Biology subjects

Volenikova, A.

Publications and source records attributed to Volenikova, A..

4 recordsLinked to original sources

bioRxiv2023

Multiple sex chromosomes of Yponomeuta ermine moths suggest a role of sexual antagonism in sex chromosome turnover in Lepidoptera

Sex chromosome-autosome fusions give rise to neo-sex chromosomes, which provide an insight into early evolution of sex chromosomes and drivers of chromosomal fusions. While sex chromosome-autosome fusions are scarce in vertebrates with female heterogamety ([female]ZW/[male]ZZ), they are common in moths and butterflies (Lepidoptera), the most species rich group with heterogametic females. This contradicts theoretical model that assumes chromosome fusions to be random and predicts them to be rare in taxa with high chromosome number such as Lepidoptera. In the present study we analyzed sex chromosomes in nine ermine moths of the genus Yponomeuta (Yponomeutidae) and their two outgroups, Teinoptila gutella (Yponomeutidae) and Plutella xylostella (Plutellidae). We employed genomic in situ hybridization to identify sex chromosomes and used a custom designed microarray to identify Z-linked genes. Our results confirmed a multiple sex chromosome system Z1Z2W to be present in T. gutella and all Yponomeuta spp. except for Y. tokyonella. The multiple sex chromosome system resulted from a fusion between the W chromosome and autosome homeologous to the Bombyx mori chromosome 2 (BmChr2). The BmChr2 bears a cluster of genes with ovary-specific expression which suggests that sexually antagonistic selection could have driven fixation of the fusion in a common ancestor of Yponomeuta and Teinoptila genera. We hypothesize that sex chromosome turnover in Lepidoptera could be driven by sexual antagonism.

evolutionary biology↗

bioRxiv2023

Fast centromeric repeat turnover provides a glimpse into satellite DNA evolution in Nothobranchius annual killifishes

Satellite DNA (satDNA) is rapidly evolving class of tandem repeats with some motifs being involved in centromere organization and function. Rapid co-evolution of centromeric satDNA and associated proteins has been mostly attributed to the so-called centromere drive. To identify repeats associated with centromeric regions and test for the role of meiotic drive in their evolution, we investigated satDNA across Southern and Coastal clades of African annual killifishes of the genus Nothobranchius. C-banding showed expansion of (peri)centromeric heterochromatin regions in the Southern-clade killifishes. Molecular cytogenetic and bioinformatic analyses further revealed that two previously identified satellites, Nfu-SatA and Nfu-SatB, are associated with centromeres only in one lineage of the Southern clade. Nfu-SatB was, however, detected outside centromeres also in other members of the Coastal clade, which is consistent with the "library" hypothesis of satDNA evolution. We also identified a novel satDNA, Cl-36, associated with (peri)centromeres in N. foerschi, N. guentheri and N. rubripinnis from the Coastal clade. Our findings could be explained by centromere drive shaping karyotype change and centromeric repeat turnover in Nothobranchius species with possible reversal of spindle polarity within the Southern clade.

genetics↗

bioRxiv2022

Sex chromosome differentiation via changes in the Y chromosome repeat landscape in African annual killifishes Nothobranchius furzeri and N. kadleci

Repetitive DNA represents an important driver of sex chromosome differentiation. Yet, repetitive sequences tend to be misrepresented or overlooked in genomic studies. We analysed repetitive DNA landscape of sex chromosomes in several populations of a turquoise killifish Nothobranchius furzeri and its sister species N. kadleci (Teleostei: Nothobranchiidae), representatives of African annual killifishes with high rate of karyotype and sex chromosome evolution. We combined bioinformatic analyses of repeatome with molecular cytogenetic techniques such as comparative genomic hybridization, fluorescence in situ hybridization with satellite sequences, genes for ribosomal RNAs (rDNA) and bacterial artificial chromosomes (BACs) and immunostaining of SYCP3 and MLH1 proteins, which marked lateral elements of synaptonemal complexes and recombination sites, respectively. We revealed that N. furzeri and N. kadleci share the XY sex chromosome system, which is thus much older than previously assumed. Sex chromosomes are mostly heteromorphic as evidenced by distinct distribution of satellite DNAs and major rDNA. Yet, the heteromorphic XY sex chromosomes pair almost exclusively regularly in meiosis, which implies synaptic adjustment. Physical mapping of BACs identified inversions on Y chromosomes of the N. kadleci populations, akin to the pattern previously reported in N. furzeri. Yet, repetitive DNA landscape of X and Y sex chromosomes either diverged in parallel in populations of both species or it evolved in their common ancestor and thus predates the inversions. The observed differentiation via repeat repatterning thus cannot be explained by the classical sexually antagonistic model. Rather, we hypothesized that relaxed meiotic drive and recombination reduced by neutral processes could drive changes in repeatome and secondary inversions could be maintained by sexually antagonistic regulatory effects resulting from early evolution of dosage compensation. Author summaryEarly differentiation of sex chromosomes is not yet satisfactorily understood despite intensive research effort. Homomorphic sex chromosomes and their rapid turnover are common in teleost fishes, which makes them excellent models for studying evolution of nascent sex chromosomes. We investigated sex chromosomes in several populations of two sister species of African annual killifishes, Nothobranchius furzeri and N. kadleci, particularly their repetitive landscape, which was misrepresented in previous genomic studies. Combination of cytogenetic and genomic approaches revealed that both species share heteromorphic XY sex chromosome system. The N. furzeri XY sex chromosomes thus evolved earlier than previously expected. In N. kadleci, Y-linked inversions analogous to those reported in N. furzeri were detected. Changes in repetitive DNA distribution on sex chromosomes are either convergent or occurred in a common ancestor of both species, prior to the inversion events. The observed sex chromosome differentiation on repetitive DNA level thus cannot be reconciled with the classical theoretical model of sex chromosome evolution driven by sexually antagonistic selection. We invoke alternative explanations such as relaxed meiotic drive and recombination reduced by neutral processes, and we hypothesize that secondary inversions could be maintained by early evolution of dosage compensation resulting in sexually antagonistic regulatory effects.

evolutionary biology↗

bioRxiv2021

A conserved role of the duplicated Masculinizer gene in sex determination of the Mediterranean flour moth, Ephestia kuehniella

Sex determination in the silkworm, Bombyx mori, is based on Feminizer (Fem), a W-linked Fem piRNA that triggers female development in WZ individuals, and the Z-linked Masculinizer (Masc), which initiates male development and dosage compensation in ZZ individuals. While Fem piRNA is missing in a close relative of B. mori, Masc determines sex in several representatives of distant lepidopteran lineages. We studied the molecular mechanisms of sex determination in the Mediterranean flour moth, Ephestia kuehniella (Pyralidae). We identified an E. kuehniella Masc ortholog, EkMasc, and its paralog resulting from a recent duplication, EkMascB. Both genes are located on the Z chromosome and encode a similar Masc protein that contains two conserved domains but has lost the conserved double zinc finger domain. We developed PCR-based genetic sexing and demonstrated a peak in the expression of EkMasc and EkMascB genes only in early male embryos. Simultaneous knock-down experiments of both EkMasc and EkMascB using RNAi during early embryogenesis led to a shift from male- to female-specific splicing of the E. kuehniella doublesex gene (Ekdsx), their downstream effector, in ZZ embryos and resulted in a strong female-biased sex-ratio. Our results thus confirmed the conserved role of both EkMasc and EkMascB genes in masculinization. We suggest that the C-terminal proline-rich domain, we have identified in all functionally confirmed Masc proteins, in conjunction with the masculinizing domain, is important for transcriptional regulation of sex determination in Lepidoptera. The function of the Masc double zinc finger domain is still unknown, but appears to have been lost in E. kuehniella. Author summaryThe sex-determining cascade in the silkworm, Bombyx mori, differs greatly from those of other insects. In B. mori, female development is initiated by Fem piRNA expressed from the W chromosome during early embryogenesis. Fem piRNA silences Masculinizer (Masc) thereby blocking the male pathway resulting in female development. It is currently unknown whether this cascade is conserved across Lepidoptera. In the Mediterranean flour moth, Ephestia kuehniella, we identified an ortholog of Masc and discovered its functional duplication on the Z chromosome, which has not yet been found in any other lepidopteran species. We provide two lines of evidence that both the EkMasc and EkMascB genes play an essential role in masculinization: (i) they show a peak of expression during early embryogenesis in ZZ but not in WZ embryos and (ii) their silencing by RNAi results in female-specific splicing of the E. kuehniella doublesex gene (Ekdsx) in ZZ embryos and in a female-biased sex ratio. Our results suggest a conserved role of the duplicated Masc gene in sex determination of E. kuehniella.

genetics↗