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101.
The influence of CO2 enrichment, phosphorus deficiency and water stress on the growth, conductance and water use of Pinus radiata D. Don 总被引:10,自引:4,他引:6
JANN P. CONROY M. KÜPPERS B. KÜPPERS J. VIRGONA E. W. R. BARLOW 《Plant, cell & environment》1988,11(2):91-98
Abstract. Seedlings of Pinus radiata D. Don were grown in growth chambers for 22 weeks with two levels of phosphorus, under either well-watered or water-stressed conditions at CO2 concentrations of either 330 or 660mm3 dm?3. Plant growth, water use efficiency and conductance were measured and the relationship between these and needle photosynthetic capacity, water use efficiency and conductance was determined by gas exchange at week 22. Phosphorus deficiency decreased growth and foliar surface area at both CO2concentrations; however, it only reduced the maximum photosynthetic rates of the needles at 660 mm3 CO2 dm?3 (plants grown and measured at the same CO2 concentration). Water stress reduced growth and foliar surface area at both CO2 concentrations. Increases in needle photosynthetic rates appeared to be partly responsible for the increased growth at high CO2 where phosphorus was adequate. This effect was amplified by accompanying increases in needle production. Phosphorus deficiency inhibited these responses because it severely impaired needle photosynthetic function. The relative increase in growth in response to high CO2 was higher in the periodically water-stressed plants. This was not due to the maintenance of cell volume during drought. Plant water use efficiency was increased by CO2 enrichment due to an increase in dry weight rather than a decrease in shoot conductance and, therefore, transpirational water loss. Changes in needle conductance and water use efficiency in response to high CO2 were generally in the same direction as those at the whole plant level. If the atmospheric CO2 level reaches the predicted concentration of 660 mm3 dm?3 by the end of next Century, then the growth of P. radiata will only be increased in areas where phosphorus nutrition is adequate. Growth will be increased in drought-affected regions but total water use is unlikely to be reduced. 相似文献
102.
Killing of Escherichia coli cells modulated by components of the stability system ParD of plasmid R1
Alicia Bravo Sagrario Ortega Gertrudis de Torrontegui Ramón Díaz 《Molecular & general genetics : MGG》1988,215(1):146-151
Summary The proteins P10 and P12 have been shown to be gene products of a new stability system, ParD, of plasmid R1. It is now shown that an R1 miniplasmid, pAB112, carrying a trans-complementable amber mutation in the gene of the P10 protein, is lethal for the host in the absence of suppression. This lethal effect is suppressed in a supF background and also by deletions in pAB112 that affect the gene of the P12 protein. These data indicate that the P12 protein has a lethal effect on the host and that this effect is neutralized by the P10 protein. The possibility that the stabilization conferred by the ParD system could be due to a counterselection, mediated by P12, of cells that lose the plasmid at cell division, is discussed. 相似文献
103.
A. M. Cashmore M. S. Albury C. Hadfield P. A. Meacock 《Molecular & general genetics : MGG》1988,212(3):426-431
Summary The yeast 2 m circle encodes four major transcribed open reading frames, A, B, C and D. Products of ORF's A, B and C, together with the inverted repeats and the other cis-acting loci ORI and STB, have been shown to be involved in plasmid maintenance. However, the function of ORF D has remained unclear. We have therefore carried out studies on 2 m derivatives with both insertional and frameshift mutations in D. Our results indicate that there is a protein product encoded by ORF D, which is involved in plasmid maintenance. When the copy number of the C gene was reduced to one, by chromosomal integration, we observed striking differences in the efficiency of partitioning of D
+ and D
– plasmid derivatives. Absence of D function could be compensated by an increase in dosage of the C gene, indicating that the D product may act to regulate C expression. Since the C product has been implicated in copy number control as well as partitioning, our data suggest that the D product may also be involved in both of these processes. 相似文献
104.
A directed conformational search algorithm using the program CONGEN (ref. 3), which samples backbone conformers, is described. The search technique uses information from the partially built structures to direct the search process and is tested on the problem of generating a full set of backbone Cartesian coordinates given only alpha-carbon coordinates. The method has been tested on six proteins of known structure, varying in size and classification, and was able to generate the original backbone coordinates with RMSs ranging from 0.30-0.87A for the alpha-carbons and 0.5-0.99A RMSs for the backbone atoms. Cis peptide linkages were also correctly identified. The procedure was also applied to two proteins available with only alpha-carbon coordinates in the Brookhaven Protein Data Bank; thioredoxin (SRX) and triacylglycerol acylhydrolase (TGL). All-atom models are proposed for the backbone of both these proteins. In addition, the technique was applied to randomized coordinates of flavodoxin to assess the effects of irregularities in the data on the final RMS. This study represents the first time a deterministic conformational search was used on such a large scale. 相似文献
105.
Summary In bacteria 5-aminolevulinate, the universal precursor in the biosynthesis of the porphyrin nucleus of hemes, chlorophylls and bilins is synthesised by two different pathways: in non-sulphur purple bacteria (Rhodobacter) or Rhizobium 5-aminolevulinate synthase condenses glycine and succinyl-CoA into 5-aminolevulinate as is the case in mammalian cells and yeast. In cyanobacteria, green and purple sulphur bacteria, as in chloroplasts of higher plants and algae a three step pathway converts glutamate into 5-aminolevulinate. The last step is the conversion of glutamate 1-semialdehyde into 5-aminolevulinate. Using a cDNA clone encoding glutamate 1-semialdehyde aminotransferase from barley, genes for this enzyme were cloned from Synechococcus PCC6301 and Escherichia coli and sequenced. The popC gene of E. coli, previously considered to encode 5-aminolevulinate synthase, appears to be a structural gene for glutamate 1-semialdehyde aminotransferase. Domains with identical amino acid sequences comprise 48% of the primary structure of the barley, cyanobacterial and putative E. coli glutamate 1-semialdehyde aminotransferases. The cyanobacterial and barley enzymes share 72% identical residues. The peptide containing a likely pyridoxamine phosphate binding lysine is conserved in all three protein sequences. 相似文献
106.
Immunological identification of yeast SCO1 protein as a component of the inner mitochondrial membrane 总被引:4,自引:0,他引:4
Summary The SCO1 gene of Saccharomyces cerevisiae encodes a 30 kDa protein which is specifically required for a post-translational step in the accumulation of subunits 1 and 2 of cytochrome c oxidase (COXI and COXII). Antibodies directed against a -Gal::SCO1 fusion protein detect SCO1 in the mitochondrial fraction of yeast cells. The SCO1 protein is an integral membrane protein as shown by its resistance to alkaline extraction and by its solubilization properties upon treatment with detergents. Based on the results obtained by isopycnic sucrose gradient centrifugation and by digitonin treatment of mitochondria, SCO1 is a component of the inner mitochondrial membrane. Membrane localization is mediated by a stretch of 17 hydrophobic amino acids in the amino-terminal region of the protein. A truncated SCO1 derivative lacking this segment, is no longer bound to the membrane and simultaneously loses its biological function. The observation that membrane localization of SCO1 is affected in mitochondria of a rho
0 strain, hints at the possible involvement of mitochondrially coded components in ensuring proper membrane insertion. 相似文献
107.
108.
Viqar Uddin Ahmad Mohammad Ghani Shah Faryal Vali Mohammad Nargis Ismail Mushtaq Noorwala 《Phytochemistry》1991,30(12)
A new flavone glucoside macrophylloside has been isolated from the whole plant of Primula macrophylla and its structure was determined by spectroscopic methods as 2′-hydroxy-7-O-β-
-glucopyranosyloxyflavone. Sitosterol glucoside was also isolated for the first time from this plant. 相似文献
109.
Cecilia Zazueta José A. Holguín Jorge Ramírez 《Journal of bioenergetics and biomembranes》1991,23(6):889-902
We describe a calcium transport that is sensitive to ruthenium red in liposomes reconstituted with mitochondrial extracts. This system is able to build an internally negative membrane potential, which allows the electrogenic influx of Ca2+ and Sr2+. Proteins with molecular weights higher than 35 kDa were incorporated to the vesicles, and enhanced the accumulation of the cation in an energy-dependent fashion. 相似文献
110.
The interaction between interleukin IL-1α and PGE2 on P388D2 on cells has been investigated. Preincubation of murine macrophage-like cells, P388D1, with IL-1α (0–73 pM) reduced the binding of PGE2 to these cells in a concentration-dependent manner. Scatchard analysis showed that IL-1α decreased the PGE2 binding by lowering both the high and low affinity receptor binding capacities (from 0.31 ± 0.02 to 0.12 ± 0.01 fmol/106 cells for the high affinity receptor binding sites and from 2.41 ± 0.12 to 1.51 ± 0.21 fmol/106 cells for the low affinity receptor binding sites). However, the dissociation constants of the receptor of the IL-1α-treated cells remained unchanged. Inhibition of PGE2 binding IL-1α did not involve changes in either protein phosphorylation or intracellular cyclic AMP levels. Our data clearly show that IL-1α inhibits the binding of PGE2 to monocytes/macrophages and may thereby counter the immunosuppressive actions of PGE2. 相似文献