Generation of ECTV-Δ036 and ECTV-DsRed using ECTV-Δ036 as a backbone. (A) Schematic representation of the ECTV region comprising EVM035 to EVM037, the plasmid pBSSK-Δ036 (used to induce the deletion of EVM036), and the resulting mutant virus ECTV-Δ036. (B) Schematic representation of the ECTV-Δ036 region comprising EVM035 to EVM037, the plasmid pBSSK-RevΔ036-DsRed (used to reintroduce EVM036 together with DsRed into ECTV-Δ036), and the resulting recombinant virus ECTV-DsRed. ECTV sequences are in gray, with a darker shade used for sequences involved in the homologous recombination (HR1 and HR2). Non-ECTV sequences are in white. **, region of EVM036 with synonymous mutations; *, the last 43 bp of EVM036 that were added as part of the EVM035 promoter.