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Chemical elicitors can increase plant defense against herbivorous insects and pathogens. The use of synthetic chemical elicitors is likely to be an alternative to traditional pesticides for crop pest control. However, only a few synthetic chemicals are reported to protect plants by regulating signaling pathways, increasing the levels of defense metabolites and interfering with insect feeding. Here, we found that the exogenous application of a phenoxycarboxylic compound, 4-chlorophenoxyacetic acid (4-CPA), can induce chemical defenses to protect rice plants from white-backed planthoppers (WBPH, Sogatella furcifera). Four-CPA was rapidly taken up by plant roots and degraded to 4-chlorophenol (4-CP). Four-CPA treatment modulated the activity of peroxidase (POD) and directly induced the deposition of lignin-like polymers using hydrogen peroxide (H2O2) as the electron acceptor. The polymers, which are thought to prevent the planthopper's stylet from reaching the phloem, were broken down by WBPH nymphs. Meanwhile, 4-CPA increased the levels of flavonoids and phenolamines (PAs). The increased flavonoids and PAs, together with the degradation product of the polymers, avoided nymphal feeding and prolonged the nymphal period for 1 day. These results indicate that 4-CPA has the potential to be used as a chemical elicitor to protect rice from planthoppers. Moreover, these findings also open a pathway for molecule structure design of phenoxycarboxylic compounds as chemical elicitors. [ABSTRACT FROM AUTHOR]

Simple Summary: Acibenzolar-S-methyl is an analogue of salicylic acid, and it is known as a plant elicitor able to induce plant endogenous defences against plant pathogens. Recently, it has been shown to also affect phloem-feeder pests, even though the mechanism is still unclear. Pear psylla (Cacopsylla pyri) is a serious threat for pear production in Europe, and its control is usually based on the use of chemical insecticides. The development of novel innovative control approaches is becoming more and more important, especially in integrated pest management. The present work investigated the possible indirect influence of acibenzolar-S-methyl, through the expression of pear Pathogenesis-Related protein (PR) coding genes, on the probing behaviour and on the survival of C. pyri nymphs and adults feeding on pear potted plants. The minor effects observed on the pest would suggest that acibenzolar-S-methyl cannot be used against psyllas, but it might be recommended on pear orchards in the primary control of other targets such as fire blight disease. European pear psylla, Cacopsylla pyri, is one of the worst pests of pear in Europe. We investigated whether acibenzolar-S-methyl (ASM) application on pear plants might affect the behaviour in C. pyri. The elicitor was applied on pear potted plants, and after 48 h, we confirmed the ASM-mediated induction of several Pathogenesis-Related protein (PR) coding genes. At the same time, an in-depth analysis was performed on the probing behaviour of adults and nymphs of C. pyri on ASM-treated pear plants by the EPG-DC system, as well as the assessment of young nymphs' survival 7 days after the ASM application. The elicitor application weakly interfered with C. pyri nymphs probing behaviour and survival, while it did not affect adult stages. These data confirm previous observations obtained on C. pyricola and suggest that the elicitor does not represent a viable tool in the control of pear psylla species, especially if used alone, but it might be used in integrated management strategies focused on other plant pathogens such as Erwinia amylovora. [ABSTRACT FROM AUTHOR]

Applying chemical elicitors is considered a promising approach for controlling pests in the field. Our previous studies have shown that gibberellin (GA) signaling positively regulates the resistance of rice (Oryza sativa) to the brown planthopper (BPH) Nilaparvata lugens (Stål). Yet, whether the exogenous application of GAs can enhance the resistance of rice to BPH remains unknown. Here, we investigated the influence of exogenous GA3 on both defense responses in rice and BPH performance. We found that pretreating rice with GA3 decreased transcript levels of a mitogen-activated protein kinase (MAPK) and three WRKY transcription factors, as well as levels of BPH-elicited jasmonic acid (JA) and three phenolic acids but increased the release of ethylene. Moreover, GA3 treatment negatively affected the survival and development of BPH nymphs as well as the fecundity of BPH female adults. These findings suggest that GA3 promotes the resistance of rice to BPH and may, thus, be used to improve pest management in rice. [ABSTRACT FROM AUTHOR]

European pear psylla, Cacopsylla pyri, is one of the worst pests of pear in Europe. We investigated whether acibenzolar-S-methyl (ASM) application on pear plants might affect the behaviour in C. pyri. The elicitor was applied on pear potted plants, and after 48 h, we confirmed the ASM-mediated induction of several Pathogenesis-Related protein (PR) coding genes. At the same time, an in-depth analysis was performed on the probing behaviour of adults and nymphs of C. pyri on ASM-treated pear plants by the EPG-DC system, as well as the assessment of young nymphs’ survival 7 days after the ASM application. The elicitor application weakly interfered with C. pyri nymphs probing behaviour and survival, while it did not affect adult stages. These data confirm previous observations obtained on C. pyricola and suggest that the elicitor does not represent a viable tool in the control of pear psylla species, especially if used alone, but it might be used in integrated management strategies focused on other plant pathogens such as Erwinia amylovora.

Marine microorganisms have proven to be a source of new natural products with a wide spectrum of biological activities relevant in different industrial sectors. The ever-increasing number of sequenced microbial genomes has highlighted a discrepancy between the number of gene clusters potentially encoding the production of natural products and the actual number of chemically characterized metabolites for a given microorganism. Homologous and heterologous expression of these biosynthetic genes, which are often silent under experimental laboratory culture conditions, may lead to the discovery of new cryptic natural products of medical and biotechnological interest. Several new genetic and cultivation-based strategies have been developed to meet this challenge. The OSMAC approach (one strain—many compounds), based on modification of growth conditions, has proven to be a powerful strategy for the discovery of new cryptic natural products. As a direct extension of this approach, the addition of chemical elicitors or epigenetic modifiers have also been used to activate silent genes. This review looks at the structures and biological activities of new cryptic metabolites from marine-derived microorganisms obtained using the OSMAC approach, the addition of chemical elicitors, and enzymatic inhibitors and epigenetic modifiers. It covers works published up to June 2021.

Synthetic chemical elicitors, so called plant strengtheners, can protect plants from pests and pathogens. Most plant strengtheners, act by modifying defense signaling pathways, and little is known about other mechanisms by which they may increase plant resistance. Moreover, whether plant strengtheners that enhance insect resistance actually enhance crop yields is often unclear. Here, we uncover how a mechanism by which 4-fluorophenoxyacetic acid (4-FPA) protects cereals from piercing-sucking insects and thereby increases rice yield in the field. Four-FPA does not stimulate hormonal signaling, but modulates the production of peroxidases, H2O2, and flavonoids and directly triggers the formation of flavonoid polymers. The increased deposition of phenolic polymers in rice parenchyma cells of 4-FPA-treated plants is associated with a decreased capacity of the white-backed plant hopper (WBPH) Sogatella furciferato reach the plant phloem. We demonstrate that application of 4-PFA in the field enhances rice yield by reducing the abundance of, and damage caused by, insect pests. We demonstrate that 4-FPA also increases the resistance of other major cereals such as wheat and barley to piercing-sucking insect pests. This study unravels a mode of action by which plant strengtheners can suppress herbivores and increase crop yield. We postulate that this represents a conserved defense mechanism of plants against piercing-sucking insect pests, at least in cereals. [ABSTRACT FROM AUTHOR]

Defense induction by exogenous applications of natural plant defense elicitors is an alternative pest control method. Such deployments not only provide resistance against herbivores but also attract their natural enemies. The influences of different doses of the plant defense elicitor cis-jasmone (CJ) (25, 50, 100 g/ha and an untreated control) on cooccurring sucking cotton, Gossypium hirsutum Linnaeus, insect pests from different feeding guilds (Thrips tabaci, Aphis gossypii, Empoasca decipiens) and their predators (Aeolothrips intermedius, Chrysoperla carnea, Coccinella septempunctata) were examined under field conditions in 2012 and 2013. CJ treatments, coinciding with different plant growth stages, were made per growing season. The abundance of apterous A. gossypii was lower on CJ-sprayed cotton plants than on untreated control plants. Similarly, the overall abundance of T. tabaci was lower on treated cotton plants irrespective of the tested dose comparing with untreated control plants. Empoasca decipiens abundance was lowest on plants treated with the lowest CJ dose (25 g/ha). An attractive effect of CJ treatments on the predatory thrips A. intermedius was detected; its highest abundances were recorded on plants treated with 100 g/ha CJ. The highest abundances of C. carnea were detected on plants treated with 100 g/h CJ in 2012, whereas no such dose-specific attraction was recorded in 2013. CJ treatments had no significant effect on C. septempunctata and alate A. gossypii abundances. The different CJ doses used had no phytotoxic effects on cotton plants and cotton yield. The results are discussed in terms of possible CJ deployment in cotton pest management. [ABSTRACT FROM AUTHOR]

Several 3,5-disubstituted isoxazoles were obtained in good yields by regiospecific 1,3-dipolar cycloaddition reactions between aromatic nitrile oxides, generated in situ from the corresponding hydroxyimidoyl chlorides, with non-symmetrical activated alkynes in the presence of catalytic amounts of copper(I) iodide. Effects of 3,5-disubstituted isoxazoles on nitric oxide and reactive oxygen species generation in Arabidopsis tissues was studied using specific diaminofluoresceine dyes as fluorescence indicators.

Inducible plant defense is a beneficial strategy for plants, which imply that plants should allocate resources from growth and reproduction to defense when herbivores attack. Plant ecologist has often studied defense responses in wild populations by biomass clipping experiments, whereas laboratory and greenhouse experiments in addition apply chemical elicitors to induce defense responses. To investigate whether field ecologists could benefit from methods used in laboratory and greenhouse studies, we established a randomized block-design in a pine-bilberry forest in Western Norway. We tested whether we could activate defense responses in bilberry ( Vaccinium myrtillus) by nine different treatments using clipping (leaf tissue or branch removal) with or without chemical treatment by methyljasmonate (Me JA). We subsequently measured consequences of induced defenses through vegetative growth and insect herbivory during one growing season. Our results showed that only Me JA-treated plants showed consistent defense responses through suppressed vegetative growth and reduced herbivory by leaf-chewing insects, suggesting an allocation of resources from growth to defense. Leaf tissue removal reduced insect herbivory equal to the effect of the MeJa treatments, but had no negative impact on growth. Branch removal did not reduce insect herbivory or vegetative growth. MeJa treatment and clipping combined did not give an additional defense response. In this study, we investigated how to induce defense responses in wild plant populations under natural field conditions. Our results show that using the chemical elicitor Me JA, with or without biomass clipping, may be a better method to induce defense response in field experiments than clipping of leaves or branches that often has been used in ecological field studies. [ABSTRACT FROM AUTHOR]

BACKGROUND Chemical elicitation is one of the most effective methods currently used to enrich plant foods in bioactive compounds. Methyl jasmonate ( MJ) has been described as a very useful elicitor of some plant compounds, polyphenols among them. The objective of this study was to determine the effects of pre-harvest MJ application on the increase in the main flavonoids and the antioxidant properties of black currant ( Ribes nigrum) cultivars. RESULTS Significant enhancement of individual and total anthocyanins was measured after elicitation with MJ, particularly when a concentration of 0.2 mmol L−1 was used. Total anthocyanins increased from 28288.74 ± 253.65 to 43561.08 ± 145.87 mg kg−1 in Ben Hope black currants after elicitation with 0.2 mmol L−1 MJ. Similarly, an increase from 35986.04 ± 287.98 to 41320.22 ± 109.38 mg kg−1 was estimated in Ben Alder cultivar. Black currant flavonols were not individually affected by the treatment; however, total flavonols increased from 3115.21 ± 12.11 to 3268.41 ± 8.91 mg kg−1 in Ben Hope and from 3016.38 ± 10.07 to 3110.95 ± 8.57 mg kg−1 in Ben Alder. Antioxidant properties of black currants as measured by DPPH and ABTS assays improved proportionally to the increase in flavonoid content after MJ elicitation. CONCLUSION Pre-harvest elicitation with MJ is proposed as a useful tool to enhance contents of anthocyanins and flavonols as well as free radical-scavenging activity of black currants. The functional black currants obtained here can be interesting for industry, for consumption as fresh fruits and for production of juice and jam. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Marine microorganisms have proven to be a source of new natural products with a wide spectrum of biological activities relevant in different industrial sectors. The ever-increasing number of sequenced microbial genomes has highlighted a discrepancy between the number of gene clusters potentially encoding the production of natural products and the actual number of chemically characterized metabolites for a given microorganism. Homologous and heterologous expression of these biosynthetic genes, which are often silent under experimental laboratory culture conditions, may lead to the discovery of new cryptic natural products of medical and biotechnological interest. Several new genetic and cultivation-based strategies have been developed to meet this challenge. The OSMAC approach (one strain—many compounds), based on modification of growth conditions, has proven to be a powerful strategy for the discovery of new cryptic natural products. As a direct extension of this approach, the addition of chemical elicitors or epigenetic modifiers have also been used to activate silent genes. This review looks at the structures and biological activities of new cryptic metabolites from marine-derived microorganisms obtained using the OSMAC approach, the addition of chemical elicitors, and enzymatic inhibitors and epigenetic modifiers. It covers works published up to June 2021. [ABSTRACT FROM AUTHOR]

This work reports the development of suspension culture system of transgenic Marsh grapefruit (Citrus paradisi Macf., Rutaceae) callus overexpressing bacterial phytoene synthase; and the use of this suspension culture to investigate the effects of β-cyclocitral on carotenoid content and composition. At a β-cyclocitral concentration of 0.5 mM and after ten days cultivation, analysis of the carotenoids showed a significant increase in the content of β-, α-carotene, and phytoene predominantly. The maximal increase in total provitamin A carotenoids content following β-cyclocitral application was ~2-fold higher than the control, reaching 245.8 μg/g DW. The trend for increased transcript levels of biosynthetic genes PSY and ZDS correlated with the enhancement of the content of these carotenes following β-cyclocitral treatment and GC-MS based metabolite profiling showed significant changes of metabolite levels across intermediary metabolism. These findings suggest that β-cyclocitral can act as a chemical elicitor, to enhance the formation of carotenes in citrus suspension-cultured cells (SCC), which could be utilized in studying the regulation of carotenoid biosynthesis and biotechnological application to the renewable production of nutritional carotenoids. The suspension cultured cells (SCC) of transgenic Marsh grapefruit callus treated with 0.5 mM β-cc for 12 days have a higher content of α/β-carotene and visually turn redder in coloration compared to the control SCC. Image 1 • β-cyclocitral application enhanced carotenes content of Citrus paradisi ' suspension-cultured cells (SCC). • β-cyclocitral application upregulate the expression of early carotenoid pathway genes in citrus SCC. • β-cyclocitral application affect intermediary metabolite pools of citrus SCC. [ABSTRACT FROM AUTHOR]

Bleached and unbleached pulp fibers were treated with 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO) mediated oxidation to obtain cellulose nanofibrils (CNFs). The resulting bleached and unbleached CNFs were mixed with salicylic acid (0, 5, 10, 20 wt%) before casting and freeze-drying or 3D-printing. A series of methods were tested and implemented to characterize the CNF materials and the porous structures loaded with salicylic acid. The CNFs were characterized with atomic force microscopy and laser profilometry, and release of salicylic acid was quantified with UV-visible absorbance spectroscopy, conductivity measurements, and inductive coupled plasma mass spectrometry (ICP-MS). Fourier-transform infrared spectroscopy (FTIR) complemented the analyses. Herein, we show that aerogels of bleached CNFs yield a greater release of salicylic acid, compared to CNF obtained from unbleached pulp. The results suggest that biodegradable constructs of CNFs can be loaded with a plant hormone that is released slowly over time, which may find uses in small scale agricultural applications and for the private home market. [ABSTRACT FROM AUTHOR]

Synthetic chemical elicitors, so called plant strengtheners, can protect plants from pests and pathogens. Most plant strengtheners act by modifying defense signaling pathways, and little is known about other mechanisms by which they may increase plant resistance. Moreover, whether plant strengtheners that enhance insect resistance actually enhance crop yields is often unclear. Here, we uncover how a mechanism by which 4-fluorophenoxyacetic acid (4-FPA) protects cereals from piercing-sucking insects and thereby increases rice yield in the field. Four-FPA does not stimulate hormonal signaling, but modulates the production of peroxidases, H 2 O 2 , and flavonoids and directly triggers the formation of flavonoid polymers. The increased deposition of phenolic polymers in rice parenchyma cells of 4-FPA-treated plants is associated with a decreased capacity of the white-backed planthopper (WBPH) Sogatella furcifera to reach the plant phloem. We demonstrate that application of 4-PFA in the field enhances rice yield by reducing the abundance of, and damage caused by, insect pests. We demonstrate that 4-FPA also increases the resistance of other major cereals such as wheat and barley to piercing-sucking insect pests. This study unravels a mode of action by which plant strengtheners can suppress herbivores and increase crop yield. We postulate that this represents a conserved defense mechanism of plants against piercing-sucking insect pests, at least in cereals., Competing Interests: The authors declare no competing interest.

Several 3,5-disubstituted isoxazoles were obtained in good yields by regiospecific 1,3-dipolar cycloaddition reactions between aromatic nitrile oxides, generated in situ from the corresponding hydroxyimidoyl chlorides, with non-symmetrical activated alkynes in the presence of catalytic amounts of copper(I) iodide. Effects of 3,5-disubstituted isoxazoles on nitric oxide and reactive oxygen species generation in Arabidopsis tissues was studied using specific diaminofluoresceine dyes as fluorescence indicators.