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標題: | 吉貝素和離層酸對於玉米穀粒β-澱粉?活性表現的影響 Effects of Gibberellic Acid and Abscisic Acid on β-Amylase Expression in Maize Kernel |
作者: | Lin-Yun Kuang 匡麟芸 |
出版年 : | 1999 |
學位: | 碩士 |
摘要: | 玉米穀粒在萌發過程中,糊粉層會合成新的α-澱粉?及β-澱粉?分子。本論文旨在探討玉米穀粒萌發時,賀爾蒙對於β-澱粉?活性的影響,以及β-澱粉?是否為一分泌性蛋白質。結果發現,玉米糊粉層中β-澱粉?活性表現對於賀爾蒙的反應與α-澱粉?類似:GA促進α-澱粉?及β-澱粉?的活性,而ABA則對這兩種酵素有抑制作用,且ABA的抑制效果會淩駕於GA作用之上,亦即GA與ABA同時存在時,糊粉層表現受ABA抑制的反應。由同位素活體標定的結果知道,在萌發第5天時,GA對於α-澱粉?及β-澱粉?新合成的促進作用並不明顯,然而ABA仍可抑制這兩種酵素的生合成。由這些結果看來,玉米穀粒糊粉層中,β-澱粉?基因表現對GA及ABA的反應和α-澱粉?相同。由於萌發之玉米穀粒中的β-澱粉?只能在糊粉層中合成,而糊粉層細胞中並無澱粉粒,為瞭解β-澱粉?是否能在玉米種子萌發時扮演澱粉水解?的角色,本實驗利用分離的糊粉層以及轉殖菸草懸浮細胞檢測β-澱粉?的分泌性。實驗中以非分泌性的phosphoglucoisomerase和分泌性的α-澱粉?做為比較之參考。在培養液中檢測到的α-澱粉?活性約為細胞內活性的50%,而β-澱粉?活性在培養液中則不及細胞的1%,且培養液中也可測到微量的phosphoglucoisomerase活性,故本論文認為玉米穀粒中的β-澱粉?並非分泌性酵素。至於存在培養液中的β-澱粉?活性推測應是導因於剝取糊粉層時的機械性傷害,或是少數細胞在培養過程中老化死亡所造成的,而非細胞分泌的結果。 The α-amylase and β-amylase molecules are synthesized in the aleurone layers of germinating maize kernels. In this thesis, the effects of GA and ABA on the β-amylase activity, and the secretion of β-amylase were studied. Both of a-and β-amylase activities in aleurone layers were stimulated by gibberellic acid, and were inhibited by abscisic acid. Based on the results from 35S-methionine labeling and immuno-precipitation, GA slightly enhanced the synthesis of α-amylase and also β-amylase, and ABA showed strong inhibitory effect on the synthesis of both α- and β-amylases, and the presence of GA could restore the β-amylase synthesis. For understanding the physiological function of aleurone β-amylase, the secretion of β-amylase from aleurone cells was examined. Non-secretory phosphoglucoisomerase and secretory α-amylase were used as reference to make a comparison with β-amylase. The activity present in medium was about half of that inside aleurone tissue. And β-amylase activity in medium was less than 1% of that in tissue. Using transgenic tobacco cells having barley high pI α-amylase and/or maize β-amylase genes to confirm the secretion test of β-amylase, the results showed that β-amylase is not a secretory protein. The small amount of β-amylase activity in medium should be caused by the mechanical damage during the isolation of f aleurone layers or the cell death during incubation period. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75058 |
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顯示於系所單位: | 植物科學研究所 |
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