Regulation of the arbuscular mycorrhizal symbiosis by microRNAs – miRcorrhiza

most of the approaches used in this study concern molecular biology, for overexpression of the microRNA, expression analysis by quantitative PCR, cytology, to visualize interactions between plants and microorganisms, and genetic, to obtain plant mutated for target genes of the microRNA

We have identified a microRNA which plays a differnetial role between AM symbiosis and nodulation. Overexpression of this microRNA upregulates the first patway and down regulates the second one. So it is the first identification of mechanisms which can differentiate between the perception of these two close symbioses.

The next steps will be to analyse the regulation of the expression of this microRNA and of this target genes, during AM symbiosis and nodulation, in order to understand the underlying mechanism that regulates both symbioses

a manuscript concerning the role of this microRNA in these two symbiosis is currently writing.

The arbuscular mycorrhizal (AM) symbiosis concerns most of land plants and provides many benefits for the life of the plant host. Interaction between the plant and the fungus begins with a molecular dialog required for successful association of both partners: plants secrete specific exudates, including strigolactones, which stimulate the fungus. The fungus releases signal molecules including lipochitooligosaccharides (Myc-LCOs) that elicit the symbiotic program of the plant host. Leguminous plants can establish in parallel a nitrogen fixing symbiosis with bacteria, which also produce LCOs (Nod factors). We have previously identified a microRNA which could play an important role in the signaling pathways triggered by those microbial LCOs. Overexpression of this microRNA leads to a downregulation and an upregulation of the Myc-LCO- and Nod factor-signaling pathways, respectively. The aim of our proposal is to decipher the mode of action of this microRNA and the role of its target genes in both symbioses. After studying the role of this microRNA in the mycorrhization and the nodulation, we will try to unravel the regulation network involving the strigolactones that controls Myc-LCO and Nod factor signaling pathways. Finally, we will direct our study on the analysis of post transcriptional regulation of the precursor of the microRNA. The expected results will help understanding how leguminous plants manage to recognize their fungal and bacterial symbionts while using similar signalling mechanisms.