The att locus of Rhodococcus fascians strain D188 is essential for full virulence on tobacco through the production of an autoregulatory compound.
The ability of Rhodococcus fascians strain D188 to provoke leafy gall formation on a variety of plant species is correlated with the linear plasmid pFiD188, on which different pathogenicity loci were identified. The att locus affects the severity of symptom development on tobacco, whereas the fas locus is essential for virulence. To gain insight into the function of the att locus, sequence and expression analyses were performed. The att locus contains nine open reading frames homologous to arginine and beta-lactam biosynthetic genes. att gene expression is transcriptionally induced by leafy gall extracts, but not by extracts of uninfected plants, and depends on the attR gene that encodes a LysR-type transcriptional regulator. The att locus proves to be essential for the formation of inducing factors (IFs) that are present in gall extracts. Because the induction of the fas locus also requires the presence of IFs in gall extracts, the att locus is proposed to play an important role in regulating the expression of the virulence loci of R. fascians.
Maes
T
T
Vakgroep Moleculaire Genetica, Departement Plantengenetica, Vlaams Interuniversitair Instituut voor Biotechnologie, Universiteit Gent, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium.
Vereecke
D
D
Ritsema
T
T
Cornelis
K
K
Thu
H N
HN
Van Montagu
M
M
Holsters
M
M
Goethals
K
K
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006639:Histidine / Q000378:metabolism; D009154:Mutation; D010941:Plant Tumors / Q000382:microbiology*; D010944:Plants / Q000378:metabolism; D012240:Rhodococcus / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D014026:Nicotiana / Q000382:microbiology* / Q000502:physiology
D001426:Bacterial Proteins; D006639:Histidine