THE EFFECTS OF INDOLEACETIC ACID AND 2,4-DICHLOROPHENOXYACETIC ACID ON THE UPTAKE AND METABOLISM OF 14C-GLUCOSE AND ON THE INCORPORATION OF 14C-LABELLED AMINO ACIDS INTO PROTEIN IN PEA ROOT TIPS

1967 ◽  
Vol 45 (9) ◽  
pp. 1751-1760 ◽  
Author(s):  
W. K. Kim ◽  
R. G. S. Bidwell
Keyword(s):  
Amino Acids ◽  
Indoleacetic Acid ◽  
Sugar Metabolism ◽  
Dichlorophenoxyacetic Acid ◽  
Root Tips ◽  
Pea Root ◽  
Main Effect ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
Rates Of Growth ◽  
Uptake And Metabolism

The effect of indoleacetic acid and 2,4-dichlorophenoxyacetic acid on the uptake and metabolism of 14C-labelled glucose and amino acids by excised pea root tips was studied. The intention was to determine whether the observed reduction of root growth by growth hormones was caused by interference in the uptake or in the metabolism of compounds by roots. The results indicate that the main effect of auxins on sugar metabolism in root tips is not on uptake, but on the subsequent metabolism of glucose. Auxins also had several specific rather than general effects on the synthesis of proteins. The production of certain amino acids from glucose was prevented, and the entry of others into protein was affected. This indicates that effects of auxin on protein metabolism were specific, and not necessarily merely consequences of decreased rates of growth and metabolism.

THE EFFECTS OF INDOLEACETIC ACID AND 2, 4-DICHLOROPHENOXYACETIC ACID ON INTERMEDIARY METABOLISM OF 14C-LABELLED ORGANIC ACIDS BY PEA ROOT TIPS

1967 ◽  
Vol 45 (10) ◽  
pp. 1789-1796 ◽  
Author(s):  
W. K. Kim ◽  
R. G. S. Bidwell
Keyword(s):  
Amino Acids ◽  
Organic Acids ◽  
Pyruvic Acid ◽  
Indoleacetic Acid ◽  
Krebs Cycle ◽  
Dichlorophenoxyacetic Acid ◽  
Root Tips ◽  
Specific Effects ◽  
Pea Root ◽  
Krebs Cycle Intermediates

The effects of indoleacetic acid (IAA) and 2, 4-dichlorophenoxyacetic acid (2, 4-D) on the metabolism of 14C-specifically labelled pyruvic, acetic, succinic, and glutamic acids by pea root tips have been examined. The conversion of 14C from the substrates into alcohol-soluble and -insoluble fractions and respired CO2 was determined, and the radioactivity of certain soluble amino acids and organic acids was measured after chromatography. While pyruvic acid decarboxylation is unaffected, the carboxylation of pyruvic acid and the entry into the Krebs cycle of acetate derived from pyruvate is inhibited by the hormones. Acetate, however, is oxidized to CO2 much more rapidly in the presence of IAA or 2, 4-D. The accumulation of 14C in Krebs cycle intermediates or amino acids derived from them is prevented by the auxins. The results indicate that IAA and 2, 4-D have an inhibiting effect either on co-carboxylase or more likely on α-lipoic acid metabolism, but not on coenzyme A (CoA). Other specific effects on the metabolism of individual amino acids are also indicated.

UPTAKE AND METABOLISM OF INDOLEACETIC ACID, NAPHTHALENEACETIC ACID, AND 2,4-DICHLOROPHENOXYACETIC ACID BY PEA ROOT SEGMENTS IN RELATION TO GROWTH INHIBITION DURING AND AFTER AUXIN APPLICATION

1967 ◽  
Vol 45 (5) ◽  
pp. 737-753 ◽  
Author(s):  
W. A. Andreae
Keyword(s):  
Growth Inhibition ◽  
Aspartic Acid ◽  
Indoleacetic Acid ◽  
Similar Degree ◽  
Dichlorophenoxyacetic Acid ◽  
Naphthaleneacetic Acid ◽  
Root Segments ◽  
Pea Root ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
A Site

Growth inhibition by applied indoleacetic acid (IAA), naphthaleneacetic acid (NAA), or 2,4-dichlorophenoxyacetic acid (2,4-D) was studied using change in fresh weight of pea root segments as the criterion of growth. Auxin metabolism of these tissues was investigated with 14C-labeled auxins applied under conditions similar to those used in the growth studies.Growth inhibition by applied auxins is independent of the rate of auxin uptake, accumulation of auxin or auxin metabolites in the tissues, or the subsequent loss of accumulated auxin from the tissues. It is also independent of the metabolic processes leading either to auxin conjugation with aspartic acid or to decarboxylation. All three auxins inhibit growth to a similar degree, which depends only on the concentration of auxin applied and the pH of the solution. Inhibition persists undiminished as long as the auxin is applied. It is suggested that growth inhibition by applied auxin occurs at a site external to the cytoplasm, i.e. the cell wall or the cytoplasmic membrane.Growth inhibition of tissues after auxin treatment has ceased is not due to the auxin remaining in the tissues but rather to the auxin released from the tissues to the solution to which they have been transferred. Untreated tissues incubated in the same transfer solution with treated tissues are equally inhibited. The persistence of growth inhibition after treatment depends upon the ability of the tissues to convert accumulated auxins to physiologically inactive metabolites. Conjugation with aspartic acid accounts for the inactivation of all the accumulated NAA metabolized and the major part of the IAA. IAA decarboxylation under these conditions plays a lesser role. Growth recovery following treatment with IAA or NAA occurs as these auxins are metabolized. 2,4-D is not metabolized to any appreciable extent during these studies, and tissues remain inhibited to a degree consistent with the concentration of 2,4-D in the transfer solution.

scholarly journals Reversion of Senescence: Effects of 2,4-Dichlorophenoxyacetic Acid and Indoleacetic Acid on Respiration, Ethylene Production, and Ripening of Banana Fruit Slices

1969 ◽  
Vol 22 (3) ◽  
pp. 601 ◽  
Author(s):  
M Vendrell
Keyword(s):  
Aqueous Solutions ◽  
Ethylene Production ◽  
Indoleacetic Acid ◽  
Dichlorophenoxyacetic Acid ◽  
Banana Fruit ◽  
Unripe Fruit ◽  
2,4 Dichlorophenoxyacetic Acid

Slices cut from green, unripe fruit were treated by infiltration with aqueous solutions of 2,4�dichlorophenoxyacetic acid (2,4�D) and indoleacetic acid (lAA). 2,4.D delayed but increased the size of those peaks in respiration and ethylene production which are induced by cutting; ripening was also delayed. These effects were proportional to concentrations of 2,4.D in the range 1O-LlO-3M. Higher concentrations caused injury.

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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