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Two Doublesex1 mutants revealed a tunable gene network underlying intersexuality in Daphnia magna

ABSTRACT: Purpose: To justify whether sex is strictly binary or variable along a spectrum, exhaustive investigation into intersexuality is necessary. In this study, by mutating the sex determining locus Doublesex1, we generated two Daphnia magna strains from which two different forms of feminized males could be obtained. mRNA sequencing of these intersex males was carried out to explore the transcritomic shift responsible for the changes in sexual phenotype. Methods: Two Doublesex1 mutants, namely Line A and Line B, were generated by microinection of designed TALENs into Daphnia magna eggs. Line A males showed severe, while Line B males showed minor bodywide feminization. Whole body mRNA profiles of 40 hour post oviposition embryos were generated for wildtype female, Line A male, Line B male and wildtype male using Illumina sequencing (mRNA sequencing service provided by Novogene). Data analysis was done using CLC Genomics Workbench software. Results: Among 731 sex-biased genes identified in this dataset, more than half (449 genes) showed non-binary expression profile in which their expression in the mutant males was at an intermediate level between wildtype female and wildtype male. Conclusions: Downstream genes of Doublesex1 cascade may fluctuate in activity and give rise to a spectrum of sexual phenotypes in Daphnia magna.

ORGANISM(S): Daphnia magna

PROVIDER: GSE150820 | GEO | 2020/05/20

REPOSITORIES: GEO

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Project description:Background: In the life history of Daphnia, the reproductive mode of parthenogenesis and sexual reproduction alternate in aquatic ecosystem, which are often affected by environmental and genetic factor. Although several functional genes on reproductive transition of Daphnia had been determined, molecular mechanism on the reproductive mode of Daphnia are still not known well, including differentially expressed genes in different developmental stages. Results: In this study, four developmental stages, juvenile female (JF), parthenogenetic female (PF), sexual female (SF) and male (M), of D. similoides sinensis were performed for transcriptome sequence, and candidate genes related to male sex determination were screened. A total of 110437 transcripts were obtained and assembled into 22996 unigenes. In the four developmental stages (JF, PF, SF and M), the number of unique unigenes is respectively 2863, 445, 437 and 586, and the number of common unigenes is 9708. The differentially expressed genes (DEGs) between male and other three female stages (M vs JF, M vs PF and M vs SF) were obtained. The GO gene enrichment analysis showed that the up-regulated genes in male were mainly enriched in hydrolase activity and peptidase activity. Thirty-six candidate genes related to male sex determination in male were significantly higher expression than those in the other three stages, including one Doublesex (Dsx) gene, one laminin gene, five trypsin genes and one serine protease genes, and one chitin synthase gene and two chitinase genes. In addition, in D. similoides sinensis male, the relative expression levels of two genes (Dsx1, antp) related to male sex determination observed in other Daphnia species were also significantly higher than those in other developmental stages. Conclusions: Our results showed that thirty-six candidate genes may involve in sex differetiation of D. similoides sinensis male, and it will provide a reference for further exploring the functional genes related to sex determination mechanism in Daphnia species. Moreover, according to previous investigations, we thought that the expression level of functional genes may be related to the development stage of organisms, and may be also affected by different Daphnia species.

Project description:Background Daphnia species reproduce by cyclic parthenogenesis involving both sexual and asexual reproduction. The sex of the offspring is environmentally determined and mediated via endocrine signalling by the mother. Interestingly, male and female Daphnia can be genetically identical, yet display large differences in behaviour, morphology, lifespan and metabolic activity. Our goal was to integrate multiple omics datasets, including gene expression, splicing, histone modification and DNA methylation data generated from genetically identical female and male Daphnia pulex under controlled laboratory settings with the aim of achieving a better understanding of the underlying epigenetic factors that may contribute to the phenotypic differences observed between the two genders. Results In this study we demonstrate that gene expression level is positively correlated with increased DNA methylation, and histone H3 trimethylation at lysine 4 (H3K4me3) at predicted promoter regions. Conversely, elevated histone H3 trimethylation at lysine 27 (H3K27me3), distributed across the entire transcript length, is negatively correlated with gene expression level. Interestingly, male Daphnia are dominated with epigenetic modifications that globally promote elevated gene expression, while female Daphnia are dominated with epigenetic modifications that reduce gene expression globally. For examples, CpG methylation (positively correlated with gene expression level) is significantly higher in almost all differentially methylated sites in male compared to female Daphnia. Furthermore, H3K4me3 modifications are higher in male compared to female Daphnia in more than 3/4 of the differentially regulated promoters. On the other hand, H3K27me3 is higher in female compared to male Daphnia in more than 5/6 of differentially modified sites. However, both sexes demonstrate roughly equal number of genes that are up-regulated in one gender compared to the other sex. Since, gene expression analyses typically assume that most genes are expressed at equal level among samples and different conditions, and thus cannot detect global changes affecting most genes. Conclusions The epigenetic differences between male and female in Daphnia pulex are vast and dominated by changes that promote elevated gene expression in male Daphnia. Furthermore, the differences observed in both gene expression changes and epigenetic modifications between the genders relate to pathways that are physiologically relevant to the observed phenotypic differences.

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Two Doublesex1 mutants revealed a tunable gene network underlying intersexuality in Daphnia magna

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