Biology subjects

Smant, G.

Publications and source records attributed to Smant, G..

17 recordsLinked to original sources

bioRxiv2026

Interspecific adaptations in root system architecture define host tolerance of Arabidopsis to biotic stresses by root feeding nematodes

Belowground, plants are exposed to a wide range of biotic stresses that vary in severity and nature, including tissue damage, disruption of vascular connectivity, and depletion of assimilates. How plants adapt their root systems to cope with different types of belowground biotic stresses is not well known. In this paper we compare above- and belowground plant adaptations to three nematode species with distinct tissue migration and feeding behaviours to study mechanisms underlying tolerance to different types of biotic stresses. We monitored both green canopy growth and changes in root system architecture of Arabidopsis inoculated with Pratylenchus penetrans, Heterodera schachtii, and Meloidogyne incognita. This revealed three distinct phases in aboveground plant responses: (i) initial growth inhibition associated with host invasion and tissue damage, (ii) persistent growth reduction associated with nematode sedentarism, and (iii) late growth stimulus in more advanced stages of infection. Specific adaptations in the root systems further revealed fundamentally different stress coping strategies. Tissue damage and intermittent feeding by P. penetrans in the root cortex did not induce significant changes in root system architecture. Tissue damage to the root cortex and prolonged feeding on host vascular cells by H. schachtii induced secondary root formation compensating for primary root growth inhibition. Prolonged feeding on host vascular cell by M. incognita alone did not induce secondary root formation, but was accompanied by typical local tissue swelling instead. Our data suggest that local secondary root formation and tissue swelling are two distinct compensatory mechanisms underlying tolerance to sedentarism by root-feeding nematodes. HighlightHow plants utilize root system plasticity to cope with different types of biotic stresses by root feeding nematodes remains largely unknown. Here, we report on specific adaptive growth responses in Arabidopsis roots to three nematode species, Pratylenchus penetrans, Heterodera schachtii, and Meloidogyne incognita, with fundamentally different strategies for host invasion, subsequent migration through host tissue, and feeding on host cells.

plant biology↗

bioRxiv2025

Globodera pallida virulence on major potato resistance has a common genetic basis across Western Europe

The potato cyst nematode Globodera pallida poses a major threat to potato production in Western Europe. Current management strategies largely depend on the use of potato varieties carrying the genetic resistance GpaVvrn. However, reports from multiple West-European countries indicate a steady rise in virulence against GpaVvrn-containing potato varieties, raising serious concerns about G. pallida control. Although recent studies have resolved the genetic basis of virulence in two Dutch G. pallida populations, it remains unclear how conserved this genetic adaptation is in populations from different regions. To investigate this, we first selected eight Dutch G. pallida populations on the GpaVvrn-containing potato variety Seresta and confirmed a previously identified virulence locus. Second, by analysing the allele frequencies of four virulence-associated SNPs in Dutch, British, and French GpaVvrn-selected G. pallida populations, we found that the same allele is consistently selected by GpaVvrn across Western Europe. Third, we analysed the propagation of eight G. pallida populations on 26 GpaVvrn-containing potato varieties and showed that a populations allele frequency of a single SNP (T173N) accurately reflects its reproduction on GpaVvrn. Fourth, we developed an allele-specific quantitative PCR (AS-qPCR) assay to determine a populations alternative allele frequency (AAF) of T173N and showed that AS-qPCR-based AAFs reliably indicate virulence levels on GpaVvrn in Dutch and German G. pallida populations. Together, these findings suggest that a common allele is consistently selected by GpaVvrn in populations from different regions across Western Europe. The AS-qPCR assay developed in this study provides a practical tool to estimate G. pallida virulence on GpaVvrn in the field, enabling field-tailored and sustainable resistance management strategies for farmers.

genetics↗

bioRxiv2025

Fantastic Antagonists and Where to Find Them: The Global Distribution of Nematode-Antagonistic Fungi

Plant-parasitic nematodes can be suppressed by antagonistic members of the local soil microbiome. Compared to bacterial antagonists, considerably more attention has been paid to nematode-suppressing fungi. However, little is known about their global distribution. As their biogeography matters from both a fundamental and an applied perspective, we set out to mine the GlobalFungi database. After filtering on sample type, biome relevance and sequencing depth, we retained approximately 28,000 samples from 484 studies. An overview of fungal nematode antagonists was generated, and subsequent analyses revealed that 82.6% of the soil samples comprised [≥]1 nematode antagonist. Most of these antagonists are not obligatory nematode parasites; they switch between trophic lifestyles including saprophytism. Nematode antagonists are frequently found across most biomes; the detection probability was highest in croplands (88% of samples), woodlands (82%), and grasslands (76%). Most of the common nematode antagonists are present on all continents and across multiple climate zones underlining their enormous ecological flexibility. With one exception, the most frequently detected antagonistic fungi belonged to the fungal order Hypocreales whose members are known to parasitize insects and fungi as well. Analysis of the impact of temperature and precipitation on common antagonists in croplands revealed mostly non-linear responses. Among a selection of six soil properties, pH was the most informative predictor for the abundance of antagonists in croplands. Insights into the prevalence and the distribution of nematode antagonists at a global scale contribute to the exploration of the nematode-suppressive potential, which appears to be more common and widespread than often assumed.

ecology↗

bioRxiv2025

Environmental sex determination in the cyst nematode Globodera pallida defaults to male development

Environmental sex determination (ESD) enables organisms to adjust their sexual fate in response to external cues. Fluctuating sex ratios have long suggested the presence of ESD in populations of plant-parasitic nematodes. We show that in the potato cyst nematode Globodera pallida sex is regulated by nutritional cues. By manipulating sucrose availability to the host plant, we could steer the sex determination of G. pallida. Whereas high-sucrose medium promotes female development, low-sucrose medium promotes male development. Transcriptome analyses on the early stages of parasitism reveal that female development requires extensive transcriptional activation and post-transcriptional regulation. We identify Gp-lin-29, a transcription factor homologous to lin-29 in Caenorhabditis elegans, as a potential regulator of ESD. Small RNA sequencing uncovered the male-biased expression of Gp-let-7, a putative repressor of Gp-lin-29, and the female-biased expression of four miRNAs, including Gp-miR-100, located at the same genomic locus as Gp-let-7. Target prediction and enrichment analyses suggest that these female-biased miRNAs actively suppress male developmental programs. Together, our findings support a model in which G. pallida juveniles follow a default male developmental trajectory unless redirected by favourable environmental cues to become female. This study provides mechanistic insight into ESD in cyst nematodes and positions G. pallida as a tractable system for exploring epigenetic regulation of developmental plasticity.

developmental biology↗

bioRxiv2025

Stationary phloem proteins and their effects on viruses, aphids, and cyst nematodes in Arabidopsis

The phloem is a specialized tissue that facilitates systemic transport of carbohydrates and signal molecules, making it a common target for viruses, phloem-feeding insects, and cyst nematodes. In Arabidopsis, the stationary phloem-associated SIEVE ELEMENT-LINING CHAPERONE1 (SLI1) and RESTRICTED TEV MOVEMENT (RTM) proteins restrict insect phloem-feeding and potyviruses systemic transport, respectively. However, their broader roles in plant-attacker interactions remain largely unexplored. We investigated the roles of SLI1, RTM1, RTM2, and RTM3 in tobacco etch virus (TEV) infection, as well as in Myzus persicae and Heterodera schachtii infestations using Arabidopsis mutants. Systemic TEV movement was quantified, aphid behaviour and reproduction were assessed, and cyst nematode infection was monitored. SLI1 did not restrict TEV systemic movement, RTM3 reduced M. persicae reproduction without altering feeding behaviour, SLI1, RTM2, and RTM3 supported H. schachtii infection and feeding site expansion, and confocal images indicated a possible role of the proteins in de novo synthesis of sieve tubes around syncytia. These findings reveal that stationary phloem proteins exert dual and target-specific effects, limiting some attackers while inadvertently facilitating others. This highlights the complexity of phloem-based immunity and underscores the need to unravel its underlying mechanisms to develop strategies to reduce multiple pest and pathogen burdens simultaneously. HighlightStationary phloem proteins SLI1, RTM1, RTM2, and RTM3 exert dual and target-specific effects against tobacco etch virus, Myzus persicae, and Heterodera schachtii.

plant biology↗

bioRxiv2025

The potato cyst nematode Globodera pallida overcomes major potato resistance through selection on standing variation at a single locus

Globodera pallida poses a major threat to potato production, with management strategies primarily relying on genetic resistance. However, reports from multiple locations in Western Europe indicate a steady increase in virulence levels among field populations, raising major concerns about G. pallida control. The evolutionary mechanisms driving this rise in virulence are poorly understood. To investigate this, we analysed the propagation of thirteen recently isolated field populations on thirty commercial potato varieties over four independent PCN resistance tests. Our findings indicate that (1) the genetic basis of resistance in potatoes is small, with the major resistance conferred by GpaV from Solanum vernei, and (2) the wide application of GpaVvrn has led to continuous selection on standing genetic variation in G. pallida field populations. To map virulence, we propagated two field populations on a GpaVvrn-resistant variety for four consecutive generations. High-coverage whole-genome sequencing of each generation revealed that GpaVvrn-mediated selection acted on a single locus of a newly assembled G. pallida Rookmaker reference genome. Examination of this virulence-associated locus identified Gp-pat-1 as a candidate gene. Silencing Gp-pat-1 increased G. pallida virulence on a GpaVvrn-resistant potato variety but had no effect on nematode virulence on a susceptible variety. Thereby classifying Gp-pat-1 as an avirulence gene and confirming its role in the breakdown of GpaVvrn-resistance. These findings demonstrate that negative selection on the Gp-pat-1 avirulence allele by GpaVvrn-mediated resistance is driving the emergence of virulence in the G. pallida field populations used in our selection experiments. Our results therefore strongly suggest that selection on Gp-pat-1 is likely underlying the current outbreak of GpaVvrn-resistance breaking populations. Our results provide a foundation for the development of molecular diagnostic tools to monitor virulence in field populations, to enhance understanding of resistance breakdown, and to inform the sustainable deployment of resistances in the field. SIGNIFICANCE STATEMENTIn Western Europe, management of the potato cyst nematode Globodera pallida primarily relies on genetic resistances in potato plants. However, resistance-breaking populations are emerging across Western Europe. Here, we identify a single resistance locus shared by all tested resistant potato varieties. We also identify a corresponding virulence locus on a newly assembled G. pallida reference genome and identify a gene within this locus that contributes to virulence. Our findings provide critical insights into the selective pressure acting on this plant-parasitic nematode, the emergence of virulence over time, and the molecular mechanism underlying resistance breakdown. These results provide much needed insights into a highly adapted soil-borne plant-pathogen.

genetics↗

bioRxiv2023

WOX11-mediated cell size control in Arabidopsis attenuates fecundity of endoparasitic cyst nematodes

O_LICyst nematodes establish permanent feeding structures called syncytia inside host root vasculature, disrupting the flow of water and minerals. In response, plants form WOX11-mediated adventitious lateral roots at nematode infection sites. WOX11-adventitious lateral rooting modulates tolerance to nematode infections, however, whether this also benefits nematode parasitism remains unknown. C_LIO_LIHere, we report on bioassays using a 35S::WOX11-SRDX transcriptional repressor mutant to investigate whether WOX11-adventitious lateral rooting promotes syncytium development and thereby female fecundity. Moreover, we chemically inhibited cellulose biosynthesis to verify if WOX11 directly modulates cell wall plasticity in syncytia. Finally, we performed histochemical analyses to test if WOX11 mediates syncytial cell wall plasticity via reactive oxygen species (ROS). C_LIO_LIRepression of WOX11-mediated transcription specifically enhanced the radial expansion of syncytial elements, increasing both syncytium size and female offspring. The enhanced syncytial hypertrophy observed in the 35S::WOX11-SRDX mutant could be phenocopied by chemical inhibition of cellulose biosynthesis and was associated with elevated levels of ROS at nematode infection sites. C_LIO_LIWe therefore conclude that WOX11 restricts radial expansion of nematode feeding structures and female fecundity, likely by modulating ROS-mediated cell wall plasticity mechanisms. Remarkably, this novel role of WOX11 in plant cell size control is independent of WOX11-adventitious rooting underlying disease tolerance. C_LI

plant biology↗

bioRxiv2023

WOX11-mediated adventitious lateral root formation modulates tolerance of Arabidopsis to cyst nematode infections

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

plant biology↗

bioRxiv2023

From root to shoot; Quantifying nematode tolerance in Arabidopsis thaliana by high-throughput phenotyping of plant development

Nematode migration, feeding site formation, withdrawal of plant assimilates, and activation of plant defence responses have a significant impact on plant growth and development. Plants display intraspecific variation in tolerance limits for root-feeding nematodes. Although disease tolerance has been recognised as a distinct trait in biotic interactions of mainly crops, we lack mechanistic insights. Progress is hampered by difficulties in quantification and laborious screening methods. We turned to the model plant Arabidopsis thaliana, since it offers extensive resources to study the molecular and cellular mechanisms underlying nematode-plant interactions. Through imaging of tolerance-related parameters the green canopy area was identified as an accessible and robust measure for assessing damage due to cyst nematode infection. Subsequently, a high-throughput phenotyping platform simultaneously measuring the green canopy area growth of 960 A. thaliana plants was developed. This platform can accurately measure cyst- and root-knot nematode tolerance limits in A. thaliana through classical modelling of tolerance limits. Furthermore, real-time monitoring provided data for a novel view of tolerance, identifying a compensatory growth response. These findings show that our phenotyping platform will enable further studies into a mechanistic understanding of tolerance to below-ground biotic stress. HighlightThe mechanisms of tolerance to root-parasitic nematodes remain unknown. We developed a high-throughput phenotyping system that enables unravelling the underlying mechanisms of tolerance to nematodes.

plant biology↗

bioRxiv2022

Root architecture plasticity in response to endoparasitic cyst nematodes is mediated by damage signaling

O_LIPlant root architecture plasticity in response to biotic stresses has not been thoroughly investigated. Infection by the endoparasitic cyst nematodes induces root architectural changes that involve the formation of secondary roots at infection sites. However, the molecular mechanisms regulating secondary root formation in response to cyst nematode infection remain largely unknown. C_LIO_LIWe first assessed whether secondary roots form in a nematode-density dependent manner by challenging wild type Arabidopsis plants with increasing numbers of cyst nematodes (Heterodera schachtii). Next, by using jasmonate-related reporter lines and knock-out mutants, we tested if tissue damage by nematodes triggers secondary root formation. Finally, we verified whether damage-induced secondary root formation depends on local auxin biosynthesis at nematode infection sites. C_LIO_LIIntracellular host invasion by H. schachtii triggers a transient local increase in jasmonates, which activates the expression of ERF109 in a COI1-dependent manner. Knock-out mutations in COI1 and ERF109 disrupt the nematode-density dependent increase of secondary roots observed in wildtype plants. Furthermore, ERF109 regulates secondary root formation upon H. schachtii infection via local auxin biosynthesis. C_LIO_LIHost invasion by H. schachtii triggers secondary root formation via the damage-induced jasmonate-dependent ERF109 pathway. This points at a novel mechanism underlying plant root plasticity in response to biotic stress. C_LI

plant biology↗

bioRxiv2021

Comparative genomics among three cyst nematode species reveals distinct evolutionary histories among effector families and an irregular distribution of effector-associated promoter motifs

Potato cyst nematodes (PCNs), an umbrella term used for two species, Globodera pallida and G. rostochiensis, belong worldwide to the most harmful pathogens of potato. Pathotype-specific host plant resistances are an essential handle for PCN control. However, the poor delineation of G. pallida pathotypes hampers the efficient use of available host plant resistances. Long-read sequencing technology allowed us to generate a new reference genome of G. pallida population D383 and, as compared to the current reference, the new genome assembly is 42 times less fragmented. For comparison of diversification patterns of six effector families between G. pallida and G. rostochiensis, an additional reference genome was generated for an outgroup, the beet cyst nematode Heterodera schachtii (IRS population). Large evolutionary contrasts in effector family topologies were observed. While VAPs diversified before the split between the three cyst nematode species, the families GLAND5 and GLAND13 only expanded in PCN after their separation from the genus Heterodera. Although DNA motifs in the promoter regions thought to be involved in the orchestration of effector expression ( DOG boxes) were present in all three cyst nematode species, their presence is not a necessity for dorsal gland-produced effectors. Notably, DOG box dosage was only loosely correlated with expression level of individual effector variants. Comparison of the G. pallida genome with those of two other cyst nematodes underlined the fundamental differences in evolutionary history between effector families. Re-sequencing of PCN populations with deviant virulence characteristics will allow for the linking of these characteristics with the composition of the effector repertoire as well as for the mapping of PCN diversification patterns resulting from extreme anthropogenic range expansion.

genomics↗

bioRxiv2021

Two evolutionary distinct effectors from a nematode and virus target RanGAP1 and 2 via the WPP domain to promote disease

The Gpa2 and Rx1 intracellular immune receptors are canonical CC-NB-LRR proteins belonging to the same R gene cluster in potato. Despite sharing high sequence homology, they have evolved to provide defence against unrelated pathogens. Gpa2 detects Gp-RBP-1 effectors secreted by the potato cyst nematode Globodera pallida whereas Rx1 recognizes the viral coat protein (CP) of Potato Virus X (PVX). How Gpa2 and Rx1 perceive their matching effectors remains unknown. Using a combination of in planta Co-Immunoprecipitation and cellular imaging, we show that both Gp-RBP-1 and PVX-CP physically interact with RanGAP2 and RanGAP1 in the cytoplasm of plant cells. Interestingly, this was also demonstrated for the eliciting variants of Gp-RBP-1 and PVX-CP indicating a role for RanGAP1 and RanGAP2 in pathogenicity independent from Gpa2 and Rx1 recognition. Indeed, knocking down both RanGAP homologs reduce cyst nematode and PVX infection. These findings show that RanGAP1/2 act as common host targets of evolutionary distinct effectors from two plant pathogens with different lifestyles. The involvement of RanGAP1/2 to pathogen virulence is a novel role not yet reported for these key host cell components and as such, their possible role in cyst nematode parasitism and viral pathogenicity are discussed. Moreover, from these findings a model emerges for their possible role as co-factor in pathogen recognition by the potato immune receptors Gpa2/Rx1.

plant biology↗

bioRxiv2021

Glycine-Rich RNA-Binding Protein 7 interacts with and potentiates effector-induced immunity by Gpa2 and Rx1 based on an intact RNA Recognition Motif

O_LIThe activity of intracellular plant Nucleotide-Binding Leucine-Rich Repeat (NB-LRR) immune receptors is fine-tuned by interactions between the receptors and their partners. Identifying NB-LRR interacting proteins is, therefore, crucial to advance our understanding of how these receptors function. C_LIO_LIA Co-Immunoprecipitation/Mass-Spectrometry screening was performed in Nicotiana benthamiana to identify host proteins associated with the Gpa2 CC-NB-LRR, which confers resistance against the potato cyst nematode Globodera pallida. A combination of biochemical, cellular, and functional assays was used to assess the role of a candidate interactor in defence. C_LIO_LIA N. benthamiana homolog of the Glycine-Rich RNA-Binding Protein 7 (NbGRP7) protein was prioritized as a novel Gpa2-interacting protein for further investigations. NbGRP7 also associates in planta with the homologous Rx1 receptor, which confers immunity to Potato Virus X. We show that NbGRP7 positively regulates extreme resistance by Rx1 and cell death by Gpa2. Mutating the NbGRP7 RNA recognition motif compromises its role in Rx1-mediated defence. Strikingly, ectopic NbGRP7 expression impacts the steady-state levels of Rx1, which relies on an intact RNA recognition motif. C_LIO_LICombined, our findings illustrate that NbGRP7 is a novel pro-immune component in effector-triggered immunity by regulating Gpa2/Rx1 functioning at a post-transcriptional level. C_LI

plant biology↗

bioRxiv2021

Comparative Genomics of two Inbred Lines of the Potato Cyst Nematode Globodera rostochiensis reveals disparate Effector Family-specific Diversification Patterns

BackgroundPotato cyst nematodes belong to the most harmful pathogens in potato, and durable management of these soil-borne parasites largely depends on host-plant resistances. These resistances are pathotype specific. The current Globodera rostochiensis pathotype scheme that defines five pathotypes (Ro1 - Ro5) is for fundamental and practical reasons barely useful. As a result, resistant potato varieties are worldwide used in a non-informed manner. ResultsWe generated two novel reference genomes of G. rostochiensis inbred lines derived from a Ro1 and a Ro5 population. These genome sequences comprise 173 and 189 scaffolds respectively, marking a {approx} 24-fold reduction in fragmentation as compared to the current reference genome. We provide copy number variations for 18 effector families. Four dorsal gland effector families were investigated in more detail. SPRYSECs, known to be implicated in immune suppression, constitute by far the most diversified family with 60 and 99 variants in Ro1 and Ro5 distributed over 18 and 26 scaffolds. In contrast, CLEs, effectors involved in feeding site induction, show strong physical clustering. The 10 and 16 variants cluster on respectively 2 and 1 scaffolds. Given that pathotypes are defined by their effectoromes, we pinpoint the disparate nature of the contributing effector families in terms of sequence diversification and loss and gain of variants. ConclusionTwo novel reference genomes allow for nearly complete inventories of effector diversification and physical organisation within and between pathotypes. Combined with insights we provide on effector family-specific diversification patterns, this constitutes a solid basis for an effectorome-based virulence scheme for this notorious pathogen.

genomics↗

bioRxiv2020

Towards 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 characterise the gonads of male Heterodera schachtii and Meloidogyne hapla in the context of spermatogenesis. We test and optimise 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.

genetics↗

bioRxiv2019

SIZ1 is a nuclear host target of the nematode effector GpRbp1 from Globodera pallida that acts as a negative regulator of basal plant defense to cyst nematodes

Soil-borne cyst nematodes are obligatory sedentary parasites that cause severe losses to cultivation of major crops such as potato and soybean. Cyst nematodes establish specialised permanent feeding sites within the roots of their host by manipulating plant morphology and physiology through secreted effectors. Here we identified host targets of effector GpRbp-1 and studied their roles in plant-nematode interactions. GpRbp-1 was found to interact in yeast and in planta with the potato and Arabidopsis homologues of Siz/PIAS-type E3 SUMO ligase SIZ1. Our results show that a pathogen effector targets the master regulator SIZ1 in plant cells, which has not been demonstrated earlier to our knowledge. The interaction of GpRbp-1 and SIZ1 localizes to the plant nucleus, suggesting that the nuclear functions of SIZ1 as regulator of plant immunity and physiology may be modulated by GpRbp-1. Furthermore, nematode infection assays and transcriptomic profiling indicate that SIZ1 is required for susceptibility to cyst nematodes. So, these data indicate that E3 SUMO ligases may play an important role in plant-nematode interactions. Based on the prediction of SUMO acceptor and interaction sites in GpRbp-1, a model is proposed in which the effector may recruit SIZ1 to be SUMOylated for full functionality in host cells.\n\nSignificance statementHere we show that a pathogen effector can target SIZ1, a key protein involved in regulating several aspects of plant biology, most likely to manipulate the SUMOylation of host proteins for successful infection of plants.

plant biology↗

bioRxiv2017

GM-CSF negatively regulates early IL-10 mediated responses

Inflammatory disorders are becoming more prevalent in the Western world. Treatment of these diseases relies on the intervention in inflammatory responses thereby restoring immune homeostasis. One cytokine that has the potential to restore immune homeostasis is the anti-inflammatory cytokine interleukin-10 (IL-10). But until now IL-10 treatment has not been as successful as anticipated. A reason for this may be that IL-10 responsiveness depends on the environment of the inflamed tissue. In this study we describe that granulocyte-macrophage colony-stimulating factor (GM-CSF) is a key cytokine that negatively regulates IL-10-mediated responses. Dendritic cells differentiated from bone marrow with GM-CSF have a reduced ability to respond to IL-10. Dendritic cells are impaired in their up-regulation of IL-10-induced SOCS3 expression and are unable to suppress LPS-induced TNF- expression at an early time point. Furthermore, GM-CSF treatment partially replicates this phenotype in macrophages. Surprisingly, GM-CSF seems to regulate IL-10 activity in macrophages without affecting STAT3 activation. Still, GM-CSF induces constitutive phosphorylation of glycogen synthase kinase 3{beta}, a signalling component downstream of the PI3K/Akt pathway. Knowledge on the exact mechanism by which GM-CSF negatively regulates IL-10 activity could give novel insights on the integration of signal transduction pathways elicited by different cytokines. Ultimately this knowledge could provide us with new therapeutic strategies to treat inflammatory disorders.

immunology↗