Roles of OsCKI1, a rice casein kinase I, in root development and plant hormone sensitivity
Roles of OsCKI1, a rice casein kinase I, in root development and plant hormone sensitivity
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DOI：
10.1046/j.1365-313x.2003.01866.x
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发表时间：
2003-10-01
期刊：
影响因子：
7.2
通讯作者：
Xue, HW
中科院分区：
文献类型：
--
作者：
Liu, W;Xu, ZH;Xue, HW
酪蛋白激酶在跨物种的细胞分裂和分化中至关重要。利用cDNA微阵列技术，在油菜素内酯（BR）处理下，克隆到一个水稻酪蛋白激酶I（CKI）的cDNA片段，并克隆到一个1939 bp的全长cDNA OsCKI 1，编码463个氨基酸。RT-PCR和北方印迹分析表明，OsCKI 1在水稻各组织中均组成型表达，并受到BR和脱落酸（阿坝）处理的上调。对大肠杆菌中表达的重组OsCKI 1蛋白进行酶活性测定，结果表明该蛋白具有磷酸化酪蛋白的能力。通过反义转基因技术研究了OsCKI 1的生理作用，结果表明，纯合转基因植株表现出根发育异常，侧根和不定根数量减少，初生根缩短，细胞伸长减少。用CKI的特异性抑制剂CKI-7处理野生型植物也证实了OsCKI 1的这些功能。有趣的是，在转基因和CKI-7处理的植物中，外源提供的IAA可以恢复正常的根发育，并且CKI缺陷的初生根和不定根中游离IAA含量的测量揭示了生长素含量的改变，这表明OsCKI 1参与生长素代谢或可能影响生长素水平。在萌发过程中，OsCKI 1对阿坝和BR处理的敏感性低于对照，表明OsCKI 1可能参与了多种ABA信号转导途径。OsCKI 1-GFP融合研究显示OsCKI 1定位于细胞核，表明可能参与基因表达的调控。在OsCKI 1基因缺失的植株中，利用cDNA芯片技术研究了基因的差异表达，结果表明与信号转导和激素代谢相关的基因确实发生了表达改变。
Casein kinases are critical in cell division and differentiation across species. A rice cDNA fragment encoding a putative casein kinase I (CKI) was identified via cDNA macroarray under brassinosteroid (BR) treatment, and a 1939-bp full-length cDNA, OsCKI1, was isolated and found to encode a putative 463-aa protein. RT-PCR and Northern blot analysis indicated that OsCKI1 was constitutively expressed in various rice tissues and upregulated by treatments with BR and abscisic acid (ABA). Enzymatic assay of recombinant OsCKI1 proteins expressed in Escherichia coli showed that the protein was capable of phosphorylating casein. The physiological roles of OsCKI1 were studied through antisense transgenic approaches, and homozygous transgenic plants showed abnormal root development, including fewer lateral and adventitious roots, and shortened primary roots as a result of reduced cell elongation. Treatment of wild-type plants with CKI-7, a specific inhibitor of CKI, also confirmed these functions of OsCKI1. Interestingly, in transgenic and CKI-7-treated plants, exogenously supplied IAA could restore normal root development, and measurement of free IAA content in CKI-deficient primary and adventitious roots revealed altered auxin content, indicating that OsCKI1 is involved in auxin metabolism or that it may affect auxin levels. Transgenic plants were less sensitive than control plants to ABA or BR treatment during germination, suggesting that OsCKI1 may be involved in various hormone-signaling pathways. OsCKI1-GFP fusion studies revealed the localization of OsCKI1 to the nucleus, suggesting a possible involvement in regulation of gene expression. In OsCKI1-deficient plants, differential gene expression was investigated using cDNA chip technology, and results indicated that genes related to signal transduction and hormone metabolism were indeed with altered expression.