qRT-PCR analysis of recombinant HEF GFP viruses. (A) Procedure for the experiment. (B) GFP/NP vRNA ratios for each virus. In total, seven viruses were analyzed: ΔPB2-PS+PB2-GFP-PB2, ΔPA-PS+PA-GFP-PA, ΔNP-PS+NP-GFP-NP, ΔM-PS+M-GFP-M, ΔPB1-PS+PB1-GFP-PB1, ΔHA-PS+HA-GFP-HA, and ΔNS-PS+NS-GFP-NS. The GFP/NP vRNA ratio for the ΔNP-PS+NP-GFP-NP virus was arbitrarily set at 1. The experiment was performed in triplicate, and the mean value ± standard deviation is shown for each virus.