Research Projects

Molecular phylogenetic analyses have established that root nodule symbiosis (RNs) is restricted to a monophyletic group of angiosperms. Non-legumes form a central vascular bundle (VB) containing nodules - like the lateral roots. In contrast, legumes form nodules with peripheral vasculature, an adaptation restricted only to the Leguminosae family. The shift of VB from the center to the periphery has given a tremendous advantage to the Leguminosae family in terms of nitrogen fixation efficiency. Under this project, we will investigate how legumes evolved the peripheral nodule vascular bundle from a central root vasculature. To this end, we have identified Medicago Tnt1 insertional mutants that develop a partially centralized nodule vascular bundle. The causative gene that has given rise to this homeotic phenotype is a bHLH transcription factor. We name this gene Nodule Vascular bundle Development (NVD1). To understand how NVD1 controls nodule vascular bundle development, we will undertake a detailed characterization of the nvd1 nodules using transcriptomic, microscopy, and biochemical approaches, to elucidate the molecular mechanism behind NVD1 medicated nodule vascular bundle patterning and will come up with a proposed pathway that controls peripheral vascular bundle patterning in legume nodule. Under this project, we are aiming to identify pathway(s) that control high nitrogen-fixing nodule shape. This project will bridge the gap between basic nodule development research and applied nitrogen fixation research by identifying a list of potential targets for targeted Genome-wide association studies (GWAs) on crop legumes.