Transcriptome and chromatin accessibility landscape of ovarian development at different egg-laying stages in taihe black-bone silky fowls

Taihe Black-Bone Silky Fowl (SF) is a famous local breed in China, known for its high nutritional and medicinal value. However, its low egg-laying rate significantly limits its economic benefits. This study aims to explore the ovarian development status, as well as the changes in the transcriptome and chromatin accessibility landscape at different egg-laying stages of SF, in order to reveal the epigenetic regulatory mechanisms underlying ovarian development in laying hens. The results showed that during peak egg-laying, serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and progesterone (P4) in the SF were higher than in the other laying periods. Meanwhile, the serum and ovarian matrix total antioxidant capacity (T-AOC) level decreased with increasing age, whereas the ovarian matrix malondialdehyde (MDA) level showed the opposite trend. Compared to the late laying period, several genes related to ovarian development and reproductive hormone secretion, including TDRD5, CCNO, CYP17A1, BMP15, and STAR, were upregulated during the peak egg-laying period. Additionally, we identified key transcription factors (TF) associated with different egg-laying periods. Specific TF, such as Fli1, Etv2, and AT2G15740, linked to the peak egg-laying period, play significant roles in cell and tissue development. The specific transcription factor Nr5a2, associated with the late laying period, has been shown to inhibit E2 production. Furthermore, genes related to poultry reproductive performance, such as STAR and WNT4, were found to be regulated by specific distal enhancers in open chromatin regions (OCR). In conclusion, this study elucidated the dynamic changes in the transcriptome and chromatin accessibility landscape during ovarian development in SF at different egg-laying stages and highlighted key TF, including Fli1, Etv2, and Nr5a2, as well as essential genes like STAR and WNT4 that regulate ovarian development. These findings provide valuable insights into the regulatory mechanisms influencing egg-laying performance in SF and offer new strategies for improving ovarian follicle development and egg production performance in poultry.