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The canonical arsRBC genes of the ars1 operon in Pseudomonas putida KT2440, which confer tolerance to arsenate and arsenite, are followed by a series of additional ORFs culminating in phoN1. The phoN1 gene encodes an acetyltransferase that imparts resistance to the glutamine synthetase inhibitor herbicide phosphinothricin (PPT). The co‐expression of phoN1 and ars genes in response to environmental arsenic, along with the physiological effects, was analysed through transcriptomics of cells exposed to the oxyanion and phenotypic characterization of P. putida strains deficient in different components of the bifan motif governing arsenic resistance in this bacterium. Genetic separation of arsRBC and phoN1 revealed that their associated phenotypes operate independently, indicating that their natural co‐regulation is not functionally required for simultaneous response to the same signal. The data suggest a scenario of associative evolution, akin to Pavlovian conditioning, where two unrelated but frequently co‐occurring signals result in one regulating the other's response – even if there is no functional link between the signal and the response. Such surrogate regulatory events may provide an efficient solution to complex regulatory challenges and serve as a genetic patch to address transient gaps in evolving regulatory networks. [ABSTRACT FROM AUTHOR]

Improving nitrogen use efficiency (NUE) is one of the main ways of increasing plant productivity through genetic engineering. The modification of nitrogen (N) metabolism can affect the hormonal content, but in transgenic plants, this aspect has not been sufficiently studied. Transgenic birch (Betula pubescens) plants with the pine glutamine synthetase gene GS1 were evaluated for hormone levels during rooting in vitro and budburst under outdoor conditions. In the shoots of the transgenic lines, the content of indoleacetic acid (IAA) was 1.5–3 times higher than in the wild type. The addition of phosphinothricin (PPT), a glutamine synthetase (GS) inhibitor, to the medium reduced the IAA content in transgenic plants, but it did not change in the control. In the roots of birch plants, PPT had the opposite effect. PPT decreased the content of free amino acids in the leaves of nontransgenic birch, but their content increased in GS-overexpressing plants. A three-year pot experiment with different N availability showed that the productivity of the transgenic birch line was significantly higher than in the control under N deficiency, but not excess, conditions. Nitrogen availability did not affect budburst in the spring of the fourth year; however, bud breaking in transgenic plants was delayed compared to the control. The IAA and abscisic acid (ABA) contents in the buds of birch plants at dormancy and budburst depended both on N availability and the transgenic status. These results enable a better understanding of the interaction between phytohormones and nutrients in woody plants. [ABSTRACT FROM AUTHOR]

The fast spread of bacteria that are resistant to many classes of antibiotics (multidrug resistant) is a global threat to human and animal health with a worrisome scenario ahead. Novel therapeutical strategies are of crucial importance to combat this phenomenon. For this purpose, we investigated the antimicrobial properties of the naturally occurring tripeptide Bialaphos and a dipeptide L-leucyl-L-phosphinoithricin, the synthesis and diastereomers separation of which are herein described. We demonstrate that these compounds are effective on clinical isolates of the human pathogen Klebsiella pneumoniae, causing hospital-acquired and community-acquired infections. The tested isolates were remarkable for their resistance to more than 20 commercial antibiotics of different classes. Based on previous literature data and our experiments consisting of glutamine supplementation, we suggest that both compounds release phosphinothricin—a well-known nanomolar inhibitor of glutamine synthetase—after their penetration in the bacterial cells; and, in this way, exert their antibacterial effect by negatively affecting nitrogen assimilation in this pathogen. [ABSTRACT FROM AUTHOR]

The bioderacemization of racemic phosphinothricin (D, L-PPT) is a promising route for the synthesis of l-phosphinothricin (L-PPT). However, the low activity and tolerance of wild-type enzymes restrict their industrial applications. Two stereocomplementary aminotransferases with high activity and substrate tolerance were identified in a metagenomic library, and a one-pot, two-stage artificial cascade biocatalytic system was developed to produce L-PPT through kinetic resolution and asymmetric amination. We observed that 500 mM D, L-PPT (100 g/L) could be converted into L-PPT with 94% final conversion and >99.9% enantiomeric excess (e.e.) within 24 h, with only 0.02 eq amino acceptor pyruvate and 1.2 eq amino donor l-aspartate required. The process could be scaled up to 10 L under sufficient oxygen and stirring. The superior catalytic performance of this system provides an eco-friendly and sustainable approach to the industrial deracemization of D, L-PPT to L-PPT.

Glufosinate is a key herbicide to manage glyphosate‐resistant weeds mainly because it is a broad‐spectrum herbicide, and transgenic glufosinate‐resistant crops are available. Although glufosinate use has increased exponentially over the past decade, the treated area with this herbicide is far less than that with glyphosate. This is because glufosinate often provides inconsistent performance in the field, which is attributed to several factors including environmental conditions, application technology, and weed species. Glufosinate is also highly hydrophilic and does not translocate well in plants, generally providing poor control of grasses and perennial species. In the soil, glufosinate is rapidly degraded by microorganisms, leaving no residual activity. While there have been concerns regarding glufosinate toxicology, its proper use can be considered safe. Glufosinate is a fast‐acting herbicide that was first discovered as a natural product, and is the only herbicide presently targeting glutamine synthetase. The mode of action of glufosinate has been controversial, and the causes for the rapid phytotoxicity have often been attributed to ammonia accumulation. Recent studies indicate that the contact activity of glufosinate results from the accumulation of reactive oxygen species and subsequent lipid peroxidation. Glufosinate disrupts both photorespiration and the light reactions of photosynthesis, leading to photoreduction of molecular oxygen, which generates reactive oxygen species. The new understanding of the mode of action provided new ideas to improve the herbicidal activity of glufosinate. Finally, a very few weed species have evolved glufosinate resistance in the field, and the resistance mechanisms are generally not well understood requiring further investigation. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

ABSTRACT: With the possibility of using ammonium glufosinate in corn, studies on its association with other herbicides are essential. The aim of this study was to assess weed control and herbicide selectivity in association with ammonium glufosinate in corn containing the pat and cp4-epsps genes. The experiment was carried out under field conditions in two sites in a randomized block design with four replications. Treatments consisted of ammonium glufosinate, glyphosate, ammonium glufosinate + glyphosate, ammonium glufosinate + nicosulfuron, ammonium glufosinate + atrazine, ammonium glufosinate + tembotrione, ammonium glufosinate + mesotrione, ammonium glufosinate + carfentrazone ethyl, ammonium glufosinate + bentazon, ammonium glufosinate + 2,4-D, control without weeding, and hand-weeded control. Visual assessments were performed regarding damage, electron transport rate in photosystem II (ETR), ammonia quantification, height, and grain yield of corn plants, as well as weed control at both sites. The application of ammonium glufosinate and its associations did not provide a reduction in productivity when compared to the hand-weeded control. Some treatments presented higher levels of visual damage and ammonia accumulation, but without a yield reduction. Therefore, herbicide mixture with ammonium glufosinate may be an alternative to weed control without damaging corn crop, which presents in its genetic constitution the cp4-epsps and pat genes.

Active ingredient of the commercial herbicide BASTA (B), phosphinothricin, acts as an inhibitor of glutamine synthetase (GS), a key enzyme in ammonium assimilation. The treatment with BASTA leads to an elevation of ammonium levels in plants and further to various physiological alterations, ammonium toxicity and lethality. Results of the present study emphasize the complexity underlying control mechanisms that determine BASTA interaction with essential oil (EO) from Nepeta rtanjensis (Nr EO), bioherbicide inducing oxidative stress in target plants. Simultaneous application of Nr EO and BASTA, two agents showing differential mode of action, suspends BASTA-induced ammonium toxicity in Arabidopsis thaliana plants. This is achieved through maintaining GS activity, which sustains a sub-toxic and/or sub-lethal ammonium concentration in tissues. As revealed by the present study, regulation of GS activity, as influenced by BASTA and Nr EO, occurs at transcriptional, posttranscriptional, and/or posttranslational levels. Two genes encoding cytosolic GS, GLN1;1 and GLN1;3 , are highlighted as the main isozymes in Arabidopsis shoots contributing to Nr EO-induced overcoming of BASTA-generated ammonium toxicity. The effects of Nr EO might be ascribed to its major component nepetalactone, but the contribution of minor EO components should not be neglected. Although of fundamental significance, the results of the present study suggest possible low efficiency of BASTA in plantations of medicinal/aromatic plants such as Nepeta species. Furthermore, these results highlight the possibility of using Nr EO as a bioherbicide in BASTA-treated crop fields to mitigate the effect of BASTA residues in contaminated soils. [ABSTRACT FROM AUTHOR]

Main conclusion: Glufosinate is primarily toxic to plants due to a massive light-dependent generation of reactive oxygen species rather than ammonia accumulation or carbon assimilation inhibition. Glutamine synthetase (GS) plays a key role in plant nitrogen metabolism and photorespiration. Glufosinate (C5H12NO4P) targets GS and causes catastrophic consequences leading to rapid plant cell death, and the causes for phytoxicity have been attributed to ammonia accumulation and carbon assimilation restriction. This study aimed to examine the biochemical and physiological consequences of GS inhibition to identify the actual cause for rapid phytotoxicity. Monocotyledonous and dicotyledonous species with different forms of carbon assimilation (C3 versus C4) were selected as model plants. Glufosinate sensitivity was proportional to the uptake of herbicide between species. Herbicide uptake also correlated with the level of GS inhibition and ammonia accumulation in planta even with all species having the same levels of enzyme sensitivity in vitro. Depletion of both glutamine and glutamate occurred in glufosinate-treated leaves; however, amino acid starvation would be expected to cause a slow plant response. Ammonia accumulation in response to GS inhibition, often reported as the driver of glufosinate phytotoxicity, occurred in all species, but did not correlate with either reductions in carbon assimilation or cell death. This is supported by the fact that plants can accumulate high levels of ammonia but show low inhibition of carbon assimilation and absence of phytotoxicity. Glufosinate-treated plants showed a massive light-dependent generation of reactive oxygen species, followed by malondialdehyde accumulation. Consequently, we propose that glufosinate is toxic to plants not because of ammonia accumulation nor carbon assimilation inhibition, but the production of reactive oxygen species driving the catastrophic lipid peroxidation of the cell membranes and rapid cell death. [ABSTRACT FROM AUTHOR]

Sugarcane being the major contributor of sugar and potential source of biofuel around the globe, occupies significant commercial importance. Red rot is the most devastating disease of sugarcane, severely affecting its quality as well as yield. Here we report the overexpression of SUGARWIN1 and SUGARWIN2 genes in any field crop for the first time. For this purpose, SUGAWIN1 and SUGARWIN2 were cloned downstream of maize ubiquitin (Ubi-1) promoter to construct two independent expression cassettes. The bar gene conferring resistance against phosphinothricin was used as selectable marker. Embryogenic calli of sugarcane were bombarded with both expression cassettes and selected on regeneration medium supplemented with phosphinothricin. The phosphinothricin-resistant shoots were rooted and then, analyzed using molecular tools at the genomic as well as transcriptomic levels. The transcriptomic analysis, using real time qPCR, showed that expression of SUGARWIN1 (SWO) and SUGARWIN2 (SWT) was higher in transgenic plants as compared to untransformed plants. Our results further demonstrated that over expression of these genes under maize ubiquitin (Ubi-1) promoter causes significant restriction in proliferation of red rot causal agent, Colletotrichum falcatum in sugarcane transgenic plants, under in vitro conditions. This report may open up exciting possibilities to extend this technology to other monocots for the development of crops with better ability to withstand fungal pathogens.

Phosphinothricin (PPT) is one of the most widely used herbicides. PTT targets glutamine synthetase (GS) activity in plants, and its phytotoxicity is ascribed to ammonium accumulation and reactive oxygen species bursts, which drives rapid lipid peroxidation of cell membranes. In agricultural fields, PPT is extensively sprayed on plant foliage; however, a portion of the herbicide reaches the soil. According to the present study, PPT absorbed via roots can be phytotoxic to Arabidopsis, inducing more adverse effects in roots than in shoots. Alterations in plant physiology caused by 10 days exposure to herbicide via roots are reflected through growth suppression, reduced chlorophyll content, perturbations in the sugar and organic acid metabolism, modifications in the activities and abundances of GS, catalase, peroxidase, and superoxide dismutase. Antagonistic interaction of Nepeta rtanjensis essential oil (NrEO) and PPT, emphasizes the existence of complex control mechanisms at the transcriptional and posttranslational level, which result in the mitigation of PPT-induced ammonium toxicity and in providing more efficient antioxidant defense of plants. Simultaneous application of the two agents in the field cannot be recommended; however, NrEO might be considered as the PPT post-treatment for reducing harmful effects of herbicide residues in the soil on non-target plants.

l-Phosphinothricin (glufosinate or 2-amino-4-((hydroxy(methyl) phosphinyl) butyric acid ammonium salt (AHPB)), which is a structural analog of glutamate, is a recognized herbicide that acts on weeds through inhibition of glutamine synthetase. Due to the structural similarity between phosphinothricin and some bisphosphonates (BPs), this study focuses on investigating the possibility of repurposing phosphinothricin as a bisphosphonate analogue, particularly in two medicine-related activities: image probing and as an anti-cancer drug. As BP is a competitive inhibitor of human farnesyl pyrophosphate synthase (HFPPS), in silico molecular docking and dynamic simulations studies were established to evaluate the binding and stability of phosphinothricin with HFPPS, while the results showed good binding and stability in the active site of the enzyme in relation to alendronate. For the purpose of inspecting bone-tissue accumulation of phosphinothricin, a technetium (99mTc)–phosphinothricin complex was developed and its stability and tissue distribution were scrutinized. The radioactive complex showed rapid, high and sustained uptake into bone tissues. Finally, the cytotoxic activity of phosphinothricin was tested against breast and lung cancer cells, with the results indicating cytotoxic activity in relation to alendronate. All the above results provide support for the use of phosphinothricin as a potential anti-cancer drug and of its technetium complex as an imaging probe. [ABSTRACT FROM AUTHOR]

Screening of gene manipulation events (transgenic, mutation/genome editing, etc.) is a cost/labor-intensive and time-consuming process in plant science research. While polymerase chain reaction (PCR) is the most commonly used method for screening, the process still requires efficient DNA extraction and subsequent confirmation. However, PCR cannot predict gene expression. To screen a larger number of transgenic plants, it would be ideal to develop a quick and reliable screening procedure. We have applied a Liberty®leaf-painting method (againstbargene under 4x35S promoter) to screen transgenic maize (Zea maysL.) plants and validated the results through PCR and quantitative real-time PCR (qRT-PCR). Liberty leaf painting at 500 mg L−1a.i. was > 95% accurate in identifying transgenic events that agreed with the PCR results. Further investigation of bar gene expression in sensitive lines that were PCR positive shows very low expression of the bar gene. We have provided a simple, and rapid assay to determine the transgene expression potential of maize plants expressing the bar gene. The herbicide can be applied to a fully expanded leaf and evaluated one week after application. Green or partially green leaf blades indicate high or moderately high expression of the bar gene and a total yellowing indicates absence or extremely low expression of the bar gene in the transgenic plants. A small volume of Liberty solution is adequate to test hundreds of maize plants, and the assay is reproducible with a high frequency (> 95%) and also displays good correlation with gene expressionin planta. [ABSTRACT FROM AUTHOR]

Phosphinothricin (PPT) is a widely used and non-selective herbicide. PPT-resistance genes, especially PPT N -acetyltransferase genes, have been used in the development of transgenic PPT-resistant crops. However, there are only a limited number of available PPT-resistance genes for use in plant biotechnology. In this study, we found that Enterobacter LSJC7 is highly resistant to PPT and can acetylate PPT to N -acetyl phosphinothricin (Ac-PPT). Furthermore, a novel PPT N -acetyltransferase gene, named LsarsN , was identified from LSJC7. When LsarsN was expressed in E. coli AW3110, it confered resistance to PPT. Ac-PPT was detected in both the culture medium and cells of AW3110 expressing the LsarsN- pET22b plasmid. The purified LsArsN protein also showed strong N -acetylation ability in vitro , and its enzymatic kinetic curve was fitted with the Michaelis-Mentan equation. Compared with wild-type LsArsN, both R72A and R74A mutants showed significantly lower PPT N -acetylation ability. In summary, our results systematically characterized LsArsN with strong ability for PPT N -acetylation, which lays the groundwork for future research into the use of this novel gene, LsarsN , to create PPT-resistant crops. [Display omitted] • Enterobacter LSJC7 is highly resistant to phosphinothricin. • LSJC7 acetylates phosphinothricin to N -acetyl phosphinothricin. • E. coli expressing LsarsN confers resistance to phosphinothricin. • LsArsN acetylates phosphinothricin in vitro. [ABSTRACT FROM AUTHOR]

Safflower is an important oilseed crop with a nutritionally desirable oil composition comprising low levels of saturated fatty acids and high levels of unsaturated fatty acids. In this study, a robust, genotype-independent plant regeneration protocol was developed for geographically diverse safflower genotypes, including one accession each from America, Australia, Egypt, Germany, Kazakhstan and three important Indian genotypes (Sharda, Bhima and PBNS-12). Use of cotyledonary nodes as explants resulted in genotype-independent regeneration on BAP (6-Benzylaminopurine), NAA (Naphthalene acetic acid) and ascorbic acid supplemented MS medium. Histological analysis revealed that multiple shoot apical meristems originated independently from peripheral cortical regions of explants. We developed a highly efficient in vitro micrografting method which enabled successful rooting of 85-90 % of regenerated shoots. An efficient genetic transformation system was also established for three Indian genotypes viz., Sharda, Bhima and PBNS-12 using the Agrobacterium strain, LBA4404 and phosphinothricin as the selection agent. This is the first report on use of phosphinothricin-based selection and cotyledonary nodes as explants for Agrobacterium-mediated transformation of safflower. Use of vacuum infiltration-assisted Agrobacterium infection and inclusion of a pre-culture step significantly increased transformation frequencies in all the three genotypes as seen by GUS assays on transformed calli. Genomic integration and transgene expression were confirmed by PCR, Southern hybridization and GUS assays. Most transgenic plants (90 %) exhibited a normal phenotype when grown under controlled conditions and produced viable seeds. This protocol would be useful for introduction of desirable traits in diverse genotypes of safflower. [ABSTRACT FROM AUTHOR]

O objetivo deste trabalho foi avaliar a sensibilidade de plantas transgênicas de citrumelo Swingle com elevada produção de prolina, ao herbicida glufosinato de amônio. As plantas utilizadas apresentavam a inserção do gene mutante da enzima delta1-pirrolina-5-carboxilato sintetase (P5CS), responsável pela biossíntese de prolina. A expressão do gene p5cs em plantas transgênicas causou aumento nas quantidades de prolina em tecidos foliares, em até cinco vezes, quando comparadas às plantas-controle tratadas com 200 µM de glufosinato de amônio. As plantas transgênicas acumularam maior quantidade de NH4+ nas folhas, em relação às plantas não-transgênicas. Os danos causados pelo herbicida foram avaliados in vitro, utilizando-se discos foliares cultivados em meio MS com diferentes concentrações de glufosinato de amônio. Observou-se maior clorose em discos foliares das plantas transgênicas, o que comprova a maior suscetibilidade de plantas de citrumelo Swingle com alta produção de prolina ao herbicida.The objective of this work was to evaluate the susceptibility to glufosinate ammonium of transgenic plants of Swingle citrumelo with high proline production. The mutant gene of the enzyme delta1-pyrroline-5-carboxylate synthetase (P5CS), the rate-limiting enzyme in proline biosynthesis, was inserted into Swingle citrumelo plants. The expression of the gene p5cs caused up to 5-fold increase on the proline content in leaf tissues of transgenic plants treated with 200 µM glufosinate ammonium, when compared with control plants. Leaves of transgenic plants accumulated higher amounts of NH4+ than the nontransgenic control. The herbicide toxicity was evaluated using leaf disks cultivated in MS medium, containing different concentrations of glufosinate ammonium. The severity of the chlorosis, observed in leaf disks of transgenic plants, confirmed the higher susceptibility of Swingle citrumelo plants, with high proline production, to this herbicide.

Objectives: To develop a host-vector system for heterologous protein co-expression and purification in the Trichoderma reesei (teleomorph Hypocrea jecorina) industrial strain RUT-C30. Results: The co-expression and purification system is based on: (i) an efficient and reliable selectable marker using bar (phosphinothricin acetyltransferase gene); (ii) a compact hygromycin B resistance marker; and (iii) a versatile integration plasmid for gene expression and knockout. Fluorescent protein genes were introduced into T. reesei and the corresponding proteins were purified from fermentation broth. The host-vector system was used in a proof-of-principle approach to achieve the co-expression of an alkaline endoglucanase and an alkaline cellobiohydrolase. Conclusions: This protocol can be used at an industrial scale to produce large amounts of proteins in T. reesei. [ABSTRACT FROM AUTHOR]

Apricot ( Prunus armeniaca L.) is one of the most recalcitrant species for genetic transformation. In this work; we report the regeneration of transgenic apricot plants from mature seed hypocotyl segments (cv. ‘Canino’ and ‘Moniquí’) for the first time. Moreover, this is the first report of the regeneration of apricot transgenic plants by means of the selective bar gene. Agrobacterium tumefaciens strain LB4404 harbouring a binary plasmid with eyfp and nptII genes (pMOG- eyfp -IV2) or a plasmid with gus and bar genes (pFGC5941- gus ), was used in this study. A gradual selection strategy with aminoglycoside antibiotics made it possible to produce transgenic plants with 1.5 ± 0.5% efficiency using 10 μM paromomycin (PAR). When buds were isolated and placed in a meristem development medium, PAR was changed to 20 μM kanamycin (KAN). As the buds developed and elongated, the concentration was increased up to 140 μM KAN based on a 20 μM increase every 4 weeks. When bar was the marker gene, the regeneration-inhibitory PPT concentration (75.7 μM) was applied immediately after the co-culture. In this case, the PPT concentration was reduced afterwards to 10.1 μM in the micropropagation medium. This strategy allowed for the regeneration of transgenic shoots with 3.8 ± 1.4% efficiency. Transformation events were monitored by detection of the reporter gene ( eyfp or gus ) expression. PCR and Southern blot analysis confirmed the stable integration of the transgenes into the apricot genome. Transformed shoots were rooted on a selective medium, acclimatised, cultured and raised under greenhouse conditions. Our results confirm that the process used in this study is an efficient transformation system for the apricot species which could be used for functional genomics studies and the development of transgenic rootstocks. [ABSTRACT FROM AUTHOR]

The establishment of a genetic transformation program requires a selection in vitro system of transformed tissues. In the Glycine genus exists few references that employ the Glufosinate-ammoniun that selective agent in transformed somatic embryos. For this reason this work had as objective to determine the minimum lethalconcentration of the herbicide Glufosinate-ammoniun in somatic embryos of Cuban soybean cultivar INCASoy-27, to use as selective agent in genetic transformation programs. The soybean somatic embryos were placed on multiplication medium that contained 2,4-dichlorophenoxyacetic acid 20 mg L-1 with different concentrations of Glufosinate-ammonium (1,0; 2,0; 3,0; 4,0; 5,0; 6,0 mg L-1). All concentrations of selective agent caused necrosis in not transformed soybean somatic embryos. The increments of selective agent concentration and culture time increased the necrosis of somatic embryos. Finally was determined the minimum lethal concentration of 6,0 mg L-1 Glufosinate-ammoniun in semisolid medium, that selective agent in the genetic transformation of somatic embryos of soybean cultivar INCASoy-27. [ABSTRACT FROM AUTHOR]

We compared the transformation frequency of a positive selection system, which employs an Escherichia coli-derived pmi (phosphomannose isomerase) gene as the selectable marker and mannose as the selective agent, to commonly used negative selection systems of bar (phosphinothricin acetyltransferase) /phosphinothricin (PPT), npt II (neomycin phosphotransferase) /G418 (geneticin), and hpt (hygromycin phosphotransferase) /Hygromycin. Transgenic sugarcane plants were obtained following biolistic transformation of callus with four different selectable marker genes. Under different selective agents, transformed callus was selectively proliferated on MS medium containing 13.57 μM of 2,4-D, regenerated on MS medium with 4.44 μM of BA, 9.29 μM of KT, and 0.89 μM of NAA, and rooted on half of MS medium with 13.38 μM of NAA and 0.44 μM of 6-BA. The results demonstrated that the transformation frequency of 4.2% scored in the pmi/mannose positive system was significantly higher than those in the negative selection systems (0.47% for bar/PPT, 1.38% for npt II/G418, and 0.63% for hpt/Hygromycin, respectively). Transgenic sugarcane plants using the pmi/mannose system were confirmed by polymerase chain reaction (PCR) analysis and chlorophenol red (CPR) assay. The CPR assay was found to efficiently and qualitatively detect the transgenic sugarcane from the nontransformed plants because medium color changes in the CPR assay were highly responsive to pmi gene expression and enzyme activity. Thus, a pmi/mannose positive selection system for sugarcane transformation was developed to obviate the use of negative selection systems based on herbicides and antibiotics. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel phosphinothricin N-acetyltransferase gene, repat, from the marine bacterium was isolated. [•] RePAT can utilize both l-phosphinothricin and l-methionine sulfoximine. [•] RePAT is a cold-adaptive enzyme. [Copyright &y& Elsevier]

We have developed marker-free transgenic wheat using a transcription factor, AtDREB1A cloned from Arabidopsis. Southern hybridization confirmed a transgenic event with a single copy insertion. PCR analysis of the T plants showed four were positive only for AtDREB1A. A T1 plant (HRCB3#17-37) was marker-free and had good expression of drought tolerance in comparison with untransformed plants. The leaf relative water content of this T transgenic plant was 12-15 % higher than that of the wild type during stress with an 8 % higher yield under water deficit conditions compared with wild type plants. [ABSTRACT FROM AUTHOR]

Highlights: [•] Phosphinothricin (PPT) was completely acetylated into N-AcPt with THF and Ac2O. [•] N-AcPt, nontoxic to WT rice, showed negative selection effect on argE transgenic rice. [•] ⩾0.1mgml−1 of N-AcPt induced self-destruction of leaf discs of argE transgenic rice. [•] Also, seed germination of them was completely restricted in ⩾0.5mgml−1 of N-AcPt. [•] This system will be useful for developing selectable marker free transgenic rice. [ABSTRACT FROM AUTHOR]

Herbicide phosphinothricin (PPT) inhibits glutamine synthetase (GS), a key enzyme in nitrogen assimilation, thus causing ammonia accumulation, glutamine depletion and eventually plant death. However, the growth response of Lotus corniculatus L. plants immersed in solutions with a broad range of PPT concentrations is biphasic, with pronounced stimulating effect on biomass production at concentrations ≤50 μM and growth inhibition at higher concentrations. The growth stimulation at low PPT concentrations is a result of activation of chloroplastic isoform GS2, while the growth suppression is caused by inhibition of both cytosolic GS1 and GS2 at higher PPT concentrations. Since the results are obtained in cell-free system (e.g. protein extracts), to which the principles of homeostasis are not applicable, this PPT effect is an unambiguous example of direct stimulation hormesis. A detailed molecular mechanism of concentration-dependent interaction of both PPT and a related GS inhibitor, methionine sulfoximine, with GS holoenzymes is proposed. The mechanism is in concurrence with all experimental and literature data. [ABSTRACT FROM AUTHOR]

l-Methionine sulfoximine (MSO) and dl-Phosphinothricin (PPT), two non-proteinogenic amino acids known as inhibitors of Glutamine Synthetase, cause a dose-dependent increase in the phosphorylation of the mTOR substrate S6 kinase 1. The effect is particularly evident in glutamine-depleted cells, where mTOR activity is very low, but is detectable for PPT also in the presence of glutamine. The stimulation of mTOR activity by either MSO or PPT is strongly synergized by essential amino acids. Thus, the non-proteinogenic amino acids MSO and PPT are mTOR activators. [ABSTRACT FROM AUTHOR]

Efficient Agrobacterium tumefaciens-mediated transformation and a higher recovery of transformed plants of cucumber cv. Poinsett76 were achieved via direct organogenesis from cotyledon explants. Stable transformants were obtained by inoculating explants with A. tumefaciens strains EHA105 or LBA4404, both harboring the binary vector pME508, which contains the neomycin phosphotransferase II ( nptII) and phosphinothricin resistance genes ( bar) conferring resistance to kanamycin and PPT, respectively, as selectable markers and the sgfp-tyg gene for the green fluorescent protein (GFP) as a visual marker driven by the constitutive CaMV35S promoter in the presence of acetosyringone (50 μM). Transformed shoots were obtained on MS Murashige and Skoog (Plant Physiol. 15: 473–497, ) medium supplemented with 1 mg L−1 benzyladenine (BA), 20 mg L−1 l-glutamine and 2 mg L−1 phosphinothricin (PPT) or 100 mg L−1 kanamycin. The regenerated shoots were examined in vivo using a hand-held long wave UV lamp for GFP expression. The GFP screening helped identify escapes and chimeric shoots at regular intervals to increase the growth of transformed shoots on cotyledon explants. Elongation and rooting of putative transformants were achieved on PPT (2 mg L−1) containing MS media with 0.5 mg L−1 gibberellic acid (GA3) and 0.6 mg L−1 indole butyric acid (IBA), respectively. PCR and Southern analyses confirmed the integration of the sgfp gene into the genome of T0 and the progenies. T1 segregation of transgenic progeny exhibited Mendelian inheritance of the transgene. The use of EHA105 resulted in 21% transformation efficiency compared to 8.5% when LBA4404 was used. This higher rate was greatly facilitated by PPT selection coupled with effective screening of transformants for GFP expression, thus making the protocol highly useful for the recovery of a higher number of transgenic cucumber plants. [ABSTRACT FROM AUTHOR]

Natural products containing carbon-phosphorus bonds (phosphonic and phosphinic acids) have found widespread use in medicine and agriculture. Recent years have seen a renewed interest in the biochemistry and biology of these compounds with the cloning of the biosynthetic gene clusters for several family members. This review discusses the commonalities and differences in the molecular logic that lie behind the biosynthesis of these compounds. The current knowledge regarding the metabolic pathways and enzymes involved in the production of a number of natural products, including the approved antibiotic fosfomycin, the widely used herbicide phosphinothricin (PT), and the clinical candidate for treatment of malaria FR-900098, is presented. Many of the enzymes involved in the biosynthesis of these compounds catalyze chemically and biologically unprecedented transformations, and a wealth of new biochemistry has been revealed through their study. These investigations have also suggested new strategies for natural product discovery. [ABSTRACT FROM AUTHOR]

Human tissue-plasminogen activator (t-PA) is a thrombolytic protein that plays an active role in dissolving fibrin clots by fibrinolysis and in activating the transition from plasminogen to plasmin in blood vessels. The recombinant tissue-plasminogen activator (rTPA) produced in plants is a soluble protein derived from human t-PA. In order to produce rTPA protein in plants, a DNA fragment encoding the t-PA protein was cloned into a plant binary plasmid that included the cauliflower mosaic virus 35S promoter, a tobacco etch virus (TEV) leader sequence, an N-terminal signal peptide of the alfala glucose-regulated endoplasmic reticular protein, and an 35S terminator. The insertion of the rTPA gene in genomic DNA of phospinothricin-resistant tobacco plants was confirmed by polymerase chain reaction (PCR). The presence of the rTPA-specific transcript in the total RNAs of transgenic plants leaves was verified by reverse transcription (RT)-PCR. Immunoblot analysis of the transformed tobacco leaves revealed single bands of 68-kDa rTPAs. Enzyme-linked immunosorbent assay experiments demonstrated that the highest level of rTPA expression was 0.0014% of the total soluble protein in tobacco plants. Fibrinolysis of rTPA was confirmed by fibrin plate assay and zymography. These studies demonstrate that plants can be employed as bioreactor systems for the production of an enzymatically active t-PA with properties similar to the recombinant t-PA produced by mammalian cells. [ABSTRACT FROM AUTHOR]

The article presents a s study which identifies a novel bacterial Phosphinothricin (PPT) N-acetyltransferase, methione sulfone N-acetylransferase (MAT) through the isolation of the PPT-gene from a soil bacterium Nocardia sp. It was found that MAT has the ability to detoxify the herbicide PPT. In addition, MAT's chloroplast expression can lead to a higher herbicide resistance than expression in the cytosol. It also shows that MAT can be used a selectable marker in plants' transformation.

Abstract: Gene ACIAD1637 from Acinetobacter baylyi ADP1 encodes a 182 amino acid putative antibiotic resistance protein. The structure of this protein (termed acepita) has been solved in space group P2 to 2.35 Å resolution. Acepita belongs to the GCN5-related N-acetyltransferase (GNAT) family, and contains the four sequence motifs conserved among family members. The structure of acepita is compared with that of pita, its homologue from Pseudomonas aeruginosa. Acepita has a similar substrate profile to pita and performs a similar function. [Copyright &y& Elsevier]

The aim of this study was to investigate the culturable bacteria living in soil cultivated with Basta®-tolerant transgenic white poplars (Populus alba L. ‘Villafranca’). Plate Count Agar medium containing phosphinothricin, the active component of Basta®, was used to isolate the herbicide-resistant bacteria (HRB). No significant changes in the size of the soil microbial flora following herbicide treatment were observed. The characterization of HRB isolates by 16S rDNA-based taxonomy revealed a predominance of Pseudomonas and Bacillus species. The screening carried out on soil samples allowed for the recovery of isolates with useful properties for biotechnological and agronomical purposes, particularly in relation to root development. Among the tested isolates, only HRB-1b, HRB-1c, and HRB-7 showed remarkable swarming ability, a valuable trait supporting the beneficial plant-microbe interactions. HRB-1c was also characterized by consistent production of indoleacetic acid (17.8 ± 0.09 μg·mL-1· (OD600 unit)-1), and it was able to stimulate the in vitro growth of Villafranca explants. Since novel tools are constantly required to enhance productivity of perennial species and to expand their use for practical purposes, the availability of bacteria that support tree growth, such as the HRB-1c isolate, represents a significant advantage. [ABSTRACT FROM AUTHOR]

Abstract: Glutamine synthetase (GS) is the main enzyme involved in ammonia assimilation in plants and is the target of phosphinothricin (PPT), an herbicide commonly used for weed control in agriculture. As a result of the inhibition of GS, PPT also blocks photorespiration, resulting in the depletion of leaf amino acid pools leading to the plant death. Hybrid transgenic poplar (Populus tremula × P. alba INRA clone 7171-B4) overexpressing cytosolic GS is characterized by enhanced vegetative growth [Gallardo, F., Fu, J., Cantón, F.R., García-Gutiérrez, A., Cánovas, F.M., Kirby, E.G., 1999. Expression of a conifer glutamine synthetase gene in transgenic poplar. Planta 210, 19–26; Fu, J., Sampalo, R., Gallardo, F., Cánovas, F.M., Kirby, E.G., 2003. Assembly of a cytosolic pine glutamine synthetase holoenzyme in leaves of transgenic poplar leads to enhanced vegetative growth in young plants. Plant Cell Environ. 26, 411–418; Jing, Z.P., Gallardo, F., Pascual, M.B., Sampalo, R., Romero, J., Torres de Navarra, A., Cánovas, F.M., 2004. Improved growth in a field trial of transgenic hybrid poplar overexpressing glutamine synthetase. New Phytol. 164, 137–145], increased photosynthetic and photorespiratory capacities [El-Khatib, R.T., Hamerlynck, E.P., Gallardo, F., Kirby, E.G., 2004. Transgenic poplar characterized by ectopic expression of a pine cytosolic glutamine syntetase gene exhibits enhanced tolerance to water stress. Tree Physiol. 24, 729–736], enhanced tolerance to water stress (El-Khatib et al., 2004), and enhanced nitrogen use efficiency [Man, H.-M., Boriel, R., El-Khatib, R.T., Kirby, E.G., 2005. Characterization of transgenic poplar with ectopic expression of pine cytosolic glutamine synthetase under conditions of varying nitrogen availability. New Phytol. 167, 31–39]. In vitro plantlets of GS transgenic poplar exhibited enhanced resistance to PPT when compared with non-transgenic controls. After 30days exposure to PPT at an equivalent dose of 275gha−1, growth of GS transgenic poplar plantlets was 5-fold greater than controls. The response of young leaves to PPT treatment depends on physiological state as indicated by GS and Rubisco (LSU) levels. Young leaves from control plants, typically in a low differentiation state, respond to the herbicide showing up-regulation of GS and LSU. In contrast, young leaves from transgenic lines, with higher initial GS and LSU levels compared to control, display up-regulation of NADP+-isocitrate dehydrogenase. Differences between control and GS transgenics in their response to PPT are discussed in relation to their differences in photosynthetic and photorespiratory capacities (). [Copyright &y& Elsevier]

The article presents a study that investigates the effect of phosphinothricin based herbicide on soil microorganisms. The research was conducted to culturable aerobic bacteria, actimocetes and fungi by monitoring its soil microbial populations and activities for 40 days using dehydrogenase activity and microcosm experiments. The study reveals that insufficient bioavailability of chemicals in soil may lead to low biological degradation of substances and susceptibility to pesticide residues. It also asserts that widespread use of glufosinate provides harmful effects on soil microorganisms as well as other activities because of the toxicity it inhibits.

Genetic modification of nitrogen metabolism via bacterial NADPH- dependent glutamate dehydrogenase (GDH; E.C.4.1.2.1) favorably alters growth and metabolism of C3 plants. The aim of this study was to examine the effect of expression of GDH in the cytoplasmic compartment of Zea mays cells. The gdhA gene from Escherichia coli , that encoded a NADPH-GDH, was ligated to the ubiquitin promoter that incorporated the first intron enhancer and used to transform Z. mays cv. ‘H99’ embryo cultures by biolistics. R0–R3 generations included selfed inbreds, back-crossed inbreds, and hybrids with B73 derivatives. The lines with the highest GDH specific activity produced infertile R0 plants. The highest specific activity of GDH from the fertile Z. mays plants was sufficient to alter phenotypes. Plant damage caused by the phosphinothricin in gluphosinate-type herbicides, glutamine synthetase (GS; EC 6.1.3.2) inhibitors, was less pronounced in Z. mays plants with gdhA pat than in gusA pat plants. Germination and grain biomass production were increased in gdhA transgenic plants in the field during seasons with significant water deficits but not over all locations. Water deficit tolerance under controlled conditions was increased. Crops modified with gdhA may have value in semi-arid locations. [ABSTRACT FROM AUTHOR]

This work describes the development of a fast and efficient methodology for Agrobacterium tumefaciens-mediated genetic transformation of internodal stem segments from potato (Solanum tuberosum L.), cultivar Désirée, using phosphinothricin (PPT, glufosinate ammonium) as a selection agent. This methodology has a transformation efficiency of 68%, inducing shoots after 4 to 5 weeks in the presence of 2 mg/L of phosphinothricin. The expression of the bar gene in leaf segments from resistant, transformed plants was demonstrated by the chlorophenol red assay, as was its presence in the genome of explants by Polymerase Chain Reaction. An additional observation was the presence of high levels of resistance to phosphinothricin (up to 500 mg/L) in the transgenic clones, with an otherwise normal phenotype. These transgenic plants were transplanted to greenhouses and after aspersion with the herbicide Finale® (Bayer CropScience) at 2.5 L/ha remained healthy and green, in contrast with the non-transgenic controls which died after 7 days. [ABSTRACT FROM AUTHOR]

A fast and efficient methodology for transforming internodal segments in stems of potato (Solanum tuberosum L.) Désirée cultivar, with Agrobacterium tumefaciens and by using phosphinothricin (PPT, gluphosinate ammonium) as selection agent, was developed. Shoots obtained with 68% transformation efficiency were induced 4 to 5 weeks later in the presence of phosphinothricin at 2 mg/L. The chlorophenol red assay was successfully employed in segments of leaves from transformed plants, demonstrating the expression of the bar gene, and its presence was confirmed in the genome of explants by polymerase chain reaction. Moreover, increased resistance of transgenic clones at phosphinothricin concentrations up to 500 mg/L was observed, also showing a normal phenotypic development. These transgenic plants were transplanted into greenhouses where they also showed to be resistant to the Finale® herbicide (Bayer CropScience) at a concentration 2.5 L/ha, growing green and vigorously as did not the non-transgenic control plants that died 7 days after treatment. [ABSTRACT FROM AUTHOR]

Three methods of transformation of pea ( Pisum sativum ssp. sativum L. var. medullare) were tested. The most efficient Agrobacterium tumefaciens-mediated T-DNA transfer was obtained using embryonic segments from mature pea seeds as initial explants. The transformation procedure was based on the transfer of the T-DNA region with the reporter gene uidA and selection gene bar. The expression of β-glucuronidase (GUS) in the regenerated shoots was tested using the histochemical method and the shoots were selected on a medium containing phosphinothricin (PPT). The shoots of putative transformants were rooted and transferred to non-sterile conditions. Transient expression of the uidA gene in the tissues after co-cultivation and in the course of short-term shoot cultivation (confirmed by histochemical analysis of GUS and by RT-PCR of mRNA) was achieved; however, we have not yet succeeded in proving stable incorporation of the transgene in the analysed plants. [ABSTRACT FROM AUTHOR]

Transgenic herbicide tolerant Acacia sinuata plants were produced by transformation with the bar gene conferring phosphinothricin resistance. Precultured hypocotyl explants were infected with Agrobacterium tumefaciens strain EHA105 in the presence of 100 μM acetosyringone and shoots regenerated on MS (Murashige and Skoog, 1962, Physiol Plant 15:473–497) medium with 13.3 μM benzylaminopurine, 2.6 μM indole-3-acetic acid, 1 g l−1 activated charcoal, 1.5 mg l−1 phosphinothricin, and 300 mg l−1 cefotaxime. Phosphinothricin at 1.5 mg l−1 was used for the selection. Shoots surviving selection on medium with phosphinothricin expressed GUS. Following Southern hybridization, eight independent shoots regenerated of 500 cocultivated explants were demonstrated to be transgenic, which represented transformation frequency of 1.6%. The transgenics carried one to four copies of the transgene. Transgenic shoots were propagated as microcuttings in MS medium with 6.6 μM 6-benzylaminopurine and 1.5 mg l−1 phosphinothricin. Shoots elongated and rooted in MS medium with gibberellic acid and indole-3-butyric acid, respectively both supplemented with 1.5 mg l−1 phosphinothricin. Micropropagation of transgenic plants by microcuttings proved to be a simple means to bulk up the material. Several transgenic plants were found to be resistant to leaf painting with the herbicide Basta. [ABSTRACT FROM AUTHOR]

Abstract: Mechanism of inhibition of glutamine synthetase (EC 6.3.1.2; GS) by phosphinothricin and its analogues was studied in some detail using molecular modeling methods. Among three possible conformations of phosphinothricin in the active site of GS, this compatible with binding mode of methionine sulfoximine, determined recently by crystallography, was found to be energetically favored. Basing on these results eleven inhibitors of GS were docked into its active site. Taking into consideration that phosphinothricin acts as suicide inhibitor, which is due to phosphorylation by the enzyme, seven of studied analogues were additionally analyzed in their phosphorylated forms. All the inhibitor–enzyme complexes were evaluated quantitatively by using eight scoring functions implemented in Insight and Sybyl program packages and significant correlation between the obtained scores and experimental pK i values was achieved. Computed surface charge distribution for five selected inhibitors in both free and phosphorylated forms and their comparison with electronic structure of enzymatic reaction transition state allowed us to determine important electronic features required to construct potent inhibitors of glutamine synthetase. [Copyright &y& Elsevier]

Perennial ryegrass is widely used for overseeding dormant bermudagrass on golf courses and sports fields in Southeastern United States to provide green color and improved playability. Late spring and summer persistence of perennial ryegrass may decrease the quality of the bermudagrass turf and reduce its winter hardiness. To help solve this problem, we developed a strategy to activate a pro-herbicide within the transgenic perennial ryegrass plants and to cause self elimination of the plants. An E. coli argE gene was introduced into perennial ryegrass by the biolistic method, which resulted in four independently transformed green plants. The mRNA of argE gene was detected in three of the plants by RT-PCR. Perennial ryegrass plants expressing the argE transgene were selectively controlled upon application of a pro-herbicide, N-acetyl- l-phosphinothricin (or N-acetyl-PPT), since the N-acetylornithinase encoded by argE gene is able to convert N-acetyl-PPT to the herbicide phosphinothricin (PPT). The non-transgenic bermudagrass plants were unaffected by the treatment. This approach provides a means to selectively remove a group of transgenic plants without affecting other plants growing with them. [ABSTRACT FROM AUTHOR]

Glufosinate-ammonium (GLA) is a postemergence herbicide applied as a foliar spray, but if applied to roots in hydroponics, GLA was herbicidal to tomato (Lycopersicon esculentum Mill.). In the present research, the efficacy of GLA directly applied into soils was compared with foliar application. The effect of degradation time in soil on efficacy also was studied. These studies were conducted in a greenhouse with tomato (Heinz 1439) in pot culture. In one experiment, GLA was applied into soil at concentrations ranging from 0 to 15 mg/kg. Symptoms of yellowing and cupping of leaves occurred within 5 days after treatment (DAT) with GLA addition above 1.5 mg/kg. At 5 DAT, biomass suppression was not evident with any GLA treatment, but GLA at 1.5 mg/kg soil was herbicidal, as measured by concentration in plant tissue. With the increase of GLA from 0 to 15 mg/kg, shoot concentration increased from near 0 to 2.95 mg N/g biomass. To compare the effects of foliar and soil applications of GLA, GLA was brushed onto foliage or was poured and washed into soil for an application of 0–3 mg/plant. At 3 DAT, plants treated with 1.5 or 3 mg foliar GLA showed symptoms of yellowing, cupping, and wilting on top leaves, whereas 5 days were required for symptoms to develop at the same amounts applied to soil. Plant growth was retarded slightly by GLA applied at more than 1.5 mg/plant. To study the effects of degradation time in soil on efficacy, GLA was added into soil at 0–3 mg/kg before tomato seedlings were transplanted and was allowed to incubate for 5–20 days. At 4 days after transplanting into these media, regardless of time of degradation, plants receiving GLA applications above 0.25 mg/kg showed toxicity symptoms of yellowing, cupping, and wilting of top leaves. The growth of all GLA-treated plants was inhibited to about half of the growth of plants not receiving GLA. All GLA treatments led to accumulation in tomato shoots, and this increase was several times that of plants receiving no GLA, ranging from 0.09 mg N/g fresh biomass with no GLA treatment to between 1.9 and 2.6 mg N/g biomass with GLA added. All elevated concentrations were herbicidal. With only 5 days allowed for GLA to degrade in soil, the tomato shoot accumulation was higher than in soil with longer degradation times. With an increase in the amount of soil-applied GLA up to 1 mg/kg, the concentration in plant tissue increased. However, if GLA was applied at more than 1 mg/kg, a further increase in concentration in plant tissue was not detected. This study suggests that soil-applied GLA is herbicidal and that 20 days is not long enough for GLA added into soil to degrade to a nonharmful concentration. [ABSTRACT FROM AUTHOR]

In previous research in hydroponics, ethylene evolution by tomato shoots (Lycopersicon esculentum Mill.) was promoted by the herbicidal action of root-applied glufosinate-ammonium (GLA). Ethylene evolution was preceded by accumulation and was detected before or concurrent with development of toxicity symptoms following GLA application. In the current experiment, aminooxyacetic acid (AOA) or silver thiosulfate (STS) was added in nutrient solutions to elucidate the relationship between accumulation, ethylene evolution, and symptom development. Aminooxyacetic acid is an inhibitor of ethylene synthesis, and STS is an inhibitor of ethylene action. In hydroponics, 4-week-old tomato seedlings were used. The GLA was added at 25 mg/L into Hoagland no. 1 nutrient solution. For the AOA and STS treatments, AOA or STS was added to concentrations of 1 mM or 25 mM, respectively. With GLA alone, foliar symptoms of injury appeared at 4 days after treatment (DAT), and plant death occurred at 10 DAT. Adding STS did not affect this process; however, AOA delayed the appearance of symptoms for 2 days, but plants died at 10 DAT. Neither AOA nor STS significantly affected plant mass relative to growth with GLA alone. With GLA alone, accumulated in shoots and roots at 2 DAT. The AOA inhibited accumulation in shoots until 6 DAT and in roots until 8 DAT. The STS had no effect on shoot accumulation relative to GLA alone but inhibited the accumulation in roots until 6 DAT. Herbicide-induced ethylene evolution occurred at 4 DAT without inhibitors and then fell. The AOA inhibited an increase in ethylene evolution during the period of the experiment, but STS had no inhibitory effect on the rise in ethylene production. This result suggests that AOA can inhibit ethylene evolution after accumulation and delay the development of toxicity symptoms. The STS had no effect on either accumulation or symptom appearance. The inhibitors did not prevent death of the plants exposed to GLA. [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine whether post-emergence application of glufosinate to transgenic crops could lead to an increase in residues or to the formation of new, hitherto unknown metabolites. Transgenic oilseed rape and maize plants were treated separately with L-glufosinate, Dglufosinate or the racemic mixture. Whereas about 90% of the applied D-glufosinate was washed off by rain and only 5-6% was metabolised, 13-35% of the applied L-glufosinate remained in the form of metabolites and unchanged herbicide in both transgenic maize and oilseed rape. The main metabolite was N-acetyl-L-glufosinate with total residues of 91% in oilseed rape and 67% in maize, together with small amounts, of 5% in oilseed rape and 28% in maize, of different methylphosphinyl fatty acids. These metabolites were probably formed from L-glufosinate by deamination and subsequent decarboxylation. The residues were distributed in all fractions of the plants, with the highest contents in treated leaves and the lowest in the grains (0.07-0.3% in maize and 0.4-0.6% in oilseed rape). There was no indication of an accumulation of total residues or of residue levels above the official tolerances for glufosinate. [ABSTRACT FROM AUTHOR]

Methionine sulfoximine, like phosphinothricin (PPT), the active agent in the herbicide BASTA®, is a glutamate analogue that inhibits growth of wildtype Arabidopsis plants through its action on glutamine synthetase. The bar gene, which confers resistance to PPT, also confers resistance to methionine sulfoximine. In this study we show that methionine sulfoximine is an effective and economical alternative to PPT as a selective agent in agar medium. [Copyright &y& Elsevier]

Phosphinothricin (PPT), the active component of a widely used herbicide, induces convulsions in rodents and humans. PPT shares structural analogy with glutamate, which could explain its powerful inhibitory effect on glutamine synthetase and its probable binding to glutamate receptors. To characterize the epileptogenic effect of PPT, electrographic and behavioural studies were carried out on PPT-treated adult mice. We investigated the role of N-methyl-d-aspartate (NMDA) receptor activation and nitric oxide (NO) production in induction of seizures triggered by PPT, by using specific NMDA antagonist and nitric oxide synthase (NOS) inhibitor. The inhibitory effect of PPT on glutamine synthetase of mouse brain was assessed after in vitro and in vivo treatments. The results obtained show that PPT induces tonic–clonic seizures and generalized convulsions in mice. They suggest that these seizures are mediated through an NMDA receptor activation and NO production, without involvement of inhibition of glutamine synthetase. [Copyright &y& Elsevier]

A novel procedure has been developed to produce rice ( Oryza sativa L.) tolerant to the herbicide phosphinothricin (PPT) by means of in vitro selection. First, sublethal and lethal concentrations of PPT on 7-day-old seedlings were determined and morphogenetic events in response to the PPT treatment evaluated. Differentiation of 6–30 microshoots on 5–40% of the treated plant material was observed on a hormone-free culture medium supplemented with a sublethal concentration of PPT. We proved that PPT is morphogenetically active, similar to the action of many other herbicides, showing cytokinin-like effects in rice tissue culture. Fertile plants were grown from those microshoots having PPT tolerance under greenhouse conditions. To the best of our knowledge, this is the first report on the production of rice plants tolerant to this herbicide without genetic transformation. Since PPT is a competitive inhibitor of glutamine synthetase (GS), total GS activity in PPT-tolerant and PPT-sensitive plants was examined comprehensively in order to decide whether this enzyme has any role in PPT tolerance. An elevated GS activity was detected in PPT-tolerant plant material which could result in an elevated PPT tolerance at unchanged concentrations of the herbicide. [ABSTRACT FROM AUTHOR]