RÉSUMÉ
OBJECTIVES: This study is performed in the frame of a bigger study dedicated to genomics and transcriptomics of parthenogenesis in vertebrates. Among vertebrates, obligate parthenogenesis was first described in the lizards of the genus Darevskia. In this genus, all found parthenogenetic species originated via interspecific hybridization. It remains unknown which genetic or genomic factors play a key role in the generation of parthenogenetic organisms. Comparative genomic and transcriptomic analysis of parthenogens and their parental species may elucidate this problem. Darevskia valentini is a paternal species for four (of seven) parthenogens of this genus, which we promote as a particularly important species for the generation of parthenogenetic forms. DATA DESCRIPTION: Total cellular RNA was isolated from kidney and liver tissues using the standard Trizol Tissue RNA Extraction protocol. Sequencing of transcriptome libraries prepared by random fragmentation of cDNA samples was performed on an Illumina HiSeq2500. Obtained raw sequences contained 117,6 million reads with the GC content of 47%. After preprocessing, raw data was assembled by Trinity and produced 491,482 contigs.
Sujet(s)
Lézards , Animaux , Lézards/génétique , Transcriptome , Parthénogenèse/génétique , Rein , Foie , ARNRÉSUMÉ
The extant reptiles are one of the most diverse clades among terrestrial vertebrates and one of a few groups with instances of parthenogenesis. Due to the hybrid origin of parthenogenetic species, reference genomes of the parental species as well as of the parthenogenetic progeny are indispensable to explore the genetic foundations of parthenogenetic reproduction. Here, we report on the first genome assembly of rock lizard Darevskia valentini, a paternal species for several parthenogenetic lineages. The novel genome was used in the reconstruction of the comprehensive phylogeny of Squamata inferred independently from 7369 trees of single-copy orthologs and a supermatrix of 378 conserved proteins. We also investigated Hox clusters, the loci that are often regarded as playing an important role in the speciation of animal groups with drastically diverse morphology. We demonstrated that Hox clusters of D. valentini are invaded with transposons and contain the HoxC1 gene that has been considered to be lost in the amniote ancestor. This study provides confirmation for previous works and releases new genomic data that will contribute to future discoveries on the mechanisms of parthenogenesis as well as support comparative studies among reptiles.
Sujet(s)
Lézards , Animaux , Génome/génétique , Lézards/génétique , Répétitions microsatellites , Parthénogenèse/génétique , PhylogenèseRÉSUMÉ
Darevskia rock lizards include 29 sexual and seven parthenogenetic species of hybrid origin distributed in the Caucasus. All seven parthenogenetic species of the genus Darevskia were formed as a result of interspecific hybridization of only four sexual species. It remains unknown what are the main advantages of interspecific hybridization along with switching on parthenogenetic reproduction in evolution of reptiles. Data on whole transcriptome sequencing of parthenogens and their parental ancestors can provide value impact in solving this problem. Here we have sequenced ovary tissue transcriptomes from unisexual parthenogenetic lizard D. unisexualis and its parental bisexual ancestors to facilitate the subsequent annotation and to obtain the collinear characteristics for comparison with other lizard species. Here we report generated RNAseq data from total mRNA of ovary tissues of D. unisexualis, D. valentini and D. raddei with 58932755, 51634041 and 62788216 reads. Obtained RNA reads were assembled by Trinity assembler and 95141, 62123, 61836 contigs were identified with N50 values of 2409, 2801 and 2827 respectively. For further analysis top Gene Ontology terms were annotated for all species and transcript number was calculated. The raw data were deposited in the NCBI SRA database (BioProject PRJNA773939). The assemblies are available in Mendeley Data and can be accessed via doi:10.17632/rtd8cx7zc3.1.
RÉSUMÉ
BACKGROUND: The hybridization of female D. raddei and male D. valentini gave rise to the parthenogenetic Caucasian rock lizard Darevskia unisexualis. A previously identified genetic polymorphism in the species consisted of one common and two allozyme clones. Analysis of microsatellites and single nucleotide polymorphisms (SNPs) from the three species yields estimates of clonal diversity and tests the hypothesis of a single origin for D. unisexualis. RESULTS: Genotyping and sequencing of four microsatellite-containing loci for 109 specimens of D. unisexualis, 17 D. valentini, and 45 D. raddei nairensis identified 12 presumptive clones, including one widespread and 11 rare clones. Most individuals in some localities had a rare clone. Clone-specific alleles in D. unisexualis were compared with those of the parental species. The results inferred a single hybridization event. Post-formation mutations best explain the less common clones. CONCLUSIONS: Interspecific analyses identify alleles inherited by D. unisexualis from its bisexual ancestors. SNP analyses fail to reject the hypothesis of a single interspecific origin of D. unisexualis, followed by microsatellite mutations in this initial clone. Microsatellites detect higher clonal diversity in D. unisexualis compared to allozymes and identify the likely origins of clones. Our approach may be applicable to other unisexual species whose origins involve interspecific hybridization.
Sujet(s)
Évolution moléculaire , Variation génétique , Lézards/génétique , Parthénogenèse/génétique , Allèles , Animaux , Cytochromes b/génétique , Femelle , Génotype , Hybridation génétique , Isoenzymes/génétique , Mâle , Répétitions microsatellites/génétique , Polymorphisme de nucléotide simpleRÉSUMÉ
BACKGROUND: The parthenogenetic Caucasian rock lizard Darevskia armeniaca, like most other parthenogenetic vertebrate species, originated through interspecific hybridization between the closely related sexual Darevskia mixta and Darevskia valentini. Darevskia armeniaca was shown to consist of one widespread allozyme clone and a few rare ones, but notwithstanding the origin of clonal diversity remains unclear. We conduct genomic analysis of D. armeniaca and its parental sexual species using microsatellite and SNP markers to identify the origin of parthenogenetic clonal lineages. RESULTS: Four microsatellite-containing loci were genotyped for 111 specimens of D. armeniaca, 17 D. valentini, and four D. mixta. For these species, a total of 47 alleles were isolated and sequenced. Analysis of the data revealed 13 genotypes or presumptive clones in parthenogenetic D. armeniaca, including one widespread clone, two apparently geographically restricted clones, and ten rare clones. Comparisons of genotype-specific markers in D. armeniaca with those of its parental species revealed three founder-events including a common and two rare clones. All other clones appeared to have originated via post-formation microsatellite mutations in the course of evolutionary history of D. armeniaca. CONCLUSION: Our new approach to microsatellite genotyping reveals allele-specific microsatellite and SNP markers for each locus studied. Interspecies comparison of these markers identifies alleles inherited by parthenospecies from parental species, and provides new information on origin and evolution of clonal diversity in D. armeniaca. SNP analyses reveal at least three interspecific origins of D. armeniaca, and microsatellite mutations in these initial clones give rise to new clones. Thus, we first establish multiple origins of D. armeniaca. Our study identifies the most effective molecular markers for elucidating the origins of clonal diversity in other unisexual species that arose via interspecific hybridization.
Sujet(s)
Lézards/génétique , Répétitions microsatellites/génétique , Parthénogenèse/génétique , Polymorphisme de nucléotide simple/génétique , Animaux , Variation génétique , Hybridation génétique , MutationRÉSUMÉ
The all-female Caucasian rock lizard Darevskia rostombekowi and other unisexual species of this genus reproduce normally via true parthenogenesis. Typically, diploid parthenogenetic reptiles exhibit some amount of clonal diversity. However, allozyme data from D. rostombekowi have suggested that this species consists of a single clone. Herein, we test this hypothesis by evaluating variation at three variable microsatellite loci for 42 specimens of D. rostombekowi from four populations in Armenia. Analyses based on single nucleotide polymorphisms of each locus reveal five genotypes or presumptive clones in this species. All individuals are heterozygous at the loci. The major clone occurs in 24 individuals and involves three populations. Four rare clones involve one or several individuals from one or two populations. Most variation owes to parent-specific single nucleotide polymorphisms, which occur as heterozygotes. This result fails to reject the hypothesis of a single hybridization founder event that resulted in the initial formation of one major clone. The other clones appear to have originated via post-formation microsatellite mutations of the major clone.