Growth Of Embryo And Gene Expression Of Amino Acid Transporters In Yolk Sac Membranes And Small Intestines Of The Domestic Pigeon(columba Livia)

The objective of this study was to investigate the growth of the embryo and the gene expression levels of amino acid transporter in the yolk sac membranes and small intestines, and the yolk nutrient utilization of the domestic pigeon(Columba livia). Two experiments in this study were divided as following:Experiment 1 was conducted to evaluate growth of embryo and gene expression of amino acid transporters in the small intestine of the domestic pigeon(Columba livia).Twenty embryos/birds from each group were sacrificed by cervical dislocation on embryonic day(E) 9, 11, 13, 15 and day of hatch(DOH). The eggs, embryos(without yolk sac), and organs were weighed to observe pigeon embryonic growth. Small intestine samples were collected for determining gene expression of amino acid/ peptide by real-time RT-PCR.Experiment 2 was conducted to investigate the effect of egg weight on the growth of the embryo, and the expression of amino acid transporter genes in the yolk sac membranes and small intestines of the domestic pigeon(Columba livia). All fertilized eggs were divided into two groups based on the weight of the eggs, light(LE) and heavy(HE). The compositions of 20 eggs from each group were measured. The remaining eggs were placed in an incubator. On E9, 11, 13, and 15 and DOH, 15 embryos/hatchlings from each group were measured for embryonic growth, and yolk sac membranes and small intestines were collected for further analysis.Results:(1) The absolute weights of yolk-free embryos and organs increased significantly during embryonic stage(P<0.05). The weights of head, brain, heart, liver, lung, kidney,gizzard, small intestine, thorax, and legs were strongly positively correlated with body weight(CC>0.80, P<0.0001). The weights of yolk sac was negatively correlated with body weight(CC=-0.64, P<0.0001). The regression equation of each organ weight and embryo weight were inconsistent, suggested that organs have their special development patterns.According to the changes of the relative weight, ten organs were classified into four groups during the embryonic developmental stage.(2) The gene expression of nutrient transporters was differentially regulated by embryonic day. Different amino acid transporters showed the different gene expression patterns. Correlation analysis showed that the gene expression of b0,+AT, Pep T1, EAAT3,NHE2, NHE3, LAT4 and y+LAT2 had strongly positive correlations with intestinal weight(CC>0.80, P<0.0001); the gene expression of CAT1, CAT2 and EAAT2 showed negative correlations with intestinal weight(CC<-0.60, P<0.0001).(3) Egg quality and embryonic growth were significantly affected by egg weight. The HEs had greater yolk weight, albumen weight, and eggshell weight than the LEs(P < 0.01).Yolk-free embryonic BW and residual yolk sac weight were affected by egg weight from E13 to DOH(P < 0.05). Yolk sac membrane weight was heavier in the HE than in the LE from E13 to E15(P < 0.05). Notably, the residual yolk sac content and relative small intestinal weight were highly significantly affected by egg weight on DOH(P < 0.01).(4) The m RNA abundances of CAT2 and Pep T1 in the yolk sac membrane were significantly affected by egg weight(P < 0.05), with a significant increase in the expression in the HE than that in the LE on E13. Compared with the LE, the m RNA abundance of EAAT2 was greater in the small intestines from the HE(P < 0.05). In contrast, the m RNA abundance of EAAT3 was greater in the LE than in the HE(P < 0.05).(5) It can be concluded that: 1) The gene expression of b0,+AT, EAAT3, LAT4, Pep T1,NHE2, NHE3 and y+LAT2 had positive correlations with intestinal weight. The gene expression of CAT1, CAT2 and EAAT2 showed negative correlations with intestinal weight(CC <-0.60, P<0.0001); 2) Embryonic growth and the gene expression of amino acid transporters in yolk sac membranes and small intestines were affected by egg weight; 3)The gene expressions of CAT2 and Pep T1 were closely related to the growth of yolk sac membrane of pigeon, and the gene expressions of EAAT2 and EAAT3 were closely related to the growth of small intestine of pigeon.