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Does salicylic acid regulate antioxidant defense system, cell death, cadmium uptake and partitioning to acquire cadmium tolerance in rice?

机译:水杨酸是否能调节抗氧化防御系统,细胞死亡,镉吸收和分配,从而获得水稻对镉的耐受性?

摘要

Salicylic acid (SA) may accelerate the cell death of cadmium-stressed roots to avoid cadmium (Cd) uptake by plants or may play positive roles in protecting the stressed roots from Cd-induced damage. To test these hypotheses, we performed a series of split-root hydroponic experiments with one-half of rice (Oryza sativa L. cv. Jiahua 1) roots exposed to 50 mu M Cd and the other half not exposed. The objectives were to elucidate the effects of SA pretreatment on the time-dependent changes of H(2)O(2) levels in roots, antioxidant defense system in different organs, root cell death and the dynamic distribution of Cd in the plants. In the split-root system, a higher Cd uptake rate was observed in the Cd-stressed portions of roots compared with the treatment with the whole roots exposed to Cd. Furthermore, an appreciable amount of Cd was translocated from the Cd-exposed roots to the unexposed roots and trace amounts of Cd were released into the external solution. The split-root method also caused the two root portions to respond differently to Cd stress. The activities of major antioxidant enzymes (superoxide dismutase, SOD; peroxidase, POD; and catalase, CAT) were significantly suppressed in the Cd-treated roots, hence leading to H(2)O(2) burst, lipid peroxidation, cell death and growth inhibition. By contrast, in the non-Cd-treated roots, the activities of enzymes (SOD, CAT, and POD) and root growth were persistently stimulated during the experimental period. The H(2)O(2) accumulation and lipid peroxidation were also induced in the non-Cd-treated roots, but they were significantly lower than those of the Cd-treated roots. The concentrations of glutathione (GSH) and non-protein thiols (NPT) in the Cd-treated roots were significantly higher than those of the untreated roots. SA pretreatment elevated enzymatic and non-enzymatic antioxidants, and the concentrations of GSH and NPT in roots and shoots, hence leading to alleviation of the oxidative damage as indicated by the lowered H(2)O(2) and MDA levels. Furthermore, SA pretreatment mitigated the Cd-induced growth inhibition in both roots and shoots and increased transpiration compared with non-SA-pretreatment under Cd exposure. It is concluded that Cd can be partly transferred from the Cd-exposed roots to Cd-unexposed roots and that cell death can be accelerated in the Cd-stressed roots in response to Cd stress. The SA-enhanced Cd tolerance in rice can be attributed to SA-elevated enzymatic and non-enzymatic antioxidants and NPT and to SA-regulated Cd uptake, transport and distribution in plant organs. (c) 2008 Elsevier GmbH. All rights reserved.
机译:水杨酸(SA)可能会加速镉胁迫根系的细胞死亡,从而避免植物吸收镉(Cd)或在保护胁迫根系免受Cd诱导的伤害中发挥积极作用。为了检验这些假设,我们用一半的水稻(Oryza sativa L. cv。Jiahua 1)根系暴露于50μM Cd且另一半未暴露的根系进行了一系列的根分裂水培实验。目的是阐明SA预处理对根中H(2)O(2)水平随时间的变化,不同器官中的抗氧化防御系统,根细胞死亡和植物体内Cd动态分布的影响。在分根系统中,与整根暴露于Cd的处理相比,在Cd胁迫的根部中观察到更高的Cd吸收率。此外,相当数量的Cd从暴露于Cd的根转移到未暴露的根,微量的Cd释放到外部溶液中。分裂根法还导致两个根部对Cd胁迫的反应不同。在镉处理的根中,主要的抗氧化酶(超氧化物歧化酶,SOD,过氧化物酶,POD和过氧化氢酶,CAT)的活性被显着抑制,从而导致H(2)O(2)爆裂,脂质过氧化,细胞死亡和生长抑制。相比之下,在未经Cd处理的根系中,在实验期间会持续刺激酶(SOD,CAT和POD)的活性和根系的生长。 H(2)O(2)积累和脂质过氧化也诱导在非镉处理的根中,但它们明显低于镉处理的根。镉处理过的根中谷胱甘肽(GSH)和非蛋白硫醇(NPT)的浓度显着高于未处理过的根。 SA预处理提高了酶促和非酶促抗氧化剂,以及根和芽中GSH和NPT的浓度,因此降低了H(2)O(2)和MDA含量,从而减轻了氧化损伤。此外,与在镉暴露下的非SA预处理相比,SA预处理减轻了Cd诱导的根和芽生长抑制,并增加了蒸腾作用。结论是,Cd可以部分地从Cd暴露的根转移到Cd未暴露的根,并且响应Cd胁迫,可以在Cd胁迫的根中加速细胞死亡。水稻中SA对Cd的耐受性增强可归因于SA升高的酶和非酶抗氧化剂和NPT,以及SA调节的Cd在植物器官中的吸收,运输和分布。 (c)2008 Elsevier GmbH。版权所有。

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