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Glucosylglycerol, a Compatible Solute, Sustains Cell Division under Salt Stress in Synechocystis sp. PCC 6803
https://ir.soken.ac.jp/records/1375
https://ir.soken.ac.jp/records/137554035f8c-6b27-41ad-8978-22f67441989d
| 名前 / ファイル | ライセンス | アクション |
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要旨・審査要旨 / Abstract, Screening Result (271.2 kB)
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本文 (13.6 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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| 公開日 | 2010-02-22 | |||||
| タイトル | ||||||
| タイトル | Glucosylglycerol, a Compatible Solute, Sustains Cell Division under Salt Stress in Synechocystis sp. PCC 6803 | |||||
| タイトル | ||||||
| タイトル | Glucosylglycerol, a Compatible Solute, Sustains Cell Division under Salt Stress in Synechocystis sp. PCC 6803 | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者名 |
FERJANI, Ali
× FERJANI, Ali |
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| フリガナ |
フェルジャニ, アリ
× フェルジャニ, アリ |
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| 著者 |
FERJANI, Ali
× FERJANI, Ali |
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| 学位授与機関 | ||||||
| 学位授与機関名 | 総合研究大学院大学 | |||||
| 学位名 | ||||||
| 学位名 | 博士（理学） | |||||
| 学位記番号 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 総研大甲第693号 | |||||
| 研究科 | ||||||
| 値 | 生命科学研究科 | |||||
| 専攻 | ||||||
| 値 | X2 分子生物機構論専攻 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 2003-03-24 | |||||
| 学位授与年度 | ||||||
| 値 | 2002 | |||||
| 要旨 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | The growth and spatial distribution of living organisms are severely restricted by a variety of environmental factors. The acclimation of organisms to a constantly changing environment involves the accumulation of organic compounds of low molecular mass collectively called compatible solutes. The accumulation of compatible solutes has been intensively investigated during the last two decades however their protective role remains hypothetical. In this research the unicellular cyanobacterium, namely Synechocystis sp. PCC 6803 (Synechocystis, hereafter), is used as a model organism to study the role of compatible solutes in the protection against salt stress. Synechocyslis cells accumulate glucosylglycerol (GG) and transiently sucrose as compatible solutes in response to an upward shift in concentrations of NaCl in the growth medium. While the molecular mechanism for GG synthesis including the regulation of expression of the ggpS gene which encodes glucosylglycerol phosphate synthase, the key enzyme for GG biosynthesis, has been intensively investigated, the role of GG in protection against salt stress remains poorly understood.<br /> In order to study the role of GG in the tolerance to salt stress, Synechocystis cells which are deficient in the biosynthesis of GG, namely ΔggpS cells, were generated by targeted mutagenesis of the ggpS gene. ΔggpS cells are much more sensitive to salt stress than wild-type cells. Furthermore, salt stress due to 450 mM NaCl inhibited cell division and significantly increased cell size of ΔggpS mutant cells, whereas the inhibition of cell division and increase in cell size were observed in wild-type cells at much higher concentrations of NaCl, such as 800 mM. Long-term incubation of ΔggpS cells with 450 mM NaCl induced cell lysis. In addition, electron microscopic analysis revealed that, in ΔggpS cells, separation of daughter cells was incomplete and the aborted division could be recognized by the presence of a structure that resembled a division ring. These results suggested that NaCl specifically inhibits cell division machinery in Synechocyslis cells.<br /> Cell cycle in a prokaryotic cell such as E. coli, could be subdivided into three major events, namely cell elongation, cell septation and cell separation. During cell elongation, DNA replication and active biosynthesis of proteins is a prerequisite for cell division. Cell septation is characterized by the formation of a division-ring followed by the formation of a septum that splits the mother cell into two daughter cells during cell separation, which indicates the end of cell cycle. In order to determine the step of cell cycle that is inhibited by NaCl, the amounts of DNA, proteins and chlorophyll per single cell were determined. In fact, the amounts of DNA, proteins and chlorophyll per cell increased about 4-, 7- and 4-fold respectively in ΔggpS cells after incubation with 450 mM NaCl for 3 days. On the other hand, in ΔggpS cells which have been grown under control conditions, the levels of these macromolecules remained almost constant after three days. This result suggested that in ΔggpS cells even under salt stress conditions cell elongation occurred normally. However, salt stress seems to arrest the cellular processes that follow cell elongation, namely cell septation and cell separation. In contrast, in wild-type cells, no arrest in cell division was observed during incubation of cells with 450 mM NaCl.<br /> On the other hand, osmotic stress due to 900 mM sorbitol, which has approximately the same osmotic effect as 450 mM NaCl, totally arrested the growth of wild-type and ΔggpS cells. While 450 mM NaCl induced a significant increase in size of ΔggpS cells 900 mM sorbitol slightly reduced (about 10～20%) the size of both wild-type and ΔggpS cells. Thus, the inhibition of cell division and the increase in cell size induced by long-term incubation with 450 mM NaCl were due to the Tonic effect of NaCl.<br /> Exogenous supplemention of GG at 1 mM to the culture medium protected ΔggpS cells against salt stress and reversed the adverse effects of NaCl on cell division and cell size. Moreover, the addition of equivalent concentrations of compatible solutes other than GG, such as sucrose, sorbitol and trehalose, failed to rescue the ΔggpS cells under salt-stress conditions. From all these observations, he suggested that GG is important for salt stress tolerance in Synechocystis cells. Also, he could successefully demonstrate for the first time in a photosynthetic organism that NaCl specifically inhibit cell division machinery. Finally, he could demonstrate accurately that the compatible solute GG is necessary for the proper functioning of cell-division machinery in Synechocystis cells under salt-stress conditions. | |||||
| 所蔵 | ||||||
| 値 | 有 | |||||
| フォーマット | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | application/pdf | |||||
