Proteomic development in a non-model endangered species of fish: application under temperature stress and in situ experiments.

Chemical pollution is one of the main drivers of aquatic biodiversity loss. Molecular responses, being the earliest and most sensitive biological signal, are valuable to assess pollutant effects. However, studying these responses is challenging in endangered wild species due to limited molecular resources. This study addresses this gap by providing the first catalog of proteins in a non-model endangered fish species, the allis shad (Alosa alosa). In southwestern France, its population collapsed in the 2000s, and recent studies suggested that poor water quality in spawning grounds could induce high early life stages mortality. To study molecular mechanisms involved, using a proteogenomic approach, a catalogue of 2,980 proteins expressed during embryo-larval stage was established, including key proteins for fitness and stress defence. These were used to develop a targeted proteomic method (MRM assay) to assess the health status of larvae. The influence of incubation temperature on the abundance of these proteins in embryos and larvae was then investigated. These proteins were then monitored in larvae exposed to water from the Garonne River, near spawning grounds on sites identified as being at risk for the species' reproduction. Protein abundances reflected physiological and toxicological differences previously observed between river-exposed and control larvae showing their pertinence to study impact of chemical pollution. These results highlight the importance of ontogeny and physiological condition in interpreting protein responses during early development. This research shows the interest of proteomics in understanding mechanisms behind aquatic populations decline and the potential of molecular mechanistic approaches for conservation biology.