title: Cucumber Metallothionein-Like 2 (CsMTL2) Exhibits Metal-Binding Properties.
abstract: We identified a novel member of the metallothionein (MT) family,Cucumis sativusmetallothionein-like 2 (CsMTL2), by screening a young cucumber fruit complementary DNA (cDNA) library. TheCsMTL2encodes a putative 77-amino acid Class II MT protein that contains two cysteine (Cys)-rich domains separated by a Cys-free spacer region. We found thatCsMTL2expression was regulated by metal stress and was specifically induced by Cd2+treatment. We investigated the metal-binding characteristics of CsMTL2 and its possible role in the homeostasis and/or detoxification of metals by heterologous overexpression inEscherichia colicells. Furthermore, we produced a deletion mutant form of the protein, CsMTL2m, that contained the two Cys-rich clusters but lacked the spacer region, inE. coli. We compared the metal-binding properties of CsMTL2 with those of CsMTL2m, the β domain of human metallothionein-like protein 1 (HsMTXb), and phytochelatin-like (PCL) heterologously expressed inE. coliusing metal-binding assays. We found thatE. colicells expressingCsMTL2accumulated the highest levels of Zn2+and Cd2+of the four transformed cell types, with levels being significantly higher than those of control cells containing empty vector.E. colicells expressing CsMTL2 had a higher tolerance for cadmium than for zinc ions. These findings show that CsMTL2 improves metal tolerance when heterologously expressed inE. coli. Future studies should examine whether CsMTL2 improves metal tolerance in planta.
authors.affiliation: Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China. yu.pan82@yahoo.com.
authors.forename: Yu
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China. pyl77111@163.com.
authors.forename: Yanglu
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China. pgu3456@163.com.|Qijiang District Bureau of Forestry, Chongqing 401420, China. pgu3456@163.com.
authors.forename: Junpeng
authors.initials: J
authors.lastname: Zhai
authors.affiliation: Institute of Vegetables and Flowers, Chongqing Academy of Agricultural Sciences, Chongqing 401329, China. xiongyan7788@126.com.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiong
authors.affiliation: Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China. ljh502@swu.edu.cn.
authors.forename: Jinhua
authors.initials: J
authors.lastname: Li
authors.affiliation: Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China. duxb163@163.com.
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Du
authors.affiliation: Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China. suchenggang@swu.edu.cn.
authors.forename: Chenggang
authors.initials: C
authors.lastname: Su
authors.affiliation: Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China. Zhangdupian@swu.edu.cn.
authors.forename: Xingguo
authors.initials: X
authors.lastname: Zhang
keywords: CsMTL2; cucumber; metal-binding properties; metallothionein