Cytokinin production by Agrobacterium and Pseudomonas spp

Akiyoshi, Donna E.; Regier, Dean A.; Gordon, Milton P.

doi:10.1128/jb.169.9.4242-4248.1987

Cited by 113 publications

(68 citation statements)

References 31 publications

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“…The coexpression of a P-450 monooxygenase, ferredoxin, and isopentenyltransferase in R. fascians could indicate a functional relationship between these enzymes by which isopentenyladenine-adenosine (generated by the isopentenyltransferase reaction) is oxidized to trans-or cis-zeatin-riboside. These latter cytokinins have been detected in R. fascians supernatants (1,25,38). The oxidation reaction from 6-isopentenyladenine to zeatin has been demonstrated not to be a property of Agrobacterium ipt or tsz genes and to be catalyzed by E. coli extracts in well-aerated tubes (17).…”

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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“…Symptoms on infected trees include hyperplasia formation on stems and branches and occasionally on leaves and fruit (23). At present, the only P. savastanoi determinants known to be involved in knot development are production of the phytohormones indole-3-acetic acid (IAA) and cytokinins (CKs) (1,16,30,42) and biosynthesis of a functional type III secretion system (TTSS), encoded by the hrp and/or hrc gene clusters, which facilitate secretion of various protein effectors into the plant cell (34, 35). …”

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Global Genomic Analysis of Pseudomonas savastanoi pv. savastanoi Plasmids

et al. 2008

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Pseudomonas savastanoi pv. savastanoi strains harbor native plasmids belonging to the pPT23A plasmid family (PFPs) which are detected in all pathovars of the related species Pseudomonas syringae examined and contribute to the ecological and pathogenic fitness of their host. However, there is a general lack of information about the gene content of P. savastanoi pv. savastanoi plasmids and their role in the interaction of this pathogen with olive plants. We designed a DNA macroarray containing 135 plasmid-borne P. syringae genes to conduct a global genetic analysis of 32 plasmids obtained from 10 P. savastanoi pv. savastanoi strains. Hybridization results revealed that the number of PFPs per strain varied from one to four. Additionally, most strains contained at least one plasmid (designated non-PFP) that did not hybridize to the repA gene of pPT23A. Only three PFPs contained genes involved in the biosynthesis of the virulence factor indole-3-acetic acid (iaaM, iaaH, and iaaL). In contrast, ptz, a gene involved in the biosynthesis of cytokinins, was found in five PFPs and one non-PFP. Genes encoding a type IV secretion system (T4SS), type IVA, were found in both PFPs and non-PFPs; however, type IVB genes were found only on PFPs. Nine plasmids encoded both T4SSs, whereas seven other plasmids carried none of these genes. Most PFPs and non-PFPs hybridized to at least one putative type III secretion system effector gene and to a variety of additional genes encoding known P. syringae virulence factors and one or more insertion sequence transposase genes. These results indicate that non-PFPs may contribute to the virulence and fitness of the P. savastanoi pv. savastanoi host. The overall gene content of P. savastanoi pv. savastanoi plasmids, with their repeated information, mosaic arrangement, and insertion sequences, suggests a possible role in adaptation to a changing environment.Pseudomonas syringae strains and related pathogens, such as Pseudomonas savastanoi strains, infect a wide range of herbaceous and woody plants causing diverse symptoms, such as leaf spots and blights, soft rots of fruits, wilts, overgrowths, scabs, and cankers (18,23). During the last decade, research on diseases caused by pseudomonads in herbaceous plants has progressed rapidly, and the application of molecular genetics and genome and plasmid sequencing (4,13,22,31,36,39) has provided new insights into determinants of pathogenicity and virulence. However, there is a general lack of knowledge on virulence and pathogenicity determinants specific for infection of woody plants. Clear examples of this are the pathogens P. savastanoi pathovars nerii, fraxini, and savastanoi, which cause knots and galls on members of the various genera of the family Oleaceae and oleander (14). Symptoms on infected trees include hyperplasia formation on stems and branches and occasionally on leaves and fruit (23). At present, the only P. savastanoi determinants known to be involved in knot development are production of the phytohormones indole-3-acetic acid (IAA) an...

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“…Isopentenyl-AMP might be expected to be membrane impermeable due to its negative charge, while a phosphatase might increase membrane permeability, thereby releasing isopentenyl-adenosine from the bacteria. Several other strains of A. tumefaciens are known to release cytokinins in response to vir gene-inducing stimuli (1,2,20,21).…”

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The Right End of the vir Region of an Octopine-Type Ti Plasmid Contains Four New Members of the vir Regulon That Are Not Essential for Pathogenesis

et al. 2000

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We sequenced the virD-virE, virE-virF, and virF-T-DNA intergenic regions of an octopine Ti plasmid. Four newly described genes were induced by the vir gene inducer acetosyringone, two of which are conserved in the nopaline-type Ti plasmid pTiC58. One gene resembles a family of phosphatase genes. Each of these genes is dispensible for tumorigenesis.Infection and colonization of plant or animal hosts often require a multifaceted attack against the host. For example, many pathogenic bacteria, including Bordetella pertussis, Yersinia spp., and Pseudomonas syringae, release multiple toxins and other virulence factors, any one of which may be dispensable for pathogenesis (5,7,8). It seems plausible that the plant pathogen Agrobacterium tumefaciens might similarly use more than one approach to invade and colonize host plants. This bacterium is well-known to transfer fragments of plasmid-encoded DNA (T-DNA) by a conjugation-like mechanism to the nuclei of host plants, where they are integrated into the host genome (23). This T-DNA directs the production of phytohormones (leading to formation of crown gall tumors) and of compounds called opines, which serve the colonizing bacteria as sources of nutrients. While it is not clear whether A. tumefaciens uses additional strategies to attack host plants, another species of Agrobacterium (A. vitus) releases a root macerating pectinase, as well as transferring T-DNA (22). This pectinase is not required for detectable tumorigenesis, while T-DNA transfer is not required for root maceration, indicating that this organism uses at least two independent strategies for pathogenesis.One way to search for undescribed strategies for host infection and colonization is to identify genes that are induced during infection and not required for T-DNA transfer. Approximately 25 genes, called vir genes, are required for T-DNA transfer (23,25). All vir genes are coordinately induced during infection by plant-released chemical signals, including phenolic compounds such as acetosyringone (11). This induction requires the sensory histidine protein kinase VirA, the response regulator VirG, and the periplasmic sugar-binding protein ChvE. Importantly, several of the genes in this regulon, including virH, virK, virL, and virM, are not required for efficient tumorigenesis (15). While it is possible that some or all of these genes play ancillary, dispensable roles in T-DNA transfer, at least some of these genes may direct other processes. We have recently demonstrated that the VirH2 protein catalyzes the O demethylation of several phenolic compounds, converting them to forms that are inactive as vir gene inducers (16). The functions of virK, virL, and virM are not understood, although virK strongly resembles a gene found on a symbiotic megaplasmid of Rhizobium sp. strain NGR234 and is thus unlikely to have any direct role in T-DNA transfer.As part of an ongoing effort to identify new genes that are part of the vir regulon and to study their roles in pathogenesis, we have sequenced approximately 15 kb of DN...

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Cytokinin production by Agrobacterium and Pseudomonas spp

Cited by 113 publications

References 31 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

Global Genomic Analysis of Pseudomonas savastanoi pv. savastanoi Plasmids

The Right End of the vir Region of an Octopine-Type Ti Plasmid Contains Four New Members of the vir Regulon That Are Not Essential for Pathogenesis

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