Abstract
BackgroundEggshell mineralization in commercially important species such as chicken, turkey or quail is of interest as a general model of calcium carbonate biomineralization. Knowledge of proteins and molecular mechanisms in eggshell assembly may also pave the way to manipulation of thickness of the calcified layer or other features. Comparison of eggshell matrix proteomes of different species may contribute to a better understanding of the mineralization process. The recent publication of the quail genome sequence now enables the proteomic analysis of the quail shell matrix and this comparison with those of chicken and turkey.ResultsThe quail eggshell proteome comprised 622 identified proteins, 311 of which were shared with chicken and turkey eggshell proteomes. Forty-eight major proteins (iBAQ-derived abundance higher than 0.1 % of total identified proteome) together covered 94 % of total proteome mass. Fifteen of these are also among the most abundant proteins in chicken and turkey eggshell matrix. Only three proteins with a percentage higher than 1.0 % of the total had not previously been identified as eggshell matrix proteins. These were an uncharacterized member of the latexin family, an uncharacterized protease inhibitor containing a Kunitz domain, and gastric intrinsic factor. The most abundant proteins were ovocleidin-116, ovalbumin and ovocalyxin-36 representing approximately 31, 13 and 8 % of the total identified proteome, respectively. The major phosphoproteins were ovocleidin-116 and osteopontin. While osteopontin phosphorylation sites were predominantly conserved between chicken and quail sequences, conservation was less in ovocleidin-116.ConclusionsOvocleidin-116 and ovocalyxin-36 are among the most abundant eggshell matrix proteins in all three species of the family Phasianidae analyzed so far, indicating that their presently unknown function is essential for eggshell mineralization. Evidence for other chicken eggshell-specific proteins in quail was inconclusive. Therefore measurement of additional eggshell proteomes, especially from species of different families and preferentially from outside the order Galliformes, will be necessary.Electronic supplementary materialThe online version of this article (doi:10.1186/s12953-015-0078-1) contains supplementary material, which is available to authorized users.
Highlights
Eggshell mineralization in commercially important species such as chicken, turkey or quail is of interest as a general model of calcium carbonate biomineralization
Other proteins are produced by eggshell gland epithelial cells but apparently not in other sections of the oviduct and not in other selected tissues analyzed. The first of these so-called eggshell-specific proteins was ovocleidin-17 (OC17) [6], subsequently shown to belong to the C-type lectin-like family of proteins [7]. This was followed by cloning and characterization of ovocleidin116 (OC116) [8,9,10], which was first identified by its N-terminal sequence in a dermatan sulfate proteoglycan preparation from chicken eggshell [11]
To ensure we obtained a representative average shell proteome, we pooled the calcified layers of eighteen washed eggshells (12.85 g) and performed demineralization and proteome analysis in triplicate
Summary
Eggshell mineralization in commercially important species such as chicken, turkey or quail is of interest as a general model of calcium carbonate biomineralization. These messages can even be detected in red isthmus and uterus after extensive amplification [4, 5] At present it is unknown what percentage of these egg white proteins found in the eggshell matrix may be contributed by these tissues. Other proteins are produced by eggshell gland epithelial cells but apparently not in other sections of the oviduct and not in other selected tissues analyzed The first of these so-called eggshell-specific proteins was ovocleidin-17 (OC17) [6], subsequently shown to belong to the C-type lectin-like family of proteins [7]. Other matrix proteins may participate in the egg’s anti-microbial defense during and after egg production [25, 26]
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