MtNF-YA1 , A Central Transcriptional Regulator of Symbiotic Nodule Development, Is Also a Determinant of Medicago truncatula Susceptibility toward a Root Pathogen.

Plant NF-Y transcription factors control a wide array of biological functions enabling appropriate reproductive and developmental processes as well as adaptation to various abiotic and biotic environments. In , was previously identified as a key determinant for nodule development and establishment of rhizobial symbiosis. Here, we highlight a new role for this protein in compatibility to , a root pathogenic oomycete. The mutant plants showed better survival rate, reduced symptoms, and increased development of their root apparatus as compared to their wild-type (WT) background A17. was specifically up-regulated by in F83005.5, a highly susceptible natural accession of while transcript level remained stable in A17, which is partially resistant. The role of in F83005.5 susceptibility was further documented by reducing expression either by overexpression of the miR169q, a microRNA targeting , or by RNAi approaches leading to a strong enhancement in the resistance of this susceptible line. Comparative analysis of the transcriptome of WT and led to the identification of 1509 differentially expressed genes. Among those, almost 36 defense-related genes were constitutively expressed in , while 20 genes linked to hormonal pathways were repressed. In summary, we revealed an unexpected dual role for this symbiotic transcription factor as a key player in the compatibility mechanisms to a pathogen.