Project description:The evolutionary plasticity of higher-order genome organization in vertebrates—and its transmission through the germ line—is central to understanding genome function and evolution. Yet, the mechanisms regulating these processes remain poorly characterized across lineages. Here, we integrate fluorescence-activated cell sorting, in situ Hi-C, and single-cell RNA sequencing to investigate germ line genome architecture in eutherians, marsupials, and reptiles, —lineages that last shared a common ancestor ~320 million years ago. We uncover lineage-specific chromatin folding patterns in germ cells, shaped by chromosome morphology and genome size, which constrain DNA loop formation and inter-chromosomal interactions during meiosis. We also explore the relationship between 3D genome remodeling and gene regulation in the context of meiotic sex chromosome inactivation. In the tammar wallaby, we identify regions of the X that escape MSCI, suggesting incomplete silencing in marsupials. These findings provide high-resolution insights into the evolution of germ line chromatin architecture and the co-evolution of genome structure and function across vertebrates.
Project description:The evolutionary plasticity of higher-order genome organization in vertebrates—and its transmission through the germ line—is central to understanding genome function and evolution. Yet, the mechanisms regulating these processes remain poorly characterized across lineages. Here, we integrate fluorescence-activated cell sorting, in situ Hi-C, and single-cell RNA sequencing to investigate germ line genome architecture in eutherians, marsupials, and reptiles, —lineages that last shared a common ancestor ~320 million years ago. We uncover lineage-specific chromatin folding patterns in germ cells, shaped by chromosome morphology and genome size, which constrain DNA loop formation and inter-chromosomal interactions during meiosis. We also explore the relationship between 3D genome remodeling and gene regulation in the context of meiotic sex chromosome inactivation. In the tammar wallaby, we identify regions of the X that escape MSCI, suggesting incomplete silencing in marsupials. These findings provide high-resolution insights into the evolution of germ line chromatin architecture and the co-evolution of genome structure and function across vertebrates.
Project description:The extraordinary range in the degree of sexual dimorphism (SD) among animal species is widely perceived to be caused in part by differences in patterns of sexual selection, but sex-specific adaptations and sex chromosome differences also play a role. Studies in insects have discovered a substantial number of sex-biased genes, but little is known about the epigenetic basis of SD. The degree and genome-wide distribution of sex-biased expression become interesting questions in hymenoptera species with haplodiploid sex-determination. To study the genetic and epigenetic architecture of SD and understand the conservation and evolution of sex-biased expression in a haplodiploid system that lacks sex chromosomes, we performed RNA-seq and whole-genome bisulfite sequencing in female and male adult samples of two parasitoid wasp species, Nasonia vitripennis and Nasonia giraulti. More than 75% of the expressed genes displayed significantly sex-biased expression. Both the number and the degree of sex-biased genes are higher than insects like Drosophila melanogaster, which have sex-chromosome mediated sex determination. Females from the two Nasonia species have far more similar expression profiles than does the contrast between the two sexes within either species. Interestingly, the extremely male- and female-biased genes are enriched for totally different functional categories: male-biased genes are highly enriched for key enzymes in sex-pheromone synthesis; female-biased genes are enriched for nuclear-located genes that are responsible for epigenetic regulation of gene expression. Unlike gene expression profiles, DNA methylomes are more similar within species, and no stable differentially methylated genes have been found between the two sexes, suggesting that DNA methylation is not directly responsible for the molecular basis of SD. However, methylation status does influence sex-biased expression: 80% of female-biased genes are methylated, which is more than two-fold higher than the genome average (30%); almost all male-biased and sex-specific genes are non-methylated, which is consistent with the fact that methylated genes have house-keeping functions and a broader expression breadth. Evolutionarily, male-biased genes have greater sequence divergence between the two species, and they are more likely to have a functional paralog in the Nasonia genome. Sex-specific genes have significantly higher non-synonymous substitution rates and dN/dS ratios. In addition, local clusters of sex-biased genes in the genome may have epigenetic properties similar to the sex chromosome. In summary, Nasonia accomplish a striking degree of sex-differential expression through a difference in ploidy along with associated differences in methylations status. Whole-genome bisulfite sequencing of 24-hour adult whole body samples of Nasonia vitripennis and Nasonia giraulti using Iilumina sequencing.
Project description:Dioecy is an important sexual system wherein, male and female flowers are borne on separate unisexual plants. Knowledge of sex-related differences can enhance our understanding in molecular and developmental processes leading to unisexual flower development. Coccinia grandis is a dioecious species belonging to Cucurbitaceae, a family well-known for diverse sexual systems. Male and female plants of C. grandis have 22A+XY and 22A+XX chromosomes respectively. Previously, we have reported a gynomonoecious form (GyM) (22A+XX) of C. grandis bearing morphologically hermaphrodite flowers (GyM-H) and female flowers (GyM-F). Also, we showed that foliar spray of silver nitrate on female C. grandis plant induces development of morphologically hermaphrodite buds (Ag-H) despite the absence of Y chromosome. To identify sex-related differences, total protein from the flower buds of male, female, GyM-H and Ag-H of C. grandis at early and middle stages of development were analysed by a powerful label-free proteomics approach on ABSCIEX Triple TOF 5600 platform.