Variability in the protein profiles in spermatozoa of two sturgeon species.

Conventional sperm analysis (i.e., motility and fertility) has been used to evaluate sperm quality. Understanding the quality of sperm on the molecular level in the sturgeons, Acipenser baerii and A. schrenckii, is essential for the improvement of the conservation of genetic resources and farming performance. In this study, we used the iTRAQ proteomics approach to perform proteomic profiling of spermatozoa associated with sperm quality in sturgeons (Data are available via ProteomeXchange with identifier PXD006108). The results showed 291 and 359 differentially expressed proteins in A. baerii and A. schrenckii, respectively, of which 72 were common to both species and all were upregulated in high quality compared with low quality samples. The differentially expressed proteins were mainly categorized into the generation of precursor metabolites and energy and oxidation, and they were localized to the mitochondria. Three distinguishing pathways, Arginine and proline metabolism, Pyruvate metabolism and the Citrate cycle (TCA cycle) were found to play an important role in energy metabolism, and some substrates could be used in the sperm medium for storage and cryopreservation. The quantity levels of two proteins, CKMT1 and LDHB, were verified by western blot analysis. Moreover, other potential biomarkers involved in oxidation reduction, ubiquitin-proteasome-dependent proteolysis, chaperones and binding activity were also discussed. Our study is the first to use the iTRAQ-based proteomics approach to analyse the sturgeon spermatozoa proteome, and the results that we obtained are valuable for the prediction of sperm quality and reproduction management in these threatened species.