Abstract
Eggs with a much higher proportion of thick albumen are preferred in the layer industry, as they are favoured by consumers. However, the genetic factors affecting the thick egg albumen trait have not been elucidated. Using RNA sequencing, we explored the magnum transcriptome in 9 Rhode Island white layers: four layers with phenotypes of extremely high ratios of thick to thin albumen (high thick albumen, HTA) and five with extremely low ratios (low thick albumen, LTA). A total of 220 genes were differentially expressed, among which 150 genes were up-regulated and 70 were down-regulated in the HTA group compared with the LTA group. Gene Ontology (GO) analysis revealed that the up-regulated genes in HTA were mainly involved in a wide range of regulatory functions. In addition, a large number of these genes were related to glycosphingolipid biosynthesis, focal adhesion, ECM-receptor interactions and cytokine-cytokine receptor interactions. Based on functional analysis, ST3GAL4, FUT4, ITGA2, SDC3, PRLR, CDH4 and GALNT9 were identified as promising candidate genes for thick albumen synthesis and metabolism during egg formation. These results provide new insights into the molecular mechanisms of egg albumen traits and may contribute to future breeding strategies that optimise the proportion of thick egg albumen.
Highlights
As consumer demand for egg products increases, much attention has been given to the internal quality of eggs
Two distinct quantitative trait locus (QTL) regions that affect egg white thinning during the production period have been identified on chromosome 2 in chicken[2], and four QTL regions that affect egg white quality have been found on chromosomes 4, 26, 7 and Z1
This study provides important findings regarding potential regulatory genes and related pathways underlying egg albumen traits, and our results will be instrumental in the use of genetic improvement methods for breeding chickens with high proportions of thick egg albumen
Summary
As consumer demand for egg products increases, much attention has been given to the internal quality of eggs. Identifying the genes underlying egg albumen traits and their incorporation into genetic evaluation systems would be valuable for poultry breeding programmes. The objective of this study was to identify differentially expressed genes (DEGs) in Rhode Island white hens with extremely high or low proportion of thick egg albumen using RNA-Seq. In addition, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were carried out to elucidate the biological functions of the differentially expressed genes. This study provides important findings regarding potential regulatory genes and related pathways underlying egg albumen traits, and our results will be instrumental in the use of genetic improvement methods for breeding chickens with high proportions of thick egg albumen
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