DNA cloning and sequencing
The PCR products were purified from agarose gels and sent for
commercial sequencing (Invitrogen, China). Some PCR products
were also cloned into the Pmd18-T vector for sequencing
according to the manufacture’s protocol (Takara). Briefly, ligation
products were used to transform TOP 10 high efficiency
competent cells and were plated onto LB/ampicillin/IPTG/XGal
plates. Multiple positive (white) colonies were picked randomly
from each cloned sample. DNAs from the colonies were sequenced
after restriction digestion verifying the presence of inserts. The
DNA sequences were initially aligned and edited using BioEd