Selective Autophagy in Plant Immunity: Mechanisms, Regulation, and Emerging Concepts in Xenophagy.

Abstract

Selective autophagy has emerged as a critical component of plant immunity, yet its role as a dedicated antimicrobial mechanism, xenophagy, remains conceptually underdeveloped. In plants, xenophagy extends beyond bulk degradation to function as a highly regulated, cargo-specific pathway that targets invading pathogens and their effector molecules for autophagic clearance. Recent evidence demonstrates that selective autophagy receptors, particularly NBR1, integrate ubiquitin-mediated recognition with ATG8-dependent sequestration, enabling the elimination of bacterial, fungal, and viral components. However, this process is not merely degradative but operates at the intersection of immune signaling, proteostasis, and cellular decision-making. Here, we synthesize current advances in plant xenophagy and propose a unifying framework in which xenophagy appears to function as a cell-autonomous immune hub comprising three interconnected modules: cargo recognition, selective sequestration, and autophagic execution, dynamically modulated by pathogen-derived countermeasures. We further examine how pathogens subvert or exploit host autophagic machinery, revealing xenophagy as a contested interface in plant-pathogen interactions. By integrating molecular, cellular, and cross-kingdom perspectives, we highlight key conceptual gaps, including the specificity of cargo selection, the regulatory logic of receptor engagement, and the coordination between autophagy and canonical immune pathways. Resolving these gaps will be essential for repositioning xenophagy as a central determinant of plant immune competence, with significant implications for engineering disease-resistant crops.