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Literatura académica sobre el tema "Tolerance to copper"

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Publicado: 10 de marzo de 2023

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Artículos de revistas sobre el tema "Tolerance to copper"

Garcia-Toledo, A., H. Babich y G. Stotzky. "Training of Rhizopus stolonifer and Cunninghamella blakesleeana to copper: cotolerance to cadmium, cobalt, nickel, and lead". Canadian Journal of Microbiology 31, n.º 5 (1 de mayo de 1985): 485–92. http://dx.doi.org/10.1139/m85-090.

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Rhizopus stolonifer and Cunninghamella blakesleeana trained after five passages to tolerate elevated concentrations of copper simultaneously acquired a tolerance to elevated levels of cadmium, cobalt, nickel, and lead. The acquired tolerance to copper was not stable in the absence of the metal, as serial transfers to a copper-free medium progressively reduced the level of tolerance, and after the sixth passage on a copper-free medium, the tolerance was equivalent to that of the nontrained parentals ("untraining"). However, the untrained fungi regained the same tolerance to copper as the original copper-trained fungi after only three passages on copper-amended medium ("retraining"). The tolerance to copper was apparently the result of physiological adaptation rather than of the selection of resistant cells or the induction of mutation. The metal may have activated genes that coded for biochemical processes that conferred tolerance to copper as well as to other heavy metals. Furthermore, the tolerance to copper of the mycelia was transferred to the sporangiospores. The copper-trained fungi did not appear to produce extracellular metabolites that complexed with and, hence, excluded and detoxified the copper. However, the mycelia of the trained fungi removed approximately twice as much copper from solution than those of the nontrained parentals, suggesting that the tolerance to copper resulted from the binding of the metal to the cell wall or from an intracellular detoxification mechanism.

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Jovicic-Petrovic, Jelena, Gordana Danilovic, Natasa Curcic, Mira Milinkovic, Natasa Stosic, Dejana Pankovic y Vera Raicevic. "Copper tolerance of Trichoderma species". Archives of Biological Sciences 66, n.º 1 (2014): 137–42. http://dx.doi.org/10.2298/abs1401137j.

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Some Trichoderma strains can persist in ecosystems with high concentrations of heavy metals. The aim of this research was to examine the variability of Trichoderma strains isolated from different ecosystems, based on their morphological properties and restriction analysis of ITS fragments. The fungal growth was tested on potato dextrose agar, amended with Cu(II) concentrations ranging from 0.25 to 10 mmol/l, in order to identify copper-resistant strains. The results indicate that some isolated strains of Trichoderma sp. show tolerance to higher copper concentrations. Further research to examine the ability of copper bioaccumulation by tolerant Trichoderma strains is needed.

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Bálint, A. F., G. Kovács, A. Börner, G. Galiba y J. Sutka. "Substitution analysis of seedling stage copper tolerance in wheat". Acta Agronomica Hungarica 51, n.º 4 (1 de diciembre de 2003): 397–404. http://dx.doi.org/10.1556/aagr.51.2003.4.4.

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The relatively copper-tolerant wheat variety Chinese Spring (recipient), the copper-sensitive variety Cappelle Desprez (donor) and their substitution lines were screened for copper tolerance in a soil pot experiment under artificial growth conditions. Chromosomes 5A, 5B, 5D and 7D of Cappelle Desprez significantly decreased the copper tolerance of the recipient variety to varying extents. By contrast, the 6B and 3D chromosomes significantly increased the copper tolerance of Chinese Spring, suggesting that a wide range of allelic differences could be expected between wheat genotypes for this character. The significant role of homologous group 5 in copper tolerance was confirmed by testing wheat-rye substitution lines. The substitution of rye chromosome 5R (5R/5A substitution line) into a wheat genetic background significantly increased the copper tolerance of the recipient wheat genotype. The results suggest that chromosomes 5R and 5A probably carry major genes or gene complexes responsible for copper tolerance, and that the copper tolerance of wheat can be improved through the substitution of a single chromosome carrying the responsible genes. At the same time, it is also possible that the effect of homologous group 5 is not specific to copper tolerance, but that the genes located on these chromosomes belong to a general stress adaptation (frost, cold, vernalisation requirements, etc.) complex, which has already been detected on this chromosome. To answer this question further studies are needed to determine the real effect of these chromosome regions and loci on copper tolerance.

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Brady, D., D. Glaum y J. R. Duncan. "Copper tolerance in Saccharomyces cerevisiae". Letters in Applied Microbiology 18, n.º 5 (mayo de 1994): 245–50. http://dx.doi.org/10.1111/j.1472-765x.1994.tb00860.x.

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Lolkema, P. C. y R. Vooijs. "Copper tolerance in Silene cucubalus". Planta 167, n.º 1 (enero de 1986): 30–36. http://dx.doi.org/10.1007/bf00446365.

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Raquel Stefanello, Patrícia Carine Hüller Goergen, Carmine Aparecida Lenz Hister y Ubirajara Russi Nunes. "Tolerance of chia seeds to copper". Acta Biológica Catarinense 5, n.º 3 (17 de diciembre de 2018): 42–49. http://dx.doi.org/10.21726/abc.v5i3.405.

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Environmental contamination by toxic metals has become a problem for plants, animals and man. Among the toxic metals present in the environment, copper (Cu) is the most important contaminant and can, when excess in water or soil, cause disturbances in the growth and development of plants, reducing the productivity of crops. The objective of this study was to evaluate the tolerance of chia seeds to copper during germination. The seeds were placed on paper soaked in aqueous copper solution at concentrations corresponding to zero (distilled water); 60; 120; 180 and 240 mg L-1. The evaluated parameters were: percentage of germination, first count, total length, shoot and root length and dry mass of seedlings. The increase of copper concentration in the substrate promoted a significant decrease in seed germination, growth and dry mass of chia seedlings. It is concluded that chia seeds moderately tolerate exposure to copper at concentrations of up to 120 mg L-1 of Cu in the germination phase and up to 60 mg L-1 in the initial development phase.

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Tilstone, G. H., M. R. Macnair y S. E. Smith. "Does copper tolerance give cadmium tolerance in Mimulus guttatus". Heredity 79, n.º 5 (noviembre de 1997): 445–52. http://dx.doi.org/10.1038/hdy.1997.183.

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Rauser, Wilfried E. y E. Keith Winterhalder. "Evaluation of copper, nickel, and zinc tolerances in four grass species". Canadian Journal of Botany 63, n.º 1 (1 de enero de 1985): 58–63. http://dx.doi.org/10.1139/b85-009.

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Clones of Agrostis gigantea, Deschampsia caespitosa, Hordeum jubatuin, and Poa compressa were evaluated for their tolerance with respect to copper, nickel, and zinc. Most of the plants originated from acidic, copper- and nickel-contaminated soils near Sudbury, Ont. Metal tolerance was assayed by measuring all of the adventitious roots growing from tillers but excluding lateral roots. Tolerance of copper, nickel, and zinc was evident in the four clones of D. caespitosa originating from Sudbury. One clone of A. gigantea originating from a roast bed showed tolerance of copper, while none showed tolerance of cither nickel or zinc. One clone of P. compressa from Sudbury indicated increased tolerance of copper and nickel, yet its root growth was inhibited at lower zinc concentrations than that of a companion clone from Sudbury and a control. The H. jubatum plants showed no tolerance of any of the metals. Copper was most toxic to all of the species, followed by nickel and then zinc.

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Stefanello, Raquel, Patrícia Carine Hüller Goergen, Carmine Aparecida Lenz Hister y Ubirajara Russi Nunes. "Tolerance of chia seeds to copper". Acta Biológica Catarinense 5, n.º 3 (13 de diciembre de 2018): 42. http://dx.doi.org/10.21726/abc.v5i3.450.

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Environmental contamination by toxic metals has become a serious problem to plants, animals, and humans. Among the toxic metals in the environment, copper (Cu) is the most important contaminant and, when in excess in water and soil, can disturb the growth and development of plants, decreasing the productivity of crops. Thus, the objective of this study was to evaluate the tolerance of chia seeds to copper. The seeds were place on paper soaked in aqueous solutions of copper at concentrations of zero (distilled water), 60, 120, 180, and 240 mg L-1. The parameters evaluated were percentage of germination, primary count, total, shoot and root length, and dry mass of the seedlings. An increase in concentration of copper in the substrate promoted a significant decrease in seed germination, growth, and dry mass of the chia seedlings. It is concluded that, during the germination phase, chia seeds moderately tolerate exposure to Cu, up to 180 mg L-1, but can be intolerant at higher concentrations.

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Thummeepak, Rapee, Renuka Pooalai, Christian Harrison, Lucy Gannon, Aunchalee Thanwisai, Narisara Chantratita, Andrew D. Millard y Sutthirat Sitthisak. "Essential Gene Clusters Involved in Copper Tolerance Identified in Acinetobacter baumannii Clinical and Environmental Isolates". Pathogens 9, n.º 1 (15 de enero de 2020): 60. http://dx.doi.org/10.3390/pathogens9010060.

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Copper is widely used as antimicrobial in agriculture and medicine. Copper tolerance mechanisms of pathogenic bacteria have been proven to be required for both copper tolerance and survival during bacterial infections. Here, we determined both copper-tolerant phenotype and genotype in A. baumannii originated from clinical and environmental samples. Using copper susceptibility testing, copper-tolerant A. baumannii could be found in both clinical and environmental isolates. Genotypic study revealed that representative copper-related genes of the cluster A (cueR), B (pcoAB), and D (oprC) were detected in all isolates, while copRS of cluster C was detected in only copper-tolerant A. baumannii isolates. Moreover, we found that copper-tolerant phenotype was associated with amikacin resistance, while the presence of copRS was statistically associated with blaNDM-1. We chose the A. baumannii strain AB003 as a representative of copper-tolerant isolate to characterize the effect of copper treatment on external morphology as well as on genes responsible for copper tolerance. The morphological features and survival of A. baumannii AB003 were affected by its exposure to copper, while whole-genome sequencing and analysis showed that it carried fourteen copper-related genes located on four clusters, and cluster C of AB003 was found to be embedded on genomic island G08. Transcriptional analysis of fourteen copper-related genes identified in AB003 revealed that copper treatment induced the expressions of genes of clusters A, B, and D at the micromolar level, while genes of cluster C were over-expressed at the millimolar levels of copper. This study showed that both clinical and environmental A. baumannii isolates have the ability to tolerate copper and carried numerous copper tolerance determinants including intrinsic copper tolerance (clusters A, B, and D) and acquired copper tolerance (cluster C) that could respond to copper toxicity. Our evidence suggests that we need to reconsider the use of copper in hospitals and other medical environments to prevent the selection and spread of copper-tolerant organisms.

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Tesis sobre el tema "Tolerance to copper"

ADAMO, GIUSY MANUELA. "Evolution of copper tolerance in yeast cells". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/29458.

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For all living organisms, copper (Cu) is an essential micronutrient taking part, with its redox chemistry, to several metabolic and regulatory cellular events. However, the same redox properties that make Cu essential are responsible for its toxicity. Indeed, Cu participates in reactions that generate Reactive Oxygen Species (ROS). ROS target main cellular macromolecules (proteins, lipids, DNA and RNA), leading to cellular dysfunctions and in the extreme case, to cell death. All living organisms evolved molecular mechanisms for Cu homeostasis. Indeed, uptake, transport and detoxification systems that actively prevent both Cu deficiency and poisoning are well conserved along the phylogenetic tree. Among eukaryotes, these mechanisms have been mainly investigated in the yeast Saccharomyces cerevisiae used as a model organism. Evolutionary engineering is a rational approach that uses the evolutionary principles to direct the selection of organisms with a desired set of phenotypes, allowing for the improvement of microbial properties. This approach can be exploited to obtain Cu-tolerant and Cu-accumulating yeast cells, with potential application in nutraceutics, as nutritional supplements, as well as in bioremediation, for the removal or recovery of metal ions. At the same time, evolutionary engineering is a valuable strategy to gain more insight into the molecular aspects of Cu tolerance in microbial cells. In the present work is described an evolutionary engineering strategy to improve Cu tolerance of natural yeasts. Strains of Saccharomyces cerevisiae and of Candida humilis originally endowed with different sensitivity and tolerance toward Cu have been exposed to increasing concentrations of Cu during cell cultivation in liquid medium. This treatment stably improved Cu tolerance of all strains. One evolved strain for each yeast species was then chosen to analyze in detail the physiological response to Cu. Compared with the original Cu-sensitive strains the two evolved strains showed improved cell viability and attenuated production of ROS. A reshaping of the profile of antioxidant enzymes and Cu-binding proteins was observed in both strains as a specific response to copper. Further investigations carried out on S. cerevisiae strains demonstrated a pivotal role of the CUP1 gene, encoding for a metallothionein. A 7-fold amplification of this gene was found associated with evolution of Cu tolerance. Finally, Cu tolerance in C. humilis cells was studied by proteomic analyses. Changes were observed in the levels of several proteins involved in the oxidative stress response (such as glycolytic enzymes), heat shock proteins, proteins involved in protein synthesis and energy production, proteins with a role in phospholipids synthesis. Cu exposure resulted in differential protein expression, in both non-evolved and Cu evolved cells. In general, changes in protein levels detected in evolved cells were smaller. On this basis, it was hypothesized that in the evolved cells copper tolerance relies only partly on the molecular mechanisms associated with the oxidative stress response. This work shows once again that evolutionary engineering is a powerful strategy to drive the gain of stable phenotypic traits. The evolved strains might found direct application in several biotechnological fields, and provide a kind of “molecular platform” for the investigation on the mechanisms of stress tolerance. The availability of data about the S. cerevisiae genome allowed a focused investigation on the molecular actors involved in Cu tolerance. In the case of C. humilis, the use of a proteomic approach allowed to compensate for the poor information available on the determinants of Cu tolerance.

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Wadey, P. "The physiology of copper tolerance in Mimulus guttatus". Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233878.

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Harper, Frances Anne. "The cost of copper tolerance in Mimulus guttatus". Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307278.

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Strange, J. "The physiology of copper tolerance in Mimulus guttatus". Thesis, University of Exeter, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383346.

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Lloyd, Deborah. "Reproductive isolation associated with the copper tolerance locus in Mimulus guttatus". Thesis, University of Exeter, 2010. http://hdl.handle.net/10036/3173.

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The evolution of reproductive isolating barriers that prevent gene flow between species is essential to the process of speciation. One such barrier is intrinsic postzygotic isolation, which proceeds as hybrid sterility or inviability, and is commonly attributed to Dobzhansky-Muller genic incompatibilities. Here, deleterious interlocus interactions occur between incompatible alleles of complementary genes when brought together in the genome of a hybrid. Although these hybrid incompatibilities are widespread, having been identified in mammals, fish, plants and fungi, still relatively little is known about the nature of the genes involved. In the model plant species Mimulus, a Dobzhansky-Muller incompatibility exists between two populations of the yellow monkey flower, Mimulus guttatus, in which the interaction between a single gene from a copper tolerant population, Copperopolis, and a small number of polymorphic genes from a second non-tolerant population, Cerig-y-drudion, results in hybrid necrosis in the F1. Hybrid necrosis, a form of hybrid inviability with phenotypic characteristics strongly similar to those of plants responding to pathogen attack, is a common barrier preventing hybridization in plants. As well as being of interest in terms of evolution, hybrid necrosis has practical implications in plant breeding as it prevents the combining of desirable traits from related species in commercial cultivars. In the cross between Copperopolis and Cerig-y-drudion, copper tolerance, conferred by a single major gene, and hybrid necrosis are tightly linked but the independent or synonymous nature of the gene(s) in the Copperopolis population that contribute to these two characteristics is unknown. A key aim of this thesis was to establish the nature of the single gene in Copperopolis that contributes to hybrid necrosis with regards to its linkage to copper tolerance. The gene for hybrid necrosis was found to be tightly linked to, but discrete from, the gene controlling copper tolerance. Three candidate genes for this hybrid necrosis locus were indentified: a Jumonji-domain containing protein with probable function as a methyltransferase, a glycosyltransferase and a possible phosphatase. Interestingly, the latter two have potential functional roles in the plant immune system. The second key aim of this thesis was to perform the first investigation into the small number of genes in the Cerig-y-drudion population that contribute to the crossing barrier. Two QTLs for hybrid necrosis were identified. One QTL on Chromosome 9 is responsible for around 20% of the hybrid necrosis whilst the second QTL on Chromosome 12 acts as an enhancer of the first QTL causing an additional 10% of necrosis. Interestingly both these QTLs contain R genes, further implicating the possible involvement of the plant immune system in this crossing barrier.

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Fuentealba, I. C. "Cellular mechanisms of toxicity and tolerance in the copper-loaded rat". Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383477.

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Gonzalez-Chavez, Ma del Carmen. "Arbuscular mycorrhizal fungi from As/Cu polluted soils, contribution to plant tolerance and importance of the external mycelium". Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312514.

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Metaxas, Anna. "Effect of the interaction between two species of marine diatoms on their individual copper tolerance". Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27597.

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The importance of species interactions in studies assessing the trace metal tolerance of individual species, has been largely overlooked. Most toxicity assessments involve single-species tests. Although relevant in some cases, this approach does not incorporate the biological enviroment of an organism as a factor that might influence its survival. On the other hand, this factor is incorporated in studies at the community level. However, the latter, not examining the mechanisms that drive the interactions in the community, do not allow for prediction of the outcome after the addition of a stress inducer, such as trace metals. The purpose of this study was to examine the effect of the interaction of two species of marine diatoms (Skeletonema costatum (Cleve) Greville and Nitzschia thermalis (Ehrenberg) Auerswald) on their individual copper tolerances. The two species were grown in unialgal cultures in order to determine their copper tolerance. 5. costatum did not exhibit growth above 5 x 10⁻⁷ M (pCu = 8.46) and N. thermalis above 6 x 10⁻⁷M added total copper (pCu = 8.36). Skeletonema exhibited increased growth rate and lag phase with increasing copper concentration (and decreasing pCu). On the other hand, Nitzschia demonstrated decreased growth rate. No effect on lag phase was observed for this species. No difference between the tolerances of two strains of S. costatum was observed. Both strains demonstrated unaffected growth at 1 x 10⁻⁷M (pCu = 9.16) and no growth at 1 x 10⁻⁵ M added total copper (pCu = 7.16). Subsequently, Skeletonema costatum and Nitzschia thermalis were grown together at three copper concentrations (1 x 10⁻⁹ M, 4 x 10⁻⁷M and 5 x 10⁻⁷M added total copper). In the unialgal cultures that were used as controls, the two species grew as predicted from their tolerance tests. However, in the mixed cultures, Nitzschia was the only species that exhibited growth, regardless of the copper concentration in the medium. This inhibition of Skeletonema in the presence of the second diatom, was attributed to a toxic Nitzschia exudate. The effect of the exudate appeared to be temporary, as demonstrated by the extended lag phase and subsequent satisfactory exponential growth rate of Skeletonema. It is suggested that exponential growth rate was resumed because the exudate degrades within a period of five days (= lag phase). It is shown that the interaction between the two diatom species is more important in determining the survival of S. costatwn than its individual copper tolerance. This is not the case for N. thermalis. Such interactions would be unaccounted for in single-species toxicity tests. On the other hand, if they are known, prediction of how a community that includes these two species would respond to copper additions becomes possible.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

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Pinto, Cecilia de Agrela. "The two-component system of a novel copper resistant operon of Marinobacter hydrocarbonoclasticus". Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/10062.

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Dissertation for the Master’s Degree in Structural and Functional Biochemistry
The majority of bacterial heavy metal resistance systems are regulated by twocomponent signal transduction systems. Stimuli from the environment interact with the histidine kinase, which in turn activates the response regulator by phosphorylation. The effector domain of the response regulator then binds to DNA, eliciting the specific response. Analysis of the Marinobacter hydrocarbonoclasticus genome revealed the presence of genes, copXAB, that code for proteins associated with copper response. The biochemical characterization of the two-component signal transduction system, copSR, is of interest due to the vital role it plays in the regulation of expression of the copXAB operon. The genes that encode for the CopR and CopS_C (cytosolic sensor domain of CopS) proteins were heterologously expressed in E.coli and expression was optimized for the production of soluble protein using LB medium. Due to solubility problems, the genes that code for these proteins were cloned as hexahistidine or glutathione S-transferase fusion proteins. CopR and its domains were optimally expressed at 16°C for 16 and 3 h after induction, respectively, whilst CopS_C was expressed at 37°C during 3 h after induction. Proteins were purified using different chromatographic strategies, most of them using affinity chromatography. The yields of pure protein per liter of growth culture obtained after complete purification from the soluble cellular extract were: 0.14 to 0.23 mg/L for CopR; 0.42 mg/L, CopR_NHis6; for the CopR_CHis6 it was 0.16 mg/L and 4.2 mg/L of CopS_C. The molecular mass of each protein was determined by gel filtration, 31 kDa for CopR, 17.5 kDa for CopR_NHis6, 15.1 kDa for CopR_CHis6 and 38.2 kDa for CopS_C. In the case of CopS_C there is the possibility that a dimer is formed, which should be evaluated. From the evaluation of disulfide bonds, using SDS PAGE and PAGE gels, all proteins or protein domains appeared to be monomers when in the presence of β-MEtOH. Circular dichroism evaluated the state of folding of the CopS_C and CopR proteins, which were shown to be folded in which the α-helix structures predominate. A model structure for CopR was also determined which agrees with this analysis. However, in the case of the CopR domains, the data obtained merely indicate folding, due to the low concentrations of the proteins. Phosphorylation and electrophoresis mobility shift assays of the CopR protein were, for the most part, inconclusive. However, in the absence of BSA, formation of the CopR:DNA complex in a gel filtration column is observed, though requires additional evaluation.

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Saint-Pierre, Édith. "Mise en évidence d'un mécanisme de tolérance chez scenedesmus quadricauda suite à une intoxication à long terme au cuivre /". Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1992. http://theses.uqac.ca.

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Mémoire (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 1992.
Résumé disponible sur Internet. CaQCU Bibliogr.: f. 69-73. Document électronique également accessible en format PDF. CaQCU

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Libros sobre el tema "Tolerance to copper"

Twiss, Michael Robert. The influence of phosphorus nutrition on copper tolerance in Scenedesmus. Ottawa: National Library of Canada, 1990.

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Hashemi, Fereshteh Sadat. Tolerance of Anabaena variabilis and other cyanobacteria to copper and other metals. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1993.

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Blum, Jason R. Metal co-tolerance in Rhode Island Bent (agrostis tenuis sibth.)--ability of plants from copper-zinc contaminated soils at Flin Flon to grow on copper-nickel contaminated soils from Sudbury. Sudbury, Ont: Laurentian University, Department of Biology, 1996.

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Maria, Faur y United States. National Aeronautics and Space Administration., eds. Theoretical and experimental research in space photovoltaics: Final report research grant no. NAG3-658 for the period January 1986 - March 1995. Cleveland, Ohio: Cleveland State University, Electrical Engineering Dept., Space Photovoltaic Research Center, 1995.

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United States. National Aeronautics and Space Administration., ed. Theoretical and experimental research in space photovoltaics: Electrodeposition of CuInxGa₁-xSe₂ (CIGS) thin layers for CdS/CIGS solar cell applications : final report, NASA research grant no. NAG3-1692 for the period January 23, 1995 to April 22, 1995. [Cleveland, Ohio?]: The Center, 1997.

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Watson, Glen D. Comparative acute toxicity of copper between two populations of the acid tolerant crayfish Cambarus robustus (Decapoda, Crustacea). Sudbury, Ont: Laurentian University, Department of Biology, 1993.

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Schultz, Caroline Luise. The role of sulphur and thiol-rich copper-binding protein in the copper tolerance of "Deschampsia cespitosa"(L.) Beauv. 1986.

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Jones, Melanie Dawn. The role of ectomycorrhizae in the tolerance of "Betula papyrifera" to copper and nickel. 1987.

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Capítulos de libros sobre el tema "Tolerance to copper"

Elmes, M., S. Haywood, J. P. Clarkson, I. C. Fuentealba y B. Jasani. "Copper Tolerance in Rats — A Histochemical and Immunocytochemical Study". En Trace Elements in Man and Animals 6, 699–700. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-0723-5_258.

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Chen, Yingxu, Mingge Yu y Dechao Duan. "Tolerance, Accumulation, and Detoxification Mechanism of Copper in Elsholtzia splendens". En Soil Biology, 317–44. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-21408-0_17.

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Lombini, A., Ch Poschenrieder, M. Llugany, E. Dinelli y J. Barceló. "Copper resistance in Silene armeria ecotypes: Does co-tolerance play a role?" En Plant Nutrition, 456–57. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/0-306-47624-x_220.

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Gladkov, Evgen Aleksandrovich, Ilina Igorevna Tashlieva, Yuliya Ivanovna Dolgikh y Olga Victorovna Gladkova. "Increasing Tolerance Agrostis Stolonifera, Festuca Rubra, Brachycome Iberidifolia, Chrysanthemum Carinatum to Copper". En Proceedings of the 2nd International Conference on BioGeoSciences, 167–74. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-04233-2_15.

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Lavalle, L., M. Portillo, P. Chiacchiarini y Edgardo Donati. "Heavy Metal Tolerance and Copper Uptake in Yeast Isolated from Patagonia/ Argentina". En Advanced Materials Research, 639–42. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-452-9.639.

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Schat, Henk, A. L. M. Hoof Nathalie, A. Tervahauta, Henk W. J. Hakvoort, Agnes N. Chardonnens, Paul L. M. Koevoets, Jos A. C. Verkleij y Wilfried H. O. Ernst. "Evolutionary Responses to Zinc and Copper Stress in Bladder Campion, Silene Vulgaris (Moench.) Garcke". En Plant Tolerance to Abiotic Stresses in Agriculture: Role of Genetic Engineering, 343–60. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4323-3_24.

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Langridge, Peter. "Micronutrient Toxicity and Deficiency". En Wheat Improvement, 433–49. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-90673-3_24.

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AbstractMicronutrients are essential for plant growth although required in only very small amounts. There are eight micronutrients needed for healthy growth of wheat: chlorine, iron, boron, manganese, zinc, copper, nickel and molybdenum. Several factors will influence the availability of micronutrients, including levels in the soil, and mobility or availability. Zinc deficiency is the most significant problem globally followed by boron, molybdenum, copper, manganese and iron. Deficiency is usually addressed through application of nutrients to seeds, or through foliar spays when symptoms develop. There is considerable genetic variation in the efficiency of micronutrient uptake in wheat, but this is not a major selection target for breeding programs given the agronomic solutions. However, for some micronutrients, the concentrations in the soil can be very high and result in toxicity. Of the micronutrients, the narrowest range between deficiency and toxicity is for boron and toxicity is a significant problem in some regions. Although not a micronutrient, aluminium toxicity is also a major factor limiting yield in many areas, usually associated with a low soil pH. Agronomic solutions for boron and aluminium toxicity are difficult and expensive. Consequently, genetic approaches have dominated the strategies for addressing toxicity and good sources of tolerance are available.

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Basílico, Gabriel, Ana Faggi y Laura de Cabo. "Tolerance to Metals in Two Species of Fabaceae Grown in Riverbank Sediments Polluted with Chromium, Copper, and Lead". En Phytoremediation, 169–78. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-99651-6_7.

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Azad, Md Abul Kalam, Fahmina Yasmine, Md Kamruzzaman, Md Hasanuzzaman Rani y Hosne Ara Begum. "Development of climate-adaptable/resilient crop varieties through induced mutation." En Mutation breeding, genetic diversity and crop adaptation to climate change, 157–71. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789249095.0016.

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Abstract For crop production to cope with problems driven by climate change, such as salinity, drought and extreme temperatures, the Bangladesh Institute of Nuclear Agriculture (BINA) released a late Boro rice variety, 'Binadhan-14' in 2013 which is tolerant to high temperature, has short duration (105-115 days) and gives average yield of 6.9 t/ha. This variety was developed by irradiating the seeds of 'Ashfal', a local salt-tolerant landrace of rice, with 200 Gy of carbon-ion beams. The late-transplanting potential of this variety also helps in avoiding seedling injury due to severe cold. Another variety, 'Binadhan-19', was developed by irradiating the seeds of 'NERICA-10' rice with 40 Gy of carbon-ion beams. This was released by the National Seed Board of Bangladesh (NSB) in 2017 as a drought-tolerant, short-duration (95-105 days) and high-yielding (average 4.0 t/ha) variety for the Aus growing season. BINA developed a salt-tolerant wheat variety, 'Binagom-1', by selecting from a segregating population, obtained from NIAB, Pakistan. This variety was released in 2016; it can tolerate salinity (up to 12 dS/m) and produces an average yield of 2.8 t/ha. Apart from these, BINA developed four salt-tolerant groundnut varieties ('Binachinabadam-5', 'Binachinabadam-6', 'Binachinabadam-7' and 'Binachinabadam-9') by irradiation with gamma-rays. All these four varieties can tolerate salinity (up to 8 dS/m) from flowering to maturity and produce pods at 1.8-3.4 t/ha under saline soil conditions. These climate-resilient varieties are playing a significant role in food security and enhancing the nutritional status of the people of Bangladesh.

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Uhlig, Christian y Satu Monni. "Crowberry (Empetrum nigrum L.), a copper-tolerant dwarf shrub". En Forest Condition in a Changing Environment, 276–77. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-015-9373-1_32.

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Actas de conferencias sobre el tema "Tolerance to copper"

Silveira, Célia M., Manolis Matzapetakis, M. Gabriela Almeida y Sofia R. Pauleta. "Copper tolerance in Marinobacter hydrocarbonoclasticus — Proteomic analysis of the periplasm". En MICROBES IN APPLIED RESEARCH - Current Advances and Challenges. WORLD SCIENTIFIC, 2012. http://dx.doi.org/10.1142/9789814405041_0124.

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Fan, Chuanhong, Ryosuke Furuya, Osamu Asai, Ken Suzuki y Hideo Miura. "Effect of the Lattice Mismatch Between Copper Thin-Film Interconnection and Base Material on the Crystallinity of the Interconnection". En ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73147.

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In the present study, a new material, ruthenium whose lattice mismatch against copper is about 6%, was used as the seed layer of electroplated copper thin-film interconnections for semiconductor devices. The crystallinity of the copper thin-film interconnections was evaluated through an EBSD (Electron Back-scattered Diffraction) method and it is found that the crystallinity of them is improved drastically compared with those electroplated on the copper seed. The resistance and electro migration (EM) tolerance of the copper interconnections are also improved a lot compared with the interconnections electroplated on copper seed. Based on these results, a new guideline to design highly reliable electroplated copper thin-film interconnection has been established.

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Codreanu, Liviu. "The assessment of copper, iron, zinc, and nickel tolerance combined with nostoc linckia biomass production". En National Scientific Symposium With International Participation: Modern Biotechnologies – Solutions to the Challenges of the Contemporary World. Institute of Microbiology and Biotechnology, Republic of Moldova, 2021. http://dx.doi.org/10.52757/imb21.017.

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Borland, William, John J. Felten, Lynne E. Dellis, Saul Ferguson, Diptarka Majumdar, Alton B. Jones, Mark S. Lux, Richard R. Traylor y Marc Doyle. "Ceramic Resistors and Capacitors Embedded in Organic Printed Wiring Boards". En ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35090.

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Combining thick-film and printed wiring board processes allows thick-film ceramic resistors and capacitors to be embedded in printed wiring boards (PWB). The resistor materials are based on lanthanum boride and cover the range of 10 ohm/square to 10 Kohm/square resistivities. The capacitor material is based on doped barium titanate. Both systems are designed to be “thick-film” printed on copper foil in the locations desired in the circuit and the foil is then fired in nitrogen at 900°C to form the ceramic component on the copper foil. The foil is then laminated, component face down, to FR4 using standard prepreg. The inner layer is then etched to reveal the components in a FR4 matrix. The resistors can be trimmed to tight tolerance at this stage and the components tested. The inner layer can then be laminated into a multilayer PWB. The process is described and the influence of board design, PWB processing and materials are presented and discussed. Examples of circuits using embedded thick-film passives are shown and results of reliability studies are presented.

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Harvey, Jennifer, John Stearns y Jack Merchant. "Development of a Lead-Free Bronze Bearing Alloy With Improved Conformability and Seizure Performance". En ASME 2022 ICE Forward Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icef2022-88792.

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Abstract Material selection for off-highway heavy duty engine bearing applications is becoming more complex as there is a growing requirement to replace the traditionally utilized copper-lead based lining alloys due to adverse health and environmental concerns surrounding heavy metals. Although upcoming legislation is increasing the drive to find alternative lead-free solutions these have not been well adopted for all applications as there are limited products available that are matched to the excellent performance of leaded materials in tolerance to debris, ability to conform and prevention of seizure events. This paper details the development of a new lead-free bronze alloy with a focus on improvements in conformability and seizure resistance compared to current lead-free materials. A new alloy composition is introduced which contains bismuth soft phase with optimized tin content which when combined with a lead-free electroplated overlay presents a robust material for applications where seizure performance might be a concern. The present development provides a suitable product that will enable the future-proofing of off-highway heavy duty applications and offers a solution to inevitable future restrictions surrounding leaded materials. Results from bespoke rig testing and engine testing are detailed that support the material development.

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Srivatsan, T. S., Meslet Al-Hajri y J. D. Troxell. "DAMAGE TOLERANT COPPER-NIOBIUM MICROCOMPOSITE". En Processing and Fabrication of Advanced Materials VIII. WORLD SCIENTIFIC, 2001. http://dx.doi.org/10.1142/9789812811431_0008.

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Gladkov, E. A. y O. N. Gladkova. "The effect of copper on cadmium‐tolerant lawn grass". En 2nd International Scientific Conference "Plants and Microbes: the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.087.

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Sridhar, Siddharth, Rumit Kumar, Kelly Cohen y Manish Kumar. "Fault Tolerance of a Reconfigurable Tilt-Rotor Quadcopter Using Sliding Mode Control". En ASME 2018 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/dscc2018-9199.

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Tilt-rotor quadcopters are a novel class of quadcopters with a servo motor attached on each arm that assist the quadcopter’s rotors to tilt to a desired angle thereby enabling thrust vectoring. Using these additional tilt angles, this type of a quadcopter can be used to achieve desired trajectories with faster maneuvering and can handle external disturbances better than a conventional quadcopter. In this paper, a non-linear controller has been designed using sliding mode technique for the pitch, roll, yaw motions and the servo motor tilt angles of the quadcopter. The dynamic model of the tilt-rotor quadcopter is presented, based on which sliding surfaces were designed to minimize the tracking errors. Using the control inputs derived from these sliding surfaces, the state variables converge to their desired values in finite-time. Further, the non-linear sliding surface coefficients are obtained by stability analysis. The robustness of this proposed sliding mode control technique is shown when a faulty motor scenario is introduced. The quadcopter transforms into a T-copter design upon motor failure thereby abetting the UAV to cope up with the instabilities experienced in yaw, pitch and roll axes and still completing the flight mission. The dynamics of the T-copter design and the derivation of the switching surface coefficients for this reconfigurable system are also presented.

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Wang, Xueqing, Zifan Zhang, Shaowei Ren, Yao Mao, Jianwei Shen y Zheng Wang. "Fault-Tolerant Control of Standard Three-Phase PMSM Drives Considering Copper Loss". En 2022 IEEE Transportation Electrification Conference and Expo, Asia-Pacific (ITEC Asia-Pacific). IEEE, 2022. http://dx.doi.org/10.1109/itecasia-pacific56316.2022.9942202.

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Vu, Duc Tan, Ngac Ky Nguyen, Eric Semail y Trung Hai Do. "Fault-Tolerant Control for Non-sinusoidal Seven-phase PMSMs with Similar Copper Losses". En 2022 IEEE Ninth International Conference on Communications and Electronics (ICCE). IEEE, 2022. http://dx.doi.org/10.1109/icce55644.2022.9852050.

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Informes sobre el tema "Tolerance to copper"

Hutchinson, M. L., J. E. L. Corry y R. H. Madden. A review of the impact of food processing on antimicrobial-resistant bacteria in secondary processed meats and meat products. Food Standards Agency, octubre de 2020. http://dx.doi.org/10.46756/sci.fsa.bxn990.

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For meat and meat products, secondary processes are those that relate to the downstream of the primary chilling of carcasses. Secondary processes include maturation chilling, deboning, portioning, mincing and other operations such as thermal processing (cooking) that create fresh meat, meat preparations and ready-to-eat meat products. This review systematically identified and summarised information relating to antimicrobial resistance (AMR) during the manufacture of secondary processed meatand meat products (SPMMP). Systematic searching of eight literature databases was undertaken and the resultantpapers were appraised for relevance to AMR and SPMMP. Consideration was made that the appraisal scores, undertaken by different reviewers, were consistent. Appraisal reduced the 11,000 initially identified documents to 74, which indicated that literature relating to AMR and SPMMP was not plentiful. A wide range of laboratory methods and breakpoint values (i.e. the concentration of antimicrobial used to assess sensitivity, tolerance or resistance) were used for the isolation of AMR bacteria.The identified papers provided evidence that AMR bacteria could be routinely isolated from SPMMP. There was no evidence that either confirmed or refuted that genetic materials capable of increasing AMR in non-AMR bacteria were present unprotected (i.e. outside of a cell or a capsid) in SPMMP. Statistical analyses were not straightforward because different authors used different laboratory methodologies.However, analyses using antibiotic organised into broadly-related groups indicated that Enterobacteriaceaeresistant to third generation cephalosporins might be an area of upcoming concern in SPMMP. The effective treatment of patients infected with Enterobacteriaceaeresistant to cephalosporins are a known clinical issue. No AMR associations with geography were observed and most of the publications identified tended to be from Europe and the far east.AMR Listeria monocytogenes and lactic acid bacteria could be tolerant to cleaning and disinfection in secondary processing environments. The basis of the tolerance could be genetic (e.g. efflux pumps) or environmental (e.g. biofilm growth). Persistent, plant resident, AMR L. monocytogenes were shown by one study to be the source of final product contamination. 4 AMR genes can be present in bacterial cultures used for the manufacture of fermented SPMMP. Furthermore, there was broad evidence that AMR loci could be transferred during meat fermentation, with refrigeration temperatures curtailing transfer rates. Given the potential for AMR transfer, it may be prudent to advise food business operators (FBOs) to use fermentation starter cultures that are AMR-free or not contained within easily mobilisable genetic elements. Thermal processing was seen to be the only secondary processing stage that served as a critical control point for numbers of AMR bacteria. There were significant linkages between some AMR genes in Salmonella. Quaternary ammonium compound (QAC) resistance genes were associated with copper, tetracycline and sulphonamide resistance by virtue of co-location on the same plasmid. No evidence was found that either supported or refuted that there was any association between AMR genes and genes that encoded an altered stress response or enhanced the survival of AMR bacteria exposed to harmful environmental conditions.

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Miller, Gad y Jeffrey F. Harper. Pollen fertility and the role of ROS and Ca signaling in heat stress tolerance. United States Department of Agriculture, enero de 2013. http://dx.doi.org/10.32747/2013.7598150.bard.

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The long-term goal of this research is to understand how pollen cope with stress, and identify genes that can be manipulated in crop plants to improve reproductive success during heat stress. The specific aims were to: 1) Compare heat stress dependent changes in gene expression between wild type pollen, and mutants in which pollen are heat sensitive (cngc16) or heat tolerant (apx2-1). 2) Compare cngc16 and apx2 mutants for differences in heat-stress triggered changes in ROS, cNMP, and Ca²⁺ transients. 3) Expand a mutant screen for pollen with increased or decreased thermo-tolerance. These aims were designed to provide novel and fundamental advances to our understanding of stress tolerance in pollen reproductive development, and enable research aimed at improving crop plants to be more productive under conditions of heat stress. Background: Each year crop yields are severely impacted by a variety of stress conditions, including heat, cold, drought, hypoxia, and salt. Reproductive development in flowering plants is highly sensitive to hot or cold temperatures, with even a single hot day or cold night sometimes being fatal to reproductive success. In many plants, pollen tube development and fertilization is often the weakest link. Current speculation about global climate change is that most agricultural regions will experience more extreme environmental fluctuations. With the human food supply largely dependent on seeds, it is critical that we consider ways to improve stress tolerance during fertilization. The heat stress response (HSR) has been intensively studied in vegetative tissues, but is poorly understood during reproductive development. A general paradigm is that HS is accompanied by increased production of reactive oxygen species (ROS) and induction of ROS-scavenging enzymes to protect cells from excess oxidative damage. The activation of the HSR has been linked to cytosolic Ca²⁺ signals, and transcriptional and translational responses, including the increased expression of heat shock proteins (HSPs) and antioxidative pathways. The focus of the proposed research was on two mutations, which have been discovered in a collaboration between the Harper and Miller labs, that either increase or decrease reproductive stress tolerance in a model plant, Arabidopsis thaliana (i.e., cngc16--cyclic nucleotide gated channel 16, apx2-1--ascorbate peroxidase 2,). Major conclusions, solutions, achievements. Using RNA-seq technology, the expression profiles of cngc16 and apx2 pollen grains were independently compared to wild type under favourable conditions and following HS. In comparison to a wild type HSR, there were 2,776 differences in the transcriptome response in cngc16 pollen, consistent with a model in which this heat-sensitive mutant fails to enact or maintain a normal wild-type HSR. In a comparison with apx2 pollen, there were 900 differences in the HSR. Some portion of these 900 differences might contribute to an improved HSR in apx2 pollen. Twenty-seven and 42 transcription factor changes, in cngc16 and apx2-1, respectively, were identified that could provide unique contributions to a pollen HSR. While we found that the functional HS-dependent reprogramming of the pollen transcriptome requires specific activity of CNGC16, we identified in apx2 specific activation of flavonol-biosynthesis pathway and auxin signalling that support a role in pollen thermotolerance. Results from this study have identified metabolic pathways and candidate genes of potential use in improving HS tolerance in pollen. Additionally, we developed new FACS-based methodology that can quantify the stress response for individual pollen in a high-throughput fashion. This technology is being adapted for biological screening of crop plant’s pollen to identify novel thermotolerance traits. Implications, both scientific and agricultural. This study has provided a reference data on the pollen HSR from a model plant, and supports a model that the HSR in pollen has many differences compared to vegetative cells. This provides an important foundation for understanding and improving the pollen HSR, and therefor contributes to the long-term goal of improving productivity in crop plants subjected to temperature stress conditions. A specific hypothesis that has emerged from this study is that pollen thermotolerance can be improved by increasing flavonol accumulation before or during a stress response. Efforts to test this hypothesis have been initiated, and if successful have the potential for application with major seed crops such as maize and rice.

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Bourgaux, Camille y Anni-Yasmin Turhan. Temporal Query Answering in DL-Lite over Inconsistent Data. Technische Universität Dresden, 2017. http://dx.doi.org/10.25368/2022.236.

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In ontology-based systems that process data stemming from different sources and that is received over time, as in context-aware systems, reasoning needs to cope with the temporal dimension and should be resilient against inconsistencies in the data. Motivated by such settings, this paper addresses the problem of handling inconsistent data in a temporal version of ontology-based query answering. We consider a recently proposed temporal query language that combines conjunctive queries with operators of propositional linear temporal logic and extend to this setting three inconsistency-tolerant semantics that have been introduced for querying inconsistent description logic knowledge bases. We investigate their complexity for DL-LiteR temporal knowledge bases, and furthermore complete the picture for the consistent case.

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Chen, Junping, Zach Adam y Arie Admon. The Role of FtsH11 Protease in Chloroplast Biogenesis and Maintenance at Elevated Temperatures in Model and Crop Plants. United States Department of Agriculture, mayo de 2013. http://dx.doi.org/10.32747/2013.7699845.bard.

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specific objectives of this proposal were to: 1) determine the location, topology, and oligomerization of FtsH11 protease; 2) identify the substrate/s of FtsH11 and the downstream components involved in maintaining thermostability of chloroplasts; 3) identify new elements involved in FtsH11 protease regulatory network related to HT adaptation processes in chloroplast; 4) Study the role of FtsH11 homologs from crop species in HT tolerance. Background to the topic: HT-tolerant varieties that maintain high photosynthetic efficiency at HT, and cope better with daily and seasonal temperature fluctuations are in great need to alleviate the effect of global warming on food production. Photosynthesis is a very complex process requiring accurate coordination of many complex systems and constant adjustments to the changing environments. Proteolytic activities mediated by various proteases in chloroplast are essential part of this process and critical for maintaining normal chloroplast functions under HT. However, little is known about mechanisms that contribute to adaptation of photosynthetic processes to HT. Our study has shown that a chloroplast-targeted Arabidopsis FtsH11 protease plays an essential and specific role in maintaining thermostability of thylakoids and normal photosynthesis at moderate HT. We hypothesized that FtsH11 homologs recently identified in other plant species might have roles similarly to that of AtFtsH1. Thus, dissecting the underlying mechanisms of FtsH11 in the adaptation mechanisms in chloroplasts to HT stress and other elements involved will aid our effort to produce more agricultural products in less favorable environments. Major conclusions, solutions, achievements - Identified the chloroplast inner envelope membrane localization of FtsH11. - Revealed a specific association of FtsH11 with the a and b subunits of CPN60. - Identified the involvement of ARC6, a protein coordinates chloroplast division machineries in plants, in FtsH11 mediated HT adaptation process in chloroplast. -Reveal possible association of a polyribonucleotide nucleotidyltransferase (cpPNPase), coded by At3G03710, with FtsH11 mediated HT adaptation process in chloroplast. - Mapped 4 additional loci in FtsH11 mediated HT adaptation network in chloroplast. - Demonstrated importance of the proteolytic activity of FtsH11 for thermotolerance, in addition to the ATPase activity. - Demonstrated a conserved role of plant FtsH11 proteases in chloroplast biogenesis and in maintaining structural and functional thermostability of chloroplast at elevated temperatures. Implications, both scientific and agricultural:Three different components interacting with FtsH11 were identified during the course of this study. At present, it is not known whether these proteins are directly involved in FtsH11mediated thermotolerance network in chloroplast and/or how these elements are interrelated. Studies aiming to connect the dot among biological functions of these networks are underway in both labs. Nevertheless, in bacteria where it was first studied, FtsH functions in heat shock response by regulating transcription level of σ32, a heat chock factor regulates HSPsexpression. FtsH also involves in control of biosynthesis of membrane components and quality control of membrane proteins etc. In plants, both Arc 6 and CPN60 identified in this study are essential in chloroplast division and developments as mutation of either one impairs chloroplast division in Arabidopsis. The facts that we have found the specific association of both α and β CPN60 with FtsH11 protein biochemically, the suppression/ enhancement of ftsh11 thermosensitive phenotype by arc6 /pnp allele genetically, implicate inter-connection of these networks via FtsH11 mediated network(s) in regulating the dynamic adaptation processes of chloroplast to temperature increases at transcriptional, translational and post-translational levels. The conserved role of FtsH11 proteases in maintaining thermostability of chloroplast at HT demonstrated here provides a foundation for improving crop photosynthetic performance at high temperatures.

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Steffens, John C. y Eithan Harel. Polyphenol Oxidases- Expression, Assembly and Function. United States Department of Agriculture, enero de 1995. http://dx.doi.org/10.32747/1995.7571358.bard.

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Polyphenol oxidases (PPOs) participate in the preparation of many plant products on the one hand and cause considerable losses during processing of plant products on the other hand. However, the physiological functions of plant PPO were still a subject of controversy at the onset of the project. Preliminary observations that suggested involvement of PPOs in resistance to herbivores and pathogens held great promise for application in agriculture but required elucidation of PPO's function if modulation of PPO expression is to be considered for improving plant protection or storage and processing of plant products. Suggestions on a possible role of PPO in various aspects of chloroplast metabolism were also relevant in this context. The characterization of plant PPO genes opened a way for achieving these goals. We reasoned that "understanding PPO targeting and routing, designing ways to manipulate its expression and assessing the effects of such modifications will enable determination of the true properties of the enzyme and open the way for controlling its activity". The objective of the project was to "obtain an insight into the function and biological significance of PPOs" by examining possible function(s) of PPO in photosynthesis and plant-pest interactions using transgenic tomato plants; extending our understanding of PPO routing and assembly and the mechanism of its thylakoid translocation; preparing recombinant PPOs for use in import studies, determination of the genuine properties of PPOs and understanding its assembly and determining the effect of PPO's absence on chloroplast performance. Results obtained during work on the project made it necessary to abandon some minor objectives and devote the effort to more promising topics. Such changes are mentioned in the 'Body of the report' which is arranged according to the objectives of the original proposal. The complex expression pattern of tomato PPO gene family was determined. Individual members of the family are differentially expressed in various parts of the plant and subjected to developmentally regulated turnover. Some members are differentially regulated also by pathogens, wounding and chemical wound signals. Wounding systemically induces PPO activity and level in potato. Only tissues that are developmentally competent to express PPO are capable of responding to the systemic wounding signal by increased accumulation of PPO mRNA. Down regulation of PPO genes causes hyper susceptibility to leaf pathogens in tomato while over expression regulation of PPO expression in tomato plants is their apparent increased tolerance to drought. Both the enhanced disease resistance conferred by PPO over expression and the increased stress tolerance due to down regulation can be used in the engineering of improved crop plants. Photosynthesis rate and variable fluorescence measurements in wild type, and PPO-null and over expressing transgenic tomato lines suggest that PPO does not enable plants to cope better with stressful high light intensities or reactive oxygen species. Rather high levels of the enzyme aggravate the damage caused under such conditions. Our work suggests that PPO's primary role is in defending plants against pathogens and herbivores. Jasmonate and ethylene, and apparently also salicylate, signals involved in responses to wounding and defense against herbivores and pathogens, enhance markedly and specifically the competence of chloroplasts to import and process pPPO. The interaction of the precursor with thylakoid membranes is primarily affected. The routing of PPO shows other unusual properties: stromal processing occurs in two sites, resulting in intermediates that are translocated across thylakoids by two different mechanisms - a DpH- and a Sec-dependent one. It is suggested that the dual pattern of processing and routing constitutes a'fail safe' mechanism, reflecting the need for a rapid and flexible response to defense challenges. Many of the observations described above should be taken into consideration when manipulation of PPO expression is contemplated for use in crop improvement.

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Yahav, Shlomo, John McMurtry y Isaac Plavnik. Thermotolerance Acquisition in Broiler Chickens by Temperature Conditioning Early in Life. United States Department of Agriculture, 1998. http://dx.doi.org/10.32747/1998.7580676.bard.

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The research on thermotolerance acquisition in broiler chickens by temperature conditioning early in life was focused on the following objectives: a. To determine the optimal timing and temperature for inducing the thermotolerance, conditioning processes and to define its duration during the first week of life in the broiler chick. b. To investigate the response of skeletal muscle tissue and the gastrointestinal tract to thermal conditioning. This objective was added during the research, to understand the mechanisms related to compensatory growth. c. To evaluate the effect of early thermo conditioning on thermoregulation (heat production and heat dissipation) during 3 phases: (1) conditioning, (2) compensatory growth, (3) heat challenge. d. To investigate how induction of improved thermotolerance impacts on metabolic fuel and the hormones regulating growth and metabolism. Recent decades have seen significant development in the genetic selection of the meat-type fowl (i.e., broiler chickens); leading to rapid growth and increased feed efficiency, providing the poultry industry with heavy chickens in relatively short growth periods. Such development necessitates parallel increases in the size of visceral systems such as the cardiovascular and the respiratory ones. However, inferior development of such major systems has led to a relatively low capability to balance energy expenditure under extreme conditions. Thus, acute exposure of chickens to extreme conditions (i.e., heat spells) has resulted in major economic losses. Birds are homeotherms, and as such, they are able to maintain their body temperature within a narrow range. To sustain thermal tolerance and avoid the deleterious consequences of thermal stresses, a direct response is elicited: the rapid thermal shock response - thermal conditioning. This technique of temperature conditioning takes advantage of the immaturity of the temperature regulation mechanism in young chicks during their first week of life. Development of this mechanism involves sympathetic neural activity, integration of thermal infom1ation in the hypothalamus, and buildup of the body-to-brain temperature difference, so that the potential for thermotolerance can be incorporated into the developing thermoregulation mechanisms. Thermal conditioning is a unique management tool, which most likely involves hypothalamic them1oregulatory threshold changes that enable chickens, within certain limits, to cope with acute exposure to unexpected hot spells. Short-tem1 exposure to heat stress during the first week of life (37.5+1°C; 70-80% rh; for 24 h at 3 days of age) resulted in growth retardation followed immediately by compensatory growth" which resulted in complete compensation for the loss of weight gain, so that the conditioned chickens achieved higher body weight than that of the controls at 42 days of age. The compensatory growth was partially explained by its dramatic positive effect on the proliferation of muscle satellite cells which are necessary for further muscle hypertrophy. By its significant effect of the morphology and functioning of the gastrointestinal tract during and after using thermal conditioning. The significant effect of thermal conditioning on the chicken thermoregulation was found to be associated with a reduction in heat production and evaporative heat loss, and with an increase in sensible heat loss. It was further accompanied by changes in hormones regulating growth and metabolism These physiological responses may result from possible alterations in PO/AH gene expression patterns (14-3-3e), suggesting a more efficient mechanism to cope with heat stress. Understanding the physiological mechanisms behind thermal conditioning step us forward to elucidate the molecular mechanism behind the PO/AH response, and response of other major organs. The thermal conditioning technique is used now in many countries including Israel, South Korea, Australia, France" Ecuador, China and some places in the USA. The improvement in growth perfom1ance (50-190 g/chicken) and thermotolerance as a result of postnatal thermal conditioning, may initiate a dramatic improvement in the economy of broiler's production.

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