UKRI/BBSRC-NSF/BIO:Hidden costs of infection: mechanisms by which parasites disrupt host-microbe symbioses and alter development

从细菌到像线虫这样的微小动物，成千上万的微生物在植物中定居。这些微生物相互影响与它们共同的寄主植物的相互作用。有些使其他微生物更容易感染宿主，而另一些则阻止其他微生物成功感染。本研究将探讨同一寄主植物上微生物之间的这些相互作用是由于资源竞争还是由寄主的免疫反应驱动的。研究人员将在一种与紫花苜蓿密切相关的植物上测试这些问题。像紫花苜蓿一样，这种植物依靠生活在根部细胞内的共生细菌来获取氮——一种重要的营养物质，也是肥料的主要成分。虽然这些共生细菌为植物提供了必需的营养，但它们也使它们的宿主更容易受到寄生线虫的感染。虽然这项研究关注的是一种植物，但几乎所有的作物都依赖共生微生物提供营养，因此了解有益微生物如何影响其宿主的疾病风险在农业上和生态上都具有重要意义。该项目的更广泛影响包括为下一代植物科学领导者提供跨学科培训；吸引来自代表性不足背景的本科生和高中生参与实践研究；并开发了一款基于微生物在植物根部定居的棋盘游戏。共享同一宿主的微生物会影响彼此的定植成功。共同定殖微生物之间的串扰通常表现为优先效应，即早期与一种微生物的接触会影响宿主对后来定殖微生物的反应。本研究将测试两种相互竞争的假设，以解释宿主相关社区中普遍存在的优先效应：一种是以防御为中心的模型，其中宿主对一个入侵者的防御反应对另一个生物体的感染具有脱靶效应；另一种是以资源为中心的模型，其中共同殖民者竞争宿主资源。该项目将在豆科植物模型紫花苜蓿中测试这些假设，通过实验感染一种寄生线虫，这种线虫会破坏与固氮细菌的共生关系。线虫抑制根瘤菌定植，而根瘤菌增加对线虫的敏感性。本研究主要有五个目标：(1)确定根瘤菌与线虫之间优先效应的时空尺度，并开发新的调控工具；探究(2)防御和(3)碳分配在这两种微生物之间产生优先效应中的相对作用；(4)确定这些优先效应背后的基因和途径；(5)培养下一代植物研究人员的基本概念生态学理论，细胞和分子生物学。该奖项是与英国UKRI/BBSRC合作项目的一部分。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。

Plants are colonized by thousands of microscopic organisms, from bacteria to tiny animals like nematode worms. These microorganisms affect each other’s interactions with their shared host plant. Some make it easier for other microorganism to infect the host, while others prevent other microorganisms from successfully infecting. This research will investigate whether these interactions between microorganisms on the same host plant are due to resource competition or driven by the host’s immune response. The researchers will test these questions in a plant that is closely related to alfalfa. Like alfalfa, this plant relies on symbiotic bacteria that live within cells in the root for nitrogen - an important nutrient and a main ingredient in fertilizers. While these symbiotic bacteria provide an essential nutrient to the plant, they also make their host more vulnerable to infection by parasitic nematode worms. While this research focuses on a single species of plant, nearly all crop plants rely on symbiotic microbes for nutrients, so understanding how beneficial microbes influence the disease risk of their host is agriculturally relevant and ecologically significant. The broader impacts of this project include providing interdisciplinary training for the next generation of leaders in plant science; engaging undergraduate and high-school students from under-represented backgrounds in hands-on research; and developing a board game based on microbial colonization of plant roots.Microorganisms that share the same host affect each other’s colonization success. Cross-talk between co-colonizing microorganisms often manifests as a priority effect, in which an early encounter with one microorganism impacts the host’s response to later colonizers. This research will test two competing hypotheses to explain pervasive priority effects in host-associated communities: a defense-centered model, in which the host’s defense response to one invader has off-target effects on infection by another organism, and a resource-centered model, in which co-colonizers compete for host resources. This project will test these hypotheses in the model legume Medicago truncatula by experimentally infecting plants with a parasitic nematode that disrupts the symbiosis with nitrogen-fixing bacteria. Nematodes inhibit rhizobia colonization, while the rhizobia increase susceptibility to nematodes. The proposed research has five objectives: (1) determine the spatio-temporal scale of priority effects between rhizobia and nematodes and develop new tools to manipulate them; interrogate the relative roles of (2) defense and (3) carbon allocation in generating priority effects between these two microorganisms; (4) identify genes and pathways that underlie these priority effects; (5) train the next generation of plant researcher in essential concepts ecological theory, cell and molecular biology. This award is funded as part of a cooperative program with the UKRI/BBSRC in the UK.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.