Betulin, Synthesized by PpCYP716A1, Is a Key Endogenous Defensive Metabolite of Peach against Aphids

Obscuroside E: A Novel Alkaloid Glycoside from Clematis obscura as an Insecticide Lead Candidate against Acyrthosiphon pisum and Plutella xylostella

To discover insecticide lead compounds from the insecticidal plant Clematis, a new alkaloid glycoside obscuroside E (1) and 17 known compounds (2-18) were identified from Clematis obscura and Clematis tibetana var. vernayi. Compound 1 displayed remarkable oral toxicities against Acyrthosiphon pisum (A. pisum) and Plutella xylostella (P. xylostella) with half-lethal concentration (LC50) values of 0.11 and 0.85 mg/mL, respectively, as well as potential antifeedant activity. Compound 1 inhibited α-amylase (α-AL) of A. pisum and P. xylostella with inhibition rates of 32.82 and 23.80% at LC70, respectively. It bound tightly to the crystal structure of α-AL in P. xylostella through five hydrogen bonds and three alkyl/pi alkyl interactions. Besides, compound 1 destroyed the microstructure of the midguts of A. pisum and P. xylostella, particularly the microvilli and nucleus. This study provides valuable insight into the better utilization of compound 1 as an insecticide lead candidate for the biocontrol of A. pisum and P. xylostella.

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.

Preparation and insecticidal activities of betulin-cinnamic acid-related hybrid compounds and insights into the stress response of Plutella xylostella L

BACKGROUND

The emergence and increasing intensification of insect pest resistance greatly shortens the service life of commercial insecticides. Hence, the continuous development of novel insecticides is extremely necessary. Discovering new insecticide molecules based on natural products with insecticidal activity has been a popular technique and has made outstanding contributions in this field.

RESULTS

A series of betulin-cinnamic acid-related hybrid compounds was prepared by molecular hybridization through the bridge of acyloxy groups and their chemical structures were unambiguously confirmed. Against A. pisum, compounds 2e, 3a-3e, 3g, 3i, 3j, and 3m showed complete antifeedant activity at 2 mg/mL; compound 5b exhibited 2.7 times the aphicidal activity of the precursor betulin. Against P. xylostella, compound 2l displayed 3.9 times the insecticidal activity of betulin. Meanwhile, some interesting structure-activity relationships were obtained. Furthermore, compound 2l could destroy the ultrastructure of midgut cells and significantly inhibit the activity of α-amylase in P. xylostella larvae. Molecular docking indicated that the lupane skeleton and p-nitrocinnamoyloxy groups played a key role in the binding of compound 2l to α-amylase.

CONCLUSION

Compounds 5b and 2l could be further optimized structurally as the secondary lead compounds for the discovery of novel insecticide molecules. © 2025 Society of Chemical Industry.

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.

In-depth physiological study on the sustainable application of a botanical insecticide with low mammalian toxicity against Aedes aegypti (Diptera: Culicidae)

Research into the exploration of bioactive insecticides as an alternative to synthetic compounds has garnered increasing attention, particularly in the context of sustainable pest management. In this study, a two-sex life table was constructed based on the Waco strain to determine whether the prolonged larval period in haedoxan A-resistant (HAR) strain Aedes aegypti is related to ecdysone-regulated development. The effect of ecdysone on the sensitivity of the 3rd-instar larvae to HA was investigated, along with the determination of 20-hydroxyecdysone (20E) content in A. aegypti. The results showed that the 20E content in larvae from HAR strain was significantly lower than that of Waco strain. And, the sensitivity of larvae treated with ecdysone to HA was increased. Two-sex life table results indicated that ecdysone can accelerate the growth and development of larvae, however, it also shortened the life span of adult mosquitoes and reduced reproduction rate. Notably, cytotoxic activity against human normal liver cell L02 demonstrated that HA was less toxic and did not cause intracellular oxidative stress compared to permethrin. Overall, these findings contribute to a deeper understanding of the mechanisms by which the larval period of A. aegypti is prolonged under HA selection. Furthermore, our results provide valuable insights for the application of HA as an effective botanical insecticide.

Comparative metabolomic analysis provides insights into the metabolite profiles of wild and cultivated Dendrobium flexicaule

BACKGROUND

Dendrobium orchids (Dendrobium spp.) are valuable medicinal and attractive ornamental plants. Due to their limited wild resources, the size of the Dendrobium spp. population required for market demand primarily depends on artificial cultivation. However, the nutritional and therapeutic value of natural products may differ as growth conditions change. In this study, we profiled metabolites from wild and cultivated Dendrobium flexicaule (D. flexicaule) to explore the variations and interrelationships among bioactive components.

RESULTS

A total of 840 annotated metabolites were discovered, 231 of which differed significantly between wild and cultivated D. flexicaule. A comparative investigation found that the types and amounts of metabolites, particularly flavonoids, lipids, amino acids and their derivatives, varied between wild and cultivated D. flexicaule. Using metabolite correlation analysis, a series of differentially abundant metabolites were found to be significantly correlated with phytohormones such as abscisic acid (ABA), salicylic acid (SA), and zeatins, indicating that plant hormones play a role in the accumulation of specific metabolites. Furthermore, many distinct metabolites were identified as key active ingredients of traditional Chinese medicines. Additionally, 78 components were discovered to be active pharmaceutical substances against various diseases, probably contributing to the diverse medical values of wild and cultivated D. flexicaule.

CONCLUSIONS

Overall, comprehensively analyzed the metabolic profiles of wild and cultivated D. flexicaule in this study, serving as a theoretical and material foundation for quality control, health efficacy, and industrial development.

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.

Enhancing aphid resistance in horticultural crops: a breeding prospective

Increasing agricultural losses caused by insect infestations are a significant problem, so it is important to generate pest-resistant crop varieties to address this issue. Several reviews have examined aphid-plant interactions from an entomological perspective. However, few have specifically focused on plant resistance mechanisms to aphids and their applications in breeding for aphid resistance. In this review, we first outline the types of resistance to aphids in plants, namely antixenosis, tolerance (cell wall lignification, resistance proteins), and antibiosis, and we discuss strategies based on each of these resistance mechanisms to generate plant varieties with improved resistance. We then outline research on the complex interactions amongst plants, viruses, and aphids, and discuss how aspects of these interactions can be exploited to improve aphid resistance. A deeper understanding of the epigenetic mechanisms related to induced resistance, i.e. the phenomenon where plants become more resistant to a stress they have encountered previously, may allow for its exploitation in breeding for aphid resistance. Wild relatives of crop plants serve as important sources of resistance traits. Genes related to these traits can be introduced into cultivated crop varieties by breeding or genetic modification, and de novo domestication of wild varieties can be used to exploit multiple excellent characteristics, including aphid resistance. Finally, we discuss the use of molecular design breeding, genomic data, and gene editing to generate new aphid-resistant, high-quality crop varieties.

Haplotype-resolved genome of a heterozygous wild peach reveals the PdaWRKY4-PdaCYP716A1 module mediates resistance to aphids by regulating betulin biosynthesis

Wild species of domesticated crops provide valuable genetic resources for resistance breeding. Prunus davidiana, a wild relative of peach with high heterozygosity and diverse stress tolerance, exhibits high resistance against aphids. However, the highly heterozygous genome of P. davidiana makes determining the underlying factors influencing resistance traits challenging. Here, we present the 501.7 Mb haplotype-resolved genome assembly of P. davidiana. Genomic comparisons of the two haplotypes revealed 18,152 structural variations, 2,699 Pda_hap1-specific and 2,702 Pda_hap2-specific genes, and 1,118 allele-specific expressed genes. Genome composition indicated 4.1% of the P. davidiana genome was non-peach origin, out of which 94.5% was derived from almond. Based on the haplotype genome, the aphid resistance quantitative trait locus (QTL) was mapped at the end of Pda03. From the aphid resistance QTL, PdaWRKY4 was identified as the major dominant gene, with a 9-bp deletion in its promoter of the resistant phenotype. Specifically, PdaWRKY4 regulates aphid resistance by promoting PdaCYP716A1-mediated anti-aphid metabolite betulin biosynthesis. Moreover, we employed a genome design to develop a breeding workflow for rapidly and precisely producing aphid-resistant peaches. In conclusion, this study identifies a novel aphid resistance gene and provides insights into genome design for the development of resistant fruit cultivars.

Molecular Interactions Between Plants and Aphids: Recent Advances and Future Perspectives

Aphids are small, notorious insect pests that negatively impact plant health and agricultural productivity through direct damage, such as sap-sucking, and indirectly as vectors of plant viruses. Plants respond to aphid feeding with a variety of molecular mechanisms to mitigate damage. These responses are diverse and highly dynamic, functioning either independently or in combination. Understanding plant-aphid interactions is crucial for revealing the full range of plant defenses against aphids. When aphids infest, plants detect the damage via specific receptor proteins, initiating a signaling cascade that activates defense mechanisms. These defenses include a complex interaction of phytohormones that trigger defense pathways, secondary metabolites that deter aphid feeding and reproduction, lectins and protease inhibitors that disrupt aphid physiology, and elicitors that activate further defense responses. Meanwhile, aphids counteract plant defenses with salivary effectors and proteins that suppress plant defenses, aiding in their successful colonization. This review offers a detailed overview of the molecular mechanisms involved in plant-aphid interactions, emphasizing both established and emerging plant defense strategies. Its uniqueness lies in synthesizing the recent progress made in plant defense responses to aphids, along with aphids' countermeasures to evade such defenses. By consolidating current knowledge, this review provides key insights for developing sustainable strategies to achieve crop protection and minimize dependence on chemical pesticides.

Combined transcriptome and metabolome analysis identifies triterpenoid-induced defense responses in Myzus persicae Sülzer-infested peach

Piercing/sucking insects such as green peach aphid (GPA) (Myzus persicae) cause direct damage by obtaining phloem nutrients and indirect damage by spreading plant viruses. To investigate the response of peach trees (Prunus persica) to aphids, the leaf transcriptome and metabolome of two genotypes with different sensitivities to GPA were studied. The gene expression of aphid-susceptible plants infested with aphids was similar to that of control plants, whereas the gene expression of aphid-resistant plants infested with aphids showed strong induced changes in gene expression compared with control plants. Furthermore, gene transcripts in defense-related pathways, including plant-pathogen interaction, MAPK signaling, and several metabolic pathways, were strongly enriched upon aphid infestation. Untargeted secondary metabolite profiling confirmed that aphid infestation induced larger changes in aphid-resistant than in aphid-susceptible peaches. Consistent with transcriptomic alterations, nine triterpenoids showed highly significant GPA-induced accumulation in aphid-resistant peaches, whereas triterpenoid abundance remained predominantly unchanged or undetected in aphid-susceptible peaches. Furthermore, some types of transcription factors (including WRKYs, ERFs, and NACs) were strongly induced upon GPA infestation in aphid-resistant, but not in aphid-susceptible peaches. These results suggested that the accumulation of specialized triterpenoids and the corresponding pathway transcripts may play a key role in peach GPA resistance.

Synergistic action and mechanism of scoparone, a key bioactive component of Artemisia capillaris, and spirodiclofen against spider mites

BACKGROUND

Plants have numerous defensive secondary metabolites to withstand insect attacks. Scoparone, which is extracted from the medicinal plant Artemisia capillaris, has potent acaricidal effects on Tetranychus cinnabarinus. Spirodiclofen, derived from a tetronic acid derivative, is a potent commercial acaricide that is extensively used globally. However, whether scoparone has synergistic effects when used in conjunction with spirodiclofen and the underlying synergistic mechanism remains unclear.

RESULTS

Scoparone exhibited a potent synergistic effect when it was combined with spirodiclofen at a 1:9 ratio. Subsequently, cytochrome P450 monooxygenase (P450) activity, RNA-Seq and qPCR assays indicated that the enzyme activity of P450 and the expression of one P450 gene from T. cinnabarinus, TcCYP388A1, were significantly inhibited by scoparone and spirodiclofen + scoparone; conversely, P450 was activated in spirodiclofen-exposed mites. Importantly, RNAi-mediated silencing of the TcCYP388A1 gene markedly increased the susceptibility of spider mites to spirodiclofen, scoparone and spirodiclofen + scoparone, and in vitro, the recombinant TcCYP388A1 protein could metabolize spirodiclofen. Molecular docking and functional analyses further indicated that R117, which is highly conserved in Arachnoidea species, may be a vital specific binding site for scoparone in the mite TcCYP388A1 protein. This binding site was subsequently confirmed using mutagenesis data, which revealed that this binding site was the sole site selected by scoparone in spider mites over mammalian or fly CYP388A1.

CONCLUSIONS

These results indicate that the synergistic effects of scoparone and spirodiclofen on mites occurs through the inhibition of P450 activity, thus reducing spirodiclofen metabolism. The synergistic effect of this potent natural product on the detoxification enzyme-targeted activity of commercial acaricides may offer a sustainable strategy for pest mite resistance management. © 2024 Society of Chemical Industry.

Development of Sustainable Insecticide Candidates for Protecting Pollinators: Insight into the Bioactivities, Selective Mechanism of Action and QSAR of Natural Coumarin Derivatives against Aphids

Plants employ abundant toxic secondary metabolites to withstand insect attack, while pollinators can tolerate some natural defensive compounds. Coumarins, as promising green alternatives to chemical insecticides, possess wide application prospects in the crop protection field. Herein, the bioactivities of 30 natural coumarin derivatives against Aphis gossypii were assessed and revealed that 6-methylcoumarin exhibited potent aphicidal activity against aphids but displayed no toxicity to honeybees. Additionally, using biochemical, bioinformatic, and molecular assays, we confirmed that the action mode of 6-methylcoumarin against aphids was by inhibiting acetylcholinesterase (AChE). Meanwhile, functional assays revealed that the difference in action site, which located in Lys585 in aphid AChE (equivalent to Val548 in honeybee AChE), was the principal reason for 6-methylcoumarin being toxic to aphids but safe to pollinators. This action site was further validated by mutagenesis data, which uncovered how 6-methylcoumarin was unique selective to the aphid over honeybee or mammalian AChE. Furthermore, a 2D-QSAR model was established, revealing that the central structural feature was H3m, which offers guidance for the future design of more potent coumarin compounds. This work provides a sustainable strategy to take advantage of coumarin analogues for pest management while protecting nontarget pollinators.

The Relationships between Waxes and Storage Quality Indexes of Fruits of Three Plum Cultivars

In the present study, the cuticular wax morphology, composition and the relationship with storage quality in three plum cultivars of Prunus salicina 'Kongxin' (KXL), Prunus salicina 'Fengtang' (FTL) and Prunus salicina 'Cuihong' (CHL) were investigated during storage at room temperature of 25 ± 1 °C. The results illustrated that the highest cuticular wax concentration was discovered in KXL, followed by FTL and the lowest in CHL. The fruit wax composition of the three plum cultivars was similar and principally composed of alkanes, alcohols, fatty acids, ketones, aldehydes, esters, triterpenes and olefins. Alcohols, alkanes and triterpenes were the dominant fruit wax compounds of the three plum cultivars. After storage for 20 d at room temperature, the variation of cuticular wax crystal structure and composition showed significant cultivar-associated differences. The total wax content decreased for FTL and CHL and increased for KXL, and the wax crystal degraded and melted together over time. The higher contents of the main components in the three plum cultivars were nonacosane, 1-triacontanol, 1-heneicosanol, nonacosan-10-one, octacosanal, ursolic aldehyde and oleic acid. Alcohols, triterpenes, fatty acids and aldehydes were most dramatically correlated with the softening of fruit and storage quality, and alkanes, esters and olefins were most significantly correlated with the water loss. Nonacosane and ursolic aldehyde can enhance the water retention of fruit. Overall, this study will provide a theoretical reference for the further precise development of edible plum fruit wax.