Response of the PI3K‐AKT signalling pathway to low salinity and the effect of its inhibition mediated by wortmannin on ion channels in turbot Scophthalmus maximus

The PI3K‐AKT signalling pathway is a crucial part of the signal transduction network and is involved in many important physiological processes and the stress response to environmental alteration. In this study, gill and kidney transcriptome data demonstrated that the PI3K‐AKT signalling pathway plays an important role in the stress response of the turbot Scophthalmus maximus when exposed to low salinity. Low‐salinity stress led to down‐regulation of gene expression, protein content and phosphorylation of AKT1 at Thr308 of the PI3K‐AKT signalling pathway. However, the abundance and phosphorylation of AKT1 protein at Ser473 and Thr308 were detected only in the gill and not in the kidney. Inhibition of the PI3K‐AKT signalling pathway mediated by wortmannin showed that wortmannin remarkably inhibited PI3K gene expression and protein synthesis as well as phosphorylation of AKT1 at Thr308 with or without low‐salinity stress. In the context of pathway inhibition, suppressed expression levels of ion channel genes demonstrated that the PI3K‐AKT signalling pathway acts on osmoregulation by positively regulating ion transport.