The dctA gene of Pseudomonas chlororaphis O6 is under RpoN control and is required for effective root colonization and induction of systemic resistance.
Transcription from the dctA gene, which encodes an organic acid transporter in the root-colonizing bacterium Pseudomonas chlororaphis O6, is under complex regulatory control. Promoter sequence analysis revealed an RpoN binding site. The regulation of transcript accumulation by the level of ammonium ions in the growth medium confirmed RpoN regulation, even in the presence of glucose. A dctA mutant colonized tobacco roots to a lesser extent than the wild-type mutant during early seedling development. Colonization by the dctA mutant, as compared to the wild type, also reduced the level of systemically induced resistance against the soft rot pathogen Erwinia carotovora SCC1. We ascribe this reduced colonization to the inability of the mutant to utilize certain organic acid components in the root exudates. The dctA mutant failed to grow on succinate and fumarate, and showed reduced growth on malate. All altered properties of the mutant were complemented by the full-length dctA gene. We propose that organic acids in root exudates may provide important nutrient sources for the beneficial root-colonizing pseudomonad.
Agricultural Plant Stress Research Center and Biotechnology Research Institute, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, Korea.
Hyo Song
HS
Nam
Anne J
AJ
Anderson
Kwang Yeol
KY
Yang
Baik Ho
BH
Cho
Young Cheol
YC
Kim
D000643:Ammonium Chloride / Q000032:analysis; D001426:Bacterial Proteins / Q000502:physiology*; D015169:Colony Count, Microbial / Q000379:methods; D029382:Dicarboxylic Acid Transporters / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000502:physiology; D005816:Genetic Complementation Test / Q000379:methods; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D016973:Pectobacterium carotovorum / Q000254:growth & development; D018517:Plant Roots / Q000382:microbiology*; D011549:Pseudomonas / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D051877:RNA Polymerase Sigma 54 / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014026:Nicotiana / Q000502:physiology*
D001426:Bacterial Proteins; D029382:Dicarboxylic Acid Transporters; D029968:Escherichia coli Proteins; C497751:rpoN protein, E coli; D000643:Ammonium Chloride; D051877:RNA Polymerase Sigma 54