Dissection of a cell-surface receptor complex involved in immunity of plants to deleterious pathogens

Plants are continuously challenged by pathogens. To defend themselves against pathogenic microorganisms, plants possess an innate immune system, by which they are able to recognise invading pathogens and activate a cellular immune response. Receptor-like proteins (RLPs) and receptor-like kinases (RLKs) located on the plasma membrane (PM) are essential for resistance to pathogens. RLPs, such as Cf-4, lack a kinase domain and the RLK SUPPRESSOR of BIR1-1 (SOBIR1) is required for Cf-4-mediated resistance to Cladosporium fulvum that secretes the effector Avr4. The bimolecular complex Cf-4/SOBIR1 further recruits BRI1-ASSOCIATED KINASE 1 (BAK1) to trigger downstream signalling upon Avr4 perception. The identification of additional RLKs and/or receptor-like cytoplasmic kinases (RLCKs) interacting with the tripartite complex Cf-4/SOBIR1/BAK1, in addition to elucidation of the mechanism by which SOBIR1 and BAK1 activate each other upon recognition of Avr4, should lead to a better understanding of the natural resistance of plants to pathogens.