Abstract：
The widespread use of nanomaterials in agriculture may introduce multiple engineered nanoparticles (ENPs) into the environment, posing a combined risk to crops. However, the precise molecular mechanisms explaining how plant tissues respond to mixtures of individual ENPs remain unclear, despite indications that their combined toxicity differs from the summed toxicity of the individual ENPs. Here, we used a variety of methods including physicochemical, biochemical, and transcriptional analyses to examine the combined effects of graphene nanoplatelets (GNPs) and titanium dioxide nanoparticles (TiO2 NPs) on hydroponically exposed lettuce (Lactuca sativa) seedlings. Results indicated that the presence of GNPs facilitated the accumulation of Ti as TiO2 NPs in the seedling roots. Combined exposure to GNPs and TiO2 NPs caused less severe oxidative damage in the roots compared to individual exposures. Yet, GNPs and TiO2 NPs alone and in combination did not cause oxidative damage in the shoots. RNA sequencing data showed that the mixture of GNPs and TiO2 NPs led to a higher number of differentially expressed genes (DEGs) in the seedlings compared to exposure to the individual ENPs. Moreover, the majority of the DEGs encoding superoxide dismutase displayed heightened expression levels in the seedlings exposed to the combination of GNPs and TiO2 NPs. The level of gene ontology (GO) enrichment in the seedlings exposed to the mixture of GNPs and TiO2 NPs was found to be greater than the level of GO enrichment observed after exposure to isolated GNPs or TiO2 NPs. Furthermore, the signaling pathways, specifically the \"MAPK signaling pathway-plant\" and \"phenylpropanoid biosynthesis,\" exhibited a close association with oxidative stress. This study has provided valuable insights into the molecular mechanisms underlying plant resistance against multiple ENPs.
摘要：
纳米材料在农业中的广泛使用可能会将多种工程纳米颗粒（ENPs）引入环境中，对农作物构成综合风险。然而,解释植物组织如何对单个ENPs的混合物作出反应的确切分子机制仍不清楚，尽管有迹象表明它们的联合毒性与单个ENPs的总毒性不同。这里,我们使用了多种方法，包括物理化学，生物化学，和转录分析，以检查石墨烯纳米片（GNPs）和二氧化钛纳米颗粒（TiO2NP）对水培暴露的莴苣（Lactucasativa）幼苗的综合影响。结果表明，GNP的存在促进了Ti作为TiO2NP在幼苗根中的积累。与单独暴露相比，联合暴露于GNP和TiO2NP对根部的氧化损伤较小。然而，GNP和TiO2NP单独或结合使用不会在芽中引起氧化损伤。RNA测序数据显示，与暴露于单个ENPs相比，GNP和TiO2NP的混合物在幼苗中导致更多数量的差异表达基因（DEG）。此外，大多数编码超氧化物歧化酶的DEGs在暴露于GNP和TiO2NP组合的幼苗中显示出更高的表达水平。发现暴露于GNP和TiO2NP混合物的幼苗中的基因本体论（GO）富集水平高于暴露于分离的GNP或TiO2NP后观察到的GO富集水平。此外，信号通路，特别是“MAPK信号通路-植物”和“苯丙素生物合成，“与氧化应激密切相关。这项研究为植物抵抗多种ENPs的分子机制提供了有价值的见解。
