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91.
Engineering increased vitamin C levels in plants by overexpression of a D-galacturonic acid reductase 总被引:18,自引:0,他引:18
Agius F González-Lamothe R Caballero JL Muñoz-Blanco J Botella MA Valpuesta V 《Nature biotechnology》2003,21(2):177-181
L-Ascorbic acid (vitamin C) in fruits and vegetables is an essential component of human nutrition. Surprisingly, only limited information is available about the pathway(s) leading to its biosynthesis in plants. Here, we report the isolation and characterization of GalUR, a gene from strawberry that encodes an NADPH-dependent D-galacturonate reductase. We provide evidence that the biosynthesis of L-ascorbic acid in strawberry fruit occurs through D-galacturonic acid, a principal component of cell wall pectins. Expression of GalUR correlated with changing ascorbic acid content in strawberry fruit during ripening and with variations in ascorbic acid content in fruit of different species of the genus Fragaria. Reduced pectin solubilization in cell walls of transgenic strawberry fruit with decreased expression of an endogenous pectate lyase gene resulted in lower ascorbic acid content. Overexpression of GalUR in Arabidopsis thaliana enhanced vitamin C content two- to threefold, demonstrating the feasibility of engineering increased vitamin C levels in plants using this gene. 相似文献
92.
A number of filamentous fungi are known to produce high levels of saline-soluble and low-molecular-mass lectins. The function of these proteins are not clear but it has been proposed that they are involved in storage of nutrients, development, recognition of other organisms, and defense reactions. A gene encoding such a lectin (AOL) was deleted in the nematode-trapping fungus Arthrobotrys oligospora by homologous recombination. The deletion mutants did not express any hemagglutinating activity or protein cross-reacting with AOL antibodies. There were no significant differences between the DeltaAOL and wild-type strains in spore (conidia) germination, saprophytic growth, and pathogenicity. Furthermore, there was no significant difference in the growth and reproduction of collembolan feeding on the various strains of A. oligospora. Thus either the previous proposed functions of AOL are not correct, or the fungus can compensate for the absence of the lectin by expressing other proteins with similar function(s) as AOL. 相似文献
93.
de Carvalho MJ Amorim Jesuino RS Daher BS Silva-Pereira I de Freitas SM Soares CM Felipe MS 《Fungal genetics and biology : FG & B》2003,39(3):204-210
Calmodulin (CaM) modulates intracellular calcium signalling and acts on several metabolic pathways and gene expression regulation in many eukaryotic organisms including human fungal pathogens, such as Candida albicans and Histoplasma capsulatum. The temperature-dependent dimorphic fungus Paracoccidioides brasiliensis is the aetiological agent of paracoccidioidomycosis (PCM). The mycelium (M) to yeast (Y) transition has been shown to be essential for establishment of the infection, although the precise molecular mechanisms of dimorphism in P. brasiliensis are still unknown. In this work, several inhibitory drugs of the Ca(2+)/calmodulin signalling pathway were tested to verify the role of this pathway in the cellular differentiation process of P. brasiliensis. EGTA and the drugs calmidazolium (R24571), trifluoperazine (TFP), and W7 were able to inhibit the M-Y transition. We have cloned and characterized the calmodulin gene from P. brasiliensis, which comprises 924 nucleotides and five introns that are in a conserved position among calmodulin genes. 相似文献
94.
Ros MA Dahn RD Fernandez-Teran M Rashka K Caruccio NC Hasso SM Bitgood JJ Lancman JJ Fallon JF 《Development (Cambridge, England)》2003,130(3):527-537
We have analyzed a new limb mutant in the chicken that we name oligozeugodactyly (ozd). The limbs of this mutant have a longitudinal postaxial defect, lacking the posterior element in the zeugopod (ulna/fibula) and all digits except digit 1 in the leg. Classical recombination experiments show that the limb mesoderm is the defective tissue layer in ozd limb buds. Molecular analysis revealed that the ozd limbs develop in the absence of Shh expression, while all other organs express Shh and develop normally. Neither Ptc1 nor Gli1 are detectable in mutant limb buds. However, Bmp2 and dHAND are expressed in the posterior wing and leg bud mesoderm, although at lower levels than in normal embryos. Activation of Hoxd11-13 occurs normally in ozd limbs but progressively declines with time. Phase III of expression is more affected than phase II, and expression is more severely affected in the more 5' genes. Interestingly, re-expression of Hoxd13 occurs at late stages in the distal mesoderm of ozd leg buds, correlating with formation of digit 1. Fgf8 and Fgf4 expression are initiated normally in the mutant AER but their expression is progressively downregulated in the anterior AER. Recombinant Shh protein or ZPA grafts restore normal pattern to ozd limbs; however, retinoic acid fails to induce Shh in ozd limb mesoderm. We conclude that Shh function is required for limb development distal to the elbow/knee joints, similar to the Shh(-/-) mouse. Accordingly we classify the limb skeletal elements as Shh dependent or independent, with the ulna/fibula and digits other than digit 1 in the leg being Shh dependent. Finally we propose that the ozd mutation is most likely a defect in a regulatory element that controls limb-specific expression of Shh. 相似文献
95.
Transcriptome analysis of root transporters reveals participation of multiple gene families in the response to cation stress 总被引:31,自引:4,他引:27
96.
Cabiscol E Piulats E Echave P Herrero E Ros J 《The Journal of biological chemistry》2000,275(35):27393-27398
We have analyzed the proteins that are oxidatively damaged when Saccharomyces cerevisiae cells are exposed to stressing conditions. Carbonyl groups generated by hydrogen peroxide or menadione on proteins of aerobically respiring cells were detected by Western blotting, purified, and identified. Mitochondrial proteins such as E2 subunits of both pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, aconitase, heat-shock protein 60, and the cytosolic fatty acid synthase (alpha subunit) and glyceraldehyde-3-phosphate dehydrogenase were the major targets. In addition we also report the in vivo modification of lipoamide present in the above-mentioned E2 subunits under the stressing conditions tested and that this also occurs with the homologous enzymes present in Escherichia coli cells that were used for comparative analysis. Under fermentative conditions, the main protein targets in S. cerevisiae cells treated with hydrogen peroxide or menadione were pyruvate decarboxylase, enolase, fatty acid synthase, and glyceraldehyde-3-phosphate dehydrogenase. Under the stress conditions tested, fermenting cells exhibit a lower viability than aerobically respiring cells and, consistently, increased peroxide generation as well as higher content of protein carbonyls and lipid peroxides. Our results strongly suggest that the oxidative stress in prokaryotic and eukaryotic cells shares common features. 相似文献
97.
Cavelaars AE Kunst AE Geurts JJ Crialesi R Grötvedt L Helmert U Lahelma E Lundberg O Matheson J Mielck A Rasmussen NK Regidor E do Rosário-Giraldes M Spuhler T Mackenbach JP 《BMJ (Clinical research ed.)》2000,320(7242):1102-1107
ObjectiveTo investigate international variations in smoking associated with educational level.DesignInternational comparison of national health, or similar, surveys.SubjectsMen and women aged 20 to 44 years and 45 to 74 years.Setting12 European countries, around 1990.ResultsIn the 45 to 74 year age group, higher rates of current and ever smoking among lower educated subjects were found in some countries only. Among women this was found in Great Britain, Norway, and Sweden, whereas an opposite pattern, with higher educated women smoking more, was found in southern Europe. Among men a similar north-south pattern was found but it was less noticeable than among women. In the 20 to 44 year age group, educational differences in smoking were generally greater than in the older age group, and smoking rates were higher among lower educated people in most countries. Among younger women, a similar north-south pattern was found as among older women. Among younger men, large educational differences in smoking were found for northern European as well as for southern European countries, except for Portugal.ConclusionsThese international variations in social gradients in smoking, which are likely to be related to differences between countries in their stage of the smoking epidemic, may have contributed to the socioeconomic differences in mortality from ischaemic heart disease being greater in northern European countries. The observed age patterns suggest that socioeconomic differences in diseases related to smoking will increase in the coming decades in many European countries. 相似文献
98.
99.
Altered Na+ and Li+ Homeostasis in Saccharomyces cerevisiae Cells Expressing the Bacterial Cation Antiporter NhaA 下载免费PDF全文
Roc Ros Consuelo Montesinos Abraham Rimon Etana Padan Ramn Serrano 《Journal of bacteriology》1998,180(12):3131-3136
The bacterial Na+(Li+)/H+ antiporter NhaA has been expressed in the yeast Saccharomyces cerevisiae. NhaA was present in both the plasma membrane and internal membranes, and it conferred lithium but not sodium tolerance. In cells containing the yeast Ena1-4 (Na+, Li+) extrusion ATPase, the extra lithium tolerance conferred by NhaA was dependent on a functional vacuolar H+ ATPase and correlated with an increase of lithium in an intracellular pool which exhibited slow efflux of cations. In yeast mutants without (Na+, Li+) ATPase, lithium tolerance conferred by NhaA was not dependent on a functional vacuolar H+ ATPase and correlated with a decrease of intracellular lithium. NhaA was able to confer sodium tolerance and to decrease intracellular sodium accumulation in a double mutant devoid of both plasma membrane (Na+, Li+) ATPase and vacuolar H+ ATPase. These results indicate that the bacterial antiporter NhaA expressed in yeast is functional at both the plasma membrane and the vacuolar membrane. The phenotypes conferred by its expression depend on the functionality of plasma membrane (Na+, Li+) ATPase and vacuolar H+ ATPase. 相似文献
100.
Silvana A. Rosú Omar J. Rimoldi Eduardo D. Prieto Lucrecia M. Curto José M. Delfino Nahuel A. Ramella M. Alejandra Tricerri 《PloS one》2015,10(5)
A number of naturally occurring mutations of human apolipoprotein A-I (apoA-I) have been associated with hereditary amyloidoses. The molecular mechanisms involved in amyloid-associated pathology remain largely unknown. Here we examined the effects of the Arg173Pro point mutation in apoA-I on the structure, stability, and aggregation propensity, as well as on the ability to bind to putative ligands. Our results indicate that the mutation induces a drastic loss of stability, and a lower efficiency to bind to phospholipid vesicles at physiological pH, which could determine the observed higher tendency to aggregate as pro-amyloidogenic complexes. Incubation under acidic conditions does not seem to induce significant desestabilization or aggregation tendency, neither does it contribute to the binding of the mutant to sodium dodecyl sulfate. While the binding to this detergent is higher for the mutant as compared to wt apoA-I, the interaction of the Arg173Pro variant with heparin depends on pH, being lower at pH 5.0 and higher than wt under physiological pH conditions. We suggest that binding to ligands as heparin or other glycosaminoglycans could be key events tuning the fine details of the interaction of apoA-I variants with the micro-environment, and probably eliciting the toxicity of these variants in hereditary amyloidoses. 相似文献