苜蓿PR10蛋白调控根瘤共生中防御反应的分子机制研究

植物自身防御反应是调控植物与不同微生物互作的关键。根瘤菌—豆科植物的共生固氮是菌植互作研究中的范例，根瘤菌的入侵、定殖以及根瘤发育等都受到宿主防御反应的严格调控。申请者前期研究在苜蓿中克隆了一个基因NAD1，该基因缺失突变体表现为根瘤防御反应过度激活，根瘤坏死和固氮活性丧失。我们发现免疫应答家族基因PR10在苜蓿nad1突变体根瘤中高度表达，在nad1突变体中转基因敲除PR10基因后，根瘤中免疫反应显著降低，根瘤恢复固氮能力。多数PR10蛋白具有核酸酶活性，这暗示PR10可能通过对核酸的降解调控根瘤中的防御反应。本申请拟通过遗传学、生物化学和分子生物学等手段研究PR10介导根瘤防御反应的分子机制，揭示PR10基因表达机制，鉴定和分析PR10下游靶标，从分子水平解析核酸降解途径参与调控共生固氮的作用机制，揭示豆科植物如何耐受根瘤菌在植物细胞内入侵、定殖、分化、固氮且不产生防御反应的机理。

The defense response of plant is the key to regulating the interaction betweenplants and microorganisms. The symbiotic nitrogen fixation of Rhizobium-legumes isan example in the study of bacterial interaction with host. The invasion,colonization and nodule development of Rhizobium are strictly regulated by host defense responses. In the previous study, our group cloned a gene NAD1, which showed excessive activation of nodule defense, loss of nodule necrosis and nitrogen fixation activity. We found that the immune response family gene PR10 is highly expressed in the Medicago truncatula nad1 nodule. After knockout of the PR10 gene in the nad1, the immune response in the nodule is significantly reduced, and the nodule restores nitrogen fixation capacity. Most PR10 proteins have nuclease activity, suggesting that PR10 may regulate defense responses in nodules by degrading nucleic acids. This application intends to study the molecular mechanism of PR10-mediated nodule defense response through genetics, biochemistry and molecular biology, reveal the mechanism of PR10 gene expression, identify and analyze the target of PR10 downstream, and analyze the nucleic acid degradation pathway at the molecular level to participate in the regulation of symbiotic nitrogen fixation. The mechanism of action reveals how the leguminous plants tolerate the mechanism of rhizobial invasion, colonization, differentiation, nitrogen fixation and no defense response in plant cells.