HETEROPLASMY, LENGTH AND SEQUENCE VARIATION IN THE MTDNA CONTROL REGIONS OF 3 PERCID FISH SPECIES (PERCA-FLUVIATILIS, ACERINA-CERNUA, STIZOSTEDION-LUCIOPERCA)

The nucleotide sequence of the control region and flanking tRNA genes of perch (Perca fluviatilis) mtDNA was determined. The organization of this region is similar to that of other vertebrates. A tandem array o f 10-bp repeats, associated with length variation and heteroplasmy was observed in the 5' end. While the location of the array corresponds t o that reported in other species, the length of the repeated unit is s horter than previously observed for tandem repeats in this region. The repeated sequence was highly similar to the Mt5 element which has bee n shown to specifically bind a putative D-loop DNA termination protein . Of 149 perch anal! zed, 74% showed length variation heteroplasmy. Si ngle-cell PCR on oocytes suggested that the high level of heteroplasmy is passively maintained by maternal transmission. The array was also observed in the two other percid species, ruffe (Acerina cernua) and z ander (Stizostedion lucioperca). The array and the associated length v ariation heteroplasmy are therefore likely to he general features of p ercid mtDNAs. hmong the perch repeats, the mutation pattern is consist ent with unidirectional slippage, and statistical analyses supported t hr notion that the various haplotypes are associated with different le vels of heteroplasmy. The variation in array length among and within s pecies is ascribed to differences in predicted stability of secondary structures made between repeat units.