Mechanical Defense Research Articles

Silicon-based plant defences, tooth wear and voles.

Plant-herbivore interactions are hypothesized to drive vole population cycles through the grazing-induced production of phytoliths in leaves. Phytoliths act as mechanical defences because they deter herbivory and lower growth rates in mammals. However, how phytoliths impair herbivore performance is still unknown. Here, we tested whether the amount of phytoliths changes tooth wear patterns. If confirmed, abrasion from phytoliths could play a role in population crashes. We applied dental microwear texture analysis (DMTA) to laboratory and wild voles. Lab voles were fed two pelleted diets with differing amounts of silicon, which produced similar dental textures. This was most probably due to the loss of food mechanical properties through pelletization and/or the small difference in silicon concentration between diets. Wild voles were trapped in Poland during spring and summer, and every year across a population cycle. In spring, voles feed on silica-rich monocotyledons, while in the summer they also include silica-depleted dicotyledons. This was reflected in the results; the amount of silica therefore leaves a traceable record in the dental microwear texture of voles. Furthermore, voles from different phases of population cycles have different microwear textures. We tentatively propose that these differences result from grazing-induced phytolith concentrations. We hypothesize that the high amount of phytoliths in response to intense grazing in peak years may result in malocclusion and other dental abnormalities, which would explain how these silicon-based plant defences help provoke population crashes. DMTA could then be used to reconstruct vole population dynamics using teeth from pellets or palaeontological material.

Human nasal epithelial cells derived from multiple subjects exhibit differential responses to H3N2 influenza virus infection in vitro

Human nasal epithelial cells derived from multiple subjects exhibit differential responses to H3N2 influenza virus infection in vitro

A minireview on adaption of young leaf redness

It is well known that the leaves of many woody plant species flush red rather than green during particular stages across their life span. Non-green leaf coloration caused by active synthesis of anthocyanin in plant organs at these stages costs the plant significant resources and energy, resulting in a reduction of primary photosynthesis. Therefore, it is likely that the coloration change is an active process and not simply a by-product of metabolism. Various hypotheses formulated to explain the potential reasons for coloration change can be divided into two categories: (1) those that suggest it is physiological adaptation for resistance to severe environments (high light, drought and low temperatures); and (2) those that suggest it protects against herbivory damage (coevolution, unpalatability, camouflage and anticamouflage, etc.). To date, there is no consensus on the relative validity of these ideas. The majority of previous work has focused on only a few species and autumn leaf color change. The relatively few studies done on red young leaves in spring mostly focused on red coloration as an independent visual signal. Future studies need to consider the chemical and mechanical defense of leaf redness, as well as the anthocyanins presented in other plant organs (thorns, stems and particularly, flowers), which may experience similar selection as leaves. The quantification of environmental factors and herbivore selection would be helpful in expansion our understanding in young leaf redness.

Infecţia de focar amigdalian – manifestări clinice principale

The tonsill represents a natural barrier against various infectious pathogens. Around the tonsillar crypts, the tissues produce an area of mechanical defence barrier formed of granulation tissue, neoformation vascularization and leukocytes. In this region a series of complex immunological processes take place, the central role being occupied by immunoglobulin A. Tonsillar outbreak infection is a particular feature of immune response, generating numerous imunopathologic reactions.

Moreau's Paradox Reversed, or Why Insectivorous Birds Reach High Densities in Savanna Trees

In West Africa, tree preferences of wintering migratory birds (and African residents) were quantified in order to assess the importance of wintering conditions on distribution, abundance and trends of insectivorous woodland birds. This study encompassed 2000 plots between 10–18°N and 0–17°W, visited in October-March 2007–2015, and covered 183 woody species and 59 bird species. Canopy surface (measured in a horizontal plane) and birds present were determined in 308,000 trees and shrubs. Absolute bird density amounted to 13 birds/ha canopy, on average, varying for the different woody species between 0 and 130 birds/ha canopy. Birds were highly selective in their tree choice, with no insectivorous birds at all in 65% of the woody species. Bird density was four times higher in acacias and other thorny species than in non-thorny trees, and seven times higher in trees with leaves having a low crude fibre content than in trees with high crude fibre foliage. Salvadora persica shrubs, but only when carrying berries, were even more attractive. Overall, densities of migratory woodland birds were highest in the (thorny) trees of the Sahelian vegetation zone. This counterintuitive finding, with highest numbers of wintering birds in the driest and most desiccated parts of West Africa (short of the Sahara), also known as Moreau's Paradox, can be explained by the foliage palatability hypothesis. The Sahelian vegetation zone has always been subject to heavy grazing from large herbivores, and as a consequence woody species have evolved mechanical defences (thorns) to withstand grazing of large herbivores, at the expense of chemical defence against arthropods. South of the Sahel, with a much lower grazing pressure, thorny trees (rich in arthropods) are replaced by (usually non-thorny) trees with less palatable foliage and a higher crude fibre content, and hence with less arthropod food for insectivorous birds.

Diet and prey selectivity of the specialist myrmecophage, Temminck's ground pangolin

AbstractThe diet of Temminck's ground pangolin Smutsia temminckii (hereafter, pangolin) has thus far been studied only in mesic savannahs. We provide arid‐zone dietary data for this species based on direct observations, and compare these to available prey species assemblages. We also report stable carbon and nitrogen isotope enrichment values for liver and scales obtained from pangolin carcasses compared to the diet. Pangolins were recorded consuming four ant (Anoplolepis steingroeveri, Camponotus fulvopilosus, two Crematogaster spp.) and one termite (Trinervitermes trinervoides) species, which represent 7.5 and 25% of the available ant and termite species respectively. The stable isotope data corroborate the direct observations and confirm that pangolins display a high degree of prey selectivity, however stable isotopes alone were not able to infer the diet of pangolins as a number of non‐prey species had similar isotopic values to prey species. Direct observations suggest that purported non‐prey species are not consumed, possibly because they have chemical or mechanical defenses or gallery structures that make them unsuitable as prey. Liver was enriched by 3.8 ± 1.2‰ (mean ± SD) and 2.5 ± 1.4‰ for δ15N and δ13C respectively, relative to the mean δ15N and δ13C values of the prey species, and scales were enriched by 2.9 ± 1.0‰ and 5.3 ± 1.8‰ respectively. We observed no seasonal variation or age or sex‐related differences in diet, either from direct observations or isotope data. These results support previous findings that pangolins have further specialized within an already unusual mammalian dietary niche.

Low-dose AgNPs reduce lung mechanical function and innate immune defense in the absence of cellular toxicity

Multiple studies have examined the direct cellular toxicity of silver nanoparticles (AgNPs). However, the lung is a complex biological system with multiple cell types and a lipid-rich surface fluid; therefore, organ level responses may not depend on direct cellular toxicity. We hypothesized that interaction with the lung lining is a critical determinant of organ level responses. Here, we have examined the effects of low dose intratracheal instillation of AgNPs (0.05 μg/g body weight) 20 and 110 nm diameter in size, and functionalized with citrate or polyvinylpyrrolidone. Both size and functionalization were significant factors in particle aggregation and lipid interaction in vitro. One day post-intratracheal instillation lung function was assessed, and bronchoalveolar lavage (BAL) and lung tissue collected. There were no signs of overt inflammation. There was no change in surfactant protein-B content in the BAL but there was loss of surfactant protein-D with polyvinylpyrrolidone (PVP)-stabilized particles. Mechanical impedance data demonstrated a significant increase in pulmonary elastance as compared to control, greatest with 110 nm PVP-stabilized particles. Seven days post-instillation of PVP-stabilized particles increased BAL cell counts, and reduced lung function was observed. These changes resolved by 21 days. Hence, AgNP-mediated alterations in the lung lining and mechanical function resolve by 21 days. Larger particles and PVP stabilization produce the largest disruptions. These studies demonstrate that low dose AgNPs elicit deficits in both mechanical and innate immune defense function, suggesting that organ level toxicity should be considered.

Geographic variation in the protective effects of ants and trichomes in a Neotropical ant–plant

Many ant–plants have pubescent leaves, but the extent to which leaf trichomes enhance the defensive capabilities of ant–plants is poorly known. Here, we examined the influence of foliar trichomes and ants on herbivory in the Neotropical ant–plant Tococa guianensis. We performed a feeding preference test and a field experiment in which we manipulated the presence of ants and trichomes in three distinct populations of T. guianensis; two associated with obligate mutualistic ants and one associated with opportunistic ants. We found that both mutualistic ants and leaf trichomes act as mechanisms of defense against herbivores in T. guianensis. However, the relative importance of each of these two mechanisms was context dependent. The magnitude of the effect of trichomes (as measured by the effect size) was relatively low and varied little among plant populations. The effect of ants on foliar herbivory was up to seven times stronger than the effect of the trichomes. Nevertheless, because the magnitude of ant effects was spatially variable—depending on whether mutualistic ants were present or not, and probably also on the local abundance of herbivores—the relative contribution of ants and trichomes for plant defense was also spatially variable. These findings indicate that mechanical defenses (leaf trichomes) alone cannot replace the biotic defenses of T. guianensis. However, trichomes can play a comparatively more important role in plant defense at times or places where mutualistic ants are not present.

The tethering of chromatin to the nuclear envelope supports nuclear mechanics.

The nuclear lamina is thought to be the primary mechanical defence of the nucleus. However, the lamina is integrated within a network of lipids, proteins and chromatin; the interdependence of this network poses a challenge to defining the individual mechanical contributions of these components. Here, we isolate the role of chromatin in nuclear mechanics by using a system lacking lamins. Using novel imaging analyses, we observe that untethering chromatin from the inner nuclear membrane results in highly deformable nuclei in vivo, particularly in response to cytoskeletal forces. Using optical tweezers, we find that isolated nuclei lacking inner nuclear membrane tethers are less stiff than wild-type nuclei and exhibit increased chromatin flow, particularly in frequency ranges that recapitulate the kinetics of cytoskeletal dynamics. We suggest that modulating chromatin flow can define both transient and long-lived changes in nuclear shape that are biologically important and may be altered in disease.

Pod and seed defensive coloration (camouflage and mimicry) in the genus Pisum

The small genusPisumis composed of two annual species,P.fulvumand the domesticated peaP.sativum. The domesticated pea has two main wild-type taxa:P.elatiusandP.humile. Members of the genusPisumare not well defended from herbivory by high levels of toxins like the seeds of many other legume species. We studied the color patterns in the pods and seeds of these three wild taxa (P.fulvum,P.elatiusandP.humile) in order to examine their potential for defensive coloration (camouflage and Batesian mimicry). All three taxa are polymorphic concerning pod and seed coloration. The mature pods of many individuals ofP.humileandP.elatiusmimic aposematic caterpillars, but some are plain green. The pods of some individuals ofP.elatiushave a zigzag or straight red marking along them that resembles the conspicuous dorsal markings of the local common venomous viper, potentially mimicking it. The pods of many individuals ofP.fulvumhave dark blotches that when compared to such patterns in animals, potentially function as camouflage. The seeds of all three species are camouflaged by either: (1) color matching with that of soil (especiallyP.fulvumandP.elatius), (2) disruptive coloration (especiallyP.humile), (3) variability in seed-coat color that may undermine the use of search images by visually oriented granivores that look for cryptic seeds (all taxa). The mature pods ofP.fulvumare also defended in many inflorescences by degenerated flowers that develop into sharp thorns. It seems that this species is still in the process of evolving this mechanical defense as the response to millennia of strong grazing pressure.

To each its own: differential response of specialist and generalist herbivores to plant defence in willows.

Plant-insect food webs tend to be dominated by interactions resulting from diffuse co-evolution between plants and multiple lineages of herbivores rather than by reciprocal co-evolution and co-cladogenesis. Plants therefore require defence strategies effective against a broad range of herbivore species. In one extreme, plants could develop a single universal defence effective against all herbivorous insects, or tailor-made strategies for each herbivore species. The evolution and ecology of plant defence has to be studied with entire insect assemblages, rather than small subsets of pairwise interactions. The present study examines whether specialists and generalists in three coexisting insect lineages, forming the leaf-chewing guild, respond uniformly to plant phylogeny, secondary metabolites, nutrient content and mechanical antiherbivore defences of their hosts, thus permitting universal plant defence strategies against specialized and generalist folivorous insects from various taxa. The extensive data on folivorous assemblages comprising three insect orders and 193 species are linked with plant phylogeny, secondary chemistry (salicylates, flavonoids and tannins), leaf morphological traits [specific leaf area (SLA) and trichome coverage], nutrient (C:N) content and growth form of eight willow (Salix) and one aspen (Populus) species growing in sympatry. Generalists responded to overall host plant chemistry and trichomes, whilst specialists responded to host plant phylogeny and secondary metabolites that are unique to willows and that are capable of being utilized as an antipredator protection. We did not find any significant impact of other plant traits, that is SLA, C:N ratio, flavonoids, tannins and growth form, on the composition of leaf-chewing communities. Our results show that the response to plant traits is differential among specialists and generalists. This finding constrains the ability of plants to develop defensive traits universally effective against herbivores and may lead to diversification of plant defensive mechanisms into several complementary syndromes, required for effective protection against generalists and specialists from multiple insect taxa comprising most leaf-chewing assemblages. These results point to the necessity of broad studies of plant-herbivore interactions, across multiple insect taxa and guilds.

Mechanics of the ptychoid defense mechanism in Ptyctima (Acari, Oribatida): One problem, two solutions

The most complex mechanical defense of oribatid mites is ptychoidy, in which the animals can retract their legs and gnathosoma into the idiosoma and encapsulate by deflecting the prodorsum. Since Acari lack most antagonistic musculature, extension of appendages is facilitated through hemolymph pressure that in mites mostly is generated by dorso-ventral compression of the opisthosoma. The hardened notogaster of box mites requires a different system of pressure generation that is also able to accommodate huge hemolymph movement accompanying ptychoidy. We compared the functional morphology of ptychoidy in one model species from each of the two ptyctime superfamilies, Euphthiracaroidea and Phthiracaroidea, using synchrotron X-ray microtomography and high-speed videography. We show that the two groups evolved very different functional modes of hydrostatic pressure control. While euphthiracaroids employ a lateral compression of the notogaster using all muscles of the opisthosomal compressor system, phthiracaroids employ a dorsoventral compression generated by only the notogaster lateral compressor and additionally the postanal muscle; these retract the temporarily unified ventral plates into the idiosoma, revealing the poam as an integral part of the opisthosomal compressor system in this group. The primitive mode of operation for generating hemolymph pressure in the Ptyctima probably was lateral compression, as molecular studies indicate that Phthiracaroidea evolved within Euphthiracaroidea. In this hypothesis, dorsoventral compression evolved secondarily in phthiracaroid mites, but whether the immediate ancestors of Ptyctima used lateral or dorsoventral compression remains to be determined.

Chromatin Association with the Nuclear Envelope Supports Stable Nuclear Mechanics

Although the nuclear lamina is considered to be the primary mechanical defense of the nucleus, lamins are part of an integrated network of lipids, proteins, and chromatin. Here, we isolate the contribution of chromatin to nuclear mechanics by employing fission yeast, which lack a nuclear lamina. We have combined a quantitative imaging platform capable of measuring 3D nuclear contours in vivo with an in vitro optical tweezers assay to probe the mechanical properties of S. pombe nuclei. In live cells, we find that association of chromatin with the inner nuclear membrane (INM) through integral membrane proteins is required for a normal mechanical response to microtubule (MT) forces. Increasing loss of integral INM proteins results in highly deformable nuclei specifically in response to exogenous MT forces. These nuclei also show a decreased capacity to recover from mechanical stress. Using optical tweezers, we find that nuclei lacking integral INM proteins are less stiff than wild type nuclei and have increased chromatin flow, particularly when force is applied at rates that recapitulate the kinetics of MT dynamics in vivo. Wild type mitotic nuclei, in which chromatin is globally released from the INM, are extremely soft and also display increased chromatin flow compared to interphase nuclei. Interestingly, decreasing the chromatin to nuclear volume ratio without altering the association of chromatin with the INM has only a slight effect on stiffness and does not alter chromatin flow. Together, these findings suggest that association of chromatin with the nuclear envelope underlies nuclear stiffness. Further, release of chromatin from the INM allows chromatin to flow into MT-dependent fluctuations of the nuclear envelope, leading to larger, longer-lasting nuclear deformations. Lastly, these results suggest that chromatin association with the lamina may contribute to the mechanical behavior of metazoan nuclei.

Jasmonic acid enhances plant cyanogenesis and resistance to herbivory in lima bean.

Jasmonic acid (JA) is a natural plant hormone ubiquitously distributed in plants and centrally involved in the induction of direct and indirect plant defenses. Defenses up-regulated by this hormone include trichomes--a direct, mechanical defense--and alkaloids--a direct chemical defense--as well as two indirect chemical defenses: volatile organic compounds (VOCs) and extrafloral nectar (EFN). Plant cyanogenesis--the release of toxic hydrogen cyanide (HCN) from preformed cyanogenic precursors in fruits, leaves, and seeds of many plants--is recognized as a direct, constitutive plant defensive trait, and is among the most widely distributed of all direct chemical plant defenses. The cyanogenic system in plants is composed of three parameters: The cyanogenic potential (HCNp; concentration of cyanogenic precursors), β-glucosidase activity, and cyanogenic capacity (HCNc; release of gaseous hydrogen cyanide). Here, we demonstrated that experimental application of aqueous solutions of JA ranging from 0.001 to 1.0 mmol L(-1), as well as insect herbivory significantly enhanced HCNc via the induction of β-glucosidase activity in wild lima bean (Phaseolus lunatus L.). In choice feeding trials with JA induced and damaged leaves, adult Mexican bean beetles--natural herbivores of lima bean--rejected leaves with enhanced β-glucosidase activity and HCNc. Our findings suggest that jasmonic acid plays a critical role in regulating activity of β-glucosidases, which determines the rate of cyanogenesis, and thus mediates direct plant defense against herbivores.

Sneezing as a mechanical defence - a numerical simulation and analysis of the nasal flow

The nose is responsible for humidification, heating and cleaning of the inhaled air. The sneeze reflex leads to a shock-like cleaning of the nose in strong particle exposure. The aim of this study was the simulation of intranasal air flow of sneezing in a realistic computer model. Based on the CT scan of a 40 year old man a three-dimensional computer model of the nasal cavity and the ethmoid sinuses was created. Flow simulations were performed for different inspiratory and expiratory velocities (± 2 m/s to ± 45 m/s) in order to simulate sneezing. RESULTS were visualized and analyzed by video simulation. During inspiration the main airflow takes place along the middle turbinate. During expiration, the flow is located more cranially. This effect is caused by the shape of the nasopharynx and the posterior portions of the nasal turbinates. During very high speeds (sneezing) also adjacent ethmoid sinuses and the olfactory region are covered by the shock-like expiratory flow. A large vortex formation in the nasopharynx is responsible for a uniform distribution of the airflow also on lower nasal areas. Sneezing is a protective reflex that provides for cleaning of the nose. From a flow rate of 10 m/s, the cranial nasal areas as well as adjacent ethmoid sinuses are covered by the -airflow. Compared to the inspiratory airflow the exhalation is not just vice versa. Particles that deposed in the cranial nasal areas during quiet breathing are removed.

Just spines—mechanical defense of malvaceous pollen against collection by corbiculate bees

Bee-pollinated plants face the dilemma that bees do not only transport pollen grains between flowers as pollen vectors but also collect large amounts of pollen that is withdrawn from pollination. Here, we show that pollen of the common hollyhock, Alcea rosea, is mechanically protected against collection by corbiculate bees. In a laboratory setup, bumblebees did not collect the large, sticky, and spinose pollen grains of A. rosea from artificial flowers unless following manipulation of the spines or the pollenkitt. Following removal of the sticky pollenkitt or bending the spines by vortexing the bumblebees readily collected the pollen. Our results show that the pollen of A. rosea is not bitter-tasting or toxic, but mechanically protected by the spines against being collected by corbiculate bees. Light microscopic (LM)-micrographs indicate that the long spines of malvaceous pollen grains are not covered by pollenkitt suggesting a new mechanism of mechanical defense against collection: pollenkitt-free spines and lipophilic pollenkitt prevent compacting pollen grains into pollen storage organs of corbiculate bees. The experimental data fit to observations at flowers of A. rosea and other malvaceous plants that honeybees and bumblebees are densely dusted with pollen but discard the pollen while packing it into their corbiculae.

The deleterious effects of non-protein amino acids from desert plants on human and animal health

Since plants lack the ability to remove themselves from sites of predation, they have evolved alternative defences to keep predators at bay. Mechanical defences include camouflage, the addition of thorns and spikes as well as growing in locations not easily accessed by herbivores. Chemical defences include the synthesis of compounds that are toxic to predatory species and can also inhibit or retard the growth of other plant species in a process termed “allelopathy”. Amongst these chemicals is a reservoir of non-protein amino acids that mediate toxicity. These non-protein amino acids can be charged by tRNA synthetases and subsequently mis-incorporated into nascent polypeptides, resulting in aberrant, dysfunctional proteins that can be toxic to predators. Some species such as the bruchid beetle Bruchus rufimanus (Chrysomelidae), which feeds on the jack bean Canavalia ensiformis (Fabaceae) plant, have evolved advanced tRNA synthetases that are able to discriminate between protein and non-protein amino acids, thus remain unaffected. Other species including livestock and humans that do not possess such selectivity are susceptible to plant toxins. In this brief review we discuss the mechanisms of action and consequences of exposure to plant-derived non-protein amino acids with a focus on those derived from plants from arid environments.

Biomechanical Properties of Hemlocks: A Novel Approach to Evaluating Physical Barriers of the Plant-Insect Interface and Resistance to a Phloem-Feeding Herbivore.

Micromechanical properties that help mediate herbivore access may be particularly important when considering herbivorous insects that feed with piercing-sucking stylets. We used microindentation to quantify the micromechanical properties of hemlock, Tsuga spp., to quantify the hardness of the feeding site of the invasive hemlock woolly adelgid, Adelges tsugae. We measured hardness of the hemlock leaf cushion, the stylet insertion point of the adelgid, across four seasons in a 1 y period for four hemlock species growing in a common garden, including eastern, western, mountain, and northern Japanese hemlocks. Leaf cushion hardness was highest in the fall and winter and lowest in summer for all species. Northern Japanese hemlock had relatively greater hardness than the remaining species. Our data contributes an additional perspective to the existing framework within which greater susceptibility and subsequent mortality of eastern hemlocks is observed. The potential application of microindentation to understanding the nature and relevance of plant mechanical defenses in plant–herbivore interactions is also demonstrated and highlighted.

Utilización de lectinas en la inhibición de la adhesión de Pasteurella multocida

El primer paso de la infección es la adhesión de los organismos patógenos a las células blanco. Esta característica les permite no solo penetrar y desplegar las estrategias ofensivas para iniciar la colonización, sino contribuir a la protección y el resguardo de estos a los mecanismos de defensa tanto inmunológicos como mecánicos del hospedero. Este proceso se lleva a cabo en gran medida por la interacción de lectinas, que son proteínas de origen no inmune con la capacidad de reconocer y aglutinar carbohidratos. Este mecanismo ha sido reportado para muchos microorganismos como virus y bacterias. En el caso particular de la Pasteurella multocida, que es una bacteria gramnegativa, patógena oportunista, que inicia la infección en el epitelio respiratorio de muchos animales, se han descrito sobre su superficie sustancias lectinas como la fimbria tipo IV y carbohidratos como el lipopolisacárido o la cápsula que reconocen carbohidratos y lectinas, respectivamente, sobre la superficie de las células epiteliales del tubo respiratorio, circunstancia que le permite adherirse y resguardarse del efecto mucociliar. Debido a que para la gran mayoría de estos microorganismos —incluida P. multocida— es evidente la disminución de la susceptibilidad a los antibacterianos y a la efectividad de las vacunas, se han buscado nuevas tácticas terapéuticas y profilácticas con el fin de interrumpir la infección de los patógenos por medio del bloqueo por competencia de la unión carbohidratos-lectina, donde se ve disminuida la unión del microorganismo al tejido y, por consiguiente, la infección.

NaMYC2 transcription factor regulates a subset of plant defense responses in Nicotiana attenuata

BackgroundTo survive herbivore attack, plants have evolved potent mechanisms of mechanical or chemical defense that are either constitutively present or inducible after herbivore attack. Due to the costs of defense deployment, plants often regulate their biosynthesis using various transcription factors (TFs). MYC2 regulators belong to the bHLH family of transcription factors that are involved in many aspects of plant defense and development. In this study, we identified a novel MYC2 TF from N. attenuata and characterized its regulatory function using a combination of molecular, analytic and ecological methods.ResultsThe transcript and targeted metabolite analyses demonstrated that NaMYC2 is mainly involved in the regulation of the biosynthesis of nicotine and phenolamides in N. attenuata. In addition, using broadly-targeted metabolite analysis, we identified a number of other metabolite features that were regulated by NaMYC2, which, after full annotation, are expected to broaden our understanding of plant defense regulation. Unlike previous reports, the biosynthesis of jasmonates and some JA-/NaCOI1-dependent metabolites (e.g. HGL-DTGs) were not strongly regulated by NaMYC2, suggesting the involvement of other independent regulators. No significant differences were observed in the performance of M. sexta on MYC2-silenced plants, consistent with the well-known ability of this specialist insect to tolerate nicotine.ConclusionBy regulating the biosynthesis of nicotine, NaMYC2 is likely to enhance plant resistance against non-adapted herbivores and contribute to plant fitness; however, multiple JA/NaCOI1-dependent mechanisms (perhaps involving other MYCs) that regulate separate defense responses are likely to exist in N. attenuata. The considerable variation observed amongst different plant families in the responses regulated by jasmonate signaling highlights the sophistication with which plants craft highly specific and fine-tuned responses against the herbivores that attack them.