3.3. Discrimination of the different RSIVs by multiplex PCR
As shown in Fig. 3, the Pst I restriction fragment of RSIV CH-1 had 92.9% nucleotide
sequence homology with RSIV Namhae (or the reference sequence of RSIV Ehime-1).
However, we found two highly variable regions with a deletion of three continuous
nucleotides in RSIV Sachun and CH-1 at position 36–38 and 432–434, respectively. Two
primers were designed using the sequences of two variable regions, 24–41 (sense primer
NF) and 425–446 (antisense primer CR) in the Pst I restriction fragment of RSIV Namhae
and CH-1, respectively. Additionally, other two primers were designed, AF (sense primer)
and AR (antisense primer), derived from the sequence of 300–319 and 836–855 in the Pst
I regions conserved in all three different RSIV isolates (Fig. 3). Although two of the
primers, NF and CR, will bind specifically only to the DNA templates of RSIV Namhae
and CH-1, respectively, the other two primers, AF and AR, will bind to the DNA templates
of all three different types of RSIVs during PCR. The binding sites of the primers in PCR
is illustrated in Fig. 4.
In a PCR assay with the AF/AR primer set, amplicons of the expected sizes (556, 832,
and 144 bp, respectively) were obtained from the DNA of all three types RSIVs, while
with the NF/AR set only RSIV Namhae showed an amplicon, and with the AF./CR primer