Fig. 8
From: Transcriptome-based analysis reveals relationship between duck eggshell color and eggshell strength
Proposed Synthesis, Transport Mechanism of Biliverdin, and Formation of Harder Eggshells in Green-Shelled Ducks’ Liver and Eggshell Gland. (A) A schematic illustrating the hypothesized synthesis and transport of biliverdin in the liver and eggshell gland of green-shelled ducks. Free heme in the liver is thought to bind to COX1, thereby activating cytochrome c oxidase activity and regulating intracellular oxidative stress. The joint regulation of bile homeostasis by DIO3 and RBPJ is proposed to facilitate the excretion of bile acids into the circulatory system. These bile acids are then absorbed by the eggshell gland, where high expression of ABCG2 is observed. It is hypothesized that biliverdin is subsequently separated and contributes to the green coloration of the eggshell. Decreased expression of SLC51B may inhibit the transport of biliverdin out of the eggshell gland, thereby promoting the green eggshell phenotype. Additionally, upregulated expression of PHLDA1, FLT3, and CACNB4 in the liver may support liver cell proliferation and homeostasis. In the eggshell gland, increased FKBP10 expression is proposed to assist protein folding, contributing to the formation of a stronger eggshell matrix. (B) CPM values of ESB key genes in eggshell gland and liver. (C) CPM values of ESB key genes in eggshell gland and liver