Ionic lead (Pb) in the environment has accumulated due to anthropogenic activities, causing a potential threat to plants and plant consumers. We conducted this study to reveal the molecular mechanism of Pb stress response in plants. The effects of Pb (5.0 and 15.0 μM) on mitosis, DNA replication, gene expression and proteins in root-tip cells of Allium cepavar.agrogarum L. were addressed. The results indicated that root growth was inhibited dramatically in Pb treatment groups. Chromosomal aberrations were observed and the mitotic index decreased during Pb treatments at different concentrations. The accumulation of reactive oxygen species (ROS) in onion roots was induced by Pb stress. Pb increased DNA damage and suppressed cell cycle progression. The above toxic effects got more serious with increasing Pb concentration and prolonging exposure time. A total of 17 proteins were expressed differentially between control and Pb exposure groups. Under Pb treatment, the decreased expression of Anx D1 indicated decreased defensive response; the decreased expression of SHMT1 indicated decreased respiration; the decreased expression of COMT2 indicated decreased response of other funtions; the increased expression of NDPK indicated increased transcription and protein synthesis; the increased expression of PR1 and CHI1 indicated increased pathogen invasion; the increased expression of ORC5 and MPK5 indicated the reduced DNA replicating activity; the decreased expression of POLD1 indicated the reduced DNA repair activity. Our results provide new insights at the proteomic level into the Pb-induced responses, defensive responses and toxic effects, and provide new molecular markers of the early events of plant responses to Pb toxicity.

人为活动导致环境中的离子铅（Pb）积累，对植物和植物消费者构成潜在威胁。我们进行了这项研究，以揭示植物中铅胁迫响应的分子机制。有丝分裂，DNA复制，基因表达和蛋白质的Pb（5.0和15.0μM）的在根尖细胞的影响洋葱变种。农杆菌L.得到了解决。结果表明，在铅处理组中根生长受到显着抑制。在不同浓度的铅处理期间，观察到染色体畸变并且有丝分裂指数降低。铅胁迫引起洋葱根中活性氧的积累。铅增加DNA损伤并抑制细胞周期进程。随着Pb浓度的增加和暴露时间的延长，上述毒性作用变得更加严重。对照组和铅暴露组之间总共表达了17种蛋白质。在铅处理下，Anx D1的表达降低表明防御反应降低。SHMT1的表达降低表明呼吸减少；COMT2表达降低表明其他功能的反应减少；NDPK表达增加表明转录和蛋白质合成增加；的表达增加PR1和为CH1标明增加的病原体入侵; ORC5和MPK5表达增加表明DNA复制活性降低。POLD1表达的降低表明DNA修复活性降低。我们的结果在蛋白质组学水平上为铅诱导的应答，防御应答和毒性作用提供了新的见识，并为植物对铅毒性的早期反应提供了新的分子标记。