Conserved Retrograde Trafficking Mechanisms Regulate Fungal Development and Pathogenicity Through Rab6‐GARP‐Retromer‐SNARE Coordination

Retrograde transport from endosomes to the trans-Golgi network (TGN) is essential for intracellular trafficking, yet its molecular mechanism remains poorly understood. In Fusarium graminearum, 10 Rab GTPases associated with the Golgi-associated retrograde protein (GARP) complex were identified through immunoprecipitation followed by mass spectrometry (IP-MS). Among these, only the deletion of FgRAB6 disrupted the proper localisation of the GARP complex to the TGN. FgRab6 directly interacts with the GARP subunit FgVps52 via a conserved Q73 residue, which is critical for fungal growth and pathogenicity. Notably, this Q73-dependent interaction is evolutionarily conserved across eukaryotic species. Upon GTP activation, FgRab6 recruits FgVps52 to the TGN, thereby facilitating the assembly of the GARP complex through the sequential recruitment of additional subunits, including FgVps51, FgVps53 and FgVps54. The fully assembled GARP complex subsequently recruits the retromer complex and ensures the precise localisation of the SNARE proteins FgSnc1, FgTlg1 and FgTlg2 at the endosomes and the TGN. Disruption of this pathway severely compromises fungal development and virulence. Collectively, these findings identify a FgRab6-GARP-retromer-coordinated vesicle trafficking pathway that mediates the retrograde transport of SNARE proteins, which is critical for the pathogenicity of F. graminearum. This work provides new mechanistic insights into vesicular transport and highlights potential targets for antifungal intervention.