水稻RNA绑定蛋白TPR1调控稻瘟病广谱抗性的分子机制

Through recent decades of efforts, a lot of progresses have been achieved in light of rice resistance against blast caused by Magnaporthe oryzae (M. oryzae), the most devastating disease for rice. However, broad-spectrum resistance to blast and its underlying mechanism remain largely unknown. We obtained a novel rice blast disease resistant mutant, h1006, through EMS-mediated mutagenesis. The h1006 mutant confers broad-spectrum resistance against M. oryzae without affecting agricultural traits or yield. By using a strategy combining map-based cloning and whole genome sequencing, we identified the tpr1 gene, which encodes an RNA binding protein, and found that disruption of the Tpr1 gene in the h1006 mutant causes broad-spectrum resistance. We propose three aims: (1) isolate one or two TPR1-associated proteins (TAPs) and one or two TPR1-associated RNAs (TARs); (2) elucidate the molecular regulation by TPR1 and TAPs on modification of key immunity-related TARs, including cleavage, degradation, and mistranslation; (3) characterize the biological roles of TAPs and TARs on tpr1-mediated blast resistance. Through these studies, we will uncover the molecular mechanism regulating broad-spectrum resistance mediated by the TPR1 RNA binding protein. Because there are no similar reports in plants previously, our work will broaden basic knowledge in understanding and applying broad-spectrum resistance to rice blast and possibly other plant diseases. Our work will also provide an important model of studying broad-spectrum resistance in other crops.

水稻稻瘟病抗病机制是植物抗病研究的热点，但广谱抗病及其分子机理报道很少。利用EMS诱变我们获得了一份稻瘟病广谱抗病水稻材料h1006，与其野生型水稻相比，该材料重要农艺性状和产量性状没有明显变化。前期的研究中我们发现编码RNA结合蛋白的基因Tpr1突变后水稻h1006表现出对稻瘟病的广谱抗病性，并且证实了TPR1能够结合RNA。本项目拟利用植物病理、植物生理、分子遗传及分子生化等技术手段研究RNA绑定蛋白TPR1如何通过与其关键互作蛋白TAPs相互作用、相互修饰，来影响参与免疫反应的关键RNA的修饰（如剪切，降解或翻译等），进而影响水稻免疫反应，从而系统阐述TPR1调控稻瘟病广谱抗性的分子机制。由于先前在拟南芥、水稻以及其他植物中尚未有类似的研究和报道，该研究将为广泛利用广谱抗病位点tpr1提高水稻稻瘟病抗性提供新的重大理论基础，还将为其他植物广谱抗病分子机制的研究提供重要借鉴。

水稻病害严重威胁粮食安全，利用广谱抗性基因进行抗病育种改良是防控病害最经济有效和环保的途径，但目前只报道了少数广谱抗性位点及其分子机制。本项目围绕赋予水稻广谱抗病性的RNA结合蛋白TPR1，又名BSR-K1，详细研究了其生化机制及遗传学功能。发现TPR1能够结合苯丙氨酸解氨酶（phenylalanine ammonia-lyase1，OsPAL1）基因的mRNA并促进它们的折叠降解。TPR1基因功能缺失时，水稻会积累更多的OsPAL1基因的mRNA，导致合成的木质素含量增加而提高抗病性；OsPAL1基因的过表达也能增强水稻木质素的合成和抗病性。进一步通过酵母双杂交鉴定出TPR1的两个互作蛋白TPR1-Associated Proteins（TAP1和TAP2），它们与TPR1在水稻不同生育期具有类似的基因表达特征。功能分析表明，TAP1和TAP2与TPR1在抗病过程中发挥类似作用，比如在TAP1和TAP2缺失的水稻突变株系中，OsPAL1的mRNA积累量增加、病原物相关（pathogen-related, PR）基因表达增强、水稻的抗病性提高。综上所述，TPR1作为一个RNA结合蛋白，通过和TAP1和TAP2相互作用以调控OsPAL1的mRNA折叠降解，进而调控水稻抗病性。本研究深化了对广谱抗性新位点TPR1分子作用机制的认识，为水稻广谱抗性育种提供了重要资源。