Shoots, Roots & Nodules: A Molecular Genetic Dissection of Local & Long Distance Signaling in M. Truncatula

结瘤是豆科植物和固氮细菌之间的共生相互作用，在农业中很重要，因为世界上33%的蛋白质来自结瘤的豆科作物。这种共生关系还允许豆科植物从空气中获得氮，这使得豆科植物能够在氮限制的土壤中生长。一旦植物和细菌通过一系列复杂的相互作用相互发出信号并作出反应，豆科植物的根就会发生结瘤。根上形成的根瘤数量取决于从茎部到根的本地和长距离信号；PI已经表明植物激素生长素可能是远距离信号。凭借这一奖项，PI将研究豆科植物紫花苜蓿（Medicago trunculata）中生长素如何控制根瘤数量，该植物已被开发为研究植物固氮的模型系统。PI先前在紫花苜蓿中发现了四种影响结节数量的超结节突变体。该奖项的四个目标是：1)克隆这些基因；2)确定这些基因如何相互作用；3)更彻底地检查每个突变体的生长素平衡；4)通过嫁接实验检测生长素等信号的转运。由于根瘤数调控通路参与根生长和根/茎通讯，这项工作也将有助于更好地了解植物如何协调茎和根的生长。实验将由PI所在机构的高中生、本科生和研究生进行。PI有指导学生的记录，并致力于通过参加暑期实习计划，包括代表性不足的高中生。

Nodulation is a symbiotic interaction between legumes and nitrogen fixing bacteria and is important in agriculture, as 33% of the world's protein comes from nodulating legume crops. This symbiosis also allows legumes to obtain nitrogen from the air, which permits legumes to grow in nitrogen-limiting soils. Nodulation occurs in the roots of legumes once the plant and bacterial partners signal and respond to each other through a complex series of interactions. The number of nodules formed on the root depends upon local and long distance signaling from the shoot to the root; the PI has shown that the plant hormone auxin is the likely long-distance signal. With this award, the PI will investigate how nodule number is controlled by auxin in the legume Medicago trunculata, which has been developed as a model system for studying nitrogen fixation in plants. The PI previously identified four supernodulation mutants in Medicago that affect nodule number. The four aims of this award are 1) to clone these genes; 2) determine how these genes interact; 3) examine the auxin hormone balance of each mutant more thoroughly; and 4) examine the transport of auxin and other signals by grafting experiments. Because the nodule number regulatory pathway is involved in root growth and root/shoot communication, this work will also lead to a better understanding of how plants coordinate shoot and root growth. The experiments will be performed by high school students, undergraduate and graduate students from the PI's home institution. The PI has a record of mentoring students and is committed to including underrepresented high school students through participation in a summer internship program.