Abstract
BackgroundEggshell is a bio-ceramic material comprising columnar calcite (CaCO3) crystals and organic proteinaceous matrix. The size, shape and orientation of the CaCO3 crystals influence the microstructural properties of chicken eggshells. However, the genetic architecture underlying eggshell crystal polymorphism remains to be elucidated.ResultsThe integral intensity of the nine major diffraction peaks, total integral intensity and degree of orientation of the crystals were measured followed by a genome-wide association study in 839 F2 hens. The results showed that the total integral intensity was positively correlated with the eggshell strength, eggshell thickness, eggshell weight, mammillary layer thickness and effective layer thickness. The SNP-based heritabilities of total integral intensity and degree of orientation were 0.23 and 0.06, respectively. The 621 SNPs located in the range from 55.6 to 69.1 Mb in GGA1 were significantly associated with TA. PLCZ1, ABCC9, ITPR2, KCNJ8, CACNA1C and IAPP, which are involved in the biological process of regulating cytosolic calcium ion concentration, can be suggested as key genes regulating the total integral intensity.ConclusionsThe findings greatly advance the understanding of the genetic basis underlying the crystal ultrastructure of eggshell quality and thus will have practical significance in breeding programs for improving eggshell quality.
Highlights
Eggshell is a bio-ceramic material comprising columnar calcite (CaCO3) crystals and organic proteinaceous matrix
We aimed to explore the genetic architecture of eggshell crystal structure to identify candidate genes, which may be valuable for the genetic improvement of eggshell quality traits
We found that six genes were significantly enriched in the blood circulation (GO:0008015): CACNA1C, IAPP, ITPR2, PLCZ1 (1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase zeta-1), ABCC9 (ATP-binding cassette sub-family C member 9) and KCNJ8 (ATP-sensitive inward rectifier potassium channel 8)
Summary
Eggshell is a bio-ceramic material comprising columnar calcite (CaCO3) crystals and organic proteinaceous matrix. The size, shape and orientation of the CaCO3 crystals influence the microstructural properties of chicken eggshells. The crystallographic texture of eggshells is correlated with the thickness and strength of the shell. The crystal size and orientation has been found to be strongly positively correlated (r = 0.65) with the thickness of the eggshell [18]. The degree of orientation of crystals has been found to explain approximately 40 % of the variance in eggshell strength [17]. All these studies have indicated that the ultrastructure of eggshell was the key factor affecting eggshell quality
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