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See detailTowards the identification of cis-elements responsible for the high expression of HMA4, an essential gene for Zn hyperaccumulation in Arabidopsis halleri.
Spielmann, Julien ULg; Nouet, Cécile ULg; Scheepers, Maxime ULg et al

Conference (2015, June 26)

A. halleri is a Zn and Cd hypertolerant and hyperaccumulator plant which stores metals in shoot vacuoles. One key step for hyperaccumulation is a highly efficient root-to-shoot translocation of metals ... [more ▼]

A. halleri is a Zn and Cd hypertolerant and hyperaccumulator plant which stores metals in shoot vacuoles. One key step for hyperaccumulation is a highly efficient root-to-shoot translocation of metals. The Zn/Cd plasmamembrane pump HMA4 (heavy metal ATPase 4) plays a central role in this process and is involved in xylem loading/unloading. Moreover, HMA4 is overexpressed in A. halleri compare to its non-tolerant and non-hyperaccumulator sister, Arabidopsis thaliana. The HMA4 overexpression is determined by a combination of gene triplication and cis-regulatory changes increasing transcription levels of each three HMA4 copies. In this study, we are focusing on the two most active HMA4 promoters and we aim to identify the cis-elements underlying high expression of HMA4 in A. halleri using promoter-reporter constructs. Through deletion analysis, two important regions for a high expression have been identified. Ongoing analysis of more detailed deletions will be presented. [less ▲]

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See detailTowards the identification of mechanisms underlying the high expression of HMA4, an essential gene for zinc hyperaccumulation in Arabidopsis halleri.
Spielmann, Julien ULg; Nouet, Cécile ULg; Scheepers, Maxime ULg et al

Poster (2015, June 08)

To maintain metal homeostasis within physiological limits independently of metal concentrations present in soil, plants developed a complex network including metal uptake, chelation, trafficking, and ... [more ▼]

To maintain metal homeostasis within physiological limits independently of metal concentrations present in soil, plants developed a complex network including metal uptake, chelation, trafficking, and storage processes. In this network, transporters have a central role. To study the molecular basis of zinc homeostasis in plants, we are using A. halleri, a zinc- and cadmium-tolerant and zinc-hyperaccumulating species representing the extreme end of natural variation in terms of metal homeostasis. Indeed, A. halleri stores high amount of metals in vacuoles of above-ground tissues (>1% Zn or 0.01% Cd in shoot dry weight). Cross-species transcriptomic studies identified about thirty genes which are constitutively over-expressed in A. halleri compared to its non-tolerant and non-hyperaccumulator sister species, Arabidopsis thaliana (1-3). HMA4 is one of these genes. It encodes a Zn/Cd plasmamembrane pump involved in xylem loading/unloading which is a key step in the hyperaccumulation process (4-5). The HMA4 overexpression is determined by a combination of gene triplication and cis-regulatory changes increasing transcription levels of each three HMA4 copies (5). We aim to identify the cis-elements underlying high expression of HMA4 in A. halleri using promoter-reporter constructs. [less ▲]

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See detailTowards the identification of cis-elements responsible for the high expression of HMA4, an essential gene for zinc hyperaccumulation in Arabidopsis halleri.
Spielmann, Julien ULg; Nouet, Cécile ULg; Scheepers, Maxime ULg et al

Poster (2015, May 13)

A. halleri is a Zn and Cd hypertolerant and hyperaccumulator plant which stores metals in shoot vacuoles. One key step for hyperaccumulation is a highly efficient root-to-shoot translocation of metals ... [more ▼]

A. halleri is a Zn and Cd hypertolerant and hyperaccumulator plant which stores metals in shoot vacuoles. One key step for hyperaccumulation is a highly efficient root-to-shoot translocation of metals. The Zn/Cd plasmamembrane pump HMA4 (heavy metal ATPase 4) plays a central role in this process and is involved in xylem loading/unloading. Moreover, HMA4 is overexpressed in A. halleri compare to its non-tolerant and non-hyperaccumulator sister, Arabidopsis thaliana. The HMA4 overexpression is determined by a combination of gene triplication and cis-regulatory changes increasing transcription levels of each three HMA4 copies. In this study, we are focusing on the two most active HMA4 promoters and we aim to identify the cis-elements underlying high expression of HMA4 in A. halleri using promoter-reporter constructs. Through deletion analysis, two important regions for a high expression have been identified. Ongoing analysis of more detailed deletions will be presented. [less ▲]

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See detailZinc triggers a complex transcriptional and post-transcriptional regulation of the metal homeostasis gene FRD3 in Arabidopsis relatives
Charlier, Jean_Benoit; Polese, Catherine; Nouet, Cécile ULg et al

in Journal of Experimental Botany (2015)

In Arabidopsis thaliana, FRD3 (Ferric Chelate Reductase Defective 3) plays a central role in metal homeostasis. FRD3 is among a set of metal homeostasis genes that are constitutively highly expressed in ... [more ▼]

In Arabidopsis thaliana, FRD3 (Ferric Chelate Reductase Defective 3) plays a central role in metal homeostasis. FRD3 is among a set of metal homeostasis genes that are constitutively highly expressed in roots and shoots of Arabidopsis halleri, a zinc hyperaccumulating and hypertolerant species. Here, we examined the regulation of FRD3 by zinc in both species to shed light on the evolutionary processes underlying the evolution of hyperaccumulation in A. halleri. We combined gene expression studies with the use of GUS and GFP reporter constructs to compare the expression profile, transcriptional and post-transcriptional regulation of FRD3 in both species. The AtFRD3 and AhFRD3 genes display a conserved expression profile. In A. thaliana, alternative transcription initiation sites from two promoters determine transcript variants which are differentially regulated by zinc supply in roots and shoots to favour the most highly translated variant under zinc excess conditions. In A. halleri, a single transcript variant with higher transcript stability and enhanced translation has been maintained. The FRD3 gene thus undergoes complex transcriptional and post-transcriptional regulation in Arabidopsis relatives. Our study reveals that a diverse set of mechanisms underlie increased gene dosage in the A. halleri lineage and illustrates how an environmental challenge can alter gene regulation. [less ▲]

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See detailComplex regulation of the FRD3 gene in Arabidopsis relatives
Charlier, Jean Benoit; Polese, Catherine ULg; Nouet, Cécile ULg et al

Poster (2014, March 31)

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See detailComplex regulation of the FRD3 gene in Arabidopsis relatives
Charlier, Jean-Benoit ULg; Polese, Catherine ULg; Nouet, Cécile ULg et al

Poster (2013, February 26)

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See detailHard Selective Sweep and Ectopic Gene Conversion in a Gene Cluster Affording Environmental Adaptation
Hanikenne, Marc ULg; Kroymann, Juergen; Trampczynska, Aleksandra et al

in PLoS Genetics (2013), 9

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See detailPromoter analysis of three HMA4 gene copies in the zinc hyperaccumulator Arabidopsis halleri
Nouet, Cécile ULg; Cebula, Justyna; Motte, Patrick ULg et al

Poster (2012, September 20)

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See detailZinc hyperaccumulation: a model to examine metal homeostasis in plants
Hanikenne, Marc ULg; Nouet, Cécile ULg; Charlier, Jean-Benoit et al

Conference (2012, September 20)

The plant Arabidopsis halleri exhibits naturally selected metal hypertolerance and extraordinarily high levels of leaf metal accumulation. Metal hyperaccumulator species attract interest as they represent ... [more ▼]

The plant Arabidopsis halleri exhibits naturally selected metal hypertolerance and extraordinarily high levels of leaf metal accumulation. Metal hyperaccumulator species attract interest as they represent an extreme end of natural variation of the metal homeostasis network. This might be useful to reveal the global functioning of metal homeostasis networks and uncover key nodes whose alterations can drastically modify metal accumulation and tolerance. In addition, metal hyperaccumulation is a compelling model to study adaptation. In the last few years, major progress has been achieved in our understanding of the mechanisms underlying metal hyperaccumulation in A. halleri. High rates of metal uptake by roots, root-to-shoot translocation and efficient shoot vacuolar sequestration play central roles in determining hyperaccumulation and hypertolerance. Enhanced functions of several metal transporter-encoding genes result from gene copy number amplification and/or (cis)-regulatory changes. We will describe the function of several transporters in zinc and cadmium hyperaccumulation and hypertolerance, and in the adjustment of nutrient homeostasis in A. halleri. Recent work aiming to determine if selection acted during the evolutionary history of A. halleri on a loci required for metal tolerance and accumulation will be presented. [less ▲]

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See detailEvolution of Metal Hyperaccumulation in Arabidopsis halleri
Hanikenne, Marc ULg; Kroymann, Juergen; Bernal, Maria et al

Conference (2012, February 06)

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See detailMetal response of transgenic tomato plants expressing P1B-ATPase
Barabasz, Anna; Wilkowska, Anna; Ruszczyńska, Anna et al

in Physiologia Plantarum (2012), 145

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See detailPromoter analysis of the three HMA4 copies in the zinc hyperaccumulator Arabidopsis halleri
Nouet, Cécile ULg; Cebula, Justyna; Motte, Patrick ULg et al

Poster (2011, August)

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See detailExpression of the metal homeostasis gene FRD3 in two Arabidopsis species
Charlier, Jean-Benoît ULg; Polese, Catherine ULg; Krämer, Ute et al

Poster (2011, August)

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See detailMetal accumulation in tobacco expressing Arabidopsis halleri metal hyperaccumulation gene depends on external supply.
Barabasz, Anna; Krämer, Ute; Hanikenne, Marc ULg et al

in Journal of Experimental Botany (2010), 61(11), 3057-67

Engineering enhanced transport of zinc to the aerial parts of plants is a major goal in bio-fortification. In Arabidopsis halleri, high constitutive expression of the AhHMA4 gene encoding a metal pump of ... [more ▼]

Engineering enhanced transport of zinc to the aerial parts of plants is a major goal in bio-fortification. In Arabidopsis halleri, high constitutive expression of the AhHMA4 gene encoding a metal pump of the P(1B)-ATPase family is necessary for both Zn hyperaccumulation and the full extent of Zn and Cd hypertolerance that are characteristic of this species. In this study, an AhHMA4 cDNA was introduced into N. tabacum var. Xanthi for expression under the control of its endogenous A. halleri promoter known to confer high and cell-type specific expression levels in both A. halleri and the non-hyperaccumulator A. thaliana. The transgene was expressed at similar levels in both roots and shoots upon long-term exposure to low Zn, control, and increased Zn concentrations. A down-regulation of AhHMA4 transcript levels was detected with 10 muM Zn resupply to tobacco plants cultivated in low Zn concentrations. In general, a transcriptional regulation of AhHMA4 in tobacco contrasted with the constitutively high expression previously observed in A. halleri. Differences in root/shoot partitioning of Zn and Cd between transgenic lines and the wild type were strongly dependent on metal concentrations in the hydroponic medium. Under low Zn conditions, an increased Zn accumulation in the upper leaves in the AhHMA4-expressing lines was detected. Moreover, transgenic plants exposed to cadmium accumulated less metal than the wild type. Both modifications of zinc and cadmium accumulation are noteworthy outcomes from the biofortification perspective and healthy food production. Expression of AhHMA4 may be useful in crops grown on soils poor in Zn. [less ▲]

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See detailEvolution of metal hyperaccumulation in Arabidopsis halleri
Hanikenne, Marc ULg; Kroymann, Juergen; Talke, Ina N. et al

Conference (2009, March 04)

Detailed reference viewed: 45 (3 ULg)