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At least 19 recordsLinked to original sources

Marine star-shaped-aggregate-forming bacteria: Agrobacterium atlanticum sp. nov.; Agrobacterium meteori sp. nov.; Agrobacterium ferrugineum sp. nov., nom. rev.; Agrobacterium gelatinovorum sp. nov., nom. rev.; and Agrobacterium stellulatum sp. nov., nom. rev.

Two new species of aerobic, gram-negative, peritrichously flagellated or nonmotile marine bacteria usually forming star-shaped aggregates were isolated from northeastern Atlantic Ocean bottom sediments. These organisms resembled eight star-shaped-aggregate-forming bacterial species from the Baltic Sea originally ascribed to the genus Agrobacterium but not included on the Approved Lists of Bacterial Names because of their questionable relationships to true agrobacteria. These two sets of star-shaped-aggregate-forming bacteria were compared by means of phenotypic data, DNA base compositions, DNA-DNA relatedness, and one-dimensional electrophoretic analysis of low-molecular-weight RNAs (5S rRNA and tRNA). According to the results of genotyping, the northeastern Atlantic Ocean isolates and three of the Baltic Sea species formed a group of closely related bacteria that could not be excluded from the genus Agrobacterium with certainty. Until more genotypic data are available, these five marine species are regarded as a distinct subdivision of the genus Agrobacterium consisting of Agrobacterium atlanticum sp. nov. (type strain, 1480T = DSM 5823T), A. meteori sp. nov. (type strain, 1513T = DSM 5824T), A. ferrugineum sp. nov. nom. rev. emend. (type strain, ATCC 25652T), A. gelatinovorum sp. nov. nom. rev. emend. (type strain, ATCC 25655T), and A. stellulatum sp. nov. nom. rev. emend. (type strain, ATCC 15215T). "A. aggregatum" proved to be a later subjective synonym of A. stellulatum, which had priority. The remaining four Baltic Sea species, "A. agile," "A. kieliense," "A. luteum," and "A. sanguineum," could not be placed in the new subdivision of Agrobacterium.

DNA, Bacterial↗

Proposal for rejection of Agrobacterium tumefaciens and revised descriptions for the genus Agrobacterium and for Agrobacterium radiobacter and Agrobacterium rhizogenes.

The 16S rRNA sequences of seven representative Agrobacterium strains, eight representative Rhizobium strains, and the type strains of Azorhizobium caulinodans and Bradyrhizobium japonicum were determined. These strains included the type strains of Agrobacterium tumefaciens, Agrobacterium rhizogenes, Agrobacterium radiobacter, Agrobacterium vitis, Agrobacterium rubi, Rhizobium fredii, Rhizobium galegae, Rhizobium huakuii, Rhizobium leguminosarum, Rhizobium loti, Rhizobium meliloti, and Rhizobium tropici. A phylogenetic analysis showed that the 15 strains of Agrobacterium and Rhizobium species formed a compact phylogenetic cluster clearly separated from the other members of the alpha subclass of the Proteobacteria. However, Agrobacterium species and Rhizobium species are phylogenetically entwined with one another, and the two genera cannot be separated. In the Agrobacterium species, the strains of biovar 1, biovar 2, Agrobacterium rubi, and Agrobacterium vitis were clearly separated. The two biovars exhibited homogeneity in their phenotypic, chemotaxonomic, and phylogenetic characteristics, and two species should be established for the two biovars. We considered the nomenclature of the two biovars, and revised descriptions of Agrobacterium radiobacter (for the biovar 1 strains) and Agrobacterium rhizogenes (for the biovar 2 strains) are proposed. The name Agrobacterium tumefaciens is rejected because the type strain of this species was assigned to Agrobacterium radiobacter, and consequently the description of the genus Agrobacterium is revised.

Agrobacterium tumefaciens↗

Establishment of an Agrobacterium-mediated transformation system for grape (Vitis vinifera L.): the role of antioxidants during grape-Agrobacterium interactions.

Very short exposures of embryogenic calli of Vitis vinifera cv. Superior Seedless grape plants to diluted cultures of Agrobacterium resulted in plant tissue necrosis and subsequent cell death. Antibiotics used for Agrobacterium elimination or as plant selectable markers were not responsible for this necrotic response. Rather, cell death seemed to be oxygen-dependent and correlated with elevated levels of peroxides. Therefore, we studied the effects on necrosis of various combinations of antioxidants during and after grape-Agrobacterium cocultivation. The combination of polyvinylpolypyrrolidone and dithiothreitol was found to improve plant viability. Tissue necrosis was completely inhibited by these antioxidants while Agrobacterium virulence was not effected. These treatments enabled the recovery of stable transgenic grape plants resistant to hygromycin.

Antioxidants↗

Complementation of Agrobacterium tumefaciens tumor-inducing aux mutants by genes from the T(R)-region of the Ri plasmid of Agrobacterium rhizogenes.

In this paper we provide information indicating that the agropine-type root-inducing (Ri) plasmid pRi1855 of Agrobacterium rhizogenes contains functional genes for auxin production (aux) in the right transferred DNA (T-DNA) region (T(R)-region). These genes were cloned and introduced into the T-region of the tumor-inducing (Ti) plasmids of mutants of Agrobacterium tumefaciens carrying an aux mutation. Depending on the Ri aux gene present, the oncogenicity of the Ti aux-1 and/or aux-2 mutations was restored, showing that the Ri aux genes are able to complement the Ti aux genes. Agrobacterium strains with an agropine-type Ri plasmid not only cause hairy root on certain plant species, but they also induce tumors on other plant species. In this paper it is shown that a mutation in either of the aux genes in the Ri plasmid leads to a total loss of tumorigenicity and a strongly diminished rhizogenicity of the host bacterium, revealing that the aux genes are important for tumor and root induction. Agrobacterium strains containing the T(R)-region but not the T(L) (left)-region of the Ri plasmid are still tumorigenic on certain plant species but are no longer capable of hairy-root induction.

Journal Article↗

Agrobacterium tumefaciens and Agrobacterium rhizogenes transformed roots of the parasitic plant Triphysaria versicolor retain parasitic competence.

Parasitic plants in the Orobanchaceae invade roots of neighboring plants to rob them of water and nutrients. Triphysaria is facultative parasite that parasitizes a broad range of plant species including maize and Arabidopsis. In this paper we describe transient and stable transformation systems for Triphysaria versicolor Fischer and C. Meyer. Agrobacterium tumefaciens and Agrobacterium rhizogenes were both able to transiently express a GUS reporter in Triphysaria seedlings following vacuum infiltration. There was a correlation between the length of time seedlings were conditioned in the dark prior to infiltration and the tissue type transformed. In optimized experiments, nearly all of the vacuum infiltrated seedlings transiently expressed GUS activity in some tissue. Calluses that developed from transformed tissues were selected using non-destructive GUS staining and after several rounds of in vivo GUS selection, we recovered uniformly staining GUS calluses from which roots were subsequently induced. The presence and expression of the transgene in Triphysaria was verified using genomic PCR, RT PCR and Southern hybridizations. Transgenic roots were also obtained by inoculating A. rhizogenes into wounded Triphysaria seedlings. Stable transformed roots were identified using GUS staining or fluorescent microscopy following transformation with vectors containing GFP, dsRED or EYFP. Transgenic roots derived from both A. tumefaciens and A. rhizogenes transformations were morphologically normal and developed haustoria that attached to and invaded lettuce roots. Transgenic roots also remained competent to form haustoria in response to purified inducing factors. These transformation systems will allow an in planta assessment of genes predicted to function in plant parasitism.

Agrobacterium tumefaciens↗

Tropane alkaloid production by hairy roots of Atropa belladonna obtained after transformation with Agrobacterium rhizogenes 15834 and Agrobacterium tumefaciens containing rol A, B, C genes only.

Atropa belladonna leaf disks were infected by a wild strain Agrobacterium rhizogenes 15834 harboring the Ri-TL-DNA and by a disarmed Agrobacterium tumefaciens strain harboring a construction with only rol ABC and npt II genes. Thirteen root lines were established and examined for their growth rate and alkaloid productivity to evaluate the possible role of rol genes in morphological differentiation and in tropane alkaloid formation. A great diversity has been observed in the growth rate of these 13 root lines. The root biomass increased up to 75 times. The total alkaloid contents were similar in the root lines obtained by infection with A. rhizogenes 15834 and A. tumefaciens rol ABC. The last ones accumulated between 4 (1.1 mg g(-1) DW) and 27 (8 mg g(-1) DW) times more alkaloids than the intact roots (0.3 mg g(-1) DW). This work has shown that the rol ABC genes were sufficient to increase tropane alkaloid production in A. belladonna hairy root cultures.

Agrobacterium tumefaciens↗

Feedback regulation of an Agrobacterium catalase gene katA involved in Agrobacterium-plant interaction.

Catalases are known to detoxify H2O2, a major component of oxidative stress imposed on a cell. An Agrobacterium tumefaciens catalase encoded by a chromosomal gene katA has been implicated as an important virulence factor as it is involved in detoxification of H2O2 released during Agrobacterium-plant interaction. In this paper, we report a feedback regulation pathway that controls the expression of katA in A. tumefaciens cells. We observed that katA could be induced by plant tissue sections and by acidic pH on a minimal medium, which resembles the plant environment that the bacteria encounter during the course of infection. This represents a new regulatory factor for catalase induction in bacteria. More importantly, a feedback regulation was observed when the katA-gfp expression was studied in different genetic backgrounds. We found that introduction of a wild-type katA gene encoding a functional catalase into A. tumefaciens cells could repress the katA-gfp expression over 60-fold. The katA gene could be induced by H2O2 and the encoded catalase could detoxify H2O2. In addition, the katA-gfp expression of one bacterial cell could be repressed by other surrounding catalase-proficient bacterial cells. Furthermore, mutation at katA caused a 10-fold increase of the intracellular H2O2 concentration in the bacteria grown on an acidic pH medium. These results suggest that the endogenous H2O2 generated during A. tumefaciens cell growth could serve as the intracellular and intercellular inducer for the katA gene expression and that the acidic pH could pose an oxidative stress on the bacteria. Surprisingly, one mutated KatA protein, exhibiting no significant catalase activity as a result of the alteration of two important residues at the putative active site, could partially repress the katA-gfp expression. The feedback regulation of the katA gene by both catalase activity and KatA protein could presumably maintain an appropriated level of catalase activity and H2O2 inside A. tumefaciens cells.

Agrobacterium tumefaciens↗

Use of Agrobacterium expressing green fluorescent protein to evaluate colonization of sonication-assisted Agrobacterium-mediated transformation-treated soybean cotyledons.

Colonization and infection of soybean cotyledons by Agrobacterium tumefaciens and subsequent elimination of bacteria from cotyledons were monitored using bacteria expressing green fluorescent protein (GFP). GFP provided a quick, non-destructive method to evaluate, in real time, Agrobacterium colonization of cotyledon surfaces as well as infection of internal cells. GFP was first detected 7 h following inoculation of the cotyledon. By 36 h, GFP expression was very intense, and was limited to the adaxial surface of the cotyledon. Expression of GFP also served as a useful indicator of successful elimination of the bacterium from plant tissue following antibiotic treatment.

Agrobacterium tumefaciens↗

Elevated temperature differentially affects virulence, VirB protein accumulation, and T-pilus formation in different Agrobacterium tumefaciens and Agrobacterium vitis strains.

That gene transfer to plant cells is a temperature-sensitive process has been known for more than 50 years. Previous work indicated that this sensitivity results from the inability to assemble a functional T pilus required for T-DNA and protein transfer to recipient cells. The studies reported here extend these observations and more clearly define the molecular basis of this assembly and transfer defect. T-pilus assembly and virulence protein accumulation were monitored in Agrobacterium tumefaciens strain C58 at different temperatures ranging from 20 degrees C to growth-inhibitory 37 degrees C. Incubation at 28 degrees C but not at 26 degrees C strongly inhibited extracellular assembly of the major T-pilus component VirB2 as well as of pilus-associated protein VirB5, and the highest amounts of T pili were detected at 20 degrees C. Analysis of temperature effects on the cell-bound virulence machinery revealed three classes of virulence proteins. Whereas class I proteins (VirB2, VirB7, VirB9, and VirB10) were readily detected at 28 degrees C, class II proteins (VirB1, VirB4, VirB5, VirB6, VirB8, VirB11, VirD2, and VirE2) were only detected after cell growth below 26 degrees C. Significant levels of class III proteins (VirB3 and VirD4) were only detected at 20 degrees C and not at higher temperatures. Shift of virulence-induced agrobacteria from 20 to 28 or 37 degrees C had no immediate effect on cell-bound T pili or on stability of most virulence proteins. However, the temperature shift caused a rapid decrease in the amount of cell-bound VirB3 and VirD4, and VirB4 and VirB11 levels decreased next. To assess whether destabilization of virulence proteins constitutes a general phenomenon, levels of virulence proteins and of extracellular T pili were monitored in different A. tumefaciens and Agrobacterium vitis strains grown at 20 and 28 degrees C. Levels of many virulence proteins were strongly reduced at 28 degrees C compared to 20 degrees C, and T-pilus assembly did not occur in all strains except "temperature-resistant" Ach5 and Chry5. Virulence protein levels correlated well with bacterial virulence at elevated temperature, suggesting that degradation of a limited set of virulence proteins accounts for the temperature sensitivity of gene transfer to plants.

Agrobacterium tumefaciens↗

VIP1, an Arabidopsis protein that interacts with Agrobacterium VirE2, is involved in VirE2 nuclear import and Agrobacterium infectivity.

T-DNA nuclear import is a central event in genetic transformation of plant cells by Agrobacterium. This event is thought to be mediated by two bacterial proteins, VirD2 and VirE2, which are associated with the transported T-DNA molecule. While VirD2 is imported into the nuclei of plant, animal and yeast cells, nuclear uptake of VirE2 occurs most efficiently in plant cells. To understand better the mechanism of VirE2 action, a cellular interactor of VirE2 was identified and its encoding gene cloned from Arabidopsis. The identified plant protein, designated VIP1, specifically bound VirE2 and allowed its nuclear import in non-plant systems. In plants, VIP1 was required for VirE2 nuclear import and Agrobacterium tumorigenicity, participating in early stages of T-DNA expression.

Amino Acid Sequence↗

Susceptibility of Agrobacterium tumefaciens Strains to Two Agrocin-Producing Agrobacterium Strains.

Sixty-five strains and isolates of Agrobacterium tumefaciens representing each of the known biotypes, were tested for in vitro and in vivo susceptibility to the agrocin-producing strains Agrobacterium radiobacter 84 and A. tumefaciens D286. No biotype 3 strain was susceptible to the effects of either of the agrocinogenic strains in vitro. On datura and tobacco, the best inhibition of tumor formation was obtained when the agrocinogenic strains were applied to wounds 24 h before the pathogens and by the concomitant application of agrocin producer and pathogen at cell ratios of 10:1 or 3:1; inhibition of infection tended to decrease progressively as the cell ratio decreased from 10:1 to 3:1 to 1:1. Generally, strain 84 was superior to D286 in inhibiting tumor formation. A combined cell suspension of 84 and D286 was as effective as 84 alone. The overall pattern of inhibition of tumor formation by biotype 1 and 2 pathogens resistant to the agrocinogenic strains in vitro was similar to that obtained with strains that were susceptible in vitro.

Journal Article↗

Evidence of Biological Control of Agrobacterium tumefaciens Strains Sensitive and Resistant to Agrocin 84 by Different Agrobacterium radiobacter Strains on Stone Fruit Trees.

The effectiveness of Agrobacterium radiobacter K84, 0341, and a K84 non-agrocin-producing mutant (K84 Agr) in biological control of crown gall on rootstocks of stone fruit trees was determined in three experiments. In experiment 1, K84 and 0341 controlled crown gall on plum plants in soil inoculated with two strains of Agrobacterium tumefaciens resistant to agrocin 84. In experiment 2, K84 controlled crown gall on peach plants in soils inoculated with strains of A. tumefaciens sensitive or resistant to agrocin 84 or with a mixture of both. However, the effectiveness of K84 was higher against the sensitive strain than against the resistant strain. There was a residual effect of K84 from one year to another in soil inoculated with the sensitive strains. In experiment 3, K84 and K84 Agr controlled crown gall on plum and peach plants in soils inoculated with strains of A. tumefaciens sensitive or resistant to agrocin 84. The control afforded by K84 was higher than that provided by K84 Agr against the sensitive strain but was similar against the resistant strain.

Journal Article↗

Agrobacterium rhizogenes GALLS protein substitutes for Agrobacterium tumefaciens single-stranded DNA-binding protein VirE2.

Agrobacterium tumefaciens and Agrobacterium rhizogenes transfer plasmid-encoded genes and virulence (Vir) proteins into plant cells. The transferred DNA (T-DNA) is stably inherited and expressed in plant cells, causing crown gall or hairy root disease. DNA transfer from A. tumefaciens into plant cells resembles plasmid conjugation; single-stranded DNA (ssDNA) is exported from the bacteria via a type IV secretion system comprised of VirB1 through VirB11 and VirD4. Bacteria also secrete certain Vir proteins into plant cells via this pore. One of these, VirE2, is an ssDNA-binding protein crucial for efficient T-DNA transfer and integration. VirE2 binds incoming ssT-DNA and helps target it into the nucleus. Some strains of A. rhizogenes lack VirE2, but they still transfer T-DNA efficiently. We isolated a novel gene from A. rhizogenes that restored pathogenicity to virE2 mutant A. tumefaciens. The GALLS gene was essential for pathogenicity of A. rhizogenes. Unlike VirE2, GALLS contains a nucleoside triphosphate binding motif similar to one in TraA, a strand transferase conjugation protein. Despite their lack of similarity, GALLS substituted for VirE2.

Acetophenones↗

Transgenic Medicago truncatula plants obtained from Agrobacterium tumefaciens -transformed roots and Agrobacterium rhizogenes-transformed hairy roots.

Medicago truncatula, barrel medic, is a forage crop that has been developed into a model legume. The development of new transformation methods is important for functional genomic studies in this species. Based on Agrobacterium tumefaciens-mediated transformation of root explants, we developed an effective system for producing M. truncatula (genotype R108) transgenic plants. Among the four A. tumefaciens strains (AGL1, C58C1, EHA105 and LBA4404) tested, EHA105 and AGL1 were most effective in regenerating transgenics. Callus induction frequency from root explants was 69.8%, and plantlet/shoot regeneration frequency was 41.3% when EHA105 was used. Transgenic nature of the regenerated plants was confirmed by PCR and Southern hybridization analyses. Progeny analysis revealed stable Mendelian meiotic transmission of transgenes. Because M. truncatula is particularly useful for the study of root endosymbiotic associations, we further developed a plant regeneration system from A. rhizogenes-transformed hairy roots of M. truncatula. Fertile true transgenic plants were regenerated from the hairy roots, thus allowing the assessment of gene functions at the whole plant level. Segregation analysis revealed that the hairy root genes could be segregated out in the progenies. By coupling A. rhizogenes-mediated hairy root transformation and the regeneration system reported here, once potential genes of interest are identified, the transformed hairy roots carrying such genes could be directly regenerated into plants for more detailed characterization of the genes.

Acetyltransferases↗

Cloning and characterization of the dxs gene, encoding 1-deoxy-d-xylulose 5-phosphate synthase from Agrobacterium tumefaciens, and its overexpression in Agrobacterium tumefaciens.

A newly isolated gene dxs11 from Agrobacterium tumefaciens (KCCM 10413), an organism with potential for the industrial production of ubiquinone-10 (UbiQ(10)), encoding a 1-deoxy-d-xylulose 5-phosphate synthase (Dxs), was cloned in Escherichia coli and its nucleotide sequence was determined. DNA sequence analysis revealed an open reading frame of 1920bp, capable of encoding a polypeptide of 640 amino acids residues with a calculated isoelectric point of pH 5.63 and a molecular mass of 68,054Da. The homodimeric enzyme was overexpressed in E. coli and purified as an active soluble form. The enzyme required thiamine diphosphate and a divalent metal ion, either Mg(2+) or Mn(2+), for enzymatic activity. The enzyme had an optimal pH and temperature of 8.0 and 37 degrees C, respectively, with a k(cat) of 26.8s(-1) and a k(cat)/K(m) of 0.67 and 1.17s(-1)M(-1) for pyruvate and d-glyceraldehyde 3-phosphate, respectively. A. tumefaciens Dxs showed a comparable catalytic efficiency to other Dxs proteins. The dxs11 gene was transformed into A. tumefaciens KCCM 10413, and the resulting recombinant, A. tumefaciens pGX11, showed higher UbiQ(10) production (502.4mg/l) and content (8.3mg/gDCW) than A. tumefaciens KCCM 10413, by 21.9 and 23.9%, respectively. This work describes Dxs from A. tumefaciens, an organism with the potential for industrial UbiQ(10) production, and the first metabolic engineering study with the non-mevalonate pathway enzyme in A. tumefaciens.

Agrobacterium tumefaciens↗

Biological Control of Agrobacterium tumefaciens, Colonization, and pAgK84 Transfer with Agrobacterium radiobacter K84 and the Tra Mutant Strain K1026.

The efficacies of Agrobacterium radiobacter K84 and K1026 in root colonization, crown gall control, and plasmid transfer were compared. Levels of root colonization by K84 and K1026 of Montclar and Nemaguard peach seedlings were similar during the 21 days of the experiment. Four strains of A. tumefaciens bv. 1 were used for soil inoculations in biological control experiments on GF677 and Adafuel peach x almond rootstocks; two were sensitive and two were resistant to agrocin 84. Both strains K84 and K1026 were very efficient in controlling the sensitive strains, but some tumors appeared with both treatments. In the biocontrol of resistant strains, no galls were observed in K1026-treated plants, but some K84-treated plants had galls. Recovery of agrobacteria from galls in experiments with sensitive and resistant strains showed that all of the isolates from the controls or K1026-treated plants and most of the isolates from K84-treated plants had the same characteristics as the inoculated strains. Nine isolates from the K84-treated plants growing in soil inoculated with one resistant strain were virulent and produced agrocin 84. These isolates had a plasmid that hybridized with a probe prepared with the BamHI C fragment from pAgK84. These results show the efficiency of K1026 in biocontrol of agrocin 84-sensitive and -resistant strains of A. tumefaciens and suggest the use of K1026 as a safer organism than K84 for biological control of crown gall.

Journal Article↗

Iron-binding compounds from Agrobacterium spp.: biological control strain Agrobacterium rhizogenes K84 produces a hydroxamate siderophore.

Iron-binding compounds were produced in various amounts in response to iron starvation by a collection of Agrobacterium strains belonging to the species A. tumefaciens, A. rhizogenes, and A. vitis. The crown gall biocontrol agent A. rhizogenes strain K84 produced a hydroxamate iron chelator in large amounts. Production of this compound, and also of a previously described antibiotic-like substance called ALS84, occurred only in cultures of strain K84 grown in iron-deficient medium. Similarly, sensitivity to ALS84 was expressed only when susceptible cells were tested in low-iron media. Five independent Tn5-induced mutants of strain K84 affected in the production of the hydroxamate iron chelator showed a similar reduction in the production of ALS84. One of these mutants, M8-10, was completely deficient in the production of both agents and grew poorly compared to the wild type under iron-limiting conditions. Thus, the hydroxamate compound has siderophore activity. A 9.1-kb fragment of chromosomal DNA containing the Tn5 insertion from this mutant was cloned and marker exchanged into wild-type strain K84. The homogenote lost the ability to produce the hydroxamate siderophore and also ALS84. A cosmid clone was isolated from a genomic library of strain K84 that restored to strain M8-10 the ability to produce of the siderophore and ALS84, as well as growth in iron-deficient medium. This cosmid clone contained the region in which Tn5 was located in the mutant. Sequence analysis showed that the Tn5 insert in this mutant was located in an open reading frame coding for a protein that has similarity to those of the gramicidin S synthetase repeat superfamily. Some such proteins are required for synthesis of hydroxamate siderophores by other bacteria. Southern analysis revealed that the biosynthetic gene from strain K84 is present only in isolates of A. rhizogenes that produce hydroxamate-type compounds under low-iron conditions. Based on physiological and genetic analyses showing a correlation between production of a hydroxamate siderophore and ALS84 by strain K84, we conclude that the two activities share a biosynthetic route and may be the same compound.

Amino Acid Sequence↗