Relevant bibliographies by topics / Two component signalling systems

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'Two component signalling systems'

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Published: 6 September 2023

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Journal articles on the topic "Two component signalling systems"

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Perraud, Anne-Laure, Verena Weiss, and Roy Gross. "Signalling pathways in two-component phosphorelay systems." Trends in Microbiology 7, no. 3 (March 1999): 115–20. http://dx.doi.org/10.1016/s0966-842x(99)01458-4.

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Macielag, Mark J., and Raul Goldschmidt. "Inhibitors of bacterial two-component signalling systems." Expert Opinion on Investigational Drugs 9, no. 10 (October 2000): 2351–69. http://dx.doi.org/10.1517/13543784.9.10.2351.

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Pawelczyk, Sonja, Kathryn A. Scott, Rebecca Hamer, Gareth Blades, Charlotte M. Deane, and George H. Wadhams. "Predicting Inter-Species Cross-Talk in Two-Component Signalling Systems." PLoS ONE 7, no. 5 (May 22, 2012): e37737. http://dx.doi.org/10.1371/journal.pone.0037737.

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Jacob-Dubuisson, Françoise, Ariel Mechaly, Jean-Michel Betton, and Rudy Antoine. "Structural insights into the signalling mechanisms of two-component systems." Nature Reviews Microbiology 16, no. 10 (July 15, 2018): 585–93. http://dx.doi.org/10.1038/s41579-018-0055-7.

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Puthiyaveetil, Sujith, and John F. Allen. "Chloroplast two-component systems: evolution of the link between photosynthesis and gene expression." Proceedings of the Royal Society B: Biological Sciences 276, no. 1665 (February 25, 2009): 2133–45. http://dx.doi.org/10.1098/rspb.2008.1426.

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Two-component signal transduction, consisting of sensor kinases and response regulators, is the predominant signalling mechanism in bacteria. This signalling system originated in prokaryotes and has spread throughout the eukaryotic domain of life through endosymbiotic, lateral gene transfer from the bacterial ancestors and early evolutionary precursors of eukaryotic, cytoplasmic, bioenergetic organelles—chloroplasts and mitochondria. Until recently, it was thought that two-component systems inherited from an ancestral cyanobacterial symbiont are no longer present in chloroplasts. Recent research now shows that two-component systems have survived in chloroplasts as products of both chloroplast and nuclear genes. Comparative genomic analysis of photosynthetic eukaryotes shows a lineage-specific distribution of chloroplast two-component systems. The components and the systems they comprise have homologues in extant cyanobacterial lineages, indicating their ancient cyanobacterial origin. Sequence and functional characteristics of chloroplast two-component systems point to their fundamental role in linking photosynthesis with gene expression. We propose that two-component systems provide a coupling between photosynthesis and gene expression that serves to retain genes in chloroplasts, thus providing the basis of cytoplasmic, non-Mendelian inheritance of plastid-associated characters. We discuss the role of this coupling in the chronobiology of cells and in the dialogue between nuclear and cytoplasmic genetic systems.
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Steel, Harrison, Aivar Sootla, Benjamin Smart, Nicolas Delalez, and Antonis Papachristodoulou. "Improving Orthogonality in Two-Component Biological Signalling Systems Using Feedback Control." IEEE Control Systems Letters 3, no. 2 (April 2019): 326–31. http://dx.doi.org/10.1109/lcsys.2018.2871663.

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Kothamachu, Varun B., Elisenda Feliu, Luca Cardelli, and Orkun S. Soyer. "Unlimited multistability and Boolean logic in microbial signalling." Journal of The Royal Society Interface 12, no. 108 (July 2015): 20150234. http://dx.doi.org/10.1098/rsif.2015.0234.

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The ability to map environmental signals onto distinct internal physiological states or programmes is critical for single-celled microbes. A crucial systems dynamics feature underpinning such ability is multistability. While unlimited multistability is known to arise from multi-site phosphorylation seen in the signalling networks of eukaryotic cells, a similarly universal mechanism has not been identified in microbial signalling systems. These systems are generally known as two-component systems comprising histidine kinase (HK) receptors and response regulator proteins engaging in phosphotransfer reactions. We develop a mathematical framework for analysing microbial systems with multi-domain HK receptors known as hybrid and unorthodox HKs. We show that these systems embed a simple core network that exhibits multistability, thereby unveiling a novel biochemical mechanism for multistability. We further prove that sharing of downstream components allows a system with n multi-domain hybrid HKs to attain 3 n steady states. We find that such systems, when sensing distinct signals, can readily implement Boolean logic functions on these signals. Using two experimentally studied examples of two-component systems implementing hybrid HKs, we show that bistability and implementation of logic functions are possible under biologically feasible reaction rates. Furthermore, we show that all sequenced microbial genomes contain significant numbers of hybrid and unorthodox HKs, and some genomes have a larger fraction of these proteins compared with regular HKs. Microbial cells are thus theoretically unbounded in mapping distinct environmental signals onto distinct physiological states and perform complex computations on them. These findings facilitate the understanding of natural two-component systems and allow their engineering through synthetic biology.
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Agrawal, Ruchi, Akancha Pandey, Mayooreshwar P. Rajankar, Narendra M. Dixit, and Deepak K. Saini. "The two-component signalling networks of Mycobacterium tuberculosis display extensive cross-talk in vitro." Biochemical Journal 469, no. 1 (June 19, 2015): 121–34. http://dx.doi.org/10.1042/bj20150268.

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Bacteria use two-component signalling systems (TCSs) to sense and respond to environmental changes. Currently, they are thought to be highly specific, with each TCS functioning independently. Here, unlike the prevalent paradigm, we show that the TCSs of M. tuberculosis cross-talk extensively, thereby proposing an alternative signalling scenario.
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Forsberg, J., M. Rosenquist, L. Fraysse, and J. F. Allen. "Redox signalling in chloroplasts and mitochondria: genomic and biochemical evidence for two-component regulatory systems in bioenergetic organelles." Biochemical Society Transactions 29, no. 4 (August 1, 2001): 403–7. http://dx.doi.org/10.1042/bst0290403.

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Redox chemistry is central to the primary functions of chloroplasts and mitochondria, that is, to energy conversion in photosynthesis and respiration. However, these bioenergetic organelles always contain very small, specialized genetic systems, relics of their bacterial origin. At huge cost, organellar genomes contain, typically, a mere 0.1 % of the genetic information in a eukaryotic cell. There is evidence that chloroplast and mitochondrial genomes encode proteins whose function and biogenesis are particularly tightly governed by electron transfer. We have identified nuclear genes for ‘bacterial’ histidine sensor kinases and aspartate response regulators that seem to be targeted to chloroplast and mitochondrial membranes. Sequence similarities to cyano-bacterial redox signalling components indicate homology and suggest conserved sensory and signalling functions. Two-component redox signalling pathways might be ancient, conserved mechanisms that permit endogenous control over the biogenesis, in situ, of bioenergetic complexes of chloroplasts and mitochondria.
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Rodrigue, Agnès, Yves Quentin, Andrée Lazdunski, Vincent Méjean, and Maryline Foglino. "Cell signalling by oligosaccharides. Two-component systems in Pseudomonas aeruginosa: why so many?" Trends in Microbiology 8, no. 11 (November 2000): 498–504. http://dx.doi.org/10.1016/s0966-842x(00)01833-3.

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Dissertations / Theses on the topic "Two component signalling systems"

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Blades, Gareth. "Re-engineering bacterial two-component signalling systems." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:2865c02d-c208-45fa-8108-d8ced9486c19.

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Bacteria use Two Component Systems (TCS) to sense and respond to changes in their external environment. TCS are used to navigate to nutrients or away from toxins (chemotaxis) and to adapt to changes in osmolarity (osomosensing). TCS are composed of a histidine protein kinase (HPK) which trans-autophosphorylates in response to environmental change, transferring the phosphoryl group to a cognate response regulator (RR). Phosphorylated RRs modulate an output response such as protein-protein interaction for chemotaxis, and transcription for osmosensing. RRs are composed of a conserved amino terminal REC domain, and where present a variable effector domain. CheY, the chemotaxis RR, contains only a REC domain, whilst OmpR, the osmosensing RR, also contains a DNA binding effector domain. Recently, TCS have been used in synthetic biology applications due to their modularity and conserved signalling mechanism. This thesis aimed to investigate whether it was possible to design a synthetic TCS composed of fused chemotaxis and osmosensing components. Synthetic RRs were designed, fusing the highly conserved REC domains of CheY and OmpR upstream of the OmpR effector domain. REC domains were fused across the α4-β5-α5 region, a region which transmits REC domain phosphorylation into effector domain activation. Synthetic RRs were designed to undergo phosphotransfer to their fused REC domains from the chemotaxis HPK, CheA, activate the attached OmpR effector domain and bind promoter DNA. Four chimeric RRs were created, although only three were structurally viable; F2, F3 and F4. Each fusion bound CheA, and F3 and F4 bound CheA with a significantly higher affinity than CheY. The chimeric RRs could all be phosphorylated byCheA-P; F4 and F3 were phosphorylated to wild-type levels. DNA binding affinitywas investigated with fluorescence anisotropy, hosphorylated and unphosphorylated F3 could not bind promoter DNA. F2 bound promoter DNA regardless of phosphorylation state. These data indicate that phosphorylation of the F2 REC domain does not lead to activation of the effector domain. F2 is likely to be constitutively active suggesting a previously unknown role for OmpR α5 as a mediator of effector domain activation. Furthermore, using a simple fusion approach to design RRs is not a viable method to create a synthetic TCS with a controllable output.
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Sheng, Xia. "Evolutionary and functional aspects of two-component signalling systems." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/17940.

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Two-component systems (TCSs) are critical for bacteria to interact with their extracellular environment. They define a type of signalling system that is composed of a transmembrane histidine kinase (HK) and a cytoplasmic response regulator (RR). In this thesis we have studied the evolutionary and functional aspects of these important signalling systems. By studying the distribution of the TCS orthologues of E.coli across more than 900 bacterial organisms, we have found that a pair of TCS proteins does not always coexist in one organism. The genomic localisation map of TCSs reveals a possible translocation mechanism for TCS evolution. The alignments of HKs and RRs have shown that HKs are genetically more divergent, probably due to their signal recognizing role. An analysis of the steady states of TCS dynamics has shown that the outputs of the TCSs are bistable if they have positive auto-regulation feedback loops in their transcriptional regulation. Our analysis has also shown that the phosphorylation process of a TCS is always monostable and the factors that affect steady states have been studied. For both orthodox and non-orthodox TCSs, autophosphorylation rates of the HKs are the most important factor to affect the steady states of the TCSs' outputs. To study the phosphorelay mechanism of the non-orthodox TCS ArcB/A, we constructed plasmids carrying different copy numbers of ArcB mutants with different phosphorylation sites ablated. By fitting our phosphorelay model to the data obtained from mutant ArcB constructs, we have found that ArcB most likely performs phosphorelay in an allosteric mechanism. Finally, Approximate Bayesian computation was used in order to evaluate the potential use of orthodox TCS and non-orthodox TCS architectures in synthetic biology contexts. Results show that neither of the orthodox TCS model or the nonorthodox TCS model are superior under all circumstances but that both models have advantages in some scenarios. In the appendix, we did some study on how the contact residue disorder would affect protein-ligand binding specificity.
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Puthiyaveetil, Sujith. "Two-component signalling systems of chloroplasts : function, distribution and evolution." Thesis, Queen Mary, University of London, 2008. http://qmro.qmul.ac.uk/xmlui/handle/123456789/121.

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Two-component signal transduction, comprising sensor kinases and response regulators, is the predominant signalling mechanism in prokaryotes. This signalling system originated in bacteria, and has spread to the eukaryotic domain of life through symbiotic, lateral gene transfer from the bacterial ancestors of chloroplasts and mitochondria. During the course of their evolution, chloroplasts, with the exception of a few instances in non-green algae, appear to have relinquished all genes encoding two-component systems to their eukaryotic host cell nuclei. In green algae and plants, chloroplast genes for two-component systems were neither known nor were chloroplast two-component proteins shown to exist as products of nuclear genes prior to the work described here. This thesis describes the identification and characterisation of a novel two-component sensor kinase in chloroplasts. This Chloroplast Sensor Kinase (CSK) is the product of a nuclear gene in algae and plants. CSK is synthesised in the cytosol of Arabidopsis thaliana and imported into the chloroplast as a protein precursor. CSK is autophosphorylated and couples photosynthetic electron transport to gene transcription in chloroplasts. The identity of the response regulator partner of CSK reveals an unexpected phylogenetic and functional relatedness of CSK with chloroplast two-component systems of non-green algae. Chloroplast two-component systems are likely to be universal in photosynthetic eukaryotes and they persist in chloroplasts as products of nuclear genes even where chloroplast genomes no longer encode them. Chloroplast twocomponent systems have homologues in extant cyanobacterial lineages, indicating their ancient cyanobacterial origin. The persistence of cyanobacterial two-component systems in chloroplasts and their function in coupling photosynthesis with chloroplast gene expression are central to the premise that chloroplasts retain genes whose expression is regulated by the activity of the photosynthetic electron transport chain, using a mechanism conserved from their cyanobacterial ancestors.
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Tomenius, Henrik. "Bacterial virulence and adaptation mediated by two-component system signalling /." Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-792-8/.

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Croxatto, Antony. "VanT, a central regulator of quorum sensing signalling in Vibrio anguillarum." Doctoral thesis, Umeå : Umeå University, Department of Molecular Biology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-702.

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Francis, Vanessa Ina. "Extensive communication between sensor kinases controlling virulence in the GacS network of Pseudomonas aeruginosa." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/17434.

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Two component systems (TCSs) are regulatory pathways in bacteria and lower eukaryotes that integrate multiple stimuli and bring about appropriate responses to promote adaptation of the bacteria to their niches. They are commonly insulated from cross-talk and form discrete regulatory systems where the sensor histidine kinase (SK) and the response regulator (RR) share high fidelity for one another. The GacS network controls the switch between acute and chronic virulence of P. aeruginosa. The network is unusual in having a 'core' SK, GacS, which is modulated directly by one other SK, RetS. Here the complex relationship between GacS and RetS is dissected to reveal three distinct mechanisms by which they interact. Two of these mechanisms involve the dephosphorylation of GacS-P by RetS and it is these mechanisms that are important in vivo for the regulation of biofilm formation, rsmY and rsmZ expression, swarming, and virulence in both Galleria mellonella and an acute model of infection in mice. This study reveals an unprecedented level of complexity in the ability of RetS to interact with GacS and suggests that RetS has a number of mechanisms by which it can downregulate the GacS network output. Furthermore, the interactions of additional SKs that have previously been linked to the GacS network were investigated. Here I demonstrate that many of these kinases can interact with one another but that RetS remained the only kinase tested that could directly interact with GacS. The interactions observed between kinases could be either stimulatory, having a synergistic impact on phosphorylation levels, or inhibitory. I also show that kinase-kinase interactions allow for the regulation of phosphorylation of downstream proteins. Finally, we searched for additional SKs that may be able to interact with the GacS network. Here I identify three new kinases, which show differing interactions with the kinases of the GacS network. The discovery of additional SKs in the GacS network indicates that the network is likely to respond to a far greater number of different signals than previously realised as it decides between acute and chronic virulence.
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Guan, Shuang. "A novel two-component signal transduction system in propionibacterium acnes and its association with a putative extracellular signalling peptide." Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/1752/.

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Propionibacterium acnes, a resident micro-organism of human skin, is thought to be involved in the development of inflammatory acne, which is an exclusive human disease affecting more than 80% of the whole population. Quorum sensing is the regulation of gene expression in response to cell density. As it is often involved in pathogenecity of bacteria, its signal transduction pathway has been suggested as potential target for new drug development. This project identified a putative unique quorum sensing system of P. acnes, consisting of a putative signalling peptide, and divergently transcribed histidine kinase and response regulator. The aim of this project is to investigate the relationship among these three components as being elements of a putative quorum sensing system. Using purified proteins and in vitro phosphorylation assays, the histidine kinase was demonstrated to phosphorylate the response regulator indicating they may constitute a legitimate pair of a two-component system, despite being encoded by divergently transcribed genes. By mapping transcriptional start site, it was found that the signalling peptide and histidine kinase were co-transcribed from the same start site, suggesting that the signalling peptide was associated with the two-component system. Gene expression analysis also revealed these three genes were co-regulated during the growth of P.acnes, which is consistent with these three genes functioning together as a part of quorum sensing system. The results of this project suggested that the signalling peptide, histidine kinase and response regulator are associated with each other and may constitute a quorum sensing system.
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Wojnowska, M. "Biochemical and structural characterisation of a two-component signalling system downstream of bacteriophytochrome photoreceptor 1 in Rhizobium NT-26." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1388782/.

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Prokaryotic signal transduction frequently involves two-component systems (TCSs), typically comprising a sensor histidine kinase (HK) and a response regulator (RR). Via a conserved phosphotransfer reaction, TCSs couple the detection of diverse stimuli with appropriate responses. The initial aim of this project was to characterise the two-component “signalome” of an arsenite oxidiser, Rhizobium NT-26, in the context of the environmental niche, and compare it to “signalomes” of other bacterial species. A light-sensing HK, bacteriophytochrome photoreceptor 1 (BphP1), was thus identified. Previous studies indicated that BphP1 and the members of its gene cluster - two single-domain RRs and a hybrid RR/HK protein, ExsG - may constitute a TCS. Functional characterisation revealed that BphP1 initiates a branched signalling pathway; however, the mediated output could not be identified. ExsG, a HWE-type HK, was shown to possess dual HK/RR activity and act as a novel type of signalling switch: phosphorylation of the N-terminal receiver domain downregulates the autokinase activity of the C-terminal kinase core. Ion mobility-mass spectrometry analysis indicated that while Asp62 phosphorylation stabilises the “closed” form of ExsG, nucleotide binding stabilises the “open” conformation. These observations led to a model in which phosphorylation of the receiver domain precludes ATP binding and thus inhibits autokinase activity. Furthermore, ExsG was demonstrated to hexamerise via the HWE core, which makes it the first non-dimeric HK. Notably, however, the basic unit of the hexameric assembly is a homodimer, and the HWE core shares homology with canonical HK cores. The results presented herein broaden the current knowledge on TCSs and identify previously unreported mechanisms involved in two-component signal transduction. The members of the BphP1 signalling cascade enrich the pool of modular communication units that can be exploited in engineering artificial signalling networks, biosensors and microorganisms with novel functionalities.
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Casali, Nicola. "Two component regulatory systems in Mycobacterium tuberculosis." Thesis, London School of Hygiene and Tropical Medicine (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322228.

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Goffri, Shalom. "Polymer FETs with crystalline two-component systems." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613082.

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Books on the topic "Two component signalling systems"

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service), ScienceDirect (Online, ed. Two-component signaling systems. San Diego, Calif: Academic Press/Elsevier, 2007.

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I, Simon Melvin, Crane Brian R, and Crane Alexandrine, eds. Two-component signaling systems. San Diego, Calif: Academic Press, 2007.

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Bejan, Adrian, and Giuseppe Grazzini, eds. Shape and Thermodynamics. Florence: Firenze University Press, 2008. http://dx.doi.org/10.36253/978-88-8453-836-9.

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Shape and Thermodynamics is a two-day international Workshop focused on the Constructal Theory of generation of configuration in nature and engineering. From the early developments related to tree configurations for the cooling of electronics, today Constructal theory is being applied to conceptual design of transportation net-works, river basins, living bodies, building materials and many other flow systems. Constructal theory is also enriching thermo-dynamics, from basic theory to design and optimization. This theory approaches design "as science", with the generation of configuration regarded as a phenomenon of all physics, based on principle (the Constructal law). For example, Constructal Theory contributes to the evolution of fuel cells, in the design of cooling channels, the optimal feeding of reactants, etc. Important applications are also found in the design of heat exchangers, district heating networks, etc. The growing scientific literature on Constructal Theory has an important Italian component, although further dissemination is timely. Moreover, the relation with other thermodynamic research areas deserves to be explored. Website: Shape and Thermodinamics
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Gross, Roy, and Dagmar Beier. Two-Component Systems in Bacteria. Caister Academic Press Limited, 2012.

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Two‐Component Signaling Systems, Part A. Elsevier, 2007. http://dx.doi.org/10.1016/s0076-6879(06)x2200-0.

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Two‐Component Signaling Systems, Part B. Elsevier, 2007. http://dx.doi.org/10.1016/s0076-6879(07)x2302-4.

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Crane, Brian, Melvin I. Simon, and Alexandrine Crane. Two-Component Signaling Systems, Part C. Elsevier Science & Technology Books, 2010.

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Crane, Brian, Melvin I. Simon, and Alexandrine Crane. Two-Component Signaling Systems, Part B. Elsevier Science & Technology Books, 2007.

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Crane, Brian, Melvin I. Simon, and Alexandrine Crane. Two-Component Signaling Systems, Part A. Elsevier Science & Technology Books, 2011.

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Defonseka, Chris. Two-Component Polyurethane Systems: Innovative Processing Methods. De Gruyter, Inc., 2019.

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Book chapters on the topic "Two component signalling systems"

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Agrawal, Ruchi, Vignesh H. Narayan, and Deepak Kumar Saini. "Two-Component Signalling Systems of M. tuberculosis: Regulators of Pathogenicity and More." In Dynamic Models of Infectious Diseases, 79–109. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-9224-5_4.

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Biondi, Emanuele G. "Two-Component Systems." In Encyclopedia of Systems Biology, 2305–6. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4419-9863-7_744.

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Stibitz, Scott. "Two-Component Systems." In Bacterial Protein Toxins, 3–23. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555817893.ch1.

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Zaidi, Sheza. "Two Component Systems." In Phase Rule and its applications, 29–62. London: CRC Press, 2022. http://dx.doi.org/10.1201/9781003297949-3.

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Gupta, Rani, and Namita Gupta. "Two-Component Systems." In Fundamentals of Bacterial Physiology and Metabolism, 557–73. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0723-3_20.

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Msadek, Tarek, Frank Kunst, and Georges Rapoport. "Two-Component Regulatory Systems." In Bacillus subtilis and Other Gram-Positive Bacteria, 727–45. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555818388.ch50.

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Stewart, Valley. "Bacterial Two-Component Regulatory Systems." In Molecular Microbiology, 141–57. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-642-72071-0_8.

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Groisman, Eduardo A., and Fred Heffron. "Regulation of Salmonella Virulence by Two-Component Regulatory Systems." In Two-Component Signal Transduction, 319–32. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555818319.ch20.

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Stock, Jeffry B., Michael G. Surette, Mikhail Levit, and Peter Park. "Two-Component Signal Transduction Systems: Structure-Function Relationships and Mechanisms of Catalysis." In Two-Component Signal Transduction, 25–51. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555818319.ch3.

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Pelosi, Lenore A., Kwasi A. Ohemeng, and John F. Barrett. "Bacterial Signal Transduction: Two-Component Signal Transduction as a Model for Therapeutic Intervention." In Cell Signalling in Prokaryotes and Lower Metazoa, 347–402. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-94-017-0998-9_11.

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Conference papers on the topic "Two component signalling systems"

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Ogunsola, Ade, Ugo Reggiani, and Leonardo Sandrolini. "Demonstrating signalling compatibility between two train control systems." In 2007 18th International Zurich Symposium on Electromagnetic Compatibility. IEEE, 2007. http://dx.doi.org/10.1109/emczur.2007.4388270.

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Oskotsky, Mark L. "Theory of two-component zoom systems." In San Diego, '91, San Diego, CA, edited by Robert E. Fischer and Warren J. Smith. SPIE, 1991. http://dx.doi.org/10.1117/12.48636.

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Guo, Minliang, Yujuan Xu, Dawei Gao, and Nan Xu. "Signal Crosstalk between Two Different Agrobacterium Two-Component Systems." In The 5th World Congress on New Technologies. Avestia Publishing, 2019. http://dx.doi.org/10.11159/icbb19.110.

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Sperl, Matthias. "Logarithmic decay in a two-component model." In SLOW DYNAMICS IN COMPLEX SYSTEMS: 3rd International Symposium on Slow Dynamics in Complex Systems. AIP, 2004. http://dx.doi.org/10.1063/1.1764224.

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Yang, Yating, and Jun Wang. "Condition-Based Maintenance for Two-component Series Systems Considering Component Reallocation." In 2022 4th International Conference on System Reliability and Safety Engineering (SRSE). IEEE, 2022. http://dx.doi.org/10.1109/srse56746.2022.10067390.

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Zhang, Xiaowen, Naihao Ye, Chengwei Liang, Xiangyu Guan, and Song Qin. "Comparative Analysis of Two-Component Signal Transduction Systems in Six Synechococcus Strains - Two-Component Signal Transduction Systems in Synechococcus." In 2009 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2009. http://dx.doi.org/10.1109/icbbe.2009.5162530.

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Sogo, T. "Hyperspherical coordinates applied to two-component boson systems." In FEW-BODY PROBLEMS IN PHYSICS: The 19th European Conference on Few-Body Problems in Physics. AIP, 2005. http://dx.doi.org/10.1063/1.1932992.

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Nakai, Hiromi. "Efficient two-component relativistic method for large systems." In INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2015 (ICCMSE 2015). AIP Publishing LLC, 2015. http://dx.doi.org/10.1063/1.4938838.

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Liu, W., and J. H. Tang. "Research of two-component system genes in phytopathogen bacteria." In International Conference on Computer Science and Systems Engineering. Southampton, UK: WIT Press, 2015. http://dx.doi.org/10.2495/csse140521.

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Wada, Hirofumi. "Dynamics of phase separation in confined two-component fluid membranes." In SLOW DYNAMICS IN COMPLEX SYSTEMS: 3rd International Symposium on Slow Dynamics in Complex Systems. AIP, 2004. http://dx.doi.org/10.1063/1.1764091.

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Reports on the topic "Two component signalling systems"

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Friedman, Haya, Julia Vrebalov, James Giovannoni, and Edna Pesis. Unravelling the Mode of Action of Ripening-Specific MADS-box Genes for Development of Tools to Improve Banana Fruit Shelf-life and Quality. United States Department of Agriculture, January 2010. http://dx.doi.org/10.32747/2010.7592116.bard.

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Fruit deterioration is a consequence of a genetically-determined fruit ripening and senescence programs, in which developmental factors lead to a climacteric rise of ethylene production in ethylene-sensitive fruits such as tomato and banana. Breeding of tomato with extended fruit shelf life involves the incorporation of a mutation in RIN, a MADS-box transcription factor participating in developmental control signalling of ripening. The RIN mode of action is not fully understood, and it may be predicted to interact with other MADS-box genes to execute its effects. The overall goal of this study was to demonstrate conservation of ripening control functions between banana and tomato and thus, the potential to genetically extend shelf-life in banana based on tools developed in tomato. The specific objectives were: 1. To increase the collection of potential RIN-like genes from banana; 2. To verify their action as developmental regulators; 3. To elucidate MADS-box gene mode of action in ripening control; 4. To create transgenic banana plants that express low levels of endogenous Le-RIN- like, MaMADS- gene(s). We have conducted experiments in banana as well as in tomato. In tomato we have carried out the transformation of the tomato rin mutant with the MaMADS1 and MaMADS2 banana genes. We have also developed a number of domain swap constructs to functionally examine the ripening-specific aspects of the RIN gene. Our results show the RIN-C terminal region is essential for the gene to function in the ripening signalling pathway. We have further explored the tomato genome databases and recovered an additional MADS-box gene necessary for fruit ripening. This gene has been previously termed TAGL1 but has not been functionally characterized in transgenic plants. TAGL1 is induced during ripening and we have shown via RNAi repression that it is necessary for both fleshy fruit expansion and subsequent ripening. In banana we have cloned the full length of six MaMADS box genes from banana and determined their spatial and temporal expression patterns. We have created antibodies to MaMADS2 and initiated ChI assay. We have created four types of transgenic banana plants designed to reduce the levels of two of the MaMADS box genes. Our results show that the MaMADS-box genes expression in banana is dynamically changing after harvest and most of them are induced at the onset of the climacteric peak. Most likely, different MaMADS box genes are active in the pulp and peel and they are differently affected by ethylene. Only the MaMADS2 box gene expression is not affected by ethylene indicating that this gene might act upstream to the ethylene response pathway. The complementation analysis in tomato revealed that neither MaMADS1 nor MaMADS2 complement the rin mutation suggesting that they have functionally diverged sufficiently to not be able to interact in the context of the tomato ripening regulatory machinery. The developmental signalling pathways controlling ripening in banana and tomato are not identical and/or have diverged through evolution. Nevertheless, at least the genes MaMADS1 and MaMADS2 constitute part of the developmental control of ripening in banana, since transgenic banana plants with reduced levels of these genes are delayed in ripening. The detailed effect on peel and pulp, of these transgenic plants is underway. So far, these transgenic bananas can respond to exogenous ethylene, and they seem to ripen normally. The response to ethylene suggest that in banana the developmental pathway of ripening is different than that in tomato, because rin tomatoes do not ripen in response to exogenous ethylene, although they harbor the ethylene response capability This study has a major contribution both in scientific and agricultural aspects. Scientifically, it establishes the role of MaMADS box genes in a different crop-the banana. The developmental ripening pathway in banana is similar, but yet different from that of the model plant tomato and one of the major differences is related to ethylene effect on this pathway in banana. In addition, we have shown that different components of the MaMADS-box genes are employed in peel and pulp. The transgenic banana plants created can help to further study the ripening control in banana. An important and practical outcome of this project is that we have created several banana transgenic plants with fruit of extended shelf life. These bananas clearly demonstrate the potential of MaMADS gene control for extending shelf-life, enhancing fruit quality, increasing yield in export systems and for improving food security in areas where Musaspecies are staple food crops.
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Houck, Marilyn, Uri Gerson, and Robert Luck. Two Predator Model Systems for the Biological Control of Diaspidid Scale Insects. United States Department of Agriculture, June 1994. http://dx.doi.org/10.32747/1994.7570554.bard.

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Hemisarcoptes (Acari: Hamisarcoptidae) is a parasite of scale insects (Diaspididae), tenacious pests of vascular plants. Hemisarcoptes also has a stenoxenic phoretic (dispersal) relationship with Chilocorus (Coleoptera: Coccinellidae). Chilocorus feeds on diaspidids, transports mites as they feed, and has been applied to the control of scales, with limited success. U.S.-Israeli cooperation focused on this mite-beetle interaction so that a two-component system could be applied to the control of scale insects effectively. Life history patterns of Hemisarcoptes were investigated in response to host plant type and physical parameters. Field and lab data indicated that mites attack all host stages of scales tested, but preferred adult females. Scale species and host plant species influenced the bionomics of Hemisarcoptes. Beetle diet also influenced survival of phoretic mites. Mites use a ventral sucker plate to extract material from Chilocorus, that is essential for development. Seven alkaloids were found in the hemolymph of Chilocorus and three were characterized. Examination of the subelytral surface of Chilocorus indicated that microsetae play a role in the number and distribution of mites a beetle transports. While Hemisarcoptes can be innoculatd into agroecosystems using various indigenous or imported Chilocorus species, the following are preferred: C. bipustulatus, C. cacti, C. distigma, C. fraternus, C. orbus, and C. tristis.
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Ramamurthy, V. Final report of research supported by DOE Grant No. DE-FG02-96ER14635: Photochemical studies of two component systems within the restricted spaces of zeolites. Office of Scientific and Technical Information (OSTI), May 2002. http://dx.doi.org/10.2172/771227.

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Yuval, Boaz, and Todd E. Shelly. Lek Behavior of Mediterranean Fruit Flies: An Experimental Analysis. United States Department of Agriculture, July 2000. http://dx.doi.org/10.32747/2000.7575272.bard.

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The Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), is a ubiquitous pest of fruit trees, causing significant economic damage both in the U.S. and in Israel. Control efforts in the future will rely heavily on the sterile insect technique (SIT). Success of such operations hinges on the competitive ability of released males. The mating system of the medfly is based on leks. These are aggregations of sexually signaling males that attract females (who then select and copulate a courting male). A major component of male competitiveness is their ability to join existing leks or establish leks that are attractive to wild females. Accordingly, we identified leks and the behaviors associated with them as critical for the success of SIT operations. The objectives of this proposal were to determine 1. what makes a good lek site, 2. what are the energetic costs of lekking, 3. how females choose leks, and finally 4. whether the copulatory success of sterile males may be manipulated by particular pre-release diets and judicious spatial dispersal. We established that males choose lek sites according to their spatial location and penological status, that they avoid predators, and within the lek tree choose the perch that affords a compromise between optimal signalling, micro-climatic conditions and predation risk (Kaspi & Yuval 1999 a&b; Field et al 2000; Kaspi & Yuval submitted). We were able to show that leks are exclusive, and that only males with adequate protein and carbohydrate reserves can participate (Yuval et al 1998; Kaspi et al 2000; Shelly et al 2000). We determined that females prefer leks formed by protein fed, sexually experienced males (Shelly 2000). Finally, we demonstrated that adding protein to the diet of sterile males significantly enhances their probability of participating in leks and copulating wild females (Kaspi & Yuval 2000).
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Wu, Yingjie, Selim Gunay, and Khalid Mosalam. Hybrid Simulations for the Seismic Evaluation of Resilient Highway Bridge Systems. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, November 2020. http://dx.doi.org/10.55461/ytgv8834.

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Bridges often serve as key links in local and national transportation networks. Bridge closures can result in severe costs, not only in the form of repair or replacement, but also in the form of economic losses related to medium- and long-term interruption of businesses and disruption to surrounding communities. In addition, continuous functionality of bridges is very important after any seismic event for emergency response and recovery purposes. Considering the importance of these structures, the associated structural design philosophy is shifting from collapse prevention to maintaining functionality in the aftermath of moderate to strong earthquakes, referred to as “resiliency” in earthquake engineering research. Moreover, the associated construction philosophy is being modernized with the utilization of accelerated bridge construction (ABC) techniques, which strive to reduce the impact of construction on traffic, society, economy and on-site safety. This report presents two bridge systems that target the aforementioned issues. A study that combined numerical and experimental research was undertaken to characterize the seismic performance of these bridge systems. The first part of the study focuses on the structural system-level response of highway bridges that incorporate a class of innovative connecting devices called the “V-connector,”, which can be used to connect two components in a structural system, e.g., the column and the bridge deck, or the column and its foundation. This device, designed by ACII, Inc., results in an isolation surface at the connection plane via a connector rod placed in a V-shaped tube that is embedded into the concrete. Energy dissipation is provided by friction between a special washer located around the V-shaped tube and a top plate. Because of the period elongation due to the isolation layer and the limited amount of force transferred by the relatively flexible connector rod, bridge columns are protected from experiencing damage, thus leading to improved seismic behavior. The V-connector system also facilitates the ABC by allowing on-site assembly of prefabricated structural parts including those of the V-connector. A single-column, two-span highway bridge located in Northern California was used for the proof-of-concept of the proposed V-connector protective system. The V-connector was designed to result in an elastic bridge response based on nonlinear dynamic analyses of the bridge model with the V-connector. Accordingly, a one-third scale V-connector was fabricated based on a set of selected design parameters. A quasi-static cyclic test was first conducted to characterize the force-displacement relationship of the V-connector, followed by a hybrid simulation (HS) test in the longitudinal direction of the bridge to verify the intended linear elastic response of the bridge system. In the HS test, all bridge components were analytically modeled except for the V-connector, which was simulated as the experimental substructure in a specially designed and constructed test setup. Linear elastic bridge response was confirmed according to the HS results. The response of the bridge with the V-connector was compared against that of the as-built bridge without the V-connector, which experienced significant column damage. These results justified the effectiveness of this innovative device. The second part of the study presents the HS test conducted on a one-third scale two-column bridge bent with self-centering columns (broadly defined as “resilient columns” in this study) to reduce (or ultimately eliminate) any residual drifts. The comparison of the HS test with a previously conducted shaking table test on an identical bridge bent is one of the highlights of this study. The concept of resiliency was incorporated in the design of the bridge bent columns characterized by a well-balanced combination of self-centering, rocking, and energy-dissipating mechanisms. This combination is expected to lead to minimum damage and low levels of residual drifts. The ABC is achieved by utilizing precast columns and end members (cap beam and foundation) through an innovative socket connection. In order to conduct the HS test, a new hybrid simulation system (HSS) was developed, utilizing commonly available software and hardware components in most structural laboratories including: a computational platform using Matlab/Simulink [MathWorks 2015], an interface hardware/software platform dSPACE [2017], and MTS controllers and data acquisition (DAQ) system for the utilized actuators and sensors. Proper operation of the HSS was verified using a trial run without the test specimen before the actual HS test. In the conducted HS test, the two-column bridge bent was simulated as the experimental substructure while modeling the horizontal and vertical inertia masses and corresponding mass proportional damping in the computer. The same ground motions from the shaking table test, consisting of one horizontal component and the vertical component, were applied as input excitations to the equations of motion in the HS. Good matching was obtained between the shaking table and the HS test results, demonstrating the appropriateness of the defined governing equations of motion and the employed damping model, in addition to the reliability of the developed HSS with minimum simulation errors. The small residual drifts and the minimum level of structural damage at large peak drift levels demonstrated the superior seismic response of the innovative design of the bridge bent with self-centering columns. The reliability of the developed HS approach motivated performing a follow-up HS study focusing on the transverse direction of the bridge, where the entire two-span bridge deck and its abutments represented the computational substructure, while the two-column bridge bent was the physical substructure. This investigation was effective in shedding light on the system-level performance of the entire bridge system that incorporated innovative bridge bent design beyond what can be achieved via shaking table tests, which are usually limited by large-scale bridge system testing capacities.
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Sreedhara, Sindhu, Adam Brandt, and Jingfan Wang. PR-681-18701-R01 Evaluating the Use of Optical Gas Imaging Cameras for Above Ground Facilities. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), December 2020. http://dx.doi.org/10.55274/r0011989.

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Natural gas is the largest primary energy source in the United States. Reliance on natural gas is only increasing as its role in electricity systems becomes more significant and that of coal diminishes. While this has air quality and health benefits over the use of coal, the global warming potential of methane - the primary component of natural gas - cannot be ignored. In order to mitigate methane leaks, periodic leak detection and repair programs are required in the United States. Various different technologies exist to detect and/or quantify methane leaks. Studying them and evaluating their performance is an important step in evaluating equivalence in emissions reductions between technologies. In this study, we evaluate the performance of two optical gas imaging cameras. The first is the FLIR GF320, an infrared camera, which we coupled with the Providence Photonics QL320 to enable it to quantify methane leaks. The second is the Rebellion Photonics mini-GCI, a hyperspectral imaging camera, which provides automated alerts when a leak is detected. Experiments to test the two systems were carried out at the Methane Emissions Technology Evaluation Center in Fort Collins, Colorado over two weeks. We tested both technologies at a variety of leak size and imaging distance combinations. In order to better simulate real-world conditions, we also tested the performance of the two systems in the presence of different types of interference. For the first technology, we evaluate the quantification performance and for the second, the detection performance. We report performance metrics at different distances, interference scenarios and leak sizes in the case of Rebellion. The two technologies differ in terms of automation, detection and quantification capabilities, imaging distance and minimum observable leak size.
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Rafaeli, Ada, Wendell Roelofs, and Anat Zada Byers. Identification and gene regulation of the desaturase enzymes involved in sex-pheromone biosynthesis of pest moths infesting grain. United States Department of Agriculture, March 2008. http://dx.doi.org/10.32747/2008.7613880.bard.

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The original objectives of the approved proposal included: 1. Establishment of the biosynthetic pathways for pheromone production using labeled precursors and GC-MS. 2. The elucidation of a circadian regulation of key enzymes in the biosynthetic pathway. 3. The identification, characterization and confirmation of functional expression of the delta-desaturases. 4. The identification of gene regulatory processes involved in the expression of the key enzymes in the biosynthetic pathway. Background to the topic: Moths constitute one of the major groups of pest insects in agriculture and their reproductive behavior is dependent on chemical communication. Sex-pheromone blends are utilized by a variety of moth species to attract conspecific mates. The sex pheromones used are commonly composed of blends of aliphatic molecules that vary in chain length, geometry, degree and position of double bonds and functional groups. They are formed by various actions of specific delta-desaturases to which chain shortening, elongation, reduction, acetylation, and oxidation of a common fatty acyl precursor is coupled. In most of the moth species sex-pheromone biosynthesis is under circadian control by the neurohormone, PBAN (pheromone-biosynthesis-activating neuropeptide). The development of specific and safe insect control strategies utilizing pheromone systems depends on a clear knowledge of the molecular mechanisms involved. In this proposal we aimed at identifying and characterizing specific desaturases involved in the biosynthetic pathway of two moth pest-speciesof stored products, P. interpunctella and S. cerealella, and to elucidate the regulation of the enzymes involved in pheromone biosynthesis. Due to technical difficulties the second stored product pest was excluded from the study at an early phase of the research project. Major conclusions: Within the framework of the planned objectives we confirmed the pheromone biosynthetic pathway of P. interpunctella and H. armigera by using labeled precursor molecules. In addition, in conjunction with various inhibitors we determined the PBAN-stimulated rate-limiting step for these biosynthetic pathways. We thereby present conclusive evidence that the enzyme Acetyl Coenzyme A Carboxylase is activated as a result of PBAN stimulation. We also found that P. interpunctella produce the main pheromone component Z9, E12 Tetradecenyl acetate through the action of a D11 desaturase working on the 16:Acid precursor. This is evidenced by the high amount of incorporation of ²H-labeled 16:Acid into pheromone when compared to the incorporation of ²H-labeled 14:Acid. However, in contrast to reports on other moth species, P. interpunctella is also capable of utilizing the 14:Acid precursor, although to a much lesser extent than the 16:Acid precursor. Despite the discovery of nine different desaturase gene transcripts in this species, from the present study it is evident that although PCR detected all nine gene transcripts, specific to female pheromone glands, only two are highly expressed whereas the other 7 are expressed at levels of at least 10⁵ fold lower showing very low abundance. These two genes correspond to D11-like desaturases strengthening the hypothesis that the main biosynthetic pathway involves a D11 desaturase.
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Hodges, Thomas K., and David Gidoni. Regulated Expression of Yeast FLP Recombinase in Plant Cells. United States Department of Agriculture, September 2000. http://dx.doi.org/10.32747/2000.7574341.bard.

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Research activities in both our laboratories were directed toward development of control of the FLP/frt recombination system for plants. As described in the text of the research proposal, the US lab has been engaged in developing regulatory strategies such as tissue-specific promoters and the steroid-inducible activation of the FLP enzyme while the main research activities in Israel have been directed toward the development and testing of a copper-regulated expression of flp recombinase in tobacco (this is an example of a promoter activation by metal ions). The Israeli lab hat additionally completed experiments of previous studies regarding factors affecting the efficiency of recombinase activity using both a gain-of-function assay (excisional-activation of a gusA marker) and loss of function assay (excision of a rolC marker) in tobacco. Site-specific recombinase systems, in particular the FLP/frt and R/RS systems of yeast and the Cre/lox system of bacteriophage P1, have become an essential component of targeted genetic transformation procedures both in animal and plant organisms. To provide more flexibility in transgene excisions by the recombinase systems as well as gene targeting, and to widen possible applications, the development of controlled or regulated recombination systems is highly desirable and was therefore the subject of this research proposal. There are a few possible mechanisms to regulate expression of a recombinase system. They include: 1) control of the recombination system by having the target sites (e.g. frt) in one plant and the flp recombinase gene in another, and bringing the two together by cross fertilization. 2) regulation of promoter activities by external stimuli such as temperature, chemicals, metal ions, etc. 3) regulation of promoter activities by internal signals, i.e. cell- or tissue-specific, or developmental regulation. 4) regulation of enzyme activity by providing cofactors essential for biochemical reactions to take place such as steroid molecules in conjunction with a steroid ligand-binding protein (domains). During the course of this research our major emphasis have been focused toward studying the feasibility of hybrid seed production in Arabidopsis, using FLP/frt. Male-sterility was induced using the antisence of a pollen- and tapetum-specific gene, bcp1, isolated from Arabidopsis. The sterility inducing gene was flanked by frt sites. Upon cross pollination of flowers of male-sterile plants with pollen from FLP-containing plants, viable seeds were produced, and the progeny hybrid plants developed normally. The major achievement from this work is the first demonstration of using a site-specific recombinase to restore fertility in male-sterile plants (see attached paper, Luo et al., Plant J 2000; 23:423-430). The implication from this finding is that site-specific recombination systems can be applied in crop plants as a useful alternative method for hybrid seed production.
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Barash, Itamar, and Robert E. Rhoads. Translational Mechanisms that Govern Milk Protein Levels and Composition. United States Department of Agriculture, November 2004. http://dx.doi.org/10.32747/2004.7586474.bard.

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Original objectives: The long term objective of the project is to achieve higher content of protein in the milk of ruminants by modulating the translational machinery in the mammary gland. The first specific aim of the BARD proposal was to characterize responsiveness of various experimental systems to combination of lactogenic hormones and amino acids with particular emphasis on discrimination between the control of total protein synthesis and milk protein synthesis. Based on the results, we planned to proceed by characterizing the stage of protein synthesis in which the stimulation by lactogenic hormones and amino acid occur and finally we proposed to identify which components of the translation machinery are modified. Background to the topic: Milk protein is the most valuable component in milk, both for direct human consumption and for manufacturing cheese and other protein-based products. Attempts to augment protein content by the traditional methods of genetic selection and improved nutritional regimes have failed. The proposal was based on recent results suggesting that the limiting factor for augmenting protein synthesis in the bovine mammary gland is the efficiency of converting amino acids to milk proteins. Major conclusions, solutions, achievements: Insulin and prolactin synergistically stimulate â-casein mRNA translation by cytoplasmatic polyadenylation. The interaction between insulin and prolactin was demonstrated two decades ago as crucial for milk-protein synthesis, but the molecular mechanisms involved were not elucidated. We found in differentiated CID 9 mouse mammary epithelial cells line that insulin and prolactin synergistically increases the rate of milk protein mRNA translation. We focused on â-casein, the major milk protein, and found that the increase in â-casein mRNA translation was reflected in a shift to larger polysomes, indicating an effect on translational initiation. Inhibitors of the PI3K, mTOR, and MAPK pathways blocked insulin-stimulated total protein and â-casein synthesis but not the synergistic stimulation. Conversely, cordycepin, a polyadenylation inhibitor, abolished synergistic stimulation of protein synthesis without affecting insulin-stimulated translation. The poly(A) tract of â-casein mRNA progressively increased over 30 min of treatment with insulin plus prolactin. The 3’-untranslated region of â-casein mRNA was found to contain a cytoplasmic polyadenylation element (CPE), and in reporter constructs, this was sufficient for the translational enhancement and mRNA-specific polyadenylation. Furthermore, insulin and prolactin stimulated phosphorylation of cytoplasmic polyadenylation element binding protein (CPEB) but did not increase cytoplasmic polyadenylation.
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Ron, Eliora, and Eugene Eugene Nester. Global functional genomics of plant cell transformation by agrobacterium. United States Department of Agriculture, March 2009. http://dx.doi.org/10.32747/2009.7695860.bard.

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The aim of this study was to carry out a global functional genomics analysis of plant cell transformation by Agrobacterium in order to define and characterize the physiology of Agrobacterium in the acidic environment of a wounded plant. We planed to study the proteome and transcriptome of Agrobacterium in response to a change in pH, from 7.2 to 5.5 and identify genes and circuits directly involved in this change. Bacteria-plant interactions involve a large number of global regulatory systems, which are essential for protection against new stressful conditions. The interaction of bacteria with their hosts has been previously studied by genetic-physiological methods. We wanted to make use of the new capabilities to study these interactions on a global scale, using transcription analysis (transcriptomics, microarrays) and proteomics (2D gel electrophoresis and mass spectrometry). The results provided extensive data on the functional genomics under conditions that partially mimic plant infection and – in addition - revealed some surprising and significant data. Thus, we identified the genes whose expression is modulated when Agrobacterium is grown under the acidic conditions found in the rhizosphere (pH 5.5), an essential environmental factor in Agrobacterium – plant interactions essential for induction of the virulence program by plant signal molecules. Among the 45 genes whose expression was significantly elevated, of special interest is the two-component chromosomally encoded system, ChvG/I which is involved in regulating acid inducible genes. A second exciting system under acid and ChvG/Icontrol is a secretion system for proteins, T6SS, encoded by 14 genes which appears to be important for Rhizobium leguminosarum nodule formation and nitrogen fixation and for virulence of Agrobacterium. The proteome analysis revealed that gamma aminobutyric acid (GABA), a metabolite secreted by wounded plants, induces the synthesis of an Agrobacterium lactonase which degrades the quorum sensing signal, N-acyl homoserine lactone (AHL), resulting in attenuation of virulence. In addition, through a transcriptomic analysis of Agrobacterium growing at the pH of the rhizosphere (pH=5.5), we demonstrated that salicylic acid (SA) a well-studied plant signal molecule important in plant defense, attenuates Agrobacterium virulence in two distinct ways - by down regulating the synthesis of the virulence (vir) genes required for the processing and transfer of the T-DNA and by inducing the same lactonase, which in turn degrades the AHL. Thus, GABA and SA with different molecular structures, induce the expression of these same genes. The identification of genes whose expression is modulated by conditions that mimic plant infection, as well as the identification of regulatory molecules that help control the early stages of infection, advance our understanding of this complex bacterial-plant interaction and has immediate potential applications to modify it. We expect that the data generated by our research will be used to develop novel strategies for the control of crown gall disease. Moreover, these results will also provide the basis for future biotechnological approaches that will use genetic manipulations to improve bacterial-plant interactions, leading to more efficient DNA transfer to recalcitrant plants and robust symbiosis. These advances will, in turn, contribute to plant protection by introducing genes for resistance against other bacteria, pests and environmental stress.
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