Nutrient availability has a great impact on root organ development such as on lateral root development and legume nodule development.
Legume plants use various mechanisms to keep the nodule number under control. One of these mechanisms is called autoregulation of nodulation (AON). It is a systemic process that involves root-shoot communication on which endogenous as well as rhizosphere signals might impinge to control nodule number. Nitrogen (N) availability greatly influences lateral root development as well as nodule development. The mechanisms by which this happens are largely unknown. However, evidence exists that some components of the AON mechanism might play an important role.
We have identified two CLE (CLAVATA3/ Embry Surrounding Region) peptides, MtCLE12 and MtCLE13, that control the autoregulation process in the model legume Medicago truncatula. Ectopic expression of these peptides abolishes nodulation while RNAi increases the nodule number. We currently study the downstream signaling components of these peptides in order to understand how plants control nodule number and lateral root development and how nitrate availability impinges on those processes.