Dataset Information

Spatial dissection of the Arabidopsis thaliana transcriptional response to downy mildew using Fluorescence Activated Cell Sorting.

ABSTRACT: Changes in gene expression form a crucial part of the plant response to infection. In the last decade, 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, with some pathogens such as downy mildew caused by the biotrophic oomycete pathogen Hyaloperonospora arabidopsidis (Hpa), whole-leaf profiling may fail to capture the complete Arabidopsis response encompassing responses of non-infected as well as infected cells within the leaf. Highly localized expression changes that occur in infected cells may be diluted by the comparative abundance of non-infected cells. Furthermore, local and systemic Hpa responses of a differing nature may become conflated. 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. We isolated haustoriated (Hpa-proximal) and non-haustoriated (Hpa-distal) cells from infected seedling samples using FACS, and measured global gene expression. When compared with an uninfected control, 278 transcripts were identified as significantly differentially expressed, the vast majority of which were differentially expressed specifically in Hpa-proximal cells. By comparing our data to previous, whole organ studies, we discovered many highly locally regulated genes that can be implicated as novel in the Hpa response, and that were uncovered for the first time using our sensitive FACS technique.

SUBMITTER: Coker TL

PROVIDER: S-EPMC4498041 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Spatial dissection of the Arabidopsis thaliana transcriptional response to downy mildew using Fluorescence Activated Cell Sorting.

Coker Timothy L R TL Cevik Volkan V Beynon Jim L JL Gifford Miriam L ML

Frontiers in plant science 20150710

Changes in gene expression form a crucial part of the plant response to infection. In the last decade, 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, with some pathogens such as downy mildew caused by the biotrophic oomycete pathogen Hyaloperonospora arabidopsidis (Hpa), whole-leaf profiling may fail to capture the complete Ara ...[more]

PMID: 26217372

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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. The whole experiment was carried out in triplicate, with two time points (5 and 7 days post-inoculation) and three cell types (pathogen-proximal, pathogen-distal and uninfected control), totalling 18 microarrays. Transgenic Arabidopsis thaliana Col-0 with the transgene pDMR6:GFP was used for all experiments. Seedling populations were inoculated with 30,000-60,000 spores/ml of Hyaloperonospora arabidopsis strain Noks1 at 7 days old, and overground tissue sampled at 5 and 7 days post-inoculation. Protoplasts were generated from these samples according to Grønlund et al. 2012 JOVE, and sorted by fluorescence activated cell sorting into a GFP-positive (pathogen-proximal) and GFP-negative (pathogen-distal) population. As a control, uninfected seedlings were also sampled at 12 and 14 days old (equivalent age of 5 and 7 days post-inoculation), protoplasts generated and sorted to yield a GFP-negative population of uninfected control cells. Gene expression was analysed using NimbleGen 12 x 135K microarrays, designed for the TAIR10 genome. Data was normalised using the Robust Multichip Averaging algorithm.

Project description:BackgroundTo limit the impact of the downy mildew disease of grapevine and reduce the need to recur to chemical treatments, an effective strategy might be recovering adaptive resistance traits in both cultivated and wild V. vinifera germplasm. Considering that stilbenes represent the most important class of phytoalexins in the Vitaceae, the constitutive expression and transcriptional activation of all the functional members of the stilbene synthase gene family were analysed in a group of nine grapevine genotypes following artificial infection with the oomycete Plasmopara viticola, the causal agent of the disease. In addition, in the same genotypes we analyzed the expression of genes encoding for two transcription factors involved in the transcriptional regulation of the stilbene synthase genes, namely VvMYB14 and VvMYB15, and of genes encoding for chalcone synthases.ResultsDowny mildew incidence and severity ranged from nihil to high in the grapevine genotypes considered, being low to moderate in a subgroup of V. vinifera genotypes. The constitutive expression of the stilbene synthase genes as well as the extent of their transcriptional activation following P. viticola inoculation appeared to be inversely related to the proneness to develop disease symptoms upon infection. In a specular manner, following P. viticola inoculation all the chalcone synthase genes were up-regulated in the susceptible grapevine genotypes and down-regulated in the resistant ones. The infection brought by P. viticola appeared to elicit a co-ordinated and sequential transcriptional activation of distinct stilbene synthase genes subsets, each of which may be regulated by a distinct and specific MYB transcription factor.ConclusionsThe present results suggest that the induction of stilbene biosynthesis may contribute to the basal immunity against the downy mildew of grapevine, thus representing an adaptive resistance trait to recover, in both cultivated and wild V. vinifera germplasm. During the early stages of P. viticola infection, an antagonistic interaction between flavonol and stilbene biosynthesis might occur, whose outcome might determine the subsequent extent of disease symptoms. Further studies are needed to decipher the possible regulatory mechanisms involved in the antagonistic crosstalk between these two metabolic pathways in resistant and susceptible genotypes in response to P. viticola.

Dataset Information

Spatial dissection of the Arabidopsis thaliana transcriptional response to downy mildew using Fluorescence Activated Cell Sorting.

Publications

Spatial dissection of the Arabidopsis thaliana transcriptional response to downy mildew using Fluorescence Activated Cell Sorting.

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