Figure 4: The compensatory amino acid substitution R31G in NP7 improves viral growth and genome packaging.

(a) Positions of Bat NP-specific amino acids in the head domain and R31G body domain of NP7 using the modelled crystal structure of SC35M NP. The program PyMOL was used to assign the indicated positions. Bat-specific amino acids are marked in the colour code used in Fig. 3b. (b) MDCKII cells were infected at an MOI of 0.001 with wt SC35M, rNP7 or rNP7-R31G. At the indicated time post infection (p.i.), viral titres were determined by plaque assay. *P<0.05; **P<0.01; ****P<0.0001. (c) Relative ratio of genome segments identified in viral particles preparations of SC35M and rNP7-R31G. RNA was prepared from virus stocks with identical infectivity (PFU) and subjected to quantitative RT-PCR. Levels of viral genome transcripts obtained with wt SC35M were set to 1. *P<0.05; **P<0.01. Student’s t test was used for two-group comparisons. Error bars indicate the mean and s.d. of at least three independent experiments.