Showing papers by "University of Johannesburg published in 2010"
TL;DR: In this article, it was shown that occurrences of BIF, GIF, Pherozoic ironstones, and exhalites surrounding VMS systems are linked to diverse environmental changes.
Abstract: Iron formations are economically important sedimentary rocks that are most common in Precambrian sedimentary successions. Although many aspects of their origin remain unresolved, it is widely accepted that secular changes in the style of their deposition are linked to environmental and geochemical evolution of Earth. Two types of Precambrian iron formations have been recognized with respect to their depositional setting. Algoma-type iron formations are interlayered with or stratigraphically linked to submarine-emplaced volcanic rocks in greenstone belts and, in some cases, with volcanogenic massive sulfide (VMS) deposits. In contrast, larger Superior-type iron formations are developed in passive-margin sedimentary rock successions and generally lack direct relationships with volcanic rocks. The early distinction made between these two iron-formation types, although mimimized by later studies, remains a valid first approximation. Texturally, iron formations were also divided into two groups. Banded iron formation (BIF) is dominant in Archean to earliest Paleoproterozoic successions, whereas granular iron formation (GIF) is much more common in Paleoproterozoic successions. Secular changes in the style of iron-formation deposition, identified more than 20 years ago, have been linked to diverse environmental changes. Geochronologic studies emphasize the episodic nature of the deposition of giant iron formations, as they are coeval with, and genetically linked to, time periods when large igneous provinces (LIPs) were emplaced. Superior-type iron formation first appeared at ca. 2.6 Ga, when construction of large continents changed the heat flux at the core-mantle boundary. From ca. 2.6 to ca. 2.4 Ga, global mafic magmatism culminated in the deposition of giant Superior-type BIF in South Africa, Australia, Brazil, Russia, and Ukraine. The younger BIFs in this age range were deposited during the early stage of a shift from reducing to oxidizing conditions in the ocean-atmosphere system. Counterintuitively, enhanced magmatism at 2.50 to 2.45 Ga may have triggered atmospheric oxidation. After the rise of atmospheric oxygen during the GOE at ca. 2.4 Ga, GIF became abundant in the rock record, compared to the predominance of BIF prior to the Great Oxidation Event (GOE). Iron formations generally disappeared at ca. 1.85 Ga, reappearing at the end of the Neoproterozoic, again tied to periods of intense magmatic activity and also, in this case, to global glaciations, the so-called Snowball Earth events. By the Phanerozoic, marine iron deposition was restricted to local areas of closed to semiclosed basins, where volcanic and hydrothermal activity was extensive (e.g., back-arc basins), with ironstones additionally being linked to periods of intense magmatic activity and ocean anoxia.
Late Paleoproterozoic iron formations and Paleozoic ironstones were deposited at the redoxcline where biological and nonbiological oxidation occurred. In contrast, older iron formations were deposited in anoxic oceans, where ferrous iron oxidation by anoxygenic photosynthetic bacteria was likely an important process. Endogenic and exogenic factors contributed to produce the conditions necessary for deposition of iron formation. Mantle plume events that led to the formation of LIPs also enhanced spreading rates of midocean ridges and produced higher growth rates of oceanic plateaus, both processes thus having contributed to a higher hydrothermal flux to the ocean. Oceanic and atmospheric redox states determined the fate of this flux. When the hydrothermal flux overwhelmed the oceanic oxidation state, iron was transported and deposited distally from hydrothermal vents. Where the hydrothermal flux was insufficient to overwhelm the oceanic redox state, iron was deposited only proximally, generally as oxides or sulfides. Manganese, in contrast, was more mobile. We conclude that occurrences of BIF, GIF, Phanerozoic ironstones, and exhalites surrounding VMS systems record a complex interplay involving mantle heat, tectonics, and surface redox conditions throughout Earth history, in which mantle heat unidirectionally declined and the surface oxidation state mainly unidirectionally increased, accompanied by superimposed shorter term fluctuations.
758 citations
TL;DR: The practical method provides for safer handling and drying of solvents than methods calling for the use of reactive metals, metal hydrides, or solvent distillation and can be used to rapidly and reliably generatesolvents with low residual water content by means of commonly available materials found in most synthesis laboratories.
Abstract: Various commonly used organic solvents were dried with several different drying agents. A glovebox-bound coulometric Karl Fischer apparatus with a two-compartment measuring cell was used to determine the efficiency of the drying process. Recommendations are made relating to optimum drying agents/conditions that can be used to rapidly and reliably generate solvents with low residual water content by means of commonly available materials found in most synthesis laboratories. The practical method provides for safer handling and drying of solvents than methods calling for the use of reactive metals, metal hydrides, or solvent distillation.
648 citations
TL;DR: In this article, the authors used the ATLAS detector to detect dijet asymmetry in the collisions of lead ions at the Large Hadron Collider and found that the transverse energies of dijets in opposite hemispheres become systematically more unbalanced with increasing event centrality, leading to a large number of events which contain highly asymmetric di jets.
Abstract: By using the ATLAS detector, observations have been made of a centrality-dependent dijet asymmetry in the collisions of lead ions at the Large Hadron Collider. In a sample of lead-lead events with a per-nucleon center of mass energy of 2.76 TeV, selected with a minimum bias trigger, jets are reconstructed in fine-grained, longitudinally segmented electromagnetic and hadronic calorimeters. The transverse energies of dijets in opposite hemispheres are observed to become systematically more unbalanced with increasing event centrality leading to a large number of events which contain highly asymmetric dijets. This is the first observation of an enhancement of events with such large dijet asymmetries, not observed in proton-proton collisions, which may point to an interpretation in terms of strong jet energy loss in a hot, dense medium.
630 citations
TL;DR: The analysis presented in this article draws on rapid-response research conducted by the author and his colleagues in five of the so-called hot spots of South Africa, and suggests that the interconnections between the local protests and militant action involving other elements of civil society are limited.
Abstract: Since 2004, South Africa has experienced a movement of local protests amounting to a rebellion of the poor. This has been widespread and intense, reaching insurrectionary proportions in some cases. On the surface, the protests have been about service delivery and against uncaring, self-serving, and corrupt leaders of municipalities. A key feature has been mass participation by a new generation of fighters, especially unemployed youth but also school students. Many issues that underpinned the ascendency of Jacob Zuma also fuel the present action, including a sense of injustice arising from the realities of persistent inequality. While the inter-connections between the local protests, and between the local protests and militant action involving other elements of civil society, are limited, it is suggested that this is likely to change. The analysis presented here draws on rapid-response research conducted by the author and his colleagues in five of the so-called ‘hot spots’.
512 citations
Open University1, University of California, Irvine2, University of Oxford3, California Institute of Technology4, Jet Propulsion Laboratory5, National Radio Astronomy Observatory6, Harvard University7, Institut d'Astrophysique de Paris8, French Alternative Energies and Atomic Energy Commission9, University of Johannesburg10, Search for extraterrestrial intelligence11, University of Crete12, University of Padua13, University of Hertfordshire14, University of Edinburgh15, Cardiff University16, National Institute of Astrophysics, Optics and Electronics17, University of Bonn18, European Space Agency19, University of Nottingham20, University of St Andrews21, Spanish National Research Council22, University of La Laguna23, Goddard Space Flight Center24, Imperial College London25, Ghent University26, University of Louisville27, University of Paris-Sud28, Liverpool John Moores University29, Ames Research Center30, University of Chicago31, University of Pennsylvania32, Rutgers University33, University of Bristol34, Aix-Marseille University35, Queen Mary University of London36, University of Colorado Boulder37, University of Maryland, College Park38, Carnegie Institution for Science39, Japan Aerospace Exploration Agency40, University of Central Lancashire41, Rutherford Appleton Laboratory42, University of British Columbia43, Durham University44, Max Planck Society45, Leiden University46
TL;DR: Early data from the Herschel Astrophysical Terahertz Large Area Survey are used to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.
Abstract: Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.
436 citations
TL;DR: Community-based natural resource management (CBNRM) has been on the ascendancy for several decades and plays a leading role in conservation strategies worldwide as mentioned in this paper, however, scholars and practitioners suggest that CBNRM is experiencing a crisis of identity and purpose, with even the most positive examples experiencing only fleeting success due to major deficiencies.
Abstract: Community-based natural resource management (CBNRM) has been on the ascendancy for several decades and plays a leading role in conservation strategies worldwide. Arriving out of a desire to rectify the human costs associated with coercive conservation, CBNRM sought to return the stewardship of biodiversity and natural resources to local communities through participation, empowerment and decentralization. Today, however, scholars and practitioners suggest that CBNRM is experiencing a crisis of identity and purpose, with even the most positive examples experiencing only fleeting success due to major deficiencies. Six case studies from around the world offer a history of how and why the global CBNRM narrative has unfolded over time and space. While CBNRM emerged with promise and hope, it often ended in less than ideal outcomes when institutionalized and reconfigured in design and practice. Nevertheless, despite the current crisis, there is scope for refocusing on the original ideals of CBNRM: ensuring social justice, material well-being and environmental integrity.
427 citations
TL;DR: In this paper, a series of experiments using a 2D petrological-thermomechanical numerical model of oceanic subduction was conducted to investigate the dependence of tectono-metamorphic and magmatic regimes at an active plate margin on upper-mantle temperature, crustal radiogenic heat production, degree of lithospheric weakening and other parameters.
326 citations
TL;DR: In this article, the authors provide a theoretical reconstruction of sub-Saharan ethics that they argue is a strong competitor to typical Western approaches to morality, and highlight respects in which the African approach provides a unitary foundation for a variety of normative and empirical conclusions that are serious alternatives to dominant Western views.
Abstract: In this article we provide a theoretical reconstruction of sub-Saharan ethics that we argue is a strong competitor to typical Western approaches to morality. According to our African moral theory, actions are right roughly insofar as they are a matter of living harmoniously with others or honouring communal relationships. After spelling out this ethic, we apply it to several issues in both normative and empirical research into morality. With regard to normative research, we compare and contrast this African moral theory with utilitarianism and Kantianism in the context of several practical issues. With regard to empirical research, we compare and contrast our sub-Saharan ethic with several of Lawrence Kohlberg's views on the nature of morality. Our aim is to highlight respects in which the African approach provides a unitary foundation for a variety of normative and empirical conclusions that are serious alternatives to dominant Western views.
256 citations
TL;DR: In this paper, an early assemblage from Sibudu Cave, KwaZulu-Natal, South Africa, was used to detect bow and arrow technology in use there 64 millennia ago.
Abstract: The invention of the bow and arrow was a pivotal moment in the human story and its earliest use is a primary quarry of the modern researcher. Since the organic parts of the weapon – wood, bone, cord and feathers – very rarely survive, the deduction that a bow and arrow was in use depends heavily on the examination of certain classes of stone artefacts and their context. Here the authors apply rigorous analytical reasoning to the task, and demonstrate that, conforming to their exacting checklist, is an early assemblage from Sibudu Cave, KwaZulu-Natal, South Africa, which therefore suggests bow and arrow technology in use there 64 millennia ago.
240 citations
TL;DR: In this paper, the combined Fe, C, and O isotope data from Kuruman BIF carbonates indicate that BIF siderites that have negative, near zero, or positive δ56Fe values may all record biological Fe cycling, where the range in δ54Fe values records differential Fe mobilization via DIR in the sediment prior to lithification.
207 citations
TL;DR: An overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data and the determination of the global energy scale was performed with an uncertainty of 4%.
Abstract: The Tile hadronic calorimeter of the ATLAS detector has undergone extensive testing in the experimental hall since its installation in late 2005. The readout, control and calibration systems have been fully operational since 2007 and the detector has successfully collected data from the LHC single beams in 2008 and first collisions in 2009. This paper gives an overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data. The detector operation status, noise characteristics and performance of the calibration systems are presented, as well as the validation of the timing and energy calibration carried out with minimum ionising cosmic ray muons data. The calibration systems’ precision is well below the design value of 1%. The determination of the global energy scale was performed with an uncertainty of 4%.
James Cook University1, University of the Witwatersrand2, Duke University3, University of Johannesburg4, University of Bern5, University of Melbourne6, University of California, Santa Cruz7, Lawrence Livermore National Laboratory8, Newcastle University9, University of New South Wales10, University of Liverpool11
TL;DR: Two partial skeletons of a new species of Australopithecus, about 1.9 million years old, are described, which imply that the transition to Homo was in stages and shows many derived features with Homo, helping to reveal its evolution.
Abstract: We describe the geological, geochronological, geomorphological, and faunal context of the Malapa site and the fossils of Australopithecus sediba. The hominins occur with a macrofauna assemblage that existed in Africa between 2.36 and 1.50 million years ago (Ma). The fossils are encased in water-laid, clastic sediments that were deposited along the lower parts of what is now a deeply eroded cave system, immediately above a flowstone layer with a U-Pb date of 2.026 ± 0.021 Ma. The flowstone has a reversed paleomagnetic signature and the overlying hominin-bearing sediments are of normal polarity, indicating deposition during the 1.95- to 1.78-Ma Olduvai Subchron. The two hominin specimens were buried together in a single debris flow that lithified soon after deposition in a phreatic environment inaccessible to scavengers.
TL;DR: A new interpretation of the stratigraphy based on surface mapping, boreholes logs and U-Pb ages is presented and it is proposed that the deposits formally known as Member 3 are in fact the distal equivalents of Member 4, which consisted of cone-like deposits and probably never filled up the cave.
TL;DR: In this article, the authors determined the Fe and Si isotope composition of coexisting mineral phases in samples from the ∼2.5 billion year old Kuruman Iron Formation (Transvaal Supergroup, South Africa) and Dales Gorges Member of the Brockman iron Formation (Hamersley Group, Australia) by UV femtosecond laser ablation coupled to a MC-ICP-MS.
TL;DR: The authors argue that the differential workings of anti-politics in practice warrant a renewed appreciation and a more explicit political operationalization of the concept, by re-emphasizing antipolitics as an essential political strategy within conservation and development interventions and as an intrinsic element of the wider political economy of neoliberalism.
Abstract: Studies on conservation and development often point out that interventions rely on anti-political manoeuvring to acquire legitimacy and support. Recent ‘aidnography’, in particular, has done much to expand and add nuance to our understanding of the complex, micro- (anti-)politics at work in conservation and development interventions. In doing this, however, aidnography seems to have led the focus away from two crucial, broader issues related to conservation and development interventions: how they are regulated through the wider, neoliberal political economy, and how this fuels and obscures (global) inequality. Drawing on empirical research on a transfrontier conservation and development intervention in Southern Africa, this article argues that the differential workings of anti-politics in practice warrant a renewed appreciation and a more explicit political operationalization of the concept. This is done by re-emphasizing anti-politics as an essential political strategy within conservation and development interventions and as an intrinsic element of the wider political economy of neoliberalism.
TL;DR: In this article, the authors provide an overview of the international development of local economic development (LED), of its contested definitions and theoretical status, and of existing scholarship on the topic of LED policy and practice specifically across sub-Saharan Africa.
Abstract: This paper locates local economic development research and practice in Africa in a global context. It provides an overview of the international development of local economic development (LED), of its contested definitions and theoretical status, and of existing scholarship on the topic of LED policy and practice specifically across sub-Saharan Africa. Currently there is much more LED research available for South Africa than for the other sub-Saharan African countries. The paper highlights the need for this imbalance to be redressed.
TL;DR: In this paper, a secondary data analysis (SDA) was performed in a quantitative research tradition on the cross-sectional survey data collected from a large South African Information and Communication Technologies (ICT) sector company (n = 2429) to investigate the predictive relationship between the work engagement-burnout continuum and turnover intentions.
Abstract: Orientation: The focus of the study was to investigate the predictive relationship between the work engagement-burnout continuum and turnover intentions. Research purpose: The main purpose of the study was to determine whether work engagement, burnout, organisational citizenship behaviour (OCB) and work alienation are predictors of turnover intentions. Motivation for the study: Organisations operating within the 21st century face significant challenges in the management of talent and human capital. One in particular is voluntary employee turnover and the lack of appropriate business models to track this process. Research design, approach and method: A secondary data analysis (SDA) was performed in a quantitative research tradition on the cross-sectional survey data collected from a large South African Information and Communication Technologies (ICT) sector company ( n = 2429). Main findings: The results of the study confirmed the predictive model (work engagement, burnout, OCB and work alienation) of turnover intention. Specifically, work engagement and OCBs were significantly negatively related to turnover intention; whilst burnout and work alienation were significantly positively related to turnover intention. Several third-variable relationships, such as biographic and demographic variables, indicated statistical significance. Practical/managerial implications: Practical implications of the study could impact on human resource (HR) value-chain activities in the form of evidence-based and improved recruitment and selection procedures, employee retention strategies and training and development interventions. Issues concerning talent management could also be addressed. Contribution/value-add: The study described in this article took Industrial/Organisational (I/O) psychological concepts and linked them in unique combinations to establish better predictive validity of a new turnover intentions model.
TL;DR: In this article, the authors investigated the effect of water pressure in a pipe on the rate of leakage from leak openings in the pipe and found that pipe stresses are significantly affected by a leak opening, and can easily exceed the material's yield strength in the vicinity of the opening.
Abstract: The effect of water pressure in a pipe on the rate of leakage from leak openings in the pipe is one of the main factors influencing leakage that is still not understood sufficiently. In this study, the behaviours of different types of leak openings (round holes and longitudinal and circumferential cracks) on pressurized pipes were investigated for different pipe materials (uPVC, steel, cast iron and asbestos cement) using finite element analysis. Linear elastic behaviour was assumed. The study found that (1) pipe stresses are significantly affected by a leak opening, and can easily exceed the material's yield strength in the vicinity of the opening; (2) round holes show the smallest expansion with pressure, followed by circumferential cracks and then longitudinal cracks; (3) the areas of all leak openings increase linearly with pressure; (4) longitudinal pipe stresses affect the behaviours of round holes and circumferential cracks, but not that of longitudinal cracks; and (5) the effect of pressure on a l...
TL;DR: Concepts, also known as conceptions or constructs, play various important roles in empirical research and, by extension, could be the subject of more explicit inquiry in mono and mixed methods research as mentioned in this paper.
Abstract: Concepts, also known as conceptions or constructs, play various important roles in empirical research and, by extension, could be the subject of more explicit inquiry in mono and mixed methods research. For empirical researchers, a concept can be understood as an abstract object, abstractum, or a mental representation. Well-being, depression, poverty, achievement, family, class, illness, democracy, power, gender, and ethnicity are examples of concepts. Concepts occupy an interesting position in that they refer either directly or indirectly to something inferred from a specific set of occurrences in conjunction with the mental formation of a notion associated with these. In 1936, Albert Einstein argued that
TL;DR: The evolutionary history of Mimosoideae is reconstructed using the most comprehensive sampling to date, with an emphasis on African species, and the phylogenetic relationships among the five recognized genera within Acacieae are reconstructed to elucidate the paleo-biogeography of mimosoids and their adaptation to open habitats in the Cenozoic.
TL;DR: In this article, the authors assess the impact of monetary policy on real house price growth in South Africa using a factor-augmented vector autoregression (FAVAR) model.
TL;DR: The low temperature state of the CeRu2Al10 has been studied by neutron powder diffraction and muon spin relaxation (muSR) by combining both techniques, and it has been shown that the transition occurring below T*~27K is unambiguously magnetic due to the ordering of the sublattice as discussed by the authors.
Abstract: The low temperature state of CeRu2Al10 has been studied by neutron powder diffraction and muon spin relaxation (muSR). By combining both techniques, we prove that the transition occurring below T*~27K, which has been the subject of considerable debate, is unambiguously magnetic due to the ordering of the Ce sublattice. The magnetic structure with propagation vector k=(1,0,0) involves collinear antiferromagnetic alignment of the Ce moments along the c-axis of the Cmcm space group with a reduced moment of 0.34(2)mu_B. No structural changes within the resolution limit have been detected below the transition temperature. However, the temperature dependence of the magnetic Bragg peaks and the muon precession frequency show an anomaly around T2~12 K indicating a possible second transition.
TL;DR: In this article, the effects of low-level laser radiation and epidermal growth factor (EGF) on adult adipose-derived stem cells (ADSCs) isolated from human adipose tissue were investigated.
Abstract: The study investigated the effects of low-level laser radiation and epidermal growth factor (EGF) on adult adipose-derived stem cells (ADSCs) isolated from human adipose tissue. Isolated cells were cultured to semi-confluence, and the monolayers of ADSCs were exposed to low-level laser at 5 J/cm2 using 636 nm diode laser. Cell viability and proliferation were monitored using adenosine triphosphate (ATP) luminescence and optical density at 0 h, 24 h and 48 h after irradiation. Application of low-level laser irradiation at 5 J/cm2 on human ADSCs cultured with EGF increased the viability and proliferation of these cells. The results indicate that low-level laser irradiation in combination with EGF enhances the proliferation and maintenance of ADSCs in vitro.
TL;DR: In this paper, the authors analyse 15 years' experience of LED planning, and identify strategic challenges that face LED planning in South Africa, where the major objective of national government promotion of local economic development (LED) is to forge robust and sustainable local economies.
Abstract: Since the democratic transition, local economic development has been a growing feature of development planning in South Africa. The major objective of national government promotion of local economic development (LED) in South Africa is to forge robust and sustainable local economies. This paper analyses 15 years' experience of LED planning, and identifies strategic challenges that face LED planning in South Africa.
TL;DR: In this article, carbonate isotope data of the 2.64-2.5 Ga old Ghaap Group (Transvaal Supergroup, South Africa) were used to contribute to the debate on early Earth oxygenation.
TL;DR: In this paper, the authors used three cases (ages 16 to 23 years old) drawn from a major study that investigated the educational implications of child sexual abuse in South Africa, and presented Black female survivors who experienced educational resilience regardless of having been sexually abused, and other contributory factors that could have driven them to react otherwise.
Abstract: The literature covering child sexual abuse within the South African context, though substantial, has ignored issues of resilience, especially relating to the victim’s racial background. Particular reference is made to the victim’s ability to draw on elements relating to his or her cultural upbringing—socialization and identification. Using three cases (ages 16 to 23 years old) drawn from a major study that investigated the educational implications of child sexual abuse in South Africa, the article presents Black female survivors who experienced educational resilience regardless of having been sexually abused, and other contributory factors that could have driven them to react otherwise. Educational resilience is evident in the following ways: (a) participants’ interpretations of their experience, (b) behavior exhibited at school, (c) determination to succeed, and (d) educational and career aspirations. These responses are then related to the identification and socialization of people of African ancestry l...
TL;DR: The aim is to help rectify this deficiency by first spelling out a moral theory grounded in the mores of many sub-Saharan peoples, and then applying it to some major bioethical issues, namely, the point of medical treatment, free and informed consent, standards of care and animal experimentation.
Abstract: The field of bioethics is replete with applications of moral theories such as utilitarianism and Kantianism. For a given dilemma, even if it is not clear how one of these western philosophical principles of right (and wrong) action would resolve it, one can identify many of the considerations that each would conclude is relevant. The field is, in contrast, largely unaware of an African account of what all right (and wrong) actions have in common and of the sorts of factors that for it are germane to developing a sound response to a given bioethical problem. My aim is to help rectify this deficiency by first spelling out a moral theory grounded in the mores of many sub-Saharan peoples, and then applying it to some major bioethical issues, namely, the point of medical treatment, free and informed consent, standards of care and animal experimentation. For each of these four issues, I compare and contrast the implications of the African moral theory with utilitarianism and Kantianism, my overall purposes being to highlight respects in which the African moral theory is distinct and to demonstrate that the field should take it at least as seriously as it does the Western theories.
TL;DR: This analysis delineates the Drimolen P. robustus dental sample as characterized by smaller teeth overall than the Swartkrans sample (and in some cases also smaller than the Kromdraai sample), as well as a greater size range.
TL;DR: A review of pyrazolyl metal complexes as nitrogen-donor catalysts, particularly in carbon-carbon coupling reactions, can be found in this paper, where the focus is on olefin oligomerization and polymerization.
01 Jan 2010
TL;DR: Plants have evolved a second line of defense that includes intracellular nucleotide binding leucine-rich repeat (NB-LRR)-containing resistance proteins, which recognize isolate-specific pathogen effectors once the cell wall has been compromised.
Abstract: The ability to distinguish 'self' from 'nonself' is the most fundamental aspect of any immune system. The evolutionary solution in plants to the problems of perceiving and responding to pathogens involves surveillance of nonself, damaged-self and altered-self as danger signals. This is reflected in basal resistance or non-host resistance, which is the innate immune response that protects plants against the majority of pathogens. In the case of surveillance of nonself, plants utilize receptor-like proteins or -kinases (RLP/Ks) as pattern recognition receptors (PRRs), which can detect conserved pathogen/microbe-associated molecular pattern (P/MAMP) molecules. P/MAMP detection serves as an early warning system for the presence of a wide range of potential pathogens and the timely activation of plant defense mechanisms. However, adapted microbes express a suite of effector proteins that often interfere or act as suppressors of these defenses. In response, plants have evolved a second line of defense that includes intracellular nucleotide binding leucine-rich repeat (NB-LRR)-containing resistance proteins, which recognize isolate-specific pathogen effectors once the cell wall has been compromised. This host-immunity acts within the species level and is controlled by polymorphic host genes, where resistance protein-mediated activation of defense is based on an 'altered-self' recognition mechanism.