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BACKGROUND: The striped stem borer (SSB, Chilo suppressalis) is one of the most destructive insect pests on rice. As a chewing insect, SSB larval feeding causes a dramatic increase in rice defense responses. However, the effects of oral secretions (OSs) during SSB feeding on rice defense remain largely unexplored. RESULTS: In this study, based on transcriptome analysis results, treatment with SSB OSs regulated the expression of genes involved in the plant defense‐related pathways of calcium, mitogen‐activated protein kinases, reactive oxygen species, jasmonic acid (JA), herbivore‐induced plant volatiles (HIPVs), and protease inhibitors. Unsurprisingly, treatment with SSB OSs elicited the accumulation of JA and JA‐isoleucine in rice. The defense mechanisms activated by the cascade not only induced the expression of trypsin inhibitors, inhibiting the normal growth of SSB larvae but also induced HIPVs emission, rendering rice attractive to a common larval parasitoid. High‐throughput proteome sequencing of SSB OSs led to 534 proteins being identified and 343 proteins with two or more unique peptides being detected. CONCLUSION: The study demonstrates that SSB OSs trigger both direct and indirect defense mechanisms in rice, akin to the effects of SSB feeding. It identifies specific proteins in SSB OSs that may influence the interactions between SSB and rice during feeding, providing valuable insights for effectors research. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Most coexisting insect species exhibit stunted growth compared to individual species on plants. This phenomenon reflects an interspecific antagonism drawing extensive attention, while the underlying mechanisms remain largely uncharacterized. Mirids (Apolygus lucorum) and cotton bollworms (Helicoverpa armigera) are two common cotton pests. We identified a secretory protein, ASP1, from the oral secretion of mirids, found in the nucleus of mirid-infested cotton leaves. ASP1 specifically targets the transcriptional co-repressor TOPLESS (TPL) and inhibits NINJA-mediated recruitment of TPL, promoting plant defense response and gossypol accumulation in cotton glands. ASP1-enhanced defense inhibits the growth of cotton bollworms on cotton plants, while having limited impact on mirids. The mesophyll-feeding characteristic allows mirids to avoid most cotton glands, invalidating cotton defense. Our investigation reveals the molecular mechanism by which mirids employ cotton defense to selectively inhibit the feeding of cotton bollworms. The study revealed the underlying mechanism by which mirids manipulate cotton defense to confront the cotton bollworms co-existing on cotton plants. The mirid-secreted protein ASP1 enhances cotton defense by specifically targeting the transcriptional co-repressor TPL, thereby inhibiting cotton bollworm feeding. [ABSTRACT FROM AUTHOR]

BACKGROUND: The fall armyworm (FAW, Spodoptera frugiperda (J.E. Smith)) is a polyphagous agricultural pest with rapidly evolving adaptations to host plants. We found the oral secretion (OS) of FAW from different plants influences plant defense response differentially, suggesting its role in adapting to host plants. However, the protein expression profile of FAW OS respond to different plants is largely unknown. RESULTS: Here, from the mass spectrometry assay, we identified a total of 256 proteins in the OS of FAW fed on cotton (Gossypium hirsutum L.), tobacco (Nicotiana benthamiana Domin), maize (Zea mays L.) and artificial diet. The FAW OS primarily comprise of 60 proteases, 32 esterases and 92 non‐enzymatic proteins. It displays high plasticity across different diets. We found that more than half of the esterases are lipases which have been reported as insect elicitors to enhance plant defense response. The lipase accumulation in cotton‐fed larvae was the highest, followed by maize‐fed larvae. In the presence of lipase inhibitors, the enhanced induction on defense genes in wounded leaves by OS was attenuated. However, the putative effectors were most highly accumulated in the OS from FAW larvae fed on maize compared to those fed on other diets. We identified that one of them (VRLP4) reduces the OS‐mediated induction on defense genes in wounded leaves. CONCLUSION: Together, our investigation presents the proteomic landscape of the OS of FAW influenced by different diets and reveals diet‐mediated plasticity of OS is involved in FAW adaptation to host plants. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Plants and insects have co-existed for almost 400 million years and their interactions can be beneficial or harmful, thus reflecting their intricate co-evolutionary dynamics. Many herbivorous arthropods cause tremendous crop loss, impacting the agro-economy worldwide. Plants possess an arsenal of chemical defenses that comprise diverse secondary metabolites that help protect against harmful herbivorous arthropods. In response, the strategies that herbivores use to cope with plant defenses can be behavioral, or molecular and/or biochemical of which salivary secretions are a key determinant. Insect salivary secretions/oral secretions (OSs) play a crucial role in plant immunity as they contain several biologically active elicitors and effector proteins that modulate plants' defense responses. Using this oral secretion cocktail, insects overcome plant natural defenses to allow successful feeding. However, a lack of knowledge of the nature of the signals present in oral secretion cocktails has resulted in reduced mechanistic knowledge of their cellular perception. In this review, we discuss the latest knowledge on herbivore oral secretion derived elicitors and effectors and various mechanisms involved in plant defense modulation. Identification of novel herbivore-released molecules and their plant targets should pave the way for understanding the intricate strategies employed by both herbivorous arthropods and plants in their interactions. [ABSTRACT FROM AUTHOR]

Key Message The incorporation of antibiotics to field-collected Chilo suppressalis larvae significantly reduce bacterial quantities and affect larval performance on rice plants. Field-collected Chilo suppressalis larvae deposit abundant bacteria onto feeding sites through oral secretion, which modulate defense responses in rice plants. Bacteria isolated from larval oral secretion (such as Enterobacter and Acinetobacter) contribute to preventing rice plants to fully activate jasmonic acid-mediated antiherbivore defenses. Our results indicate insect-associated bacteria play an important role for C. suppressalis to adapt to rice plants, which could also be treated as targets for developing novel pest management strategies.

Salivary proteins in the oral secretion (OS) of chewing insects play a crucial role in insect-plant interactions during feeding. The rice leaf folder Cnaphalocrocis medinalis , a notorious pest in global rice production, triggers defense responses during feeding, but little is known about its salivary proteins. In this study, we confirmed that C. medinalis releases OS during feeding. By employing transcriptomic analysis and liquid chromatography-tandem mass spectroscopy (LC-MS/MS), we examined the salivary proteins from labial salivary glands and OS from C. medinalis. A total of 14,397 genes were expressed at the RNA level and 229 salivary proteins were identified. Comparative analysis with other 25 arthropod species revealed that 43 proteins were unique to C. medinalis. Expression pattern analysis revealed that most of the selected genes were highly expressed in the gut and the larval stages (4th–5th instar). These findings provide a comprehensive resource for future functional studies of salivary proteins, offering new insights into the molecular mechanisms by which C. medinalis modulates plant defenses and potential applications in pest management. [Display omitted] • The rice leaf folder Cnaphalocrocis medinalis release oral secretions when feeding on plants. • 229 salivary proteins were identified from C. medinalis oral secretions. • Salivary proteins from C. medinalis may be involved in digestion, immunity, detoxification, herbivore offense, etc. [ABSTRACT FROM AUTHOR]

Plant defenses in response to chewing insects are generally regulated by jasmonic acid (JA) signaling pathway, whereas salicylic acid (SA) signaling is mainly involved in plant defense against biotrophic pathogens and piercing-sucking insects. Previous studies showed that both JA- and SA-related defenses in rice plants were triggered by the infestation of the rice striped stem borer (SSB, Chilo suppressalis), a destructive pest causing severe damage to rice production. Herbivore-associated microbes play an important role in modulating plant–insect interaction, and thus we speculate that the SSB symbiotic microbes acting as a hidden player may cause this anomalous result. The antibiotics (AB) treatment significantly depressed the performance of field-collected SSB larvae on rice plants, and reduced the quantities of bacteria around the wounds of rice stems compared to non-AB treatment. In response to mechanical wounding and oral secretions (OS) collected from non-AB treated larvae, rice plants exhibited lower levels of JA-regulated defenses, but higher levels of SA-regulated defenses compared to the treatment of OS from AB-treated larvae determined by using a combination of biochemical and molecular methods. Among seven culturable bacteria isolated from the OS of SSB larvae, Enterobacter and Acinetobacter contributed to the suppression of JA signaling-related defenses in rice plants, and axenic larvae reinoculated with these two strains displayed better performance on rice plants. Our findings demonstrate that SSB larvae exploit oral secreted bacteria to interfere with plant anti-herbivore defense and avoid fully activating the JA-regulated antiherbivore defenses of rice plants. Key Message: The incorporation of antibiotics to field-collected Chilo suppressalis larvae significantly reduce bacterial quantities and affect larval performance on rice plants. Field-collected Chilo suppressalis larvae deposit abundant bacteria onto feeding sites through oral secretion, which modulate defense responses in rice plants. Bacteria isolated from larval oral secretion (such as Enterobacter and Acinetobacter) contribute to preventing rice plants to fully activate jasmonic acid-mediated antiherbivore defenses. Our results indicate insect-associated bacteria play an important role for C. suppressalis to adapt to rice plants, which could also be treated as targets for developing novel pest management strategies. [ABSTRACT FROM AUTHOR]

The innate machineries for regulation of plant defense responses against herbivores are strikingly based on stress response-associated phytohormones. However, the dynamics of the effects of distinct types of chewing herbivores’ oral secretion (OS) on phytohormone regulation are not well known. We explored the phytohormone regulation in maize leaves in response to OS from larvae of a specialist herbivore (Mythimna separata) and a generalist herbivore (Spodoptera litura). In response to mechanical damage with application of those OSs, maize leaves rapidly upregulated the endogenous levels of oxylipins and abscisic acid (ABA) in quantitatively similar manners. Moreover, it appeared that bacteria in OS were responsible for the coordination of ABA levels. Our findings suggest that, during predation by the specialist and generalist lepidopteran herbivores, their OSs similarly upregulate phytohormone levels and the presence of their oral bacterial community makes a minor impact on maize defense responses.

The innate machineries for regulation of plant defense responses against herbivores are strikingly based on stress response-associated phytohormones. However, the dynamics of the effects of distinct types of chewing herbivores' oral secretion (OS) on phytohormone regulation are not well known. We explored the phytohormone regulation in maize leaves in response to OS from larvae of a specialist herbivore (Mythimna separata) and a generalist herbivore (Spodoptera litura). In response to mechanical damage with application of those OSs, maize leaves rapidly upregulated the endogenous levels of oxylipins and abscisic acid (ABA) in quantitatively similar manners. Moreover, it appeared that bacteria in OS were responsible for the coordination of ABA levels. Our findings suggest that, during predation by the specialist and generalist lepidopteran herbivores, their OSs similarly upregulate phytohormone levels and the presence of their oral bacterial community makes a minor impact on maize defense responses. [ABSTRACT FROM AUTHOR]

BACKGROUND Plants have evolved sophisticated defense responses to insect herbivore attack, which often involve elicitors in the insects' oral secretions. The major eliciting compounds in insect oral secretions across different species and their potency in inducing volatile emissions have not yet been fully characterized and compared. RESULTS: Seven lepidopteran insects with variable duration of association with maize were selected, five species known as pests for a long time (Ostrinia furnacalis, Spodoptera exigua, Spodoptera litura, Mythimna separata, and Helicoverpa armigera) and two newly emerging pests (Athetis lepigone and Athetis dissimilis). Oral secretions of the newly emerging pests have the highest total contents of Fatty Acid‐Amino Acid Conjugates (FACs), and their relative composition was well separated from that of the other five species in principal compound analysis. Redundancy analyses suggested that higher quantity of FACs was mainly responsible for the increases in maize volatiles, of which (E)‐3,8‐dimethyl‐1,4,7‐nonatriene (DMNT) and (E, E)‐4,8,12‐trimethyltrideca‐1,3,7,11‐tetraene (TMTT) were the most strongly inducible compounds. Adding FACs to the oral secretion of S. litura larvae significantly increased the emissions of TMTT and DMNT, confirming the key role of FACs in inducing volatile emissions in maize plants. Additional experiments with artificial diet spiked with linolenic acid suggested that variation in FACs is due to differences in internal FAC degradation and fatty acid excretion. CONCLUSION: Compared with two newly emerging pests A. lepigone and A. dissimilis, the long‐term pests could diminish the volatile emission by maize through reducing the FAC content in their oral secretions, which may lower the risk of attracting natural enemies. [ABSTRACT FROM AUTHOR]

In this explorative mixed-method pilot study, we set out to have a closer look at the largely under-recognized and under-investigated symptom of thick mucus in patients with ALS and its impact on patients and relatives. Thick mucus is a highly distressing symptom for both patients and caregivers. It complicates the use of non-invasive ventilation and is therefore an important prognostic factor of survival. Methods: In our preliminary study, we used a cross-sectional design, including ten ALS patients with thick mucus who were matched to ten ALS patients without thick mucus. Lung function tests and laboratory and sputum analysis were performed and questionnaires administered in order to determine associated factors of thick mucus accumulation. In a qualitative study using semi-structured interviews, we analysed the impact of thick mucus on patients and caregivers. Results: Reduced respiratory parameters as well as a higher degree of bulbar impairment were associated with the presence of thick mucus. Quality of life of patients and caregivers was strongly impaired by thick mucus accumulation. Conclusions: Thick mucus in patients with ALS has a strong impact on quality of life. Reduced cough flow and severely impaired bulbar function appear to be indicative parameters. We suggest that healthcare providers actively explore the presence of thick mucus in their patients and that it becomes included in commonly used screening tools.

One of the most prevalent bioactive molecules present in the oral secretion (OS) of lepidopteran insects is fatty acid amino acid conjugates (FACs). Insect dietary components have influence on the synthesis and retaining the pool of FACs in the OS. We noted differential and diet-specific accumulation of FACs in the OS of Helicoverpa armigera by using Liquid Chromatography-Quadrupole Time of Flight Mass Spectrometry. Interestingly, we identified FACs hydrolyzing enzyme aminoacylase (HaACY) in the OS of H. armigera through proteomic analysis. Next, we have cloned, expressed, and purified active recombinant HaACY in the bacterial system. Recombinant HaACY hydrolyzes all the six identified FACs in the OS of H. armigera larvae fed on host and non-host plants and releases respective fatty acid and glutamine. In these six FACs, fatty acid moieties vary while amino acid glutamine was common. Glutamine obtained upon hydrolysis of FACs by HaACY might serve as an amino acid pool for insect growth and development. To understand the substrate choices of HaACY, we chemically synthesized, purified, and characterized all the six FACs. Interestingly, rHaACY also shows hydrolysis of synthetic FACs into respective fatty acid and glutamine. Our results underline the importance of diet on accumulation of FACs and role of aminoacylase(s) in regulating the level of FACs and glutamine. Graphical abstract: Schematics of synthesis and hydrolysis FACs in H. armigera larave. Demonstrating the impact of diet on the accumulation of FACs and the involvement of aminoacylase in maintaining FACs levels in H. armigera oral secretion. Number of arrows represents the approximate level of FACs and aminoacylase in H. armigera. [Display omitted] • Plant-based diet influences levels of FACs and aminoacylase in the OS of Helicoverpa armigera. • Simple synthesis and purification protocols for FACs were developed. • Recombinant H. armigera aminoacylase hydrolyses FACs with specific preferences. • Glutamine released upon FACs hydrolysis may serve as a nitrogen source for H. armigera. [ABSTRACT FROM AUTHOR]

Green plants emit green leaf volatiles (GLVs) as a general damage response. These compounds act as signals for the emitter plant, neighboring plants, and even for insects in the ecosystem. However, when oral secretions from certain caterpillars are applied to wounded leaves, GLV emissions are significantly decreased or modified. We examined four caterpillar species representing two lepidopteran families for their capacity to decrease GLV emissions from Zea mays leaf tissue. We also investigated the source of the GLV modifying components in the alimentary tract of the various caterpillars. In Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), and Manduca sexta (Linnaeus) (Lepidoptera: Sphingidae), we found three distinct mechanisms to modify GLV emission: a heat-stable compound in the gut, a heat-labile enzyme in salivary gland homogenate (previously described in Bombyx mori (Linnaeus) (Lepidoptera: Bombycidae), and an isomerase in the salivary gland homogenate, which catalyzes the conversion of (Z)-3-hexenal to (E)-2-hexenal (previously described in M. sexta). These mechanisms employed by caterpillars to suppress or modify GLV emission suggest a counteraction against the induced indirect volatile defenses of a plant and provides further insights into the ecological functions of GLVs. [ABSTRACT FROM AUTHOR]

Cotton plants induce high levels of gossypol in response to herbivore damage. However, little is known about the mechanisms by which insect herbivory modulates gossypol biosynthesis in cotton plants. Here, we report the mechanism by which herbivore damage or insect-originated elicitors modulate the biosynthesis of gossypol and jasmonic acid (JA) in plants. Spodoptera exigua larval-damaged (HD) cotton plants and mechanically damaged plants treated with S. exigua oral secretion (MDOS) showed higher levels of gossypol and JA as well as increased transcript levels of genes involved in the biosynthesis of both secondary plant metabolites, compared to undamaged (UD) or mechanically damaged (MD) plants. In correlation with the observed induction of gossypol and JA, S. exigua larvae that fed on HD and MDOS cotton plants showed significantly reduced weight. The findings provide a better insight into the molecular mechanisms mediating herbivore-induced plant defense.

Immature stages of insects are generally susceptive to their natural enemies, but many species developed defensive and evasive mechanisms to circumvent predation. Gregarious larvae of the noctuid moth Dyops cf. cuprescens feed on leaves of young Cecropia pachystachya shrubs colonized by Azteca ants. Ants avoid contact with larval clusters, retreating to the nest when larvae are moving near the stems. Provoked encounters revealed that Dyops caterpillars present several specialized behaviors to avoid and overcome ant attacks, such as fleeing to under leaf, jumping off the leaf, curling and wriggling vigorously the anterior portion of the body, spitting droplets of oral fluids, or killing ants by pouncing them. These mechanisms allow the caterpillars to overcome ant attacks and consume leaves of ant-colonized plants. By feeding on a heavily protected plant, larvae can enjoy not only a competitor-free plant, but possibly also the enemy-free space created by the aggressive ants.

Cotton plants induce high levels of gossypol in response to herbivore damage. However, little is known about the mechanisms by which insect herbivory modulates gossypol biosynthesis in cotton plants. Here, we report the mechanism by which herbivore damage or insect-originated elicitors modulate the biosynthesis of gossypol and jasmonic acid (JA) in plants.Spodoptera exigualarval-damaged (HD) cotton plants and mechanically damaged plants treated withS. exiguaoral secretion (MDOS) showed higher levels of gossypol and JA as well as increased transcript levels of genes involved in the biosynthesis of both secondary plant metabolites, compared to undamaged (UD) or mechanically damaged (MD) plants. In correlation with the observed induction of gossypol and JA,S. exigualarvae that fed on HD and MDOS cotton plants showed significantly reduced weight. The findings provide a better insight into the molecular mechanisms mediating herbivore-induced plant defense. [ABSTRACT FROM AUTHOR]

The potential roles of the oral secretions (OS) of spruce budworm (SBW; Choristoneura fumiferana Clemens) larvae and factors that may affect the volume of OS disgorged were investigated in the laboratory. Experiments revealed that diet-fed SBW larvae readily disgorge OS when induced ("milked"), with minimal overall cost to their development and eventual pupal weight. Exposure of conspecific larvae to OS throughout larval development negatively affected survival and male pupal weight; however, male development time was faster when exposed to OS. Female pupal weight and development time were not affected. Preliminary experiments suggested that OS had a repellent effect on a co-occurring herbivore, the false hemlock looper, Nepytia canosaria (Walker). OS produced by larvae that fed on three host tree species and on artificial diet significantly increased the grooming time of ants (Camponotus sp.), indicating that SBW OS have an anti-predator function. The volume of OS is significantly greater in L6 than in L4 or L5, with the volume produced by L6 depending on weight and age as well as feeding history at time of milking. These findings indicate that SBW OS function as both an intra- and interspecific epideictic pheromone and as an anti-predator defensive mechanism, while incurring minimal metabolic costs. [ABSTRACT FROM AUTHOR]

The Ca2+ sensor protein CML37 acts as positive defense regulator upon herbivory in Arabidopsis. After Spodoptera littoralis feeding, CML37 enhances the jasmonate pathway by promoting JAR1 activity and thereby downstream defense activation.Throughout their life, plants are challenged by various abiotic and biotic stress factors. Among those are attacks from herbivorous insects. The molecular mechanisms underlying the detection of herbivores and the subsequent signal transduction are not well understood. As a second messenger, fluxes in intracellular Ca2+ levels play a key role in mediating stress response pathways. Ca2+ signals are decoded by Ca2+ sensor proteins such as calmodulin-like proteins (CMLs). Here, we demonstrate that recombinant CML37 behaves like a Ca2+ sensor in vitro and, in Arabidopsis, AtCML37 is induced by mechanical wounding as well as by infestation with larvae of the generalist lepidopteran herbivore Spodoptera littoralis. Loss of function of CML37 led to a better feeding performance of larvae suggesting that CML37 is a positive defense regulator. No herbivory-induced changes in secondary metabolites such as glucosinolates or flavonoids were detected in cml37 plants, although a significant reduction in the accumulation of jasmonates was observed, due to reduced expression of JAR1 mRNA and cellular enzyme activity. Consequently, the expression of jasmonate-responsive genes was reduced as well. Summarizing, our results suggest that the Ca2+ sensor protein, CML37, functions as a positive regulator in Ca2+ signaling during herbivory, connecting Ca2+ and jasmonate signaling. [ABSTRACT FROM PUBLISHER]

Carnivorous sundew plants catch and digest insect prey for their own nutrition. The sundew species Drosera capensis shows a pronounced leaf bending reaction upon prey capture in order to form an 'outer stomach'. This formation is triggered by jasmonates, phytohormones typically involved in defence reactions against herbivory and wounding. Whether jasmonates still have this function in D. capensis in addition to mediating the leaf bending reaction was investigated here. Wounded, insect prey-fed and insect-derived oral secretion-treated leaves of D. capensis were analysed for jasmonates (jasmonic acid, JA; jasmonic acid-isoleucine conjugate, JA-Ile) using LC- MS/ MS. Prey-induced jasmonate accumulation in D. capensis leaves was persistent, and showed high levels of JA and JA- Ile (575 and 55.7 pmol·g·FW−1, respectively), whereas wounding induced a transient increase of JA (maximum 500 pmol·g·FW−1) and only low (3.1 pmol·g·FW−1) accumulation of JA-Ile. Herbivory, mimicked with a combined treatment of wounding plus oral secretion ( W+ OS) obtained from Spodoptera littoralis larvae induced both JA (4000 pmol·g·FW−1) and JA- Ile (25 pmol·g·FW−1) accumulation, with kinetics similar to prey treatment. Only prey and W+ OS, but not wounding alone or OS, induced leaf bending. The results indicate that both mechanical and chemical stimuli trigger JA and JA- Ile synthesis. Differences in kinetics and induced jasmonate levels suggest different sensing and signalling events upon injury and insect-dependent challenge. Thus, in Drosera, jasmonates are still part of the response to wounding. Jasmonates are also employed in insect-induced reactions, including responses to herbivory and carnivory. [ABSTRACT FROM AUTHOR]

Context. Non-front-fanged colubroid snakes (NFFC; formerly and artificially taxonomically assembled as 'colubrids') comprise the majority of extant ophidian species. Although the medical risks of bites by a handful of species have been documented, the majority of these snakes have oral products (Duvernoy's secretions, or venoms) with unknown biomedical properties/unverified functions and their potential for causing harm in humans is unknown. Case details. Described are three cases of local envenoming from NFFC bites inflicted respectively by the mangrove or ringed cat-eyed snake ( Boiga dendrophila, Colubridae), the Western beaked snake ( Rhamphiophis oxyrhynchus, Lamprophiidae) and the rain forest cat-eyed snake ( Leptodeira frenata, Dipsadidae). The effects ranged from mild pain, edema and erythema to severe pain, progressive edema, and blistering with slowly resolving arthralgia; there were no systemic effects. Discussion. Although these three taxa occasionally inflict bites with mild to moderate local effects, there is no current evidence of systemic involvement. Two of these cases were reported to one of the authors for medical evaluation, and although verified, thus constitute reliably reported cases, but low-quality evidence. Type-1 local hypersensitivity may contribute to some cases, but most local effects observed or reported in these three cases were consistent with the effects of venom/oral product components. [ABSTRACT FROM AUTHOR]

Abstract: Insect herbivory on plants is a complex incident consisting of at least two different aspects, namely mechanical damage and chemical challenge, as feeding insects introduce oral secretions (OS) into the wounded tissue of the attacked plant. Mechanical wounding alone is sufficient to induce a set of defense-related reactions in host plants, but some early events such as membrane potential (Vm) changes and cytosolic Ca2+-elevations can be triggered only by herbivores suggesting that OS-derived molecules are involved in those processes. Following an assay-guided purification based on planar lipid bilayer membrane technique in combination with proteomic analysis, a porin-like protein (PLP) of most likely bacterial origin was determined from collected OS of Spodoptera littoralis larvae. PLP exhibited channel-forming activity. Further, early defense-related events in plant–insect interaction were evaluated by using a purified fraction and α-hemolysin (α-HL) as a commercial pore-forming compound. Both up-regulated the calmodulin-like CML42 in Arabidopsis thaliana, which only responds to oral secretion and not to wounding. An elevation of in vivo [Ca2+]cyt was not observed. Because membrane channel formation is a widespread phenomenon in plant–insect interactions, this PLP might represent an example for microbial compounds from the insect gut which are initially involved in plant–insect interactions. [Copyright &y& Elsevier]

Numerous herbivores orally secrete defense compounds to detoxify plant toxins. However, little is known about the role of orally secreted enzymes by a specialized pest, Plutella xylostella , in the detoxification of plant defense compounds. Three glucosinolate sulfatases (GSSs) or two sulfatase-modifying factors (SUMF1s) mutant strains were established on the basis of CRISPR/Cas9 technology to validate the existence of a species-specific GSSs-SUMF1s system. In comparison to the bioassay data from mutant strains of GSS1 / GSS2 or SUMF1a / SUMF1b , GSS3 had a minimal role because no significant change was found in GSS3 under different feeding contexts. Antibody-based technologies were used to examine GSSs-related deficient strains, and the results showed that the GSS1 protein was primarily released through larval oral secretion. On the basis of high-performance liquid chromatography, we found that GSS1 was secreted to pre-desulfate the typical plant defensive glucosinolates known as 4-(methylsulfinyl)butyl glucosinolate (4MSOB-GL) to suppress the production of the toxic substance, which is referred to as pre-detoxification strategy. These findings highlighted that the GSSs-SUMF1s system is the key factor for counteradaptation of -/- under different feeding contexts. Antibody-based technologies were used to examine GSSs-related deficient strains, and the results showed that the GSS1 protein was primarily released through larval oral secretion. On the basis of high-performance liquid chromatography, we found that GSS1 was secreted to pre-desulfate the typical plant defensive glucosinolates known as 4-(methylsulfinyl)butyl glucosinolate (4MSOB-GL) to suppress the production of the toxic substance, which is referred to as pre-detoxification strategy. These findings highlighted that the GSSs-SUMF1s system is the key factor for counteradaptation of P. xylostella to cruciferous plants, which strengthens the concept that herbivores deploy pre-detoxification strategies to disrupt the plant chemical defenses to facilitate the colonization process.

Upon herbivory, plants can swiftly reallocate newly acquired resources to different tissues within a plant. Although the herbivore-induced movement of resources is apparent, the movement direction and the role of the remobilized resources are not well understood. Here, we used a two-pronged approach combining radioisotope and metabolomic techniques to shed light on whole-plant resource reallocation and changes in primary metabolism within the tomato, Solanum lycopersicum (L.) (Solanaceae), model in response to simulated herbivory by the specialist Manduca sexta (L.) (Lepidoptera: Sphingidae). Manduca sexta regurgitant applied to damaged leaves, but not mechanical damage alone, increased 11 C-photosynthate allocation to roots but did not affect 11 CO2 fixation and leaf export. Changes in primary metabolite concentrations occurred mostly in sink tissues (apex and roots) as well as in damaged leaves. Both damage treatments (with and without M. sexta regurgitant application) resulted in increased concentrations of primary metabolites relative to undamaged plants in the apex and decreased concentrations in the roots, but there were also extensive changes specific to each damage treatment. Mechanical damage alone led to changes consistent with water stress caused by tissue damage. Manduca sexta led to metabolite increases in the apex consistent with an increase in glucose breakdown, metabolite increases in damaged leaves consistent with starch degradation, and metabolite decreases in roots suggesting a high use of metabolites. A possible explanation for the observed patterns in the aboveground tissues might be an increase in carbohydrate degradation to support defense production in attacked leaves and vulnerable developing leaves, and/or subsequent remobilization to belowground tissues to support high carbohydrate demand for respiration, enhanced nutrient uptake, and storage. [ABSTRACT FROM AUTHOR]

Oral secretions of herbivorous lepidopteran larvae contain a mixture of saliva and regurgitant from the insect gut. Different compounds from the oral secretions can be recognized by the host plants and, thus, represent elicitors that induce plant defenses against feeding herbivores. Exogenously applied oral secretions can initiate the biosynthesis of jasmonates, phytohormones involved in the regulation of plant defense. However, it is not known (a) whether or not non-manipulated insects indeed release oral secretions including gut-derived compounds into a leaf wound during the natural feeding process, or (b) whether they adjust the release of gut components to the state of plant defense. We addressed these questions by using Arabidopsis thaliana as host plant and larvae of the generalist herbivorous insect Spodoptera littoralis. We investigated the conversion of the plant-derived jasmonate precursor, cis-12-oxophytodienoic acid ( cis-OPDA), to iso-OPDA by the larvae. This enzymatic reaction is mediated by a specific glutathione- S-transferase in the insect gut, but not in the plant. Any presence of iso-OPDA in plant tissue, thus, indicated that gut content had been regurgitated into the plant wound. Our study demonstrates that the plant is the only source for the substrate cis-OPDA by using aos (allene oxide synthase) mutants that are unable to synthesize OPDA. The fact that iso-OPDA accumulated over time on feeding-damaged leaves shows that the feeding larvae are constantly regurgitating on leaves. Although the larvae provided the signaling compounds that were recognized by the plant and elicited defense reactions, the larval regurgitation behavior did not depend on whether they fed on a defensive wild type plant or on a non defensive coi1-16 plant. This suggests that S. littoralis larvae do not adjust regurgitation to the state of plant defense. [ABSTRACT FROM AUTHOR]

In this explorative mixed-method pilot study, we set out to have a closer look at the largely under-recognized and under-investigated symptom of thick mucus in patients with ALS and its impact on patients and relatives. Thick mucus is a highly distressing symptom for both patients and caregivers. It complicates the use of non-invasive ventilation and is therefore an important prognostic factor of survival. Methods: In our preliminary study, we used a cross-sectional design, including ten ALS patients with thick mucus who were matched to ten ALS patients without thick mucus. Lung function tests and laboratory and sputum analysis were performed and questionnaires administered in order to determine associated factors of thick mucus accumulation. In a qualitative study using semi-structured interviews, we analysed the impact of thick mucus on patients and caregivers. Results: Reduced respiratory parameters as well as a higher degree of bulbar impairment were associated with the presence of thick mucus. Quality of life of patients and caregivers was strongly impaired by thick mucus accumulation. Conclusions: Thick mucus in patients with ALS has a strong impact on quality of life. Reduced cough flow and severely impaired bulbar function appear to be indicative parameters. We suggest that healthcare providers actively explore the presence of thick mucus in their patients and that it becomes included in commonly used screening tools. [ABSTRACT FROM AUTHOR]

Nest material, nitrogen and amino acid composition of nests were examined in a New World swarm-founding polistine wasp, Polybia paulista. This wasp used minute vegetable chips, which were a dominant material, plant hairs, and mud and/or inorganic particles as nest building materials. A SEM observation and nitrogen and amino acid contents indicated that the amount of oral secretion used for construction and maintenance of the nests was quite small, compared with that used in Polistes nests. Such a small amount of oral secretion used for nest building is considered to be associated with their social organization (division of labor) and nest material. This study hypothesized that the amounts of oral secretion used for nest building are determined by an interaction among social organization, nest material and environmental factors, such as precipitation. Twenty-four amino acids were detected from protein in the nests of P. paulista, of which serine, glycine, alanine, valine, proline, aspartic acid and glutamic acid were major components. Amino acid composition of the protein in the nests of P. paulista differed distinctly from those of other so far known polistine and vespine wasps. The present result supports the view that amino acid composition of the protein in nests reflects phylogenetical relationships among wasps. [ABSTRACT FROM PUBLISHER]

Amino acid composition of protein in oral secretion, which is widely used for construction and maintenance of social wasp nests, was analyzed in pre-emergence nests of Polistes chinensis. More than 20 amino acids were detected from field and laboratory nests, among which glycine, serine, alanine, valine and proline were major amino acids in all samples analyzed. The amino acid composition was very similar among various nest parts, and between field and laboratory nests. Foundresses of P. chinensis produce essentially similar kinds of oral secretion despite variation in their nest sites and in the environment around their nests. The composition of P. chinensis is similar to those so far known among other Polistes species, while different in intergenus comparisons. Amino acid composition of protein in oral secretion may reflect phylogenetical relationships among wasps. The chemical nature of oral secretion, especially the presence of proline in its amino acids, as well as the quantity of secretion production may play an important role to harden their nests. Wasps live their social life on nests which are maintained by such secretion characteristics. [ABSTRACT FROM AUTHOR]

After herbivore attack, plants launch a suite of direct and indirect defense responses that must be coordinated if plants are to realize a fitness benefit from these responses. Here we characterize the volatile emissions in the native tobacco plant, Nicotiana attenuata Torr. ex Wats., that are elicited by tobacco hornworm (Manduca sexta L.) attack and are known to function as attractants for parasitoids. To provide the first ecophysiological comparison of examples of both types of defense in the same species, we characterize the elicitation and signaling mechanisms, the resources required, and the potential costs and benefits of the volatile release and compare these traits with those of the well-described induced direct defense in this species, nicotine production. The release of (E)-β-ocimene, cis-α-bergamotene and linalool is dramatically induced within 24 h by application of methyl jasmonate (MeJA), caterpillar feeding, and the treatment of mechanical wounds with larval oral secretions (OS), but not by mechanical damage alone. Plants from different geographic locations produce volatile blends that differ in composition. The most consistently released component from all genotypes, cis-α-berga-motene, is positively related to the amount of MeJA and the level of wounding if OS are applied to the wounds. The volatile release is strongly light dependent, dropping to undetectable quantities during dark periods, even when temperatures are elevated to match those of the light period. Inhibitors of wound-induced jasmonate accumulation (salicylates and auxins), which are known to inhibit wound-induced nicotine production, do not inhibit the release of volatiles. By individually inducing different leaf positions with OS and, on other plants, excising them after induction, we demonstrate that the emission is largely a systemic, whole-plant response, which is maximally triggered when the second fully expanded leaf is induced. We conclude that while both are whole-plant, systemic responses that utilize recently acquired resources for their production and are activated by the jasmonate cascade, the elicitation of the volatile release exhibits greater tissue sensitivity and utilizes additional signaling components than does nicotine production. In contrast to the large investment of fitness-limiting resources required for induced nicotine production or the resources used in benzyl acetone release from flowers for pollinator attraction, the resource requirements for the volatile release are minor. Hence the argument that the volatile release incurs comparatively large physiological costs cannot be supported in this system. [ABSTRACT FROM AUTHOR]

The allocation pattern of proteinaceous resources was estimated in preemergence colonies of Polistes chinensis. Foundresses that nested at exposed sites consumed a larger relative amount of proteinaceous resources to produce oral secretion, which is used for construction and maintenance of nests, than those at sheltered sites. Numbers of immatures reared by foundresses were smaller in exposed nests than those in sheltered ones, and further, workers that emerged from exposed nests were significantly smaller in size than those from sheltered ones. Foundresses had to partition available proteinaceous resources not only among the first batch of the brood but also, before that, between brood nourishment and secretion production in response to given environmental conditions. [ABSTRACT FROM AUTHOR]

For more than 350 million years, there have been ongoing dynamic interactions between plants and insects. In several cases, insects cause-specific feeding damage with ensuing herbivore-associated molecular patterns that invoke characteristic defense responses. During feeding on plant tissue, insects release oral secretions (OSs) containing a repertoire of molecules affecting plant defense (effectors). Some of these OS components might elicit a defense response to combat insect attacks (elicitors), while some might curb the plant defenses (suppressors). Few reports suggest that the synthesis and function of OS components might depend on the host plant and associated microorganisms. We review these intricate plant-insect interactions, during which there is a continuous exchange of molecules between plants and feeding insects along with the associated microorganisms. We further provide a list of commonly identified inducible plant produced defensive molecules released upon insect attack as well as in response to OS treatments of the plants. Thus, we describe how plants specialized and defense-related metabolism is modulated at innumerable phases by OS during plant-insect interactions. A molecular understanding of these complex interactions will provide a means to design eco-friendly crop protection strategies. [Display omitted] • Reviewed characterized constituents of the insect herbivore's oral secretion (OS). • Synthesis of constituents of insects OS is influenced by diet and related microbes. • Updates on the active molecules from OS viz , effectors. • Highlighted the potential markers to study the induced plant defense mechanisms@. [ABSTRACT FROM AUTHOR]

• Plant-based diets influence the Helicoverpa armigera oral secretion composition. • Identified tomato metabolites upon application of oral secretions on wounded leaves. • Upregulated biosynthetic pathway genes of chlorogenic acid and trehalose in tomato. • Chlorogenic acid significantly impeded Helicoverpa armigera larval growth. Little is known about how different plant-based diets influence the insect herbivores' oral secretion (OS) composition and eventually the plant defense responses. We analyzed the OS composition of the generalist Lepidopteran insect, Helicoverpa armigera feeding on the host plant tomato (OS H), non-host plant capsicum (OS NH), and artificial diet (OS AD) using Liquid Chromatography-Quadrupole Time of Flight Mass Spectrometry. Higher numbers and levels of alkaloids and terpenoids were observed in OS H and OS NH , respectively while OS AD was rich in phospholipids. Interestingly, treatment of H. armigera OS AD , OS H and OS NH on wounded tomato leaves showed differential expression of (i) genes involved in JA and SA biosynthesis and their responsive genes, and (ii) biosynthetic pathway genes of chlorogenic acid (CGA) and trehalose, which exhibited increased accumulation along with several other plant defensive metabolites. Specifically, high levels of CGA were detected after OS H and OS NH treatments in tomato leaves. There was higher expression of the genes involved in phenylpropanoid biosynthesis, which may lead to the increased accumulation of CGA and related metabolites. In the insect bioassay, CGA significantly inhibited H. armigera larval growth. Our results underline the differential accumulation of plant and insect OS metabolites and identified potential plant metabolite(s) affecting insect growth and development. [ABSTRACT FROM AUTHOR]

The amount of oral secretion, which mostly consists of proteinaceous materials, used for the construction and maintenance of nests by foundresses of Polistes chinensis was analysed in 95 field nests (1994–1996). The amounts always exceeded 50% of mean percent secretion to total the dry nest weights, and it was greater in nests built at sites exposed to direct rainfall than in those at sheltered sites. Further, exposed nests built in 1995 (a rainy year) were much smaller than those of 1994 and 1996, and the amount of secretion in that year was much greater than in the other years. The nitrogen content of adult workers, immatures, those left inside cells and the oral secretion in nests of 1996 showed that 10–20% of total protein resources brought in during the founding phase may be devoted to producing the secretion. The results suggest that the foundresses may regulate the amounts of oral secretion used for such purposes in response to environmental conditions. [ABSTRACT FROM PUBLISHER]

Amino acid composition of the protein in the oral secretion, which is widely used for construction and maintenance of social wasp nests, was analyzed in preemergence nests of Polistes ( Polistes) riparius. The kinds and proportion (%) of amino acids of the protein detected from nests of P. riparius were very similar to those of a consubgeneric species, P. ( P.) chinensis, but were conspicuously different from those of other social wasp genera. Further, it was estimated that protein contents in oral secretion of P. riparius were nearly the same as those of P. chinensis; namely, foundresses of P. riparius, which build much larger nests than those of P. chinensis, did not reduce relative protein contents to produce more oral secretion at a smaller cost. Amino acid composition may reflect phylogenetic relationships among wasp taxa. [ABSTRACT FROM AUTHOR]

This paper is about the cellular responses of plants to chewing insect attacks. We deployed a recently developed experimental system to monitor the responsiveness of Arabidopsis thaliana (Arabidopsis) to the application of oral secretion (OS) from Lepidopteran generalist herbivore Spodoptera litura ( S. litura ). Oral secretion from S. litura contains gut regurgitant and saliva. We identified significant differences in the wound closure morphologies (e.g., dried and sealed tissue) between mechanically damaged leaves with and without an application of S. litura OS at the site-of-injury. Experimental controls were mechanically wounded leaves. Wounds were walled off by visible vertical cross sections. Cell death was restricted to the immediate areas of the wounds. In contrast, mechanically damaged leaves treated with S. litura OS did not display a clear sealing pattern due to an absence of a defined vertical cross section at the wound site. Notably, OS treated leaves exhibited a wider area of visible premature senescence (the declining of chlorophyll content caused by death of chloroplasts) around the injury than controls. More pronounced senescence was also observed around the injury in S. litura OS treated wounds than in controls. Heat inactivated S. litura OS elicited a similar response to non-heat inactivated samples. The causal compound is heat stable and thus not a protein. Our results suggest that S. litura OS: (1) inhibited wound recovery responses in leaves; (2) promoted senescence around injured areas. The function of senescence may be to relocate nutritional resources to support plant survival when attacked., (© 2018 The Japanese Society for Plant Cell and Molecular Biology.)

Herbivore attack induces defense responses in plants, activating several signaling cascades. As a result, molecules deterrent to the herbivores are produced and accumulated in plants. Expression of defense mechanism/traits requires reorganization of the plant metabolism, redirecting the resources otherwise meant for growth. In the present work, protein profile of Capsicum annuum leaves was examined after herbivore attack/induction. Majority of proteins identified as differentially accumulated, were having roles in redox metabolism and photosynthesis. For example, superoxide dismutase and NADP oxidoreductase were upregulated by 10- and 6-fold while carbonic anhydrase and fructose-1,6-bisphosphatase were downregulated by 9- and 4-fold, respectively. Also, superoxide dismutase, NADPH quinone oxidoreductase and NADP dependent isocitrate dehydrogenase transcripts showed a higher accumulation in induced leaf tissues at early time points. In general, proteins having role in defense and damage repair were upregulated while those involved in photosynthesis appeared downregulated. Thus metabolic reconfiguration to balance defense and tolerance was evident in the stress-induced leaves., (Copyright © 2013 Elsevier Masson SAS. All rights reserved.)