The Arabidopsis AHK4 histidine kinase is a cytokinin-binding receptor that transduces cytokinin signals across the membrane
The Arabidopsis AHK4 histidine kinase is a cytokinin-binding receptor that transduces cytokinin signals across the membrane
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DOI：
10.1093/pcp/pce127
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发表时间：
2001-09-01
影响因子：
4.9
通讯作者：
Mizuno, T
中科院分区：
文献类型：
--
作者：
Yamada, H;Suzuki, T;Mizuno, T
普通组氨酸到天冬氨酸(His-->；Asp)磷酸转导是原核生物和真核生物中传播某些环境刺激的信号转导范例，其中组氨酸(His)-激酶作为环境信号的感受器起着核心作用。对于高等植物拟南芥，最近的研究表明，His-Kinase(AHK4/CRE1/WOL)是细胞分裂素的感受器，细胞分裂素是一类重要的植物激素，对细胞分裂和分化起调节作用。有趣的是，AHK4能够在真细菌大肠杆菌中作为细胞分裂素传感器发挥作用(Suzuki等人。2001年，植物细胞生理学。42：107)。在这里，我们进一步证明AHK4是一种初级受体，它以高度特异的方式直接结合多种天然和合成的细胞分裂素(例如，不仅N-6-取代的氨基嘌呤，如异戊烯基腺嘌呤、反式玉米素、苯基腺嘌呤，以及二苯基脲的衍生物，如噻二唑脲)(K-d=4.55+/-0.48x10(-9)M)。AHK4有一个推测的胞外区，在这个胞外区内的单一氨基酸替换(Thr-301到ILE)会导致其失去结合细胞分裂素的能力。这种特殊的突变对应于先前报道的wol等位基因(木腿)，该等位基因导致血管形态发生的显著表型缺陷。综上所述，有证据表明AHK4及其同系物(AHK3和可能的AHK2)是可以通过A.thaliana的质膜转导细胞分裂素信号的受体激酶。
Common histidine-to-aspartate (His --> Asp) phosphorelay is a paradigm of signal transduction in both prokaryotes and eukaryotes for the propagation of certain environmental stimuli, in which histidine (His)-kinases play central roles as sensors for environmental signals. For the higher plant, Arabidopsis thaliana, it was recently suggested that the His-kinase (AHK4 / CRE1 / WOL) is a sensor for cytokinins, which are a class of plant hormones important for the regulation of cell division and differentiation. Interestingly, AHK4 is capable of functioning as a cytokinin sensor in the eubacterium, Escherichia coli (Suzuki et al. 2001, Plant Cell Physiol. 42: 107). Here we further show that AHK4 is a primary receptor that directly binds a variety of natural and synthetic cytokinins (e.g. not only N-6-substituted aminopurines such as isopentenyl-adenine, trans-zeatin, benzyl-adenine, but also diphenylurea derivatives such as thidiazuron), in a highly specific manner (K-d = 4.55 +/- 0.48x10(-9) M). AHK4 has a presumed extracellular domain, within which a single amino acid substitution (Thr-301 to Ile) was shown to result in loss of its ability to bind cytokinins. This particular mutation corresponds to the previously reported wol allele (wooden leg) that causes a striking phenotype defective in vascular morphogenesis. Collectively, evidence is presented that AHK4 and its homologues (AHK3 and possibly AHK2) are receptor kinases that can transduce cytokinin signals across the plasma membrane of A. thaliana.