High amount of copper is toxic to most organisms, but endophytic fungi can develop survival strategies to tolerate and respond to environmental stressors such as heavy metal contaminants. While high copper induces oxidative stress, it is still unclear which genes are associated with copper tolerance. Here, we performed a metatranscriptome analysis of endophytic fungi isolated from a black nightshade plant Solanum nigrum L. growing on mine tailings of a gold processing area. Initial screening revealed the presence of a copper-tolerant strain of Fusarium oxysporum, designated as IB-SN1W, which tolerated up to 1000 ppm and 300 ppm copper in solid and liquid media, respectively. Differential gene expression analysis by RNA sequencing showed that 23% of contigs are uniquely expressed in the copper-treated fungus. These genes are involved in copper ion import, polyamine transport, oxidoreductase activity, and oxidative stress response. Catalase transcripts were also highly upregulated in IB-SN1W compared to a non-tolerant F. oxysporum strain. Catalase inhibition decreased copper-tolerance in IB-SN1W, while the addition of antioxidants prevented the copper-dependent growth inhibition in the non-tolerant strain. Overall, these results suggest that oxidative stress response contributes to copper tolerance in F. oxysporum.

大量的铜对大多数生物体是有毒的，但内生真菌可以开发生存策略来耐受和应对环境压力，如重金属污染物。虽然高铜诱导氧化应激，但尚不清楚哪些基因与铜耐受性相关。在这里，我们对从生长在黄金加工区尾矿上的黑色茄属植物Solanum nigrum L. 中分离出的内生真菌进行了宏转录组分析。初步筛选显示存在耐铜菌株尖孢镰刀菌( Fusarium oxysporum)，指定为 IB-SN1W，在固体和液体介质中分别耐受高达 1000 ppm 和 300 ppm 的铜。通过 RNA 测序的差异基因表达分析表明，23% 的重叠群在铜处理的真菌中独特表达。这些基因参与铜离子输入、多胺转运、氧化还原酶活性和氧化应激反应。与非耐受尖孢镰刀菌菌株相比，IB-SN1W 中的过氧化氢酶转录物也高度上调。过氧化氢酶抑制降低了 IB-SN1W 中的铜耐受性，而添加抗氧化剂阻止了非耐受菌株中的铜依赖性生长抑制。总的来说，这些结果表明氧化应激反应有助于尖孢镰刀菌的铜耐受性。