The elongator protein PlElp3b is involved in mycelial growth, autophagy, and virulence of Phytophthora litchii

Abstract Litchi downy blight, caused by the phytopathogenic oomycete Phytophthora litchii , is one of the most devastating diseases impacting litchi cultivation, resulting in significant economic loss. The elongator protein complex is crucial for the growth and virulence of filamentous fungi; however, the specific role of the elongator protein component Elp3 within oomycetes remains poorly understood. In this study, we identified and characterized two homologs of Elp3, namely PlElp3a and PlElp3b, in P. litchii . The targeted deletion of PlELP3b utilizing the CRISPR/Cas9 gene editing technique resulted in impaired vegetative proliferation and reproductive development. Furthermore, the elimination of PlELP3b was found to affect the sensitivity of P. litchii to various stressors. The Atg8 protein, recognized as a marker for autophagy across multiple species, was analyzed using Western blotting, revealing that PlElp3b is essential for maintaining autophagic homeostasis by modulating mCherry-PlAtg8 degradation. Notably, PlElp3b showed no interaction with PlAtg8 in yeast two-hybrid assays. Furthermore, virulence evaluations indicated that the lack of PlELP3b significantly reduced the virulence of P. litchii . Collectively, our findings underscore the critical functions of PlElp3b in regulating radial growth, stress response, sexual reproduction, autophagic equilibrium, and virulence in P. litchii . This research enhances the understanding of the pathogenic mechanisms of the elongator protein employed by P. litchii and offers valuable insights for the formulation of more effective strategies for managing oomycete-related diseases.