Summary Leaf mineral composition, the leaf ionome, reflects the complex interaction between a plant and its environment including local soil composition, an influential factor that can limit species distribution and plant productivity. Here we addressed within‐species variation in plant–soil interactions and edaphic adaptation using Arabidopsis halleri, a well‐suited model species as a facultative metallophyte and metal hyperaccumulator.We conducted multi‐element analysis of 1972 paired leaf and soil samples from 165 European populations of A. halleri, at individual resolution to accommodate soil heterogeneity. Results were further confirmed under standardized conditions upon cultivation of 105 field‐collected genotypes on an artificially metal‐contaminated soil in growth chamber experiments.Soil‐independent between‐ and within‐population variation set apart leaf accumulation of zinc, cadmium and lead from all other nutrient and nonessential elements, concurring with differential hypothesized ecological roles in either biotic interaction or nutrition. For these metals, soil–leaf relationships were element‐specific, differed between metalliferous and nonmetalliferous soils and were geographically structured both in the field and under standardized growth conditions, implicating complex scenarios of recent ecological adaptation.Our study provides an example and a reference for future related work and will serve as a basis for the molecular–genetic dissection and ecological analysis of the observed phenotypic variation.

Iron (Fe) is an essential plant micronutrient, and its deficiency limits plant growth and development on alkaline soils. Under Fe deficiency, plant responses include up-regulation of genes involved in Fe uptake from the soil. However, little is known about shoot responses to Fe deficiency. Using microarrays to probe gene expression in Kas-1 and Tsu-1 ecotypes of Arabidopsis thaliana, and comparison with existing Col-0 data, revealed conserved rosette gene expression responses to Fe deficiency. Fe-regulated genes included known metal homeostasis-related genes, and a number of genes of unknown function. Several genes responded to Fe deficiency in both roots and rosettes. Fe deficiency led to up-regulation of Cu,Zn superoxide dismutase (SOD) genes CSD1 and CSD2, and down-regulation of FeSOD genes FSD1 and FSD2. Eight microRNAs were found to respond to Fe deficiency. Three of these (miR397a, miR398a, and miR398b/c) are known to regulate transcripts of Cu-containing proteins, and were down-regulated by Fe deficiency, suggesting that they could be involved in plant adaptation to Fe limitation. Indeed, Fe deficiency led to accumulation of Cu in rosettes, prior to any detectable decrease in Fe concentration. ccs1 mutants that lack functional Cu,ZnSOD proteins were prone to greater oxidative stress under Fe deficiency, indicating that increased Cu concentration under Fe limitation has an important role in oxidative stress prevention. The present results show that Cu accumulation, microRNA regulation, and associated differential expression of Fe and CuSOD genes are coordinated responses to Fe limitation.

SummaryExtraordinarily high leaf metal concentrations in metal hyperaccumulator plants may serve as an elemental defence against herbivores. However, mixed results have been reported and studies using comparative approaches are missing.We investigated the deterrent and toxic potential of metals employing the hyperaccumulator Arabidopsis halleri. Effects of zinc (Zn) and cadmium (Cd) on the preferences of three Brassicaceae specialists were tested in paired-choice experiments using differently treated plant material, including transgenic plants. In performance tests, we determined the toxicity and joint effects of both metals incorporated in an artificial diet on the survival of a generalist.Feeding by all specialists was significantly reduced by metal concentrations from above 1000 lg Zn g À1 DW and 18 lg Cd g À1 DW. By contrast, metals did not affect oviposition.Generalist survival decreased with increasing concentrations of individual metals, whereby the combination of Zn and Cd had an additive toxic effect even at the lowest applied concentrations of 100 lg Zn g À1 and 2 lg Cd g À1 . Metal hyperaccumulation protects plants from herbivory resulting from deterrence and toxicity against a wide range of herbivores. The combination of metals exacerbates toxicity through joint effects and enhances elemental defence. Thus, metal hyperaccumulation is ecologically beneficial for plants.

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Iron is essential for plants. However, excess iron is toxic, leading to oxidative stress and decreased productivity. Therefore, plants must use finely tuned mechanisms to keep iron homeostasis in each of their organs, tissues, cells and organelles. A few of the genes involved in iron homeostasis in plants have been identified recently, and we used some of their protein sequences as queries to look for corresponding genes in the rice (Oryza sativa) genome. We have assigned possible functions to thirty-nine new rice genes. Together with four previously reported sequences, we analyzed a total of forty-three genes belonging to five known protein families: eighteen YS (Yellow Stripe), two FRO (Fe 3+ -chelate reductase oxidase), thirteen ZIP (Zinc regulated transporter / Iron regulated transporter Protein), eight NRAMP (Natural Resistance -Associated Macrophage Protein), and two Ferritin proteins. The possible cellular localization and number of potential transmembrane domains were evaluated, and phylogenetic analysis performed for each gene family. Annotation of genomic sequences was performed. The presence and number of homologues in each gene family in rice and Arabidopsis is discussed in light of the established iron acquisition strategies used by each one of these two plants.