Project description:Obligate biotrophs such as the virulent powdery mildew Golovinomyces orontii alter plant host cellular architecture, metabolism, and defense in order to acquire nutrients while suppressing cell death and senescence. G. orontii exclusively infects epidermal cells of Arabidopsis with clearly defined stages of infection. Host factors mediating the powdery mildew (PM) interaction are often expressed in the mesophyll cells underlying the infected epidermal cells. Therefore, in order to identify Arabidopsis processes and regulators mediating this PM interaction, we used UV laser microdissection to isolate cells at the PM infection site for global expression profiling. As part of this process, we optimized and/or developed novel tissue preparation, RNA extraction and amplification, and quality control protocols resulting in highly correlated biological replicate data. We focused on the growth and reproduction stage of the PM infection (5 days post infection) when the number of reproductive structures, conidiophores, can be quantified. Site-specific profiling increased our sensitivity dramatically, allowing us to identify specific processes, process components, and their putative regulators hidden in previous whole leaf global expression analyses. For example, the known cell cycle regulator MYB3R4 exhibits altered expression at the site of infection, as do a subset of cell-cycle-associated genes. Furthermore, null myb3r4 mutants exhibit enhanced resistance to PM with reduced conidiophores per colony, suggesting cell cycle control plays an important role in the PM interaction. Experiment Overall Design: Arabidopsis whole leaves from wild type Columbia-0 and enhanced disease susceptibility mutant eds16-1, a null isochorismate synthase 1 (At1g74710) mutant were harvested at 5 days after Golovinomyces orontii infection, microwave-fixed, paraffin-embedded and sectioned. Groups of epidermal and mesophyll cells (~20 cells/group) surrounding the G. orontii infected epidermal cell were cut using a Leica AS laser microdissection (LMD) system. In parallel, groups of epidermal and mesophyll cells were collected from uninfected leaves at 5 days from wild type Arabidopsis. LMD-isolated cells, whole leaf, whole leaf amplified and tissue scrape samples were used for RNA extraction and hybridization to Affymetrix Arabidopsis ATH1 microarrays. Gene expression profiles were obtained for wild type from all samples and for ics1 mutant from LMD infected samples. The experiment includes 2 biological replicates.
Project description:To elucidate host processes and components required for the sustained growth and reproduction of the obligate biotrophic fungus Golovinomyces orontii on Arabidopsis thaliana, laser microdissection was used to isolate cells at the site of infection at 5 days postinfection for downstream global Arabidopsis expression profiling. Site-specific profiling increased sensitivity dramatically, allowing us to identify specific host processes, process components, and their putative regulators hidden in previous whole-leaf global expression analyses. For example, 67 transcription factors exhibited altered expression at the powdery mildew (PM) infection site, with subsets of these playing known or inferred roles in photosynthesis, cold/dehydration responses, defense, auxin signaling, and the cell cycle. Using integrated informatics analyses, we constructed putative regulatory networks for a subset of these processes and provided strong support for host cell cycle modulation at the PM infection site. Further experimentation revealed induced host endoreduplication occurred exclusively at the infection site and led us to identify MYB3R4 as a transcriptional regulator of this process. Induced endoreduplication was abrogated in myb3r4 mutants, and G. orontii growth and reproduction were reduced. This suggests that, by increasing gene copy number, localized endoreduplication serves as a mechanism to meet the enhanced metabolic demands imposed by the fungus, which acquires all its nutrients from the plant host. Keywords: endoreduplication, cell cycle, obligate biotroph
Project description:The edr1 mutant of Arabidopsis thaliana displays enhanced resistance to the powdery mildew Golovinomyces cichoracearum, resulting in cell death and an absence of visible disease symptoms. To better characterize and understand the defense response of edr1, a time course of early signaling responses was performed after inoculation with powdery mildew and compared to the responses of wild-type Col-0. These time points represent early stages in the infection process, before any signs of susceptibility or resistance are visible. Four-week-old Col-0 and edr1 plants were inoculated with powdery mildew and whole rosettes were collected at 0, 18, 36, and 96 hours post inoculation. Each sample is a pool of four rosettes processed together.
Project description:LC-MS/MS data were collected from uninfected and parallel Golovinomyces orontii MGH1- infected Arabidopsis thaliana leaf tissue (leaves 7-9) at 12 days post inoculation to understand the manipulation of host lipid metabolism by the powdery mildew.
Project description:Clubroot caused by the protist pathogen Plasmodiophora brassicae Woronin is a major disease in Brassica crops. Growing clubroot-resistant cultivars is the most effective and practical control strategy, but resistance genes can often be overcome by emerging pathotypes. In this study, we identified PMR4 as a potential host susceptibility factor that can be targeted as a novel genetic resource for durable clubroot resistance. Recessive PMR4 mutations in Arabidopsis thaliana conferred strong resistance to multiple P. brassicae pathotypes, independent of salicylic acid-mediated plant immunity. Using CRISPR/Cas9, we edited two PMR4 orthologs in the Brassica napus genome, and the resulting homozygous mutants exhibited resistance to both powdery mildew and clubroot diseases. While PMR4 is known to mediate callose deposition at wound and powdery mildew infection sites in leaves, this study reveals that P. brassicae infection induces callose deposition in Arabidopsis and B. napus roots in a PMR4-dependent manner. The Arabidopsis pmr4-1 mutation does not affect P. brassicae primary infection but blocks the pathogen entry from epidermal cells to stele in a jasmonic acid signaling-dependent manner, which is also correlated with enriched lignin-like and suberin compounds in periderm cell walls. Together, these findings establish PMR4-encoded callose synthase as a host susceptibility factor that facilitates P. brassicae secondary infection in host roots and demonstrate its potential as a gene-editing target for enhancing resistance to both powdery mildew and clubroot diseases as well as other possible biotic and abiotic stresses in Brassicaceae crops.
Project description:Laser capture microdissection (LCM) provides a useful method for isolating specific cells or tissues from biological samples. Here, we adapted microdissection protocols to allow high-resolution transcript analysis of different tissues from developing Arabidopsis seed. However, to obtain enough RNA for microarray analyses it was necessary to amplify the RNA. Microarray analyses, using endosperm derived RNA amplified by two-round IVT, reproducibly identified endosperm enriched marker genes. Keywords: LCM Endosperm Arabidopsis
Project description:Arabidopsis does not support the growth and asexual reproduction of the barley pathogen, Blumeria graminis f. sp. hordei Bgh). A majority of germlings fail to penetrate the epidermal cell wall and papillae. To gain additional insight into this interaction, we determined whether the salicylic acid (SA) or jasmonate (JA)/ethylene (ET) defence pathways played a role in blocking barley powdery mildew infections. Only the eds1 mutant and NahG transgenics supported a modest increase in penetration success by the barley powdery mildew. We also compared the global gene expression patterns of Arabidopsis inoculated with the non-host barley powdery mildew to those inoculated with a virulent, host powdery mildew, Erysiphe cichoracearum. Genes repressed by inoculations with non-host and host powdery mildews relative to non-inoculated control plants accounted for two-thirds of the differentially expressed genes. A majority of these genes encoded components of photosynthesis and general metabolism. Consistent with this observation, Arabidopsis growth was inhibited following inoculation with Bgh, suggesting a shift in resource allocation from growth to defence. A number of defence-associated genes were induced during both interactions. These genes likely are components of basal defence responses, which do not effectively block host powdery mildew infections. In addition, genes encoding defensins, anti-microbial peptides whose expression is under the control of the JA/ET signalling pathway, were induced exclusively by non-host pathogens. Ectopic activation of JA/ET signalling protected Arabidopsis against two biotrophic host pathogens. Taken together, these data suggest that biotrophic host pathogens must either suppress or fail to elicit the JA/ET signal transduction pathway. An all pairs experiment design type is where all labeled extracts are compared to every other labeled extract. Keywords: all_pairs
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:Differential expression of genes between Arabidopsis WRKY18/40 knock out and wild type plants, after 8 h post inoculation of powdery mildew pathogen.
Project description:The edr1 mutant of Arabidopsis thaliana displays enhanced resistance to the powdery mildew Golovinomyces cichoracearum, resulting in cell death and an absence of visible disease symptoms. To better characterize and understand the defense response of edr1, a time course of early signaling responses was performed after inoculation with powdery mildew and compared to the responses of wild-type Col-0. These time points represent early stages in the infection process, before any signs of susceptibility or resistance are visible.