Optimization of single-strand conformation polymorphism and sequence analysis of the mitochondrial control region in Pagellus bogaraveo (Sparidae, Teleostei): rationalized tools in fish population biology.

We report the isolation and sequencing of 400-550 base pairs (bp) of the mitochondrial DNA (mtDNA) control region of eight species of Sparidae (Perciformes, Teleostei). This sequence information allowed us to design specific primers to one of these species (Pagellus bogaraveo). The new set of primers was used to test a rationalized approach to study the mtDNA nucleotide variability at the intraspecific level. The single-strand conformation polymorphism (SSCP) technique was applied to detect sequence variation in two non-overlapping fragments of the control region of 32 individuals of P. bogaraveo. To assess the sensitivity of the method, the nucleotide sequence of the analysed region was determined for all the specimens. The results showed that, for one of the two fragments, SSCP analysis was able to detect 100% of the underlying genetic variability. In sharp contrast, nucleotide variation of the second DNA fragment was completely unresolved by SSCP under different experimental conditions. This suggests that the resolution power of SSCP is crucially dependent on the nature of the fragment subjected to the analysis; therefore, a preliminary test of the sensitivity of the method should be performed on each specific DNA fragment before starting a large-scale survey. A rationalized approach, combining the SSCP technique and a simplified sequencing procedure, is proposed for studying intraspecific polymorphism at the mtDNA control region in fish.