The plant produces a small RNA precursor, either a long double-stranded RNA or a pre-microRNA, with sequence similarity to a fungal gene (1). Researchers have engineered the sequence into the genomes of crop plants or model organisms and demonstrated superior fungal resistance, although one recent study showed plants may naturally encode sequences to protect themselves against pathogens.
Evidence points to the idea that the small RNA precursors can pass directly to the fungal cell (2) or undergo processing into small RNAs prior to transfer (3). If the precursor leaves the plant intact, the fungus’s processing machinery chops it up (4). In either case, the result is a plant small RNA inside the fungal cell, though the mechanism of transfer remains unknown.
Upon additional processing in the fungal cell, a single strand of the small RNA becomes part of the RNA-induced silencing complex (RISC), which then destroys an mRNA with a ...
