CAREER: Deciphering the roles of nodule-specific PLAT domain genes in the nitrogen-fixing symbiosis and host-strain specificity

职业：破译根瘤特异性 PLAT 结构域基因在固氮共生和宿主菌株特异性中的作用

• 批准号: 2146440
• 负责人: Catalina Pislariu
• 金额: $ 101.8万
• 依托单位: Texas Woman's University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2146440&HistoricalAwards=false
• 关键词: CAREER; Deciphering; roles; nodule; specific

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117- 2) Although nitrogen is the most abundant gas in the Earth’s atmosphere, it cannot be assimilated by plants and animals unless it is reduced to ammonium and other bioavailable forms, in a process called nitrogen fixation. The conventional way of growing most of the world’s crops is to apply reduced forms of nitrogen as fertilizer. Although it promotes crop yields, much of the fertilizer leaches out into groundwater, streams, and oceans, causing severe ecological disturbances, including overgrowth of plant life, oxygen depletion, and death of animal life. Due to overuse, more than 500 sites of coastal waters worldwide are now declared ‘dead zones’. A group of soil bacteria collectively known as rhizobia can reduce (fix) nitrogen. Legumes establish mutually beneficial associations (symbioses) with compatible rhizobia, by allowing their selective entry into newly developed organs (root nodules), thus acquiring an internal source of fertilizer. Nitrogen fixation efficiency varies in different legume-rhizobia associations; therefore, for high yields, fertilizer nitrogen needs to be applied on legume crops. This shuts down symbiotic nitrogen fixation (SNF). The project seeks to uncover new mechanisms of host-strain specificity to improve SNF efficiency, informing the development of crop varieties and engineered bacterial strains that can enhance the economic potential of SNF for low-input, sustainable agriculture. Research activities from this project will be integrated into an inquiry- and project-based revamped graduate course-lab, and into various educational activities including training of undergraduate and graduate students, a postdoctoral researcher, and training disadvantaged middle- and high school girls from rural Texas. An intriguing aspect of SNF is host-strain specificity, critical for efficient nitrogen fixation, but, still, poorly understood at the genetic and the molecular level. Because the rhizosphere contains multiple rhizobial strains at any time, it is critical for a legume host to distinguish between friend and foe, and, also, to distinguish between efficient and less efficient friends, for optimal nitrogen fixation. The proposed research builds on the hypothesis that the Medicago truncatula MtNPD1 gene (nodule-specific polycystin-1, lipoxygenase, alpha-toxin domain-containing protein) orchestrates rhizobial selection in order to maintain effective nitrogen fixation in root nodules. The host-strain specific phenotype of the npd1 mutant implies that MtNPD1 may be interacting with certain bacterial factors to promote survival and normal function of compatible strains inside root nodules. An assortment of molecular, genetic, proteomic, genomic, and microscopic approaches will be used to decipher the biological roles of MtNPD1 and the other four members of this nodule-specific gene family. The main goals of the project are to identify plant and/or bacterial protein partners of MtNPD1, refine intracellular MtNPD1 localization in a strain-dependent manner, and identify bacterial factors linked to the NPD1 gene function and host-strain specificity using pan-genome analysis and genomic library switching between strains with contrasting fate in npd1 nodules. Altogether, the proposed work is poised to enhance our understanding of how M. truncatula selects favorable symbiotic partners, thus optimizing SNF with specific rhizobial strains.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

虽然氮是地球大气中最丰富的气体，但它不能被植物和动物吸收，除非它被还原为铵和其他生物可利用的形式，在一个称为固氮的过程中。种植世界上大多数作物的传统方法是施用还原形式的氮作为肥料。虽然它提高了作物产量，但大部分肥料会渗入地下水，河流和海洋，造成严重的生态干扰，包括植物过度生长，氧气耗尽和动物死亡。由于过度使用，全世界有500多个沿海沃茨被宣布为“死亡区”。一组土壤细菌统称为根瘤菌可以减少（固定）氮。豆科植物与相容的根瘤菌建立互利关系（共生），允许它们选择性地进入新发育的器官（根瘤），从而获得内部肥料来源。固氮效率在不同的豆科植物根瘤菌协会不同，因此，高产，氮肥需要施加在豆科作物。这关闭了共生固氮（SNF）。该项目旨在揭示宿主菌株特异性的新机制，以提高SNF效率，为作物品种和工程菌株的开发提供信息，从而提高SNF在低投入、可持续农业中的经济潜力。从这个项目的研究活动将被整合到一个调查和基于项目的改造研究生课程实验室，并纳入各种教育活动，包括本科生和研究生，博士后研究员的培训，并培训弱势初中和高中女孩从农村得克萨斯州。 SNF的一个有趣的方面是宿主-菌株特异性，这对有效固氮至关重要，但在遗传和分子水平上仍然知之甚少。因为根际在任何时候都含有多种根瘤菌菌株，所以对于豆科植物宿主来说，区分朋友和敌人是至关重要的，并且，为了最佳的固氮，区分高效和低效的朋友也是至关重要的。这项研究基于以下假设：蒺藜苜蓿MtNPD 1基因（根瘤特异性多囊蛋白-1、脂氧合酶、含α毒素结构域的蛋白质）协调根瘤菌的选择，以维持根瘤的有效固氮。npd 1突变体的宿主菌株特异性表型意味着MtNPD 1可能与某些细菌因子相互作用，以促进根瘤内相容菌株的存活和正常功能。一个分类的分子，遗传，蛋白质组学，基因组学和显微镜的方法将被用来破译MtNPD 1和其他四个成员的这个结节特异性基因家族的生物学作用。该项目的主要目标是确定MtNPD 1的植物和/或细菌蛋白伴侣，以菌株依赖的方式完善细胞内MtNPD 1定位，并使用泛基因组分析和NPD 1结节中具有对比命运的菌株之间的基因组文库切换来确定与NPD 1基因功能和宿主菌株特异性相关的细菌因子。总而言之，所提出的工作是准备加强我们的理解如何M。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。