Transcriptome Analysis of the Ovaries of Taihe Black-Bone Silky Fowls at Different Egg-Laying Stages

Abstract

The poor egg-laying performance and short peak egg-laying period restrict the economic benefits of enterprises relating to the Taihe black-bone silky fowl. Ovaries are the main organ for egg production in poultry. Unlike that of mammals, the spawning mechanism of poultry has rarely been reported. As a prominent local breed in China, the reproductive performance of Taihe black-bone silky fowls is in urgent need of development and exploitation. To further explore the egg-laying regulation mechanism in the different periods of Taihe black-bone silky fowls, the ovarian tissues from 12 chickens were randomly selected for transcriptome analysis, and 4 chickens in each of the three periods (i.e., the pre-laying period (102 days old, Pre), peak laying period (203 days old, Peak), and late laying period (394 days old, Late)). A total of 12 gene libraries were constructed, and a total of 9897 differential expression genes (DEGs) were identified from three comparisons; the late vs. peak stage had 509 DEGs, the pre vs. late stage had 5467 DEGs, and the pre vs. peak stage had 3921 DEGs (pre-stage: pre-egg-laying period (102 days old), peak-stage: peak egg-laying period (203 days old), and late-stage: late egg-laying period (394 days old)). In each of the two comparisons, 174, 84, and 2752 differentially co-expressed genes were obtained, respectively, and 43 differentially co-expressed genes were obtained in the three comparisons. Through the analysis of the differential genes, we identified some important genes and pathways that would affect reproductive performance and ovarian development. The differential genes were LPAR3, AvBD1, SMOC1, IGFBP1, ADCY8, GDF9, PTK2B, PGR, and CD44, and the important signaling pathways included proteolysis, extracellular matrices, vascular smooth muscle contraction, the NOD-like receptor signaling pathway and the phagosome. Through the analysis of the FPKM (Fragments Per Kilobase of exon model per Million mapped fragments) values of the genes, we screened three peak egg-laying period-specific expressed genes: IHH, INHA, and CYP19A1. The twelve genes and five signaling pathways mentioned above have rarely been reported in poultry ovary studies, and our study provides a scientific basis for the improvement of the reproductive performance in Taihe black-bone silky fowls.