Les peroxydases végétales de classe III

Copper is both a nutrient and an environmental toxin that is taken up by plants. In order to determine the subcellular localization of copper and to assess the resulting metabolic changes, we exposed 14-day-old bean seedlings to nutrient solutions containing varying concentrations of Cu(2+) ions for 3 days. Biochemical analyses revealed that the cell wall was the major site of Cu(2+) accumulation in the leaves of treated plants. Excess copper modified the activity of lignifying peroxidases in both soluble and ionic cell wall-bound fraction. The activity of ionic GPX (guaiacol peroxidase, EC 1.11.1.7) was increased by 50 and 75 µM CuSO₄. The activities of both ionic CAPX (coniferyl alcohol peroxidase, EC 1.11.1.4) and NADH oxidase were increased by both copper concentrations tested. While soluble CAPX activity decreased in leaves treated by all copper concentrations tested, the activity of soluble NADH oxidase remained unchanged at 50 µM and was enhanced at 75 µM. Treatment with CuSO₄ also increased the abundance of total phenol compounds and induced stimulation in the activity of PAL (phenylalanine ammonia lyase, EC. 4.3.1.5). Using histochemistry in combination with fluorescence microscopy we show that bean leaves from copper-exposed plants displayed biochemical and structural modifications reinforcing the cell walls of their xylem tissues. On the other hand, the perivascular fiber sclerenchyma appeared to be less developed in treated leaves.

Section: Introductionmentioning

confidence: 99%

Cell Wall Accumulation of Cu Ions and Modulation of Lignifying Enzymes in Primary Leaves of Bean Seedlings Exposed to Excess Copper

Bouazizi¹,

Jouili²,

Geitmann

et al. 2010

“…It has been suggested that the polymerization of monolignols to lignin is mediated by the interaction of two types of peroxidases: nicotinamide adenine dinucleotide (NADH) oxidase and coniferyl alcohol peroxidase (EC 1.11.1.4). NADH oxidase catalyzes the generation of H 2 O 2 during the oxidation of monolignols, and coniferyl alcohol peroxidase polymerizes monolignol (coniferyl, synapyl, and p-coumaryl alcohol) to lignin [3].…”

Section: Introductionmentioning

confidence: 99%

Structural Changes of Cell Wall and Lignifying Enzymes Modulations in Bean Roots in Response to Copper Stress

Bouazizi¹,

Jouili²,

Geitmann

et al. 2009

Fourteen-day-old bean seedlings were cultured in nutrient solution containing Cu(2+) ions at various concentrations (50 and 75 microM of CuSO(4)) for 3 days. This excess of copper induced a reduction in the water volume absorbed by the plants. Moreover, this reduction was accompanied by an increase of the amount of copper taken up by the roots. Analysis by native gel electrophoresis of cell wall peroxidase activities in the roots revealed a stimulation of two anionic isoforms (A(2) and A(3)) under cupric stress conditions. Moreover, the activity of phenylalanine ammonia lyase (EC. 4.3.1.5), which plays an important role in plant defense, was enhanced. Copper-treated bean roots showed modifications in the cell walls of various tissues. Label for lignin, callose, and suberin with berberine-aniline blue revealed abnormal cell wall thickenings in the endodermis, the phloem, and the xylem, especially in plants treated with 75 microM CuSO(4).

“…In fact, in the case of aluminium, several researches have reported that Al treatment was marked by a significant stimulation on peroxidases activities [1,2]. These enzymes have been involved in several processes such as cell wall rigidification [3], auxin catabolism [4], ethylene metabolism [5] and stress responses [6]. In fact, it has been reported that peroxidase induction is a general response of higher plant to metallic stress conditions [7].…”

Section: Introductionmentioning

confidence: 99%

Protein and Peroxidase Modulations in Sunflower Seedlings (Helianthus annuus L.) Treated with a Toxic Amount of Aluminium

Jouili¹,

Bouazizi²,

Ferjani³

2010

The aim of this study is to investigate the effect of aluminium treatment on peroxidases activities and protein content in both soluble and cell-wall-bound fractions of sunflower leaves, stems and roots. Fourteen-day-old seedlings, grown in a nutrient solution, were exposed to a toxic amount of aluminium (500 μM AlNO(3)) for 72 h. Under stress conditions, biomass production, root length and leaf expansion were significantly reduced. Also, our results showed modulations on soluble and ionically cell-wall-bound peroxidases activities. In soluble fraction, peroxidases activities were enhanced in all investigated organs. This stimulation was also observed in ionically cell-wall-bound fraction in leaves and stems. Roots showed a differential behaviour: peroxidase activity was severely reduced. Lignifying peroxidases activities assayed using coniferyl alcohol and H(2)O(2) as substrates were also modulated. Significant stimulation was shown on soluble fraction in leaves, stems and roots. In ionically cell-wall-bound fraction lignifying peroxidases were enhanced only in stems but severely inhibited in roots. Also, aluminium toxicity caused significant increase on cell wall protein content in sunflower roots.