Trypsin Proteinase Inhibitors Research Articles

Rice bean (Vigna umbellata Thunb. Ohwi and Ohashi) protection against Callosobruchus maculatus F.” by presence of protein profile

To identify defence responses of rice bean against Callosobruchus maculatus, 10 genotypes of rice bean and a mungbean variety, PAU 911 as susceptible check were evaluated. The rice bean genotypes were found to restrain the growth and development of C. maculatus at different larval stages. To justify these results, seeds of different test genotypes were examined for the presence of plant protease inhibitors which inhibit insect proteases causing reduction in the availability of amino acids necessary for their growth and development. Trypsin, chymotrypsin and cysteine protease inhibitor content was significantly higher in rice bean genotypes which ranged from 299.99 to 342.97 TIU g−1 seeds, 235.07 to 251.45 CIU/g seeds and 1060.70 to 1574.99 CPIU/g seeds, respectively as compared to mungbean variety, PAU 911 (235.52 TIU/g seeds, 217.91 CIU/g seeds and 499.99 CPIU/g seeds, respectively). The protein profile showed a polypeptide band of 25–30 kDa corresponding to presence of protease inhibitors in rice bean genotypes except PAU 911. The results indicate that protease inhibitors in different genotypes of rice bean are very effective against C. maculatus.

Current understanding of the genomic, genetic, and molecular control of insect resistance in rice

Rice (Oryza sativa) is both a vital source of food and a key model cereal for genomic research. Insect pests are major factors constraining rice production. Here, we provide an overview of recent progress in functional genomics research and the genetic improvements of insect resistance in rice. To date, many insect resistance genes have been identified in rice, and 14 such genes have been cloned via a map-based cloning approach. The proteins encoded by these genes perceive the effectors of insect and activate the defense pathways, including the expression of defense-related genes, including mitogen-activated protein kinase, plant hormone, and transcription factors; and defense mechanism against insects, including callose deposition, trypsin proteinase inhibitors (TryPIs), secondary metabolites, and green leaf volatiles (GLVs). These ongoing functional genomic studies provide insights into the molecular basis of rice–insect interactions and facilitate the development of novel insect-resistant rice varieties, improving long-term control of insect pests in this crucial crop.

Different soybean cultivars respond differentially to damage in a herbivore-specific manner and decreas herbivore performance

This study demonstrates that soybean cultivars respond differentially to damage in a herbivore-specific manner, and trigger responses decreasing herbivore performance. Soybean crops are affected by a great number of insect herbivores, resulting in devastating yield losses. Secondary metabolites like proteinase inhibitors and phenolic compounds are part of plants’ defense mechanisms against insect pests. However, the specificity of soybean defense responses to different attacking herbivores is poorly known. To investigate species-specific foliage responses to herbivory, we used two different commercial soybean cultivars (DM 4210 and DM 5.8i) widely used in Argentina with diverse susceptibility to insects’ attack and two species of phytophagous insects, thrips (Caliothrips phaseoli; Thysanoptera) and lepidopteran larvae (Spodoptera frugiperda; Lepidoptera) with a different way of feeding. Benzoic acid derivative levels were increased by damage of both insect species in the foliage of the field-grown soybean cultivars, whereas trypsin protease inhibitors activity was induced in cultivar (cv) DM 4210 by fall armyworm damage and malonyl genistein content in cv DM 5.8i after thrips’ attack. Although survivorship and mass of fall armyworm larvae were not differentially affected in field conditions by soybean cultivars, larvae reared in the laboratory that fed on cv DM 5.8i gained more mass than those on DM 4210. Conversely, thrips performance, natural colonization, and preference of feeding were higher on cv DM 4210 than on cv DM 5.8i. The differential effects of soybean cultivars on insectspecies’ performance were explained not only by induced defenses, but also by differences of constitutive defenses between cultivars. This study demonstrated that soybean cultivars responded differentially to damage in a herbivore-specific manner, and triggered responses decreased herbivore performance.

Purification and characterization of protease inhibitors from rice bean (Vigna umbellata) and their efficacy against Spodoptera litura (Fabricius) gut proteinases

A protease inhibitor from rice bean was isolated and purified to assess its potential against gut proteases of Spodoptera litura, a devastating pest of several economically important crops globally. The purified inhibitor showed a single band protein on SDS-PAGE corresponding to molecular weight of 24.0 kDa. The inhibitor was purified to near homogeneity with 181.55 fold purification and final yield of 29.18 per cent. The inhibitory potential of purified rice bean trypsin protease inhibitor on larvae of Spodoptera gut proteases was studied which showed maximum azocaseinolytic (1.93U), trypsin (0.66U) and chymotrypsin activity (0.37 U) in second larval instar which gradually decreased upto late fifth larval instar stage. Inhibitory assay revealed that rice bean trypsin inhibitors were strong inhibitor of Spodoptera litura and inhibited more than 80 per cent for trypsin and around 69 per cent for chymotrypsin activity. To further determine the efficacy of rice bean protease inhibitors, feeding assays were conducted by adding rice bean flour in larval artificial diet. High mortality rate was observed in Spodoptera litura larvae after 72 hrs when rice bean was given as sole diet (100% rice bean composition). The results obtained from present study provide important clues in designing strategies for sustainable use of rice bean protease inhibitors in developing insect-tolerant transgenic plants.

Pathogen-Mediated Tritrophic Interactions: Baculovirus-Challenged Caterpillars Induce Higher Plant Defenses than Healthy Caterpillars.

Although the tritrophic interactions of plants, insect herbivores and their natural enemies have been intensely studied for several decades, the roles of entomopathogens in their indirect modulation of plant-insect relationships is still unclear. Here, we employed a sublethal dose of a baculovirus with a relatively broad host range (AcMNPV) to explore if feeding by baculovirus-challenged Helicoverpa zea caterpillars induces direct defenses in the tomato plant. We examined induction of plant defenses following feeding by H. zea, including tomato plants fed on by healthy caterpillars, AcMNPV-challenged caterpillars, or undamaged controls, and subsequently compared the transcript levels of defense related proteins (i.e., trypsin proteinase inhibitors, peroxidase and polyphenol oxidase) and other defense genes (i.e., proteinase inhibitor II and cysteine proteinase inhibitor) from these plants, in addition to comparing caterpillar relative growth rates. As a result, AcMNPV-challenged caterpillars induced the highest plant anti-herbivore defenses. We examined several elicitors and effectors in the secretions of these caterpillars (i.e., glucose oxidase, phospholipase C, and ATPase hydrolysis), which surprisingly did not differ between treatments. Hence, we suggest that the greater induction of plant defenses by the virus-challenged caterpillars may be due to differences in the amount of these secretions deposited during feeding or to some other unknown factor(s).

Specificity of Herbivore Defense Responses in a Woody Plant, Black Poplar (Populus nigra)

The specificity of woody plant defense responses to different attacking herbivores is poorly known. We investigated the responses of black poplar (Populus nigra) to leaf feeding by three lepidopteran species (Lymantria dispar, Laothoe populi and Amata mogadorensis) and two leaf beetle species (Phratora vulgatissima and Chrysomela populi). Of the direct defenses monitored, increases in trypsin protease inhibitor activity and the salicinoid salicin were triggered by herbivore damage, but this was not herbivore-specific. Moreover, the majority of leaf salicinoid content was present constitutively and not induced by herbivory. On the other hand, volatile emission profiles did vary among herbivore species, especially between coleopterans and lepidopterans. Monoterpenes and sesquiterpenes were induced in damaged and adjacent undamaged leaves, while the emission of green leaf volatiles, aromatic and nitrogen-containing compounds (known to attract herbivore enemies) was restricted to damaged leaves. In conclusion, indirect defenses appear to show more specific responses to attacking herbivores than direct defenses in this woody plant.

Nutritional and Antinutritional Factors of Some Pulses Seed and Their Effects on Human Health

The Food and Agriculture Organization (FAO) realizes about fifteen pulses (primary and minor) such as dry peas, black beans, chickpeas, roman bean, beans, and lentils etc. cultivated worldwide over a hundred countries. Similarly pulses especially bean, chickpea and lentil are really popular in Turkish Cuisine culture and there are many meals made with the pulses in Turkey. Thus, seed quality of the pulses is too significant for producers to be sold at higher prices. Moreover, it is also important for human health with over nutrition rates and has high levels of minerals as well as folate and other B-vitamins and diminished rate of diseases particularly resulting from obesity due to the high level of fiber and protein rates. But pulses seeds have also antinutritional factors such as some enzyme inhibitors (trypsin and chymotrypsin proteinase inhibitors), phytic acid, flatulence factors, lectins and saponins, and some different allergens. The factors cause some health problem such as mineral (Fe, Zn, Mg etc.) deficiency of human body. So, we prepared the review to show situation of some pulses in Turkey and in the world and to explain some antinutritional factors (secondary metabolites) of pulses seeds besides some nutritional characteristics.

Field-grown soybean induces jasmonates and defensive compounds in response to thrips feeding and solar UV-B radiation

Solar UV-B radiation has been reported to enhance constitutive and inducible plant defenses against herbivore insects in many species. However, the induction of plant defenses depends on the phytohormone profile induced by the specific herbivore feeding guild. No study has shown the impact of soybean leaf chemical defenses induced by thrips herbivory in combination with solar UV-B radiation on thrips performance. To uncover plant responses to herbivory in crop conditions, we proposed the hypothesis that solar UV-B radiation will increase constitutive and inducible defenses and phytohormones related with defenses in field-grown soybean, therefore affecting thrips performance. In this study two soybean cultivars (cv.) were grown in field conditions under attenuated or solar UV-B radiation and damaged by 6 days of herbivory of Caliothrips phaseoli. Our field experiments showed similar survivorship levels of thrips that fed on foliage grown under either attenuated or solar UV-B radiation, while survivorship of thrips that fed on cv. Williams was lower than those that fed on cv Charata. Cv Williams produced different flavonols and higher trypsin protease inhibitor (TPI) activity levels and more genistin than cv Charata. The increment of jasmonic acid (JA)-regulated defenses against insects in foliage of cv Williams was explained by the induction of JA and JA-Ile after herbivory and solar UV-B exposure. Independently of the UV-B environment herbivory induced salicylic acid (SA) and 12-oxo-phytodienoic acid (cis-OPDA) in both cvs. To our knowledge no study before has showed a complete profile of defensive hormones and defensive compounds induced by thrips feeding and solar UV-B.

OsLRR-RLK1, an early responsive leucine-rich repeat receptor-like kinase, initiates rice defense responses against a chewing herbivore.

Plants are constantly exposed to a variety of environmental stresses, including herbivory. How plants perceive herbivores on a molecular level is poorly understood. Leucine-rich repeat receptor-like kinases (LRR-RLKs), the largest subfamily of RLKs, are essential for plants to detect external stress signals, and may therefore also be involved in herbivore perception. Here, we employed RNA interference silencing, phytohormone profiling and complementation, as well as herbivore resistance assays, to investigate the requirement of an LRR-RLK for the initiation of rice (Oryza sativa) defenses against the chewing herbivore striped stem borer (SSB) Chilo suppressalis. We discovered a plasma membrane-localized LRR-RLK, OsLRR-RLK1, whose transcription is strongly up-regulated by SSB attack and treatment with oral secretions of Spodoptera frugiperda. OsLRR-RLK1 acts upstream of mitogen-activated protein kinase (MPK) cascades, and positively regulates defense-related MPKs and WRKY transcription factors. Moreover, OsLRR-RLK1 is a positive regulator of SSB-elicited, but not wound-elicited, levels of jasmonic acid and ethylene, trypsin protease inhibitor activity and plant resistance towards SSB. OsLRR-RLK1 therefore plays an important role in herbivory-induced defenses of rice. Given the well-documented role of LRR-RLKs in the perception of stress-related molecules, we speculate that OsLRR-RLK1 may be involved in the perception of herbivory-associated molecular patterns.

Expressing OsMPK4 Impairs Plant Growth but Enhances the Resistance of Rice to the Striped Stem Borer Chilo suppressalis.

Mitogen-activated protein kinases (MPKs) play a central role not only in plant growth and development, but also in plant responses to abiotic and biotic stresses, including pathogens. Yet, their role in herbivore-induced plant defenses and their underlying mechanisms remain largely unknown. Here, we cloned a rice MPK gene, OsMPK4, whose expression was induced by mechanical wounding, infestation of the striped stem borer (SSB) Chilo suppressalis, and treatment with jasmonic acid (JA), but not by treatment with salicylic acid (SA). The overexpression of OsMPK4 (oe-MPK4) enhanced constitutive and/or SSB-induced levels of JA, jasmonoyl-l-isoleucine (JA-Ile), ethylene (ET), and SA, as well as the activity of elicited trypsin proteinase inhibitors (TrypPIs), and reduced SSB performance. On the other hand, compared to wild-type plants, oe-MPK4 lines in the greenhouse showed growth retardation. These findings suggest that OsMPK4, by regulating JA-, ET-, and SA-mediated signaling pathways, functions as a positive regulator of rice resistance to the SSB and a negative regulator of rice growth.

Proteomic analysis of labial saliva of the generalist cabbage looper (Trichoplusia ni) and its role in interactions with host plants

Insect saliva is one of the first secretions to come in contact with plants during feeding. The composition and role of caterpillar saliva has not been as thoroughly studied as that of sucking insects. This study focuses on characterizing the proteome of the cabbage looper (Trichoplusia ni) saliva using iTRAQ labeling and LC-MS/MS. We also measured how the saliva proteome changed when larvae were reared on different diets – cabbage, tomato, and an artificial pinto bean diet. We identified 254 proteins in the saliva out of which 63 were differentially expressed. A large percentage (56%) of the proteins identified function in protein metabolism, followed by proteins involved in vesicle transport (6%) and oxidoreductase activity (5%), among other categories. Several proteins identified are antioxidants or reactive oxygen species (ROS) scavengers. Among these ROS scavengers, we identified a catalase and further analyzed its gene expression and enzymatic activity. We also applied commercial, purified catalase on tomato and measured the activity of defensive proteins – trypsin proteinase inhibitor, polyphenol oxidase and peroxidase. Catalase gene expression was significantly higher in the salivary glands of larvae fed on tomato. Also, catalase suppressed the induction of tomato trypsin proteinase inhibitor levels, but not the induction of polyphenol oxidase or peroxidase. These results add to our understanding of proteomic plasticity in saliva and its role in herbivore offense against plant defenses.

Solar UV-B radiation and ethylene play a key role in modulating effective defenses against Anticarsia gemmatalis larvae in field-grown soybean.

Solar UV-B radiation has been reported to enhance plant defenses against herbivore insects in many species. However, the mechanism and traits involved in the UV-B mediated increment of plant resistance are unknown in crops species, such as soybean. Here, we studied defense-related responses in undamaged and Anticarsia gemmatalis larvae-damaged leaves of two soybean cultivars grown under attenuated or full solar UV-B radiation. We determined changes in jasmonates, ethylene (ET), salicylic acid, trypsin protease inhibitor activity, flavonoids, and mRNA expression of genes related with defenses. ET emission induced by Anticarsia gemmatalis damage was synergistically increased in plants grown under solar UV-B radiation and was positively correlated with malonyl genistin concentration, trypsin proteinase inhibitor activity and expression of IFS2, and the pathogenesis protein PR2, while was negatively correlated with leaf consumption. The precursor of ET, aminocyclopropane-carboxylic acid, applied exogenously to soybean was sufficient to strongly induce leaf isoflavonoids. Our results showed that in field-grown soybean isoflavonoids were regulated by both herbivory and solar UV-B inducible ET, whereas flavonols were regulated by solar UV-B radiation only and not by herbivory or ET. Our study suggests that, although ET can modulate UV-B-mediated priming of inducible plant defenses, some plant defenses, such as isoflavonoids, are regulated by ET alone.

Flower-specific jasmonate signaling regulates constitutive floral defenses in wild tobacco

Optimal defense (OD) theory predicts that within a plant, tissues are defended in proportion to their fitness value and risk of predation. The fitness value of leaves varies greatly and leaves are protected by jasmonate (JA)-inducible defenses. Flowers are vehicles of Darwinian fitness in flowering plants and are attacked by herbivores and pathogens, but how they are defended is rarely investigated. We used Nicotiana attenuata, an ecological model plant with well-characterized herbivore interactions to characterize defense responses in flowers. Early floral stages constitutively accumulate greater amounts of two well-characterized defensive compounds, the volatile (E)-α-bergamotene and trypsin proteinase inhibitors (TPIs), which are also found in herbivore-induced leaves. Plants rendered deficient in JA biosynthesis or perception by RNA interference had significantly attenuated floral accumulations of defensive compounds known to be regulated by JA in leaves. By RNA-seq, we found a JAZ gene, NaJAZi, specifically expressed in early-stage floral tissues. Gene silencing revealed that NaJAZi functions as a flower-specific jasmonate repressor that regulates JAs, (E)-α-bergamotene, TPIs, and a defensin. Flowers silenced in NaJAZi are more resistant to tobacco budworm attack, a florivore. When the defensin was ectopically expressed in leaves, performance of Manduca sexta larvae, a folivore, decreased. NaJAZi physically interacts with a newly identified NINJA-like protein, but not the canonical NINJA. This NINJA-like recruits the corepressor TOPLESS that contributes to the suppressive function of NaJAZi on floral defenses. This study uncovers the defensive function of JA signaling in flowers, which includes components that tailor JA signaling to provide flower-specific defense.

Salt-tolerant and -sensitive alfalfa (Medicago sativa) cultivars have large variations in defense responses to the lepidopteran insect Spodoptera litura under normal and salt stress condition.

In nature, plants are often exposed to multiple stress factors at the same time. Yet, little is known about how plants modulate their physiology to counteract simultaneous abiotic and biotic stresses, such as soil salinity and insect herbivory. In this study, insect performance bioassays, phytohormone measurements, quantification of transcripts, and protein determination were employed to study the phenotypic variations of two alfalfa (Medicago sativa) cultivars in response to insect Spodoptera litura feeding under normal and salt stress condition. When being cultivated in normal soil, the salt-tolerant alfalfa cultivar Zhongmu-1 exhibited lower insect resistance than did the salt-sensitive cultivar Xinjiang Daye. Under salinity stress, the defense responses of Xinjiang Daye were repressed, whereas Zhongmu-1 did not show changes in resistance levels. It is likely that salinity influenced the resistance of Xinjiang Daye through suppressing the accumulation of jasmonic acid-isoleucine (JA-Ile), which is the bioactive hormone inducing herbivore defense responses, leading to attenuated trypsin proteinase inhibitor (TPI) activity. Furthermore, exogenous ABA supplementation suppressed the insect herbivory-induced JA/JA-Ile accumulation and levels of JAR1 (jasmonate resistant 1) and TPI, and further decreased the resistance of Xinjiang Daye, whereas Zhongmu-1 showed very little response to the increased ABA level. We propose a mechanism, in which high levels of abscisic acid induced by salt treatment may affect the expression levels of JAR1 and consequently decrease JA-Ile accumulation and thus partly suppress the defense of Xinjiang Daye against insects under salt stress. This study provides new insight into the mechanism by which alfalfa responds to concurrent abiotic and biotic stresses.

Solar UV-B radiation modulates chemical defenses against Anticarsia gemmatalis larvae in leaves of field-grown soybean

Although it is well known that solar ultraviolet B (UV-B) radiation enhances plant defenses, there is less knowledge about traits that define insect resistance in field-grown soybean. Here we study the effects of solar UV-B radiation on: a) the induction of phenolic compounds and trypsin proteinase inhibitors (TPI) in soybean undamaged leaves or damaged by Anticarsia gemmatalis neonates during six days, and b) the survival and mass gain of A. gemmatalis larvae that fed on soybean foliage. Two soybean cultivars (cv.), Charata and Williams, were grown under plastic with different transmittance to solar UV-B radiation, which generated two treatments: ambient UV-B (UVB+) and reduced UV-B (UVB−) radiation. Solar UV-B radiation decreased survivorship by 30% and mass gain by 45% of larvae that fed on cv. Charata, but no effect was found in those larvae that fed on cv. Williams. TPI activity and malonyl genistin were induced by A. gemmatalis damage in both cultivars, but solar UV-B radiation and damage only synergistically increased the induction of these compounds in cv. Williams. Although TPI activity and genistein derivatives were induced by herbivory, these results did not explain the differences found in survivorship and mass gain of larvae that fed on cv. Charata. However, we found a positive association between lower larval performance and the presence of two quercetin triglycosides and a kaempferol triglycoside in foliage of cv. Charata, which were identified by HPLC-DAD/MS2. We conclude that exclusion of solar UV-B radiation reduce resistance to A. gemmatalis, due to a reduction in flavonol concentration in a cultivar that has low levels of genistein derivatives like cv. Charata.

Application and bioactive properties of CaTI, a trypsin inhibitor from Capsicum annuum seeds: membrane permeabilization, oxidative stress and intracellular target in phytopathogenic fungi cells.

During the last few years, a growing number of antimicrobial peptides have been isolated from plants and particularly from seeds. Recent results from our laboratory have shown the purification of a new trypsin inhibitor, named CaTI, from chilli pepper (Capsicum annuum L.) seeds. This study aims to evaluate the antifungal activity and mechanism of action of CaTI on phytopathogenic fungi and detect the presence of protease inhibitors in other species of this genus. Our results show that CaTI can inhibit the growth of the phytopathogenic fungi Colletotrichum gloeosporioides and C. lindemuthianum. CaTI can also permeabilize the membrane of all tested fungi. When testing the inhibitor on its ability to induce reactive oxygen species, an induction of reactive oxygen species (ROS) and nitric oxide (NO) particularly in Fusarium species was observed. Using CaTI coupled to fluorescein isothiocyanate (FITC), it was possible to determine the presence of the inhibitor inside the hyphae of the Fusarium oxysporum fungus. The search for protease inhibitors in other Capsicum species revealed their presence in all tested species. This paper shows the antifungal activity of protease inhibitors such as CaTI against phytopathogenic fungi. Antimicrobial peptides, among which the trypsin protease inhibitor family stands out, are present in different species of the genus Capsicum and are part of the chemical arsenal that plants use to defend themselves against pathogens. © 2017 Society of Chemical Industry.

Ratoon rice generated from primed parent plants exhibit enhanced herbivore resistance.

Rice ratooning is practiced in many rice-growing countries for achieving increased rice production with limited labour input. Here, we report that attack by insect herbivores, or treatment with a defense signaling compound in parent plants, can prime anti-herbivore defense responses in subsequent ratoon plants. We compared the defense responses of rice ratoons generated from parent plants that had been either infested by Cnaphalocrocis medinalis (rice leaffolder, LF) caterpillars or treated with methyl jasmonate (MeJA) during vegetative growth, with ratoons generated from control parent plants. Ratoon plants generated from parents receiving prior LF infestation or MeJA treatment exhibited higher jasmonic acid (JA) levels, as well as elevated levels of transcripts of defense-related genes associated with JA signaling. In addition, elevated activities of peroxidase, polyphenol oxidase and trypsin protease inhibitor were observed, as well as enhanced resistance towards subsequent LF infestation. Pre-priming of ratoon defense responses was significantly reduced in plants where expression of OsAOS (allene oxide synthase, involved in JA biosynthesis) or OsCOI1 (CORONATINE INSENSITIVE1, involved in JA perception) was inhibited by RNA interference. Our results indicate that herbivore exposure or MeJA treatment in rice parent plants enhances anti-herbivore resistance in subsequently generated ratoons through priming of JA-mediated defenses.

Fall Armyworm-Associated Gut Bacteria Modulate Plant Defense Responses.

Mechanical damage caused by insect feeding along with components present in insect saliva and oral secretions are known to induce jasmonic acid-mediated defense responses in plants. This study investigated the effects of bacteria from oral secretions of the fall armyworm Spodoptera frugiperda on herbivore-induced defenses in tomato and maize plants. Using culture-dependent methods, we identified seven different bacterial isolates belonging to the family Enterobacteriacea from the oral secretions of field-collected caterpillars. Two isolates, Pantoea ananatis and Enterobacteriaceae-1, downregulated the activity of the plant defensive proteins polyphenol oxidase and trypsin proteinase inhibitors (trypsin PI) but upregulated peroxidase (POX) activity in tomato. A Raoultella sp. and a Klebsiella sp. downregulated POX but upregulated trypsin PI in this plant species. Conversely, all of these bacterial isolates upregulated the expression of the herbivore-induced maize proteinase inhibitor (mpi) gene in maize. Plant treatment with P. ananatis and Enterobacteriaceae-1 enhanced caterpillar growth on tomato but diminished their growth on maize plants. Our results highlight the importance of herbivore-associated microbes and their ability to mediate insect plant interactions differently in host plants fed on by the same herbivore.

Nematode Root Herbivory in Tomato Increases Leaf Defenses and Reduces Leaf Miner Oviposition and Performance

The outcome of plant-mediated interactions among herbivores from several feeding guilds has been studied intensively. However, our understanding on the effects of nematode root herbivory on leaf miner oviposition behavior and performance remain limited. In this study, we evaluated whether Meloidogyne incognita root herbivory affects Tuta absoluta oviposition preference on Solanum lycopersicum plants and the development of the resulting offspring. To investigate the M. incognita-herbivory induced plant systemic responses that might explain the observed biological effects, we measured photosynthetic rates, leaf trypsin protease inhibitor activities, and analyzed the profile of volatiles emitted by the leaves of root-infested and non-infested plants. We found that T. absoluta females avoided laying eggs on the leaves of root-infested plants, and that root infestation negatively affected the pupation process of T. absoluta. These effects were accompanied by a strong suppression of leaf volatile emissions, a decrease in photosynthetic rates, and an increase in the activity of leaf trypsin protease inhibitors. Our study reveals that root attack by nematodes can shape leaf physiology, and thereby increases plant resistance.

Pathways for plant‐mediated negative feedback to insect herbivores: accounting for non‐linear effects of larval density on plant quality and quantity

AbstractChanges in plant traits induced by herbivore damage can produce a negative feedback to increasing herbivore densities. Several aspects of these plant‐mediated feedbacks are predicted to influence herbivore population dynamics, but the degree to which feedbacks are non‐linear, whether their strength varies among plant genotypes, and whether they occur via changes in the quality of plant tissue or the amount of tissue available have rarely been examined. In this study, we damaged five genotypes of the perennial weed Carolina horsenettle, Solanum carolinense L. (Solanaceae), with eight densities of the false potato beetle, Leptinotarsa juncta (Germar) (Coleoptera: Chysomelidae, Chrysomelini). To account for plant quantity available to beetles, we measured the leaf area of each plant after imposing larval density treatments. We then measured the oviposition preference of L. juncta adults for damaged vs. undamaged plants and the relative growth rate (RGR) of L. juncta larvae on each plant, as well as plant trypsin proteinase inhibitor (tryPI) expression. We found that L. juncta females strongly preferred to oviposit on undamaged S. carolinense, and that preference for a plant decreased as the density of damaging larvae increased. In addition, we found decreased larval RGR and increased production of tryPIs with greater initial larval density. Effects of larval density on insect preference, performance, and tryPI expression were linear and did not vary among plant genotypes. Larval density effects were not solely due to reduced plant quantity, as plant leaf area had no effect on oviposition preference or larval performance. This suggests that effects were most likely due to changes in the quality of plant tissue. Thus, negative feedback on increasing larval density can be mediated by the effects of induced resistance on both oviposition preference and larval performance. Published models suggest that the linear, quality‐mediated feedbacks observed in this experiment are predicted to stabilize herbivore population dynamics.