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Title: | 阿拉伯芥A1及A2型熱休克轉錄因子之功能研究 Functional Analysis of Class A1 and A2 Heat Shock Transcriptional Factors in Arabidopsis |
Authors: | Hsiang-chin Liu 劉祥欽 |
Advisor: | 常怡雍(Yee-yung Charng) |
Co-Advisor: | 施明哲(Ming-Che Shih) |
Keyword: | 熱逆境,熱逆境轉錄因子,非生物逆境,植物耐熱能力,熱休克蛋白, Heat stress,Heat shock transcriptional factor,Non-biotic stress,Plant thermotolerance,Heat shock protein, |
Publication Year : | 2013 |
Degree: | 博士 |
Abstract: | 在真核生物中,熱休克反應(heat shock response)主要是由Heat shock factor(HSF)所調控。但參與植物熱休克反應的主要調控者仍沒有廣泛地被鑑定出來。這個主要調控者被認為可能是HSFA1,因為共抑制(cosuppression)蕃茄中的HSFA1a會明顯的抑制熱休克反應及降低熱耐受性。然而目前為止,仍沒有明確的證據顯示阿拉伯芥(Arabidopsis)中的四個HSFA1(HSFA1a/b/d/e)具此類似的功能。不論是單一或雙重剔除的突變株,其熱休克反應及熱耐受性皆無受到明顯影響。這可能是因為多個類似功能之基因所造成的互補效應。為了研究各別HSFA1的功能,我將HSFA1a/b及HSFA1d/e的雙重突變株互交,進而得到三重及四重突變株。實驗發現,HSFA1a/b/d是熱休克反應的主要調控者,而HSFA1e只有在種子耐熱能力的調控有部分功能。然而在植物的發育上,這四個HSFA1皆具有重疊的重要功能。微陣列分析發現HSFA1調控了超過65%的熱誘導基因,但當植物喪失HSFA1a/b/d時,非致死高溫仍可以誘導出相對微弱但顯著的後生耐熱能力(acquired thermotolerance),這個現象說明了可能有兩套以上的熱感應及熱反應的機制存在於植物細胞中。
植物的熱誘導系統有一個不同於酵母菌及動物的特點就是他們擁有數個本身也會受熱誘導的HSF,而HSFA2是其中反應最強的一個。在蕃茄的系統中,HSFA2跟HSFA1a會結合成異質聚合體來啟動熱休克蛋白(heat shock protein, HSP)基因的轉錄。但是到目前為止,並沒有明確的證據指出HSFA2可以在沒有HSFA1的情況下獨立運作。因此,我將HSFA2持續表現在HSFA1a/b/d/e同時被破壞的突變株中,藉此來闡明HSFA2的獨立功能。我發現HSFA2與HSFA1個別偏好調控熱休克反應中的某些基因。另外,HSFA2可以取代HSFA1在發育以及抵抗某些環境逆境的功能。有趣的是針對廣義的熱逆境(從27°C到45°C)及氧化逆境,HSFA2可以賦予植物良好的耐受性,但是對高鹽及高滲透壓的逆境則較無作用。總結以上,我們的研究闡明阿拉伯芥中的HSFA1及HSFA2可以獨立運行其功能,並指出它們功能上的共通性及特異性。 Heat shock factors (HSFs) are the well-known master regulators of heat shock response (HSR) in eukaryotes. In tomato, cosuppression of HSFA1a largely reduced HSR and thermotolerance, which suggests the master role of HSFA1 in plants. However, the seeking of a master regulator of HSR in Arabidopsis is not yet accomplished that the single or double KO mutation of four HSFA1s (HSFA1a/b/d/e) in previous studies did not obviously abolish the HSR and thermotolerance. In this study, triple and quadruple KO mutants of HSFA1s clearly demonstrated their overlapping roles not only in HSR but also in development and the tolerance to other stresses. About 65% heat-upregulated genes were under the control of HSFA1s as revealed by microarray data, which indicated that a small portion of HSR was independent of HFSA1s. Indeed, a minimal but significant level of acquired thermotolerance was still induced without HSFA1a/b/d by a relatively milder heat stress regime. This phenomenon suggests at least two heat-sensing and -responding mechanisms exist in plant cells. Plants have several heat-induced HSFs, which is a unique feature only found in plants but not in yeast and animals. Among them, HSFA2 is the most induced one. In tomato, HSFA2 together with HSFA1a form the hetero-oligomeric complexes to activate the transcription of HSP genes. However, no direct evidence showed whether HSFA2 could function independently without HSFA1s. To this end, HSFA2 was constitutively expressed in the HSFA1a/b/d/e quadruple knockout mutant for evaluation of its independent function. I found that HSFA1s and HSFA2 differentially regulated the HSR genes. Moreover, HSFA2 could replace the functions of HSFA1s in development and tolerance to a wide range of heat stress from 27°C to 45°C, and to H2O2 but not salt and osmotic stresses. Taken together, the findings reveal that HSFA1s and HSFA2 can work independently and have overlapping and distinct functions in Arabidopsis. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/6281 |
Fulltext Rights: | 同意授權(全球公開) |
Appears in Collections: | 植物科學研究所 |
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ntu-102-1.pdf | 16.97 MB | Adobe PDF | View/Open |
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