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<p>Superoxide dismutase (SOD) is a key antioxidant enzyme that functions as a primary defense system against cellular oxidative stress. Here, we determined two novel <i>SOD</i> genes, <i>FsMnSOD</i> and <i>FsCuZnSOD</i>, from the freshwater diatom <i>Fragilaria saxoplanctonica</i>, and examined their molecular features and transcriptional responses to environmental contaminants. <i>FsMnSOD</i> and <i>FsCuZnSOD</i> encoded 240 amino acids (aa) with conserved metal-binding residues and 160 aa with conserved metal-binding site residues in diatoms, respectively. The phylogenetic analysis revealed that the two FsSODs formed distinct branches, clearly separated from the SODs of other diatom species. The transcriptional levels of both <i>FsSODs</i> were significantly upregulated by metals arsenic and zinc but little affected by other tested metals (Cd, Cr, Cu, and Ni). Additional pesticide treatments showed that metolachlor considerably induced the <i>FsSOD</i> expression, whereas atrazine and chlorpyrifos had little effect. Overall, these gene responses were consistent with ROS production in the cells exposed to each contaminant. These results suggest that <i>FsSODs</i> may play a crucial role in the oxidative stress defense system of the diatom. In addition, their specific and sensitive responses can be used as potential biomarkers for assessing the molecular toxicity of As, Zn, and S-MET in freshwater ecosystems.</p>

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Evaluation of two novel superoxide dismutases (SODs) from the freshwater diatom Fragilaria saxoplanctonica and their specific responses to metals and pesticides

  • 期刊论文

  • 发表日期：

    2026年6月18日

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  • Hee-Jin Kang,
  • Han-Sol Kim,
  • Taehee Kim,
  • Jang-Seu Ki

摘要

Superoxide dismutase (SOD) is a key antioxidant enzyme that functions as a primary defense system against cellular oxidative stress. Here, we determined two novel SOD genes, FsMnSOD and FsCuZnSOD, from the freshwater diatom Fragilaria saxoplanctonica, and examined their molecular features and transcriptional responses to environmental contaminants. FsMnSOD and FsCuZnSOD encoded 240 amino acids (aa) with conserved metal-binding residues and 160 aa with conserved metal-binding site residues in diatoms, respectively. The phylogenetic analysis revealed that the two FsSODs formed distinct branches, clearly separated from the SODs of other diatom species. The transcriptional levels of both FsSODs were significantly upregulated by metals arsenic and zinc but little affected by other tested metals (Cd, Cr, Cu, and Ni). Additional pesticide treatments showed that metolachlor considerably induced the FsSOD expression, whereas atrazine and chlorpyrifos had little effect. Overall, these gene responses were consistent with ROS production in the cells exposed to each contaminant. These results suggest that FsSODs may play a crucial role in the oxidative stress defense system of the diatom. In addition, their specific and sensitive responses can be used as potential biomarkers for assessing the molecular toxicity of As, Zn, and S-MET in freshwater ecosystems.