Fasani Elisa, DalCorso Giovanni, Varotto Claudio, Li Mingai, Visioli Giovanna, Mattarozzi Monica, Furini Antonella
Department of Biotechnology, University of Verona, Strada Le Grazie 15, Verona, 37134, Italy.
Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, San Michele all'Adige (TN), 38010, Italy.
New Phytol. 2017 Jun;214(4):1614-1630. doi: 10.1111/nph.14529. Epub 2017 Mar 23.
In the hyperaccumulator Arabidopsis halleri, the zinc (Zn) vacuolar transporter MTP1 is a key component of hypertolerance. Because protein sequences and functions are highly conserved between A. halleri and Arabidopsis thaliana, Zn tolerance in A. halleri may reflect the constitutively higher MTP1 expression compared with A. thaliana, based on copy number expansion and different cis regulation. Three MTP1 promoters were characterized in A. halleri ecotype I16. The comparison with the A. thaliana MTP1 promoter revealed different expression profiles correlated with specific cis-acting regulatory elements. The MTP1 5' untranslated region, highly conserved among A. thaliana, Arabidopsis lyrata and A. halleri, contains a dimer of MYB-binding motifs in the A. halleri promoters absent in the A. thaliana and A. lyrata sequences. Site-directed mutagenesis of these motifs revealed their role for expression in trichomes. A. thaliana mtp1 transgenic lines expressing AtMTP1 controlled by the native A. halleri promoter were more Zn-tolerant than lines carrying mutations on MYB-binding motifs. Differences in Zn tolerance were associated with different distribution of Zn among plant organs and in trichomes. The different cis-acting elements in the MTP1 promoters of A. halleri, particularly the MYB-binding sites, are probably involved in the evolution of Zn tolerance.
在超积累植物遏蓝菜中，锌（Zn）液泡转运蛋白MTP1是超耐受性的关键组成部分。由于遏蓝菜和拟南芥之间的蛋白质序列和功能高度保守，基于拷贝数扩增和不同的顺式调控，遏蓝菜中的锌耐受性可能反映出其MTP1表达量相比拟南芥持续更高。对遏蓝菜生态型I16中的三个MTP1启动子进行了表征。与拟南芥MTP1启动子的比较揭示了与特定顺式作用调控元件相关的不同表达谱。MTP1 5'非翻译区在拟南芥、琴叶拟南芥和遏蓝菜中高度保守，在遏蓝菜启动子中含有一个MYB结合基序二聚体，而在拟南芥和琴叶拟南芥序列中不存在。对这些基序进行定点诱变揭示了它们在毛状体中表达的作用。由遏蓝菜天然启动子控制表达AtMTP1的拟南芥mtp1转基因系比携带MYB结合基序突变的系更耐锌。锌耐受性的差异与锌在植物器官和毛状体中的不同分布有关。遏蓝菜MTP1启动子中不同的顺式作用元件，特别是MYB结合位点，可能参与了锌耐受性的进化。
