ISHS Acta Horticulturae 338: VI International Workshop on Fireblight
A ROLE FOR SURFACE COMPONENTS IN ERWINIA AMYLOVORA PATHOGENICITY |
| Authors: | J. Laurent, M. Menggad, D. Expert |
| Keywords: | Mutant, phage, lipopolysaccharide, EDTA |
| Abstract:
Several approaches can be designed to detect modifications of the surface characteristics of Erwinia amylovora insertional mutants. We focused on the sensitivity either to phages or to various agents known to interfere with outer membrane stability with subsequent analyses by SDS-PHAGE of lipopolysaccharide (LPS) or outer-membrane proteins (OMP). Out of more than 50 single insertion mutants altered in pathogenicity, 8 showed surface modifications. Six of these mutants map in the large hrp cluster of E. amylovora chromosome. Most of them display sensitivity to the phage Ffm, sodium deoxycholate and EDTA associated with a modified LPS electrophoretic profile. The mutation corresponding to PMV6089, an acapsular mutant, maps in a genomic region involved in amylovoran synthesis. The last non-pathogenic mutant, PMV6028, mapping in a still unknown region, exhibited a phenotype relevant to outer membrane modifications. On the other hand about 1,000 clones from our mutants library of E. amylovora were screened for membrane alterations. On the basis of sensitivity to sodium deoxycholate, EDTA or antibiotics, 29 prototrophic clones are potential membrane mutants with a unique transposon insertion. These mutants displayed a large diversity of phenotypes. None of them proved to have lost the ability to produce exudate when inoculated to apple calli. They will be assayed for symptom production by inoculating susceptible hosts. In such a way we expect to isolate mutants which would be altered in the very early steps of the infection process. | |
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