DECIPHERING THE TRANSCRIPTIONAL NETWORK CONTROLLED BY NF-YA1 TRANSCRIPTION FACTOR DURING ROOT-NODULE SYMBIOSIS IN MEDICAGO TRUNCATULA

RÍPODAS, CAROLINA; COURRÈGES-CLERCQ, JORDAN; LEPAGE, AGNES; NIEBEL, ANDREAS

Estocolmo

Conferencia; European Nitrogen Fixation Conference 2018; 2018

Legume plants are able to associate with nitrogen-fixing bacteria from the soil, called Rhizobia. The presence of the bacteria in the rhizosphere induce a developmental program in the plant that culminates with the formation of a new specialized organ, the nodule, inside which bacteria convert atmospheric nitrogen into ammonia for the benefit of the host plant. During the establishment of this rhizobial symbiosis, the transcription factor (TF) NF-YA1 plays a central role, in particular by controlling nodule meristem formation and function in the model legume Medicago truncatula 1,2 . MtNF-YA1 belongs to the family of CCAAT-box binding TFs, conserved in all eukaryotic systems3. In order to better understand the mode of action of this TF, and to identify and characterize potential MtNF-YA1 targets, we performed a comparative RNAseq analysis between the Mtnf-ya1-1 KO mutant and wild type plants. This analysis identified a total of 956 differentially expressed genes whose expression significantly changed between the samples analyzed. Among these potential targets of NF-YA1, we focused on a TF of the ethylene response factors (ERF) family called LEP (Leafy Petiole), proposed to play a role in the regulation of cell divisions in leaf petioles in A. thaliana4. MtLEP is characterized by a specific and early expression during nodular organogenesis in the wild-type plant but absent when MtNF-YA1 is mutated. We characterized the expression pattern of MtLEP in different organs of Medicago and during nodule development using RT-qPCR and promoter reporter constructs. In order to gain insight into the role of MtLEP during root infection and nodule organogenesis, we performed a functional analysis of LEP using RNAi, CRISPR/CAS9 and ectopic expression approaches.