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: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.
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:The root knot nematode, Meloidogyne incognita, is an obligate parasite that causes significant damage to a broad range of host plants. Infection is associated with secretion of proteins surrounded by proliferating cells. Many parasites are known to secrete effectors that interfere with plant innate immunity, enabling infection to occur; they can also release pathogen-associated molecular patterns (PAMPs, e.g., flagellin) that trigger basal immunity through the nematode stylet into the plant cell. This leads to suppression of innate immunity and reprogramming of plant cells to form a feeding structure containing multinucleate giant cells. Effectors have generally been discovered using genetics or bioinformatics, but M. incognita is non-sexual and its genome sequence has not yet been reported. To partially overcome these limitations, we have used mass spectrometry to directly identify 486 proteins secreted by M. incognita. These proteins contain at least segmental sequence identity to those found in our 3 reference databases (published nematode proteins; unpublished M. incognita ESTs; published plant proteins). Several secreted proteins are homologous to plant proteins, which they may mimic, and they contain domains that suggest known effector functions (e.g., regulating the plant cell cycle or growth). Others have regulatory domains that could reprogram cells. Using in situ hybridization we observed that most secreted proteins were produced by the subventral glands, but we found that phasmids also secreted proteins. We annotated the functions of the secreted proteins and classified them according to roles they may play in the development of root knot disease. Our results show that parasite secretomes can be partially characterized without cognate genomic DNA sequence. We observed that the M. incognita secretome overlaps the reported secretome of mammalian parasitic nematodes (e.g., Brugia malayi), suggesting a common parasitic behavior and a possible conservation of function between metazoan parasites of plants and animals.
