Ethylene-induced host responses enhance resistance against the root-parasitic plant Phelipanche aegyptiaca

The root parasitic plant Phelipanche aegyptiaca and related species pose a grand challenge for agriculture. By directly attaching to host crops to acquire resources, they can severely decrease yields. At the same time, their underground location hides them from sight for much of their life and protects them from typical weed control methods. New strategies for parasitic weed control are needed, with host resistance among the most attractive, but the mechanisms by which hosts respond to parasitic plant attacks are still unclear. In plants, the phytohormone ethylene is a crucial modulator responding to various stresses such as flooding and pathogen attack, and our data suggest that ethylene signaling may be important in host response to P. aegyptiaca . Here, we demonstrated that ethylene plays a role against P. aegyptiaca using two host plants, Arabidopsis and tomato. Arabidopsis plants with the ethylene reporter construct ( EBS::GUS ) were analyzed and revealed that stress from excess water and P. aegyptiaca parasitism both induced ethylene responses in the host Arabidopsis roots. We also observed that applying an ethylene precursor (ACC) to host roots inhibits the attachment of P. aegyptiaca . Lines of Arabidopsis and tomato with mutations in Ethylene-Resistant 1 ( ETR1 ) and Constitutive Triple-Response 1 ( CTR1 ) have altered tolerance to P. aegyptiaca , suggesting that the ethylene signaling pathway is associated with enhanced resistance to parasitism. These results point to ethylene-mediated responses as a starting point to gain insight into host response to parasitism, with potential to increase host resistance to parasitic plants.