Hdh-GSK in Pacific abalone: Insights into its roles in metamorphosis, stress response, and innate immunity

Glycogen synthase kinases (GSKs) regulate key physiological processes in eukaryotes, but their role in Pacific abalone remains unexplored. In this study, the GSK gene was identified and characterized from Pacific abalone (Haliotis discus hannai), and the expression was analyzed to investigate the role of GSK in early development, stress response, and innate immunity. The Hdh-GSK cDNA sequence comprised 1436 bp, with a 456 bp open reading frame (ORF) that encodes 151 deduced amino acid residues. Structurally, the Hdh-GSK protein contains a binding site for the Batabulin ligand (an anti-tumor agent). Hdh-GSK was significantly expressed in the digestive gland, a prime immune organ in aquatic organisms. Notably, higher expression during embryonic and larval development suggests the Hdh-GSK performs a dynamic role in the early development of Pacific abalone. Furthermore, Hdh-GSK expression was significantly higher in individuals exhibiting average and rapid growth than those with stunted or minimal growth. Further, Hdh-GSK expression was upregulated during starvation. Short-term heat stress (6-12 h) upregulated its expression, while prolonged stress led to downregulation, likely linked to ROS production. Cd-toxicity downregulated Hdh-GSK expression in a dose- and time-dependent manner. Immune challenges with Vibrio parahaemolyticus, LPS and poly(I:C) significantly downregulated Hdh-GSK expression (aside from an initial slight increase with bacteria and LPS), suggesting its role in anti-inflammatory responses. Overall, this study's findings suggest that Hdh-GSK may be a key candidate gene for elucidating molecular processes during early development, growth, and innate immunity in Pacific abalone.