HrpL negatively regulates flagellar system in Erwinia amylovora
Résumé
Several previous works seem to indicate that flagellar and hrp genes of Erwinia amylovora are counter-regulated. In the present paper, this hypothesis is confirmed by the analysis of several parameters linked to flagella synthesis in E. amylovora grown in hrp- or non hrp-inducing conditions. Moreover, amongst the various hrp mutants tested, the hrpL regulatory mutant only was more motile, produced more flagellins and showed more flagella than the wild-type strain when cultivated on a hrp-inducing medium. A plasmid carrying hrpL introduced into a hrpL mutant decreased its motility and flagellin production. These results strongly suggest that flagellar synthesis of E. amylovora is under the negative control of HrpL, a positive regulator of hrp genes.