Regulation of the symbiotic identity

Team SYMUNITY / Pascal Ratet


Characterization of symbiotic mutants affected in organ identity

We are studying the role of the NOOT-like genes, belonging to the NOOT-BOP-COCH-like gene family (NBCL), in symbiotic organ identity. They code for BTB/POZ and Ankyrin domain-containing proteins orthologs of the BOP1 and BOP2 proteins from Arabidopsis. We have shown that the Medicago NOOT1 and NOOT2 genes are both necessary for nodule identity (Couzigou et al., 2012; Magne et al., 2018a) (Figure 2). For this nodule organ identity project we use genetic studies in legume plants like Medicago truncatula, Lotus japonicus and Pisum sativum (Magne et al., 2018a; 2018b). This Evo-Devo approach allows us to have a better view of the role of the NBCL genes in different legume plants. In addition we have now initiated the study of possible NOOT interacting partners in Medicago. The interactions will be studied using Yeast Two Hybrid or in planta interactions and the corresponding mutants will also be characterized.

Figure 2. Magne et al. (2018a), Plant Physiology cover: The homeotic Medicago truncatula noot1noot2 double mutant shows a complete loss of nodule identity characterized by a complete nodule-to-root identity reversion. This homeotic conversion confirms that the nodule vasculature is ontologically related to root and highlight the evolutionary pathway at the origin of the symbiotic organ.


Role of NOOT-like / NBCL genes in Brachypodium distachyon

We are studying the role of the NOOT/BOP homologs in a monocot (cereals) context in order to know if their roles in organ identity are conserved in these plants. There are two genes BdUNICULME4-LIKE (BdCUL4-LIKE) andBdLAXATUM-A-LIKE (BdLAXA-LIKE)orthologousto the barley HvCul4 and HvLax-a, in Brachypodium distachyon. To explore the roles of BdCUL4-LIKE and BdLAXA-LIKE in the development of the non-domesticated grass B. distachyon, TILLING mutant alleles were isolated in collaboration with A. Bendhamane (IPS2) and R. Sibout (INRA Angers). The characterization of these mutants will show the role of these genes in development in a monocot context.