Fig. 4

Genetic variation in the HA sequence after passaging of reassortant viruses. A Genetic distance of HA sequences. The genetic distance of the HA sequences of the PB1-, PA- and NP-reassortant viruses after five passages in MDCK cells (triangles) and mouse lung (circles) is plotted relative to the wt A2093-H9N2 virus. The genetic distance of the WSN-H1N1 after five passages is plotted relative to the wt WSN-H1N1 virus. Two independent experiments were performed in cells and mice, that were analyzed by NGS and are plotted separately, as RUN1 and RUN2. Further details on the NGS results are shown in Additional file 2: Table S5. ** significant difference in the genetic distance compared to the WSN-H1N1 strain. B Non-synonymous numbers over open read frame (ORF) of HA nucleotide sequence. The number of substitutions (SBS) is plotted for the PB1, PA and NP reassortant viruses, and the wt A2093-H9N2 and WSN-H1N1 viruses, after passaging in MDCK cells and mice lung. Numbers in the bracket indicated non-synonymous numbers with F_i > 0.01, and the total SBS number separating by “/”