The operon for cytokinin biosynthesis of Erwinia herbicola pv. gypsophilae contains two promoters and is plant induced.
The operon for cytokinin biosynthesis in the gall-forming bacterium Erwinia herbicola pv. gypsophilae (Ehg) has been previously shown to reside on an indigenous plasmid (pPATH(Ehg)) that is mandatory for pathogenicity. This operon consists of two genes: the first open reading frame (pre-etz) is of unknown function, whereas the second one (etz) encodes for isopentenyl transferase. Northern hybridization performed with the wild-type strain Ehg824-1 grown in Luria-Bertani broth demonstrated two transcripts of which an etz-specific transcript (1.0 kb) was predominant. Fusion of upstream DNA fragments of both pre-etz and etz to the ice nucleation reporter gene inaZ in pVSP61 showed high ice nucleation activity in both cultures, confirming the presence of two independent promoters. An increase of 1-1.5 orders in transcriptional activity of these promoters was observed following inoculation of gypsophila cuttings. Mutants of Ehg824-1 were generated by insertion of inaZ into pre-etz and etz using the transposon reporter Tn3-Spice. An increase of about two orders in transcriptional activity was recorded with both mutants following inoculation of gypsophila or bean cuttings. A similar induction was also observed when the bacteria were applied to the leaf surface of these plants. Unlike other virulence genes present on the pPATH(Ehg), neither pre-etz nor etz was regulated by the adjacent hrp gene cluster.
Guo
M
M
Department of Plant Sciences, Tel-Aviv University, Israel.
Manulis
S
S
Barash
I
I
Lichter
A
A
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D003583:Cytokinins / Q000096:biosynthesis / Q000235:genetics*; D004885:Erwinia / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial / Q000502:physiology*; D009154:Mutation; D009876:Operon; D063245:Plant Development; D010935:Plant Diseases / Q000382:microbiology; D010941:Plant Tumors / Q000209:etiology* / Q000235:genetics; D010944:Plants / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014166:Transferases
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003583:Cytokinins; C063113:ice nucleation protein; D014166:Transferases; C095094:Etz protein, Erwinia herbicola