臺灣博碩士論文加值系統

本論文主要探討玉米葉片之澱粉水解酵素在老化過程中的變化。分別以整棵植株及初生葉為材料，發現隨著葉齡的增加，會有α-澱粉水解酵素活性上升及β-澱粉水解酵素活性下降的現象。利用西方免疫檢定，發現老化過程中β-澱粉水解酵素活性強度和其蛋白質分子的量成正相關，顯示酵素活性下降的原因是蛋白質的破壞，而不是失活(inactivation)所致。不論是植株葉片之自然老化或葉圓盤之人為老化的試驗結果，都指出β-澱粉水解酵素活性的上升或β-澱粉水解酵素活性的下降，皆與一般用做老化指標之可溶性蛋白質含量的變化，呈現高度的相關性；顯示澱粉水解酵素的活性變化可以做為玉米葉片老化之良好指標，β-澱粉水解酵素尤其適合。北方或條帶轉印之雜合反應的結果指出，只有在發育中之未完全展開的葉片內才有β-澱粉水解酵素mRNA的累積，葉片一旦展開之後，其mRNA量即逐漸下降；而當此mRNA下降之時，β-澱粉水解酵素的活性卻仍因其蛋白質量的增加而提高。葉片切離植物體後，其β-澱粉水解酵素活性的下降情形不因外加植物荷爾蒙Gibberellin、Zeatin或Abscisic acid而有所改變，但α-澱粉水解酵素活性則會受到ABA的促進，和蔗糖的抑制；由此推論，在玉米葉片老化過程中，β-澱粉水解酵素活性下降與α-澱粉水解酵素活性上升的現象，應是透過不同的調控機制。

Changes of amylase activities in aging maize leaves were studied. The increase in α-amylase activity was accompanied with the decrease in β-amylase activity along the age gradient in a mature plant. Results from immunoblot analyses showed that β-amylase activity was closely correlated with the protein quantity of β-amylase during leaf senescence, and the decrease of β-amylase could be attributed to the protein degradation but not inactivation. No matter whole plant or leaf disc system was studied, leaf total soluble protein showed a highly positive correlation with β-amylase activity, and also a negative correlation with α-amylase activity during senescence. Therefore, changes in α- and β-amylase activities should be able to play a good index for leaf senescence just as total soluble protein content has been used. Based on RNA slot analysis, β-amylase mRNA was synthesized and accumulated when leaf expansion was in progress. Once the leaf reached full expansion, the β-amylase mRNA gradually decreased while the enzyme activity was still increasing owing to the protein synthesis and accumulation. In leaf disc system, the decrease of β-amylase activity during senescence could not be altered by adding phytohormones such as gibberellic acid, zeatin and abscisic acid. And α-amylase activity in leaf discs was enhanced by abscisic acid and repressed by sucrose. These results suggested that regulation of increasing α-amylase and decreasing β-amylase in senescing maize leaf might not share a common mechanism.

前言
材料與方法
結果
一、成熟葉片中之β-澱粉水解酵素
二、初生葉中之β-澱粉水解酵素
三、年輕植株葉片中的β-澱粉水解酵素
四、葉片之人工老化與澱粉水解酵素的變化
五、荷爾蒙及醣類對於葉片老化過程中澱粉水解酵素活性的影響
討論
參考文獻
圖表

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