Fig. 4.

Construction of EGFP/Δ5a amplicon. (A) The 5a ORF was replaced with the EGFP ORF. Open boxes represent ORF of the IBV genome. Black lines represent PCR products. Arrows indicate the restriction enzyme sites inserted into the PCR products. (B) PCR products containing EGFP in place of ORF 5a. M represents the 1-kb DNA molecular size marker; lane 1, PCR product of EGFP, denoted as F in (A); lane 2, PCR product of M ORF and junction of 5′ of ORF 5a, denoted as G in (A); lane 3; PCR product encompassing 3′ end of 5a ORF and downstream of the ORF through 3′ UTR of IBV, denoted as H in (A). (C) Underlined are IBV sequences and bold are EGFP sequences.