The davDT operon of Pseudomonas putida, involved in lysine catabolism, is induced in response to the pathway intermediate delta-aminovaleric acid.
Pseudomonas putida KT2440 is a soil microorganism that attaches to seeds and efficiently colonizes the plant's rhizosphere. Lysine is one of the major compounds in root exudates, and P. putida KT2440 uses this amino acid as a source of carbon, nitrogen, and energy. Lysine is channeled to delta-aminovaleric acid and then further degraded to glutaric acid via the action of the davDT gene products. We show that the davDT genes form an operon transcribed from a single sigma70-dependent promoter. The relatively high level of basal expression from the davD promoter increased about fourfold in response to the addition of exogenous lysine to the culture medium. However, the true inducer of this operon seems to be delta-aminovaleric acid because in a mutant unable to metabolize lysine to delta-aminovaleric acid, this compound, but not lysine, acted as an effector. Effective induction of the P. putida P(davD) promoter by exogenously added lysine requires efficient uptake of this amino acid, which seems to proceed by at least two uptake systems for basic amino acids that belong to the superfamily of ABC transporters. Mutants in these ABC uptake systems retained basal expression from the davD promoter but exhibited lower induction levels in response to exogenous lysine than the wild-type strain.
Revelles
Olga
O
Department of Biochemistry and Molecular and Cell Biology of Plants, Estación Experimental del Zaidín, CSIC, E-18008 Granada, Spain.
Espinosa-Urgel
Manuel
M
Molin
Soeren
S
Ramos
Juan L
JL
D021542:Amino Acids, Neutral / Q000494:pharmacology*; D001483:Base Sequence; D001692:Biological Transport; D008239:Lysine / Q000378:metabolism*; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D016958:Pseudomonas putida / Q000235:genetics* / Q000378:metabolism
D021542:Amino Acids, Neutral; C013809:5-aminovaleric acid; D008239:Lysine