Efficiency of FPNI-PCR
FPNI-PCR facilitates the rapid identification of target genomic sequences by permitting the use of short-cuts for a number of the steps between tissue isolation and target product sequencing, thereby reducing the input of time and effort compared to other current methods of flanking sequence cloning. For example, FPNI-PCR can be employed to generate target genomic products when cell lysates are used to supply the DNA templates (Figure (Figure4).4). For this procedure, we extracted cell lysates from the young leaves of transgenic tobacco, petunia hybrida and Rosa hybrida using the rapid NaOH extraction method. We found no difference in the success of target product amplification from these cell lysates compared to that from the higher quality DNA templates as purified by the CTAB method. In addition, we found no differences between the results of direct sequencing of the FPNI-PCR products compared to indirect sequencing of the cloned products within the PMD18-T vector. FPNI-PCR has the advantage that, after the first step (12-15 cycles), we can proceed to the second step directly, without requiring the prior dilution of the products from the first PCR step. When using such practices, we commonly achieved > 85% positive cloning of target products following the secondary PCR reaction. Thus, we were able to amplify target products using just 42-45 PCR cycles, and this was completed in less than 3 hours from the start of tissue extraction. When proceeding through the third PCR and final sequencing steps, FPNI-PCR was found to provide 100% positive results in our working tests of genomic cloning. In total, the procedure was completed in just 54-57 cycles, taking less than 4 hours.