Defense Syndrome Research Articles

Distribution characteristics of traditional Chinese medicine syndromes in 4 367 adult influenza patients: a Meta-analysis

To systematically evaluate the distribution characteristics of traditional Chinese medicine (TCM) syndromes in adult influenza patients and to provide a basis for the TCM syndrome differentiation of influenza. The CNKI, CBM, Wanfang, VIP, PubMed, Embase, Cochrane Library databases were searched to collect cross-sectional studies on the distribution pattern of TCM syndromes in adult patients with influenza. The risk of bias assessment tool for cross-sectional studies developed by the Joanna Briggs Institute (JBI) evidence-based health care center was used to evaluate the literature quality, and the Stata 15.1 software was used to conduct a Meta-analysis of the pooled effect sizes of the included studies. A total of 11 studies with 4 367 influenza patients were included. Quality assessment results of JBI showed that the risk bias was higher in the sample size calculation, and the description of sampling modalities and response rate was unclear. There were 17 influenza syndromes after specification, and a single group rate Meta-analysis was performed of the syndromes with ≥ 50 incident cases showed that there were 9 syndromes with an incidence ≥ 10% and statistical significance, the top 5 syndromes were syndrome of wind and heat invading the defense [n = 1 583, RATE = 34.3%, 95% confidence interval (95%CI) was 22.2%-46.3%], syndrome of exterior cold and interior heat (n = 1 122, RATE = 36.1%, 95%CI was 21.2%-51.1%), syndrome of wind-cold fettering the exterior (n = 860, RATE = 19.4%, 95%CI was 10.7%-28.0%), syndrome of heat and toxin in the lung (n = 217, RATE = 17.1%, 95%CI was 9.1%-25.0%), and syndrome of disease involving both defense phase and qi phase (n = 184, RATE = 38.8%, 95%CI was 14.2%-63.5%). The results of the subgroup analysis in different geographical regions showed that the frequency of distribution of syndrome of wind and heat invading the defense and heat and toxin in the lung was higher in the South (RATE: 36.5%, 18.6%) than in the North (RATE: 30.9%, 15.4%), and the frequency of distribution of syndrome of wind-cold fettering the exterior and exterior cold and interior heat in the North (RATE: 23.8%, 40.1%) was higher than that in the South (RATE: 15.7%, 32.3%). There are 9 common TCM syndromes of influenza, including wind and heat invading the defense syndrome, exterior cold and interior heat syndrome, wind-cold fettering the exterior syndrome, heat and toxin in the lung syndrome, disease involving both defense phase and qi phase syndrome, wind and heat complicated by dampnessinvading the surface syndrome, wind and cold complicated by dampnessinvading the surface syndrome, defense phase syndrome and dampness and heatinvading the surface syndrome, which can provide a reference for the TCM syndrome differentiation and treatment of influenza.

Leaf defense syndromes in tropical ferns

Vascular plants exhibit defense syndromes, a variety of interdependent defensive traits against herbivores, which may considerably differ between plant groups. Although ferns are an abundant component of tropical forest understories, studies of fern–herbivore interactions are scarce, and none has focused on the underlying defense syndromes. To examine the potential defense syndromes of 34 species of tropical ferns of Brazilian forests, we measured ten leaf traits and examined their correlation with parallelly assessed leaf damages. The first three components of categorical PCA were related (1) with SLA, water content, nitrogen, and phosphorus (33.2% of variance); (2) with tannins and saponins, but negatively with trichome density (22.5%); and (3) with phenol concentrations (16.1%). We identified three groups of fern species with similar leaf damages but different defense syndromes: (I) 14 species were of high nutritional quality (= high SLA, N and water content), but a variable trichome density; (II) 4 species were of low nutritional quality, but had high phenol concentrations, and often a high trichome density; and (III) 16 species were of intermediate nutritional quality and had a low trichome density or were glabrous. Most species (groups I and III) including tree ferns used chemical defenses to protect their highly valuable, nutritious leaves. Group II, exemplified by bracken fern, combined however a low nutritional quality with a powerful chemical defense, including high phenol concentrations, and many trichomes. Because leaf damages did not differ significantly among groups, we conclude that each defense syndrome provides species with a similar resistance against their herbivores.

Induction of the sticky plant defense syndrome in wild tobacco.

Many plants engage in protective mutualisms, offering resources such as extrafloral nectar and shelters to predatory arthropods in exchange for protection against herbivores. Recent work indicates that sticky plants catch small insects and provide this carrion to predators who defend the plants against herbivores. In this study, we investigated whether wild tobacco, Nicotiana attenuata, fits this sticky plant defense syndrome that has been described for other sticky plants. We developed a bioassay for stickiness involving the number of flies that adhered to flowers, the stickiest tissues. In surveys conducted over three field seasons at four sites, we found that the number of carrion that adhered to a plant was positively correlated with the number of predators that we observed foraging over its surfaces. The number of predators was positively correlated with the number of seed capsules that the plant produced, a measure of lifetime female reproductive success. Structural equationmodeling indicated strong support for the causal path linking carrion numbers to predator numbers to capsule production. We investigated whether stickiness was an inducible trait and examined two potential cues. We found that experimental clipping of rosette leaves induced greater stickiness, although clipping of neighboring sagebrush leaves did not. Damage to leaf tissue is likely to be a more reliable predictor of risk than is damage to a neighboring plant. The sticky plant defense syndrome is a widespread protective mutualism; its strength and ecological relevance can adjust as risk of herbivory changes.

Recalculating growth and defense strategies under competition: key roles of photoreceptors and jasmonates.

The growth-defense trade-off in plant biology has gained enormous traction in the last two decades, highlighting the importance of understanding how plants deal with two of the greatest challenges for their survival and reproduction. It has been well established that in response to competition signals perceived by informational photoreceptors, shade-intolerant plants typically activate the shade-avoidance syndrome (SAS). In turn, in response to signals of biotic attack, plants activate a suite of defense responses, many of which are directed to minimize the loss of plant tissue to the attacking agent (broadly defined, the defense syndrome, DS). We argue that components of the SAS, including increased elongation, apical dominance, reduced leaf mass per area (LMA), and allocation to roots, are in direct conflict with configurational changes that plants require to maximize defense. We hypothesize that these configurational trade-offs provide a functional explanation for the suppression of components of the DS in response to competition cues. Based on this premise, we discuss recent advances in the understanding of the mechanisms by which informational photoreceptors, by interacting with jasmonic acid (JA) signaling, help the plant to make intelligent allocation and developmental decisions that optimize its configuration in complex biotic contexts.

Functions of stone cells and oleoresin terpenes in the conifer defense syndrome.

Conifers depend on complex defense systems against herbivores. Stone cells (SC) and oleoresin are physical and chemical defenses of Sitka spruce that have been separately studied in previous work. Weevil oviposit at the tip of the previous year's apical shoot (PYAS). We investigated interactions between weevil larvae and trees in controlled oviposition experiments with resistant (R) and susceptible (S) Sitka spruce. R trees have an abundance of SC in the PYAS cortex. SC are mostly absent in S trees. R trees and S trees also differ in the composition of oleoresin terpenes. Transcriptomes of R and S trees revealed differences in long-term weevil-induced responses. Performance of larvae was significantly reduced on R trees compared with S trees under experimental conditions that mimicked natural oviposition behavior at apical shoot tips and may be attributed to the effects of SC. In oviposition experiments designed for larvae to feed below the area of highest SC abundance, larvae showed an unusual feeding behavior and oleoresin appeared to function as the major defense. The results support a role for both SC and oleoresin terpenes and possible synergies between these traits in the defense syndrome of weevil-resistant Sitka spruce.

Dormancy-defense syndromes and tradeoffs between physical and chemical defenses in seeds of pioneer species.

Seeds of tropical pioneer trees have chemical and physical characteristics that determine their capacity to persist in the soil seed bank. These traits allow seeds to survive in the soil despite diverse predators and pathogens, and to germinate and recruit even decades after dispersal. Defenses in seedlings and adult plants often are described in terms of tradeoffs between chemical and physical defense, but the interplay of defensive strategies has been evaluated only rarely for seeds. Here we evaluated whether classes of seed defenses were negatively correlated across species (consistent with tradeoffs in defense strategies), or whether groups of traits formed associations across species (consistent with seed defense syndromes). Using 16 of the most common pioneer tree species in a neotropical lowland forest in Panama we investigated relationships among four physical traits (seed fracture resistance, seed coat thickness, seed permeability, and seed mass) and two chemical traits (number of phenolic compounds and phenolic peak area), and their association with seed persistence. In addition, seed toxicity was assessed with bioassays in which we evaluated the activity of seed extracts against representative fungal pathogens and a model invertebrate. We did not find univariate tradeoffs between chemical and physical defenses. Instead, we found that seed permeability - a trait that distinguishes physical dormancy from other dormancy types - was positively associated with chemical defense traits and negatively associated with physical defense traits. Using a linear discriminant analysis and a hierarchical cluster analysis we found evidence to distinguish three distinct seed defense syndromes that correspond directly with seed dormancy classes (i.e., quiescent, physical, and physiological). Our data suggest that short and long-term persistence of seeds can be achieved via two strategies: having permeable seeds that are well defended chemically, corresponding to the physiologically dormant defense syndrome; or having impermeable seeds that are well defended physically, corresponding to the physically dormant defense syndrome. In turn, transient seeds appear to have a lower degree of chemical and physical defenses, corresponding to the quiescent defense syndrome. Overall, we find that seed defense and seed dormancy are linked, suggesting that environmental pressures on seed persistence and for delayed germination can select for trait combinations defining distinct dormancy-defense syndromes.

Antiherbivory defense mechanisms along an environmental gradient in restinga

ABSTRACT Plant-herbivore interactions have directed the evolution of defense mechanisms in plants, which can vary intraspecifically according to environmental quality. This study evaluated variation in the production of antiherbivory defenses in plant species distributed along an environmental gradient of restinga. The study was performed in Parque Estadual Acarai, state of Santa Catarina, Brazil. Three species of four plant formations with different abiotic conditions were selected for study. Specific leaf area; water, nitrogen and carbon content; and presence of phenols, tannins, lignin and alkaloids, were evaluated in leaves of ten plants per species per plant formation. The results indicated that Symphyopappus casarettoi possesses Low Nutritional Quality Syndrome, characterized by low specific leaf area, presence of secondary metabolites and low nitrogen content. Dodonaea viscosa and Varronia curassavica possess Nutrition and Defense Syndrome, characterized by a balance between nutritional quality (high nitrogen content and lower C:N ratio) and protection (greater thickness of leaves and higher density of trichomes). The results did not confirm the Resource Availability Hypothesis. The absence of a pattern in antiherbivory response due to the environmental gradient may indicate that the investment in defense by plants is not unidirectional and that certain morpho-anatomical attributes are typically related to conservation of resources.

Community-level relaxation of plant defenses against herbivores at high elevation

Ecological gradients shape the evolution of plant functional traits through variation in climate, abiotic factors, and biological processes. While recent observations highlight elevation clines in functional trait variation, several traits vary independently of others and vary in species-specific manner, thereby hindering community-level generalization. In this study, we examined whether whole plant communities at different elevations independently converge to elevation-specific trait values. Using a combination of field-derived trait quantification and a literature survey, we analyzed eight functional traits relating to plant palatability [specific leaf area (SLA), leaf dry matter content, carbon-to-nitrogen ratio], and defenses (spines, trichomes, silica, and the relative importance of phenolic- or non-phenolic-based chemical defenses in plants) of plants growing along several mountain transects in Switzerland, and computed community-level means for each trait. We observed a general decline of most defense traits in communities at high elevations. The individual traits’ patterns underlined a concerted decline of the physico-chemical defense syndrome at high elevation, and low SLA values at high elevation also indicate investment in the production of leaves with slow turnover rates. In addition, we found that high-elevation plant trait values tend to converge, while at low elevation, to diverge within communities. Our data suggest that community-level defense syndromes along elevation gradients are influenced by ecological filtering. Lower herbivore pressures select for reduced plant defenses, while harsh environmental conditions select for investment in tolerance-related traits. Secondly, since species are highly variable in their functional trait space within communities, niche-partitioning theory might explain which variabilities of the defense functional space are selected within communities, particularly at low elevation.

High elevation Plantago lanceolata plants are less resistant to herbivory than their low elevation conspecifics: is it just temperature?

Traits that mediate species interactions are evolutionarily shaped by biotic and abiotic drivers, yet we know relatively little about the relative importance of these factors. Herbivore pressure, along with resource availability and ‘third‐party’ mutualists, are hypothesized to play a major role in the evolution of plant defence traits. Here, we used the model system Plantago lanceolata, which grows along steep elevation gradients in the Swiss Alps, to investigate the effect of elevation, herbivore pressure, mycorrhizal inoculation and temperature on plant resistance. Over a 1200 m elevation gradient, the levels of herbivory and iridoid glycosides (IGs) declined with increasing elevation. By planting seedlings at three different elevations, we further showed that both low‐elevation growing conditions and mycorrhizal inoculation resulted in increased plant resistance to herbivores. Finally, using a temperature‐controlled experiment comparing high‐ and low‐elevation ecotypes, we showed that high‐elevation ecotypes are less resistant to herbivory, and that lower temperatures impair IGs deployment after herbivore attack. We thus propose that both lower herbivore pressure, and colder temperatures relax the defense syndrome of high elevation plants.

Prickles, latex, and tolerance in the endemic Hawaiian prickly poppy (Argemone glauca): variation between populations, across ontogeny, and in response to abiotic factors

Covariance among plant defense traits is predicted to occur both within and among plant species, potentially leading to characteristic defense syndromes. I examined patterns of variation in prickle density, latex exudation, and tolerance in order to assess whether traits varied between populations, across plant ontogeny, and as phenotypic plasticity in response to water and light limitation and physical damage using the endemic Hawaiian prickly poppy, Argemone glauca, as a model system. Plants produced copious latex, had extremely variable prickle densities, and were generally tolerant of 50% defoliation. However, expression patterns differed among defense traits. Prickle density was consistent across ontogeny and was not induced by either water limitation or mechanical damage, but was significantly induced under high light conditions. In contrast, latex exudation increased significantly across ontogeny and was reduced by water limitation, but had no response to mechanical damage or light. Prickles, latex, and tolerance differed considerably between populations, suggesting different evolutionary histories for these populations. These disparate patterns indicate that latex and prickles are unlinked within A. glauca, potentially as a result of differences in their function, and providing little evidence that they jointly function as a defense syndrome. Moreover, this study provides the first description patterns of variation for multiple defense traits in an island endemic, and high levels of prickles, latex, and tolerance suggest that A. glauca is well defended against herbivores. Future research in the field will provide additional insights into the functional ecology of these traits in A. glauca.

Ontogenetic and Temporal Variations in Herbivory and Defense ofHandroanthus spongiosus(Bignoniaceae) in a Brazilian Tropical Dry Forest

We compared the richness and abundance of free-feeding herbivore insects (sap-sucking and leaf-chewing), leaf herbivory damage, leaf toughness and total phenolic content between two ontogenetic stages (juvenile and reproductive) of Handroanthus spongiosus (Rizzini) S. O. Grose (Bignoniaceae) throughout the rainy season in a Brazilian seasonally dry tropical forest. Twenty marked individuals of H. spongiosus were sampled per ontogenetic stage in each period of the rainy season (beginning, middle, and end). Herbivore richness and abundance did not differ between ontogenetic stages, but higher percentage of leaf damage, higher concentration of phenolic compounds, and lower leaf toughness were observed for juvenile individuals. The greatest morphospecies abundance was found at the beginning of the rainy season, but folivory increment was higher at the end, despite the fact that leaf toughness and total phenolic content increased in the same period. No significant relationships between leaf damage and both total phenolic content and leaf toughness were observed. These results suggest that insect richness and abundance do not track changes in foliage quality throughout plant ontogeny, but their decrease along rainy season confirms what was predicted for tropical dry forests. The general trends described in the current study corroborate those described in the literature about herbivores and plant ontogeny. However, the lack of relationship between herbivore damage and the two plant attributes considered here indicates that the analyses of multiple defensive traits (the defense syndrome) must be more enlightening to determine the mechanisms driving temporal and spatial patterns of herbivore attack.

Induced Responses to Herbivory and Jasmonate in Three Milkweed Species

We studied constitutive and induced defensive traits (latex exudation, cardenolides, proteases, and C/N ratio) and resistance to monarch caterpillars (Danaus plexippus) in three closely related milkweed species (Asclepias angustifolia, A. barjoniifolia and A. fascicularis). All traits showed significant induction in at least one of the species. Jasmonate application only partially mimicked the effect of monarch feeding. We found some correspondence between latex and cardenolide content and reduced larval growth. Larvae fed cut leaves of A. angustifolia grew better than larvae fed intact plants. Addition of the cardenolide digitoxin to cut leaves reduced larval growth but ouabain (at the same concentration) had no effect. We, thus, confirm that latex and cardenolides are major defenses in milkweeds, effective against a specialist herbivore. Other traits such as proteases and C/N ratio additionally may be integrated in the defense scheme of those plants. Induction seems to play an important role in plants that have an intermediate level of defense, and we advocate incorporating induction as an additional axis of the plant defense syndrome hypothesis.

Convergence in defense syndromes of young leaves in tropical rainforests

In tropical forests, the majority of damage by herbivores or pathogens occurs on young leaves, yet the patterns of damage and the factors that influence them are poorly known. By measuring damage throughout leaf development and maturation for five species in a Panamanian forest, we showed that leaf toughening, which only occurs over a few days once the leaf is fully expanded, is the main factor decreasing damage in mature leaves. Although rates of damage to young leaves are, on average, orders of magnitude greater than on mature leaves, there is significant interspecific variation in young leaf defenses and in damage rates. In a survey of 55 species of shade-tolerant plants, we found that each species only invested in a subset of the potential defensive mechanisms for young leaves. We measured rates of young leaf expansion, nitrogen content, delayed chloroplast development, synchrony of leaf production and rates of damage in the field. On a subset of 24 species, we also measured phenolic compounds, checked for the presence of saponins and alkaloids, and conducted bioassays using lepidopteran, coleopteran and orthopteran herbivores and four fungal pathogens to test for toxicity of young leaf extracts. Certain combinations of traits repeatedly co-occurred across unrelated species suggesting convergent evolution. We argue that selection has repeatedly led to tradeoffs among defenses such that species fall along an escape/defense continuum. At one extreme are species with a ‘defense’ strategy, which includes effective chemical defense, slow leaf expansion, normal greening and low rates of damage (less than 20% of the leaf area lost). At the other extreme are ‘escape’ species which have ineffective chemical defenses and, as a consequence, have high rates of leaf damage, >60% of leaf area lost during expansion. In partial compensation for ineffective chemical defense, these species have very rapid leaf expansion (doubling in area every day) which minimizes the window of vulnerability, delayed chloroplast development (white young leaves) which contain fewer resources, and synchronous leaf production to satiate herbivores. Thus, interspecific variation in young leaf damage rates is explained by differences in defense combinations along this escape/defense continuum. Because apparently beneficial traits such as effective chemical defense and rapid leaf expansion do not occur in the same species, we suggest that physiological constraints limit the defense combinations of any one species to a restricted subset of those observed. However, the defense and escape strategies do not represent different tradeoffs that have equal fitness, as species with the escape syndrome suffer much higher rates of damage. We hypothesize that the escape syndrome arose over evolutionary time among plants that failed to evolve effective secondary metabolites while herbivores succeeded in evolving adaptations to the chemistry of their host plant. Hence the defense syndrome should provide the greatest fitness, whereas the escape syndrome minimizes damage given the failure of the plant’s secondary metabolites to provide protection.