ANALYSIS OF AN ERWINIA-CHRYSANTHEMI GENE-CLUSTER INVOLVED IN PECTIN DEGRADATION

A group of four genes of Erwinia chrysanthemi involved in pectin degradation has been characterized. These four genes form independent transcription units and are regulated by the negative regulatory gene, kdgR. The functions of two of these genes are known: kduD codes for the 2-keto-3-deoxygluconate oxydoreductase and kdul for the 5-keto-4-deoxyuronate isomerase, two enzymes of the pectin degradation pathway. kdgC has 36% homology with pectate lyase genes of the periplasmic family but its product does not seem to have pectinolytic activity. The fourth gene, kdgF, could have a role in the pathogenicity of E. chrysanthemi. A comparison of the regulatory regions of all the genes controlled by kdgR allowed better definition of the KdgR-binding-site consensus.