ENHANCED DISEASE RESISTANCE 1 (EDR1) is a negative regulator of powdery mildew resistance, cell death and ethylene-induced senescence. To identify components involved in EDR1 signaling, we performed a forward genetic screen foredr1suppressors. In this screen, we identified thehpr1-4mutation, which partially suppressesedr1-mediated resistance to the powdery mildew pathogenGolovinomyces cichoracearumand mildew-induced cell death. However, thehpr1-4mutation enhanced the ethylene-induced senescence phenotype ofedr1. Thehpr1-4single mutant displayed enhanced susceptibility to the bacterial pathogenPseudomonas syringaepv.tomatoDC3000 and the oomycete pathogenHyaloperonospora arabidopsidisNoco2. ArabidopsisHPR1encodes a homolog of human HPR1, a component of the conserved THO/transcription export (THO/TREX) complex that is required for mRNA export in yeast and humans.HPR1is expressed in various organs and throughout all developmental stages. HPR1 localizes to the nucleus, and, significantly, mRNA export is compromised in thehpr1-4mutant. Taken together, these data demonstrate that HPR1 plays an important role in disease resistance in plants, and that the THO/TREX complex is functionally conserved among plants, yeast and humans. Our data indicate a general link between mRNA export, defense responses and ethylene signaling in plants.