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.

该奖项的全部或部分资金根据《2021 年美国救援计划法案》（公法 117-2）提供。虽然氮气是地球大气中最丰富的气体，但它不能被植物和动物同化，除非将其还原为铵。世界上大多数作物的传统种植方式是施用还原形式的氮作为肥料，尽管它可以提高作物产量，但大部分肥料都被称为固氮。渗入地下水、溪流和海洋，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 多个沿海水域现已被宣布为“死亡区”。一组统称为根瘤菌的土壤细菌可以通过允许豆类选择性地进入新发育的器官（根）来减少（固定）氮，从而与相容的根瘤菌建立互利的关联（共生）。不同豆科植物-根瘤菌群落的固氮效率各不相同；因此，为了获得高产，需要对豆科作物施用氮肥，这会关闭共生固氮（SNF）。提高 SNF 效率，为作物品种和工程菌株的开发提供信息，从而增强 SNF 在低投入、可持续农业方面的经济潜力。将被纳入基于探究和项目的改进的研究生课程实验室，并纳入各种教育活动，包括培训本科生和研究生、博士后研究员以及培训来自德克萨斯州农村的弱势初中和高中女孩，这是一个有趣的方面。 SNF 的机制是宿主菌株特异性，对于有效固氮至关重要，但在遗传和分子水平上仍然知之甚少，因为根际随时含有多种根瘤菌菌株，因此豆科植物宿主区分朋友至关重要。和敌人，此外，为了区分效率较低的朋友，以实现最佳固氮作用，拟议的研究建立在蒺藜苜蓿 MtNPD1 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）协调根瘤菌的假设之上。 npd1 突变体的宿主菌株特异性表型意味着 MtNPD1 可能与根瘤相互作用。某些细菌因素促进根瘤内相容菌株的存活和正常功能将使用各种分子、遗传、蛋白质组、基因组和微观方法来破译MtNPD1和该根瘤特异性的其他四个成员的生物学作用。该项目的主要目标是鉴定 MtNPD1 的植物和/或细菌蛋白伴侣、以菌株依赖性方式进行细胞内 MtNPD1 定位，并鉴定与细化 NPD1 基因功能相关的细菌因子。和宿主菌株特异性，使用泛基因组分析和基因组文库在 npd1 根瘤中具有对比命运的菌株之间切换。总之，拟议的工作旨在增强我们对 M. truncatula 如何选择有利的共生伙伴的理解，从而优化具有特定根瘤菌的 SNF。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。