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

Engineering disease resistance in plants has traditionally relied on modifying 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, designated RXLR Effector Bait Tag (REBT). REBT bound PsAvh5 and a subset of WY1-type RXLR effectors, whereas recognition was constrained by the accessibility of the WY1 motif within full-length effectors. By fusing REBT to an ATG8-interacting motif (AIM), we generated AIM-REBT, a genetically encoded chimeric protein degrader (GE-CPDs) designed to recruit plant autophagy. In planta, AIM-REBT reduced the accumulation of REBT-bound effectors in a manner requiring 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 demonstrate robust resistance against multiple Phytophthora spp. in tobacco, soybean, and potato. Resistance was attenuated in NbATG8a-silenced leaves and was not observed against the unrelated fungal pathogen Alternaria alternata, supporting target-dependent activity. Under the tested conditions, stable AIM-REBT expression caused no obvious growth-related defects in tobacco or potato. These findings provide proof of concept that pathogen-effector recognition can be coupled to host degradation pathways to directly reduce intracellular virulence factors and complement existing disease-resistance engineering strategies.