Research of Cytokinin Signaling

本研究旨在更好地了解细胞分裂素信号通路。为此，我们分离出对细胞分裂素反应改变的拟南芥突变体。我们使用强转录增强子（4x35s增强子）或化学物质作为诱变剂。我们之前在具有强转录增强子的转化子中分离出具有组成型细胞分裂素反应的cki1和cki2突变体。在这项研究中，我们分离了cki2突变的致病基因，并表明该基因编码一种组氨酸激酶。CK12产物的典型特征是它被预测驻留在细胞质上，而拟南芥中所有其他组氨酸激酶被预测驻留在棕榈膜上。在ck2突变体中，在CK12基因的编码区插入了4x 35S增强子。CK12基因的转录在增强子内启动，可能导致产物缺乏其Nterminal区域的一部分。我们还分离出细胞分裂素高敏感突变体和低敏感突变体ckh1和ckl1的致病基因，这两种突变体分别是从EMS诱变人群中分离出来的。CKH1基因编码一种与TAFs相似的产物，TAFs是转录起始复合物的成员。CKL1基因编码组氨酸激酶，强调了细胞分裂素感知中双组分系统的重要性。

This research was aimed at a better understanding of the cytokinin signaling pathway. For this purpose we have isolated Arabidopsis mutants that exhibit altered responses to cytokinins. We used either a strong transcriptional enhancer(4x35s enhancer) or a chemical as a mutagen. We previously isolated the cki1 and cki2 mutants, which exhibit constitutive cytokinin responses, among transformants with the strong transcriptional enhancer. In this study we have isolated the causal gene for cki2 mutant, and shown that the gene codes for a histidine kinase. The typical feature of the CK12 product is that it is predicted to reside at the cytoplasm, while all other histidine kinases in Arabidopsis are predicted to reside at the palsmamembrane. In the cki2 mutant, the 4x 35S enhancer was inserted in the coding region of the CK12 gene. Transcription of the CK12 gene initiated within the enhancer, probably resulting in the production of a product lacking part of its Nterminal region. We have also isolated the causal genes for cytokinin hyper and less-sensitive mutants, ckh1 and ckl1 respectively, which were isolated from an EMS mutagenized population. The CKH1 gene code for a product with similarity to TAFs, which are members of the transcriptional initiation complex. The CKL1 gene coded for a histidine kinase, emphasizing the importance of the two-component systems in cytokinin perception.