Cloning and expression of a novel lipase gene from Pseudomonas fluorescens B52

Here we describe an advanced polymerase chain reaction (PCR) technique, the compatible ends ligation inverse PCR (CELI-PCR) for chromosome walking. In CELI-PCR, several restriction enzymes, which produce compatible cohesive ends, were used to digest target DNA simultaneously or sequentially to produce DNA fragments of suitable size. DNA fragments were then easily circularized and PCR amplification could be carried out efficiently. The previous limitations of inverse PCR were overcome, such as unavailable restriction sites, poor template DNA circularization, and low amplification efficiency. Therefore, successive chromosome walking was performed successfully. Our work, isolating a 11,395-bp fragment from Gossypium hirsutum, was presented as an example to describe how CELI-PCR was carried out.