Transcriptomic and metabolomic changes in lettuce triggered by microplastics-stress. Environmental pollution (Barking, Essex : 1987) Microplastics (MPs) are a global threat to the environment, and plant uptake of MP particles (≤0.2 μm) is a particular cause for concern. However, physiological and molecular mechanisms underlying MP-induced growth inhibition need to be clarified. Towards this goal, we conducted a hydroponic experiment to investigate the accumulation of MPs, changes in physiology, gene expression, and metabolites in lettuce from a series of concentrations of fluorescence-labelled polystyrene MPs (0, 10, 20, 30, 40, 50 mg L, ∼0.2 μm). Our results showed that MPs accumulated in the lettuce root tips and leaf veins, resulting in the hypertonic injury of lettuce, and the down-regulation of genes related to ion homeostasis. Stress-related genes were up-regulated, and sphingolipid metabolism increased in response to MP additions, causing increased biosynthesis of ascorbic acid, terpenoid, and flavonoids in root exudates. Our findings provide a molecular-scale perspective on the response of leafy vegetables to MP-stress at a range of concentrations. This enables more comprehensive evaluation of the risks of MPs to human health and the ecological environment. 10.1016/j.envpol.2023.121081

Effect of Polystyrene Microplastics on Rice Seed Germination and Antioxidant Enzyme Activity. Zhang Qiuge,Zhao Mengsai,Meng Fansong,Xiao Yongli,Dai Wei,Luan Yaning Toxics The accumulation and distribution of microplastics (MPs) in agricultural soils, including rice fields, is well studied. However, only a few studies have investigated the uptake of MPs by rice plants and the consequential toxic effects of MPs under solid-phase culture conditions. Hence, in this study, we explored the effects of different concentrations of polystyrene MPs (PS-MPs, with a size of 200 nm) on rice seed germination, root growth, antioxidant enzyme activity, and transcriptome. PS-MPs exhibited no significant effect on the germination of rice seeds ( > 0.05). However, PS-MPs significantly promoted root length (10 mg L; < 0.05), and significantly reduced antioxidant enzyme activity (1000 mg L; < 0.05). Staining with 3,3-diaminobenzidine and nitrotetrazolium blue chloride further revealed significant accumulation of reactive oxygen species in the roots of rice treated with PS-MPs. In addition, transcriptome data analysis revealed that PS-MPs induce the expression of genes related to antioxidant enzyme activity in plant roots. Specifically, genes related to flavonoid and flavonol biosynthesis were upregulated, whereas those involved in linolenic acid and nitrogen metabolism were downregulated. These results enhance our understanding of the responses of agricultural crops to MP toxicity. 10.3390/toxics9080179

Effects of individual and combined polystyrene nanoplastics and phenanthrene on the enzymology, physiology, and transcriptome parameters of rice (Oryza sativa L.). Chemosphere Owing to their wide distribution, easy production, and resistance to degradation, microplastics (MPs) represent a globally emerging group of pollutants of concern. Furthermore, their decomposition can result in the generation of nanoplastics (NPs), which cause further environmental issues. Currently, the impact of the combination of these plastics with other organic pollutants on crop growth remains poorly investigated. In this study, a hydroponic experiment was conducted for seven days to evaluate the effects of 50 nm, 50 mg/L polystyrene (PS), and 1 mg/L phenanthrene (Phe) on the growth of rice plants. The results revealed that both Phe and PS inhibited growth and improved the antioxidant potential of rice. Relative to Phe alone, exposure to a combination of PS and Phe reduced Phe accumulation in the roots and shoots by 67.73% and 36.84%, respectively, and decreased the pressure on the antioxidant system. Exposure to Phe alone destroyed the photosynthetic system of rice plant leaves, whereas a combination of PS and Phe alleviated this damage. Gene Ontology (GO) analysis of the rice transcriptomes revealed that detoxification genes and phenylalanine metabolism were suppressed under exposure to Phe, which consequently diminished the antioxidant capacity and polysaccharide synthesis in rice plants. Kyoto Encyclopaedia of Genes and Genomes (KEGG) transcriptome analysis revealed that the combined presence of both PS and Phe improved photosynthesis and energy metabolism and alleviated the toxic effects of Phe by altering the carbon fixation pathway and hormone signal transduction in rice plants. The combination of PS and Phe also prevented Phe-associated damage to rice growth. These findings improve our understanding of the effects of MP/NPs and polycyclic aromatic hydrocarbons on crops. 10.1016/j.chemosphere.2022.135341

The phytotoxicity of microplastics to the photosynthetic performance and transcriptome profiling of Nicotiana tabacum seedlings. Ecotoxicology and environmental safety Microplastics (MPs), as emerging "new generation" organic contaminants, have attracted extensive attention regarding their severe toxicity to aquatic and terrestrial organisms. However, the responses of plant photosynthesis to soil MP pollution are unclear. In this study, Nicotiana tabacum seedlings were grown in soils containing 0~1000 g·kg polyethylene (PE)-MPs for 48 days. PE-MPs significantly increased the superoxide anion content by 15.3~44.8% but decreased the chlorophyll content and Rubisco activity by 4.3~14.0% and 4.23~30.9%, respectively. PE-MPs also inhibited RuBP carboxylation activation and regeneration, restrained light use efficiency, and prevented dark respiration, thereby reducing the light-saturated photosynthesis rate. The changed shape of OJIP transients indicated that PE-MP toxicity inhibited not only the primary photochemistry rate but also photoelectrochemical quenching, resulting in decreased quantum yields. RNA-Seq revealed thousands of differentially expressed genes (DEGs), among which 79 highly expressed DEGs were enriched in photosynthesis-related processes. Functional annotation revealed that the reduction in environment stress was mainly due to the repressed expression of light harvesting-, electron transport- and photosystem-related genes in chloroplasts. This study regarding the physiological and molecular responses of photosynthetic performance to soil PE-MP pollution provides a new viewpoint for exploring the plant photosynthesis regulating and protective mechanisms under soil MP stresses. 10.1016/j.ecoenv.2021.113155

Effects of polystyrene nanoplastics with different functional groups on rice (Oryza sativa L.) seedlings: Combined transcriptome, enzymology, and physiology. The Science of the total environment Plastic particles originate from the daily use of plastics and have become a new form of pollutant. However, the effects of nanoplastics (NPs) on higher plants remain largely unclear, thus requiring further research. In this study, rice plants were exposed to polystyrene (PS) NPs with different functional groups to determine their toxicity. The presence of NPs reduced the biomass and photosynthetic capacity of rice. Compared with control (CK), the heights of rice plants exposed to no-modified PS, carboxyl-modified PS (PS-COOH) and amino-modified PS (PS-NH) groups decreased by 13.59%, 26.61%, and 42.71%, while the dry shoot weight decreased by 47.46%, 50.09%, and 71.04%, respectively. All treatments activated the antioxidant levels of rice and reduced photosynthesis. Transcriptome analysis showed that NPs induced the expression of genes related to antioxidant enzyme activity in rice roots. Rice could partially reduce the xenobiotic toxicity caused by external sources by regulating phenylpropane biosynthesis and the processes involved in cell detoxification. PS mainly affected the process of RNA metabolism, while PS-COOH mainly affected ion transport, and PS-NH mainly affected the synthesis of macromolecular protein, which had different effects on rice growth. 10.1016/j.scitotenv.2022.155092