探討外加穀胱甘肽如何增加阿拉伯芥對非生物性逆境之耐受性機制

Study of the mechanism of exogenously applied glutathione on abiotic stress tolerance in Arabidopsis

張菀玲(Wan-Ling Chang)

指導教授 ： 林讚標

國立臺灣大學/生命科學院/植物科學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.10925

摘要

穀胱甘肽 (GSH) 是由三個胺基酸 (麩氨酸、半胱氨酸及甘氨酸) 組成的簡單含硫化物，是植物以及許多生物體內的主要非蛋白質硫醇化物。穀胱甘肽參與許多細胞反應，尤其穀胱甘肽的抗氧化功能在維持細胞內的氧化還原平衡扮演重要角色。根據我們先前觀察，外加GSH可以增進阿拉伯芥對於非生物性逆境的抗性，特別是乾旱及鹽逆境，然而，這方面的機制尚未明瞭。本研究針對外施GSH對阿拉伯芥之生理反應及基因調控層面進行深入探討。將野生型幼苗處理GSH 4天及12天後，以微陣列分析受到GSH影響的基因群，其結果顯示，外加GSH影響野生型植物的許多基因表現，尤其在ABA新陳代謝、生物性逆境及非生物性逆境方面，另外，外加GSH也可能增強細胞壁的生合成、讓細胞壁更有彈性。再者，ABA生合成之關鍵酵素NCED3的基因表現量於處理GSH 24小時左右被誘導、但之後表現量回歸至正常，故我們推測，在處理24小時內就可能影響ABA含量及訊息傳遞網絡。除此之外，外加GSH能夠增加葉片重量、延遲葉老化及延遲葉綠素衰退。特別是以GSH處理的植物株，其老化標幟基因SAG12及SEN4較對照組有顯著延遲表現的現象。葉光合作用能力之代表基因RbcS，在GSH處理植株中也有延遲衰退的現象。總而言之，阿拉伯芥外加GSH能夠藉由提升ABA含量、增加細胞壁彈性及延遲老化來增加逆境的耐受性。

關鍵字

穀胱甘肽微陣列分析 ； 乾旱逆境 ； 老化

並列摘要

Glutathione (L-γ-glutamyl-L-cysteinyl-Gly) is a simple sulfur compound composed of three amino acids and is the major non-protein thiol in many organisms including plants. Glutathione is involved in a plethora of cellular processes in addition to its role as an antioxidant and in the maintenance of cellular redox homeostasis. According to our previous observation, exogenously applied glutathione reduced form (GSH) could improve abiotic stress tolerance of Arabidopsis, especially under drought and salt stress. However, the underlying mechanism has not been elucidated. The aim of this study was to investigate the physiological response and gene modulation of exogenously supplied GSH to the Arabidopsis. Here, the wild-type seedling treated with GSH for 4 and 12 days, were analyzed by using the microarray assay to find out the genes influenced by the GSH. Our microarray data showed that exogenous GSH has immense effects on gene expressions, especially the genes involved in ABA metabolism, biotic stress and abiotic stress in wild-type plants. In addition, exogenous GSH may enhance cell wall biosynthesis and kept the cell wall more flexible. The expression of NCED3, a key enzyme in ABA synthesis, was induced after treated with GSH for 24 hours, but returned to normal thereafter. We proposed that the ABA signal transduction networks and content were induced in the early hour of GSH treatments. Furthermore, exogenously applied GSH could increase leaf weight, delay leaf senescence and slow down chlorophyll degradation. In our data, SAG12 and SEN4, the senescence marker gene, exhibited significantly delayed induction in GSH treated plants. The RbcS, the photosynthetic capacity marker gene, also showed delayed decrease of gene expression level in GSH treated plants. In summary, exogenous GSH might enhance stress tolerance by elevating ABA level, promoting growth capacity, making cell wall more flexible, and delaying leaf aging in Arabidopsis.

並列關鍵字

glutathione ； microarray ； drought stress ； senescence

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