Plant Secondary Metabolites as Defense Tools against Herbivores for Sustainable Crop Protection

Understanding the structure and function of HPI, a rubber tree serine protease inhibitor, and its interaction with subtilisin

Protease inhibitors are crucial in regulating enzymatic activity and have extensive applications in medicine, biotechnology, and agriculture. This study characterizes a recombinant protease inhibitor from Hevea brasiliensis (rHPI), highlighting its unique structural features and inhibitory potential. Using Matrix-Assisted Laser Desorption/Ionization (MALDI) analysis, the inhibitor exhibits one distinct peak around 7.54 kDa. Enzymatic assays using N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide as a substrate confirmed the inhibitor's activity against subtilisin Carlsberg, a widely utilized serine protease in industry and biotechnology. The crystal structure of rHPI, resolved at 1.73 Å, reveals a topology closely resembling eglin c, including a single alpha-helix, two parallel beta-strands, and a distinctive binding loop spanning residues 40-51. Disordered regions at the N- and C-termini contribute to its structural uniqueness. Despite lacking disulfide bonds and featuring an Arg residue instead of Trp at the P'8 position, rHPI maintains a high affinity for subtilisin. Isothermal titration calorimetry (ITC) showed that this interaction is entropically driven. Molecular docking and dynamics simulations of the rHPI-subtilisin complex revealed the formation of antiparallel β-sheets, hydrogen bonding involving the protein backbone, and a salt bridge between His64 of subtilisin and Asp47 of rHPI. These findings provide valuable insights into the molecular basis of rHPI's inhibitory activity and offer a framework for the rational design of novel subtilisin inhibitors with potential applications in agricultural and industrial settings.

GLR3.6T807I Mutation of Casuarina equisetifolia Is Associated With a Decreased JA Response to Insect Feeding by Lymantria xylina

Lymantria xylina is the most important defoliator, damaging the effective coastal windbreak tree species Casuarina equisetifolia. However, the underlying genetic mechanisms through which C. equisetifolia responds to L. xylina attacks remain unknown. Here, we compared the transcriptional, phytohormone and metabolic differences between susceptible (S) and resistant (R) C. equisetifolia cultivars in response to L. xylina feeding. The main L. xylina-induced resistance in C. equisetifolia was a jasmonate (JA) response and JA synthesis was highly induced by L. xylina feeding at both the transcriptional and metabolic levels, thus promoting flavonoid accumulation. The JA response was highly activated by L. xylina feeding on the R but not in the S cultivar, although the JA signalling pathway was intact in both cultivars. We found a single amino acid mutation in the homologues of glutamate receptor-like protein 3.6 (CeGLR3.6T807I) in the S cultivar. Compared with the GLR3.6 homologues in the R cultivar, phosphorylation of CeGLR3.6T807I was not induced by insect feeding, leading to a decreased JA response in the S cultivar. Collectively, this study provides new insights into the function of CeGLR3.6 in regulating the JA response of C. equisetifolia to L. xylina feeding.

Tomato Defenses Under Stress: The Impact of Salinity on Direct Defenses Against Insect Herbivores

Abiotic stressors, such as salt stress, can reduce crop productivity, and when combined with biotic pressures, such as insect herbivory, can exacerbate yield losses. However, salinity-induced changes to plant quality and defenses can in turn affect insect herbivores feeding on plants. This study investigates how salinity stress in tomato plants (Solanum Lycopersicum cv. Better Boy) impacts the behavior and performance of a devastating insect pest, the tomato fruitworm caterpillar (Helicoverpa zea). Through choice assays and performance experiments, we demonstrate that salt-stressed tomato plants are poor hosts for H. zea, negatively affecting caterpillar feeding preferences and growth rates. While changes in plant nutritional quality were observed, the primary factor influencing insect performance appears to be direct ionic toxicity, which significantly impairs multiple life history parameters of H. zea including survival, pupation, adult emergence, and fecundity. Plant defense responses show complex interactions between salt stress and herbivory, with two proteinase inhibitor genes - PIN2 and AspPI, showing a higher induced response to insect herbivory under salt conditions. However, plant defenses do not seem to be the main driver of reduced caterpillar performance on salt-treated plants. Furthermore, we report reduced oviposition by H. zea moths on salt-treated plants, which was correlated with altered volatile emissions. Our findings reveal that H. zea exhibits optimal host selection behaviours for both larval feeding and adult oviposition decisions, which likely contribute to its success as an agricultural pest. This research provides insights into the complex interactions between abiotic stress, plant physiology, and insect behaviour, with potential implications for pest management strategies in saline agricultural environments.

Discovery of Sennidin B as a Potent Multitarget Inhibitor of Insect Chitinolytic Enzymes

Natural products with multitarget inhibitory activity against insect chitinolytic enzymes offer the potential for developing environmentally friendly insecticides. However, most inhibitors show limited efficacy, hindering their practical application. In this study, inspired by the dimeric structure of phlegmacin B1, sennidin B, a rhein analogue, was identified as an effective inhibitor of insect chitinolytic enzymes. Sennidin B exhibited a nanomolar Ki value (80 nM) against OfChi-h from Ostrinia furnacalis, showing at least a 600-fold improvement in potency compared to rhein. Molecular dynamics simulations revealed that sennidin B adopts a folded conformation within the enzyme's active site, enhancing binding affinity through π-π stacking interactions with a key tryptophan residue. Insecticidal assays demonstrated 100% mortality at 5 mM and suppression of larval development at 1 mM. This study positions sennidin B as a lead compound for the development of insecticides targeting the molting process and provides a strategy for the discovery of multitarget inhibitors.

Structure and release function of fragrance glands

Volatile compounds serve physiological, signaling, and defensive purposes in plants and have beneficial effects on the growth, reproduction, resistance, and yield of horticultural plants. They are released through fragrance glands and become gasses by passing through the plasma membrane, cell walls that contain water, and cuticle. Transporter proteins facilitate their transport and reduce the resistance of these barriers. They also regulate the rate of release and concentration of volatiles inside and outside of the membrane. However, there has been no summary of the structure and function of the fragrance glands of horticultural plants, as well as an introduction to the latest research progress on the mechanism of the transport of volatiles. This review focuses on the structure and function of the release of aromas in horticultural plants and explores the mechanism of the release of volatiles through a transporter model. Additionally, it considers the factors that affect their release and ecological functions and suggests directions for future research.

Plant-aphid interactions: recent trends in plant resistance to aphids

Aphids are highly destructive agricultural pests characterized by complex life cycles and phenotypic variability, facilitating their adaptation to diverse climates and host plants. Their feeding behavior leads to plant deformation, wilting, stunted growth, disease transmission, and significant yield losses. Given the economic risks aphids pose, regular updates on their seasonal behaviors, adaptive mechanisms, and destructive activities are critical for improving management strategies to mitigate crop losses. This review comprehensively synthesizes recent studies on aphids as plant pests, the extrinsic factors influencing their life cycles, and the intricate interactions between aphids and their hosts. It also highlights recent advancements in biological control measures, including natural enemies, antibiosis, and antixenosis. Additionally, we explore plant defense mechanisms against aphids, focusing on the roles of cell wall components such as lignin, pectin and callose deposition and the genetic regulations underlying these defenses. Aphids, however, can evolve specialized strategies to overcome general plant defenses, prompting the development of targeted mechanisms in plants, such as the use of resistance (R) genes against specific aphid species. Additionally, plant pattern recognition receptors (PRRs) recognize compounds in aphid saliva, which triggers enhanced phloem sealing and more focused immune responses. This work enhances understanding of aphid-plant interaction and plant resistance and identifies key research gaps for future studies.

Insights into recent advances in secondary metabolites (SMs)-mediated defense responses in plants

Climate change induces various environmental stressors that restrict plant processes, thereby limiting overall crop productivity. Plant secondary metabolites (SMs) enable plants to quickly detect a broad array of environmental stressors and respond in accordance to rapidly changing environmental scenarios. Notably, SMs regulate defense signaling cascades and provide defensive functions to safeguard plants against various biotic and abiotic stressors. In this review, we provide an overview of insights into recent advances in types and biosynthetic pathways of SMs. We emphasize the mechanisms of different biotic and abiotic elicitors-induced SMs synthesis and accumulation to regulate defense responses. In addition, SMs-mediated regulation of plant processes act through phytohormones signaling cascades is discussed. Finally, we show that transcriptional factors regulating SMs biosynthesis and associated regulatory networks could be used for creating resilient plants. Overall, this comprehensive review gives insight into recent advances regarding crucial roles of SMs in enhanced resistance and provides new ideas for the development of stress-resistant varieties under current climate change scenarios.

From Tradition to Science: Chemical, Nutritional, and Cytotoxic Characterization of Erythroxylum coca from Indigenous Colombian Communities

Erythroxylum coca, commonly known as "coca" is a plant native to the South American Andes, recognized for its high alkaloid content and potential medical and nutritional applications. This study aimed to characterize the chemical, nutritional, and cytotoxic properties of two E. coca morphotypes (Palo and Caimo) cultivated by Colombian indigenous communities, with the goal of promoting legal uses and economic opportunities in the region. Comprehensive analyses included the evaluation of sugars, organic acids, total polyphenols, flavonoids, antioxidant capacity, volatile compounds, and cytotoxic activity. Chemical analysis revealed that E. coca leaves contain over 50% dietary fiber, while stems surpass 76%, primarily consisting of insoluble fiber. Significant amounts of sucrose, glucose, and fructose were detected, with succinic acid identified as the predominant organic acid. Cytotoxicity evaluation demonstrated that while both morphotypes are safe for consumption, they also exhibit cytotoxic activity against L929 murine fibroblast cell line. Volatile compound analysis highlighted the presence of hexadecanoic and octadecanoic acids, alongside characteristic alkaloids such as cocaine and benzoylecgonine. These findings underscore the nutritional, chemical, and cytotoxic potential of E. coca as a sustainable crop. Its cultivation and research can serve as a valuable resource for indigenous communities, contributing to the development of local economies and fostering its legal and beneficial applications.

Timbe (Acaciella angustissima) as an Alternative Source of Compounds with Biological Activity: Antidiabetic

Background/Objectives: Timbe (Acaciella angustissima) is a legume recognized for its environmental benefits, such as soil restoration, wildlife nutrition, and the presence of biologically active compounds. This study investigates the antioxidant, pharmacological, and antimicrobial properties of Timbe. Methods: The total phenolic content, flavonoids, and condensed tannins from Timbe flowers, seeds, and pods were quantified, and their antioxidant activity was evaluated using the DPPH and ABTS assays. Enzymatic activities were assessed through α-amylase, α-glucosidase, and ACE-I inhibition, and antimicrobial properties were tested against various bacterial strains. Results: The pods and flowers exhibited higher antioxidant capacities compared to seeds, effectively neutralizing free radicals. Flavonoids and condensed tannins showed positive correlations with antioxidant activity and the inhibition of α-amylase and α-glucosidase, suggesting the potential benefits of these metabolites in blood glucose control. Timbe also demonstrated ACE-I inhibition, particularly the flowers. Regarding antimicrobial activity, the pods displayed moderate inhibition against E. coli, K. pneumoniae, and S. aureus. Conclusions: The results indicate that different parts of Timbe (flowers, seeds, and pods) possess significant therapeutic potential for preventing and treating metabolic disorders and bacterial infections.

Plant Secondary Metabolites-Central Regulators Against Abiotic and Biotic Stresses

As global climates shift, plants are increasingly exposed to biotic and abiotic stresses that adversely affect their growth and development, ultimately reducing agricultural productivity. To counter these stresses, plants produce secondary metabolites (SMs), which are critical biochemical and essential compounds that serve as primary defense mechanisms. These diverse compounds, such as alkaloids, flavonoids, phenolic compounds, and nitrogen/sulfur-containing compounds, act as natural protectants against herbivores, pathogens, and oxidative stress. Despite the well-documented protective roles of SMs, the precise mechanisms by which environmental factors modulate their accumulation under different stress conditions are not fully understood. This review provides comprehensive insights into the recent advances in understanding the functions of SMs in plant defense against abiotic and biotic stresses, emphasizing their regulatory networks and biosynthetic pathways. Furthermore, we explored the unique contributions of individual SM classes to stress responses while integrating the findings across the entire spectrum of SM diversity, providing a comprehensive understanding of their roles in plant resilience under multiple stress conditions. Finally, we highlight the emerging strategies for harnessing SMs to improve crop resilience through genetic engineering and present novel solutions to enhance agricultural sustainability in a changing climate.

Metagenomics and plant-microbe symbioses: Microbial community dynamics, functional roles in carbon sequestration, nitrogen transformation, sulfur and phosphorus mobilization for sustainable soil health

Biogeochemical cycles are fundamental processes that regulate the flow of essential elements such as carbon, nitrogen, and phosphorus, sustaining ecosystem productivity and global biogeochemical equilibrium. These cycles are intricately influenced by plant-microbe symbioses, which facilitate nutrient acquisition, organic matter decomposition, and the transformation of soil nutrients. Through mutualistic interactions, plants and microbes co-regulate nutrient availability and promote ecosystem resilience, especially under environmental stress. Metagenomics has emerged as a transformative tool for deciphering the complex microbial communities and functional genes driving these cycles. By enabling the high-throughput sequencing and annotation of microbial genomes, metagenomics provides unparalleled insights into the taxonomic diversity, metabolic potential, and functional pathways underlying microbial contributions to biogeochemical processes. Unlike previous reviews, this work integrates recent advancements in metagenomics with complementary omics approaches to provide a comprehensive perspective on how plant-microbe interactions modulate biogeochemical cycles at molecular, genetic, and ecosystem levels. By highlighting novel microbial processes and potential biotechnological applications, this review aims to guide future research in leveraging plant-microbe symbioses for sustainable agriculture, ecosystem restoration, and climate change mitigation.

Phytochemicals from Musa acuminata Colla peel exhibit cathepsin B inhibition and anti-inflammatory activity

Rheumatoid arthritis (RA) is a chronic inflammatory illness in which inflammatory mediators and cathepsin B and other proteases play a role in disease progression. The existing treatments may have negative side effects. Therefore, an alternative natural therapy for RA has been considered safe and beneficial. Secondary metabolites from plants have been suggested as one such alternative. In our present study phytochemicals from Musa acuminata (banana) peel have been explored for their anti-cathepsin B and anti-inflammatory potential. The crude phytochemical extract inhibited cathepsin B with an IC50 value of 1.151 mg/ml. One hundred phytochemicals were identified by GC-MS in the extract. Cathepsin B inhibitory potential of each identified phytochemical was assessed using in-silico studies and revealed stigmasterol, campesterol, methyl linolenate, and methyl linoleate possessed more favourable binding energy than positive control (E-64-cathepsin B complex) and inhibited cathepsin B in-vitro. The combinatorial action of compounds resulted in synergistic cathepsin B inhibition where a combination of campesterol, stigmasterol, and methyl linolenate showed maximum inhibition of 97.80 %. Methyl linolenate showed the least inhibition constant among other compounds. Cell line studies with methyl linolenate showed no toxicity to SW982 cells and also downregulated p65 expression at 5 μM in TNF-α induced SW982 human synovial fibroblast cells indicating its anti-inflammation role. Thus, the study has shown that banana peel may serve as a resource for exploring phytochemicals for their anti-inflammatory role in RA as a nutraceutical. Being an edible plant, it may be suggested as a dietary supplement to combat RA and cathepsin B associated pathologies.

Toxicological evaluation of Isosecotanapartholide from Artemisia vulgaris L.: oral acute and sub-acute toxicity in BALB/c mice

Isosecotanapartholide (ISTP) isolated from Artemisia vulgaris, having fumigant property, was tested for acute and sub-acute toxicity in BALB/c mice. The male and female BALB/c mice were given ISTP orally for 7 days at doses of 200, 800 and 1600 mg/kg body weight (bw) for the acute toxicity assay. For sub-acute toxicity test, ISTP was given orally for 14 days at doses of 50 and 500 mg/kg bw. The general appearance, behaviour, weight gain, water intake and feed intake, relative organ weight, haematological indices, histopathological sections and biochemical markers were examined. In the study, ISTP at doses up to 1600 mg/kg bw in acute and 500 mg/kg bw in sub-acute studies, the vital organs like heart, kidney, uterus and testis revealed no adverse effects and mortality. Both acute and sub-acute toxicity assays show that Isosecotanapartholide is safe in mammalian system and can be used as an effective natural substitute for synthetic insecticides.

Influence of phloem lectin CsPP2-A1 on aphid development via mediation of phenylpropanoid and flavonoid biosynthesis in cucumber

BACKGROUND

Aphid, Aphis gossypii Glover, is a pest that significantly affects cucumbers (Cucumis sativus L.). Phloem protein 2 (PP2) is a conserved phloem lectin. Our previous study showed that the expression of CsPP2-A1 under aphid attack affected the accumulation of flavonoids and total phenolics in cucumber. The novel mechanism of lectin CsPP2-A1 mediating secondary metabolites affecting aphid resistance in cucumbers needs to be investigated.

RESULTS

The weight and length of aphids on CsPP2-A1 overexpression (CsPP2-A1-OE) cucumber plants significantly reduced compared to wild-type (WT). Conversely, aphids on CsPP2-A1 RNA interference (CsPP2-A1-RNAi) plants showed the opposite trend. Using secondary metabolomics, small molecular weight secondary metabolites were qualitatively and quantitatively assessed in WT and transgenic cucumber plants after aphid inoculation. The overexpression of CsPP2-A1 resulted in the up-regulation of differential metabolites (DMs) in phenylpropanoid biosynthesis, whereas interference expression of CsPP2-A1 led to a down-regulation of DMs in the flavonoid biosynthesis. Concurrently, it was observed that the CAD activity and the expression of the CsPAL, and CsCAD in OE-2 were up-regulated significantly. A significant reduction in the activities of CHI, F3H, and the expression of CsF3H, CsCHS, CsFLS, and CsCCR was noted in RNAi-2.

CONCLUSION

CsPP2-A1 indirectly affects the growth and development of aphids via mediation of phenylpropanoid and flavonoid biosynthesis. The indirect effects of the interaction of CsPP2-A1 with aphids offer insights into plant-insect interaction studies. © 2025 Society of Chemical Industry.

Cellular strategies for surviving the alpine extremes: methylerythritol phosphate pathway-driven isoprenoid biosynthesis and stress resilience

High altitude conditions pose a significant challenge to all earth's inhabitants including flora. Low atmospheric pressure (thin air), intense ultraviolet (UV) light, and ultra-low temperatures combine to cause oxidative stress in plants. In these abiotic stress conditions, plants exhibit various ecophysiological, morphological, and biochemical adaptations to cope with stress. Morphologically, plants may develop smaller, thicker leaves with protective trichomes or waxy cuticles against intense UV radiation, and minimize water loss in the thin, dry air. However biochemically, plants increase the production of UV-absorbing compounds like flavonoids and phenolic acids along with antioxidant enzymes for neutralizing reactive oxygen species (ROS). To protect against these stress conditions plants start producing specialized metabolites, i.e., isoprenoids, phenolic acids, flavonoids, sterols, carotenoids, etc. The production of these specialized metabolites occurs through MEP (methylerythritol phosphate) and MVA (mevalonic acid) pathways. Although, this article aims to review the scientific complexities of high-altitude plants by providing an in-depth explanation of the MEP pathway, including its regulation, sources and causes of oxidative stress in plants, functions and roles of isoprenoids in stress tolerance, and the adaptation strategies that support alpine plant survival and acclimation. The MEP pathway's products, several carotenoids, viz., phytoene, lycopene, β-carotene, etc., and terpenoids, viz., geraniol, citral, phytol, etc., act as potent scavengers of ROS, providing defense against oxidative damage. Also, phytohormones, viz., abscisic acid, salicylic acid, and jasmonic acid play crucial roles in modulating plant responses to oxidative stress. To date, little scientific literature is available specifically on high-altitude plants with respect to MEP pathway and oxidative stress management. Understanding the interaction between the MEP pathway and oxidative stress in high-altitude plants can provide insight into the implications for improving crop resilience and producing bioactive chemicals with potential human health benefits.

Application of flavonoid compounds suppresses the cotton aphid, Aphis gossypii

Introduction

The cotton aphid Aphis gossypii is a significant polyphagous crop pest and has evolved a high level of resistance to neonicotinoids and other insecticides. Flavonoids, plant phytonutrients, have shown promise as natural insect deterrents and growth inhibitors. However, comprehensive evaluations of the effects of flavonoids on A. gossypii are currently lacking.

Methods

In this study, we first evaluated the effects of seven flavonoids (kaempferol, genistein, daidzein, naringenin, rutin, luteolin, and apigenin) on aphid settling behavior using choice assays, followed by electrical penetration graph (EPG) recordings to assess their influence on feeding activity. We then measured honeydew excretion and conducted life table analysis under laboratory conditions to assess effects on growth and reproduction. Under greenhouse conditions, all seven flavonoids were tested for their inhibitory effects on A. gossypii population growth over 12 days. Based on the results, three effective flavonoids were selected for further testing at four concentrations (1×, 2×, 3×, and 4× of 1 μg/μL) to assess dose-dependent effects.

Results

We found that all seven flavonoids significantly deterred aphid settling on host plants. Kaempferol, daidzein, naringenin, rutin, luteolin, and apigenin significantly reduced the total duration of phloem feeding and the proportion of time spent on phloem-related activities. And also, each of seven flavonoids reduced honeydew production compared to controls. In the laboratory, all flavonoids reduced adult longevity and fecundity, and kaempferol, genistein, daidzein, naringenin, luteolin and apigenin also reduced the net reproductive rate (R0), intrinsic rate of increase (rm), and finite rate of increase (λ). Naringenin, apigenin, and kaempferol significantly inhibited A. gossypii population growth in a dose-dependent manner over 12 days.

Discussion

These results demonstrate that the seven flavonoids, especially naringenin, apigenin, and kaempferol tested provided effective management of A. gossypii populations by deterring host settling, reducing phloem feeding, honeydew production, and decreasing reproductive rates. This study highlights the potential of flavonoids as eco-friendly control agents against A. gossypii.

The influence of changing fire regimes on specialized plant-animal interactions

Ecological effects of changing fire regimes are well documented for plant and animal populations, but less is known about how fire influences, and is influenced by, specialized plant-animal interactions. In this review, we identified mutualistic (pollination, seed dispersal and food provision), commensal (habitat provision) and antagonistic (seed predation, herbivory and parasitism) plant-animal interactions from fire-prone ecosystems. We focused on specialized interactions where a single genus depended on one to two genera in a single family of plant or animal. We categorized the plant partner's post-fire reproductive mode to assess the likely outcome of changing fire regimes on ecological functions provided by these interactions. Traits underlying specialization in fire-prone ecosystems for plants were: post-fire reproductive mode, time to maturity, morphology and phenology; and, for animals: dispersal, specialized organs, nesting and egg deposition substrates, plant consumption behaviours and pollinator behaviours. Finally, we identified a number of cases where stabilizing feedbacks maintained plant-animal interactions under natural fire regimes. Potential reinforcing feedbacks were also identified, but were more likely to happen abruptly and result in collapse of the plant-animal partnership, or partner switching. Our synthesis reveals how fire regime changes impact fire-dependent specialist plant-animal interactions and potentially drive eco-evolutionary dynamics in fire-prone ecosystems globally.This article is part of the theme issue 'Novel fire regimes under climate changes and human influences: impacts, ecosystem responses and feedbacks'.

CeJAZ3 suppresses longifolene accumulation in Casuarina equisetifolia, affecting the host preference of Anoplophora chinensis

BACKGROUND

Casuarina equisetifolia, a crucial species of coastal windbreaks, is highly susceptible to infestation by Anoplophora chinensis. This stem-boring pest poses a significant threat to the health and sustainability of Casuarina equisetifolia forests. Understanding the molecular mechanisms underlying the host preference of A. chinensis to Casuarina equisetifolia is essential for developing effective pest management strategies.

RESULTS

Through field surveys, we identified two cultivars of Casuarina equisetifolia that exhibited differing levels of host preference for A. chinensis. Further analysis of multi-omics data (phenomics, transcriptomics, and metabolomics) from these cultivars revealed that longifolene plays a significant role in attracting A. chinensis to Casuarina equisetifolia. Additionally, the jasmonic acid (JA) signaling pathway was found to suppress longifolene accumulation, primarily through the interaction between the jasmonate ZIM-domain (JAZ) proteins and the terpene synthase (TPS) gene. Moreover, we identified a critical JAZ component, CeJAZ3, whose overexpression led to the down-regulation of TPS expression levels and, consequently, a reduced release of longifolene.

CONCLUSION

We confirmed that the negative regulator of host preference, CeJAZ3, in the JA signaling pathway can suppress the expression of TPSs, thereby down-regulating the accumulation of longifolene in Casuarina equisetifolia and indirectly suppressing the attraction of host plants to A. chinensis, which provides a basis for the integrated management of A. chinensis. © 2024 Society of Chemical Industry.

Comparative metabolomics elucidates the early defense response mechanisms to Plutella xylostella infestation in Brassica napus

Plutella xylostella (diamondback moth; DBM) is a significant pest of Brassica crops, causing billions of dollars in annual global damage and developing resistance to many insecticides. Climate change is increasing the frequency and severity of infestations by influencing the moth's reproduction and expanding its range, leading to increased crop losses. In this study, we examined the early metabolomic responses of four Brassica napus accessions to DBM infestation, focusing on identifying the metabolic basis of tolerance. Phenotypic analysis showed that R4220 and R4415 were highly susceptible, with remaining leaf areas of 27 and 38%, respectively, while the tolerant accessions R4637 and R5064 retained 85 and 91% of their leaf area post-infestation. Metabolomic profiling revealed a distinct separation between tolerant and sensitive accessions under both control and infested conditions. Notably, tolerant accessions exhibited differential accumulation of metabolites, with abundant metabolites belonging to lipid and lipid-like molecules, organic acids and derivatives, and benzenoids. Additionally, 31 metabolites were found to be consistently expressed at higher levels in tolerant accessions as compared to sensitive ones, notably tridecanedioic acid, 3,5-dihydroxyphenylglycine and benzoxazine-6-carboxylic acid. Furthermore, KEGG analysis revealed that pathways such as phenylpropanoid biosynthesis, aminoacyl-tRNA biosynthesis and ABC transporters were enriched, indicating their critical roles in the defense mechanisms. This comprehensive analysis of metabolomic alterations provides valuable insights into the biochemical pathways underpinning insect tolerance in rapeseed, potentially guiding the development of more resilient cultivars and leading a pathway to improve crop farming for sustainable agriculture.

A premature termination codon mutation in the onion AcCER2 gene is associated with both glossy leaves and thrip resistance

Plant epicuticular waxes (EW) play a critical role in defending against biotic and abiotic stresses. Notably, onions (Allium cepa L.) present a distinctive case where the mutant with defect in leaf and stalk EW showed resistance to thrips compared with the wild type with integral EW. We identified a premature stop codon mutation in the AcCER2 gene, an ortholog of CER2 gene in Arabidopsis thaliana that has been proved essential for the biosynthesis of very long-chain fatty acids (VLCFAs), in the onions with glossy leaf and stalks in our experiments. The data hinted at the possibility that this mutation might impede the elongation process of VLCFAs from C28 to C32, thereby hindering the production of 16-hentriacontanone, a primary constituent of onion EW. Transcriptomic analysis revealed substantial alterations in expression of genes in the pathways related not only to lipid synthesis and transport but also to signal transduction and cell wall modification in glossy mutants. Meanwhile, metabolomic profiling indicates a remarkable increase in flavonoid accumulation and a significant reduction in soluble sugar content in glossy mutants. These findings suggested that the enhanced resistance of glossy mutants to thrips might be a consequence of multiple physiological changes, and our integrated multiomics analysis highlighting the regulatory role of AcCER2 in these processes. Our study has yielded valuable insights into the biosynthesis of onion EW and has provided an initial hypothesis for the mechanisms underlying thrip resistance. These findings hold significant promise for the breeding programs of thrip-resistant onion.

The Good, the Bad, and the Epigenetic: Stress-Induced Metabolite Regulation and Transgenerational Effects

BACKGROUND

Plants face a wide range of environmental stresses that disrupt growth and productivity. To survive and adapt, they undergo complex metabolic reprogramming by redirecting carbon and nitrogen fluxes toward the biosynthesis of protective secondary metabolites such as phenylpropanoids, flavonoids, and lignin. Recent research has revealed that these stress-induced metabolic processes are tightly regulated by epigenetic mechanisms, including DNA methylation, histone modifications, chromatin remodeling, and non-coding RNAs.

METHODS

This review synthesizes current findings from studies on both model and crop plants, examining the roles of key epigenetic regulators in controlling secondary metabolism under stress. Special focus is placed on dynamic changes in DNA methylation, histone acetylation, and the action of small RNAs such as siRNAs and miRNAs in transcriptional and post-transcriptional regulation.

RESULTS

Evidence indicates that stress triggers rapid and reversible epigenetic modifications that modulate gene expression linked to secondary metabolic pathways. These modifications not only facilitate immediate metabolic responses but can also contribute to stress memory. In some cases, this memory is retained and transmitted to the next generation, influencing progeny stress responses. However, critical knowledge gaps remain, particularly concerning the temporal dynamics, tissue specificity, and long-term stability of these epigenetic marks in crops.

CONCLUSIONS

Understanding how epigenetic regulation governs secondary metabolite production offers promising avenues to enhance crop resilience and productivity in the context of climate change. Future research should prioritize dissecting the stability and heritability of these modifications to support the development of epigenetically informed breeding strategies.

Brassica rapa treatments with methyl salicylate enhance foraging capacity of generalist natural enemies in a concentration-dependent manner

The aphid Myzus persicae Sulzer (Hemiptera: Aphididae) causes significant crop damage by feeding on plant tissues, transmitting viruses, and reducing agricultural productivity. Challenges associated with chemical control methods, such as the development of pest resistance and adverse environmental impacts, highlight the need to enhance the efficacy of natural enemies for sustainable pest management. Methyl salicylate (MeSA) has been extensively studied in pest management using baited traps and slow-release packets; however, its role in enhancing natural enemy behavior through induced plant defenses remains underexplored. This study examines the effect of MeSA applied to Brassica rapa (Brassicales: Brassicaceae) on the behavior and performance of 2 key biocontrol agents, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and Aphidius gifuensis Ashmead (Hymenoptera: Braconidae). We hypothesized that MeSA enhances the attraction of natural enemies in a concentration-dependent manner. To test this, 4 MeSA concentrations (25, 50, 75, and 100 mg/L) were applied, with control plants treated using deionized water. Bioassays were then conducted to evaluate predator preferences, parasitism rates, foraging behavior, and behavioral responses in the olfactometer. Results showed that MeSA-treated plants significantly attract natural enemies, with pronounced effects at higher concentrations. Specifically, MeSA increased parasitism rates, improved predator foraging efficiency, and heightened predator preference for treated plants. This study demonstrates the potential of MeSA in enhancing biological control strategies against M. persicae by improving the efficacy of natural enemies. The findings highlight the potential of applying MeSA treatment to enhance the recruitment of biological control agents by inducing plant defenses, offering a sustainable approach to reducing aphid infestations in pest management programs.

Genome-wide identification and expression analysis of the ADH gene family in Artemisia annua L. under UV-B stress

ADHs are key genes that catalyze the interconversion between alcohols and aldehydes, which play crucial roles in plant adaptation to a range of abiotic stresses. However, the characterization and evolutionary pathways of ADH genes in the antimalarial plant Artemisia annua are still unclear. This study identified 49 ADH genes in A. annua and conducted a detailed analysis of their structural features, conserved motifs, and duplication types, revealing that tandem and dispersed duplications are the primary mechanisms of gene expansion. Evolutionary analysis of ADH genes between A. annua (AanADH) and A. argyi (AarADH) revealed dynamic changes, with 35 genes identified deriving from their most recent common ancestor in both species. ADH1, crucial for artemisinin production, had two copies in both species, expanding via dispersed duplication in A. annua but whole-genome duplication in A. argyi. CREs and WGCNA analysis suggested that AanADH genes may be regulated by UV-B stress. Following short-term UV-B treatment, 16 DEGs were identified, including ADH1 (AanADH6 and AanADH7), and these genes were significantly downregulated after two hours treatment (UV2h) and upregulated after four hours treatment (UV4h). The expression changes of these genes were further confirmed by GO enrichment analysis and qRT-PCR experiments. Overall, this study comprehensively characterized the ADH gene family in A. annua and systematically identified AanADH genes that were responsive to UV-B stress, providing a foundation for further research on their roles in abiotic stress responses.

Fall Armyworm Frass Induce Sorghum Defenses Against Insect Herbivores

The fall armyworm (FAW; Spodoptera frugiperda) is a global invasive agricultural pest. Sorghum (Sorghum bicolor), an important monocot crop cultivated worldwide, faces significant challenges from FAW, which has become a major threat to sorghum production. Plants have evolved a wide array of defense mechanisms to combat insect assault. Caterpillar secretions contain both elicitors and effectors, which can either amplify or suppress plant defenses, thereby influencing plant defense responses. In this study, we examined the role of FAW frass in modulating sorghum defenses. Our results suggest that frass application significantly induced sorghum defenses that impacted subsequent FAW herbivory. We also found that the exogenous frass application significantly elevated the phytohormone levels, specifically jasmonic acid and abscisic acid levels, potentially contributing to enhanced sorghum defense against FAW. Furthermore, FAW frass-treated plants exhibited transient increase in total flavonoids, a class of secondary metabolites, which was previously shown to have a detrimental impact on FAW growth and survival. FAW frass application on sorghum plants mitigated proliferation of specialist aphids (sugarcane aphids), though its effect on generalist aphids (greenbugs) was less pronounced. These findings highlight the role of FAW frass in mediating plant responses against both chewing and piercing-sucking insect pests, providing valuable insights into sorghum's defense mechanisms and its potential for pest management strategies.

Influence of Plant Growth-Promoting Rhizobacteria (PGPR) Inoculation on Phenolic Content and Key Biosynthesis-Related Processes in Ocimum basilicum Under Spodoptera frugiperda Herbivory

Plants are naturally subjected to various types of biotic stresses, including pathogenic microorganisms and herbivory by insects, which trigger different signaling pathways and related defense mechanisms. Inoculation with microorganisms, such as plant growth-promoting rhizobacteria (PGPR), can be seen as a form of stress because it triggers a systemic resistance response in plants similar to that caused by insect herbivory. However, these interactions have typically been studied independently, which has limited the understanding of their combined effects. This study examines the effects of Bacillus amyloliquefaciens GB03 inoculation and Spodoptera frugiperda herbivory on the total phenolic contents of Ocimum basilicum. We also analyze the levels of endogenous phytohormones and the activity of phenylalanine ammonia-lyase (PAL), a crucial enzyme involved in the biosynthesis of phenolic defense-related metabolites. The results indicate that the total phenolic content significantly increased only in plants that were both inoculated by GB03 and damaged by larvae. Additionally, PAL activity showed an increase in plants that were damaged by larvae and in those subjected to the combined treatment of larval damage and inoculation with GB03. Regarding phytohormones, in plants damaged by insects, the levels of salicylic acid (SA) increased, regardless of whether they were inoculated or not, while the levels of jasmonic acid-isoleucine (JA-ile) rose in all treatments compared to the control. This study highlights the intricate relationships among beneficial microbes, herbivores, and plant defense mechanisms, emphasizing their potential impact on improving plant resilience and the production of secondary metabolites. Furthermore, understanding the independent effects of PGPR inoculation, beyond its interaction with herbivory, could provide valuable insights into its role as a sustainable alternative for enhancing plant defense responses and promoting crop productivity.

Metabolomic profiling of shade response and in silico analysis of PAL homologs imply the potential presence of bifunctional ammonia lyases in conifers

Norway spruce and Scots pine show enhanced lignin synthesis under shade, along with differential expression of defense-related genes that render disease resilience. In general, phenylalanine (Phe) is the precursor for lignin synthesis in plants, and tyrosine (Tyr) forms an additional lignin precursor specifically in grasses. Phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) from the lignin biosynthesis pathway use either Phe or Tyr as precursors for lignin production, respectively. Grasses possess a bifunctional phenylalanine/tyrosine ammonia-lyase (PTAL) that potentially can use both Phe and Tyr for lignin biosynthesis. Metabolomic profiles of seedlings revealed higher levels of Phe and Tyr under shade in Scots pine, while Norway spruce showed differential regulation of only Tyr under shade. Sequence analysis and phylogeny of PAL homologs in the two conifers, coupled with correlation of up-regulation of precursors for lignin synthesis (Phe/Tyr) and enhanced lignin synthesis along with differential expression of PAL homologs under shade, suggest the potential presence of a bifunctional ammonia-lyases (BAL) in conifers. This finding is novel and comparable to PTALs in grasses. Exome sequence analysis revealed a latitudinal variation in allele frequencies of SNPs from coding regions of putative PAL and BAL in Norway spruce, which may impact enzyme activity affecting lignin synthesis. Metabolomic analysis additionally identified metabolites involved in plant immunity, defense and stress response.

Andean medicinal plants and their secondary metabolites: Connections between Aymara traditional medicine and modern pharmacology

This review examines Aymara traditional medicine, which is deeply rooted in cultural perceptions of health and disease, and its utilization of medicinal plants rich in secondary metabolites-such as flavonoids, alkaloids, and saponins-to support immune function, emphasizing the synergy between ancestral knowledge and modern scientific research. Adhering to PRISMA 2020 guidelines, this review incorporates empirical studies from 2013 to 2024 on secondary metabolites and Aymara medicine, with a focus on the immunomodulatory effects of plants, while excluding non-indexed or irrelevant studies. Potential limitations include publication bias and reliance on secondary data. Three key plant genera-Azorella, Centaurium, and Amaranthus-were identified for their traditional medicinal uses, highlighting their pharmacological benefits, such as anti-inflammatory, antioxidant, and hepatoprotective effects. Specifically, xanthones, a class of secondary metabolites found in Centaurium, exhibit notable antioxidant, anti-inflammatory, antitumoral, and cardioprotective properties, which support their traditional use in treating hypertension and related ailments. Centaurium spp. is characterized by its bioactive compounds (secoiridoids, flavonoids, phenolic acids, and xanthones), offering valuable immunomodulatory, anti-inflammatory, digestive, and antimicrobial properties recognized in both scientific and traditional Aymara medicine for treating diseases and maintaining physical and spiritual balance. Overall, the study of secondary metabolites in Andean medicinal plants like Azorella, Centaurium, and Amaranthus underscores their diverse bioactive compounds with pharmacological properties, highlighting the Aymara community's integration of traditional and modern medicine through holistic practices that promote health, balance, and resilience against disease, while emphasizing the potential of these practices to enhance contemporary healthcare.

Multi-Omics and Physiological Analysis Reveal Crosstalk Between Aphid Resistance and Nitrogen Fertilization in Wheat

The availability of nitrogen (N) can dramatically influence crops resistance to herbivorous insects. However, the interaction between N fertilization and crop resistance to insects is not well understood. In this study, the effects of N fertilization on the grain aphid (Sitobion miscanthi) were investigated using three wheat (Triticum aestivum) cultivars with different aphid resistances. We measured aphid life cycle parameters, fecundity, survival rate, weight and feeding behavior, in conjunction with wheat metabolomics, transcriptomics and alien introgression analysis. Our results demonstrated that higher N application benefits aphid feeding across all three wheat cultivars. We also reveal that the highly resistant cultivar (ZM9) can only exert its resistance-advantage under low N fertilization, losing its advantage compared to moderately resistant cultivar YN19 and susceptible cultivar YN23 under higher N fertilization. The effects of N fertilization on wheat-aphid interactions were due to changes in the regulation of carbon and nitrogen metabolism. Integration of multi-omics highlighted specific aphid-induced differentially expressed genes (DEGs, e.g., TUB6, Tubulin 6; ENODL20, Early nodulin-like protein 20; ACT7 Actin 7; Prx47, Peroxidase 47) and significantly different metabolites (SDMs, e.g., crotonoside, guanine, 2'-O-methyladenosine, ferulic acid) in ZM9. Additionally, we report the unique SDMs-DEGs interactions, associated with introgression during wheat domestication, may help infer aphid resistance. In summary, this study provides new insights into the relationships between N fertilization practices, defense responses and integrated pest management for sustainable wheat production.

Plant secondary metabolites against biotic stresses for sustainable crop protection

Sustainable agriculture practices are indispensable for achieving a hunger-free world, especially as the global population continues to expand. Biotic stresses, such as pathogens, insects, and pests, severely threaten global food security and crop productivity. Traditional chemical pesticides, while effective, can lead to environmental degradation and increase pest resistance over time. Plant-derived natural products such as secondary metabolites like alkaloids, terpenoids, phenolics, and phytoalexins offer promising alternatives due to their ability to enhance plant immunity and inhibit pest activity. Recent advances in molecular biology and biotechnology have improved our understanding of how these natural compounds function at the cellular level, activating specific plant defense through complex biochemical pathways regulated by various transcription factors (TFs) such as MYB, WRKY, bHLH, bZIP, NAC, and AP2/ERF. Advancements in multi-omics approaches, including genomics, transcriptomics, proteomics, and metabolomics, have significantly improved the understanding of the regulatory networks that govern PSM synthesis. These integrative approaches have led to the discovery of novel insights into plant responses to biotic stresses, identifying key regulatory genes and pathways involved in plant defense. Advanced technologies like CRISPR/Cas9-mediated gene editing allow precise manipulation of PSM pathways, further enhancing plant resistance. Understanding the complex interaction between PSMs, TFs, and biotic stress responses not only advances our knowledge of plant biology but also provides feasible strategies for developing crops with improved resistance to pests and diseases, contributing to sustainable agriculture and food security. This review emphasizes the crucial role of PSMs, their biosynthetic pathways, the regulatory influence of TFs, and their potential applications in enhancing plant defense and sustainability. It also highlights the astounding potential of multi-omics approaches to discover gene functions and the metabolic engineering of genes associated with secondary metabolite biosynthesis. Taken together, this review provides new insights into research opportunities for enhancing biotic stress tolerance in crops through utilizing plant secondary metabolites.

Insecticidal activity of two Pelargonium essential oils and head transcriptome analysis of stored-product pest Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in response to citronellyl formate fumigation

Tribolium castaneum (Herbst) is one of the most common stored-product pests, causing enormous economic losses and developing widespread resistance to chemical insecticides. Natural products derived from essential oils (EOs) are well-known for insecticidal activity against agricultural pests, especially in the management of stored-product pests. In this study, the chemical constituents and repellent, contact and fumigation toxicity activities of two Pelargonium EOs against T. castaneum were evaluated. Moreover, the fumigation mechanism of citronellyl formate was assessed by head transcriptome sequencing and RNA interference (RNAi). A total of 28 and 39 compounds were identified by gas chromatography-mass spectrometry, accounting for 98.58 and 97.33 % of P. roseum and P. asperum EOs, and the major components were citronellol, (1S)-(1)-β-pinene and citronellyl formate. (1S)-(1)-β-Pinene exhibited strong contact toxicity activity (LD50 = 19.72 μg/adult), while citronellyl formate exhibited strong repellent and fumigation toxicity activities, with the LC50 value of 11.93 mg/L air. Under the stress of citronellyl formate, 1222 differentially expressed genes were identified, including 554 up-regulated and 668 down-regulated genes, which was further verified by qRT-PCR. Among odorant-binding proteins (OBPs), only TcGOBP70 was up-regulated, suggesting that GOBP70 is more likely to be involved in the defense of T. castaneum by recognizing, binding and transporting citronellyl formate. Additionally, RNAi against TcGOBP70 dramatically increased the contact and fumigation toxicity activities of citronellyl formate, with mortality rates of 73 and 75 %, respectively. Therefore, our findings not only provided theoretical bases for the comprehensive utilization of the Pelargonium species but also established potential targets for controlling T. castaneum adults.

Genome-wide identification and expression profiling of WRKY gene family in grain Amaranth (Amaranthus hypochondriacus L.) under salinity and drought stresses

BACKGROUND

The WRKY gene family plays a significant role in plant growth, development, and responses to biotic and abiotic stresses. However, the role of the WRKY gene family has not been reported in Amaranthus hypochondriacus. This study presents a comprehensive genome-wide analysis of the WRKY gene family in grain amaranth (A. hypochondriacus L.), a resilient crop known for its high nutritional value and adaptability to challenging environments.

RESULTS

In this study, 55 WRKY genes (AhyWRKY1-55) were identified in A. hypochondriacus and distributed unevenly across 16 scaffolds. Of these, 50 contained conserved WRKY domains and were classified into three main groups. Group II was further divided into five subgroups (IIa-IIe) based on phylogenetic analysis, with each clade being well supported by conserved motifs. Additionally, the gene structure analysis revealed variations in exon-intron organization. In contrast, motif analysis showed the presence of conserved domains that were similar within the group but differed between groups, suggesting their functional diversity. Cis-acting elements related to plant growth and development and light, hormones, and stress responses were identified. Synteny analysis revealed that 34 (61.8%) of the genes originated from tandem duplication, indicating the role of tandem duplication in the expansion of the A. hypochondriacus WRKY gene family. Protein-protein interaction analysis suggested that AhyWRKY3, AhyWRKY27, AhyWRKY28, AhyWRKY36, and AhyWRKY52 were hub genes involved in the complex protein interaction network. Using in silico and real-time quantitative PCR, expression analysis revealed tissue- and condition-specific expression patterns of AhyWRKY genes. Notably, under drought stress, AhyWRKY39, AhyWRKY40, AhyWRKY54, and AhyWRKY01 showed increased expression, while under salt stress, AhyWRKY40, AhyWRKY54, AhyWRKY39, AhyWRKY49, and AhyWRKY8 were upregulated at 30 days, suggesting that these genes may play key role in response to salinity stress.

CONCLUSIONS

The present study provides valuable insights into the organization and evolutionary patterns of the WRKY gene family in amaranth. It also identifies putative candidate WRKY genes that may play a role in conferring drought and salt tolerance. Overall, this study lays a foundation for further functional validation of these WRKY candidate genes, facilitating their exploitation in the amaranth genetic improvement programs to develop stress-resilient varieties.

Sustainable pest management using plant secondary metabolites regulated azadirachtin nano-assemblies

Biopesticides have emerged as a global trend to minimize the risks associated with synthetic agrochemicals. However, their stability and efficacies remain challenges for widespread application. Herein, co-assembled nanoparticles (AT NPs or AP NPs) based on azadirachtin (AZA) and tannic acid (TA) or phenylalanine (PA) are constructed in aqueous solution through self-assembly technology. The small particle size, low PDI, high ζ-potential, and related other physicochemical characteristics of nanoparticles can improve wettability, adhesiveness, rain erosion resistance, and photostability compared to the commercial AZA formulation. Importantly, co-assemblies with bidirectional pH-responsive disassembly in acidic or alkaline solutions, allow them to respond to microenvironmental stimuli of targets and enable controlled release of AZA. The nanosystems demonstrated remarkable in vitro and in vivo insecticidal activities against Ostrinia furnacalis and Aphis gossypii. This study illustrates a distinctive perspective for developing eco-friendly nanosystems, highlighting a water-based treatment method for biopesticides with improved physicochemical properties and utilization efficiency.

Jasmonic Acid (JA) Signaling Pathway in Rice Defense Against Chilo suppressalis Infestation

Jasmonic acid (JA) signaling plays a crucial role in rice defense against the striped stem borer, Chilo suppressalis, a notorious pest causing significant yield losses. This review explores the current understanding of JA-mediated defense mechanisms in rice, focusing on the molecular basis, regulatory elements, and practical implications for pest management. JA biosynthesis and signaling pathways are induced upon C. suppressalis infestation, leading to the activation of various defense responses. These include upregulation of JA-responsive genes involved in the production of proteinase inhibitors, volatile organic compounds, and other defensive compounds. The review also discusses the crosstalk between JA and other hormonal pathways, such as salicylic acid and ethylene, in fine-tuning defense responses. Structural modifications in rice plants, such as cell wall reinforcement and accumulation of secondary metabolites, have been highlighted as key components of JA-mediated defense against C. suppressalis. Furthermore, the practical applications of this knowledge in breeding insect-resistant rice varieties and developing sustainable pest management strategies were explored. Future research directions are proposed to further elucidate the complexities of JA signaling in rice-insect interactions and harness this knowledge to enhance crop protection.

Investigating the effect of chitosan on the expression of P5CS, PIP, and PAL genes in rapeseed (Brassica napus L.) under salt stress

Chitosan, a non-toxic and biodegradable compound, enhances plant growth and secondary metabolite production, presenting innovative approaches to mitigating plant stress. Salinity, a common abiotic stress, significantly impairs plant growth and development. This study investigates the effects of chitosan on the physiological, biochemical, and gene expression responses of salt-stressed Brassica napus L. exposed to NaCl concentrations of 0, 50, 100, and 150 mM. Chitosan was applied as a foliar spray at concentrations of 0, 5 and 10 mg/L. The research focuses on gene expression changes in P5CS, PIP, and PAL genes in the roots and shoots of Brassica napus, revealing notable alterations, particularly in PIP expression under saline conditions. The study also observed enhanced PAL enzyme activity, increased chlorophyll and proline levels, and changes in iron, potassium, and nitrogen content. These findings demonstrate chitosan's potential to improve plant resilience to salt stress. By modulating gene expression and enhancing physiological responses, chitosan presents a promising solution for enhancing plant tolerance to salinity, with valuable implications for agricultural practices.

Fall Armyworm-Induced Secondary Metabolites in Sorghum Defend Against Its Attack

The fall armyworm (FAW), Spodoptera frugiperda, is one of the major agricultural pests that has invaded China. The FAW is a polyphagous insect with the gramineous crop sorghum being a key host plant. However, the basis of sorghum's chemical defense against FAW feeding is still unclear. In this study, we investigated the potential defensive mechanism of sorghum against this insect species. It was found that FAW larvae preferred maize over sorghum, the selection and damage rates for sorghum plants by larvae were significantly lower than those of maize plants, and feeding on sorghum restricted larval weight. The non-target metabolomics revealed that the feeding of FAW larvae altered the plant secondary metabolite spectra in maize and sorghum, resulting in species-specific differential secondary metabolites (DSMs). Of these, 19 DSMs were specific in maize, and 51 in sorghum, and only 6 were found in both species. Two-choice and no-choice feeding assays found that gambogenic acid and chimonanthine, two DSMs unique to sorghum, were found to deter larval feeding and decrease the larval weight. These findings reveal that the defense of sorghum against FAW is regulated by changing the response spectra of secondary metabolites and that the induced metabolites have a defensive function by acting as antifeedants, which provides new insights into employing bioactive plant compounds against polyphagous insects.

Exploring the benefits of AMF colonization for improving wheat growth, physiology and metabolism, and antimicrobial activity under biotic stress from aphid infection

BACKGROUND

This study examines the effectiveness of arbuscular mycorrhizal fungi (AMF, Rhizophagus irregularis) as a bioprotection strategy to improve wheat's physiological and biochemical responses. This study utilized soil inoculation with AMF and plant-controlled infestation with aphids, conducted over four weeks with three replicates per treatment.

RESULTS

Although aphid infestation reduced root colonization by 26.8% and hyphal length by 30.7%, with no effect on arbuscular numbers (p < 0.05), AMF treatment improved growth, physiology, and metabolism of AMF-treated plants, especially under aphid infestation. AMF-treated plants showed a 51% increase in fresh weight and a 38% improvement in photosynthetic rates under infestation, indicating enhanced photosynthetic efficiency compared to controls. At the metabolism level, AMF application, particularly in infested plants, increased the levels of several amino acids, such as asparagine and glutamine, which increased by 23% and 20%, respectively. AMF treatment significantly boosted nitrogen metabolism enzymes, with activity increasing up to 4.8-fold in infested plants and arginase activity rising by 49% in infested and 290% in non-infested conditions. This metabolic shift elevated antioxidant levels, increasing flavonoids by 40% and polyphenols by 95% under aphid infestation. Additionally, antimicrobial efficacy improved, with AMF-treated plant extracts showing 30-67% larger inhibition zones against pathogens like Staphylococcus epidermidis and Salmonella typhimurium than untreated plants (p < 0.05).

CONCLUSIONS

This research examined the potential of AMF as a sustainable pest management tool, specifically focusing on its ability to enhance crop health and boost defenses against biotic stress. The study further highlights how AMF treatment improves antimicrobial efficacy, which can be integrated into farming practices to maintain plant growth while offering distinct advantages over conventional pest management strategies.

The Enhancement of Biomass Accumulation, Caffeoylquinic Acid Derivative Production, and Antioxidant Activity of Rhaponticum carthamoides Transformed Roots Cultured in a Nutrient Sprinkle Bioreactor

Rhaponticum carthamoides (Willd.) Iljin. is an endemic plant species found in Siberia, Mongolia, and Kazakhstan. Its roots and rhizomes are used to treat physical fatigue and weakness following illness. The present study examines the scaling up of caffeoylquinic acid (CQA) derivative and flavonoid production in R. carthamoides transformed roots. The transformed roots were grown in shaken Erlenmeyer flasks of varying volumes (0.5-2 L), a temporary immersion system (TIS) (Rita® and PlantForm bioreactors), and a nutrient sprinkle bioreactor (NSB) in Woody Plant medium for 35 days. The highest dry biomass production was achieved in the 0.5 L and 1 L flasks and in the NSB bioreactor, yielding 22.2 to 20.4 g/L-approximately 14 to 23 times the weight of the inoculum. The accumulation of individual specialized metabolites varied depending on the culture system used. The peak amount of CQAs (544.5 mg/L), in terms of the increase in dry weight and metabolite levels, was obtained in the NSB bioreactor. The primary CQAs were chlorogenic acid (5-CQA) and a tri-CQA 1. The highest concentration of 5-CQA (7.38 mg/g DW) was found in the roots cultivated in the NSB bioreactor. In contrast, the tri-CQA 1 dominated in the roots from 2 L shaken Erlenmeyer flasks (8.44 mg/g DW). Our findings demonstrate that transformed roots growing in an NSB bioreactor are an effective system for increasing CQA production, potentially serving as an alternative source. This biotechnological approach could help reduce the overexploitation of field-grown R. carthamoides, a currently threatened species.

Adaptability Analysis of Tuta absoluta to Different Hosts and Related Salivary Genes Identification

Tuta absoluta is a significant agricultural pest primarily affecting Solanaceae plants, resulting in substantial economic losses in agriculture. Insect saliva is an intermediary between insects and plants, playing a crucial role in modulating host adaptability and plant defense. This study analyzed the adaptive differences of T. absoluta on four plants using the two-sex life table method. Results indicated that the host adaptability of T. absoluta to tobacco is worse than its adaptability to the other three varieties of tomatoes. The salivary gland transcriptome analysis and signal peptide prediction revealed that Trypsin, B5 V51-1498, and Ta74 were highly expressed in the salivary glands of T. absoluta subjected to tobacco treatment and exhibit the characteristics of secretory proteins, alongside significant feeding selection differences. Our findings elucidate the adaptive strategies of T. absoluta larvae on various Solanaceae plants and offer new insights into the salivary protein-mediated plant defense processes.

Eavesdropping the pivotal defensive representatives of plant-thrips interaction

The substantial economic impact of thrips on crop yield and productivity enthused us to review comprehensive research findings associated with plant-thrips interaction. An attempt has been made to summarize a broad spectrum of knowledge on thrips infestation in different crops regarding defensive traits including plant morphological features, biochemical alterations and transcriptional profiling of defensive genes along with effective thrips management strategies. Thrips feeding mechanism involves puncturing the outer (epidermal) layer of host tissue and evoking the plant defence mechanism. Plants respond to thrips attacks by activating the defensive genes, which lead to the production of physical barriers (trichomes, waxes, and papillae) and biochemical compounds (primary and secondary metabolites). It is imperative to appreciate the physiological responses, metabolic changes, and regulation at the transcriptional level of various phytoconstituents during thrips feeding. The literature survey revealed that leaf size, papillae and trichome density, total phenols, tannins and genes associated with phenylalanine metabolism and flavonoid biosynthesis contribute to plant resistance against thrips infestation. Thus, this comprehensive overview will serve as a roadmap for researchers, guiding future studies and the development of sustainable pest management practices to mitigate thrips-related damage and enhance crop resilience.

Plant Defense Responses to Insect Herbivores Through Molecular Signaling, Secondary Metabolites, and Associated Epigenetic Regulation

Over millions of years of interactions, plants have developed complex defense mechanisms to counteract diverse insect herbivory strategies. These defenses encompass morphological, biochemical, and molecular adaptations that mitigate the impacts of herbivore attacks. Physical barriers, such as spines, trichomes, and cuticle layers, deter herbivores, while biochemical defenses include the production of secondary metabolites and volatile organic compounds (VOCs). The initial step in the plant's defense involves sensing mechanical damage and chemical cues, including herbivore oral secretions and herbivore-induced VOCs. This triggers changes in plasma membrane potential driven by ion fluxes across plant cell membranes, activating complex signal transduction pathways. Key hormonal mediators, such as jasmonic acid, salicylic acid, and ethylene, orchestrate downstream defense responses, including VOC release and secondary metabolites biosynthesis. This review provides a comprehensive analysis of plant responses to herbivory, emphasizing early and late defense mechanisms, encompassing physical barriers, signal transduction cascades, secondary metabolites synthesis, phytohormone signaling, and epigenetic regulation.

Quercetin, a natural flavonoid induced by the spider mite Tetranychus urticae or alamethicin, is involved in the defense of lima bean against spider mites

BACKGROUND

Phaseolus lunatus, commonly known as the lima bean, is a leguminous crop cultivated in various regions worldwide. It is native to tropical America and is extensively grown in both tropical and temperate climates. Lima beans are highly nutritious and versatile, serving not only as a food and vegetable, but also as a source of green manure. During cultivation, lima beans can be vulnerable to numerous pests, including the spider mite, Tetranychus urticae. In large-scale outbreaks, T. urticae can cause significant yield losses or even crop failure, posing a serious threat to agricultural production. The treatment of lima bean plants with T. urticae or alamethicin (ALA) has been shown to enhance their insect-resistant defense responses. Understanding the transcriptional and metabolic mechanisms underlying these defense responses to T. urticae and ALA is crucial for improving herbivore resistance in lima bean crops.

RESULT

By integrated analysis of transcriptomics and metabolomics data, we found that both T. urticae and ALA treatments significantly induced the flavonoid biosynthesis pathway. Both treatments increased the flavonoid content in lima bean leaves by upregulating the expression of key genes in this pathway, potentially contributing to enhanced resistance to phytophagous insects. Notably, quercetin has been shown to reduce the number of eggs per female and survival rate of T. urticae.

CONCLUSION

These findings provide a novel theoretical basis for understanding the response mechanisms of lima beans to T. urticae and ALA, while highlighting potential metabolites and genes that could be targeted to improve plant resistance to spider mite damage. © 2025 Society of Chemical Industry.

The General Principle of the Warburg Effect as a Possible Approach for Cancer Immunotherapy: The Regulatory Effect of Plant Extracts Could Change the Game

The interpretation of the biochemistry of immune metabolism could be considered an attractive scientific field of biomedicine research. In this review, the role of glycolysis in macrophage polarization is discussed together with mitochondrial metabolism in cancer cells. In the first part, the focus is on the Warburg effect and redox metabolism during macrophage polarization, cancer development, and management of the immune response by the cancer cells. The second part addresses the possibility of impacts on the Warburg effect through targeting peroxisome proliferator-activated receptors (PPARs). This could be an activator of native immune responses. Because of the reported serious adverse effects of using synthetic ligands for PPARs in combination with chemotherapeutics, searches for less toxic and more active PPAR inhibitors, as well as blocking undesirable cellular PPAR-dependent processes, are in progress. On the other hand, recent research in modern immunotherapy has focused on the search for gentle immune-modulating natural compounds with harmless synergistic chemotherapeutic efficacy that can be used as an adjuvant. It is a well-known fact that the plant kingdom is a source of important therapeutic agents with multifaceted effectiveness. One of these is the known association with PPAR activities. In this regard, the secondary metabolites extracted from plants could change the game.

The cross-resistance to etofenprox in Nilaparvata lugens with a high adaptability to resistant rice variety IR56

BACKGROUND

The application of resistant rice varieties and insecticides represents two crucial strategies for managing the brown planthopper (BPH), Nilaparvata lugens (Stål). Insects often employ similar detoxification mechanisms to metabolize plant secondary metabolites and insecticides, which poses a potential risk that BPH population adapted to resistant rice may also obtain resistance to some insecticides.

RESULTS

Here in a BPH population (R-IR56) that has adapted to the resistant rice variety IR56 through continuous selection, the moderate resistance to etofenprox was observed. Insect P450s often contribute to insecticide resistance in insects. Through transcriptome sequencing of R-IR56 and control populations, it was found that two P450 genes, CYP439A1 and CYP439A2, were over-expressed in R-IR56. RNA interference confirmed the importance of two P450s in etofenprox resistance in vivo. The metabolite identification and catalytic activity of recombinant P450 proteins revealed the metabolism of etofenprox by both CYP439A1 and CYP439A2 in vitro, which catalyzed an O-de-ethylation on etofenprox. However, the up-regulation of two P450 genes did not contribute to the adaptation of BPH to IR56 variety.

CONCLUSION

The study reveals that BPH adapted to resistant rice variety IR56 exhibits a moderate level of resistance to etofenprox, but the cross-resistance to etofenprox in BPH is unidirectional. The findings here provide theoretical guidance for the integrated pest management strategy, especially focusing on the interplay between applications of resistant variety and insecticides. © 2025 Society of Chemical Industry.

Mechanisms underlying the effects of cyanogenesis on development and reproduction of Tetranychus urticae: Insights from enzyme activity and gene expression aspects

Cyanogenic plants can release toxic hydrogen cyanide (HCN) to defend against herbivory by hydrolyzing the cyanogenic glycosides (CNGs) with its β-glucosidases (β-GLUs). Numerous studies have speculated this CNG-mediated toxicity by a plant-pest interaction manner. However, the specific toxic effect of HCN was not well-demonstrated because of the interference of other ingested metabolites. Additionally, the physiological- and biochemical-based mode of action of HCN were seldom determined. To fill those knowledge gaps, the two-spotted spider mite (TSSM), Tetranychus urticae, was used as a model organism to elucidate the toxic mechanism of HCN. In addition, three CNG-enzyme combinations were screened for effective cyanogenesis and TSSM lethality. Linamarin-β-GLU (lima bean-derived) presented prompt HCN release, and molecular docking indicated higher binding energy and more robust binding sites compared with other two groups, i.e., lotaustralin-β-GLU (lima bean-derived) and amygdalin-β-GLU (almond-derived). Meanwhile, this combination led to higher TSSM mortality. Moreover, we found that the median lethal concentration of this combination will significantly prolong the developmental duration, and decrease the longevity and fecundity of TSSM. Besides, the population growth was also significantly suppressed. Furthermore, the sustainable activation of enzyme activity and the encoding gene expression related to physiological process such as detoxification (cytochrome P450, glutathione S-transferase, UDP-glucuronosyltransferase and β-cyanoalanine synthase), antioxidation (superoxide dismutase, catalase and peroxidase), neural transduction (acetylcholinesterase) and respiration (cytochrome c oxidase) were attributed to the detrimental impact on development and reproduction of TSSM. The present findings can provide insight regarding reasonable utilization of toxic chemicals in pest management and creation of novel pest-resistant germplasm.

Polyphenolic Compounds in Fabaceous Plants with Antidiabetic Potential

Diabetes mellitus (DM) is a chronic non-communicable disease with an increasing prevalence in Latin America and worldwide, impacting various social and economic areas. It causes numerous complications for those affected. Current treatments for diabetes include oral hypoglycemic drugs, which can lead to adverse effects and health complications. Other natural alternatives for DM treatment have been studied as adjunct therapies that could reduce or eliminate the need for antidiabetic medications. Several natural supplements may offer an alternative way to improve the quality of life for patients with DM, and they may have other nutraceutical applications. Due to their phenolic compound content, some leguminous substances have been proposed as these alternatives. Phenolic compounds, with their high antioxidant activity, have shown promising potential in insulin synthesis, secretion, and the functionality of the endocrine pancreas. This review provides valuable information on various leguminous plants with anti-diabetic properties, including antioxidant, hypoglycemic, anti-fat-induced damage, and anti-apoptotic properties in vitro and in vivo, attributed to the high content of phenolic compounds in their seeds. Natural products with antidiabetic and pharmacological treatment potential improve diabetes management by offering more effective and complementary alternatives. To integrate these herbal remedies into modern medicine, further research on phenolic compound type, doses, efficacy, and safety in the human population is needed.

Spraying calcium chloride helps to enhance the resistance of kidney bean plants to western flower thrips

BACKGROUND

The western flower thrips (WFT), Frankliniella occidentalis (Thysanoptera: Thripidae), is a significant pest in horticulture and ornamental agriculture. While exogenous calcium (Ca) has been shown to confer plant immune responses against thrips, the detailed mechanisms of this interaction remain to be elucidated for improved thrips management strategies. This study aimed to assess the impact of exogenous Ca on WFT feeding behavior and to explore its role in enhancing the defense mechanisms of kidney bean plants against WFT attacks. We compared WFT feeding preferences and efficiency on kidney bean plants treated with H2O or Ca, and examined whether exogenous Ca improves plant defense responses to thrips attack.

RESULTS

WFT exhibited less preference for feeding on Ca-treated plants over H2O-treated ones. The total duration of WFT's long-ingestion probes was significantly reduced on Ca-treated plants, indicating impaired feeding efficiency. Furthermore, WFT infestation activated both jasmonic acid (JA) and salicylic acid (SA) signaling pathways in kidney bean plants, and exogenous Ca application led to elevated levels of endogenous Ca2+ and CaM, up-regulation of genes associated with JA and SA pathways (LOX, AOS, PAL, and β-1,3-glucanase), and increased accumulation of JA, SA, flavonoids, and alkaloids.

CONCLUSION

Our findings demonstrate that the application of exogenous Ca enhances endogenous Ca2+, JA, and SA signaling pathways in kidney bean plants. This enhancement results in an up-regulation of the biosynthesis of flavonoid and alkaloid, thereby equipping the plants with an enhanced defense against WFT infestation. © 2024 Society of Chemical Industry.

Therapeutic Potential of Polyphenols in Cellular Reversal of Patho-Mechanisms of Alzheimer's Disease Using In Vitro and In Vivo Models: A Comprehensive Review

Alzheimer's disease (AD) is considered one of the most common neurological conditions associated with memory and cognitive impairment and mainly affects people aged 65 or above. Even with tremendous progress in modern neuroscience, a permanent remedy or cure for this crippling disease is still unattainable. Polyphenols are a group of naturally occurring potent compounds that can modulate the neurodegenerative processes typical of AD. The present comprehensive study has been conducted to find out the preclinical and clinical potential of polyphenols and elucidate their possible mechanisms in managing AD. Additionally, we have reviewed different clinical studies investigating polyphenols as single compounds or cotherapies, including those currently recruiting, completed, terminated, withdrawn, or suspended in AD treatment. Natural polyphenols were systematically screened and identified through electronic databases including Google Scholar, PubMed, and Scopus based on in vitro cell line studies and preclinical data demonstrating their potential for neuroprotection. A total of 63 significant polyphenols were identified. A multimechanistic pathway for polyphenol's mode of action has been proposed in the study. Out of 63, four potent polyphenols have been identified as promising potential candidates, based on their reported clinical efficacy. Polyphenols hold tremendous scope for the development of a future drug molecule as a phytopharmaceutical that may be incorporated as an adjuvant to the therapeutic regime. However, more high-quality studies with novel delivery methods and combinatorial approaches are required to overcome obstacles such as bioavailability and blood-brain barrier crossing to underscore the therapeutic potential of these compounds in AD management.

Mitogen-activated protein kinase 4 phosphorylates MYC2 transcription factors to regulate jasmonic acid signaling and herbivory responses in maize

Regulation of responses induced by herbivory and jasmonic acid (JA) remains poorly understood in the important staple crop maize (Zea mays). MYC2 is the key transcription factor regulating many aspects of JA signaling, while mitogen-activated protein kinases (MAPKs or MPKs) play important roles in various plant physiological processes. Using a combination of reverse genetics, transcriptome analysis, and biochemical assays, we elucidated the important role of mitogen-activated protein kinase 4 (MPK4) in maize resistance to insects and in JA signaling. Silencing MPK4 increased the JA and jasmonoyl-isoleucine levels elicited by wounding or simulated herbivory but decreased maize resistance to armyworm (Mythimna separata) larvae. We showed that MPK4 is required for transcriptional regulation of many genes responsive to methyl jasmonate, indicating the important role of maize MPK4 in JA signaling. Biochemical analyses indicated that MPK4 directly phosphorylates MYC2s at Thr115 of MYC2a and Thr112 of MYC2b. Compared with nonphosphorylated MYC2s, phosphorylated MYC2s were more prone to degradation and exhibited enhanced transactivation activity against the promoters of several benzoxazinoid biosynthesis genes, which are important for maize defense against insects. This study reveals the essential role of maize MPK4 in JA signaling and provides insights into the functions of MAPKs in maize.

Anticholinesterase Activity and Bioactive Compound Profiling of Six Hop (Humulus lupulus L.) Varieties

Hops (Humulus lupulus L.) are widely recognized for their use in brewing, but they also possess significant pharmacological properties due to their rich bioactive compounds, with many varieties exhibiting diverse characteristics. This study investigates the chemical composition and biological activities of extracts from six hop varieties, focusing on quantifying xanthohumol and lupulone using High-Performance Liquid Chromatography (HPLC) and Total Phenolic Content (TPC) analysis. The hop varieties demonstrated significant variability in bioactive compound concentrations, with Aurora showing the highest xanthohumol (0.665 mg/g) and Zwiegniowski the highest lupulone (9.228 mg/g). TPC analysis revealed Aurora also had the highest phenolic content (22.47 mg GAE/g). Antioxidant activities were evaluated using DPPH, ABTS, CUPRAC, and FRAP assays, with Aurora and Oregon Fuggle displaying the most potent capacities. Aurora, in particular, showed the highest activity across multiple assays, including significant acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and tyrosinase inhibition, with IC50 values of 24.39 mg/mL, 20.38 mg/mL, and 9.37 mg/mL, respectively. The chelating activity was also assessed, with Apolon demonstrating the strongest metal ion binding capacity (IC50 = 1.04 mg/mL). Additionally, Aurora exhibited the most effective hyaluronidase inhibition (IC50 = 10.27 mg/mL), highlighting its potential for anti-inflammatory applications. The results underscore the influence of genetic and environmental factors on the bioactive compound profiles of hop varieties and their biological activity offering promising avenues for pharmaceutical and nutraceutical applications. However, further studies are needed to fully understand the potential interactions between hop cones components.

Integrated metabolomics and proteomics analysis reveals the accumulation mechanism of bioactive components in Polygonatum odoratum

Polygonatum odoratum (Mill.) Druce is rich in bioactive components with high medicinal value. To maximize the clinical benefits, it is of great significance to efficiently extract key bioactive components from appropriate growth stages in which they are most abundant. In this study, we analyzed the changes of metabolite accumulation and protein expression in P. odoratum rhizomes at different growth stages using targeted metabolomics combined with proteomics, and identified a total of 1,237 differentially abundant metabolites (DAMs). Flavonoids accumulated most in winter, and the biosynthesis pathways associated with flavonoids, isoflavonoids, flavones and flavonols exhibited significant differentially expressed proteins (DEPs). Among them, PGT, FLS, CYP75B1, HIDH, IF7MAT, and UFT73C6 were positively correlated with flavonoid accumulation. Steroid saponins accumulated most in spring, and the biosynthetic pathways of steroid and brassinosteroid biosynthesis exhibited DEPs. Among them, FDFT1, TM7SF2, DHCR7, CAS1, and 3BETAHSDD were positively correlated with steroidal saponin accumulation. In summary, these results revealed the accumulation of secondary metabolites P. odoratum in different growth stages, which can provide an effective reference for the extraction of specific bioactive components and the study of their regulatory mechanisms.