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Molecular characterization of genes essential for early development of germ cells in rice
https://ir.soken.ac.jp/records/1442
https://ir.soken.ac.jp/records/1442e7f2fb84-2239-4a1b-a3a2-2d50fa4bac2d
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Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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公開日 | 2010-03-24 | |||||
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タイトル | Molecular characterization of genes essential for early development of germ cells in rice | |||||
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タイトル | Molecular characterization of genes essential for early development of germ cells in rice | |||||
言語 | en | |||||
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言語 | eng | |||||
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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 |
上田, 弥生
× 上田, 弥生 |
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フリガナ |
ウエダ, ヤヨイ
× ウエダ, ヤヨイ |
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著者 |
UEDA, Yayoi
× UEDA, Yayoi |
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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 | |||||
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学位名 | 博士(理学) | |||||
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内容記述タイプ | Other | |||||
内容記述 | 総研大甲第1249号 | |||||
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値 | 生命科学研究科 | |||||
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値 | 18 遺伝学専攻 | |||||
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学位授与年月日 | 2009-03-24 | |||||
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値 | 2008 | |||||
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内容記述タイプ | Other | |||||
内容記述 | In flowering plants, after the transition from vegetative growth to reproductive development, primordial germ cell initials differentiate from somatic cells in flowers. Several genes that control the early stages of germ-cell development have been identified, however, little is known about the molecular mechanism determining the germ cell fate during sexual reproduction in plants. The <i>MEL1 (MEIOSIS ARRESIED ATLEPTOTENE1)</i> is the only plant ARGONAUTE (AGO) gene specifically expressing at the primordial germ cells. AGO proteins are known to be a key player in gene-silencing pathways guided by small RNAs. PlWl-domain containing subfamily has important roles in maintaining germ stem cells in animal. In plant, however, there is no <i>AGO</i> gene which belonging to PIWI subfamily. Therefore, a specific AGO gene system in plant germ cell development would be suggested.<br /> In this study, I focused on the characterization gene expressed at early stages of germ cells development specifically in relation to the MEL1 function. MEL1 is well-characterized ARGONAUTE family that has essential functions in germ cell development. To date the rice <i>MEL1</i> is the only gene available for investigating a genetic system conducting plant germ cell initiation and maintenance. A large portion of the genes identified specific in very early stages in germ cell development had unknown function However, comparison of gene expression profiles between wild-type and <i>mell-1</i> mutant down- or up-regulated in<i>mell-1</i> mutant revealed many possible causal genes for <i>mell-1</i> dysfunction, i.e. most of which are not characterized previously. Of these genes, the <i>OsSPLl4</i>, one of<i> SQUAMOSA(SQUA)</i> promoter-binding-like(<i>SPL</i>) family genes, encoding a putative transcription factor, revealed to up-regulated in the <i>mell-l</i> mutant in both Affymetrix (Fold change=4.37) and Agilent (=3.01) microarray. Sequence and experimental analyses indicated that eleven <i>OsSPL</i> genes including <i>OsSPL14</i> were putative targets of <i>OsmiR156</i>, suggesting a possibility that the <i>OsSPL14</i> should be directly targeted by the rice MEL1 AGO with <i>miR156</i> microRNA as a guide molecule. Moreover, the volume of <i>miR156</i> RNA detected in the co-IP fraction with the anti-MEL1antibody 3.2-fold more than in that with the pre-immune serum. The detection level of <i>miRl56</i> depended on that of the MEL1 protein, as the <i>miR156</i> co-IP with the MEL1 immune complex protein, but few or not with precipitates recovered using <i>mell-1</i> mutant or preimmune serum. These data strongly suggest that the MEL1forms a complex with the <i>miR156</i> microRNA <i>in vivo</i>. These results strongly suggested that the <i>miR156</i>microRNA was one of good candidates of guide RNA molecules of the MEL1 AGO.<br /> Analysis performed in each section and results obtained from the analysis are summarized as follows.<br /> In the Section 1, the whole transcriptome profiles of plant reproductive process, including early stages that are difficult to be dissected in <i>Arabidopsis</i>, was obtained by using the Affymetrix rice genome array analysis and provided as a dataset of rice reproductive expression atlas. In addition, using the atlas data, the gene expression patterns of several genes that the are highly expressed in early development stage were investigated. A large part of genes that are expressed in early reproductive development remains uncharacterized because most of pre-meiotic stage specific genes were not categorized to any functions by GO analysis. However, the expression patterns of other meiosis-related genes were well corresponded previous reports. The specific genes that were found in this study may have the crucial function at early germ cells development stages.<br /> In the section 2, to confirm the spatial and temporal expression of the <i>MEL1</i> gene, mRNA <i>in situ</i> hybridization was performed on the anther sections with the <i>MSP1</i> gene as cellular marker of young anther tissues. Expression of the <i>MEL1</i> was earlier than that of the <i>MSP1</i>, which clearly indicates that the <i>MEL1</i>mRNA expression start at the archesporial initials. The <i>MEL1</i> expression is not required for the germ-cell initiation, but for the maintenance of germ cells. In the Section 2, <i>in situ</i> hybridization of the <i>OsNOZZLE(OsNZZ)</i>, a putative rice ortholog of <i>Arabidopsis</i> <i>SPOLOCYTELESS|NOZZLE</i> was also performed. Different from the <i>MEL1</i> and the, <i>MSP1</i>,the <i>OsNZZ</i> mRNA was expressed both in developing anther wall layers and sporogenous cells similar that of <i>Arabidopsis</i> <i>SPL/NZZ</i>, but it was not detected in archesporial cells. Although their function is not the same as <i>Arabidopsis</i> SPL/NZZ, OsNZZ</i> may have function in early germ cell development.<br /> In the Section 3, the microarray at 1-cm young panicle, several genes responsive for environmental stresses and/or hormone-responsive genes up-regulated. It suggests that absence of the MEL1 may cause stressful condition, thus many stress-response genes and ethylene signaling-related gene are induced. TheMEL1 may inhibits stress responses in germ cells to accomplish precise germ cell division and meiosis. In addition, some transposable element-like transcripts were also up-regulated in <i>mel-1</i> mutant. It was demonstrated that <i>Drosophila piwi </i> mutations impact retrotransposon mobility. MEL1 may also suppress the activity of transposable elements during rice germ-cell development. On the other hand, many genes related to cell structure and cycle were down-regulated in the <i>mell-1</i> mutant. These results may indicated that in<i>mell-1</i> mutant, the failure of pre-meiotic mitosis of sporogenous cells in the <i>mell-1</i> mutant anther (Nonomura et al. 2007) was caused by down-regulation of these genes. At pre-meiotic S/G2 stage of young anthers, few genes were affected by the <i>mell-1</i> mutation. Most of up- and down-regulation of genes in the later stages of pre-meiotic germ-cell development might be secondary effects of <i>mell-1</i> mutation.<br /> Finally, the Section 4 suggested a possibility that the rice MEL1 AGO directly regulated the <i>OsSPL14</i>gene with the plant specific microRNA, <i>miR156</i> as described above.<br /><br /> Results obtained in this thesis will provide new and useful information to understand the gene functions in initiation of germ cells development and maintenance of germ cell identity in rice. | |||||
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値 | 有 | |||||
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内容記述タイプ | Other | |||||
内容記述 | application/pdf |