Comparative transcriptome analysis reveals genes related to the yolk ratio of duck eggs

Single-cell RNA sequencing revealed the liver heterogeneity between egg-laying duck and ceased-laying duck

BACKGROUND

In the late phase of production, ducks untimely cease laying, leading to a lower feed conversion. Liver plays a vital role in the synthesis and transport of yolk materials during egg formation in birds. However, the molecular mechanism of liver in ceased-laying duck is far from clear, higher resolution and deeper analysis is needed. Sing-cell RNA-sequencing of 10 × Genomics platform can help to map the liver single cell gene expression atlas of Shaoxing duck and provide new insights into the liver between egg-laying and ceased-laying ducks.

RESULTS

About 20,000 single cells were profiled and 22 clusters were identified. All the clusters were identified as 6 cell types. The dominant cell type is hepatocyte, accounted for about 60% of all the cells. Of note, the heterogeneity of cells between egg-laying duck and ceased-laying duck mainly occurred in hepatocytes. Cells of cluster 3 and 12 were the unique hepatocyte states of egg-laying ducks, while cells of cluster 0 and 15 were the unique hepatocyte states of ceased-laying ducks. The expression mode of yolk precursor transporters, lipid metabolizing enzymes and fibrinogens were different in hepatocytes between egg-laying duck and ceased-laying duck. APOV1, VTG2, VTG1, APOB, RBP, VTDB and SCD might be activated in egg-laying ducks, while APOA1, APOA4, APOC3, FGB and FGG might be activated in ceased-laying ducks.

CONCLUSIONS

Our study further proofs that APOV1 and APOB play key roles in egg production, rather than APOA1 and APOA4. It is also the first to detect a correlation between the higher expression of APOC3, FGB, FGG and ceased-laying in duck.

Salted duck eggs: the source for pathogens and antibiotic resistant bacteria

Salted duck eggs as a convenient food are very popular in China and Southeast Asia. Generally, they are produced by traditional curing methods. Here we used traditional methods to profile the bacterial community of salted duck eggs purchased from markets to systematically investigate their microbiological safety. 77 bacteria belonging to 14 genera were isolated. Bacillus related to flavor formation of salted duck eggs were the dominant genus. However, there existed some clinical pathogens which can cause food poisoning, such as Klebsiella pneumoniae, Staphylococcus aureus, and Aeromonas hydrophila. Moreover, PCA analysis showed that the composition of bacteria was related to the source and storage time rather than sampling sites. Besides, bacteria in the shell, intima and egg white of salted duck eggs were cross-linked. In addition, antimicrobial susceptibility testing indicated that resistant bacteria reached to 47.9%. And there was also no significant difference in bacterial resistance with sampling sites. Consequently, it's necessary to strengthen the food quality of salted duck eggs and improve personal dietary habit.

SUPPLEMENTARY INFORMATION

Supplementary information accompanies this paper at 10.1007/s13197-020-04962-w.