Relationships between cytokinin production, presence of plasmids, and fasciation caused by strains of
            <i>Corynebacterium fascians</i>

Murai, Norimoto; Skoog, Folke; Doyle, M. Ellin; Hanson, R S

doi:10.1073/pnas.77.1.619

Cited by 70 publications

(45 citation statements)

References 27 publications

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“…These strains were unable to fasciate tobacco and geranium (Pelargonium zonale) plants (3). Less-pathogenic strains were also described in later reports on R. fascians (27,31) and do not fasciate tobacco (unpublished data). Therefore, it is tempting to speculate that these isolates lack specifically the downstream genes present in highly virulent strains such as D188.…”

Section: Figmentioning

confidence: 93%

“…fascians (42) has for a long time been considered as the prototype of a plant-bacterium interaction requiring only cytokinin production to cause neoplastic growth (15). Several cytokinins have been detected in small amounts in the supernatants of some virulent R. fascians cultures (25,30,31) but not in other virulent cultures (1,8), indicating that the phytopathogenicity of R. fascians involves more than mere cytokinin secretion. Indeed, we have previously demonstrated that fasciation is a multigenic trait with determinants located both on extrachromosomal linear plasmids (Fi plasmids) and on the chromosome (8).…”

Section: Figmentioning

confidence: 99%

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The fas operon of Rhodococcus fascians encodes new genes required for efficient fasciation of host plants

et al. 1994

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Three virulence loci (fas, ftt, and hyp) of Rhodococcus fascians D188 have been identified on a 200-kb conjugative linear plasmid (pFiD188). The fas locus was delimited to a 6.5-kb DNA fragment by insertion mutagenesis, single homologous disruptive recombination, and in trans complementation of different avirulent insertion mutants. The locus is arranged as a large operon containing six open reading frames whose expression is specifically induced during the interaction with host plants. One predicted protein is homologous to P-450 cytochromes from actinomycetes. The putative ferredoxin component is of a novel type containing additional domains homologous to transketolases from chemoautotrophic, photosynthetic, and methylotrophic microorganisms. Genetic analysis revealed thatfas encodes, in addition to the previously identified ipt, at least two new genes that are involved in fasciation development, one of which is only required on older tobacco plants.The interaction between Rhodococcus fascians and host plants leads to the loss of apical dominance and the development of multiple malformed shoots at the site of infection (fasciation). This proliferation is governed by multiple bacterial loci located both on a linear Fi plasmid and on the chromosome (reference 8 and unpublished results). From the three identified loci on pFiD188, only inactivation of one (fas) leads to a complete loss of phytopathogenicity. In this locus, an open reading frame (ORF) coding for an isopentenyltransferase (ipt) has been identified by sequence homology to other cytokinin biosynthesis genes and by biochemical approaches (8). Expression of ipt in R. fascians is regulated by an inducing factor which can only be detected in significant amounts in extracts from tumor tissues (induced by R. fascians) (8).In this paper, we present genetic data that allowed the definition of the fas locus on a 6.5-kb DNA fragment whose complete nucleotide sequence was determined. Six ORFs directed in the same orientation as the previously defined ipt were identified. ORFi and the amino-terminal part of ORF2 have extensive homologies, to P-450 cytochromes and ferredoxins from actinomycetes, whereas the carboxy-terminal portion of ORF2 has conserved regions homologous to the aminoterminal part of transketolases from chemoautotrophic, photosynthetic, or methylotrophic microorganisms.The isolation of new fas mutants and complementation analysis revealed that fas encodes new genes involved in fasciation of the host plant.MATERIALS AND METHODS Bacterial strains and plasmids. Growth conditions and antibiotic concentrations for R. fascians strains have been described previously (11). The Escherichia coli strains used for

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Section: Figmentioning

confidence: 93%

Section: Figmentioning

confidence: 99%

The fas operon of Rhodococcus fascians encodes new genes required for efficient fasciation of host plants

et al. 1994

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“…Previous work has shown that several R. fascians strains harbor large plasmids (13,16,17). The presence of a 99-kilobase-pair (kb) plasmid in a strain called MW2 and the simultaneous loss of cadmium resistance, hydrocarbon utilization, and virulence correlated with the loss of this plasmid have been reported by Murai (16).…”

mentioning

confidence: 96%

Conjugative transfer of cadmium resistance plasmids in Rhodococcus fascians strains

Desomer¹,

D’Haese²,

Montagu³

1988

J Bacteriol

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The presence of a 138-kilobase plasmid (pD188) correlated with increased resistance to cadmium in Rhodococcusfascians D188. This plasmid could be transferred by a conjugation-like system in matings between R. fascians strains. Transconjugants expressed the cadmium resistance and could be used as donors in subsequent matings. Four other R. fascians strains (NCPPB 1488, NCPPB 1675, NCPPB 2551, and ATCC 12974) could also be used as donors for cadmium resistance in matings. Strain NCPPB 1675 showed a 100% cotransfer of cadmium and chloramphenicol resistance markers.Rhodococcus fascians (basonym Corynebacterium fascians) (22) is a gram-positive plant-pathogenic bacterium that causes fasciation of dicotyledonous (21) and monocotyledonous plants, such as members of the family Liliaceae (9,15,23). Previous work has shown that several R. fascians strains harbor large plasmids (13,16,17). The presence of a 99-kilobase-pair (kb) plasmid in a strain called MW2 and the simultaneous loss of cadmium resistance, hydrocarbon utilization, and virulence correlated with the loss of this plasmid have been reported by Murai (16). On the contrary, Lawson et al. (13) claimed that the single large plasmid (112 kb) they found was present in virulent as well as avirulent strains. Although the relationship between the strains used in the analyses by Murai (16) and Lawson et al. (13) was not clear, it seemed likely to the authors of the latter study that a number of strains in both studies had identical origins, especially the avirulent isolate (CF16) used by Murai (16).The genetic analysis of these phenotypic traits has been hindered by the lack of an appropriate system for the introduction and exchange of genetic material. Exchange of chromosomal markers has been well documented for the genus Rhodococcus (1, 4), but there is no evidence for the transfer of plasmids in this genus.In this paper, we report the isolation of a 138-kb plasmid (pD188) present in the cadmium-resistant R. fascians strain D188, the construction of isogenic strains with and without pD188, and the use of these strains for the assignment of the cadmium resistance gene(s) to the plasmid. Furthermore, we describe the conjugal transfer of plasmid pD188 and other plasmids between different R. fascians strains.Mutant isolates of the cadmium-resistant R. fascians strain D188 were obtained in three ways.First, a cadmium-sensitive mutant, labeled D188-1 (Table 1), was obtained by culturing strain D188 at 37°C, which is the upper growth limit.Another class of cadmium-sensitive mutants was obtained unexpectedly by selecting mutants resistant to rifampin. These rifampin-resistant mutants (e.g., strain D188-2; Table 1) were obtained at very low frequency (3 x 10-10) in an unmutagenized culture of R. fascians D188. Their colony size was reduced, and they had a longer generation time. The inability of the rifampin-resistant mutant to maintain the 138-kb plasmid is an unsolved question. Curing by rifampin has been reported in Escherichia coli and Staphylococcus * Corresponding a...

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“…Moreover, it is known that R. fascians can produce at least 11 different cytokinins in vitro (2,18,24,28,48,51). In R. fascians, cytokinins probably originate from two sources, either release from tRNA (36,38) and/or condensation of isopentenyl pyrophosphate and 5Ј-AMP (14). Nevertheless, hitherto no clear correlation between known cytokinins and symptom development could be established (16,18), suggesting that new cytokinin-like molecules could be involved in the formation of the leafy gall (23).…”

mentioning

confidence: 99%

Biosynthesis of Auxin by the Gram-Positive PhytopathogenRhodococcus fasciansIs Controlled by Compounds Specific to Infected Plant Tissues

Vandeputte

Öden

Mol

et al. 2005

Appl Environ Microbiol

118

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The role and metabolism of indole-3-acetic acid in gram-negative bacteria is well documented, but little is known about indole-3-acetic acid biosynthesis and regulation in gram-positive bacteria. The phytopathogen Rhodococcus fascians, a gram-positive organism, incites diverse developmental alterations, such as leafy galls, on a wide range of plants. Phenotypic analysis of a leafy gall suggests that auxin may play an important role in the development of the symptoms. We show here for the first time that R. fascians produces and secretes the auxin indole-3-acetic acid. Interestingly, whereas noninfected-tobacco extracts have no effect, indole-3-acetic acid synthesis is highly induced in the presence of infected-tobacco extracts when tryptophan is not limiting. Indole-3-acetic acid production by a plasmid-free strain shows that the biosynthetic genes are located on the bacterial chromosome, although plasmid-encoded genes contribute to the kinetics and regulation of indole-3-acetic acid biosynthesis. The indole-3-acetic acid intermediates present in bacterial cells and secreted into the growth media show that the main biosynthetic route used by R. fascians is the indole-3-pyruvic acid pathway with a possible rate-limiting role for indole-3-ethanol. The relationship between indole-3-acetic acid production and the symptoms induced by R. fascians is discussed.The phytopathogenic actinomycete Rhodococcus fascians induces the development of a wide range of malformations on its numerous monocotyledonous and dicotyledonous host plants: leaf deformation, growth inhibition, witches' brooms, fasciations, and leafy galls (reference 23 and references therein). The leafy-gall structure, considered an extreme form of apical dominance (59), is the most severe outcome of the R. fasciansplant interaction. Consisting of small misshapen leaves and numerous buds that are inhibited for further outgrowth, the leafy gall is believed to result from the alteration of the endogenous hormone balance of the host plant (23). Leafy-gall features, such as leaf wrinkling, shoot multiplication, and delayed senescence, are typical cytokinin effects. In this respect, R. fascians pathogenicity has been linked to a linear plasmid (pFiD188) that carries different virulence genes. On pFiD188 an isopentenyl transferase (ipt) homologue is located that is essential for symptom development and has been found in all virulent strains examined thus far (14,15,53). Moreover, it is known that R. fascians can produce at least 11 different cytokinins in vitro (2,18,24,28,48,51). In R. fascians, cytokinins probably originate from two sources, either release from tRNA (36, 38) and/or condensation of isopentenyl pyrophosphate and 5Ј-AMP (14). Nevertheless, hitherto no clear correlation between known cytokinins and symptom development could be established (16,18), suggesting that new cytokinin-like molecules could be involved in the formation of the leafy gall (23).Formation of a leafy gall cannot be attributed solely to the action of cytokinin. Some leafy-gall charac...

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Relationships between cytokinin production, presence of plasmids, and fasciation caused by strains of Corynebacterium fascians

Cited by 70 publications

References 27 publications

The fas operon of Rhodococcus fascians encodes new genes required for efficient fasciation of host plants

The fas operon of Rhodococcus fascians encodes new genes required for efficient fasciation of host plants

Conjugative transfer of cadmium resistance plasmids in Rhodococcus fascians strains

Biosynthesis of Auxin by the Gram-Positive PhytopathogenRhodococcus fasciansIs Controlled by Compounds Specific to Infected Plant Tissues

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