GmSABP2-1 encodes methyl salicylate esterase and functions in soybean defense against soybean cyst nematode.

KEY MESSAGE: The soybean gene GmSABP2-1 encodes methyl salicylate esterase and its overexpression led to significant reduction in development of pathogenic soybean cyst nematode. Soybean cyst nematode (SCN, Heterodera glycines) is one of the most devastating pests of soybean (Glycine max L. Merr.). In searching for SCN-defense genes, a soybean gene of the methylesterase (MES) family was found to be upregulated in an SCN-resistant soybean line and downregulated in an SCN-susceptible line upon SCN infection. This gene was designated as GmSABP2-1. Here, we report on biochemical and overexpression studies of GmSABP2-1 to examine its possible function in SCN resistance. The protein encoded by GmSABP2-1 is closely related to known methyl salicylate esterases. To determine the biochemical function of GmSABP2-1, a full-length cDNA of GmSABP2-1 was cloned into a protein expression vector and expressed in Escherichia coli. The resulting recombinant GmSABP2-1 was demonstrated to catalyze the demethylation of methyl salicylate. The biochemical properties of GmSABP2-1 were determined. Its apparent Km value was 46.2 ± 2.2 µM for methyl salicylate, comparable to those of the known methyl salicylate esterases. To explore the biological significance of GmSABP2-1 in soybean defense against SCN, we first overexpressed GmSABP2-1 in transgenic hairy roots of an SCN-susceptible soybean line. When infected with SCN, GmSABP2-1-overexpressing hairy roots showed 84.5% reduction in the development of SCN beyond J2 stage. To provide further genetic evidence for the role of GmSABP2-1 in SCN resistance, stable transgenic soybean plants overexpressing GmSABP2-1 were produced. Analysis of the GmSABP2-1-overexpressing lines showed a significant reduction in SCN development compared to non-transgenic plants. In conclusion, we demonstrated that GmSABP2-1 encodes methyl salicylate esterase and functions as a resistance-related gene against SCN.

Control of the plant-parasitic nematode Meloidogyne incognita in soil and on tomato roots by Clonostachys rosea.

AIMS: Clonostachys rosea is a well-known mycoparasite that has recently been investigated as a bio-based alternative to chemical nematicides for the control of plant-parasitic nematodes. In the search for a promising biocontrol agent, the ability of the C. rosea strain PHP1701 to control the southern root-knot nematode Meloidogyne incognita was tested. METHODS AND RESULTS: Control of M. incognita in vitro and in soil by C. rosea strain PHP1701 was significant and concentration dependent. Small pot greenhouse trials confirmed a significant reduction in tomato root galling compared to the untreated control. In a large greenhouse trial, the control effect was confirmed in early and mid-season. Tomato yield was higher when the strain PHP1701 was applied compared to the untreated M. incognita-infected control. However, the yield of non-M. incognita-infected tomato plants was not reached. A similar reduction in root galling was also observed in a field trial. CONCLUSIONS: The results highlight the potential of this fungal strain as a promising biocontrol agent for root-knot nematode control in greenhouses, especially as part of an integrated pest management approach. We recommend the use of C. rosea strain PHP1701 for short-season crops and/or to reduce M. incognita populations on fallow land before planting the next crop.

Silencing Ditylenchus destructor cathepsin L-like cysteine protease has negative pleiotropic effect on nematode ontogenesis.

Ditylenchus destructor is a migratory plant-parasitic nematode that severely harms many agriculturally important crops. The control of this pest is difficult, thus efficient strategies for its management in agricultural production are urgently required. Cathepsin L-like cysteine protease (CPL) is one important protease that has been shown to participate in various physiological and pathological processes. Here we decided to characterize the CPL gene (Dd-cpl-1) from D. destructor. Analysis of Dd-cpl-1 gene showed that Dd-cpl-1 gene contains a signal peptide, an I29 inhibitor domain with ERFNIN and GNFD motifs, and a peptidase C1 domain with four conserved active residues, showing evolutionary conservation with other nematode CPLs. RT-qPCR revealed that Dd-cpl-1 gene displayed high expression in third-stage juveniles (J3s) and female adults. In situ hybridization analysis demonstrated that Dd-cpl-1 was expressed in the digestive system and reproductive organs. Silencing Dd-cpl-1 in 1-cell stage eggs of D. destructor by RNAi resulted in a severely delay in development or even in abortive morphogenesis during embryogenesis. The RNAi-mediated silencing of Dd-cpl-1 in J2s and J3s resulted in a developmental arrest phenotype in J3 stage. In addition, silencing Dd-cpl-1 gene expression in female adults led to a 57.43% decrease in egg production. Finally, Dd-cpl-1 RNAi-treated nematodes showed a significant reduction in host colonization and infection. Overall, our results indicate that Dd-CPL-1 plays multiple roles in D. destructor ontogenesis and could serve as a new potential target for controlling D. destructor.

Soybean MKK2 establishes intricate signalling pathways to regulate soybean response to cyst nematode infection.

Mitogen-activated protein kinase (MPK) cascades play central signalling roles in plant immunity and stress response. The soybean orthologue of MPK kinase2 (GmMKK2) was recently identified as a potential signalling node whose expression is upregulated in the feeding site induced by soybean cyst nematode (SCN, Heterodera glycines). To investigate the role of GmMKK2 in soybean-SCN interactions, we overexpressed a catabolically inactive variant referred to as kinase-dead variant (KD-GmMKK2) using transgenic hairy roots. KD-GmMKK2 overexpression caused significant reduction in soybean susceptibility to SCN, while overexpression of the wild-type variant (WT-GmMKK2) exhibited no effect on susceptibility. Transcriptome analysis indicated that KD-GmMKK2 overexpressing plants are primed for SCN resistance via constitutive activation of defence signalling, particularly those related to chitin, respiratory burst, hydrogen peroxide and salicylic acid. Phosphoproteomic profiling of the WT-GmMKK2 and KD-GmMKK2 root samples upon SCN infection resulted in the identification of 391 potential targets of GmMKK2. These targets are involved in a broad range of biological processes, including defence signalling, vesicle fusion, chromatin remodelling and nuclear organization among others. Furthermore, GmMKK2 mediates phosphorylation of numerous transcriptional and translational regulators, pointing to the presence of signalling shortcuts besides the canonical MAPK cascades to initiate downstream signalling that eventually regulates gene expression and translation initiation. Finally, the functional requirement of specific phosphorylation sites for soybean response to SCN infection was validated by overexpressing phospho-mimic and phospho-dead variants of two differentially phosphorylated proteins SUN1 and IDD4. Together, our analyses identify GmMKK2 impacts on signalling modules that regulate soybean response to SCN infection.

Temperature Effects on Expression Levels of hsp Genes in Eggs and Second-Stage Juveniles of Meloidogyne hapla Chitwood, 1949.

Meloidogyne hapla is one of the most important nematode pathogens. It is a sedentary, biotrophic parasite of plants that overwinters in the soil or in diseased roots. The development of M. hapla is temperature dependent. Numerous studies have been performed on the effect of temperature on the development of M. hapla, but only a few of them analyzed the heat shock protein (hsp) genes. The aim of the study was to perform expression profiling of eight hsp genes (Mh-hsp90, Mh-hsp1, Mh-hsp4, Mh-hsp6, Mh-hsp60, Mh-dnj19, Mh-hsp43, and Mh-hsp12.2) at two development stages of M. hapla, i.e., in eggs and second-stage juveniles (J2). The eggs and J2 were incubated under cold stress (5 °C), heat stress (35 °C, 40 °C), and non-stress (10 °C, 20 °C, and 30 °C) conditions. Expression profiling was performed by qPCR. It was demonstrated that only two genes, Mh-hsp60 and Mh-dnj19, have been upregulated by heat and cold stress at both development stages. Heat stress upregulated the expression of more hsp genes than cold stress did. The level of upregulation of most hsp genes was more marked in J2 than in eggs. The obtained results suggest that the Mh-hsp90 and Mh-hsp1 genes can be used as bioindicators of environmental impacts on nematodes of the Meloidogyne genus.

Root uptake of cereal benzoxazinoids grants resistance to root-knot nematode invasion in white clover.

Plants synthesize a plethora of chemical defence compounds, which vary between evolutionary lineages. We hypothesize that plants evolved the ability to utilize defence compounds synthesized and released by neighbouring heterospecific plants. In two experiments, we incubated clover (Trifolium repens L.) seedlings with individual benzoxazinoid (BX) compounds (2,4-dihydroxy-1,4-benzoxazin-3-one, 2-hydroxy-1,4-benzoxazin-3-one, benzoxazolinone, and 6-methoxy- benzoxazolin-2-one), a group of bioactive compounds produced by cereals, to allow clover BX uptake. Subsequently, we transplanted the seedlings into soil and quantified BX root and shoot content and invasion of root-knot nematodes in clover roots up to 8 weeks after transplantation. We show that clover root uptake of BXs substantially enhanced clover's resistance against the root-knot nematode Meloidogyne incognita. This effect lasted up to 6 weeks after the clover roots were exposed to the BXs. BXs were absorbed by clover roots, and then translocated to the shoots. As a result of clover metabolization, we detected the parent BXs and a range of their transformation products in the roots and shoots. Based on these novel findings, we envisage that co-cultivation of crop species with complementary and transferable chemical defence systems can add to plant protection.

Exploiting fly ash as an ecofriendly pesticide/nematicide on Abesmoschus esculuntus: Insights into soil amendment-induced antioxidant fight against nematode mediated ROS.

Conventional pest control measures, such as chemical pesticides and nematicides, have limited efficacy and raise environmental concerns, necessitating sustainable and eco-friendly alternatives for pest management. Therefore, to find a complementary eco-friendly pesticide/nematicide, this study investigated the role of fly ash (FA) in managing a notorious pest, Meloidogyne javanica and its impact on the growth and physiology of Abelmoschus esculentus. Molecular characterization using SSU and LSU rDNA gene markers confirmed the identity of Indian M. javanica as belonging to the same species. Biotic stress induced by nematode infection was significantly alleviated (P < 0.05) by FA application at a 20% w/v, regulating of ROS accumulation (44.1% reduction in superoxide anions and 39.7% reduction in hydrogen peroxide content) in the host plant. Moreover, FA enhanced antioxidant defence enzymes like superoxide dismutase (46.6%) and catalase (112%) to combat nematode induced ROS. Furthermore, the application of FA at a 20% concentration significantly improved the biomass and biochemical attributes of okra. Fly ash also upregulated the activity of the important osmo-protectant proline (11.5 µmol/g FW) to mitigate nematode stress in host cells. Suppression of disease indices like gall index and reproduction factor, combined with in-vitro experiments, revealed that FA exhibits strong nematode mortality capacity and thus can be used as a sustainable and eco-friendly control agent against root-knot nematodes.

Conceptual Framework of Epigenetic Analyses of Plant Responses to Sedentary Endoparasitic Nematodes.

Epigenetic modifications including miRNA regulation, DNA methylation, and histone modifications play fundamental roles in establishing the interactions between host plants and parasitic nematodes. Over the past decade, an increasing number of studies revealed the key functions of various components of the plant epigenome in the regulation of gene expression and shaping plant responses to nematode infection. In this chapter, we provide a conceptual framework for methods used to investigate epigenetic regulation during plant-nematode interactions. We focus specifically on current and emerging methods used to study miRNA regulation and function. We also highlight various methods and analytical tools used to profile DNA methylation patterns and histone modification marks at the genome level. Our intention is simply to explain the advantages of various methods and how to overcome some limitations. With rapid development of single-cell sequencing technology and genome editing, advanced and new methodologies are expected to emerge in the near future to further improve our understanding of epigenetic regulation and function during plant-nematode interactions.

Transcription factor WOX11 modulates tolerance to cyst nematodes via adventitious lateral root formation.

The transcription factor WUSCHEL-RELATED HOMEOBOX 11 (WOX11) in Arabidopsis (Arabidopsis thaliana) initiates the formation of adventitious lateral roots upon mechanical injury in primary roots. Root-invading nematodes also induce de novo root organogenesis leading to excessive root branching, but it is not known if this symptom of disease involves mediation by WOX11 and if it benefits the plant. Here, we show with targeted transcriptional repression and reporter gene analyses in Arabidopsis that the beet cyst nematode Heterodera schachtii activates WOX11-mediated adventitious lateral rooting from primary roots close to infection sites. The activation of WOX11 in nematode-infected roots occurs downstream of jasmonic acid-dependent damage signaling via ETHYLENE RESPONSE FACTOR109, linking adventitious lateral root formation to nematode damage to host tissues. By measuring different root system components, we found that WOX11-mediated formation of adventitious lateral roots compensates for nematode-induced inhibition of primary root growth. Our observations further demonstrate that WOX11-mediated rooting reduces the impact of nematode infections on aboveground plant development and growth. Altogether, we conclude that the transcriptional regulation by WOX11 modulates root system plasticity under biotic stress, which is one of the key mechanisms underlying the tolerance of Arabidopsis to cyst nematode infections.

Overexpression of GmPAL Genes Enhances Soybean Resistance Against Heterodera glycines.

Soybean cyst nematode (Heterodera glycines, soybean cyst nematode [SCN]) disease adversely affects the yield of soybean and leads to billions of dollars in losses every year. To control the disease, it is necessary to study the resistance genes of the plant and their mechanisms. Isoflavonoids are secondary metabolites of the phenylalanine pathway, and they are synthesized in soybean. They are essential in plant response to biotic and abiotic stresses. In this study, we reported that phenylalanine ammonia-lyase (PAL) genes GmPALs involved in isoflavonoid biosynthesis, can positively regulate soybean resistance to SCN. Our previous study demonstrated that the expression of GmPAL genes in the resistant cultivar Huipizhi (HPZ) heidou are strongly induced by SCN. PAL is the rate-limiting enzyme that catalyzes the first step of phenylpropanoid metabolism, and it responds to biotic or abiotic stresses. Here, we demonstrate that the resistance of soybeans against SCN is suppressed by PAL inhibitor l-α-(aminooxy)-ß-phenylpropionic acid (L-AOPP) treatment. Overexpression of eight GmPAL genes caused diapause of nematodes in transgenic roots. In a petiole-feeding bioassay, we identified that two isoflavones, daidzein and genistein, could enhance resistance against SCN and suppress nematode development. This study thus reveals GmPAL-mediated resistance against SCN, information that has good application potential. The role of isoflavones in soybean resistance provides new information for the control of SCN. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

The phenylalanine ammonia-lyase inhibitor AIP induces rice defence against the root-knot nematode Meloidogyne graminicola.

The phenylalanine ammonia-lyase (PAL) enzyme catalyses the conversion of l-phenylalanine to trans-cinnamic acid. This conversion is the first step in phenylpropanoid biosynthesis in plants. The phenylpropanoid pathway produces diverse plant metabolites that play essential roles in various processes, including structural support and defence. Previous studies have shown that mutation of the PAL genes enhances disease susceptibility. Here, we investigated the functions of the rice PAL genes using 2-aminoindan-2-phosphonic acid (AIP), a strong competitive inhibitor of PAL enzymes. We show that the application of AIP can significantly reduce the PAL activity of rice crude protein extracts in vitro. However, when AIP was applied to intact rice plants, it reduced infection of the root-knot nematode Meloidogyne graminicola. RNA-seq showed that AIP treatment resulted in a rapid but transient upregulation of defence-related genes in roots. Moreover, targeted metabolomics demonstrated higher levels of jasmonates and antimicrobial flavonoids and diterpenoids accumulating after AIP treatment. Furthermore, chemical inhibition of the jasmonate pathway abolished the effect of AIP on nematode infection. Our results show that disturbance of the phenylpropanoid pathway by the PAL inhibitor AIP induces defence in rice against M. graminicola by activating jasmonate-mediated defence.

Metabolites from Lysobacter gummosus YMF3.00690 Against Meloidogyne javanica.

The strains in Lysobacter spp. have the potential to control plant-parasitic nematodes. In our experiment, L. gummosus YMF3.00690 showed antagonistic effects against plant root-knot nematode. Nine metabolites were isolated and identified from cultures of L. gummosus YMF3.00690, of which compound 1 was identified as a new metabolite tetrahydro-4,4,6-trimethyl-6-[(tetrahydro-6,6-dimethyl-2-oxo-4(1H)-pyrimidinylidene) methyl]-2(1H)-pyrimidinone. The activity assay showed that two compounds, 5-(hydroxymethyl)-1H-pyrrole-2-carbaldehyde (2) and 1H-pyrrole-2-carboxylic acid (3), had nematicidal activities against Meloidogyne javanica with mortalities of 69.93 and 90.54% at 400 ppm for 96 h, respectively. These two compounds were further tested for the inhibition activity of eggs hatching, and compound 3 showed a significant inhibition rate of 63.36% at 50 ppm for 48 h. In the chemotactic activity assay, three compounds (1 to 3) were found to have concentration-dependent chemotactic activity, of which compound 1 showed attractive activity. This experiment explored the active metabolites of L. gummosus YMF3.00690 against M. javanica and laid the foundation for biopesticide development.

The Globodera rostochiensis Gr29D09 Effector with a Role in Defense Suppression Targets the Potato Hexokinase 1 Protein.

The potato cyst nematode (Globodera rostochiensis) is an obligate root pathogen of potatoes. G. rostochiensis encodes several highly expanded effector gene families, including the Gr4D06 family; however, little is known about the function of this effector family. We cloned four 29D09 genes from G. rostochiensis (named Gr29D09v1/v2/v3/v4) that share high sequence similarity and are homologous to the Hg29D09 and Hg4D06 effector genes from the soybean cyst nematode (Heterodera glycines). Phylogenetic analysis revealed that Gr29D09 genes belong to a subgroup of the Gr4D06 family. We showed that Gr29D09 genes are expressed exclusively within the nematode's dorsal gland cell and are dramatically upregulated in parasitic stages, indicating involvement of Gr29D09 effectors in nematode parasitism. Transgenic potato lines overexpressing Gr29D09 variants showed increased susceptibility to G. rostochiensis. Transient expression assays in Nicotiana benthamiana demonstrated that Gr29D09v3 could suppress reactive oxygen species (ROS) production and defense gene expression induced by flg22 and cell death mediated by immune receptors. These results suggest a critical role of Gr29D09 effectors in defense suppression. The use of affinity purification coupled with nanoliquid chromatography-tandem mass spectrometry identified potato hexokinase 1 (StHXK1) as a candidate target of Gr29D09. The Gr29D09-StHXK1 interaction was further confirmed using in planta protein-protein interaction assays. Plant HXKs have been implicated in defense regulation against pathogen infection. Interestingly, we found that StHXK1 could enhance flg22-induced ROS production, consistent with a positive role of plant HXKs in defense. Altogether, our results suggest that targeting StHXK1 by Gr29D09 effectors may impair the positive function of StHXK1 in plant immunity, thereby aiding nematode parasitism. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

The regeneration conferring transcription factor complex ERF115-PAT1 coordinates a wound-induced response in root-knot nematode induced galls.

The establishment of root-knot nematode (RKN; Meloidogyne spp.) induced galls in the plant host roots likely involves a wound-induced regeneration response. Confocal imaging demonstrates physical stress or injury caused by RKN infection during parasitism in the model host Arabidopsis thaliana. The ERF115-PAT1 heterodimeric transcription factor complex plays a recognized role in wound-induced regeneration. ERF115 and PAT1 expression flanks injured gall cells likely driving mechanisms of wound healing, implying a local reactivation of cell division which is also hypothetically involved in gall genesis. Herein, functional investigation revealed that ectopic ERF115 expression resulted in premature induction of galls, and callus formation adjacent to the expanding female RKN was seen upon PAT1 upregulation. Smaller galls and less reproduction were observed in ERF115 and PAT1 knockouts. Investigation of components in the ERF115 network upon overexpression and knockdown by qRT-PCR suggests it contributes to steer gall wound-sensing and subsequent competence for tissue regeneration. High expression of CYCD6;1 was detected in galls, and WIND1 overexpression resulted in similar ERF115OE gall phenotypes, also showing faster gall induction. Along these lines, we show that the ERF115-PAT1 complex likely coordinates stress signalling with tissue healing, keeping the gall functional until maturation and nematode reproduction.

Metabolic variations in root tissues and rhizosphere soils of weak host plants potently lead to distinct host status and chemotaxis regulation of Meloidogyne incognita in intercropping.

Root-knot nematodes (RKNs) inflict extensive damage to global agricultural production. Intercropping has been identified as a viable agricultural tool for combating RKNs, but the mechanisms by which intercropped plants modulate RKN parasitism are still not well understood. Here, we focus on the cucumber-amaranth intercropping system. We used a range of approaches, including the attraction assay, in vitro RNA interference (RNAi), untargeted metabolomics, and hairy root transformation, to unveil the mechanisms by which weak host plants regulate Meloidogyne incognita chemotaxis towards host plants and control infection. Amaranth roots showed a direct repellence to M. incognita through disrupting its chemotaxis. The in vitro RNAi assay demonstrated that the Mi-flp-1 and Mi-flp-18 genes (encoding FMRFamide-like peptides) regulated M. incognita chemotaxis towards cucumber and controlled infection. Moreover, M. incognita infection stimulated cucumber and amaranth to accumulate distinct metabolites in both root tissues and rhizosphere soils. In particular, naringenin and salicin, enriched specifically in amaranth rhizosphere soils, inhibited the expression of Mi-flp-1 and Mi-flp-18. In addition, overexpression of genes involved in the biosynthesis of pantothenic acid and phloretin, both of which were enriched specifically in amaranth root tissues, delayed M. incognita development in cucumber hairy roots. Together, our results reveal that both the distinct host status and disruption of chemotaxis contribute to M. incognita inhibition in intercropping.

Syncytium Induced by Plant-Parasitic Nematodes.

Plant-parasitic nematodes from the genera Globodera, Heterodera (cyst-forming nematodes), and Meloidogyne (root-knot nematodes) are notorious and serious pests of crops. They cause tremendous economic losses between US $80 and 358 billion a year. Nematodes infect the roots of plants and induce the formation of specialised feeding structures (syncytium and giant cells, respectively) that nourish juveniles and adults of the nematodes. The specialised secretory glands enable nematodes to synthesise and secrete effectors that facilitate migration through root tissues and alter the morphogenetic programme of host cells. The formation of feeding sites is associated with the suppression of plant defence responses and deep reprogramming of the development and metabolism of plant cells.In this chapter, we focus on syncytia induced by the sedentary cyst-forming nematodes and provide an overview of ultrastructural changes that occur in the host roots during syncytium formation in conjunction with the most important molecular changes during compatible and incompatible plant responses to infection with nematodes.

Transcriptome Analysis of GmPUB20A Overexpressing and RNA-Interferencing Transgenic Hairy Roots Reveals Underlying Negative Role in Soybean Resistance to Cyst Nematode.

Ubiquitination genes are key components of plant responses to biotic stress. GmPUB20A, a ubiquitination gene, plays a negative role in soybean resistance to soybean cyst nematode (SCN). In this study, we employed high-throughput sequencing to investigate transcriptional changes in GmPUB20A overexpressing and RNA-interfering transgenic hairy roots. Totally, 7661 differentially expressed genes (DEGs) were identified. Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that DEGs were significantly enriched in disease resistance and signal transduction pathways. In addition, silencing Glyma.15G021600 and Glyma.09G284700 by siRNA, the total number of nematodes was decreased by 33.48% and 27.47% than control plants, respectively. Further, GUS activity and reactive oxygen species (ROS) assays revealed that GmPUB20A, Glyma.15G021600, and Glyma.09G284700 respond to SCN parasitism and interfere with the accumulation of ROS in plant roots, respectively. Collectively, our study provides insights into the molecular mechanism of GmPUB20A in soybean resistance to SCN.

Novel Genes and Key Signaling Molecules Involved in the Repulsive Response of Meloidogyne incognita against Biocontrol Bacteria.

The ability of the model organism, Caenorhabditis elegans, to distinguish and escape from pathogenic bacteria has been extensively studied; however, studies on the repulsive response of Meloidogyne incognita are still in their infancy. We have recently demonstrated that biocontrol bacteria induce a repulsive response in M. incognita via two classical signaling pathways. The present study aimed to identify the novel genes and signaling molecules of M. incognita that potentially contribute to its defense reaction. Analysis of the transcriptome data of M. incognita with and without a repulsive response against Bacillus nematocida B16 obtained 15 candidate genes, of which the novel genes Minc3s01748g26034 and Minc3s02548g30585 were found to regulate the aversive behavior of M. incognita, and their functions were further validated. To further confirm the neuronal localization of the two novel genes in M. incognita, in situ hybridization was conducted using the digoxin-labeled probes of ten tag genes, and preferentially profiled the localization of amphid sensory neurons of M. incognita. Analysis of the overviewed neuronal map suggested that Minc3s01748g26034 and Minc3s02548g30585 functioned in ASK/ASI and CEPD/V neurons, respectively. During their interactions, the volatile compounds 3-methyl-butyric acid and 2-methyl-butyric acid produced by the biocontrol bacteria were predicted as the primary signaling molecules that promoted the repulsive behavior of M. incognita against biocontrol bacteria. The findings provided novel insights into the mechanisms underlying the repulsive response of M. incognita that are different from the canonical molecular pathways previously found in C. elegans and can aid in developing novel strategies for controlling root-knot nematodes.

Soybean-SCN Battle: Novel Insight into Soybean's Defense Strategies against Heterodera glycines.

Soybean cyst nematode (SCN, Heterodera glycines, Ichinohe) poses a significant threat to global soybean production, necessitating a comprehensive understanding of soybean plants' response to SCN to ensure effective management practices. In this study, we conducted dual RNA-seq analysis on SCN-resistant Plant Introduction (PI) 437654, 548402, and 88788 as well as a susceptible line (Lee 74) under exposure to SCN HG type 1.2.5.7. We aimed to elucidate resistant mechanisms in soybean and identify SCN virulence genes contributing to resistance breakdown. Transcriptomic and pathway analyses identified the phenylpropanoid, MAPK signaling, plant hormone signal transduction, and secondary metabolite pathways as key players in resistance mechanisms. Notably, PI 437654 exhibited complete resistance and displayed distinctive gene expression related to cell wall strengthening, oxidative enzymes, ROS scavengers, and Ca2+ sensors governing salicylic acid biosynthesis. Additionally, host studies with varying immunity levels and a susceptible line shed light on SCN pathogenesis and its modulation of virulence genes to evade host immunity. These novel findings provide insights into the molecular mechanisms underlying soybean-SCN interactions and offer potential targets for nematode disease management.

Meloidogyne enterolobii MeMSP1 effector targets the glutathione-S-transferase phi GSTF family in Arabidopsis to manipulate host metabolism and promote nematode parasitism.

Meloidogyne enterolobii is an emerging root-knot nematode species that overcomes most of the nematode resistance genes in crops. Nematode effector proteins secreted in planta are key elements in the molecular dialogue of parasitism. Here, we show the MeMSP1 effector is secreted into giant cells and promotes M. enterolobii parasitism. Using co-immunoprecipitation and bimolecular fluorescent complementation assays, we identified glutathione-S-transferase phi GSTFs as host targets of the MeMSP1 effector. This protein family plays important roles in plant responses to abiotic and biotic stresses. We demonstrate that MeMSP1 interacts with all Arabidopsis GSTF. Moreover, we confirmed that the N-terminal region of AtGSTF9 is critical for its interaction, and atgstf9 mutant lines are more susceptible to root-knot nematode infection. Combined transcriptome and metabolome analyses showed that MeMSP1 affects the metabolic pathways of Arabidopsis thaliana, resulting in the accumulation of amino acids, nucleic acids, and their metabolites, and organic acids and the downregulation of flavonoids. Our study has shed light on a novel effector mechanism that targets plant metabolism, reducing the production of plant defence-related compounds while favouring the accumulation of metabolites beneficial to the nematode, and thereby promoting parasitism.