The biological clock has been studied to play a critical role in the reproductive system of various living organisms like swine. To examine the effects of estrus cycle on the expression of ovarian biological clock-related gene in Xiang pig, in this study, we analyzed the expression and alternative splicing of biological clock-related genes in ovary during estrus and diestrous periods. In total, we detected 90 clock-related genes expressed in the ovaries of the Xiang pigs and found 33 clock-related genes differentially expressed between estrous and diestrous stages. We identified 44 differential splicing events from the transcripts of 34 biological clock-related genes. Furthermore, we also found 20 genes including the core clock components, arntl and cry1 were differentially regulated only at AS level and 14 genes, including per1 and clock, were differentially regulated at both expression and AS levels. We also proved that the core clock genes per1, cry1, clock and arntl and the clockrelated genes, ppp1cb and ntrk1 were rhythmically expressed in Xiang pig ovaries by RT-qPCR experiments. The results demonstrated that the biological clock in the ovaries of Xiang pigs might play an important role in regulating the ovarian physiological functions by the transcriptional and post-transcriptional regulation
