TYPE III EFFECTORS OF E. AMYLOVORA: SYNERGISTIC AND ANTAGONISTIC EFFECTS

Functional Type III secretion systems (TTSS) are required for pathogenicity of most gram-negative phytopathogenic bacteria including Ralstonia solanacearum, Erwinia amylovora, Pseudomonas syringae, Xanthomonas campestris, Pantoea stewartii, and Erwina herbicola pv. Gypsophilae. TTSS allows secretion into the medium and injection into the plant cell of bacterial proteins.
Collectively, these bacterial proteins, called TTSS effectors, manipulate plant cell metabolism thereby playing a determinant role in disease initiation.
Several effectors transiting through E. amylovora TTSS have been described.
Among them, HrpN, HrpW and DspA/E are the focus of this review.
Mutants affected in the biosynthesis of HrpN, HrpW or DspA/E is affected in their pathogenicity on host plants and their HR phenotype on non-host plants.
HrpN and DspA/E act synergistically to trigger an oxidative stress on host plants.
On the contrary, HrpN and HrpW act antagonistically on the triggering of cell death, HrpW being able to suppress HrpN induced cell death.
Finally, DspA/E alone is able to trigger cell death on host and non-host plant, inhibiting at the same time some plant defense reactions.
Therefore, these three effectors are important to modulate cell death and plant defense reactions on host and non-host plants.

XI International Workshop on Fire Blight

M.A. Barny, T. Boureau, A. Degrave, M. Fagard, F. Bouteau, S. Gaubert, D. Reboutier, M.N. Brisset

E. amylovora, TTSS, DspA/E, HrpN, HrpW

https://doi.org/10.17660/ActaHortic.2008.793.30