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The title compound (C17H25NO3) is a perhydroindoleacetic acid which exhibits hypoglycemic activity. The cyclohexyl ring adopts a sofa conformation. The molecule contains an intramolecular O-H...O hydrogen bond.
The effect of indolylacetic acid (IAA) on proton conductivity of tylacoid membranes of isolated pea chloroplasts at pH 5.5-8.0 and of artificial phospholipid membranes at pH 7.5 were studied. IAA was shown to decrease the stationary proton gradient value and increase those of the dissociation constant and electron transport rate in chloroplasts, while in the artificial phospholipid membranes it increased the proton conductivity. The membrane lipid phase is supposed to be a possible result of phytohormone action, IAA transporting the protons according to the monomeric mechanism.
The sensitivity to auxin of the H(+)-ATPase-mediated proton translocation was investigated in vitro using purified plasma membrane vesicles from tobacco leaves. In vivo pretreatment of tobacco plants with auxin promotes a 100-fold increase of the in vitro sensitivity to auxin. This effect is specific for biologically active auxins and is dose- and time-dependent. In addition, pretreatment with auxin induces the accumulation of several polypeptides in the plasma membrane. These polypeptides constitute the first set of hormone-responsive polypeptides evidenced in plant membranes.
The rates of reaction of seven indole-3-acetic acid derivatives with horseradish peroxidase compound 1 at pH 5 were measured by stopped flow, and the reduction potentials and pKa of their radical cations were determined by pulse radiolysis. Reasonable correlation of these properties with Hammett substituent parameters was found, but not with Brown-Okamoto (theta +) parameters. The rates of reaction with compound I correlate well with the reduction potentials under the same conditions, with rates of reaction that increase by ca. 2.5 orders of magnitude with a 100 mV decrease in the reduction potential. This relationship is in agreement with that previously estimated for the reaction of compound I with phenols and anilines, suggesting that the rate of reaction depends solely on the reduction potential of the substrate radical, even for compounds of dissimilar structure.
The genetic advantages to the use of Arabidopsis thaliana mutants for the study of auxin metabolism previously have been partially offset by the complexity of indolic metabolism in this plant and by the lack of proper methods. To address some of these problems, we developed isotopic labeling methods to determine amounts and examine the metabolism of indolic compounds in Arabidopsis. Isolation and indentification of endogenous indole-3-acetonitrile (IAN; a possible precursor of the auxin indole-3-acetic acid [IAA]) was carried out under mild conditions, thus proving its natural occurrence. We describe here the synthesis of 13C1-labeled IAN and its utility in the gas chromatography-mass spectrometry quantification of endogenous IAN levels. We also quantified the nonenzymatic conversion of IAN to IAA under conditions used to hydrolyze IAA conjugates. 13C1-Labeled IAN was used to assess the contribution of IAN to measured IAA following hydrolysis of IAA conjugates. We studied the stability and breakdown of the indolic glucosinolate glucobrassicin, which is known to be present in Arabidopsis. This is potentially an important concern when using Arabidopsis for studies of indolic biochemistry, since the levels of indolic auxins and auxin precursors are well below the levels of the indolic glucosinolates. We found that under conditions of extraction and base hydrolysis, formation of IAA from glucobrassicin was negligible.
Rhizospheric bacterial strains are known to produce indole-3-acetic acid (IAA) through different pathways, and such IAA may be beneficial to plants at low concentrations. IAA biosynthesis by a natural isolate of Azospirillum brasilense SM was studied and observed to be tryptophan-inducible and -dependent in nature. While our work demonstrated the operation of the indole pyruvic acid pathway, the biochemical and molecular evidence for the genes of the indole acetamide (IAM) pathway were lacking in A. brasilense SM. This led us to use the IAM pathway genes as targets for metabolic engineering, with the aim of providing an additional pathway of IAA biosynthesis and improving IAA levels in A. brasilense SM. The introduction of the heterologous IAM pathway, consisting of the iaaM and iaaH genes, not only increased the IAA levels by threefold but also allowed constitutive expression of the same genes along with efficient utilization of IAM as a substrate. Such an engineered strain showed a superior effect on the lateral branching of sorghum roots as well as the dry weight of the plants when compared with the wild-type strain. Such an improved bioinoculant could be demonstrated to enhance root proliferation and biomass productivity of treated plants compared with the parental strain.
Positively charged nylon blotting membranes were used as an anion binding medium to trap [14C]indoleactic acid (IAA) as it exited cells at the basal ends of Coleus blumei L. stem and Zea mays L. coleoptile segments. Autoradiography was used to visualize where the [14C] that moved out of the cut ends was localized on the nylon membrane. Diffusion of [14C]IAA from the initial point of contact with the nylon membrane was minimal. Comparison of the autoradiograms with anatomical tissue prints of the cut ends of the segments was used to determine what tissues participate in IAA movement. The results of these initial studies were consistent with other reports suggesting that [14C]IAA movement was primarily associated with vascular tissues in both C. blumei stems and corn coleoptiles, but the resolution was not sufficient to identify which vascular tissues were involved in IAA transport. With further refinements, this technique could also be used for studying the movement of other small charged molecules through plant tissues.
There has been a continuing interest in the possible role of the trace amine tryptamine in the etiology of neuropsychiatric disorders. We have therefore examined cerebrospinal fluid (CSF) levels of indole-3-acetic acid (IAA), the major metabolite of tryptamine, in a large group of normals and in several patient populations. No differences in CSF IAA levels (ng/ml, mean +/- SEM) were observed between normals (4.39 +/- 0.37, n = 36), anorectics (4.40 +/- 0.42, n = 35), schizophrenics (4.06 +/- 0.05, n = 17), manics (4.32 +/- 0.63, n = 10), or depressives (5.23 +/- 0.49, n = 39). A significant elevation (p = 0.05) was found in the subgroup of retarded depressives (RDC) where levels of 5.90 +/- 0.80 (n = 19) were observed. An age effect (r = 0.39, p = 0.02, n = 36) was observed in normals; however IAA was not reduced to either height or weight. IAA tended to be higher (but not significantly) in females in all groups studied; this difference also was not significant when all diagnostic groups (except anorectics) were combined (female: 4.95 +/- 0.44, n = 45; male: 4.46 +/- 0.30, n = 66). In general, the results indicate that tryptamine turnover is not altered in the disorders studied. The functional significance of the slight elevation seen in retarded depressives is not clear.
Agrobacterium tumefaciens induces crown gall tumors by transferring a piece of its tumor-inducing plasmid into plant cells. This transferred DNA encodes the synthesis of indole acetic acid (IAA) and cytokinin, and their overproduction results in tumor formation. The transfer is initiated by a two-component regulatory system, VirA/G recognizing plant signal molecules in the plant rhizosphere and activating a regulon on the tumor-inducing plasmid, which is required for the processing and transfer of DNA and protein. Although a great deal is known about vir gene activation, nothing is known about whether or how the vir gene regulon is inactivated after plant cell transformation. Presumably, just as a mechanism exists for activating the vir gene regulon only when a plant is in the immediate environment, a mechanism should exist for inactivating the same regulon once it has fulfilled its mission to transferred DNA into plant cells. We now show that IAA inactivates vir gene expression by competing with the inducing phenolic compound acetosyringone for interaction with VirA. IAA does not inhibit the vir genes in cells containing a constitutive sensor virA locus, which does not require any signal molecules to become phosphorylated. At higher concentrations, IAA inhibits the growth of Agrobacterium and many other plant-associated bacteria but not the growth of bacteria that occupy other ecological niches. These observations provide the missing link in the cycle of vir gene activation and inactivation.
A variation in the ventricular fluid 5-HIAA concentration has been observed during the phases of the sleep-wake cycle in man. This variation affects the NREM phase, during which 5-HIAA increases markedly, rather than the waking state and the REM phase. The results are discussed in relation to the possible relevance of serotonin to the sleep mechanism.
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