Identification of C-terminal Regions in Arabidopsis thaliana Phytochelatin Synthase 1 Specifically Involved in Activation by Arsenite
Identification of C-terminal Regions in Arabidopsis thaliana Phytochelatin Synthase 1 Specifically Involved in Activation by Arsenite
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DOI：
10.1093/pcp/pcx204
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发表时间：
2018-03-01
影响因子：
4.9
通讯作者：
Kiyono, Masako
中科院分区：
文献类型：
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作者：
Uraguchi, Shimpei;Sone, Yuka;Kiyono, Masako
植物螯合素（PCs）是植物细胞中无机砷（As）等有毒元素的主要螯合剂。它们的合成赋予耐受性并影响植物内部的移动性。先前的研究表明，不同的金属/类金属离子对PC合成的激活作用不同。在这里，我们确定了c端部分参与亚砷酸盐[As(III)]依赖性激活AtPCS1，拟南芥初级PC合成酶。AtPCS1突变体cad1-6中的T-DNA插入导致c端调控域的截断，这对镉（Cd）和锌（Zn）的激活有不同的影响。将cad1-6与AtPCS1零突变体cad1-3和tono质体PC转运体双突变体abcc1/2进行比较，发现cad1-6的As（III）超敏性与cad1-3相同。与Col-0相比，cad1-6和cad1-3在茎部的As分布均有所增加，而cad1-6和cad1-3在茎部的Zn积累均较低。与这些表型相一致的是，暴露于As（III）的植株中的PC积累在cad1-6和cad1-3中均处于痕量水平，这表明cad1-6的截断AtPCS1在响应As（III）时存在PCS活性缺陷。利用裂变酵母的pcs缺陷突变体对AtPCS1的c端缺失序列进行分析，发现了As（III）依赖的PC合成在c端结构域内的重要区域，这与之前认为的Cd或zn依赖的激活区域不同。有趣的是，我们发现了一个比野生型蛋白更强烈激活的截断变体。该变异可能被用作更好地限制砷在植物中的迁移的工具。
Phytochelatins (PCs) are major chelators of toxic elements including inorganic arsenic (As) in plant cells. Their synthesis confers tolerance and influences within-plant mobility. Previous studies had shown that various metal/metalloid ions differentially activate PC synthesis. Here we identified C-terminal parts involved in arsenite[As(III)] dependent activation of AtPCS1, the primary Arabidopsis PC synthase. The T-DNA insertion in the AtPCS1 mutant cad1-6 causes a truncation in the C-terminal regulatory domain that differentially affects activation by cadmium (Cd) and zinc (Zn). Comparisons of cad1-6 with the AtPCS1 null mutant cad1-3 and the double mutant of tonoplast PC transporters abcc1/2 revealed As(III) hypersensitivity of cad1-6 equal to that of cad1-3. Both cad1-6 and cad1-3 showed increased As distribution to shoots compared with Col-0, whereas Zn accumulation in shoots was equally lower in cad1-6 and cad1-3. Supporting these phenotypes of cad1-6, PC accumulation in the As(III)-exposed plants were at trace level in both cad1-6 and cad1-3, suggesting that the truncated AtPCS1 of cad1-6 is defective in PCS activity in response to As(III). Analysis of a C-terminal deletion series of AtPCS1 using the PCS-deficient mutant of fission yeast suggested important regions within the C-terminal domain for As(III)-dependent PC synthesis, which were different from the regions previously suggested for Cd- or Zn-dependent activation. Interestingly, we identified a truncated variant more strongly activated than the wild-type protein. This variant could potentially be used as a tool to better restrict As mobility in plants.