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:111,556,278 high-quality reads were obtained by a deep-sequencing approach that show an exact match to the genome of Meloidogyne incognita from the library of J2 juveniles of M. incognita (Mi). Based on these Solexa reads, 89 M. incognita microRNA genes were identified, which grouped into 67 non-redundant miRNAs with mature sequences. All of these candidate miRNAs were confirmed by qRT-PCR, and 26 of them could be detected in the library of the galls of cucumber root infected by M. incognita (GC). MiR-100 was found in a cluster with let-7, which is similar with B. malayi, a human parasitic nematode. Based on the results of deep sequencing, the expression of miR-100 was much more abundant than that of let-7, which indicated that they may not be co-expressed. The ortholog of let-7, a key regulator that controls the nematode from L4 to adult in C. elegans, could be frequently sequenced in the GC library, the later stages of development of M. incognita, while it had a relative low expression level in J2, which indicated that let-7 may have a similar role in the development regulation in plant parasitic nematodes. Frequently sequenced microRNAs, including miR-71, miR-100 and miR-124, should play an important role in the growth and proliferation of M. incognita.
Project description:The biocontrol agent Pythium oligandrum, which is a member of phylum Oomycota, can control diseases caused by a taxonomically wide range of plant pathogens, including fungi, bacteria, and oomycetes. However, whether P. oligandrum could control diseases caused by plant root-knot nematodes (RKNs) was unknown. We investigated a recently isolated P. oligandrum strain GAQ1, and the P. oligandrum CBS530.74 strain, for the control of RKN Meloidogyne incognita infection of tomato (Solanum lycopersicum L.). Initially, P. oligandrum culture filtrates were found to be lethal to M. incognita second-stage juveniles (J2s) with up to 84% mortality at 24 h after treatment compared to 14% in the control group. Consistent with the lethality to M. incognita J2s, tomato roots treated with P. oligandrum culture filtrates reduced the attraction of nematodes, and the number of nematodes penetrating the roots was reduced by up to 78%. In a greenhouse pot trial, P. oligandrum GAQ1 inoculation of tomato plants significantly reduced the gall number by 58% in plants infected with M. incognita. Notably, P. oligandrum GAQ1 mycelial treatment significantly increased tomato plant height (by 36%), weight (by 27%), and root weight (by 48%). Transcriptome analysis of tomato seedling roots inoculated with the P. oligandrum GAQ1 strain identified ~2,500 differentially expressed genes. The enriched GO terms and annotations in the up-regulated genes suggested modulation of plant hormone-signaling and defense-related pathways in response to P. oligandrum. In conclusion, our results support that P. oligandrum GAQ1 can serve as a potential biocontrol agent for M. incognita control in tomato. Multiple mechanisms appear to contribute to the biocontrol effect involving direct inhibition of M. incognita, potential priming of tomato plant defenses, and plant growth promotion.
Project description:111,556,278 high-quality reads were obtained by a deep-sequencing approach that show an exact match to the genome of Meloidogyne incognita from the library of J2 juveniles of M. incognita (Mi). Based on these Solexa reads, 89 M. incognita microRNA genes were identified, which grouped into 67 non-redundant miRNAs with mature sequences. All of these candidate miRNAs were confirmed by qRT-PCR, and 26 of them could be detected in the library of the galls of cucumber root infected by M. incognita (GC). MiR-100 was found in a cluster with let-7, which is similar with B. malayi, a human parasitic nematode. Based on the results of deep sequencing, the expression of miR-100 was much more abundant than that of let-7, which indicated that they may not be co-expressed. The ortholog of let-7, a key regulator that controls the nematode from L4 to adult in C. elegans, could be frequently sequenced in the GC library, the later stages of development of M. incognita, while it had a relative low expression level in J2, which indicated that let-7 may have a similar role in the development regulation in plant parasitic nematodes. Frequently sequenced microRNAs, including miR-71, miR-100 and miR-124, should play an important role in the growth and proliferation of M. incognita. Identifying microRNAs of M. incognita based on deep-sequencing of the small RNAs of an Mi library, the J2 juveniles, and comparing their expression levels with those in a GC library, the gall of cucumber root infected with M. incognita.
Project description:Solanum torvum Sw is worldwide employed as rootstock for eggplant cultivation because of its vigour and resistance/tolerance to the most serious soil-borne diseasesas bacterial, fungal wilts and root-knot nematodes. A 30,0000 features custom combimatrix chip was designed and microarray hybridizations were conducted for both control and 14 dpi (day post inoculation) with Meloidogyne incognita-infected roots samples. We also tested the chip with samples from the phylogenetically-related nematode-susceptible eggplant species Solanum melongena.The genes identified from S. torvum catalogue, bearing high homology to knownnematode resistance genes, were further investigated in view of their potential role in the nematode resistance mechanism. total RNA was extracted from control and 14 days post-infection (infection with root-knot nematode Meloidogyne incognita) from roots of Solanum torvum and Solanum melongena. Three biological replicates were used for each condition and genotype for a total of 12 samples.
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.
Project description:In this experiment we measured the transcriptional response of ten tomato cultivars when infected by the plant-parasitic nematode M. incognita. The ten cultivars showed differential levels of susceptibility to M. incognita infection. Ten-days old plants were exposed to nematodes and harvested 1, 2, 3, 4, 7, or 10 days post infection. Galls or representative uninfected tissues were harvested and used for RNA sequencing. The data was used to investigate the link between susceptibility to M. incognita infection and gene expression in tomato.
Project description:The global imperative to enhance crop protection while preserving the environment has increased interest in the application of biological pesticides. Bacillus thuringiensis (Bt) is a Gramm-positive bacterium that can produce nematicidal proteins and accumulate them in parasporal crystals. Root-knot nematodes are obligate root plant parasitic which are distributed worldwide, causing severe damages to the infested plants and, consequently, large yield reductions. In this work, we have evaluated the toxicity of the crystal proteins Cry5, Cry21, App6, and Xpp55 against two root-knot nematodes belonging to the Meloidogyne genus (M. incognita and M. javanica). The results show that all four proteins, when solubilized, were highly toxic for both nematode species. To check the potential of using Bt strains producing nematicidal crystal proteins as biopesticides to control plant parasitic nematodes in the field, in planta assays were conducted, using two wild Bt strains which produced Cry5 or a combination of App6 and Cry5 proteins. The tests were carried out with cucumber or with tomato plants infested with M. javanica J2, subjected to irrigation with spore+cristal mixtures of the respective strains. The results showed that the efficacy of the nematicidal activity was plant-dependent, as Bt was able to reduce emerged J2 in tomato plants but not in cucumber plants. In addition, the toxicity observed in the in planta assays was much lower than expected, highlighting the challenge of the crystal proteins to exert their toxicity. This emphasizes the delivery of the Bt proteins as crucial for its use to control root-knot nematodes.
Project description:Transgenic tobacco (Nicotiana tabacum) expressing Caenorhabditis elegans cell death genes, Ced4 and Ced3, show evidence suggesting such expressions protect the plants from infestation by the plant parasitic nematode Meloidogyne incognita. Although positive results have been correlated with the gene expressions (data in preparation for publication; a draft of the publication can be provided upon request), the mechanism by which the nematode protection is manifested is not clearly understood. One possibility is that the C. elegans cell death proteins produced by the transgenic plants are being ingested and incorporated into the nematode’s own cell death pathway, leading to their demise. Alternatively, it is also possible that expression of the C. elegans cell death genes promotes the endogenous resistance genes of the plant, leading to nematode resistance. We want to test the later hypothesis by conducting a reference design microarray experiment to establish the expression profile of Ced3, and Ced4 homozygous plants and Ced3xCed4 double heterozygous plants in comparison with wild-type tobacco plants. If the hypothesis is correct, we expect to detect increased expression of pathogenicity-related genes in the transgenic plants. Furthermore, characterization of the expression profiles in these transgenic plants will provide us directionality for our future research on the elucidation of this resistance mechanism. Keywords: Reference design 27 hybs total