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S G Pueppke

Publications and source records attributed to S G Pueppke.

At least 37 records · Page 2Linked to original sources
PubMed1992

Broad-host-range Rhizobium species strain NGR234 secretes a family of carbamoylated, and fucosylated, nodulation signals that are O-acetylated or sulphated.

Rhizobium species strain NGR234 is the most promiscuous known rhizobium. In addition to the non-legume Parasponia andersonii, it nodulates at least 70 genera of legumes. Here we show that the nodulation genes of this bacterium determine the production of a large family of Nod-factors which are N-acylated chitin pentamers carrying a variety of substituents. The terminal non-reducing glucosamine is N-acylated with vaccenic or palmitic acids, is N-methylated, and carries varying numbers of carbamoyl groups. The reducing N-acetyl-glucosamine residue is substituted on position 6 with 2-O-methyl-L-fucose which may be acetylated or sulphated or non-substituted. All three internal residues are N-acetylated. At pico- to nanomolar concentrations, these signal molecules exhibit biological activities on the tropical legumes Macroptilium and Vigna (Phaseoleae), as well as on both the temperate genera Medicago (Trifoliae) and Vicia (Viciae). These data strongly suggest that the uniquely broad host range of NGR234 is mediated by the synthesis of a family of varied sulphated and non-sulphated lipo-oligosaccharide signals.

Acetylation↗
PubMed1992

Differential expression of nodS accounts for the varied abilities of Rhizobium fredii USDA257 and Rhizobium sp. strain NGR234 to nodulate Leucaena spp.

Transfer of a cosmid containing nodSU from Rhizobium sp. NGR234 to Rhizobium fredii USDA257 expands the host range for nodulation to include the perennial tropical legumes, Leucaena leucocephala and Leucaena diversifolia. Complementation experiments with a series of subclones established that nodS and its associated nod-box promoter from NGR234 are sufficient to confer this extended host-range phenotype to L. leucocephala. Strain USDA257 contains its own copy of nodSU, including upstream nod-box sequences. Although both nucleotide and deduced amino acid sequences of the reading frames are homologous between the two strains, there are gaps within the promoter region and the 5'-end of nodS of USDA257. Consequently, the deduced NodS protein of USDA257 is shorter than its counterpart from NGR234, and the distance between the nod-box and the initiation codon is greater. A 36 bp deletion encompasses the extreme right border of the USDA257 nod-box and extends into the upstream leader sequence. Transcriptional fusions with both nod-boxes confirmed that the promoter from NGR234 is flavonoid-inducible, and that the nod-box from USDA257 is not. These observations were corroborated by Northern analysis with a nodS-containing Xhol fragment as hybridization probe. Flavonoid-induced cells of NGR234 gave an intense signal, but those of USDA257 yielded only a weak trace of hybridization. EcoRI fragments with homology to nodSU of USDA257 are present in 17 of 35 tested strains, including several representatives of Bradyrhizobium japonicum, Rhizobium sp., R. loti, and R. fredii. Two wild-type, leucaena-nodulating strains of Rhizobium sp. lack this homology. We conclude that a genetic defect in expression of nodS accounts for the inability of USDA257 to nodulate leucaena and that diverse rhizobia may have evolved alternative mechanisms to nodulate this legume species.

Amino Acid Sequence↗
PubMed1991

Inheritance of Resistance to Crown Gall in Pisum sativum.

We screened a total of 1365 pea (Pisum sativum) lines for response to inoculation with Agrobacterium tumefaciens, strain B6, and characterized resistance in one cultivar, Sweet Snap. Sweet Snap seedlings were highly resistant to tumorigenesis under most conditions. Resistance was overcome at inoculum concentrations of greater than 10(9) bacteria per milliliter. At such high concentrations, very small tumors developed on Sweet Snap in response to four wide-host-range Agrobacterium strains, but tumors on other cultivars were two-to sevenfold larger than those that formed on Sweet Snap. The hypervirulent strain A281 induced larger tumors on Sweet Snap than did other Agrobacterium strains, but tumors on other genotypes were more than 100% larger than those on Sweet Snap. Physiological experiments suggested that tumorigenesis in Sweet Snap is not blocked in early stages of infection, and genetic analysis indicated that inheritance of resistance to crown gall is a quantitative trait. In addition to the observed resistance in Sweet Snap, three ;supersusceptible' genotypes, which developed very large tumors, also were identified.

Journal Article↗
PubMed1991

nolC, a Rhizobium fredii gene involved in cultivar-specific nodulation of soybean, shares homology with a heat-shock gene.

Rhizobium fredii strain USDA257 does not nodulate soybean (Glycine max (L.) Merr.) cultivar McCall. Mutant 257DH5, which contains a Tn5 insert in the bacterial chromosome, forms nodules on this cultivar, but acetylene-reduction activity is absent. We have sequenced the region corresponding to the site of Tn5 insertion in this mutant and find that it lies within a 1176bp open reading frame that we designate nolC. nolC encodes a protein of deduced molecular weight 43564. Nucleotide sequences homologous to nolC are present in several other Rhizobium strains, as well as Agrobacterium tumefaciens, but not in Pseudomonas syringae pathovar glycinea. nolC lacks significant sequence homology with known genes that function in nodulation, but is 61% homologous to dnaJ, an Escherichia coli gene that encodes a 41 kDa heat-shock protein. Both R. fredii USDA257 and mutant 257DH5 produce heat-shock proteins of 78, 70, 22, and 16kDa. A 4.3kb EcoRI-HindIII subclone containing nolC expresses a single 43kDa polypeptide in mini-cells. A longer, 9.4kb EcoRI fragment expresses both the 43kDa polypeptide and a 78kDa polypeptide that corresponds in size to that of the largest heat-shock protein. Thus, although nolC has strong sequence homology to dnaJ and appears to be linked to another heat-shock gene, it does not directly function in the heat-shock response.

Amino Acid Sequence↗
PubMed1991

Characterization of an Unusual New Agrobacterium tumefaciens Strain from Chrysanthemum morifolium Ram.

We characterized five isolates of Agrobacterium tumefaciens from naturally occurring galls on Chrysanthemum morifolium. The isolates are similar, possibly identical, members of a single strain of A. tumefaciens that we designate Chry5. The strain is a biotype I, as indicated by its response to both newly described and traditional biotype tests. Chry5 produces tumors on at least 10 plant species. It is unusual in its ability to form efficiently large tumors on soybean (Glycine max), a species normally refractory to transformation. Chry5 is unable to utilize octopine or mannopine as a carbon source. Although Chry5 can catabolize a single isomer each of nopaline and succinamopine, it differs from other known nopaline and succinamopine strains in its insensitivity to agrocin 84. This pattern of opine catabolism is unique among Agrobacterium strains examined to date. All five isolates of Chry5 contain at least two plasmids, one of which shares homology with pTiB6.

Journal Article↗
PubMed1990

Modulation of Host Gene Expression during Initiation and Early Growth of Nodules in Cowpea, Vigna unguiculata (L.) Walp.

Inoculation of 2-day-old cowpea (Vigna unguiculata [L.] Walp.) seedlings with Rhizobium fredii USDA257 results in proficient nodulation of the tap root. The most abundant nodulation occurs in a region roughly corresponding to the position of the root tip at the time of inoculation. We have examined plant gene expression in this region, after inoculation with either USDA257 or a nonnodulating mutant, 257B3. After isolation of mRNA and in vitro translation, the protein products were separated by two-dimensional gel electrophoresis. Seven proteins are induced within 2.5 days after inoculation with USDA257. One additional induced protein is detectable by 3.5 days after inoculation, and three more appear by day 6. Three of the proteins that are differentially expressed at 2.5 and 3.5 days after inoculation are produced at equivalent levels after 6 days, indicating transient induction of these genes during early stages of nodule development. Several proteins were more abundant in translations of mRNA from roots that had been inoculated with the nonnodulating mutant. This was particularly true after 6 days, when nine proteins were in this class. Thus, altered plant gene expression in carefully selected, highly responsive tissue can be detected 2 days before emerging nodules are visible on the roots, and 6 to 7 days before acetylene reduction is detectable. Additionally, comparisons of ionically bound cell wall proteins isolated 6 days after inoculation revealed four that were unique to nodulating roots, suggesting that some of the nodulation-induced genes may code for structural proteins.

Journal Article↗
PubMed1990

Nodulation of Soybean by a Transposon-Mutant of Rhizobium fredii USDA257 Is Subject to Competitive Nodulation Blocking by Other Rhizobia.

Rhizobium fredii USDA257 fails to nodulate the improved soybean [Glycine max (L.)Merr.] cultivar McCall in plastic growth pouches. Mutant 257DH4, which was derived from USDA257 by transposon mutagenesis, forms nitrogen fixing nodules under these conditions. If USDA257 is present in inocula containing the mutant, most infections are arrested prior to organization of the nodule meristem, and nodule number is reduced by 95%. The improved cultivars Essex, Harosoy, Hodgson 78, and Viçoja, as well as a supernodulating mutant of Williams, respond like McCall to inoculation with such mixtures of bacteria. Nodulation blocking on McCall can be elicited by rhizobia other than USDA257, provided that they meet two criteria: Blocking strains must themselves be able to induce cortical cells of McCall to divide, and such divisions must proceed to the stage of nodule meristem formation. Nodulation by the mutant remains sensitive to a challenge inoculation with USDA257 for only the first 6 to 12 hours after inoculation. Nodulation blocking involving mutant 257DH4 thus appears to be a rapid, generalized process.

Journal Article↗
PubMed1990

Cultivar-Specific Interactions of Soybean with Rhizobium fredii Are Regulated by the Genotype of the Root.

Rhizobium fredii USDA257 forms nitrogen-fixing nodules on soybean cultivar Peking, but not on cultivar McCall. This pattern of nodulation persists when McCall and Peking seedlings are cultivated together in plastic growth pouches. Reciprocal grafting experiments confirm that the root genotype, and not that of the shoot, regulates such cultivar specificity. When Peking roots are grafted onto McCall seedlings, the nodulation responses of roots similarly remain unaffected. Transposon-mutant 257DH4, which is derived from USDA257, can form nitrogen-fixing nodules on McCall. Such nodulation is blocked by the presence of USDA257 in the inoculum. Grafting experiments indicate that blocking is not due to a translocatable inhibitor produced by McCall roots or triggered by their interaction with USDA257. Thus, neither freely diffusible nor graft-transmissible substances are involved in cultivar-specific interactions of soybean with R. fredii and its derivatives.

Journal Article↗
PubMed1989

Use of a Root Tumorigenesis Assay to Detect Genotypic Variation in Susceptibility of Thirty-four Cultivars of Pisum sativum to Crown Gall.

We developed a quantitative assay to measure tumorigenesis on roots and root crowns, the natural sites of Agrobacterium tumefaciens infection. Efficiency of tumor formation and tumor weight on seedlings of Pisum sativum ;Little Marvel' were directly proportional to the logarithm of inoculum concentration. Depth of wounding prior to inoculation also significantly influenced tumor weight but not efficiency. Mean weight of tumors that developed in response to inoculation with strain B6 varied significantly among 34 different commercial cultivars. Tumors on the most susceptible cultivar, Target, were more than tenfold heavier than those formed on the least susceptible cultivar, Sweet Snap. Efficiency of tumorigenesis on ;Sweet Snap' was also relatively low: only 64% of inoculated seedlings developed tumors compared with 89 to 100% efficiencies for all other cultivars.

Journal Article↗
PubMed1989

Variation in Binding and Virulence of Agrobacterium tumefaciens Chromosomal Virulence (chv) Mutant Bacteria on Different Plant Species.

Chromosomal virulence (chv) mutants of Agrobacterium tumefaciens have been reported to be deficient in binding to cells of zinnia, tobacco, and bamboo. The mutants are nonpathogenic on stems of Kalanchoë, sunflower, tomato, Jerusalem artichoke, and tobacco, but they cause tumors on tubers of Solanum tuberosum. We used a root cap cell binding assay to test ability of cells from individual plants of 13 different plant species to bind parent or chv mutant bacteria. The same plants were then inoculated to test for disease response. Cells from nine of the plant species were grossly deficient in their abilities to bind mutant bacteria, and the plants inoculated with mutant bacteria failed to form tumors. In contrast, root cap cells as well as root hairs and root surfaces of S. tuberosum, S. okadae, and S. hougasii bound chv mutant bacteria as well as wild type. Nevertheless, S. tuberosum roots inoculated with mutant bacteria did not develop tumors. Although S. okadae plants inoculated with mutant bacteria formed a few tumors, and S. hougasii developed as many tumors in response to chv mutants as in response to the parent strain, the tumors induced by mutant bacteria were smaller.

Journal Article↗
PubMed1988

Early Infection and Competition for Nodulation of Soybean by Bradyrhizobium japonicum 123 and 138.

Interactions of soybean with Bradyrhizobium japonicum 123 (serogroup 123) and 138 (serogroup c1) were used to examine the relationship between early infection rates, competition for nodulation, and patterns of nodule occupancy. Both strains formed more infections in autoclaved soil (sterile soil) than in untreated soil (unsterile soil). Inoculation did not increase numbers of infection threads in unsterile soil-grown plants, where infection of proximal portions of primary roots was complete by 5 days after planting. Both strains infected and nodulated at similar rates in sterile soil. Nodules were always clustered on the upper root system, regardless of inoculation and soil treatment. Sixty-seven percent of the nodules of uninoculated plants grown in unsterile soil were occupied by rhizobia belonging to serogroups other than 123 or c1. Inoculation with strain 123 or 138 increased occupancy by that strain at the expense of residency by other rhizobia. Eighty-three percent of all nodules on plants dually inoculated with both strains in sterile soil contained strain 138. The corresponding value for plants inoculated in unsterile soil was 31%. Neither inoculum strain dominated occupancy of first-formed nodules in unsterile soil. It appears that north central Missouri soil may not have populations of highly competitive serogroup 123 and that early infection and nodulation rates do not contribute to the competitive success of strain 138.

Journal Article↗
PubMed1987

Heat shock triggers rapid protein phosphorylation in soybean seedings.

Heat shock arrests the synthesis of many cellular proteins and simultaneously initiates expression of a unique set of proteins, termed heat shock proteins. We have found that heat shock rapidly triggers phosphorylation of a set of proteins in soybean seedlings. Although the kinetics of phosphorylation and the heat shock response are similar, the major identified phosphorylation products do not comigrate with heat shock proteins on polyacrylamide gels. Cadmium, which is known to induce the heat shock response, stimulates phosphorylation of the same set of proteins. The rapidity of phosphorylation suggests that it may play a pivotal role in sensing and transducing elevated temperature stress in plants.

Cadmium↗
PubMed1987

Responses of Rj(1) and rj(1) Soybean Isolines to Inoculation with Bradyrhizobium japonicum.

We evaluated the symbiotic phenotypes of nodulation-restrictive and normal soybean isolines by inoculating Clark (genotypically Rj(1)Rj(1)) and mutant Clark-rj(1) (genotypically rj(1)rj(1)) seedlings in plastic growth pouches. Nodules first appeared on Clark seedlings inoculated with Bradyrhizobium japonicum USDA 94 after 6 days. The mean number of nodules per plant was 13.9 +/- 0.8 after 24 days. In contrast, Clark-rj(1) seedlings first nodulated at 12 days, and the mean number of nodules per plant was only 1.7 +/- 0.3 at 24 days. Segments from infectible zones of primary roots, i.e. near the position occupied by the root tip at the time of inoculation, were sectioned serially. Clark roots contained cortical cell divisions and a few infection threads in question mark-shaped root hairs by 2 days after inoculation. Typical nodules developed soon thereafter. Analogous serially sectioned segments from Clark-rj(1) roots lacked these responses. This prompted us to section nodules and adjacent tissues from other parts of Clark and Clark-rj(1) roots. Clark roots contained cortical cell divisions, many associated with infected root hairs. Cortical cell divisions occasionally were present in Clark-rj(1), and a few infection threads were visible in surface cells. The presence of infection threads within Clark-rj(1) nodules was confirmed by transmission electron microscopy. Thus, although B. japonicum USDA 94 fails to elicit the wild-type spectrum of responses in the infectible zones of primary roots, it can infect Clark-rj(1) via infection threads.

Journal Article↗
PubMed1987

Regulation of nodulation in the soybean-Rhizobium symbiosis : strain and cultivar variability.

Double inoculation (15 h apart) of the soybean cultivar Williams with Bradyrhizobium japonicum I-110ARS reveals a rapid regulatory plant response that inhibits nodulation of distal portions of the primary root (M Pierce, WD Bauer 1984 Plant Physiol 73: 286-290). Only living, homologous rhizobia elicit the response. We conducted similar double inoculation experiments to test the hypothesis that this is a universal phenomenon in soybean symbioses. We investigated interactions of the cultivar McCall with the slow-growing strain Bradyrhizobium sp. 3185 (=3G4b16) and strains of the fast-growing soybean symbiont, Rhizobium fredii (USDA191 [Nod(+) on McCall] and USDA257 [Nod(-) on McCall]). Nodulation was not detectably inhibited when USDA257 was included in various combinations with an inoculum of USDA191. Strain USDA257 cohabited nodules with strain USDA191 when plants were inoculated sequentially with both strains, but USDA257 did not nodulate McCall when a sterile culture filtrate of USDA191 was added to USDA257 inoculum. There was only a slight inhibition of nodulation of distal portions of the primary root in double inoculation experiments with McCall and strain 3185. Because these results were unexpected, we repeated the experiments with Williams and strain I-110ARS. The response was similar to that observed in the McCall x 3185 interaction. Regulation of nodulation on the primary root thus appears to be variable and depend on strain X cultivar interactions.

Journal Article↗
PubMed1986

Compatible and incompatible rhizobia alter membrane potentials of soybean root cells.

Inoculation with Rhizobium japonicum or R. meliloti reduced the electrical transmembrane potential (E(m)) of soybean (Glycine max [L.] Merr.) root cells within 1 day. The response could be attributed to altered diffusion potential (E(D)). E(m) values return to control levels by the second day after inoculation, but again were reduced in R. meliloti-inoculated tissue on the seventh day. Increased concentrations of sodium phosphate in the perfusion solution magnified the effects of inoculation on E(m). Neither heat-killed rhizobia nor living cells of Pseudomonas fluorescens elicited the response. The E(m) and E(D) of nodule cells were nearly 20% lower than corresponding values from adjacent cortical cells of the root.

Journal Article↗
PubMed1985

Isotherm for Adsorption of Agrobacterium tumefaciens to Susceptible Potato (Solanum tuberosum L.) Tissues.

Potato tuber disks were submerged in suspensions containing 10 to 10 cells of Agrobacterium tumefaciens B6 per ml. After 60 min, the disks were rinsed and homogenized, and portions of the homogenates were plated to measure the number of adsorbed bacteria. At low initial bacterial concentrations (10/ml), 5 to 23% of the bacteria adsorbed. At higher bacterial concentrations, the corresponding value was approximately 1.2%. Adsorption was a reversible equilibrium process. Binding saturation was not achieved, and adsorbed bacteria were confined to monolayers on the surfaces of tissue prepared for scanning electron microscopy. Adsorption of strain B6 to potato tuber tissues is described accurately by the Freundlich adsorption isotherm and may be a nonspecific phenomenon.

Journal Article↗
PubMed1984

Adsorption of slow- and fast-growing rhizobia to soybean and cowpea roots.

Roots of soybean (Glycine max [L.] Merr. cv Hardee) and cowpea (Vigna unguiculata [L.] Walp. cv Pink Eye Purple Hull) were immersed in suspensions containing 10(4)Rhizobium cells per milliliter of a nitrogen-free solution. After 30 to 120 minutes the roots were rinsed, and the distal 2-centimeter segments excised and homogenized. Portions of the homogenates then were plated on a yeast-extract mannitol medium for bacterial cell counts. The adsorption capacities of four slow-growing rhizobia and a fast-growing R. meliloti strain varied considerably. Adsorption was independent of plant species and of the abilities of the Rhizobium strains to infect and nodulate. R. lupini 96B9 had the greatest adsorption capacity, and Rhizobium sp. 3G4b16 the least. Rhizobium sp. 229, R. japonicum 138, and R. meliloti 102F51 were intermediate, except on cowpea, where the adsorption of strain 102F51 was similar to that of strain 3G4b16. The initial adsorption rates of bacteria cultured in synthetic media and in the presence of soybean roots were about the same. Addition of soybean lectin to the bacterial inoculum failed to influence initial adsorption rates. Both treatments, however, reduced the numbers of bacteria that bound after incubation with roots for 120 minutes. The relationship between the logarithm of the number of strain 138 cells bound per soybean root segment and the logarithm of the density of bacteria in the inoculum was linear over five orders of magnitude. Binding of strain 138 to soybean roots was greatest at room temperature (27 degrees C) and substantially attenuated at both 4 and 37 degrees C. Although R. lupini 96B9 strongly rejected a model hydrophobic plastic surface, there were no simple correlations between bacterial binding to model hydrophobic and hydrophilic plastic surfaces and bacterial adsorption to roots.

Journal Article↗