The genome and lifestage-specific transcriptomes of a plant-parasitic nematode and its host reveal susceptibility genes involved in trans-kingdom synthesis of vitamin B5.

Plant-parasitic nematodes are a major threat to crop production in all agricultural systems. The scarcity of classical resistance genes highlights a pressing need to find new ways to develop nematode-resistant germplasm. Here, we sequence and assemble a high-quality phased genome of the model cyst nematode Heterodera schachtii to provide a platform for the first system-wide dual analysis of host and parasite gene expression over time, covering all major parasitism stages. Analysis of the hologenome of the plant-nematode infection site identified metabolic pathways that were incomplete in the parasite but complemented by the host. Using a combination of bioinformatic, genetic, and biochemical approaches, we show that a highly atypical completion of vitamin B5 biosynthesis by the parasitic animal, putatively enabled by a horizontal gene transfer from a bacterium, is required for full pathogenicity. Knockout of either plant-encoded or now nematode-encoded steps in the pathway significantly reduces parasitic success. Our experiments establish a reference for cyst nematodes, further our understanding of the evolution of plant-parasitism by nematodes, and show that congruent differential expression of metabolic pathways in the infection hologenome represents a new way to find nematode susceptibility genes. The approach identifies genome-editing-amenable targets for future development of nematode-resistant crops.

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.

miR778 mediates gene expression, histone modification, and DNA methylation during cyst nematode parasitism.

Despite the known critical regulatory functions of microRNAs, histone modifications, and DNA methylation in reprograming plant epigenomes in response to pathogen infection, the molecular mechanisms underlying the tight coordination of these components remain poorly understood. Here, we show how Arabidopsis (Arabidopsis thaliana) miR778 coordinately modulates the root transcriptome, histone methylation, and DNA methylation via post-transcriptional regulation of the H3K9 methyltransferases SU(var)3-9 homolog 5 (SUVH5) and SUVH6 upon infection by the beet cyst nematode Heterodera schachtii. miR778 post-transcriptionally silences SUVH5 and SUVH6 upon nematode infection. Manipulation of the expression of miR778 and its two target genes significantly altered plant susceptibility to H. schachtii. RNA-seq analysis revealed a key role of SUVH5 and SUVH6 in reprograming the transcriptome of Arabidopsis roots upon H. schachtii infection. In addition, chromatin immunoprecipitation (ChIP)-seq analysis established SUVH5 and SUVH6 as the main enzymes mediating H3K9me2 deposition in Arabidopsis roots in response to nematode infection. ChIP-seq analysis also showed that these methyltransferases possess distinct DNA binding preferences in that they are targeting transposable elements under noninfected conditions and protein-coding genes in infected plants. Further analyses indicated that H3K9me2 deposition directed by SUVH5 and SUVH6 contributes to gene expression changes both in roots and in nematode feeding sites and preferentially associates with CG DNA methylation. Together, our results uncovered multi-layered epigenetic regulatory mechanisms coordinated by miR778 during Arabidopsis-H. schachtii interactions.

Targeted transcriptomics reveals signatures of large-scale independent origins and concerted regulation of effector genes in Radopholus similis.

The burrowing nematode, Radopholus similis, is an economically important plant-parasitic nematode that inflicts damage and yield loss to a wide range of crops. This migratory endoparasite is widely distributed in warmer regions and causes extensive destruction to the root systems of important food crops (e.g., citrus, banana). Despite the economic importance of this nematode, little is known about the repertoire of effectors owned by this species. Here we combined spatially and temporally resolved next-generation sequencing datasets of R. similis to select a list of candidates for the identification of effector genes for this species. We confirmed spatial expression of transcripts of 30 new candidate effectors within the esophageal glands of R. similis by in situ hybridization, revealing a large number of pioneer genes specific to this nematode. We identify a gland promoter motif specifically associated with the subventral glands (named Rs-SUG box), a putative hallmark of spatial and concerted regulation of these effectors. Nematode transcriptome analyses confirmed the expression of these effectors during the interaction with the host, with a large number of pioneer genes being especially abundant. Our data revealed that R. similis holds a diverse and emergent repertoire of effectors, which has been shaped by various evolutionary events, including neofunctionalization, horizontal gene transfer, and possibly by de novo gene birth. In addition, we also report the first GH62 gene so far discovered for any metazoan and putatively acquired by lateral gene transfer from a bacterial donor. Considering the economic damage caused by R. similis, this information provides valuable data to elucidate the mode of parasitism of this nematode.

Esophageal Gland RNA-Seq Resource of a Virulent and Avirulent Population of the Soybean Cyst Nematode Heterodera glycines.

The soybean cyst nematode Heterodera glycines is the most economically devastating pathogen of soybean in the United States and threatens to become even more damaging through the selection of virulent nematode populations in the field that can overcome natural resistance mechanisms in soybean cultivars. This pathogen, therefore, demands intense transcriptomic/genomic research inquiries into the biology of its parasitic mechanisms. H. glycines delivers effector proteins that are produced in specialized gland cells into the soybean root to enable infection. The study of effector proteins, thus, is particularly promising when exploring novel management options against this pathogen. Here, we announce the availability of a gland cell-specific RNA-seq resource. These data represent an expression snapshot of gland cell activity during early soybean infection of a virulent and an avirulent H. glycines population, providing a unique and highly valuable resource for scientists examining effector biology and nematode virulence.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Toward genetic modification of plant-parasitic nematodes: delivery of macromolecules to adults and expression of exogenous mRNA in second stage juveniles.

Plant-parasitic nematodes are a continuing threat to food security, causing an estimated 100 billion USD in crop losses each year. The most problematic are the obligate sedentary endoparasites (primarily root knot nematodes and cyst nematodes). Progress in understanding their biology is held back by a lack of tools for functional genetics: forward genetics is largely restricted to studies of natural variation in populations and reverse genetics is entirely reliant on RNA interference. There is an expectation that the development of functional genetic tools would accelerate the progress of research on plant-parasitic nematodes, and hence the development of novel control solutions. Here, we develop some of the foundational biology required to deliver a functional genetic tool kit in plant-parasitic nematodes. We characterize the gonads of male Heterodera schachtii and Meloidogyne hapla in the context of spermatogenesis. We test and optimize various methods for the delivery, expression, and/or detection of exogenous nucleic acids in plant-parasitic nematodes. We demonstrate that delivery of macromolecules to cyst and root knot nematode male germlines is difficult, but possible. Similarly, we demonstrate the delivery of oligonucleotides to root knot nematode gametes. Finally, we develop a transient expression system in plant-parasitic nematodes by demonstrating the delivery and expression of exogenous mRNA encoding various reporter genes throughout the body of H. schachtii juveniles using lipofectamine-based transfection. We anticipate these developments to be independently useful, will expedite the development of genetic modification tools for plant-parasitic nematodes, and ultimately catalyze research on a group of nematodes that threaten global food security.

Phytonematode peptide effectors exploit a host post-translational trafficking mechanism to the ER using a novel translocation signal.

Cyst nematodes induce a multicellular feeding site within roots called a syncytium. It remains unknown how root cells are primed for incorporation into the developing syncytium. Furthermore, it is unclear how CLAVATA3/EMBRYO SURROUNDING REGION (CLE) peptide effectors secreted into the cytoplasm of the initial feeding cell could have an effect on plant cells so distant from where the nematode is feeding as the syncytium expands. Here we describe a novel translocation signal within nematode CLE effectors that is recognized by plant cell secretory machinery to redirect these peptides from the cytoplasm to the apoplast of plant cells. We show that the translocation signal is functionally conserved across CLE effectors identified in nematode species spanning three genera and multiple plant species, operative across plant cell types, and can traffic other unrelated small peptides from the cytoplasm to the apoplast of host cells via a previously unknown post-translational mechanism of endoplasmic reticulum (ER) translocation. Our results uncover a mechanism of effector trafficking that is unprecedented in any plant pathogen to date, andthey illustrate how phytonematodes can deliver effector proteins into host cells and then hijack plant cellular processes for their export back out of the cell to function as external signaling molecules to distant cells.

Large tandem duplications affect gene expression, 3D organization, and plant-pathogen response.

Rapid plant genome evolution is crucial to adapt to environmental changes. Chromosomal rearrangements and gene copy number variation (CNV) are two important tools for genome evolution and sources for the creation of new genes. However, their emergence takes many generations. In this study, we show that in Arabidopsis thaliana, a significant loss of ribosomal RNA (rRNA) genes with a past history of a mutation for the chromatin assembly factor 1 (CAF1) complex causes rapid changes in the genome structure. Using long-read sequencing and microscopic approaches, we have identified up to 15 independent large tandem duplications in direct orientation (TDDOs) ranging from 60 kb to 1.44 Mb. Our data suggest that these TDDOs appeared within a few generations, leading to the duplication of hundreds of genes. By subsequently focusing on a line only containing 20% of rRNA gene copies (20rDNA line), we investigated the impact of TDDOs on 3D genome organization, gene expression, and cytosine methylation. We found that duplicated genes often accumulate more transcripts. Among them, several are involved in plant-pathogen response, which could explain why the 20rDNA line is hyper-resistant to both bacterial and nematode infections. Finally, we show that the TDDOs create gene fusions and/or truncations and discuss their potential implications for the evolution of plant genomes.

A new esophageal gland transcriptome reveals signatures of large scale de novo effector birth in the root lesion nematode Pratylenchus penetrans.

BACKGROUND: The root lesion nematode Pratylenchus penetrans is a migratory plant-parasitic nematode responsible for economically important losses in a wide number of crops. Despite the importance of P. penetrans, the molecular mechanisms employed by this nematode to promote virulence remain largely unknown. RESULTS: Here we generated a new and comprehensive esophageal glands-specific transcriptome library for P. penetrans. In-depth analysis of this transcriptome enabled a robust identification of a catalogue of 30 new candidate effector genes, which were experimentally validated in the esophageal glands by in situ hybridization. We further validated the expression of a multifaceted network of candidate effectors during the interaction with different plants. To advance our understanding of the "effectorome" of P. penetrans, we adopted a phylogenetic approach and compared the expanded effector repertoire of P. penetrans to the genome/transcriptome of other nematode species with similar or contrasting parasitism strategies. Our data allowed us to infer plausible evolutionary histories that shaped the effector repertoire of P. penetrans, as well as other close and distant plant-parasitic nematodes. Two remarkable trends were apparent: 1) large scale effector birth in the Pratylenchidae in general and P. penetrans in particular, and 2) large scale effector death in sedentary (endo) plant-parasitic nematodes. CONCLUSIONS: Our study doubles the number of validated Pratylenchus penetrans effectors reported in the literature. The dramatic effector gene gain in P. penetrans could be related to the remarkable ability of this nematode to parasitize a large number of plants. Our data provide valuable insights into nematode parasitism and contribute towards basic understating of the adaptation of P. penetrans and other root lesion nematodes to specific host plants.

Targeted suppression of soybean BAG6-induced cell death in yeast by soybean cyst nematode effectors.

While numerous effectors that suppress plant immunity have been identified from bacteria, fungi, and oomycete pathogens, relatively little is known for nematode effectors. Several dozen effectors have been reported from the soybean cyst nematode (SCN). Previous studies suggest that a hypersensitive response-like programmed cell death is triggered at nematode feeding sites in soybean during an incompatible interaction. However, virulent SCN populations overcome this incompatibility using unknown mechanisms. A soybean BAG6 (Bcl-2 associated anthanogene 6) gene previously reported by us to be highly up-regulated in degenerating feeding sites induced by SCN in a resistant soybean line was attenuated in response to a virulent SCN population. We show that GmBAG6-1 induces cell death in yeast like its Arabidopsis homolog AtBAG6 and also in soybean. This led us to hypothesize that virulent SCN may target GmBAG6-1 as part of their strategy to overcome soybean defence responses during infection. Thus, we used a yeast viability assay to screen SCN effector candidates for their ability to specifically suppress GmBAG6-1-induced cell death. We identified several effectors that strongly suppressed cell death mediated by GmBAG6-1. Two effectors identified as suppressors showed direct interaction with GmBAG6-1 in yeast, suggesting that one mechanism of cell death suppression may occur through an interaction with this host protein.

Screening soybean cyst nematode effectors for their ability to suppress plant immunity.

The soybean cyst nematode (SCN), Heterodera glycines, is one of the most destructive pathogens of soybeans. SCN is an obligate and sedentary parasite that transforms host plant root cells into an elaborate permanent feeding site, a syncytium. Formation and maintenance of a viable syncytium is an absolute requirement for nematode growth and reproduction. In turn, sensing pathogen attack, plants activate defence responses and may trigger programmed cell death at the sites of infection. For successful parasitism, H. glycines must suppress these host defence responses to establish and maintain viable syncytia. Similar to other pathogens, H. glycines engages in these molecular interactions with its host via effector proteins. The goal of this study was to conduct a comprehensive screen to identify H. glycines effectors that interfere with plant immune responses. We used Nicotiana benthamiana plants infected by Pseudomonas syringae and Pseudomonas fluorescens strains. Using these pathosystems, we screened 51 H. glycines effectors to identify candidates that could inhibit effector-triggered immunity (ETI) and/or pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI). We identified three effectors as ETI suppressors and seven effectors as PTI suppressors. We also assessed expression modulation of plant immune marker genes as a function of these suppressors.

A role for Arabidopsis growth-regulating factors 1 and 3 in growth-stress antagonism.

Growth-regulating factors (GRFs) belong to a small family of transcription factors that are highly conserved in plants. GRFs regulate many developmental processes and plant responses to biotic and abiotic stimuli. Despite the importance of GRFs, a detailed mechanistic understanding of their regulatory functions is still lacking. In this study, we used ChIP sequencing (ChIP-seq) to identify genome-wide binding sites of Arabidopsis GRF1 and GRF3, and correspondingly their direct downstream target genes. RNA-sequencing (RNA-seq) analysis revealed that GRF1 and GRF3 regulate the expression of a significant number of the identified direct targets. The target genes unveiled broad regulatory functions of GRF1 and GRF3 in plant growth and development, phytohormone biosynthesis and signaling, and the cell cycle. Our analyses also revealed that clock core genes and genes with stress- and defense-related functions are most predominant among the GRF1- and GRF3-bound targets, providing insights into a possible role for these transcription factors in mediating growth-defense antagonism and integrating environmental stimuli into developmental programs. Additionally, GRF1 and GRF3 target molecular nodes of growth-defense antagonism and modulate the levels of defense- and development-related hormones in opposite directions. Taken together, our results point to GRF1 and GRF3 as potential key determinants of plant fitness under stress conditions.

SCNBase: a genomics portal for the soybean cyst nematode (Heterodera glycines).

Soybean is an important worldwide crop, and farmers continue to experience significant yield loss due to the soybean cyst nematode (SCN), Heterodera glycines. This soil-borne roundworm parasite is rated the most important pathogen problem in soybean production. The infective nematodes enter into complex interactions with their host plant by inducing the development of specialized plant feeding cells that provide the parasites with nourishment. Addressing the SCN problem will require the development of genomic resources and a global collaboration of scientists to analyze and use these resources. SCNBase.org was designed as a collaborative hub for the SCN genome. All data and analyses are downloadable and can be analyzed with three integrated genomic tools: JBrowse, Feature Search and BLAST. At the time of this writing, a number of genomic and transcriptomic data sets are already available, with 43 JBrowse tracks and 21 category pages describing SCN genomic analyses on gene predictions, transcriptome and read alignments, effector-like genes, expansion and contraction of genomic repeats, orthology and synteny with related nematode species, Single Nucleotide Polymorphism (SNPs) from 15 SCN populations and novel splice sites. Standard functional gene annotations were supplemented with orthologous gene annotations using a comparison to nine related plant-parasitic nematodes, thereby enabling functional annotations for 85% of genes. These annotations led to a greater grasp on the SCN effectorome, which include over 3324 putative effector genes. By designing SCNBase as a hub, future research findings and genomic resources can easily be uploaded and made available for use by others with minimal needs for further curation. By providing these resources to nematode research community, scientists will be empowered to develop novel, more effective SCN management tools.

Re-targeting of a plant defense protease by a cyst nematode effector.

Plants mount defense responses during pathogen attacks, and robust host defense suppression by pathogen effector proteins is essential for infection success. 4E02 is an effector of the sugar beet cyst nematode Heterodera schachtii. Arabidopsis thaliana lines expressing the effector-coding sequence showed altered expression levels of defense response genes, as well as higher susceptibility to both the biotroph H. schachtii and the necrotroph Botrytis cinerea, indicating a potential suppression of defenses by 4E02. Yeast two-hybrid analyses showed that 4E02 targets A. thaliana vacuolar papain-like cysteine protease (PLCP) 'Responsive to Dehydration 21A' (RD21A), which has been shown to function in the plant defense response. Activity-based protein profiling analyses documented that the in planta presence of 4E02 does not impede enzymatic activity of RD21A. Instead, 4E02 mediates a re-localization of this protease from the vacuole to the nucleus and cytoplasm, which is likely to prevent the protease from performing its defense function and at the same time, brings it in contact with novel substrates. Yeast two-hybrid analyses showed that RD21A interacts with multiple host proteins including enzymes involved in defense responses as well as carbohydrate metabolism. In support of a role in carbohydrate metabolism of RD21A after its effector-mediated re-localization, we observed cell wall compositional changes in 4E02 expressing A. thaliana lines. Collectively, our study shows that 4E02 removes RD21A from its defense-inducing pathway and repurposes this enzyme by targeting the active protease to different cell compartments.

Heterodera glycines utilizes promiscuous spliced leaders and demonstrates a unique preference for a species-specific spliced leader over C. elegans SL1.

Spliced leader trans-splicing (SLTS) plays a part in the maturation of pre-mRNAs in select species across multiple phyla but is particularly prevalent in Nematoda. The role of spliced leaders (SL) within the cell is unclear and an accurate assessment of SL occurrence within an organism is possible only after extensive sequencing data are available, which is not currently the case for many nematode species. SL discovery is further complicated by an absence of SL sequences from high-throughput sequencing results due to incomplete sequencing of the 5'-ends of transcripts during RNA-seq library preparation, known as 5'-bias. Existing datasets and novel methodology were used to identify both conserved SLs and unique hypervariable SLs within Heterodera glycines, the soybean cyst nematode. In H. glycines, twenty-one distinct SL sequences were found on 2,532 unique H. glycines transcripts. The SL sequences identified on the H. glycines transcripts demonstrated a high level of promiscuity, meaning that some transcripts produced as many as nine different individual SL-transcript combinations. Most uniquely, transcriptome analysis revealed that H. glycines is the first nematode to demonstrate a higher SL trans-splicing rate using a species-specific SL over well-conserved Caenorhabditis elegans SL-like sequences.

The genome of the soybean cyst nematode (Heterodera glycines) reveals complex patterns of duplications involved in the evolution of parasitism genes.

BACKGROUND: Heterodera glycines, commonly referred to as the soybean cyst nematode (SCN), is an obligatory and sedentary plant parasite that causes over a billion-dollar yield loss to soybean production annually. Although there are genetic determinants that render soybean plants resistant to certain nematode genotypes, resistant soybean cultivars are increasingly ineffective because their multi-year usage has selected for virulent H. glycines populations. The parasitic success of H. glycines relies on the comprehensive re-engineering of an infection site into a syncytium, as well as the long-term suppression of host defense to ensure syncytial viability. At the forefront of these complex molecular interactions are effectors, the proteins secreted by H. glycines into host root tissues. The mechanisms of effector acquisition, diversification, and selection need to be understood before effective control strategies can be developed, but the lack of an annotated genome has been a major roadblock. RESULTS: Here, we use PacBio long-read technology to assemble a H. glycines genome of 738 contigs into 123 Mb with annotations for 29,769 genes. The genome contains significant numbers of repeats (34%), tandem duplicates (18.7 Mb), and horizontal gene transfer events (151 genes). A large number of putative effectors (431 genes) were identified in the genome, many of which were found in transposons. CONCLUSIONS: This advance provides a glimpse into the host and parasite interplay by revealing a diversity of mechanisms that give rise to virulence genes in the soybean cyst nematode, including: tandem duplications containing over a fifth of the total gene count, virulence genes hitchhiking in transposons, and 107 horizontal gene transfers not reported in other plant parasitic nematodes thus far. Through extensive characterization of the H. glycines genome, we provide new insights into H. glycines biology and shed light onto the mystery underlying complex host-parasite interactions. This genome sequence is an important prerequisite to enable work towards generating new resistance or control measures against H. glycines.

Homeostasis in the soybean miRNA396-GRF network is essential for productive soybean cyst nematode infections.

Heterodera glycines, the soybean cyst nematode, penetrates soybean roots and migrates to the vascular cylinder where it forms a feeding site called the syncytium. MiRNA396 (miR396) targets growth-regulating factor (GRF) genes, and the miR396-GRF1/3 module is a master regulator of syncytium development in model cyst nematode H. schachtii infection of Arabidopsis. Here, we investigated whether this regulatory system operates similarly in soybean roots and is likewise important for H. glycines infection. We found that a network involving nine MIR396 and 23 GRF genes is important for normal development of soybean roots and that GRF function is specified in the root apical meristem by miR396. All MIR396 genes are down-regulated in the syncytium during its formation phase while, specifically, 11 different GRF genes are up-regulated. The switch to the syncytium maintenance phase coincides with up-regulation of MIR396 and down-regulation of the 11 GRF genes specifically via post-transcriptional regulation by miR396. Furthermore, interference with the miR396-GRF6/8-13/15-17/19 regulatory network, through either overexpression or knockdown experiments, does not affect the number of H. glycines juveniles that enter the vascular cylinder to initiate syncytia, but specifically inhibits efficient H. glycines development to adult females. Therefore, homeostasis in the miR396-GRF6/8-13/15-17/19 regulatory network is essential for productive H. glycines infections.

An Effector from the Cyst Nematode Heterodera schachtii Derepresses Host rRNA Genes by Altering Histone Acetylation.

Cyst nematodes are plant-pathogenic animals that secrete effector proteins into plant root cells to alter host gene expression and reprogram these cells to form specialized feeding sites, known as syncytia. The molecular mechanisms of these effectors are mostly unknown. We determined that the sugar beet cyst nematode (Heterodera schachtii) 32E03 effector protein strongly inhibits the activities of Arabidopsis thaliana histone deacetylases including the HDT1 enzyme, which has a known function in the regulation of rRNA gene expression through chromatin modifications. We determined that plants expressing the 32E03 coding sequence exhibited increased acetylation of histone H3 along the rDNA chromatin. At low 32E03 expression levels, these chromatin changes triggered the derepression of a subset of rRNA genes, which were conducive to H. schachtii parasitism. By contrast, high levels of 32E03 caused profound bidirectional transcription along the rDNA, which triggered rDNA-specific small RNA production leading to RNA-directed DNA methylation and silencing of rDNA, which inhibited nematode development. Our data show that the 32E03 effector alters plant rRNA gene expression by modulating rDNA chromatin in a dose-dependent manner. Thus, the 32E03 effector epigenetically regulates plant gene expression to promote cyst nematode parasitism.

The novel cyst nematode effector protein 30D08 targets host nuclear functions to alter gene expression in feeding sites.

Cyst nematodes deliver effector proteins into host cells to manipulate cellular processes and establish a metabolically hyperactive feeding site. The novel 30D08 effector protein is produced in the dorsal gland of parasitic juveniles, but its function has remained unknown. We demonstrate that expression of 30D08 contributes to nematode parasitism, the protein is packaged into secretory granules and it is targeted to the plant nucleus where it interacts with SMU2 (homolog of suppressor of mec-8 and unc-52 2), an auxiliary spliceosomal protein. We show that SMU2 is expressed in feeding sites and an smu2 mutant is less susceptible to nematode infection. In Arabidopsis expressing 30D08 under the SMU2 promoter, several genes were found to be alternatively spliced and the most abundant functional classes represented among differentially expressed genes were involved in RNA processing, transcription and binding, as well as in development, and hormone and secondary metabolism, representing key cellular processes known to be important for feeding site formation. In conclusion, we demonstrated that the 30D08 effector is secreted from the nematode and targeted to the plant nucleus where its interaction with a host auxiliary spliceosomal protein may alter the pre-mRNA splicing and expression of a subset of genes important for feeding site formation.