The Phytophthora infestans avirulence gene Avr4 encodes an RXLR-dEER effector.

Resistance in potato against the oomycete Phytophthora infestans is conditioned by resistance (R) genes that are introgressed from wild Solanum spp. into cultivated potato. According to the gene-for-gene model, proteins encoded by R genes recognize race-specific effectors resulting in a hypersensitive response (HR).