Sarrette, B. | Search bioRxiv

bioRxiv2026

A novel pathosystem between Aeschynomene evenia and Aphanomyces euteiches reveals new immune components in quantitative legume root-rot resistance.

Legumes are pivotal for sustainable agriculture, yet their productivity is hindered by soilborne pathogens such as Aphanomyces euteiches. This study introduces Aeschynomene evenia as a novel model to investigate legume immunity and its interplay with Nod factor-independent symbiosis (NFIS). Inoculation of A. evenia accessions with A. euteiches strains revealed a range of quantitative resistance levels. Phenotypic and cytological analyses showed a compatible interaction, including root browning, intracellular colonisation, and oospore production; along with partial resistance traits such as phenolic accumulation at the endodermal barrier. Transcriptomic analyses at 1 and 3 dpi identified 3,403 differentially expressed genes (DEGs), with upregulated genes associated with pathogen perception, immune signalling and specialised metabolite biosynthesis. Kinase-mediated signalling, ROS homeostasis, and WRKY transcription factors were among the most enriched functional categories. Comparative transcriptomics with Medicago truncatula confirmed conserved immune responses, while A. evenia displayed broader transcriptional repression. Integration with symbiotic transcriptomic data revealed overlapping gene signatures, including AeRLCK2 and AeCRK, previously found to be NFIS-specific, as putative dual-function kinases. Aerlck2 and Aecrk mutants exhibited enhanced resistance to A. euteiches, supporting their roles in immune regulation. This work positions A. evenia-A. euteiches as a valuable system to dissect legume quantitative resistance and its intersection with symbiosis.

plant biology↗

bioRxiv2023

Medicago truncatula SOBIR1 controls specificity in the Rhizobium-legume symbiosis

Medicago truncatula Nod Factor Perception (MtNFP) is a lysin-domain Receptor-Like Kinase (LysM-RLK) that plays a key role in the Rhizobium-legume symbiosis, and is involved in plant immunity. MtNFP also has an inactive kinase domain, suggesting that the protein is involved in different receptor complexes. Using the MtNFP pseudo-kinase domain as a bait in a Yeast two Hybrid screen, we identified M. truncatula SUPPRESSOR OF BIR1 (MtSOBIR1) as a new interactor of MtNFP. We showed that an interaction between the two RLKs can occur in planta and that the kinase domain of MtSOBIR1 is active and can transphosphorylate the pseudo-kinase domain of MtNFP. Like in other plants, our data suggest a positive role of MtSOBIR1 in immunity; MtSOBIR1 could functionally complement an Atsobir1 mutant for defence activation, and a Mtsobir1 mutant was defective in pathogen-induced defence gene expression. We also showed that MtSOBIR1 has a symbiotic role with Mtsobir1 mutants showing a strong symbiotic phenotype in a plant genotype- and rhizobial strain-specific manner. The symbiotic role was apparent both at an early stage of rhizobial infection and in nodules. Together, these data suggest that, like MtNFP, MtSOBIR1 has a dual role, and can control immunity in both pathogenic and beneficial situations, with positive or negative roles, respectively.

plant biology↗