Transcriptome-wide mapping of internal mRNA N-methylguanosine in sporulated and unsporulated oocysts of Eimeria tenella reveals stage-specific signatures.

Background: Growing evidence indicates that N-methylguanosine (mG) modification plays critical roles in epigenetic regulation. However, no data regarding mG modification are currently available in Eimeria tenella, a highly virulent species causing coccidiosis in chickens.

Methods: In the present study, we explore the distribution of internal messenger RNA (mRNA) mG modification in sporulated and unsporulated oocysts of E. tenella as well as its potential biological functions during oocyst development using methylated RNA immunoprecipitation sequencing (MeRIP-seq) and mRNA sequencing (mRNA-seq), and the mRNA-seq and MeRIP-seq data were verified by the quantitative reverse transcription polymerase chain reaction (RT-qPCR) and MeRIP-qPCR, respectively.

Results: Our data showed that mG peaks were detected throughout the whole mRNA body, and the coding DNA sequence (CDS) region displayed the most methylation modification. Compared with unsporulated oocysts, 7799 hypermethylated peaks and 1945 hypomethylated peaks were identified in sporulated oocysts. Further combined analysis of differentially methylated genes (DMGs) and differentially expressed genes (DEGs) showed that there was a generally positive correlation between mG modification levels and gene transcript abundance. Unsurprisingly, the mRNA-seq and MeRIP-seq data showed good consistency with the results of the RT-qPCR and MeRIP-qPCR, respectively. Gene Ontology (GO) and pathway enrichment analysis of DEGs with altered mG-methylated peaks were involved in diverse biological functions and pathways, including DNA replication, RNA transport, spliceosome, autophagy-yeast, and cAMP signaling pathway.

Conclusions: Altogether, our findings revealed the potential significance of internal mG modification in E. tenella oocysts, providing some directions and clues for later in-depth research.