Positive regulator of basal resistance and of effector-triggered immunity specifically mediated by TIR-NB-LRR resistance proteins. Disruption by bacterial effector of EDS1-TIR-NB-LRR resistance protein interactions constitutes the first step in resistance activation (PubMed:22158819). Triggers early plant defenses and hypersensitive response independently of PAD4, and then recruits PAD4 to potentiate plant defenses through the accumulation of salicylic acid (PubMed:11574472). Nuclear localization is essential for basal and TIR-NB-LRR-conditioned immunity and for reprogramming defense gene expression, while cytoplasmic EDS1 is required to induce a complete immune response (PubMed:20617163). Heterodimerization with PAD4 or SGA101 is necessary for TNL-mediated effector-triggered immunity (PubMed:24331460). Contributes to nonhost resistance against E.amylovora (PubMed:22316300). Has no direct lipase activity (PubMed:16040633). Homodimer (PubMed:11574472, PubMed:22158819, PubMed:24331460). Interacts with RPS4, RPS6, SNC1, SRFR1, AvrRps4 and HopA1 (PubMed:22158818, PubMed:22158819). Interacts with PAD4 (via N-terminus) (PubMed:11574472, PubMed:24331460). Interacts with SAG101 (PubMed:16040633, PubMed:24331460). EDS1-SAG101 and EDS1-PAD4 form separate complexes in pathogen-unchallenged cells (PubMed:16040633). Found in both the nucleus and diffuse in the cytosol when associated with PAD4, in the nucleus and in punctate spots in the cytoplasm when interacting with SRFR1, SNC1 or RPS4, only in the nucleus when associated with SAG101 and in the cytosol when it dimerizes. Interacts with AvrRps4 and HopA1 effectors in microsomes. Up-regulated by salicylic acid or upon avirulent bacterial pathogen infection. The N-terminal domain (1-384) is necessary and sufficient for interaction with SAG101.