Exogenous glutathione enhances cadmium accumulation and alleviates its toxicity in Populus x canescens
Exogenous glutathione enhances cadmium accumulation and alleviates its toxicity in Populus x canescens
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外源谷胱甘肽增强白杨中镉的积累并减轻其毒性
DOI：
10.1093/treephys/tpx132
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发表时间：
2017-12-01
期刊：
影响因子：
4
通讯作者：
Luo, Zhi-Bin
中科院分区：
文献类型：
--
作者：
Ding, Shen;Ma, Chaofeng;Luo, Zhi-Bin
谷胱甘肽(GSH)在木本植物对镉(Cd)的耐性中起着重要作用，但其潜在的机制仍不清楚。为了阐明木本植物GSH介导的Cd耐性的生理和转录调控机制，本研究以毛白杨×canescens(Ait.)史密斯幼苗0或75μM CD与三个外部谷胱甘肽水平之一。谷胱甘肽的治疗包括丁硫氨酸亚磺胺(BSO，一种GSH生物合成的抑制剂)、无外源性GSH和外源性GSH。外源GSH提高了杨树根系对Cd~(2+)的吸收速率，增加了杨树体内Cd的含量，降低了Cd诱导的根中H_2O_2水平，提高了Cd处理的根系和叶片中内源GSH的含量。此外，外源谷胱甘肽诱导了一些基因的转录水平上调，其中包括可能参与镉吸收的锌铁调节转运蛋白6.2和自然抗性相关巨噬细胞蛋白1.3，参与镉解毒的谷胱甘肽合成酶2，参与镉解毒的金属耐受性蛋白1和三磷酸腺苷结合盒转运蛋白C3，参与镉解毒的γ谷氨酰半胱氨酸合成酶和植物螯蛋白合成酶家族蛋白1。寡肽转运蛋白7(OPT7)可能参与了镉胁迫下菜豆叶片对镉的解毒作用。相比之下，BSO对Cd引发的杨树生理和转录调控反应往往表现出相反的效应。这些结果表明，外源GSH可以促进Cd在杨树体内的积累，减轻其毒害作用。这可能是由于外源GSH诱导的根中Cd~(2+)净内流增加，Cd在地上部分积累更多，对活性氧的清除更强，以及参与Cd吸收、解毒和积累的几个基因转录过表达所致。
Glutathione (GSH) plays an important role in cadmium (Cd) tolerance in woody plants, but the underlying mechanisms remain largely unknown. To elucidate the physiological and transcriptional regulation mechanisms of GSH-mediated Cd tolerance in woody plants, we exposed Populus × canescens (Ait.) Smith saplings to either 0 or 75 μM Cd together with one of three external GSH levels. Glutathione treatments include buthionine sulfoximine (BSO, an inhibitor of GSH biosynthesis), no external GSH and exogenous GSH. External GSH resulted in higher Cd2+ uptake rate in the roots, greater Cd amount in poplars, lower Cd-induced H2O2 levels in the roots, and higher contents of endogenous GSH in Cd-treated roots and leaves. Furthermore, external GSH led to upregulated transcript levels of several genes including zinc/iron regulated transporter related protein 6.2 (ZIP6.2) and natural resistance-associated macrophage protein 1.3 (NRAMP1.3), which probably take part in Cd uptake, glutathione synthetase 2 (GS2) implicated in Cd detoxification, metal tolerance protein 1 (MTP1) and ATP-binding cassette transporter C3 (ABCC3) involved in Cd vacuolar accumulation in the roots, γ-glutamylcysteine synthetase (ECS) and phytochelatin synthetase family protein 1 (PCS1) involved in Cd detoxification, and oligopeptide transporter 7 (OPT7) probably implicated in Cd detoxification in the leaves of Cd-exposed P. × canescens. In contrast, BSO often displayed the opposite effects on Cd-triggered physiological and transcriptional regulation responses in poplars. These results suggest that exogenous GSH can enhance Cd accumulation and alleviate its toxicity in poplars. This is probably attributed to external-GSH-induced higher net Cd2+ influx in the roots, greater Cd accumulation in aerial parts, stronger scavenging of reactive oxygen species, and transcriptional overexpression of several genes involved in Cd uptake, detoxification and accumulation.