Abstract
BackgroundAcipenseriformes take a basal position among Actinopteri and demonstrate a striking ploidy variation among species. The sterlet (Acipenser ruthenus, Linnaeus, 1758; ARUT) is a diploid 120-chromosomal sturgeon distributed in Eurasian rivers from Danube to Enisey. Despite a high commercial value and a rapid population decline in the wild, many genomic characteristics of sterlet (as well as many other sturgeon species) have not been studied.ResultsCell lines from different tissues of 12 sterlet specimens from Siberian populations were established following an optimized protocol. Conventional cytogenetic studies supplemented with molecular cytogenetic investigations on obtained fibroblast cell lines allowed a detailed description of sterlet karyotype and a precise localization of 18S/28S and 5S ribosomal clusters. Localization of sturgeon specific HindIII repetitive elements revealed an increased concentration in the pericentromeric region of the acrocentric ARUT14, while the total sterlet repetitive DNA fraction (C0t30) produced bright signals on subtelomeric segments of small chromosomal elements. Chromosome and region specific probes ARUT1p, 5, 6, 7, 8 as well as 14 anonymous small sized chromosomes (probes A-N) generated by microdissection were applied in chromosome painting experiments. According to hybridization patterns all painting probes were classified into two major groups: the first group (ARUT5, 6, 8 as well as microchromosome specific probes C, E, F, G, H, and I) painted only a single region each on sterlet metaphases, while probes of the second group (ARUT1p, 7 as well as microchromosome derived probes A, B, D, J, K, M, and N) marked two genomic segments each on different chromosomes. Similar results were obtained on male and female metaphases.ConclusionsThe sterlet genome represents a complex mosaic structure and consists of diploid and tetraploid chromosome segments. This may be regarded as a transition stage from paleotetraploid (functional diploid) to diploid genome condition. Molecular cytogenetic and genomic studies of other 120- and 240-chromosomal sturgeons are needed to reconstruct genome evolution of this vertebrate group.
Highlights
Acipenseriformes take a basal position among Actinopteri and demonstrate a striking ploidy variation among species
A detailed investigation of sturgeon biology including molecular characterization of chromosomal complement and understanding of genetic mechanisms of sex determination are essential for improvement of aquaculture and development of a viable conservation strategy
The same reasons resulted in the lack of accurate knowledge about the system of sex determination of all members of Acipenseriformes
Summary
Acipenseriformes take a basal position among Actinopteri and demonstrate a striking ploidy variation among species. Despite a high commercial value and a rapid population decline in the wild, many genomic characteristics of sterlet (as well as many other sturgeon species) have not been studied. A great interest in the study of the sturgeon genomes (Acipenseridae, Acipenseriformes) is primarily connected with a high commercial value of the representatives of the family and a necessity in conservation measures due to a rapid population decline in the wild. A detailed investigation of sturgeon biology including molecular characterization of chromosomal complement and understanding of genetic mechanisms of sex determination are essential for improvement of aquaculture and development of a viable conservation strategy. Despite a high interest in sturgeon biology, the phylogenetic relationships between species, the number of chromosomes and other important biological characteristics remained controversial for a long time.
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