Properties of the 5-enol-pyruvyl-shikimate-3-phosphate synthase isoforms isolated from maize cultured cells

Forlani, Giuseppe

doi:10.1016/s0176-1617(97)80084-3

Cited by 22 publications

(25 citation statements)

References 36 publications

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“…The constants for the inhibition of EPSP synthase by glyphosate were found to be in the micromolar range not only against PEP (of competitive type), but with respect to shikimate-3-phosphate (incompetitive), also (e.g. Forlani 1997). Additionally, for the inhibition of DAHP synthase by the 5-chloro-pyridyl derivative of aminomethylene bisphosphonic acid the K I s were significantly lower (0.14 and 0.06 mM against E4P and PEP, respectively; .…”

Section: Resultsmentioning

confidence: 99%

The Herbicidally Active Compound N-2-(6-Methyl-Pyridyl)-Aminomethylene Bisphosphonic Acid Inhibits In Vivo Aromatic Biosynthesis

Forlani

Lejczak

Kafarski

1999

J Plant Growth Regul

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The effect of N-2-(6-methyl-pyridyl)-aminomethylene bisphosphonic acid (M-pyr-AMBPA), a compound previously shown to exhibit herbicidal properties on whole plants and to inhibit in vitro activity of the first enzyme in the shikimate pathway, 3-deoxy-d-arabino-heptulosonate-7-phosphate (DAHP) synthase, was investigated on Nicotiana plumbaginifolia suspension cultured cells and compared to that of the herbicide glyphosate. The addition of M-pyr-AMBPA from 10(-4) to 10(-3) M was found to cause a severe cell growth reduction. Kinetic analysis of partially purified DAHP synthase accounted for non-competitive inhibition type with respect to both phospho-enol-pyruvate and erythrose-4-phosphate, with K(I) values of 0.43 and 0.62 mM, respectively. Amino acid pool measurements of cells grown in the presence of sublethal doses of M-pyr-AMBPA pointed to an actual reduction of free aromatic amino acids, showing that DAHP synthase inhibition takes place in vivo, and suggesting that the interference of this aminophosphonate with plant aromatic biosynthesis may account for a large part of its phytotoxicity. However, exogenous supply of a mixture of phenylalanine, tyrosine and tryptophan failed to achieve full reversal of cell growth inhibition, yet the occurrence of other target(s) cannot be ruled out.

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Section: Resultsmentioning

confidence: 99%

The Herbicidally Active Compound N-2-(6-Methyl-Pyridyl)-Aminomethylene Bisphosphonic Acid Inhibits In Vivo Aromatic Biosynthesis

Forlani

Lejczak

Kafarski

1999

J Plant Growth Regul

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“…To address the question of whether either of the EPSP-synthase isoforms purified (Forlani et al 1994) and characterised (Forlani 1997) from maize suspensioncultured cells play a specific role during the defence response, the hypersensitive reaction was triggered by addition of a cell wall hydrolysate purified from a maize pathogen, F. acuminatum. This strain was selected because it is the most effective of six different fungal isolates obtained from either the leaf or lower part of the stem of maize plants (G. Forlani, E. Nielsen and A. M. Picco, unpublished results).…”

Section: Discussionmentioning

confidence: 99%

“…A specific role of isozyme II in the plant defence response may be consistent with its properties. A higher catalytic efficiency and stability (Forlani 1997) might derive from a higher selective pressure, most likely exerted under conditions of high demand for aromatic amino acids, such as those that follow pathogen infiltration.…”

Section: Discussionmentioning

confidence: 99%

“…EPSP-synthase activity was measured at 35°C by determining release of inorganic phosphate using the malachite-green dye assay method (Forlani 1997). In a final volume of 0.1 mL the reaction mixture contained 50 mM Hepes-NaOH buffer (pH 7.4) 1 mM S3P, 1 mM PEP, 0.5 mM ammonium molybdate and a limiting amount (up to 10 pkat) of enzyme.…”

Section: -Enol-pyruvyl-shikimate-3-phosphate Synthasementioning

confidence: 99%

“…Two isozymes, both functionally located in the plastid, have been purified to homogeneity from cultured Z. mays cells (Forlani et al 1994), but even thorough biochemical characterisation failed to show any difference that could account for a specific role in plant cell metabolism (Forlani 1997). To address the question of whether one of these forms is preferentially expressed during the dynamic defence response, they were resolved and quantified in extracts from cultured cells exposed to mycelial wall fragments purified from Fusarium acuminatum, a fungal pathogen of maize.…”

Section: Introductionmentioning

confidence: 99%

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Differential expression of 5-enol-pyruvyl-shikimate-3-phosphate synthase isoforms in elicitor-treated, cultured maize cells

Forlani¹

2002

Functional Plant Biol.

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Abstract. The expression of two 5-enol-pyruvyl-shikimate-3-phosphate synthase (EC 2.5.1.19) isoforms was investigated in Zea mays L. suspension-cultured cells following exposure to a fungal elicitor. Activity levels of isozyme II specifically increased soon after treatment, in strict connection with induction of phenylalanine ammonia-lyase (PAL) and attainment of a new free-phenylalanine homeostasis at a higher concentration. However, a few days later, activity of the other enzyme form was also significantly enhanced, concomitant with a sharp rise in overall amino acid content, a further increase in PAL level and a resumption of cell lysis. Besides strengthening the hypothesis that an entire set of genes encoding for shikimate pathway enzymes (whose expression is specifically involved in plant dynamic defence) may exist, a general change in the levels of several amino acids seems to point towards a reprogramming of their metabolism in elicited cells.

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Metabolism of the phosphonate herbicide glyphosate by a non‐nitrate‐utilizing strain of Penicillium chrysogenum

Klimek

Lejczak

Kafarski

et al. 2001

Pest Management Science

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A Penicillium chrysogenum strain was isolated for its ability to grow in minimal medium containing the herbicide glyphosate as the only nitrogen source. The presence of concentrations up to 25 mM progressively stimulated the fungal growth rate, which was negligible in media lacking reduced nitrogen. However, glyphosate utilization never exceeded 1 mmol g-1 mycelial dry mass, and below a threshold concentration both herbicide uptake and fungal growth were subject to a lag phase, suggesting that the herbicide may enter the cell by either simple passive diffusion or inducible carriers. Amino acids, possible products of glyphosate breakdown, as well as ammonia, were found to replace the herbicide in restoring mycelial growth. Cells were devoid of detectable nitrate reductase activity, thus the isolate seems to be impaired in its ability to convert nitrate to ammonium. In vitro activity of 5-enol-pyruvyl-shikimate-3-phosphate synthase, the target site of glyphosate action, was highly sensitive to the herbicide. Fungal growth rate was considerably lower when the herbicide was also the only phosphorus source, whereas glyphosate utilization was substantially unaffected, suggesting an unusual route for its degradation. Herbicide metabolism was strongly reduced when other sources of organic nitrogen were made available.

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Properties of the 5-enol-pyruvyl-shikimate-3-phosphate synthase isoforms isolated from maize cultured cells

Cited by 22 publications

References 36 publications

The Herbicidally Active Compound N-2-(6-Methyl-Pyridyl)-Aminomethylene Bisphosphonic Acid Inhibits In Vivo Aromatic Biosynthesis

The Herbicidally Active Compound N-2-(6-Methyl-Pyridyl)-Aminomethylene Bisphosphonic Acid Inhibits In Vivo Aromatic Biosynthesis

Differential expression of 5-enol-pyruvyl-shikimate-3-phosphate synthase isoforms in elicitor-treated, cultured maize cells

Metabolism of the phosphonate herbicide glyphosate by a non‐nitrate‐utilizing strain of Penicillium chrysogenum

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