vRNA NS-Gluc is less competitive than natural NS in replication. RdRp assays were performed by cotransfecting pPolI-NS and pPolI-NS-Gluc respectively with pDZ-M as well as expression plasmids PA, PB1, PB2 and NP. At 30 h post transfection, the cells were harvested and total RNA were extracted. (a) The concentrations of vRNA NS and NS-Gluc were normalized to vRNA M, and the relative concentrations were presented; (b) The concentrations of mRNA NS, NS-Gluc and M were normalized to mRNA NP, and the relative concentrations were shown. The standard deviations were calculated based on three replicates. *** p < 0.001; * p < 0.05; students’ t test.