Identification of Yellowfin seabream (Acanthopagrus latus) Gcga and Gcgb Genes and Effects of Fasting Strategies on Their Expression

The yellowfin seabream (Acanthopagrus latus) is an important aquaculture species, yet endocrine gene regulation during practical fasting and feeding schedules remains poorly understood. Here, we identified and characterized two duplicated proglucagon genes (Gcga and Gcgb) and examined tissue distribution of expression and transcriptional responses to feeding-related challenges. Sequence and phylogenetic analyses confirmed that Gcga and Gcgb cluster with teleost proglucagon paralogs and contain conserved peptide domains. Both genes were broadly expressed, with the strongest relative qRT-PCR signal detected in brain and fin, while other tissues (including intestine, gill, stomach, and liver) showed comparatively low but detectable expression. Because the liver is a central metabolic organ and displayed reproducible feeding-dependent regulation, we further quantified hepatic transcription under two paradigms. In a short-term starvation–refeeding trial, hepatic Gcga was significantly suppressed during fasting and rebounded after refeeding, whereas Gcgb showed a distinct, weaker response. In an acute peri-feeding assay, hepatic Gcga and Gcgb displayed rapid but differential regulation around meal time, and Gcgb expression differed between feeding and non-feeding groups. Together, these results support transcriptional divergence between the two proglucagon paralogs in nutritional regulation within a liver-focused metabolic-response model. Our findings provide baseline molecular information for A. latus and offer endocrine insights relevant to evaluating feeding strategies in aquaculture.