Journal articles: 'Constitutive and induced defence'

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Boots, Mike, and Alex Best. "The evolution of constitutive and induced defences to infectious disease." Proceedings of the Royal Society B: Biological Sciences 285, no. 1883 (July 25, 2018): 20180658. http://dx.doi.org/10.1098/rspb.2018.0658.

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In response to infectious disease, hosts typically mount both constitutive and induced defences. Constitutive defence prevents infection in the first place, while induced defence typically shortens the infectious period. The two routes to defence, therefore, have very different implications not only to individuals but also to the epidemiology of the disease. Moreover, the costs of constitutive defences are likely to be paid even in the absence of disease, while induced defences are likely to incur the most substantial costs when they are used in response to infection. We examine theoretically the evolutionary implications of these fundamental differences. A key result is that high virulence in the parasite typically selects for higher induced defences even if they result in immunopathology leading to very high disease mortality. Disease impacts on fecundity are critical to the relative investment in constitutive and induced defence with important differences found when parasites castrate their hosts. The trade-off between constitutive and induced defence has been cited as a cause of the diversity in defence, but we show that the trade-off alone is unlikely to lead to diversity. Our models provide a framework to examine relative investment in different defence components both experimentally and in the field.

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Hamilton, Ruth, Mike Siva-Jothy, and Mike Boots. "Two arms are better than one: parasite variation leads to combined inducible and constitutive innate immune responses." Proceedings of the Royal Society B: Biological Sciences 275, no. 1637 (January 29, 2008): 937–45. http://dx.doi.org/10.1098/rspb.2007.1574.

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Parasites represent a major threat to all organisms which has led to the evolution of an array of complex and effective defence mechanisms. Common to both vertebrates and invertebrates are innate immune mechanisms that can be either constitutively expressed or induced on exposure to infection. In nature, we find that a combination of both induced and constitutive responses are employed by vertebrates, invertebrates and, to an extent, plants when they are exposed to a parasite. Here we use a simple within-host model motivated by the insect immune system, consisting of both constitutive and induced responses, to address the question of why both types of response are maintained so ubiquitously. Generally, induced responses are thought to be advantageous because they are only used when required but are too costly to maintain constantly, while constitutive responses are advantageous because they are always ready to act. However, using a simple cost function but with no a priori assumptions about relative costs, we show that variability in parasite growth rates selects for a strategy that combines both constitutive and induced defences. Differential costs are therefore not necessary to explain the adoption of both forms of defence. Clearly, hosts are likely to be challenged by variable parasites in nature and this is sufficient to explain why it is optimal to deploy both arms of the innate immune system.

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Miyazaki, Junji, Warwick N. Stiller, Thy T. Truong, Qian Xu, Charles H. Hocart, Lewis J. Wilson, and Iain W. Wilson. "Jasmonic acid is associated with resistance to twospotted spider mites in diploid cotton (Gossypium arboreum)." Functional Plant Biology 41, no. 7 (2014): 748. http://dx.doi.org/10.1071/fp13333.

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The twospotted spider mite (Tetranychus urticae Koch) is capable of dramatically reducing the yield of cotton crops and is often difficult and expensive to control. This study investigated and compared two important plant hormones, jasmonic acid (JA) and salicylic acid (SA), as constitutive and/or induced defence response components in a mite susceptible commercial cotton cultivar, Sicot 71 (Gossypium hirsutum L.) and a resistant diploid cotton BM13H (Gossypium arboreum L.). Foliar application of JA and methyl jasmonate (MeJA) reduced the mite population and leaf damage but application of other potential elicitors, SA and methyl salicylate (MeSA) did not. The concentrations of JA and SA in leaf tissues of induced and non-induced Sicot 71 and BM13H were quantified by liquid chromatography coupled to electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS). The JA content was constitutively higher in BM13H than Sicot 71 and also highly induced by mite infestation in BM13H but not in Sicot 71. However, SA was not significantly induced in either BM13H or Sicot 71. The expression levels of JA related genes, LOX, AOS and OPR were measured by quantitative PCR and elevated expression levels of JA related genes were detected in mite-infested BM13H. Therefore, JA and MeJA were implicated as key biochemical components in both the constitutive and induced defence responses of BM13H to spider mites.

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Schmidtberg, Henrike, Christian Röhrich, Heiko Vogel, and Andreas Vilcinskas. "A switch from constitutive chemical defence to inducible innate immune responses in the invasive ladybird Harmonia axyridis." Biology Letters 9, no. 3 (June 23, 2013): 20130006. http://dx.doi.org/10.1098/rsbl.2013.0006.

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The harlequin ladybird, Harmonia axyridis , has emerged as a model species for invasion biology, reflecting its remarkable capacity to outcompete native ladybird species when introduced into new habitats. This ability may be associated with its prominent resistance to pathogens and intraguild predation. We recently showed that the constitutive antibacterial activity present in the haemolymph of H. axyridis beetles can be attributed to the chemical defence compound harmonine. Here, we demonstrate that H. axyridis differs from other insects, including the native ladybird Coccinella septempunctata, by reducing rather than increasing the antimicrobial activity of its haemolymph following the injection of bacteria. However, both species produce new or more abundant proteins in the haemolymph, indicating that bacterial challenge induces innate immune responses associated with the synthesis of immunity-related proteins. Our results suggest that H. axyridis beetles can switch from constitutive chemical defence to inducible innate immune responses, supporting hypothesis that inducible antimicrobial peptides protect host beetles against pathogens that survive constitutive defences. These alternative antimicrobial defence mechanisms may reflect a trade-off resulting from fitness-related costs associated with the simultaneous synthesis of harmonine and antimicrobial peptides/proteins.

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Rodríguez-Romero, Manuela, Alejandro Gallardo, Andrea Pérez, and Fernando Pulido. "Interactive effects of biotic stressors and provenance on chemical defence induction by holm oak (Quercus ilex)." Trees 36, no. 1 (December 10, 2021): 227–40. http://dx.doi.org/10.1007/s00468-021-02201-z.

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Abstract Key Message The patterns of induced chemical defences in Quercus ilex leaves are specific to the biotic stress factor that causes them. Interactive effects between stressors depend on provenance. Abstract Quercus forests are suffering serious decline worldwide, closely linked to the consequences of climate change. The increase of biotic stressors threatens the survival of the holm oak (Quercus ilex), a dominant tree species in the Mediterranean Basin. A better understanding of its resistance mechanisms is urgently required to enable a better control of its decline. In this work, the ability of holm oaks from six Iberian provenances to respond to multiple biotic damage is studied through an analysis of their induced chemical defence patterns. Using 2016 seedlings established in a common garden trial (6 regions × 12 families/region × 7 seedlings/family × 4 treatments), biotic damage was induced at the root level (by infection with the widespread pathogen Phytophthora cinnamomi) and at the above-ground level (by mechanical defoliation). The levels of constitutive and induced total phenols, total tannins and condensed tannins were measured. Results showed that (1) the defensive chemical patterns present significant local and geographical variation, (2) survival to stress is more related to constitutive defences than induced ones, (3) the induced response is stressor-specific, and (4) there is an interactive effect amongst stressors whose sign (induction/inhibition) depends on the provenance. These findings on biotic stressor effects on the chemical defences and survival of holm oak can contribute to the development of genetic material selection programs in the integrated control of the widespread decline of Quercus.

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Ruiz, N., D. Ward, and D. Saltz. "Calcium oxalate crystals in leaves of Pancratium sickenbergeri : constitutive or induced defence?" Functional Ecology 16, no. 1 (February 2002): 99–105. http://dx.doi.org/10.1046/j.0269-8463.2001.00594.x.

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JOLIVET, CÉLINE, and GIORGINA BERNASCONI. "Experimental analysis of constitutive and induced defence in a plant?seed?predator system." Functional Ecology 20, no. 6 (December 2006): 966–72. http://dx.doi.org/10.1111/j.1365-2435.2006.01196.x.

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Lindgren, B. S., and K. F. Raffa. "Evolution of tree killing in bark beetles (Coleoptera: Curculionidae): trade-offs between the maddening crowds and a sticky situation." Canadian Entomologist 145, no. 5 (June 11, 2013): 471–95. http://dx.doi.org/10.4039/tce.2013.27.

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AbstractBark beetles (Coleoptera: Curculionidae: Scolytinae) play important roles in temperate conifer ecosystems, and also cause substantial economic losses. Although their general life histories are relatively similar, different species vary markedly in the physiological condition of the hosts they select. Most of ∼6000 known species colonise dead or stressed trees, a resource they share with a large diversity of insects and other organisms. A small number of bark beetle species kill healthy, live trees. These few are of particular interest as they compete directly with humans for resources. We propose that tree killing evolved when intense interspecific competition in the ephemeral, scarce resource of defence-impaired trees selected for genotypes that allowed them to escape this limitation by attacking relatively healthy trees. These transitions were uncommon, and we suggest they were facilitated by (a) genetically and phenotypically flexible host selection behaviours, (b) biochemical adaptations for detoxifying a wide range of defence compounds, and (c) associations with symbionts, which together aided bark beetles in overcoming formidable constitutive and induced host defences. The ability to detoxify terpenes influenced the evolutionary course of pheromonal communication. Specifically, a mate attraction system, which was exploited by intraspecific competitors in locating poorly defended hosts, became a system of cooperative attack in which emitters benefit from the contributions responders make in overcoming defence. This functional shift in communication was driven in part by linkage of beetle semiochemistry to host defence chemistry. Behavioural and phenological adaptations also improved the beetles’ abilities to detect when tree defences are impaired, and, where compatible with life history adaptations to other selective forces, for flight to coincide with seasonally predictable host stress agents. We propose a conceptual model, whereby the above mechanisms enable beetles to concentrate on those trees that offer an optimal trade-off between host defence and interspecific competition, along dynamic gradients of tree vigour and stand-level beetle density. We offer suggestions for future research on testing elements of this model.

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Schulte, Rebecca D., Barbara Hasert, Carsten Makus, Nico K. Michiels, and Hinrich Schulenburg. "Increased responsiveness in feeding behaviour of Caenorhabditis elegans after experimental coevolution with its microparasite Bacillus thuringiensis." Biology Letters 8, no. 2 (August 31, 2011): 234–36. http://dx.doi.org/10.1098/rsbl.2011.0684.

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Immune responses, either constitutive or induced, are costly. An alternative defence strategy may be based on behavioural responses. For example, avoidance behaviour reduces contact with pathogens and thus the risk of infection as well as the requirement of immune system activation. Similarly, if pathogens are taken up orally, preferential feeding of pathogen-free food may be advantageous. Behavioural defences have been found in many animals, including the nematode Caenorhabditis elegans . We here tested nematodes from a laboratory based evolution experiment which had either coevolved with their microparasite Bacillus thuringiensis (BT) or evolved under control conditions. After 48 generations, coevolved populations were more sensitive to food conditions: in comparison with the controls, they reduced feeding activity in the presence of pathogenic BT strains while at the same time increasing it in the presence of non-pathogenic strains. We conclude that host–parasite coevolution can drive changes in the behavioural responsiveness to bacterial microbes, potentially leading to an increased defence against pathogens.

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Martinez-Swatson, Karen, Rasmus Kjøller, Federico Cozzi, Henrik Toft Simonsen, Nina Rønsted, and Christopher Barnes. "Exploring evolutionary theories of plant defence investment using field populations of the deadly carrot." Annals of Botany 125, no. 5 (October 31, 2019): 737–50. http://dx.doi.org/10.1093/aob/mcz151.

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Abstract Background and Aims There are a number of disparate models predicting variation in plant chemical defences between species, and within a single species over space and time. These can give conflicting predictions. Here we review a number of these theories, before assessing their power to predict the spatial–temporal variation of thapsigargins between and within populations of the deadly carrot (Thapsia garganica). By utilizing multiple models simultaneously (optimum defence theory, growth rate hypothesis, growth–differentiation balance hypothesis, intra–specific framework and resource exchange model of plant defence), we will highlight gaps in their predictions and evaluate the performance of each. Methods Thapsigargins are potent anti-herbivore compounds that occur in limited richness across the different plant tissues of T. garganica, and therefore represent an ideal system for exploring these models. Thapsia garganica plants were collected from six locations on the island of Ibiza, Spain, and the thapsigargins quantified within reproductive, vegetative and below-ground tissues. The effects of sampling time, location, mammalian herbivory, soil nutrition and changing root-associated fungal communities on the concentrations of thapsigargins within these in situ observations were analysed, and the results were compared with our model predictions. Key Results The models performed well in predicting the general defence strategy of T. garganica and the above-ground distribution of thapsigargins, but failed to predict the considerable proportion of defences found below ground. Models predicting variation over environmental gradients gave conflicting and less specific predictions, with intraspecific variation remaining less understood. Conclusion Here we found that multiple models predicting the general defence strategy of plant species could likely be integrated into a single model, while also finding a clear need to better incorporate below-ground defences into models of plant chemical defences. We found that constitutive and induced thapsigargins differed in their regulation, and suggest that models predicting intraspecific defences should consider them separately. Finally, we suggest that in situ studies be supplemented with experiments in controlled environments to identify specific environmental parameters that regulate variation in defences within species.

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Bixenmann, Ryan J., Phyllis D. Coley, Alexander Weinhold, and Thomas A. Kursar. "High herbivore pressure favors constitutive over induced defense." Ecology and Evolution 6, no. 17 (July 29, 2016): 6037–49. http://dx.doi.org/10.1002/ece3.2208.

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Kvedaras, O. L., M. An, Y. S. Choi, and G. M. Gurr. "Silicon enhances natural enemy attraction and biological control through induced plant defences." Bulletin of Entomological Research 100, no. 3 (September 9, 2009): 367–71. http://dx.doi.org/10.1017/s0007485309990265.

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AbstractSilicon (Si) is known to have a role in constitutive plant defence against arthropod pests, and recent work has illustrated involvement in induced plant defences. The present tri-trophic study tested the hypothesis that Si increases natural enemy attraction to pest-infested plants and improves biological control. Cucumber plants treated with potassium silicate (Si+) and untreated control plants (Si−) were maintained in separately vented glasshouse compartments. Y-tube olfactometer studies showed that adult Dicranolaius bellulus were significantly more attracted to Si+ plants upon which Helicoverpa armigera larvae had fed compared with Si−, pest-infested plants. Predators were not significantly more attracted to Si+ plants when comparing uninfested cucumbers. In a field experiment, we placed H. armigera-infested and uninfested Si+ and Si− cucumber plants in a lucerne stand. Removal rates of H. armigera egg baits showed predation was greater for Si+ infested plants than for other treatments. Results suggest that Si applied to plants with a subsequent pest infestation increases the plants' attractiveness to natural enemies; an effect that was reflected in elevated biological control in the field.

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PELTONEN, S. "Induced defence responses of cereals to pathogen attack." Agricultural and Food Science 8, no. 4-5 (January 4, 1999): 479–92. http://dx.doi.org/10.23986/afsci.5642.

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The defence responses of plants are usually composed of a multitude of structural and biochemical events. Some occur constitutively, whereas others, which are emphasised in this review, are formed in response to pathogen attack and are considered as active reactions of plants. Induction of defence mechanisms can be observed in all plants regardless of their genetic background. Thus, this phenomenon can occur in cultivars with or without known genes for disease resistance. The general defence features of plants may contribute significantly to the overall disease resistance of plants and increasing evidence for the role of different defence molecules are being obtained from molecular studies. In this review, induction of defence mechanisms, especially phenylpropanoid metabolism and its role in the defence responses of cereals to pathogen attack is addressed. Also, induced resistance as a potential tool for disease control in cereals will be briefly discussed.;

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Pedras, M. Soledade C. "AWARD LECTURE / CONFÉRENCE D'HONNEUR Prospects for controlling plant fungal diseases Alternatives based on chemical ecology and biotechnology." Canadian Journal of Chemistry 82, no. 9 (September 1, 2004): 1329–35. http://dx.doi.org/10.1139/v04-105.

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Plants produce a diverse array of secondary metabolites associated with important defence and resistance mechanisms. In general, within the same plant family the chemical structures of these metabolites are related and suggest common biogenetic precursors. Crucifers are known to produce constitutive and induced tryptophan derived metabolites. Pathogenic fungi can resist such defences utilizing a variety of processes, as for example, enzymatic detoxification. On the other hand, to facilitate their penetration and colonization of the plant tissues, fungal phytopathogens can produce phytotoxic metabolites, some of which are selectively toxic to host-plants. However, plants may be resistant to these pathogens partly due to their ability to detoxify these selective phytotoxins. Nonetheless, the outcome of these interactions frequently favours the pathogen and can lead to enormous yield losses or even major plant epidemics. An overview of some of the most recent studies of metabolic pathways and stress responses in crucifers and several of their pathogens is presented. Potential strategies to prevent and control plant microbial diseases based on chemical ecology studies and biotechnology will be discussed. Key words: phytoalexin, phytotoxin, chemical defence, metabolic detoxification, destruxin B.

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Kobayashi, I., L. J. Murdoch, A. R. Hardham, and H. Kunoh. "Cell biology of early events in the plant resistance response to infection by pathogenic fungi." Canadian Journal of Botany 73, S1 (December 31, 1995): 418–25. http://dx.doi.org/10.1139/b95-278.

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In addition to passive (or constitutive) defence mechanisms, plants have evolved a range of active (or inducible) responses that occur rapidly on infection with an incompatible (avirulent) pathogen and that are thought to play a major role in the expression of resistance. These defence reactions are only induced if the plant possesses the ability to recognize and respond to the pathogen. Signal reception by the host must initiate a cascade of events that lead to the expression of resistance. Some resistance responses, such as callose deposition, do not require the expression of new genes. Many responses, for example the synthesis and secretion of toxic compounds or molecules that enhance the strength of physical barriers, result from changes in the pattern of gene transcription. Other defence phenomena include hypersensitive cell collapse, intercellular signalling, and the induction of defence gene transcripts in surrounding cells. Changes in cell biochemistry and physiology are accompanied by characteristic structural modifications in the infected cells, such as the redeployment of selected organelles and dramatic modifications of the host cell wall. Recent evidence indicates that microtubules and microfilaments of the plant cytoskeleton facilitate the rapid localization of these and other plant defence responses to the region of infection. Key words: plant resistance, plant cytoskeleton, microtubules, microfilaments, fungal pathogens, polarity of defence response.

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Arenson, Kenneth J. "The Paradox of Disallowing Duress as a Defence to Murder." Journal of Criminal Law 78, no. 1 (February 2014): 65–79. http://dx.doi.org/10.1350/jcla.2014.78.1.892.

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The common law has long recognised that what would otherwise constitute murder should be reduced to the lesser offence of voluntary manslaughter in instances where the accused was induced to kill because of provocative conduct on the part of the deceased that does not amount to lawful excuse or justification such as self-defence or defence of others. In what is often termed as a reasonable concession to human frailty, the law has opted to treat those who kill under such circumstances as less morally blameworthy than those who kill in the absence of such provocation or other mitigating circumstances such as a genuinely held, albeit objectively unreasonable belief, that the use of deadly force was necessary in self-defence or the defence of another person. In sharp contrast, the common law has steadfastly declined to allow the defence of duress to be interposed in like manner as a partial defence to the crime of murder. The discussion to follow will examine whether this disparate treatment is justifiable in light of the stated underpinnings of these defences. The discussion will conclude by exploring various proposals for reform and the extent to which they are likely to result in sanctions that are commensurate with the relative degrees of moral culpability of those who seek to interpose these defences as complete or partial defences to the crime of murder.

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López-Uribe, Margarita M., Andrea Fitzgerald, and Michael Simone-Finstrom. "Inducible versus constitutive social immunity: examining effects of colony infection on glucose oxidase and defensin-1 production in honeybees." Royal Society Open Science 4, no. 5 (May 2017): 170224. http://dx.doi.org/10.1098/rsos.170224.

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Honeybees use a variety of defence mechanisms to reduce disease infection and spread throughout the colony. Many of these defences rely on the collective action of multiple individuals to prevent, reduce or eradicate pathogens—often referred to as ‘social immunity’. Glucose oxidase (GOX) and some antimicrobial peptides (e.g. defensin-1 or Def1) are secreted by the hypopharyngeal gland of adult bees on larval food for their antiseptic properties. Because workers secrete these compounds to protect larvae, they have been used as ‘biomarkers’ for social immunity. The aim of this study was to investigate if GOX and Def1 are induced after pathogen exposure to determine whether its production by workers is the result of a collective effort to protect the brood and colony in response to a pathogen challenge. Specifically, we quantified GOX and Def1 in honeybee adults before and after colony-level bacterial infection by American foulbrood ((AFB), Paenibacillus larvae ). Overall, our results indicate that levels of GOX and Def1 are not induced in response to pathogenic infections. We therefore conclude that GOX and Def1 are highly constitutive and co-opted as mechanisms of social immunity, and these factors should be considered when investigating immunity at the individual and colony level in social insects.

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Silberstein, L., B. Z. Siegel, S. M. Siegel, A. Mukhtar, and M. Galun. "Comparative Studies on Xanthoria Parietina, a Pollution Resistant Lichen, and Ramalina Duriaei, a Sensitive Species. II. Evaluation of Possible Air Pollution-Protection Mechanisms." Lichenologist 28, no. 4 (July 1996): 367–83. http://dx.doi.org/10.1006/lich.1996.0034.

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AbstractSurveys of the distribution of the lichens Xanthoria panetina and Ramalina duriaei in Israel showed that environments with air pollution had no damaging effectson X. panetina, whereas R. duriaei had disappeared from polluted environments: physiological studies supported this relative sensitivity. Investigations of possible defence mechanisms protecting X. parietina from the damaging effects of air pollution showed a multitude of possible protective systems. These included constitutive avoidance such as: efficient buffering capacity; a relatively high potassium content; and antioxidation by parietin, and induced tolerance such as: SO2 oxidation to non-toxic sulphate; increased glutathione content; induced praline and arginine synthesis; and increased detoxification of active oxygen forms.

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Naglik, Julian R. "Candida Immunity." New Journal of Science 2014 (August 25, 2014): 1–27. http://dx.doi.org/10.1155/2014/390241.

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The human pathogenic fungus Candida albicans is the predominant cause of both superficial and invasive forms of candidiasis. C. albicans primarily infects immunocompromised individuals as a result of either immunodeficiency or intervention therapy, which highlights the importance of host immune defences in preventing fungal infections. The host defence system utilises a vast communication network of cells, proteins, and chemical signals distributed in blood and tissues, which constitute innate and adaptive immunity. Over the last decade the identity of many key molecules mediating host defence against C. albicans has been identified. This review will discuss how the host recognises this fungus, the events induced by fungal cells, and the host innate and adaptive immune defences that ultimately resolve C. albicans infections during health.

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Bukovinszky, Tibor, Erik H. Poelman, Rieta Gols, Georgios Prekatsakis, Louise E. M. Vet, Jeffrey A. Harvey, and Marcel Dicke. "Consequences of constitutive and induced variation in plant nutritional quality for immune defence of a herbivore against parasitism." Oecologia 160, no. 2 (March 7, 2009): 299–308. http://dx.doi.org/10.1007/s00442-009-1308-y.

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Edwards, P. J., S. D. Wratten, and S. Greenwood. "Palatability of British trees to insects: constitutive and induced defences." Oecologia 69, no. 2 (May 1986): 316–19. http://dx.doi.org/10.1007/bf00377640.

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Kersch‐Becker, Mônica F., and Jennifer S. Thaler. "Constitutive and herbivore‐induced plant defences regulate herbivore population processes." Journal of Animal Ecology 88, no. 7 (May 2019): 1079–88. http://dx.doi.org/10.1111/1365-2656.12993.

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Thatcher, Louise, and Karam Singh. "The Arabidopsis altered in stress response2 is Impaired in Resistance to Root and Leaf Necrotrophic Fungal Pathogens." Plants 8, no. 3 (March 11, 2019): 60. http://dx.doi.org/10.3390/plants8030060.

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The Arabidopsis thaliana Glutathione S-transferase Phi8 (GSTF8) gene is recognised as a marker for early defence and stress responses. To identify regulators of these responses, a forward genetic screen for Arabidopsis mutants with up-regulated GSTF8 promoter activity was conducted by screening a mutagenized population containing a GSTF8 promoter fragment fused to the luciferase reporter gene (GSTF8:LUC). We previously identified several enhanced stress response (esr) mutants from this screen that conferred constitutive GSTF8:LUC activity and increased resistance to several pathogens and/or insects pests. Here we identified a further mutant constitutively expressing GSTF8:LUC and termed altered in stress response2 (asr2). Unlike the esr mutants, asr2 was more susceptible to disease symptom development induced by two necrotrophic fungal pathogens; the root pathogen Fusarium oxysporum, and the leaf pathogen Alternaria brassicicola. The asr2 allele was mapped to a 2.1 Mbp region of chromosome 2 and narrowed to four candidate loci.

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Huang, Jianbei, Alexander Rücker, Axel Schmidt, Gerd Gleixner, Jonathan Gershenzon, Susan Trumbore, and Henrik Hartmann. "Production of constitutive and induced secondary metabolites is coordinated with growth and storage in Norway spruce saplings." Tree Physiology 40, no. 7 (April 9, 2020): 928–42. http://dx.doi.org/10.1093/treephys/tpaa040.

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Abstract A mechanistic understanding of how trees balance the trade-offs between growth, storage and defense is limited but crucial for predicting tree responses to abiotic and biotic stresses. Here we investigated how trees allocate storage of non-structural carbohydrates (NSC) to growth and constitutive and induced secondary metabolites (SM). We exposed Norway spruce (Picea abies) saplings to 5 weeks of complete darkness to induce light and/or carbon limitation and then applied methyl jasmonate (MeJA) to simulate biotic attack. We measured changes in biomass, NSC (sum of soluble sugars and starches), and constitutive and induced SM (sum of phenolic compounds and terpenoids) in current-year developing and previous-year mature needles and branches, as well as volatiles emitted from the canopy. Under darkness, NSC storage was preferentially used for constitutive biosynthesis of monoterpenes rather than biosynthesis of stilbenes and growth of developing organs, while SM stored in mature organs cannot be remobilized and recycled. Furthermore, MeJA-induced production of SM was constrained by low NSC availability in developing organs but not in mature organs grown in the dark. Emissions of volatiles were suppressed in the dark but after 1 h of re-illumination, emissions of both constitutive and induced monoterpene hydrocarbons recovered rapidly, whereas emissions of linalool and sesquiterpene produced via de novo synthesis did not recover. Our results highlight that light and/or carbon limitation may constrain constitutive and JA-induced biosynthesis of SM in coordination with growth, NSC storage and mobilization.

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Rossi, A., and M. G. Santoro. "Induction by prostaglandin A1 of haem oxygenase in myoblastic cells: an effect independent of expression of the 70 kDa heat shock protein." Biochemical Journal 308, no. 2 (June 1, 1995): 455–63. http://dx.doi.org/10.1042/bj3080455.

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Prostaglandins of the A type (PGA) induce the synthesis of 70 kDa heat shock proteins (hsp70) in a large variety of mammalian cells. Induction of hsp70 has been associated with a cytoprotective effect of PGA1 after virus infection or thermal injury. In the present report we provide evidence that, in murine myoblasts, PGA1 is not able to induce hsp70 expression, whereas it increases the synthesis of the constitutive protein, hsc70, and dramatically induces the synthesis of a 32 kDa protein (p32). The p32 protein has been identified as haem oxygenase. PGA1 acts at the transcriptional level by inducing haem oxygenase mRNA synthesis, and the signal for induction appears to be associated with decreased intracellular GSH levels. Haem oxygenase, a low-molecular-mass stress protein induced in mammalian cells by oxidant stress, is known to be part of a general inducible antioxidant defence pathway. The fact that prostaglandin synthesis is stimulated in muscle during contraction and in the heart in response to ischaemia raises the possibility that induction of haem oxygenase by PGA in myoblasts could be part of a protective mechanisms in operation during stress and hypoxia.

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Keeling, Christopher I., and Jörg Bohlmann. "Genes, enzymes and chemicals of terpenoid diversity in the constitutive and induced defence of conifers against insects and pathogens." New Phytologist 170, no. 4 (June 2006): 657–75. http://dx.doi.org/10.1111/j.1469-8137.2006.01716.x.

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De La Cruz Diaz, Jacinto S., and Daniel H. Kaplan. "Constitutive TGFβ signaling prevents inflammation-induced Langerhans cell migration." Journal of Immunology 204, no. 1_Supplement (May 1, 2020): 220.33. http://dx.doi.org/10.4049/jimmunol.204.supp.220.33.

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Abstract Keratinocytes (KCs) that form the epidermis create a unique barrier niche for cells of the immune system such as Langerhans cells (LCs) and CD8+ resident memory T cells (TRM). These leukocytes provide host-defense but also initiate and maintain autoimmune skin diseases. Hence, elucidating the mechanisms by which CD8+ TRM and LC maintain epidermal residency is of great therapeutic interest. Both cell types require active TGFβ1 to maintain their steady-state epidermal retention. In the epidermis, inactive LAP-TGFβ1 is exclusively activated into active TGFβ1 by integrins ανβ6 and ανβ8 expressed by KCs. However, the relationship between TGFβ1 and LC migration in response to inflammatory stimuli remains unknown. To determine whether enforced TGFβ1 signaling can overcome inflammation-induce LC migration, we generated huLangerin-CreERT2x TGFβRI-CALxL mice (TGFβR1-CALC) that allow for tamoxifen-induced ligand-independent TGFβRI signaling. Enforced TGFβRI signaling in LC prevented migration in response to UVB, chemical haptens, C. albicans epicutaneous infection as well as dermal injection of TNFα and IL1β. LC from TGFβR1-CALC mice did not egress from the epidermis or enter the draining lymph nodes. Notably, in WT mice, we did not observe reduced KC expression of integrin ανβ6 or ανβ8 and levels of pSMAD2 in LC did not decrease in inflammatory contexts. Thus, although enforced TGFβRI signaling can overcome inflammation-induced migratory signals, but the loss of TGFβRI signaling is not required for LC migration. These data are consistent with a model in which TGFβRI signaling drives a LC-intrinsic retention program under homeostatic conditions that is overcome or inhibited by inflammatory cues.

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Li, Ran, Ming Wang, Yang Wang, Meredith C. Schuman, Arne Weinhold, Martin Schäfer, Guillermo H. Jiménez-Alemán, Andrea Barthel, and Ian T. Baldwin. "Flower-specific jasmonate signaling regulates constitutive floral defenses in wild tobacco." Proceedings of the National Academy of Sciences 114, no. 34 (August 7, 2017): E7205—E7214. http://dx.doi.org/10.1073/pnas.1703463114.

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Optimal defense (OD) theory predicts that within a plant, tissues are defended in proportion to their fitness value and risk of predation. The fitness value of leaves varies greatly and leaves are protected by jasmonate (JA)-inducible defenses. Flowers are vehicles of Darwinian fitness in flowering plants and are attacked by herbivores and pathogens, but how they are defended is rarely investigated. We used Nicotiana attenuata, an ecological model plant with well-characterized herbivore interactions to characterize defense responses in flowers. Early floral stages constitutively accumulate greater amounts of two well-characterized defensive compounds, the volatile (E)-α-bergamotene and trypsin proteinase inhibitors (TPIs), which are also found in herbivore-induced leaves. Plants rendered deficient in JA biosynthesis or perception by RNA interference had significantly attenuated floral accumulations of defensive compounds known to be regulated by JA in leaves. By RNA-seq, we found a JAZ gene, NaJAZi, specifically expressed in early-stage floral tissues. Gene silencing revealed that NaJAZi functions as a flower-specific jasmonate repressor that regulates JAs, (E)-α-bergamotene, TPIs, and a defensin. Flowers silenced in NaJAZi are more resistant to tobacco budworm attack, a florivore. When the defensin was ectopically expressed in leaves, performance of Manduca sexta larvae, a folivore, decreased. NaJAZi physically interacts with a newly identified NINJA-like protein, but not the canonical NINJA. This NINJA-like recruits the corepressor TOPLESS that contributes to the suppressive function of NaJAZi on floral defenses. This study uncovers the defensive function of JA signaling in flowers, which includes components that tailor JA signaling to provide flower-specific defense.

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Schrumpf, Jasmijn A., Dennis K. Ninaber, Anne M. van der Does, and Pieter S. Hiemstra. "TGF-β1 Impairs Vitamin D-Induced and Constitutive Airway Epithelial Host Defense Mechanisms." Journal of Innate Immunity 12, no. 1 (April 10, 2019): 74–89. http://dx.doi.org/10.1159/000497415.

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Airway epithelium is an important site for local vitamin D (VD) metabolism; this can be negatively affected by inflammatory mediators. VD is an important regulator of respiratory host defense, for example, by increasing the expression of hCAP18/LL-37. TGF-β1 is increased in chronic obstructive pulmonary disease (COPD), and known to decrease the expression of constitutive host defense mediators such as secretory leukocyte protease inhibitor (SLPI) and polymeric immunoglobulin receptor (pIgR). VD has been shown to affect TGF-β1-signaling by inhibiting TGF-β1-induced epithelial-to-mesenchymal transition. However, interactions between VD and TGF-β1, relevant for the understanding host defense in COPD, are incompletely understood. Therefore, the aim of the present study was to investigate the combined effects of VD and TGF-β1 on airway epithelial cell host defense mechanisms. Exposure to TGF-β1 reduced both baseline and VD-induced expression of hCAP18/LL-37, partly by increasing the expression of the VD-degrading enzyme CYP24A1. TGF-β1 alone decreased the number of secretory club and goblet cells and reduced the expression of constitutive host defense mediators SLPI, s/lPLUNC and pIgR, effects that were not modulated by VD. These results suggest that TGF-β1 may decrease the respiratory host defense both directly by reducing the expression of host defense mediators, and indirectly by affecting VD-mediated effects such as expression of hCAP18/LL-37.

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Dahl, Jonas, and Barbara L. Peckarsky. "Does living in streams with fish involve a cost of induced morphological defences?" Canadian Journal of Zoology 81, no. 11 (November 1, 2003): 1825–28. http://dx.doi.org/10.1139/z03-177.

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Previous studies have shown that chemical cues from brook trout (Salvelinus fontinalis) induce relatively longer caudal filaments and heavier exoskeletons in the mayfly Drunella coloradensis. These characters constitute morphological defences that reduce larval mortality from brook trout predation. There is also a potential fitness cost of living in streams with trout, as D. coloradensis females emerge at smaller sizes from streams with fish compared with females in streams without fish. In this study, we obtained additional data to evaluate the hypothesis that these costs of living in streams with fish could be attributed to inducible defences. A field survey of seven different streams showed that mature (black wing pad) female larvae from streams with fish invested a smaller proportion of their body mass in eggs than females maturing in streams without fish. Furthermore, a negative relationship between female allocation to eggs and to morphological defence characters (relative length of the caudal filament) provides evidence of a cost of inducible defences in this species.

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Spiers, James D., Fred T. Davies, Chuanjiu He, Terri W. Starman, Scott A. Finlayson, Scott A. Senseman, and Kevin M. Heinz. "Fertilization Affects Constitutive and Wound-Induced Chemical Defenses in Gerbera jamesonii." Journal of Environmental Horticulture 29, no. 4 (December 1, 2011): 180–84. http://dx.doi.org/10.24266/0738-2898-29.4.180.

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Abstract The total phenolic content and jasmonic acid (JA) content of foliage from gerbera (Gerbera jamesonii ‘Festival Salmon’) subjected to low and high fertilization rates were measured to determine effects of fertilization on phytochemicals implicated in defense of insect pests. Gerbera seedlings were fertilized with low (only supplied with initial fertilizer charge present in professional growing media) or high (200 mg·liter−1 N; recommended rate) fertilization rates. Since JA is induced in response to wounding, treatments consisted of ± mechanical wounding with a hemostat to one physiologically mature leaf and the subsequent harvest of that leaf at specified time intervals (0, 0.5, 1, 3, and 10 h) for JA quantification. Total phenolic content was measured in mature and newly formed leaves. Plants receiving low fertility had reduced aboveground dry mass, were deficient in nitrogen and phosphorous, and had approximately a 9-fold higher concentration of total phenolics in mature leaf tissue compared to high fertility plants. Newly formed leaves had greater concentrations of phenolics than mature leaves in low fertility plants. In response to wounding, JA accumulation was more rapid and higher concentrations of JA were sustained longer in low fertility plants than in high fertility plants. These results show that altering fertilization does affect phytochemicals implicated in defense against insect pests, and these chemical defenses are increased in the foliage of low fertility gerberas.

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Ito, Kiyoshi, and Satoki Sakai. "Optimal defense strategy against herbivory in plants: Conditions selecting for induced defense, constitutive defense, and no-defense." Journal of Theoretical Biology 260, no. 3 (October 2009): 453–59. http://dx.doi.org/10.1016/j.jtbi.2009.07.002.

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Eberhardt, HJ. "The Regulation and Biochemical Action of Natural Fungicides in Tobacco." Beiträge zur Tabakforschung International/Contributions to Tobacco Research 16, no. 4 (November 1, 1995): 157–70. http://dx.doi.org/10.2478/cttr-2013-0644.

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AbstractThe biochemical interactions between the tobacco plant and a fungal pathogen are complex and poorly understood. Upon infection, the fungus overcomes the natural defence mechanism of the host by the lytic activity of enzymes and by suppressing the hypersensitive reaction of N. tabacum. The ability of the tobacco plant to resist a fungal attack is based on macroscopic properties and the biosynthesis of natural fungicides. The physical and biochemical character of the leaf surface (e.g. trichome exudates, cuticular components) may prevent the fungus from entering the organism. Constitutive natural fungicides such as phenolics and terpenes operate as enzyme inhibitors, or impair the germination of the fungal spores. Newly synthesized polysaccharides of the cell wall of leaf cells may delay the penetration of the fungus. Lignification of the surrounding cells occurs to protect the healthy tissue against attack. Toxic substances created during the melanization process of the tobacco plant can destroy the fungal cells. Biosynthesis of natural fungicides, such as phytoalexins, pathogenesis-related proteins and proteinase inhibitors is induced by exogenous or endogenous elicitors. These active protection systems may interfere with the fungal metabolism. Phytoalexins and pathogenesis-related proteins are highly effective defence responses which offer a broad spectrum of variability and resistance against a fungal infection. New strategies for engineering crop protection are based on these defence systems.

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Liu, Mu, Xiaoyun Pan, Zhijie Zhang, Mark van Kleunen, and Bo Li. "Testing the shifting defense hypothesis for constitutive and induced resistance and tolerance." Journal of Pest Science 93, no. 1 (September 16, 2019): 355–64. http://dx.doi.org/10.1007/s10340-019-01162-0.

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Mullineaux, Philip, Louise Ball, Carolina Escobar, Barbara Karpinska, Gary Creissen, and Stanislaw Karpinski. "Are diverse signalling pathways integrated in the regulation of Arabidopsis antioxidant defence gene expression in response to excess excitation energy?" Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 355, no. 1402 (October 29, 2000): 1531–40. http://dx.doi.org/10.1098/rstb.2000.0713.

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When low–light–grown Arabidopsis rosettes are partially exposed to excess light (EL), the unexposed leaves become acclimated to excess excitation energy (EEE) and consequent photo–oxidative stress. This phenomenon, termed systemic acquired acclimation (SAA), is associated with redox changes in the proximity of photosystem II, changes in foliar H 2 O 2 content and induction of antioxidant defences. The induction of extra–plastidial antioxidant systems is important in the protection of the chloroplast under EL conditions. A larger range of transcripts encoding different antioxidant defence enzymes may be induced in the systemically acclimated leaves and these include those encoded by the glutathione peroxidase ( GPX2 ) and glutathione–S–transferase ( GST ) genes, which are also highly induced in the hypersensitive response and associated systemic acquired resistance (SAR) in incompatible plantpathogen interactions. Furthermore, the expression of the SAR–inducible pathogenesis–related protein gene, PR2 , is enhanced in SAA leaves. Wounded leaf tissue also shows enhanced systemic induction of a cytosolic ascorbate peroxidase gene ( APX2 ) under EL conditions. These and other considerations, suggest H 2 O 2 and other reactive oxygen species (ROS) could be the common factor in signalling pathways for diverse environmental stresses. These effects may be mediated by changes in the level and redox state of the cellular glutathione pool. Mutants with constitutive expression of a normally EL–inducible APX2 gene have much reduced levels of foliar glutathione. The expression of APX1 and APX3 , encoding cytosolic and peroxisome–associated isoforms, respectively, are also under phytochrome–A–mediated control. The expression of these genes is tightly linked to the greening of plastids in etiolated seedlings. These data suggest that part of the developmental processes that bring about the acclimation of leaves to high light includes the configuration of antioxidant defences. Therefore, the linkage between immediate responses of leaves to EL, acclimation of chloroplasts to EEE and the subsequent changes to leaf form and function in high light could be mediated by the activity of foliar antioxidant defences and changes in the concentration of ROS.

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Christopher, Kenneth, Thomas F. Mueller, Rachel DeFina, Yurong Liang, Jianhua Zhang, Robert Gentleman, and David L. Perkins. "The graft response to transplantation: a gene expression profile analysis." Physiological Genomics 15, no. 1 (September 29, 2003): 52–64. http://dx.doi.org/10.1152/physiolgenomics.00139.2002.

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Little is known regarding the graft response to transplantation injury. This study investigates the posttransplantation response of genes that are constitutively expressed in the heart. Constitutive heart and lymph node tissue-restricted gene expression was first analyzed with DNA microarrays. To demonstrate changes following transplantation in genes constitutively expressed in the heart, we performed vascularized murine heart transplants in allogeneic (BALB/c to B6), syngeneic (B6 to B6), and alymphoid (BALB/c-RAG2−/− to B6-RAG1−/−) experimental groups. Temporal induction of genes posttransplant relative to constitutive expression was evaluated with DNA microarrays. Dendrograms and self-organizing maps were generated to determine the dissimilarity between the experimental groups and to identify subsets of differentially expressed genes within the groups, respectively. Expression patterns of selected genes were confirmed by real-time PCR. Biological processes were assigned to genes induced posttransplant using the AnnBuilder package via the Gene Ontology Database. Post-transplant, a shift was noted in genes classified as defense, communication, and metabolism. Our results identify novel components of the graft response to transplantation injury and rejection.

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Zhang, Peng‐Jun, Chan Zhao, Zi‐Hong Ye, and Xiao‐Ping Yu. "Trade‐off between defense priming by herbivore‐induced plant volatiles and constitutive defense in tomato." Pest Management Science 76, no. 5 (January 8, 2020): 1893–901. http://dx.doi.org/10.1002/ps.5720.

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Melo Machado, R. C., J. Sant'Ana, M. C. Blassioli-Moraes, R. A. Laumann, and M. Borges. "Herbivory-induced plant volatiles from Oryza sativa and their influence on chemotaxis behaviour of Tibraca limbativentris stal. (Hemiptera: Pentatomidae) and egg parasitoids." Bulletin of Entomological Research 104, no. 3 (March 12, 2014): 347–56. http://dx.doi.org/10.1017/s0007485314000133.

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AbstractThe rice stem bug, Tibraca limbativentris Stal. (Hemiptera: Pentatomidae) is one of the most important pests of rice crops, especially irrigated crops. Plant defence strategies against these bugs may involve the emission of chemical compounds, which are released following herbivore attacks, directly or indirectly harming pest performance. The aim of this study was to evaluate the influence of constitutive and herbivory-induced volatiles from rice plants (Oryza sativa L.) on the behavioural responses of T. limbativentris adults and egg parasitoids Trissolcus basalis (Wollaston) and Telenomus podisi (Ashmead) (Hymenoptera, Platygastridae). Plant volatiles were collected from undamaged plants of the rice cultivar IRGA 424 and from plants that suffered herbivory by five males or five females of T. limbativentris. Air-entrainment extracts were analysed by GC–flame ionization detector and GC–MS, and insect responses evaluated in a ‘Y’ olfactometer. T. limbativentris feeding damaged on rice plants induced the release of 16 volatiles compounds in a higher amounts compared to undamaged plants The main compounds induced were (E)-2-hexenal, (E)-2-octen-1-ol, methyl salicylate and α-muurolene. Female bugs were significantly attracted to air-entrainment extracts containing volatiles from undamaged plants compared with air-entrainment extracts containing volatiles emitted from plants damaged by T. limbativentris, whereas males showed no preference. Telenomus podisi females were significantly attracted to volatiles from air-entrainment extracts of plants damaged by females, whereas T. basalis showed no preference. These results suggest that rice plants may be emitting defence compounds, which could be avoided by T. limbativentris females and also acted indirectly by attracting natural enemies.

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Wuyts, Nathalie, Rony Swennen, and Dirk De Waele. "Activity of phenylalanine ammonia-lyase, peroxidase and polyphenol oxidase in roots of banana (Musa acuminata AAA, cvs Grande Naine and Yangambi km5) before and after infection with Radopholus similis." Nematology 8, no. 2 (2006): 201–9. http://dx.doi.org/10.1163/156854106777998674.

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AbstractPhenylpropanoids – phenolic compounds – take part in the wound and defence responses of plants and are frequently correlated with resistance. Enzymes directly or indirectly functional in the phenylpropanoid pathway are induced in plants in response to wounding and infection by pathogens, including sedentary endoparasitic nematodes. The activity of three of these enzymes, phenylalanine ammonia-lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO), was analysed in banana roots before and 1, 3 and 7 days after inoculation with the burrowing nematode Radopholus similis and in comparison with mechanically wounded roots. Constitutive activities of PAL, PO and PPO were lower in the resistant cv. Yangambi km5 (Musa acuminata AAA) than in the susceptible cv. Grande Naine (Musa acuminata AAA). During the experiment, levels increased to those of cv. Grande Naine, but only for R. similis-inoculated roots of cv. Yangambi km5 enzyme activities at 3 and 7 days after the onset of the experiment were values significantly higher than constitutive ones. At 7 days after the treatments, PO activity was significantly higher in wounded roots of cv. Grande Naine than in control and nematode-inoculated roots. The level of PAL activity in nematode-treated roots of cv. Yangambi km5 at 7 days after inoculation was 2.3-fold higher than control and wounded roots and up to six-fold higher than cv. Grande Naine roots. We concluded that PAL was induced in R. similis-inoculated roots of the resistant cultivar only and that this response was different from wound induction. For PO and PPO we concluded that levels in the resistant cultivar increased to those of the susceptible cultivar as a response to general stress in the plants during the experiment. Nevertheless, final levels of PO and PPO activity in R. similis-inoculated roots of the resistant cultivar were significantly higher than constitutive ones.

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Zandt, Peter A. Van. "PLANT DEFENSE, GROWTH, AND HABITAT: A COMPARATIVE ASSESSMENT OF CONSTITUTIVE AND INDUCED RESISTANCE." Ecology 88, no. 8 (August 2007): 1984–93. http://dx.doi.org/10.1890/06-1329.1.

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Välimäki, Kaisa, Gábor Herczeg, and Juha Merilä. "Morphological anti-predator defences in the nine-spined stickleback: constitutive, induced or both?" Biological Journal of the Linnean Society 107, no. 4 (October 5, 2012): 854–66. http://dx.doi.org/10.1111/j.1095-8312.2012.01989.x.

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Rapley, Luke P., Geoff R. Allen, Brad M. Potts, and Noel W. Davies. "Constitutive or induced defences - how does Eucalyptus globulus defend itself from larval feeding?" Chemoecology 17, no. 4 (September 2007): 235–43. http://dx.doi.org/10.1007/s00049-007-0382-z.

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Kaplan, Ian, Rayko Halitschke, André Kessler, Sandra Sardanelli, and Robert F. Denno. "CONSTITUTIVE AND INDUCED DEFENSES TO HERBIVORY IN ABOVE- AND BELOWGROUND PLANT TISSUES." Ecology 89, no. 2 (February 2008): 392–406. http://dx.doi.org/10.1890/07-0471.1.

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Charles, Marie Thérèse, Kablan Tano, Alain Asselin, and Joseph Arul. "Physiological basis of UV-C induced resistance to Botrytis cinerea in tomato fruit. V. Constitutive defence enzymes and inducible pathogenesis-related proteins." Postharvest Biology and Technology 51, no. 3 (March 2009): 414–24. http://dx.doi.org/10.1016/j.postharvbio.2008.08.016.

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He, Ping, Randall F. Warren, Tiehan Zhao, Libo Shan, Lihuang Zhu, Xiaoyan Tang, and Jian-Min Zhou. "Overexpression of Pti5 in Tomato Potentiates Pathogen-Induced Defense Gene Expression and Enhances Disease Resistance to Pseudomonas syringae pv. tomato." Molecular Plant-Microbe Interactions® 14, no. 12 (December 2001): 1453–57. http://dx.doi.org/10.1094/mpmi.2001.14.12.1453.

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The tomato Pti5 gene encodes a pathogen-inducible ethylene response element-binding protein-like transcription factor that interacts with the disease resistance gene product Pto. Overexpression of Pti5 or Pti5-VP16, a translational fusion with a constitutive transcriptional activation domain, in tomato enhanced resistance to Pseudomonas syringae pv. tomato. Constitutive expression of Pti5 or Pti5-VP16 did not affect the basal level of pathogenesis-related gene expression, but it accelerated pathogen-induced expression of GluB and Catalase. The results demonstrate a positive role of Pti5 in defense gene regulation and disease resistance and suggest that a pathogen-activated posttran-scriptional regulatory step is necessary for the pathogen induction of the defense gene expression.

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Bila, Ivanna, Olha Dzydzan, Iryna Brodyak, and Natalia Sybirna. "Agmatine prevents oxidative-nitrative stress in blood leukocytes under streptozotocin-induced diabetes mellitus." Open Life Sciences 14, no. 1 (July 23, 2019): 299–310. http://dx.doi.org/10.1515/biol-2019-0033.

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AbstractChanges in cellular metabolism, development of oxidative-nitrative stress and intensification of glycation and lipid peroxidation (LPO), are significant processes that occur during diabetes mellitus (DM)-associated chronic hyperglycemia. These processes contribute to deviations in the structural organization and functional activity of leukocytes. The development of oxidative-nitrative stress in peripheral blood cells during DM can be prevented by agmatine, an endogenous metabolite of L-arginine, which is a nitric oxide synthase (NOS) inhibitor, and possesses hypoglycemic properties. The administration of agmatine to animals with DM lead to the inhibition of both constitutive and inducible NOS in leukocytes, which in turn decreased total nitrite/nitrate (NOx) levels. Additionally, we observed corresponding increases in reduced glutathione content and activity of antioxidant enzymes (SOD, CAT, GPx, GR), along with decreased levels of the thiobarbituric acid reactive substance, advanced oxidation protein products (AOPPs) and advanced glycosylation end-products (AGEs) as compared to the non-treated diabetic group. Our results indicate that treatment of diabetic animals with agmatine restores redox homeostasis and a balances antioxidant defence system enzymes in leukocytes. This corrective effect on the functional capacity of leukocytes is exerted by preventing oxidative-nitrative stress in animals with DM.

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Moreira, Xoaquín, Kailen A. Mooney, Sergio Rasmann, William K. Petry, Amparo Carrillo-Gavilán, Rafael Zas, and Luis Sampedro. "Trade-offs between constitutive and induced defences drive geographical and climatic clines in pine chemical defences." Ecology Letters 17, no. 5 (February 19, 2014): 537–46. http://dx.doi.org/10.1111/ele.12253.

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Van Alstyne, KL, L. Sutton, and SA Gifford. "Inducible versus constitutive antioxidant defenses in algae along an environmental stress gradient." Marine Ecology Progress Series 640 (April 23, 2020): 107–15. http://dx.doi.org/10.3354/meps13263.

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Optimal defense theory (ODT) predicts that antiherbivore defenses should be constitutive when plants are frequently attacked and inducible when the probability of attack is low. Like antiherbivore defenses, antioxidant defenses can be inducible or constitutive. We hypothesized the ODT predictions should apply to antioxidant defenses; thus, species inhabiting environments where oxidative stresses occur frequently should produce constitutive antioxidant defenses, whereas species in environments where stresses occur less frequently should produce inducible defenses. We tested this hypothesis by attempting to induce production of the antioxidant precursor dimethylsulfoniopropionate (DMSP) in 4 ulvoid algae species that experience different levels of environmental stress because they are zoned along a tidal gradient. The 2 lower intertidal species Ulvaria obscura and Ulva fenestrata, which experience oxidative stresses less frequently, induced DMSP production in response to applications of the chemical oxidant hydrogen peroxide within 7 d, whereas the higher intertidal species Ulva linza and Ulva intestinalis, which regularly experience oxidative stress, did not have increased DMSP concentrations. This study demonstrates a novel waterborne signaling mechanism for DMSP induction in marine macroalgae and provides evidence of selection for inducible antioxidant defenses in organisms experiencing less frequent environmental stresses.

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Body, Mélanie J. A., Matthew S. Zinkgraf, Thomas G. Whitham, Chung-Ho Lin, Ryan A. Richardson, Heidi M. Appel, and Jack C. Schultz. "Heritable Phytohormone Profiles of Poplar Genotypes Vary in Resistance to a Galling Aphid." Molecular Plant-Microbe Interactions® 32, no. 6 (June 2019): 654–72. http://dx.doi.org/10.1094/mpmi-11-18-0301-r.

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Insect galls are highly specialized structures arising from atypical development of plant tissue induced by insects. Galls provide the insect enhanced nutrition and protection against natural enemies and environmental stresses. Galls are essentially plant organs formed by an intimate biochemical interaction between the gall-inducing insect and its host plant. Because galls are plant organs, their development is likely to be governed by phytohormones involved in normal organogenesis. We characterized concentrations of both growth and defensive phytohormones in ungalled control leaves and galls induced by the aphid Pemphigus betae on narrowleaf cottonwood Populus angustifolia that differ genotypically in resistance to this insect. We found that susceptible trees differed from resistant trees in constitutive concentrations of both growth and defense phytohormones. Susceptible trees were characterized by significantly higher constitutive cytokinin concentrations in leaves, significantly greater ability of aphids to elicit cytokinin increases, and significantly lower constitutive defense phytohormone concentrations than observed in resistant trees. Phytohormone concentrations in both constitutive and induced responses in galled leaves exhibited high broad-sense heritability that, respectively, ranged from 0.39 to 0.93 and from 0.28 to 0.66, suggesting that selection can act upon these traits and that they might vary across the landscape. Increased cytokinin concentrations may facilitate forming strong photosynthate sinks in the galls, a requirement for galling insect success. By characterizing for the first time the changes in 15 phytohormones belonging to five different classes, this study offers a better overview of the signaling alteration occurring in galls that has likely been important for their ecology and evolution. [Formula: see text] Copyright © 2019 The Author(s). This is an open-access article distributed under the CC BY-NC-ND 4.0 International license .

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Blanc, Catherine, Fania Coluccia, Floriane L’Haridon, Martha Torres, Marlene Ortiz-Berrocal, Elia Stahl, Philippe Reymond, et al. "The Cuticle Mutant eca2 Modifies Plant Defense Responses to Biotrophic and Necrotrophic Pathogens and Herbivory Insects." Molecular Plant-Microbe Interactions® 31, no. 3 (March 2018): 344–55. http://dx.doi.org/10.1094/mpmi-07-17-0181-r.

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We isolated previously several Arabidopsis thaliana mutants with constitutive expression of the early microbe-associated molecular pattern–induced gene ATL2, named eca (expresión constitutiva de ATL2). Here, we further explored the interaction of eca mutants with pest and pathogens. Of all eca mutants, eca2 was more resistant to a fungal pathogen (Botrytis cinerea) and a bacterial pathogen (Pseudomonas syringae) as well as to a generalist herbivorous insect (Spodoptera littoralis). Permeability of the cuticle is increased in eca2; chemical characterization shows that eca2 has a significant reduction of both cuticular wax and cutin. Additionally, we determined that eca2 did not display a similar compensatory transcriptional response, compared with a previously characterized cuticular mutant, and that resistance to B. cinerea is mediated by the priming of the early and late induced defense responses, including salicylic acid– and jasmonic acid–induced genes. These results suggest that ECA2-dependent responses are involved in the nonhost defense mechanism against biotrophic and necrotrophic pathogens and against a generalist insect by modulation and priming of innate immunity and late defense responses. Making eca2 an interesting model to characterize the molecular basis for plant defenses against different biotic interactions and to study the initial events that take place in the cuticle surface of the aerial organs.

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Journal articles on the topic 'Constitutive and induced defence'

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