Phytohormones,as signaling molecules,play critical roles in regulating cell-to-cell and cell-to-environment communications.The mechanisms plant cells use to perceive phytohormones remain hot research topics in plant biology.Previous studies indicated that most plant hormones are perceived by non-covalent physical interactions with their corresponding receptors.After signaling pathways are initiated,the ligands usually dissociate with their binding receptors,which can interact with other receptor molecules or go through a degradation pathway.Therefore,ligand-receptor interaction is distinct from substrate-enzyme association.Recently,Xie and colleagues resolved a 3D structure of a strigolactone-induced AtD14-D3-ASK1 receptor complex.Strigolactones could be cleaved into a covalent-linked intermediate molecule in the reaction center of AtD14,the receptor of strigolactones.Further analyses revealed detailed molecular mechanisms of strigolactone-induced ligand-receptor complex formation and subsequent signaling initiation.Such a mechanism has never been reported in plants.These results provide significant insights into our better understanding of cellular signaling in plants.%植物激素在调控细胞与细胞及细胞与环境的相互作用中起着至关重要的作用.作为一种信号分子,植物激素如何被植物细胞感知一直是植物生物学研究的热点.与底物-酶相互作用的结果不同,激素分子与受体结合后会触发信号转导,但激素分子一般不会被受体修饰,信号转导起始后激素分子通常会从复合体中释放出来被重新利用或降解.近期,我国科学家通过对独脚金内酯及其受体复合体(AtD14-D3-ASK1)的结构学解析,发现独脚金内酯的生物活性分子CLIM (covalently linked intermediate molecule)是独脚金内酯被其受体水解后得到的中间分子.研究表明,CLIM与受体AtD14的催化中心以共价键相结合,进而激活其信号转导.该研究揭示了一种全新的“底物-酶-活性分子-受体”激素识别机制.这种配体-受体作用新机制的发现为植物激素研究开拓了新的视野.
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