Engineering an effector-targeted genetically encoded degrader to enhance plant resistance against Phytophthora...

Engineering disease resistance in plants has traditionally relied on modification of pathogen perception, host susceptibility, or immune signaling. Here, we explore a complementary strategy that couples pathogen-effector recognition to host proteostasis, aiming to reduce the intracellular accumulation of delivered virulence factors. We identified a minimal α-helical peptide from soybean GmRNF181, which we designated the RXLR effector bait tag (REBT). The REBT bound PsAvh5 and a subset of WY1-type RXLR effectors, but recognition was constrained by the accessibility of the WY1 motif within full-length effectors. By fusing the REBT to an ATG8-interacting motif (AIM), we generated AIM-REBT, a genetically encoded chimeric protein degrader designed to recruit plant autophagy. In planta, AIM-REBT reduced the accumulation of REBT-bound effectors in a manner that required both the AIM module and effector binding, and the observed effects were consistent with ATG8a-associated, autophagy/vacuole-related clearance. Transient and stable expression assays demonstrated robust resistance against multiple Phytophthora species in tobacco, soybean, and potato. Resistance was attenuated in NbATG8a-silenced leaves and was not observed against the unrelated fungal pathogen Alternaria alternata, demonstrating target-dependent activity. Under the tested conditions, stable AIM-REBT expression caused no obvious growth-related defects in tobacco or potato. These findings demonstrate that pathogen-effector recognition can be coupled to host degradation pathways to directly reduce the accumulation of intracellular virulence factors, complementing existing strategies for disease-resistance engineering.