ITRAQ-based Proteomic Analyses For Identification Of Candidate Proteins Underlying The Fecundity Of Breeder Cocks

The egg and meat quality of China domestic chicken breeds and their disease resistance ability are excellent, but their fecundity is low. To move forward, researches discovered that percentage of azoospermia in domestic breeds is higher and sperm concentration always decreases with the reduce of semen volume. Fecundity of domestic breeds is low and the matching ratio of male to female arises which cause the increase of production cost and the decrease of genetic improvement. Recent research finds that, semen volume of roosters is a trait with medium heritability, it has a large potential of genetic selecting and can be improved by selection. The aim of this research is to interpret the mechanism that affect fecundity and identify the differently expressed protein.Proteins, as the products of genes can directly influence the spermatogenic function of testis. In this study, we chose cocks of both low fecundity and normal to compare their auxological and morphological feature and identify the differently expressed protein using isobaric tags for relative and absolute quantitation(i TRAQ) technology and bioinformation analysis. Western Blotting was also used to verify the result. The results can build the basis for further understanding the mechanism of low-fecundity chickens. The main research contents and conclusions are as follows:Trial 1. Sample selection. Two-hundred 42-week-old Beijing You male chickens were housed in the same environment, 25low-fecundity and 25 normal ones were selected by semen quality detection and mating trial. At 52 weeks old, testis were obtained for tissue sectioning to observe the size and measure the testis state parameters such as diameter and area of seminiferous tubules, length of spermatogenic epithelium, and Johnsen score. In order to compare the testis state parameters comprehensively. Result showed that weight and testis state parameters of low-fecundity cocks were significantly lower than normal ones(P<0.05).Three couples of compatriot low-fecundity and normal breeder cocks were chosen to be the samples for i TRAQ.Trial 2. Filtration, analysis and verification of total proteins of testis. Intercomparisons were conducted not only among units, but also between two groups. Glutathione S-transferase(GST), Aspartate aminotransferase(Asp AT) and Histone H2 A were higher up-regulated proteins; DNA-Damage binding Protein(DDB2) and Protein Tyrosine Phosphatase Re HZptor Type G(PTPRG) were down-regulated. GST was also found to be one of differently expressed proteins between the two groups. Purine and pyridine metabolism, arginine and proline metabolism, electron transport and oxidative phosphorylation and protein transport were found to be the may pathways by PATHWAY analysis. The Western Blotting results of GST, Asp AT and Histone H2 A were in accordance with i TRAQ results.AS the results of trial two, proteins DDB2、CENP-I、Asp AT、GST、S100-A6 and histone H2 A were proposed as candidate proteins; Asp AT、GST、DDB2 and histone H2 A were important candidate proteins. Pathways of Gn RH signaling, Purine and pyridine metabolism, electron transport and oxidative phosphorylation and protein transport were found to be the main pathways.