Arbuscular mycorrhizal fungi (AMF) are considered a potential biotechnological tool for mitigating heavy metal (HM) toxicity. A greenhouse experiment was conducted to evaluate the impacts of the AM fungus Rhizophagus irregularis on cadmium (Cd) uptake, mycorrhizal colonization, and some plant growth parameters of Medicago sativa (alfalfa) in Cd-polluted soils. In addition, expression of two metal chelators (MsPCS1 (phytochelatin synthase) and MsMT2 (metallothionein)) and two metal transporter genes (MsIRT1 and MsNramp1) was analyzed using quantitative real-time PCR (qRT-PCR). Cd addition had a significant negative effect on mycorrhizal colonization. However, AMF symbiosis promoted the accumulation of biomass under both stressed and unstressed conditions compared with non-mycorrhizal (NM) plants. Results also showed that inoculation with R. irregularis significantly reduced shoot Cd concentration in polluted soils. Transcripts abundance of MsPCS1, MsMT2, MsIRT1, and MsNRAMP1 genes were downregulated compared with NM plants indicating that metal sequestration within hyphal fungi probably made Cd concentration insufficient in root cells for induction of these genes. These results suggest that reduction of shoot Cd concentration in M. sativa colonized by R. irregularis could be a promising strategy for safe production of this plant in Cd-polluted soils.

中文翻译：

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不规则根瘤菌可调节紫花苜蓿中镉的吸收，金属转运蛋白和螯合剂基因的表达。

丛枝菌根真菌（AMF）被认为是减轻重金属（HM）毒性的潜在生物技术工具。进行了温室试验，以评估AM真菌不规则根瘤菌对Cd污染土壤中镉（Cd）吸收，菌根定植以及某些苜蓿（苜蓿）植物生长参数的影响。此外，两个金属螯合剂（MsPCS1（植物螯合素合酶）和MsMT2（金属硫蛋白））和两个金属转运蛋白基因（MsIRT1和MsNramp1）的表达使用定量实时PCR（qRT-PCR）进行分析。镉的添加对菌根定植有明显的负面影响。但是，与非菌根（NM）植物相比，AMF共生在胁迫和非胁迫条件下均促进了生物量的积累。结果还表明，用不规则红球菌接种显着降低了污染土壤中芽镉的浓度。MsPCS1，MsMT2，MsIRT1和MsNRAMP1的转录本丰富与NM植物相比，该基因的表达下调，表明菌丝真菌中的金属螯合可能使根细胞中的Cd浓度不足以诱导这些基因。这些结果表明，减少由不规则红斑菌定植的紫花苜蓿的芽中Cd浓度可能是在Cd污染土壤中安全生产该植物的一种有前途的策略。