MOLECULAR CHARACTERISTICS AND FUNCTIONAL ANALYSIS OF ANTIOXIDANT-RELATED GENES <italic>NRF2, SIRT1,</italic> AND <italic>OXR1</italic> IN HYBRID PUFFERFISH (<italic>TAKIFUGU RUBRIPES</italic> × <italic>TAKIFUGU OBSCURUS</italic>)

Abstract

Takifugu, commonly known as pufferfish, belongs to the family Tetraodontidae within the order Tetraodontiformes and is a warm-water marine benthic fish. This species is distributed along the coasts of China and in the western North Pacific. While primarily found in marine environments, some populations also inhabit freshwater. The fish is renowned for its rich, succulent skin, which contains spines and melts in the mouth, offering an aromatic and exquisite flavor, especially in wild specimens. However, with the increasing demand and production of pufferfish, intensive aquaculture practices have been associated with oxidative stress, leading to economic losses. To investigate the response mechanisms of hybrid pufferfish (Takifugu rubripes × Takifugu obscurus) to oxidative stress, this study cloned the cDNA sequences of key antioxidant genes Nrf2, SIRT1, and OXR1, followed by molecular characterization and functional analysis of these genes. Quantitative real-time PCR was employed to assess the tissue distribution of these genes. Results indicated that Nrf2 was highly expressed in the liver, spleen, and muscle, while SIRT1 exhibited high expression levels in the heart, liver, brain, and spleen. OXR1 was predominantly expressed in the liver, brain, and eyes. Structural prediction analyses of the Nrf2 protein revealed a conserved Neh1 functional domain, suggesting its function may be similar across species. Further investigations using eukaryotic expression assays demonstrated that the transfection of Nrf2 could induce the upregulation of the ho-1 gene in cells. Under oxidative stress conditions, this led to enhanced cell viability and a reduction in reactive oxygen species levels, indicating that Nrf2 possesses antioxidant functions. The findings of this study enhance the understanding of antioxidant genes in pufferfish and contribute to the elucidation of the physiological and biochemical mechanisms employed by these fish in response to oxidative stress.