223 research outputs found
A novel constrained LArge Time INcrement method for modelling quasi-brittle failure
No full textA novel LArge Time INcrement (LATIN) method is developed. At variance with existing LATIN methods, the proposed algorithm is capable of tracing snap-backs in quasi-brittle materials. Special attention is given to algorithmic implementation as well as to robust and automated choice of algorithmic variables. The performance of the method is verified by its application to numerical examples exhibiting snap-back and bifurcation phenomena in their mechanical response
Mesoscopic modelling of masonry using weak and strong discontinuities
No full textA mesoscopic masonry model is presented in which joints are modelled by weak and strong discontinuities through the partition of unity property of finite element shape functions. A Drucker-Prager damage model describes joint degradation whereas the bricks remain linear elastic throughout the simulations. Analogies and differences amongst strong and weak discontinuity models are discussed, with special emphasis on kinematic description and implementation. Mesh sensitivity and performance of the presented models are illustrated by two-brick, three-point bending and shear wall tests
Effects of protective panels on charring of timber elements in timber frame assemblies
No full textPanels protect timber elements in timber frame assemblies during fire. The influence of the panels can be incorporated into calculations according to EN 1995-1-2, Annex C. The number of panels incorporated in this standard is limited. Moreover, the calculations performed according to this standard result in overestimation of the charred area. In this work, experimental analysis of the protective behaviour was performed. Small scale fire tests were used to monitor the temperature inside the timber element and the timber frame assembly. The measured results are compared with calculations according to the standard.The authors would like to acknowledge NBN (www.NBN.be) and FOD economy for the financial support to this project
Experimental and analytical assessment of racking resistance of partially anchored timber frame walls
No full textThe resistance to horizontal loads provided by timber constructions is determined by the racking resistance of the timber frame walls within the structure. In Eurocode 5 (EN 1995-1-1), two methods are described to assess the racking resistance of these structural elements. Method A refers to a mechanical model while method B is empirically based and therefore less attractive. When using method A, the full anchorage of the leading stud is needed. Moreover contributions of wall panels with openings in the racking resistance is neglected. In this paper, an experimental campaign studying the racking resistance of partially anchored walls with different wall and loading configurations is presented. The study shows that window and door openings lead to a reduction of the racking resistance of the wall depending on the size of the opening. Additionally, a comparison between the experimental data and several design methods for the assessment of the racking resistance of the wall panels is made
Three-dimensional modelling of masonry using the partition of unity method
No full textThis paper uses the Generalized Finite Element method for the introduction of the cohesive joint behaviour to model masonry. Cracked joints are modelled as displacement discontinuities and are introduced in the finite element model by additional degrees of freedom. These degrees of freedom are activated when the stress state in the joint reaches a critical level. The joint behaviour is governed by a rigid plasticity model.Structural EngineeringCivil Engineering and Geoscience
A smooth yield surface based on interpolation of Bézier curves for masonry modelling
No full textA smooth yield surface for the modelling of masonry on mesoscopic scale is presented, using interpolation by second order Bzier curves. The cracked joints are modelled as displacement discontinuities using the partition of unity property of finite element shape functions.Structural EngineeringCivil Engineering and Geoscience
Do Management Profiles Matter? An Analysis of Belgian Dairy Farmers
No full textTo assess the performance of a farmer and to identify best practice among a group of farmers, the assumption is often made that all farmers maximize profits and thus share the same business goals. However, performance differs due to personal characteristics, objectives and strategies. A survey carried out among 73 Belgian dairy farmers revealed that for only 34% of the farmers "profit maximization" is a primary objective. A regression analysis revealed that self-declared profit maximizers only obtained a higher farm income per liter, not per labour unit. Through cluster analysis, four main groups of farmers were found with similar objectives and management ideas: (A) risk-taking and progressive cow farmers, (B) riskaverse and progressive labour savers, (C) risk-neutral and relatively conservative profit maximizers and (D) risk-averse and conservative cow farmers. Gross margin per liter was highest for the labour savers. Other performance parameters were higher for cluster B only compared to cluster D. Scale economies were found for all performance parameters except for gross margin per liter.farm management, farmers' objectives, farm performance, dairy, extension, Farm Management,
The use of a real-time luciferase assay to quantify gene expression dynamics in the living yeast cell
No full text[EN] A destabilized version of firefly luciferase was used in living yeast cells as a real-time reporter for gene expression. This highly sensitive and non-invasive system can be simultaneously used upon many different experimental conditions in small culture aliquots. This allows the dose-response behaviour of gene expression driven by any yeast promoter to be reported and can be used to quantify important parameters, such as the threshold, sensitivity, response time, maximal activity and synthesis rate for a given stimulus. We applied the luciferase assay to the nutrient-regulated GAL1 promoter and the stress-responsive GRE2 promoter. We find that luciferase expression driven by the GAL1 promoter responds dynamically to growing galactose concentrations, with increasing synthesis rates determined by the light increment in the initial linear phase of activation. In the case of the GRE2 promoter, we demonstrate that the very short-lived version of luciferase used here is an excellent tool to quantitatively describe transient transcriptional activation. The luciferase expression controlled by the GRE2 promoter responds dynamically to a gradual increase of osmotic or oxidative stress stimuli, which is mainly based on the progressive increase of the time the promoter remains active. Finally, we determined the dose-response behaviour of a single transcription factor binding site in a synthetic promoter context, using the stress response element (STRE) as an example. Taken together, the luciferase assay described here is an attractive tool to rapidly and precisely determine and compare kinetic parameters of gene expression. Copyright (c) 2012 John Wiley & Sons, Ltd.We thank Takayoshi Kuno for the kind gift of plasmid pGL3, containing the destabilized firefly luciferase gene. This study was supported by the Ministerio de Ciencia e Innovacion (Grant Nos BFU2008-00271 and BFU2011-23326). A.R. is the recipient of an FPI predoctoral fellowship from the Ministerio de Ciencia e Innovacion.Rienzo, A.; Pascual-Ahuir Giner, MD.; Proft, MH. (2012). The use of a real-time luciferase assay to quantify gene expression dynamics in the living yeast cell. Yeast. 29(6):219-231. doi:10.1002/yea.2905S219231296Alberti, S., Gitler, A. D., & Lindquist, S. (2007). A suite of Gateway®cloning vectors for high-throughput genetic analysis inSaccharomyces cerevisiae. Yeast, 24(10), 913-919. doi:10.1002/yea.1502Cormack, B. (1998). Green fluorescent protein as a reporter of transcription and protein localization in fungi. Current Opinion in Microbiology, 1(4), 406-410. doi:10.1016/s1369-5274(98)80057-xDeng, L., Sugiura, R., Takeuchi, M., Suzuki, M., Ebina, H., Takami, T., … Kuno, T. (2006). Real-Time Monitoring of Calcineurin Activity in Living Cells: Evidence for Two Distinct Ca2+-dependent Pathways in Fission Yeast. Molecular Biology of the Cell, 17(11), 4790-4800. doi:10.1091/mbc.e06-06-0526Gasch, A. P. (2007). Comparative genomics of the environmental stress response in ascomycete fungi. Yeast, 24(11), 961-976. doi:10.1002/yea.1512Hahn, S., & Young, E. T. (2011). Transcriptional Regulation inSaccharomyces cerevisiae: Transcription Factor Regulation and Function, Mechanisms of Initiation, and Roles of Activators and Coactivators. Genetics, 189(3), 705-736. doi:10.1534/genetics.111.127019Harbison, C. T., Gordon, D. B., Lee, T. I., Rinaldi, N. J., Macisaac, K. D., Danford, T. W., … Young, R. A. (2004). Transcriptional regulatory code of a eukaryotic genome. Nature, 431(7004), 99-104. doi:10.1038/nature02800Kuge, S. (1997). Regulation of yAP-1 nuclear localization in response to oxidative stress. The EMBO Journal, 16(7), 1710-1720. doi:10.1093/emboj/16.7.1710Kundu, S., & Peterson, C. L. (2010). Dominant Role for Signal Transduction in the Transcriptional Memory of Yeast GAL Genes. Molecular and Cellular Biology, 30(10), 2330-2340. doi:10.1128/mcb.01675-09Marchler, G., Schüller, C., Adam, G., & Ruis, H. (1993). A Saccharomyces cerevisiae UAS element controlled by protein kinase A activates transcription in response to a variety of stress conditions. The EMBO Journal, 12(5), 1997-2003. doi:10.1002/j.1460-2075.1993.tb05849.xMartínez-Montañés, F., Pascual-Ahuir, A., & Proft, M. (2010). Toward a Genomic View of the Gene Expression Program Regulated by Osmostress in Yeast. OMICS: A Journal of Integrative Biology, 14(6), 619-627. doi:10.1089/omi.2010.0046Martínez-Pastor, M. T., Marchler, G., Schüller, C., Marchler-Bauer, A., Ruis, H., & Estruch, F. (1996). The Saccharomyces cerevisiae zinc finger proteins Msn2p and Msn4p are required for transcriptional induction through the stress response element (STRE). The EMBO Journal, 15(9), 2227-2235. doi:10.1002/j.1460-2075.1996.tb00576.xMateus, C., & Avery, S. V. (2000). Destabilized green fluorescent protein for monitoring dynamic changes in yeast gene expression with flow cytometry. Yeast, 16(14), 1313-1323. doi:10.1002/1097-0061(200010)16:143.0.co;2-oJ. Miraglia, L., J. King, F., & Damoiseaux, R. (2011). Seeing the Light: Luminescent Reporter Gene Assays. Combinatorial Chemistry & High Throughput Screening, 14(8), 648-657. doi:10.2174/138620711796504389Ni, L., Bruce, C., Hart, C., Leigh-Bell, J., Gelperin, D., Umansky, L., … Snyder, M. (2009). Dynamic and complex transcription factor binding during an inducible response in yeast. Genes & Development, 23(11), 1351-1363. doi:10.1101/gad.1781909Pelet, S., Rudolf, F., Nadal-Ribelles, M., de Nadal, E., Posas, F., & Peter, M. (2011). Transient Activation of the HOG MAPK Pathway Regulates Bimodal Gene Expression. Science, 332(6030), 732-735. doi:10.1126/science.1198851Proft, M. (2001). Regulation of the Sko1 transcriptional repressor by the Hog1 MAP kinase in response to osmotic stress. The EMBO Journal, 20(5), 1123-1133. doi:10.1093/emboj/20.5.1123Proft, M., & Struhl, K. (2004). MAP Kinase-Mediated Stress Relief that Precedes and Regulates the Timing of Transcriptional Induction. Cell, 118(3), 351-361. doi:10.1016/j.cell.2004.07.016Rep, M., Proft, M., Remize, F., Tamas, M., Serrano, R., Thevelein, J. M., & Hohmann, S. (2001). The Saccharomyces cerevisiae Sko1p transcription factor mediates HOG pathway-dependent osmotic regulation of a set of genes encoding enzymes implicated in protection from oxidative damage. Molecular Microbiology, 40(5), 1067-1083. doi:10.1046/j.1365-2958.2001.02384.xRobertson, J. B., & Johnson, C. H. (2011). Luminescence as a Continuous Real-Time Reporter of Promoter Activity in Yeast Undergoing Respiratory Oscillations or Cell Division Rhythms. Yeast Genetic Networks, 63-79. doi:10.1007/978-1-61779-086-7_4Robertson, J. B., Stowers, C. C., Boczko, E., & Hirschie Johnson, C. (2008). Real-time luminescence monitoring of cell-cycle and respiratory oscillations in yeast. Proceedings of the National Academy of Sciences, 105(46), 17988-17993. doi:10.1073/pnas.0809482105Varela, J. C., Praekelt, U. M., Meacock, P. A., Planta, R. J., & Mager, W. H. (1995). The Saccharomyces cerevisiae HSP12 gene is activated by the high-osmolarity glycerol pathway and negatively regulated by protein kinase A. Molecular and Cellular Biology, 15(11), 6232-6245. doi:10.1128/mcb.15.11.6232Yosef, N., & Regev, A. (2011). Impulse Control: Temporal Dynamics in Gene Transcription. Cell, 144(6), 886-896. doi:10.1016/j.cell.2011.02.01
Deciphering dynamic dose responses of natural promoters and single cis elements upon osmotic and oxidative stress in yeast
No full text[EN] Fine-tuned activation of gene expression in response to stress is the result of dynamic interactions of transcription factors with specific promoter binding sites. In the study described here we used a time-resolved luciferase reporter assay in living Saccharomyces cerevisiae yeast cells to gain insights into how osmotic and oxidative stress signals modulate gene expression in a dose-sensitive manner. Specifically, the dose-response behavior of four different natural promoters (GRE2, CTT1, SOD2, and CCP1) reveals differences in their sensitivity and dynamics in response to different salt and oxidative stimuli. Characteristic dose-response profiles were also obtained for artificial promoters driven by only one type of stress-regulated consensus element, such as the cyclic AMP-responsive element, stress response element, or AP-1 site. Oxidative and osmotic stress signals activate these elements separately and with different sensitivities through different signaling molecules. Combination of stress-activated cis elements does not, in general, enhance the absolute expression levels; however, specific combinations can increase the inducibility of the promoter in response to different stress doses. Finally, we show that the stress tolerance of the cell critically modulates the dynamics of its transcriptional response in the case of oxidative stress.This work was supported by the Ministerio de Economa y Competitividad (grant BFU2011-23326 to M.P.) and the Ministerio de Ciencia e Innovacion (predoctoral FPI grant to A.R.).Dolz Edo, L.; Rienzo, A.; Poveda Huertes, D.; Pascual-Ahuir Giner, MD.; Proft, MH. (2013). Deciphering dynamic dose responses of natural promoters and single cis elements upon osmotic and oxidative stress in yeast. Molecular and Cellular Biology. 33(11):2228-2240. https://doi.org/10.1128/MCB.00240-13S222822403311Gasch, A. P., Spellman, P. T., Kao, C. M., Carmel-Harel, O., Eisen, M. B., Storz, G., … Brown, P. O. (2000). Genomic Expression Programs in the Response of Yeast Cells to Environmental Changes. Molecular Biology of the Cell, 11(12), 4241-4257. doi:10.1091/mbc.11.12.4241Ni, L., Bruce, C., Hart, C., Leigh-Bell, J., Gelperin, D., Umansky, L., … Snyder, M. (2009). Dynamic and complex transcription factor binding during an inducible response in yeast. Genes & Development, 23(11), 1351-1363. doi:10.1101/gad.1781909Posas, F., Chambers, J. R., Heyman, J. A., Hoeffler, J. P., de Nadal, E., & Ariño, J. (2000). The Transcriptional Response of Yeast to Saline Stress. Journal of Biological Chemistry, 275(23), 17249-17255. doi:10.1074/jbc.m910016199Rep, M., Krantz, M., Thevelein, J. M., & Hohmann, S. (2000). The Transcriptional Response ofSaccharomyces cerevisiaeto Osmotic Shock. Journal of Biological Chemistry, 275(12), 8290-8300. doi:10.1074/jbc.275.12.8290Yale, J., & Bohnert, H. J. (2001). Transcript Expression inSaccharomyces cerevisiaeat High Salinity. Journal of Biological Chemistry, 276(19), 15996-16007. doi:10.1074/jbc.m008209200Causton, H. C., Ren, B., Koh, S. S., Harbison, C. T., Kanin, E., Jennings, E. G., … Young, R. A. (2001). Remodeling of Yeast Genome Expression in Response to Environmental Changes. Molecular Biology of the Cell, 12(2), 323-337. doi:10.1091/mbc.12.2.323Martínez-Pastor, M. T., Marchler, G., Schüller, C., Marchler-Bauer, A., Ruis, H., & Estruch, F. (1996). The Saccharomyces cerevisiae zinc finger proteins Msn2p and Msn4p are required for transcriptional induction through the stress response element (STRE). The EMBO Journal, 15(9), 2227-2235. doi:10.1002/j.1460-2075.1996.tb00576.xSchmitt, A. P., & McEntee, K. (1996). Msn2p, a zinc finger DNA-binding protein, is the transcriptional activator of the multistress response in Saccharomyces cerevisiae. Proceedings of the National Academy of Sciences, 93(12), 5777-5782. doi:10.1073/pnas.93.12.5777Beck, T., & Hall, M. N. (1999). The TOR signalling pathway controls nuclear localization of nutrient-regulated transcription factors. Nature, 402(6762), 689-692. doi:10.1038/45287Gorner, W., Durchschlag, E., Martinez-Pastor, M. T., Estruch, F., Ammerer, G., Hamilton, B., … Schuller, C. (1998). Nuclear localization of the C2H2 zinc finger protein Msn2p is regulated by stress and protein kinase A activity. Genes & Development, 12(4), 586-597. doi:10.1101/gad.12.4.586Saito, H., & Posas, F. (2012). Response to Hyperosmotic Stress. Genetics, 192(2), 289-318. doi:10.1534/genetics.112.140863De Nadal, E., Ammerer, G., & Posas, F. (2011). Controlling gene expression in response to stress. Nature Reviews Genetics, 12(12), 833-845. doi:10.1038/nrg3055Martínez-Montañés, F., Pascual-Ahuir, A., & Proft, M. (2010). Toward a Genomic View of the Gene Expression Program Regulated by Osmostress in Yeast. OMICS: A Journal of Integrative Biology, 14(6), 619-627. doi:10.1089/omi.2010.0046Alepuz, P. M. (2003). Osmostress-induced transcription by Hot1 depends on a Hog1-mediated recruitment of the RNA Pol II. The EMBO Journal, 22(10), 2433-2442. doi:10.1093/emboj/cdg243Nadal, E. d., Casadome, L., & Posas, F. (2003). Targeting the MEF2-Like Transcription Factor Smp1 by the Stress-Activated Hog1 Mitogen-Activated Protein Kinase. Molecular and Cellular Biology, 23(1), 229-237. doi:10.1128/mcb.23.1.229-237.2003Proft, M. (2001). Regulation of the Sko1 transcriptional repressor by the Hog1 MAP kinase in response to osmotic stress. The EMBO Journal, 20(5), 1123-1133. doi:10.1093/emboj/20.5.1123Proft, M., & Serrano, R. (1999). Repressors and Upstream Repressing Sequences of the Stress-RegulatedENA1Gene inSaccharomyces cerevisiae: bZIP Protein Sko1p Confers HOG-Dependent Osmotic Regulation. Molecular and Cellular Biology, 19(1), 537-546. doi:10.1128/mcb.19.1.537Rep, M., Reiser, V., Gartner, U., Thevelein, J. M., Hohmann, S., Ammerer, G., & Ruis, H. (1999). Osmotic Stress-Induced Gene Expression inSaccharomyces cerevisiaeRequires Msn1p and the Novel Nuclear Factor Hot1p. Molecular and Cellular Biology, 19(8), 5474-5485. doi:10.1128/mcb.19.8.5474Ruiz-Roig, C., Noriega, N., Duch, A., Posas, F., & de Nadal, E. (2012). The Hog1 SAPK controls the Rtg1/Rtg3 transcriptional complex activity by multiple regulatory mechanisms. Molecular Biology of the Cell, 23(21), 4286-4296. doi:10.1091/mbc.e12-04-0289Vendrell, A., Martínez-Pastor, M., González-Novo, A., Pascual-Ahuir, A., Sinclair, D. A., Proft, M., & Posas, F. (2011). Sir2 histone deacetylase prevents programmed cell death caused by sustained activation of the Hog1 stress-activated protein kinase. EMBO reports, 12(10), 1062-1068. doi:10.1038/embor.2011.154De Nadal, E., Zapater, M., Alepuz, P. M., Sumoy, L., Mas, G., & Posas, F. (2004). The MAPK Hog1 recruits Rpd3 histone deacetylase to activate osmoresponsive genes. Nature, 427(6972), 370-374. doi:10.1038/nature02258Proft, M., & Struhl, K. (2002). Hog1 Kinase Converts the Sko1-Cyc8-Tup1 Repressor Complex into an Activator that Recruits SAGA and SWI/SNF in Response to Osmotic Stress. Molecular Cell, 9(6), 1307-1317. doi:10.1016/s1097-2765(02)00557-9Zapater, M., Sohrmann, M., Peter, M., Posas, F., & de Nadal, E. (2007). Selective Requirement for SAGA in Hog1-Mediated Gene Expression Depending on the Severity of the External Osmostress Conditions. Molecular and Cellular Biology, 27(11), 3900-3910. doi:10.1128/mcb.00089-07Capaldi, A. P., Kaplan, T., Liu, Y., Habib, N., Regev, A., Friedman, N., & O’Shea, E. K. (2008). Structure and function of a transcriptional network activated by the MAPK Hog1. Nature Genetics, 40(11), 1300-1306. doi:10.1038/ng.235Cook, K. E., & O’Shea, E. K. (2012). Hog1 Controls Global Reallocation of RNA Pol II upon Osmotic Shock in Saccharomyces cerevisiae. G3: Genes|Genomes|Genetics, 2(9), 1129-1136. doi:10.1534/g3.112.003251Proft, M., Gibbons, F. D., Copeland, M., Roth, F. P., & Struhl, K. (2005). Genomewide Identification of Sko1 Target Promoters Reveals a Regulatory Network That Operates in Response to Osmotic Stress inSaccharomyces cerevisiae. Eukaryotic Cell, 4(8), 1343-1352. doi:10.1128/ec.4.8.1343-1352.2005Vincent, A. C., & Struhl, K. (1992). ACR1, a yeast ATF/CREB repressor. Molecular and Cellular Biology, 12(12), 5394-5405. doi:10.1128/mcb.12.12.5394Wong, K. H., & Struhl, K. (2011). The Cyc8-Tup1 complex inhibits transcription primarily by masking the activation domain of the recruiting protein. Genes & Development, 25(23), 2525-2539. doi:10.1101/gad.179275.111Ikner, A., & Shiozaki, K. (2005). Yeast signaling pathways in the oxidative stress response. Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, 569(1-2), 13-27. doi:10.1016/j.mrfmmm.2004.09.006Temple, M. D., Perrone, G. G., & Dawes, I. W. (2005). Complex cellular responses to reactive oxygen species. Trends in Cell Biology, 15(6), 319-326. doi:10.1016/j.tcb.2005.04.003Toone, W. M., & Jones, N. (1999). AP-1 transcription factors in yeast. Current Opinion in Genetics & Development, 9(1), 55-61. doi:10.1016/s0959-437x(99)80008-2Brombacher, K., Fischer, B. B., Rüfenacht, K., & Eggen, R. I. L. (2006). The role of Yap1p and Skn7p-mediated oxidative stress response in the defence ofSaccharomyces cerevisiae against singlet oxygen. Yeast, 23(10), 741-750. doi:10.1002/yea.1392Lee, J., Godon, C., Lagniel, G., Spector, D., Garin, J., Labarre, J., & Toledano, M. B. (1999). Yap1 and Skn7 Control Two Specialized Oxidative Stress Response Regulons in Yeast. Journal of Biological Chemistry, 274(23), 16040-16046. doi:10.1074/jbc.274.23.16040Fernandes, L., Rodrigues-Pousada, C., & Struhl, K. (1997). Yap, a novel family of eight bZIP proteins in Saccharomyces cerevisiae with distinct biological functions. Molecular and Cellular Biology, 17(12), 6982-6993. doi:10.1128/mcb.17.12.6982Gulshan, K., Rovinsky, S. A., Coleman, S. T., & Moye-Rowley, W. S. (2005). Oxidant-specific Folding of Yap1p Regulates Both Transcriptional Activation and Nuclear Localization. Journal of Biological Chemistry, 280(49), 40524-40533. doi:10.1074/jbc.m504716200Kuge, S. (1997). Regulation of yAP-1 nuclear localization in response to oxidative stress. The EMBO Journal, 16(7), 1710-1720. doi:10.1093/emboj/16.7.1710Delaunay, A., Isnard, A.-D., & Toledano, M. B. (2000). H2O2 sensing through oxidation of the Yap1 transcription factor. The EMBO Journal, 19(19), 5157-5166. doi:10.1093/emboj/19.19.5157Kuge, S., Arita, M., Murayama, A., Maeta, K., Izawa, S., Inoue, Y., & Nomoto, A. (2001). Regulation of the Yeast Yap1p Nuclear Export Signal Is Mediated by Redox Signal-Induced Reversible Disulfide Bond Formation. Molecular and Cellular Biology, 21(18), 6139-6150. doi:10.1128/mcb.21.18.6139-6150.2001Koziol, S., Zagulski, M., Bilinski, T., & Bartosz, G. (2005). Antioxidants protect the yeastSaccharomyces cerevisiaeagainst hypertonic stress. Free Radical Research, 39(4), 365-371. doi:10.1080/10715760500045855Bilsland, E., Molin, C., Swaminathan, S., Ramne, A., & Sunnerhagen, P. (2004). Rck1 and Rck2 MAPKAP kinases and the HOG pathway are required for oxidative stress resistance. Molecular Microbiology, 53(6), 1743-1756. doi:10.1111/j.1365-2958.2004.04238.xRienzo, A., Pascual-Ahuir, A., & Proft, M. (2012). The use of a real-time luciferase assay to quantify gene expression dynamics in the living yeast cell. Yeast, 29(6), 219-231. doi:10.1002/yea.2905Baker Brachmann, C., Davies, A., Cost, G. J., Caputo, E., Li, J., Hieter, P., & Boeke, J. D. (1998). Designer deletion strains derived fromSaccharomyces cerevisiae S288C: A useful set of strains and plasmids for PCR-mediated gene disruption and other applications. Yeast, 14(2), 115-132. doi:10.1002/(sici)1097-0061(19980130)14:23.0.co;2-2Winzeler, E. A. (1999). Functional Characterization of the S. cerevisiae Genome by Gene Deletion and Parallel Analysis. Science, 285(5429), 901-906. doi:10.1126/science.285.5429.901Galiazzo, F., & Labbe-Bois, R. (1993). Regulation of Cu,Zn- and Mn-superoxide dismutase transcription in Saccharomyces cerevisiae. FEBS Letters, 315(2), 197-200. doi:10.1016/0014-5793(93)81162-sGaray-Arroyo, A., & Covarrubias, A. A. (1999). Three genes whose expression is induced by stress inSaccharomyces cerevisiae. Yeast, 15(10A), 879-892. doi:10.1002/(sici)1097-0061(199907)15:10a3.0.co;2-qKwon, M. (2003). Oxidative stresses elevate the expression of cytochrome c peroxidase in Saccharomyces cerevisiae. Biochimica et Biophysica Acta (BBA) - General Subjects, 1623(1), 1-5. doi:10.1016/s0304-4165(03)00151-xPascual-Ahuir, A., Posas, F., Serrano, R., & Proft, M. (2001). Multiple Levels of Control Regulate the Yeast cAMP-response Element-binding Protein Repressor Sko1p in Response to Stress. Journal of Biological Chemistry, 276(40), 37373-37378. doi:10.1074/jbc.m105755200Schüller, C., Brewster, J. L., Alexander, M. R., Gustin, M. C., & Ruis, H. (1994). The HOG pathway controls osmotic regulation of transcription via the stress response element (STRE) of the Saccharomyces cerevisiae CTT1 gene. The EMBO Journal, 13(18), 4382-4389. doi:10.1002/j.1460-2075.1994.tb06758.xAguilera, J., & Prieto, J. (2001). The Saccharomyces cerevisiae aldose reductase is implied in the metabolism of methylglyoxal in response to stress conditions. Current Genetics, 39(5-6), 273-283. doi:10.1007/s002940100213Aguilera, J., Rodríguez-Vargas, S., & Prieto, J. A. (2005). The HOG MAP kinase pathway is required for the induction of methylglyoxal-responsive genes and determines methylglyoxal resistance in Saccharomyces cerevisiae. Molecular Microbiology, 56(1), 228-239. doi:10.1111/j.1365-2958.2005.04533.xAzevedo, D., Tacnet, F., Delaunay, A., Rodrigues-Pousada, C., & Toledano, M. B. (2003). Two redox centers within Yap1 for H2O2 and thiol-reactive chemicals signaling. Free Radical Biology and Medicine, 35(8), 889-900. doi:10.1016/s0891-5849(03)00434-9Proft, M., & Struhl, K. (2004). MAP Kinase-Mediated Stress Relief that Precedes and Regulates the Timing of Transcriptional Induction. Cell, 118(3), 351-361. doi:10.1016/j.cell.2004.07.016Rep, M., Albertyn, J., Thevelein, J. M., Prior, B. A., & Hohmann, S. (1999). Different signalling pathways contribute to the control of GPD1 gene expression by osmotic stress in Saccharomyces cerevisiae. Microbiology, 145(3), 715-727. doi:10.1099/13500872-145-3-71
Bladschade in CAM bromelia's: een hydrofysiologische studie
No full textBladschade in CAM-bromelia's: een hydrofysiologische studie Het voorkomen van necrotische vlekken op de bladeren van Aechmea planten is een vaak voorkomend probleem in de bromeliateelt. Bladvlekken situer en zich voornamelijk op de bladbocht met uitlopers naar de bladtop. Deze vorm van bladschade doet zich voor in verschillende stadia van de brome lia productieketen; zowel onder serrecondities als tijdens verpakking en transport. Het aantal Aechmea kwekers neemt hierdoor gestaag af, w at onvermijdelijk zal leiden tot het verdwijnen van deze planten op de m arkt. Tot op heden ontbreekt een geïntegreerde studie van dit bladschade probl eem. Om het vertrouwen van Aechmea kwekers te bewaren is een wetenschapp elijk gefundeerd begrip van het onstaan van deze vorm van bladschade noo dzakelijk. Het onderzoeken en begrijpen van het bladschade inductiemecha nisme en de beïnvloedende factoren, vormde de uitdaging van deze doctora atsstudie. Dit onderzoek werd opgebouwd rond een preliminaire hypothese over het on tstaan van bladschade. Op microscopisch niveau vertaalde de bladschade z ich in gescheurde chlorenchymcellen, mogelijks veroorzaakt door letale t urgordrukken in het blad. De impact van hydrofysiologische parameters op de opbouw van turgordruk, vormde daarom het centrale element van deze t hesis. In een later stadium werden de bevindingen omgezet naar concrete teelttechnische parameters. Er werd aangetoond dat hoge relatieve luchtvochtigheid tijdens de nacht (98-100%), de transpiratie van CAM (crassulacean acid metabolism) plante n aanzienlijk kan verhinderen. Onder deze omstandigheden werd een verhog ing van de turgordruk in het blad genoteerd (+ 0.23 MPa in 24 uur). Het is bijgevolg ten sterkste aangeraden te sturen naar een luchtvochtigheid onder 95% door ventilatie, verwarming, of geforceerde condensatie op ko ude oppervlakken. Het langdurig nat zijn van bladeren (condensatie), wat extra wateropname veroorzaakt, is een belangrijke risicofactor voor het ontstaan van blad schade. Bladprikjes vertoonden immers verhoogde turgordrukken tot +0.3 M Pa, in minder dan 12 uur na incubatie in demiwater. Controle op bladcond ensatie vereist een gecombineerde registratie en verwerking van zowel de bladtemperatuur als de lucht dauwpunt temperatuur. Naast bladcondensatie verhoogt ook de normale watergift de kans op blads chade problemen. Organische zuurconcentraties in het blad vertoonden een simultaan verloop met de absolute osmotische potentiaal en de turgordru k. Bijgevolg is het aangewezen watergift te vermijden bij hoge zuurconce ntraties, meer bepaald in de vroege morgen. EC waarden in het blad bleken belangrijke parameters in de bladschade pr oblematiek. Inductie van bladschade was niet mogelijk bij EC waarden ond er 200 µS.cm-1; waarden boven 400 µS.cm-1 resulteerden echter in maximale bladschade. Daar ook genetische achtergrond een invloed heeft op bladschade gevoelig heid, werden twee Aechmea cultivars (sterk en matig gevoelig) getes t op diverse morfologische en fysiologische parameters, gerelateerd aan de plantwaterhuishouding. Aangetoonde verschillen tussen de twee cultiva rs op basis van deze parameters vormen een waardevolle aanvulling voor d e huidige selectiecriteria. Naast groeikracht zijn de gebruikte selectie procedures immers grotendeels gebaseerd op uitwendige plantkarakteristie ken, zoals kleurrijke bloeiwijzen, bladkleur en plantvorm. Als resultaat van dit onderzoek kunnen hydrenchym dikte en koolstofreser ve in de dagelijkse CAM-cyclus (zetmeel versus oplosbare suikers) als be langrijkste complementaire selectiecriteria vooropgesteld worden.status: Publishe
- …
