生长素和茉莉酸共受体的分子和功能进化

受体蛋白是如何在进化过程中识别不同的配体来响应体内、外信号一直是生命科学研究的主题之一。具有共同祖先的生长素和茉莉酸受体TIR1/AFB和COI1蛋白在进化过程中分别利用化学结构截然不同的IAA和JA-Ile作为配体。结合系统发育分析、蛋白质祖先序列重建和分子对接模拟，初步研究发现JA-Trp可能是TIR1/AFB及COI1蛋白祖先蛋白的配体而且现存COI1蛋白保留JA-Trp的古代配体活性。在已有基础上，我们提出了JA-Trp 参与调节JA 信号脱敏及IAA 与JA 信号动态平衡的模型。本项目将进一步在拟南芥中用实验证明这个模型并在森林草莓中加以验证。对森林草莓COI1蛋白功能的研究也将填补蔷薇科植物COI1蛋白功能的空白，并进一步揭示COI1蛋白在不同植物族系中的功能进化。由于植物在生长和防卫中的投入权衡是决定植物生态适应和作物产量的关键因素，我们的研究也将为提高作物产量提供新的思路。

How receptor proteins have evoloved to recognize their specific ligands to perceive and response to various interal and external cues is a common theme in life sciences. During evolution, the structurally similar TIR1/AFB and COI1 proteins have diverged from a common F-box containing ancestor to function as the coreceptors of auxin and jasmonate (JA) phytohormones respectively. Capitalizing on chemically distinct indole-3-acetic acid (IAA) or jasmonyl-isoleucine as their cognate ligands is posited to be one of the driving forces for their divergence. The evolution of the ligand affinities of these two group proteins, however, remains untackled. By combining in silico analyses and experimental validation, we will explore the ligand affinity evolution of TIR1/AFB and COI1 proteins in land plants. Our preliminary findings suggest that their distinct ligand affinities have diverged from that of an ancestral protein with high affinity to jasmonoyl-tryptophan (JA-Trp). In addition, the ancient JA-Trp affinity could be retained in extant COI1 proteins. In this project, we will demonstrate in Arabidopsis thaliana that JA-Trp is invoved both in desensitation of JA signal and in orchestrating the homeostasis between auxin and JA signaling. In addition, we will confirm these results in woodland straberry, which will provide further insights into the functional divergence of COI1 prteins in various land plant lineages. Since the homeostasis betwwen plant growth and defense is critical for plant ecological adaption and crop yield, our findings will thus provide new avenue for improve crop yield.