Proteomic Profiling of Early Life Stages of European Grayling (<i>Thymallus thymallus</i>)

Salmonids are teleost fish of profound research and economic interest. Embryonic development is a key aspect of salmonid biology that can be critically affected by environmental parameters. Still, their proteome during embryogenesis remains largely unexplored. This study investigates the proteome of the eyed-egg and hatching stages of embryonic development of a salmonid species, European grayling (Thymallus thymallus), using a shotgun proteomic approach. To deal with limited grayling protein resources, the generated spectra were compared against an all-salmonid database using search and multiple protein grouping algorithms to infer identifications. Functional enrichment analysis was carried out at different levels (gene ontologies, pathways, networks) using zebrafish as a reference genome. A total of 213 and 239 proteins were confidently detected in eyed and hatching stages, respectively. Cell cycle, energy, and protein metabolism were the major processes common to both stages. Nuclear activity and brain and eye development were the predominant functions in the eyed-stage proteome, while central nervous system, skeletal muscle, and heart development prevailed in the hatching stage. Overall, this research constitutes the first effort to describe the proteome during embryogenesis in grayling or any salmonid species. It also presents a systematic approach by which existing resources can enable proteome research in salmonids.