Species-specific divergence in Phytophthora infestans resistance between Nicotiana benthamiana and potato mediated by 1-aminocyclopropane-1-carboxylic acid pretreatment

Late blight, caused by Phytophthora infestans , is a devastating oomycete disease threatening global potato ( Solanum tuberosum ) production. 1-Aminocyclopropane-1-carboxylic acid (ACC), has also been proposed to act as a bioactive signal in plant stress responses, but its contribution to plant immunity remains elusive. Here, we show that ACC pretreatment exerts opposite effects on P. infestans resistance in Nicotiana benthamiana and the potato cultivar ‘Favorita’, revealing strong species-specific transcriptional reprogramming. In N. benthamiana , differentially expressed genes (DEGs) are enriched in defense-related pathways, including plant-pathogen interactions, hormone signaling, and secondary metabolism. In potato, DEGs mainly involve primary metabolism, cell wall remodeling, and photosynthesis regulation. The jasmonic acid (JA) biosynthesis and signaling pathway emerge as a central hub underlying this divergence. ACC markedly induces JA-related genes in N. benthamiana but fails to activate them in potato. Exogenous MeJA enhances resistance, whereas the JA biosynthesis inhibitor DIECA weakens the ACC-associated resistant phenotype in N. benthamiana and aggravates disease in potato. Antioxidant-enzyme assays and DAB staining support distinct ROS-associated responses between the two species. Transient expression assays of JA- and protease inhibitor-related candidate genes further support their roles as downstream contributors to disease resistance. Collectively, our findings suggest that ACC pretreatment produces species-specific defense outcomes against P. infestans through differential recruitment of a JA-associated regulatory network and downstream defense layers, including protease inhibitors and ROS-associated responses. These results refine our understanding of ACC/ethylene-associated immune regulation and provide candidate targets for sustainable late blight management and resistance breeding.