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At least 19 recordsLinked to original sources
PubMed2026

The link between phosphate starvation-triggered anthocyanin biosynthesis and jasmonate-driven regulation in tomato.

Phosphate Starvation Response (PSR) in plants integrates inorganic phosphate (Pi) sensing with hormonal and metabolic reprogramming. Recent evidence supports a PSR-jasmonate (JA)-anthocyanin axis in which the PSR-associated PHOSPHATE STARVATION RESPONSE (PHR)/PHR-like-SYG1-PHO81-XPR1-inositol pyrophosphate 8 (PHR/PHL-SPX-InsP8) module gates transcriptional activation, while the core JA components JASMONATE ZIM-DOMAIN (JAZ) and MYELOCYTOMATOSIS 2 (MYC2) mediate hormone-induced activation of secondary metabolism. In Solanum lycopersicum, PHR/PHL transcription factors (TFs) serve as core PSR hubs, with expanded regulatory networks and InsP-associated control layers that tune SPX buffering and transcriptional output. Downstream, JA signaling and MYC2-dependent transcription interface with anthocyanin regulators, including key MYB and bHLH TFs that form the MYB-basic helix-loop-helix (bHLH)-WD40 repeat (MBW) complex, thereby regulating tissue capacity for pigmentation under Pi starvation (PiS). Anthocyanin-rich tomato cultivars such as 'Indigo Rose' exemplify how genetic configuration can enhance MBW responsiveness and potentiate pigment accumulation under PiS. Here, we collate recent advances linking PSR gating, JA response, and anthocyanin biosynthesis regulation in tomato, and propose a working model with testable predictions to accelerate causal validation, and enable breeding strategies targeting phosphorus use efficiency and nutritional quality.

Solanum lycopersicum↗
PubMed1976

[Variations of enzymatic activities in an asporogenic mutant of Bacillus megaterium for various nutritional deficiencies].

An asporogenous mutant of Bacillus megaterium KM, blocked at stage I of sporulation, is cultivated in different conditions which usually lead to sporulation (Nitrogen, carbon, phosphate starvation). Aklaline phosphatase appears only in inorganic phosphate starvation like the wild type, but a glucose dehydrogenase activity also appears in phosphate starvation and so, is dissociated from sporulation.

Alcohol Oxidoreductases↗
PubMed1979

Regulation of phosphate accumulation in the unicellular cyanobacterium Synechococcus.

The phosphorus contents of acid-soluble pools, lipid, ribonucleic acid, and acid-insoluble polyphosphate were lowered in Synechococcus in proportion to the reduction in growth rate in phosphate-limited but not in nitrate-limited continuous culture. Phosphorus in these cell fractions was lost proportionately during progressive phosphate starvation of batch cultures. Acid-insoluble polyphosphate was always present in all cultural conditions to about 10% of total cell phosphorus and did not turn over during balanced exponential growth. Extensive polyphosphate formation occurred transiently when phosphate was given to cells which had been phosphate limited. This material was broken down after 8 h even in the presence of excess external orthophosphate, and its phosphorus was transferred into other cell fractions, notably ribonucleic acid. Phosphate uptake kinetics indicated an invariant apparent K(m) of about 0.5 muM, but V(max) was 40 to 50 times greater in cells from phosphate-limited cultures than in cells from nitrate-limited or balanced batch cultures. Over 90% of the phosphate taken up within the first 30 s at 15 degrees C was recovered as orthophosphate. The uptake process is highly specific, since neither phosphate entry nor growth was affected by a 100-fold excess of arsenate. The activity of polyphosphate synthetase in cell extracts increased at least 20-fold during phosphate starvation or in phosphate-restricted growth, but polyphosphatase activity was little changed by different growth conditions. The findings suggest that derepression of the phosphate transport and polyphosphate-synthesizing systems as well as alkaline phosphatase occurs in phosphate shortage, but that the breakdown of polyphosphate in this organism is regulated by modulation of existing enzyme activity.

Biological Transport↗
PubMed1976

Control of teichoic and teichuronic acid biosynthesis in Bacillus subtilis 168trp. Evidence for repression of enzyme synthesis and inhibition of enzyme activity.

Phosphate starvation induced teichuronic acid synthesis in cells of Bacillus subtilis 168trp-which had previously been grown with excess phosphate. This induction was prevented when protein systhesis was inhibited immediately prior to phosphate starvation and under these conditions cells continued to form teichoic acid. The converse was true when phosphate was added to cells previously grown in a phosphate-limited chemostat. The increase in teichoic acid synthesis normally following phosphate addition was prevented by chloramphenicol or amino acid starvation and cells continued to make teichuronic acid. This suggestion that repression of enzyme synthesis is involved in controlling the type of wall polymer made was supported by the low levels of UDP-glucose dehydrogenase found in cells grown with excess phosphate and of CDP-glycerol pyrophosphorylase in phosphate-limited cells. The greater amounts of teichoic acid made under phosphate limitation and of teichuronic acid with excess phosphate when protein synthesis was also inhibited indicated that modulation of enzyme activity occurs. Glycerol starvation of a glycerol-requiring mutant did not derepress teichuronic acid synthesis, indicating that glycerol-containing imtermediates do not act as repressors.

Bacillus subtilis↗
PubMed1975

[Variations in enzyme activities in different sporulation conditions of Bacillus megaterium].

Glucose dehydrogenase and alkaline phosphatase activities have been studied for various conditions of sporulation of Bacillus megaterium KM (carbon, nitrogen, phosphate starvation). Glucose dehydrogenase appears in all conditions of sporulation, even with excess of glucose or gluconate. Alkaline phosphatase, usually dereprimed in phosphate starvation, does not increase during sporulation of Bacillus megaterium when phosphate is present.

Alcohol Oxidoreductases↗
PubMed1975

Phosphate uptake in Chlorella pyrenoidosa : II. Effect of pH and of SH reagents.

The sensitivity of the phosphate transport system to pCMPS after phosphate starvation is dependent on protein synthesis. This fact is related to the development of transport activity at alkaline pH. In non-starved cells, the presence of only one peak of maximal activity for phosphate uptake at neutral pH (at low and high concentration) has been observed. However, in phosphate starved cells, two peaks of maximal activity (at low phosphate concentration) at neutral and alkaline pH are present. In starved cells, pCMPS inhibits more intensely the phosphate transport activity at alkaline pH than at neutral pH. By contrast, NEM inhibits the phosphate transport more strongly at neutral than at alkaline pH. Phosphate uptake at neutral and alkaline pH are sensitive to osmotic shock, but phosphate uptake at alkaline pH is decreased more than at neutral pH. The results could be interpreted either by assuming that the membrane surroundings change during phosphate starvation or that two transport systems are present in starved cells whereas only one transport system exists in non-starved cells.

4-Chloromercuribenzenesulfonate↗
PubMed1978

[Interrelationship between metabolic and genetic regulation of alkaline and acid phosphatases in E. coli cells].

The effect of exogenous orthophosphate and mutations in regulatory genes of alkaline phosphatase on the level of nonspecific acid phosphatase was studied. The level of this enzyme as well as the level of alkaline phosphatase were shown to be regulated by exogenous orthophosphate being derepressed under phosphate starvation. The derepression of acid phosphatase is accompanied by more rapid secretion of enzyme from membranes to soluble fraction. Mutations in all the four regulatory genes decrease the level of enzyme in cells. Genes phoR and phoS, participating in regulation of alkaline phosphatase, are required for the derepression of acid phosphatase under the conditions of phosphate starvation.

Acid Phosphatase↗
PubMed1975

Genetic control of phosphate-metabolizing enzymes in Neurospora crassa: relationships among regulatory mutations.

In Neurospora crassa, the phosphate-metabolizing enzymes are made during phosphate starvation, but not under phosphate sufficiency. The synthesis of these enzymes is controlled by three regulatory genes: pcon-nuc-2, preg and nuc-1, pcon-nuc-2 and preg are closely linked. A model of the hierarchical relationships among these regulatory genes is presented. Studies of double mutants and revertants confirm several predictions of the model. It has been found that nuc-2 (null) and pcon-c (constitutive) mutations reside in the same cistron. preg-c (constitutive) mutations are epistatic to nuc-2 mutations. nuc-1 (null) mutations are epistatic to all others.

Alkaline Phosphatase↗
PubMed1979

Mathematical model of cell growth and phosphatase biosynthesis in Saccharomyces carlsbergensis under phosphate limitation.

The rate kinetics of growth and acid phosphate formation in the batch culture of Saccharomyces carlsbergensis LAM 1068 was studied under varying degrees of phosphate limitation. The mathematical model that was developed is concerned with the time lag for exponential growth, the biphasic growth on a substrate (glucose) and its product (ethanol), sustained growth on conservative phosphate, and the derepression of acid phosphatase. The numerical calculations using appropriate parametric constants successfully described the variation in the cell mass, glucose, ethanol, and inorganic phosphate concentrations, and the enzyme activity of acid phosphatase during aerobic growth of S. carlsbergensis under five different conditions of phosphate starvation. A simulation study revealed that the optimum initial phosphate concentration in the medium giving a high productivity of acid phosphatase was 2.0 mg phosphorus/g glucose liter.

Acid Phosphatase↗
PubMed1976

Studies on the control of development. Correlation of initiucleotides in Bacillus subtilis.

Unusual highly phosphorylated nucleotides are found in sporulating cells of Bacillus subtilis. Adenosine 3'(2')-diphosphate 5'-diphosphate, ppApp (highly phosphorylated nucleotide I), and adenosine 3(2')-dephosphate 5'-triphosphate, pppApp (highllls are starved for carbon and nitrogen sources. These nucleotides are correlated with sporulation because only ribosomes from sporulating but not vegetative cells are able to synthesize ppApp and pppApp in vitro. Two other nucleotides, adenosine 3'(2')-triphosphate 5'-triphosphate, pppAppp (highly phosphorylated nucleotide IV), and a nucleotide with a tentative structure of ppZpUp (highly phosphorylated nucleotide III), where Z is an undetermined sugar, also seem to be involved in regulation of sporulation, especially initiation of sporulation. Sporulation can be initiated even in the presence of amino acids, salts, vitamins etc. in logarithmically growing or stationary-phase cells when carbon sources, i.g. glucose, are used up or artifically removed from the medium. A drastic increase in spore titer is observed 4--5 h later. Also, carbon starvation causes accumulation of the highly phosphorylated nucleotides pppAppp and ppZpUp. On the other hand, sporulation is prevented under the same conditions when excess glucose is maintained in the medium. Correlated with this inhibition of sporulation is the inhibition of formation of highly phosphorylated nucleotides, pppAppp and ppZpUp. Since synthesis of these nucleotides is closely related to sporulation, we anticipate that these substances can cause initiation of development in B. subtilis. Further evidence for our hypothesis on initiation of sporulation by highly phosphorylated nucleotides is that phosphate starvation also causes sporulation with prior accumulation of pppAppp and ppZpUp. Apparently, as long as phosphate is present to synthesize phosphorylated metabolites of glucose, formation of highly phosphorylated nucleotides is repressed. Derepression occurs when either lack of glucose or phosphate or both prevents synthesis of phosphorylated metabolites of glucose allowing synthesis of highly phosphorylated nucleotides. These nucleotides, representing the signal 'lack of glucose or phosphate', then somehow cause changes in gene activity, initiating the complex process of sporulation. Whether or not pppAppp alone or together wtih ppZpUp or even further substances (nucleotides, proteins etc.) is necessary for the above described processes will be answered with the help of suitable mutants lacking the ability to synthesize either one or both regulatory nucleotides. Guanosine 3'(2')-diphosphate 5'-diphosphate, ppGpp, and guanosine 3'(2')-diphosphate 5'-triphosphate, pppGpp, are not involved in regulation of devlopment as is shown by using a normally sporulating mutant of B. subtilis, unable to synthesize these nucleotides.

Amino Acids↗
PubMed2026

Plant genetic and root-associated microbial diversity modulate Lactuca sativa responsiveness to a soil inoculum under phosphate deficiency.

Microbial-based approaches offer a promising strategy to decrease the use of chemical fertilizers in agriculture. Among them, arbuscular mycorrhizal fungi (AMF), which extend root surface area and enhance phosphate uptake, and phosphate-solubilizing bacteria (PSB) are particularly relevant. However, their effectiveness depends strongly on plant genetic diversity. To identify genetic markers underlying plant responses to beneficial soil microbes, we studied a panel of 128 fully sequenced Lactuca sativa varieties under controlled phosphate-starvation conditions and treated with AMF and PSB. Lettuce genetic variation showed a strong effect on physiological and morphological responses to microbial inoculation. Genome-wide association studies identified specific genomic regions associated with changes in leaf phosphate content and shoot biomass following treatment. Beyond genetic factors, we observed shifts in fungal β-diversity and increased bacterial α-diversity associated with phenotypic variation. We also identified 44 amplicon sequence variants associated with agriculturally relevant traits. Among these, six bacterial strains were experimentally validated through in vitro and pot experiments for their effects on leaf phosphate concentration and shoot biomass. Overall, we highlighted key genetic, microbial, and physiological mechanisms that may enhance microbial treatments for improved plant phosphate management in lettuce.

16S and ITS metabarcoding↗
PubMed1979

Mechanisms controlling the two phosphate uptake systems in Neurospora crassa.

The development of the high-affinity and low-affinity phosphate uptake systems of Neurospora crassa has been followed during germination and early growth. The ratio between the activities of the two systems became constant by the time exponential growth began, although the value of this ratio depended on the external phosphate concentration. The regulatory mechanisms controlling the systems were investigated by following the changes that resulted when exponentially growing germlings adapted to one phosphate concentration were shifted to a different concentration. The high-affinity system was derepressed under conditions of phosphate starvation, and inhibited irreversibly by feedback inhibition under conditions of over-supply. The low-affinity system was also derepressed and subject to feedback inhibition under comparable conditions, but, in contrast, inhibition of this system was reversible. A detailed description is given of the interplay between the systems during adaptation to changes in phosphate supply. Changes that occurred in the internal phosphate pool support the hypothesis that this metabolite is responsible for controlling the activities of the systems, either by triggering derepression of new uptake system synthesis or by inhibiting the existing system by feedback.

Biological Transport, Active↗
PubMed1978

Extracellular manganese-stimulated deoxyribonuclease as a marker event in sporulation of Bacillus subtilis.

A considerable amount of Mn2+-stimulated DNAase (deoxyribonuclease) activity is released by Bacillus subtilis 168 during sporulation in a glucose-deficient medium; much smaller amounts are released during starvation for phosphate or nitrogen. Protein synthesis is required. Two forms of evidence are presented that production of the DNAase is associated with events late in stage II of sporulation. 19 Thymidine starvation, which inhibits the biochemical events associated with sporulation, also inhibits release of the DNAase. 2. Several asporogenous mutants blocked at stage II or earlier and unable to produce alkaline phosphatase (a stage-II event) do not produce the enzyme. Mutants blocked towards the end of stage II or later produce both enzymes. During sporulation of the wild-type strain, the DNAase appears about 1 h after alkaline phosphatase. The results suggest that production of the DNAase is controlled by a still-undiscovered stage-II genetic locus.

Bacillus subtilis↗
PubMed1975

Regulation of carbohydrate metabolism in lymphoid tissue. Quantitative aspects of [U-14C]glucose oxidation by rat spleen slices.

When washed spleen slices from fed rats are incubated with 3 mm-[U-14C]glucose, the rate of glucose utilization (46.2 mumol/h per g dry wt.) is sufficient to account, theoretically, for 80% of the O2 consumption. Measurement of net lactate production, however, and the fate of the radioactive carbon, indicates that the contribution of glucose to the respiratory fuel of the tissue is only 25-30% whereas 60-70% of the glucose utilized is converted into lactate. At saturating glucose concentrations (above 5 mm) its contribution to the respiratory fuel of the slice is increased to a maximum value of 34-39%. Only 2% of the glucose utilized is metabolized via the oxidative steps of the pentose phosphate pathway. Starvation for 72 h marginally increases both the rate of glucose utilization (by 21%) and its net contribution to the respiratory fuel (by 29%). Insulin, glucagon, adrenaline and adenosine 3':5'-cyclic monophosphate have no significant effect on either the rate of glucose utilization or on the pattern of radioactive isotope distribution. The uptake of glucose is increased by only 20%, whereas the production of lactate doubles when slices are incubated under anaerobic conditions. In assessing the suitability of spleen slices for metabolic studies, the only serious major perturbation, compared with the freeze-clamped organ, is an elevated mitochondrial [NAD+]/[NADH] ratio (connected with increased endogenous NH3 production) that is partially restored to normal values on incubation with glucose. Equal proportions of erythrocytes and leucocytes are found in the washed spleen slice. Metabolic contributions of the constituent cell populations in the washed slice are calculated and it is concluded that lymphocytes account for the major part of the glycolytic metabolism (80-90%), whereas the contribution of erythrocytes is insignificant.

Adenosine Diphosphate↗
PubMed1979

Evidence for new factors in the coordinate regulation of energy metabolism in Escherichia coli. Effects of hypoxia, chloramphenicol succinate, and 2,4-dinitrophenol on glucose utilization, glycogen synthesis, adenylate energy charge, and hexose phosphates during the first two periods of nitrogen starvation.

We studied the effects of decreased aeration, chloramphenicol succinate, and 2,4-dinitrophenol on the cellular rates of glycogen synthesis and glucose utilization and on the cellular concentrations of adenine nucleotides, glucose 6-phosphate, fructose 1,6-diphosphate, and phosphoenolpyruvate during the first two periods of nitrogen starvation of Escherichia coli W4597(K). A quantitative relationship between the changes in the rates and the accompanying changes in the hexose phosphates is demonstrated. However, the relationship for glycogen synthesis is different in different sets of metabolic conditions. We suggest that this difference reflects a change in the steady state level of a previously unknown effector of ADP-glucose synthetase (glucose 1-phosphate adenylyltransferase, EC 2.7.7.27) the rate-limiting enzyme of bacterial glycogen synthesis. We show that the properties of the hypothetical in vivo effector are consistent with the inhibitory effects of ppGpp (guanosine 3'-diphosphate 5'-diphosphate) and pppGpp (guanosine 3'-diphosphate 5'-triphosphate) on this enzyme in vitro. In addition, tetracycline, an inhibitor of the synthesis of these nucleotides, apparently prevents the change in the quantitative relationship. The relationship between glucose utilization and the hexose phosphates is altered at the transition to Period II of nitrogen starvation. We propose that this change reflects the alteration of the cellular steady state level of an unknown effector of the glucose phosphotransferase system. In contrast to the ATP-hexose phosphate system of shared regulatory effects, the specific effects of the unknown effectors allow the rates of glucose utilization and glycogen synthesis to be altered independently of each other and independently of changes in the rate of glycolysis. This independence allows a greater latitude of response for the individual pathways in more severe metabolic stress or in accommodating the metabolic changes necessary for long term survival.

Adenine Nucleotides↗