Glutathione S-transferases modulate Cu tolerance in Oryza sativa
Glutathione S-transferases modulate Cu tolerance in Oryza sativa
复制标题
谷胱甘肽 S-转移酶调节水稻的铜耐受性
DOI：
10.1016/j.envexpbot.2018.07.007
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发表时间：
2018-11-01
影响因子：
5.7
通讯作者：
Hu, Zhubing
中科院分区：
文献类型：
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作者：
Li, Lu;Hou, Mengjiao;Hu, Zhubing
沿着铜基杀菌剂和肥料的广泛使用，铜污染土壤已成为导致作物产量损失的主要问题。为了提高水稻的耐铜性，我们进行了铜敏感性筛选，获得了耐铜品种（B1139）和铜敏感品种（B1195）。在此，通过分析根尖的RNA-Seq转录组谱，当暴露于过量Cu 2+时，20个谷胱甘肽S-转移酶（GST）基因在Cu耐受性B1139和Cu敏感性B1195之间差异表达。铜处理B1195根系GST活性的下降速度比铜处理B1139快，表明GST活性的不同可能影响水稻对铜的耐性。这进一步得到了铜过敏症在水稻幼苗缺乏最丰富的GST蛋白，OsGSTF 2的观察，证明GST蛋白调节水稻的铜耐受性。这至少部分地导致B1139和B1195之间不同的Cu耐受性。同源模建表明，GST酶的活性中心有一个可能的Cu ~（2+）结合位点OsGSTF 2（H41）。体外分析表明，Cu ~（2+）干扰OsGSTF 2蛋白的GST活性，说明Cu ~（2+）可能通过与OsGSTF 2（H41）位点结合而降低GST活性。因此，OsGSTF 2（H41 G）的组氨酸41位氨基酸被甘氨酸取代导致OsGSTF 2的GST活性降低。此外，OsGSTF 2的异位表达增强了大肠杆菌的Cu耐受性，表明GST蛋白可能通过结合细胞中的游离Cu 2+来减轻Cu毒性。
Along with the widespread use of copper (Cu)-based fungicides and fertilizers, Cu-contaminated soil has been a major issue resulting in the loss of crop yield. To improve Cu tolerance in Oryza sativa, we previously carried out a screen of Cu sensitivity and obtained the Cu tolerant (B1139) and the Cu sensitive (B1195) rice varieties. Here, by analyzing an RNA-Seq transcriptome profile of root tips, 20 glutathione S-transferase (GST) genes were differently expressed between the Cu tolerant B1139 and the Cu sensitive B1195 when exposed to excess Cu2+. A more rapid decrease of root GST activity occurred in Cu-treated B1195 than in Cu-treated B1139, suggesting that different GST activity might affect Cu tolerance in rice. This is further supported by the observation of Cu hypersensitivity in rice seedlings deficient of the most abundant GST protein, OsGSTF2, demonstrating that GST proteins modulate Cu tolerance in rice. This, at least partially, leads to different Cu tolerance between B1139 and B1195. Furthermore, homologous modeling showed that a putative Cu2+ binding site, OsGSTF2(H41) locates at the active center of GST enzyme. In vitro analysis demonstrated that Cu2+ interferes with the GST activity of OsGSTF2 protein, indicating that GST activity reduction by Cu2+ might be the binding of Cu2+ to the OsGSTF2(H41) site. Consistently, amino acid replacement of histidine 41 with glycine (OsGSTF2(H41G)) resulted in decreased GST activity of OsGSTF2. Additionally, ectopic expression of OsGSTF2 enhances Cu tolerance in Escherichia coli, suggesting that the GST proteins might alleviate Cu toxicity by the binding of free Cu2+ in cells.