title: Bean metal-responsive element-binding transcription factor confers cadmium resistance in tobacco.
abstract: Cadmium (Cd) is highly toxic to plants. Modulation of Cd-responsive transcription is an important way for Cd detoxification in plants. Metal-responsive element (MRE) is originally described in animal metallothionein genes. Although functional MREs also exist in Cd-regulated plant genes, specific transcription factors that bind MRE to regulate Cd tolerance have not been identified. Previously, we showed that Cd-inducible bean (Phaseolus vulgaris) stress-related gene2 (PvSR2) produces a short (S) PvSR2 transcript (S-PvSR2) driven by an intronic promoter. Here, we demonstrate that S-PvSR2 encodes a bean MRE-binding transcription factor1 (PvMTF-1) that confers Cd tolerance in tobacco (Nicotiana tabacum). PvMTF-1 expression was up-regulated by Cd at the levels of RNA and protein. Importantly, expression of PvMTF-1 in tobacco enhanced Cd tolerance, indicating its role in regulating Cd resistance in planta. This was achieved through direct regulation of a feedback-insensitive Anthranilate Synthase α-2 chain gene (ASA2), which catalyzes the first step for tryptophan biosynthesis. In vitro and in vivo DNA-protein interaction studies further revealed that PvMTF-1 directly binds to the MRE in the ASA2 promoter, and this binding depends on the zinc finger-like motif of PvMTF-1. Through modulating ASA2 up-regulation by Cd, PvMTF-1 increased free tryptophan level and subsequently reduced Cd accumulation, thereby enhancing Cd tolerance of transgenic tobacco plants. Consistent with this observation, tobacco transiently overexpressing ASA2 also exhibited increased tolerance to Cd. We conclude that PvMTF-1 is a zinc finger-like transcription factor that links MRE to Cd resistance in transgenic tobacco through activation of tryptophan biosynthesis.
authors.affiliation: College of Life Science, Capital Normal University, Beijing 100048, China.
authors.forename: Na
authors.initials: N
authors.lastname: Sun
authors.affiliation: College of Life Science, Capital Normal University, Beijing 100048, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Liu
authors.affiliation: College of Life Science, Capital Normal University, Beijing 100048, China.
authors.forename: Wentao
authors.initials: W
authors.lastname: Zhang
authors.affiliation: College of Life Science, Capital Normal University, Beijing 100048, China.
authors.forename: Wanning
authors.initials: W
authors.lastname: Yang
authors.affiliation: College of Life Science, Capital Normal University, Beijing 100048, China.
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Bei
authors.affiliation: College of Life Science, Capital Normal University, Beijing 100048, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Ma
authors.affiliation: College of Life Science, Capital Normal University, Beijing 100048, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Qiao
authors.affiliation: College of Life Science, Capital Normal University, Beijing 100048, China qixiaoting@cnu.edu.cn.
authors.forename: Xiaoting
authors.initials: X
authors.lastname: Qi
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D001483:Base Sequence; D002104:Cadmium / Q000633:toxicity*; D047369:Chromatin Immunoprecipitation; D003001:Cloning, Molecular; D003080:Cold Temperature; D017343:Genes, Plant; D008969:Molecular Sequence Data; D027805:Phaseolus / Q000187:drug effects / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D026723:Polyadenylation / Q000187:drug effects; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D036226:Seedlings / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014364:Tryptophan / Q000096:biosynthesis; D015854:Up-Regulation / Q000187:drug effects; D016335:Zinc Fingers
chemical_list: D010940:Plant Proteins; D020033:Protein Isoforms; D015534:Trans-Activators; D014157:Transcription Factors; D002104:Cadmium; D014364:Tryptophan