3-fold increase of the activity of the purified tombusvirus replicase on TBSV (2)RNA template ( Figure 6B , lanes 2-3 versus 1). To test if AtRH20 can interact with the TBSV p33 replication protein, we used the membrane-based split-ubiquitin assay [31] . We found that AtRH20, similar to Ded1p, interacted with p33 protein in yeast ( Figure S6A ). Altogether, these data strongly suggest that plants also have DEAD-box helicases that could play similar role to the yeast Ded1p DEAD-box helicase in tombusvirus (+)RNA synthesis.