Plant-parasitic Cyst Nematodes Research Articles

Identification and characterization of microRNA396 and its targets in Cucumis metuliferus infected with Meloidogyne incognita

MicroRNAs (miRNAs), a class of non-coding small RNAs, play an important role in biotic and abiotic stresses. Previously, great progress has been made in miRNA-guided gene regulation in plant-parasitic cyst nematodes interactions. However, little is known about miRNAs regulation of nematode stress response in Cucumis metuliferus, which is a relative of cultivated cucumber or melon and highly resistant to the root-knot nematode Meloidogyne incognita. On the basis of our investigation recently, five cmu-miR396 precursors were firstly identified and characterized from C. metuliferus in this study. Subquently, a total of 12 genes were predicted to be as the potential targets of cmu-miR396 and their function involved in transcription factor, metabolism, signal transduction and stress response. Moreover, three cmu-GRFs genes with significant differential expression in roots of C. metuliferus were successfully amplified and confirmed by RT-PCR experimently. Additionally, the analysis was performed for the phylogeny and subcellular localization of cmu-GRFs protein, and the three transcription factors cmu-GRFs were confirmed as the candidate targets of cmu-miR396 through 5′RLM-RACE assays. These data laid a foundation for further functional analyses to reveal the roles played by miR396 during the interaction between C. metuliferus and M. incognita, leading to a better understanding of the mechanisms and underlying regulatory networks of miR396-mediated resistance to M. incognita in C. metuliferus.

The Bacterial Gq Signal Transduction Inhibitor FR900359 Impairs Soil-Associated Nematodes

The cyclic depsipeptide FR900359 (FR) is derived from the soil bacterium Chromobacterium vaccinii and known to bind Gq proteins of mammals and insects, thereby abolishing the signal transduction of their Gq protein-coupled receptors, a process that leads to severe physiological consequences. Due to their highly conserved structure, Gq family of proteins are a superior ecological target for FR producing organisms, resulting in a defense towards a broad range of harmful organisms. Here, we focus on the question whether bacteria like C. vaccinii are important factors in soil in that their secondary metabolites impair, e.g., plant harming organisms like nematodes. We prove that the Gq inhibitor FR is produced under soil-like conditions. Furthermore, FR inhibits heterologously expressed Gαq proteins of the nematodes Caenorhabditis elegans and Heterodera schachtii in the micromolar range. Additionally, in vivo experiments with C. elegans and the plant parasitic cyst nematode H. schachtii demonstrated that FR reduces locomotion of C. elegans and H. schachtii. Finally, egg-laying of C. elegans and hatching of juvenile stage 2 of H. schachtii from its cysts is inhibited by FR, suggesting that FR might reduce nematode dispersion and proliferation. This study supports the idea that C. vaccinii and its excreted metabolome in the soil might contribute to an ecological equilibrium, maintaining and establishing the successful growth of plants.

An eggshell-localised annexin plays a key role in the coordination of the life cycle of a plant-parasitic nematode with its host.

Host-specific plant pathogens must coordinate their life cycles with the availability of a host plant. Although this is frequently achieved through a response to specific chemical cues derived from the host plant, little is known about the molecular basis of the response to such cues and how these are used to trigger activation of the life cycle. In host-specific plant-parasitic cyst nematodes, unhatched juvenile nematodes lie dormant in the eggshell until chemical cues from a suitable host plant are detected and the hatching process is initiated. The molecular mechanisms by which hatch is linked to the presence of these chemical cues is unknown. We have identified a novel annexin-like protein that is localised to the eggshell of the potato cyst nematode Globodera rostochiensis. This annexin is unique in having a short peptide insertion that structural modelling predicts is present in one of the calcium-binding sites of this protein. Host-induced gene silencing of the annexin impacts the ability of the nematode to regulate and control permeability of the eggshell. We show that in the presence of the chemicals that induce hatching annexin lipid binding capabilities change, providing the first molecular link between a nematode eggshell protein and host-derived cues. This work demonstrates how a protein from a large family has been recruited to play a critical role in the perception of the presence of a host and provides a new potential route for control of cyst nematodes that impact global food production.

A key virulence effector from cyst nematodes targets host autophagy to promote nematode parasitism.

Autophagy, an intracellular degradation system conserved in eukaryotes, has been increasingly recognized as a key battlefield in plant-pathogen interactions. However, the role of plant autophagy in nematode parasitism is mostly unknown. We report here the identification of a novel and conserved effector, Nematode Manipulator of Autophagy System 1 (NMAS1), from plant-parasitic cyst nematodes (Heterodera and Globodera spp.). We used molecular and genetic analyses to demonstrate that NMAS1 is required for nematode parasitism. The NMAS1 effectors are potent suppressors of reactive oxygen species (ROS) induced by flg22 and cell death mediated by immune receptors in Nicotiana benthamiana, suggesting a key role of NMAS1 effectors in nematode virulence. Arabidopsis atg mutants defective in autophagy showed reduced susceptibility to nematode infection. The NMAS1 effectors contain predicted AuTophaGy-related protein 8 (ATG8)-interacting motif (AIM) sequences. In planta protein-protein interaction assays further demonstrated that NMAS1 effectors specifically interact with host plant ATG8 proteins. Interestingly, mutation in AIM2 of GrNMAS1 from the potato cyst nematode Globodera rostochiensis abolishes its interaction with potato StATG8 proteins and its activity in ROS suppression. Collectively, our results reveal for the first time that cyst nematodes employ a conserved AIM-containing virulence effector capable of targeting a key component of host autophagy to promote disease.

Two new root endophyte and nematode cyst parasite species of the widely distributed genus Laburnicola

Fungal root endophytes, including the common form group of dark septate endophytes (DSEs), represent different taxonomic groups with potentially diverse life strategies. During surveys of DSE communities and of nematode cysts colonizing fungi, isolates representing Laburnicola (Didymosphaeriaceae, Pleosporales) lineages were discovered. Here we carried out a comprehensive study of the phylogenetic relationships and taxonomy of fungi collected from plant roots in Hungary, Mongolia, and Kazakhstan and from eggs of the cereal cyst nematode Heterodera filipjevi in Turkey. In addition to the study of the morphology and culture characteristics of the strains, four loci (internal transcribed spacer, partial large and small subunit regions of nuclear ribosomal DNA and partial translation elongation factor 1-alpha) were used to infer the molecular phylogenetic relationships of the strains within Laburnicola. The isolates were found to represent two distinct lineages, which are described here as novel species, Laburnicola nematophila and L. radiciphila. The interaction of the strains with plants and nematodes was examined using in vitro bioassays, which revealed endophytic interactions with the plant roots and parasitic interactions with the nematode eggs. Analyses of similar ITS sequences found in public databases revealed that members of the genus Laburnicola are widely distributed characteristic members of the plant microbiome, and they are reported as parasites of plant parasitic cyst nematodes here for the first time.

Characterization and response of two potato receptor-like kinases to cyst nematode infection

ABSTRACT Plant-parasitic cyst nematodes (Heterodera and Globodera spp.) secrete CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) effector proteins, which act as ligand mimics of plant CLE peptides to promote successful nematode infection. Previous studies of the Arabidopsis-beet cyst nematode (BCN; H. schachtii) pathosystem showed that Arabidopsis CLE receptors including CLAVATA1 (CLV1), CLV2, and RECEPTOR-LIKE PROTEIN KINASE 2 (RPK2) are required for BCN CLE signaling. Studies further revealed that nematode CLE signaling through GmCLV2 and StCLV2, an Arabidopsis CLV2 orthologue from soybean (Glycines max) and potato (Solanum tuberosum), respectively, is required for the soybean cyst nematode (SCN; H. glycines) and the potato cyst nematode (PCN; G. rostochiensis) to induce disease in their respective host plant. In this study, we identified and characterized two additional potato receptors, StRPK2 and StCLV1, homologues of Arabidopsis RPK2 and CLV1, for a role in PCN parasitism. Using promoter-reporter lines we showed that both StRPK2 and StCLV1 are expressed in the potato root but vary in their spatial expression patterns. Interestingly, StRPK2 but not StCLV1 was found to be expressed and upregulated at PCN infection sites. Nematode infection assays on StRPK2-knockdown lines revealed a decrease in nematode infection. Collectively, our results suggest that parallel CLE signaling pathways involving StCLV2 and StRPK2 are important for PCN parasitism and that manipulation of nematode CLE signaling may represent a viable means to engineer nematode resistance in crop plants including potato.

Volatile Organic Compounds from a Lichen-Associated Bacterium, Paenibacillus etheri, Interact with Plant-Parasitic Cyst Nematodes.

Healthy food is one of the major challenges to develop in this century. Plant-parasitic nematodes cause significant damage to many crops worldwide and till now, the use of chemical nematicides is the main means to control their populations. These chemical products must be replaced by more environmental-friendly control methods. Biocontrol methods seem to be one promising option, and the number of biopesticides derived from living organisms has increased in the last decades. To develop new plant protection products, we have decided to combine our skills in natural products chemistry and nematology and to focus on the lichen microecosystem as underexploited ecological niches of microorganisms. We present herein the potential of lichen-associated bacterial suspensions from Paenibacillus etheri as nematicides against the beet cyst nematode Heterodera schachtii and the potato cyst nematode Globodera pallida, in particular the effects of volatile organic compounds (VOCs) produced by the bacteria. A solid phase micro-extraction method associated to gas chromatography-mass spectrometry analysis of 14 day cultures was used to analyze these VOCs in order to identify the main produced compounds (isoamyl acetate and 2-phenylethyl acetate) and to evaluate them on the nematodes.

A novel sugar beet cyst nematode effector 2D01 targets the Arabidopsis HAESA receptor-like kinase.

Plant-parasitic cyst nematodes use a stylet to deliver effector proteins produced in oesophageal gland cells into root cells to cause disease in plants. These effectors are deployed to modulate plant defence responses and developmental programmes for the formation of a specialized feeding site called a syncytium. The Hg2D01 effector gene, coding for a novel 185-amino-acid secreted protein, was previously shown to be up-regulated in the dorsal gland of parasitic juveniles of the soybean cyst nematode Heterodera glycines, but its function has remained unknown. Genome analyses revealed that Hg2D01 belongs to a highly diversified effector gene family in the genomes of H. glycines and the sugar beet cyst nematode Heterodera schachtii. For functional studies using the model Arabidopsis thaliana-H. schachtii pathosystem, we cloned the orthologous Hs2D01 sequence from H. schachtii. We demonstrate that Hs2D01 is a cytoplasmic effector that interacts with the intracellular kinase domain of HAESA (HAE), a cell surface-associated leucine-rich repeat (LRR) receptor-like kinase (RLK) involved in signalling the activation of cell wall-remodelling enzymes important for cell separation during abscission and lateral root emergence. Furthermore, we show that AtHAE is expressed in the syncytium and, therefore, could serve as a viable host target for Hs2D01. Infective juveniles effectively penetrated the roots of HAE and HAESA-LIKE2 (HSL2) double mutant plants; however, fewer nematodes developed on the roots, consistent with a role for this receptor family in nematode infection. Taken together, our results suggest that the Hs2D01-AtHAE interaction may play an important role in sugar beet cyst nematode parasitism.

FMRFamid-like neuropeptides as modulators of locomotory reactions in plant parasitic cyst nematodes

The purpose of the research is analysis of world literature dedicated to studies of physiological role and functional importance of FMRFamide-like neuropeptides – components of peptidergic nervous system in cyst nematode plant parasites using an example of 2nd stage larvae of potato and soy nematodes Globodera pallida and Heterodera glycines.The main physiological and functional characteristics of endogenous FMRFamid-like neuropeptides had been found in studies of functional role of flp genes expression of which was discovered in various nerve structures of potato and soy nematodes. The work shows the role of endogenous FMRFamid-like neuropeptides in such plant nematodes' behavior elements as locomotions promoting the parasites' life activity. The functional importance of flp genes coding these biologically active substances and possibilities of using data on physiological effects of neuropeptides on plant nematodes' activity for development of new anthelminthic precise effect drugs are discussed.

Bioassay Directed Fractionation of Petroleum Ether Extract of Aerial Parts of Ceriops tagal: Isolation of Lupeol as the Nematicidal Agent against Cyst Nematode Heterodera zeae.

Plant parasitic cyst nematode Heterodera zeae is a pest, causing substantial economic losses in agriculture. Organic pesticides, based on plant products have emerged as eco-benign nematicidal agents. Ceriops tagal is a well-known marine medicinal plant which has not been evaluated against any nematode. Petroleum ether extract of the aerial parts of the plant (CTP), exhibited promising activity against infective stage larvae of H. zeae. On subjecting to classical solvent-solvent separation, it afforded petroleum ether soluble (CTP-S), methanol soluble (CTPMS-1, CTPMS-2) and insoluble (CTPM-IN-2) fractions, which exhibited activity against the cyst nematode within 24 h exposure. GC, GC/MS and HR-ESI-MS analyses of CTPMS-1 and CTPMS-2 fractions resulted in the identification of a number of compounds, including pentacyclic triterpenoids, lupeol (1), betunal (2), betulin (3), lupenone (4), betulonaldehyde (5), betulonic acid (7), methyl 3-acetoxy-27-O-(3,4-dihydroxy-E-cinnamoyl)-20(29)-lupen-28-oate (8) and β-amyrin, along with phenylpropanoid esters, fatty acids and their derivatives, benzamide, and indole derivatives. CTPM-IN-2 which mainly contained lupeol (1) exhibited maximum nematicidal activity, with 91 % and 93 % mortality of the larvae of H. zeae, after exposure for 72 h at the concentration of 0.5 % and 1 %, respectively. Its fractionation and purification through column chromatography resulted in the isolation and identification of four lupane-type triterpenoids 1, 3, 4 and betulinic acid (6). One of its most abundant column fractions CC-9-18 (145 mg) which exhibited substantial activity, with 81 % mortality at the lowest concentration of 0.125 % after 48 h of incubation mainly contained lupeol. It seems lupeol, a wide spread bio-privileged triterpenoid is the nematicidal principle of the plant as its authentic sample showed LC50 value of 0.061 after 72 h exposure. It is for the first time that nematicidal activity is reported for any part of C. tagal and that of lupeol against H. zeae. Pentacyclic triterpenoids 1-8 are biosynthetically related. Of the twenty-four compounds isolated or identified in the present investigation only five constituents 1, 3, 6, 7 and palmitic acid have been isolated previously from C. tagal.

Metabolic Analysis of the Development of the Plant-Parasitic Cyst Nematodes Heterodera schachtii and Heterodera trifolii by Capillary Electrophoresis Time-of-Flight Mass Spectrometry.

The cyst nematodes Heterodera schachtii and Heterodera trifolii, whose major hosts are sugar beet and clover, respectively, damage a broad range of plants, resulting in significant economic losses. Nematodes synthesize metabolites for organismal development and social communication. We performed metabolic profiling of H. schachtii and H. trifolii in the egg, juvenile 2 (J2), and female stages. In all, 392 peaks were analyzed by capillary electrophoresis time-of-flight mass spectrometry, which revealed a lot of similarities among metabolomes. Aromatic amino acid metabolism, carbohydrate metabolism, choline metabolism, methionine salvage pathway, glutamate metabolism, urea cycle, glycolysis, gluconeogenesis, coenzyme metabolism, purine metabolism, pyrimidine metabolism, and tricarboxylic acid (TCA) cycle for energy conversion (β-oxidation and branched-chain amino acid metabolism) energy storage were involved in all stages studied. The egg and female stages synthesized higher levels of metabolites compared to the J2 stage. The key metabolites detected were glycerol, guanosine, hydroxyproline, citric acid, phosphorylcholine, and the essential amino acids Phe, Leu, Ser, and Val. Metabolites, such as hydroxyproline, acetylcholine, serotonin, glutathione, and glutathione disulfide, which are associated with growth and reproduction, mobility, and neurotransmission, predominated in the J2 stage. Other metabolites, such as SAM, 3PSer, 3-ureidopropionic acid, CTP, UDP, UTP, 3-hydroxy-3-methylglutaric acid, 2-amino-2-(hydroxymethyl-1,3-propanediol, 2-hydroxy-4-methylvaleric acid, Gly Asp, glucuronic acid-3 + galacturonic acid-3 Ser-Glu, citrulline, and γ-Glu-Asn, were highly detected in the egg stage. Meanwhile, nicotinamide, 3-PG, F6P, Cys, ADP-Ribose, Ru5P, S7P, IMP, DAP, diethanolamine, p-Hydroxybenzoic acid, and γ-Glu-Arg_divalent were unique to the J2 stage. Formiminoglutamic acid, nicotinaminde riboside + XC0089, putrescine, thiamine 2,3-dihydroxybenzoic acid, 3-methyladenine, caffeic acid, ferulic acid, m-hydrobenzoic acid, o- and p-coumaric acid, and shikimic acid were specific to the female stage. Overall, highly similar identities and quantities of metabolites between the corresponding stages of the two species of nematode were observed. Our results will be a valuable resource for further studies of physiological changes related to the development of nematodes and nematode–plant interactions.

Plant parasitic cyst nematodes redirect host indole metabolism via NADPH oxidase‐mediated ROS to promote infection

Reactive oxygen species (ROS) generated in response to infections often activate immune responses in eukaryotes including plants. In plants, ROS are primarily produced by plasma membrane-bound NADPH oxidases called respiratory burst oxidase homologue (Rboh). Surprisingly, Rbohs can also promote the infection of plants by certain pathogens, including plant parasitic cyst nematodes. The Arabidopsis genome contains 10 Rboh genes (RbohA-RbohJ). Previously, we showed that cyst nematode infection causes a localised ROS burst in roots, mediated primarily by RbohD and RbohF. We also found that plants deficient in RbohD and RbohF (rbohD/F) exhibit strongly decreased susceptibility to cyst nematodes, suggesting that Rboh-mediated ROS plays a role in promoting infection. However, little information is known of the mechanism by which Rbohs promote cyst nematode infection. Here, using detailed genetic and biochemical analyses, we identified WALLS ARE THIN1 (WAT1), an auxin transporter, as a downstream target of Rboh-mediated ROS during parasitic infections. We found that WAT1 is required to modulate the host's indole metabolism, including indole-3-acetic acid levels, in infected cells and that this reprogramming is necessary for successful establishment of the parasite. In conclusion, this work clarifies a unique mechanism that enables cyst nematodes to use the host's ROS for their own benefit.

Volatiles from the fungus Fusarium oxysporum affect interactions of Brassica rapa plants with root herbivores

1. Soil is a diverse and heterogeneous environment where chemicals mediate numerous interactions between soil organisms and plants. To date, studies have extensively addressed volatile‐mediated interactions between soil microorganisms and the effects of microbial volatiles on plant growth. Yet, to our knowledge, it remains to be explored whether volatiles from soil‐borne fungi can influence plant interactions with root herbivores, facilitating or hampering performance of competitors that share the same host plant.2. In the present study, we investigated the effects of volatiles emitted by the soil‐borne fungus Fusarium oxysporum on the performance of two root herbivores: the plant parasitic cyst nematode, Heterodera schachtii, and the insect root herbivore, Delia radicum, upon infestation of Brassica rapa roots.3. Fungal volatiles slowed down the development of the root nematode cysts but increased their size, suggesting an enhanced egg load. In contrast, the performance of the insect root herbivore was unaffected by the exposure of roots to fungal volatiles. Additionally, fungal volatiles promoted the growth of plants infested with the root nematode, but not of those infested with the insect root herbivore.4. Together, our data show that volatiles from a soil‐borne fungus can affect root interactions with root herbivores. Increased production of nematode eggs and plant growth promotion suggest a specific modulation of root‐herbivore interactions by fungal volatiles.

New Peptaibiotics and a Cyclodepsipeptide from Ijuhya vitellina: Isolation, Identification, Cytotoxic and Nematicidal Activities.

Fungal associations with nematodes have attracted scientific attention because of the need to develop new biocontrol agents. In this context, Ijuhya vitellina, an antagonistic fungus previously isolated from the plant parasitic cyst nematode Heterodera filipjevi, was selected to carry out an in-depth metabolomic study for its active metabolites. Herein, three new nonapeptide peptaibols with leucinostatin based sequences were isolated and identified by 1, 2D NMR, and HR-ESI-MS-MS. The absolute configuration was assigned based on Marfay’s analysis and Mosher ester formation. The new leucinostatins manifested moderate nematicidal effect against the plant pathogenic nematode Pratylenchus penetrans with LD90 values ranging from 5 to 7 µg/mL. Furthermore, a cyclodepsipeptide, named arthrichitin D, with five amino acid residues attached to a 3-hydroxy-2,4-dimethylhexadeca-4,6-dienoic fatty acid chain was discovered and showed weak nematicidal effect against Caenorhabditis elegans. Chaetoglobosin B and its 19-O-acetyl derivative were also obtained as minor metabolites, and the activity of chaetoglobosin B on the actin cytoskeleton of mammalian cells was assessed.

Host factors influence the sex of nematodes parasitizing roots of Arabidopsis thaliana.

Plant-parasitic cyst nematodes induce hypermetabolic syncytial nurse cells in the roots of their host plants. Syncytia are their only food source. Cyst nematodes are sexually dimorphic, with their differentiation into male or female strongly influenced by host environmental conditions. Under favourable conditions with plenty of nutrients, more females develop, whereas mainly male nematodes develop under adverse conditions such as in resistant plants. Here, we developed and validated a method to predict the sex of beet cyst nematode (Heterodera schachtii) during the early stages of its parasitism in the host plant Arabidopsis thaliana. We collected root segments containing male-associated syncytia (MAS) or female-associated syncytia (FAS), isolated syncytial cells by laser microdissection, and performed a comparative transcriptome analysis. Genes belonging to categories of defence, nutrient deficiency, and nutrient starvation were over-represented in MAS as compared with FAS. Conversely, gene categories related to metabolism, modification, and biosynthesis of cell walls were over-represented in FAS. We used β-glucuronidase analysis, qRT-PCR, and loss-of-function mutants to characterize FAS- and MAS-specific candidate genes. Our results demonstrate that various plant-based factors, including immune response, nutrient availability, and structural modifications, influence the sexual fate of the cyst nematodes.

Root endodermal barrier system contributes to defence against plant-parasitic cyst and root-knot nematodes.

Plant-parasitic nematodes (PPNs) cause tremendous yield losses worldwide in almost all economically important crops. The agriculturally most important PPNs belong to a small group of root-infecting sedentary endoparasites that includes cyst and root-knot nematodes. Both cyst and root-knot nematodes induce specialized long-term feeding structures in root vasculature from which they obtain their nutrients. A specialized cell layer in roots called the endodermis, which has cell walls reinforced with suberin deposits and a lignin-based Casparian strip (CS), protects the vascular cylinder against abiotic and biotic threats. To date, the role of the endodermis, and especially of suberin and the CS, during plant-nematode interactions was largely unknown. Here, we analyzed the role of suberin and CS during interaction between Arabidopsis plants and two sedentary root-parasitic nematode species, the cyst nematode Heterodera schachtii and the root-knot nematode Meloidogyne incognita. We found that nematode infection damages the endodermis leading to the activation of suberin biosynthesis genes at nematode infection sites. Although feeding sites induced by both cyst and root-knot nematodes are surrounded by endodermis during early stages of infection, the endodermis is degraded during later stages of feeding site development, indicating periderm formation or ectopic suberization of adjacent tissue. Chemical suberin analysis showed a characteristic suberin composition resembling peridermal suberin in nematode-infected tissue. Notably, infection assays using Arabidopsis lines with CS defects and impaired compensatory suberization, revealed that the CS and suberization impact nematode infectivity and feeding site size. Taken together, our work establishes the role of the endodermal barrier system in defence against a soil-borne pathogen.

Arabidopsis tonoplast intrinsic protein and vacuolar H+-adenosinetriphosphatase reflect vacuole dynamics during development of syncytia induced by the beet cyst nematode Heterodera schachtii

Plant parasitic cyst nematodes induce specific hypermetabolic syncytial nurse cell structures in host roots. A characteristic feature of syncytia is the lack of the central vacuole and the formation of numerous small and larger vesicles. We show that these structures are formed de novo via widening of ER cisternae during the entire development of syncytium, whereas in advanced stages of syncytium development, larger vacuoles are also formed via fusion of vesicles/tubules surrounding organelle-free pre-vacuole regions. Immunogold transmission electron microscopy of syncytia localised the vacuolar markers E subunit of vacuolar H+-adenosinetriphosphatase (V-ATPase) complex and tonoplast intrinsic protein (γ-TIP1;1) mostly in membranes surrounding syncytial vesicles, thus indicating that these structures are vacuoles and that some of them have a lytic character. To study the function of syncytial vacuoles, changes in expression of AtVHA-B1, AtVHA-B2 and AtVHA-B3 (coding for isoforms of subunit B of V-ATPase), and TIP1;1 and TIP1;2 (coding for γ-TIP proteins) genes were analysed. RT-qPCR revealed significant downregulation of AtVHA-B2, TIP1;1 and TIP1;2 at the examined stages of syncytium development compared to uninfected roots. Expression of VHA-B1 and VHA-B3 decreased at 3 dpi but reached the level of control at 7 dpi. These results were confirmed for TIP1;1 by monitoring At-γ-TIP-YFP reporter construct expression. Infection test conducted on tip1;1 mutant plants showed formation of larger syncytia and higher numbers of females in comparison to wild-type plants indicating that reduced levels or lack of TIP1;1 protein promote nematode development.

Canonical and noncanonical ethylene signaling pathways that regulate Arabidopsis susceptibility to the cyst nematode Heterodera schachtii.

Plant-parasitic cyst nematodes successfully exploit various phytohormone signaling pathways to establish a new hormonal equilibrium that facilitates nematode parasitism. Although it is largely accepted that ethylene regulates plant responses to nematode infection, a mechanistic understanding of how ethylene shapes plant-nematode interactions remains largely unknown. In this study, we examined the involvement of various components regulating ethylene perception and signaling in establishing Arabidopsis susceptibility to the cyst nematode Heterodera schachtii using a large set of well-characterized single and higher order mutants. Our analyses revealed the existence of two pathways that separately engage ethylene with salicylic acid (SA) and cytokinin signaling during plant response to nematode infection. One pathway involves the canonical ethylene signaling pathway in which activation of ethylene signaling results in suppression of SA-based immunity. The second pathway involves the ethylene receptor ETR1, which signals independently of SA acid to affect immunity, instead altering cytokinin-mediated regulation of downstream components. Our results reveal important mechanisms through which cyst nematodes exploit components of ethylene perception and signaling to affect the balance of hormonal signaling through ethylene interaction with SA and cytokinin networks. This hormonal interaction overcomes plant defense and provokes a susceptible response.

Arabidopsis HIPP27 is a host susceptibility gene for the beet cyst nematode Heterodera schachtii.

Sedentary plant-parasitic cyst nematodes are obligate biotrophs that infect the roots of their host plant. Their parasitism is based on the modification of root cells to form a hypermetabolic syncytium from which the nematodes draw their nutrients. The aim of this study was to identify nematode susceptibility genes in Arabidopsis thaliana and to characterize their roles in supporting the parasitism of Heterodera schachtii. By selecting genes that were most strongly upregulated in response to cyst nematode infection, we identified HIPP27 (HEAVY METAL-ASSOCIATED ISOPRENYLATED PLANT PROTEIN 27) as a host susceptibility factor required for beet cyst nematode infection and development. Detailed expression analysis revealed that HIPP27 is a cytoplasmic protein and that HIPP27 is strongly expressed in leaves, young roots and nematode-induced syncytia. Loss-of-function Arabidopsis hipp27 mutants exhibited severely reduced susceptibility to H.schachtii and abnormal starch accumulation in syncytial and peridermal plastids. Our results suggest that HIPP27 is a susceptibility gene in Arabidopsis whose loss of function reduces plant susceptibility to cyst nematode infection without increasing the susceptibility to other pathogens or negatively affecting the plant phenotype.

Novel RNA viruses within plant parasitic cyst nematodes.

The study of invertebrate–and particularly nematode–viruses is emerging with the advancement of transcriptome sequencing. Five single-stranded RNA viruses have now been confirmed within the economically important soybean cyst nematode (SCN; Heterodera glycines). From previous research, we know these viruses to be widespread in greenhouse and field populations of SCN. Several of the SCN viruses were also confirmed within clover (H. trifolii) and beet (H. schachtii) cyst nematodes. In the presented study, we sequenced the transcriptomes of several inbred SCN populations and identified two previously undiscovered viral-like genomes. Both of these proposed viruses are negative-sense RNA viruses and have been named SCN nyami-like virus (NLV) and SCN bunya-like virus (BLV). Finally, we analyzed publicly available transcriptome data of two potato cyst nematode (PCN) species, Globodera pallida and G. rostochiensis. From these data, a third potential virus was discovered and called PCN picorna-like virus (PLV). PCN PLV is a positive-sense RNA virus, and to the best of our knowledge, is the first virus described within PCN. The presence of these novel viruses was confirmed via qRT-PCR, endpoint PCR, and Sanger sequencing with the exception of PCN PLV due to quarantine restrictions on the nematode host. While much work needs to be done to understand the biological and evolutionary significance of these viruses, they offer insight into nematode ecology and the possibility of novel nematode management strategies.