Disruption of the MEKK1-MKK1/MKK2-MPK4 kinase cascade leads to activation of immunity mediated by the nucleotide-binding leucine-rich repeat (NLR) immune receptor SUMM2, which monitors the phosphorylation status of CRCK3. Here we report that two receptor-like kinases (RLKs), MDS1, and MDS2, function redundantly to promote SUMM2-mediated immunity. Activation of SUMM2-mediated immunity is dependent on MDS1, and to a less extent on MDS2. MDS1 associates with CRCK3 in planta and can phosphorylate CRCK3 in vitro, suggesting that it may target CRCK3 ...
