Type 1 Metallothionein (ZjMT) Is Responsible for Heavy Metal Tolerance in Ziziphus jujuba.
Metallothioneins (MTs) are a family of low molecular weight, cysteine-rich, metal-binding proteins that are able to make cells to uptake heavy metals from the environment. Molecular and functional characterization of this gene family improves understanding of the mechanisms underlying heavy metal tolerance in higher organisms. In this study, a cDNA clone, encoding 74-a.a. metallothionein type 1 protein (ZjMT), was isolated from the cDNA library of Ziziphus jujuba. At the N- and C-terminals of the deduced amino acid sequence of ZjMT, six cysteine residues were arranged in a CXCXXXCXCXXXCXC and CXCXXXCXCXXCXC structure, respectively, indicating that ZjMT is a type 1 MT. Quantitative PCR analysis of plants subjected to cadmium stress showed enhanced expression of ZjMT gene in Z. jujuba within 24 h upon Cd exposure. Escherichia coli cells expressing ZjMT exhibited enhanced metal tolerance and higher accumulation of metal ions compared with control cells. The results indicate that ZjMT contributes to the detoxification of metal ions and provides marked tolerance against metal stresses. Therefore, ZjMT may be a potential candidate for tolerance enhancement in vulnerable plants to heavy metal stress and E. coli cells containing the ZjMT gene may be applied to adsorb heavy metals in polluted wastewater.
College of Chemistry and Chemical Engineering, Taiyuan University of Technology, 030024 Taiyuan, China. liuxuguang@tyut.edu.cn.
Lan-Song
LS
Li
Yu-Ping
YP
Meng
Qiu-Fen
QF
Cao
Yong-Zhen
YZ
Yang
Fan
F
Wang
Hu-Sheng
HS
Jia
Shu-Biao
SB
Wu
Xu-Guang
XG
Liu
D000595:Amino Acid Sequence; D002104:Cadmium / Q000378:metabolism / Q000633:toxicity; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019216:Metals, Heavy / Q000378:metabolism* / Q000633:toxicity; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D016415:Sequence Alignment; D031957:Ziziphus / Q000187:drug effects / Q000378:metabolism*
D018076:DNA, Complementary; D019216:Metals, Heavy; D011993:Recombinant Fusion Proteins; D002104:Cadmium; D008668:Metallothionein