Functional Dissection of the Turnip Crinkle Virus Coat Protein Links ATG8 Association to Autophagy-Associated...

The coat protein (CP) of turnip crinkle virus (TCV) plays multifaceted roles in viral infection, acting as both an avirulence (Avr) factor recognized by the resistance protein HRT and a viral suppressor of RNA silencing (VSR). However, how these dual activities are coordinated remains unclear. Here, we demonstrate that the position of a fluorescent protein (FP) tag on CP functionally separates its two activities. C-terminal tagging (CP-GFP) preserved the ability to trigger HRT-dependent hypersensitive response (HR) but abolished silencing suppression, whereas N-terminal tagging (YFP-CP) retained VSR activity but failed to induce HR. These functional differences correlated with distinct subcellular localizations: Avr activity required both nuclear and cytoplasmic localization, while VSR function was confined to the cytoplasm. We further show that the N-terminal region of CP associates with autophagy-related protein 8 (ATG8), linking CP to autophagy-associated antiviral pathways. Autophagy-deficient atg5 and atg7 mutants exhibited enhanced susceptibility to TCV, supporting a role for autophagy in antiviral defence during infection. Together, our findings reveal that TCV CP contains spatially and mechanistically separable determinants for Avr and VSR functions and identify CP-ATG8 association as a potential interface between viral infection and host autophagy-associated regulation.