The sperm proteome of the Pacific oyster Crassostrea gigas and immunolocalization of heat shock proteins

The Pacific oyster Crassostrea gigas is a potential model organism of bivalve mollusks. Comprehensive studies on the proteome of its sperm are necessary to expand our understanding on its reproduction and development, which however are still poor currently. In this study, to improve the situation, we conducted a proteomic analysis on the sperm based on two-dimensional electrophoresis combined with protein identification through mass spectra data. Fifty-six protein spots with constant and relatively high expression levels were selected for protein identification. Among them, 36 were identified (corresponding to 31 proteins), including cytoskeletal proteins, proteins involved in energy supply, protein modifiers, signal regulators, antioxidant proteins, and others. We proposed that these proteins might play important roles in sperm motility, gamete interaction, and oxidation resistance. In particular, we observed several heat shock proteins that were proved to play essential roles in animal sperms. A further immunofluorescence experiment revealed a mitochondria localization of Hsp60s and wide distributions of Hsp70s, indicating these proteins might function in various processes such as mitochondrial function, gamete interaction, and regulation of receptor activity. Our data will provide fundamental supports for the studies on the mechanisms of fertilization and contribute to expand the understandings on reproduction and development of bivalve mollusks.