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Poster

Session: Session 1 Presenting Authors at Posters (Odds)

P-333 - Spatiotemporal dynamics of cross-kingdom RNAi: haustoria as a conduit for small RNA delivery into plant cells

Monday, July 14, 2025
13:30 - 15:15  
Location: Confex Hall 3
RNA on the move: Advances in Cross-Species communiation &Translational Research
Cross-kingdom RNA interference (ckRNAi) plays a critical role in plant-microbe interactions, with microbial small RNAs (sRNAs) modulating host gene expression. In the biotrophic oomycete Hyaloperonospora arabidopsidis (Hpa), the exact timing and spread of Hpa-induced ckRNAi within infected Arabidopsis thaliana remains poorly understood. To investigate the spatiotemporal dynamics of Hpa sRNA delivery, we focused on the stages of infection where cross-kingdom RNAi is likely to occur. Using a GUS reporter system in transgenic Arabidopsis lines, we tracked the onset and spread of Hpa-induced ckRNAi at different infection stages (early, established, and late phases). We hypothesized that the haustoria, the primary site of biomolecular exchange during infection, would mediate the delivery of Hpa-derived sRNAs into plant cells. Our results indicate that sRNA delivery is localized to haustoria-invaded plant cells, with no evidence of systemic spread, and the presence of RNAi activity is detectable in cells adjacent to the infected ones. The delivery of Hpa sRNAs appears to be more efficient in fully established haustoria. Interestingly, at later infection stages, the efficiency of Hpa sRNA delivery diminishes as Hpa begins to develop propagation structures such as oospores and sporangia. These findings highlight haustoria as one key conduit for sRNA delivery and suggest that the delivery mechanism is tightly regulated during the infection process.