阿拉伯芥內CIA2蛋白調節Chaperonin10基因之表現分析
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2009
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植物體內進行光合作用時，葉綠體扮演了非常重要的角色。然而葉綠體內大部分的蛋白質是由細胞核內的基因進行轉錄後，送到細胞質中轉譯產生蛋白質，再藉由葉綠體外膜以及內膜上的轉運蛋白機組(translocon complex)送進葉綠體內。隨後，這些進入葉綠體的蛋白質，必須經由chaperonin 60 (Cpn60)以及chaperonin 10 (Cpn10)所組成的複合體，將其摺疊成成熟的構形，蛋白質才能具有正常的功能。在阿拉伯芥中有兩個同源基因AT2G44650 (Cpn10-II)及AT3G60210 (Cpn10-III)與編譯葉綠體型Cpn10蛋白有關，但是根據我們之前微矩陣以及染色質免疫沉澱分析的研究發現，Cpn10-II表現會受到轉錄因子CIA2的調節，而Cpn10-III則不會明顯地受到CIA2的影響。在此研究中，轉殖植株實驗顯示CIA2不但能調節Cpn10-II基因表現量，並且是造成Cpn10-II有專門組織表現的主因。定量反轉錄聚合酶連鎖反應則顯示Cpn10-II在植株中的表現量的確受CIA2的調節，而且其表現量亦隨植齡的增加而遞減。Cpn10-III基因則是在缺少CIA2轉錄因子的植株中，相對轉錄表現較野生型植株中來得高。這些結果顯示Cpn10-II基因確實會受到CIA2蛋白的調控，而Cpn10-III基因會在Cpn10-II基因表現降低時提高，以彌補Cpn10-II基因的功能。
Chloroplast plays an important role in plant photosynthesis. However, most chloroplastic proteins are transcribed in nucleus, translated in cytoplasm, and then imported into chloroplasts through translocon complex. Therefore, theses nuclear-encoded chloroplastic proteins have to be folded correctly afterwards by chaperonin complex which are assembled with Chaperonin 60 (Cpn60) and Chaperonin 10 (Cpn10) to maintain their biological functions in chloroplasts. Two chloroplastic Cpn10-encoding genes, AT2G44650 (Cpn10-II) and AT3G60210 (Cpn10-III), are found in Arabidopsis thaliana based on homological search. According to our previous microarray and chromatin immuno-precipatation (ChIP) analyses, we found a transcription factor CIA2 which could directly regulate the expression of Cpn10-II gene but not Cpn10-III. In this study, the results of transgenic studies reveal that CIA2 is responsible for regulating the yield of protein and tissue specificity of Cpn10-II expression. Quantitative RT-PCR analyses also suggest that Cpn10-II expression is up-regulated by CIA2 in an age-dependent manner. In contrast, Cpn10-III seems to have higher expression in cia2 and cia2/Cpn10-II plants. We conclude that Cpn10-II expression is indeed regulated by CIA2, and the Cpn10-II defect can be compensated by Cpn10-III.
Chloroplast plays an important role in plant photosynthesis. However, most chloroplastic proteins are transcribed in nucleus, translated in cytoplasm, and then imported into chloroplasts through translocon complex. Therefore, theses nuclear-encoded chloroplastic proteins have to be folded correctly afterwards by chaperonin complex which are assembled with Chaperonin 60 (Cpn60) and Chaperonin 10 (Cpn10) to maintain their biological functions in chloroplasts. Two chloroplastic Cpn10-encoding genes, AT2G44650 (Cpn10-II) and AT3G60210 (Cpn10-III), are found in Arabidopsis thaliana based on homological search. According to our previous microarray and chromatin immuno-precipatation (ChIP) analyses, we found a transcription factor CIA2 which could directly regulate the expression of Cpn10-II gene but not Cpn10-III. In this study, the results of transgenic studies reveal that CIA2 is responsible for regulating the yield of protein and tissue specificity of Cpn10-II expression. Quantitative RT-PCR analyses also suggest that Cpn10-II expression is up-regulated by CIA2 in an age-dependent manner. In contrast, Cpn10-III seems to have higher expression in cia2 and cia2/Cpn10-II plants. We conclude that Cpn10-II expression is indeed regulated by CIA2, and the Cpn10-II defect can be compensated by Cpn10-III.
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cpn10, groES, groEL, CIA2