伴矿景天植物螯合肽合酶基因的克隆及功能分析

重金属超积累植物由于长期生长在高浓度的重金属环境中,使得经由植物螯合肽（phytochelatins, PCs）解毒途径来应对重金属毒害代价高昂。我们从Zn/Cd超积累植物伴矿景天（Sedum plumbizincicola）中克隆了植物螯合肽合酶（phytochelatin synthase, PCS）基因SepPCS。该基因在裂殖酵母和拟南芥中表达后都具有PCS活性,而且能够互补它们的PCs缺失突变体的Cd敏感表型。SepPCS在伴矿景天中的表达受到高浓度Cd处理的诱导。与其近亲非超积累生态型东南景天（S. alfredii）相比,虽然伴矿景天地上部PCs与Cd的摩尔比远低于东南景天,但是在高浓度Cd处理时PCs含量以及PCs与Cd的摩尔比急剧增加。我们推测在伴矿景天应对Cd毒害的过程中, PCs起到一定的作用,并且在高浓度Cd胁迫时地上部PCs依赖的解毒作用有所加强。

Cloning and Functional Analysis of Phytochelatin Synthase Gene from Sedum plumbizincicola

Phytochelatin （PCs）-dependent mechanisms are costly for hyperaccumulators to detoxify toxic metals as they grow in heavy metal-rich habitats. In this study we report the isolation and functional characterization of the phytochelatin synthase （PCS） gene SepPCS from the hyperaccumulator Sedum plumbizincicola. Ectopic ex-pression of SepPCS complemented PCs biosynthesis as well as cadmium （Cd） tolerance in the PCs-deficient yeast or Arabidopsis mutantΔpcs and cad1-3 respectively. SepPCS expression is up-regulated in response to high level Cd treatment. Furthermore, the molar ratio of PCs and Cd in S. plumbizincicola is far less than that in the non-hyperaccumulating ecotype of S. alfredii, though this ratio in S. plumbizincicola shoots increased rapidly when exposed to high concentration Cd treatments, consistent with the expression pattern of SepPCS. These re-sults imply that PCs biosynthesis might play a minor role in Cd tolerance in the hyperaccumulator S. plumbizinc-icola, but the importance of this mechanism might increase with elevated Cd concentrations.