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

Abstract

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.