• 作者： 陳益明; 林秋榮
• 作者服務機構： 國立臺灣大學植物學系
• 中文摘要： 本篇綜合報告是作者十年來研究植物生長素（auxin）改變植物體核糖核酸（RNA）的生合成與植物生長之關係，以過去所得之一些結果及其他相關的文獻加以綜合。 核糖核酸之代謝，在正常或經植物生長素引起之生長轉變都會產生顯著的改變。正常生長中的黃豆幼苗，在細胞分裂或細胞延長之早期，都會有顯著之RNA累積現象，但在完全延長的細胞內則無RNA的累積；在成熟區的細胞其RNA量則有少量的減少。若施噴2,4-D（一種人工合成的植物生長素）接會導致幼苗生長類型之改變（圖一），而且RNA的代謝也發生顯著的改變：在a區的細胞分裂受到抑制；a區與b區的細胞延長會停頓；但是b區與c區的細胞則被誘導而變成腫脹。經植物生長素處理12小時後，在c區的細胞開始被誘導而進行細胞分裂，同時也大量累積RNA，尤其是rRNA。在c區的成熟部細胞在此時也開始引起細胞核仁之體積的增大，rRNA的合成速率增加約8至10倍。因植物幼苗經植物生長素的處理，促使增加核仁RNA polymerase I的活性，並且促進其轉錄rRNA基因合成rRNA鏈之增長速率。由於rRNA的大量合成，進而在核仁聚合成前核糖體（preribosomal particles）及其累積，再加上部份核仁染色質上的蛋白質的增加是導致核仁腫脹之最大可能原因。 在細胞核內之RNA polymerase I的活性會隨植物之生長情況而調節：增加或降低其活性。植物生長素的處理也會誘導改變黃豆幼苗（切離的或整株的）下胚軸內可轉譯的mRNA族群。從黃豆下胚軸延長部或成熟部切離的組織，經2,4-D處理60分鐘接再分離它的poly(A)+RNA，並且在試管中轉譯蛋白質，由結果發現至少有10至12種新蛋白質的出現。這些特殊的mRNA是經上述處理後才開始轉錄出的。這些mRNA所轉譯出的蛋白質，其分子量介於24,000至32,000 dal-tons之間。 經2,4-D處理過的核仁染色質對核酸分解（nuclease）是比不經植物生長素處理者敏感。因2,4-D處理過後，它會促進染色質上的組蛋白H1及酸性蛋白質的磷酸化作用，這些可能是促進rRNA的合成及轉譯出新蛋白質的重要原因。 由上面所列舉的研究結果將可提供植物生長素調節植物之生長及其基因表現之間的相互關係。
• 英文摘要： This paper reviews the results of our research in the past ten years and other related papers that havebeen directed toward the regulation of RNA synthesis by auxin in relation to growth in higher plants There are marked changes in RNA metabolism associated with normal or auxin-induced growth tran-sitions in plant tissues. During normal development in soybean seedlings, there is a large net accumulationof RNA in the dividing and elongating cells, but net accumulation of RNA ceases in the fully elongated cellsand a small net decrease in RNA content occurs in mature cells. Treatment of the seedlings with auxinleads to very marked aberrations in the growth pattern and in RNA metabolism. Cell division is inhibitedin zone a, cell elongation ceases in zones a and b and radial elanrgement of cells is induced in zones b and c(Fig. 1）. After 12 hr of auxin treatment, cell division is initiated and the accumulation of RNA, especiallyrRNA, is induced at zone c. Auxin treatment of quiescent mature tissue (zone c) leads to a dramatic increase in nucleolar volumeassociated with a 8-to 10-fold increase in the rate of rRNA synthesis. This is due to the auxin enhancementof the nucleolar RNA polymerase I activity in the transcription of rRNA through the increase in the pro-pagation rate. The large accumulation of preribosomal particles and a small increase in nucleolar chromatinprotein correlates with the morphological enlargement of nucleoli. Auxin treatment also induces changes in the population of translatable mRNA in excised or intactsoybean hypocotyl. The in vitro translation products of poly(A)+RNA isolated from 2,4-D treated elon-gating or mature hypocotyl are analyzed by 2-D gel electrophoresis indicating at least 10 to 12 polypeptidesare modulated upward. The nucleolar chromatin from 2,4-D treated tissues are much more sensitive to nuclease digestionthan that from non-treated tissues. The enhancement of phosphorylation of H1 histone and some of acidicproteins in chromatin may be a significant cue for an increase in synthesis of rRNA and also mRNA for newproteins in response to auxin. The results presented here will provide the basis for investigating the causal relationship betweenauxin-regulated gene expression and auxin-induced physiological processes.
• 中文關鍵字： Soybean seedlings; RNA polymerases; RNA syntesis; poly(A)+ RNA in vitro transla- tion; nuclei; nucleoli; chromatin; phosphorylation of nuclear proteins; DEAE-cellulose chromatography; nucleosomes
• 英文關鍵字： --