Nitrogen is a critical element on which all life depends. However, only certain microbial species are capable of converting ("fixing") elemental nitrogen into a biologically useable form; multicellular organisms can only utilize nitrogen that is already fixed. Legumes are able to obtain nitrogen by forming an intimate symbiotic relationship with nitrogen-fixing bacteria called rhizobia. Because of this unique ability to acquire nitrogen symbiotically, legumes play a critical role in agriculture and in natural environments.
The interaction between legumes and rhizobia is by far the best characterized model for studying symbiosis. It is also a highly complex system: the bacteria enter the host, differentiate inside the host cell, fix nitrogen, and exchange the reduced nitrogen for photosynthate provided by the host. The host provides a specialized host root organ, the nodule, in which physiological conditions are accurately controlled. Nodule formation, development, and function depend on a suite of cellular programs which are triggered by highly specific molecular dialogs between the two partners. Recent years have seen major advances in our understanding of the initial recognition between legumes and rhizobia. On the other hand, the genetic components and biochemical mechanisms further downstream remains to be elucidated. This EaGER project will address this need and develop a novel genetic screen to identify legume genes required for host-bacterial signaling during the intermediate and late stages of symbiotic nitrogen fixation.
If successful, this project may provide technical approaches for researchers in all legume symbiosis systems. Contributing to the field of host-microbe interactions, this body of information will be published and materials will be made available to interested groups from the scientific community. The project will provide research training for postdoctoral researchers and undergraduate students. In addition, the project will provide research opportunities to undergraduates and local high school students.
