Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Molybdate and selenate are structural analogs of sulfate that inhibit synthesis of adenosine 5'-phosphosulfate by ATP sulfurylase (sulfate adenylyltransferase, ATP:sulfate adenylyltransferase, EC 2.7.7.4) in crude extracts of tobacco XD cells. Both of these anions derepress ATP sulfurylase in cells growing on sulfate, but not in cells growing on L-cysteine. However, the two anions appear to derepress by different mechanisms. Molybdate caused derepression only at concentrations that were in excess over sulfate and were sufficient to inhibit growth and protein accumulation, indicating that the derepression resulted from sulfur starvation. Selenate caused derepression at one-tenth the concentration of sulfate, a concentration of selenate that was subtoxic, while toxic levels of selenate produced far less derepression. The susceptibility of the tobacco cells to selenate toxicity was high under conditions of sulfur nutrition that derepress ATP sulfurylase, and low under conditions that repress ATP sulfurylase, in agreement with the idea that selenate acts via a functional sulfate assimilation pathway. Since it is known that selenate is incorporated into analogs of sulfur compounds, it is proposed that the tobacco cells synthesize the seleno-analog of the end product of the sulfate pathway responsible for repression, and the seleno-analog antagonizes the normal end product in the repression mechanism, the net result being derepression of ATP sulfurylase by selenate.
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PMID:Derepression of ATP sulfurylase by the sulfate analogs molybdate and selenate in cultured tobacco cells. 26 28

The ATP sulfurylase of cultured tobacco cells is repressed during growth on readily assimiliated sulfur sources, such as sulfate, L-cysteine, or L-methionine, but it is derepressed during growth on slowly assimiliated sulfur sources, such as L-djenkolate or glutathione, or during sulfur starvation. The enzyme is not induced by sulfate. The enzyme level in the cells begins to rise 12 to 24 h after the derepression conditions are initiated and continues to rise for 3 to 4 days, up to as much as 25 times above the initial specific activity. Addition of a repressing sulfur source to derepressed cells causes the enzyme to decay. Derepression by sulfur limitation does not occur in cells starved for nitrogen, a circumstance in which turnover synthesis of protein is known to continue. Upon addition of a nitrogen source to such cells, the development of the enzyme begins within 12 h, along with the resumption of growth and net protein synthesis. Derepression occurs in cells growing on the slowly assimilated nitrogen in urea, reaching specific activities very similar to those which develop in cells grown on nitrate, in spite of the lower protein accumulation rate on urea. Thus the ATP sulfurylase of tobacco cells appears to be regulated by both a negative feedback mechanism in which an end product of the sulfate assimilation pathway is the effector, and by a positive mechanism which serves to couple the regulation of the sulfate assimilation pathway to the cells' potential for nitrogen assimilation, i.e. net protein synthesis. The sulfur compounds which affect the development of ATP sulfurylase in vivo have no effect on the enzyme activity in vitro. Furthermore, extracts with high activity contain no activator and extracts with low activity contain no inhibitor of ATP sulfurylase. Cycloheximide, at a concentration which strongly inhibits amino acid incorporation into protein, inhibits derepression. ATP sulfurylase does not decay in cells inhibited by cycloheximide. Therefore, the changes in ATP sulfurylase of tobacco cells appear to involve changes in the rate of formation or degradation of the enzyme.
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PMID:Regulation of adenosine triphosphate sulfurylase in cultured tobacco cells. Effects of sulfur and nitrogen sources on the formation and decay of the enzyme. 84 48

To determine if the ATP sulfurylase reaction is a regulatory step for the SO4(2-)-assimilation pathway in plants, an Arabidopsis thaliana ATP sulfurylase cDNA, APS2, was fused to the 35S promoter of the cauliflower mosaic virus and introduced by Agrobacterium tumefaciens-mediated transformation into isolated Bright Yellow 2 tobacco (Nicotiana tabacum) cells. The ATP sulfurylase activity in transgenic cells was 8-fold that in control cells, and was correlated with the expression of a specific polypeptide revealed by western analysis using an anti-ATP sulfurylase antibody. The molecular mass of this polypeptide agreed with that for the overexpressed mature protein. ATP sulfurylase overexpression had no effect on [35S]SO4(2-) influx or ATP sulfurylase activity regulation by S availability, except that ATP sulfurylase activity variations in response to S starvation in transgenic cells were 8 times higher than in the wild type. There were also no differences in cell growth or sensitivity to SeO4(2-) (a toxic SO4(2-) analog) between transgenic and wild-type cells. We propose that in Bright Yellow 2 tobacco cells, the ATP sulfurylase derepression by S deficiency may involve a posttranscriptional mechanism, and that the ATP sulfurylase abundance is not limiting for cell metabolism.
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PMID:Effect of ATP sulfurylase overexpression in bright yellow 2 tobacco cells. Regulation Of atp sulfurylase and SO4(2-) transport activities. 953 47

Pseudomonas aeruginosa PAO1 grew in defined synthetic medium with any of a broad variety of single sulfur sources, including sulfate, cysteine, thiocyanate, alkanesulfonates, organosulfate esters and methionine, but not with aromatic sulfonates, thiophenols or organothiocyanates or isothiocyanates. During growth with any of these compounds except sulfate, cysteine or thiocyanate, a set of 10 sulfate starvation-induced (SSI) proteins was strongly up-regulated, as observed by two-dimensional protein electrophoresis of total cell extracts. A comparable level of up-regulation was found for the hydrolytic enzyme arylsulfatase, which has previously been used as a marker enzyme for the sulfate starvation response. One of the SSI proteins was identified by N-terminal sequencing as a high-affinity periplasmic sulfate-binding protein, and another was related to thiol-specific antioxidants, but the N-terminal sequences of the other SSI proteins revealed no similarity to N-termini of proteins of known function, and they probably represent uncharacterized enzymes involved in sulfur scavenging when preferred sulfur sources are absent. To study the role that cysteine biosynthetic intermediates play in the synthesis of these proteins in vivo, we isolated mini-Tn5 transposon mutants of P. aeruginosa with insertions in the cysN and cysI genes, which encode subunits of ATP-sulfurylase and sulfite reductase, respectively. These two genes were cloned and sequenced. cysI showed high similarity to the cognate gene in Escherichia coli, whereas cysN encoded a 69.3 kDa protein with two domains corresponding to the E. coli CysN and CysC proteins. Sulfate no longer repressed synthesis of the SSI proteins in cysN mutants, but repression was restored by sulfite; in the cysI mutant, sulfate, sulfite and sulfide all led to repression of SSI protein synthesis. This suggests that there are at least two independent corepressors of the sulfate starvation response in this species.
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PMID:Regulation of the sulfate starvation response in Pseudomonas aeruginosa: role of cysteine biosynthetic intermediates. 961 12

Sulfate uptake and ATP sulfurylase activity in the roots of Arabidopsis thaliana and Brassica napus were enhanced by S deprivation and reduced following resupply of SO4(2-). Similar responses occurred in split-root experiments where only a portion of the root system was S-deprived, suggesting that the regulation involves inter-organ signaling. Phloem-translocated glutathione (GSH) was identified as the likely transducing molecule responsible for regulating SO4(2-) uptake rate and ATP sulfurylase activity in roots. The regulatory role of GSH was confirmed by the finding that ATP sulfurylase activity was inhibited by supplying Cys except in the presence of buthionine sulfoximine, an inhibitor of GSH synthesis. In direct and remote (split-root) exposures, levels of protein detected by antibodies against the Arabidopsis APS3 ATP sulfurylase increased in the roots of A. thaliana and B. napus during S starvation, decreased after SO4(2-) restoration, and declined after feeding GSH. RNA blot analysis revealed that the transcript level of APS1, which codes for ATP sulfurylase, was reduced by direct and remote GSH treatments. The abundance of AST68 (a gene encoding an SO4(2-) transporter) was similarly affected by altered sulfur status. This report presents the first evidence for the regulation of root genes involved in nutrient acquisition and assimilation by a signal that is translocated from shoot to root.
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PMID:Inter-organ signaling in plants: regulation of ATP sulfurylase and sulfate transporter genes expression in roots mediated by phloem-translocated compound. 1034 46

ATP sulfurylase (ATP: sulfate adenylyl transferase, EC 2.7.7.4), the first enzyme of the sulfate assimilation pathway, is present in the chloroplast and cytosol of plants. In Arabidopsis thaliana cDNA cloning revealed the existence of three ATP sulfurylase isoforms (APS1, -2, and -3) all of which appear to be localized in plastids. In the present study the cytosolic isoform was sought by searching the expressed sequence tag (EST) database and by screening A. thaliana genomic libraries. A fourth isoform, APS4, was identified, but it also encodes a plastid-localized isoform. The APS genes all contain four introns. The introns are located at identical positions within the coding sequence of each of the APS genes. A putative TATA box was identified in the promoter of the APS3 and APS4 genes, but no regions of sequence similarity were found among the other promoters. Combined analysis of an APS4 cDNA and genomic clone revealed that the deduced protein is 469 amino acids and is most homologous to the A. thaliana APS1 subclass. The APS4 cDNA was able to functionally complement a yeast ATP sulfurylase (met3) mutant and the recombinant enzyme displayed ATP sulfurylase activity. The APS4 protein exhibits a plastid targeting peptide at its amino terminus that, when fused to green fluorescent protein, was able to target the reporter to chloroplasts. APS4 mRNA was detected at a similar steady-state level in roots and leaves, and its expression was not induced by sulfur starvation or by O-acetylserine treatment. Having identified a fourth plastid-localized ATP sulfurylase, the origin of cytosolic isoform in A. thaliana remains unclear. Based on sequence analysis, it is hypothesized that APS2 may encode the cytosolic ATP sulfurylase.
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PMID:Functional characterization of a gene encoding a fourth ATP sulfurylase isoform from Arabidopsis thaliana. 1080 50

The dual role of glutathione as a transducer of S status (A.G. Lappartient and B. Touraine [1996] Plant Physiol 111: 147-157) and as an antioxidant was examined by comparing the effects of S deprivation, glutathione feeding, and H2O2 (oxidative stress) on SO42- uptake and ATP sulfurylase activity in roots of intact canola (Brassica napus L.). ATP sulfurylase activity increased and SO42- uptake rate severely decreased in roots exposed to 10 mM H2O2, whereas both increased in S-starved plants. In split-root experiments, an oxidative stress response was induced in roots remote from H2O2 exposure, as revealed by changes in the reduced glutathione (GSH) level and the GSH/oxidized glutathione (GSSG) ratio, but there was only a small decrease in SO42- uptake rate and no effect on ATP sulfurylase activity. Feeding plants with GSH increased GSH, but did not affect the GSH/GSSG ratio, and both ATP sulfurylase activity and SO42- uptake were inhibited. The responses of the H2O2-scavenging enzymes ascorbate peroxidase and glutathione reductase to S starvation, GSH treatment, and H2O2 treatment were not to glutathione-mediated S demand regulatory process. We conclude that the regulation of ATP sulfurylase activity and SO42- uptake by S demand is related to GSH rather than to the GSH/GSSG ratio, and is distinct from the oxidative stress response.
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PMID:Glutathione-Mediated Regulation of ATP Sulfurylase Activity, SO42- Uptake, and Oxidative Stress Response in Intact Canola Roots. 1222 97

The activity of ATP sulfurylase extracted from roots of intact canola (Brassica napus L. cv Drakkar) increased after withdrawal of the S source from the nutrient solution and declined after refeeding SO42- to S-starved plants. The rate of SO42- uptake by the roots was similarly influenced. Identical responses were obtained in SO42- -fed roots when one-half of the root system was starved for S. The internal levels of SO42- and glutathione (GSH) declined after S starvation of the whole root system, but only GSH concentration declined in +S roots of plants from split root experiments. The concentration of GSH in phloem exudates decreased upon transfer of plants to S-free solution. Supplying GSH or cysteine to roots, either exogenously or internally via phloem sap, inhibited both ATP sulfurylase activity and SO42- uptake. Buthionine sulfoximine, an inhibitor of GSH synthesis, reversed the inhibitory effect of cysteine on ATP sulfurylase. It is hypothesized that GSH is responsible for mediating the responses to S availability. ATP sulfurylase activity and the SO42- uptake rate are regulated by similar demand-driven processes that involve the translocation of a phloem-transported message (possibly GSH) to the roots that provides information concerning the nutritional status of the leaves.
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PMID:Demand-Driven Control of Root ATP Sulfurylase Activity and SO42- Uptake in Intact Canola (The Role of Phloem-Translocated Glutathione). 1222 81

MicroRNAs (miRNAs) are approximately 21-nucleotide RNAs, some of which have been shown to play important gene-regulatory roles during plant development. We developed comparative genomic approaches to systematically identify both miRNAs and their targets that are conserved in Arabidopsis thaliana and rice (Oryza sativa). Twenty-three miRNA candidates, representing seven newly identified gene families, were experimentally validated in Arabidopsis, bringing the total number of reported miRNA genes to 92, representing 22 families. Nineteen newly identified target candidates were confirmed by detecting mRNA fragments diagnostic of miRNA-directed cleavage in plants. Overall, plant miRNAs have a strong propensity to target genes controlling development, particularly those of transcription factors and F-box proteins. However, plant miRNAs have conserved regulatory functions extending beyond development, in that they also target superoxide dismutases, laccases, and ATP sulfurylases. The expression of miR395, the sulfurylase-targeting miRNA, increases upon sulfate starvation, showing that miRNAs can be induced by environmental stress.
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PMID:Computational identification of plant microRNAs and their targets, including a stress-induced miRNA. 1520 Sep 56

A high-affinity-type sulfate transporter (Group 1: ZmST1;1, Accession No. AF355602) has been cloned from maize seedlings by RT-PCR. Tissue and cell specific localisation of this sulfate transporter has been determined along the developmental gradient of the root and in leaves of different ages. In S-sufficient conditions there was uniform low expression of ZmST1;1 in the root and very low expression in the leaves. Increased mRNA abundance and sulfate influx capacity indicated that S-starvation increased ZmST1;1 expression in roots, especially at the top of the root (just behind the seed, the area possessing most laterals and root hairs) compared to the root tip. Similarly a group 2, probable low affinity-type sulfate transporter, ZmST2;1, and also ATP-sulfurylase and APS-reductase but not OAS(thiol)lyase were induced by S-starvation and showed highest expression in the upper section of the root. S-starvation increased root/shoot ratio by 20 % and increased root lateral length and abundance in the region closest to the root tip. As the increase in root proliferation was not as great as the increase in mRNA pools, it was clear that there was a higher cellular abundance of the mRNAs for sulfate transporters, ATP-sulfurylase, and APS-reductase in response to sulfur starvation. In the leaves, the sulfate transporters, ATP-sulfurylase and APS-reductase were induced by S-starvation with the most mature leaf showing increased mRNA abundance first. In situ hybridization indicated that ZmST1;1 was expressed in epidermal and endodermal cell layers throughout the root whilst OAS(thiol)lyase was highly expressed in the root cortex.
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PMID:Coordinated expression of sulfate uptake and components of the sulfate assimilatory pathway in maize. 1524 23


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