Selection for higher fertility reflects in the seminal fluid proteome of modern domestic chicken

The high egg-laying capacity of the modern domestic chicken (i.e. White Leghorn, WL) has arisen from the low egg-laying ancestor Red Junglefowl (RJF) via continuous trait selection and breeding. To investigate whether this long-term selection impacted the seminal fluid (SF)-proteome, 2DE electrophoresis-based proteomic analyses and immunoassays were conducted to map SF-proteins/cytokines in RJF, WL and a 9th generation Advanced Intercross Line (AIL) of RJF/WL-L13, including individual SF (n=4, from each RJF, WL and AIL groups) and pools of the SF from 15 males of each group, analyzed by 2DE to determine their degree of intra-group (AIL, WL, and RJF) variability using Principal Component Analysis (PCA); respectively an inter-breed comparative analysis of intergroup fold change of specific SF protein spots intensity between breeds. The PCA clearly highlighted a clear intra-group similarity among individual roosters as well as a clear inter-group variability (e.g. between RJF, WL and AIL) validating the use of pools to minimize confounding individual variation. Protein expression varied considerably for processes related to sperm motility, nutrition, transport and survival in the female, including signaling towards immunomodulation. The major conserved SF-proteins were serum albumin and ovotransferrin. Aspartate aminotransferase, annexin A5, arginosuccinate synthase, glutathione S-transferase 2 and l-lactate dehydrogenase-A were RJF-specific. Glyceraldehyde-3-phosphate dehydrogenase appeared specific to the WL-SF while angiotensin-converting enzyme, γ-enolase, coagulation factor IX, fibrinogen α-chain, hemoglobin subunit α-D, lysozyme C, phosphoglycerate kinase, Src-substrate protein p85, tubulins and thioredoxin were AIL-specific. The RJF-SF contained fewer immune system process proteins and lower amounts of the anti-inflammatory/immunomodulatory TGF-β2 compared to WL and AIL, which had low levels- or lacked pro-inflammatory CXCL10 compared to RJF. The seminal fluid proteome differs between ancestor and modern chicken, with a clear enrichment of proteins and peptides related to immune-modulation for sperm survival in the female and fertility.