Bacteriophage Mu as a genetic tool to study Erwinia amylovora pathogenicity and hypersensitive reaction on tobacco.
Erwinia amylovora 1430 was shown to be sensitive to Mu G(-) particles. Infection resulted either in lytic development or in lysogenic derivatives with insertion of the Mu genome at many sites in the bacterial chromosome. We used the Mu d1Bx::Tn9 (lac Apr Cmr) derivative, called Mu dX, to identify mutants affected in pathogenicity and in their ability to induce a hypersensitive reaction (HR) on tobacco plants. Inoculation of 1,400 lysogenic derivatives on apple root calli led to the identification of 12 mutants in three classes: (i) class 1 mutants were nonpathogenic and unable to induce an HR on tobacco plants; (ii) class 2 mutants were nonpathogenic but retained the ability to induce an HR; and (iii) class 3 mutants showed attenuated virulence. Of the 12 mutants, 8 had a single insertion of the Mu dX prophage. For class 1 and 2 mutants, reversion to pathogenicity was concomitant with the loss of the Mu dX prophage. Furthermore, revertants from the class 1 mutants also recovered the ability to induce an HR on tobacco plants. Five of the six class 3 mutants were impaired in exopolysaccharide production. No changes of the envelope structure (lipopolysaccharide and outer membrane proteins) were correlated with differences in pathogenicity. One class 3 mutant did not produce any functional siderophore, suggesting that iron uptake could be involved in pathogenicity.
Vanneste
J L
JL
Pathologie Végétale, Paris, France.
Paulin
J P
JP
Expert
D
D
D010583:Bacteriophage mu / Q000235:genetics*; D015139:Blotting, Southern; D002876:Chromosomes, Bacterial; D004885:Erwinia / Q000235:genetics / Q000472:pathogenicity*; D004926:Escherichia coli / Q000235:genetics; D005814:Genes, Viral; D008242:Lysogeny; D009154:Mutation; D010947:Plants, Toxic; D015183:Restriction Mapping; D014026:Nicotiana / Q000382:microbiology*; D014774:Virulence