Roles of OsCKI1, a rice casein kinase I, in root development and plant hormone sensitivity

5.914
Wei Liu, Zhi-Hong Xu, Da Luo, Hong-Wei Xue
The Plant Journal, 2003, 36(2): 189-202  DOI: 10.1046/j.1365-313X.2003.01866.x;      追溯原文......本站官方QQ群:62473826
Oryza sativa; casein kinase I (CKI); brassinosteroid (BR); abscisic acid (ABA); auxin

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.

编码水稻酪蛋白激酶I的基因OsCKI1在根系发育和激素应答中的作用

酪蛋白激酶在许多物种的细胞分裂及分化过程中都有重要作用。在水稻中,以经过油菜素内酯处理的水稻幼苗为材料,通过cDNA微矩阵的方法得到了一个全长1939bp的基因OsCKI1。该基因编码的蛋白产物属I型酪蛋白激酶(CKIs),含463个氨基酸。RT-PCR及Northern blot结果显示,基因OsCKI1在水稻各组织中表现为组成型表达,并且其表达受油菜素内酯(BR)及脱落酸(ABA)的诱导。在大肠杆菌中对该基因进行原核表达,酶活测定显示该蛋白产物可磷酸化酪蛋白。通过构建OsCKI1的反义载体并转化水稻,对该基因的生理功能进行了研究。对转基因植株的纯系表型进行了观察,显示其根部发育异常,表现为具有较短的初生根、侧根及不定根数目少于对照。进一步研究显示初生根的变短是由于细胞延伸受抑制引起的。以CKI的特异性抑制剂,CKI-7处理野生型植株,也对OsCKI1缺失引起的表型进行了确认。值得注意的是,以外源生长素(IAA)处理转基因及经CKI-7处理过的野生型植株,都能恢复根部表型,使其生长正常。对反义植株初生根及次生根的游离生长素含量测定结果显示,OsCKI1可能在IAA的代谢途径中发挥作或者影响生长素水平。转基因植株的种子在萌发时对ABA及BR的处理都表现为不敏感,暗示该基因可能在各种激素信号转导途径中都有作用。利用OsCKI1-GFP融合蛋白对亚细胞定位进行了研究,显示主要定位于核中,可能参与了基因表达的调节。同时,以该反义转基因植株为材料,通过cDNA芯片的技术研究了受OsCKI1调节的基因的表达谱,结果显示该基因的缺失的确影响了参与信号转导及激素代谢途径的许多基因的表达。


基因列表
  杂种衰退;酪蛋白激酶 hbd2; OsCKI1; LTG1; LTRPK1