Common Symbiotic Signaling Pathway: Filling the Gaps to Understand the Early Events of the Symbiotic Interaction Between Legumes and Rhizobia

Legumes have the ability to symbiotically interact with both arbuscular mycorrhiza (AM) fungi and nitroxigen-fixing rhizobia. Different studies have demonstrated that the early events of these symbioses are controlled by a set of genes belonging to the Common Symbiotic Pathway (CSP). Different attempts have been made to identify new regulators of the CSP. However, most of these studies were performed in late stages of these symbioses. Recent phosphoproteomic and transcriptomic analyses reveal that there are different proteins and genes whose phosphorylation or expression level are significantly modified after 1h treatment with LCOs and NFs. These data suggest the existence of potential yet-uncharacterized regulators. Thus, our objective is to identify and characterize new members of the CSP. To achieve this goal we performed a data mining analysis by using phosphoproteomic and transcriptomic data from Medicago truncatula roots treated with LCO or NFs. For this analysis we used three criteria: 1) increase in the expression or phosphorylation level by 1h treatment with NFs or LCOs treatments, 2) the candidate gene must be expressed in root or nodules only, and 3) the candidate gene must be absent in the A. thaliana genome. Currently, we have identified five candidates genes that fit with the three criteria. Here, we present evidence that support the role of one of the candidates in the establishment of the symbiosis with both AM and rhizobia.