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

Much remains to be understood about how a group of cells or a tissue senses and regulates its size. Dictyostelium discoideum cells sense and regulate the size of groups and fruiting bodies using a secreted 450-kDa complex of proteins called counting factor (CF). Low levels of CF result in large groups, and high levels of CF result in small groups. We previously found three components of CF (D. A. Brock and R. H. Gomer, Genes Dev. 13:1960-1969, 1999; D. A. Brock, R. D. Hatton, D.-V. Giurgiutiu, B. Scott, R. Ammann, and R. H. Gomer, Development 129:3657-3668, 2002; and D. A. Brock, R. D. Hatton, D.-V. Giurgiutiu, B. Scott, W. Jang, R. Ammann, and R. H. Gomer, Eukaryot. Cell 2:788-797, 2003). We describe here a fourth component, CF60. CF60 has similarity to acid phosphatases, although it has very little, if any, acid phosphatase activity. CF60 is secreted by starving cells and is lost from the 450-kDa CF when a different CF component, CF50, is absent. Although we were unable to obtain cells lacking CF60, decreasing CF60 levels by antisense resulted in large groups, and overexpressing CF60 resulted in small groups. When added to wild-type cells, conditioned starvation medium from CF60 overexpressor cells as well as recombinant CF60 caused the formation of small groups. The ability of recombinant CF60 to decrease group size did not require the presence of the CF component CF45-1 or countin but did require the presence of CF50. Recombinant CF60 does not have acid phosphatase activity, indicating that the CF60 bioactivity is not due to a phosphatase activity. Together, the data suggest that CF60 is a component of CF, and thus this secreted signal has four different protein components.
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PMID:A 60-kilodalton protein component of the counting factor complex regulates group size in Dictyostelium discoideum. 1696 35

This study compares the influence of phosphate (Pi) deprivation on the coordinate synthesis of the principle Pi-starvation inducible (PSI) acid phosphatase (AP) isozymes in a suspension cell culture with the homologous in planta system. Tomato suspension cells express three PSI purple AP isozymes: a heterodimeric intracellular AP (IAP) composed of 63 and 57 kDa subunits, and two monomeric secreted APs (SAPs) (84 kDa SAP1 and 57 kDa SAP2) localized in the culture media. Immunoblots probed with rabbit antibodies raised against purified SAP1 or IAP indicated the immunological distinctiveness of SAP1 relative to IAP and SAP2. Time-course studies of cells and seedlings undergoing a transition from Pi sufficiency to Pi deficiency revealed a close relationship between total IAP or SAP activity and relative amounts of antigenic IAP or SAP polypeptides. Upregulation of the pre-existing IAP in 6-day-old Pi-deficient (-Pi) suspension cells coincided with a 20-fold reduction in intracellular free Pi levels, which occurred 2 d prior to initial accumulation of SAP1 and SAP2 in the culture media. Similarly, root-specific SAP synthesis in -Pi seedlings occurred at least 7 d following IAP induction in roots or shoots. Preferential sequestration of limiting Pi to the leaves of the -Pi seedlings was suggested by the delayed induction of leaf versus root IAP. Our results confirm recent transcript profiling studies suggesting that PSI proteins are subject to both temporal and tissue-specific syntheses in- Pi plants.
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PMID:Differential synthesis of phosphate-starvation inducible purple acid phosphatase isozymes in tomato (Lycopersicon esculentum) suspension cells and seedlings. 1708 Jun 45

Growth of suspension-cultured Catharanthus roseus cells ceased during phosphate starvation, but the cells grew again upon addition of Pi even after long-term starvation. The metabolic fate of [(33)P]Pi was studied in 1-week-old stationary phase cells in ordinary culture and in 1- or 2-week-old Pi-starved cells. Immediately after administration, the most heavily labelled organic compounds are nucleotides, followed by sugar phosphates. Two weeks Pi starvation slowed down the speed of incorporation of (33)P into nucleotides. The RNA, protein, and free nucleotide content all decreased gradually during Pi starvation; however, these compounds, especially nucleotides, increased markedly in the 24 h after addition of Pi. These responses are found in all cells examined, although the total amounts of these compounds were lower in the long-term Pi-deficient cells. Of the nucleotides, a marked increase was observed in nucleoside triphosphates and UDP-glucose. The transcript level of phosphate transporter and the activities of acid phosphatase, 5'- and 3'-nucleotidase, and adenosine nucleosidase were all reduced by the addition of Pi. In contrast, the activities of adenine phosphoribosyltransferase, nicotinate phosphoribosyltransferase, and nicotinamidase, which are salvage enzymes of purine and pyridine nucleotides, were markedly increased in the Pi-fed cells. Little or no increase was observed in adenosine kinase. In the light of these results, the possible involvement of net nucleotide synthesis in the initial metabolic events of recovery from Pi deficiency are discussed.
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PMID:Involvement of rapid nucleotide synthesis in recovery from phosphate starvation of Catharanthus roseus cells. 1718 41

A phosphate starvation-induced acid phosphatase cDNA was cloned from the rice, Oryza sativa. The cDNA encoding O. sativa acid phosphatase (OsACP1) has 1100 bp with an open reading frame of 274 amino acid residues. The deduced amino acid sequence of OsACP1 cDNA showed 53% identity to tomato acid phosphatase and 46-50% identity to several other plant phosphatases. OsACP1 expression was up-regulated in the rice plant and in cell culture in the absence of phosphate (Pi). The induced expression of OsACP1 was a specific response to Pi starvation, and was not affected by the deprivation of other nutrients. OsACP1 expression was responsive to the level of Pi supply, with transcripts of OsACP1 being abundant in Pi-deprived root. The OsACP1 cDNA was expressed as a 30 kDa polypeptide in baculovirus-infected insect Sf9 cells. In addition, the OsACP1 gene was introduced into Arabidopsis via Agrobacterium-mediated transformation. Functional expression of the OsACP1 gene in the transgenic Arabidopsis lines was confirmed by Northern blot and Western blot analyses, as well as phosphatase activity assays. These results suggest that the OsACP1 gene can be used to develop new transgenic dicotyledonous plants able to adapt to Pi-deficient conditions.
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PMID:A phosphate starvation-induced acid phosphatase from Oryza sativa: phosphate regulation and transgenic expression. 1741 67

Phytases are enzymes that catalyze liberation of inorganic phosphates from phytate, the major organic phosphorus in soil. Tobacco (Nicotiana tabacum) responds to phosphorus starvation with an increase in extracellular phytase activity. By a three-step purification scheme, a phosphatase with phytase activity was purified 486-fold from tobacco root exudates to a specific activity of 6,028 nkat mg(-1) and an overall yield of 3%. SDS-PAGE revealed a single polypeptide of 64 kDa, thus indicating apparent homogeneity of the final enzyme preparation. Gel filtration chromatography suggested that the enzyme was a ca. 56 kDa monomeric protein. De novo sequencing by tandem mass spectrometry resulted in a tryptic peptide sequence that shares high homology with several plant purple acid phosphatases. The identity of the enzyme was further confirmed by molybdate-inhibition assay and cDNA cloning. The purified enzyme exhibited pH and temperature optima at 5.0-5.5 and 45 degrees C, respectively, and were found to have high affinities for both p-nitrophenyl phosphate (pNPP; K(m)=13.9 microM) and phytate (K(m)=14.7 microM), but a higher kcat for pNPP (2,056 s(-1)) than phytate (908 s(-1)). Although a broad specificity of the enzyme was observed for a range of physiological substrates in soil, maximum activity was achieved using mononucleotides as substrates. We conclude that the phytase activity in tobacco root exudates is exhibited by a purple acid phosphatase and its catalytic properties are pertinent to its role in mobilizing organic P in soil.
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PMID:Phytase activity in tobacco (Nicotiana tabacum) root exudates is exhibited by a purple acid phosphatase. 1789 89

In Saccharomyces cerevisiae, the PHO pathway regulates expression of phosphate-responsive genes such as PHO5, which encodes repressible acid phosphatase (rAPase). In this pathway, Pho81p functions as an inhibitor of the cyclin-cyclin-dependent kinase (CDK) complex Pho80p-Pho85p. However, the mechanism regulating the inhibitory activity of Pho81p is poorly understood. Through use of the yeast two-hybrid system, we identified the UbL-UbA protein Ddi1p as a Pho81p-binding protein. Further, Pho81p levels were found to be low under high-phosphate condition and high during phosphate starvation, indicating that Pho81p is regulated by phosphate concentration. However, our results revealed that Ddi1p and its associated protein Rad23p are not involved in the decrease in Pho81p level under high-phosphate condition. Significantly, the Deltaddi1Deltarad23 strain exhibited a remarkable increase in rAPase activity at an intermediate-phosphate concentration of 0.4mM, suggesting that Ddi1p and Rad23p play a cooperative role as negative regulators in the PHO pathway.
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PMID:Ddi1p and Rad23p play a cooperative role as negative regulators in the PHO pathway in Saccharomyces cerevisiae. 1803 52

The present study was designed to identify nutrient-dependent changes in extracellular pH and acid phosphatase secretion in the biA1 palC4 mutant strain of Aspergillus nidulans. The palC4 mutant was selected as lacking alkaline phosphatase, but having substantially increased acid phosphatase activity when grown on solid minimal medium under phosphate starvation, pH 6.5. Gene palC was identified as a putative member of a conserved signaling cascade involved in ambient alkaline sensing whose sole function is to promote the proteolytic activation of PacC at alkaline pH. We showed that both poor growth and conidiation of the palC4 mutant strain on solid medium, alkaline pH, were relative to its hypersensitivity to Tris (hydroxymethyl) aminomethane buffer. Also, the secretion of acid phosphatase was repressed when both the wild-type and palC4 mutant strains were grown in low-phosphate yeast extract liquid medium, pH 5.0, indicating that the secretion of this enzyme is not necessary to regenerate inorganic phosphate from the organic phosphate pool present in yeast extract.
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PMID:Identification of nutrient-dependent changes in extracellular pH and acid phosphatase secretion in Aspergillus nidulans. 1805 93

PHO1 was previously identified in Arabidopsis (Arabidopsis thaliana) as a protein involved in loading inorganic phosphate (Pi) into the xylem of roots and its expression was associated with the vascular cylinder. Seven genes homologous to AtPHO1 (PpPHO1;1-PpPHO1;7) have been identified in the moss Physcomitrella patens. The corresponding proteins harbor an SPX tripartite domain in the N-terminal hydrophilic portion and an EXS domain in the conserved C-terminal hydrophobic portion, both common features of the plant PHO1 family. Northern-blot analysis showed distinct expression patterns for the PpPHO1 genes, both at the tissue level and in response to phosphate deficiency. Transgenic P. patens expressing the beta-glucuronidase reporter gene under three different PpPHO1 promoters revealed distinct expression profiles in various tissues. Expression of PpPHO1;1 and PpPHO1;7 was specifically induced by Pi starvation. P. patens homologs to the Arabidopsis PHT1, DGD2, SQD1, and APS1 genes also responded to Pi deficiency by increased mRNA levels. Morphological changes associated with Pi deficiency included elongation of caulonemata with inhibition of the formation of side branches, resulting in colonies with greater diameter, but reduced mass compared to Pi-sufficient plants. Under Pi-deficient conditions, P. patens also increased the synthesis of ribonucleases and of an acid phosphatase, and increased the ratio of sulfolipids over phospholipids. These results indicate that P. patens and higher plants share some common strategies to adapt to Pi deficiency, although morphological changes are distinct, and that the PHO1 proteins are well conserved in bryophyte despite the lack of a developed vascular system.
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PMID:Characterization of the PHO1 gene family and the responses to phosphate deficiency of Physcomitrella patens. 1805 86

Adaptation of plants to phosphate (Pi) deficiency is a complex process involving host of biochemical changes. These changes are integrated at transcriptional level by Pi starvation mediated signal transduction pathway. Many of the signaling processes are regulated by reversible protein phosphorylation directed by protein kinases and protein phosphatases. In this study, we report the characterization of a protein phosphatase gene (LePS2;1) from tomato induced during phosphate starvation. The bacterially expressed recombinant LePS2;1 protein readily dephosphorylated a synthetic phospho-Ser/Thr peptide. Okadaic acid, an inhibitor of Ser/Thr protein phosphatases, suppressed the enzyme activity. Western blot analysis revealed the Pi starvation dependent accumulation of LePS2;1 protein. Over-expression of LePS2;1 in tomato plants resulted in increased anthocyanin accumulation and acid phosphatase activity under Pi sufficient condition. Transgenic plants exhibited distinct changes in morphology and delayed flower initiation. These results provide evidence that the protein phosphatase LePS2;1, plays an important role in phosphate starvation induced processes in tomato. To our knowledge this is the first comprehensive analysis of a protein phosphatase induced during phosphate starvation.
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PMID:Biochemical and molecular analysis of LePS2;1: a phosphate starvation induced protein phosphatase gene from tomato. 1845 47

Recurrent application of animal manure to the soil often results in accumulation of phosphorus (P) in the soil over time. Use of temperate forages like Lolium multiflorum capable of extracting excess P from manure impacted soil is an attractive strategy for P phytoremediation. Two genotypes of L. multiflorum, 'Gulf and Marshall' were grown in soil and hydroponic media containing various concentrations of poultry manure and their P accumulation potential was determined. A decline in the biomass with an increase in manure concentration beyond 10 g kg(-1) soil in Gulf and 25 g kg(-1) soil in Marshall was noticed. Gulf grass accumulated more P content (7 g kg(-1) dry weight) as compared to Marshall (6 g kg(-1) dry weight) in both roots and shoots. Maximum shoot P content was observed in the soil amended with 10 g poultry manure, while root P was highest at the concentration of 50 g poultry manure kg(-1) in the soil. Both cultivars yielded the highest biomass when grown in the presence of 10 g poultry manure in modified Hoagland's media. Presence of chelators in the media did not produce any noticeable effect on P accumulation in either grass and the biomass was appreciably enhanced by all concentrations of the chelators. Gulf and Marshall ryegrass seedlings were grown hydroponically in various poultry manure fractions. Both phytase and acid phosphatase (APase) enzyme activities in the root increased substantially in response to P-sufficient condition. In the presence of various poultry manure fractions, an intermediate level of both enzymes was measured compared to the P-sufficient condition, while the lowest enzyme activity was observed in the absence of any P source in the media. The level of APase and phytase activities was more or less the same in the two grasses under various growth conditions. An additional APase isoform was induced specifically in response to P-starvation from the two grass cultivars. Phytase and APase assays carried out in the P-starved and P-replenished grass seedlings further confirmed that during P deficiency, the enzyme activity was lowest and results of PAGE indicated that an APase isoform was induced under P-starvation.
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PMID:Effect of P sources on growth, P accumulation and activities of phytase and acid phosphatases in two cultivars of annual ryegrass (Lolium multiflorum L.). 1848 20


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