Defense mechanisms of Takifugu fasciatus in fatty liver adaptation and tetrodotoxin resistance

Fat accumulation and tetrodotoxin (TTX) resistance are critical adaptive traits that enable pufferfish to cope with migratory behavior and environmental fluctuations. Here, we integrate whole-genome sequencing, transcriptomic, and electrophysiological analyses to investigate the molecular mechanisms underlying fatty acid metabolism and TTX tolerance in Takifugu fasciatus. A high-quality genome assembly (372.8 Mb, with 94.9% of sequences anchored to 22 chromosomes) suggests that the ancestral freshwater population of T. fasciatus adapted to marine environments approximately 130,000 years ago. DGAT2 and GPAT3 are identified as key regulators of lipid biosynthesis. RNA interference (RNAi)-mediated silencing of these genes significantly reduces hepatic triglyceride levels and lipid droplet accumulation. Four amino acid substitutions are found in NaV1.4 channels of T. fasciatus, with a D400E mutation in Domain I that significantly enhancing TTX resistance. These findings highlight conserved lipid metabolism pathways and NaV channel mutations as key evolutionary strategies for environmental adaptation in pufferfish. Integrative genomic, transcriptomic and electrophysiology reveal molecular mechanisms of lipid metabolism and tetrodotoxin resistance in Takifugu fasciatus, highlighting DGAT2/GPAT3-mediated lipid biosynthesis and NaV1.4 mutations as key adaptations