Browsing by Author "May, B."

The sturgeon microsatellite LS-39 was amplified across 10 different species of Acipenserinae and exhibited the potential to identify the black caviar producer Acipenser stellatus on a genomic DNA level. This was because of a fixed allele of 111 bp, which was absent in the other species which were investigated. Concerning the source of sturgeon species, LS-39 is the first nuclear marker described to examine black caviar. Furthermore, new light is shed on the controversial ploidy state of sturgeons. The present authors findings at this microsatellite locus support the hypothesis that extant similar to 120 chromosomal species are modern diploids, whereas sturgeons with similar to 240 chromosomes should be considered as modern tetraploids.

Data from 1238 fishes from 19 sturgeon species and 1 paddlefish were used to analyze heteroplasmy in sturgeon. Lengths of central repeat units ranged from 74 to 83 bp among sturgeon species. No repeat sequence was found in the paddlefish, Polyodon spathula. A general feature of the repeat units was the presence of termination associated sequence (TAS) motifs. About 50% of 138 interspecific mutations observed among the D-loop sequences are located 10 bp down- and upstream from these TAS motifs. Interestingly, most homoplasmic species showed deletions upstream to the TAS motifs, whereas deletions downstream to the TAS motifs: observed in two species do not seem to preclude heteroplasmy. Calculations of secondary structures and thermal stabilities of repeat units showed DeltaG values for all heteroplasmic species to be <-8 and for most homoplasmic species G value to be >-8. Most heteroplasmic fishes had two and/or three repeat units. No homoplasmic sturgeon with >2 repeat units were observed. Molecular phylogeny based on the entire cytochrome b showed that heteroplasmy probably resulted fr om a single evolutionary event. Our data demonstrate that heteroplasmy is present in most sturgeon species and suggest that the thermal stability of the secondary structure of the repeat unit in combination with mutations downstream of the TAS sequences influences heteroplasmy.