Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.31 (beta-glucuronidase)
7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 13.8 kb DNA sequence containing the promoters and the structural genes of the Arabidopsis thaliana nit2/nit1/nit3 gene cluster has been isolated and characterized. The coding regions of nit2, nit1 and nit3 spanned 1.9, 1.8 and 2.1 kb, respectively. The architecture of the three genes is highly conserved. Each isoform consists of five exons separated by four introns. The introns are very similar with respect to size and position, but differ considerably in sequence composition. In contrast to the coding sequences the three promoters are very different in sequence, size and in their repertoire of cis elements, suggesting differential regulation of the three nitrilase isoenzymes by the developmental program of the plant and by diverse environmental factors. The nit1 promoter was subjected to analysis in planta. Translational fusions placing the nit1 full-length promoter and a series of 5'-deletion fragments in front of the uidA gene encoding beta-glucuronidase (GUS) were used for Agrobacterium tumefaciens-mediated transformation of Nicotiana tabacum. GUS expression was highest in fully expanded leaves and in the shoot apex as well as in the apices of developing lateral buds, whereas the GUS activity displayed by developing younger leaflets was restricted to the tips of the expanding leaves. Within the root tissue GUS expression was restricted to the root tips and the tips of newly forming lateral roots. Structural features of the nitrilase gene family and nitrilase gene expression patterns are discussed in context with current knowledge of auxin biosynthesis and auxin effects on different tissues.
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PMID:Structural analysis of the nit2/nit1/nit3 gene cluster encoding nitrilases, enzymes catalyzing the terminal activation step in indole-acetic acid biosynthesis in Arabidopsis thaliana. 948 65

The promoter of the nit1 gene, encoding the predominantly expressed isoform of the Arabidopsis thaliana (L.) Heynh. nitrilase isoenzyme family, fused to the beta-glucuronidase gene (uidA) drives beta-glucuronidase expression in the root system of transgenic A. thaliana and tobacco plants. This expression pattern was shown to be controlled developmentally, suggesting that the early differentiation zone of root tips and the tissue surrounding the zone of lateral root primordia formation may constitute sites of auxin biosynthesis in plants. The root system of A. thaliana was shown to express functional nitrilase enzyme. When sterile roots were fed [2H]5-L-tryptophan, they converted this precursor to [2H]5-indole-3-acetonitrile and [2H]5-indole-3-acetic acid. This latter metabolite was further metabolized into base-labile conjugates which were the predominant form of [2H]5-indole-3-acetic acid extracted from roots. When [1-13C]-indole-3-acetonitrile was fed to sterile roots, it was converted to [1-13C]-indole-3-acetic acid which was further converted to conjugates. The results prove that the A. thaliana root system is an autonomous site of indole-3-acetic acid biosynthesis from L-tryptophan.
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PMID:Indole-3-acetic acid is synthesized from L-tryptophan in roots of Arabidopsis thaliana. 976 5

The expression of nitrilase in Arabidopsis during the development of the clubroot disease caused by the obligate biotroph Plasmodiophora brassicae was investigated. A time course study showed that only during the exponential growth phase of the clubs was nitrilase prominently enhanced in infected roots compared with controls. NIT1 and NIT2 are the nitrilase isoforms predominantly expressed in clubroot tissue, as shown by investigating promoter-beta-glucuronidase fusions of each. Two peaks of beta-glucuronidase activity were visible: an earlier peak (21 d post inoculation) consisting only of the expression of NIT1, and a second peak at about 32 d post inoculation, which predominantly consisted of NIT2 expression. Using a polyclonal antibody against nitrilase, it was shown that the protein was mainly found in infected cells containing sporulating plasmodia, whereas in cells of healthy roots and in uninfected cells of inoculated roots only a few immunosignals were detected. To determine which effect a missing nitrilase isoform might have on symptom development, the P. brassicae infection in a nitrilase mutant (nit1-3) of Arabidopsis was investigated. As a comparison, transgenic plants overexpressing NIT2 under the control of the cauliflower mosaic virus 35S promoter were studied. Root galls were smaller in nit1-3 plants compared with the wild type. The phenotype of smaller clubs in the mutant was correlated with a lower free indole-3-acetic acid content in the clubs compared with the wild type. Overexpression of nitrilase did not result in larger clubs compared with the wild type. The putative role of nitrilase and auxins during symptom development is discussed.
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PMID:Expression and localization of nitrilase during symptom development of the clubroot disease in Arabidopsis. 1067 30

Three of the nitrilase isoenzymes of Arabidopsis thaliana (L.) Heynh. are located on chromosome III in tandem and these genes (NIT2/NIT1/NIT3 in the 5'-->3' direction) encode highly similar polypeptides. Copy DNAs encompassing the entire coding sequences for all three nitrilases were expressed in Escherichia coli as fusion proteins containing a C-terminal hexahistidine extension. All three nitrilases were obtained as enzymatically active proteins, and their characteristics were determined, including a detailed comparative analysis of their substrate preferences. All three nitrilases converted indole-3-acetonitrile (IAN) to indole-3-acetic acid (IAA), albeit, compared to the most effective substrates found, phenylpropionitrile (PPN), allylcyanide, (phenylthio)acetonitrile and (methylthio)acetonitrile, with low affinity and velocity. The preferred substrates are either naturally occurring substrates, which may originate from glucosinolate breakdown, or they are close relatives of these. Thus, a major function of NIT1, NIT2 and NIT3 is assigned to be the conversion to carboxylic acids of nitriles from glucosinolate turnover or degradation. While all nitrilases exhibit a similar pH optimum around neutral, and NIT1 and NIT3 exhibit a similar temperature optimum around 30 degrees C independent of the substrate analyzed (IAN, PPN), NIT2 showed a remarkably different temperature optimum for IAN (15 degrees C) and PPN (35-40 degrees C). A potential role for NIT2 in breaking seed dormancy in A. thaliana by low temperatures (stratification), however, was ruled out, although NIT2 was the predominantly expressed nitrilase isoform in developing embryos and in germinating seeds, as judged from an analysis of beta-glucuronidase reporter gene expression under the control of the promoters of the four isogenes. It is possible that NIT2 is involved in supplying IAA during seed development rather than during stratification.
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PMID:Enzymatic characterization of the recombinant Arabidopsis thaliana nitrilase subfamily encoded by the NIT2/NIT1/NIT3-gene cluster. 1152 7

Arabidopsis thaliana expresses four nitrilases, three of which (NIT1, NIT2 and NIT3) are able to convert indole-3-acetonitrile to indole-3-acetic acid (IAA), the plant growth hormone, while the isozyme NIT4 is a beta-cyano-l-alanine hydratase/nitrilase. NIT3 promoter activity is marginal in leaves or roots of vegetative plants and undetectable in bolting and flowering plants, but its level increases strongly when plants experience sulphur deprivation. No other nitrilase genes respond to sulphur supply/deficiency. Neither N- nor P-deprivation cause detectable changes in NIT3 promoter activity. In transgenic plants expressing uidA under the control of the NIT3 promoter (NIT3p::uidA), sulphate deprivation leads to the appearance of beta-glucuronidase activity in shoots and particularly in roots, most strongly in the conductive tissues and lateral root primordia. Deletion analysis allowed localization of the sulphur-responsive element to a 317 bp segment of the NIT3 promoter encompassing nt -2151 to -1834 upstream of the transcriptional start point. Both nitrilase polypeptide and nitrilase activity were also induced by sulphur starvation. NIT3 promoter activity was strongly induced by O-acetylserine, suggesting that, as is the case with enzymes of sulphate assimilation, sulphate deficiency may be communicated to NIT3 via an increase in the level of the cysteine precursor, O-acetylserine. During sulphur deprivation, a preferential depletion of the pool of the indole-3-acetonitrile precursor glucobrassicin compared with that of total glucosinolates was noticed. In the absence of an external sulphate supply, plants developed longer roots with a higher number of lateral roots. The increased growth of the root system occurred at the expense of shoot growth which was retarded under conditions of sulphur starvation. Taken together, these results suggest that a regulatory loop appears to exist by which sulphate deficiency, through an increase in glucobrassicin turnover and nitrilase 3 accumulation, initiates the production of extra auxin leading to increased root growth and branching, thus allowing the root system to penetrate new areas of soil effectively to gain access to fresh supplies of sulphur.
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PMID:A role for nitrilase 3 in the regulation of root morphology in sulphur-starving Arabidopsis thaliana. 1196 96

The major regulatory shoot signal is auxin, whose synthesis in young leaves has been a mystery. To test the leaf-venation hypothesis [R. Aloni (2001) J Plant Growth Regul 20: 22-34], the patterns of free-auxin production, movement and accumulation in developing leaf primordia of DR5::GUS-transformed Arabidopsis thaliana (L.) Heynh. were visualized. DR5::GUS expression was regarded to reflect sites of free auxin, while immunolocalization with specific monoclonal antibodies indicated total auxin distribution. The mRNA expression of key enzymes involved in the synthesis, conjugate hydrolysis, accumulation and basipetal transport of auxin, namely indole-3-glycerol-phosphate-synthase, nitrilase, IAA-amino acid hydrolase, chalcone synthase and PIN1 as an essential component of the basipetal IAA carrier, was investigated by reverse transcription-polymerase chain reaction. Near the shoot apex, stipules were the earliest sites of high free-auxin production. During early stages of primordium development, leaf apical dominance was evident from strong beta-glucuronidase activity in the elongating tip, possibly suppressing the production of free auxin in the leaf tissues below it. Hydathodes, which develop in the tip and later in the lobes, were apparently primary sites of high free-auxin production, the latter supported by auxin-conjugate hydrolysis, auxin retention by the chalcone synthase-dependent action of flavonoids and also by the PIN1-component of the carrier-mediated basipetal transport. Trichomes and mesophyll cells were secondary sites of free-auxin production. During primordium development there are gradual shifts in sites and concentrations of free-auxin production occurring first in the tip of a leaf primordium, then progressing basipetally along the margins, and finally appearing also in the central regions of the lamina. This developmental pattern of free-auxin production is suggested to control the basipetal maturation sequence of leaf development and vascular differentiation in Arabidopsis leaves.
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PMID:Gradual shifts in sites of free-auxin production during leaf-primordium development and their role in vascular differentiation and leaf morphogenesis in Arabidopsis. 1262 72

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