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

Abstract

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.

Foliar Application of Copper Nanoparticles Increases the Fruit Quality and the Content of Bioactive Compounds in Tomatoes

“…This is consistent with the results shown in this study. It has been shown that cell wall lignification occurs in plants with copper stress [37]. Additionally, there is a relationship between the accumulation of copper in the cell wall and the responses of lignifying enzymes such as phenylalanine ammonia lyase (PAL).…”

“…Additionally, there is a relationship between the accumulation of copper in the cell wall and the responses of lignifying enzymes such as phenylalanine ammonia lyase (PAL). This response catalyzes the transformation of L-phenylalanine to cinnamic acid, which is the first step of the phenylpropanoid pathway leading to the synthesis of lignin [37,38]. Nair and Chung [14] observed root lignification when CuO NPs were applied, and mentioned that NPs could have translocated through the vascular tissues, and their subsequent dissolution to Cu ions could have given rise to the observed lignification.…”

Interaction of Brassinosteroids and Polyamines Enhances Copper Stress Tolerance in Raphanus Sativus

“…Cu has emerged as a major environmental pollutant in the past few decades because of its excessive use in manufacturing and agricultural industries (Bouazizi et al, 2011). Cu build-up in the food chain has resulted in reports of Cu toxicity in humans due to the consumption of Cu-ladened food commodities (Chary et al, 2008; Desai and Kaler, 2008; Bouazizi et al, 2011).…”

“…Cu build-up in the food chain has resulted in reports of Cu toxicity in humans due to the consumption of Cu-ladened food commodities (Chary et al, 2008; Desai and Kaler, 2008; Bouazizi et al, 2011). Radish ( Raphanus sativus L.) tubers, which represent a rich source of antidiabetics, antioxidants, and multipotent chemopreventive factors, are particularly prone to the toxic effects of high levels of Cu, resulting in a reduction in biomass and a detrimental impact on its nutritional profile (Baek et al, 2008; Sfaxi-Bousbih et al, 2010; Sun et al, 2010).…”

Copper excess promotes propagation and induces proteomic change in root cultures of Hyoscyamus albus L.

“…As vacuoles were included in the soluble fraction, these results seem 387 consistent with the common response of plants to toxic metals. In bean (Phaseolus vulgaris L.) 388 leaves, the cell wall was the major site of Cu ion accumulation(Bouazizi et al, 2011). Similarly, 389 root cells of Bechmeria nivea (L.) Gaud.…”