Characterization of the complete mitochondrial genome and identification of signature sequence of Indian wild pig

Abstract

Mitochondrial DNA (mtDNA) serves as a valuable molecular marker for constructing matrilineal genealogies and tracing the evolutionary history of animals. This study aimed to characterize the complete mitochondrial genome of the Indian wild pig (IWB) (Sus scrofa cristatus) and identify IWB-specific DNA sequences that could be used as genomic signatures to differentiate IWB from domestic Indian pigs (IDP) in forensic cases. For the purpose, three wild IWB from a rescue centre were used for the characterization of the mitochondrial genome of the IWB. The mitochondrial genome was sequenced by the primer walking technique using 30 overlapping primers. The mitochondrial genome of the IWB was found to be 16,689 bp long containing 37 genes coding for 2 rRNAs, 22 tRNAs, 13 protein coding genes, and 1 D-loop region similar to the mitogenome of other pigs. Sequence analysis of the D-loop of IWB with other IDP indicated some signature sequence for IWB like duplication and transition event from 1090th to 1099th position, deletion of a 10 bp sequence at the 755th position, insertion of (CA) at the 137th position, and substitution of AT to GA at the 638th position. These variations specially the duplication along with transition event causes creation of unique signature sequence (-ACACAAACCT-) in the IWB that could serve as signature sequences for the IWB and be used as markers for differentiation of IWB from IDP breeds in academic as well as forensic or vetero-legal cases. Overall, a total of 36 polymorphic positions were identified in the IWB, with 29 sites being unique to the IWB only and seven being common to the Doom and HDK75 pig breeds. None of the common polymorphic sites were identified in prevailing domestic pig populations. Phylogenetic analysis of the mitochondrial genome revealed the distinct separation of the IWB from IDP. The results of genetic distance evaluation showed that the Doom pig breed was the closest to the IWB. This study provides valuable insights into the mitogenome characterisation, signature sequence and genetic distance analysis of the IWB and establishes a foundation for future studies on the conservation of this protected species.