Arabidopsis EDR1 Protein Kinase Regulates the Association of EDS1 and PAD4 to Inhibit Cell Death.

ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) and PHYTOALEXIN DEFICIENT4 are sequence-related lipase-like proteins that function as a complex to regulate defense responses in Arabidopsis by both salicylic acid-dependent and independent pathways. Here, we describe a gain-of-function mutation in (S135F) that enhances resistance and cell death in response to infection by the powdery mildew pathogen Golovinomyces cichoracearum. The mutant duanyu15634 protein accumulates to wild-type levels in Arabidopsis cells, thus these phenotypes are unlikely to be due to duanyu15634 over accumulation. The phenotypes are similar to loss-of-function mutations in the protein kinase EDR1 (Enhanced Disease Resistance1), and previous work has shown that loss of or EDS1 suppresses edr1-mediated phenotypes, placing these proteins downstream of EDR1. Here, we show that EDR1 directly associates with EDS1 and duanyu15634 and inhibits their interaction in yeast and plant cells. We propose a model whereby EDR1 negatively regulates defense responses by interfering with the heteromeric association of EDS1 and Our data indicate that the S135F mutation likely alters an EDS1-independent function of potentially shedding light on a yet-unknown duanyu15634 signaling function.

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