The X-ray fluorescence screening of multiple elements in herbarium specimens from the Neotropical region reveals new records of metal accumulation in plants.

Plants have developed a diversity of strategies to take up and store essential metals in order to colonize various types of soils including mineralized soils. Yet, our knowledge of the capacity of plant species to accumulate metals is still fragmentary across the plant kingdom. In this study, we have used the X-ray fluorescence technology to analyze metal concentration in a wide diversity of species of the Neotropical flora that was not extensively investigated so far. In total, we screened more than 11 000 specimens representing about 5000 species from herbaria in Paris and Cuba. Our study provides a large overview of the accumulation of metals such as manganese, zinc, and nickel in the Neotropical flora. We report 30 new nickel hyperaccumulating species from Cuba, including the first records in the families Connaraceae, Melastomataceae, Polygonaceae, Santalaceae, and Urticaceae. We also identified the first species from this region of the world that can be considered as manganese hyperaccumulators in the genera Lomatia (Proteaceae), Calycogonium (Melastomataceae), Ilex (Aquifoliaceae), Morella (Myricaceae), and Pimenta (Myrtaceae). Finally, we report the first zinc hyperaccumulator, Rinorea multivenosa (Violaceae), from the Amazonas region. The identification of species able to accumulate high amounts of metals will become instrumental to support the development of phytotechnologies in order to limit the impact of soil metal pollution in this region of the world.

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 Ca2+-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 Pb2+ and Cd2+ 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 Pb2+ toxicity, while AtCNGC11, AtCNGC13, AtCNGC16 and AtCNGC20 function in Cd2+ toxicity in Arabidopsis. Ion content analysis verified that the mutations of AtCNGC1 and AtCNGC13 resulted in reduced Pb2+ accumulation, while the mutations of AtCNGC11, AtCNGC15 and AtCNGC19 resulted in less Pb2+ and Cd2+ accumulation in plants. These findings provide functional evidence which support the roles of these AtCNGCs in the uptake and transport of Pb2+ or Cd2+ ion in plants.