Effective Gene Silencing in Plants by Synthetic Trans-Acting siRNAs Derived From Minimal Precursors

Synthetic trans-acting small interfering RNAs (syn-tasiRNAs) are 21-nucleotide small RNAs designed to induce highly specific and efficient gene silencing in plants. Traditional approaches rely on the transgenic expression of ~1 kb <i>TAS</i> precursors, which limits their use in non-model species, under strict GMO regulations, and in size-constrained expression or delivery systems. This protocol describes a rapid workflow for the design, assembly, and delivery of syn-tasiRNAs derived from much shorter precursors, referred to as minimal precursors. The pipeline includes in silico design of highly specific syn-tasiRNA sequences, cloning of minimal precursors into plant expression or potato virus X (PVX)-based viral vectors through Golden Gate or Gibson assembly, and delivery to plants through <i>Agrobacterium</i>-mediated expression or by spraying crude extracts containing recombinant PVX expressing the minimal precursors. These methodologies make syn-tasiRNA-based tools more accessible and broadly applicable for plant research and biotechnology across diverse species and experimental contexts. Key features • Syn-tasiRNAs allow the simultaneous silencing of multiple genes with high specificity, as they are computationally designed to avoid off-target effects. • This protocol describes the design and obtention of syn-tasiRNAs for the simultaneous silencing of one or several endogenous genes in any plant species. • This protocol also describes a non-transgenic alternative for applying syn-tasiRNAs to plants using a viral vector to induce whole-plant gene silencing. • This protocol can also be applied to induce antiviral protection against pathogenic viruses, reducing viral mutational escapes when expressing multiple syn-tasiRNAs targeting different viral sites.