Oomycetes of the genus Phytophthora are devastating plant pathogens that affect many commercially important plants. Considerable efforts have been made to investigate the transcriptional response of individual plant species to phytophthora infection, often showing a concerted upregulation of pathogen-response (PR) gene families, which are also induced upon infection by fungi and other biotic and even non-biotic stressors. By integrating four transcriptomics datasets derived from three different plants (arabidopsis, soybean, cocoa), a core set of upregulated sequence clusters was derived, which represents a conserved multi-species response to phytophthora infections. We annotated more than 300 common induced gene clusters and subjected them to bioinformatical analysis. Besides the expected PR genes, several novel gene families without known links to biotic stress were found to be strongly induced in all tested datasets. Among the most prominent response genes are two families of putatively secreted peptides and a family of predicted mitochondrial complex-IV associated proteins. Interestingly, the latter sequences are related to the mammalian NDUFA4 family, which also contains members with constitutive and pathogen-induced expression. This recurrent functional diversification points toward an important role of complex IV regulation within the biotic defense response in multiple kingdoms.