Mutation in the edd gene encoding the 6-phosphogluconate dehydratase of Pseudomonas chlororaphis O6 impairs root colonization and is correlated with reduced induction of systemic resistance

Aims: The primary objective of this study was to determine the role of 6-phosphogluconate dehydratase in root colonization and the induction of systemic resistance by the rhizobacterium, Pseudomonas chlororaphis O6. Methods and Results: The edd gene encoding for 6-phosphogluconate dehydratase, which is one of the key enzymes in glucose utilization, was cloned. Transcription of the gene was higher in medium containing sugars than with organic acids. An edd mutant failed to grow on glucose but grew on organic acids. The edd mutant colonized tobacco roots at wild-type levels early after inoculation, but levels were lower by 12 days. The edd mutant failed to induce the systemic resistance in tobacco to a soft-rot pathogen at wild-type level. Conclusions: 6-Phosphogluconate dehydratase in P. chlororaphis O6 contributes to root colonization and induction of systemic resistance presumably as the consequence of its essential role in the Entner-Doudoroff (ED) pathway. Significance and Impact of the study: Metabolism of sugars through the ED pathway in P. chlororaphis O6 may be important because it facilitates the production of inducers of systemic resistance including butanediol.