CAREER:IDENTIFICATION AND CHARACTERIZATION OF NOVEL GENETIC PLAYERS IN THE EARLY SIGNALING PATHWAYS OF PLANT-MICROBE SYMBIOSES

在集约化农业中过度使用化肥和农药等农用化学品，不仅增加了种植成本，而且对各种生态系统造成严重的健康危害和威胁。可持续农业旨在为未来保护自然储备，需要最少的化学投入，促进有效的养分循环，并加强关键的微生物驱动过程，如养分获取和对植物病原体的保护。根瘤菌和菌根真菌是土壤有益微生物的主要类群，它们帮助植物满足对氮和磷的需求，从而显著减少氮肥和磷肥的外源施用。虽然菌根关联在大多数陆地植物中广泛存在，但固氮根瘤菌关联仅限于豆科植物。本项目旨在剖析豆科植物与根瘤菌共生的分子机制，设计并将这种共生机制引入谷类作物。这对农民来说将是一个巨大的福音，因为能够与固氮根瘤菌建立共生关系的谷物作物品种的可用性将最大限度地降低其种植成本。除了进一步了解植物-微生物共生的现有知识外，该项目还将为研究人员的研究和教育目标的整合提供充足的空间，并支持独特的教育计划，致力于为来自第一代，低收入，代表性不足的少数群体的本科生，K-12教师和威斯康星州公立学校的学生提供基于研究的学习平台。作物和微生物之间的共生关系在提高农业生产力和可持续性方面发挥着至关重要的作用。在农业生态系统中，促进作物营养的两个最重要的共生系统是豆科植物的根结瘤和丛枝菌根。对模式豆科植物如荆芥（Medicago truncatula）和日本莲花（Lotus japonicus）的遗传学研究使我们了解了控制这些共生关联建立的分子机制，并表明两种共生关系之间存在共同共生途径（Common Symbiotic Pathway， CSP），其中荆芥（Medicago truncatula） DOES NOT MAKE INFECTIONS 1、2和3 （DMI1、DMI2和DMI3）发挥了核心作用。这开启了一种令人兴奋的可能性，即操纵这种保守的CSP来改善共生微生物和作物植物之间的联系。为了实现这一令人兴奋的目标，需要对共生信号转导机制有一个全面的了解。本项目旨在通过基因抑制因子筛选，鉴定和表征早期信号通路中的新基因，然后通过全基因组测序绘制抑制因子位点，克隆新基因进行功能表征。该项目将使研究人员能够识别在常规的结瘤缺陷突变体筛选中遗漏的新成分，并产生新的分子机制知识，使共生关联可以应用于豆类和非豆类作物。因此，该项目不仅将为控制植物-微生物共生的分子机制提供基本见解，而且还将确定在谷类作物中设计更有效的固氮关联的潜在目标。该奖项反映了美国国家科学基金会的法定使命，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。

Excessive use of agrochemicals, such as fertilizers and pesticides in intensive agriculture has not only increased the cost of cultivation but also poses severe health hazards and threats to various ecosystems. Sustainable agriculture aims at preserving the natural reserves for the future, demands minimum chemical inputs, promotes efficient nutrient recycling, and enhances the critical microbial-driven processes, such as nutrient acquisition and protection against plant pathogens. Rhizobia and mycorrhizal fungi are the primary groups of beneficial soil microbes, which help the plants in meeting their demand for nitrogen and phosphorous, thereby significantly reducing the exogenous application of nitrogen and phosphate fertilizers. Although mycorrhizal associations are widely prevalent among most land plants, nitrogen-fixing rhizobial associations are limited only to legumes. This project aims at dissecting the molecular mechanisms of legume-rhizobia symbiosis to engineer and introduce this symbiotic machinery into cereal crops. This will be a great boon to the farmers, as the availability of cereal crop cultivars that are capable of establishing symbiotic associations with nitrogen-fixing rhizobia will minimize their cost of cultivation manifold. In addition to furthering existing knowledge on plant-microbe symbioses, the project will provide ample scope for the integration of research and educational goals of the researcher and support unique educational programs dedicated to provide a research based-learning platform to undergraduate students from first-generation, low-income, under-represented minority groups, K-12 teachers and students of Wisconsin public schools. Symbiotic associations between crops and microbes play an essential role in enhancing the productivity and sustainability of our agriculture. The two most important symbioses in agroecosystems that promote crop nutrition are legume root nodulation and arbuscular mycorrhization. Genetic studies in the model legumes, such as Medicago truncatula and Lotus japonicus led to current understanding of the molecular mechanisms controlling the establishment of these mutualistic associations and suggest the existence of a Common Symbiotic Pathway (CSP) between both symbioses, in which Medicago truncatula DOES NOT MAKE INFECTIONS 1, 2 and 3 (DMI1, DMI2 and DMI3) play a central role. This opens the exciting possibility of manipulating this conserved CSP to improve the associations between symbiotic microbes and crop plants. To achieve this exciting goal, a thorough understanding of symbiotic signal transduction machinery is required. This CAREER project aims at identifying and characterizing novel genetic players in the early signaling pathway through genetic suppressor screening followed by mapping the suppressor loci through whole genome sequencing to clone the novel genes for functional characterization. This project will allow the investigators to identify novel components that have been missed in conventional screens for nodulation-defective mutants and generate new knowledge of the molecular mechanisms allowing symbiotic associations that could be applied to legume and non-legume crops. Therefore, this project will not only provide fundamental insights into the molecular mechanisms controlling plant-microbe symbioses, but will also identify potential targets for engineering more efficient nitrogen-fixing associations in cereal crops.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.