TAIL-PCR amplification was conducted using a random combination of the three nested
specific primers, SP1 to SP3, with one of the four random primers, AP1 to AP4. A single 1710 bp
specific band was obtained when SP1 to SP3 were paired with AP3 in the third round of amplification;
no specific bands were obtained if SP1 to SP3 were paired with AP1, AP2, or AP4 (Figure 2a). As
the sequence of the 1710 bp band matched that of the 5'-end of the peanut chitinase gene, the
amplification product was considered to be the upstream promoter sequence for the peanut chitinase
gene and was named Ah-Chi-Pro. A 1650 bp band was generated using primers Chi-F and Chi-R,
and named Ah-Chi-P. This amplification product was inserted into the pMD18-T vector to obtain
the recombinant plasmid pMD18-T-Ah-Chi-P; construction of the plasmid was verified by PCR and
double-digestion with BamHI and NcoI, which produced the 1650 bp construct (Figure 2b,c).