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標題: | 玉米α-澱粉水解?之cDNA基因選殖與其在葉片老化過程中的表現 Cloning of maize α-amylase cDNA and the expression of α-amylase during leaf senescence |
作者: | Chiung-Swey Chang 張瓊穗 |
出版年 : | 2000 |
學位: | 碩士 |
摘要: | 依本研究室的研究結果,知道萌發後的玉米種子中至少出現四個α-amylase的同功?,而文獻中截至目前,只找到了一個玉米α-amylase基因序列;為了明瞭玉米之α-amylase基因的組成及表現,本論文實驗建構了cDNA基因庫及利用SMART-RACE系統,篩選獲得兩個全長(full length)的α-amylase mRNA序列,分別命名為ZmAAs1、ZmAAs2。依南方墨點分析結果顯示,台農351玉米之父本TA80-1410及母本TA80-2598的基因組內,α-amylase為多基因家族(multigene family)所調控。玉米種子浸潤後,胚逐漸發育成幼苗,芽鞘與初生葉等具幼苗專一性之組織,在幼苗生長後期會逐漸老化枯萎,當組織之鮮重與總蛋白質含量迅速下降時,α-amylase活性則快速提高,兩者呈現顯著的負相關,顯示α-amylase的基因表現與老化現象有很密切的關係;成熟植株上之不同葉齡的葉片亦存在α-amylase活性與葉齡梯度間的負相關性;甚至人為老化處理的葉圓盤體系也具有相似的表現趨勢。依本論文之觀察,α-amylase的活性表現可以當作玉米葉片老化的參考指標,而且營養組織老化時所表現之主要澱粉水解?,為相當於穀粒中之AA4同功?(即電場中泳動最快的4號α-amylase)。芽鞘組織之鮮重在達到最大值前,組織內之總可溶性蛋白質已開始下降,同時α-amylase之mRNA也可被偵測到,隨後才有酵素活性的出現,故可推論組織老化時所表現的α-amylase酵素活性應是受基因轉錄作用所調控;至於是否後轉錄層次的調節作用也參與了α-amylase活性表現的調控機制,仍需等待進一步的研究證實。 According to the previous experimental results, more than 4 isoforms of α-amylase were present in the germinating maize kernels. However, only one maize α-amylase cDNA gene has been reported. For understanding the structure and the expression of α-amylase genes in maize, a partial clone of α-amylase cDNA gene was screened from a maize cDNA library derived from germinating scutellar mRNA, and two full length α-amylase mRNA sequences, named ZmAAs1 and ZmAAs2, were obtained by SMART-RACE system. Based on the result of Southern analysis, α-amylases are encoded by a multigene family in maize. Upon imbibition, the embryonic axis of maize seed grew and developed into a seedling. The coleoptile and primary leaf which are seedling-specific organs turned aged after reaching their maximal growth. There was a significant correlation between the increment of α-amylase activity and the decrease of total soluble protein content in the course of organ-senescence. It was suggested that the increment of α-amylase activity may play a good index for organ senescence just like the reduction of protein content has been used. Based on patterns of zymogrpaphs, the major α-amylase isoform expressed during senescence was α-amylase-4. The coleoptile began to lose its cellular proteins before reaching its full size and maximal weight, meanwhile, the mRNA of α-amylase became detectable and α-amylase activity followed. So, it was concluded that the expression of α-amylase activity during leaf senescence should be under the transcriptional control. However, the post-transcriptional regulation could not be excluded. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75125 |
全文授權: | 未授權 |
顯示於系所單位: | 植物科學研究所 |
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