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 non-metalliferous 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.
Extraordinarily 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 μg Zn g−1 DW and 18 μg Cd g−1 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 μg Zn g−1 and 2 μg Cd g−1.
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.
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.
Etiolated growth in darkness or the irreversible transition to photomorphogenesis in the light engages alternative developmental programs operating across all organs of a plant seedling. Dark-grown ...Arabidopsis de-etiolated by zinc (dez) mutants exhibit morphological, cellular, metabolic, and transcriptional characteristics of light-grown seedlings. We identify the causal mutation in TRICHOME BIREFRINGENCE encoding a putative acyl transferase. Pectin acetylation is decreased in dez, as previously found in the reduced wall acetylation2-3 mutant, shown here to phenocopy dez. Moreover, pectin of dez is excessively methylesterified. The addition of very short fragments of homogalacturonan, tri-galacturonate, and tetra-galacturonate, restores skotomorphogenesis in dark-grown dez and similar mutants, suggesting that the mutants are unable to generate these de-methylesterified pectin fragments. In combination with genetic data, we propose a model of spatiotemporally separated photoreceptive and signal-responsive cell types, which contain overlapping subsets of the regulatory network of light-dependent seedling development and communicate via a pectin-derived dark signal.
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•Several cell-wall mutants mimic light-grown seedlings when grown in darkness•Pectin-derived tri- and tetra-galacturonate restore normal dark-specific morphology•Cell-wall signaling allows cell-cell communication in light-dependent development•Accumulation of a plastid-derived oxylipin abolishes biogenesis of the dark signal
Sinclair et al. report that several cell-wall-defective mutants mimic light-grown seedlings when grown in darkness, thus bypassing photoreception and subsequent signaling. Etiolated seedling growth can be restored by adding small fragments of the pectin homogalacturonan, suggesting their function as a dark signal in cell-cell communication.
Nanotechnology is the new industrial revolution of our century. Its development leads to an increasing use of nanoparticles and thus to their dissemination. Their fate in the environment is of great ...concern and especially their possible transfer in trophic chains might be an issue for food safety. However, so far our knowledge on this topic has been restricted by the lack of appropriate techniques to characterize their behavior in complex matrices. Here, we present in detail the use of cutting-edge beam-based techniques for nanoparticle in situ localization, quantification and speciation in a crop plant species (Lactuca sativa). Lettuce seedlings have been exposed to TiO2 and Ag nanoparticles and analyzed by inductively coupled plasma spectrometry, micro-particle induced X-ray emission coupled to Rutherford backscattering spectroscopy on nuclear microprobe, micro-X-ray fluorescence spectroscopy and X-ray absorption near edge structure spectroscopy. The benefits and drawbacks of each technique are discussed, and the types of information that can be drawn, for example on the translocation to edible parts, change of speciation within the plant, detoxification mechanisms, or impact on the plant ionome, are highlighted. Such type of coupled approach would be an asset for nanoparticle risk assessment.
•NP fate in plants was investigated by an original combination of techniques.•NPs were translocated to the shoot with different oxidation states for Ag.•Exposure to Ag-NPs and high concentration of TiO2-NPs strongly altered root ionome.•XANES results suggest that Ag-NPs can be internalized in root both as ions and as NP.•Combining micro-spectroscopy and statistics was essential to obtain these results.
Iron is essential to plants. However, when free and in excess, iron can catalyze the formation of oxygen free radicals. Ferritin, a protein capable of storing up to 4500 atoms of iron, can act as an ...iron buffer inside plant cells. Using a strategy based in amplicon size difference, we were able to analyze the expression profile of the two rice ferritin genes (
OsFER1 and
OsFER2). Both genes are expressed, although with different regulation and organ distribution. Exposure to copper, Paraquat, SNP and excess iron led to accumulation of ferritin mRNA, remarkably of
OsFER2. The iron-induced expression was abolished by treatment with GSH, indicating that the induction observed is dependent of an oxidative step.
OsFER2 mRNA levels in rice flag leaves and panicles at different reproductive stages were higher than
OsFER1 mRNA levels. No ferritin mRNA was detected in rice seeds. However, imbibition under light led to ferritin expression, which was abolished when seeds were kept in the dark, suggesting a light-regulated induction. Ferritin mRNA accumulation was seen in the dark only when seeds were germinated in the presence of externally supplied iron. We suggest that the primary role of rice ferritins is related to defense against iron-mediated oxidative stress.
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