- 學位論文
增加穀胱甘肽含量促進阿拉伯芥的生長活力與逆境的耐受性
Increased concentration of total glutathione improves vigor and stress tolerances of Arabidopsis
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摘要
GSH（glutathione，穀胱甘肽）是由三個胺基酸 （麩胺酸、半胱胺酸及甘胺酸） 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。GSH參與許多細胞反應，尤其GSH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。在本篇研究中，我們得到增加與減少功能的GSH合成基因GSH1的轉殖株，然後處理非生物逆境。在GSH1大量表現的轉基因植物中，有較高的GSH含量，同時在含鹽和ABA的培養基裡有較高的發芽率和較長的根。GSH1大量表現的轉基因植物在乾旱和鹽害的逆境中也有較高的存活率。同時以熱逆境處理GSH1大量表現的植株，其存活率較高。同時也發現GSH1大量表現的轉基因植物會影響植物體內脯胺酸（proline）的含量，但是不影響離層素（ABA）的含量。以乾旱大量表現的RD29A啟動子接上GSH1的大量表現轉殖株，發現比野生型的阿拉伯芥更有生長活力，同時也能對抗乾旱逆境。GSH1大量表現的轉基因植物，其老化標幟基因SAG12較野生型有延遲表現的現象。另外以monochlorobimane染GSH，觀察GSH在植株體內的分佈情形，發現到在逆境時GSH會優先累積在生長點和最年輕的葉子，GSH保護生長點不受逆境影響。總之，在本篇的研究中提供了許多證據說明內生性提高GSH的含量可以在逆境的狀況下保護阿拉伯芥，尤其是在生長點和新葉的部份。同時也新發現到GSH可以延緩植物的老化。
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. We suggested that GSH plays an important role to increase the vigor of plants. Whether endogenous elevated level of GSH also has the same effect needs to be evaluated. In this study, gain-of-function and loss-of-function of GSH synthesis mutants were obtained from different sources, and abiotic stress were applied to these mutant plants.GSH1 overexpressing lines accumulating much higher GSH content and much higher GSH/GSSG ratio showed higher germination rate and longer root length than wild-type plants in the salt-containing petri dish. Overexpression lines also showed some tolerance in drought and salt test, and exhibited higher survival rate in heat stress test. GSH1 overexpression influenced proline content, but didn’t influence ABA content. SAG12, the senescence marker gene, exhibited significantly delayed induction in GSH1 overexpression plants indicating the effect of GSH in the leaf senescence. We observed that higher GSH accumulation in shoot apical meristem under stress when the GSH was stained with monochlorobimane indicating. GSH protects preferencially shoot apical meristem and youngest leaves under stress. In conclusion, in this study we presented evidence to support endogenous GSH plays an important role to protect Arabidopsis under stress environment, especially the apical meristem and youngest leaves, and a new function in leaf senescence.
參考文獻
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