Project description:Gibel carp (Carassius gibelio) is a cyprinid fish that originated in eastern Eurasia and is considered as invasive in European freshwater ecosystems. The populations of gibel carp in Europe are mostly composed of asexually reproducing triploid females (i.e., reproducing by gynogenesis) and sexually reproducing diploid females and males. Although some cases of coexisting sexual and asexual reproductive forms are known in vertebrates, the molecular mechanisms maintaining such coexistence are still in question. Both reproduction modes are supposed to exhibit evolutionary and ecological advantages and disadvantages. To better understand the coexistence of these two reproduction strategies, we performed transcriptome profile analysis of gonad tissues (ovaries), and studied the differentially expressed reproduction-associated genes in sexual and asexual females. We used high-throughput RNA sequencing to generate transcriptomic profiles of gonadal tissues of triploid asexual females and males, diploid sexual males and females of gibel carp, as well as diploid individuals from two closely-related species, C. auratus and Cyprinus carpio. Using SNP clustering, we showed the close similarity of C. gibelio and C. auratus with a basal position of C. carpio to both Carassius species. Using transcriptome profile analyses, we showed that many genes and pathways are involved in both gynogenetic and sexual reproduction in C. gibelio; however, we also found that 1500 genes, including 100 genes involved in cell cycle control, meiosis, oogenesis, embryogenesis, fertilization, steroid hormone signaling and biosynthesis were differently expressed in the ovaries of asexual and sexual females. We suggest that the overall downregulation of reproduction-associated pathways in asexual females, and their maintenance in sexual ones, allow for their stable coexistence, integrating the evolutionary and ecological advantages and disadvantages of the two reproductive forms. However, we showed that many sexual-reproduction-related genes are maintained and expressed in asexual females, suggesting that gynogenetic gibel carp retains the genetic toolkits for meiosis and sexual reproduction. These findings shed new light on the evolution of this asexual and sexual complex.
Project description:Genome-wide analysis of DNA methylation for asexual and sexual stages of Cordyceps militaris DNA methylation is a basic epigenetic mechanism found in eukaryotes, but its patterns and roles vary significantly among diverse taxa. In fungi, DNA methylation has various effects on diverse biological processes; however, its function underlying the sexual development of fungi remains unclear. Cordyceps militaris, readily performing sexual reproduction, provides a remarkably rich model for understanding epigenetic processes in sexual development. The methylome was surveyed to assess DNA methylation patterns of the nascent fruiting body in C. militaris at single-base resolution by genomic bisulfite sequencing (BS-Seq). The results showed that around 0.4 % of cytosines are methylated, and that there is no difference compared with the DNA methylation level (0.39 %) during asexual development. However, 225 differentially methylated regions (DMRs) were identified between the stages. Moreover, RNA-Seq analysis indicated that the DMRs have no direct relation with the genes for fungal sexual development in C. militaris. DNA methylation regions from the BS-Seq show a striking correspondence to regions predicted to be repetitive and repeat-induced point mutation (RIP) mutated, suggesting that DNA methylation functions as a genome defense mechanism in sexual development. These results provide a comprehensive characterization of DNA methylation in the sexual development of C. militaris, which will contribute to future investigations of epigenetics in fungi. Bisulphite converted genomic DNA from the mycelium and fruitingbody of Cordyceps militaris
