Primers and PCR conditions used in this study.

*Restriction sites (underlined) introduced in primers: GGTACC (KpnI), GGATCC (BamHI), ACTAGT (SpeI), and TCTAGA (XbaI). Default PCR conditions were: initial denaturation, 95°C/5 min; denaturation, 94°C/30 s; number of cycles, 30; and final extension, 72°C/7 min.*引物中引入的下划线标注的限制性酶切位点（restriction sites）依次为：GGTACC（KpnI）、GGATCC（BamHI）、ACTAGT（SpeI）以及TCTAGA（XbaI）。聚合酶链式反应（PCR）的默认反应条件为：初始变性步骤为95℃/5分钟；变性步骤为94℃/30秒；循环总数为30次；最终延伸步骤为72℃/7分钟。