Перегляд за Автор "Dedukh, D.V."

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Crossing experiments reveal gamete contribution into appearance of di-and triploid hybrid frogs in Pelophylax esculentus population systems
(Chromosome Research, 2015) Dedukh, D.V.; Litvinchuk, S.N.; Rosanov, J.M.; Shabanov, D.A.; Krasikova, A.K.
Speciation through hybridization is connected with appearance of interspecies hybrids which can survive and reproduce owing to changes in their gametogenesis. In animals, these changes lead to appearance of clonal animals, which for successful reproduction usually depend on parental species and lack of recombination during gamete formation. Polyploidization can resolve these problems and may lead to emergence of new species. Pelophylax esculentus complex (complex of European water frogs) represents one of the appropriate models for studying interspecies hybridization and processes of polyploidization. Hybrid nature of the P. esculentus (RL genotype, 2n=26) was confirmed after crossings of two parental species P. ridibundus (RR genotype, 2n=26) and P. lessonae (LL genotype, 2n=26). Nevertheless absence of one parental species (P. lessonae) and abundance of triploid hybrid frogs (RRL and LLR genotypes, 3n=39) in population systems at the East of Ukraine challenged us to understand how di- and triploid hybrids can appear and prosper in population systems where hybrids exist only with P. ridibundus (R-E type population system). To answer this question we performed cytogenetic analysis of tadpoles appeared after artificial crossing experiments of diploid and triploid hybrids. Moreover, we identified karyotypes transmitted in growing oocytes of females participated in the crossings. Genome composition of mature frogs and tadpoles was established using FISH revealing interstitial (TTAGGG)n repeat sites that differed in two parental species. After crossings of six triploid hybrid females with RRL genotype and one female with LLR genotype with diploid hybrid males and triploid hybrid males with RRL genotype, tadpoles with karyotypes corresponding to P. ridibundus karyotypeappeared.Lampbrushchromosomesobtainedfrom oocytes of all triploid females participated in the crossings were represented by 13 bivalents corresponding to P. ridibundus chromosomes. Analysis of lampbrush chromosomes from oocytes of additional 11 hybrid females with RRL genome composition also revealed oocytes with 13 bivalents corresponding to P. ridibundus chromosomes. We suppose that such oocytes can overcome meiosis and form haploid gametes withP. ridibundusgenome. After crossings oftwo pairs of diploid hybrids we obtained triploid tadpoles with RRL andLLRkaryotypes.Oocytesfromdiploidhybrid females participated in the crossing and four additional diploid hybrid females contained 26 bivalents corresponding to P. ridibundus and P. lessonae chromosomes.Suchoocytespresumablycanformdiploidgametes after meiotic division. One diploid female after crossing with P. ridibundus male produced both P. ridibundus and diploid P. esculentus tadpoles and had oocytes with 26 bivalents corresponding to P. ridibundus and P. lessonae chromosomes. Other six diploid hybrid females had oocytes with 13 bivalents corresponding to P. ridibundus chromosomes. Crossings of seven diploid males with P. ridibundus females or triploid females with RRL genome composition resulted in appearance of tadpoles with karyotypes corresponding to P. ridibundus karyotype. Thus diploid males most probably produced haploid gametes with P. ridibundus genome. We suggest that triploid hybrid frogs cannot reproduce independently from diploid hybrids. In studied population systems, diploid hybrid females are likely to be responsible for appearance of triploid hybrids as well as new diploid hybrids.