The porcine estrous cycle is influenced by reproductive hormones, which affect porcine reproduction and result in physiological changes in the reproductive organs. The ovary is involved in ovulation, luteinization, corpus luteum development, and luteolysis. Here, we aimed to provide a comprehensive understanding of the gene expression patterns in porcine ovarian transcriptomes during the estrous cycle through differentially expressed genes profiling and description of molecular mechanisms. The transcriptomes of porcine ovary were obtained during the estrous cycle at three-day intervals from day 0 to day 18 using RNA-seq. At seven time points of the estrous cycle, 4414 DEG were identified; these were classified into three clusters according to their expression patterns. During the late metestrus and diestrus periods, the expression in cluster 1 increased rapidly, and steroid biosynthesis was significant in the pathway. Cluster 2 gene expression patterns represented the cytokine–cytokine receptor interaction in significant pathways. In cluster 3, the hedgehog signaling pathway was selected as the significant pathway. Our study exhibited dynamic gene expression changes with these three different patterns of cluster 1, 2, and 3. The results helped identify the functions and related significant genes especially during the late metestrus and diestrus periods in the estrous cycle.

Identification of lncRNA-mRNA interactions and genome-wide lncRNA annotation in animal transcriptome profiling Running Title (within 10 words) lncRNA annotation and lncRNA function in animal transcriptome

Background The mechanism of estrous cycles of pigs should be explored because their reproductive traits are useful for manipulating productivity and solving problems such as infertility. These estrous cycles should be elucidated to understand the complex interactions between various reproductive tissues (including the ovary, oviduct, and endometrium) and the complex range of hormone secretions during estrous cycles. Long non-coding RNAs (lncRNAs) regulate target genes at transcriptional, post-transcriptional, and post-translational regulation levels in various species. However, unlike mRNAs, lncRNAs in pigs have not been sufficiently annotated, and understanding at the protein level of coding genes has limitations in determining the mechanism of the reproductive traits of porcine. In this study, the lncRNAs of porcine ovary, oviduct, and endometrium were investigated on days 0, 3, 6, 9, 12, 15, and 18 of the estrous cycle. In addition, the characteristics and functions of the identified lncRNAs were explored. Results 19,021 novel lncRNA transcripts were selected, and the comparison of the characteristics of the newly identified lncRNA and mRNA showed that similar to those of previous studies. Four lncRNA networks were chosen through network analysis. The cis-acting genes of lncRNAs included in each network were identified, and expression patterns were compared. The main lncRNAs (XLOC_021792, XLOC_017111, ENSSSCG00000050977, XLOC_000342, ENSSSCG00000050380, ENSSSCG00000045111, XLOC_008338, XLOC_004128, and ENSSSCG00000040267) were determined from the network by considering the cis-acting genes. Specific novel lncRNAs were discovered in the reproductive tissues during the swine estrous cycle, and their time-serial expression dynamics were confirmed. Conclusions As the main lncRNAs are involved in the development of each reproductive tissue and hormone action, they can be utilized as potential biomarkers to help improve and develop the reproductive traits of pigs.