Tn5insertion inkdgR, a regulatory gene of the polygalacturonate pathway inErwinia chrysanthemi

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Tn5 mutagenesis was performed on the Erwinia chrysanthemi strain 3937 with the transposon vector pMO194. The vector is spontaneously lost from the cell and Tn5 transposes randomly on the chromosome. A mutant with a derepressed expression of a kduD-lac fusion was obtained. In this mutant, Tn5 was inserted in a regulatory gene, named kdgR, resulting in constitutive expression of genes of the polygalacturonate degradative pathway (pelA, pelD, pelE, ogl, kduI, kduD, kdgT, kdgK and kdgA). Constitutive expression of these genes after inactivation of the kdgR gene by Tn5 insertion suggests that kdgR is a negative regulatory gene. The kdgR mutation was mapped near the trp locus on the E. chrysanthemi chromosome.