Enhanced metal tolerance correlates with heterotypic variation in SpMTL, a metallothionein-like protein from the hyperaccumulator Sedum plumbizincicola
Enhanced metal tolerance correlates with heterotypic variation in SpMTL, a metallothionein-like protein from the hyperaccumulator Sedum plumbizincicola
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DOI：
10.1111/pce.12929
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发表时间：
2017-08-01
影响因子：
7.3
通讯作者：
Gong, Ji-Ming
中科院分区：
文献类型：
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作者：
Peng, Jia-Shi;Ding, Ge;Gong, Ji-Ming
金属超积累机制的研究主要局限于菊科植物，因此，从菊科以外的系统中获得相应的认识具有重要意义。本研究构建并筛选了Cd/Zn超富集植物Pdum plumbizincicola的cDNA文库，并鉴定了一个新的金属硫蛋白样蛋白编码基因SpMTL。SpMTL显示出与其他已知MT蛋白的功能相似性，也与来自非高血压的其直向同源物相似。然而，三个额外的半胱氨酸残基中观察到SpMTL，似乎是超富集植物特异性。去除这三个残基显着降低其耐受镉的能力和化学计量的镉对SpMTL（镉/SpMTL的摩尔比）的水平相当的Cd/SaMTL和Cd/SeMTL在相应的非超积累的亲属。SpMTL在S.在非超积累植物根中，Pbumbizincicola的根比其直向同源物的根的水平高得多。有趣的是，观察到的SpMTL在根中的转录水平和镉在叶中的积累之间的正相关。综合以上结果，我们认为SpMTL基因转录水平的提高和蛋白质序列的异型变异可能是导致S.铅藻属
Mechanistic insight into metal hyperaccumulation is largely restricted to Brassicaceae plants; therefore, it is of great importance to obtain corresponding knowledge from system outside the Brassicaceae. Here, we constructed and screened a cDNA library of the Cd/Zn hyperaccumulator Sedum plumbizincicola and identified a novel metallothionein-like protein encoding gene SpMTL. SpMTL showed functional similarity to other known MT proteins and also to its orthologues from non-hyperaccumulators. However, three additional cysteine residues were observed in SpMTL and appeared to be hyperaccumulator specific. Removal of these three residues significantly decreased its ability to tolerate Cd and the stoichiometry of Cd against SpMTL (molar ratio of Cd/SpMTL) to a level comparable to those of Cd/SaMTL and Cd/SeMTL in the corresponding non-hyperaccumulating relatives. SpMTL expressed in S. plumbizincicola roots at a much higher level than those of its orthologues in the non-hyperaccumulator roots. Interestingly, a positive correlation was observed between transcript levels of SpMTL in roots and Cd accumulation in leaves. Taking these results together, we propose that elevated transcript levels and heterotypic variation in protein sequences of SpMTL might contribute to the trait of Cd hyperaccumulation and hypertolerance in S. plumbizincicola.