JCJC - Jeunes chercheuses & jeunes chercheurs

Characterization of DspA-induced cell death in Arabidopsis – DspCellDeath

Submission summary

Fire blight is a devastating bacterial disease of Maloideae, a tribe of Rosaceous plants that includes Apple. The causal agent is the enterobacteria Erwinia amylovora whose pathogenicity relies on a type III secretion system (T3SS) allowing the secretion in the plant apoplast or the injection into the plant cells of proteinaceous effectors. Contrary to most other bacterial plant pathogens, E. amylovora pathogenicity relies on a small number of type III effectors (T3Es). At least two of them, HrpN and DspA/E, are important virulence factor. The T3E DspA/E is injected in plant cells and is absolutely required for pathogenicity as dspA/E mutants are non pathogenic. Furthermore, transient expression in plant cells indicates that DspA/E is also sufficient to induce cell death in host and non host plants. We have shown that E. amylovora induces a necrotic symptom and defence responses in Arabidopsis that are similar to those induced in host Apple plant and that these responses, as in host, are mainly induced by the T3SS. We have also shown that DspA/E is required for induction of necrotic symptoms on Arabidopsis. The aim of the present project is to determine the mode of action of DspA/E inside the plant cell using Arabidopsis as a model system. We will use a combination of approaches involving Arabidopsis molecular genetics, cell biology and Yeast genetics. In order to characterize DspA-induced cell death and associated responses we will analyze responses of Arabidopsis to wild-type E. amylovora compared to T3SS-defective tts mutant and dspA/E mutant bacteria; as a complementary approach, we will analyze Arabidopsis transgenic plants expressing DspA/E conditionally using the oestradiol-inducible XVE system. The responses analyzed will concern necrotic symptoms (macroscopic scoring and cell death quantification by electrolyte leakage measurement), defence marker gene modulation and modulation of transcriptome. To localize DspA inside the plant cell, transgenic plants expressing an oestradiol-inducible GFP-DspA will be produced. In parallel, a screen will be performed in Yeast to identify mutants that suppress DspA-induced cell death. Arabidopsis orthologues of yeast suppressor genes, as well as candidate Arabidopsis genes whose expression is modulated specifically by DspA/E will be identified and corresponding mutants existing in public collections will be retrieved. These mutants will be characterized in order to determine whether they are affected in DspA/E-induced cell death and associated responses in Arabidopsis. The characterization of DspA/E-induced cell death will allow us to identify the cellular components and cellular mechanisms involved in this process. Ultimately, these results will be valuable in the search to fight fire blight attack on Apple tree and other members of the Maloidae family.

Project coordination

mathilde FAGARD (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Help of the ANR 200,000 euros
Beginning and duration of the scientific project: - 48 Months

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