Torii Keiko U
Department of Biology, University of Washington, Seattle, Washington 98195, USA.
Int Rev Cytol. 2004;234:1-46. doi: 10.1016/S0074-7696(04)34001-5.
Leucine-rich repeat receptor kinases (LRR-RKs) comprise the largest subfamily of transmembrane receptor-like kinases in plants, with over 200 members in Arabidopsis. LRR-RKs regulate a wide variety of developmental and defense-related processes including cell proliferation, stem cell maintenance, hormone perception, host-specific as well as non-host-specific defense response, wounding response, and symbiosis. Several studies indicate that LRR-RKs act as dimers, and some may form a receptor complex with leucine-rich repeat receptor-like proteins (LRR-RPs) that lack a cytoplasmic kinase domain. Despite the fact that structural features of LRR-RKs are fairy similar, five available ligand molecules for LRR-RKs are structurally diverse, from steroids (brassinolides) to peptides (phytosulfokine and systemin) and secreted proteins (CLV3). Precise ligand-binding sites of LRR-RKs are not understood. However, the extracellular "island" domain that intercepts the LRR domain in some LRR-RKs may play an important role in ligand binding. Advances in unveiling components of three LRR-RK signaling pathways, namely BRI1 in steroid signaling, CLV1 in meristem maintenance, and FLS2 in bacterial elicitor perception, revealed an intriguing link between plant LRR-RK and animal receptor signaling pathways. Finally, rapid progress made in LRR-RK research beyond the model system Arabidopsis has provided exciting, novel insights into the evolution of the LRR-RK signaling system in plants, such as BRI1 utilized in the wound-responsive signaling pathway in Solanaceae plants and recruitment of CLV1 in nodule development in leguminous plants.
富含亮氨酸重复序列的受体激酶（LRR-RKs）是植物中最大的跨膜受体样激酶亚家族，拟南芥中有200多个成员。LRR-RKs调节多种与发育和防御相关的过程，包括细胞增殖、干细胞维持、激素感知、宿主特异性以及非宿主特异性防御反应、创伤反应和共生。多项研究表明，LRR-RKs以二聚体形式发挥作用，有些可能与缺乏细胞质激酶结构域的富含亮氨酸重复序列的受体样蛋白（LRR-RPs）形成受体复合物。尽管LRR-RKs的结构特征非常相似，但LRR-RKs的五种已知配体分子在结构上却各不相同，从类固醇（油菜素内酯）到肽（植物磺肽素和系统素）以及分泌蛋白（CLV3）。LRR-RKs精确的配体结合位点尚不清楚。然而，在一些LRR-RKs中截获LRR结构域的细胞外“岛”结构域可能在配体结合中起重要作用。揭示三条LRR-RK信号通路（即类固醇信号通路中的BRI1、分生组织维持中的CLV1和细菌激发子感知中的FLS2）的组成成分方面的进展，揭示了植物LRR-RK与动物受体信号通路之间的有趣联系。最后，在模式植物拟南芥之外的LRR-RK研究中取得的快速进展，为植物LRR-RK信号系统的进化提供了令人兴奋的新见解，例如茄科植物伤口响应信号通路中利用的BRI1以及豆科植物根瘤发育中CLV1的募集。
