Castells Enric, Casacuberta Josep M
Departament de Genètica Molecular Vegetal, Laboratori de Genètica Molecular Vegetal, CSIC-IRTA, Jordi Girona 18, Barcelona, Spain.
J Exp Bot. 2007;58(13):3503-11. doi: 10.1093/jxb/erm226. Epub 2007 Oct 20.
The structure of plant receptor-like kinases (RLKs) is similar to that of animal receptor tyrosine kinases (RTKs), and consists of an extracellular domain, a transmembrane span, and a cytoplasmic domain containing the conserved kinase domain. The mechanism by which animal RTKs, and probably plant RLKs, signal includes the dimerization of the receptor, their intermolecular phosphorylation, and the phosphorylation of downstream signalling proteins. However, atypical RTKs with a kinase-dead domain that signal through phosphorylation-independent mechanisms have also been described in animals. In the last few years, some atypical RLKs have also been reported in plants. Here these examples and their possible signalling mechanisms are reviewed. Plant genomes contain a much larger number of genes coding for receptor kinases than other organisms. The prevalence of atypical RLKs in plants is analysed here. A sequence analysis of the Arabidopsis kinome revealed that 13% of the kinase genes do not retain some of the residues that are considered as invariant within kinase catalytic domains, and are thus putatively kinase-defective. This percentage rises to close to 20% when analysing RLKs, suggesting that phosphorylation-independent mechanisms mediated by atypical RLKs are particularly important for signal transduction in plants.
植物类受体激酶（RLKs）的结构与动物受体酪氨酸激酶（RTKs）相似，由一个胞外结构域、一个跨膜区和一个包含保守激酶结构域的胞质结构域组成。动物RTKs以及可能的植物RLKs的信号传导机制包括受体二聚化、分子间磷酸化以及下游信号蛋白的磷酸化。然而，动物中也描述了具有激酶失活结构域且通过非磷酸化依赖机制进行信号传导的非典型RTKs。在过去几年中，植物中也报道了一些非典型RLKs。本文对这些例子及其可能的信号传导机制进行了综述。植物基因组中编码受体激酶的基因数量比其他生物体多得多。本文分析了植物中非典型RLKs的普遍性。对拟南芥激酶组的序列分析表明，13%的激酶基因没有保留激酶催化结构域内被认为是不变的一些残基，因此被推测为激酶缺陷型。在分析RLKs时，这一比例上升至接近20%，表明由非典型RLKs介导的非磷酸化依赖机制对植物中的信号转导尤为重要。
