Genome-wide analysis of DNA methylation in the sexual stage of the insect pathogenic fungus Cordyceps militaris. Cordyceps militaris

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. Overall design: Bisulphite converted genomic DNA from the mycelium and fruitingbody of Cordyceps militaris