GAiNS · Gibberellic acid signaling and dynamics during arbuscular mycorrhizal symbiosis and rhizobial-legume symbiosis

The association of microbes at the root-soil interface is an ancient adaptation integral for nutrient acquisition. Most land plants, including trees and crops, associate with mutualistic fungi called mycorrhizae. Legumes have adapted specialized root structures termed nodules for association with nitrogen-fixing bacteria (rhizobia). While there are differences among the species that beneficially associate with plants, there is a large overlap in the key players regulating both symbioses. One important regulator is gibberellin or gibberellic acid (GA), a plant hormone that has diverse and important functions in plant growth and development. While GA inhibits infection events, there is conflicting evidence for the role of GA as an important positive and negative regulator of nodule organogenesis. Here, I propose to determine the mechanism of GA regulation in symbiosis in the model plants Medicago truncatula and barley (Hordeum vulgare). My approach combines the use of a state-of-the-art GA biosensor to characterize and model GA fluctuations in symbiosis in combination with transcriptomic and genetic approaches to characterize GA-signaling response in M. truncatula and H. vulgare. Upon completion of this project, we will gain an understanding of the dynamics of GA signaling in symbiosis and define downstream GA targets that are of special interest for engineering enhanced symbiosis in cereal species.