Stoichiometry of Novel Protein Modifications in Livers of Warm‐adapted Threespine Sticklebacks from Baja California (Mexico)

Abstract

The purpose of this study was to investigate molecular phenotypes that have enabled the survival of a species above its typical lethal temperature limit. A unique population of threespine sticklebacks (Gasterosteus aculeatus) from Baja California, Mexico are surviving and able to function normally at temperatures close to 30 degrees Celsius, a temperature that is higher than normal for this species. Understanding how this warm‐adapted population is able to function at high temperatures at the molecular level may give insight into the mechanisms that have allowed for their survival, and the potential for other populations to adapt to increasing temperatures due to global climate change. Livers from sticklebacks of this unique warm‐adapted population (Baja California, Mexico) were compared to those of a typical cold‐adapted population (Anchorage, Alaska) using gel‐free quantitative proteomics by liquid chromatography‐mass spectrometry (LC‐MS/MS) in order to identify post‐translational modifications (PTMs) in proteins involved in redox and detoxifying biochemical pathways. The stoichiometry of these proteins were then compared between the two populations. Nineteen novel PTMs were identified in 11 different redox proteins, with major differences in stoichiometry detected between the two populations for catalase, alcohol dehydrogenase 1, three glutathione‐s‐transferase isozymes, and carbonyl reductase [NADPH] 1. Further investigation into the functional significance of these PTMs has the potential to reveal novel mechanisms by which adaptation to high temperatures affects redox regulation and detoxification mechanisms. It is well known that adaptation to high temperature affects gene and protein sequences at evolutionary time‐scales and the expression of abundances of particular mRNAs and proteins. Our study provides evidence that specific covalent protein modifications also represent important targets of evolutionary selection during high temperature adaptation of fish. Such modifications result in modulation of protein structure and function leading to concomitant changes in molecular and higher‐order phenotypes that provide an apparent adaptive advantage at elevated habitat temperature.Support or Funding InformationThis work was supported by the National Science Foundation, IOB 1355098.