Journal articles: 'Plant defenses'

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Dalling, James W., Adam S. Davis, A. Elizabeth Arnold, Carolina Sarmiento, and Paul-Camilo Zalamea. "Extending Plant Defense Theory to Seeds." Annual Review of Ecology, Evolution, and Systematics 51, no. 1 (November 2, 2020): 123–41. http://dx.doi.org/10.1146/annurev-ecolsys-012120-115156.

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Plant defense theory explores how plants invest in defenses against natural enemies but has focused primarily on the traits expressed by juvenile and mature plants. Here we describe the diverse ways in which seeds are chemically and physically defended. We suggest that through associations with other traits, seeds are likely to exhibit defense syndromes that reflect constraints or trade-offs imposed by selection to attract dispersers, enable effective dispersal, ensure appropriate timing of seed germination, and enhance seedling performance. We draw attention to seed and reproductive traits that are analogous to defense traits in mature plants and describe how the effectiveness of defenses is likely to differ at pre- and postdispersal stages. We also highlight recent insights into the mutualistic and antagonistic interactions between seeds and microbial communities, including fungi and endohyphal bacteria, that can influence seed survival in the soil and subsequent seedling vigor.

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Hines, P. J. "Plant Defenses." Science Signaling 4, no. 203 (December 13, 2011): ec347-ec347. http://dx.doi.org/10.1126/scisignal.4203ec347.

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Fritz, R. "Plant Defenses." Science 256, no. 5057 (May 1, 1992): 680–81. http://dx.doi.org/10.1126/science.256.5057.680.

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Zhang, Peng-Jun, Jia-Ning Wei, Chan Zhao, Ya-Fen Zhang, Chuan-You Li, Shu-Sheng Liu, Marcel Dicke, Xiao-Ping Yu, and Ted C. J. Turlings. "Airborne host–plant manipulation by whiteflies via an inducible blend of plant volatiles." Proceedings of the National Academy of Sciences 116, no. 15 (March 25, 2019): 7387–96. http://dx.doi.org/10.1073/pnas.1818599116.

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The whitefly Bemisia tabaci is one of the world’s most important invasive crop pests, possibly because it manipulates plant defense signaling. Upon infestation by whiteflies, plants mobilize salicylic acid (SA)-dependent defenses, which mainly target pathogens. In contrast, jasmonic acid (JA)-dependent defenses are gradually suppressed in whitefly-infested plants. The down-regulation of JA defenses make plants more susceptible to insects, including whiteflies. Here, we report that this host–plant manipulation extends to neighboring plants via airborne signals. Plants respond to insect attack with the release of a blend of inducible volatiles. Perception of these volatiles by neighboring plants usually primes them to prepare for an imminent attack. Here, however, we show that whitefly-induced tomato plant volatiles prime SA-dependent defenses and suppress JA-dependent defenses, thus rendering neighboring tomato plants more susceptible to whiteflies. Experiments with volatiles from caterpillar-damaged and pathogen-infected plants, as well as with synthetic volatiles, confirm that whiteflies modify the quality of neighboring plants for their offspring via whitefly-inducible plant volatiles.

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Lima, T. E., A. L. B. Sartori, and M. L. M. Rodrigues. "Plant antiherbivore defenses in Fabaceae species of the Chaco." Brazilian Journal of Biology 77, no. 2 (September 5, 2016): 299–303. http://dx.doi.org/10.1590/1519-6984.12815.

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Abstract The establishment and maintenance of plant species in the Chaco, one of the widest continuous areas of forests in the South American with sharp climatic variations, are possibly related to biological features favoring plants with particular defenses. This study assesses the physical and chemical defenses mechanisms against herbivores of vegetative and reproductive organs. Its analyses of 12 species of Fabaceae (Leguminosae) collected in remnants of Brazilian Chaco shows that 75% present structural defense characters and 50% have chemical defense – defense proteins in their seeds, like protease inhibitors and lectins. Physical defenses occur mainly on branches (78% of the species), leaves (67%), and reproductive organs (56%). The most common physical characters are trichomes and thorns, whose color represents a cryptic character since it does not contrast with the other plant structures. Defense proteins occur in different concentrations and molecular weight classes in the seeds of most species. Protease inhibitors are reported for the first time in seeds of: Albizia niopoides, Anadenanthera colubrina, Mimosa glutinosa, Prosopis rubriflora, and Poincianella pluviosa. The occurrence of physical and chemical defenses in members of Fabaceae indicate no associations between defense characters in these plant species of the Chaco.

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Gewin, Virginia. "Priming Plant Defenses." Frontiers in Ecology and the Environment 3, no. 6 (August 2005): 299. http://dx.doi.org/10.2307/3868557.

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Hines, P. J. "Coordinating Plant Defenses." Science's STKE 2007, no. 375 (February 27, 2007): tw72. http://dx.doi.org/10.1126/stke.3752007tw72.

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Arnason, John T., and Mark A. Bernards. "Impact of constitutive plant natural products on herbivores and pathogensThe present review is one in the special series of reviews on animal–plant interactions." Canadian Journal of Zoology 88, no. 7 (July 2010): 615–27. http://dx.doi.org/10.1139/z10-038.

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Plants defend themselves from pests with deterrent or toxic phytochemicals. In addition to the development of preformed mechanical barriers such as cutin and suberin, the first line of defense for plants against pathogens and herbivores is constitutive (preformed) biologically active inhibitors. Because of the adaptation of insects and pathogens to these inhibitors, plants have evolved a stunning diversity of new and different bioactive molecules to combat pests. Some representative mechanisms of plant defense include the use of antimicrobial, anitfeedant, and phototoxic molecules. Examples of natural product defenses of specific plant families are also described. Diversity and redundancy in plant defenses is key to slowing pest resistance to host-plant defenses.

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Sobral, Mar, Luis Sampedro, Isabelle Neylan, David Siemens, and Rodolfo Dirzo. "Phenotypic plasticity in plant defense across life stages: Inducibility, transgenerational induction, and transgenerational priming in wild radish." Proceedings of the National Academy of Sciences 118, no. 33 (August 13, 2021): e2005865118. http://dx.doi.org/10.1073/pnas.2005865118.

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As they develop, many plants deploy shifts in antiherbivore defense allocation due to changing costs and benefits of their defensive traits. Plant defenses are known to be primed or directly induced by herbivore damage within generations and across generations by long-lasting epigenetic mechanisms. However, little is known about the differences between life stages of epigenetically inducible defensive traits across generations. To help fill this knowledge gap, we conducted a multigenerational experiment to determine whether defense induction in wild radish plants was reflected in chromatin modifications (DNA methylation); we then examined differences between seedlings and reproductive plants in current and transgenerational plasticity in chemical (glucosinolates) and physical (trichomes) defenses in this species. Herbivory triggered genome methylation both in targeted plants and their offspring. Within one generation, both defenses were highly inducible at the seedling stage, but only chemical defenses were inducible in reproductive plants. Across generations, herbivory experienced by mother plants caused strong direct induction of physical defenses in their progeny, with effects lasting from seedling to reproductive stages. For chemical defenses, however, this transgenerational induction was evident only in adults. Transgenerational priming was observed in physical and chemical defenses, particularly in adult plants. Our results show that transgenerational plasticity in plant defenses in response to herbivore offense differs for physical and chemical defense and changes across plant life stages.

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Oukala, Nadira, Victoria Pastor, and Kamel Aissat. "Bacterial Endophytes: The Hidden Actor in Plant Immune Responses against Biotic Stress." Plants 10, no. 5 (May 19, 2021): 1012. http://dx.doi.org/10.3390/plants10051012.

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Bacterial endophytes constitute an essential part of the plant microbiome and are described to promote plant health by different mechanisms. The close interaction with the host leads to important changes in the physiology of the plant. Although beneficial bacteria use the same entrance strategies as bacterial pathogens to colonize and enter the inner plant tissues, the host develops strategies to select and allow the entrance to specific genera of bacteria. In addition, endophytes may modify their own genome to adapt or avoid the defense machinery of the host. The present review gives an overview about bacterial endophytes inhabiting the phytosphere, their diversity, and the interaction with the host. Direct and indirect defenses promoted by the plant–endophyte symbiont exert an important role in controlling plant defenses against different stresses, and here, more specifically, is discussed the role against biotic stress. Defenses that should be considered are the emission of volatiles or antibiotic compounds, but also the induction of basal defenses and boosting plant immunity by priming defenses. The primed defenses may encompass pathogenesis-related protein genes (PR family), antioxidant enzymes, or changes in the secondary metabolism.

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Pérez-Hedo, Meritxell, Miquel Alonso-Valiente, Sandra Vacas, Carolina Gallego, José L. Rambla, Vicente Navarro-Llopis, Antonio Granell, and Alberto Urbaneja. "Eliciting tomato plant defenses by exposure to herbivore induced plant volatiles." Entomologia Generalis 41, no. 3 (June 8, 2021): 209–18. http://dx.doi.org/10.1127/entomologia/2021/1196.

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Basu, Saumik, Natalia Moroz, Benjamin W. Lee, Kiwamu Tanaka, Liesl Oeller, Chase W. Baerlocher, and David W. Crowder. "Diversity and Traits of Multiple Biotic Stressors Elicit Differential Defense Responses in Legumes." Agriculture 13, no. 11 (November 3, 2023): 2093. http://dx.doi.org/10.3390/agriculture13112093.

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In agroecosystems, plants frequently confront multiple biotic stressors, including herbivores and pathogens. The nature of these interactions plays a crucial role in mediating the activation of plant defense mechanisms. However, induction of plant chemical defenses has been more well studied than the induction of physical defenses. Here, we assessed the physical and chemical defense responses of pea (Pisum sativum) plants after exposure to three stressors: a vector herbivore (pea aphid, Acrythosiphon pisum), a non-vector herbivore (pea leaf weevil, Sitona lineatus), and a virus (Pea enation mosaic virus, PEMV). We used various histochemical staining techniques show that viruliferous A. pisum (transmitting PEMV) strongly induced callose deposition (aniline blue staining) and antioxidant-mediated defenses (DAB and NBT staining) in peas, primarily through accumulating reactive oxygen species (ROS). High-throughput phenotyping showed that viruliferous aphids reduced plant photosynthetic efficiency, but plants infected with PEMV had increased cell death (trypan blue staining). However, herbivory by aphids and weevils did not strongly induce defenses in peas, even though weevil feeding significantly reduced pea leaf area. These results show that not all herbivores induce strong defensive responses, and plant responses to vector species depends on their virus infection status. More broadly, our results indicate that variable stressors differentially regulate various plant responses through intricate chemical and physical defense pathways.

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Milius, Susan. "Spying on Plant Defenses." Science News 162, no. 16 (October 19, 2002): 246. http://dx.doi.org/10.2307/4014107.

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González-Coloma, Azucena, Carmen López-Balboa, Omar Santana, Matías Reina, and Braulio M. Fraga. "Triterpene-based plant defenses." Phytochemistry Reviews 10, no. 2 (June 11, 2010): 245–60. http://dx.doi.org/10.1007/s11101-010-9187-8.

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Lawal, Ibrahim, Aminu Yusuf Fardami, Fatima Isma’il Ahmad, Sani Yahaya, Abdullahi Sani Abubakar, Muhammad Abdullahi Sa’id, Musa Marwana, and Kamilu Adamu Maiyadi. "A Review on Nematophagus Fungi: A Potential Nematicide for the Biocontrol of Nematodes." Journal of Environmental Bioremediation and Toxicology 5, no. 1 (August 5, 2022): 26–31. http://dx.doi.org/10.54987/jebat.v5i1.677.

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Filamentous fungi offer an interesting biocontrol alternative. Trichoderma, mycorrhizal, and endophytic fungi are the main filamentous fungi used to induce nematode resistance. They can reduce plant-parasitic nematode damage by producing lytic enzymes, antibiosis, paralysis, and parasitism. They minimize space and resource competition by increasing nutrient and water uptake, or by modifying root morphology and/or rhizosphere interactions, which benefits plant growth. Filamentous fungi can induce nematode resistance by activating hormone-mediated plant-defense mechanisms (salicylic and jasmonic acid, strigolactones). Altering the transport of chemical defense components or the synthesis of secondary metabolites and enzymes can also boost plant defenses. Using filamentous fungi as BCAs against plant-parasitic nematodes is a promising biocontrol strategy in agriculture. By increasing a plant's ability to absorb nutrients and water, or by changing root shape and/or rhizosphere interactions, they reduce competition for space and resources. Filamentous fungi can activate hormone-mediated plant defenses (e.g., strigolactones, salicylic and jasmonic acids). Changing how chemical defense components are transported or synthesizing secondary metabolites and enzymes can improve a plant's defenses. Using filamentous fungi as BCAs in agriculture is a promising, long-lasting biocontrol method against plant-parasitic nematodes.

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Kessler, André, and Alexander Chautá. "The ecological consequences of herbivore-induced plant responses on plant–pollinator interactions." Emerging Topics in Life Sciences 4, no. 1 (June 15, 2020): 33–43. http://dx.doi.org/10.1042/etls20190121.

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Plant induced responses to herbivory have long been found to function as plant direct and indirect defenses and to be major drivers of herbivore community and population dynamics. While induced defenses are generally understood as cost-saving strategies that allow plants to allocate valuable resources into defense expression, it recently became clear that, in particular, induced metabolic changes can come with significant ecological costs. In particular, interactions with mutualist pollinators can be significantly compromised by herbivore-induced changes in floral morphology and metabolism. We review recent findings on the evidence for ecological conflict between defending against herbivores and attracting pollinators while using similar modes of information transfer (e.g. visual, olfactory, tactile). Specifically, we discuss plant traits and mechanisms through which plants mediate interactions between antagonists and mutualist and present functional hypotheses for how plants can overcome the resulting conflicts.

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Pereira, Cássio Cardoso, Maria Gabriela Boaventura, Gislene Carvalho de Castro, and Tatiana Cornelissen. "Are extrafloral nectaries efficient against herbivores? Herbivory and plant defenses in contrasting tropical species." Journal of Plant Ecology 13, no. 4 (May 31, 2020): 423–30. http://dx.doi.org/10.1093/jpe/rtaa029.

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Abstract Aims Plants have limited resources for defenses and species that invest in biotic defenses might exhibit leaves that invest less in other types of defenses. We have investigated whether plants that have few mechanical defenses, but have extrafloral nectaries (EFNs) patrolled by ants, are less prone to herbivory, compared with plants without EFNs that have tougher leaves. Methods Data from the literature were extracted to examine the reported levels of herbivory in plants with or without EFNs. In a savanna vegetation in southern Brazil, field data were collected in leaves from six tropical species and herbivory and specific leaf area (SLA) levels were measured. We further evaluated differences in herbivory and SLA among species and between plants with or without EFNs. In order to test the relationship between herbivory and leaf toughness we regressed average herbivory and average SLA per plant. Important Findings Plants exhibited variable levels of leaf damage, but plants without ant defenses experienced the highest levels of leaf area loss to herbivory. Levels of mechanical defenses were also variable among the plant species. Plants without EFNs were tougher, exhibiting lower values of SLA. Although plants without EFNs had more sclerophyllous leaves, this mechanical defense was not sufficient to impair and/or reduce herbivore feeding, suggesting that the biotic defenses performed by patrolling ants might be more effective than investment in mechanical defenses associated with leaf palatability.

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David, Aaron S., Andrea Carmona Cortes, Gregory S. Wheeler, and Ellen C. Lake. "Localized Induced Defenses Limit Gall Formation by Eriophyid Mite Against Invasive Lygodium microphyllum (Schizaeales: Lygodiaceae)." Environmental Entomology 50, no. 4 (June 3, 2021): 814–20. http://dx.doi.org/10.1093/ee/nvab049.

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Abstract A potential barrier to the establishment of weed biological control agents is interference from other management tactics that induce plant defenses. Methods that suppress the weed such as feeding by other biological control agents or mechanical removal are especially disposed to inducing plant defenses and potentially limiting agent establishment. Here, we focused on the invasive weed Lygodium microphyllum (Cav.) R. Br. (Schizaeales: Lygodiaceae, Old World climbing fern) and one of its biological control agents, the mite Floracarus perrepae Knihinicki and Boczek (Acariformes: Eriophyidae). We experimentally induced plant defenses in potted plants via damage or application of jasmonic acid, a hormone typically involved in plant defenses, and measured the responses of the mite in a screenhouse. Localized damage to the pinnae (e.g., leaflets) via cutting or larval feeding from a second biological control agent, Neomusotima conspurcatalis (Warren) (Lepidoptera; Crambidae), reduced F. perrepae gall formation, but not the number of mites per gall. In contrast, damage to rachises (e.g., stems) did not affect galling, likely because plant defense responses were not systemic. Application of jasmonic acid reduced gall formation but not the numbers of mites within galls. Taken together, we found that localized damage interfered with gall formation but not within-gall reproduction. However, these effects on the mite from induced plant defenses are likely short-lived, and therefore interference between management tactics is unlikely to affect F. perrepae establishment and performance.

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Koussoroplis, Apostolos-Manuel, Toni Klauschies, Sylvain Pincebourde, David Giron, and Alexander Wacker. "A comment on “Variability in plant nutrients reduces insect herbivore performance”." Rethinking Ecology 4 (May 10, 2019): 79–87. http://dx.doi.org/10.3897/rethinkingecology.4.32252.

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In their recent contribution, Wetzel et al. [Wetzel et al. (2016) Variability in plant nutrients reduces insect herbivore performance. Nature 539: 425-427] predict that variance in the plant nutrient level reduces herbivore performance via the nonlinear averaging effect (named Jensen’s effect by the authors) while variance in the defense level does not. We argue that the study likely underestimates the potential of plant defenses’ variance to cause Jensen’s effects for two reasons. First, this conclusion is based on the finding that the average Jensen’s effect of various defense traits on various herbivores is zero which does not imply that the Jensen’s effect of specific defense traits on specific herbivores is null, just that the effects balance each other globally. Second, the study neglects the nonlinearity effects that may arise from the synergy between nutritive and defense traits or between co-occurring defenses on herbivore performance. Covariance between interacting plant defense traits, or between plant nutritive and defense traits, can affect performance differently than would nutritive or single plant defense variance alone. Overlooking the interactive effects of plant traits and the traits’ covariance could impair the assessment of the true role of plant trait variability on herbivore populations in natural settings.

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Callis-Duehl, Kristine L., Heather J. McAuslane, Adrian J. Duehl, and Douglas J. Levey. "The Effects of Silica Fertilizer as an Anti-Herbivore Defense in Cucumber." Journal of Horticultural Research 25, no. 1 (June 27, 2017): 89–98. http://dx.doi.org/10.1515/johr-2017-0010.

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AbstractThis study aims to improve our understanding of silicon’s role in deterring herbivores from Cucumis sativa. We hypothesized that silicon’s role in plant defense is due to the presence of silica augmenting other physical and/or chemical defenses used by the plant. Using C. sativa plants treated with either a silica fertilizer treatment (Si+) or a control solution (Si-), we monitored feeding preferences of two types of herbivores, a chewing herbivore (Diabrotica balteata) and a piercing/sucking herbivore (Bemisia tabaci). Leaves from treatment plants were visited less and eaten less than leaves from control plants. We then assessed the differences in physical defenses by comparing the leaf structural components, nutrient and water content, and trichome density between treatment and control plants. For chemical plant defenses, we measured leaf carbon and nitrogen levels in, and volatile organic compounds (VOCs) from treatment and control plants. We found no significant difference between treatment and control plants in: lignin content, most elemental plant nutrients, water content, trichome density, and quantity of carbon and nitrogen. We did see an increase in the VOC Indole, known for plant defense priming, an increase in phosphorous levels and a decrease in cellulose levels in silica treated plants.

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Ballhorn, Daniel J., Stefanie Kautz, Martin Heil, and Adrian D. Hegeman. "Analyzing plant defenses in nature." Plant Signaling & Behavior 4, no. 8 (August 2009): 743–45. http://dx.doi.org/10.4161/psb.4.8.9088.

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Hines, P. J. "An End to Plant Defenses." Science Signaling 4, no. 178 (June 21, 2011): ec172-ec172. http://dx.doi.org/10.1126/scisignal.4178ec172.

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Reina-Pinto, José J., and Alexander Yephremov. "Surface lipids and plant defenses." Plant Physiology and Biochemistry 47, no. 6 (June 2009): 540–49. http://dx.doi.org/10.1016/j.plaphy.2009.01.004.

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van Dam, Nicole M. "Belowground Herbivory and Plant Defenses." Annual Review of Ecology, Evolution, and Systematics 40, no. 1 (December 2009): 373–91. http://dx.doi.org/10.1146/annurev.ecolsys.110308.120314.

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Riddihough, G. "RNA Interference and Plant Defenses." Science Signaling 1, no. 33 (August 19, 2008): ec297-ec297. http://dx.doi.org/10.1126/scisignal.133ec297.

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Coley, Phyllis D. "Gap size and plant defenses." Trends in Ecology & Evolution 8, no. 1 (January 1993): 1–2. http://dx.doi.org/10.1016/0169-5347(93)90119-a.

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Larson, Richard A. "Plant defenses against oxidative stress." Archives of Insect Biochemistry and Physiology 29, no. 2 (1995): 175–86. http://dx.doi.org/10.1002/arch.940290207.

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Rioja, Cristina, Vladimir Zhurov, Kristie Bruinsma, Miodrag Grbic, and Vojislava Grbic. "Plant-Herbivore Interactions: A Case of an Extreme Generalist, the Two-Spotted Spider Mite Tetranychus urticae." Molecular Plant-Microbe Interactions® 30, no. 12 (December 2017): 935–45. http://dx.doi.org/10.1094/mpmi-07-17-0168-cr.

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Plant-herbivore interactions evolved over long periods of time, resulting in an elaborate arms race between interacting species. While specialist herbivores evolved specific strategies to cope with the defenses of a limited number of hosts, our understanding of how generalist herbivores deal with the defenses of a plethora of diverse host plants is largely unknown. Understanding the interaction between a plant host and a generalist herbivore requires an understanding of the plant’s mechanisms aimed at defending itself and the herbivore’s mechanisms intended to counteract diverse defenses. In this review, we use the two-spotted spider mite (TSSM), Tetranychus urticae (Koch) as an example of a generalist herbivore, as this chelicerate pest has a staggering number of plant hosts. We first establish that the ability of TSSM to adapt to marginal hosts underlies its polyphagy and agricultural pest status. We then highlight our understanding of direct plant defenses against spider mite herbivory and review recent advances in uncovering mechanisms of spider mite adaptations to them. Finally, we discuss the adaptation process itself, as it allows TSSM to overcome initially effective plant defenses. A high-quality genome sequence and developing genetic tools, coupled with an ease of mite experimental selection to new hosts, make TSSM an outstanding system to study the evolution of host range, mechanisms of pest xenobiotic resistance and plant-herbivore interactions. In addition, knowledge of plant defense mechanisms that affect mite fitness are of practical importance, as it can lead to development of new control strategies against this important agricultural pest. In parallel, understanding mechanisms of mite counter adaptations to these defenses is required to maintain the efficacy of these control strategies in agricultural practices.

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Bittner, Norbert, Janik Hundacker, Ander Achotegui-Castells, Olle Anderbrant, and Monika Hilker. "Defense of Scots pine against sawfly eggs (Diprion pini) is primed by exposure to sawfly sex pheromones." Proceedings of the National Academy of Sciences 116, no. 49 (November 20, 2019): 24668–75. http://dx.doi.org/10.1073/pnas.1910991116.

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Plants respond to insect infestation with defenses targeting insect eggs on their leaves and the feeding insects. Upon perceiving cues indicating imminent herbivory, such as damage-induced leaf odors emitted by neighboring plants, they are able to prime their defenses against feeding insects. Yet it remains unknown whether plants can amplify their defenses against insect eggs by responding to cues indicating imminent egg deposition. Here, we tested the hypothesis that a plant strengthens its defenses against insect eggs by responding to insect sex pheromones. Our study shows that preexposure of Pinus sylvestris to pine sawfly sex pheromones reduces the survival rate of subsequently laid sawfly eggs. Exposure to pheromones does not significantly affect the pine needle water content, but results in increased needle hydrogen peroxide concentrations and increased expression of defense-related pine genes such as SOD (superoxide dismutase), LOX (lipoxygenase), PAL (phenylalanine ammonia lyase), and PR-1 (pathogenesis related protein 1) after egg deposition. These results support our hypothesis that plant responses to sex pheromones emitted by an herbivorous insect can boost plant defensive responses to insect egg deposition, thus highlighting the ability of a plant to mobilize its defenses very early against an initial phase of insect attack, the egg deposition.

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Widemann, Emilie, Kristie Bruinsma, Brendan Walshe-Roussel, Cristina Rioja, Vicent Arbona, Repon Kumer Saha, David Letwin, et al. "Multiple indole glucosinolates and myrosinases defend Arabidopsis against Tetranychus urticae herbivory." Plant Physiology 187, no. 1 (June 19, 2021): 116–32. http://dx.doi.org/10.1093/plphys/kiab247.

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Abstract Arabidopsis (Arabidopsis thaliana) defenses against herbivores are regulated by the jasmonate (JA) hormonal signaling pathway, which leads to the production of a plethora of defense compounds. Arabidopsis defense compounds include tryptophan-derived metabolites, which limit Arabidopsis infestation by the generalist herbivore two-spotted spider mite, Tetranychus urticae. However, the phytochemicals responsible for Arabidopsis protection against T. urticae are unknown. Here, we used Arabidopsis mutants disrupted in the synthesis of tryptophan-derived secondary metabolites to identify phytochemicals involved in the defense against T. urticae. We show that of the three tryptophan-dependent pathways found in Arabidopsis, the indole glucosinolate (IG) pathway is necessary and sufficient to assure tryptophan-mediated defense against T. urticae. We demonstrate that all three IGs can limit T. urticae herbivory, but that they must be processed by myrosinases to hinder T. urticae oviposition. Putative IG breakdown products were detected in mite-infested leaves, suggesting in planta processing by myrosinases. Finally, we demonstrate that besides IGs, there are additional JA-regulated defenses that control T. urticae herbivory. Together, our results reveal the complexity of Arabidopsis defenses against T. urticae that rely on multiple IGs, specific myrosinases, and additional JA-dependent defenses.

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Wu, Tingquan, An Guo, Yanying Zhao, Xiaomeng Wang, Ying Wang, Dan Zhao, Xiaojie Li, Haiying Ren, and Hansong Dong. "Ectopic Expression of the Rice Lumazine Synthase Gene Contributes to Defense Responses in Transgenic Tobacco." Phytopathology® 100, no. 6 (June 2010): 573–81. http://dx.doi.org/10.1094/phyto-100-6-0573.

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Lumazine synthase (LS) catalyzes the penultimate reaction in the multistep riboflavin biosynthesis pathway, which is involved in plant defenses. Plant defenses are often subject to synergistic effects of jasmonic acid and ethylene whereas LS is a regulator of jasmonic acid signal transduction. However, little is known about whether the enzyme contributes to defense responses. To study the role of LS in plant pathogen defenses, we generated transgenic tobacco expressing the rice (Oryza sativa) LS gene, OsLS. OsLS was cloned and found to have strong identity with its homologues in higher plants and less homology to microbial orthologues. The OsLS protein localized to chloroplasts in three OsLS-expressing transgenic tobacco (LSETT) lines characterized as enhanced in growth and defense. Compared with control plants, LSETT had higher content of both riboflavin and the cofactors flavin mononucleotide and flavin adenine dinucleotide. In LSETT, jasmonic acid and ethylene were elevated, the expression of defense-related genes was induced, levels of resistance to pathogens were enhanced, and resistance was effective to viral, bacterial, and oomycete pathogens. Extents of OsLS expression correlated with increases in flavin, jasmonic acid, and ethylene content, and correlated with increases in resistance levels, suggesting a role for OsLS in defense responses.

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Schimmel, Bernardus, Juan Alba, Nicky Wybouw, Joris Glas, Tomas Meijer, Robert Schuurink, and Merijn Kant. "Distinct Signatures of Host Defense Suppression by Plant-Feeding Mites." International Journal of Molecular Sciences 19, no. 10 (October 20, 2018): 3265. http://dx.doi.org/10.3390/ijms19103265.

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Tomato plants are attacked by diverse herbivorous arthropods, including by cell-content-feeding mites, such as the extreme generalist Tetranychus urticae and specialists like Tetranychus evansi and Aculops lycopersici. Mite feeding induces plant defense responses that reduce mite performance. However, T. evansi and A. lycopersici suppress plant defenses via poorly understood mechanisms and, consequently, maintain a high performance on tomato. On a shared host, T. urticae can be facilitated by either of the specialist mites, likely due to the suppression of plant defenses. To better understand defense suppression and indirect plant-mediated interactions between herbivorous mites, we used gene-expression microarrays to analyze the transcriptomic changes in tomato after attack by either a single mite species (T. urticae, T. evansi, A. lycopersici) or two species simultaneously (T. urticae plus T. evansi or T. urticae plus A. lycopersici). Additionally, we assessed mite-induced changes in defense-associated phytohormones using LC-MS/MS. Compared to non-infested controls, jasmonates (JAs) and salicylate (SA) accumulated to higher amounts upon all mite-infestation treatments, but the response was attenuated after single infestations with defense-suppressors. Strikingly, whereas 8 to 10% of tomato genes were differentially expressed upon single infestations with T. urticae or A. lycopersici, respectively, only 0.1% was altered in T. evansi-infested plants. Transcriptome analysis of dual-infested leaves revealed that A. lycopersici primarily suppressed T. urticae-induced JA defenses, while T. evansi dampened T. urticae-triggered host responses on a transcriptome-wide scale. The latter suggests that T. evansi not solely down-regulates plant gene expression, but rather directs it back towards housekeeping levels. Our results provide valuable new insights into the mechanisms underlying host defense suppression and the plant-mediated facilitation of competing herbivores.

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Santamaria, M. Estrella, Ana Arnaiz, Irene Rosa-Diaz, Pablo González-Melendi, Gara Romero-Hernandez, Dairon A. Ojeda-Martinez, Alejandro Garcia, Estefania Contreras, Manuel Martinez, and Isabel Diaz. "Plant Defenses Against Tetranychus urticae: Mind the Gaps." Plants 9, no. 4 (April 7, 2020): 464. http://dx.doi.org/10.3390/plants9040464.

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The molecular interactions between a pest and its host plant are the consequence of an evolutionary arms race based on the perception of the phytophagous arthropod by the plant and the different strategies adopted by the pest to overcome plant triggered defenses. The complexity and the different levels of these interactions make it difficult to get a wide knowledge of the whole process. Extensive research in model species is an accurate way to progressively move forward in this direction. The two-spotted spider mite, Tetranychus urticae Koch has become a model species for phytophagous mites due to the development of a great number of genetic tools and a high-quality genome sequence. This review is an update of the current state of the art in the molecular interactions between the generalist pest T. urticae and its host plants. The knowledge of the physical and chemical constitutive defenses of the plant and the mechanisms involved in the induction of plant defenses are summarized. The molecular events produced from plant perception to the synthesis of defense compounds are detailed, with a special focus on the key steps that are little or totally uncovered by previous research.

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Kliebenstein, Daniel, Deana Pedersen, Bridget Barker, and Thomas Mitchell-Olds. "Comparative Analysis of Quantitative Trait Loci Controlling Glucosinolates, Myrosinase and Insect Resistance in Arabidopsis thaliana." Genetics 161, no. 1 (May 1, 2002): 325–32. http://dx.doi.org/10.1093/genetics/161.1.325.

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Abstract Evolutionary interactions among insect herbivores and plant chemical defenses have generated systems where plant compounds have opposing fitness consequences for host plants, depending on attack by various insect herbivores. This interplay complicates understanding of fitness costs and benefits of plant chemical defenses. We are studying the role of the glucosinolate-myrosinase chemical defense system in protecting Arabidopsis thaliana from specialist and generalist insect herbivory. We used two Arabidopsis recombinant inbred populations in which we had previously mapped QTL controlling variation in the glucosinolate-myrosinase system. In this study we mapped QTL controlling resistance to specialist (Plutella xylostella) and generalist (Trichoplusia ni) herbivores. We identified a number of QTL that are specific to one herbivore or the other, as well as a single QTL that controls resistance to both insects. Comparison of QTL for herbivory, glucosinolates, and myrosinase showed that T. ni herbivory is strongly deterred by higher glucosinolate levels, faster breakdown rates, and specific chemical structures. In contrast, P. xylostella herbivory is uncorrelated with variation in the glucosinolate-myrosinase system. This agrees with evolutionary theory stating that specialist insects may overcome host plant chemical defenses, whereas generalists will be sensitive to these same defenses.

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Stamp, Nancy. "MISCONCEPTIONS ABOUT PLANT–HERBIVORE INTERACTIONS, ESPECIALLY PLANT DEFENSES." Bulletin of the Ecological Society of America 85, no. 4 (October 2004): 201–5. http://dx.doi.org/10.1890/0012-9623(2004)85[201:mapiep]2.0.co;2.

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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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Viswanath, Kotapati Kasi, Song-Yi Kuo, Chin-Wei Tu, Yau-Heiu Hsu, Ying-Wen Huang, and Chung-Chi Hu. "The Role of Plant Transcription Factors in the Fight against Plant Viruses." International Journal of Molecular Sciences 24, no. 9 (May 8, 2023): 8433. http://dx.doi.org/10.3390/ijms24098433.

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Plants are vulnerable to the challenges of unstable environments and pathogen infections due to their immobility. Among various stress conditions, viral infection is a major threat that causes significant crop loss. In response to viral infection, plants undergo complex molecular and physiological changes, which trigger defense and morphogenic pathways. Transcription factors (TFs), and their interactions with cofactors and cis-regulatory genomic elements, are essential for plant defense mechanisms. The transcriptional regulation by TFs is crucial in establishing plant defense and associated activities during viral infections. Therefore, identifying and characterizing the critical genes involved in the responses of plants against virus stress is essential for the development of transgenic plants that exhibit enhanced tolerance or resistance. This article reviews the current understanding of the transcriptional control of plant defenses, with a special focus on NAC, MYB, WRKY, bZIP, and AP2/ERF TFs. The review provides an update on the latest advances in understanding how plant TFs regulate defense genes expression during viral infection.

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Kshatriya, Kristina, and Jonathan Gershenzon. "Disarming the defenses: Insect detoxification of plant defense-related specialized metabolites." Current Opinion in Plant Biology 81 (October 2024): 102577. http://dx.doi.org/10.1016/j.pbi.2024.102577.

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Djami-Tchatchou, Arnaud T., Gregory A. Harrison, Chris P. Harper, Renhou Wang, Michael J. Prigge, Mark Estelle, and Barbara N. Kunkel. "Dual Role of Auxin in Regulating Plant Defense and Bacterial Virulence Gene Expression During Pseudomonas syringae PtoDC3000 Pathogenesis." Molecular Plant-Microbe Interactions® 33, no. 8 (August 2020): 1059–71. http://dx.doi.org/10.1094/mpmi-02-20-0047-r.

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Modification of host hormone biology is a common strategy used by plant pathogens to promote disease. For example, the bacterial pathogen strain Pseudomonas syringae DC3000 (PtoDC3000) produces the plant hormone auxin (indole-3-acetic acid [IAA]) to promote PtoDC3000 growth in plant tissue. Previous studies suggest that auxin may promote PtoDC3000 pathogenesis through multiple mechanisms, including both suppression of salicylic acid (SA)-mediated host defenses and via an unknown mechanism that appears to be independent of SA. To test if host auxin signaling is important during pathogenesis, we took advantage of Arabidopsis thaliana lines impaired in either auxin signaling or perception. We found that disruption of auxin signaling in plants expressing an inducible dominant axr2-1 mutation resulted in decreased bacterial growth and that this phenotype was suppressed by introducing the sid2-2 mutation, which impairs SA synthesis. Thus, host auxin signaling is required for normal susceptibility to PtoDC3000 and is involved in suppressing SA-mediated defenses. Unexpectedly, tir1 afb1 afb4 afb5 quadruple-mutant plants lacking four of the six known auxin coreceptors that exhibit decreased auxin perception, supported increased levels of bacterial growth. This mutant exhibited elevated IAA levels and reduced SA-mediated defenses, providing additional evidence that auxin promotes disease by suppressing host defense. We also investigated the hypothesis that IAA promotes PtoDC3000 virulence through a direct effect on the pathogen and found that IAA modulates expression of virulence genes, both in culture and in planta. Thus, in addition to suppressing host defenses, IAA acts as a microbial signaling molecule that regulates bacterial virulence gene expression.

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Chuang, Wen-Po, Swayamjit Ray, Flor Edith Acevedo, Michelle Peiffer, Gary W. Felton, and Dawn S. Luthe. "Herbivore Cues from the Fall Armyworm (Spodoptera frugiperda) Larvae Trigger Direct Defenses in Maize." Molecular Plant-Microbe Interactions® 27, no. 5 (May 2014): 461–70. http://dx.doi.org/10.1094/mpmi-07-13-0193-r.

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In addition to feeding damage, herbivores release cues that are recognized by plants to elicit defenses. Caterpillar oral secretions have been shown to trigger herbivore defense responses in several different plant species. In this study, the effects of two fall armyworm (Spodoptera frugiperda) oral secretions (saliva and regurgitant) on caterpillar defense responses in maize (Zea mays) were examined. Only minute amounts of regurgitant were deposited on the maize leaf during larval feeding bouts and its application to leaves failed to induce the expression of several herbivore defense genes. On the other hand, caterpillars consistently deposited saliva on leaves during feeding and the expression of several maize defense genes significantly increased in response to saliva application and larval feeding. However, feeding by ablated caterpillars with impaired salivation did not induce these defenses. Furthermore, bioassays indicated that feeding by unablated caterpillars significantly enhanced defenses when compared with that of ablated caterpillars. Another critical finding was that the maize genotype and stage of development affected the expression of defense genes in response to wounding and regurgitant treatments. These results demonstrate that fall armyworm saliva contains elicitors that trigger herbivore defenses in maize.

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Tooker, John F., and Consuelo M. De Moraes. "Gall insects and indirect plant defenses." Plant Signaling & Behavior 3, no. 7 (July 2008): 503–4. http://dx.doi.org/10.4161/psb.3.7.6184.

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42

Adler, T. "How Temperature, Plant Defenses Alter Bugs." Science News 149, no. 25 (June 22, 1996): 389. http://dx.doi.org/10.2307/3979930.

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Quintero, Carolina, Kasey E. Barton, and Karina Boege. "The ontogeny of plant indirect defenses." Perspectives in Plant Ecology, Evolution and Systematics 15, no. 5 (October 2013): 245–54. http://dx.doi.org/10.1016/j.ppees.2013.08.003.

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Heath, Michèle C. "Nonhost resistance and nonspecific plant defenses." Current Opinion in Plant Biology 3, no. 4 (August 2000): 315–19. http://dx.doi.org/10.1016/s1369-5266(00)00087-x.

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Adie, Bruce, José Manuel Chico, Ignacio Rubio-Somoza, and Roberto Solano. "Modulation of Plant Defenses by Ethylene." Journal of Plant Growth Regulation 26, no. 2 (May 10, 2007): 160–77. http://dx.doi.org/10.1007/s00344-007-0012-6.

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Larson, Richard A. "Insect defenses against phototoxic plant chemicals." Journal of Chemical Ecology 12, no. 4 (April 1986): 859–70. http://dx.doi.org/10.1007/bf01020256.

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Hammerschmidt, R. "Localizing defenses." Physiological and Molecular Plant Pathology 63, no. 6 (December 2003): 291–92. http://dx.doi.org/10.1016/j.pmpp.2004.06.001.

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Hammerschmidt, R. "Inducing Defenses." Physiological and Molecular Plant Pathology 66, no. 5 (May 2005): 161–62. http://dx.doi.org/10.1016/j.pmpp.2005.10.001.

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Serteyn, Laurent, Céleste Quaghebeur, Marc Ongena, Nuri Cabrera, Andrea Barrera, Marco A. Molina-Montenegro, Frédéric Francis, and Claudio C. Ramírez. "Induced Systemic Resistance by a Plant Growth-Promoting Rhizobacterium Impacts Development and Feeding Behavior of Aphids." Insects 11, no. 4 (April 8, 2020): 234. http://dx.doi.org/10.3390/insects11040234.

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The effects of microorganisms on plant-insect interactions have usually been underestimated. While plant growth-promoting rhizobacteria (PGPR) are known to induce plant defenses, endosymbiotic bacteria hosted by herbivorous insects are often beneficial to the host. Here, we aimed to assess whether PGPR-induced defenses in broad bean plants impact the pea aphid, depending on its genotype and the presence of endosymbionts. We estimated aphid reproduction, quantified defense- and growth-related phytohormones by GC-MS, and measured different plant growth and physiology parameters, after PGPR treatment. In addition, we recorded the feeding behavior of aphids by electropenetrography. We found that the PGPR treatment of broad bean plants reduced the reproduction of one of the pea aphid clones. We highlighted a phenomenon of PGPR-induced plant defense priming, but no noticeable plant growth promotion. The main changes in aphid probing behavior were related to salivation events into phloem sieve elements. We suggest that the endosymbiont Hamiltonella defensa played a key role in plant-insect interactions, possibly helping aphids to counteract plant-induced resistance and allowing them to develop normally on PGPR-treated plants. Our results imply that plant- and aphid-associated microorganisms add greater complexity to the outcomes of aphid-plant interactions.

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Tan, Ching-Wen, Michelle Peiffer, Kelli Hoover, Cristina Rosa, Flor E. Acevedo, and Gary W. Felton. "Symbiotic polydnavirus of a parasite manipulates caterpillar and plant immunity." Proceedings of the National Academy of Sciences 115, no. 20 (April 30, 2018): 5199–204. http://dx.doi.org/10.1073/pnas.1717934115.

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Obligate symbioses occur when organisms require symbiotic relationships to survive. Some parasitic wasps of caterpillars possess obligate mutualistic viruses called “polydnaviruses.” Along with eggs, wasps inject polydnavirus inside their caterpillar hosts where the hatching larvae develop inside the caterpillar. Polydnaviruses suppress the immune systems of their caterpillar hosts, which enables egg hatch and wasp larval development. It is unknown whether polydnaviruses also manipulate the salivary proteins of the caterpillar, which may affect the elicitation of plant defenses during feeding by the caterpillar. Here, we show that a polydnavirus of the parasitoid Microplitis croceipes, and not the parasitoid larva itself, drives the regulation of salivary enzymes of the caterpillar Helicoverpa zea that are known to elicit tomato plant-defense responses to herbivores. The polydnavirus suppresses glucose oxidase, which is a primary plant-defense elicitor in the saliva of the H. zea caterpillar. By suppressing plant defenses, the polydnavirus allows the caterpillar to grow at a faster rate, thus improving the host suitability for the parasitoid. Remarkably, polydnaviruses manipulate the phenotypes of the wasp, caterpillar, and host plant, demonstrating that polydnaviruses play far more prominent roles in shaping plant–herbivore interactions than ever considered.

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Journal articles on the topic 'Plant defenses'

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