Acts as a second functional copy of EDS1. Can mediate HRT-mediated resistance to turnip crinkle virus. Interacts (via N-terminus) with PAD4 and SAG101 (PubMed:22072959). Part of a nuclear complex made of EDS1, PAD4 and SAG101, that can be redirected to the cytoplasm in the presence of an extranuclear form of EDS1 (PubMed:22072959). Does not interact with itself or with EDS1 (PubMed:22072959). Found in both the nucleus and diffuse in the cytosol when associated with PAD4 and only in the nucleus when associated with SAG101. Up-regulated by salicylic acid or upon turnip crinkle virus infection. No effect on RPS4-mediated resistance against avrRps4 bacteria, due to the redundancy with EDS1. Ecotypes cv. Landsberg erecta and cv. Di-17 express a probably non-functional truncated protein comprising of only the first 162 amino acids. This protein is not expressed in cv. Wassilewskija.