DETECTION OF HRP-SECRETED PROTEINS IN STRAIN CFBP1430 OF ERWINIA AMYLOVORA

The hrp chromosomic region of Erwinia amylovora is involved in the pathogenicity of the bacteria and in its ability to induce an hypersensitive response (HR) on non-host plants.
The hrp cluster encodes the components of a type III secretion system.
HrpN, a major HR elicitor and a virulence factor, was shown to be secreted by the Hrp system in strain Ea321. Our purpose was to confirm the Hrp secretion of HrpN in strain CFBP1430 and to identify others Hrp-secreted proteins.
We first determined an inducing medium for hrp genes expression; the highest level of expression was observed in a M9 galactose minimal medium at 25°C. HrpN was not detected in the supernatant of strain CFBP1430 grown in liquid inducing medium at 25°C but in the supernatant of strain CFBP1430 grown on solid inducing medium at 25°C. In these last conditions, we also detected two new Hrp-secreted proteins of 200 and 54 kDa.
The 200 kDa protein is DspA, an essential pathogenicity factor.
Its secretion is dependent on the expression of dspB which shares chemical and physical features with the Syc chaperones identified in the Yersinia genus.
The 54 kDa protein is HrpW which does not play an essential role in the pathogenicity of the bacteria but acts as a negative effector of the HR.

VIII International Workshop on Fire Blight

S. Gaudriault, M.-A. Barny

https://doi.org/10.17660/ActaHortic.1999.489.60