The symbiotic transcription factor MtEFD and cytokinins are positively acting in the Medicago truncatula and Ralstonia solanacearum pathogenic interaction

Summary A plant–microbe dual biological system was set up involving the model legume M edicago truncatula and two bacteria, the soil‐borne root pathogen R alstonia solanacearum and the beneficial symbiont S inorhizobium meliloti . Comparison of transcriptomes under symbiotic and pathogenic conditions highlighted the transcription factor M t EFD (Ethylene response Factor required for nodule Differentiation) as being upregulated in both interactions, together with a set of cytokinin‐related transcripts involved in metabolism, signaling and response. M t RR 4 ( R esponse R egulator), a cytokinin primary response gene negatively regulating cytokinin signaling and known as a target of M t EFD in nodulation processes, was retrieved in this set of transcripts. Refined studies of M t EFD and Mt RR 4 expression during M . truncatula and R . solanacearum interaction indicated differential kinetics of induction and requirement of central regulators of bacterial pathogenicity, H rp G and H rp B . Similar to M t RR 4 , M t EFD upregulation during the pathogenic interaction was dependent on cytokinin perception mediated by the M t CRE 1 (Cytokinin REsponse 1) receptor. The use of M . truncatula efd‐1 and cre1‐1 mutants evidenced M t EFD and cytokinin perception as positive factors for bacterial wilt development. These factors therefore play an important role in both root nodulation and root disease development.