title: Genes expressed in Pseudomonas putida during colonization of a plant-pathogenic fungus.
abstract: In vivo expression technology (IVET) was employed to study colonization of Phytophthora parasitica by a biological control bacterium, Pseudomonas putida 06909, based on a new selection marker. The pyrB gene, which encodes aspartate transcarbamoylase, an enzyme used for pyrimidine biosynthesis, was cloned from P. putida 06909. A pyrB-disrupted mutant did not grow in pyrimidine-deficient media unless it was complemented with pyrBC' behind an active promoter. Thirty clones obtained from P. putida 06909 that were expressed on fungal hyphae but not on culture media were isolated by IVET based on the promoterless transcriptional fusion between pyrBC' and lacZ. Nineteen of these clones were induced during late-stage bacterial growth in vitro, while 11 of the clones were expressed only when they were inoculated onto fungal hyphae. Restriction analysis of these 11 clones revealed that there were five unique clones. Sequence analyses of three of the five unique clones showed that the 3' ends of the clones fused to pyrB were similar to genes encoding diacylglycerol kinase (DAGK), bacterial ABC transporters, and outer membrane porins. The sequences of the two other clones were not similar to the sequences of any of the genes in the database used. A LuxR family response regulator was found upstream of DAGK, and a LysR family response regulator was found upstream of the ABC transporter. The location of the inducible promoter of two clones suggested that DAGK and the ABC transporter are induced and may play a role in colonization of the fungus P. parasitica by P. putida 06909.
authors.affiliation: Department of Plant Pathology, University of California, Riverside, California 92521-0122, USA.
authors.forename: S W
authors.initials: SW
authors.lastname: Lee
authors.forename: D A
authors.initials: DA
authors.lastname: Cooksey
mesh_terms: D001221:Aspartate Carbamoyltransferase / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D015870:Gene Expression; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D010572:Pest Control, Biological; D010838:Phytophthora / Q000382:microbiology* / Q000472:pathogenicity; D010935:Plant Diseases / Q000382:microbiology; D011401:Promoter Regions, Genetic; D016958:Pseudomonas putida / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D001221:Aspartate Carbamoyltransferase