This study investigated the factors that caused the differences in egg production during the development of ovarian follicles in Leizhou black ducks. Leizhou black ducks population was divided into 2 groups as high-yield group ( HG ) and low-yield group ( LG ). The number of eggs ( NE ), age at first egg ( AFE ), weight at first egg, and egg weight ( EW ) of both groups were recorded, and differences were analyzed using the t test. The logistic model was used to simulate the egg production curves to analyze the production rules. The ovarian follicles of both duck groups were collected to count the number of different grades sized follicles, weigh the ovaries, and observe follicular sections to analyze the developmental differences. Ovarian transcriptomic sequencing was performed to investigate differentially expressed genes and signal pathways in both duck groups. The results revealed a significant difference ( P < 0.01) in the NE laid, AFE, and EW between both groups. Comparatively, HG had significantly more ( P < 0.01) large yellow follicles ( LYF ) than LG. The density of medullary layer cells of the follicle section was greater in HG than LG ducks. Transcriptome sequencing revealed a total of 1,027 differentially expressed genes between the HG and LG ducks of which 495 genes were upregulated, and 532 genes were downregulated. Fifty genes were related to reproduction and reproductive processes. Kyoto Encyclopedia of Genes and Genomes–enriched signaling pathways revealed 274 signal pathways enriched in these differentially expressed genes of which the steroid biosynthesis pathway was significantly enriched. Analysis (Q < 0.05) showed that HSD3β → gonadotropin-releasing hormone ( GnRH ) and estrogen receptor ( ESR ) → LHβ/ERK1/2 were enriched in the steroid biosynthesis signal pathway. Follicle-stimulating hormone signal pathway mediated by HSD3β → GnRH and ESR → LHβ/ERK1/2 may be involved in ovarian follicle development to regulate LYF reserve process and affect its ovulation cycle, which in turn influence the egg production of Leizhou black ducks.

This study determined the growth performance, correlations of linear body dimensions, slaughter performance and the fitting model of two generations of Leizhou Black Ducks. Fifteen (15) male and 225 female parents forming generation 0 were selected from the Leizhou duck population. Fifteen (15) families were created in the ratio of 1 male:15 females. Eggs from all the families were collected and numbered according to the family. Generation 1 ducklings were selected and grouped into families in the same ratio. Body weights (BWs) and linear body dimensions were recorded every 2 weeks from weeks 0 to 16. Logistic, Gompertz and Von Bertalanffy models were employed to ascertain the growth model of both sexes of Leizhou Black Ducks. Except for weeks 0–2, generation 1 families had greater BWs than the generation 0 families ( p < .05). Males from both generations had significantly higher ( p < .01) BWs than females at 16 weeks old. Significant positive correlations were observed between BWs and measured body dimensions for both sexes except for between BW and pelvis width (PW) where negative correlations ( p > .05) were observed for males at week 10 and females at 16 weeks old. There was a significant negative correlation ( p < .01) between body length and PW in males at 10 weeks. The accuracy rate of Logistic, Gompertz and Von Bertalanffy models was at 0.972 and similar was obtained by all three models with Von Bertalanffy being the best model. Live weight of generation 1 before slaughter was significantly higher ( p < .01) than generation 0, whereas no significant differences were seen in the other carcass traits. These findings provide insights into breeding Leizhou Black Duck to enhance growth performance and hybrid production.

Our previous study on the ovarian transcriptomic analysis in Leizhou black duck revealed that the ESR2 gene was involved in hormone regulation in reproduction and the estrogen signaling pathway related to reproductive performance was enriched. This suggested that ESR2 may have a functional role in the reproductive performance of the Leizhou black duck. Thus, this study aimed at evaluating the polymorphism of the ESR2 gene and its association with egg-laying traits and the distribution pattern of ESR2 mRNA in laying and non-laying Leizhou black ducks. In this study, genomic DNA was extracted from blood samples of 101 Leizhou black ducks to identify single nucleotide polymorphisms ( SNPs ) of the ESR2 gene to elucidate molecular markers highly associated with egg-laying traits. Four each of laying and non-laying Leizhou black ducks were selected to collect different tissues to analyze the ESR2 gene expression. A total of 23 SNPs were identified and association analysis of the single SNP sites showed that SNPs g.56805646 T>C and exon 3-20G>A were significantly ( P < 0.05) associated with egg weight. Ducks with CT and AG genotypes had significantly higher (P < 0.05) egg weights than their respective other genotypes. Haplotype association analysis of g.56805646 T>C and exon 3-20G>A showed that the haplotypes were significantly associated with egg weight. Higher egg weight was seen in individuals with H3H4 haplotypes. In the hypothalamus-pituitary-gonadal ( HPG ) axis, the results of qRT/PCR showed that ESR2 mRNA was significantly ( P < 0.05) expressed in the ovaries of both duck groups than in the hypothalamus and pituitary. In the oviduct, ESR2 was significantly ( P < 0.05) higher in the infundibulum and magnum of laying and non-laying ducks respectively. This study provides a molecular marker for selecting Leizhou black ducks for egg production. In addition, it offers theoretical knowledge for studying the related biological functions of the ESR2 gene at the cellular level.

Sweet potato (Ipomoea batatas (L.) Lam.) has several phytochemicals including anthocyanin that provide many special health-promoting functions as well as other functional components. Sweet potato is thought to be a health-giving food owing to the numerous diversities of natural products, especially antioxidants. Anthocyanins are natural hydrosoluble pigments which give the purple, blue and red colouration evident in fruits, leaves, flowers, and storage organs. Anthocyanins are beneficial to human health due to their potent antioxidative properties which protect against several chronic disorders, thus a valuable constituent in the human diet. The pathway for biosynthesis of anthocyanin has been clearly defined with its key regulatory genes identified and segregated in diverse species.Cyanidin or Peonidin 3-sophoroside-5-glucoside with associated acylated derivate are the two primary anthocyanins identified in purple-fleshed sweet potato. Anthocyanins in sweet potato are of great importance to plants, animals, humans and possess scientific benefits as well. This article provides a summary of current findings on the function, structure, and biosynthesis of anthocyanin in sweet potato.

BackgroundOur previous study on the ovarian transcriptomic analysis in Leizhou black duck revealed that the ESR2 gene was involved in hormone regulation in reproduction and the estrogen signaling pathway related to reproductive performance was enriched. This suggested that ESR2 may have a functional role in the reproductive performance of the Leizhou black duck. Thus, this study aimed at evaluating the polymorphism of the ESR2 gene and its association with egg-laying traits and the distribution pattern of ESR2 mRNA in laying and non-laying Leizhou black ducks. MethodIn this study, genomic DNA was extracted from blood samples of 101 Leizhou black ducks to identify single nucleotide polymorphisms (SNPs) of the ESR2 gene to elucidate molecular markers highly associated with egg-laying traits. Four (4) each of laying and non-laying Leizhou black ducks were selected to collect different tissues to analyze the ESR2 gene expression. ResultsA total of 23 SNPs were identified and association analysis of the single SNP sites showed that SNPs g.56805646 T>C and exon 3-20G>A were significantly (P < 0.05) associated with egg weight. Ducks with CT and AG genotypes had significantly higher (P < 0.05) egg weights than their respective other genotypes. Haplotype association analysis of g.56805646 T>C and exon 320G>A showed that the haplotypes were significantly associated with egg weight where higher egg weight was seen in individuals with H3H4 haplotypes. In the hypothalamus-pituitary-gonadal (HPG) axis, the results of qRT/PCR showed that ESR2 mRNA was significantly (P < 0.05) expressed in the ovaries of both duck groups than in the hypothalamus and pituitary. In the oviduct, ESR2 was significantly (P < 0.05) higher in the infundibulum and magnum of laying and nonlaying ducks respectively. ConclusionThis study provides molecular marker for selecting Leizhou black ducks for egg production and provides theoretical knowledge for the study of the related biological functions of the ESR2 gene at the cellular level.

BackgroundEstrogen receptor 2 (ESR2) plays significant biological roles in the reproductive system and ovarian follicle development. This study, therefore, aimed to reveal the expression pattern and cell-specific localization of ESR2 in the ovarian follicles of Leizhou black ducks. MethodFour laying Leizhou black ducks at 43 weeks old were annihilated and different grade-sized follicles were collected for immunohistochemistry and expression profile study. The follicles were grouped into seven (7) as small white follicles (SWF), large white follicles (LWF), small yellow follicles (SYF), large yellow follicles (LYF), follicle 5 (F5), follicle 2 (F2), and follicle 1 (F1). ResultsThe qRT/PCR results displayed that ESR2 mRNA was expressed in all follicles with the highest (P < 0.05) level of expression found in F1 compared to other follicles. Immunohistochemistry analysis of the cell-specific localization of ESR2 protein revealed that ESR2 was distributed in both granulosa and theca cells region in all the follicles examined. There was a significantly higher localization of ESR2 protein in the granulosa cells than the theca cells of SWF, SYF, LYF, F2, and F1. Comparatively, ESR2 was highly expressed in the granulosa cells of LYF than in all the other follicles. ConclusionThese results provide theoretical knowledge for the in-depth study of the related biological functions of the ESR2 gene and its application at the cellular level.

Background Ovary is an important reproductive organ for poultry. MicroRNA (miRNA) is a highly conserved class of small non-coding RNA that function in a specific manner to post-transcriptionally regulate gene expression in organisms. Currently, miRNA has been studied extensively but research on duck ovarian tissue is relatively rare. Thus, in this study, we performed the first miRNA analysis of ovarian tissues in Leizhou black ducks with low and high rates of egg production. Method: Using high-throughput sequencing technology, miRNA library was constructed to obtain miRNA expression profile; differentially expressed miRNAs were screened, to predict miRNA target genes. Results A total of 29 differentially expressed miRNAs were obtained from the miRNA library, of which 7 were up-regulated and 22 were down-regulated. Verification of 12 randomly selected miRNAs, using RT-qPCR technology showed the results are consistent with the sequencing data, indicating that the sequencing results are reliable. The GO enrichment and KEGG pathway enrichment analysis of differential miRNAs showed that target genes were significantly enriched in signal pathways related to ovarian development, such as the oxytocin signaling pathway, GnRH signaling pathway, progesterone-mediated oocyte maturation, and AMPK signal pathway. Conclusion The research results enrich the data resources of duck miRNAs, and provide a theoretical basis for further research on the laying performance of poultry and molecular-assisted breeding of poultry in the future.

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