Abstract: This study aimed to analyze the expression profiles of long non-coding RNA (lncRNA) in sheep ovarian tissues at different reproductive cycles, understand the lncRNA expression and its regulatory mechanism, and provide a theoretical basis for sheep breeding research. In this study, Hu sheep were selected as the research object, and 3 ewes aged from 1.5 to 2.5 years old in luteal phase and follicular phase were selected, respectively. lncRNA in ovarian tissues were screened by high-throughput sequencing. Bioinformatics analysis was used to predict the target genes of differentially expressed lncRNAs. GO and KEGG enrichment analysis were used to identify pathways related to sheep reproduction. The results showed that a total of 1 379 differentially expressed lncRNAs were obtained in this study, of which 1 158 were up-regulated and 221 down-regulated. GO and KEGG enrichment analysis showed that the differentially expressed lncRNAs and their target genes mainly involved in ovarian follicle development, ovulation cycle process, calcium signaling pathway, oocyte meiosis, oxytocin signaling pathway, MAPK signaling pathway, thyroid hormone synthesis signaling pathway, and estrogen signaling pathway. Key lncRNAs might regulate reproduction by regulating genes involved in these signaling pathways and biological processes. Specifically, MAPK1, ADCY1, ADCY5, PPP3CA and CDC23, which are targeted by LNC_011239, LNC_012847, LNC_003902, LNC_003906, LNC_003907 and others, might play key regulatory roles. The results of qRT-PCR showed that the expression levels of 5 randomly selected lncRNAs were consistent with the sequencing results. In this study, RNA-Seq technology was used to screen lncRNAs in luteal and follicular ovarian tissues, and the differences were analyzed to provide the basis for revealing the molecular mechanism of sheep reproductive capacity.

Key words: ovary, lncRNA, RNA-seq, sheep