Biology subjects

Grundler, F. M. W.

Publications and source records attributed to Grundler, F. M. W..

7 recordsLinked to original sources

bioRxiv2026

Integrated genomic analyses reveal hierarchical organisation of quantitative resistance to biologically distinct soil-borne pathogens in wheat

Quantitative disease resistance is essential for durable crop protection, yet how numerous small-effect loci are organised across genomic and functional scales remains poorly understood. We investigated resistance to four distinct soil-borne pathogens in bread wheat (Triticum aestivum) by integrating genome-wide association mapping, linkage disequilibrium (LD)-defined hotspot analysis, comparative genomics, epistatic network analysis, haplotype analysis, functional annotation, transcriptomics and experimental evaluation. Resistance was highly polygenic and pathogen- and environment-dependent, with associated loci distributed across all three wheat subgenomes. Approximately two-thirds of hotspot components were shared among pathosystems, although evidence for excess sharing varied among comparisons and null models. Epistatic hubs were enriched within shared components, while interaction networks were dominated by interchromosomal and cross-subgenome interactions. Haplotype effects depended on local genomic context. Despite limited sharing of individual genes, convergence increased at the putative gene-family and broader defence-related functional levels. These findings support a hierarchical model in which pathogen- and environment-dependent resistance architectures are organised through partially shared genomic regions, local haplotypes and genetic interaction networks, with increasing convergence at broader functional levels. Limited transferability of individual marker associations in the independent panel further highlights the potential of multilocus breeding strategies that integrate favourable haplotypes, recurrent genomic regions, and diverse resistance mechanisms.

plant biology↗

bioRxiv2026

The receptor kinase NILR1 confers nematode resistance through developmental rather than canonical immune signaling

O_LINILR1 contributes to quantitative resistance against Heterodera schachtii and signals through a brassinosteroid-type kinase cascade, but whether its contribution engages canonical immune signaling or follows a distinct, developmentally biased logic has remained unclear. C_LIO_LIWe profiled early transcriptional responses of wild-type and nilr1 roots to H. schachtii by RNA-seq at 30 min and 3 h post inoculation and analyzed them using a genotype x treatment interaction model, complemented by gene set enrichment and integration with cell-type-resolved, brassinosteroid-responsive regulatory networks. C_LIO_LIWe found that canonical PTI marker transcription and flg22-induced ROS production were preserved or even elevated in nilr1, indicating that the tested PTI outputs are largely maintained despite increased susceptibility. Instead, genes whose nematode-induced responses showed NILR1-sensitive interaction effects were enriched for a HAT7/GTL1 centred cortex developmental module, and genetic disruption of GTL1/DF1 moderately altered H. schachtii parasitism, consistent with a role for this module in shaping host permissiveness. C_LIO_LIOur data support a model in which NILR1 contributes to nematode resistance primarily via developmental, brassinosteroid-type signaling rather than via the canonical PTI outputs assayed here, consistent with a co-option of BRI1 clade (LRR-RLK-Xb) architecture -- a receptor family classically associated with development -- into a pathway that modulates susceptibility to a plant-parasitic nematode. C_LI

plant biology↗

bioRxiv2023

The biological activity of bacterial rhamnolipids is linked to their molecular structure

Biosurfactants are amphiphilic compounds of microbial origin with a wide range of industrial applications. Rhamnolipids (RLs) offer a broad range of potential applications as biosurfactants in industry and agriculture. Several studies report a high capacity for controlling different plant pests and pathogens and consider RLs as promising candidates for bio-based plant protection agents. RLs are a class of glycolipids consisting of one (mRLs) or two (dRLs) rhamnose moieties linked to a single or branched {beta}-fatty acid. Due to the diversity of RLs, so far little is known about the relation between molecular structure and biological activity. Engineering the synthesis pathway allowed us to differentiate between the activities of mixtures of pure mRL and of pure dRL congeners and elaborated HPLC techniques further enabled to analyse the activity of single congeners. In a model system with the plant Arabidopsis thaliana and the plant-parasitic nematode Heterodera schachtii we demonstrate that RLs can significantly reduce infection, whereas their impact on the host plant varies depending on their molecular structure. While mRLs reduced plant growth even at low concentration, dRLs showed no or a beneficial impact on plant development. In addition, the effect of RLs on plant H2O2 production was measured as an indicator of plant defense activity. Treatment with mRLs or dRLs at a concentration of 50 ppm increased H2O2 production. Lower concentrations of up to 10 ppm were used to stimulate plants prior to a treatment with water or flagellin (flg22), a bacterial inducer of plant defense responses. At 10 ppm both mRLs and dRLs fostered an increased response to flg22. However, mRLs also led to an increased response to water, the non-inducing negative control, indicating a generally elevated stress level. Neither mRLs nor dRLs induced expression of plant defense marker genes of salicylic acid, jasmonic acid and ethylene pathways within a 1 hour and 48 hours treatment. Due to the negative effect of mRLs on plants further studies were concentrated on dRLs. Treatment of pre-parasitic infective juveniles of H. schachtii revealed that dRLs did not increase mortality even at a very high concentration of 755 ppm. In order to analyse the effect of single dRL congeners nematode infection assays were performed. While dRL congeners with a C10-C8 acyl chain increased nematode infection, dRLs with C10-C12 and C10-C12:1 acyl chains reduced nematode infection even at concentrations below 2 ppm. Plant growth was not reduced by C10-C8 dRLs, but by C10-C12 and C10-C12:1 dRLs at concentrations of 8.3 ppm. H2O2 production was increased compared to the water control upon treatment with C10-C8 dRLs at a concentration of 200 ppm, while C10-C12 and C10-C12:1 dRLs triggered the same effect already at 50 ppm. Our experiments show a clear structure-effect relation. In conclusion, functional assessment and analysis of mode of action of RLs in plants require careful consideration of their molecular structure and composition.

molecular 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

Transcriptomic analysis of resistant and susceptible responses in a new model root-knot nematode infection system using Solanum torvum and Meloidogyne arenaria

Root-knot nematodes (RKNs) are among the most devastating pests in agriculture. Solanum torvum Sw. (turkey berry) has been used as a rootstock for eggplant (aubergine) cultivation because of its resistance to RKNs, including Meloidogyne incognita and M. arenaria. We previously found that a pathotype of M. arenaria, A2-J, is able to infect and propagate in S. torvum. In vitro infection assays showed that S. torvum induces the accumulation of brown pigments during avirulent pathotype A2-O infection, but not during virulent A2-J infection. This experimental system is advantageous because resistant and susceptible responses can be distinguished within a few days, and because a single plant genome can yield information about both resistant and susceptible responses. Comparative RNA-sequencing analysis of S. torvum inoculated with A2-J and A2-O at early stages of infection was used to parse the specific resistance and susceptible responses. Infection with A2-J did not induce statistically significant changes in gene expression within one day post-inoculation (DPI), but afterward, A2-J specifically induced the expression of chalcone synthase, spermidine synthase, and genes related to cell wall modification and transmembrane transport. Infection with A2-O rapidly induced the expression of genes encoding class III peroxidases, sesquiterpene synthases, and fatty acid desaturases at 1 DPI, followed by genes involved in defense, hormone signaling, and the biosynthesis of lignin at 3 DPI. Both isolates induced the expression of suberin biosynthetic genes, which may be triggered by wounding during nematode infection. Histochemical analysis revealed that A2-O, but not A2-J, induced lignin accumulation at the root tip, suggesting that physical reinforcement of cell walls with lignin is an important defense response against nematodes. The S. torvum-RKN system can provide a molecular basis for understanding plant-nematode interactions.

plant biology↗

bioRxiv2018

Inhibition of acetyl-CoA carboxylase by spirotetramat causes lipid depletion and surface coat deficiency in nematodes

Plant-parasitic nematodes pose a significant threat to agriculture causing annual yield losses worth more than 100 billion US$. Nematode control often involves the use of nematicides, but many of them including non-selective fumigants have been phased out, particularly due to ecotoxicological concerns. Thus new control strategies are urgently needed. Spirotetramat (SPT) is used as phloem-moble systemic insecticide targeting acetyl-CoA carboxylase (ACC) of pest insects and mites upon foliar application. Our studies revealed that SPT known to be activated in planta to SPT-enol acts as a developmental inhibitor of the free-living nematode Caenorhabditis elegans and the plant-parasitic nematode Heterodera schachtii. Exposure to SPT-enol leads to larval arrest and disruption of the life cycle. Furthermore, SPT-enol inhibits nematode ACC activity, affects storage lipids, fatty acid composition and disrupts surface coat synthesis. Silencing of H. schachtii ACC by RNAi induced similar phenotypes and thus mimics the effects of SPT-enol, supporting the conclusion that SPT-enol acts on nematodes by inhibiting ACC. Our studies demonstrated that the inhibition of de novo lipid biosynthesis by interfering with nematode ACC is a new nematicidal mode of action addressed by spirotetramat, a well-known systemic insecticide for sucking pest control.

biochemistry↗

bioRxiv2017

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

SummarySedentary plant-parasitic cyst nematodes are obligate biotrophs that infect the roots of their host plant. Their parasitism is based on 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 susceptibility to other pathogens or negatively affecting plant phenotype.

plant biology↗