Fig. 2.
The BCoV SLI/II domain and SLIII domain, individually and together, support virus replication in the MHV background. (A) Scheme showing RNA domains in the BCoV 5′ UTR tested by reverse genetics for support of replication in the MHV genomic background. Stem-loop structures coinciding with domains in MHV (solid line) and BCoV (stippled line) are depicted. Filled circles on SLIV identify the AUG start codon for the nsp1 ORF. Note that the short form of stem-loop IV is depicted. (B) Plaque phenotypes for wt MHV and corresponding chimeras. Nonviable chimeras formed no visible syncytia during the first through third blind cell passages, and transfected cells appeared indistinguishable from mock-infected cells. (C) Growth kinetics of wt MHV, chimera B1–84/M, and chimera B85–141/M. (D) Growth kinetics of wt MHV and chimera B1–141/M. For growth kinetics, the results of two tests for each construct are shown.