117,507 research outputs found
Distribution of plant gamma-glutamyl-transferase at subcellular and tissue level
No full textEdinburg
Localization of gamma-glutamyl-transferase gene transcripts, protein and activity in plant tissues
No full textOne of the less well-known aspects of glutathione (GSH) metabolism is its degradation. Two pathways have been suggested: in one, the glycine residue is first removed by a carboxypeptidase, then cysteine is hydrolyzed by a -glutamyl cyclo-transferase; in another, glutathione degradation is initiated by gamma-glutamyl transferase/transpeptidase (GGT) activity. The latter is well described in mammals, where it is thought to have a key role in cell redox balance and glutathione salvage from the extracellular space, but it is little known in plants. Previous investigations on UV-B photo-oxidative stress conditions in maize leaves showed an increase in cys-gly content that reportedly results from glutathione degradation by means of GGT activity; this study presents the results of our investigations on this enzyme in plants.
As predicted by sequence analysis on known plant GGTs, there is a substantial similarity with GGTs from other organisms as concerns the presence of the amino acid residues needed for substrate binding and catalytic activity, glycosylation sites, the cleavage site and the putative transmembrane domain at the N terminus.
By means of an enzyme-histochemical procedure, we localized GGT activity in various tissues from different plant species. Our results show that GGT activity is mainly localized in the parenchymal cells of conductive tissues closely associated with vascular bundles, but also in the stomata and epidermal cells. In maize leaves, GGT transcript localization, as revealed by in situ hybridization, correlates with the distribution of GGT activity. Immunocytochemical analysis confirms the localization of GGT in the plasma membrane, but also reveals its presence within the cell walls.
The role of GGT in plant metabolism remains largely unknown. The histochemically-detected localization of GGT activity suggests that this enzyme may be involved in GSH redistribution in plant organs and tissues. GGT promotes the removal of a gamma-glutamyl moiety and the resulting cys-gly may either be degraded to its constituent amino acids and transported across the plasma membrane, or it may take part in redox signaling by influencing the redox state of free thiols of membrane proteins. It is therefore feasible to suggest that GGT fulfills important functions in addition to GSH degradation
Spatialization of soil carbon stock in a rural landscape - a study case in the Southeast of Brazil.
No full textAgriculture is one of the main responsible for the increase of CO2 atmospheric in Brazil. However, the adoption of conservation farming practices is an alternative to mitigate climate change. Geoprocessing tools can assist in land use mapping process and associate different landscape parameters in an integrated spatial analysis. To carry out this study, the C stock was calculated and spatialized using the software Arcis® 10.2. A gradual C stock values categorization is presented according to land use cover map. It was observed that Annual e Perennial crops land use classes presented the lowest values of C stock. That showed the fragility of agrosystems concerning C stocks, but in the other hand, the great opportunity and importance of to improve agricultural management practices seeking decrease the impact of food production into the global C cycle
Estoque de carbono no solo e avaliação de serviços ecossistêmicos em paisagens rurais.
No full textO objetivo desse estudo foi analisar, de forma integrada, valores de estoque de carbono no solo com mapas de uso e cobertura, utilizando ferramentas de geoprocessamento, tendo em vista a identificação de áreas prestadoras de serviços ecossistêmicos
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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