Heteroplasmy and length variation in the tRNApro- Dloop regions of three sturgeon species (A. stellatus, A. gueldenstaedtii and H. huso) from the Turkish coast of the Black Sea

Objective: To determine tandem repeat polymorphism and heteroplasmy in three sturgeon species (A. stellatus, A. gueldenstaedtii and H. huso) from the Turkish coast of Black Sea. Methods: tRNApro and D-loop segment of mtDNA from three sturgeon species were amplified via PCR and sequenced. For each species, homoplasmic individuals with different product lengths, repeat motifs and regions were determined and the repeat numbers and frequencies were calculated. The variation in mtDNA size present in the overall sample of sturgeon from Turkish waters was apportioned into hierarchical components. Also, the statistical approach described by other researchers was used for the calculation of inter- species and intra-species genetic variation. Results: The results showed that all three species reveal 2-6 copies of different mtDNA length variants attributable to varying copy numbers of an 82-84bp repeat sequences. A total of 9.9% of the sturgeons were heteroplasmic, bearing three to five repeat variants. The highest number of observed repeat units rate was 45.8% in 3 repeats morph in A. gueldenstaedtii. The mean genetic diversity within individuals (Kb) was higher in A. gueldenstaedtii and A. stellatus than in H. huso (0.625, 0.620, and 0.500, respectively). Conclusion: The repeat region, responsible for length variations and heteroplasmy, is located near the end of the D-loop and control region separated by only a few nucleotides from the tRNApro gene.