褪黑素提高拟南芥对纳米氧化锌胁迫的耐受性OA

[Objective]With the widespread application of nanomaterials and their subsequent release into the environment,their impact on the growth and development of flora and fauna has become increasingly significant.Melatonin(N-acetyl-5-methoxy-tryptamine)plays an important role in regulating plant physiological activities,however,the physiological and molecular mecha-nisms by which it modulates plant responses to metal nanoparticles remain poorly understood.The aim of this study was to ex-plore the mechanisms by which exogenous melatonin alleviates zinc oxide nanoparticle(nZnO)stress,providing a theoretical foundation for understanding the molecular basis of plant responses to nanoparticle toxicity.[Methods]Using the model plant Arabidopsis thaliana,this study employed pharmacological and molecular biological approaches to investigate the effects of ex-ogenous melatonin(10,50,and 100 μmol/L)in minitagating the stress induced by 20 mg/L nZnO.[Results]Compared to the control,20 mg/L nZnO inhibited primary root(PR)growth by 38.7%while increasing the number of lateral root(LR)primor-dia by 14.5%.While exogenous melatonin alone did not significantly affect PR growth,it significantly reduced the nZnO-in-duced growth inhibition.Under nZnO stress,supplementation with 50 μmol/L melatonin increased the number of LR primor-dia by 38%,indicating that melatonin improved root system architecture under stress.nZnO stress significantly elevated reac-tive oxygen species(ROS)levels in root tips.Supplementation with 10,50,and 100 μmol/L melatonin reduced root H2O2 content by 28.6%,46.4%,and 32.1%,respectively.Similarly,malondialdehyde(MDA)levels,which rose significantly under nZnO stress,were reduced by 34.9%,30.2%,and 39.5%by the three melatonin concentrations,respectively.This suggested that melatonin significantly alleviated nZnO-induced oxidative damage.RT-qPCR analysis showed that exogenous melatonin significantly induced the expression of antioxidant enzyme genes CSD2 and CAT3.Enzyme assays revealed that 50 μmol/L melatonin significantly increased SOD and CAT activities by 77.7%and 73.0%,respectively,compared to nZnO treatment alone.Melatonin treatment significantly enhanced chlorophyll content;specifically,10 and 50 μmol/L melatonin in-creased chlorophyll content by 97.7%and 79.1%,respectively,compared to the nZnO-only treatment.Furthermore,exoge-nous melatonin up-regulated the expression of genes involved in nutrient and ion absorption while down-regulating genes related to ethylene biosynthesis and signaling.This dual action alleviated the senescence and growth inhibition caused by nZnO,ulti-mately improving the tolerance of A.thaliana seedlings.[Conclusion]These findings provided a theoretical basis for an in-depth understanding of the molecular mechanism by which melatonin enhances stress tolerance and alleviates nanoparticle toxici-ty in plants.