Abstract

Silver nanoparticles (AgNPs) are particularly among the widely used nanomaterials in medicine, industry, and agriculture. The small size and large surface area of AgNPs and other nanomaterials result in their high reactivity in biological systems. To better understand the effects of AgNPs on plants at the molecular level, tomato (Lycopersicon esculentum L.) seedlings were exposed to 30 mg/L silver in the form of nanoparticle (AgNPs), ionic (AgNO₃), or bulk (Ag⁰) in 50% Hoagland media for 7 days. The effects of silver on the expression of plant membrane transporters H⁺-ATPase, vacuolar type H⁺-ATPase (V-ATPase), and enzymes isocitrate dehydrogenase (IDH), and catalase in roots was assessed using RT-qPCR and immunofluorescence-confocal microscopy. We observed significantly higher expression of catalase in plants exposed to AgNPs (Fold of expression 1.1) and AgNO₃ (Fold of expression 1.2) than the control group. The immunofluorescence imaging of the proteins confirmed the gene expression data; the expression of the enzyme catalase was upregulated 41, 216, and 770% higher than the control group in plants exposed to AgNPs, Ag⁰, and AgNO₃, respectively. Exposure to AgnO₃ resulted in the upregulation (fold of expression 1.2) of H⁺-ATPase and downregulation (fold of expression 0.7) of V-ATPase. A significant reduction in the expression of the redox-sensitive tricarboxylic cycle (TCA) enzyme mitochondrial IDH was observed in plants exposed to AgNPs (38%), AgNO₃ (48%), or Ag⁰ (77%) compared to the control. This study shows that exposure to silver affects the expression of genes and protein involved in membrane transportation and oxidative response. The ionic form of silver had the most significant effect on the expression of genes and proteins compared to other forms of silver. The results from this study improve our understanding about the molecular effects of different forms of silver on important crop species.

Novelty statement

Silver nanoparticles released into the environment can be oxidized and be transformed into ionic form. Both the particulate and ionic forms of silver can be taken by plants and affect plants physiological and molecular responses. Despite the extensive research in this area, there is a scarce of information about the effects of silver nanoparticles on the expression of membrane transporters especially H⁺-ATPase involved in regulating cells' electrochemical charge, and the activity of enzymes involved in oxidative stress responses. This is a unique study that evaluates the expression of cellular proton transporters and enzymes of redox balance and energy metabolisms such as membrane transporters, H⁺-ATPase, and V-ATPases, and enzymes catalase and IDH. The results provide us valuable information about the impact of silver on plants at the molecular level by evaluating the expression of genes and proteins.

• Key Message

• The exposure of plants to silver as an environmental stressor affects the expression of genes and proteins involved in maintaining cell’s electrochemical gradient (H⁺-ATPase, V-ATPase) and redox potential (IDH, catalase).

摘要

银纳米粒子 (AgNPs) 特别是在医学、工业和农业中广泛使用的纳米材料之一。AgNPs 和其他纳米材料的小尺寸和大表面积导致它们在生物系统中的高反应性。为了在分子水平上更好地了解 AgNPs 对植物的影响，番茄 ( Lycopersicon esculentum L. ) 幼苗暴露于 30 mg/L 的纳米颗粒 (AgNPs)、离子 (AgNO ₃ ) 或块状 (Ag ⁰ ) 在 50% Hoagland 培养基中放置 7 天。银对植物膜转运蛋白 H ⁺ -ATPase、液泡型 H ^{+表达的影响}使用 RT-qPCR 和免疫荧光共聚焦显微镜评估根中的 -ATPase (V-ATPase)、异柠檬酸脱氢酶 (IDH) 和过氧化氢酶。我们观察到暴露于 AgNPs（表达式 1.1 的倍数）和 AgNO ₃（表达式 1.2 的倍数）的植物中过氧化氢酶的表达明显高于对照组。蛋白质的免疫荧光成像证实了基因表达数据；^{在暴露于 AgNPs、Ag 0}和 AgNO ₃的植物中，过氧化氢酶的表达分别比对照组高 41%、216% 和 770% 。暴露于 AgnO ₃导致 H ^{+的上调（表达 1.2 的倍数）}-ATP酶和V-ATP酶的下调（表达倍数0.7）。_{与对照相比，在暴露于 AgNPs (38%)、AgNO 3} (48%) 或 Ag ⁰ (77%)的植物中观察到氧化还原敏感的三羧酸循环 (TCA) 酶线粒体 IDH 的表达显着降低。这项研究表明，接触银会影响参与膜转运和氧化反应的基因和蛋白质的表达。与其他形式的银相比，离子形式的银对基因和蛋白质的表达具有最显着的影响。这项研究的结果提高了我们对不同形式的银对重要作物物种的分子影响的理解。

新颖性声明

释放到环境中的银纳米颗粒可以被氧化并转化为离子形式。银的颗粒和离子形式都可以被植物吸收并影响植物的生理和分子反应。尽管在该领域进行了广泛的研究，但关于银纳米粒子对膜转运蛋白表达的影响的信息很少，尤其是参与调节细胞电化学电荷的 H ⁺ -ATP 酶，以及参与氧化应激反应的酶的活性。这是一项独特的研究，评估了细胞质子转运蛋白和氧化还原平衡酶和能量代谢酶的表达，例如膜转运蛋白、H ⁺-ATP酶和V-ATP酶，以及过氧化氢酶和IDH酶。该结果通过评估基因和蛋白质的表达，为我们提供了有关银在分子水平上对植物影响的宝贵信息。

• 关键信息

• 植物暴露于银作为环境压力源会影响参与维持细胞电化学梯度（H ⁺ -ATPase，V-ATPase）和氧化还原电位（IDH，过氧化氢酶）的基因和蛋白质的表达。