受体蛋白激酶FERONIA响应RALF多肽信号的机制

The mechanism of plant cell expansion is not only a theory focuses in cell signaling transduction, but also a technical bottlenecks remaining to be solved in the application fields for Agriculture and Forestry. Rapid alkalinization factor (RALF) can suppress cell elongation through inhibiting the activity of PM H+-ATPase. FERONIA (FER) receptor kinase can sense RALF peptide directly, but the detailed mechanism that how the FER function as the receptor of RALF is still not clear. Applicant found that FER can interact with another receptor kinase PIK3 directly on plasma membrane, both of the pik3 and fer mutant were insensitive to RALF peptide. Based on these data, this application want to explore three scientific questions: (1) To illustrate the detailed biochemical mechanism of the interaction between FER and PIK3, and to clarify whether FER and PIK3 could work together to sense RALF signal by mutual phosphorylation; (2) To dissect whether the interaction of FER and PIK3 is RALF peptide signaling-dependent and the FER/PIK3 complex whether function as a co-receptor of RALF peptide; (3) To preliminarily study the downstream signal events of RALF-FER/PIK3 pathway, identify the PIK3 interacting proteins. The aim of this application is to promote the understanding molecular mechanisms of RALF-FER signal network which have important role in the cell expansion. In view of the evolutionary conservation of the RALF-FER/PIK3 signaling complex in the plant kingdom, our research conclusions will provide a new target for the crops’ molecular breeding.

植物细胞生长的调控机制不仅是细胞信号转导领域关注度极高的理论焦点，也是农、林等应用领域亟需解决的技术瓶颈。多肽信号RALF能快速抑制质膜氢泵活性从而抑制细胞伸长。受体激酶FER可直接感受RALF多肽信号，但该响应过程早期精细分子机制尚不清楚。申请人发现FER与受体蛋白激酶PIK3在细胞膜上直接互作，pik3及fer突变体都对RALF信号不敏感。基于此，拟探讨三个科学问题：（1）阐明FER与PIK3互作的精细生化机制，分析FER与PIK3的互作是否促进彼此的磷酸化；（2）分析FER/PIK3的互作是否依赖于RALF分子并形成了RALF响应复合体/共受体；（3）初步探讨RALF-FER/PIK3信号途径的下游事件，鉴定PIK3的互作蛋白。本研究旨在促进对RALF-FER信号网络调节细胞生长机制的理解。鉴于该网络在植物界的重要性及保守性，也将为优良农作物品种的分子育种设计提供一个新的靶标。

生物体进化出了复杂的细胞伸长调节机制，植物细胞因为有细胞壁的原因，不仅需要调节细胞膜，而且还需要调节细胞壁酸碱变化来协调细胞伸长，因此植物细胞的细胞伸长调节机制尤为复杂。受体蛋白激酶FERONIA(FER) 定位于细胞膜，通过感受快速碱化因子RALF多肽，启动多个蛋白，比如氢泵AHA, 的磷酸化反应，最终使细胞壁碱化并抑制细胞伸长。但是目前对FER如何响应RALF信号的精细机制并不清楚。本课题研究发现，一个细胞质受体激酶RIPK在细胞膜上以依赖于RALF1多肽的形式与FER互作。生化分析发现FER-RIPK可以通过促进彼此磷酸化响应RALF1信号。FER和RIPK的磷酸化水平都被RALF1快速上调，并且RALF1诱导FER和RIPK的磷酸化，依赖于FER-RIPK的存在。遗传学分析显示，RIPK和FER类似，都正调节根对RALF1信号的响应。因此RALF1-FER-RIPK的互作代表了一个多肽信号响应的机制。