穀胱甘肽氧化還原狀態影響文心蘭的高室溫誘導
開花機制

前人研究指出高溫誘導文心蘭開花與維生素C (ascorbate, AsA)及穀胱甘肽(glutathione, GSH) 的氧化還原狀態相關，並受AsA-GSH循環及穀胱甘肽生合成路徑影響。其參與酵素包含穀胱甘肽還原酶glutathione reductase (OgGR), γ-ECS,γ-glutamylcysteine synthetase (OgGSH1)及穀胱甘肽合成酶glutathione synthase (OgGSH2)。文心蘭GIGANTEA (GI) 及 FLOWERING LOCUS T (FT) 等開花基因的表現量亦顯著上升。然而，高溫誘導文心蘭開花路徑中，穀胱甘肽氧化還原狀態如何調控開花基因的表現，目前尚不明瞭。首先，我們利用氧化態維生素C處理文心蘭，結果可使穀胱甘肽還原態下降、氧化態上升、脫氫維他命C還原酶活性上升，所以可確定AsA-GSH循環存在於文心蘭中。接著，我們利用文心蘭穀胱甘肽還原酶(OgGR), γ-ECS (OgGSH1)及穀胱甘肽合成酶(OgGSH2)等基因，分別過表現於阿拉伯芥，結果顯示經30度高溫處理後，過表現轉殖株較WT延遲開花，且穀胱甘肽還原酶活性下降、穀胱甘肽氧化還原比例會隨時間提高，而WT則下降。反之在阿拉伯芥之穀胱甘肽代謝相關突變株，cad2、pad2 及gr1，與過表現轉殖株作比較之結果顯示，經30度高溫處理後，pad2, cad2, gr1有提早開花的情形，且穀胱甘肽還原酶活性及穀胱甘肽氧化還原比例均顯著下降。因此可知，雖然穀胱甘肽氧化還原比例於過表現轉植株及突變株本身即不相同，但處理高溫後即可明顯看到開花與穀胱甘肽氧化還原比例存有正向關聯性。此外，我們亦釣取文心蘭GI的啟動子，並預測感興趣的cis-element，結果說明文心蘭的GI可能被環境逆境調控，故推測文心蘭的GI和環境逆境所產生的氧化還原變化有交互作用。文心蘭的GI蛋白表現於細胞質及細胞核，說明文心蘭的GI具有調控下游開花基因的潛力。根據實驗結果推測，高溫造成的穀胱甘肽氧化還原變化並使文心蘭提早開花的路徑，是藉由穀胱甘肽的生合成及代謝途徑，進而影響下游GI的表現所造成的結果。

關鍵字

維他命Ｃ-穀胱甘肽循環；穀胱甘肽氧化還原比例；開花；高溫；文心蘭

並列摘要

Previous study reveals that high ambient temperature make Oncidesa early flowering through changing ascorbate (AsA) and glutathione (GSH) redox status (AsA/DHA) (GSH/GSSG) via AsA-GSH cycle and GSH biosynthesis. Glutathione reductase (OgGR), γ-glutamylcysteine synthetase (OgGSH1) and glutathione synthase (OgGSH2), as well as floral genes, such as GIGANTEA (GI) and FLOWERING LOCUS T (FT) are related to this pathway. However, the mechanism of GSH redox regulated floral genes on high temperature-induced flowering in Oncidesa is still unknown. First, we treat Oncidesa with dehydroascorbate for 14 days and find glutathione content decrease and glutathione disulfide content increase and dehydroascorbate reductase activity increase. Therefore, we can confirm that the AsA-GSH cycle exist in Oncidesa. Thus, we over-express OgGR, OgGSH1, and OgGSH2 in Arabidopsis to study the role of GSH on high temperature-induced flowering. The results show the overexpression plant delay flowering and increase of GSH redox. Otherwise, GSH metabolism related mutants in Arabidopsis, cad2, pad2, and gr1 which are opposite to the overexpression lines, showed early flowering with low GSH content, indicating GSH redox status and which key regulating enzyme involved in high-temperature induced flowering. We clone GI promoter from Oncidesa, and predict the cis-element, revealing that GI is probably regulated by stress, and implies the interaction between GI and redox signaling. Moreover, Oncidesa GI is located in nucleus, indicating that GI potentially regulate downstream floral gene. We suggest that the change of GSH redox ratio under high-temperature can induce early flowering via GSH biosynthesis/metabolism and influence the gene expression of GI in Oncidesa.

並列關鍵字

AsA-GSH cycle ； GSH redox ； flowering ； high temperature ； Oncidesa

參考文獻

黃怡菁。(1997)。文心蘭基本生長週期與花期修剪產期調節. 高雄區農業專訊22:16-17.

謝家綺。(2014) 。穀胱甘肽的氧化與還原狀態在維他命C-穀胱甘肽循環鏈中與文心蘭開花機制之關聯性。國立台灣大學植物科學研究所碩士論文。

許榮華。 (2013) 。台灣文心蘭切花產銷現況及產業經營需求。台中區農業改良場一○一年專題討論專集.

Ali, M. B., Hahn, E. J., and Paek, K. Y. (2005). Effects of temperature on oxidative stress defense systems, lipid peroxidation and lipoxygenase activity in Phalaenopsis. Plant Physiol. Biochem. 43: 213-223.

Almeselmani, M., Deshmukh, R. K., Sairam, R. K., Kushwaha, S. R., and Singh, T. P. (2006). Protective role of antioxidant enzymes under high temperature stress. Plant Sci. 171: 382–388.

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穀胱甘肽氧化還原狀態影響文心蘭的高室溫誘導開花機制

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