Transcriptome reveals the exposure effects of CeO2 nanoparticles on pakchoi (Brassica chinensis L.) photosynthesis

In this study, soil-grown pakchoi after 2 weeks seedling cultivation were exposed to CeO2 nanoparticles (CeO2 NPs) at 0.7, 7, 70, and 350 mg kg-1 for 30 days. Results showed that chlorophyll content and photosynthetic assimilation rate were decreased significantly under all treatments with the largest decrease of 34.16% (0.7 mg kg-1 CeO2 NPs), however, sub-stomatal CO2 was increased dramatically under low dose of CeO2 NPs (0.7 mg kg-1). There were 4576, 3548, 2787, and 2514 genes up/down regulated significantly by 0.7, 7, 70, and 350 mg kg-1 CeO2 NPs, respectively, and 767 genes affected under all treatments. In addition, 0.7 mg kg-1 CeO2 NPs up-regulated 10 chlorophyll synthesis genes, 20 photosynthesis genes, and 10 carbon fixation enzyme genes; while 350 mg kg-1 CeO2 NPs down-regulated 5 photosynthesis genes and 28 auxin-activated genes. Among the key genes of photosynthesis, Ferredoxin-NADP reductase (PetH) was upregulated in 0.7, 7 and 70 mg kg-1 treatments, while Photosystem II lipoprotein (Psb27) was downregulated under 7, 70 and 350 mg kg-1 treatments. Top 20 metabolic pathways affected by CeO2 NPs including plant hormone, amino acids, and glutathione, and carbon metabolism These results provide information about utilizing CeO2 NPs more safely and effectively in the future.