Role of a 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase in Plant-Microbe Symbiotic Signaling Pathways

豆类如大豆、苜蓿或花生具有与土壤细菌（称为根瘤菌）相关联的独特能力。 这种共生导致根瘤的形成，根瘤菌在根瘤内将空气中的氮转化为植物可吸收的形式。 在美国，这种共生关系每年节省约45亿美元的化肥成本，并防止与过度使用化肥相关的生态和健康问题。 根瘤菌-豆科植物共生具有高度的种特异性，即特定的豆科植物只与特定的根瘤菌共生。 这种特异性机制主要受根瘤菌产生并被其宿主植物识别的LCO（Lipo-Chito-Oligosaccharide）信号的结构控制。LCO还介导与共生真菌的关联，共生真菌存在于豆类中，但也存在于许多其他非豆类作物如玉米、小麦和棉花中。LCO现在被农民用作豆类和非豆类作物的植物生长促进剂。植物中的遗传分析允许鉴定LCO受体和蛋白质，如HMGR 1（3-羟基-3-甲基戊二酰辅酶A还原酶1），其与LCO受体相互作用并且是建立共生协会所需的。 该项目将导致更好地理解允许豆类识别共生LCO的机制以及允许LCO受体和HMGR 1介导根瘤菌和共生真菌的根瘤发育的下游途径。 在短期内，了解这些机制可以通过更有效地使用LCO作为植物生长促进剂对产量提高产生直接影响。 这些知识还将有助于改善植物-微生物联合体的建立，在次优和紧张的田间条件下具有特别高的影响。 从长远来看，通过这些机制设计新的共生协会可能有助于提高我们农业的可持续性，用于食品，饲料和生物燃料生产。

Legumes such as soybeans, alfalfa or peanuts have the unique ability to associate with soil bacteria named rhizobia. This symbiosis leads to the formation of root nodules inside which the rhizobia transform air nitrogen into forms assimilable by the plant. Every year, in the United States, this symbiosis saves around $4.5 billion in fertilizer costs and prevents ecological and health issues associated with the excessive use of chemical fertilizers. The rhizobium-legume symbiosis presents a high level of species specificity which means that specific legumes only associate with specific rhizobia. This specificity mechanism is mostly controlled by the structure of LCO (Lipo-Chito-Oligosaccharide) signals produced by the rhizobia and recognized by their host plants. LCOs also mediate associations with symbiotic fungi which occur in legumes but also in many other non-legume crops such as corn, wheat and cotton. LCOs are now used by farmers as plant growth promoters for legume and non-legume crops. Genetic analysis in plants allowed the identification of LCO receptors and proteins such as HMGR1 (3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase 1) that interact with LCO receptors and are required for the establishment of symbiotic associations. This project will lead to a better understanding of the mechanisms allowing legumes to recognize symbiotic LCOs and of the downstream pathways allowing LCO receptors and HMGR1 to mediate the development of root nodules with rhizobia and associations with symbiotic fungi. In the short term, understanding these mechanisms can have a direct impact on yield improvement through a more efficient use of LCOs as plant growth promoters. This knowledge will also help improve the establishment of plant-microbe associations, with especially high impact under suboptimal and stressful field conditions. In the long term, engineering new symbiotic associations through these mechanisms may help improve the sustainability of our agriculture for food, feed and biofuel production.