Dietary soybean or seaweed (Kappaphycus sp.) modulates taste-related gene (tas1r1 and tas1r2.2) expression in Nile tilapia (Oreochromis niloticus).

Abstract

Taste perception plays a central role in fish feeding behaviour by influencing feed recognition, intake, and nutrient sensing. As aquaculture increasingly adopts plant-based ingredients to replace fishmeal, understanding how these diets affect gustatory mechanisms is critical. This study evaluated TAS-family taste receptor genes in Nile tilapia (Oreochromis niloticus) fed nutritionally formulated diets containing fishmeal (TFM), soybean meal (TSB), red seaweed (Kappaphycus sp., TSW), alongside a natural meal (TNM) reference. Fish were reared for 62 days under controlled conditions, after which growth performance was evaluated, and tongue transcriptomes were analysed using RNA sequencing to identify diet-associated gene expression changes. Candidate TAS1R and TAS2R receptors were identified through conserved domain screening and phylogenetic validation, and differential expression analysis was performed using DESeq2. Growth performance did not differ significantly among diets, although the soybean group showed the highest weight gain. Under the conditions of this study, most taste-related genes remained transcriptionally stable across formulated diets, indicating limited responsiveness of the gustatory system to ingredient substitution. Transcriptional differences were mainly observed in comparisons involving the TNM (TSB vs TNM and TSW vs TNM), where tas1r1 was upregulated, suggesting altered amino acid sensing relative to the non-formulated diet. Among formulated diets, tas1r2.2 was upregulated in the TSW vs TFM comparison, indicating potential modulation of carbohydrate-related taste pathways associated with seaweed inclusion. No reliable TAS2R transcripts were detected, likely due to low expression or tissue-specific distribution. Overall, taste receptor expression in Nile tilapia appears resilient to dietary variation, with selective modulation of TAS1R genes providing molecular insight into chemosensory adaptation to sustainable feed ingredients.