阿拉伯芥中熱休克轉錄因子AtHSFA6b係透過與離層酸相關的訊號而被誘導並調控多種非生物性逆境反應

植物在生長發育的過程中可能會遭受到許多逆境，包括溫度、鹽分以及水分逆境等。而熱休克反應是植物對抗熱逆境的重要機制之一，過程中藉由熱休克轉錄因子調控熱休克蛋白質的產生來保護細胞，以降低熱逆境的損害。分析微陣列晶片中的資料，顯示阿拉伯芥的熱休克轉錄因子會被多種生物性或非生物性逆境所誘導，其中在熱休克轉錄因子A6群中之AtHSFA6a會被滲透逆境所誘導，AtHSFA6b則主要會被冷、鹽分、滲透以及乾旱逆境誘導；此外，兩者皆會被離層酸誘導表現。顯示這兩者可能會參與在離層酸所調控的逆境反應當中。在本篇文章中，我們利用遺傳及分子層次的分析來調查阿拉伯芥AtHSFA6中之兩個成員在遭遇逆境時所扮演的角色。首先，我們確定了兩者皆會受離層酸、鹽與滲透逆境所誘導；在離層酸缺失及對離層酸不敏感的突變株中，證實離層酸相關的訊號傳遞對於AHSFA6b的表現是必須的；同時AHSFA6b啟動子中之離層酸反應序列(ABRE)對其感應ABA是不可或缺的，以上結果顯示AtHSFA6b參與在離層酸相關的訊號路徑之中。藉由觀察突變株和轉植株在子葉綠化、根系生長以及其對鹽分耐受性的差異，結果顯示AtHSFA6b確實參與在離層酸所調控的非生物逆境反應當中；此外，耐熱性的測試結果也顯示AtHSFA6b同樣也參與在先天耐熱性及誘導耐熱性的調控過程之中。我們的研究結果說明了，AtHSFA6b除了在複雜的熱休克轉錄因子調控網絡當中扮演重要角色外；另外加入了一條新的調控路徑，那就是在離層酸所調控的非生物性逆境反應中也扮演著正向的調控因子。

關鍵字

離層酸；熱休克轉錄因子；鹽逆境

並列摘要

Plants face various environmental stresses, such as drought, salinity, heat and cold directly. In response to heat stress (HS), heat shock response (HSR) is a conserved mechanism of increasing heat shock protein (HSP) genes expression through a heat shock factors (HSFs)-dependent mechanism. According to microarray databases, AtHSFA6a is induced by salt and osmotic stress, while AtHSFA6b expression is responsive to cold, salt, osmotic and drought treatment; in addition both genes are upregulated by ABA treatment suggesting the AtHSFA6s may involve in ABA-mediated responses. This report describes our investigation of the role of AtHSFA6s in response to abiotic stress in Arabidopsis by genetic and molecular approaches. Both AtHSFA6s were induced by abscisic acid (ABA), salt and osmotic stress. Downregulated AtHSFA6b expression in ABA-deficient and ABA-insensitive mutants indicates that ABA signaling is required for AtHSFA6b expression. Notably, ABRE acts as the functional cis-element in the promoter region of AtHSFA6b, suggests AtHSFA6b is a member involved in ABA-dependent pathway. Analysis of cotyledon greening, root growth and salt tolerance in mutant lines and transgenic plants indicated that AtHSFA6b participates in ABA-mediated stress responses and acts as a positive regulator. In addition, thermotolerance tests also showed AtHSFA6b is involved in basal- and acquired-thermotolerance. These studies reveal AtHSFA6b is a positive regulator in ABA-mediated stresses, and add a new signaling pathway into the complex HSF network.

並列關鍵字

abscisic acid ； heat shock factor ； salt stress

參考文獻

Abebe, T., Guenzi, A.C., Martin, B., and Cushman, J.C. (2003). Tolerance of mannitol-accumulating transgenic wheat to water stress and salinity. Plant physiology 131, 1748-1755.

Baniwal, S.K., Chan, K.Y., Scharf, K.D., and Nover, L. (2007). Role of heat stress transcription factor HsfA5 as specific repressor of HsfA4. The Journal of biological chemistry 282, 3605-3613.

Banti, V., Mafessoni, F., Loreti, E., Alpi, A., and Perata, P. (2010). The heat-inducible transcription factor HsfA2 enhances anoxia tolerance in Arabidopsis. Plant physiology 152, 1471-1483.

Busch, W., Wunderlich, M., and Schoffl, F. (2005). Identification of novel heat shock factor-dependent genes and biochemical pathways in Arabidopsis thaliana. The Plant journal 41, 1-14.

Charng, Y.Y., Liu, H.C., Liu, N.Y., Hsu, F.C., and Ko, S.S. (2006). Arabidopsis Hsa32, a novel heat shock protein, is essential for acquired thermotolerance during long recovery after acclimation. Plant physiology 140, 1297-1305.

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阿拉伯芥中熱休克轉錄因子AtHSFA6b係透過與離層酸相關的訊號而被誘導並調控多種非生物性逆境反應

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