Endophytic bacteria derived from metal hyperaccumulators have demonstrated potential for improving copper (Cu) remediation in host plants; however, their potential application in non-host crops remains unclear. In this study, endophytic bacteria isolated from Commelina communis growing in mining areas and their mitigation effects on Cu toxicity in non-host rice were comprehensively evaluated. Among the isolated endophytes, Bacillus sp. D2 exhibited the highest Cu resistance, producing indole-3-acetic acid (IAA) at a concentration of 0.93 mg/L and exhibiting ACC deaminase activity of 13.88 μmol/mg·h under 200 mg/L Cu stress. Pot-experiment results revealed that Bacillus sp. D2 addition significantly increased the biomass and lengths of shoots under Cu stress conditions by 47.6% and 14.2%, respectively. Furthermore, Bacillus sp. D2 inoculation significantly reduced oxidative damage, enhanced antioxidant responses, and modulated plant hormone levels in Cu-exposed rice. Notably, Bacillus sp. D2 inoculation substantially decreased the upward translocation of Cu from underground roots to aboveground tissues. Moreover, Bacillus sp. D2 effectively alleviated Cu toxicity in rice plants by regulating the expression levels of genes involved in antioxidant systems (tAPx, Csd2, and FeSOD1), Cu transporters (AtPDR8 and HMA3), as well as metallothionein (MT2c). These results highlight the value of Bacillus sp. D2 as a bioinoculant for improving crop growth while reducing the risks associated with copper contamination in naturally Cu-contaminated soils.

中文翻译：

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一石二鸟：通过接种来自超蓄积器 Commelina communis 的抗铜内生菌，减轻铜毒性并抑制其在非宿主水稻 （Oryza sativa L.） 中的向上运输


源自金属超蓄积剂的内生细菌已显示出改善寄主植物中铜 （Cu） 修复的潜力;然而，它们在非寄主作物中的潜在应用仍不清楚。本研究综合评价了矿区生长的 Commelina communis 分离的内生菌及其对非寄主水稻 Cu 毒性的缓解作用。在分离的内生菌中，芽孢杆菌属D2 表现出最高的 Cu 抵抗性，在 200 mg/L Cu 胁迫下产生浓度为 0.93 mg/L 的吲哚-3-乙酸 （IAA），ACC 脱氨酶活性为 13.88 μmol/mg·h。盆栽实验结果表明，芽孢杆菌属D2 添加显著提高了铜胁迫条件下的生物量和枝条长度，分别提高了 47.6% 和 14.2%。此外，芽孢杆菌属接种 D2 可显著降低 Cu 暴露水稻的氧化损伤，增强抗氧化反应，并调节植物激素水平。值得注意的是，芽孢杆菌属D2 接种显着减少了 Cu 从地下根向上易位到地上组织的转移。此外，芽孢杆菌属D2 通过调节抗氧化系统相关基因 （tAPx、Csd2 和 FeSOD1）、Cu 转运蛋白 （AtPDR8 和 HMA3） 以及金属硫蛋白 （MT2c） 的表达水平，有效缓解水稻植物中 Cu 的毒性。这些结果突出了 Bacillus sp 的价值。D2 作为生物接种剂，可改善作物生长，同时降低与天然铜污染土壤中铜污染相关的风险。