Abstract: This study was aimed to excavate the microRNAs that regulate the reproduction of Xiang pigs from the small RNA sequencing data of Xiang pigs ovaries, it is of great significance fo analyze the molecular mechanism of miRNAs regulating ovarian function and reproductive traits in pig. In this study, four estrus pigs and four diestrus pigs were used as the test animals. The ovary tissues were collected from Xiang pigs after slaughter. The total RNA was extracted from ovary tissues for small RNA sequencing, the profile of miRNAs expression were calculated with bioinformatics selection, and the different expression target genes were predicted and the GO function enrichment and KEGG pathway enrichment analysis of the target genes were performed. The results showed that miRNAs were no uniformly distributed on chromosomes, mainly on chromosome 1 and chromosome X. Total of 627 known porcine miRNAs were expressed in the ovaries of Xiang pigs, of which 34 were differently expressed miRNAs. The top five expression levels of miRNAs were miR-23, let-7i-5p, miR-103, miR-30E-5p and miR-1271-5p. The results of GO function analysis showed that the main biological processes involved in target genes were cellular processes mainly distributed in cells and the main molecular function was binding. KEGG pathway analysis significantly enriched gonadotropin-releasing hormone receptor pathway, insulin-like growth factor pathway and EGF receptor signaling pathway, which were associated with oocyte development and maturation. Therefore, it was speculated that miR-23b, let-7i-5p, miR-103, miR-30e-5p and miR-1271-5p could be used as candidate miRNAs affecting the reproductive regulation of Xiang pigs. In this study, five miRNA molecules that might regulate the reproduction of Xiang pigs were preliminarily screened, which could provide a theoretical basis for improving the litter size of Xiang pigs at molecular level.

Key words: miRNA; ovary; target gene; fertility; Xiang pigs