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911.
912.
随着水体富营养化的加剧,有害藻类水华和赤潮的爆发日趋频繁,导致水质的恶化,水体资源丧失其功能和价值。修复藻型富营养化水体生态系统可以从控制藻类繁殖和调整藻类群落结构方面着手,使整个水生 相似文献
913.
Megy S Bertho G Gharbi-Benarous J Baleux F Benarous R Girault JP 《FEBS letters》2006,580(22):5411-5422
The interaction of the P-beta-Cat(19-44) peptide, a 26 amino acid peptide (K(19)AAVSHWQQQSYLDpSGIHpSGATTTAP(44)) that mimics the phosphorylated beta-Catenin antigen, has been studied with its monoclonal antibody BC-22, by transferred nuclear Overhauser effect NMR spectroscopy (TRNOESY) and saturation transfer difference NMR (STD NMR) spectroscopy. This antibody is specific to diphosphorylated beta-Catenin and does not react with the non-phosphorylated protein. Phosphorylation of beta-Catenin at sites Ser33 and Ser37 on the DSGXXS motif is required for the interaction of beta-Catenin with the ubiquitin ligase SCF(beta-TrCP). beta-TrCP is involved in the ubiquitination and proteasome targeting of the oncogenic protein beta-Catenin, the accumulation of which has been implicated in various human cancers. The three-dimensional structure of the P-beta-Cat(19-44) in the bound conformation was determined by TRNOESY NMR experiments; the peptide adopts a compact structure in the presence of mAb with formation of turns around Trp25 and Gln26, with a tight bend created by the DpS(33)GIHpS(37) motif; the peptide residues (D32-pS37) forming this bend are recognized by the antibody as demonstrated by STD NMR experiments. STD NMR studies provide evidence for the existence of a conformational epitope containing tandem repeats of phosphoserine motifs. The peptide's epitope is predominantly located in the large bend and in the N-terminal segment, implicating bidentate association. These findings are in excellent agreement with a recently published NMR structure required for the interaction of beta-Catenin with the SCF(beta-TrCP) protein. 相似文献
914.
Remize F Gaudin A Kong Y Guzzo J Alexandre H Krieger S Guilloux-Benatier M 《Archives of microbiology》2006,185(6):459-469
Optimization of malolactic fermentation in wine depends mainly on better understanding of nitrogen nutritional requirements of Oenococcus oeni. Four widely used starter strains and the reference ATCC BAA-1163 strain were grown in media containing different N sources: free amino acids, oligopeptides (0.5–10 kDa) or polypeptides (> 10 kDa). Amino acid auxotrophies were determined by the single omission technique. The tested strains were indifferent to only two to four amino acids and two of the starter strains appeared to be particularly demanding. Nitrogen consumption was investigated and a significant level of nitrogen was consumed by O. oeni only in the free amino acid medium. In media containing complex nitrogen sources, a global balance above 5 mg N l−1 was enough to ensure biomass formation of all tested strains. Moreover, for all strains, bacterial growth yield was higher in the presence of nitrogen from peptides than that from free amino acids. However, no direct relationship between the bacterial growth level and the amount of nitrogen metabolized could be established. These findings were discussed in relation to the physiology of wine malolactic bacteria. 相似文献
915.
916.
Daisuke Igarashi Yoshihiro Izumi Yuko Dokiya Kazuhiko Totsuka Eiichiro Fukusaki Chieko Ohsumi 《Planta》2009,229(3):633-644
The metabolism of vegetative organs in plants changes during the development of the reproductive organs. The regulation of
this metabolism is important in the control of crop productivity. However, the complexity of the regulatory systems makes
it difficult to elucidate their mechanisms. To examine these mechanisms, we constructed model experiments using Arabidopsis
to analyze metabolic and gene expression changes during leaf-stage progression and after removal of the reproductive organs.
Leaf gene expression levels and content of major amino acids, both of which decreased during leaf-stage progression, increased
after removal of the reproductive organs. In particular, the levels of expression of cytokinin biosynthesis genes and cytokinin-responsive
genes and the cytokinin content increased after removal of the reproductive organs. Analysis of plants with knockout of a
cytokinin-biosynthetic gene (AtIPT3) and a cytokinin receptor gene (AHK3) indicated that glutamate dehydrogenase genes (GDH3) were regulated by cytokinin signaling. These data suggest that cytokinins regulate communication between reproductive and
vegetative organs, and that GDH3 is one target of the cytokinin-mediated regulation of nitrogen metabolism.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
917.
918.
Ecological ramifications of the direct foliar uptake of nitrogen 总被引:1,自引:0,他引:1
Sparks JP 《Oecologia》2009,159(1):1-13
The foliar incorporation of various reactive forms of nitrogen (N) has been identified and studied for nearly 30 years. However,
the ecosystem-level ramifications of this uptake pathway have only recently been considered by the scientific community. In
this review, I present our current understanding of the foliar uptake process and then discuss why this pathway of N addition
to ecosystems should be considered separately from the bulk deposition of N to the soil surface. Direct foliar uptake is a
direct addition of N to plant metabolism and could potentially more readily influence plant growth compared to soil-deposited
N. Current ecosystem process models do not partition reactive N between foliar and soil entry pathways and the influence of
N deposition on ecosystem C sequestration is likely inadequately represented in most models. I also outline several research
priorities for the future understanding of the ecological consequences of foliar uptake of reactive N. 相似文献
919.
Conservation of nitrogen increases with precipitation across a major grassland gradient in the Central Great Plains of North America 总被引:1,自引:0,他引:1
Regional analyses and biogeochemical models predict that ecosystem N pools and N cycling rates must increase from the semi-arid
shortgrass steppe to the sub-humid tallgrass prairie of the Central Great Plains, yet few field data exist to evaluate these
predictions. In this paper, we measured rates of net N mineralization, N in above- and belowground primary production, total
soil organic matter N pools, soil inorganic N pools and capture in resin bags, decomposition rates, foliar 15N, and N use efficiency (NUE) across a precipitation gradient. We found that net N mineralization did not increase across
the gradient, despite more N generally being found in plant production, suggesting higher N uptake, in the wetter areas. NUE
of plants increased with precipitation, and δ15N foliar values and resin-captured N in soils decreased, all of which are consistent with the hypothesis that N cycling is
tighter at the wet end of the gradient. Litter decomposition appeared to play a role in maintaining this regional N cycling
trend: litter decomposed more slowly and released less N at the wet end of the gradient. These results suggest that immobilization
of N within the plant–soil system increases from semi-arid shortgrass steppe to sub-humid tallgrass prairie. Despite the fact
that N pools increase along a bio-climatic gradient from shortgrass steppe to mixed grass and tallgrass prairie, this element
becomes relatively more limiting and is therefore more tightly conserved at the wettest end of the gradient. Similar to findings
from forested systems, our results suggest that grassland N cycling becomes more open to N loss with increasing aridity. 相似文献
920.