Shikimic Acid Accumulation Research Articles

Accumulation of Shikimic Acid: A Technique for Screening Glyphosate Efficacy

Biochemical changes in leaves of 3-week-old oil seed rape (Brassica napus L. cv. Iris) plants were determined shortly after treatment with different doses of glyphosate. Secondary effects of N-(phosphonomethyl)glycine (glyphosate) on activity of the enzyme phenylalanine ammonia-lyase was not related to dose of glyphosate by any known model within the first 48 h after spraying. Accumulation of shikimic acid was related to the dose of glyphosate by a nonlinear logistic dose−response modelas early as 5 h after spraying. Within the same period shikimic acid accumulation made it possible to distinguish between a formulation of the pure isopropylamine salt of glyphosate and formulations containing different surfactants. ED50 estimates based on accumulation of shikimic acid gave a good indication of the relative strength of the evaluated glyphosate formulations. Ranking of ED50 based on accumulation of shikimic acid was the same as achieved by visual assessment of plant death 14 days after spraying. Keywords: Gl...

Carbohydrate mobilization following shoot defoliation and decapitation in hybrid poplar.

The effects of shoot defoliation, decapitation, and disbudding on carbon mobilization were investigated in rooted cuttings of Populus maximowiczii x nigra L. 'MN9'. Ten days after complete shoot defoliation or decapitation, the stem starch concentration of treated plants declined to one-half that of intact plants, and there were similar or greater reductions in the concentrations of glucose, fructose, sucrose, galactose, and shikimic acid. Partial shoot defoliation (50%) and complete disbudding had no effect on stem starch concentration, but stem sucrose concentration was reduced in all treatments. Sucrose depletion preceded and may have induced other changes in the carbon status of plants subjected to leaf or shoot removal. Four days after shoot decapitation, the sucrose concentration of roots of treated plants was reduced to 25% of that of intact plants. However, the concentrations of fructose and glucose increased in the roots of treated plants and was followed by the accumulation of shikimic acid, salicyl alcohol, unknown compound A and salicin. The possible role of increased concentrations of root organic solutes in the water relations and regrowth process of decapitated plants is discussed.

Changes of shikimate pathway in glyphosate tolerant alfalfa cell lines with reduced embryogenic ability

Glyphosate tolerant cell lines were selected from highly embryogenic cell suspension culture ofMedicago sativa L. Resistant cell lines showed significant reduction of embryogenic ability and during long-term culture in the presence of glyphosate gradual loss of this ability was observed. After glyphosate treatment the increased activity of 5-enolpyruvylshikimate-3-phosphate synthase in tolerant cell lines overcame the block in aromatic amino acid synthesis which was observed in control cell lines. Glyphosate caused marked increase in the content of shikimic acid in both control and tolerant cell lines but the accumulation of shikimic acid was considerably lower in tolerant calli. Significant qualitative and quantitative differences were found in the content of individual phenolic acids. The considerable decrease in the amount of cinnamic acid derivates and broader spectrum of hydroxybenzoic acids suggest in tolerant cell lines the activation of alternative pathway not regulated by phenylalanine ammonia lyase. The possible role of altered pool of phenolic acids on the embryogenic ability is discussed.

Glyphosate toxicity in the shoot apical region of the tomato plant: I. Plastid swelling is the initial ultrastructural feature following in vivo inhibition of 5-enolpyruvylshikimic acid 3-phosphate synthase

Glyphosate induces swelling and eventual bursting of the plastids in the young tissue of the shoot apical region of tomato plants. This rapid and specific effect parallels the concentration of glyphosate in the tissues and the degree of in vivo inhibition of 5-enolpyruvylshikimic acid 3-phosphate synthase as measured by the accumulation of shikimic acid and shikimic acid 3-phosphate. The chloroplasts of the young apical leaves begin to swell between 16 and 20 hr after treatment of the plants with a sublethal glyphosate dose and burst after 4 days. Glyphosate-induced swelling of the proplastids begins much later (at 2 days) in the apical meristem itself than in the apical leaves. The meristem recovers 5 days after glyphosate treatment because the cells containing the damaged proplastids become displaced toward the rib meristem according to the inherent pattern of cell division.

Mode of action of glyphosate in Candida maltosa.

The broad-spectrum herbicide glyphosate inhibits the growth of Candida maltosa and causes the accumulation of shikimic acid and shikimate-3-phosphate. Glyphosate is a potent inhibitor of three enzymes of aromatic amino acid biosynthesis in this yeast. In relation to tyrosine-sensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase and dehydroquinate synthase, the inhibitory effect appears at concentrations in the mM range, but 5-enolpyruvylshikimate 3-phosphate (EPSP) synthase is inhibited by micromolar concentrations of glyphosate. Inhibition of partially purified EPSP synthase reaction by glyphosate is competitive with respect to phosphoenolpyruvate (PEP) with a Ki-value of 12 microM. The app. Km for PEP is about 5-fold higher and was 62 microM. Furthermore, the presence of glyphosate leads to derepression of many amino acid biosynthetic enzymes.

Enzymological Basis for glyphosate action in Candida maltosa

Summary The broad-spectrum herbicide glyphosate, which causes the accumulation of shikimic acid and shikimate-3-phosphate, inhibits 3 enzymes of aromatic amino acid biosynthesis in Candida maltosa . In relation to tyrosine-sensitive DAHP synthase and dehydroquinate synthase, the inhibitory effect appears at concentrations in the mM range, but EPSP synthase is inhibited 100-fold stronger. Inhibition of partially purified EPSP synthase reaction by glyphosate is competitive with respect to phosphoenolpyruvate with a K i -value of 12 μ M. The app. K m for phosphoenolpyruvate is about 5-fold higher and was 62 μ M. Furthermore, in yeasts cultured in the presence of glyphosate does increase synthesis of anthranilate synthase, PR transferase, IGP synthase, chorismate mutase and aromatic aminotransferase, but also synthesis of enzymes of several unrelated pathways. This regulatory system is referred to as “general control of amino acid biosynthesis”.

Effects of Glyphosate on Shikimic Acid Accumulation in Tobacco Cell Cultures with Low and High Yields of Cinnamoyl Putrescines

To study the flow of carbon through the shikimate pathway in tobacco cell cultures with low and high yields of cinnamoyl putrescines, the cell cultures were treated with glyphosate. In the presence of glyphosate the levels of free shikimic acid were increased more than 300-fold by both cell lines. Despite of a normally 10-fold higher level of cinnamoyl putrescines, the high yielding cell line accumulated only 25% more free shikimic acid than the low yielding cell line. This result together with earlier observations indicated that the increased formation of cinnamoyl putrescines was rather limited by the activity of phenylalanine ammonia lyase than by increased substrate supply caused by alterations in the shikimate pathway

The herbicide glyphosate is a potent inhibitor of 5-enolpyruvylshikimic acid-3-phosphate synthase

The broadspectrum herbicide glyphosate (N-[phosphonomethyl]-glycine), which causes the accumulation of shikimic acid in plant tissues, inhibits the enzymatic conversion of shikimic acid to anthranilic acid in a cell-free extract of Aerobacter , aerogenes 50% at 5 to 7 μM concentrations. Of the four enzymes involved in the transformation, only 5-enolpyruvylshikimic acid-3-phosphate synthase is inhibited by the herbicide.

Alicyclic acid metabolism in plants

When the epicotyls of etiolated pea seedlings were fed with 40 mM potassium quinate solution in the dark for 24 hr, a marked accumulation of shikimic acid occurred in the tissue. This effect was much more pronounced in epicotyls preliminarily starved in a phosphate solution for 24 hr. On the other hand, supplying shikimate to the epicotyls brought about no significant accumulation of quinic acid. Tracer studies with14C-shikimate have shown that, in the epicotyls, shikimic acid was rapidly metabolized and fairly high radioactivities were observed in the amino acid fraction. However, feeding of14C-shikimate together with unlabeled alicyclic acids resulted in a reduction of shikimate utilization. When3H-quinate was fed to the epicotyls, radioactivities were retained mostly in an acidic fraction, indicating the sluggish conversion of quinic acid. In starved epicotyls, however, nearly half of the absorbed radioactivity was consumed. In tracer experiments the conversion of quinate to shikimate was clearly observed, whereas the reverse reaction was not. From these findings the metabolic role of quinic acid in quinate-less pea seedlings is discussed.