Phytochelatin-mediated metal detoxification pathway is crucial for an organomercurial phenylmercury tolerance in Arabidopsis
Phytochelatin-mediated metal detoxification pathway is crucial for an organomercurial phenylmercury tolerance in Arabidopsis
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DOI：
10.1007/s11103-021-01221-0
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发表时间：
2021-11
影响因子：
5.1
通讯作者：
Shimpei Uraguchi;Y. Ohshiro;Yuto Otsuka;E. Wada;Fumii Naruse;Kakeru Sugaya;Kenichiro Nagai;A. Wongkaew;Ryosuke Nakamura;Yasukazu Takanezawa;S. Clemens;Naoko Ohkama‐Ohtsu;M. Kiyono
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文献类型：
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作者：
Shimpei Uraguchi;Y. Ohshiro;Yuto Otsuka;E. Wada;Fumii Naruse;Kakeru Sugaya;Kenichiro Nagai;A. Wongkaew;Ryosuke Nakamura;Yasukazu Takanezawa;S. Clemens;Naoko Ohkama‐Ohtsu;M. Kiyono
关键信息有机汞苯汞可激活 AtPCS1，AtPCS1 是一种已知用于拟南芥中无机金属（类）离子解毒的酶，而诱导的金属螯合肽植物螯合素对于苯汞的解毒至关重要。无机形式的金属（类）离子，包括无机汞 [Hg(II)]。然而，PC/PCS 系统在植物有机汞解毒中的可能作用仍然难以捉摸。我们发现有机汞苯汞 (PheHg) 在拟南芥植物中诱导 PC 合成为 Hg(II)，而甲基汞则不然。对AtPCS1突变植物的分析和使用AtPCS1重组蛋白的体外测定表明，AtPCS1是A中的主要PCS。拟南芥负责 PheHg 响应性 PC 合成。 AtPCS1突变体cad1-3和cad1-6以及PC-金属(loid)复合物转运蛋白AtABCC1和AtABCC2的双突变体显示出对PheHg以及Hg(II)的敏感性增强。 cad1-3 对 PheHg 应激的超敏性通过 AtPCS1-GFP 自身启动子驱动的表达得到补充。互补系共聚焦显微镜显示AtPCS1-GFP优先在成熟区和伸长区的表皮细胞以及分生区侧根冠细胞的最外层表达。此外，体外PC-金属结合测定表明PC与PheHg之间的结合亲和力与Hg(II)相当。然而，植物离子组谱以及 PheHg 和 Hg(II) 胁迫下的根形态存在差异。这些结果表明，PheHg 植物毒性与 Hg(II) 不同，但 AtPCS1 介导的 PC 合成、复合物形成以及 AtABCC1 和 AtABCC2 的液泡隔离对于根表面细胞类型中的 PheHg 和 Hg(II) 解毒具有相似的功能。
Key messageAn organomercurial phenylmercury activates AtPCS1, an enzyme known for detoxification of inorganic metal(loid) ions in Arabidopsis and the induced metal-chelating peptides phytochelatins are essential for detoxification of phenylmercury.AbstractSmall thiol-rich peptides phytochelatins (PCs) and their synthases (PCSs) are crucial for plants to mitigate the stress derived from various metal(loid) ions in their inorganic form including inorganic mercury [Hg(II)]. However, the possible roles of the PC/PCS system in organic mercury detoxification in plants remain elusive. We found that an organomercury phenylmercury (PheHg) induced PC synthesis inArabidopsis thalianaplants as Hg(II), whereas methylmercury did not. The analyses of AtPCS1 mutant plants and in vitro assays using the AtPCS1-recombinant protein demonstrated that AtPCS1, the major PCS inA. thaliana, was responsible for the PheHg-responsive PC synthesis. AtPCS1 mutantscad1-3andcad1-6, and the double mutant of PC-metal(loid) complex transporters AtABCC1 and AtABCC2 showed enhanced sensitivity to PheHg as well as to Hg(II). The hypersensitivity ofcad1-3to PheHg stress was complemented by the own-promoter-driven expression of AtPCS1-GFP. The confocal microscopy of the complementation lines showed that the AtPCS1-GFP was preferentially expressed in epidermal cells of the mature and elongation zones, and the outer-most layer of the lateral root cap cells in the meristematic zone. Moreover, in vitro PC-metal binding assay demonstrated that binding affinity between PC and PheHg was comparable to Hg(II). However, plant ionomic profiles, as well as root morphology under PheHg and Hg(II) stress, were divergent. These results suggest that PheHg phytotoxicity is different from Hg(II), but AtPCS1-mediated PC synthesis, complex formation, and vacuolar sequestration by AtABCC1 and AtABCC2 are similarly functional for both PheHg and Hg(II) detoxification in root surficial cell types.