Effect of Temperature on the Embryogenesis of Three Geographically Distinct Populations of Meloidogyne incognita Is Driven by Intrinsic Thermal Acclimation Reaction.

Research interest in the mechanisms enabling plant-parasitic nematodes to adjust their physiological performance and cope with changing temperatures has intensified in light of global warming. Here, we show that geographically distinct populations of the root-knot nematode Meloidogyne incognita, which is prevalent in the three main pepper-growing regions in Israel-Carmel Valley (Carmel), Jordan Valley (JV), and Arava Rift (Arava)-possess persistent differences in their thermal acclimation capacity, which affect pre- and postembryonic development. The optimal temperature for embryonic growth completion was 25°C for the Carmel population; 25 and 30°C for the JV population; and 30°C for the Arava population. Cumulative hatching percentages showed variations among populations; relative to hatching at 25°C, the Carmel population experienced hatching reduction at the higher studied temperatures 30 and 33°C, while the JV and Arava populations exhibited an increase in hatching at 30 and 33°C, respectively. Juvenile survival indicates that at the lowest temperature (20°C), the Carmel population gained the highest survival rates throughout the experimental duration, while at the same duration at 33°C, the Arava population gained the highest survival rate. Infective juveniles of the Carmel population demonstrated increased penetration of tomato roots at 25°C compared to the JV and Arava populations. Inversely, at 33°C, increased penetration was observed for the Arava compared to the Carmel and JV populations. Altogether, the Arava population's performance at 33°C might incur distinct fitness costs, resulting in consistent attenuation compared to the Carmel population at 25°C. Precisely defining a population's thermal acclimation response might provide essential information for models that predict the impact of future climate change on these populations.

Optimizing sustainable control of Meloidogyne javanica in tomato plants through gamma radiation-induced mutants of Trichoderma harzianum and Bacillus velezensis.

This study investigates the efficacy of Trichoderma spp. and Bacillus spp., as well as their gamma radiation-induced mutants, as potential biological control agents against Meloidogyne javanica (Mj) in tomato plants. The research encompasses in vitro assays, greenhouse trials, and molecular identification methodologies to comprehensively evaluate the biocontrol potential of these agents. In vitro assessments reveal significant nematicidal activity, with Bacillus spp. demonstrating notable effectiveness in inhibiting nematode egg hatching (16-45%) and inducing second-stage juvenile (J2) mortality (30-46%). Greenhouse trials further confirm the efficacy of mutant isolates, particularly when combined with chitosan, in reducing nematode-induced damage to tomato plants. The combination of mutant isolates with chitosan reduces the reproduction factor (RF) of root-knot nematodes by 94%. By optimizing soil infection conditions with nematodes and modifying the application of the effective compound, the RF of nematodes decreases by 65-76%. Molecular identification identifies B. velezensis and T. harzianum as promising candidates, exhibiting significant nematicidal activity. Overall, the study underscores the potential of combined biocontrol approaches for nematode management in agricultural settings. However, further research is essential to evaluate practical applications and long-term efficacy. These findings contribute to the development of sustainable alternatives to chemical nematicides, with potential implications for agricultural practices and crop protection strategies.

Genetic variations underlying root-knot nematode resistance in sweetpotato.

Root-knot nematode (Meloidogyne incognita) causes severe crop damage and large economic losses worldwide. Several cultivars of sweetpotato [Ipomoea batatas (L.) Lam)] have been developed with root-knot nematode-resistant traits; however, many of these cultivars do not have favorable agronomic characteristics. To understand the genetic traits underlying M. incognita resistance in sweetpotato, whole genome resequencing was conducted on three RKN-susceptible (Dahomi, Shinhwangmi, and Yulmi) and three RKN-resistant (Danjami, Pungwonmi, and Juhwangmi) sweetpotato cultivars. Three SNPs (single nucleotide polymorphisms) in promotor sequences were shared in RKN-resistant cultivars and were correlated with disease resistance. One of these SNPs was located in G6617|TU10904, which encoded a homolog of RIBOSOMAL PROTEIN EL15Z, and was associated with reduced expression in RKN-resistant cultivars only. Alongside SNP analysis, mRNA-seq data were analyzed for the same cultivars with and without nematode infection, and 18 nematode-sensitive genes were identified that responded in a cultivar-specific manner. Of these genes, expression of G8735|TU14367 was lower in sensitive cultivars than in RKN-resistant cultivars. Overall, this study identified two genes that potentially have key roles in the regulation of nematode resistance and will be useful targets for nematode resistance breeding programs.

Optimization and utilization of emerging waste (fly ash) for growth performance of chickpea (Cicer arietinum L.) plant and mitigation of root-knot nematode (Meloidogyne incognita) stress.

The sustainable management of large amounts of fly ash (FA) is a concern for researchers, and we aim to determine the FA application in plant development and nematicidal activity in the current study. A pot study is therefore performed to assess the effects of adding different, FA-concentrations to soil (w/w) on the infection of chickpea plants with the root-knot nematode Meloidogyne incognita. Sequence characteristic amplified region (SCAR) and internal transcribed spacer (ITS) region-based-markers were used to molecularly confirm M. incognita. With better plant growth and chickpea yield performance, FA enhanced the nutritious components of the soil. When compared with untreated, uninoculated control (UUC) plants, the inoculation of M. incognita dramatically reduced chickpea plant growth, yield biomass, and metabolism. The findings showed that the potential of FA to lessen the root-knot nematode illness in respect of galls, egg-masses, and reproductive attributes may be used to explain the mitigating effect of FA. Fascinatingly, compared with the untreated, inoculated control (UIC) plants, the FA treatment, primarily at 20%, considerably (p ≤ 0.05) boosted plant growth, yield biomass, and pigment content. Additionally, when the amounts of FA rose, the activity of antioxidants like superoxide dismutase-SOD, catalase-CAT, and peroxidase-POX as well as osmo-protectants like proline gradually increased. Therefore, our findings imply that 20% FA can be successfully applied as a potential strategy to increase biomass yield and plant growth while simultaneously reducing M. incognita infection in chickpea plants.

Differential induction of defense genes in hexaploid wheat roots by the plant-parasitic nematodes Pratylenchus neglectus and P. thornei.

Pratylenchus neglectus and P. thornei are among the most destructive root lesion nematodes of wheat in the Pacific Northwest, United States of America and throughout the world. The aim of this study was to determine whether both nematode species were similar in their ability to induce defense genes in roots of wheat genotype Scarlet, and whether a combination of both species induced a different pattern of gene induction than each species alone. The long-term aspect of the research was to identify nematode-inducible promoters for deploying defense genes in roots in breeding programs. The root transcriptomes of genotype Scarlet were obtained after a one-week infection period with each nematode species separately, or both species combined. Root defense gene expression was induced for all three treatments relative to the no-nematode control, but P. thornei affected expression to a greater extent compared to P. neglectus. The species combination induced the highest number of defense genes. This result was not predicted from nematode enumeration studies, in which P. thornei colonization was substantially lower than that of P. neglectus, and the nematode combination did not show a significant difference. Quantitative real time polymerase chain reaction (qRT-PCR) assays for Dehydrin2, Glucan endo-1,3-beta-glucosidase, 1-cys-Peroxiredoxin, Pathogenesis-related protein 1 and Late embryogenesis-abundant proteins 76 and group 3 authenticated the induction observed in the transcriptome data. In addition, a near-isogenic line of Scarlet harboring genetic resistance to fungal soilborne pathogens, called Scarlet-Rz1, showed similar or higher levels of defense gene expression compared to fungus-susceptible Scarlet in qRT-PCR assays. Finally, transcriptome expression patterns revealed nematode-inducible promoters that are responsive to both P. neglectus and P. thornei.

Study on the Function of SlWRKY80 in Tomato Defense against Meloidogyne incognita.

WRKY transcription factors (TFs) can participate in plant biological stress responses and play important roles. SlWRKY80 was found to be differentially expressed in the Mi-1- and Mi-3-resistant tomato lines by RNA-seq and may serve as a key node for disease resistance regulation. This study used RNAi to determine whether SlWRKY80 silencing could influence the sensitivity of 'M82' (mi-1/mi-1)-susceptible lines to M. incognita. Further overexpression of this gene revealed a significant increase in tomato disease resistance, ranging from highly susceptible to susceptible, combined with the identification of growth (plant height, stem diameter, and leaf area) and physiological (soluble sugars and proteins; root activity) indicators, clarifying the role of SlWRKY80 as a positive regulatory factor in tomato defense against M. incognita. Based on this phenomenon, a preliminary exploration of its metabolic signals revealed that SlWRKY80 stimulates different degrees of signaling, such as salicylic acid (SA), jasmonic acid (JA), and ethylene (ETH), and may synergistically regulate reactive oxygen species (ROS) accumulation and scavenging enzyme activity, hindering the formation of feeding sites and ultimately leading to the reduction of root gall growth. To our knowledge, SlWRKY80 has an extremely high utilization value for improving tomato resistance to root-knot nematodes and breeding.

Nematode-trapping fungus Arthrobotrys oligospora recruited rhizosphere microorganisms to cooperate in controlling root-knot nematodes in tomato.

AIMS: The objective of this study was to elucidate the role and mechanism of changes in the rhizosphere microbiome following Arthrobotrys oligospora treatment in the biological control of root-knot nematodes and identify the key fungal and bacterial species that collaborate with A. oligospora to biocontrol root-knot nematodes. METHODS AND RESULTS: We conducted a pot experiment to investigate the impact of A. oligospora treatment on the biocontrol efficiency of A. oligospora against Meloidogyne incognita infecting tomatoes. We analyzed the rhizosphere bacteria and fungi communities of tomato by high-throughput sequencing of the 16S rRNA gene fragment and the internal transcribed spacer (ITS). The results indicated that the application of A. oligospora resulted in a 53.6% reduction in the disease index of M. incognita infecting tomato plants. The bacterial diversity of rhizosphere soil declined in the A. oligospora-treated group, while fungal diversity increased. The A. oligospora treatment enriched the tomato rhizosphere with Acidobacteriota, Firmicutes, Bradyrhizobium, Sphingomonadales, Glomeromycota, and Purpureocillium. These organisms are involved in the utilization of rhizosphere organic matter, nitrogen, and glycerolipids, or play the role of ectomycorrhiza or directly kill nematodes. The networks of bacterial and fungal co-occurrence exhibited a greater degree of stability and complexity in the A. oligospora treatment group. CONCLUSIONS: This study demonstrated the key fungal and bacterial species that collaborate with the A. oligospora in controlling the root-knot nematode and elaborated the potential mechanisms involved. The findings offer valuable insights and inspiration for the advancement of bionematicide based on nematode-trapping fungi.

Protective role of native root-associated bacterial consortium against root-knot nematode infection in susceptible plants.

Root-knot nematodes (RKNs) are a global menace to agricultural crop production. The role of root-associated microbes (RAMs) in plant protection against RKN infection remains unclear. Here we observe that cucumber (highly susceptible to Meloidogyne incognita) exhibits a consistently lower susceptibility to M. incognita in the presence of native RAMs in three distinct soils. Nematode infection alters the assembly of bacterial RAMs along the life cycle of M. incognita. Particularly, the loss of bacterial diversity of RAMs exacerbates plant susceptibility to M. incognita. A diverse range of native bacterial strains isolated from M. incognita-infected roots has nematode-antagonistic activity. Increasing the number of native bacterial strains causes decreasing nematode infection, which is lowest when six or more bacterial strains are present. Multiple simplified synthetic communities consisting of six bacterial strains show pronounced inhibitory effects on M. incognita infection in plants. These inhibitory effects are underpinned via multiple mechanisms including direct inhibition of infection, secretion of anti-nematode substances, and regulation of plant defense responses. This study highlights the role of native bacterial RAMs in plant resistance against RKNs and provides a useful insight into the development of a sustainable way to protect susceptible plants.

Redundancy in microbiota-mediated suppression of the soybean cyst nematode.

BACKGROUND: Soybean cyst nematodes (SCN) as animal parasites of plants are not usually interested in killing the host but are rather focused on completing their life cycle to increase population, resulting in substantial yield losses. Remarkably, some agricultural soils after long-term crop monoculture show a significant decline in SCN densities and suppress disease in a sustainable and viable manner. However, relatively little is known about the microbes and mechanisms operating against SCN in such disease-suppressive soils. RESULTS: Greenhouse experiments showed that suppressive soils (S) collected from two provinces of China and transplantation soils (CS, created by mixing 10% S with 90% conducive soils) suppressed SCN. However, SCN suppressiveness was partially lost or completely abolished when S soils were treated with heat (80 °C) and formalin. Bacterial community analysis revealed that the specific suppression in S and CS was mainly associated with the bacterial phylum Bacteroidetes, specifically due to the enrichment of Chitinophaga spp. and Dyadobacter sp., in the cysts. SCN cysts colonized by Chitinophaga spp. showed dramatically reduced egg hatching, with unrecognizable internal body organization of juveniles inside the eggshell due to chitinase activity. Whereas, Dyadobacter sp. cells attached to the surface coat of J2s increased soybean resistance against SCN by triggering the expression of defence-associated genes. The disease-suppressive potential of these bacteria was validated by inoculating them into conducive soil. The Dyadobacter strain alone or in combination with Chitinophaga strains significantly decreased egg densities after one growing cycle of soybeans. In contrast, Chitinophaga strains alone required more than one growing cycle to significantly reduce SCN egg hatching and population density. CONCLUSION: This study revealed how soybean monoculture for decades induced microbiota homeostasis, leading to the formation of SCN-suppressive soil. The high relative abundance of antagonistic bacteria in the cyst suppressed the SCN population both directly and indirectly. Because uncontrolled proliferation will likely lead to quick demise due to host population collapse, obligate parasites like SCN may have evolved to modulate virulence/proliferation to balance these conflicting needs. Video Abstract.

The root-knot nematode effector MiEFF12 targets the host ER quality control system to suppress immune responses and allow parasitism.

Root-knot nematodes (RKNs) are microscopic parasitic worms able to infest the roots of thousands of plant species, causing massive crop yield losses worldwide. They evade the plant's immune system and manipulate plant cell physiology and metabolism to transform a few root cells into giant cells, which serve as feeding sites for the nematode. RKN parasitism is facilitated by the secretion in planta of effector molecules, mostly proteins that hijack host cellular processes. We describe here a conserved RKN-specific effector, effector 12 (EFF12), that is synthesized exclusively in the oesophageal glands of the nematode, and we demonstrate its function in parasitism. In the plant, MiEFF12 localizes to the endoplasmic reticulum (ER). A combination of RNA-sequencing analysis and immunity-suppression bioassays revealed the contribution of MiEFF12 to the modulation of host immunity. Yeast two-hybrid, split luciferase and co-immunoprecipitation approaches identified an essential component of the ER quality control system, the Solanum lycopersicum plant bap-like (PBL), and basic leucine zipper 60 (BZIP60) proteins as host targets of MiEFF12. Finally, silencing the PBL genes in Nicotiana benthamiana decreased susceptibility to Meloidogyne incognita infection. Our results suggest that EFF12 manipulates PBL function to modify plant immune responses to allow parasitism.

MiR398b Targets Superoxide Dismutase Genes in Soybean in Defense Against Heterodera glycines via Modulating Reactive Oxygen Species Homeostasis.

MicroRNAs play crucial roles in plant defense responses. However, the underlying mechanism by which miR398b contributes to soybean responses to soybean cyst nematode (Heterodera glycines) remains elusive. In this study, by using Agrobacterium rhizogenes-mediated transformation of soybean hairy roots, we observed that miR398b and target genes GmCCS and GmCSD1b played vital functions in soybean-H. glycines interaction. The study revealed that the abundance of miR398b was downregulated by H. glycines infection, and overexpression of miR398b enhanced the susceptibility of soybean to H. glycines. Conversely, silencing of miR398b improved soybean resistance to H. glycines. Detection assays revealed that miR398b rapidly senses stress-induced reactive oxygen species, leading to the repression of target genes GmCCS and GmCSD1b and regulating the accumulation of plant defense genes against nematode infection. Moreover, exogenous synthetic ds-miR398b enhanced soybean sensitivity to H. glycines by modulating H2O2 and O2- levels. Functional analysis demonstrated that overexpression of GmCCS and GmCSD1b in soybean enhanced resistance to H. glycines. RNA interference-mediated repression of GmCCS and GmCSD1b in soybean increased susceptibility to H. glycines. RNA sequencing revealed that a majority of differentially expressed genes in overexpressed GmCCS were associated with oxidative stress. Overall, the results indicate that miR398b targets superoxide dismutase genes, which negatively regulate soybean resistance to H. glycines via modulating reactive oxygen species levels and defense signals.

Biocontrol potential of endophytic fungi against phytopathogenic nematodes on potato (Solanum tuberosum L.).

Root-knot nematodes (RKNs) are a vital pest that causes significant yield losses and economic damage to potato plants. The use of chemical pesticides to control these nematodes has led to environmental concerns and the development of resistance in the nematode populations. Endophytic fungi offer an eco-friendly alternative to control these pests and produce secondary metabolites that have nematicidal activity against RKNs. The objective of this study is to assess the efficacy of Aspergillus flavus (ON146363), an entophyte fungus isolated from Trigonella foenum-graecum seeds, against Meloidogyne incognita in filtered culture broth using GC-MS analysis. Among them, various nematicidal secondary metabolites were produced: Gadoleic acid, Oleic acid di-ethanolamide, Oleic acid, and Palmitic acid. In addition, biochemical compounds such as Gallic acid, Catechin, Protocatechuic acid, Esculatin, Vanillic acid, Pyrocatechol, Coumarine, Cinnamic acid, 4, 3-indol butyl acetic acid and Naphthyl acetic acid by HPLC. The fungus was identified through morphological and molecular analysis, including ITS 1-4 regions of ribosomal DNA. In vitro experiments showed that culture filtrate of A. flavus had a variable effect on reducing the number of egg hatchings and larval mortality, with higher concentrations showing greater efficacy than Abamectin. The fungus inhibited the development and multiplication of M. incognita in potato plants, reducing the number of galls and eggs by 90% and 89%, respectively. A. flavus increased the activity of defense-related enzymes Chitinas, Catalyse, and Peroxidase after 15, 45, and 60 days. Leaching of the concentrated culture significantly reduced the second juveniles' stage to 97% /250 g soil and decreased the penetration of nematodes into the roots. A. flavus cultural filtrates via soil spraying improved seedling growth and reduced nematode propagation, resulting in systemic resistance to nematode infection. Therefore, A. flavus can be an effective biological control agent for root-knot nematodes in potato plants. This approach provides a sustainable solution for farmers and minimizes the environmental impact.

Light signaling regulates root-knot nematode infection and development via HY5-SWEET signaling.

BACKGROUND: Meloidogyne incognita is one of the most important plant-parasitic nematodes and causes tremendous losses to the agricultural economy. Light is an important living factor for plants and pathogenic organisms, and sufficient light promotes root-knot nematode infection, but the underlying mechanism is still unclear. RESULTS: Expression level and genetic analyses revealed that the photoreceptor genes PHY, CRY, and PHOT have a negative impact on nematode infection. Interestingly, ELONGATED HYPOCOTYL5 (HY5), a downstream gene involved in the regulation of light signaling, is associated with photoreceptor-mediated negative regulation of root-knot nematode resistance. ChIP and yeast one-hybrid assays supported that HY5 participates in plant-to-root-knot nematode responses by directly binding to the SWEET negative regulatory factors involved in root-knot nematode resistance. CONCLUSIONS: This study elucidates the important role of light signaling pathways in plant resistance to nematodes, providing a new perspective for RKN resistance research.

Unraveling the enigma of root-knot nematodes: from origins to advanced management strategies in agriculture.

MAIN CONCLUSION: Integrated management strategies, including novel nematicides and resilient cultivars, offer sustainable solutions to combat root-knot nematodes, crucial for safeguarding global agriculture against persistent threats. Root-knot nematodes (RKN) pose a significant threat to a diverse range of host plants, with their obligatory endoparasitic nature leading to substantial agricultural losses. RKN spend much of their lives inside or in contact by secreting plant cell wall-modifying enzymes resulting in the giant cell development for establishing host-parasite relationships. Additionally, inflicting physical harm to host plants, RKN also contributes to disease complexes creation with fungi and bacteria. This review comprehensively explores the origin, history, distribution, and physiological races of RKN, emphasizing their economic impact on plants through gall formation. Management strategies, ranging from cultural and physical to biological and chemical controls, along with resistance mechanisms and marker-assisted selection, are explored. While recognizing the limitations of traditional nematicides, recent breakthroughs in non-fumigant alternatives like fluensulfone, spirotetramat, and fluopyram offer promising avenues for sustainable RKN management. Despite the success of resistance mechanisms like the Mi gene, challenges persist, prompting the need for integrative approaches to tackle Mi-virulent isolates. In conclusion, the review stresses the importance of innovative and resilient control measures for sustainable agriculture, emphasizing ongoing research to address evolving challenges posed by RKN. The integration of botanicals, resistant cultivars, and biological controls, alongside advancements in non-fumigant nematicides, contributes novel insights to the field, laying the ground work for future research directions to ensure the long-term sustainability of agriculture in the face of persistent RKN threats.

Unraveling the Roles of Neuropeptides in the Chemosensation of the Root-Knot Nematode Meloidogyne javanica.

The identification of novel drug targets in plant-parasitic nematodes (PPNs) is imperative due to the loss of traditional nematicides and a lack of replacements. Chemosensation, which is pivotal for PPNs in locating host roots, has become a focus in nematode behavioral research. However, its underlying molecular basis is still indistinct in such a diverse group of PPNs. To characterize genes participating in chemosensation in the Javanese root-knot nematode Meloidogyne javanica, RNA-sequencing of the second-stage juveniles (J2s) treated with tomato root exudate (TRE) for 1 h and 6 h was performed. Genes related to chemosensation in M. javanica mainly responded to TRE treatment at 1 h. Moreover, a gene ontology (GO) analysis underscored the significance of the neuropeptide G protein-coupled receptor signaling pathway. Consequently, the repertoire of putative neuropeptides in M. javanica, including FMRFamide-like peptides (FLPs), insulin-like peptides (ILPs), and neuropeptide-like peptides (NLPs), were outlined based on a homology analysis. The gene Mjflp-14a, harboring two neuropeptides, was significantly up-regulated at 1 h TRE treatment. Through peptide synthesis and J2 treatment, one of the two neuropeptides (MjFLP-14-2) was proven to influence the J2 chemotaxis towards tomato root tips. Overall, our study reinforces the potential of nematode neuropeptides as novel targets and tools for root-knot nematode control.

CRISPR/Cas9-induced knockout of an amino acid permease gene (AAP6) reduced Arabidopsis thaliana susceptibility to Meloidogyne incognita.

BACKGROUND: Plant-parasitic root-knot nematode (Meloidogyne incognita) causes global yield loss in agri- and horticultural crops. Nematode management options rely on chemical method. However, only a handful of nematicides are commercially available. Resistance breeding efforts are not sustainable because R gene sources are limited and nematodes have developed resistance-breaking populations against the commercially available Mi-1.2 gene-expressing tomatoes. RNAi crops that manage nematode infection are yet to be commercialized because of the regulatory hurdles associated with transgenic crops. The deployment of the CRISPR/Cas9 system to improve nematode tolerance (by knocking out the susceptibility factors) in plants has emerged as a feasible alternative lately. RESULTS: In the present study, a M. incognita-responsive susceptibility (S) gene, amino acid permease (AAP6), was characterized from the model plant Arabidodpsis thaliana by generating the AtAAP6 overexpression line, followed by performing the GUS reporter assay by fusing the promoter of AtAAP6 with the ß-glucuronidase (GUS) gene. Upon challenge inoculation with M. incognita, overexpression lines supported greater nematode multiplication, and AtAAP6 expression was inducible to the early stage of nematode infection. Next, using CRISPR/Cas9, AtAAP6 was selectively knocked out without incurring any growth penalty in the host plant. The 'Cas9-free' homozygous T3 line was challenge inoculated with M. incognita, and CRISPR-edited A. thaliana plants exhibited considerably reduced susceptibility to nematode infection compared to the non-edited plants. Additionally, host defense response genes were unaltered between edited and non-edited plants, implicating the direct role of AtAAP6 towards nematode susceptibility. CONCLUSION: The present findings enrich the existing literature on CRISPR/Cas9 research in plant-nematode interactions, which is quite limited currently while compared with the other plant-pathogen interaction systems.

Host-induced RNA interference targeting the neuromotor gene FMRFamide-like peptide-14 (Mi-flp14) perturbs Meloidogyne incognita parasitic success in eggplant.

KEY MESSAGE: The study demonstrates the successful management of Meloidogyne incognita in eggplant using Mi-flp14 RNA interference, showing reduced nematode penetration and reproduction without off-target effects across multiple generations. Root-knot nematode, Meloidogyne incognita, causes huge yield losses worldwide. Neuromotor function in M. incognita governed by 19 neuropeptides is vital for parasitism and parasite biology. The present study establishes the utility of Mi-flp14 for managing M. incognita in eggplant in continuation of our earlier proof of concept in tobacco (US patent US2015/0361445A1). Mi-flp14 hairpin RNA construct was used for generating 19 independent transgenic eggplant events. PCR and Southern hybridization analysis confirmed transgene integration and its orientation, while RT-qPCR and Northern hybridization established the generation of dsRNA and siRNA of Mi-flp14. In vitro and in vivo bio-efficacy analysis of single-copy events against M. incognita showed reduced nematode penetration and development at various intervals that negatively impacted reproduction. Interestingly, M. incognita preferred wild-type plants over the transgenics even when unbiased equal opportunity was provided for the infection. A significant reduction in disease parameters was observed in transgenic plants viz., galls (40-48%), females (40-50%), egg masses (35-40%), eggs/egg mass (50-55%), and derived multiplication factor (60-65%) compared to wild type. A unique demonstration of perturbed expression of Mi-flp14 in partially penetrated juveniles and female nematodes established successful host-mediated RNAi both at the time of penetration even before the nematodes started withdrawing plant nutrients and later stage, respectively. The absence of off-target effects in transgenic plants was supported by the normal growth phenotype of the plants and T-DNA integration loci. Stability in the bio-efficacy against M. incognita across T1- to T4-generation transgenic plants established the utility of silencing Mi-flp14 for nematode management. This study demonstrates the significance of targeting Mi-flp14 in eggplant for nematode management, particularly to address global agricultural challenges posed by M. incognita.

Glycine max polygalacturonase inhibiting protein 11 (GmPGIP11) functions in the root to suppress Heterodera glycines parasitism.

Pathogen-secreted polygalacturonases (PGs) alter plant cell wall structure by cleaving the α-(1 â†’ 4) linkages between D-galacturonic acid residues in homogalacturonan (HG), macerating the cell wall, facilitating infection. Plant PG inhibiting proteins (PGIPs) disengage pathogen PGs, impairing infection. The soybean cyst nematode, Heterodera glycines, obligate root parasite produces secretions, generating a multinucleate nurse cell called a syncytium, a byproduct of the merged cytoplasm of 200-250 root cells, occurring through cell wall maceration. The common cytoplasmic pool, surrounded by an intact plasma membrane, provides a source from which H. glycines derives nourishment but without killing the parasitized cell during a susceptible reaction. The syncytium is also the site of a naturally-occurring defense response that happens in specific G. max genotypes. Transcriptomic analyses of RNA isolated from the syncytium undergoing the process of defense have identified that one of the 11 G. max PGIPs, GmPGIP11, is expressed during defense. Functional transgenic analyses show roots undergoing GmPGIP11 overexpression (OE) experience an increase in its relative transcript abundance (RTA) as compared to the ribosomal protein 21 (GmRPS21) control, leading to a decrease in H. glycines parasitism as compared to the overexpression control. The GmPGIP11 undergoing RNAi experiences a decrease in its RTA as compared to the GmRPS21 control with transgenic roots experiencing an increase in H. glycines parasitism as compared to the RNAi control. Pathogen associated molecular pattern (PAMP) triggered immunity (PTI) and effector triggered immunity (ETI) components are shown to influence GmPGIP11 expression while numerous agricultural crops are shown to have homologs.

Evaluation of Chemical-Inducible Gene Expression Systems for Beet Cyst Nematode Infection Assays in Arabidopsis thaliana.

Cyst nematodes co-opt plant developmental programs for the establishment of a permanent feeding site called a syncytium in plant roots. In recent years, the role of plant developmental genes in syncytium formation has gained much attention. One main obstacle in studying the function of development-related genes in syncytium formation is that mutation or ectopic expression of such genes can cause pleiotropic phenotypes, making it difficult to interpret nematode-related phenotypes or, in some cases, impossible to carry out infection assays due to aberrant root development. Here, we tested three commonly used inducible gene expression systems for their application in beet cyst nematode infection assays of the model plant Arabidopsis thaliana. We found that even a low amount of ethanol diminished nematode development, deeming the ethanol-based system unsuitable for use in cyst nematode infection assays, whereas treatment with estradiol or dexamethasone did not negatively affect cyst nematode viability. Dose and time course responses showed that in both systems, a relatively low dose of inducer (1 µM) is sufficient to induce high transgene expression within 24 h of treatment. Transgene expression peaked at 3 to 5 days post-induction and began to decline thereafter, providing a perfect window for inducible transgenes to interfere with syncytium establishment while minimizing any adverse effects on root development. These results indicate that both estradiol- and dexamethasone-based inducible gene expression systems are suitable for cyst nematode infection assays. The employment of such systems provides a powerful tool to investigate the function of essential plant developmental genes in syncytium formation. [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.

Fortifying nematode resistance through susceptibility gene inactivation.

The predominant genetic defense mechanism against soybean cyst nematode (SCN) in 95% of the North America market is under threat by virulent SCN populations. Usovsky et al. identified GmSNAP02 as an SCN susceptibility gene through fine-mapping of unique bi-parental populations. Loss-of-function of GmSNAP02 confers enhanced resistance to more virulent SCN.