Quantitative proteomics unravels root-specific response mechanisms and phytotoxicity of four typical UV filters in pakchoi (Brassica rapa L. ssp. chinensis)

Common UV filters (OBZ, AVB, OCR, OMC) widely exist in the environment and organisms, raising global concerns about their ecological and physiological risks. However, the molecular response mechanisms of higher plants to these emerging contaminants remain largely unexplored. To address this research gap, we herein employed quantitative proteomics to examine root-specific responses in pakchoi (Brassica rapa ssp. chinensis) following exposure to each of the four UV filters. Across all treatments, a total of 8656 proteins were quantified, with 632, 482, 251, and 393 differentially expressed proteins (DEPs) identified under OBZ, AVB, OCR, and OMC exposure, respectively. These DEPs were primarily enriched in key metabolic pathways, including reactive oxygen species (ROS) scavenging, glycolysis (EMP)-tricarboxylic acid (TCA) cycle, respiratory electron transport chain, fatty acid metabolism, and amino acid biosynthesis. All four UV filters induced pronounced oxidative stress in pakchoi roots, as indicated by elevated ROS levels and increased lipid peroxidation. Proteins involved in EMP (6-phosphofructokinase, pyruvate kinase) and the TCA cycle (isocitrate dehydrogenase, malate dehydrogenase) exhibited significant downregulation. In contrast, proteins associated with fatty acid metabolism (aldehyde dehydrogenase, long-chain fatty acid omega-monooxygenase, acyl-CoA oxidase and Delta3-Delta2-enoyl-CoA isomerase) were predominantly upregulated. These proteomic patterns suggest a potential alteration in EMP-TCA cycle, and lipid metabolic processes. Concurrently, proteins associated with antioxidant enzymes (glutathione S-transferases, peroxidases and catalases) were predominantly upregulated. These proteomic findings are consistent with the increased peroxidases and catalases enzyme activity observed at the physiological level. Collectively, these findings provide a comprehensive proteomic overview of pakchoi root responses to UV filter exposure and offer novel insights into the underlying mechanisms of phytotoxicity, and provide a reference for the breeding of crop resistant varieties to ensure agricultural productivity and food safety.