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PubMed2005

Differential effects of glyphosate and roundup on human placental cells and aromatase.

Roundup is a glyphosate-based herbicide used worldwide, including on most genetically modified plants that have been designed to tolerate it. Its residues may thus enter the food chain, and glyphosate is found as a contaminant in rivers. Some agricultural workers using glyphosate have pregnancy problems, but its mechanism of action in mammals is questioned. Here we show that glyphosate is toxic to human placental JEG3 cells within 18 hr with concentrations lower than those found with agricultural use, and this effect increases with concentration and time or in the presence of Roundup adjuvants. Surprisingly, Roundup is always more toxic than its active ingredient. We tested the effects of glyphosate and Roundup at lower nontoxic concentrations on aromatase, the enzyme responsible for estrogen synthesis. The glyphosate-based herbicide disrupts aromatase activity and mRNA levels and interacts with the active site of the purified enzyme, but the effects of glyphosate are facilitated by the Roundup formulation in microsomes or in cell culture. We conclude that endocrine and toxic effects of Roundup, not just glyphosate, can be observed in mammals. We suggest that the presence of Roundup adjuvants enhances glyphosate bioavailability and/or bioaccumulation.

Adjuvants, Pharmaceutic↗

PubMed2006

The current status and environmental impacts of glyphosate-resistant crops: a review.

Glyphosate [N-(phosphonomethyl) glycine]-resistant crops (GRCs), canola (Brassica napus L.), cotton (Gossypium hirsutum L.), maize (Zea mays L.), and soybean [Glycine max (L.) Merr.] have been commercialized and grown extensively in the Western Hemisphere and, to a lesser extent, elsewhere. Glyphosate-resistant cotton and soybean have become dominant in those countries where their planting is permitted. Effects of glyphosate on contamination of soil, water, and air are minimal, compared to some of the herbicides that they replace. No risks have been found with food or feed safety or nutritional value in products from currently available GRCs. Glyphosate-resistant crops have promoted the adoption of reduced- or no-tillage agriculture in the USA and Argentina, providing a substantial environmental benefit. Weed species in GRC fields have shifted to those that can more successfully withstand glyphosate and to those that avoid the time of its application. Three weed species have evolved resistance to glyphosate in GRCs. Glyphosate-resistant crops have greater potential to become problems as volunteer crops than do conventional crops. Glyphosate resistance transgenes have been found in fields of canola that are supposed to be non-transgenic. Under some circumstances, the largest risk of GRCs may be transgene flow (introgression) from GRCs to related species that might become problems in natural ecosystems. Glyphosate resistance transgenes themselves are highly unlikely to be a risk in wild plant populations, but when linked to transgenes that may impart fitness benefits outside of agriculture (e.g., insect resistance), natural ecosystems could be affected. The development and use of failsafe introgression barriers in crops with such linked genes is needed.

Argentina↗

PubMed2004

[Glyphosate-resistant cotton (Gossypium hirsutum L.) Transformed with aroAM12 gene via Agrobacterium tumefaciens].

A mutant, aroAM12, exhibiting resistance to glyphosate produced in a previous study using the staggered extension process with aroA genes from Salmonella typhimurium and Eschrichia coli. In this paper, we constructed a vector pGRA1300 carrying aroAM12 gene, comprising transit peptide of Arabidopsis EPSPS, under the control of the CaMV35S promoter and used as selectable marker for cotton plant (Gossypium hirsutum L.) transformation. Transgenic cottons with increased resistance to glyphosate were obtained by cotransformtion of hypocotyl segments with Agrobacterium tumefaciens and selected directly on medium containing glyphosate. Regeneration of glyphosate-resistant calli was carried out on a MS basic medium containing 2,4-D 0.1 mg/L, KT 0.1 mg/L, cefotaxime 500 mg/L and glyphosate 60 micromol/L. Globular embryos were induced and then developed by culturing on MSB (MS salts+B(5) vitamins) medium supplemented with asparagine 1 g/L and glutamine 2 g/L, but not containing hormone, for 40 d. The developed plantlets were then removed and cultured on an MS medium. After about 20 d, the deeply-rooted shoots were in soil. PCR analysis showed that the aroAM12 gene was present in all T(0) transgenic plants. The integration of the aroAM12 gene in the genomic DNA of cotton was further confirmed by Southern blot, which showed that the transgenic plants carried one or two copies of the aroAM12 genes. Western blot analysis showed that a 48-kD band of was detected in all T(0) transgenic plants. There was no apparent corelation between copy numbers and the expression level of the aroAM12 gene. Greenhouse screening for glyphosate resistance was performed to test 65 independent T(0) plants by spraying (three times) with an aqueous suspension at a dose corresponding to 9.317 kg/ha of Roundup (once every 5 d). After 15 d, phenotype examination was carried out of the plants in comparison with untransformed control plants. Under these conditions, it was observed that the plants transformed with pGRA1300 showed high resistance to glyphosate whereas the control plants were all killed. The glyphosate resistance of T(1) generation was measured by spraying with Roundup, the numbers of glyphosate resistance and sensitive phenotypes showed Mendelian segregation ratio.

Agrobacterium tumefaciens↗

PubMed1994

Surfactant-Increased Glyphosate Uptake into Plasma Membrane Vesicles Isolated from Common Lambsquarters Leaves.

Plasma membrane vesicles were isolated from mature leaves of lambsquarters (Chenopodium album L.) to investigate whether this membrane is a barrier to glyphosate uptake and whether surfactants possess differential abilities to enhance glyphosate permeability. Amino acids representing several structural classes showed [delta]pH-dependent transport, indicating that the proteins necessary for active, proton-coupled amino acid transport were present and functional. Glyphosate uptake was very low compared to the acidic amino acid glutamate, indicating that glyphosate is not utilizing an endogenous amino acid carrier to enter the leaf cells and that the plasma membrane appears to be a significant barrier to cellular uptake. In addition, glyphosate flux was much lower than that measured for either bentazon or atrazine, both lipid-permeable herbicides that diffuse through the bilayer. Glyphosate uptake was stimulated by 0.01% (v:v) MON 0818, the cationic surfactant used in the commercial formulation of this herbicide for foliar application. This concentration of surfactant did not disrupt the integrity of the plasma membrane vesicles, as evidenced by the stability of imposed pH gradients and active amino acid transport. Nonionic surfactants that disrupt the cuticle but that do not promote glyphosate toxicity in the field also increased glyphosate transport into the membrane vesicles. Thus, no correlation was observed between whole plant toxicity and surfactant-aided uptake. Current data suggest that surfactant efficacy may be the result of charged surfactants' ability to diffuse away from the cuticle into the subtending apoplastic space, where they act directly on the plasma membrane to increase glyphosate uptake.

Journal Article↗

PubMed2005

Rice (Oryza sativa) response to drift rates of glyphosate.

Greenhouse and field studies were conducted to investigate response of two rice varieties, Priscilla and Cocodrie, to sub-lethal rates of glyphosate in terms of injury, shikimate accumulation and yield. In the greenhouse, more shikimate accumulated in Cocodrie than Priscilla at comparable glyphosate rates applied to plants at the three-leaf stage. In field studies, glyphosate was applied to both varieties when they were 74-cm tall and in the internode separation growth stage. Visual injury, plant height, and leaf-tissue samples for shikimate analysis were collected at 3, 7, 14, 21 and 28 days after treatment (DAT). Rice yield was also determined. Noticeable visual injury and height reduction to both varieties was observed as early as 7 and 3 DAT in Cocodrie and Priscilla, respectively. Shikimate levels in leaves began to increase in both varieties by 3 DAT in a dose-dependent manner and reached a peak between 7 and 14 DAT. Elevated shikimate levels were still detectable by 28 DAT. Similar levels of shikimate accumulated in both varieties at comparable glyphosate rates. However, glyphosate treatment at comparable rates reduced rice yields more in Cocodrie than in Priscilla. The highest rate of glyphosate reduced yield in Cocodrie by 92% whereas there was only a 60% yield reduction in Priscilla. Shikimate levels in glyphosate-treated rice were strongly correlated to yield reductions across both varieties and appeared to be a better predictor of yield reduction than was visual injury. Visual injury coupled with measured shikimate levels can be used collaboratively to identify glyphosate exposure and estimate subsequent rice yield reductions.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2006

Influence of glyphosate on Rhizoctonia and Fusarium root rot in sugar beet.

This study tests the effect of glyphosate application on disease severity in glyphosate-resistant sugar beet, and examines whether the increase in disease is fungal or plant mediated. In greenhouse studies of glyphosate-resistant sugar beet, increased disease severity was observed following glyphosate application and inoculation with certain isolates of Rhizoctonia solani Kuhn and Fusarium oxysporum Schlecht. f. sp. betae Snyd. & Hans. Significant increases in disease severity were noted for R. solani AG-2-2 isolate R-9 and moderately virulent F. oxysporum isolate FOB13 on both cultivars tested, regardless of the duration between glyphosate application and pathogen challenge, but not with highly virulent F. oxysporum isolate F-19 or an isolate of R. solani AG-4. The increase in disease does not appear to be fungal mediated, since in vitro studies showed no positive impact of glyphosate on fungal growth or overwintering structure production or germination for either pathogen. Studies of glyphosate impact on sugar beet physiology showed that shikimic acid accumulation is tissue specific and the rate of accumulation is greatly reduced in resistant cultivars when compared with a susceptible cultivar. The results indicate that precautions need to be taken when certain soil-borne diseases are present if weed management for sugar beet is to include post-emergence glyphosate treatments.

Beta vulgaris↗

PubMed2006

Transformation and segregation of GFP fluorescence and glyphosate resistance in horseweed (Conyza canadensis) hybrids.

The goal of this research was to generate a breeding population of horseweed segregating for glyphosate resistance. In order to generate a marker to select between hybrids of glyphosate resistant (GR) and glyphosate susceptible (GS) horseweed, a GR horseweed accession from western Tennessee was transformed with a green fluorescent protein (GFP) transgene. The GFP marker allowed for the simple and accurate determination of GR hybrid plants by visual observation. GR plants were shown to be transgenic via the green fluorescence under UV light, and resistant to glyphosate when sprayed with the field-use-rate 0.84 kg acid equivalent ha(-1) of glyphosate (i.e. Roundup) herbicide. An in vitro screen for glyphosate resistance in seedlings was developed, and a 5 microM glyphosate concentration was found to reduce dry weight in GS seedlings but not in GR seedlings. The GR plants containing GFP were then hand-crossed with GS plants from eastern Tennessee under greenhouse conditions, with GS plants acting as the pollen acceptor. Resulting seed was collected and germinated for GFP fluorescence screening. Seedlings that exhibited the transgenic GFP phenotype were selected as F(1) hybrids between GR and GS horseweed. Thirty GSxGR hybrids were produced on the basis of a green-fluorescent GFP phenotype of GR plants. GSxGFP/GR F(1) hybrids produced F(2) seeds, and F(2) plants were shown to segregate for GFP fluorescence and glyphosate resistance independently. Both traits segregated at a Mendelian 3:1 ratio, indicating a single gene is responsible for each phenotype.

Conyza↗

PubMed2004

Evaluation of transgenic cotton varieties and a glyphosate application on seedling disease incidence.

A study was conducted to determine whether stand densities of transgenic cotton (Gossypium hirsutum) varieties, with or without glyphosate, were similar to conventional varieties of the same lineage group in Georgia and Mississippi. Transgenic and conventional cotton varieties were placed into five lineage groups of related varieties and seedling disease was evaluated in three greenhouse tests and a field trial using Rhizoctonia solani AG-4. Seed vigor was determined by standard germination studies were conducted evaluating conventional and transgenic varieties of similar lineage. Results showed that no interactions occurred for the heights and dry weight data across treatments within the lineage groups in any of the experiments. No interactions were shown between stand densities at different inoculum rates and inoculated versus uninoculated pots (plots). Across all greenhouse studies, stand counts of PM 1220 were similar to the transgenic varieties PM 1220 RR and PM 1220 B/RR with or without a glyphosate application. In the field trial, PM 1220 B/RR + glyphosate had significantly lower stands than all other treatments expect PM 1220 RR (no glyphosate treatment) prior to and after glyphosate application. Stand densities for varieties within the lineage group DPL 5415 were also inconsistent when compared between the greenhouse and field trials with no apparent trends occurring. However, the Coker 312 varieties containing glyphosate tolerance had consistently lower stand counts compared to the conventional variety of Coker 312 but only during the greenhouse studies. Seed germination of Coker 312 could not be correlated with either the greenhouse or field trial data. In general, the commercially available varieties such as PM 1220, DPL 5690, DPL 5415, and DPL 50 with glyphosate tolerance had similar stand count, height, and dry weight data when compared to the conventional varieties from the same lineage group regardless of a glyphosate application. When differences did occur, no consistent trends could be determined within these four lineage groups.

Crops, Agricultural↗

PubMed1988

The essential role of cobalt in the inhibition of the cytosolic isozyme of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Nicotiana silvestris by glyphosate.

The prime molecular target of glyphosate (N-[phosphonomethyl]glycine), a potent herbicidal and antimicrobial agent, is known to be the shikimate-pathway enzyme, 5-enol-pyruvylshikimate-3-phosphate synthase. Inhibition by glyphosate of an earlier pathway enzyme that is located in the cytosol of higher plants, 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DS-Co), has raised the possibility of dual enzyme targets in vivo. With the recent appreciation that magnesium (and manganese) can replace cobalt as the divalent-metal activator of DS-Co, it has now been possible to show that sensitivity of DS-Co to inhibition by glyphosate is obligately dependent upon the presence of cobalt. Evidence for a cobalt(II):glyphosate complex with octahedral coordination was obtained through examination of the effect of glyphosate upon the visible electronic spectrum of aqueous solutions of cobalt(II) chloride. The presence of glyphosate increased the concentration of cobalt(II) chloride required for enzyme activity, and the concentration of cobalt(II) chloride markedly affected the concentration of glyphosate required for inhibition of DS-Co activity. The extent to which DS-Co is vulnerable to inhibition by glyphosate in vivo depends, therefore, upon the unknown extent to which DS-Co molecules in the cytosol might be associated with cobalt.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2006

Chlorination kinetics of glyphosate and its by-products: modeling approach.

Chlorination reactions of glyphosate, glycine, and sodium cyanate were conducted in well-agitated reactors to generate experimental kinetic measurements for the simulation of chlorination kinetics under the conditions of industrial water purification plants. The contribution of different by-products to the overall degradation of glyphosate during chlorination has been identified. The kinetic rate constants for the chlorination of glyphosate and its main degradation products were either obtained by calculation according to experimental data or taken from published literature. The fit of the kinetic constants with experimental data allowed us to predict consistently the concentration of the majority of the transitory and terminal chlorination products identified in the course of the glyphosate chlorination process. The simulation results conducted at varying aqueous chlorine/glyphosate molar ratios have shown that glyphosate is expected to degrade in fraction of a second under industrial aqueous chlorination conditions. Glyphosate chlorination products are not stable under the conditions of drinking water chlorination and are degraded to small molecules common to the degradation of amino acids and other naturally occurring substances in raw water. The kinetic studies of the chlorination reaction of glyphosate, together with calculations based on kinetic modeling in conditions close to those at real water treatment plants, confirm the reaction mechanism that we have previously suggested for glyphosate chlorination.

Chlorine↗

PubMed2002

Glyphosate-resistant goosegrass. Identification of a mutation in the target enzyme 5-enolpyruvylshikimate-3-phosphate synthase.

The spontaneous occurrence of resistance to the herbicide glyphosate in weed species has been an extremely infrequent event, despite over 20 years of extensive use. Recently, a glyphosate-resistant biotype of goosegrass (Eleusine indica) was identified in Malaysia exhibiting an LD(50) value approximately 2- to 4-fold greater than the sensitive biotype collected from the same region. A comparison of the inhibition of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) activity by glyphosate in extracts prepared from the resistant (R) and sensitive (S) biotypes revealed an approximately 5-fold higher IC(50)(glyphosate) for the (R) biotype. Sequence comparisons of the predicted EPSPS mature protein coding regions from both biotypes revealed four single-nucleotide differences, two of which result in amino acid changes. One of these changes, a proline to serine substitution at position 106 in the (R) biotype, corresponds to a substitution previously identified in a glyphosate-insensitive EPSPS enzyme from Salmonella typhimurium. Kinetic data generated for the recombinant enzymes suggests that the second substitution identified in the (R) EPSPS does not contribute significantly to its reduced glyphosate sensitivity. Escherichia coli aroA- (EPSPS deficient) strains expressing the mature EPSPS enzyme from the (R) biotype exhibited an approximately 3-fold increase in glyphosate tolerance relative to strains expressing the mature EPSPS from the (S) biotype. These results provide the first evidence for an altered EPSPS enzyme as an underlying component of evolved glyphosate resistance in any plant species.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2006

Glyphosate-induced anther indehiscence in cotton is partially temperature dependent and involves cytoskeleton and secondary wall modifications and auxin accumulation.

Yield reduction caused by late application of glyphosate to glyphosate-resistant cotton (Gossypium hirsutum; GRC) expressing CP4 5-enol-pyruvylshikmate-3-P synthase under the cauliflower mosaic virus-35S promoter has been attributed to male sterility. This study was aimed to elucidate the factors and mechanisms involved in this phenomenon. Western and tissue-print blots demonstrated a reduced expression of the transgene in anthers of GRC compared to ovules of the same plants. Glyphosate application to GRC grown at a high temperature regime after the initiation of flower buds caused a complete loss of pollen viability and inhibition of anther dehiscence, while at a moderate temperature regime only 50% of the pollen grains were disrupted and anther dehiscence was normal. Glyphosate-damaged anthers exhibited a change in the deposition of the secondary cell wall thickenings (SWT) in the endothecium cells, from the normal longitudinal orientation to a transverse orientation, and hindered septum disintegration. These changes occurred only at the high temperature regime. The reorientation of SWT in GRC was accompanied by a similar change in microtubule orientation. A similar reorientation of microtubules was also observed in Arabidopsis (Arabidopsis thaliana) seedlings expressing green fluorescent protein tubulin (tubulin alpha 6) following glyphosate treatment. Glyphosate treatment induced the accumulation of high levels of indole-3-acetic acid in GRC anthers. Cotton plants treated with 2,4-dichlorophenoxyacetic acid had male sterile flowers, with SWT abnormalities in the endothecium layer similar to those observed in glyphosate-treated plants. Our data demonstrate that glyphosate inhibits anther dehiscence by inducing changes in the microtubule and cell wall organization in the endothecium cells, which are mediated by auxin.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1987

Metabolism of glyphosate in an Arthrobacter sp. GLP-1.

The metabolism of glyphosate [N-(phosphonomethyl)glycine] in a bacterium tentatively identified as an Arthrobacter sp., capable of growth on this herbicide as its sole phosphorus source, has been investigated using solid-state NMR techniques as well as radiotracer analysis. The pathway involves the conversion of glyphosate to glycine, a C1 unit and phosphate. The phosphonomethyl carbon is specifically incorporated into the amino acids serine, cysteine, methionine, and histidine, as well as into purine bases and thymine, indicating the involvement of tetrahydrofolate in single-carbon transfer reactions. Glycine derived from glyphosate is utilized in purine and protein biosynthesis. This pathway for glyphosate degradation in a gram-positive bacterium is similar to that previously reported for Pseudomonas sp. PG2982 [Jacob et al. (1985) J. Biol. Chem. 260, 5899-5905] and is distinct from that reported for soil metabolism of glyphosate where aminomethylphosphonic acid has been shown to be a major metabolite. Preliminary evidence is presented which indicates that the conversion of glyphosate to glycine and the C1 unit involves the intermediate formation of sarcosine. Thus, the primary event in glyphosate degradation by Arthrobacter sp. GLP-1 is the cleavage of its C-P bound. This report constitutes the first demonstration of the metabolism of glyphosate in a gram-positive bacterium.

Arthrobacter↗

PubMed2005

The effect of Saccharomyces cerevisiae on the stability of the herbicide glyphosate during bread leavening.

AIMS: To investigate the ability of baker's yeast (Saccharomyces cerevisiae) to degrade the herbicide glyphosate during the fermentation cycle of the breadmaking process. METHODS AND RESULTS: Aqueous glyphosate was added to bread ingredients and kneaded by commercially available breadmaking equipment into dough cultures. Cultures were incubated in the breadmaker throughout the fermentation cycle. The recovery of glyphosate levels following fermentation was determined, thus allowing an estimation of glyphosate degradation by yeast. CONCLUSIONS: It was shown, for the first time, that S. cerevisiae plays a role in metabolizing glyphosate during the fermentation stages of breadmaking. Approximately 21% was degraded within 1 h. SIGNIFICANCE AND IMPACT OF THE STUDY: As a result of projected increases in the glyphosate use on wheat and the role of bread as a dietary staple, this may contribute to more informed decisions being made relating to the use of glyphosate on glyphosate-resistant wheat, from a public health/regulatory perspective.

Bread↗

PubMed1988

Metabolism of glyphosate in Pseudomonas sp. strain LBr.

Metabolism of glyphosate (N-phosphonomethylglycine) by Pseudomonas sp. strain LBr, a bacterium isolated from a glyphosate process waste stream, was examined by a combination of solid-state 13C nuclear magnetic resonance experiments and analysis of the phosphonate composition of the growth medium. Pseudomonas sp. strain LBr was capable of eliminating 20 mM glyphosate from the growth medium, an amount approximately 20-fold greater than that reported for any other microorganism to date. The bacterium degraded high levels of glyphosate, primarily by converting it to aminomethylphosphonate, followed by release into the growth medium. Only a small amount of aminomethylphosphonate (about 0.5 to 0.7 mM), which is needed to supply phosphorus for growth, could be metabolized by the microorganism. Solid-state 13C nuclear magnetic resonance analysis of strain LBr grown on 1 mM [2-13C,15N]glyphosate showed that about 5% of the glyphosate was degraded by a separate pathway involving breakdown of glyphosate to glycine, a pathway first observed in Pseudomonas sp. strain PG2982. Thus, Pseudomonas sp. strain LBr appears to possess two distinct routes for glyphosate detoxification.

Biodegradation, Environmental↗

PubMed1995

Cloning and sequencing of the genes involved in glyphosate utilization by Pseudomonas pseudomallei.

Thirty-four strains of Pseudomonas pseudomallei isolated from soil were selected for their ability to degrade the phosphonate herbicide glyphosate. All strains tested were able to grow on glyphosate as the only phosphorus source without the addition of aromatic amino acids. One of these strains, P. pseudomallei 22, showed 50% glyphosate degradation in 40 h in glyphosate medium. From a genomic library of this strain constructed in pUC19, we have isolated a plasmid carrying a 3.0-kb DNA fragment which confers to E. coli the ability to use glyphosate as a phosphorus source. This 3.0-kb DNA fragment from P. pseudomallei contained two open reading frames (glpA and glpB) which are involved in glyphosate tolerance and in the modification of glyphosate to a substrate of the Escherichia coli carbon-phosphorus lyase. glpA exhibited significant homology with the E. coli hygromycin phosphotransferase gene. It was also found that the hygromycin phosphotransferase genes from both P. pseudomallei and E. coli confer tolerance to glyphosate.

Amino Acid Sequence↗

PubMed1986

Glyphosate catabolism by Pseudomonas sp. strain PG2982.

The pathway for the degradation of glyphosate (N-phosphonomethylglycine) by Pseudomonas sp. PG2982 has been determined by using metabolic radiolabeling experiments. Radiorespirometry experiments utilizing [3-14C]glyphosate revealed that approximately 50 to 59% of the C-3 carbon was oxidized to CO2. Fractionation of stationary-phase cells labeled with [3-14C]glyphosate revealed that from 45 to 47% of the assimilated label is distributed to proteins and that the amino acids methionine and serine are highly labeled. Adenine and guanine received 90% of the C-3 label found in the nucleic acid fraction, and the only pyrimidine base labeled was thymine. These results indicated that C-3 of glyphosate was at some point metabolized to a C-1 compound whose ultimate fate could be both oxidation to CO2 and distribution to amino acids and nucleic acid bases that receive a C-1 group from the C-1-donating coenzyme tetrahydrofolate. Pulse-labeling of PG2982 cells with [3-14C]glyphosate resulted in the isolation of [3-14C]sarcosine as an intermediate in glyphosate degradation. Examination of crude extracts prepared from PG2982 cells revealed the presence of a sarcosine-oxidizing enzyme that oxidizes sarcosine to glycine and formaldehyde. These results indicate that the first step in glyphosate degradation by PG2982 is cleavage of the carbon-phosphorus bond, resulting in the release of sarcosine and a phosphate group. The phosphate group is utilized as a source of phosphorus, and the sarcosine is degraded to glycine and formaldehyde. This pathway is supported by the results of [1,2-14C]glyphosate metabolism studies, which show that radioactivity in the proteins of labeled cells is found only in the glycine and serine residues.

Adenine↗

PubMedDate not supplied

Influence of glyphosate on flower morphogenesis and pigmentation in Petunia hybrida.

Glyphosate showed a remarkable effect inducing the change of flower symmetry from the actinomorphic to the zygomorphic type in Petunia hybrida. Glyphosate [N-(phosphonomethyl)glycine] reduced the anthocyanin content and showed a weak inhibitory effect against phenylalanine ammonia-lyase (PAL) activity. L-2-Aminooxy-3-phenylpropionic acid (APA), an inhibitor of PAL activity, reduced the anthocyanin content but had no effect on flower shape. Additional phenylalanine or trans-cinnamic acid, the intermediates of glyphosate inhibition against PAL activity, could not recover the change of flower shape induced by glyphosate. These results suggested that the reduction of PAL activity alone could not account for the two characteristic changes of flower symmetry and pigmentation induced by glyphosate. On the other hand, the results of application of glyphosate-related compounds suggested that the structure of glyphosate contributed to induce the morphological change of Petunia flower. Glyphosate may thus be a very useful agent in the elucidation of unresolved questions of flower morphogenesis and the related metabolism.

Flowers↗