Cell Wall-bound Peroxidase Activity Research Articles

Aluminum oxide nanoparticles affect the cell wall structure and lignin composition slightly altering the soybean growth

Aluminum oxide (Al2O3) nanoparticles (NPs) are among the nanoparticles most used industrially, but their impacts on living organisms are widely unknown. We evaluated the effects of 50–1000 mg L−1 Al2O3 NPs on the growth, metabolism of lignin and its monomeric composition in soybean plants. Al2O3 NPs did not affect the length of roots and stems. However, at the microscopic level, Al2O3 NPs altered the root surface inducing the formation of cracks near to root apexes and damage to the root cap. The results suggest that Al2O3 NPs were internalized and accumulated into the cytosol and cell wall of roots, probably interacting with organelles such as mitochondria. At the metabolic level, Al2O3 NPs increased soluble and cell wall-bound peroxidase activities in roots and stems but reduced phenylalanine ammonia-lyase activity in stems. Increased lignin contents were also detected in roots and stems. The Al2O3 NPs increased the p-hydroxyphenyl monomer levels in stems but reduced them in roots. The total phenolic content increased in roots and stems; cell wall-esterified p-coumaric and ferulic acids increased in roots, while the content of p-coumaric acid decreased in stems. In roots, the content of ionic aluminum (Al+3) was extremely low, corresponding to 0.0000252% of the aluminum applied in the nanoparticulate form. This finding suggests that all adverse effects observed were due to the Al2O3 NPs only. Altogether, these findings suggest that the structure and properties of the soybean cell wall were altered by the Al2O3 NPs, probably to reduce its uptake and phytotoxicity.

OPDA and ABA accumulation in Pb-stressed Zygophyllum fabago can be primed by salicylic acid and coincides with organ-specific differences in accumulation of phenolics

Salicylic acid (SA) is a well-known priming agent that is widely used to protect plants against stressing agents, including heavy metals as Pb. A better understanding of the mechanisms that enable plants to counteract Pb toxicity would help to select strategies for land reclamation programs. Here we used a metallicolous population of Zygophyllum fabago to assess the extent to which SA pretreatment modulates Pb-induced changes in phenol metabolism and stress-related phytohormone levels in roots and leaves. Our data revealed that accumulation of different phytohormones, lignin, soluble and wall-bound phenolics as well as peroxidase (PRX) activity in Pb-stressed plants differed after SA-pretreatment. Exposure to Pb led to the induction of soluble and cell wall-bound PRX activities, particularly those involved in the oxidation of coniferyl alcohol and ferulic acid, while pretreatment with SA reduced the Pb-induced stimulation of PRX activities in roots but increased them in leaves. SA-treatment by itself induced accumulation of ABA and the JA-precursor 12-oxo-phytodienoic acid (OPDA) in the roots. Pb in turn inhibited these SA-induced effects with the exception of OPDA accumulation that was primed by the pretreatment. The SA treatment also induced accumulation of OPDA in leaves but suppressed the accumulation of JA-Ile although with relatively small absolute changes. Notably, Pb-induced accumulation of ABA was primed in the leaves of SA-pretreated plants. Together our data suggest that priming of OPDA accumulation in the roots and of ABA in the leaves by SA-pretreatment may play important regulatory roles, possibly via regulating PRX activities, for Pb stress in plants.

Lignin-induced growth inhibition in soybean exposed to iron oxide nanoparticles

Plants are occasionally exposed to environmental perturbations that limit their growth. One of these perturbations is the exposure to and interaction with various nanoparticles (NPs) that are discarded continuously into the environment. Hitherto, no study has been carried out evaluating the effects of iron oxide (γ-Fe2O3) NPs on soybean growth and lignin formation, as proposed herein. For comparative purposes, we also submitted soybean plants to non-nanoparticulate iron (FeCl3). Exposure of the plants to γ-Fe2O3 NPs increased cell wall-bound peroxidase (POD) activity but decreased phenylalanine ammonia lyase (PAL) activity due, probably, to the negative feedback of accumulated phenolic compounds. In contrast, FeCl3 decreased cell wall-bound POD activity. Both γ-Fe2O3 NPs and FeCl3 increased the lignin content of roots and stems. However, significant lignin-induced growth inhibition was noted only in stems after exposure to NPs, possibly due to changes in lignin monomer composition. In this case, γ-Fe2O3 NPs decreased the guaiacyl monomer content of roots but increased that of stems. The high levels of monomer guaiacyl in stems resulting from the action of γ-Fe2O3 NPs decreased syringyl/guaiacyl ratios, generating more highly cross-linked lignin followed by the stiffening of the cell wall and growth inhibition. In contrast, FeCl3 increased the contents of monomers p-hydroxyphenyl and syringyl in roots. The observed increase in the syringyl/guaiacyl ratio in plant roots submitted to FeCl3 agrees with the lack of effect on growth, due to the formation of a less condensed lignin. In brief, we here describe that γ-Fe2O3 NPs and FeCl3 act differently in soybean plants.

Determination of zinc oxide nanoparticles toxicity in root growth in wheat (Triticum aestivumL.) seedlings

The effect of zinc oxide nanoparticles (ZnONPs) was studied in wheat (Triticum aestivum L.) seedlings under in vitro exposure conditions. To avoid precipitation of nanoparticles, the seedlings were grown in half strength semisolid Murashige and Skoog medium containing 0, 50, 100, 200, 400 and 500 mg L(-1) of ZnONPs. Analysis of zinc (Zn) content showed significant increase in roots. In vivo detection using fluorescent probe Zynpyr-1 indicated accumulation of Zn in primary and lateral root tips. All concentrations of ZnONPs significantly reduced root growth. However, significant decrease in shoot growth was observed only after exposure to 400 and 500 mg L(-1) of ZnONPs. The reactive oxygen species and lipid peroxidation levels significantly increased in roots. Significant increase in cell-wall bound peroxidase activity was observed after exposure to 500 mg L(-1) of ZnONPs. Histochemical staining with phloroglucinol-HCl showed lignification of root cells upon exposure to 500 mg L(-1) of ZnONPs. Treatment with propidium iodide indicated loss of cell viability in root tips of wheat seedlings. These results suggest that redox imbalances, lignification and cell death has resulted in reduction of root growth in wheat seedlings exposed to ZnONPs nanoparticles.

Over-expression of TaEXPB23, a wheat expansin gene, improves oxidative stress tolerance in transgenic tobacco plants

Expansins are cell wall proteins inducing cell wall loosening and participate in all plant growth and development processes which are associated with cell wall modifications. Here, TaEXPB23, a wheat expansin gene, was investigated and the tolerance to oxidative stress was strongly enhanced in over-expression tobacco plants. Our results revealed that over-expressing TaEXPB23 influenced the activity of antioxidant enzymes: in particular, the activity of the cell wall-bound peroxidase. The enhanced tolerance to oxidative stress and increased cell wall-bound peroxidase activity were partly inhibited by an anti-expansin antibody. The Arabidopsis expansin mutant atexpb2 showed reduced cell wall-bound peroxidase activity and decreased oxidative stress tolerance. In addition, atexpb2 exhibited lower chlorophyll contents and the germination rate compared to wild type (WT). Taken together, these results provided a new insight on the role of expansin proteins in plant stress tolerance by cell wall bound peroxidase.

The effects of dopamine on root growth and enzyme activity in soybean seedlings

In the present study, we investigated the effects of dopamine, an allelochemical exuded from the velvetbean (Mucuna pruriens L DC. var utilis), on the growth and cell viability of soybean (Glycine max L. Merrill) roots. We analyzed the effects of dopamine on superoxide dismutase, phenylalanine ammonia-lyase and cell wall-bound peroxidase activities as well as its effects on lignin contents in the roots. Three-day-old seedlings were cultivated in half-strength Hoagland nutrient solution (pH 6.0), without or with 0.25 to 1.0 mM dopamine, in a growth chamber (25°C, 12L:12D photoperiod, irradiance of 280 μmol m−2 s−1) for 24 h. In general, the length, fresh weight and dry weight of roots, cell viability, PAL and POD activities decreased, while SOD activities increased after dopamine treatment. The content of lignin was not altered. The data demonstrate the susceptibility of soybean to dopamine and reinforce the role of this catecholamine as a strong allelochemical. The results also suggest that dopamine-induced inhibition in soybean roots is not related to the production of lignin, but may be related to damage caused by reactive oxygen species.

Root Growth and Enzymes Related to the Lignification of Maize Seedlings Exposed to the Allelochemical L-DOPA

L-3,4-Dihydroxyphenylalanine (L-DOPA) is a known allelochemical exuded from the roots of velvet bean (Mucuna pruriens L. Fabaceae). In the current work, we analyzed the effects of L-DOPA on the growth, the activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), and peroxidase (POD), and the contents of phenylalanine, tyrosine, and lignin in maize (Zea mays) roots. Three-day-old seedlings were cultivated in nutrient solution with or without 0.1 to 2.0 mM L-DOPA in a growth chamber (25°C, light/dark photoperiod of 12/12, and photon flux density of 280 μmol m−2 s−1) for 24 h. The results revealed that the growth (length and weight) of the roots, the PAL, TAL, and soluble and cell wall-bound POD activities decreased, while phenylalanine, tyrosine, and lignin contents increased after L-DOPA exposure. Together, these findings showed the susceptibility of maize to L-DOPA. In brief, these results suggest that the inhibition of PAL and TAL can accumulate phenylalanine and tyrosine, which contribute to enhanced lignin deposition in the cell wall followed by a reduction of maize root growth.

The effects of l-DOPA on root growth, lignification and enzyme activity in soybean seedlings

In the present study, we investigated the effects of l-DOPA (l-3,4-dihydroxyphenylalanine), an allelochemical exuded from the velvetbean (Mucuna pruriens L DC. var. utilis), on the growth and cell viability of soybean (Glycine max L. Merrill) roots. We analyzed the effects of l-DOPA on phenylalanine ammonia lyase (PAL), cinnamyl-alcohol dehydrogenase (CAD) and cell wall-bound peroxidase (POD) activities as well as its effects on phenylalanine, tyrosine and lignin contents in the roots. 3-day-old seedlings were cultivated in half-strength Hoagland nutrient solution (pH 6.0), with or without 0.5 mM l-DOPA, in a growth chamber at 25 °C for 6, 12, 18 or 24 h with a day/night regime of 1:1, and a photon flux density of 280 μmol m−2 s−1. In general, the length, fresh weight and dry weight of the roots decreased followed by a significant loss of cell viability. Phenylalanine, tyrosine and lignin contents as well as PAL, CAD and cell wall-bound POD activities increased after l-DOPA treatment. These results reinforce the susceptibility of soybean to l-DOPA, which increases the enzyme activity in the phenylpropanoid pathway and, therefore, provides precursors for the polymerization of lignin. In brief, these findings suggest that the inhibition of soybean root growth induced by exogenously applied l-DOPA may be due to excessive production of lignin in the cell wall.

Phenylalanine ammonia-lyase and cell wall peroxidase are cooperatively involved in the extensive formation of ferulate network in cell walls of developing rice shoots

The relationship between the formation of cell wall-bound ferulic acid (FA) and diferulic acid (DFA) and the change in activities of phenylalanine ammonia-lyase (PAL) and cell wall-bound peroxidase (CW-PRX) was studied in rice shoots. The length and the fresh mass of shoots increased during the growth period from day 4 to 6, while coleoptiles ceased elongation growth on day 5. The amounts of FA and DFA isomers as well as cell wall polysaccharides continued to increase during the whole period. The activities of PAL and CW-PRX greatly increased in the same manner during the period. There were close correlations between the PAL activity and ferulate content or between the CW-PRX activity and DFA content. The expression levels of investigated genes for PAL and putative CW-PRX showed good accordance with the activities of these enzymes. These results suggest that increases in PAL and CW-PRX activities are cooperatively involved in the formation of ferulate network in cell walls of rice shoots and that investigated genes may be, at least in part, associated with the enzyme activities. The substantial increase in such network probably causes the maturation of cell walls and thus the cessation of elongation growth of coleoptiles.

Exogenous caffeic acid inhibits the growth and enhances the lignification of the roots of soybean ( Glycine max)

The allelopathic effect of caffeic acid was tested on root growth, phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities, hydrogen peroxide (H 2O 2) accumulation, lignin content and monomeric composition of soybean ( Glycine max) roots. We found that exogenously applied caffeic acid inhibited root growth, decreased the PAL activity and H 2O 2 content and increased the soluble and cell wall-bound POD activities. The p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) monomers and total lignin (H + G + S) increased in the caffeic acid-exposed roots. When applied in conjunction with piperonylic acid (PIP, an inhibitor of the cinnamate 4-hydroxylase, C4H), caffeic acid equalized the inhibitory effect of PIP, whereas the application of methylene dioxocinnamic acid (MDCA, an inhibitor of the 4-coumarate:CoA ligase, 4CL) plus caffeic acid decreased lignin production. These results indicate that exogenously applied caffeic acid can be channeled into the phenylpropanoid pathway via the 4CL reaction, resulting in an increase of lignin monomers that solidify the cell wall and inhibit root growth.

Cadmium-induced lignification restricts soybean root growth

The effects of cadmium (Cd), a well-known environmental pollutant with high toxicity to plants, were tested on root growth, cell viability, phenylalanine ammonia-lyase (PAL) soluble plus cell wall-bound peroxidase (POD) activities, hydrogen peroxide (H 2O 2) levels, and the content and monomeric composition of lignin in soybean ( Glycine max) roots. Three-day-old seedlings were cultivated in half-strength Hoagland’s solution (pH 6.0), with or without 25–100 μM CdCl 2 in a growth chamber (25 °C, 12/12-h light/dark photoperiod, irradiance of 280 μmol m −2 s −1) for 24 h. In general, root length and the fresh and dry weights decreased followed by loss of cell viability after Cd treatment. PAL activity, soluble and cell wall-bound POD activities, and H 2O 2 and lignin contents increased significantly after Cd exposure. The lignin monomeric composition of Cd-exposed roots revealed a significant increase of p-hydroxyphenyl (H) and syringyl (S) units. These results suggest that the effects caused by Cd may be due to excessive production of monolignols forming lignin, which solidifies the cell wall and restricts root growth.

Cell wall-bound peroxidase activity and lignin formation in azuki bean epicotyls grown under hypergravity conditions

The effects of accelerated gravity stimuli on the cell wall-bound peroxidase activity and the lignin content were investigated along epicotyls of azuki bean (Vigna angularis) seedlings. The endogenous growth occurred primarily in the upper regions of the epicotyl, but no growth was detected in the middle or basal regions. Hypergravity treatment at 300g for 6h suppressed elongation growth and stimulated lateral expansion of the upper regions. The content of acetyl bromide-soluble lignin increased gradually from the apical to the basal regions of epicotyls. Hypergravity treatment stimulated the increase in the lignin content in epicotyls, particularly in the middle and basal regions. The peroxidase activity in the protein fraction extracted with a high ionic strength buffer from the cell wall preparation also increased gradually toward the basal region, and hypergravity treatment increased the activity in all epicotyl regions. There was a close correlation between the lignin content and the enzyme activity. These results suggest that hypergravity increases the activity of cell wall-bound peroxidase followed by increases of the lignin formation in epicotyl cell walls, which may contribute to increasing the rigidity of cell walls against the gravitational force.

The Effects of Bacillus pumilus, Isolated from Wheat Rhizosphere, on Resistance in Wheat Seedling Roots against the Take‐all Fungus, Gaeumannomyces graminis var. tritici

AbstractThe aim of this study was to verify that induced resistance was another mechanism through which Bacillus pumilus 7 km can suppress Gaeumannomyces graminis (Sacc.) Von Arx and Oliver var. tritici Walker (Ggt). Also, plant growth‐promotion activity of B. pumilus 7 km and its effect on disease severity of take‐all were evaluated. Soil was drenched with B. pumilus 7 km and disease severity, root and shoot fresh weights and root and shoot heights were evaluated. The activities of soluble peroxidase (SPOX), ionically cell wall‐bound peroxidase (CWPOX), β‐1,3‐glucanase, β‐1,4‐glucanase and the contents of total phenolic compounds were also determined. The results indicated that disease severity in the bacterized roots was significantly less than the pathogen control roots. Also this isolate promoted root height, root and shoot fresh weights, compared with the healthy control plants. Wheat plants treated with B. pumilus 7 km showed increased presence of SPOX, CWPOX, β‐1,3‐glucanase, β‐1,4‐glucanase and phenolic compounds in bacterized roots challenged with the pathogen. In this treatment, maximum SPOX, β‐1,3‐glucanase and β‐1,4‐glucanase activities on day 4 and CWPOX activity on day 8 were recorded. Also, maximum total phenolic concentration on day 6 was recorded. The results suggest that the inhibitory effect of B. pumilus 7 km on the take‐all may be related to its ability to enhance defense responses in the wheat roots.

Phenolics, lignin content and peroxidase activity in Picea omorika lines

We analyzed low molecular mass phenolics, lignin content and both soluble and cell wall bound peroxidase activity in the needles of three Picea omorika (Pancic) Purkyne lines grown in the generative seed orchard. The highest values of the total phenol content as well as of catechine, caffeic acid, coniferyl alcohol, isoferulic acid and lignin concentration were detected in B5 line (semidichotomy line). The soluble guaiacol peroxidase activity was the highest in A3 line (line borealis). The highest activity of cell wall bound peroxidases was measured in B5 line, and it was in correlation with lignin content.

Exogenous jasmonic acid mimics herbivore‐induced systemic increase in cell wall bound peroxidase activity and reduction in leaf expansion

Summary Jasmonic acid (JA), a ubiquitous regulator of the wound response in plants, is part of a long distance defence signalling pathway and when applied exogenously induces several defence related responses in many species including the activation of proteinase inhibitor (PIN) proteins and defence‐related metabolites. There is evidence for an induced systemic resistance mechanism linking increased cell wall peroxidase activity with reductions in leaf expansion rates in Rumex obtusifolius, following limited grazing by the chrysomelid beetle Gastrophysa viridula. We hypothesised that herbivory induces strengthening of cell walls in distal, non‐damaged tissue through increases in peroxidase activity and that this mechanism was mediated systemically by JA. JA was applied to the fully expanded fourth leaf of R. obtusifolius and expansion of leaf 8 was measured over 19 days. Treatment with exogenous JA induced a temporary reduction in the expansion rate of leaf 8 beginning 6 days after treatment. This reduction continued until day 7 and reduced final leaf areas in treated plants by approximately 20%. Final epidermal cell areas in leaf 8 were reduced by approximately 25%, while epidermal cell numbers remained unchanged. Cell wall bound peroxidase activity was measured in leaf 8 over a 6‐day period following application of JA to leaf 4. Activity increased approximately 9‐fold 2 days after treatment, before returning to control activities on day 3. Treatment of leaf 4 with JA reduced the gregariousness of G. viridula larvae on the fully expanded leaf 8. We postulate that JA acts as a signalling molecule in a long‐distance pathway responsible for inducing resistance to future attack through increases in cell wall bound peroxidase activity leading to cell wall toughening, while incurring a potential ecological cost in the form of reductions in subsequent leaf expansion.

Changes in peroxidase activity and isoenzymes in spruce needles after exposure to different concentrations of cadmium

We studied the guaiacol peroxidase activity, isoenzyme pattern and metal content in the needles of 2-year-old spruce grown on soils supplemented with cadmium concentrations from 1 to 21 mg kg −1. Following exposure to cadmium, an initial increase and subsequent decrease in the activity of the soluble fraction was observed. A parallel change of their isoenzyme pattern occurred. An increase of the cell wall-bound peroxidase activity under prolonged metal treatment was evident. The results obtained show that peroxidase activity and isoenzyme pattern could be used to evaluate the capacity of one part of the defense system in spruce seedlings to withstand metal stress.

Induction of an acidic isozyme of peroxidase and acquired resistance to wilt disease in response to treatment of tomato roots with 2-furoic acid, 4-hydroxybenzoic hydrazide or salicylic hydrazide

Thirty nine derivatives of salicylic acid, nicotinic acid or furoic acid were tested for their ability to induce cell wall bound peroxidase activity in an attempt to identify inducers of acquired resistance. The activity of cell wall bound peroxidase in tomato hypocotyls was enhanced by treatment of roots with 4-hydroxybenzoic hydrazide (4HBHZ), salicylic hydrazide (SHZ), or 2-furoic acid (2FA). Isoelectric focusing revealed that an acidic isozyme (pI 4.6) of peroxidase was induced specifically by treatment with these compounds. The isozyme was induced independently to wounding or pathogen infection. Dipping roots in solutions of these compounds at concentrations of 0.1 μm4HBHZ, 1.0 μmSHZ and 10 μm2FA also induced resistance against the tomato wilt disease caused byFusarium oxysporumf.sp.lycopersici.

A comparative study of the effects of abscisic acid and methyl jasmonate on seedling growth of rice

The effects of abscisic acid (ABA) and methyl jasmonate (MJ) on growth of rice seedlings were compared. The lowest tested concentration of ABA and MJ that inhibited seedling growth was found to be 4.5 and 0.9 µM, respectively. Growth inhibition by ABA is reversible, whereas that by MJ is irreversible. GA3 was found to be more effective in reversing inhibition of shoot growth by ABA than by MJ. KCl partially relieved MJ-inhibited, but not ABA-inhibited, growth of rice seedlings. The beneficial effect of K+ on growth of rice seedlings in MJ medium could not be replaced by Li+, Na+ or Cs+. MJ treatment caused a marked release of K+ into the medium. In order to understand whether cell wall-bound peroxidase activity was inversely related to rice seedling growth, effects of ABA and MJ on cell wall-bound peroxidase activity were also examined. Results indicated that both ABA and MJ increased cell wall-bound peroxidase activity in roots and shoots of rice seedlings. Although MJ (4.5 µM) was less effective in inhibiting root growth than ABA (9 µM), MJ was found to increase more cell wall-bound peroxidase activity in roots than ABA.

Effects of ethrel on peroxidase of iceberg lettuce leaf tissue

Abstract The effect of ethrel (0.1–1.0 mM) on the development of both peroxidase activity and brown spots in 56-day old lettuce leaves was studied. The results showed that ethrel reduces both soluble and cell wall-bound peroxidase activity in lettuce leaves, the effect being independent of the incubation medium pH, the ethylene-releasing ability of ethrel therefore being not limiting. At the same time, brown spots appeared in lettuce leaves only after incubation at high concentration (1.0 mM). These results suggest that the ethrel treatments that led to the development of brown spots were not related with the effect of ethrel in inducing peroxidase, thus ruling out any key control of peroxidase in the development of ethylene-induced brown spots.

Changes in soluble and cell wall-bound peroxidase activities with growth in anoxia-treated rice ( Oryza sativa L.) coleoptiles and roots

The activity of soluble and cell wall-bound (1.0 M NaCl extractable) peroxidase in relation to growth of anoxia-grown Indica rice seedlings ( Oryza sativa L. cv. Taichung Native 1) was examined. Guaiacol and syringaldazine were used to assay for peroxidase activity. In air-grown coleoptiles, guaiacol or syringaldazine peroxidase activity initially decreased or remained constant, respectively, in the early period but then both increased as coleoptile elongation ceased. In air-grown roots, both guaiacol and syringaldazine peroxidase activities decreased slightly during the growth period. In response to anoxia, coleoptile elongation was stimulated but root growth was seriously inhibited. Anoxia induced a significant decrease in activity of cell wall-bound guaiacol and syringaldazine peroxidase while soluble peroxidase activity was not affected in coleoptiles. In contrast to coleptiles, anoxia-grown roots showed an increase in cell wall-bound guaiacol and syringaldazine peroxidase activities. When transferred to aerobic conditions, cell wall-bound guaiacol and syringaldazine peroxidase activities in anoxia-grown coleoptiles and roots recovered almost to the air-control levels. On exposure to ABA, the enhancement of coleoptile elongation and the decrease of cell wall-bound peroxidase activity in anoxia-grown coleoptiles were inhibited. These results indicate that there is a reciprocal correlation between growth and cell wall-bound peroxidase levels in etiolated rice seedlings.