Sequential amplification of flanking sequences by Y-shaped adaptor dependent extension using multiple templates.

Y-shaped adaptor dependent extension (YADE) method is a useful tool to amplify the flanking sequence of a known DNA sequence, but its efficiency is frequently limited by the restriction sites around the known sequence. In this paper, we demonstrated that using multiple templates derived from several restrictions and ligations could dramatically increase the efficiency of YADE method and render it suitable for sequential amplification of flanking sequences. With templates originating from 7 digestions, a 2,228-bp 5'-upstream sequence of a cotton small GTPase gene was obtained by two rounds of sequential YADE amplifications. The results demonstrated that the YADE method with multiple templates may be a useful tool for sequential PCR walking in complex genomes.