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Zhou W, Qi Z, Chen J, Tan Z, Wang H, Wang C, Yi Z. Rooting ability of rice seedlings increases with higher soluble sugar content from exposure to light. PLoS One 2020; 15:e0241060. [PMID: 33079962 PMCID: PMC7575106 DOI: 10.1371/journal.pone.0241060] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 10/07/2020] [Indexed: 11/29/2022] Open
Abstract
Rooting ability of rice seedling for mechanical transplanting has a large impact on grain yield. This study explored the relationship between endogenous soluble sugar content and rooting ability of rice seedlings. We placed 15-day-old rice seedlings in controlled environment cabinets with stable light and sampled after 0, 3, 6, 9, 12, and 24 hours of light to measure their soluble sugar content, nitrate content, starch content, soluble protein content and rooting ability. The soluble sugar content of the rice seedlings before rooting increased rapidly from 65.1 mg g-1 to 126.3 mg g-1 in the first 9 hours of light and then tended to stabilize; however, few significant changes in the other physiological indices were detected. With the light exposure time increasing from 3 hours to 12 hours, the rooting ability measured with fresh weight, dry weight, total length, and number of new roots increased by 91.7%, 120.0%, 60.6% and 30.3%, respectively. Rooting ability was related more closely to soluble sugar content than to nitrate-nitrogen content of rice seedlings before rooting and their correlation coefficients were 0.8582–0.8684 and 0.7045–0.7882, respectively. The stepwise regression analysis revealed that the soluble sugar content before rooting explained 73.6%–75.4% of the variance, and the nitrate-nitrogen content explained an additional 7.3%–14.2% of the variance in rooting ability, indicating that compared with nitrate-nitrogen content, soluble sugar content of rice seedlings before rooting was more dominant in affecting rooting ability. This study provides direct evidence of the relationship between the rooting ability and endogenous soluble sugar content of rice seedlings.
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Affiliation(s)
- Wanlai Zhou
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, Sichuan, China
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, Hunan, China
- College of Agronomy, Hunan Agricultural University, Changsha, Hunan, China
| | - Zhiyong Qi
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, Sichuan, China
| | - Jing Chen
- College of Agronomy, Hunan Agricultural University, Changsha, Hunan, China
| | - Zhijian Tan
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, Hunan, China
| | - Hongying Wang
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, Hunan, China
| | - Chaoyun Wang
- Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, Hunan, China
- * E-mail: (CW); (ZY)
| | - Zhenxie Yi
- College of Agronomy, Hunan Agricultural University, Changsha, Hunan, China
- * E-mail: (CW); (ZY)
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Abstract
The morpheein model of allosteric regulation can be applied as a novel approach to the discovery of small molecule allosteric modulators of protein function. Morpheeins are homo-oligomeric proteins where, under physiological conditions, the oligomer can dissociate, the dissociated units can change conformation, and the altered conformational state can reassociate to a structurally and functionally distinct oligomer. This phenomenon serves as a basis for allostery, as a basis for conformational diseases, as a basis for drug discovery, and may be applicable to personalized medicine such as in the prediction of drug side effects. Each of these relationships has been established for the prototype morpheein, porphobilinogen synthase, where the conformational disease is a porphyria and the drug application is in antimicrobial discovery. These data are presented along with a discussion of other drug targets for which the morpheein model of allostery may apply. Such targets include HIV integrase, TNFα, β-tryptase, and p53.
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Affiliation(s)
- Eileen K Jaffe
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Ave, Philadelphia, PA 19111 U.S.A
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Lawrence SH, Ramirez UD, Tang L, Fazliyez F, Kundrat L, Markham GD, Jaffe EK. Shape shifting leads to small-molecule allosteric drug discovery. ACTA ACUST UNITED AC 2008; 15:586-96. [PMID: 18559269 DOI: 10.1016/j.chembiol.2008.04.012] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2007] [Revised: 04/17/2008] [Accepted: 04/21/2008] [Indexed: 11/19/2022]
Abstract
Enzymes that regulate their activity by modulating an equilibrium of alternate, nonadditive, functionally distinct oligomeric assemblies (morpheeins) constitute a recently described mode of allostery. The oligomeric equilibrium for porphobilinogen synthase (PBGS) consists of high-activity octamers, low-activity hexamers, and two dimer conformations. A phylogenetically diverse allosteric site specific to hexamers is proposed as an inhibitor binding site. Inhibitor binding is predicted to draw the oligomeric equilibrium toward the low-activity hexamer. In silico docking enriched a selection from a small-molecule library for compounds predicted to bind to this allosteric site. In vitro testing of selected compounds identified one compound whose inhibition mechanism is species-specific conversion of PBGS octamers to hexamers. We propose that this strategy for inhibitor discovery can be applied to other proteins that use the morpheein model for allosteric regulation.
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Breinig S, Kervinen J, Stith L, Wasson AS, Fairman R, Wlodawer A, Zdanov A, Jaffe EK. Control of tetrapyrrole biosynthesis by alternate quaternary forms of porphobilinogen synthase. Nat Struct Mol Biol 2003; 10:757-63. [PMID: 12897770 DOI: 10.1038/nsb963] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2003] [Accepted: 07/15/2003] [Indexed: 11/09/2022]
Abstract
Porphobilinogen synthase (PBGS) catalyzes the first common step in the biosynthesis of tetrapyrroles (such as heme and chlorophyll). Although the predominant oligomeric form of this enzyme, as inferred from many crystal structures, is that of a homo-octamer, a rare human PBGS allele, F12L, reveals the presence of a hexameric form. Rearrangement of an N-terminal arm is responsible for this oligomeric switch, which results in profound changes in kinetic behavior. The structural transition between octamer and hexamer must proceed through an unparalleled equilibrium containing two different dimer structures. The allosteric magnesium, present in most PBGS, has a binding site in the octamer but not in the hexamer. The unprecedented structural rearrangement reported here relates to the allosteric regulation of PBGS and suggests that alternative PBGS oligomers may function in a magnesium-dependent regulation of tetrapyrrole biosynthesis in plants and some bacteria.
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Affiliation(s)
- Sabine Breinig
- Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111-2497, USA
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Jaffe EK. An unusual phylogenetic variation in the metal ion binding sites of porphobilinogen synthase. CHEMISTRY & BIOLOGY 2003; 10:25-34. [PMID: 12573695 DOI: 10.1016/s1074-5521(02)00296-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Porphobilinogen synthase (PBGS), which catalyzes the first common step in tetrapyrrole biosynthesis, contains a unique phylogenetic variation in the use of metal ions. Using sequence, structure, and enzymological information, this work codifies the phylogenetic segregation of metal utilization in PBGS from archaea, bacteria, and eucarya. All PBGS contain an active site metal binding sequence, determined herein to be either DXCXCX(Y/F)X(3)G(H/Q)CG or DXALDX(Y/F)X(3)G(H/Q)DG. The former dictates a requirement for zinc. Most PBGS that do not require zinc require magnesium and/or potassium instead. Most PBGS are also found to contain the binding determinants for an allosteric magnesium that resides outside the active site. The phylogenetic distribution of PBGS metal ion utilization suggests that the primordial PBGS required zinc and supports a hypothesis that the loss of the zinc site was concurrent with the advent of oxygenic photosynthesis.
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Affiliation(s)
- Eileen K Jaffe
- Institute for Cancer Research, Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, PA 19111, USA.
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Heldt HW, Chon CJ, Lorimer GH. Phosphate requirement for the light activation of ribulose- 1,5-biphosphate carboxylase in intact spinach chloroplasts. FEBS Lett 2001. [DOI: 10.1016/0014-5793(78)80761-3] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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7
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Gardemann A, Stitt M, Heldt HW. Regulation of spinach ribulose 5-phosphate kinase by 3-phosphoglycerate. FEBS Lett 2001. [DOI: 10.1016/0014-5793(82)80352-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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8
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Leegood RC, Furbank RT. Stimulation of photosynthesis by 2% oxygen at low temperatures is restored by phosphate. PLANTA 1986; 168:84-93. [PMID: 24233739 DOI: 10.1007/bf00407013] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/1985] [Accepted: 12/03/1985] [Indexed: 06/02/2023]
Abstract
The effect of phosphate feeding on the influence of low (2%) oxygen on photosynthetic carbon assimilation has been investigated in leaf discs of spinach (Spinacia oleracea L.) at 12°C. The following observations were made. First, after the transition from 20% O2 to 2% O2, the rate of CO2 uptake was inhibited at CO2 concentrations between about 250 and about 800 μl CO2·l(-1). Second, phosphate feeding stimulated the rate of CO2 uptake in 20% O2 at higher concentrations of CO2 (500-900 μl·l(-1)). Third, phosphate feeding stimulated the rate of CO2 uptake in 2% O2 at all but the highest (900 μl·l(-1)) and lowest 74 (μl·l(-1)) concentrations of CO2 employed. Phosphate thereby restored the stimulation of photosynthesis by 2% O2 and it did so over a wide range of lower temperatures. Fourth, oscillatory behaviour, however generated, was dampened by phosphate feeding, even at very low concentrations of CO2. Contents of leaf metabolites were measured during the transition to 2% O2 in control and phosphate-fed leaf discs. During this period the ratio glycerate-3-phosphate/triose phosphate rose steeply, but fell again only in the phosphate-treated leaf discs. These data, taken together with measured ATP/ADP ratios, showed that assimilatory power, the ratio [ATP]·[NAD(P)H]/[ADP]·[Pi]·[NAD(P)], decreased when leaves were exposed to 2% O2, but that this decrease was minimised by previous feeding of phosphate. The mechanism of phosphate limitation is discussed in the light of the results.
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Affiliation(s)
- R C Leegood
- Research Institute for Photosynthesis, Department of Botany, University of Sheffield, S10 2TN, Sheffield, UK
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Nikolau BJ, Hawke JC. Purification and characterization of maize leaf acetyl-coenzyme A carboxylase. Arch Biochem Biophys 1984; 228:86-96. [PMID: 6141767 DOI: 10.1016/0003-9861(84)90049-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Maize leaf acetyl-CoA carboxylase was purified from whole tissue homogenates by precipitation with polyethylene glycol and ammonium sulfate, and gel filtration. Recoveries were approximately 5% with 100-fold increases in specific activity. The molecular weight of the native enzyme is estimated at 500,000 from the elution volume of a calibrated Ultrogel AcA 22 column. Electrophoresis in polyacrylamide gel containing 1% sodium dodecyl sulfate revealed a single subunit of Mr 60,000-61,000. Investigation of the kinetic properties of the purified enzyme indicates that Mg X ATP is the active substrate, with free ATP inhibiting and Mg2+ activating the enzyme. Km's for acetyl-CoA and HCO3- are about 0.1 and 2 mM, respectively. ADP inhibition is competitive with respect to ATP, but uncompetitive with respect to acetyl-CoA. The observed responses of purified acetyl-CoA carboxylase to changes in pH, and in concentrations of Mg2+, ATP, and ADP, and the reported changes in the chloroplastic concentrations of these effectors during light-dark transitions of chloroplasts are consistent with increased acetyl-CoA carboxylase activity upon illumination of chloroplasts.
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Kombrink E, Wöber G. Chloroplast phosphofructokinase in the green alga, Dunaliella marina: partial purification and kinetic and regulatory properties. Arch Biochem Biophys 1982; 213:602-19. [PMID: 6462110 DOI: 10.1016/0003-9861(82)90590-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Bacterial symbionts and low 13C/12C ratios in tissues of Pogonophora indicate unusual nutrition and metabolism. Nature 1981. [DOI: 10.1038/293616a0] [Citation(s) in RCA: 106] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Solomonson L, Spehar A. Stimulation of cyanide formation by ADP and its possible role in the regulation of nitrate reductase. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(17)30200-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Wolosiuk RA, Buchanan BB. Regulation of chloroplast phosphoribulokinase by the ferredoxin/thioredoxin system. Arch Biochem Biophys 1978; 189:97-101. [PMID: 213020 DOI: 10.1016/0003-9861(78)90119-4] [Citation(s) in RCA: 106] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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HATCH M. Regulation of Enzymes in C4 Photosynthesis* *Abbreviations used in the text: NADP-ME-type, NADP malic enzyme type; PCKtype, PEP carboxykinase type; NAD-ME-type, NAD malic enzyme type; PCR cycle, Photosynthetic Carbon Reduction Cycle; PEP, phosphoenolpyruvate. CURRENT TOPICS IN CELLULAR REGULATION 1978. [DOI: 10.1016/b978-0-12-152814-0.50005-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Abstract
It may be concluded that the conversion of PGA to DPGA plays a key role in induction and in the regulation of cycle activity. The high concentrations of PGA in actively photosynthesizing chloroplasts reflect this role and the control exerted by adenylate ratios. Thus the cycle can operate at its maximum rate only in the presence of high PGA and low ribulose 5-phosphate concentrations. Once induction is complete, the reductive pentose phosphate pathway will continue to function at its maximum rate if sink activity within the cytoplasm makes available sufficient Pi to support rapid export of triose phosphate. If triose phosphate tends to build up in the straoma, it will favor pentose monophosphate accumulation. A relative excess of ribulose 5-phosphate would, in turn, inhibit PGA reduction (and hence its own formation) by drawing too heavily on the available ATP.
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