Transfer of egg white proteins and activation of proteases during the development ofAnas platyrhynchos domesticaembryo

Abstract

The route of egg white transfer into the yolk and the mechanisms underlying the digestion of egg proteins are unexplored in the fertilized egg of the duck, Anas platyrhynchos domestica. Here, we investigated the route(s) of egg white transfer and we determined the type of activated proteases during duck embryo development. Initially, we tested the electrophoretic patterns of egg proteins throughout development. Then, we used lysozyme as a reference protein to follow egg white transfer and we measured its activity. After that, we determined the type of activated proteases by employing different types of protease inhibitors. Several presumptive egg white protein bands appeared in different egg compartments. Also, lysozyme activity was detected chronologically on day 15 in the extraembryonic fluid, on day 17 in the amniotic and intestinal fluids and on day 19 in the yolk. Furthermore, acidic aspartic proteases seemed to be activated at hatch in the intestine and late in development in the yolk. Our results suggest that the main route of egg white transfer into the yolk is through the amniotic cavity and intestinal lumen. Also, the transferred egg white and endogenous yolk proteins are probably digested by the activated acidic proteases in the intestine and yolk.

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

“…Moreover, the time of aspartic protease activation differed between the two species, as this activation occurred early before the major transfer of egg white in chicken (Wouters et al, 1985). In the turkey Meleagris gallopavo and the duck Anas platyrhynchos domestica, aspartic proteases appeared to be activated in the egg yolk at late stages (Shbailat et al, 2016;Shbailat & Abuassaf, 2018), after the major transfer of egg white proteins into the yolk, which began on day 17 and day 18 in turkey (Shbailat & Safi, 2015) and duck (Shbailat & Abuassaf, 2018), respectively. In addition, weak activity of cysteine protease(s) was also suggested to be present in turkey egg yolk at late developmental stages (Shbailat et al, 2016).…”

“…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).…”

The physicochemical features of eggshell, thick albumen, amniotic fluid, and yolk during chicken embryogenesis

“… Cunningham (1974) showed a decrease in lysozyme activity during the first 12 d of incubation of chicken eggs. Shbailat and Abuassaf (2018) analyzed the diffusion route of duck egg albumen into the egg yolk, simultaneously specifying the type of activated proteases. The study used lysozyme as a reference protein to track egg albumen transfer by measuring its activity.…”