Fate of egg proteins during the development ofColumba livia domesticaembryo

Abstract

The transfer of egg white into the yolk and consumption of yolk proteins by the embryo are largely unexplored in the pigeon Columba livia domestica. Here, we investigated the route of egg white transfer as well as the degradation and uptake of yolk proteins by the pigeon embryo. Initially, we tested the electrophoretic patterns of proteins in different egg compartments throughout development. Then, we used lysozyme as a reference protein to follow the egg white transfer, and we measured its activity using Micrococcus lysodeikticus as a substrate. Moreover, we determined the general protease activity during different developmental stages in the yolk using casein. Finally, we examined the expression of aminopeptidase-N (APN) and oligopeptide transporter PepT1 genes in the yolk sac membrane (YSM) from incubation day 8 until day 17. Several electrophoretic bands of presumptive egg white proteins appeared in different egg compartments. Also, lysozyme activity was detected chronologically in the egg compartments. It appeared on day 12 in the amniotic and intestinal fluids and on day 14 in the yolk. Moreover, protease activity in the yolk increased significantly on day 14 and thereafter. APN expression was largest on day 8 and reduced generally afterward, whereas PepT1 expression peaked between days 13 and 15 but then reduced substantially. Our results suggest that the egg white proteins move through the amnion and intestine into the yolk where they undergo degradation by the activated proteases. Furthermore, the YSM appears to have a role in protein consumption, and this role decreases toward hatch.

Pigeon egg white protein-based transparent durable hydrogel via monodisperse ionic surfactant-mediated protein condensation

“…“Total” indicates the PEW solution before adding surfactants. Major proteins are indicated (OVT, ovotransferrin; OVA1, ovalbumin 1; OVA2, ovalbumin 2; and OVM, ovomucoid) 15 , 16 . …”

Cysteine and Aspartic Proteases Underlie the Digestion of Egg Yolk Proteins during the Development of Columba livia domestica Embryo

“…Egg white ultimately transfers into the yolk before being consumed by the developing embryo (Sugimoto et al, 1984). The major route of egg white transfer is through the amniotic fluid into the intestinal lumen, and then to the yolk (Carinci & Manzoli-Guidotti, 1968;Baintner & Fehér, 1974;Sugimoto et al, 1989;Yoshizaki et al, 2002;Shbailat & Safi, 2015;Shbailat & Abuassaf, 2018;Shbailat & Aslan, 2018).…”

“…Before their uptake by the embryo, yolk contents appear to undergo digestion either inside the egg yolk itself or in the endodermal cells of YSM. In the egg yolk of different avian species, the digestion of yolk proteins was concurrent with the activation of several classes of proteases, which suggests that the proteins are degraded by the activated proteases (Sugimoto & Yamada, 1986;Yoshizaki et al, 2002Yoshizaki et al, , 2004Shbailat et al, 2016;Shbailat & Abuassaf, 2018;Shbailat & Aslan, 2018). The proteases were activated either before the major transfer of egg white into the yolk (Wouters et al, 1985;Yoshizaki et al, 2004) or after it (Sugimoto & Yamada, 1986;Shbailat et al, 2016;Shbailat & Abuassaf, 2018;Shbailat & Aslan, 2018).…”

“…After that, the newly synthesized products are exocytosed from the basal surfaces of endodermal cells into the blood vessels in the extraembryonic splanchnic mesoderm, which deliver them to the embryo circulation (Nakazawa et al, 2011;Sheng & Foley, 2012;Bauer et al, 2013;van der Wagt et al, 2020). It is worth mentioning that another route of nutrient delivery into the embryo, slightly before hatching, is the back flow of yolk from yolk sac through yolk stalk into the embryo intestine (Yadgary et al, 2011;Dong et al, 2012;Shbailat & Aslan, 2018;van der Wagt et al, 2020).…”

“…These findings support that the lysosomal proteases have roles in the digestion of yolk proteins and lipoproteins that were endocytosed by the endodermal cells. Furthermore, the genes encoding the oligopeptide transporter PepT1 and various amino acid transporters were demonstrated to be expressed in the YSMs of pigeons (Dong et al, 2012;Chen et al 2016;Shbailat & Aslan, 2018) and chickens (Yadgary et al, 2011;Speier et al, 2012;Yadgary et al, 2014). Encoded PepT1 and other amino acid transporters seemed to participate in the transfer of protein products into the endodermal cells of YSM after their digestion in the egg yolk.…”