Project description:Introduction: Hemibiotrophic Phytophthora are a group of agriculturally and ecologically important pathogenic oomycetes causing severe decline in plant growth and fitness. The lifestyle of these pathogens consists of an initial biotrophic phase followed by a switch to a necrotrophic phase in the latter stages of infection. Between these two phases is the biotrophic to necrotrophic switch (BNS) phase, the timing and controls of which are not well understood particularly in Phytophthora spp. where host resistance has a purely quantitative genetic basis. Methods: To investigate this we sequenced and annotated the genome of Phytophthora medicaginis, causal agent of root rot and substantial yield losses to Fabaceae hosts. We analysed the transcriptome of P. medicaginis across three phases of colonisation of a susceptible chickpea host (Cicer arietinum) and performed co-regulatory analysis to identify putative small secreted protein (SSP) effectors that influence timing of the BNS in a quantitative pathosystem. Results: The genome of P. medicaginis is ~78 Mb, comparable to P. fragariae and P. rubi which also cause root rot. Despite this, it encodes the second smallest number of RxLR (arginine-any amino acid-leucine-arginine) containing proteins of currently sequenced Phytophthora species. Only quantitative resistance is known in chickpea to P. medicaginis, however, we found that many RxLR, Crinkler (CRN), and Nep1-like protein (NLP) proteins and carbohydrate active enzymes (CAZymes) were regulated during infection. Characterisation of one of these, Phytmed_10271, which encodes an RxLR effector demonstrates that it plays a role in the timing of the BNS phase and root cell death. Discussion: These findings provide an important framework and resource for understanding the role of pathogenicity factors in purely quantitative Phytophthora pathosystems and their implications to the timing of the BNS phase.
Project description:Phytophthora parasitica is one of the most widespread Phytophthora species, which is known to cause root rot, foot rot/gummosis and brown rot of fruits in citrus. In this study, we have analyzed the transcriptome of a commonly used citrus rootstock Carrizo citrange in response to P. parasitica infection using the RNA-seq technology. In total, we have identified 6692 differentially expressed transcripts (DETs) among P. parasitica-inoculated and mock-treated roots. Of these, 3960 genes were differentially expressed at 24 hours post inoculation and 5521 genes were differentially expressed at 48 hours post inoculation. Gene ontology analysis of DETs suggested substantial transcriptional reprogramming of diverse cellular processes particularly the biotic stress response pathways in Carrizo citrange roots. Many R genes, transcription factors, and several other genes putatively involved in plant immunity were differentially modulated in citrus roots in response to P. parasitica infection. Analysis reported here lays out a strong foundation for future studies aimed at improving resistance of citrus rootstocks to P. parasitica.
Project description:Phytophthora cinnamomi Rands (Pc) is a hemibiotrophic oomycete and the causal agent of Phytophthora root rot (PRR) of the commercially important fruit crop avocado (Persea americana Mill.). Plant defense against pathogens is modulated by phytohormone signaling pathways such as salicylic acid (SA), jasmonic acid (JA), ethylene (ET), auxin and abscisic acid. The role of specific signaling pathways induced and regulated during hemibiotroph-plant interactions has been widely debated. Some studies report SA mediated defense while others hypothesize that JA responses restrict the spread of pathogens. This study aimed to identify the role of SA- and JA- associated genes in the defense strategy of a resistant avocado rootstock, Dusa® in response to Pc infection. Transcripts associated with SA-mediated defense pathways and lignin biosynthesis were upregulated at 6 hours post-inoculation (hpi). Results suggest that auxin, reactive oxygen species (ROS) and Ca2+ signaling was also important during this early time point, while JA signaling was absent. Both SA and JA defense responses were shown to play a role during defense at 18 hpi. Induction of genes associated with ROS detoxification and cell wall digestion (β-1-3-glucanase) was also observed. Most genes induced at 24 hpi were linked to JA responses. Other processes at play in avocado at 24 hpi include cell wall strengthening, the formation of phenolics and induction of arabinogalactan, a gene linked to Pc zoospore immobility. This study represents the first transcriptome wide analysis of a resistant avocado rootstock treated with SA and JA compared to Pc infection. The results provide evidence of a biphasic defense response against the hemibiotroph, which initially involves SA-mediated gene expression followed by the enrichment of JA-mediated defense from 18 to 24 hpi. Genes and molecular pathways linked to Pc resistance are highlighted and may serve as future targets for manipulation in the development of PRR resistant avocado rootstocks.
Project description:Total RNA extracted from Phytophthora sojae (strain P6497) and infected soybean hypocotyls (cultivar Harosoy) provided template for synthesis of cDNA probes used in the microarray hybridizations. Infected plant hypocotyls were sampled 6 h, 12 h, 24 h, and 48 h after inoculation. Mycelia were grown on synthetic media (H&S) or vegetable juice media (V8). Zoospores were sampled at 0 h, 2 h and 6 h after inducing encystment and germination by agitation. We used microarrays to characterize gene expression patterns in the root rot pathogen Phytophthora sojae and its host Glycine max. Keywords: infection time course, zoospore germination time course, media formulation response
Project description:Total RNA extracted from Phytophthora sojae (strain P6497) and infected soybean hypocotyls (cultivar Harosoy) provided template for synthesis of cDNA probes used in the microarray hybridizations. Infected plant hypocotyls were sampled 6 h, 12 h, 24 h, and 48 h after inoculation. Mycelia were grown on synthetic media (H&S) or vegetable juice media (V8). Zoospores were sampled at 0 h, 2 h and 6 h after inducing encystment and germination by agitation. We used microarrays to characterize gene expression patterns in the root rot pathogen Phytophthora sojae and its host Glycine max. Keywords: infection time course, zoospore germination time course, media formulation response 28 samples from 9 treatments; 2 to 5 biological replicates per treatment.
Project description:Phytophthora infestans, the causal agent of potato late blight, is a devastating plant disease that leads to Irish potato famine and threatens world-wide food security. Despite the genome of P. infestans has provided fundamental resource for studying the aggressiveness of this pandemic pathogen, the epigenomes remain poorly understood. Here, utilizing liquid chromatography-tandem mass spectrometry (LC-MS/MS), we demonstrate post-translational modifications (PTM) at P. infestans core histone H3. The PTMs not only include these prevalent modifications in eukaryotes, and also some novel marks, such as H3K53me2 and H3K122me3. We focused on the trimethylations of H3K4, H3K9 and H3K27 and H3K36, and profiled P. infestans epigenomes employing Native Chromatin Immunoprecipitation followed by sequencing (N-ChIP-seq). In parallel, we mapped P. infestans chromomatin accessibility by Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq). We found that adaptive genomic compartments display significantly higher levels of H3K9me3 and H3K27me3, and are generally in condense chromatin. Interestingly, we observed that genes encoding virulence factors, such as effectors, are enriched in open chromatin regions that barely have the four histone modifications. With a combination of genomic, epigenomic, transcriptomic strategies, our study illustrates the epigenetic states in P. infestans, which will help to study genomic functions and regulations in this pathogen.
Project description:Phytophthora infestans, the causal agent of potato late blight, is a devastating plant disease that leads to Irish potato famine and threatens world-wide food security. Despite the genome of P. infestans has provided fundamental resource for studying the aggressiveness of this pandemic pathogen, the epigenomes remain poorly understood. Here, utilizing liquid chromatography-tandem mass spectrometry (LC-MS/MS), we demonstrate post-translational modifications (PTM) at P. infestans core histone H3. The PTMs not only include these prevalent modifications in eukaryotes, and also some novel marks, such as H3K53me2 and H3K122me3. We focused on the trimethylations of H3K4, H3K9 and H3K27 and H3K36, and profiled P. infestans epigenomes employing Native Chromatin Immunoprecipitation followed by sequencing (N-ChIP-seq). In parallel, we mapped P. infestans chromomatin accessibility by Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq). We found that adaptive genomic compartments display significantly higher levels of H3K9me3 and H3K27me3, and are generally in condense chromatin. Interestingly, we observed that genes encoding virulence factors, such as effectors, are enriched in open chromatin regions that barely have the four histone modifications. With a combination of genomic, epigenomic, transcriptomic strategies, our study illustrates the epigenetic states in P. infestans, which will help to study genomic functions and regulations in this pathogen.