Transient down‐regulation of the RNA silencing machinery increases efficiency of Agrobacterium‐mediated transformation of Arabidopsis

Summary Agrobacterium tumefaciens is a plant pathogen that is widely used in plant transformation. As the process of transgenesis includes the delivery of single‐stranded T ‐ DNA molecule, we hypothesized that transformation rate may negatively correlate with the efficiency of the RNA ‐silencing machinery. Using mutants compromised in either the transcriptional or post‐transcriptional gene‐silencing pathways, two inhibitors of stable transformation were revealed— AGO 2 and NRPD 1a. Furthermore, an immunoprecipitation experiment has shown that NRPD 1, a subunit of P ol IV , directly interacts with A grobacterium T ‐ DNA in planta . Using the T obacco rattle virus ( TRV )‐based virus‐induced gene silencing ( VIGS ) technique, we demonstrated that the transient down‐regulation of the expression of either AGO 2 or NRPD 1a genes in reproductive organs of A rabidopsis, leads to an increase in transformation rate. We observed a 6.0‐ and 3.5‐fold increase in transformation rate upon transient downregulation of either AGO 2 or NRPD 1a genes, respectively. This is the first report demonstrating the increase in the plant transformation rate via VIGS ‐mediated transient down‐regulation of the components of epigenetic machinery in reproductive tissue.