It is not yet known if additional members of the large helicase family could perform similar function to Ded1p during TBSV replication. Our in vitro data with AtRH20 plant helicase protein, which is very similar to Ded1p ( Figure S7 ), suggests that this protein can likely perform similar function in plant infections. For example, AtRH20 has been shown to boost TBSV (+)RNA synthesis in vitro ( Figure 6 ) and bind to p33 replication protein ( Figure S6A ), which can facilitate its recruitment into the VRC. Since more than 50 RNA helicases are present in plants, further experiments will be needed to define if additional host helicases might also be involved in TBSV replication.