EUNIS Habitat Classification: Expert system, characteristic species combinations and distribution maps of European habitats

Aim: The EUNIS Habitat Classification is a widely used reference framework for European habitat types (habitats), but it lacks formal definitions of individual habitats that would enable their unequivocal identification. Our goal was to develop a tool for assigning vegetation‐plot records to the habitats of the EUNIS system, use it to classify a European vegetation‐plot database, and compile statistically‐derived characteristic species combinations and distribution maps for these habitats. Location: Europe. Methods: We developed the classification expert system EUNIS‐ESy, which contains definitions of individual EUNIS habitats based on their species composition and geographic location. Each habitat was formally defined as a formula in a computer language combining algebraic and set‐theoretic concepts with formal logical operators. We applied this expert system to classify 1,261,373 vegetation plots from the European Vegetation Archive (EVA) and other databases. Then we determined diagnostic, constant and dominant species for each habitat by calculating species‐to‐habitat fidelity and constancy (occurrence frequency) in the classified data set. Finally, we mapped the plot locations for each habitat. Results: Formal definitions were developed for 199 habitats at Level 3 of the EUNIS hierarchy, including 25 coastal, 18 wetland, 55 grassland, 43 shrubland, 46 forest and 12 man‐made habitats. The expert system classified 1,125,121 vegetation plots to these habitat groups and 73,188 to other habitats, while 63,064 plots remained unclassified or were classified to more than one habitat. Data on each habitat were summarized in factsheets containing habitat description, distribution map, corresponding syntaxa and characteristic species combination. Conclusions: EUNIS habitats were characterized for the first time in terms of their species composition and distribution, based on a classification of a European database of vegetation plots using the newly developed electronic expert system EUNIS‐ESy. The data provided and the expert system have considerable potential for future use in European nature conservation planning, monitoring and assessment

Phytochelatins: Sulfur-Containing Metal(loid)-Chelating Ligands in Plants

Phytochelatins (PCs) are small cysteine-rich peptides capable of binding metal(loid)s via SH-groups. Although the biosynthesis of PCs can be induced in vivo by various metal(loid)s, PCs are mainly involved in the detoxification of cadmium and arsenic (III), as well as mercury, zinc, lead, and copper ions, which have high affinities for S-containing ligands. The present review provides a comprehensive account of the recent data on PC biosynthesis, structure, and role in metal(loid) transport and sequestration in the vacuoles of plant cells. A comparative analysis of PC accumulation in hyperaccumulator plants, which accumulate metal(loid)s in their shoots, and in the excluders, which accumulate metal(loid)s in their roots, investigates the question of whether the endogenous PC concentration determines a plant’s tolerance to metal(loid)s. Summarizing the available data, it can be concluded that PCs are not involved in metal(loid) hyperaccumulation machinery, though they play a key role in metal(loid) homeostasis. Unraveling the physiological role of metal(loid)-binding ligands is a fundamental problem of modern molecular biology, plant physiology, ionomics, and toxicology, and is important for the development of technologies used in phytoremediation, biofortification, and phytomining

Translocation of Ni and Zn in Odontarrhena corsica and Noccaea caerulescens:the effects of exogenous histidine and Ni/Zn interactions

Aims: Nickel (Ni) and zinc (Zn) interactions during their uptake and root-to-shoot translocation and the potential role of histidine therein were studied in different populations of the Ni/Zn hyperaccumulator Noccaea caerulescens and the Ni hyperaccumulator Odontarrhena corsica. Methods: The effect of exogenous L-histidine supply on Ni and Zn uptake and translocation in N. caerulescens and O. corsica, and xylem loading in shoot-excised root systems of different N. caerulescens populations, were studied under separate and combined exposure. Results: In O. corsica, Zn inhibited both the translocation and the uptake of Ni, whereas Ni did not significantly affect Zn uptake or translocation. In N. caerulescens, both in intact plants and shoot-excised root systems, Zn usually inhibited the uptake, but not the translocation of Ni, whereas Ni did not affect the uptake, but inhibited the translocation of Zn, though not in two populations with low Zn xylem loading capacity. Exogenous histidine supply did not significantly affect Zn translocation in O. corsica and intact plants of an ultramafic population of N. caerulescens, but enhanced Zn xylem loading in two calamine populations of N. caerulescens and Ni translocation in all of them. Conclusions: High free L-histidine concentrations in roots might promote Ni hyperaccumulation in obligate Ni hyperaccumulators, such as O. corsica, in nature. The high histidine concentration in roots of N. caerulescens, which is primarily a Zn hyperaccumulator, might not only explain its species-wide conserved capacity to hypertranslocate Ni, but may also contribute to its Zn translocation capacity, at least in non-ultramafic populations

Zinc accumulation and distribution over tissues in Noccaea сaerulescens in nature and in hydroponics:a comparison

Aims: Zinc distribution at the tissue level is studied almost exclusively in lab-grown plants. It is essential to establish to what extent the patterns observed in lab-grown plants are corresponding with those in nature. To this end, we compared Zn localization in Noccaea caerulescens growing in its natural environment, a zinc/lead mine tailing, with that in hydroponically grown plants of the same origin. Methods: Zinc concentrations in plants and soil were determined by flame AAS and Zn localization in leaf tissues was studied using Zn indicators Zincon and Zinpyr-1. Results: The mean Zn concentration in plants at the mine tailings was around 15,000 mg/kg DW, which corresponded well with the Zn concentration in the leaves of plants grown at 1600 μM Zn in the nutrient solution. The Zn distribution patterns in leaves of plants sampled from the mine and plants grown in hydroponics were identical. Zn-dependent staining was the most intensive in water-storage epidermal cells, guard cells and vascular bundles, and less intensive in subsidiary and mesophyll cells. Conclusions: Zinc distribution in hydroponically grown plants is representative for plants in nature. Preferential Zn sequestration in leaves, particularly in water-storage epidermal cells, restricts metal accumulation in mesophyll and contributes to Zn hypertolerance

Intra-specific variation in zinc, cadmium and nickel hypertolerance and hyperaccumulation capacities in Noccaea caerulescens

Aims: The study aimed at characterizing the patterns of natural variation in the tolerance and accumulation capacities for zinc (Zn), cadmium (Cd), and nickel (Ni) between and within edaphic ecotypes of the Zn/Cd/Ni hyperaccumulator, Noccaea caerulescens. Methods: Tolerance was assessed in a hydroponic ‘sequential exposure’ test, using the lowest concentration that completely arrested root growth as an end point. Accumulation was measured as the foliar metal concentration after six weeks of growth at 5 µM Zn, 2 µM Cd, or 1 µM Ni. Results: Zn and Cd tolerance were positively correlated, and highest in the calamine ecotype. Ni tolerance was without significant ecotypic variation. The ultramafic ecotype was as Zn-tolerant as the non-metallicolous one, but much more sensitive to Cd. The accumulation capacities for Zn, Cd and Ni were all positively correlated and without significant ecotypic variation. Zn hyperaccumulation capacity was species-wide, but Cd and Ni hyperaccumulation capacities were lacking in four populations (all calamine). Conclusions: There is considerable independent variation among populations regarding their Zn, Cd, and Ni accumulation capacities. This variation is most pronounced within the calamine ecotype, because some populations apparently had adopted an exclusion strategy for Zn or Cd hypertolerance, whereas others had not

Zinc- and nickel-induced changes in fatty acid profiles in the zinc hyperaccumulator Arabidopsis halleri and non-accumulator Arabidopsis lyrata

This pilot study aimed at comparing zinc (Zn) and nickel (Ni) effects on the fatty acid (FA) profiles, oxidative stress and desaturase activity in the Zn hyperaccumulator Arabidopsis halleri and the excluder Arabidopsis lyrata to allow a better picture of the physiological mechanisms which may contribute to metal tolerance or acclimation. The most significant changes in the FA composition were observed in the shoots of the hyperaccumulator and in the roots of the excluder, and were not only metal-dependent, but also species-specific, since the most significant changes in the shoots of A. halleri were observed under Ni treatment, though Ni, in contrast to Zn, was accumulated mainly in its roots. Several FAs appeared in the roots and shoots of A. lyrata only upon metal exposure, whereas they were already found in control A. halleri. In both species, there was an increase in oleic acid under Ni treatment in both organs, whereas in Zn-treated plants the increase was shown only for the shoots. A rare conjugated α-parinaric acid was identified only in the shoots of metal-treated A. halleri. In the shoots of the hyperaccumulator, there was an increase in the content of saturated FAs and a decrease in the content of unsaturated FAs, while in the roots of the excluder, the opposite pattern was observed. These metal-induced changes in FA composition in the shoots of A. halleri can lead to a decrease in the fluidity of membranes, which could diminish the penetration of ROS into the membrane and thus maintain its stability

A toolset to study functions of Cytosolic non-specific dipeptidase 2 (CNDP2) using Drosophila as a model organism

Abstract Background Expression of the CNDP2 gene is frequently up- or down-regulated in different types of human cancers. However, how the product of this gene is involved in cell growth and proliferation is poorly understood. Moreover, our knowledge of the functions of the CNDP2 orthologs in well-established model organisms is scarce. In particular, the function of the D. melanogaster ortholog of CNDP2, encoded by the CG17337 gene (hereafter referred to as dCNDP2), is still unknown. Results This study was aimed at developing a set of genetic and molecular tools to study the roles of dCNDP2. We generated a dCNDP2 null mutation (hereafter ∆dCNDP2) using CRISPR/Cas9-mediated homologous recombination (HR) and found that the ∆dCNDP2 mutants are homozygous viable, morphologically normal and fertile. We also generated transgenic fly lines expressing eGFP-tagged and non-tagged dCNDP2 protein, all under the control of the UAS promoter, as well as polyclonal antibodies specific to dCNDP2. Using these tools, we demonstrate that only one of the two predicted dCNDP2 isoforms is expressed throughout the different tissues tested. dCNDP2 was detected in both the cytoplasm and the nucleus, and was found to be associated with multiple sites in the salivary gland polytene chromosomes. Conclusions The dCNDP2 gene is not essential for fly viability under standard laboratory conditions. The subcellular localization pattern of dCNDP2 suggests that this protein might have roles in both the cytoplasm and the nucleus. The genetic and molecular tools developed in this study will allow further functional characterization of the conserved CNDP2 protein using D. melanogaster as a model system

Transcriptional effects of cadmium on iron homeostasis differ in calamine accessions of Noccaea caerulescens

Calamine accessions of the zinc/cadmium/nickel hyperaccumulator, Noccaea caerulescens, exhibit striking variation in foliar cadmium accumulation in nature. The Ganges accession (GA) from Southern France displays foliar cadmium hyperaccumulation (>1000 μg g−1 DW), whereas the accession La Calamine (LC) from Belgium, with similar local soil metal composition, does not (−1 DW). All calamine accessions are cadmium hypertolerant. To find out the differences between LC and GA in their basic adaptation mechanisms, we bypassed the cadmium excluding phenotype of LC by exposing the plants to 50 μm cadmium in hydroponics, achieving equal cadmium accumulation in the shoots. The iron content increased in the roots of both accessions. GA exhibited significant decreases in manganese and zinc contents in the roots and shoots, approaching those in LC. Altogether 702 genes responded differently to cadmium exposure between the accessions, 157 and 545 in the roots and shoots, respectively. Cadmium-exposed LC showed a stress response and had decreased levels of a wide range of photosynthesis-related transcripts. GA showed less changes, mainly exhibiting an iron deficiency-like response. This included increased expression of genes encoding five iron deficiency-regulated bHLH transcription factors, ferric reduction oxidase FRO2, iron transporters IRT1 and OPT3, and nicotianamine synthase NAS1, and decreased expression of genes encoding ferritins and NEET (a NEET family iron-sulfur protein), which is possibly involved in iron transfer, distribution and/or management. The function of the IRT1 gene in the accessions was compared. We conclude that the major difference between the two accessions is in the way they cope with iron under cadmium exposure.</p