The small yellow croaker (Larimichthys polyactis), a commercially important marine species in the Sciaenidae family, has historically been recognized as one of China's "four major marine products" because of its cultural heritage and economic value. Following breakthroughs in artificial breeding protocols in 2015, this species attained large-scale aquaculture viability by 2020. However, its sustainable production faces critical challenges due to emerging environmental stressors, particularly recurrent marine heat waves exceeding physiological thresholds and Pseudomonas plecoglossicida-induced visceral white nodule disease (VWND), which collectively cause high mortality rates under severe conditions. These pressures necessitate urgent exploration of molecular adaptation mechanisms to safeguard aquaculture sustainability. The fish liver, a pivotal organ for xenobiotic detoxification and immunological regulation, exhibits heightened sensitivity to environmental perturbations, making it a strategic biomarker organ for physiological stress studies. Glutamine-fructose-6-phosphate transaminase-1 (GFPT1), the rate-limiting enzyme in the hexosamine biosynthetic pathway (HBP), governs cellular metabolism by regulating the biosynthesis of UDP-GlcNAc, an essential substrate for N-linked protein glycosylation. Through this mechanism, GFPT1 ensures the proper folding of stress-responsive chaperones and maintains endoplasmic reticulum (ER) homeostasis via the unfolded protein response (UPR). Dysregulation of GFPT1 disrupts UPR-mediated autophagy-apoptosis homeostasis, establishing its role as a master regulator of immunometabolic adaptation. Notably, gfpt1 emerged as a hub gene in both high-temperature tolerance quantitative trait locus (QTL) mapping and transcriptomic analysis of P. plecoglossicida-infected L. polyactis, suggesting its evolutionary importance in stress resilience. To characterize gfpt1 responses to heat stress and pathogen challenge, we successfully cloned and annotated the full-length complete coding sequence (CDS) of L. polyactis gfpt1 via E. coli-based cloning, revealing a 2,049-bp CDS encoding a 682-amino acid protein with conserved PLN02981 superfamily domains critical for enzymatic activity. Phylogenetic analysis demonstrated high sequence conservation (99.37% identity) with its congener, Larimichthys crocea, highlighting the evolutionary conservation of enzymatic function. Quantitative real-time PCR (RT-qPCR) analysis utilizing β-actin as an internal reference gene demonstrated constitutive gfpt1 expression across all examined tissues (brain, intestine, muscle, gill, liver, kidney, spleen, skin, and heart), with expression levels in the liver being significantly higher compared to those in other organs (P＜0.05), consistent with the liver's evolutionary role as a metabolic command center in teleosts. To characterize stress-specific gfpt1 dynamics, two experimental approaches were implemented: a high-temperature challenge model comparing 32℃ heat stress versus 20 ℃ ambient controls, with liver sampling at 0, 6, 12, and 24 h post-exposure, and a P. plecoglossicida-infected model with liver sampling at 0, 6, 12, 24, 48, 72, and 96 h post-injection. The results showed that, under 32℃ heat stress, sustained gfpt1 upregulation (P＜0.05) was observed in liver tissue, peaking at 6 h post-exposure. However, no significant temporal differences were detected among sampling time points (6–24 h, P＞0.05). In contrast, P. plecoglossicida infection induced dynamic gfpt1 expression oscillations: initial downregulation at 6 h post-infection (P＜0.05), followed by upregulation, which peaked at 48 h (P＜0.05), transient normalization at 12, 24, and 72 h, and final downregulation at 96 h (P＜0.05). These divergent expression patterns demonstrate that gfpt1 mediates divergent molecular pathways in L. polyactis under abiotic (high-temperature) and biotic (pathogenic) stresses, highlighting its dual regulatory roles in stress adaptation and immune modulation. The 6 h post-exposure expression amplitude and 48 h post-infection surge establish hepatic gfpt1 as a quantifiable biomarker for high-temperature resilience prediction and VWND outbreak alerts, respectively, providing actionable metrics for IoT-integrated aquaculture health monitoring systems. The current findings establish gfpt1 as a biomarker for aquaculture health monitoring and thermal resilience prediction, offering critical insights into teleost stress response mechanisms and strategies for sustainable mariculture. These results provide valuable insights for addressing key challenges in L. polyactis aquaculture and advance our knowledge of the stress response mechanisms in marine teleosts.