For DNA amplification, the PCR thermocycler(Perkin-Elmer: Gene Amp System 2400) was programmed as follows: incubation at 94 °C for 5 min; 30 cycles at 94 °C for 45 s, 48 °C for 45 s, 72 °C for 1min, followed by one final extension cycle of 7 min at 72 °C.