Cyclin-dependent kinases (CDK) 為ㄧ群唯有與Cyclin蛋白結合後方具有活性之蛋白質激酶。其能夠透過磷酸化下游標的蛋白質參與基因表現或是細胞週期的調控。在動物系統中，共有九種CDK已被發現並命名為CDK1-9。其中CDK7, CDK8, CDK9 具有磷酸化RNA polymerase II (RNAPII)之C-terminal domain (CTD)以及許多其他種類的轉錄因子之能力。因此一般認為這三種CDK是透過對CTD的磷酸化參與著基因表現的調控。在植物中目前也已有五種CDK被發現, 分別為CDKA, CDKB, CDKC, CDKD, 以及CDKE。其中只有A型與B型的CDK受到較為廣泛的研究，但其他植物CDK的研究則付之闕如。
　　在本篇中，我們選殖出了阿拉伯芥中的E型CDK (AtCDKE)，以及與其結合之C型cyclin (AtCYCC1)。序列分析指出AtCDKE與CDK8極為相似，暗示了其可能參與基因表現的調控。AtCDKE表現於花粉, 子房, 葉脈及絨毛上，而AtCYCC1的蛋白質只能夠在花中偵測到。利用綠色螢光蛋白進行分析發現，AtCDKE與AtCYCC1皆位於核內，但AtCYCC1亦可在細胞質中發現。根據以上結果，AtCDKE-AtCYCC1複合物可能參與了朵發育的調控。進一步以南方墨點分析AtCDKE的啟動子區域發現，在葉子的DNA中，AtCDKE的譯碼區有受到甲基化的情形。前人對於植物DNA甲基化的研究已指出數個與花朵發育相關的基因有受到甲基化調控的跡象，最近的報告亦提出AtCDKE的突變株之花器發育亦受到影響。因此，綜合以上結果，我們認為AtCDKE-AtCYCC1為ㄧ與花器發育相關的複合物，而且與其他花器發育相關的基因共同受到DNA 甲基化的調控。

　　Cyclin dependent kinase is defined as its activation requires the binding of cyclin partner. In animal, 9 groups of CDK have been identified and named CDK1-CDK9. The CDK7, CDK8, and CDK9 have been known to be able to phosphorylate the C-terminal domain (CTD) of RNA polymerase II (RNAPII) or a variety of transcription factors. Therefore, these CDK are though to be involved in gene expression regulation. In plants, 5 groups of CDK have been identified and the nomenclature CDKA-E was adopted. Comparing with the A- and B- type plant CDK which were extensively studied, relevant research for other pant CDK is lacking.
　　In present study, we isolated an E-type CDK, AtCDKE, and its interacting cyclin, ATCYCC1, from Arabidopsis thaliana. Tissue specific analysis shows AtCDKE was expressed in leaves and flowers, whereas AtCYCC1 proteins were apparently detected in flowers. The subcellular localization of both proteins were also investigated by fusing them with a green fluorescence protein (GFP). While AtCDKE is loalized in nucleus, the AtCYCC1 could be detected in either nuclear or cytoplasmic regions. Such results suggested that AtCDKE-AtCYCC1 complex is involved in the regulation of flower development by exerting its effect on transcriptional control. Moreover, DNA-gel blot analysis shows that the coding region of AtCDKE is methylated. DNA methylation has been known to be involved in the regulation of many flower-related genes’ expression. Recently reports also indicated that AtCDKE controls the development of flowers. Therefore, we suggests that AtCDKE-AtCYCC1 complex is involved in floral development and regulated co-ordinately with other flower-related genes by DNA methylation.

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