Comparative analysis of the follicular transcriptome of Zhedong white geese (Anser Cygnoides) with different photoperiods

The laying performance of geese is mainly determined by follicular development and atresia, while follicular status is regulated by photoperiod. To understand the effect of photoperiod on the development of goose follicles, artificial light was used to change the photoperiod. In this study, ten healthy 220-day-old Zhedong white geese (Anser Cygnoides) with similar body weights and similar reproductive start times were reared for 60 days under long photoperiod (15 L:9 D) and short photoperiod (9 L:15 D) artificial light with the intensity controlled at 30 lux, and follicles were collected. Follicle development was analyzed by observing the morphology of follicle tissue, the localization of autophagosomes and autolysosomes, and the expression levels of apoptosis-related protein factors. Small white follicles (SWFs) were selected for RNA sequencing and bioinformatics analysis of the transcriptome. Under a long photoperiod, microtubule-associated protein 1 light chain 3 (LC3) and Caspase-3 were expressed in the granulosa cell layer and oocytes, respectively. LC3 and Caspase-3 protein expression was increased in SWF and large white follicles (LWFs), and there were more autophagosomes and autolysosomes in granulosa cells. RNA-seq found 93 differentially expressed genes (DEGs) in the short-photoperiod group, including 55 upregulated DEGs and 38 downregulated DEGs, distributed in 37 gene ontology categories. Kyoto Encyclopedia of Genes and Genomes-enriched signaling pathways revealed 5 pathways enriched in upregulated DEGs, including protein digestion and absorption, ECM-receptor interaction and regulation of lipolysis in adipocytes, and 4 pathways enriched in downregulated DEGs, such as fatty acid biosynthesis. Ten differentially expressed genes related to extracellular matrix and fatty acid metabolism (THBS2, COL12A1, MRC2, TUBA, COL1A1, COL11A1, HSPG2, FABP, MGLL, and OLAH) may be involved in the photoperiod regulation of follicle development in Zhedong white geese. The differentially expressed genes screened in this study will provide new ideas to further understand the molecular mechanism underlying photoperiod-mediated regulation of follicle development in Zhedong white geese.