Distinct Evolutionary Trajectories of Major Intracellular Proteolytic Systems in Gilthead Seabream and European Seabass

Abstract

Simple Summary Cells continuously remove damaged or unnecessary proteins to function properly. This process is controlled by several protein-degradation systems. Teleost fish experienced an additional, whole genome duplication event known as the teleost-specific whole-genome duplication (Ts3R), which created extra copies of many genes; some copies were subsequently lost, whereas others may have undergone functional or regulatory divergence. We studied three major proteolytic systems; the ubiquitin–proteasome system, calpains and cathepsins in gilthead seabream and European seabass. We compared their genes and evolutionary relationships and examined their expression during development and across adult tissues. Most ubiquitin–proteasome system genes were present as single copies and broadly expressed, whereas calpains and cathepsins contained more duplicated genes, several of which displayed distinct expression patterns among developmental stages or tissues. These findings indicate that the three systems followed different evolutionary trajectories and identify duplicated genes with distinct expression patterns that may be associated with regulatory divergence in teleost fishes.