Studies of binding interactions between Dufulin and southern rice black-streaked dwarf virus P9-1

Southern rice black-streaked dwarf virus (SRBSDV) is an important rice virus that can cause considerable crop losses. During infection, SRBSDV P9-1 accumulates viroplasms in SRBSDV-infected plant and insect cells, which may facilitate the formation of SRBSDV particles. Our field trial results showed that Dufulin inhibited infection activity in SRBSDV-infected rice. However it is not clear how Dufulin inhibits the infection activity. Therefore we studied the interactions between Dufulin and SRBSDV using P9-1 as a potential target, and found that Dufulin inhibited SRBSDV P9-1 gene expression and had a micromole affinity for the arginine 175 residue. Substituting arginine with glycine resulted in a mutant that was significantly less sensitive to Dufulin. Based on these results, we speculate that Dufulin inhibits the virulence of SRBSDV by binding with arginine 175 in the internal pore of P9-1 octameric protein.