Dataset Information

Extraordinary centromeres: differences in the meiotic chromosomes of two rock lizards species Darevskia portschinskii and Darevskia raddei.

ABSTRACT: According to the synthesis of 30 years of multidisciplinary studies, parthenogenetic species of rock lizards of genus Darevskia were formed as a result of different combination patterns of interspecific hybridization of the four bisexual parental species: Darevskia raddei, D. mixta, D. valentini, and D. portschinskii. In particular, D. portschinskii and D. raddei are considered as the parental species for the parthenogenetic species D. rostombekowi. Here for the first time, we present the result of comparative immunocytochemical study of primary spermatocyte nuclei spreads from the leptotene to diplotene stages of meiotic prophase I in two species: D. portschinskii and D. raddei. We observed similar chromosome lengths for both synaptonemal complex (SC) karyotypes as well as a similar number of crossing over sites. However, unexpected differences in the number and distribution of anti-centromere antibody (ACA) foci were detected in the SC structure of bivalents of the two species. In all examined D. portschinskii spermatocyte nuclei, one immunostained centromere focus was detected per SC bivalent. In contrast, in almost every studied D. raddei nuclei we identified three to nine SCs with additional immunostained ACA foci per SC bivalent. Thus, the obtained results allow us to identify species-specific karyotype features, previously not been detected using conventional mitotic chromosome analysis. Presumably the additional centromere foci are result of epigenetic chromatin modifications. We assume that this characteristic of the D. raddei karyotype could represent useful marker for the future studies of parthenogenetic species hybrid karyotypes related to D. raddei.

SUBMITTER: Spangenberg V

PROVIDER: S-EPMC6359900 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Extraordinary centromeres: differences in the meiotic chromosomes of two rock lizards species Darevskia portschinskii and Darevskia raddei.

Spangenberg Victor V Arakelyan Marine M Galoyan Eduard E Pankin Mark M Petrosyan Ruzanna R Stepanyan Ilona I Grishaeva Tatiana T Danielyan Felix F Kolomiets Oxana O

PeerJ 20190130

According to the synthesis of 30 years of multidisciplinary studies, parthenogenetic species of rock lizards of genus Darevskia were formed as a result of different combination patterns of interspecific hybridization of the four bisexual parental species: Darevskia raddei, D. mixta, D. valentini, and D. portschinskii. In particular, D. portschinskii and D. raddei are considered as the parental species for the parthenogenetic species D. rostombe ...[more]

PMID: 30723630

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Project description:BackgroundThe majority of parthenogenetic vertebrates derive from hybridization between sexually reproducing species, but the exact number of hybridization events ancestral to currently extant clonal lineages is difficult to determine. Usually, we do not know whether the parental species are able to contribute their genes to the parthenogenetic vertebrate lineages after the initial hybridization. In this paper, we address the hypothesis, whether some genotypes of seven phenotypically distinct parthenogenetic rock lizards (genus Darevskia) could have resulted from back-crosses of parthenogens with their presumed parental species. We also tried to identify, as precise as possible, the ancestral populations of all seven parthenogens.ResultsWe analysed partial mtDNA sequences and microsatellite genotypes of all seven parthenogens and their presumed ansectral species, sampled across the entire geographic range of parthenogenesis in this group. Our results confirm the previous designation of the parental species, but further specify the maternal populations that are likely ancestral to different parthenogenetic lineages. Contrary to the expectation of independent hybrid origins of the unisexual taxa, we found that genotypes at multiple loci were shared frequently between different parthenogenetic species. The highest proportions of shared genotypes were detected between (i) D. sapphirina and D. bendimahiensis and (ii) D. dahli and D. armeniaca, and less often between other parthenogens. In case (ii), genotypes at the remaining loci were notably distinct.ConclusionsWe suggest that both observations (i-ii) can be explained by two parthenogenetic forms tracing their origin to a single initial hybridization event. In case (ii), however, occasional gene exchange between the unisexual and the parental bisexual species could have taken place after the onset of parthenogenetic reproduction. Indeed, backcrossed polyploid hybrids are relatively frequent in Darevskia, although no direct evidence of recent gene flow has been previously documented. Our results further suggest that parthenogens are losing heterozygosity as a result of allelic conversion, hence their fitness is expected to decline over time as genetic diversity declines. Backcrosses with the parental species could be a rescue mechanism which might prevent this decline, and therefore increase the persistance of unisexual forms.

Project description:Darevskia rock lizards is a unique complex taxa, including more than thirty species, seven of which are parthenogenetic. In mixed populations of Darevskia lizards, tri- and tetraploid forms can be found. The most important issues in the theory of reticulate evolution of Darevskia lizards are the origin of parthenogenetic species and their taxonomic position. However, there is little data on how meiosis proceeds in these species. The present work reports the complex results of cytogenetics in a diploid parthenogenetic species - D. unisexualis. Here we detail the meiotic prophase I progression and the specific features оf mitotic chromosomes organization. The stages of meiosis prophase I were investigated by immunocytochemical analysis of preparations obtained from isolated primary oocytes of D. unisexualis in comparison with maternal species D. raddei nairensis. It has been shown that in D. unisexualis at the leptotene-zygotene stages the axial elements and the synaptonemal complex (SC) form typical "bouquets". At the pachytene-diplotene stage, 18 autosomal SC-bivalents and thickened asynapted sex Z and w univalents were observed. The presence of SYCP1 protein between the lateral elements of autosomal chromosomes proved the formation of assembled SCs. Comparative genomic hybridization (CGH) on the mitotic metaphase chromosomes of D. unisexualis was carried out using the genomic DNA isolated from the parental species D. raddei nairensis and D. valentini. In the pericentromeric regions of half of the mitotic chromosomes of D. unisexualis, specific regions inherited from maternal species have been found. Following our results, we suggest a model for diploid germ cells formation from diploid oocytes without premeiotic duplication of chromosomes in the oogenesis of diploid parthenogenetic lizards D. unisexualis. Taken as a whole, our findings confirm the hybrid nature of D. unisexualis and shed light on heterozygosity and automixis in diploid parthenogenetic forms.

Dataset Information

Extraordinary centromeres: differences in the meiotic chromosomes of two rock lizards species Darevskia portschinskii and Darevskia raddei.

Publications

Extraordinary centromeres: differences in the meiotic chromosomes of two rock lizards species <i>Darevskia portschinskii</i> and <i>Darevskia raddei</i>.

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