Direct Defense Research Articles

Luca Incurvati* Conceptions of Set and the Foundations of Mathematics.

On one level, the book under review is, as the author indicates in his very brief concluding chapter, a defense of the iterative conception of set. But exposition of that conception and its direct defense against criticisms take up only two of its seven substantive chapters. For the defense mainly consists of chapter-length examinations of rival conceptions, denominated the naïve, the limitation-of-size, the stratified, and the graph conceptions, examinations that begin in each case with the examiner not unsympathetic, but finish with him unconvinced, so that the iterative conception wins in the end by what he calls ‘inference to the best conception’. It is the book’s role as a one-stop source for both technical information and philosophical commentary on the various conceptions just listed, never before treated at length and with comparisons all in one place, that makes the book an indispensable reference work for anyone interested in the philosophy of set theory. But though the book is much more thorough than, say, [Holmes, 2017], the article on alternative set theories in the Stanford Encyclopedia, still Incurvati’s work does not pretend to be — well, encyclopedic. There are minor topics he leaves out that in their day excited flashes of interest, notably Vopenkism, about which one used to hear a lot, and more importantly coverage of the topics that are included does not pretend to be exhaustive. On the contrary, one of the book’s virtues is that, for all the information it provides, it shows also how open-ended investigation of the different conceptions remains: almost every paragraph raises further issues for future exploration, and it is bound to generate discussion for years to come.

Protection of Dialysis Staff From COVID-19 Infection: Setting Up and Impact of Extended Blood Lines During Dialysis.

Protection of Dialysis Staff From COVID-19 Infection: Setting Up and Impact of Extended Blood Lines During Dialysis.

Top‐down effects from parasitoids may mediate plant defence and plant fitness

Abstract Plants face many environmental stresses that can impact their survival, development and fitness. Insects are the most diverse, abundant and threatening herbivores in nature. As a consequence, plants produce direct chemical and physical defences to reduce herbivory. They also release volatiles to recruit natural enemies that indirectly protect them from herbivory. The recruitment of parasitic wasps can benefit plant fitness because they ultimately kill their insect hosts. Recently, studies showed that parasitoids can indirectly mediate plant defences by modulating herbivore oral secretions. In addition to the direct benefits of parasitoids in terms of reducing herbivore survival, we tested if the reduction in induced defences by parasitized caterpillars compared to non‐parasitized caterpillars may reduce the costs associated with defence expression. We provide evidence that tomato plants treated with saliva from parasitized caterpillars have significantly higher fitness parameters including increased flower numbers (16.3%) and heavier fruit weight (13.5%), compared to plants treated with saliva from non‐parasitized caterpillars. Since plants were grown without actual herbivores, the higher values for these fitness parameters were due to lower costs of induced defences and not due to reduced herbivory by parasitized caterpillars. Furthermore, the resulting seed germination time was shorter and the germination rate was higher when the maternal plants were previously exposed to parasitized herbivore treatment compared to control (non‐treated) plants. Overall, application of saliva did not result in transgenerational priming of offspring defence responses. However, offspring of parents exposed to caterpillar saliva had lower constitutive levels and higher induced levels of trypsin inhibitor than offspring from unexposed parents. This study shows that the saliva of parasitized caterpillars can modulate plant defences and further demonstrates that the lower induction of plant defences is associated with elevated plant fitness in the absence of herbivore feeding, suggesting that induced plant defences are costly. A free Plain Language Summary can be found within the Supporting Information of this article.

Phaeophyceaean (Brown Algal) Extracts Activate Plant Defense Systems in Arabidopsis thaliana Challenged With Phytophthora cinnamomi.

Seaweed extracts are important sources of plant biostimulants that boost agricultural productivity to meet current world demand. The ability of seaweed extracts based on either of the Phaeophyceaean species Ascophyllum nodosum or Durvillaea potatorum to enhance plant growth or suppress plant disease have recently been shown. However, very limited information is available on the mechanisms of suppression of plant disease by such extracts. In addition, there is no information on the ability of a combination of extracts from A. nodosum and D. potatorum to suppress a plant pathogen or to induce plant defense. The present study has explored the transcriptome, using RNA-seq, of Arabidopsis thaliana following treatment with extracts from the two species, or a mixture of both, prior to inoculation with the root pathogen Phytophthora cinnamomi. Following inoculation, five time points (0−24 h post-inoculation) that represented early stages in the interaction of the pathogen with its host were assessed for each treatment and compared with their respective water controls. Wide scale transcriptome reprogramming occurred predominantly related to phytohormone biosynthesis and signaling, changes in metabolic processes and cell wall biosynthesis, there was a broad induction of proteolysis pathways, a respiratory burst and numerous defense-related responses were induced. The induction by each seaweed extract of defense-related genes coincident with the time of inoculation showed that the plants were primed for defense prior to infection. Each seaweed extract acted differently in inducing plant defense-related genes. However, major systemic acquired resistance (SAR)-related genes as well as salicylic acid-regulated marker genes (PR1, PR5, and NPR1) and auxin associated genes were found to be commonly up-regulated compared with the controls following treatment with each seaweed extract. Moreover, each seaweed extract suppressed P. cinnamomi growth within the roots of inoculated A. thaliana by the early induction of defense pathways and likely through ROS-based signaling pathways that were linked to production of ROS. Collectively, the RNA-seq transcriptome analysis revealed the induction by seaweed extracts of suites of genes that are associated with direct or indirect plant defense in addition to responses that require cellular energy to maintain plant growth during biotic stress.

Silicon: its ameliorative effect on plant defense against herbivory

Plants protect themselves against pest attack utilizing both direct and indirect modes of defense. The direct mode of defense includes morphological, biochemical, and molecular barriers that affect feeding, growth, and survival of herbivores whereas the indirect mode of defense includes release of a blend of volatiles that attract natural enemies of the pests. Both of these strategies adopted by plants are reinforced if the plants are supplied with one of the most abundant metalloids, silicon (Si). Plants absorb Si as silicic acid (Si(OH)4) and accumulate it as phytoliths, which strengthens their physical defense. This deposition of Si in plant tissue is up-regulated upon pest attack. Further, Si deposited in the apoplast, suppresses pest effector molecules. Additionally, Si up-regulates the expression of defense-related genes and proteins and their activity and enhances the accumulation of secondary metabolites, boosting induced molecular and biochemical defenses. Moreover, Si plays a crucial role in phytohormone-mediated direct and indirect defense mechanisms. It is also involved in the reduction of harmful effects of oxidative stress resulting from herbivory by accelerating the scavenging process. Despite increasing evidence of its multiple roles in defense against pests, the practical implications of Si for crop protection have received less attention. Here, we highlight recent developments in Si-mediated improved plant resistance against pests and its significance for future use in crop improvement.

RCA-SOC: A novel adversarial defense by refocusing on critical areas and strengthening object contours

The success of deep learning is greatly attributed to its representation capability especially in computer vision tasks. However, recent studies have shown that deep neural networks (DNNs) are often vulnerable to adversarial attacks. To determine the common ground of various attacks, we compare the difference between clean and adversarial examples via the model hidden feature visualization method, i.e. heatmap, as adversarial perturbations are usually imperceptible for human visual systems. It was observed that the adversarial examples generated by various attack methods are capable of fooling DNNs by scattering critical areas of the image and blurring object contours. Inspired by these findings, we created a direct but effective defense by Refocusing on Critical Areas and Strengthening Object Contours, briefly RCA-SOC. It is a pixel attention weight-based defense composed of a pixel channel attention and a pixel plane attention. Critical areas of the images can be reconstructed by the pixel channel attention, while object contour is strengthened by the pixel plane attention. The effect of RCA-SOC against different attacks were demonstrated on scalable models and datasets. Furthermore, current state-of-the-art defense methods were shown to improve when cascaded with RCA-SOC. To demonstrate its practical application, RCA-SOC also showed its effectiveness in a case study of not suitable for work (NSFW) recognition.

Silicon Alters Leaf Surface Morphology and Suppresses Insect Herbivory in a Model Grass Species.

Grasses accumulate large amounts of silicon (Si) which is deposited in trichomes, specialised silica cells and cell walls. This may increase leaf toughness and reduce cell rupture, palatability and digestion. Few studies have measured leaf mechanical traits in response to Si, thus the effect of Si on herbivores can be difficult to disentangle from Si-induced changes in leaf surface morphology. We assessed the effects of Si on Brachypodium distachyon mechanical traits (specific leaf area (SLA), thickness, leaf dry matter content (LDMC), relative electrolyte leakage (REL)) and leaf surface morphology (macrohairs, prickle, silica and epidermal cells) and determined the effects of Si on the growth of two generalist insect herbivores (Helicoverpa armigera and Acheta domesticus). Si had no effect on leaf mechanical traits; however, Si changed leaf surface morphology: silica and prickle cells were on average 127% and 36% larger in Si supplemented plants, respectively. Prickle cell density was significantly reduced by Si, while macrohair density remained unchanged. Caterpillars were more negatively affected by Si compared to crickets, possibly due to the latter having a thicker and thus more protective gut lining. Our data show that Si acts as a direct defence against leaf-chewing insects by changing the morphology of specialised defence structures without altering leaf mechanical traits.

Direct and indirect plant defenses induced by (Z)-3-hexenol in tomato against whitefly attack

Plants have evolved induced defense mechanisms against insect herbivore attacks. The application of plant elicitors can enhance the biological control of crop pests by inducing plant defense responses, and (Z)-3-hexenol (z3HOL) is recognized as a herbivore-induced plant volatile that plays an important role in the chemical communication between plants and pests. We investigated whether z3HOL can activate the defense mechanism of tomato (Solanum lycopersicum) against the whitefly Bemisia tabaci, one of the major insect pests of cultivated tomato. Exposure to z3HOL vapors in the glass jars decreased weight gain and oviposition in B. tabaci and negatively influenced the feeding behavior of B. tabaci by shortening the total feeding period and phloem ingestion and increasing the frequency of stylet puncture. Furthermore, exposure to z3HOL induced jasmonic acid- and salicylic acid-mediated defense responses and enhanced B. tabaci-induced volatile emissions in tomato. The elevated release of tomato volatiles increased the attraction of the parasitoid Encarsia formosa and improved its parasitism on B. tabaci. Our results indicate that z3HOL can serve as an elicitor that triggers direct and indirect defense responses against B. tabaci by modulating signaling pathways in tomato. These findings will not only help us to gain a better understanding of how z3HOL influences the crop community, but also provide new insights into the potential application of z3HOL in integrated pest management systems.

Nonglandular silicified trichomes are essential for rice defense against chewing herbivores.

Interspecific New Rice for Africa (NERICA) varieties have been recently developed and used in Sub-Saharan Africa but herbivore resistance properties of these plants remain poorly understood. Here we report that, compared to a local Japanese cultivar Nipponbare, NERICA 1, 4 and 10 are significantly more damaged by insect herbivores in the paddy fields. In contrast to high levels of leaf damage from rice skippers and grasshoppers, constitutive and induced volatile organic compounds for indirect plant defense were higher or similar in NERICAs and Nipponbare. Accumulation of direct defense secondary metabolites, momilactones A and B, and p-coumaroylputrescine (CoP) was reduced in NERICAs, while feruloylputrescine accumulated at similar levels in all varieties. Finally, we found that Nipponbare leaves were covered with sharp nonglandular trichomes impregnated with silicon but comparable defense structures were virtually absent in herbivory-prone NERICA plants. As damage to the larval gut membranes by Nipponbare silicified trichomes that pass intact through the insect digestive system, occurs, and larval performance is enhanced by trichome removal from otherwise chemically defended Nipponbare plants, we propose that silicified trichomes work as an important defense mechanism of rice against chewing insect herbivores.

Herbivory and anti-herbivore defences in wild and cultivated Cnidoscolus aconitifolius: disentangling domestication and environmental effects.

Phenotypic changes in plants during domestication may disrupt plant–herbivore interactions. Because wild and cultivated plants have different habitats and some anti-herbivore defences exhibit some plasticity, their defences may be also influenced by the environment. Our goal was to assess the effects of domestication and the environment on herbivory and some anti-herbivore defences in chaya (Cnidoscolus aconitifolius) in its centre of domestication. Herbivores, herbivory, and direct and indirect anti-herbivore defences were assessed in wild and cultivated plants. The same variables were measured in the field and in a common garden to assess environmental effects. Our results show that domestication increased herbivory and herbivore abundance, but reduced direct and some indirect defences (ants). The environment also affected the herbivore guild (herbivore abundance and richness) and some direct and indirect defences (trichome number and ants). There was also an interaction effect of domestication and the environment on the number of trichomes. We conclude that domestication and the environment influence herbivory and anti-herbivore defences in an additive and interactive manner in chaya.

Correction to: Transcriptional and metabolite analysis reveal a shift in direct and indirect defences in response to spider‑mite infestation in cucumber (Cucumis sativus).

In the above mentioned publication, part of Fig.1b was distorted (48h after TSSM Infestation). The original article has been corrected and the proper version of Fig.1 is also published here.

Cochlear supporting cells function as macrophage-like cells and protect audiosensory receptor hair cells from pathogens

To protect the audiosensory organ from tissue damage from the immune system, the inner ear is separated from the circulating immune system by the blood-labyrinth barrier, which was previously considered an immune-privileged site. Recent studies have shown that macrophages are distributed in the cochlea, especially in the spiral ligament, spiral ganglion, and stria vascularis; however, the direct pathogen defence mechanism used by audiosensory receptor hair cells (HCs) has remained obscure. Here, we show that HCs are protected from pathogens by surrounding accessory supporting cells (SCs) and greater epithelial ridge (GER or Kölliker’s organ) cells (GERCs). In isolated murine cochlear sensory epithelium, we established Theiler’s murine encephalomyelitis virus, which infected the SCs and GERCs, but very few HCs. The virus-infected SCs produced interferon (IFN)-α/β, and the viruses efficiently infected the HCs in the IFN-α/β receptor-null sensory epithelium. Interestingly, the virus-infected SCs and GERCs expressed macrophage marker proteins and were eliminated from the cell layer by cell detachment. Moreover, lipopolysaccharide induced phagocytosis of the SCs without cell detachment, and the SCs phagocytosed the bacteria. These results reveal that SCs function as macrophage-like cells, protect adjacent HCs from pathogens, and provide a novel anti-infection inner ear immune system.

Transcriptional and metabolite analysis reveal a shift in direct and indirect defences in response to spider-mite infestation in cucumber (Cucumis sativus)

Key messageCucumber plants adapt their transcriptome and metabolome as result of spider mite infestation with opposite consequences for direct and indirect defences in two genotypes.Plants respond to arthropod attack with the rearrangement of their transcriptome which lead to subsequent phenotypic changes in the plants’ metabolome. Here, we analysed transcriptomic and metabolite responses of two cucumber (Cucumis sativus) genotypes to chelicerate spider mites (Tetranychus urticae) during the first 3 days of infestation. Genes associated with the metabolism of jasmonates, phenylpropanoids, terpenoids and l-phenylalanine were most strongly upregulated. Also, genes involved in the biosynthesis of precursors for indirect defence-related terpenoids were upregulated while those involved in the biosynthesis of direct defence-related cucurbitacin C were downregulated. Consistent with the observed transcriptional changes, terpenoid emission increased and cucurbitacin C content decreased during early spider-mite herbivory. To further study the regulatory network that underlies induced defence to spider mites, differentially expressed genes that encode transcription factors (TFs) were analysed. Correlation analysis of the expression of TF genes with metabolism-associated genes resulted in putative identification of regulators of herbivore-induced terpenoid, green-leaf volatiles and cucurbitacin biosynthesis. Our data provide a global image of the transcriptional changes in cucumber leaves in response to spider-mite herbivory and that of metabolites that are potentially involved in the regulation of induced direct and indirect defences against spider-mite herbivory.

Growing up aspen: ontogeny and trade-offs shape growth, defence and reproduction in a foundation species.

Intraspecific variation in foundation species of forest ecosystems can shape community and ecosystem properties, particularly when that variation has a genetic basis. Traits mediating interactions with other species are predicted by simple allocation models to follow ontogenetic patterns that are rarely studied in trees. The aim of this research was to identify the roles of genotype, ontogeny and genotypic trade-offs shaping growth, defence and reproduction in aspen. We established a common garden replicating >500 aspen genets in Wisconsin, USA. Trees were measured through the juvenile period into the onset of reproduction, for growth, defence chemistry (phenolic glycosides and condensed tannins), nitrogen, extrafloral nectaries, leaf morphology (specific leaf area), flower production and foliar herbivory and disease. We also assayed the TOZ19 sex marker and heterozygosity at ten microsatellite loci. We found high levels of genotypic variation for all traits, and high heritabilities for both the traits and their ontogenetic trajectories. Ontogeny strongly shaped intraspecific variation, and trade-offs among growth, defence and reproduction supported some predictions while contradicting others. Both direct resistance (chemical defence) and indirect defence (extrafloral nectaries) declined during the juvenile stage, prior to the onset of reproduction. Reproduction was higher in trees that were larger, male and had higher individual heterozygosity. Growth was diminished by genotypic allocation to both direct and indirect defence as well as to reproduction, but we found no evidence of trade-offs between defence and reproduction. Key traits affecting the ecological communities of aspen have high levels of genotypic variation and heritability, strong patterns of ontogeny and clear trade-offs among growth, defence and reproduction. The architecture of aspen's community genetics - its ontogeny, trade-offs and especially its great variability - is shaped by both its broad range and the diverse community of associates, and in turn further fosters that diversity.

Induction of defensive proteins in Solanaceae by salivary glucose oxidase of Helicoverpa zea caterpillars and consequences for larval performance

Salivary glucose oxidase (GOX) is one of the most abundant salivary proteins in generalist caterpillar Helicoverpa zea. GOX has been hypothesized to benefit H. zea by modulating direct defense responses of plants. Although the function of this protein has been studied, its role remains unclear. The study aims to test the hypothesis that GOX induces similar defensive responses among Solanaceous plants, and has similar consequences for larval performance of H. zea. Using six different plants in Solanaceae, including tomato (Solanum lycopersicum cv. Better Boy and S. lycopersicum var. cerasiforme), bell pepper (Capsicum annuum cv. Revolution), habanero pepper (Capsicum chinense), tomatillo (Physalis philadelphica cv. Tamayo), and tobacco (N. benthamiana), we tested the impact of GOX on induction of two common defense proteins, trypsin protease inhibitors (TPI) and polyphenol oxidases (PPO), and on relative growth rate of H. zea larvae. We found that GOX specifically induced TPI activity in tomato and habanero pepper, and the level of defense protein depended on leaf location. In addition, prior application of GOX did not increase the performance of H. zea in any plant tested. Changes in performance in tomato and habanero pepper matched the induction of TPI. In summary, our findings indicate that GOX induces similar defense responses in some Solanacean plants, but largely depends on species/genotype of plant, and that the presence of GOX did not benefit larval H. zea by modulating direct defense responses of plants. Other mechanisms must be involved in driving the evolution of this salivary protein.

Immuno- and glyco-histochemistry as a tool to evaluate the oregano supplemented feed effects in pig gut.

Among oregano properties, its antioxidant and antibacterial effects are particularly interesting. Oregano is also able to induce a higher glycoconjugate production in gut, creating a physical barrier against microorganisms. This study evaluated the effects of adding an aqueous extract of oregano (OAE) to the diet of two homogenous groups of pigs during the finisher phase. The diets were as follows: control commercial diet (CTR group) and CTR diet supplemented (2 g/kg) with OAE (O group). Samples of ileum and caecum from the two groups were examined by conventional histochemistry to analyze complex carbohydrates and by immunohistochemistry to detect Bcl-2 Associate X protein (BAX), an indicator of oxidative stress. Glyco-histochemistry showed significant differences between the two groups. Immunohistochemistry revealed a lower presence of BAX in O group. The OAE supplementation improved the production of glycoconjugates, able to enhance in pig the protection of intestinal mucosa by means of direct and indirect defense actions. The reduced BAX immunostaining observed in O group may be an indicator of enhanced antioxidant action promoted by oregano. The results of this study can be used in further research to identify ways to improve endogenous defence ability, with the aim of reducing antibiotic use and preventing antimicrobial resistance.

Geopolitical rivalry of global powers and its implications in Nepal

National unity and independence, territorial integrity, people's sovereignty and national security are the supreme priority for any sovereign and independent country across the world. The essence of national unity and security is the most important and highly sensitive issue for Nepal in account of its geopolitical sensitivities and geostrategic balance as Nepal is located between two giant nuclear countries and rising global powers – India and China. Analyzing the national interests and national security policy of all three countries – India, China and the US, it is open secret that they have direct strategic, defense and security interests in Nepal. They, therefore, have strategic rivalry to extend their political, diplomatic, economic, strategic, defense and security and cultural influence in Nepal because of its geopolitical importance and geostrategic sensitivity. The emerging triangular strategic rivalry may undermine Nepal’s national interests and national security in the future as their rivalry gets intensified. It is a grave situation for Nepal which will have significant immediate as well as long-term implications. Nepal, therefore, should thoughtfully study to analyze the emerging global powers’ defense, military, security and foreign policies and strategies and should protect and preserve Nepal’s national interests and national security maintaining diplomatic and strategic balance among them.

Oregano Feed Supplementation Affects Glycoconjugates Production in Swine Gut.

Simple SummaryThe European ban towards antibiotics is increasing the number of studies on the effects of feed additives, such as plant extracts, in order to enhance the health and welfare status of domestic animals intended for human consumption. Origanum vulgare possesses multiple pharmacological characteristics and its antioxidant and antibacterial properties are particularly interesting. Besides, a recent study aimed at evaluating the effects of oregano aqueous extract supplementation in poultry nutrition gave encouraging results regarding the secretion of glycoconjugates in the gut which increases tissue hydration and protects the intestinal mucosa from pathogenic bacteria, viruses, and parasites. Therefore, we investigated the effects of oregano feed supplementation on antioxidant and defense ability of pig gut. Our results showed that there was improved production of glycoconjugates in the duodenum and colon of pigs fed with supplementation of oregano aqueous extract, enhancing protection of the mucosa of these sections of the intestine. Also, we observed an enhanced antioxidant action in the two examined gut tract samples of the group supplemented with oregano. Findings can be used in further research to identify ways to improve endogenous defense ability with to reduce antibiotic use and prevent antimicrobial resistance.This study evaluated the effects of adding oregano aqueous extract (OAE) to the diet of pig slaughtered at finisher stage. Study was performed to identify glycoconjugates and evaluate the oxidative stress levels in the duodenum and colon intestinal tracts. Glycohistochemistry was performed by staining with Periodic acid–Schiff (PAS), Alcian blue (AB) pH 2.5, AB-PAS, AB pH 1, AB pH 0.5, low iron diamine, and high iron diamine. Serial sections were pre-treated with sialidase V before staining with AB pH 2.5 (Sial-AB) preceded or not by saponification. To study oxidative stress, an immunohistochemical analysis was applied to investigate the presence of the oxidative stress target molecule Bcl-2 Associate X protein (BAX). Findings show that oregano aqueous extract supplementation improves the production of the secretion glycoconjugates involved in direct and indirect defense, thus enhancing the protection of the pig intestinal mucosa. Moreover, the reduced BAX protein immunostaining observed in both duodenum and colon of swine of the oregano-supplemented group respect to that observed in the control group suggests an enhanced antioxidant action by oregano adding. Findings could be useful for other studies aiming to reduce antibiotic use and prevent antimicrobial resistance.

Silencing JA hydroxylases in Nicotiana attenuata enhances jasmonic acid-isoleucine-mediated defenses against Spodoptera litura

Jasmonic acid (JA) plays important roles in plant resistance to insect herbivores. One important derivative of JA is 12-OH-JA, which is produced by two independent pathways: direct hydroxylation of JA by jasmonate-induced oxygenases (JOXs) or hydrolyzation of 12-OH-JA-Ile.Yet the function of 12-OH-JA in plant–herbivore interactions remains largely unknown. In this study, we silenced four JOX homologs independently in the wild tobacco Nicotiana attenuata by virus-induced gene silencing (VIGS), and found that all four JOX homologs are involved in JA hydroxylation. Simultaneously silencing the four JA hydroxylases in VIGS-NaJOXs plants decreased herbivory-induced 12-OH-JA by 33%, but JA and JA-Ile levels increased by 45% and 30%, respectively, compared to those in control plants. Compared to direct hydroxylation from JA, hydrolyzation from 12-OH-JA-Ile is equally important for herbivory-induced 12-OH-JA accumulation: in the 12-OH-JA-Ile deficient irJAR4/6 plants, 12-OH-JA decreased 34%. Moreover, VIGS-NaJOXs plants exhibited enhanced resistance to the generalist herbivore Spodoptera litura. The poor larval performance was strongly correlated with high levels of several JA-Ile-dependent direct defense metabolites in the VIGS-NaJOXs plants. When we simultaneously silenced all four JA hydroxylases in the JA-Ile-deficient irJAR4/6 background, the enhanced herbivore resistance diminished, demonstrating that enhanced herbivore resistance resulted from elevated JA-Ile levels. Given that silencing these NaJOX-like genes did not detectably alter plant growth but highly increased plant defense levels, we propose that JOX genes are potential targets for genetic improvement of herbivore-resistant crops.

Morphophysiological basis of plant defense mechanisms against insect pests

Plants have been interacting with insects for several hundred million years, leading to the development of an intricate and dynamic defense system against insect herbivores. This defense system is further categorized as direct and indirect defense responses based on their expression. Specific or direct defensive responses are mediated by various morphological, biochemical and molecular mechanisms to counteract the effects of herbivore attack while indirect defense is mediated by releasing volatile mixtures to attract natural enemies of plant eating insect herbivores. The structural defense includes both morphological and anatomical traits viz., thorns, spines etc., whereas biochemical mechanisms of defense against the herbivores are wide-ranging, highly dynamic and includes production of different secondary metabolites-terpenes, phenolics and N-containing compounds. The molecular defense mechanisms include intracellular wound signalling viz., systemin signalling and jasmonate regulation of defense responsive genes. The defensive compounds are developed either constitutively or in response to plant damage, affecting insect herbivores’ feeding, development, and survival. In addition, plants also release volatile organic compounds which attract the herbivores’ natural enemies. These strategies either act independently or in conjunction with each other.