Project description:We used Arabidopsis full-genome microarrays to characterize plant transcript accumulations at different stages of infection with the biotrophic oomycete downy mildew pathogen, Hyaloperonospora arabidopsidis : initiation (< 1 dpi) and maintenance of infection (> 4 dpi).
Project description:The downy mildew oomycete Hyaloperonospora arabidopsidis, an obligate filamentous pathogen, infect Arabidopsis by forming feeding structures called haustoria inside the host cell. Previous transcriptome analysis revealed host genes specifically induced during infection. However, whole infected tissue-derived RNA profiling may fail to capture the key transcriptional events that may occur exclusively in haustoriated host cells where the pathogen injects virulence effectors to modulate host immunity for successful accommodation. To understand the interaction between Arabidopsis and H. arabidopsidis at the cellular level, we established a new translating ribosome affinity purification (TRAP) system applicable to pathogen-responsive promoters, enabling haustoriated cell-specific RNA profiling. Among the host genes specifically expressed in H. arabidopsidis-haustoriated cells, we found genes that promote either susceptibility or resistance to the pathogen, providing new insights into the Arabidopsis/downy mildew interaction. We also expect that our new TRAP system could be applicable to several stimulus-specific contexts as well as other plant–pathogen interactions.
Project description:We used Arabidopsis full-genome microarrays to characterize plant transcript accumulations in wild-type plants and pskr1-5 mutants, 3 days after water treatment and inoculation with the biotrophic oomycete downy mildew pathogen, Hyaloperonospora arabidopsidis.
Project description:We used Arabidopsis full-genome microarrays to characterize plant transcript accumulations in map65-3 and ugt76b1 mutants, 3 days after water treatment and inoculation with the biotrophic oomycete downy mildew pathogen, Hyaloperonospora arabidopsidis (Hpa)
Project description:We used Arabidopsis full-genome microarrays to characterize plant transcript accumulations at different stages of infection with the biotrophic oomycete downy mildew pathogen, Hyaloperonospora arabidopsidis : initiation (< 1 dpi) and maintenance of infection (> 4 dpi). In two independent experiments, cotyledons from the ecotype Wassilewskija (WS) were inoculated with water, or with Hyaloperonospora arabidopsidis to establish a compatible interaction. Affymetrix ATH1 microarrays were used to profile Arabidopsis transcript accumulations at the initiation (mixed samples at 8 and 24 hours post inoculation, hpi; early stage) and maintenance (mixed samples at 4 and 6 days post inoculation; late stage) of the compatible interaction.
Project description:We used Arabidopsis full-genome microarrays to characterize plant transcript accumulations in wild-type plants and clv mutants, 3 days after water treatment and inoculation with the biotrophic oomycete downy mildew pathogen, Hyaloperonospora arabidopsidis.
Project description:Here we report on the identification of Arabidopsis genes that are induced during compatible but not during incompatible interactions with the downy mildew pathogen Hyaloperonospora arabidopsidis. This set of so-called compatible specific (CS) genes contrasts the large group of defence-associated genes that is differentially expressed during both compatible and incompatible interactions. From the 17 identified CS-genes, 6 belong to the ERF family of transcription factor genes, suggesting that these ERFs have a role during compatibility. The majority of CS-genes are differentially regulated in response to various forms of abiotic stress. In silico analysis of the CS-genes revealed an over-representation of DREB1A/CBF3 binding sites and EveningElement motifs in their promoter regions. The CS-ERFs are closely related to the CBF transcription factors and could potentially bind the DREB1A/CBF3 promoter elements in the CS-genes. Transcript levels of CS-genes peak at 2-3 days post inoculation, when pathogen growth is highest, and decline at later stages of infection. The induction of several CS-genes was found to be isolate-dependant. This suggests that the identified CS-genes could be the direct or indirect targets of downy mildew effector proteins that promote disease susceptibility.
Project description:Here we report on the identification of Arabidopsis genes that are induced during compatible but not during incompatible interactions with the downy mildew pathogen Hyaloperonospora arabidopsidis. This set of so-called compatible specific (CS) genes contrasts the large group of defence-associated genes that is differentially expressed during both compatible and incompatible interactions. From the 17 identified CS-genes, 6 belong to the ERF family of transcription factor genes, suggesting that these ERFs have a role during compatibility. The majority of CS-genes are differentially regulated in response to various forms of abiotic stress. In silico analysis of the CS-genes revealed an over-representation of DREB1A/CBF3 binding sites and EveningElement motifs in their promoter regions. The CS-ERFs are closely related to the CBF transcription factors and could potentially bind the DREB1A/CBF3 promoter elements in the CS-genes. Transcript levels of CS-genes peak at 2-3 days post inoculation, when pathogen growth is highest, and decline at later stages of infection. The induction of several CS-genes was found to be isolate-dependant. This suggests that the identified CS-genes could be the direct or indirect targets of downy mildew effector proteins that promote disease susceptibility. Compatible interaction - Arabidopsis Ler inoculated with Cala2 compared to Ler with mock inoculation with 3 biological replicates. Each biological replicate is analysed by 4 technical dyeswapped replicates. Incompatible interaction - Arabidopsis Ler inoculated with Waco9 compared to Ler with mock inoculation with 3 biological replicates. Each biological replicate is analysed by 4 technical dyeswapped replicates.
Project description:Plants have evolved strong innate immunity mechanisms, but successful pathogens evade or suppress plant immunity via effectors delivered into the plant cell. Hyaloperonospora arabidopsidis (Hpa) causes downy mildew on Arabidopsis thaliana, and a genome sequence is available for isolate Emoy2. Here, we exploit the availability of genome sequences for Hpa and Arabidopsis to measure gene-expression changes in both Hpa and Arabidopsis simultaneously during infection. Using a high-throughput cDNA tag sequencing method, we reveal expression patterns of Hpa predicted effectors and Arabidopsis genes in compatible and incompatible interactions, and promoter elements associated with Hpa genes expressed during infection. By resequencing Hpa isolate Waco9, we found it evades Arabidopsis resistance gene RPP1 through deletion of the cognate recognized effector ATR1. Arabidopsis salicylic acid (SA)-responsive genes including PR1 were activated not only at early time points in the incompatible interaction but also at late time points in the compatible interaction. By histochemical analysis, we found that Hpa suppresses SA-inducible PR1 expression, specifically in the haustoriated cells into which host-translocated effectors are delivered, but not in non-haustoriated adjacent cells. Finally, we found a highly-expressed Hpa effector candidate that suppresses responsiveness to SA. As this approach can be easily applied to host-pathogen interactions for which both host and pathogen genome sequences are available, this work opens the door towards transcriptome studies in infection biology that should help unravel pathogen infection strategies and the mechanisms by which host defense responses are overcome.
Project description:Changes in gene expression form a crucial part of the plant response to pathogen infection. Whole-leaf expression profiling has played a valuable role in identifying genes and processes that contribute to the interactions between the model plant Arabidopsis thaliana and a diverse range of pathogens. However, for highly localised infections, such as downy mildew caused by the biotrophic oomycete pathogen Hyaloperonospora arabidopsidis (Hpa), whole-leaf profiling may fail to capture the complete Arabidopsis response. Highly localised expression changes may be diluted by the comparative abundance of non-responding leaf cells or the Hpa oomycete evading detection by cells. Furthermore, local and systemic Hpa responses of a differing nature may become convoluted. To address this we applied the technique of Fluorescence Activated Cell Sorting (FACS), typically used for analyzing plant abiotic responses, to the study of plant-pathogen interactions. Using the promoter of Downy Mildew Resistant 6 (DMR6) linked to GFP as a fluorescent marker of pathogen-contacting cells, we isolated Hpa-proximal and Hpa-distal cells from infected leaf samples using FACS, and measured global gene expression.