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S Aoki - One of the best experts on this subject based on the ideXlab platform.

  • water vapor vertical profiles on mars in dust storms observed by tgo nomad
    Journal of Geophysical Research, 2019
    Co-Authors: Ann Carine Vandaele, Frank Daerden, Giuliano Liuzzi, I R Thomas, Justin T Erwin, Loïc Trompet, Geronimo L. Villanueva, S Aoki, Severine Robert
    Abstract:

    It has been suggested that dust storms efficiently transport water vapor from the near‐surface to the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust storms is important to understand water escape. During Martian Year 34, two dust storms occurred on Mars: a global dust storm (June to mid‐September 2018) and a regional storm (January 2019). Here we present water vapor vertical profiles in the periods of the two dust storms (Ls = 162–260° and Ls = 298–345°) from the solar occultation measurements by Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). We show a significant increase of water vapor abundance in the middle atmosphere (40–100 km) during the global dust storm. The water enhancement rapidly occurs following the onset of the storm (Ls~190°) and has a peak at the most active period (Ls~200°). Water vapor reaches very high altitudes (up to 100 km) with a volume mixing ratio of ~50 ppm. The water vapor abundance in the middle atmosphere shows high values consistently at 60°S‐60°N at the growth phase of the dust storm (Ls = 195°–220°), and peaks at latitudes greater than 60°S at the decay phase (Ls = 220°–260°). This is explained by the seasonal change of meridional circulation: from equinoctial Hadley circulation (two Cells) to the solstitial one (a single Pole‐to‐Pole Cell). We also find a conspicuous increase of water vapor density in the middle atmosphere at the period of the regional dust storm (Ls = 322–327°), in particular at latitudes greater than 60°S.

Satoru Kobayashi - One of the best experts on this subject based on the ideXlab platform.

  • role of mitochondrial ribosome dependent translation in germline formation in drosophila embryos
    Mechanisms of Development, 2005
    Co-Authors: Reiko Amikura, Kimihiro Sato, Satoru Kobayashi
    Abstract:

    In Drosophila, mitochondrially encoded ribosomal RNAs (mtrRNAs) form mitochondrial-type ribosomes on the polar granules, distinctive organelles of the germ plasm. Since a reduction in the amount of mtrRNA results in the failure of embryos to produce germline progenitors, or Pole Cells, it has been proposed that translation by mitochondrial-type ribosomes is required for germline formation. Here, we report that injection of kasugamycin (KA) and chloramphenicol (CH), inhibitors for prokaryotic-type translation, disrupted Pole Cell formation in early embryos. The number of mitochondrial-type ribosomes on polar granules was significantly decreased by KA treatment, as shown by electron microscopy. In contrast, ribosomes in the mitochondria and mitochondrial activity were unaffected by KA and CH. We further found that injection of KA and CH impairs production of Germ Cell-less (Gcl) protein, which is required for Pole Cell formation. The above observations suggest that mitochondrial-type translation is required for Pole Cell formation, and Gcl is a probable candidate for the protein produced by this translation system.

  • presence of mitochondria type ribosomes outside mitochondria in germ plasm of drosophila embryos
    Proceedings of the National Academy of Sciences of the United States of America, 2001
    Co-Authors: Reiko Amikura, Akira Nakamura, Maki Kashikawa, Satoru Kobayashi
    Abstract:

    Mitochondrially encoded large and small ribosomal RNAs (mtlrRNA and mtsrRNA) are transported out of mitochondria to polar granules, the distinctive organelles of germ plasm in Drosophila. Reduction of the extramitochondrial mtlrRNA amount leads to the failure of embryos to form the germ-line progenitors, or Pole Cells, suggesting that mtlrRNA, along with mtsrRNA, functions on the polar granules to specify the germ line. In this study, we provide several lines of evidence showing that there are mitochondria-type ribosomes on the polar granules during a short period before Pole Cell formation. Our ultrastructural analysis reveals that these ribosomes include both mitochondrial rRNAs and at least two mitochondrial ribosomal proteins (S12 and L7/L12). Furthermore, these ribosomes are integrated into well developed polysomes on the surface of polar granules. We propose that translation dependent on mitochondria-type ribosomes is an important mechanism underlying germ-line formation.

  • mitochondrial small ribosomal rna is present on polar granules in early cleavage embryos of drosophila melanogaster
    Development Growth & Differentiation, 1999
    Co-Authors: Maki Kashikawa, Reiko Amikura, Akira Nakamura, Satoru Kobayashi
    Abstract:

    In Drosophila, formation of the germline progenitors, the Pole Cells, is induced by polar plasm localized in the posterior Pole region of early embryos. The polar plasm contains polar granules, which act as a repository for the factors required for Pole Cell formation. It has been postulated that the factors are stored as mRNA and are later translated on polysomes attached to the surface of polar granules. Here, the identification of mitochondrial small ribosomal RNA (mtsrRNA) as a new component of polar granules is described. The mtsrRNA was enriched in the polar plasm of the embryos immediately after oviposition and remained in the polar plasm throughout the cleavage stage until Pole Cell formation. In situ hybridization at an ultrastructural level revealed that mtsrRNA was enriched on the surface of polar granules in cleavage embryos. Furthermore, the localization of mtsrRNA in the polar plasm depended on the normal function of oskar, vasa and tudor genes, which are all required for Pole Cell formation. The temporal and spatial distribution of mtsrRNA is essentially identical to that of mitochondrial large ribosomal RNA (mtlrRNA), which has been shown to be required for Pole Cell formation. Taken together, it is speculated that mtsrRNA and mtlrRNA are part of the translation machinery localized to polar granules, which is essential for Pole Cell formation.

  • presence of mitochondrial large ribosomal rna outside mitochondria in germ plasm of drosophila melanogaster
    Science, 1993
    Co-Authors: Satoru Kobayashi, Reiko Amikura, Masukichi Okada
    Abstract:

    Mitochondrial large ribosomal RNA (mtlrRNA) has been identified as a cytoplasmic factor that induces Pole Cell formation in embryos whose ability to form a germ line has been abolished by treatment with ultraviolet light. In situ hybridization analyses reveal that mtlrRNA is enriched in germ plasm and is tightly associated with polar granules, the distinctive organelles of germ plasm, which supports the idea that mtlrRNA functions in Pole Cell formation. This suggests that a product from the mitochondrial genome, along with nuclear products, participates in a key event in embryonic development: determination of the germ line.

Severine Robert - One of the best experts on this subject based on the ideXlab platform.

  • water vapor vertical profiles on mars in dust storms observed by tgo nomad
    Journal of Geophysical Research, 2019
    Co-Authors: Ann Carine Vandaele, Frank Daerden, Giuliano Liuzzi, I R Thomas, Justin T Erwin, Loïc Trompet, Geronimo L. Villanueva, S Aoki, Severine Robert
    Abstract:

    It has been suggested that dust storms efficiently transport water vapor from the near‐surface to the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust storms is important to understand water escape. During Martian Year 34, two dust storms occurred on Mars: a global dust storm (June to mid‐September 2018) and a regional storm (January 2019). Here we present water vapor vertical profiles in the periods of the two dust storms (Ls = 162–260° and Ls = 298–345°) from the solar occultation measurements by Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). We show a significant increase of water vapor abundance in the middle atmosphere (40–100 km) during the global dust storm. The water enhancement rapidly occurs following the onset of the storm (Ls~190°) and has a peak at the most active period (Ls~200°). Water vapor reaches very high altitudes (up to 100 km) with a volume mixing ratio of ~50 ppm. The water vapor abundance in the middle atmosphere shows high values consistently at 60°S‐60°N at the growth phase of the dust storm (Ls = 195°–220°), and peaks at latitudes greater than 60°S at the decay phase (Ls = 220°–260°). This is explained by the seasonal change of meridional circulation: from equinoctial Hadley circulation (two Cells) to the solstitial one (a single Pole‐to‐Pole Cell). We also find a conspicuous increase of water vapor density in the middle atmosphere at the period of the regional dust storm (Ls = 322–327°), in particular at latitudes greater than 60°S.

Jeremy A. Lynch - One of the best experts on this subject based on the ideXlab platform.

  • Transcriptomic and functional analysis of the oosome, a unique form of germ plasm in the wasp Nasonia vitripennis
    BMC biology, 2019
    Co-Authors: Honghu Quan, Deanna Arsala, Jeremy A. Lynch
    Abstract:

    The oosome is the germline determinant in the wasp Nasonia vitripennis and is homologous to the polar granules of Drosophila. Despite a common evolutionary origin and developmental role, the oosome is morphologically quite distinct from polar granules. It is a solid sphere that migrates within the cytoplasm before budding out and forming Pole Cells. To gain an understanding of both the molecular basis of oosome development and the conserved essential features of germ plasm, we quantified and compared transcript levels between embryo fragments that contained the oosome and those that did not. The identity of the differentially localized transcripts indicated that Nasonia uses a distinct set of molecules to carry out conserved germ plasm functions. In addition, functional testing of a sample of localized transcripts revealed potentially novel mechanisms of ribonucleoprotein assembly and Pole Cell Cellularization in the wasp. Our results demonstrate that the composition of germ plasm varies significantly within Holometabola, as very few mRNAs share localization to the oosome and polar granules. Some of this variability appears to be related to the unique properties of the oosome relative to the polar granules in Drosophila, and some may be related to differences in Pole formation between species. This work will serve as the basis for further investigation into the patterns of germline determinant evolution among insects, the molecular basis of the unique properties of the oosome, and the incorporation of novel components into developmental networks.

  • Transcriptomic and functional analysis of the oosome, a unique form of germ plasm in the wasp Nasonia vitripennis
    2018
    Co-Authors: Honghu Quan, Jeremy A. Lynch
    Abstract:

    Background: The oosome is the germline determinant in the wasp Nasonia vitripennis and is homologous to the polar granules of Drosophila. Despite a common evolutionary origin and developmental role, the oosome is morphologically quite distinct from polar granules. It is a solid sphere that migrates within the cytoplasm before budding out and forming Pole Cells. Results: To gain an understanding of both the molecular basis of the novel form of the oosome, and the conserved essential features of germ plasm, we quantified and compared transcript levels between embryo fragments that contained the oosome, and those that did not. The identity of the localized transcripts indicated that Nasonia uses different molecules to carry out conserved germ plasm functions. In addition, functional testing of a sample of localized transcripts revealed potentially novel mechanisms of ribonucleoprotein assembly and Pole Cell Cellularization in the wasp. Conclusions: Our results demonstrate that numerous novel and unexpected molecules have been recruited in order produce the unique characteristics of the oosome and Pole Cell formation in Nasonia. This work will serve as the basis for further investigation into the patterns of germline determinant evolution among insects, the molecular basis of extreme morphology of ribonucleoproteins, and the incorporation of novel components into developmental networks.

Reiko Amikura - One of the best experts on this subject based on the ideXlab platform.

  • role of mitochondrial ribosome dependent translation in germline formation in drosophila embryos
    Mechanisms of Development, 2005
    Co-Authors: Reiko Amikura, Kimihiro Sato, Satoru Kobayashi
    Abstract:

    In Drosophila, mitochondrially encoded ribosomal RNAs (mtrRNAs) form mitochondrial-type ribosomes on the polar granules, distinctive organelles of the germ plasm. Since a reduction in the amount of mtrRNA results in the failure of embryos to produce germline progenitors, or Pole Cells, it has been proposed that translation by mitochondrial-type ribosomes is required for germline formation. Here, we report that injection of kasugamycin (KA) and chloramphenicol (CH), inhibitors for prokaryotic-type translation, disrupted Pole Cell formation in early embryos. The number of mitochondrial-type ribosomes on polar granules was significantly decreased by KA treatment, as shown by electron microscopy. In contrast, ribosomes in the mitochondria and mitochondrial activity were unaffected by KA and CH. We further found that injection of KA and CH impairs production of Germ Cell-less (Gcl) protein, which is required for Pole Cell formation. The above observations suggest that mitochondrial-type translation is required for Pole Cell formation, and Gcl is a probable candidate for the protein produced by this translation system.

  • presence of mitochondria type ribosomes outside mitochondria in germ plasm of drosophila embryos
    Proceedings of the National Academy of Sciences of the United States of America, 2001
    Co-Authors: Reiko Amikura, Akira Nakamura, Maki Kashikawa, Satoru Kobayashi
    Abstract:

    Mitochondrially encoded large and small ribosomal RNAs (mtlrRNA and mtsrRNA) are transported out of mitochondria to polar granules, the distinctive organelles of germ plasm in Drosophila. Reduction of the extramitochondrial mtlrRNA amount leads to the failure of embryos to form the germ-line progenitors, or Pole Cells, suggesting that mtlrRNA, along with mtsrRNA, functions on the polar granules to specify the germ line. In this study, we provide several lines of evidence showing that there are mitochondria-type ribosomes on the polar granules during a short period before Pole Cell formation. Our ultrastructural analysis reveals that these ribosomes include both mitochondrial rRNAs and at least two mitochondrial ribosomal proteins (S12 and L7/L12). Furthermore, these ribosomes are integrated into well developed polysomes on the surface of polar granules. We propose that translation dependent on mitochondria-type ribosomes is an important mechanism underlying germ-line formation.

  • mitochondrial small ribosomal rna is present on polar granules in early cleavage embryos of drosophila melanogaster
    Development Growth & Differentiation, 1999
    Co-Authors: Maki Kashikawa, Reiko Amikura, Akira Nakamura, Satoru Kobayashi
    Abstract:

    In Drosophila, formation of the germline progenitors, the Pole Cells, is induced by polar plasm localized in the posterior Pole region of early embryos. The polar plasm contains polar granules, which act as a repository for the factors required for Pole Cell formation. It has been postulated that the factors are stored as mRNA and are later translated on polysomes attached to the surface of polar granules. Here, the identification of mitochondrial small ribosomal RNA (mtsrRNA) as a new component of polar granules is described. The mtsrRNA was enriched in the polar plasm of the embryos immediately after oviposition and remained in the polar plasm throughout the cleavage stage until Pole Cell formation. In situ hybridization at an ultrastructural level revealed that mtsrRNA was enriched on the surface of polar granules in cleavage embryos. Furthermore, the localization of mtsrRNA in the polar plasm depended on the normal function of oskar, vasa and tudor genes, which are all required for Pole Cell formation. The temporal and spatial distribution of mtsrRNA is essentially identical to that of mitochondrial large ribosomal RNA (mtlrRNA), which has been shown to be required for Pole Cell formation. Taken together, it is speculated that mtsrRNA and mtlrRNA are part of the translation machinery localized to polar granules, which is essential for Pole Cell formation.

  • presence of mitochondrial large ribosomal rna outside mitochondria in germ plasm of drosophila melanogaster
    Science, 1993
    Co-Authors: Satoru Kobayashi, Reiko Amikura, Masukichi Okada
    Abstract:

    Mitochondrial large ribosomal RNA (mtlrRNA) has been identified as a cytoplasmic factor that induces Pole Cell formation in embryos whose ability to form a germ line has been abolished by treatment with ultraviolet light. In situ hybridization analyses reveal that mtlrRNA is enriched in germ plasm and is tightly associated with polar granules, the distinctive organelles of germ plasm, which supports the idea that mtlrRNA functions in Pole Cell formation. This suggests that a product from the mitochondrial genome, along with nuclear products, participates in a key event in embryonic development: determination of the germ line.