植物激素独脚金内酯的受体识别和信号传导调控的分子机制

Hormones are important for regulating biological activities in both animals and plants. Comprehending hormone action will help uncover the essence of life activities and improve the quality of human life. Hormone perception by its receptor is the crucial point for understanding of hormone action. Enormous efforts made by biologists over the past century have established a general perception mechanism for all the hormones: active form of hormone, which is generated through sequential actions of biosynthesis enzymes, specifically and noncovalently binds its receptor to trigger hormone signal transduction, and eventually dissociates from its receptor without being altered. This feature of reversibility distinguishes hormone-receptor interaction from substrate-enzyme interaction. Hormone strigolactones (SL) play a vital role in the control of plant branching, a key agronomic trait to determine crop yield. Here we present a novel mechanism for hormone perception, which unexpectedly integrates both substrate-enzyme reaction and hormone-receptor interaction, through discovery of CLIM (the covalently-linked intermediate molecule) as a novel active hormone molecule and identification of the α/β hydrolase D14 as a non-canonical receptor that generates and perceives the active form of SL. Once this work was published in Nature, it has been cited and highly evaluated by peers worldwide. However, the precise chemical reaction process, whether this mechanism could be occur in other hormone perception and regulation pathway, remain exclusive. The applicant will investigate all these questions in this project and aim to the further elucidation of this novel hormone regulation pathway from a molecular level.

激素对各种生命活动起着核心的调节作用，其功能的发挥依赖于受体蛋白对激素分子的正确识别。生命科学中对激素受体的认识，近百年一直遵循“活性分子-受体”识别机制，受体非共价可逆地结合天然激素分子，触发信号传导。申请人在前期工作中，与合作者一起以一种调控植物分枝的重要植物激素独脚金内酯（Strigolactone，SL）为对象，首次揭示了一种新型的“底物-酶-活性分子-受体”激素识别机制，受体D14将激素分子加工成为活性分子，再共价结合活性分子，触发信号传导后将活性分子加工成为无生物活性的“废弃物”。这是首次发现激素受体具有识别和合成的双重特性，在Nature发表后受到广泛关注和认可。本项目拟进一步开展SL激素通路调控的分子机制的研究，阐明不同SL激素受体识别和调控下游通路的机制。

项目实施两年来，根据项目的总体目标开展工作，利用生化手段明确了催化位点、底物结合位点、变构位点三个区域对SLs分子加工的过程中的不同影响，解析得到一个三维结构，证实了催化氨基酸突变后，SLs分子依然能够正常结合在底物结合位点，进一步明确了底物结合过程-变构过程-催化反应过程的先后关系，明确了SLs分子加工的时序机制。此外，项目实施中，根据国际相关研究团队的重要进展，增加了研究内容，获得了D3 全长蛋白与 D14 突变蛋白（D14-G158E）与SL复合物的晶体，并将在后续工作中解析该结构，进一步明确SLs分子的加工机制。在项目资助下，在包括PNAS、Nature Microbiology和Nature Communications上发表研究论文三篇。顺利完成了预定目标。