- 學位論文
阿拉伯芥熱休克轉錄因子HSFC1之功能性研究
Functional Study of Heat Shock Factor HSFC1 in Arabidopsis
摘要
熱休克反應(HSR)是植物在面對高溫逆境時用來抗熱的機制之一，其過程是藉由熱休克轉錄因子(HSF)調控熱休克蛋白(HSP)的生成來保護細胞。在阿拉伯芥中總共存在有21個不同的HSF，約有一半的HSF會參與在HSR的訊息傳導中；這當中又以HSF-A群被認為和HSR的放大和維持有關。HSF-B群則不具有轉錄活性，由於可和A群競爭熱逆境相關基因上的熱休克反應序列(HSE)被視作HSR的調控因子。HSF-C群在阿拉伯芥中只有一個成員(HSFC1)；雖然在其他植物中HSF-C群的功能已被認為和鹽分、乾旱逆境有關，但在阿拉伯芥中HSFC1的作用目前仍然未知；因此，在本篇研究中將研究HSFC1的功能。在雙分子螢光互補系統、GUS 組織染色和萌芽率分析下，我們發現HSFC1可能和生長發育有關。而HSFC1會被鹽和離層酸(ABA)誘導表現，以及在ABA缺失及對ABA不敏感的突變株中HSFC1表現量下降表明對於HSFC1可能和ABA相關的訊號傳遞是有關的。在HSFC1啟動子中我們發現除了ABA反應序列(ABRE)外還有其他生物及非生物性反應相關序列存在，代表HSFC1可能參與除了ABA相關的訊息傳導以外的路徑。雖然在HSFC1突變體的轉殖株中與ABA相關反應基因確實有受到影響，但因為HSFC1本身不帶有基因活化特性, 我們無法斷言此現象是由HSFC1直接或間接造成。我們試著觀察在鹽逆境和ABA處理下是否會影響HSFC1轉殖株萌芽率、萌芽後生長情況及根長生長，但除了有較低的萌芽率外，其他測試下表現和野生株的差別不大。我們的研究發現HSFC1可能和生長發育有關以及會影響ABA訊息傳導路徑的下游相關基因表現，但是如何影響及透過何者影響則需要未來更進一步的研究。
並列摘要
Heat stress response (HSR) is a conserved mechanism for plants to overcome heat stress (HS), or higher than optimal temperatures. The increase in heat shock protein (HSP) genes expression protects plant cells from heat stress, and this mechanism is controlled by heat shock factors (HSFs). The Arabidopsis heat shock transcription factor family contains 21 HSF members; about half are involved in the signaling cascade of HSR. The class-A HSF members are suggested to amplify and/or sustain HSP expression. The HS-inducible class-B HSF members, which lack a typical activation domain, are considered HSR regulators due to their competition with the binding capacity of HS elements (HSEs) in HS-related genes to class-A HSFs. There has only been one HSF in class-C (HSFC1) reported in Arabidopsis, although HSFCs have been found to be involved in salt and drought stress response in other plants. However, the function of HSFC1 in Arabidopsis has remained uncharacterized. We concluded from our bimolecular fluorescence complementation (BiFC) assay, HSFC1 promoter β-galactosidase (GUS) expression, and germination rate of HSFC1 overexpression and dominant-negative mutant lines that Arabidopsis HSFC1 might have a role in plant development. In addition, we found that HSFC1 can be induced by salt (NaCl) and ABA, and the expression of HSFC1 was altered in ABA-deficient and ABA-insensitive mutants. This implied that ABA signaling is required for proper HSFC1 expression. The cis-elements harbored in the promoter region of HSFC1 suggest that HSFC1 is involved in biotic and abiotic signaling pathways. We also analyzed the ABA-responsible genes in HSFC1 mutants and found the expression of these genes to be affected. However, we cannot conclude whether the effects are directly caused by HSFC1, since HSFC1 has no typical transcription activation motif. We also analyzed seed germination, post-germination seedling growth, and root growth of HSFC1-mutant lines under salt and ABA treatments; although the seed germination rate was affected in HSFC1-mutant lines, salt and ABA treatment did not significantly affect post-germination seedling growth and root growth as compared with HSFC1 mutants and wild-type plants. In conclusion, our results suggest that HSFC1 putatively plays a role in Arabidopsis development and ABA signaling response.
參考文獻
延伸閱讀
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- Liu, C. C. (2014). 阿拉伯芥熱休克因子結合蛋白之交互作用體研究 [master's thesis, National Taiwan University]. Airiti Library. https://doi.org/10.6342/NTU.2014.00445
- Huang, T. C. (2007). Abiotic Stresses Induce Heat Shock Factors to Regulate Small Heat Shock Protein Genes Expression in Arabidopsis thaliana [master's thesis, National Taiwan University]. Airiti Library. https://doi.org/10.6342/NTU.2007.03331