Cross-kingdom RNA trafficking and environmental RNAi for powerful innovative pre- and post-harvest plant protection

Abstract

​Small RNA (sRNA) induces RNA interference (RNAi) in almost all eukaryotes. While sRNAs can move within an organism, they can also move between interacting organisms to induce gene silencing, a phenomenon called 'cross-kingdom RNAi'. Some sRNAs from pathogens or pests move into host cells and suppress host immunity in both plants and animals; whereas some host sRNAs travel into pathogen/pest cells to inhibit their virulence. Moreover, uptake of exogenous RNAs from the environment was recently discovered in certain fungal pathogens, which makes it possible to suppress fungal diseases by directly applying pathogen-targeting RNAs on crops and post-harvest products. This new-generation of RNA-based fungicides is powerful, environmentally friendly, and can be easily adapted to control multiple diseases simultaneously.

Figure 1. Cross-kingdom RNAi and spray induced gene silencing are effective strategies for preventing pre- and post-harvest diseases

This schematic illustrates the movement of RNAs between plant fungal pathogens and their hosts and how spray-induced gene silencing (SIGS) can be used to counteract pathogen virulence. Pathogen-derived sRNA effectors are delivered into the host, where they suppress host immune responses (red and blue block arrows). The spray application of gene-specific RNAs can suppress virulence through RNA interference in multiple pathogens (red and blue block arrows) either on crops or post-harvest products. These RNAs can either translocate directly to the eukaryotic pathogen or indirectly through the host (red and blue arrows). SIGS-based protection can be prolonged by incorporated RNAs into clay nanosheets (in grey) that protect RNAs from degradation and from being washed away. These RNAs can also spread systemically between cells or to other tissues in the plant (purple arrows), most likely through plasmodesmada and vascular phloem structures. The background represents the variety of crops and post-harvest products in which SIGS can be used to prevent loss from disease.