly derived from unicellular eukaryotes, to identify potential hosts of mirusviruses. Mirusvirus marker sequences were identified in 1,348 assemblies spanning 284 genera across eight supergroups of eukaryotes. The habitats of the putative mirusvirus hosts included not only marine but also other diverse environments. Among the major capsid protein (MCP) signals in the genome assemblies, we identified 85 sequences that showed high sequence and structural similarities to reference mirusvirus MCPs. A phylogenetic analysis of these sequences revealed their distant evolutionary relationships with the seven previously reported mirusvirus clades. Most of the scaffolds with these MCP sequences encoded multiple mirusvirus homologs, underscoring the impact of mirusviral infection on the evolution of the host genome. We also identified three circular mirusviral genomes within the genomic data of the oil producing thraustochytrid Schizochytrium sp. and the endolithic green alga Ostreobium quekettii. Overall, mirusviruses probably infect a wide spectrum of eukaryotes and are more diverse than previously reported. HighlightsO_LIMirusvirus signals detected in genomic data from eight eukaryotic supergroups. C_LIO_LIHabits of putative mirusvirus hosts not limited to marine environments. C_LIO_LIMajor capsid sequences from these assemblies show new mirusviral lineages. C_LIO_LIThree circular mirusvirus genomes were identified. C_LI

microbiology↗

Complex genomes of early nucleocytoviruses revealed by ancient origins of viral aminoacyl-tRNA synthetases

Aminoacyl-tRNA synthetases (aaRSs), also known as tRNA ligases, are essential enzymes in translation. Owing to their functional essentiality, these enzymes are conserved in all domains of life and used as informative markers to trace the evolutionary history of cellular organisms. Unlike cellular organisms, viruses generally lack aaRSs because of their obligate parasitic nature, but several large and giant DNA viruses in the phylum Nucleocytoviricota encode aaRSs in their genomes. The discovery of viral aaRSs led to the idea that the phylogenetic analysis of aaRSs can shed light on ancient viral evolution. However, conflicting results have been reported from previous phylogenetic studies: one posited that nucleocytoviruses recently acquired their aaRSs from their host eukaryotes, while another hypothesized that the viral aaRSs have ancient origins. Here, we investigated 4,168 nucleocytovirus genomes, including metagenome-assembled genomes derived from large-scale metagenomic studies. In total, we identified 780 viral aaRS sequences in 273 viral genomes. We generated and examined phylogenetic trees of these aaRSs with a large set of cellular sequences to trace evolutionary relationships between viral and cellular aaRSs. The analyses firmly establish that the origins of some viral aaRSs predate the last common eukaryotic ancestor. Inside viral aaRS clades, we identify intricate evolutionary trajectories of viral aaRSs with horizontal transfers, losses, and displacements. Overall, these results suggest that ancestral nucleocytoviruses already developed complex genomes with an expanded set of aaRSs in the proto-eukaryotic era.

evolutionary biology↗

Global distribution and diversity of marine Parmales

Parmales (Bolidophyceae) is a minor eukaryotic phytoplankton group, sister to diatoms, that exists as two distinct forms of unicellular organisms: silicified cells and naked flagellates. Since their discovery, many field studies of Parmales have been performed, but their global distribution remains under-investigated. Here, we compile over 3,000 marine DNA metabarcoding datasets targeting the V4 region of the 18S rRNA gene from the EukBank database. By linking this large dataset with the latest morphological and genetic information, we provide updated estimates on the diversity and distribution of Parmales in the global ocean at a fine taxonomic resolution. Parmalean amplicon sequence variants (ASVs) were detected in nearly 90% of the analyzed samples. However, the relative abundance of parmaleans in the eukaryotic community is less than 0.2% on average, and the estimated true richness of parmalean ASVs is about 316 ASVs, confirming their low abundance and low diversity. Phylogenetic analysis clearly divides these algae into four clades, and three known morphotypes of silicified cells were classified into three different clades. The abundance of Parmales is generally high in the pole and decreases toward the tropics, and individual clades/subclades show further distinctions in distributions. Overall, our results suggest their clade/subclade-specific adaptation to different ecological niches.

microbiology↗

Gene transfer among viruses substantially contributes to gene gain of giant viruses

Horizontal gene transfers (HGTs) integrate all forms of life and viruses into a vast network of gene flow, which facilitates the transmission of genes beyond vertical inheritance and enhances genomic evolution. HGT is known to occur between closely related viruses. We hypothesized that there is frequent HGT among nucleocytoviruses, a group of diverse but evolutionarily related DNA viruses encoding hundreds to thousands of genes. However, the frequency of viral HGT (vHGT) has not been systematically investigated for nucleocytoviruses. We reconciled over 4,700 gene trees with a robust viral species tree that contains 195 reference viral genomes mainly from cultivation as a reference to infer evolutionary events, including gene gains (gene duplication, origination, and vHGT) and losses. The inferred evolutionary scenarios revealed that the genomes of these viruses have undergone numerous gene gain and loss events, with vHGT representing 28% to 42% of gene gain events in each viral order. By integrating the evolutionary paths of multiple viruses, our data suggest that vHGT is crucial for nucleocytovirus evolution.

evolutionary biology↗

Characterization of sinking and suspended microeukaryotic communities in spring Oyashio waters

Microeukaryotes are important components of sinking particles contributing to carbon export from the surface to deep oceans. The knowledge of the sinking microeukaryotic communities and their dynamics is limited. We applied 18S rDNA metabarcoding method to investigate the microeukaryotic communities in sinking and suspended particles distinguished by marine snow catchers (MSC) during spring in the Oyashio region. Sinking particles displayed distinct communities and lower diversity than did suspended particles. The community compositions of the sinking particles varied with depth, suggesting that microeukaryotes were selectively removed through disaggregation or decomposition during settling. Prymnesiophyceae and diatoms were effectively removed, as indicated by their decreased abundance in the sinking particles at increasing depths. Conversely, phototrophic dinoflagellates maintained a higher abundance in the sinking particles across depths, indicating resistance to disaggregation and decomposition. Heterotrophic dinoflagellates and Spirotrichea were enriched in sinking particles and marine stramenopiles (MAST) groups were enriched in suspended particles. Sinking heterotrophic protist communities in the deep layers were similar to those in the surface layers, whereas they differed from the suspended ones in the same layer. Therefore, heterotrophic protists in surface layers were transported to deeper layers. Overall, our results demonstrate the functional differences among microeukaryotes in the biological carbon pump.

microbiology↗

A 1.5 Mb continuous endogenous viral element region in the arbuscular mycorrhizal fungus Rhizophagus irregularis

Most fungal viruses are RNA viruses and no double-stranded DNA virus that infects fungi is known to date. A recent study detected DNA polymerase genes that originated from large dsDNA viruses in the genomes of basal fungi, suggestive of the existence of dsDNA viruses capable of infecting fungi. In this study, we searched for viral infection signatures in chromosome-level genome assemblies of the arbuscular mycorrhizal fungus Rhizophagus irregularis. We identified a continuous 1.5 Mb putative viral region on a chromosome in R. irregularis strain 4401. Phylogenetic analyses revealed that the viral region is related to viruses in the family Asfarviridae of the phylum Nucleocytoviricota. Single-copy marker genes from Nucleocytoviricota were detected as single-copy genes in the viral region. Furthermore, this viral region was absent in the genomes of four other R. irregularis strains and had fewer signals of fungal transposable elements than the other genomic regions. These results suggest a recent and single insertion of a large dsDNA viral genome in the genome of this fungal strain, providing strong evidence of the recent infection of the fungus by a dsDNA virus.

microbiology↗

A rapid genome-wide analysis of isolated giant viruses only using MinION sequencing

Following the discovery of Acanthamoeba polyphaga mimivirus, diverse giant viruses have been isolated. However, only a small fraction of these isolates has been completely sequenced, limiting our understanding of the genomic diversity of giant viruses. MinION is a portable and low-cost long-read sequencer that can be readily used in a laboratory. Although MinION provides highly error-prone reads that require correction through additional short-read sequencing, recent studies assembled high-quality microbial genomes only using MinION sequencing. Here, we evaluated the accuracy of MinION-only genome assemblies for giant viruses by re-sequencing a prototype marseillevirus. Assembled genomes presented over 99.98% identity to the reference genome with a few gaps, demonstrating a high accuracy of the MinION-only assembly. As a proof of concept, we de novo assembled five newly isolated viruses. Average nucleotide identities to their closest known relatives suggest that the isolates represent new species of marseillevirus, pithovirus, and mimivirus. Assembly of subsampled reads demonstrated that their taxonomy and genomic composition could be analyzed at the 50x sequencing coverage. We also identified a pithovirus gene whose homologues were detected only in metagenome-derived relatives. Collectively, we propose that MinION-only assembly is an effective approach to rapidly perform a genome-wide analysis of isolated giant viruses.

microbiology↗

Genomic adaptation of giant viruses in polar oceans

Despite being perennially frigid, polar oceans form an ecosystem hosting high and unique biodiversity. Various organisms show different adaptative strategies in this habitat, but how viruses adapt to this environment is largely unknown. Viruses of phyla Nucleocytoviricota and Mirusviricota are groups of eukaryote-infecting large and giant DNA viruses with genomes encoding a variety of functions. Here, by leveraging the Global Ocean Eukaryotic Viral database, we investigate the biogeography and functional repertoire of these viruses at a global scale. We first confirm the existence of an ecological barrier that clearly separates polar and nonpolar viral communities, and demonstrate that temperature drives dramatic changes in the virus-host network at the polar/nonpolar boundary. Ancestral niche reconstruction suggests that adaptation of these viruses to polar conditions has occurred repeatedly over the course of evolution, with polar-adapted viruses in the modern ocean being scattered across their phylogeny. Numerous viral genes are specifically associated with polar adaptation, although most of their homologues are not identified as polar-adaptive genes in eukaryotes. These results suggest that giant viruses adapt to cold environments by changing their functional repertoire, and this viral evolutionary strategy is independent of the polar adaptation of their hosts.

microbiology↗

Global observation of plankton communities from space

Satellite remote sensing from space is a powerful way to monitor the global dynamics of marine plankton. Previous research has focused on developing models to predict the size or taxonomic groups of phytoplankton. Here we present an approach to identify representative communities from a global plankton network that included both zooplankton and phytoplankton and using global satellite observations to predict their biogeography. Six representative plankton communities were identified from a global co-occurrence network inferred using a novel rDNA 18S V4 planetary-scale eukaryotic metabarcoding dataset. Machine learning techniques were then applied to train a model that predicted these representative communities from satellite data. The model showed an overall 67% accuracy in the prediction of the representative communities. The prediction based on 17 satellite-derived parameters showed better performance than based only on temperature and/or the concentration of chlorophyll a. The trained model allowed to predict the global spatiotemporal distribution of communities over 19-years. Our model exhibited strong seasonal changes in the community compositions in the subarctic-subtropical boundary regions, which were consistent with previous field observations. This network-oriented approach can easily be extended to more comprehensive models including prokaryotes as well as viruses.

ecology↗

Genome analysis of Parmales, a sister group of diatoms, reveals the evolutionary specialization of diatoms from phago-mixotrophs to photoautotrophs

The order Parmales (Bolidophyceae) is a minor group of pico-sized eukaryotic marine phytoplankton that contains species with cells surrounded by silica plates. Previous studies revealed that Parmales is a member of ochrophytes and sister to diatoms (Bacillariophyta), the most successful phytoplankton group in the modern ocean. Therefore, parmalean genomes can serve as a reference to elucidate both the evolutionary events that differentiated these two lineages and the genomic basis for the ecological success of diatoms vs. the more cryptic lifestyle of parmaleans. Here, we compared the genomes of eight parmaleans and five diatoms to explore their physiological and evolutionary differences. Parmaleans were predicted to be phago-mixotrophs. By contrast, diatoms have undergone loss of genes related to phagocytosis, indicating the ecological specialization from phago-mixotroph to photoautotroph in the early evolution of diatoms. Furthermore, diatoms showed significant enrichment in gene sets involved in silica metabolism, nutrient uptake capacity, carbon concentrating mechanisms, and iron uptake in comparison with parmaleans. Overall, our results suggest a strong evolutionary link between the loss of phago-mixotrophy and specialization to a silicified photoautotrophic life stage early in diatom evolution after diverging from the Parmales lineage.

microbiology↗

Discovery of a class of giant virus relatives displaying unusual functional traits and prevalent within plankton: the Mirusviricetes

DNA viruses have a major influence on the ecology and evolution of cellular organisms, but their overall diversity and evolutionary trajectories remain elusive. Here, we performed a phylogeny-guided genome-resolved metagenomic survey of the sunlit oceans and discovered plankton-infecting relatives of herpesviruses that form a putative new phylum dubbed Mirusviricota. The virion morphogenesis module of this large monophyletic clade is typical of viruses from the realm Duplodnaviria, with the major capsid protein fold being a likely structural intermediate between the capsid proteins of Caudoviricetes (tailed phages) and Herpesvirales (animal-infecting viruses). Yet, a substantial fraction of Mirusviricota genes, including hallmark transcription machinery genes missing in herpesviruses, are closely related homologs of large and giant eukaryotic DNA viruses from another viral realm. The remarkable chimeric attributes of Mirusviricota provide missing links in the evolution of both herpesviruses and giant viruses. Furthermore, mirusviruses are widespread and transcriptionally active from pole to pole, encoding complex functional traits used during the infection of microbial eukaryotes. The Mirusviricota prevalence, functional activity, diversification, and atypical evolutionary traits point to a lasting role of mirusviruses in the ecology of marine ecosystems that might have not only predated but also contributed to the emergence of herpesviruses and giant viruses.

evolutionary biology↗

Prevalence of viral frequency-dependent infection in coastal marine prokaryotes revealed using monthly time series virome analysis

Viruses infecting marine prokaryotes have large impacts on the diversity and dynamics of their hosts. Model systems suggest viral infection is frequency-dependent and constrained by the virus-host encounter rate. However, it is unclear whether the frequency-dependent infection is pervasive among the abundant prokaryotic populations with different growth strategies (i.e. r-strategy and K-strategy). To address this question, we performed a comparison of prokaryotic and viral communities using 16S rRNA amplicon and virome sequencing based on samples collected monthly for two years at a Japanese coastal site, Osaka Bay. Concurrent seasonal shifts observed in prokaryotic and viral community dynamics indicated that abundances of viruses correlated with that of their predicted host phyla (or classes). Co-occurrence network analysis between abundant prokaryotes and viruses revealed 6 423 co-occurring pairs, suggesting a tight coupling of host and viral abundances and their "one to many" correspondence. Although dominant K-strategist like species, such as SAR11, showed few co-occurring viruses, a fast succession of their viruses suggests viruses infecting these populations changed continuously. Our results suggest the frequency-dependent viral infection prevailed in coastal marine prokaryotes regardless of host taxa and growth strategy.

microbiology↗

Tight association between microbial eukaryote and Imitervirales communities in the Pacific Arctic Ocean

Viruses are important regulatory factors of marine microbial community including microeukaryotes. However, little is known about their role in the northern Chukchi Sea of the Arctic basin, which remains oligotrophic conditions in summer. To elucidate linkages of microbial eukaryotic community with viruses as well as environmental variables, we investigated the community structures of microeukaryotes (3-144 {micro}m and 0.2-3 {micro}m size fractions) and Imitervirales (0.2-3 {micro}m size fraction), a major group of viruses infecting marine microeukaryotes. Surface water samples were collected at 21 ocean stations located in the northeastern Chukchi Sea (NECS), an adjacent area outside the Beaufort Gyre (Adjacent Sea; AS), and two melt ponds on sea ice in the summer of 2018. At the ocean stations, nutrient concentrations were low in most of the locations expect at the shelf in the AS. The community variations were significantly correlated between eukaryotes and Imitervirales, even within the NECS characterized by relatively homogeneous environmental conditions. The association of the eukaryotic community with the viral community was stronger than that with geographical and physicochemical environmental factors. These results suggest that Imitervirales are actively infecting their hosts even in cold and oligotrophic sea water in the Arctic Ocean.

molecular biology↗

RNA-seq of the medusavirus suggests remodeling of the host nuclear environment at an early infection stage

Nucleo-cytoplasmic large DNA viruses (NCLDVs) undergo a cytoplasmic or nucleo-cytoplasmic cycle, and the latter involves both nuclear and cytoplasmic compartments to proceed viral replication. Medusavirus, a recently isolated NCLDV, has a nucleo-cytoplasmic replication cycle in amoebas during which the host nuclear membrane apparently remains intact, a unique feature among amoeba-infecting giant viruses. The medusavirus genome lacks most transcription genes but encodes a full set of histone genes. To investigate the infection strategy, we performed a time-course RNA-seq experiment. All the viral genes were transcribed and classified into five temporal expression clusters. The immediate early genes (cluster 1, 42 genes) were mostly (83%) of unknown functions, frequently (95%) associated with a palindromic promoter-like motif, and enriched (45%) in putative nuclear-targeting genes. The later genes (clusters 2-5) were assigned to various functional categories. The viral linker histone H1 gene was in cluster 1, whereas the four core histone genes were in cluster 3, suggesting they had distinct roles during the course of the virus infection. The transcriptional profile of the host amoeba, Acanthamoeba castellanii, genes was greatly altered post-infection. Several encystment-related host genes showed increased representation levels at 48 hours post-infection, which is consistent with the previously reported amoeba encystment upon medusavirus infection. Overall, the transcriptional landscape during the course of medusavirus infection suggests that the virus modifies the host nuclear environment immediately after the initiation of infection. - ImportanceMedusavirus is an amoeba-infecting giant virus that was isolated from a hot spring in Japan. It belongs to the proposed family "Medusaviridae" in the phylum Nucleocytoviricota. Unlike other amoeba-infecting giant viruses, medusavirus initiates its DNA replication in the host nucleus without disrupting the nuclear membrane. Our RNA-seq analysis of its infection course uncovered ordered viral gene expression profiles. We identified temporal expression clusters of viral genes and associated putative promoter motifs. The subcellular localization prediction showed a clear spatiotemporal correlation between gene expression timing and localization of the encoded proteins. Notably, the immediate early expression cluster was enriched in genes targeting the nucleus, suggesting the priority of remodeling the host intra-nuclear environment during infection. The transcriptional profile of the amoeba genes was greatly altered post-infection. Notably, the expression of encystment-related genes increased 48 hours post-infection, suggesting that encystment may be an antiviral strategy of amoeba.

microbiology↗

Discovery of viral myosin genes with complex evolutionary history within plankton

Nucleocytoplasmic large DNA viruses (NCLDVs) infect diverse eukaryotes and form a group of viruses with capsids encapsulating large genomes. Recent studies are increasingly revealing a spectacular array of functions encoded in their genomes, including genes for energy metabolisms, nutrient uptake, as well as cytoskeleton. Here, we report the discovery of genes homologous to myosins, the major eukaryotic motor proteins previously unrecognized in the virosphere, in environmental genomes of NCLDVs from the surface of the oceans. Interestingly, these genes were often accompanied by kinesin genes in the environmental genomes, suggesting a role of these viral proteins in the intracellular viral particle transport. Phylogenetic analyses indicate that most viral myosins (named "virmyosins") belong to the Imitervirales order, except for one belonging to the Phycodnaviridae family. On the one hand, the phylogenetic positions of virmyosin-encoding Imitervirales are scattered within the Imitervirales. On the other hand, Imitervirales virmyosin genes form a monophyletic group in the phylogeny of diverse myosin sequences. Furthermore, phylogenetic trends for the virmyosin genes and viruses containing them were incongruent. Based on these results, we argue that multiple transfers of myosin homologs have occurred not only from eukaryotes to viruses but also between viruses, supposedly during co-infections of the same host.

microbiology↗

Insights into biotic and abiotic modulation of ocean mesopelagic communities

For decades, marine plankton have been investigated for their capacity to modulate biogeochemical cycles and provide fishery resources. Between the sunlit (epipelagic) layer and the deep dark waters, lies a vast and heterogeneous part of the ocean: the mesopelagic zone. How plankton composition is shaped by environment has been well-explored in the epipelagic but much less in the mesopelagic ocean. Here, we conducted comparative analyses of trans-kingdom community assemblages thriving in the mesopelagic oxygen minimum zone (OMZ), mesopelagic oxic, and their epipelagic counterparts. We identified nine distinct types of intermediate water masses that correlate with variation in mesopelagic community composition. Furthermore, oxygen, NO - and particle flux together appeared as the main drivers governing these communities. Novel taxonomic signatures emerged from OMZ while a global co-occurrence network analysis showed that about 70% of the abundance of mesopelagic plankton groups is organized into three community modules. One module gathers prokaryotes, pico-eukaryotes and Nucleo-Cytoplasmic Large DNA Viruses (NCLDV) from oxic regions, and the two other modules are enriched in OMZ prokaryotes and OMZ pico-eukaryotes, respectively. We hypothesize that OMZ conditions led to a diversification of ecological niches, and thus communities, due to selective pressure from limited resources. Our study further clarifies the interplay between environmental factors in the mesopelagic oxic and OMZ, and the compositional features of communities.

ecology↗

Year-round dynamics of amplicon sequence variant communities differ among eukaryotes, Mimiviridae, and prokaryotes in a coastal ecosystem

Coastal seawater is the habitat of different microbial communities. These communities are affected by seasonal environmental changes and fluctuating nutrient availability, as well as competitive and cooperative interspecific interactions. In this work, we investigated the seasonal dynamics of communities of eukaryotes, a major group of double-stranded DNA viruses infecting eukaryotes (i.e. Mimiviridae), as well as prokaryotes in the Uranouchi Inlet, Kochi, Japan. We performed metabarcoding using ribosomal RNA genes and the Mimiviridae polB gene as marker genes in 43 seawater samples collected during 20 months. Communities characterized by the compositions of amplicon sequence variants (ASVs) showed synchronic seasonal cycles for eukaryotes, Mimiviridae, and prokaryotes. However, the community dynamics showed intriguing differences in several aspects such as the recovery rate after a year. We further show that the differences in the community dynamics can be explained by differences in the recurrence/persistence levels of individual ASVs among eukaryotes, Mimiviridae, and prokaryotes. Mimiviridae ASVs were less persistent than eukaryotic ASVs, and prokaryotic ASVs were the most persistent. We argue that the differences in the specificity of interactions (i.e. virus-eukaryote vs prokaryote-eukaryote) as well as the survival strategies are at the origin of the distinct community dynamics among eukaryotes, Mimiviridae, and prokaryotes. One sentence summaryA one year observation of coastal microbial communities revealed similar but different community dynamics for eukaryotes, a group of large viruses, and prokaryotes.

microbiology↗