The parasitic plant Phtheirospermum japonicum suppresses host immunity

The parasitic plant Phtheirospermum japonicum invades the host root xylem to extract nutrients and water. We show that this invasion triggers a phosphate-starvation response in its host, Arabidopsis thaliana, causing systemic suppression of immunity, including defence responses against microbial pathogens. Consequently, plants infested by xylem-feeding parasitic plants were more susceptible to secondary infections, underscoring the need to consider multitrophic interactions when improving crop resilience to parasitic infestation.