Identification of the Yellowfin seabream (Acanthopagrus latus) Gcga and Gcgb and effects of fasting strategies on their expression levels

The yellowfin seabream ( Acanthopagrus latus ) is a commercially significant aquaculture species, little is known about how its two proglucagon genes ( Gcga and Gcgb ) differentiate functionally during fasting. In this study, we identified the varied tissue distributions and reactions to fasting and refeeding of Gcga and Gcgb in A. latus . According to phylogenetic study, Gaga is comparatively conserved, however Gcgb has adaptive traits unique to teleosts. Gcga is primarily expressed in the liver (32.8%), indicating a key role in metabolic regulation, while Gcgb is significantly expressed in the gills (41.2%), suggesting a potential role in osmoregulation, according to tissue expression profiling. Fasting significantly downregulated hepatic Gcga expression ( p  < 0.05), reflecting its sensitivity to energy status, while Gcgb expression remained stable, indicating its role in maintaining essential physiological functions. Hepatic Gcga expression was considerably downregulated ( p  < 0.05) during fasting, revealing its sensitivity to energy status, whereas Gcgb expression stayed constant, suggesting its significance in preserving vital physiological processes. Refeeding caused a temporary suppression of Gcgb expression while restoring Gcga expression. The acute nutritional response of Gcga in contrast to the short-term fasting resistance of Gcgb was further demonstrated by periodic fasting trials. These findings reveal a functional difference between A. latus's Gcga (metabolic control) and Gcgb (osmoregulatory maintenance), offering important information for aquaculture feeding strategy optimization.