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標題: | 千年桐特異第二型二醯基甘油醯基轉移酶 (Diacylglycerol Acyltransferase 2,DGAT2) 提高阿拉伯芥油量與生長勢之研究 Tung Diacylglycerol Acyltransferase 2 Elevates Oil Level in Transgenic Arabidopsis and Promotes Growth Potential through Activating IAA Biosynthesis. |
作者: | Wan-Ying Wu 吳宛穎 |
指導教授: | 葉開溫(Kai-Wun Yeh) |
關鍵字: | 千年桐,二醯基甘油醯基轉移酶,生長素,花生酸, Vernicia montana,DGAT,IAA,arachidic acid (20:0), |
出版年 : | 2012 |
學位: | 碩士 |
摘要: | 植物累積油質主要是利用兩種類型的二醯基甘油醯基轉移酶 (DGAT1 及DGAT2)來進行,而其中第二類型的DGAT (DGAT2)通常被視為作用在植物特異脂肪酸的累積,但其生理功能卻尚未被加以研究。本研究利用千年桐中與桐油酸累積有關的VmDGAT2,將其轉入無DGAT2酵素活性的阿拉伯芥中,進而分析轉殖植物在提高DGAT2活性後對於代謝產物,如:脂肪酸與賀爾蒙;外表型,如:營養及生殖生長的影響,藉此探究此一基因的功能與生理意義。大量表現VmDGAT2的轉殖株較野生型植物提高25-30% 油質含量和30-50% 總蛋白質含量,因此,其種子的平均重量為野生的1.1-1.3倍。分析生長勢發現,轉殖株較野生型具有較大的葉片與較長的根系。此外,轉殖株與野生型在開花時間上並無明顯的差異,而由於轉殖株因具有較多長角果,所以其種子產量大幅提高為野生型的2.2-2.5倍(種子數x種子重)。進一步分析發現轉殖株內的生長素含量為野生型的1.5-2倍,而生長素的生合成基因NITRILASE (NIT)與生長素調控細胞分裂的E2F TRANSCRIPTION FACTOR 3 (E2F3)基因,其表現量在轉殖株中亦較高於野生型,造成子葉中的上皮細胞與根尖組織的分生細胞數目都為野生型的1.2-1.5倍。據此,推測轉殖株因具有較高含量的生長素而較野生型植物具有較為明顯的生長勢。進一步分析轉殖株的脂肪酸組成,發現主要提高的脂肪酸類為飽和脂肪酸和單不飽和脂肪酸,包含近期被發現可作為訊號分子參與在多種賀爾蒙反應的二十碳脂肪酸群,如,花生酸。在阿拉伯生野生型中,施加花生酸 (20:0)明顯較施加棕梠酸 (16:0)或控制組的植物具有較旺盛的根系發育,且NIT與E2F3的基因表現亦明顯地提高。利用pDR5::GFP的植物偵測對於生長素的訊息傳遞,發現在外施加花生酸 (20:0)其螢光強度亦較外施加棕梠酸 (16:0)或控制組的植物大幅地提高。因此推測大量表現VmDGAT2的轉殖株,可提高三酸甘油脂含量外,其中累積較多的花生酸 (20:0),具有刺激生長素的生合成效果,進而提高轉殖植物的生長勢與種子產量。 A cDNA clone encoding DGAT2 in seed of tung tree (Vernicia montana) was isolated and characterized. Expression profile revealed that DGAT2 was temporally expressed during the deposit of eleostearic acid in seed maturation, and was up-regulated by abscisic acid, jasmonic acid, high temperature and in rich sulfuric and nitrogenous nutrition. Transgenic Arabidopsis overexpressing VmDGAT2 exhibits the increasing seed weight with elevated triacylglycerol (TAG) content up to 40%, and a remarkably active growth biomass, including the increasing epidermal cells in cotyledon and elongated root tissues. The growth biomass promotion in transgenic plants was correlated with an increased indole-3-acetic acid (IAA) level and up-regulated expression of NITRILASE (NIT) and E2F TRANSCRIPTION FACTOR 3 (E2F3) genes compared with wild type. Detailed comparisons of seed neutral lipids indicated that VmDGAT2 substantially modified TAG pool, with significant increase in most of the major TAG species existing in native Arabidopsis. Further analysis demonstrated the elevated expression level of NIT1 and E2F3 was attributed to the increased arachidic acid (20:0) content in transgenic Arabidopsis. Our data demonstrated that DGAT2 effectively increased the yields of plant oil content and fatty acid profiles. We also provide the first evidence that DGAT2 promotes plant growth biomass through elevating IAA level. Arachidic acid (20:0) is a potential stimulator to trigger the de novo biosynthesis of IAA. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/65771 |
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顯示於系所單位: | 植物科學研究所 |
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