Osvaldo Ferrarese-Filho

Lignification and Related Enzymes in Glycine max Root Growth-Inhibition by Ferulic Acid

Changes in soluble and cell wall bound peroxidase (POD, EC 1.11.1.7) activity, phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity, and lignin content in roots of ferulic acid-stressed soybean (Glycine max (L.) Merr.) seedlings and their relationships with root growth were investigated. Three-day-old soybean seedlings were cultivated in half-strength Hoagland nutrient solution containing 1.0 mM ferulic acid for 24–72 hr. Length, fresh weight, and dry weight of roots decreased, while soluble and cell wall bound POD activity, PAL activity, and lignin content increased after ferulic acid treatment. These enzymes probably participate in root growth reduction in association with cell wall stiffening related to the formation of cross-linking among cell wall polymers and lignin production.

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(2)O(2)) levels, and the content and monomeric composition of lignin in soybean (Glycine max) roots. Three-day-old seedlings were cultivated in half-strength Hoaglands 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 μmolm(-2)s(-1)) for 24h. 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(2)O(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.

The acetyl bromide method is faster, simpler and presents best recovery of lignin in different herbaceous tissues than Klason and thioglycolic acid methods.

We compared the amount of lignin as determined by the three most traditional methods for lignin measurement in three tissues (sugarcane bagasse, soybean roots and soybean seed coat) contrasting for lignin amount and composition. Although all methods presented high reproducibility, major inconsistencies among them were found. The amount of lignin determined by thioglycolic acid method was severely lower than that provided by the other methods (up to 95%) in all tissues analyzed. Klason method was quite similar to acetyl bromide in tissues containing higher amounts of lignin, but presented lower recovery of lignin in the less lignified tissue. To investigate the causes of the inconsistencies observed, we determined the monomer composition of all plant materials, but found no correlation. We found that the low recovery of lignin presented by the thioglycolic acid method were due losses of lignin in the residues disposed throughout the procedures. The production of furfurals by acetyl bromide method does not explain the differences observed. The acetyl bromide method is the simplest and fastest among the methods evaluated presenting similar or best recovery of lignin in all the tissues assessed.

Ferulic acid: a key component in grass lignocellulose recalcitrance to hydrolysis

In the near future, grasses must provide most of the biomass for the production of renewable fuels. However, grass cell walls are characterized by a large quantity of hydroxycinnamic acids such as ferulic and p-coumaric acids, which are thought to reduce the biomass saccharification. Ferulic acid (FA) binds to lignin, polysaccharides and structural proteins of grass cell walls cross-linking these components. A controlled reduction of FA level or of FA cross-linkages in plants of industrial interest can improve the production of cellulosic ethanol. Here, we review the biosynthesis and roles of FA in cell wall architecture and in grass biomass recalcitrance to enzyme hydrolysis.

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(2)O(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(2)O(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.

Peroxidase and phenylalanine ammonia-lyase activities, phenolic acid contents, and allelochemicals-inhibited root growth of soybean

The influence of the allelochemicals ferulic (FA) and vanillic (VA) acids on peroxidase (POD, EC 1.11.1.7) and phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activities and their relationships with phenolic acid (PhAs) contents and root growth of soybean (Glycine max (L.) Merr.) were examined. Three-day-old seedlings were cultivated in nutrient solution containing FA or VA (0.1 to 1 mM) for 48 h. Both compounds (at 0.5 and 1 mM) decreased root length (RL), fresh weight (FW) and dry weight (DW) and increased PhAs contents. At 0.5 and 1 mM, FA increased soluble POD activity (18% and 47%, respectively) and cell wall (CW)-bound POD activity (61% and 34%), while VA increased soluble POD activity (33% and 17%) but did not affect CW-bound POD activity. At 1 mM, FA increased (82%) while VA reduced (32%) PAL activities. The results are discussed on the basis of the role of these compounds on phenylpropanoid metabolism and root growth and suggest that the effects caused on POD and PAL activities are some of the many mechanisms by which allelochemicals influence plant growth.

Glyphosate affects lignin content and amino acid production in glyphosate-resistant soybean

Farmers report that some glyphosate-resistant soybean varieties are visually injured by glyphosate. Glyphosate is the main herbicide that directly affects the synthesis of secondary compounds. In this work, we evaluated the effect of increasing rates of glyphosate on lignin and amino acid content, photosynthetic parameters and dry biomass in the early maturity group cultivar BRS 242 GR soybean. Plants were grown in half-strength complete nutrient solution and subjected to various rates of glyphosate either as a single or in sequential applications. All parameters evaluated were affected by increasing glyphosate rates. The effects were more pronounced as glyphosate rates increased, and were more intense with a single total application than sequential applications at lower rates.

Peroxidase and lipid peroxidation of soybean roots in response to p-coumaric and p-hydroxybenzoic acids

The scope of the present study was to investigate how the p-coumaric (p-CA) and p-hydroxybenzoic (p-HD) acids affect the peroxidase (POD, EC 1.11.1.7) activity, the lipid peroxidation (LP) and the root growth of soybean (Glycine max (L.) Merr.). Three-day-old seedlings were cultivated in nutrient solution containing p-CA or p-HD (0.1 to 1 mM) for 48 h. After uptake, both compounds (at 0.5 and 1 mM) decreased root length (RL), fresh weight (FW) and dry weight (DW) while increased soluble POD activity, cell wall (CW)-bound POD activity (with 1 mM p-CA and 0.5 mM p-HD) and LP.

The role of L-DOPA in plants

Since higher plants regularly release organic compounds into the environment, their decay products are often added to the soil matrix and a few have been reported as agents of plant-plant interactions. These compounds, active against higher plants, typically suppress seed germination, cause injury to root growth and other meristems, and inhibit seedling growth. Mucuna pruriens is an example of a successful cover crop with several highly active secondary chemical agents that are produced by its seeds, leaves and roots. The main phytotoxic compound encountered is the non-protein amino acid L-3,4-dihydroxyphenylalanine (L-DOPA), which is used in treating the symptoms of Parkinson disease. In plants, L-DOPA is a precursor of many alkaloids, catecholamines, and melanin and is released from Mucuna into soils, inhibiting the growth of nearby plant species. This review summarizes knowledge regarding L-DOPA in plants, providing a brief overview about its metabolic actions.

Heat stress causes alterations in the cell-wall polymers and anatomy of coffee leaves (Coffea arabica L.)

Coffee plants were subjected to heat stress (37 °C) and compared with control plants (24 °C). Cell wall polysaccharides were extracted using water (W), EDTA (E) and 4M NaOH (H30 and H70). In addition, monolignols were analyzed, and the leaves were observed by microscopy. Plants under heat stress accumulated higher contents of arabinose and galactose in fraction W. Xylose contents were observed to decrease in H30 fractions after the heat stress, whereas galactose and uronic acid increased. H70 fractions from plants exposed to heat stress showed increased xylose contents, whereas the contents of arabinose and glucose decreased. Differences in the molar-mass profiles of polysaccharides were also observed. The primary monolignol contents increased after the heat stress. Structural alterations in palisade cells and ultrastructural damage in chloroplasts were also observed. Our results demonstrate that the chemical profile of coffee cell-wall polymers and structural cell anatomy change under heat stress.