title: Functional characterization of a csoR-cueA divergon in Bradyrhizobium liaoningense CCNWSX0360, involved in copper, zinc and cadmium cotolerance.
abstract: Random mutagenesis in a symbiotic nitrogen-fixing Bradyrhizobium liaoningense CCNWSX0360 (Bln0360) using Tn5 identified five copper (Cu) resistance-related genes. They were functionally sorted into three groups: transmembrane transport (cueA and tolC); oxidation (copA); and protection of the membrane barrier (lptE and ctpA). The gene cueA, together with the upstream csoR (Cu-sensitive operon repressor), constituted a csoR-cueA divergon which plays a crucial role in Cu homeostasis. Deletion of cueA decreased the Cu tolerance of cells, and complementation of this mutant restored comparable Cu resistance to that of the wild-type. Transcriptional and fusion expression analysis demonstrated that csoR-cueA divergon was up-regulated by both the monovalent Cu+and divalent Zn2+/Cd2+, and negatively regulated by transcriptional repressor CsoR, via a bidirectional promoter. Deletion of csoR renders the cell hyper-resistant to Cu, Zn and Cd. Although predicted to encode a Cu transporting P-type ATPase (CueA), cueA also conferred resistance to zinc and cadmium; two putative N-MBDs (N-terminal metal binding domains) of CueA were required for the Cu/Zn/Cd tolerance. Moreover, cueA is needed for nodulation competitiveness of B. liaoningense in Cu rich conditions. Together, the results demonstrated a crucial role for the csoR-cueA divergon as a component of the multiple-metal resistance machinery in B. liaoningense.
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Mingzhe
authors.initials: M
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Mingmei
authors.initials: M
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Zhefei
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Xihui
authors.initials: X
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Minxia
authors.initials: M
authors.lastname: Chou
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Gehong
authors.initials: G
authors.lastname: Wei
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020369:Bradyrhizobium / Q000187:drug effects* / Q000235:genetics; D002104:Cadmium / Q000378:metabolism*; D003300:Copper / Q000378:metabolism*; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial; D017353:Gene Deletion; D020869:Gene Expression Profiling; D005816:Genetic Complementation Test; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D016254:Mutagenesis, Insertional; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D026901:Membrane Transport Proteins; D012097:Repressor Proteins; D002104:Cadmium; D003300:Copper; D015032:Zinc