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  • 1
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    Proposal of a Twin Aarginine Translocator System-Mediated Constraint against Loss of ATP Synthase Genes from Nonphotosynthetic Plastid Genomes (2015)
    Oxford University Press
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    Publication Date: 2015-09-22
    Description: Organisms with nonphotosynthetic plastids often retain genomes; their gene contents provide clues as to the functions of these organelles. Yet the functional roles of some retained genes—such as those coding for ATP synthase—remain mysterious. In this study, we report the complete plastid genome and transcriptome data of a nonphotosynthetic diatom and propose that its ATP synthase genes may function in ATP hydrolysis to maintain a proton gradient between thylakoids and stroma, required by the twin arginine translocator (Tat) system for translocation of particular proteins into thylakoids. Given the correlated retention of ATP synthase genes and genes for the Tat system in distantly related nonphotosynthetic plastids, we suggest that this Tat-related role for ATP synthase was a key constraint during parallel loss of photosynthesis in multiple independent lineages of algae/plants.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 2
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    Serial block-face scanning electron microscopy combined with double-axis electron beam tomography provides new insight into cellular relationships (2013)
    Oxford University Press
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    Publication Date: 2013-04-02
    Description: To evaluate the advantages of combination of two advanced electron microscopic technologies such as serial block-face scanning electron microscopy and double-axis electron beam tomography, we analyzed the three-dimensional morphology of cellular relationships between dendritic and plasma cells in the synovial membrane from patients with rheumatoid arthritis, using the combined approach.
    Print ISSN: 0022-0744
    Electronic ISSN: 1477-9986
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Published by Oxford University Press on behalf of The Japanese Electron Microscopy Society.
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  • 3
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    Nucleomorph Genome Sequences of Two Chlorarachniophytes, Amorphochlora amoebiformis and Lotharella vacuolata (2015)
    Oxford University Press
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    Publication Date: 2015-06-13
    Description: Many algal groups acquired complex plastids by the uptake of green and red algae through multiple secondary endosymbioses. As a result of gene loss and transfer during the endosymbiotic processes, algal endosymbiont nuclei disappeared in most cases. However, chlorarachniophytes and cryptophytes still possess a relict nucleus, so-called the nucleomorph, of the green and red algal endosymbiont, respectively. Nucleomorph genomes are an interesting and suitable model to study the reductive evolution of endosymbiotically derived genomes. To date, nucleomorph genomes have been sequenced in four cryptophyte species and two chlorarachniophyte species, including Bigelowiella natans (373 kb) and Lotharella oceanica (610 kb). In this study, we report complete nucleomorph genome sequences of two chlorarachniophytes, Amorphochlora amoebiformis and Lotharella vacuolata , to gain insight into the reductive evolution of nucleomorph genomes in the chlorarachniophytes. The nucleomorph genomes consist of three chromosomes totaling 374 and 432 kb in size in A. amoebiformis and L. vacuolata , respectively. Comparative analyses among four chlorarachniophyte nucleomorph genomes revealed that these sequences share 171 function-predicted genes (86% of total 198 function-predicted nucleomorph genes), including the same set of genes encoding 17 plastid-associated proteins, and no evidence of a recent nucleomorph-to-nucleus gene transfer was found. This suggests that chlorarachniophyte nucleomorph genomes underwent most of their reductive evolution prior to the radiation of extent members of the group. However, there are slight variations in genome size, GC content, duplicated gene number, and subtelomeric regions among the four nucleomorph genomes, suggesting that the genomes might be undergoing changes that do not affect the core functions in each species.
    Electronic ISSN: 1759-6653
    Topics: Biology
    Published by Oxford University Press
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  • 4
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    Diurnal Transcriptional Regulation of Endosymbiotically Derived Genes in the Chlorarachniophyte Bigelowiella natans (2016)
    Oxford University Press
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    Publication Date: 2016-09-13
    Description: Chlorarachniophyte algae possess complex plastids acquired by the secondary endosymbiosis of a green alga, and the plastids harbor a relict nucleus of the endosymbiont, the so-called nucleomorph. Due to massive gene transfer from the endosymbiont to the host, many proteins involved in plastid and nucleomorph are encoded by the nuclear genome. Genome sequences have provided a blueprint for the fate of endosymbiotically derived genes; however, transcriptional regulation of these genes remains poorly understood. To gain insight into the evolution of endosymbiotic genes, we performed genome-wide transcript profiling along the cell cycle of the chlorarachniophyte Bigelowiella natans , synchronized by light and dark cycles. Our comparative analyses demonstrated that transcript levels of 7,751 nuclear genes (35.7% of 21,706 genes) significantly oscillated along the diurnal/cell cycles, and those included 780 and 147 genes for putative plastid and nucleomorph-targeted proteins, respectively. Clustering analysis of those genes revealed the existence of transcriptional networks related to specific biological processes such as photosynthesis, carbon metabolism, translation, and DNA replication. Interestingly, transcripts of many plastid-targeted proteins in B. natans were induced before dawn, unlike other photosynthetic organisms. In contrast to nuclear genes, 99% nucleomorph genes were found to be constitutively expressed during the cycles. We also found that the nucleomorph DNA replication would be controlled by a nucleus-encoded viral-like DNA polymerase. The results of this study suggest that nucleomorph genes have lost transcriptional regulation along the diurnal cycles, and nuclear genes exert control over the complex plastid including the nucleomorph.
    Electronic ISSN: 1759-6653
    Topics: Biology
    Published by Oxford University Press
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  • 5
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    Group II Intron-Mediated Trans-Splicing in the Gene-Rich Mitochondrial Genome of an Enigmatic Eukaryote, Diphylleia rotans (2016)
    Oxford University Press
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    Publication Date: 2016-03-01
    Description: Although mitochondria have evolved from a single endosymbiotic event, present day mitochondria of diverse eukaryotes display a great range of genome structures, content and features. Group I and group II introns are two features that are distributed broadly but patchily in mitochondrial genomes across branches of the tree of eukaryotes. While group I intron-mediated trans -splicing has been reported from some lineages distantly related to each other, findings of group II intron-mediated trans -splicing has been restricted to members of the Chloroplastida. In this study, we found the mitochondrial genome of the unicellular eukaryote Diphylleia rotans possesses currently the second largest gene repertoire. On the basis of a probable phylogenetic position of Diphylleia , which is located within Amorphea, current mosaic gene distribution in Amorphea must invoke parallel gene losses from mitochondrial genomes during evolution. Most notably, although the cytochrome c oxidase subunit ( cox ) 1 gene was split into four pieces which located at a distance to each other, we confirmed that a single mature mRNA that covered the entire coding region could be generated by group II intron-mediated trans -splicing. This is the first example of group II intron-mediated trans -splicing outside Chloroplastida. Similar trans- splicing mechanisms likely work for bipartitely split cox2 and nad3 genes to generate single mature mRNAs. We finally discuss origin and evolution of this type of trans -splicing in D. rotans as well as in eukaryotes.
    Electronic ISSN: 1759-6653
    Topics: Biology
    Published by Oxford University Press
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  • 6
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    Polyploidy of Endosymbiotically Derived Genomes in Complex Algae (2014)
    Oxford University Press
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    Publication Date: 2014-04-30
    Description: Chlorarachniophyte and cryptophyte algae have complex plastids that were acquired by the uptake of a green or red algal endosymbiont via secondary endosymbiosis. The plastid is surrounded by four membranes, and a relict nucleus, called the nucleomorph, remains in the periplastidal compartment that is the remnant cytoplasm of the endosymbiont. Thus, these two algae possess four different genomes in a cell: Nuclear, nucleomorph, plastid, and mitochondrial. Recently, sequencing of the nuclear genomes of the chlorarachniophyte Bigelowiella natans and the cryptophyte Guillardia theta has been completed, and all four genomes have been made available. However, the copy number of each genome has never been investigated. It is important to know the actual DNA content of each genome, especially the highly reduced nucleomorph genome, for studies on genome evolution. In this study, we calculated genomic copy numbers in B. natans and G. theta using a real-time quantitative polymerase chain reaction approach. The nuclear genomes were haploid in both species, whereas the nucleomorph genomes were estimated to be diploid and tetraploid, respectively. Mitochondria and plastids contained a large copy number of genomic DNA in each cell. In the secondary endosymbioses of chlorarachniophytes and cryptophytes, the endosymbiont nuclear genomes were highly reduced in size and in the number of coding genes, whereas the chromosomal copy number was increased, as in bacterial endosymbiont genomes. This suggests that polyploidization is a general characteristic of highly reduced genomes in broad prokaryotic and eukaryotic endosymbionts.
    Electronic ISSN: 1759-6653
    Topics: Biology
    Published by Oxford University Press
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  • 7
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    Maximizing T c by tuning nematicity and magnetism in FeSe 1−x S x superconductors (2017)
    Springer Nature
    Details
    Publication Date: 2017-10-26
    Description: Maximizing T c by tuning nematicity and magnetism in FeSe 1−x S x superconductors Nature Communications, Published online: 26 October 2017; doi:10.1038/s41467-017-01277-x The overlap between different phases has hindered the understanding of how each phase affects superconductivity in FeSe. Here, Matsuura et al. achieve a complete separation of non-magnetic nematic and antiferromagnetic phases for FeSe 1-x S x , observing a tetragonal phase in between with a strikingly enhanced T c .
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 8
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    Overexpression of Molecular Chaperone Genes in Nucleomorph Genomes (2014)
    Oxford University Press
    Details
    Publication Date: 2014-05-24
    Description: Chlorarachniophytes and cryptophytes possess complex plastids that were acquired by the ingestion of a green and red algal endosymbiont, respectively. The plastids are surrounded by four membranes, and a relict nucleus, called the nucleomorph, remains in the periplastidal compartment, which corresponds to the remnant cytoplasm of the endosymbiont. Nucleomorphs contain a greatly reduced genome that possesses only several hundred genes with high evolutionary rates. We examined the relative transcription levels of the genes of all proteins encoded by the nucleomorph genomes of two chlorarachniophytes and three cryptophytes using an RNA-seq transcriptomic approach. The genes of two heat shock proteins, Hsp70 and Hsp90, were highly expressed under normal conditions. It has been shown that molecular chaperone overexpression allows an accumulation of genetic mutations in bacteria. Our results suggest that overexpression of heat shock proteins in nucleomorph genomes may play a role in buffering the mutational destabilization of proteins, which might allow the high evolutionary rates of nucleomorph-encoded proteins.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 9
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    Gene Content Evolution in Discobid Mitochondria Deduced from the Phylogenetic Position and Complete Mitochondrial Genome of Tsukubamonas globosa (2014)
    Oxford University Press
    Details
    Publication Date: 2014-02-14
    Description: The unicellular eukaryotic assemblage Discoba (Excavata) comprises four lineages: the Heterolobosea, Euglenozoa, Jakobida, and Tsukubamonadida. Discoba has been considered as a key assemblage for understanding the early evolution of mitochondrial (mt) genomes, as jakobids retain the most gene-rich (i.e., primitive) genomes compared with any other eukaryotes determined to date. However, to date, mt genome sequences have been completed for only a few groups within Discoba, including jakobids, two closely related heteroloboseans, and kinetoplastid euglenozoans. The Tsukubamonadida is the least studied lineage, as the order was only recently established with the description of a sole representative species, Tsukubamonas globosa . The evolutionary relationship between T. globosa and other discobids has yet to be resolved, and no mt genome data are available for this particular organism. Here, we use a "phylogenomic" approach to resolve the relationship between T. globosa , heteroloboseans, euglenozoans, and jakobids. In addition, we have characterized the mt genome of T. globosa (48,463 bp in length), which encodes 52 putative protein-coding and 29 RNA genes. By mapping the gene repertoires of discobid mt genomes onto the well-resolved Discoba tree, we model gene loss events during the evolution of discobid mt genomes.
    Electronic ISSN: 1759-6653
    Topics: Biology
    Published by Oxford University Press
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  • 10
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    IGF-I gene transfer by electroporation promotes regeneration in a muscle injury model (2003)
    Springer Nature
    Details
    Publication Date: 2003-04-01
    Print ISSN: 0969-7128
    Electronic ISSN: 1476-5462
    Topics: Biology , Medicine
    Published by Springer Nature
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