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

Two Escherichia coli strains in which alpha-amylase production differed were used to study in depth some characteristics related to beta-glucuronidase induction by starch. The beta-glucuronidase background activity in Luria broth medium was comparable for the two isolates, but only amylase positive S1 was able to grow on starch molecules supplied as the sole carbon source. In this case growth resulted at higher beta-glucuronidase levels (p < 0.01) with respect to basal activity and the induced expression was maximal (6.1-fold) when cultures reached the stationary phase. Growth in the presence of a protein synthesis inhibitor (chloramphenicol) was associated with a marked reduction of activity. The beta-glucuronidase activity of amylase negative M94 remained unchanged during starvation on starch medium, but an induced response was observed with methylumbelliferyl-glucuronide. These results further support the hypothesis that starch metabolism is involved in the complex beta-glucuronidase regulation of E. coli strains. This is relevant not only for basic research but also to investigating gut microbial enzymology.
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PMID:Implications of alpha-amylase production and beta-glucuronidase expression in Escherichia coli strains. 1051 Aug 69

The unique capability of rice (Oryza sativa L.) seedlings to grow under anoxic conditions may result in part from their ability to express alpha-amylase and maintain the supply of sugar needed for energy metabolism. Previous studies have demonstrated that under aerobic conditions the Amy1 and Amy2 subfamily genes are regulated primarily by phytohormones while the Amy3 subfamily genes are induced during sugar starvation. The expression patterns for these alpha-amylase genes were considerably different in anoxic vs. aerobic rice seedlings. The level of total alpha-amylase mRNA under anoxic conditions was decreased in aleurone layers while it increased in the embryo. Anoxic conditions greatly diminished the expression of the Amy1A gene in aleurone. Conversely, expression of many Amy3 subfamily genes was up-regulated and prolonged in embryo tissues under anoxic conditions.
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PMID:Differential expression of rice alpha-amylase genes during seedling development under anoxia. 1052 16

When Bacillus subtilis is subjected to phosphate starvation, genes of the Pho regulon are either induced or repressed. Among those induced are genes encoding alkaline phosphatases (APases). A set of isogenic mutants, with a beta-galactosidase gene transcriptionally fused to the inactivated target gene, was used to identify genes that influence the operation of the Pho regulon. One such gene was nhaC (previously yheL). In the absence of NhaC, growth and APase production were enhanced, while the production of other non-Pho-regulon secretory proteins (proteases and alpha-amylase) did not change. The influence of NhaC on growth, APase synthesis, and its own expression was dependent on the external Na+ concentration. Other monovalent cations such as Li+ or K+ had no effect. We propose a role for NhaC in the uptake of Na+. nhaC appears to be encoded by a monocistronic operon and, contrary to previous reports, is not in the same transcriptional unit as yheK, the gene immediately upstream. The increase in APase production was dependent on an active PhoR, the sensor kinase of the two-component system primarily responsible for controlling the Pho regulon. Transcriptional fusions showed that the phoPR operon and both phoA (encoding APaseA) and phoB (encoding APaseB) were hyperinduced in the absence of NhaC and repressed when this protein was overproduced. This suggests that NhaC effects APase production via phoPR.
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PMID:Bacillus subtilis NhaC, an Na+/H+ antiporter, influences expression of the phoPR operon and production of alkaline phosphatases. 1127 10

Expression of alpha-amylase genes in cereals is induced by both gibberellin (GA) and sugar starvation. In a transient expression assay, a 105-bp sugar response sequence (SRS) in the promoter of a sugar starvation highly inducible rice alpha-amylase gene, alphaAmy3, was shown previously to confer sugar response and to enhance the activity of the rice Act1 promoter in rice protoplasts. A 230-bp SRS-like sequence was also found in the promoter of another sugar starvation highly inducible rice alpha-amylase gene, alphaAmy8. The alphaAmy8 SRS contains a GA response sequence and was designated as alphaAmy8 SRS/GARS. In the present study, a transgenic approach was employed to characterize the function of the alpha-amylase gene SRSs in rice. We found that the alphaAmy3 SRS significantly enhances the endogenous expression pattern of the Act1 promoter in various rice tissues throughout their developmental stages. By contrast, the alphaAmy8 SRS/GARS significantly enhances Act1 promoter activity only in embryos and endosperms of germinating rice seeds. A minimal promoter fused to the alphaAmy8 SRS/GARS is specifically active in rice embryo and endosperm and is subject to sugar repression and GA induction in rice embryos. This sugar repression was found to override GA induction of alphaAmy8 SRS/GARS activity. Our study demonstrates that the alpha-amylase transcriptional enhancers contain cis-acting elements capable of enhancing endogenous expression patterns or activating sugar-sensitive, hormone-responsive, tissue-specific, and developmental stage-dependent expression of promoters in transgenic rice. These enhancers may facilitate the design of highly active and tightly regulated composite promoters for monocot transformation and gene expression. Our study also reveals the existence of cross-talk between the sugar and GA signaling pathways in cereals and provides a system for analyzing the underlying molecular mechanisms involved.
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PMID:Rice alpha-amylase transcriptional enhancers direct multiple mode regulation of promoters in transgenic rice. 1183 81

The expression of alpha-amylase genes in cereals is induced by both gibberellin (GA) and sugar starvation. All alpha-amylase genes isolated from cereals contain a TATCCA element or its variants at positions approximately 90 to 150 bp upstream of the transcription start sites. The TATCCA element was shown previously to be an important component of the GA response complex and the sugar response complex of alpha-amylase gene promoters. In the present study, three cDNA clones encoding novel MYB proteins with single DNA binding domains were isolated from a rice suspension cell cDNA library and designated OsMYBS1, OsMYBS2, and OsMYBS3. Gel mobility shift experiments with OsMYBSs showed that they bind specifically to the TATCCA element in vitro. Yeast one-hybrid experiments demonstrated that OsMYBS1 and OsMYBS2 bind to the TATCCA element and transactivate a promoter containing the TATCCA element in vivo. Transient expression assays with barley half-seeds showed that OsMYBS1 and OsMYBS2 transactivate a promoter containing the TATCCA element when sugar is provided, whereas OsMYBS3 represses transcription of the same promoter under sugar starvation. Transient expression assays also showed that these three OsMYBSs cooperate with a GA-regulated transcription factor, HvMYBGa, in the transactivation of a low-pI barley alpha-amylase gene promoter in the absence of GA. Two-hybrid experiments with barley half-seeds showed that OsMYBS1 is able to form a homodimer. The present study demonstrates that differential DNA binding affinity, promoter transactivation ability, dimerization, and interactions with other protein factors determine the biological function of OsMYBSs. This study also suggests that common transcription factors are involved in the sugar and hormonal regulation of alpha-amylase gene expression in cereals.
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PMID:Three novel MYB proteins with one DNA binding repeat mediate sugar and hormone regulation of alpha-amylase gene expression. 1217 34

Tolerance to low oxygen availability is likely to be due to the interaction of several factors. Sugar availability is one of the elements required to support anaerobic metabolism. In cereal grains the availability of soluble sugars is limited, while starch is stored in large amounts. Degradation of starch under anoxia is therefore needed to avoid sugar starvation leading to rapid cell death. The striking difference in the ability to produce alpha-amylase when comparing the anoxia-tolerant rice (Oryza sativa L.) grains with grains of other cereals is not easily explained. Rice is able to respond to gibberellins under anoxia, but the response is too slow to explain the rapid production of alpha-amylase enzyme. In the present work we demonstrated that alpha-amylase production during the first 2 d after imbibition is mostly due to the activity of the Ramy3D gene, encoding for the G and H isoforms of alpha-amylase. The induction of Ramy3D transcription is likely to result from a low sugar content in the grains incubated under anoxia. The ability of rice embryos to sense sugars under anoxia is reported.
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PMID:Sugar modulation of alpha-amylase genes under anoxia. 1250 35

A DNA fragment corresponding to part of an SNF1 (sucrose non-fermenting-1)-related protein kinase (SnRK1) transcript was amplified by a polymerase chain reaction (PCR) from a wheat (Triticum aestivum) endosperm cDNA library. It was used to construct a chimaeric gene, pUasSnRKN, comprising a ubiquitin promoter, the SnRK1 PCR product in the antisense orientation and the nopaline synthase (Nos) gene terminator. This construct was used in transient gene expression experiments in cultured wheat embryos together with a series of reporter gene constructs. These included the wheat alpha amylase gene alpha-Amy2 promoter with UidA (Gus) coding region (palpha2GT), rice actin promoter with Gus (pActIDGus), ubiquitin promoter with Gus (pAHC25) and actin promoter with green fluorescent protein (GFP) gene (pAct1Is-GFP1). All of the reporter genes were found to be active when bombarded into scutellae isolated from immature grains at 25 d post-anthesis and incubated on MS medium for 24 h prior to bombardment. However, co-bombardment of palpha2GT with equimolar amounts of pUasSnRKN resulted in no detectable Gus activity, indicating that the antisense SnRK1 construct repressed the alpha-Amy2 promoter. Co-bombardment with pUasSnRKN had no effect on the activity of the other promoters used in the study. A triple bombardment with palpha2GT, pAct1Is-GFP-1 and pUasSnRKN resulted in clear green fluorescence, indicating that the bombarded cells were still viable, but no Gus activity. RT-PCR analysis showed clearly that the antisense SnRK1 gene was expressing. Northern and RT-PCR analyses confirmed that SnRK1 and both alpha-amylase genes, alpha-Amy1 and alpha-Amy2, are expressed in cultured wheat embryos harvested from grain 25 d post-anthesis. Expression of alpha-Amy1 and alpha-Amy2 was up-regulated by sugar starvation.
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PMID:Antisense SNF1-related (SnRK1) protein kinase gene represses transient activity of an alpha-amylase (alpha-Amy2) gene promoter in cultured wheat embryos. 1255 17

The roots of alternate-bearing citrus (Murcott, a Citrus reticulata hybrid) trees undergo extreme fluctuations of carbohydrate abundance and starvation. Using this system, we investigated the effect of root carbohydrate (total soluble sugar, sucrose and starch) depletion on carbohydrate-related gene expression. A series of genes, including those coding for starch phosphorylase ( STPH-L and STPH-H), ADP-glucose pyrophosphorylase, small subunit ( Agps), R1, plastidic ADP/ATP transporter ( AATP), phosphoglucomutase ( PGM-P and PGM-C), sucrose synthase ( CitSuS1 and CitSuSA), sucrose transporter ( SUT1 and SUT2), hexokinase ( HK) and alpha-amylase ( alpha-AMY), have been isolated and their expression analyzed. The genes were found to respond differentially to carbohydrate depletion. STPH-L, STPH-H, Agps, R1, AATP, PGM-P, PGM-C, CitSuS1 and HK were down-regulated while SUT1 and alpha-AMY were up-regulated during carbohydrate depletion. Two other genes, CitSuSA and SUT2, did not respond to carbohydrate depletion. Fruit removal, which interrupted the carbohydrate depletion induced by heavy fruiting, reversed these gene expression patterns. Trunk girdling and whole-plant darkening treatments, which brought about root carbohydrate depletion, induced the same changes in gene expression obtained in the alternate-bearing system. The possible roles of the up- and down-regulated genes in the metabolism of carbohydrate-depleted citrus roots are discussed. Although the specific signals involved have not been determined, the results support the feast/famine hypothesis of carbohydrate regulation proposed by Koch [K.E. Koch (1996) Annu Rev Plant Physiol Plant Mol Biol 47:509-540].
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PMID:Effects of carbohydrate starvation on gene expression in citrus root. 1272 44

Eisenstadt, Jerome M. (Brandeis University, Waltham, Mass.) and Harold P. Klein. Evidence for the de novo synthesis of the alpha-amylase of Pseudomonas saccharophila. J. Bacteriol. 82:798-807. 1961.-Chloramphenicol at a concentration of 20 mug per ml inhibited the appearance of the inducible alpha-amylase of Pseudomonas saccharophila. This inhibition was observed when induction was attempted in buffer or in a complete medium. Preinduced cells were also prevented from forming this enzyme under similar conditions. Under all the conditions tested, there was no lag in chloramphenicol inhibition, thus suggesting an absence of any protein precursor in amylase formation. Cells suspended in a complete medium without a nitrogen source lost their capacity to form this enzyme when subsequently induced in buffer. When cells were grown in the presence of radioactive sulfate and then subjected to starvation, the radioactivity of the amino acid pool diminished only slightly. However, examination of the free amino acid pool by paper chromatography showed that the loss of enzyme inducibility was accompanied by the disappearance of glutamine, aspartic acid, and a third, unidentified, compound. Enzyme-forming ability was restored by the addition, to starved cells of casein hydrolysate, glutamate, glutamine, or aspartate. Other amino acids tested were ineffective in this regard. When cells were induced in buffer in the presence of labeled methionine, amylase was formed at a linear rate over a 3-hr period. Furthermore, both the cellular proteins and the extracellular amylase became labeled at a linear rate. These observations are discussed in relation to the problem of protein turnover, and are interpreted as evidence for the de novo synthesis of alpha-amylase in this organism.
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PMID:Evidence for the de novo synthesis of the alpha-amylase of Pseudomonas saccharophila. 1388 95

Welker, N. E. (Western Reserve University, Cleveland, Ohio and University of Illinois, Urbana), and L. Leon Campbell. De novo synthesis of alpha-amylase by Bacillus stearothermophilus. J. Bacteriol. 86:1202-1210. 1963.-The pH optimum for the synthesis of alpha-amylase by washed-cell suspensions was 6.7. alpha-Amylase synthesis began soon after the addition of the inducer (maltose, methyl-beta-d-maltoside, or phenyl-alpha-d-glucoside, at 10(-3)m), proceeded at a linear rate for 60 min, and then leveled off. Cell suspensions without inducer produced small amounts of alpha-amylase. The addition of glucose (2 x 10(-3)m), sucrose (10(-3)m), or glycerol (4 x 10(-3)m) to washed-cell suspensions failed to stimulate the production of alpha-amylase. Nitrogen starvation of washed cells for 60 min with fructose as a carbon source or by induction with pure maltose showed that the ability to produce alpha-amylase was lost. Examination of the amino acid pool at this time showed a general depletion of amino acids and the complete disappearance of tyrosine, phenyl-alanine, proline, and valine. Replenishment of the amino acid pool with casein hydrolysate (0.5%) restored the ability of the cells to produce alpha-amylase. Chloramphenicol and 8-azaguanine were shown to inhibit alpha-amylase synthesis. Inhibition was observed immediately upon the addition of chloramphenicol to cell suspensions preinduced for varying periods of time. Actinomycin D and mitomycin C also inhibited alpha-amylase synthesis when added to induced washed-cell suspensions. The amino acid analogues, norvaline, norleucine, and ethionine, inhibited alpha-amylase formation by 72, 53, and 38%, respectively. p-Fluorophenylalanine inhibited the synthesis of active alpha-amylase by 92% and the incorporation of proline-C(14) into alpha-amylase and cellular proteins by 95 and 74%, respectively.
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PMID:DE NOVO SYNTHESIS OF ALPHA-AMYLASE BY BACILLUS STEAROTHERMOPHILUS. 1408 90


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