A Transmembrane Hybrid-Type Histidine Kinase in Arabidopsis Functions as an Osmosensor
A Transmembrane Hybrid-Type Histidine Kinase in Arabidopsis Functions as an Osmosensor
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DOI：
10.1105/tpc.11.9.1743
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发表时间：
1999-09
期刊：
影响因子：
11.6
通讯作者：
T. Urao;B. Yakubov;R. Satoh;K. Yamaguchi-Shinozaki;M. Seki;T. Hirayama;K. Shinozaki
中科院分区：
文献类型：
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作者：
T. Urao;B. Yakubov;R. Satoh;K. Yamaguchi-Shinozaki;M. Seki;T. Hirayama;K. Shinozaki
水分亏缺和由此产生的渗透胁迫会影响植物的生长。为了了解植物细胞如何监控和响应水分胁迫下的渗透变化，我们从脱水的拟南芥植物中分离了一条cdna。该基因编码一种新的杂交型组氨酸激酶ATHK1。限制性片段长度多态图谱显示ATHK1基因位于2号染色体上。预测的ATHK1蛋白在N端有两个假定的跨膜区，结构上与酵母渗透传感器合成的N端致死规则1(SLN1)相似。在正常生长条件下，ATHK1转录本在根中的含量高于其他组织，并在高渗透压或低渗透压条件下积累。由ATHK1启动子驱动的β-葡萄糖醛酸酶活性的组织化学分析进一步表明，ATHK1基因转录上调，以响应外部渗透压的变化。ATHK1基因的过表达抑制了温度敏感型渗透感受缺陷酵母突变体sln1-ts的致死性。相反，其中保守的His或Asp残基被取代的ATHK1 cDNAs未能补充sln1-ts突变体，表明ATHK1具有组氨酸激酶的功能。将ATHK1c DNA导入酵母双突变体Sln1ΔSho1Δ中，可抑制高盐条件下的致死性，并激活高渗透压甘油反应1丝裂原活化蛋白激酶。这些结果表明，ATHK1作为一个渗透感受器将应激信号传递到下游的MAPK级联。
Water deficit and the resulting osmotic stress affect plant growth. To understand how plant cells monitor and respond to osmotic change from water stress, we isolated a cDNA from dehydrated Arabidopsis plants. This cDNA encodes a novel hybrid-type histidine kinase, ATHK1. Restriction fragment length polymorphism mapping showed that the ATHK1 gene is on chromosome 2. The predicted ATHK1 protein has two putative transmembrane regions in the N-terminal half and has structural similarity to the yeast osmosensor synthetic lethal of N-end rule 1 (SLN1). The ATHK1 transcript was more abundant in roots than other tissues under normal growth conditions and accumulated under conditions of high or low osmolarity. Histochemical analysis of β-glucuronidase activities driven by the ATHK1 promoter further indicates that the ATHK1 gene is transcriptionally upregulated in response to changes in external osmolarity. Overexpression of the ATHK1 cDNA suppressed the lethality of the temperature-sensitive osmosensing-defective yeast mutant sln1-ts. By contrast, ATHK1 cDNAs in which conserved His or Asp residues had been substituted failed to complement the sln1-ts mutant, indicating that ATHK1 functions as a histidine kinase. Introduction of the ATHK1 cDNA into the yeast double mutant sln1Δ sho1Δ, which lacks two osmosensors, suppressed lethality in high-salinity media and activated the high-osmolarity glycerol response 1 (HOG1) mitogen-activated protein kinase (MAPK). These results imply that ATHK1 functions as an osmosensor and transmits the stress signal to a downstream MAPK cascade.