BRC-BIO: Familiarity with friends: Transgenerational effects as a mechanism for partner choice in the legume-rhizobia mutualism

互利主义具有根本的重要性，存在于每一个生物体层面，在那里它们促进相互作用的伙伴的健康和生存。例如，氮是植物生长所需的必需营养素，但植物无法获得最丰富的形式，使其成为一种有限的资源。豆科植物通过与共生细菌（称为根瘤菌）形成有益的伙伴关系克服了这一限制，在那里它们获得可用的氮以换取碳代谢物。问题是，在建立关系之前，工厂没有关于其合作伙伴质量的信息。选择正确的互利共生细菌伙伴，同时排除寄生细菌，是至关重要的，因为形成互利共生关系的过程需要植物消耗能量，否则可以用于生长。许多豆科植物物种已经表现出一定程度的特异性，利用信号传导来限制与相容的根瘤菌物种的伙伴关系。一旦伙伴关系启动，就会有额外的分子信号触发植物免疫系统。任何一种类型的信号都可能在宿主植物上留下对单个根瘤菌菌株特异性的印记或记忆。这项研究探讨了这一记忆可能是遗传的假设，并帮助后代的宿主植物选择有益的菌株，由于熟悉，更好地了解非遗传遗传性，并提供深入了解互惠关系的维护。该项目还为本科生提供资助的研究经验，这已被证明可以提高多样性和增加STEM的保留。互惠的起源和维持提出了一个进化难题，因为双方都希望以自己的利益行事。与所有的互惠关系一样，存在着主人被伴侣利用的风险，从而导致关系破裂。选择一个忠诚和有益的伙伴的能力可以稳定伙伴关系。然而，机制，允许合作伙伴的选择尚未被发现在豆科植物根瘤菌互惠共生，尽管有证据表明，宿主植物能够优先与更有益的合作伙伴。该项目研究了选择的合作伙伴可能通过遗传（宿主植物和根瘤菌基因），表观遗传和环境因素的组合来确定的预测。研究小组将使用有胡子的三叶草，三叶草，来确定前几代的跨代效应是否会影响宿主植物对共生伙伴的选择。该项目将量化结核占有率，以确定是否以前暴露于菌株及其效力告知宿主植物选择使用荧光标记，qPCR和metabarcoding的组合，以区分根瘤菌在菌株水平。该奖项反映了NSF的法定使命，并已被认为是值得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的支持。

Mutualisms are of fundamental importance and found at every organismal level, where they facilitate the fitness and survival of the interacting partners. For example, nitrogen is an essential nutrient required for plant growth, yet the most abundant form is inaccessible to plants, making it a limiting resource. Legumes have overcome this limitation by forming beneficial partnerships with symbiotic bacteria, known as rhizobia, where they receive usable nitrogen in exchange for carbon metabolites. The problem is that prior to establishing the relationship, the plant has no information about the quality of its partner. Choosing the right mutualistic bacterial partner, while excluding parasitic bacteria, is essential because the process to form the mutualistic relationship requires the plant to expend energy that could otherwise be used for growth. Many legume species already show some degree of specificity using signaling to limit partnership with compatible rhizobia species. Once the partnership is initiated, there is additional molecular signaling that triggers the plant immune system. Either type of signaling may leave an imprint or memory on the host plant that is specific to individual rhizobia strains. This study examines the hypothesis that this memory may be heritable and help future generations of the host plant choose beneficial strains due to familiarity, giving a better understanding of non-genetic heritability and providing insight into the maintenance of mutualistic relationships. This project also provides undergraduate students with funded research experience, which has been shown to improve diversity and increase retention in STEM.The origination and maintenance of mutualisms presents an evolutionary conundrum as both partners are expected to act in their own self-interest. As with all mutualisms, there is a risk of the host being exploited by their partner leading to the breakdown of the relationship. The ability to choose a faithful and beneficial partner can stabilize the partnership. However, the mechanism that allows for partner choice has not yet been uncovered in the legume-rhizobia mutualism, despite evidence that host plants are able to preferentially nodulate with more beneficial partners. This project examines the prediction that the selected partner will likely be determined through a combination of genetic (host plant and rhizobia genes), epigenetic and environmental elements. Using the bearded clover, Trifolium barbigerum, the research team will determine whether transgenerational effects from previous generations can influence the host plant’s choice of symbiotic partner. This project will quantify nodule occupancy to determine whether previous exposure to a strain and its efficacy inform host plant selection using a combination of fluorescent labeling, qPCR and metabarcoding to distinguish rhizobia at the strain level.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.