Summary A role for DNA hypomethylation has recently been suggested in the interaction between bacteria and plants; it is unclear whether this phenomenon reflects a conserved response. Treatment of plants of monocot rice and dicot tomato with nematode‐associated molecular patterns from different nematode species or bacterial pathogen‐associated molecular pattern flg22 revealed global DNA hypomethylation. A similar hypomethylation response was observed during early gall induction by Meloidogyne graminicola in rice. Evidence for the causal impact of hypomethylation on immunity was revealed by a significantly reduced plant susceptibility upon treatment with DNA methylation inhibitor 5‐azacytidine. Whole‐genome bisulphite sequencing of young galls revealed massive hypomethylation in the CHH context, while not for CG or CHG nucleotide contexts. Further, CHH hypomethylated regions were predominantly associated with gene promoter regions, which was not correlated with activated gene expression at the same time point but, rather, was correlated with a delayed transcriptional gene activation. Finally, the relevance of CHH hypomethylation in plant defence was confirmed in rice mutants of the RNA‐directed DNA methylation pathway and DECREASED DNA METHYLATION 1. We demonstrated that DNA hypomethylation is associated with reduced susceptibility in rice towards root‐parasitic nematodes and is likely to be part of the basal pattern‐triggered immunity response in plants.

For more than three decades, served as a model for plant biology research. At present only a few protein families have been studied in detail in . This study focused on all sequences with lectin motifs in the genome of . Based on amino acid sequence similarity (BLASTp searches), 217 putative lectin genes were retrieved belonging to 9 out of 12 different lectin families. The domain organization and genomic distribution for each lectin family were analyzed. Domain architecture analysis revealed that most of these lectin gene sequences are linked to other domains, often belonging to protein families with catalytic activity. Many protein domains identified are known to play a role in stress signaling and defense, suggesting a major contribution of the putative lectins in development and plant defense. This genome-wide screen for different lectin motifs will help to unravel the functional characteristics of lectins. In addition, phylogenetic trees and WebLogos were created and showed that most lectin sequences that share the same domain architecture evolved together. Furthermore, the amino acids responsible for carbohydrate binding are largely conserved. Our results provide information about the evolutionary relationships and functional divergence of the lectin motifs in .

Abstract Ascorbic acid (AA) is the major antioxidant buffer produced in the shoot tissue of plants. Previous studies on root-knot nematode (RKN; Meloidogyne graminicola)-infected rice (Oryza sativa) plants showed differential expression of AA-recycling genes, although their functional role was unknown. Our results confirmed increased dehydroascorbate (DHA) levels in nematode-induced root galls, while AA mutants were significantly more susceptible to nematode infection. External applications of ascorbate oxidase (AO), DHA, or reduced AA, revealed systemic effects of ascorbate oxidation on rice defence versus RKN, associated with a primed accumulation of H2O2 upon nematode infection. To confirm and further investigate these systemic effects, a transcriptome analysis was done on roots of foliar AO-treated plants, revealing activation of the ethylene (ET) response and jasmonic acid (JA) biosynthesis pathways in roots, which was confirmed by hormone measurements. Activation of these pathways by methyl-JA, or ethephon treatment can complement the susceptibility phenotype of the rice Vitamin C (vtc1) mutant. Experiments on the jasmonate signalling (jar1) mutant or using chemical JA/ET inhibitors confirm that the effects of ascorbate oxidation are dependent on both the JA and ET pathways. Collectively, our data reveal a novel pathway in which ascorbate oxidation induces systemic defence against RKNs.

Strawberry cultivation is associated with high mineral fertilizer doses and extensive use of chemical plant protection products. Based on previous research, we expected that chitin application to peat substrate would increase the nutrient availability and activate the plant’s systemic defense response, resulting in higher strawberry yields and less disease symptoms. We set up two experiments in which the temporal variability and differences in initial nutrient concentrations of the growing media were taken into account. Chitin treatment resulted in the attraction of plant-growth promoting fungal genera towards the plant root, such as Mortierella and Umbelopsis. In addition, by the end of the experiments 87 mg mineral N/L substrate was mineralized, which can be related to the observed increase in plant shoot biomass. This however led to nutrient imbalances in plant shoots and fruits: N concentration in the leaves increased over 30%, exceeding the optimal range, while P and K deficiencies occurred, with concentrations lower than 50% of the optimal range. This may explain the decreased fruit yield and disease resistance of the fruits towards Botrytis cinerea. In contrast, chitin caused a clear defense priming effect in the strawberry leaves, with a strong induction of the jasmonic acid response, resulting in less foliar disease symptoms. Chitin causes positive effects on shoot growth and foliar disease resistance, but caution needs to be taken for nutrient imbalances leading to negative influences on root growth, fruit production and disease susceptibility towards B. cinerea.

Background Sugar beet (Beta vulgaris subsp. vulgaris) is an economically important crop that provides nearly one third of the global sugar production. The beet cyst nematode (BCN), Heterodera schachtii, causes major yield losses in sugar beet and other crops worldwide. The most effective and economic approach to control this nematode is growing tolerant or resistant cultivars. To identify candidate genes involved in susceptibility and resistance, the transcriptome of sugar beet and BCN in compatible and incompatible interactions at two time points was studied using mRNA-seq. Results In the susceptible cultivar, most defense-related genes were induced at 4 dai while suppressed at 10 dai but in the resistant cultivar Nemakill, induction of genes involved in the plant defense response was observed at both time points. In the compatible interaction, alterations in phytohormone-related genes were detected. The effect of exogenous application of Methyl Jasmonate and ET-generator ethephon on susceptible plants was therefore investigated and the results revealed significant reduction in plant susceptibility. Genes putatively involved in the resistance of Nemakill were identified, such as genes involved in phenylpropanoid pathway and genes encoding CYSTM domain-containing proteins, F-box proteins, chitinase, galactono-1,4-lactone dehydrogenase and CASP-like protein. Also, the transcriptome of the BCN was analyzed in infected root samples and several novel potential nematode effector genes were found. Conclusions Our data provides detailed insights into the plant and nematode transcriptional changes occurring during compatible and incompatible interactions between sugar beet and BCN. Many important genes playing potential roles in susceptibility or resistance of sugar beet against BCN, as well as some BCN effectors with a potential role as avr proteins were identified. In addition, our findings indicate the effective role of jasmonate and ethylene in enhancing sugar beet defense response against BCN. This research provides new molecular insights into the plant-nematode interactions that can be used to design novel management strategies against BCN.

AbstractEpigenetic processes play a crucial role in the regulation of plant stress responses, but their role in plant-pathogen interactions remains poorly understood. Although histone modifying enzymes have been observed to be deregulated in galls induced by root-knot nematodes (RKN, Meloidogyne graminicola) in rice, their influence on plant defence and their genome-wide impact have not been comprehensively investigated.In this study, we applied 3 chemical inhibitors of histone modifying enzymes on rice 24h before inoculation with RKN. Despite their distinct described effects on histone modifications, application of different concentrations led in all cases to reduced susceptibility to RKN. Infection assays on two overexpression lines of histone lysine methyltransferases and one histone deacetylase showed contrasting results in susceptibility, indicating that each histone mark has a specific role in plant defence against RKN in rice. At genome-wide level, three histone marks, H3K9ac, H3K9me2 and H3K27me3 were studied by chromatin-immunoprecipitation (ChIP)-sequencing on RKN-induced galls at 3 days post inoculation. While levels of H3K9ac and H3K27me3 were strongly enriched, H3K9me2 was generally depleted in galls versus control root tips. Differential histone peaks were generally associated with plant defence related genes. In conclusion, our results indicate that histone modifications respond dynamically to RKN infection, and specifically target plant-defence related genes.One-sentence summaryPost-translational histone modifications show a dynamic genome-wide response to root-knot nematode infection in rice and are specifically associated with plant defence genes.

Rice (Oryza sativa) is one of the main staple crops worldwide but suffers from important yield losses due to different abiotic and biotic stresses. Analysis of quantitative trait loci (QTL) is a classical genetic method which enables the creation of more resistant cultivars but does not yield information on the genes directly involved or responsible for the desired traits. Lectins are known as proteins with diverse functions in plants. Some of them are abundant proteins in seeds and are considered as storage/defense proteins while other lectins are known as stress-inducible proteins, implicated in stress perception and signal transduction as part of plant innate immunity. We investigated the distribution of lectin sequences in different QTL related to stress tolerance/resistance, morphology, and physiology through mapping of the lectin sequences and QTL regions on the chromosomes and subsequent statistical analysis. Furthermore, the domain structure and evolutionary relationships of the lectins in O. sativa spp. indica and japonica were investigated. Our results revealed that lectin sequences are statistically overrepresented in QTLs for (a)biotic resistance/tolerance as well as in QTLs related to economically important traits such as eating quality and sterility. These findings contribute to the characterization of the QTL sequences and can provide valuable information to the breeders.

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