The metabolic basis for 2,4-D resistance in two variant cell lines of carrot

2002 ◽  
Vol 29 (5) ◽  
pp. 575 ◽  
Author(s):  
Nello Ceccarelli ◽  
Alessandra Mondin ◽  
Roberto Lorenzi ◽  
Piero Picciarelli ◽  
Fiorella Lo Schiavo
Keyword(s):  
Cell Lines ◽  
External Medium ◽  
Dichlorophenoxyacetic Acid ◽  
Wild Type ◽  
Variant Cell ◽  
Resistant Lines ◽  
High Concentrations ◽  
Metabolic Basis ◽  
2,4 Dichlorophenoxyacetic Acid

In the present work, the characterization of two variant cell lines of carrot capable of growing in high (92 μmol L–1) concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) is reported. Both these cell lines (4w77 and 4w13) show a significantly lower uptake of 2,4-D with respect to wild-type (wt) cells. In contrast to wt cells, influx of IAA is not reduced by the addition of 100 μM 2,4-D and the presence of this compound appears to stimulate IAA uptake. When grown in the presence of high concentrations of 2,4-D, both 4w77 and 4w13 cells show behavioural differences: instead of lowering the endogenous level of free IAA, the two resistant lines react to the high exogenous concentrations of auxin by raising the level of the free hormone. In 4w77 cells, this is accomplished by reduction of auxin released in the external medium or converted to amide-linked conjugates. In 4w13 cells, the final level of endogenous IAA is an equilibrium between increased synthesis of IAA and a massive release into the medium of the ester- and free-forms of IAA. Both cell lines show disturbances in embryogenesis: line 4w77 forms globular embryos that only mature into aberrant forms having multiple axes, whereas line 4w13 has completely lost its morphogenic capacity.

Characterization of the Reproductive Mode in Guayule In Vitro

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 483a-483
Author(s):  
Roy N. Keys ◽  
Dennis T. Ray ◽  
David A. Dierig
Keyword(s):  
Field Experiments ◽  
Reproductive Mode ◽  
Dichlorophenoxyacetic Acid ◽  
Initial Field ◽  
Breeding Lines ◽  
Reproductive Modes ◽  
Desert Southwest ◽  
2,4 Dichlorophenoxyacetic Acid

Guayule (Parthenium argentatum Gray, Asteraceae) is a latex-producing perennial desert shrub that is potentially of economic importance as an industrial crop for the desert Southwest. It is known to possess complex reproductive modes. Diploids are predominantly sexual and self-incompatible, while polyploids show a range of apomictic potential and self-compatibility. This paper describes the development of a relatively rapid and simple technique for characterizing reproductive modes of breeding lines of P. argentatum. Initial field experiments were based on an auxin test used successfully to characterize reproductive mode in the Poaceae. The application of 2,4-dichlorophenoxyacetic acid inhibited embryo formation in P. argentatum, but this was not the case with other auxins tested. Results of field experiments were ambiguous because: 1) the floral structure of P. argentatum is such that auxins might not have penetrated to the ovules, and 2) there was potential self-fertilization by pollen released within isolation bags. Therefore, in vitro culture of flower heads was tested because it provided much better control of environmental conditions, growth regulator application, and pollen release. Auxin alone, or in combination with gibberellic acid or kinetin, inhibited parthenogenesis in vitro. Embryo production did not vary using two substantially different nutrient media. In vitro flower head culture using a (Nitsch and Nitsch) liquid nutrient medium without growth regulators, enabled characterization of the reproductive mode of seven breeding lines, ranging from predominantly sexual to predominantly apomictic. The results of this technique were substantiated using RAPD analyzes of progeny arrays from controlled crosses.

scholarly journals Characterization of Hapten-Protein Conjugates: Antibody Generation and Immunoassay Development for Chlorophenoxyacetic Acid Pesticides

2009 ◽  
Vol 92 (6) ◽  
pp. 1773-1779 ◽  
Author(s):  
Robin C Boro ◽  
K Vikas Singh ◽  
C Raman Suri
Keyword(s):  
Inhibitory Concentration ◽  
Dichlorophenoxyacetic Acid ◽  
Protein Conjugation ◽  
Protein Conjugates ◽  
Highly Sensitive ◽  
Ic50 Values ◽  
Chlorophenoxyacetic Acid ◽  
2,4 Dichlorophenoxyacetic Acid

Abstract The generation of specific and sensitive antibodies against small molecules is greatly dependent upon the characteristics of the hapten-protein conjugates. In this study, we report a new fluorescence-based method for the characterization of hapten-protein conjugates. The method is based on an effect promoted by hapten-protein conjugation density upon the fluorescence intensity of the intrinsic tryptophan chromophore molecules of the protein. The proposed methodology is applied to quantify the hapten-protein conjugation density for two different chlorophenoxyacetic acid pesticides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenoxybutyric acid (2,4-DB), coupled to carrier protein. Highly sensitive anti-2,4-D and anti-2,4-DB antibodies were obtained using these well-characterized hapten-protein conjugates. The generated antibodies were used in an immunoassay format demonstrating inhibitory concentration (IC50) values equal to 30 and 7 ng/mL for 2,4-D and 2,4-DB, respectively. Linearity was observed in the concentration range between 0.1500 ng/mL with LODs around 4 and 3 ng/mL for 2,4-D and 2,4-DB, respectively, in standard water samples. The proposed method was successfully applied for the determination of the extent of hapten-protein conjugation to produce specific antibodies for immunoassay development against pesticides.

scholarly journals  Effect of 2,4-D as a novel inducer of embryogenesis in microspores of Brassica napus L.

2011 ◽  
Vol 47 (No. 3) ◽  
pp. 114-122 ◽  
Author(s):  
S.H. Ardebili ◽  
M.E. Shariatpanahi ◽  
R. Amiri ◽  
M. Emamifar ◽  
M. Oroojloo ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Heat Shock ◽  
Microspore Embryogenesis ◽  
Control Treatment ◽  
Dichlorophenoxyacetic Acid ◽  
Brassica Napus L ◽  
High Concentrations ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
Short Time ◽  
First Time

The effect of 2,4-dichlorophenoxyacetic acid (2,4-D) applied at high concentrations for a short time was investigated as a novel stress for induction of microspore embryogenesis for the first time. Brassica napus L. cvs. Topas and Hyola 420 were used as model plants for testing this hypothesis. Microspores were subjected to 2,4-D at 4 concentrations (15, 25, 35 and 45 mg/l) for 15–45 min while the classical heat shock was used as the control treatment. Among 2,4-D treatments in Topas, the highest yield of torpedo-stage embryos was achieved at 15 mg/l 2,4-D for 30 min while more normal plantlets were produced when 2,4-D (25 mg/l for 30 min) was applied to the microspores. In Hyola 420 the results showed a lower number of embryos and normal plantlets at all concentrations of 2,4-D. Although Hyola 420 was almost equally embryogenic as Topas after heat shock treatment, large differences between genotypes (concerning embryogenic response) occurred after 2,4-D treatment. However, the mean number of embryos and regenerants was higher in heat shock as compared to 2,4-D induced stress (one magnitude of order). According to the results obtained, 2,4-D can be introduced as a new stress for induction of embryogenesis in microspores similarly like in zygotic and somatic cells. This novel stress is very important for plant species whose microspores are extremely sensitive to classical stresses.

scholarly journals Purification and Characterization of Two Enantioselective α-Ketoglutarate-Dependent Dioxygenases, RdpA and SdpA, from Sphingomonas herbicidovorans MH

2006 ◽  
Vol 72 (7) ◽  
pp. 4853-4861 ◽  
Author(s):  
Tina A. Müller ◽  
Thomas Fleischmann ◽  
Jan Roelof van der Meer ◽  
Hans-Peter E. Kohler
Keyword(s):  
Amino Acids ◽  
Divalent Cations ◽  
Propanoic Acid ◽  
Dichlorophenoxyacetic Acid ◽  
Purification And Characterization ◽  
Subgroup Ii ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
Acid Herbicides ◽  
Growth Experiments

ABSTRACT α-Ketoglutarate-dependent (R)-dichlorprop dioxygenase (RdpA) and α-ketoglutarate-dependent (S)-dichlorprop dioxygenase (SdpA), which are involved in the degradation of phenoxyalkanoic acid herbicides in Sphingomonas herbicidovorans MH, were expressed and purified as His6-tagged fusion proteins from Escherichia coli BL21(DE3)(pLysS). RdpA and SdpA belong to subgroup II of the α-ketoglutarate-dependent dioxygenases and share the specific motif HXDX24TX131HX10R. Amino acids His-111, Asp-113, and His-270 and amino acids His-102, Asp-104, and His 257 comprise the 2-His-1-carboxylate facial triads and were predicted to be involved in iron binding in RdpA and SdpA, respectively. RdpA exclusively transformed the (R) enantiomers of mecoprop [2-(4-chloro-2-methylphenoxy)propanoic acid] and dichlorprop [2-(2,4-dichlorophenoxy)propanoic acid], whereas SdpA was specific for the (S) enantiomers. The apparent Km values were 99 μM for (R)-mecoprop, 164 μM for (R)-dichlorprop, and 3 μM for α-ketoglutarate for RdpA and 132 μM for (S)-mecoprop, 495 μM for (S)-dichlorprop, and 20 μM for α-ketoglutarate for SdpA. Both enzymes had high apparent Km values for oxygen; these values were 159 μM for SdpA and >230 μM for RdpA, whose activity was linearly dependent on oxygen at the concentration range measured. Both enzymes had narrow cosubstrate specificity; only 2-oxoadipate was able to replace α-ketoglutarate, and the rates were substantially diminished. Ferrous iron was necessary for activity of the enzymes, and other divalent cations could not replace it. Although the results of growth experiments suggest that strain MH harbors a specific 2,4-dichlorophenoxyacetic acid-converting enzyme, tfdA-, tfdAα-, or cadAB-like genes were not discovered in a screening analysis in which heterologous hybridization and PCR were used.

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