Arabidopsis CNGC Family Members Contribute to Heavy Metal Ion Uptake in Plants

Heavy metal ions, including toxic concentrations of essential ions, negatively affect diverse metabolic and cellular processes. Heavy metal ions are known to enter cells in a non-selective manner; however, few studies have examined the regulation of heavy metal ion transport. Plant cyclic nucleotide-gated channels (CNGCs), a type of Ca(2+)-permeable-channel, have been suggested to be involved in the uptake of both essential and toxic cations. To determine the candidates responsible for heavy metal ion transport, a series of Arabidopsis CNGC mutants were examined for their response to Pb(2+) and Cd(2+) ions. The primary focus was on root growth and the analysis of the concentration of heavy metals in plants. Results, based on the analysis of primary root length, indicated that AtCNGC1, AtCNGC10, AtCNGC13 and AtCNGC19 play roles in Pb(2+) toxicity, while AtCNGC11, AtCNGC13, AtCNGC16 and AtCNGC20 function in Cd(2+) toxicity in Arabidopsis. Ion content analysis verified that the mutations of AtCNGC1 and AtCNGC13 resulted in reduced Pb(2+) accumulation, while the mutations of AtCNGC11, AtCNGC15 and AtCNGC19 resulted in less Pb(2+) and Cd(2+) accumulation in plants. These findings provide functional evidence which support the roles of these AtCNGCs in the uptake and transport of Pb(2+) or Cd(2+) ion in plants.