探討淹水逆境於阿拉伯芥SUS1與SUS4基因之轉錄調控

因氧氣在水中的擴散速率約為在大氣中的萬分之一，故植物遭受水患時，即對細胞造成缺氧逆境。氧氣不足，使得細胞代謝作用由有氧呼吸轉換為發酵反應來產生能量，因此參予在醣類移動與發酵反應相關的基因均被活化而大量表現，其中Sucrose synthase (SUS)酵素負責催化蔗糖分解為果糖與尿嘧啶雙磷酸葡萄糖，提供基質予下游的糖解作用與發酵反應。雖前人研究對SUS的功能已進行詳細的分析，但針對缺氧時，SUS基因的活化機制仍尚未釐清。故先使用semi-quantitative PCR的方式檢測SUS基因在植物根部遭遇水患時的表現情況，結果指出根部組織的SUS1與SUS4基因表現確實在缺氧逆境下被活化，且作用於轉錄層次的調控。接著利用5’ deletion 的方式分析SUS.11與SUS4的啟動子，並以luciferase做為報導基因，企圖找出參予缺氧調控機制的cis-element ，進一步了解其細胞訊息傳導的路徑。實驗結果指出距離轉錄起始點-1000到-600的區域，可能具有cis-element參予缺氧時調控SUS4基因表現的機制; 而針對SUS1.1基因，則是-1000到-300區域。

關鍵字

水患；阿拉伯芥；轉錄調控； sucrose synthase ； 5’promoter deletion assay

並列摘要

Oxygen diffusion is about 10 000 times slower in water than that in air. When plants were subjected to flooding the root cells switch from aerobic respiration to anaerobic fermentation in response to oxygen deprivation (hypoxia). Cellular regulation was performed to increase the transcript levels of genes that are involved in mobilization of sugars, glycolysis and fermentation pathway. During submergence the expression of sucrose synthase (SUS) gene was up-regulated to catalyze degradation of sucrose into fructose and UDP-glucose, which are substrates for glycolysis. Although a large number of studies have been made on sucrose synthase gene function, little is known about the mechanism of transcriptional regulation of SUS genes under flooding. Here, we characterize gene expression patterns of the SUS gene family in Arabidopsis during flooding. The transcript levels of SUS1 and SUS4 increased in roots but in different manners during flooding. Expression cassettes with truncated promoter fragments of SUS1 and SUS4 linked to firefly (Photinus pyralis) luciferase coding sequence were also developed to detect promoter activity. The results from the 5’ promoter deletion analyses suggested that the region between -1000 and -600 (from transcription start site) in promoter of SUS4 was essential for flooding-induced gene expression. For SUS1 gene, the critical cis-element(s) may locate on -600~-300 region for transcriptional regulation under flooding.

並列關鍵字

hypoxia ； Arabidopsis ； transcriptional regulation ； sucrose synthase ； 5’promoter deletion assay

參考文獻

Amor, Y., Haigler, C.H., Johnson, S., Wainscott, M., and Delmer, D.P. (1995). A membrane-associated form of sucrose synthase and its potential role in synthesis of cellulose and callose in plants. Proc Natl Acad Sci U S A 92: 9353-9357.

Anguenot, R., Nguyen-Quoc, B., Yelle, S., and Michaud, D. (2006). Protein phosphorylation and membrane association of sucrose synthase in developing tomato fruit. Plant Physiol Biochem. 44: 294-300.

Armstrong, W. (1980). Aeration in higher plants. Advances in botanical research 7: 225-332.

Babb, V.M., and Haigler, C.H. (2001). Sucrose phosphate synthase activity rises in correlation with high-rate cellulose synthesis in three heterotrophic systems. Plant Physiol. 127: 1234-1242.

Bailey-Serres, J., and Voesenek, L.A. (2008). Flooding stress: acclimations and genetic diversity. Annu Rev Plant Biol. 59: 313-339.

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探討淹水逆境於阿拉伯芥SUS1與SUS4基因之轉錄調控

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