Project description:Magnaporthe oryzae (rice blast) and the root-knot nematode Meloidogyne graminicola are causing two of the most important pathogenic diseases jeopardizing rice production. Here, we show that root-knot nematode infestation on rice roots leads to important above-ground changes in plant immunity gene expression, which is correlated with significantly enhanced susceptibility to blast disease.
Project description:Epigenetic 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 are deregulated in galls induced by root-knot nematode (RKN, Meloidogyne graminicola) in rice, their influence on plant defence and their genome-wide impact has not been comprehensively investigated. 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. Total RNA sequencing was performed to assess the effect of histone modification changes on gene expression.
Project description:Ascorbic acid (AA) is known to play a vital role in plant growth and detoxification of reactive oxygen species, however little is known about the significance of AA oxidation in plant defence against pathogens. • The role of ascorbate oxidation in rice defence against root-knot nematodes, Meloidogyne graminicola, was tested with application of AA, ascorbate oxidase (AO), dehydroascorbic acid (DHA), biosynthesis inhibitors and use of mutants. Transcriptome analysis was done on AO treated plants, and hormone measurements were executed to confirm the results. Biochemical analyses were used to study oxidative stress markers, including accumulation of H2O2, , malondialdehyde and AA/DHA.
Project description:Biotrophic plant pathogens have evolved sophisticated strategies to manipulate their host. They derive all of their nutrients from living plant tissues, by making intimate contact with their host while avoiding a resistance response. Rice is one of the most important crop plants worldwide and an excellent model system for studying monocotyledonous plants. Estimates of annual yield losses due to plant-parasitic nematodes on this crop range from 10 to 25% worldwide. One of the agronomically most important nematodes attacking rice is the rice root knot nematode Meloidogyne graminicola. Attack of plant roots by sedentary plant parasitic nematodes, like the root knot nematodes (RKN; Meloidogyne spp.) involves the development of specialized feeding cells in the vascular tissue. The second stage juvenile of the RKN punctures selected vascular cells with its stylet, injects pharyngeal secretions, and this ultimately leads to the reorganisation of these cells into typical feeding structures called giant cells (GCs), from which the nematode feeds for the remainder of its sedentary life cycle (Gheysen & Mitchum, 2011). Morphological and physiological reprogramming of the initial feeding cell leads to nucleus enlargement, proliferation of mitochondria and plastids, metabolic activation, cell cycle alterations and cell wall changes (Gheysen and Mitchum, 2011). The hyperplasia and hypertrophy of the surrounding cells leads to the formation of a root gall, which is typically formed at the root tips in the case of the rice RKN M. graminicola. In comparison with other RKN, M. graminicola has a very fast life cycle, with swelling of the root tips observed as early as 1 day after infection (dai). At 3 dai, terminal hook-like galls are clearly visible (Bridge et al., 2005). After 3 moults the nematodes are mature, around 10 dai. The M. graminicola females lay their eggs inside the galls, while most other RKN deposit egg masses at the gall surface, and hatched juveniles can reinfect the same or adjacent roots. In well-drained soil at 22-29 degrees C the life cycle of M. graminicola is completed in 19 days. 2 biological replicates of nematode infected giant cells and control vascular cells were sampled at two time points: 7 and 14 dai
Project description:Next to their essential roles in plant growth and development, phytohormones play a central role in plant immunity against pathogens. In this study we examined the role of hormones in the antagonism of the plant-pathogenic oomycete Pythium arrhenomanes against the root-knot nematode Meloidogyne graminicola in rice roots. Hormone measurements and gene expression analyses showed that the jasmonate (JA) pathway is induced early upon P. arrhenomanes infection. Exogenous application of methyl-jasmonate (MeJA) on the plant confirmed that JA is needed for basal defence against both P. arrhenomanes and M. graminicola in rice. Whereas M. graminicola suppresses root JA levels to increase host susceptibility, Pythium inoculation boosts JA accumulation up to levels that can no longer be repressed by the nematode in double-inoculated plants. Exogenous MeJA supply phenocopied the defence-inducing capacity of P. arrhenomanes against the root-knot nematode, whereas the antagonism was weakened in JA-insensitive mutants. Transcriptome analysis confirmed upregulation of JA biosynthesis and signalling genes upon P. arrhenomanes infection, and additionally revealed induction of genes involved in biosynthesis of diterpenoid phytoalexins, consistent with strong activation of the gene encoding the JA-inducible transcriptional regulator DITERPENOID PHYTOALEXIN FACTOR. Next to that, our results provide evidence for induced expression of genes encoding ERF83, and related PR proteins, as well as auxin depletion in P. arrhenomanes infected rice roots, which potentially further contributes to the reduced nematode susceptibility seen in double-infected plants.
Project description:Biotrophic plant pathogens have evolved sophisticated strategies to manipulate their host. They derive all of their nutrients from living plant tissues, by making intimate contact with their host while avoiding a resistance response. Rice is one of the most important crop plants worldwide and an excellent model system for studying monocotyledonous plants. Estimates of annual yield losses due to plant-parasitic nematodes on this crop range from 10 to 25% worldwide. One of the agronomically most important nematodes attacking rice is the rice root knot nematode Meloidogyne graminicola. Attack of plant roots by sedentary plant parasitic nematodes, like the root knot nematodes (RKN; Meloidogyne spp.) involves the development of specialized feeding cells in the vascular tissue. The second stage juvenile of the RKN punctures selected vascular cells with its stylet, injects pharyngeal secretions, and this ultimately leads to the reorganisation of these cells into typical feeding structures called giant cells (GCs), from which the nematode feeds for the remainder of its sedentary life cycle (Gheysen & Mitchum, 2011). Morphological and physiological reprogramming of the initial feeding cell leads to nucleus enlargement, proliferation of mitochondria and plastids, metabolic activation, cell cycle alterations and cell wall changes (Gheysen and Mitchum, 2011). The hyperplasia and hypertrophy of the surrounding cells leads to the formation of a root gall, which is typically formed at the root tips in the case of the rice RKN M. graminicola. In comparison with other RKN, M. graminicola has a very fast life cycle, with swelling of the root tips observed as early as 1 day after infection (dai). At 3 dai, terminal hook-like galls are clearly visible (Bridge et al., 2005). After 3 moults the nematodes are mature, around 10 dai. The M. graminicola females lay their eggs inside the galls, while most other RKN deposit egg masses at the gall surface, and hatched juveniles can reinfect the same or adjacent roots. In well-drained soil at 22-29ºC the life cycle of M. graminicola is completed in 19 days.
Project description:We used mRNA sequencing to study the effects of foliar piperonylic acid treatment on the transcriptome of rice plants (cv. Nipponbare) and infection by M. graminicola to gain insights in the molecular basis of piperonylic acid-induced disease resistance against this nematode
Project description:High-coverage whole genome sequencing of 11 Brazilian isolates of the root-knot nematode Meloidogyne incognita, presenting different host plant preferences and different geographical origins. Four M. incognita host races had been proposed in the past, based on host (in)compatibility on four different plant strains. The objective was to assess whether genomic variations (SNP) correlate with host range compatibility, geographical origin and host plant of origin.