RXLR effectors of Phytophthora infestans: delivery, host targets and immune suppression

Phytophthora infestans, the pathogen responsible for the devastating potato disease known as late blight, poses a significant threat to plant health. A major determinant of its pathogenic success is the deployment of cytoplasmic effector proteins, particularly the RXLR class of effectors, which accumulate within the host cells and manipulate plant immune responses. These effectors function as key virulence factors that interfere with multiple layers of plant defense, including pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). Recent studies have revealed that RXLR effectors target diverse host cellular processes such as transcriptional regulation, post-translational modifications, vesicle trafficking, autophagy, chloroplast-mediated immune signalling, and protein stability. By converging on these critical immune hubs, RXLR effectors reprogram host cellular networks to promote pathogen colonization and disease progression. Advances in genomics, structural biology, and host-interactor screening have significantly expanded our understanding of RXLR effector diversity, their molecular mechanisms, and their interactions with host susceptibility factors. In this review, we synthesize current knowledge on the functional roles of RXLR effectors of P. infestans, highlighting their subcellular localization, host targets, and mechanisms of immune suppression. We also discuss emerging concepts in effector biology and their implications for developing durable resistance strategies against late blight disease.