Leafy gall formation is controlled by fasR, an AraC-type regulatory gene in Rhodococcus fascians.
Rhodococcus fascians can interact with many plant species and induce the formation of either leafy galls or fasciations. To provoke symptoms, R. fascians strain D188 requires pathogenicity genes that are located on a linear plasmid, pFiD188. The fas genes are essential for virulence and constitute an operon that encodes, among other functions, a cytokinin synthase gene. Expression of the fas genes is induced by extracts of infected plant tissue only. We have isolated an AraC-type regulatory gene, fasR, located on pFiD188, which is indispensable for pathogenesis and for fas gene expression. The combined results of our experiments show that in vitro expression of the fas genes in a defined medium is strictly regulated and that several environmental factors (pH, carbon and nitrogen sources, phosphate and oxygen content, and cell density) and regulatory proteins are involved. We further show that expression of the fas genes is controlled at both the transcriptional and the translational levels. The complex expression pattern probably reflects the necessity of integrating a multitude of signals and underlines the importance of the fas operon in the pathogenicity of R. fascians.
Temmerman
W
W
Vakgroep Moleculaire Genetica, Departement Plantengenetica, Vlaams Interuniversitair Instituut voor Biotechnologie, Universiteit Gent, B-9000 Ghent, Belgium.
Vereecke
D
D
Dreesen
R
R
Van Montagu
M
M
Holsters
M
M
Goethals
K
K
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016366:Open Reading Frames; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D010944:Plants / Q000382:microbiology*; D010957:Plasmids; D015183:Restriction Mapping; D012240:Rhodococcus / Q000235:genetics* / Q000472:pathogenicity*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014774:Virulence / Q000235:genetics*
D001426:Bacterial Proteins; C414536:FasR protein, Rhodococcus fascians; D014157:Transcription Factors