Fig. 1

Schematic representation of two modified CsCMV-NC expression vectors

The previous pCsCMV-NC plasmid contains a duplicated 90-bp putative CsCMV-CM CP subgenomic promoter (SGP1) (GenBank accession number MW175326; nt 5,534–5,623) and a Nimble Cloning (NC) frame sequence (adapter 1–Sfi I–ccdB–Sfi I–adapter 2). The SGP1 consisted of a 60-bp region upstream and a 30-bp region downstream of the CP start codon, respectively. In addition, SGP2 represented an authentic CP promoter. The two PCR products obtained from amplification of the pCsCMV-NC template using the CsCMV-5Fov/NC42-R or NC53-R primers, together with the NC-F/pGr35S-R primers, were assembled to generate the pCsCMV1-NC and pCsCMV2-NC constructs, respectively. The length of the sequence downstream of the CP start codon in SGP1 within pCsCMV-NC was extended from 30 to 42 and 53 bp. The resulting SGPs were denoted as SGP3 in pCsCMV1-NC and SGP4 in pCsCMV2-NC