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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The study of plant ribonuclease (RNase) functions is complicated by a complex profile of RNase activities detected in tissues. Thus, isolation of individual RNase genes will be desirable for the further understanding of function of each RNase. Here, we describe the isolation of cDNAs encoding two RNases, ZRNaseI and ZRNaseII, in differentiating tracheary elements (TEs) induced from isolated mesophyll cells of Zinnia elegans. Both the ZRNaseI and ZRNaseII exhibit putative secretion signal sequences at the amino-terminal ends with predicted molecular masses of 24 247 Da and 22 448 Da as mature proteins, respectively. DNA gel blot analysis showed that both RNases in Zinnia appear to be encoded by a small gene family. RNA gel blot analysis showed that the expression of the ZRNaseI gene was associated with the late stage of in vitro TE differentiation, whereas the ZRNaseII gene was mainly induced in response to stress. Neither RNase gene was induced in response to phosphate starvation, or to H2O2 challenge in the cultured mesophyll cells, or to senescence in the leaves. In young leaves, the ZRNaseI gene was not induced in response to wounding. But the ZRNaseII gene was markedly induced by 6 h after wounding. Tissue print hybridization showed that the expression of the ZRNaseI gene was preferentially associated with the differentiation TEs in Zinnia stems, while the ZRNaseII mRNA was not detected in unwounded Zinnia organs. Taken together, the results indicated that the ZRNaseI gene is expressed during the process of xylogenesis both in vitro and in the plant, whereas the ZRNaseII gene is predominantly induced in response to wounding. The identification of these RNase genes provides molecular tools for the dissection of the process of autolysis during xylogenesis, and for the dissection of the role of RNase in wounding response.
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PMID:Isolation and characterization of cDNAs encoding xylogenesis-associated and wounding-induced ribonucleases in Zinnia elegans. 862 3

The control of rRNA synthesis in the etiological agent of epidemic typhus, Rickettsia prowazekii, a slowly growing obligate intracytoplasmic bacterium, was investigated. Transcription of the rickettsial 16S rRNA gene (rrs), of which there is only a single copy, was controlled by a single promoter region, and the site for the initiation of transcription (base A) was found 117 bp upstream of the rrs coding region for the mature product. The promoter region contained an Escherichia coli promoter-like sequence, TTGACA-N17-TATAAC, centered 139 bp upstream of the coding region for the mature product. To investigate whether transcription of the rickettsial rrs responds to amino acid starvation conditions, total RNA was isolated from R. prowazekii-infected mouse L929 cells with or without methionine starvation. The level of newly synthesized 16S rRNA precursors in R. prowazekii, as analyzed by ribonuclease protection assays, decreased significantly after methionine starvation for 6 h and then recovered within 12 h after the addition of methionine. The chemical half-lives of the 16S rRNA precursors in the methionine-starved rickettsiae did not differ significantly from those in the normal rickettsiae. These results suggest that R. prowazekii regulates transcription of the rrs in response to amino acid starvation conditions.
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PMID:Transcriptional analysis of the 16s rRNA gene in Rickettsia prowazekii. 862 5

The expression of at least 24 distinct genes of Pseudomonas aeruginosa PAO1 is under direct control of the "ferric uptake regulator" (Fur). Novel targets of the Fur protein were isolated in a powerful SELEX (systematic evolution of ligands by exponential enrichment)-like cycle selection consisting of in vitro DNA-Fur interaction, binding to anti-Fur antibody, purification on protein G, and PCR amplification. DNA fragments obtained after at least three exponential enrichment cycles were cloned and subjected to DNA mobility-shift assays and DNase I footprint analyses to verify the specific interaction with the Fur protein in vitro. Iron-dependent expression of the corresponding genes in vivo was monitored by RNase protection analysis. In total, 20 different DNA fragments were identified which represent actual Pseudomonas iron-regulated genes (PIGs). While four PIGs are identical to already known genes (pfeR, pvdS, tonB, and fumC, respectively), 16 PIGs represent previously unknown genes. Homology studies of the putative proteins encoded by the PIGs allowed us to speculate about their possible function. Two PIG products were highly similar to siderophore receptors from various species, and three PIG products were significantly homologous to alternative sigma factors. Furthermore, homologs of the Escherichia coli ORF1-tolQ, nuoA, stringent starvation protein Ssp, and of a two-component regulatory system similar to the Pseudomonas syringae LemA sensor kinase were identified. The putative gene products of seven additional PIGs did not show significant homologies to any known proteins. The PIGs were mapped on the P.aeruginosa chromosome. Their possible role in iron metabolism and virulence of P. aeruginosa is discussed.
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PMID:Gene repression by the ferric uptake regulator in Pseudomonas aeruginosa: cycle selection of iron-regulated genes. 863 80

In Escherichia coli, amino acid starvation results in the coordinate inhibition of a variety of metabolic activities, including fatty acid and phospholipid biosynthesis. By using primer extension analysis we identified the fabH promoter responsible for transcription of the fabH, fabD and fabG genes encoding fatty acid biosynthetic enzymes. The response of the fabH promoter to amino acid starvation was determined in vivo. Transcripts originating from the fabH promoter were quantified by employing a ribonuclease protection assay. The fabH promoter was subject to relA-dependent stringent control and was repressed approximately 4-fold upon amino acid starvation. The results suggest that inhibition of transcription initiation of lipid biosynthetic genes in starved cells contributes to the stringent control of lipid biosynthesis.
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PMID:Identification of promoter and stringent regulation of transcription of the fabH, fabD and fabG genes encoding fatty acid biosynthetic enzymes of Escherichia coli. 864 95

During the course of screening plants for novel antifungal activity, we found that a high-molecular-mass fraction of an extract from leaves of Engelmannia pinnatifida exhibited potent and broad-spectrum antifungal activity. In this study a 30 kDa protein from E. pinnatifida leaves was purified to homogeneity by ammonium sulphate precipitation, gel filtration, Mono-Q and C18 reverse-phase column chromatographies. The purified protein showed potent antifungal activity against various plant pathogens with as little as 50 ng. The N-terminal amino acid sequence of the purified protein was determined as XXTKFDFFTLALQXPAXF, where X indicates an unidentified residue. This sequence showed 35-50% sequence identity with purified style glycoproteins associated with self-incompatibility from wild tomato, tobacco and petunia, a phosphate-starvation-induced ribonuclease from cultured tomato cells and the SIR 63.4 kDa protein from yeast.
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PMID:Isolation and characterization of a 30 kDa protein with antifungal activity from leaves of Engelmannia pinnatifida. 867 Jan 44

Insulin-like growth factor-I (IGF-I) exerts its effect through the IGF-I receptor. To investigate the effects of nutritional status on chicken IGF-I receptor gene expression, a solution hybridization/RNase protection assay for IGF-I receptor mRNA was developed. A cDNA clone corresponding to the carboxyl-terminal region of the IGF-I receptor was obtained by reverse transcription-PCR (RT-PCR). Sequence analysis of the clone showed that this region of the chicken IGF-I receptor is highly divergent from the human IGF-I receptor. IGF-I receptor mRNA was detected in all tissues examined from newly hatched chickens. The rank order of the IGF-I receptor mRNA levels was liver < thigh muscle < stomach < heart < lung < kidney < brain. In 1-week-old chickens, 5 days of starvation caused a 2.5- to 3-fold increase in the mRNA in muscle and kidney. Starvation of 4-week-old chickens for 5 days caused a 1.7 to 2.2-fold increase in IGF-I receptor mRNA levels in kidney, liver, and muscle. In contrast, IGF-I receptor mRNA levels in brain failed to change. The mRNA levels were reduced to the control level by refeeding of the starved chickens for 24h. These data suggest a tissue- and development-specific response of chicken IGF-I receptor gene expression to nutritional status.
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PMID:Nutritional regulation of insulin-like growth factor-I receptor mRNA levels in growing chickens. 869 14

To better understand the mechanisms that regulate stable RNA synthesis, we have analyzed the RNA polymerase I and III transcriptional activities of extracts isolated from cells propagated under a variety of conditions. Under balanced growth conditions the levels of both RNA polymerase I- and III-specific transcription increased proportionally with growth rate. Upon nutritional starvation, RNA polymerase I transcription rapidly declined, followed by 5 S rDNA and eventually tDNA transcription. Transcriptional activities in extracts were restored when the nongrowing cultures were resuspended in fresh medium, although growth did not resume. The differential expression of 5 S rDNA and tDNA genes in extracts prepared from cells subjected to partial starvation was traced to a 5 S rDNA-specific inhibitor and not to a defect in any RNA polymerase III transcription factor. Characterization of this inhibitor indicated that it was not 5 S rRNA. It was sensitive to phenol extraction and resistant to RNase, and its target did not appear to be transcription factor IIIA. Not all treatments that slowed or stopped growth down-regulated the stable RNA transcription apparatus. Cells that have been subjected to either energy starvation or cycloheximide treatment still retain the ability to synthesize stable RNA in vitro, suggesting the presence of alternative regulatory mechanisms.
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PMID:Regulation of the RNA polymerase I and III transcription systems in response to growth conditions. 870 32

We characterised a cDNA encoding an S-like RNase (RNase NE) from the styles of the self-incompatible plant, Nicotiana alata. RNase NE is 86% identical to an extracellular RNase from tomato cell cultures, RNase LE. DNA hybridisation experiments indicate that there are ca. 5-6 sequences related to RNase NE in the N. alata genome and that RNase NE is not linked to the self-incompatibility (S) locus. RNase NE is expressed in the styles, petals and immature anthers but not in the vegetative tissues of N. alata plants under normal growth conditions. Under phosphate-limited conditions, RNase NE expression is induced in roots but not leaves of N. alata. A transcript hybridising to RNase NE is also induced in N. plumbaginifolia cell cultures in response to phosphate starvation. RNase NE is likely to play a role in the response of N. alata to phosphate limitation, possibly by scavenging phosphate from sources of RNA in the root environment. We also discuss the evolutionary relationships between the S- and S-like RNase genes in plants.
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PMID:Molecular characterisation of an S-like RNase of Nicotiana alata that is induced by phosphate starvation. 875 89

Expression of the hemolytic phospholipase C (PlcH) of Pseudomonas aeruginosa is induced under phosphate starvation conditions or in the presence of the osmoprotectants choline and glycine betaine. Because choline and glycine betaine may serve as carbon and energy sources in addition to conferring osmoprotection to P. aeruginosa, it seemed possible that induction of plcH is subject to catabolite repression control (CRC) by tricarboxylic cycle intermediates such as succinate. Total phospholipase (PLC) activity in osmoprotectant-induced cultures of P. aeruginosa PAO1 supplemented with 20 mM succinate was three- to fourfold lower than the levels in cultures supplemented with the non-catabolite-repressive substrate lactate. Analyses of osmoprotectant-dependent plcH expression in a derivative of strain PAO1 containing a plcH::lacZ operon fusion showed that (i) succinate prevented induction of plcH expression by osmoprotectants; and (ii) addition of succinate reduced or shut down further expression of plcH in osmoprotectant-induced bacteria, while cultures supplemented with lactate had little or no change in plcH expression. RNase protection analysis confirmed that repression of plcH occurs at the transcriptional level. However, a P. aeruginosa mutant decoupled in CRC exhibited a phenotype similar to that of the wild-type strain (PAO1) with respect to succinate-dependent repression of plcH expression. Osmoprotectant-induced total PLC activities, levels of expression of plcH measured with the same plcH::lacZ fusion, and levels of plcH transcription in a CRC-deficient strain reflected those seen in strain PAO1. This indicates that CRC of plcH functions by a distinct mechanism which differs from that regulating the glucose or mannitol catabolic pathway. A strain carrying a mutation in vfr, which encodes the Escherichia coli Crp homolog in P. aeruginosa, still exhibited a wild-type phenotype with respect to osmoprotectant-dependent expression and CRC of plcH. These data indicate that there is a novel CRC system that regulates the expression of plcH in P. aeruginosa.
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PMID:Osmoprotectant-dependent expression of plcH, encoding the hemolytic phospholipase C, is subject to novel catabolite repression control in Pseudomonas aeruginosa PAO1. 924 77

A main feature of leaf senescence is the hydrolysis of macromolecules by hydrolases of various types, and redistribution of released materials. We have initiated a study for the characterization of RNases involved in nucleic acid catabolism during senescence. Using a PCR-based cloning approach we isolated from tomato two senescence-induced RNase cDNA clones. Each of these cDNAs hybridized to a senescence-induced transcript in northern analysis. One RNase cDNA was identical to the tomato LX RNase while the second corresponded to the LE RNase. Both LX and LE RNase genes had originally been demonstrated to be induced after phosphate starvation of tomato cell culture but nothing was known about their expression or function in plants. We observed that the expression of the LX and LE genes is induced in leaves during an advanced stage of senescence with the LX transcript level being much more induced than that of LE. Low-level expression of the RNase genes was observed in flowers and artificially senescing detached leaves while no expression could be detected in stems, roots, or fruits at different ripening stages. Ethylene activated the LX gene expression in detached young leaves while LE gene expression, which could be transiently induced by wounding, appeared to be activated by abscisic acid. We suggest that the LX RNase has a role in RNA catabolism in the final stage of senescence, and LE may function during wounding as a plant defense protein.
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PMID:Senescence-induced RNases in tomato. 948 84


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