start-ver=1.4 cd-journal=joma no-vol=4 cd-vols= no-issue= article-no= start-page=1044 end-page=1055 dt-received= dt-revised= dt-accepted= dt-pub-year=2018 dt-pub=20180512 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Organelle DNA degradation contributes to the efficient use of phosphate in seed plants en-subtitle= kn-subtitle= en-abstract= kn-abstract= Mitochondria and chloroplasts (plastids) both harbour extranuclear DNA that originates from the ancestral endosymbiotic bacteria. These organelle DNAs (orgDNAs) encode limited genetic information but are highly abundant, with multiple copies in vegetative tissues, such as mature leaves. Abundant orgDNA constitutes a substantial pool of organic phosphate along with RNA in chloroplasts, which could potentially contribute to phosphate recycling when it is degraded and relocated. However, whether orgDNA is degraded nucleolytically in leaves remains unclear. In this study, we revealed the prevailing mechanism in which organelle exonuclease DPD1 degrades abundant orgDNA during leaf senescence. The DPD1 degradation system is conserved in seed plants and, more remarkably, we found that it was correlated with the efficient use of phosphate when plants were exposed to nutrient-deficient conditions. The loss of DPD1 compromised both the relocation of phosphorus to upper tissues and the response to phosphate starvation, resulting in reduced plant fitness. Our findings highlighted that DNA is also an internal phosphate-rich reservoir retained in organelles since their endosymbiotic origin. en-copyright= kn-copyright= en-aut-name=TakamiTsuneaki en-aut-sei=Takami en-aut-mei=Tsuneaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=OhnishiNorikazu en-aut-sei=Ohnishi en-aut-mei=Norikazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KuritaYuko en-aut-sei=Kurita en-aut-mei=Yuko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=IwamuraShoko en-aut-sei=Iwamura en-aut-mei=Shoko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=OhnishiMiwa en-aut-sei=Ohnishi en-aut-mei=Miwa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=KusabaMakoto en-aut-sei=Kusaba en-aut-mei=Makoto kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=MimuraTetsuro en-aut-sei=Mimura en-aut-mei=Tetsuro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=SakamotoWataru en-aut-sei=Sakamoto en-aut-mei=Wataru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= affil-num=1 en-affil= Institute of Plant Science and Resources, Okayama University kn-affil= affil-num=2 en-affil= Institute of Plant Science and Resources, Okayama University kn-affil= affil-num=3 en-affil= Faculty of Agriculture, Ryukoku University kn-affil= affil-num=4 en-affil=Department of Biology, Graduate School of Science, Kobe University kn-affil= affil-num=5 en-affil=Department of Biology, Graduate School of Science, Kobe University kn-affil= affil-num=6 en-affil=Graduate School of Science, Hiroshima University kn-affil= affil-num=7 en-affil=Department of Biology, Graduate School of Science, Kobe University kn-affil= affil-num=8 en-affil= Institute of Plant Science and Resources, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=1 cd-vols= no-issue= article-no= start-page=0137 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2017 dt-pub=20170526 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Silicate?SiO reaction in a protoplanetary disk recorded by oxygen isotopes in chondrules en-subtitle= kn-subtitle= en-abstract= kn-abstract= The formation of planetesimals and planetary embryos during the earliest stages of the solar protoplanetary disk largely determined the composition and structure of the terrestrial planets. Within a few million years of the birth of the Solar System, chondrule formation and the accretion of the parent bodies of differentiated achondrites and the terrestrial planets took place in the inner protoplanetary disk 1,2 . Here we show that, for chondrules in unequilibrated enstatite chondrites, high-precision 17O values (where 17O is the deviation of the 17O value from a terrestrial silicate fractionation line) vary significantly (ranging from ?0.49 to +0.84) and fall on an array with a steep slope of 1.27 on a three-oxygen-isotope plot. This array can be explained by the reaction between an olivine-rich chondrule melt and an SiO-rich gas derived from vaporized dust and nebular gas. Our study suggests that a large proportion of the building blocks of planetary embryos formed by successive silicate?gas interaction processes: silicate?H2O followed by silicate?SiO interactions under more oxidized and reduced conditions, respectively, within a few million years of the formation of the Solar System. en-copyright= kn-copyright= en-aut-name=TanakaRyoji en-aut-sei=Tanaka en-aut-mei=Ryoji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=NakamuraEizo en-aut-sei=Nakamura en-aut-mei=Eizo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=10 cd-vols= no-issue=1 article-no= start-page=3022 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=201907 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Origin of ocean island basalts in the West African passive margin without mantle plume involvement en-subtitle= kn-subtitle= en-abstract= kn-abstract= The geochemical variabilities in intraplate basalts (IB) from the West African passive margin (WAPM) region, have generally been employed to indicate the presence of recycled materials in an associated upwelling mantle plume. However, the absence of time-progressive linear hotspot tracks in WAPM-IB make it difficult to explain their genesis solely by the mantle plume hypothesis. Here, we show that the Sr?Nd?Hf?Pb isotopic variations in basalts from most of the WAPM-IB could have mainly attributed to the derivation from two types of fusible regions of the refertilized subcontinental lithospheric mantle (SCLM) and the sub-lithospheric mantle. The locations and magma genesis of WAPM-IB are strongly related to the distance from the Mesozoic rift axis and the structure of the rifted SCLM. The melting of the source region can possibly be attributed to small-scale mantle convection at the base of the SCLM without the involvement of a mantle plume. en-copyright= kn-copyright= en-aut-name=BelayIyasu Getachew en-aut-sei=Belay en-aut-mei=Iyasu Getachew kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TanakaRyoji en-aut-sei=Tanaka en-aut-mei=Ryoji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KitagawaHiroshi en-aut-sei=Kitagawa en-aut-mei=Hiroshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KobayashiKatsura en-aut-sei=Kobayashi en-aut-mei=Katsura kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=NakamuraEizo en-aut-sei=Nakamura en-aut-mei=Eizo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University kn-affil= affil-num=4 en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University kn-affil= affil-num=5 en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University kn-affil= END