Stearoyl-CoA desaturase (SCD) is known to be an important rate-limiting enzyme in the production of monounsaturated fatty acids (MUFAs). However, the role of this enzyme in goose follicular development is poorly understood. To investigate the metabolic mechanism of SCD during goose follicular development, we observed its expression patterns in vivo and in vitro using quantitative reverse-transcription (qRT)-PCR. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine a cellular model of SCD function in granulosa cells (GCs) via SCD overexpression and knockdown. qRT-PCR analysis showed that SCD was abundantly expressed in the GC layer, and was upregulated in preovulatory follicles. Peak expression was found in F1 and prehierarchal follicles with diameters of 4–6 mm and 8–10 mm, respectively. We further found that mRNA expression and corresponding enzyme activity occur in a time-dependent oscillation pattern in vitro, beginning on the first day of GC culture. By LC-MS/MS, we identified numerous changes in metabolite activation and developed an overview of multiple metabolic pathways, 10 of which were associated with lipid metabolism and enriched in both the overexpressed and knockdown groups. Finally, we confirmed cholesterol and pantothenol or pantothenate as potential metabolite biomarkers to study SCD-related lipid metabolism in goose GCs.

Stearoyl-CoA desaturase (SCD) is a key enzyme catalyzing the rate-limiting step in monounsaturated fatty acids (MUFAs) production. There may be a mechanism by which SCD is involved in lipid metabolism, which is assumed to be essential for goose follicular development. For this reason, a cellular model of SCD function in goose granulosa cells (GCs) via SCD overexpression and knockdown was used to determine the role of SCD in GC proliferation using flow cytometry. We found that SCD overexpression induced and SCD knockdown inhibited GCs proliferation. Furthermore, ELISA analysis showed that SCD overexpression increased the total cholesterol (TC), progesterone, and estrogen levels in GCs, while SCD knockdown decreased TC, progesterone, and estrogen levels (p < 0.05). Combining these results with those of related multi-omics reports, we proposed a mechanism of SCD regulating the key lipids and differentially expressed gene (DEGs) in glycerophospholipid and glycerolipid metabolism, which participate in steroidogenesis mediated by the lipid droplet deposition in goose GCs. These results add further insights into understanding the lipid metabolism mechanism of goose GCs.

A deep understanding of the dynamics and mechanisms of male reproductive tract development is necessary for adoption of either genetic techniques or environmental management practices for improving fertility and hatchability in poultry. However, compared with other poultry such as chickens and ducks, less is known about the age- and breed-related changes in the reproductive tract development of domestic goose ganders exhibiting relatively poor reproductive performance as well as the regulatory mechanisms. In the present study, by taking 2 Chinese domestic goose breeds (Sichuan White goose, SW and Gang goose, GE; Anser cygnoides) and one European goose breed (Landes goose, LD; Anser anser) as the experimental objects, we comprehensive analyzed the morphological, histological, and genome-wide transcriptomic variations in their testicular and external genital development during the period from hatching to sexual maturity. Results from histomorphological analysis demonstrated that the reproductive tract of all goose breeds developed in both age- and breed-dependent manners, and the left and right testis developed asymmetrically throughout posthatch development. The tenth week posthatch was a critical developmental stage for all goose ganders, because both the testicular and external genital histomorphological parameters significantly changed before and after this period. During the first 10 wk posthatch, the weight, organ index, or size of male reproductive organs developed more rapidly in SW than in LD, and so were the testicular parenchymal-to-interstitial ratio and the external genital lymphatic lumen diameter. However, the testicular seminiferous epithelium thickness, seminiferous tubule diameter, and Leydig cell number, as well as the external genital keratinized epithelium thickness were significantly higher in LD than in SW at 10 wk of age. Through comparative transcriptomics analysis and RT-qPCR validation, several pathways related to germ and somatic cell function, organ remodeling, and energy metabolism were thought to be responsible for the developmental variations in the early testicular development between Chinese and European domestic ganders, where 10 hub genes involved in the cell cycle, RNA polymerase II-dependent transcription, and mitotic cell division pathways might play essential roles. These data shed new light on the interbreed differences in the male goose reproductive tract development and the molecular mechanisms regulating male goose testicular functions and fertility.

Semen quality has an important impact on the reproductive performance of ganders, and the quantity and quality of spermatozoa in semen are the determinants of semen quality. In our practical work, a small number of azoospermic ganders were observed in adult goose breeding populations, but the underlying regulatory mechanisms remain unknown. In the present study, we firstly compared the morphological and histological differences in the testes of ganders from normozoospermic group (NG) and azoospermic group (AG), and then analyzed the testicular expression patterns of circRNAs, miRNAs, and mRNAs between the two groups by using whole-transcriptome sequencing technology. Results from histomorphological analysis demonstrated that the body weight alone was not accountable for the occurrence of gander azoospermia, and the possible cause might be the observed testicular abnormalities. At the morphological level, the left, right, and bilateral testicular weights, the right and bilateral testicular organ indexes, and the long, short, and dorsoventral diameters of the left, right and bilateral testes were significantly lower in AG than in NG (P < 0.05). At the histological level, most testicular histological parameters, such as the testicular parenchymal area, the diameter of seminiferous tubules, and the number of germ cells, were significantly higher (P < 0.05) in NG than in AG. The RNA-seq results showed that a total of 683 differentially expressed circRNAs (DEcircRNAs), 24 differentially expressed miRNAs (DEmiRNAs), and 1,118 differentially expressed Genes (DEGs) were identified in the gander testes between NG and AG. Subsequent functional enrichment analysis revealed that most of the DEGs and the target genes of DEcircRNAs and DEmiRNAs were significantly enriched in either the biological processes related to male gonad development, spermatid development, and regulation of cell differentiation or the KEGG terms including the MAPK, TGF-beta, Wnt, and cell cycle signaling pathways. By constructing the core ceRNA regulatory networks, several key DEcircRNAs, including 1:98100313|98104995, 1:171413706|171419341, 6:3414226|3418193, and 2:115876735|115880760, were identified to regulate the expression of TGFB2 and BCL2 through interactions with specific miRNAs such as novel-miR-265 and novel-miR-266, and such interactions could play crucial roles in regulating the gander testicular cell apoptosis, proliferation, and spermatogenesis. This study provides novel insights into the function and molecular mechanisms of ceRNAs in regulating the gander testicular development and semen quality.

As an important non-genetic factor, the rearing system has significant effects on male poultry reproductive system development. However, compared with other poultry such as chickens and ducks, less is known about the effects and mechanisms of rearing system on the gander reproductive organ development and semen quality. In the present study, the testicular morphological, histological, and transcriptomic responses of three goose breeds to the two dryland rearing systems (i.e., cage rearing system, CRS and net-floor mixed rearing system, MRS) were systematically analyzed and compared. Results from histomorphological analysis demonstrated that the effects of rearing system on the gander testicular development were age-dependent, and moreover, the CRS may be more conducive than MRS to the testicular development and semen quality during the period from post-hatch week 10 to week 43. At week 30, compared to Sichuan White goose (SW), the rearing system showed more pronounced effects on the testicular size, weight, and organ index of Gang goose (GE) and Landes goose (LD). However, such effects were mitigated in LD and even reversed in GE at week 43. Meanwhile, most testicular histological parameters of three goose breeds were higher under MRS than under CRS at week 30, while the converse was seen in some histological parameters of either GE or LD at week 43. Moreover, the semen quality was generally better under CRS than under MRS at week 43. Through comparative transcriptomics analysis, the Wnt signaling pathway together with several involved hub genes were identified to have important roles in mediating the effects of rearing system on the goose testicular development. Moreover, the metabolism-related, cell cycle, and Wnt signaling pathways could be partially responsible for differences in the goose breed-related testicular development and semen quality under CRS, where a number of genes involved in meiosis could have crucial roles. These results would not only provide novel insights into the effects and mechanisms of rearing system on male poultry reproductive performance, but they would also be helpful for the optimization and selection of dryland rearing systems in male geese.

Sperm motility is a critical indicator of semen quality and determines the reproduction performance in male poultry. However, compared to chickens and ducks, very little is known about the physiological basis of varying levels of sperm motility as well the underlying regulatory mechanisms in geese. To address this, in the present study, a systematic comparison of semen quality parameters and histomorphological characteristics and genome-wide transcriptomic profiles of testes and epididymis were performed in ganders with high and low sperm motility. Our results showed that the size, weight, and organ index of bilateral testes and epididymis of ganders from high sperm motility (HSM) group tended to be higher (P > 0.05) than those of ganders from low sperm motility (LSM) group, implying better reproductive organ development in HSM. The ejaculate volume, sperm density, sperm viability, and semen quality factor of the ganders were observed to be significantly higher in HSM than in LSM (P < 0.01), and the opposite was seen in sperm deformity rate (P < 0.01). Moreover, the ganders in HSM showed significantly higher testicular seminiferous epithelial thickness and seminiferous tubule diameter (P < 0.05), higher number of Sertoli cells (SC), spermatids (Sd), and spermatozoa (Sa, P < 0.05), as well as greater diameter and area of epididymal proximal efferent ductule (PED, P < 0.05) than those in LSM. Comparative transcriptomic analysis identified 1,828 and 483 differentially expressed genes (DEGs) in the testis and epididymis of ganders between HSM and LSM, respectively. Functional enrichment analysis revealed that these DEGs were significantly enriched in the Wnt signaling, Apelin signaling, melanogenesis, and GnRH signaling pathways. The protein-protein interaction network analysis further highlighted the hub genes. The testicular DEGs including PLCB1, PLCB2, WNT11, WNT4, and LRP6 were identified to regulate sperm motility through the Wnt signaling pathway, while the epididymal DEGs including WNT3A, WNT9B, SOX2, and SOX10 could affect sperm motility by regulating epididymal cellular proliferation and differentiation. These data provided new insights into the regulatory mechanisms of male poultry reproductive organ development and sperm quality and would be helpful for developing molecular approaches in the genetic improvement of goose fertility.