design: Sus scrofa oocyte mitochondrial fraction was enriched, and total DNAs were extracted by QIAGEN QIAamp DNA Micro Kit. BS-seq library was constructed from the enriched oocyte mtDNAs by Zymo Pico Methyl-Seq Library Prep Kit, according to the manufacturers instructions.  Each NGS library was sequenced by Illumina MiSeq instrument using 150 bp paired-end sequencing chemistry.