Abstract：
The increases in titanium dioxide nanoparticles (TiO2-NPs) released into the environment have raised concerns about their toxicity. However, their phytotoxic impact on plants is not well studied. Therefore, this study aimed at a deeper understanding of the TiO2-NPs phytotoxic impact on barley (Hordeum vulgare) growth and stress defense. We also hypothesized that soil inoculation with bioactive Rhodospirillum sp. JY3 strain can be applied as a biological fertilizer to alleviate TiO2-NPs phytotoxicity. At TiO2-NPs phytotoxicity level, photosynthesis was significantly retarded (∼50% reduction) in TiO2-NPs treated-barley plants which accordingly affect the biomass of barley plants. This retardation was accompanied by a remarkable induction of oxidative damage (H2O2, lipid peroxidation) with a concomitant reduction in the antioxidant defense metabolism. At a glance, Rhodospirillum sp. JY3 ameliorated the reduction in growth by enhancing the photosynthetic efficiency in contaminated barley plants. Moreover, Rhodospirillum sp. JY3 inoculation reduced the oxidative damage induced by TiO2-NPs via quenching H2O2 production and lipid peroxidation. Regarding the antioxidant defense arsenal, Rhodospirillum sp. JY3 enhanced both enzymatic (e.g. peroxidase (POX), catalase (CAT), superoxide dismutase (SOD), …. etc.) and non-enzymatic (glutathione (GSH), ascorbate (ASC), polyphenols, flavonoids, tocopherols) antioxidants in shoots and to a greater extent roots of barley plants. Moreover, the inoculation significantly enhanced the heavy metal-detoxifying metabolites (eg. phytochelatins, glutaredoxin, thioredoxin, peroxiredoxin) as well as metal-detoxifying enzymes in barley shoots and more apparently in roots of TiO2-NPs stressed plants. Furthermore, there was an organ-specific response to TiO2-NPs and Rhodospirillum sp. JY3. To this end, this study shed light, for the first time, on the molecular bases underlie TiO2-NPs stress mitigating impact of Rhodospirillum sp. JY3 and it introduced Rhodospirillum sp. JY3 as a promising eco-friendly tool in managing environmental risks to maintain agricultural sustainability.
摘要：
释放到环境中的二氧化钛纳米颗粒（TiO2-NP）的增加引起了人们对其毒性的担忧。然而,它们对植物的植物毒性影响尚未得到很好的研究。因此,这项研究旨在更深入地了解TiO2-NP对大麦（大麦）生长和胁迫防御的植物毒性影响。我们还假设土壤接种了生物活性红螺菌。JY3菌株可作为生物肥料施用以减轻TiO2-NPs的植物毒性。在TiO2-NP植物毒性水平下，在TiO2-NP处理的大麦植物中，光合作用显着延迟（〜50％减少），从而影响大麦植物的生物量。这种延迟伴随着氧化损伤（H2O2，脂质过氧化）的显着诱导，并伴随着抗氧化剂防御代谢的减少。一目了然,红螺旋藻sp.JY3通过提高受污染的大麦植物的光合效率来改善生长的减少。此外，红螺旋藻sp.JY3接种通过淬灭H2O2的产生和脂质过氧化降低了TiO2-NP诱导的氧化损伤。关于抗氧化剂防御武器库，红螺旋藻sp.JY3增强了两种酶(例如过氧化物酶(POX)，过氧化氢酶(CAT),超氧化物歧化酶（SOD），....等。)和非酶(谷胱甘肽(GSH)，抗坏血酸（ASC），多酚，黄酮类化合物，生育酚）大麦植物的芽和更大程度的根中的抗氧化剂。此外，接种显着增强了重金属解毒代谢物（例如植物螯合素，谷氧还蛋白,硫氧还蛋白,过氧化物酶）以及大麦芽中的金属解毒酶，更明显的是在TiO2-NP胁迫植物的根中。此外，对TiO2-NP和红螺菌有器官特异性反应。JY3。为此,这项研究揭示了，第一次,在分子基础上，TiO2-NPs的胁迫缓解作用。JY3和它引入了红螺螺旋藻。JY3作为一个有前途的生态友好型工具，在管理环境风险，以保持农业的可持续性。
