Resumen
The present study investigates the response of the marine fish cobia, Rachycentron canadum, to stressors as measured by phosphorylation of the a-subunit of the translational initiation factor, eIF2. eIF2a is the target of phosphorylation by a family of kinases that respond to a range of physiological stressors. Phosphorylation of eIF2a inhibits overall protein synthesis, but also facilitates the reprogramming of gene expression to adapt to, and recover from, stress. The deduced coding sequence of cobia eIF2a has 94% identity to both zebrafish (Danio rerio) and human eIF2a sequences with identical phosphorylation and kinase docking sites. Here we use cobia larvae and a cobia cell line derived from muscle (Cm cells) to investigate the response of cobia eIF2a to various stressors. In Cm cells, phosphorylation of eIF2a is increased by nutrient deficiency and endoplasmic reticulum stress (ER stress), consistent with the activation of the eIF2 kinases, GCN2, and PERK. In cobia juveniles, diet and water temperature affect the phosphorylation state of eIF2a. We conclude that evaluation of eIF2a phosphorylation could function as an early marker to evaluate diet, environmental stressors, and disease in cobia and may be of particular use in optimizing conditions for rearing cobia larvae and juveniles.