Publications

microbial modification of sugars as building blocks for chemicals.	investigations on the microbial modification of sucrose to the corresponding 3-keto-derivative were carried out with resting cells of agrobacterium tumefaciens ncppb 396. this highly specific oxidation to yield the 3-keto-derivative has been analysed kinetically with varying substrate and cell mass concentrations. the formation of the corresponding 3-keto-derivative depended strongly on the reaction time and the aeration rate and was maximal at aeration rates up to 11.5 volume air/cultivation vo ...	1992	1368064
distribution of an l-isoaspartyl protein methyltransferase in eubacteria.	a protein carboxyl methyltransferase (ec 2.1.1.77) that recognizes age-damaged proteins for potential repair or degradation reactions has been found in all vertebrate tissues and cells examined to date. this enzyme catalyzes the transfer of methyl groups from s-adenosylmethionine to the carboxyl groups of d-aspartyl or l-isoaspartyl residues that are formed spontaneously from normal l-aspartyl and l-asparaginyl residues. a similar methyltransferase has been found in two bacterial species, escher ...	1992	1729230
rhizobium meliloti produces a family of sulfated lipooligosaccharides exhibiting different degrees of plant host specificity.	we have shown that a rhizobium meliloti strain overexpressing nodulation genes excreted high amounts of a family of n-acylated and 6-o-sulfated n-acetyl-beta-1,4-d-glucosamine penta-, tetra-, and trisaccharide nod factors. either a c(16:2) or a c(16:3) acyl chain is attached to the nonreducing end subunit, whereas the sulfate group is bound to the reducing glucosamine. one of the tetrasaccharides is identical to the previously described nodrm-1 factor. the two pentasaccharides as well as nodrm-1 ...	1992	1729688
opine catabolism and conjugal transfer of the nopaline ti plasmid ptic58 are coordinately regulated by a single repressor.	the ti plasmids of agrobacterium tumefaciens are conjugal elements whose transfer is strongly repressed. transfer is induced by the conjugal opines, a group of unique carbon compounds synthesized in crown gall tumors. the opines also induce ti plasmid-encoded genes required by the bacteria for opine catabolism. we have cloned and sequenced a gene from the ti plasmid ptic58, whose product mediates the opine-dependent regulation of conjugal transfer and catabolism of the conjugal opines, agrocinop ...	1992	1731335
the vird2 protein of a. tumefaciens contains a c-terminal bipartite nuclear localization signal: implications for nuclear uptake of dna in plant cells.	here we show that the vird2 protein of a. tumefaciens functions as a nuclear localizing protein in plant cells. the nuclear localization signal of vird2 consists of two regions containing 4-5 basic amino acids (krpr and rkrer), located within the c-terminal 34 amino acids. these regions conform to the kr/kxr/k motif required for numerous nuclear localized nonplant eukaryotic proteins. each region independently directs a beta-glucuronidase reporter protein to the nucleus; however, both regions ar ...	1992	1732061
opine transport genes in the octopine (occ) and nopaline (noc) catabolic regions in ti plasmids of agrobacterium tumefaciens.	the occ and noc regions of octopine and nopaline ti plasmids in agrobacterium tumefaciens are responsible for the catabolic utilization of octopine and nopaline, respectively. opine-inducible promoters, genes for regulatory proteins and for catabolic enzymes, had been identified in previous work. however, both regions contained additional dna stretches which were under the control of opine-inducible promoters, but the functions were unknown. we investigated these stretches by dna sequence and fu ...	1992	1732218
characterization of the agrobacterium tumefaciens heat shock response: evidence for a sigma 32-like sigma factor.	we have characterized the heat shock response of agrobacterium tumefaciens and compared it with the well-characterized escherichia coli heat shock response. four major heat shock proteins with apparent molecular masses of 98, 75, 65, and 20 kda were identified by pulse-labelling cultures after temperature upshift. the three largest proteins comigrated with proteins that were antigenically related to the e. coli heat shock proteins sigma 70, dnak, and groel, respectively. the heat shock proteins ...	1992	1732231
mutation of the miaa gene of agrobacterium tumefaciens results in reduced vir gene expression.	vir regulon expression in agrobacterium tumefaciens involves both chromosome- and ti-plasmid-encoded gene products. we have isolated and characterized a new chromosomal gene that when mutated results in a 2- to 10-fold reduction in the induced expression of vir genes by acetosyringone. this reduced expression occurs in ab minimal medium (ph 5.5) containing either sucrose or glucose and containing phosphate at high or low concentrations. the locus was cloned and used to complement a. tumefaciens ...	1992	1735704
a self-transmissible, narrow-host-range endogenous plasmid of rhodobacter sphaeroides 2.4.1: physical structure, incompatibility determinants, origin of replication, and transfer functions.	rhodobacter sphaeroides 2.4.1 naturally harbors five cryptic endogenous plasmids (c. s. fornari, m. watkins, and s. kaplan, plasmid 11:39-47, 1984). the smallest plasmid (prs241e), with a molecular size of 42 kb, was observed to be a self-transmissible plasmid which can transfer only to certain strains of r. sphaeroides. transfer frequencies can be as high as 10(-2) to 10(-3) per donor under optimal mating conditions in liquid media in the absence of oxygen. prs241e, designated the s factor, was ...	1992	1735707
the agrobacterium tumefaciens vir gene transcriptional activator virg is transcriptionally induced by acid ph and other stress stimuli.	a set of agrobacterium tumefaciens operons required for pathogenesis is coordinately induced during plant infection by the vira and virg proteins. the intracellular concentration of virg increases in response to acidic media, and this response was proposed to be regulated at the level of transcription at a promoter (p2) that resembles the escherichia coli heat shock promoters. to test this hypothesis, we first constructed a virg-lacz transcriptional fusion. a strain containing this fusion had hi ...	1992	1735712
the central domain of rhizobium leguminosarum dctd functions independently to activate transcription.	sigma 54-dependent transcriptional activators such as escherichia coli ntrc, rhizobium meliloti nifa, and rhizobium leguminosarum dctd share similar central and carboxy-terminal domains but differ in the structure and function of their amino-terminal domains. we have deleted the amino-terminal and carboxy-terminal domains of r. leguminosarum dctd and have demonstrated that the central domain of dctd, like that of nifa, is transcriptionally competent.	1992	1735730
isolation and genetic analysis of an agrobacterium tumefaciens avirulent mutant with a chromosomal mutation produced by transposon mutagenesis.	a transposon 5 (tn5) insertion was introduced into the genome of a. tumefaciens (a-208 strain harboring a nopaline type ti-plasmid) using a conjugative pjb4ji plasmid containing tn5. five thousand transconjugants were assayed for virulence on carrot (daucus carota l.) disks; 54 isolates were avirulent or very attenuated. the cellular localization (plasmid or chromosome) of the tn5 insertion in those isolates were identified by southern hybridization analysis. an avirulent mutant (b-90 strain) wi ...	1992	1369092
depolarization of alfalfa root hair membrane potential by rhizobium meliloti nod factors.	although much is known about the bacterial genetics of early nodulation, little is known about the plant cell response. alfalfa root hair cells were impaled with intracellular microelectrodes to measure a membrane potential depolarizing activity in rhizobium meliloti cell-free filtrates, a plant response dependent on the bacterial nodulation genes. the depolarization was desensitized by repeated exposure to factors and was not observed in a representative nonlegume. a purified extracellular nod ...	1992	10744524
signals in root nodule organogenesis and endocytosis of rhizobium.		1992	12297652
stimulation of nodulation in field peas (pisum sativum) by low concentrations of ammonium in hydroponic culture.	although the inhibitory effects of high concentrations of mineral n (> 1.0 mm) on nodule development and function have often been studied, the effects of low, static concentrations of nh4+ (< 1.0 mm) on nodulation are unknown. in the present experiments we examine the effects of static concentrations of nh4+ at 0, 0.1 and 0.5 mm in flowing, hydroponic culture on nodule establishment and nitrogenase activity in field peas [pisum sativum l. cv. express (svalöf ab)] for the initial 28 days after p ...	1992	11537678
genetic analysis of rhizobium leguminosarum bv. phaseoli mutants defective in nodulation and nodulation suppression.	nodulation-defective rhizobia and their nodule-forming derivatives containing cloned dna from the wild type were used to study nodulation suppression in phaseolus vulgaris l. non-nitrogen-fixing derivatives which formed rhizobia-containing white nodules induced partial suppression. comparison of this with the complete suppression by fix derivatives and a fix mutant which formed rhizobia-containing pink nodules suggests that the extent of suppression may be related to successive stages of nodule ...	1992	16348664
extracellular polysaccharide is not responsible for aluminum tolerance of rhizobium leguminosarum bv. phaseoli ciat899.	strain uhm-5, a psym exo derivative of the aluminum-tolerant rhizobium leguminosarum bv. phaseoli strain ciat899, was equally tolerant of aluminum (al) as the parental culture. dialyzed culture supernatants of the wild-type cells grown in yem broth (10 cells ml) contained 185 mug of glucose equivalents ml whereas uhm-5 culture supernatants yielded 2 mug of glucose ml. the exo derivative and the parental strain gave essentially similar growth in medium containing from 0 to 300 mum al, indicating ...	1992	16348680
chemotaxis of rhizobium meliloti towards nodulation gene-inducing compounds from alfalfa roots.	luteolin, a flavone present in seed exudates of alfalfa, induces nodulation genes (nod) in rhizobium meliloti and also serves as a biochemically specific chemoattractant for the bacterium. the present work shows that r. meliloti rcr2011 is capable of very similar chemotactic responses towards 4',7-dihydroxyflavone, 4',7-dihydroxyflavanone, and 4,4'-dihydroxy-2-methoxychalcone, the three principal nod gene inducers secreted by alfalfa roots. chemotactic responses to the root-secreted nod inducers ...	1992	16348685
diversity among rhizobia effective with robinia pseudoacacia l.	the diversity of rhizobia that form symbioses with roots of black locust (robinia pseudoacacia l.), an economically important leguminous tree species, was examined by inoculating seedling root zones with samples of soil collected from the united states, canada, and china. bacteria were isolated from nodules, subcultured, and verified to be rhizobia. the 186 isolates varied significantly in their resistance to antibiotics and nacl, their growth on different carbohydrates, and their effect on the ...	1992	16348730
utilization of carbon substrates, electrophoretic enzyme patterns, and symbiotic performance of plasmid-cured clover rhizobia.	plasmids in rhizobium spp. are relatively large, numerous, and difficult to cure. except for the symbiotic plasmid, little is known about their functions. the primary objective of our investigation was to obtain plasmid-cured derivatives of rhizobium leguminosarum bv. trifolii by using a direct selection system and to determine changes in the phenotype of the cured strains. three strains of rhizobia were utilized that contained three, four, and five plasmids. phenotypic effects observed after cu ...	1992	16348739
effect of light and organic acids on oxygen uptake by btai 1, a photosynthetic rhizobium.	a photosynthetic rhizobium, strain btai 1, was cultured ex planta to investigate its photosynthetic-respiratory system and the response of this interactive system to light quantity and quality and to the addition of organic acids. oxygen uptake, as measured with an oxygen electrode, is diminished upon illumination, with the amount of decrease related to light intensity. this oxygen-sparing effect is correlated with the wavelengths of light that are associated with bacteriochlorophyll absorbance. ...	1992	16348817
nodules initiated by rhizobium meliloti exopolysaccharide mutants lack a discrete, persistent nodule meristem.	infection of alfalfa with rhizobium meliloti exo mutants deficient in exopolysaccharide results in abnormal root nodules that are devoid of bacteria and fail to fix nitrogen. here we report further characterization of these abnormal nodules. tightly curled root hairs or shepherd's crooks were found after inoculation with rm 1021-derived exo mutants, but curling was delayed compared with wild-type rm 1021. infection threads were initiated in curled root hairs by mutants as well as by wild-type r. ...	1992	16668605
gibberellins and the legume-rhizobium symbiosis : i. endogenous gibberellins of lima bean (phaseolus lunatus l.) stems and nodules.	the content of gibberellin-like substances in nodules formed by bradyrhizobium species strain 127e14 on roots of lima bean (phaseolus lunatus l.) has been previously found to be relatively high. the objectives of the present study were to purify and identify the endogenous gibberellins from the stems and nodules of lima bean. by sequential silica gel partition column chromatography, c(18) reverse-phase high performance liquid chromatography, and combined gas chromatography-mass spectrometry, the ...	1992	16668617
regulation of nodule glutamine synthetase by co(2) levels in bean (phaseolus vulgaris l.).	nodulated bean (phaseolus vulgaris) plants were grown for 17 days after infection in normal (0.02%) co(2) and from day 8 to 17 in high (0.1%) co(2) in order to increase nitrogen fixation and define how nodule glutamine synthetase (gs) isoforms are regulated by the ammonia derived from the bacteroid. nitrogenase activity was detected by day 10, and by day 17 activity was over twofold higher in 0.1% of co(2) compared with plants grown in 0.02% co(2) and inoculated with rhizobium wild-type strain c ...	1992	16668681
growth and movement of spot inoculated rhizobium meliloti on the root surface of alfalfa.	inoculum droplets of approximately 10 nanoliter volume and containing about 10 rhizobium meliloti cells were placed onto the root surface of alfalfa seedlings in plastic growth pouches at either the root tip, the position of the smallest emergent root hairs, or at a site midway between these points. the droplets were initially confined to an area of about 0.2 square millimeter at the point of application. by 48 and 96 hours after inoculation, the inoculum bacteria and their progeny were distribu ...	1992	16668744
dissection of nodule development by supplementation of rhizobium leguminosarum biovar phaseoli purine auxotrophs with 4-aminoimidazole-5-carboxamide riboside.	purine auxotrophs of rhizobium leguminosarum biovar phaseoli cfn42 elicit uninfected pseudonodules on bean (phaseolus vulgaris l.). addition of 4-aminoimidazole-5-carboxamide (aica) riboside to the root medium during incubation of the plant with these mutants leads to enhanced nodule development, although nitrogenase activity is not detected. nodules elicited in this manner had infection threads and anatomical features characteristic of normal nodules, such as peripheral vasculature rather than ...	1992	16668898
trigonelline and stachydrine released from alfalfa seeds activate nodd2 protein in rhizobium meliloti.	spectroscopic data (nuclear magnetic resonance, mass spectrometry, ultraviolet-visible) in this study identify trigonelline and stachydrine as major components of alfalfa (medicago sativa l.) seed rinse. moreover, biological assays show that these natural products induce nodulation (nod) gene transcription in rhizobium meliloti by activating the regulatory protein nodd2, but not the homologous nodd1 protein. these findings contrast with the fact that the only previously identified nodd2 activato ...	1992	16669069
localized changes in flavonoid biosynthesis in roots of lotus pedunculatus after infection by rhizobium loti.	two-dimensional paper chromatography in four solvent systems, high-sensitivity spray reagents, and uv absorption spectroscopy were used to separate and characterize flavonoids and isoflavonoids in roots and root nodules of 20-d-old lotus pedunculatus cav. seedlings were grown either under sterile conditions or after inoculation with fix(+) or fix(-) strains of rhizobium loti. flavonoids rather than isoflavonoids predominated in all tissues. flavonoid profiles in sterile and denodulated root tiss ...	1992	16652981
labeling of carbon pools in bradyrhizobium japonicum and rhizobium leguminosarum bv viciae bacteroids following incubation of intact nodules with co(2).	the aim of the work reported here was to ascertain that the patterns of labeling seen in isolated bacteroids also occurred in bacteroids in intact nodules and to observe early metabolic events following exposure of intact nodules to (14)co(2). intact nodules of soybean (glycine max l. merr. cv ripley) inoculated with bradyrhizobium japonicum usda 110 and pea (pisum sativum l. cv progress 9) inoculated with rhizobium leguminosarum bv viciae isolate 128c53 were detached and immediately fed (14)co( ...	1992	16653034
the psenod12 gene is expressed at two different sites in afghanistan pea pseudonodules induced by auxin transport inhibitors.	a number of early nodulin genes are expressed in specific cell types as pea (pisum sativum) root nodules develop. the pisum sativum early nodulin psenod2 is detected only in the uninfected cells of the nodule parenchyma, whereas psenod12 is expressed at two spatially removed sites: in root hairs and adjacent cortical cells, both of which can be invaded by rhizobium entering through infection threads, and in derivatives of newly divided root inner cortical cells that establish the nodule primordi ...	1992	16653180
gibberellins and the legume-rhizobium symbiosis : iii. quantification of gibberellins from stems and nodules of lima bean and cowpea.	lima bean (phaseolus lunatus l.) plants inoculated with bradyrhizobium sp. strain 127e14 displayed a period of marked internode elongation that was not observed in plants inoculated with other compatible bradyrhizobia, including strain 127e15. when strain 127e14 nodulated an alternate host, cowpea (vigna unguiculata l. walp), a similar, although less dramatic growth response induced by the bacteria was observed. it has been speculated that the elongative growth promotion brought about by inocula ...	1992	16653229
isolation of rhizobium meliloti nod gene inducers from alfalfa rhizosphere soil.	methanolic extracts of alfalfa rhizosphere soil induce more nod gene transcription in rhizobium meliloti than extracts of nonrhizosphere soil. six peaks of nod-inducing activity were separated by high-performance liquid chromatography from rhizosphere soil extract, and one compound was identified by h nuclear magnetic resonance, mass spectrometry, and uv-visible spectra as a formononetin-7-o-glycoside that activates both nodd1 and nodd2 proteins. the unanticipated presence of a glycoside in rhiz ...	1993	16348881
involvement of genes on a megaplasmid in the acid-tolerant phenotype of rhizobium leguminosarum biovar trifolii.	the acid-tolerant rhizobium leguminosarum biovar trifolii strain anu1173 exhibited several new phenotypes when cured of its symbiotic (sym) plasmid and the second largest megaplasmid. strain p22, which has lost these two plasmids, had reduced exopolysaccharide production and cell mobility on ty medium. the parent strain anu1173 was able to grow easily in laboratory media at ph 4.5, whereas the derivative strain p22 was unable to grow in media at a ph of <4.7. the intracellular ph of strain anu11 ...	1993	16348908
effects of ph and osmotic stress on cellular polyamine contents in the soybean rhizobia rhizobium fredii p220 and bradyrhizobium japonicum a1017.	homospermidine is a polyamine present in its highest concentrations in root nodule bacteria. by using the soybean rhizobia rhizobium fredii p220 and bradyrhizobium japonicum a1017, the effects of the ph and osmolarity of the medium on rhizobial growth and cellular polyamine contents were investigated. elevation of medium ph repressed the growth of slowly growing b. japonicum a1017 and resulted in a slight increase in cellular putrescine, while homospermidine content was not significantly affecte ...	1993	16348911
studies of the physiological and genetic basis of acid tolerance in rhizobium leguminosarum biovar trifolii.	acid-tolerant rhizobium leguminosarum biovar trifolii anu1173 was able to grow on laboratory media at a ph as low as 4.5. transposon tn5 mutagenesis was used to isolate mutants of strain anu1173, which were unable to grow on media at a ph of less than 4.8. the acid-tolerant strain anu1173 maintained a near-neutral intracellular ph when the external ph was as low as 4.5. in contrast, the acid-sensitive mutants as25 and as28 derived from anu1173 had an acidic intracellular ph when the external ph ...	1993	16348956
foliar chlorosis in symbiotic host and nonhost plants induced by rhizobium tropici type b strains.	rhizobium tropici ciat899 induced chlorosis in the leaves of its symbiotic hosts, common bean (phaseolus vulgaris l.), siratro (macroptilium atropurpureum urb.), and leucaena leucocephala (lam.) de wit. chlorosis induction by strains ciat899 and ct9005, an exopolysaccharide-deficient mutant of ciat899, required carbon substrate. when the bacteria were added at planting in a solution of mannitol (50 g/liter), as few as 10 cells of ciat899 were sufficient to induce chlorosis in bean plants. all ca ...	1993	16348994
stable tagging of rhizobium meliloti with the firefly luciferase gene for environmental monitoring.	a system for stable tagging of gram-negative bacteria with the firefly luciferase gene, luc, is described. a previously constructed fusion constitutively expressing luc from the lambdap(r) promoter was used. stable integration into the bacterial genome was achieved by use of mini-tn5 delivery vectors. the procedure developed was applied for tagging of representative gram-negative bacteria, such as escherichia coli, rhizobium meliloti, pseudomonas putida, and agrobacterium tumefaciens. the system ...	1993	16349015
production and excretion of nod metabolites by rhizobium leguminosarum bv. trifolii are disrupted by the same environmental factors that reduce nodulation in the field.	lipooligosaccharides (nod metabolites) have been shown to be essential for the successful nodulation of legumes. in strains of rhizobium leguminosarum bv. trifolii, nod metabolites were detected predominantly within the cell and to a lesser extent in the periplasmic space and the growth medium. the production, and in particular the excretion, of nod metabolites was restricted by a range of environmental conditions which are associated with poor nodulation in the field. lowering the medium ph fro ...	1993	16349071
production of rhizobium inoculants for lupinus nootkatensis on nutrient-supplemented pumice.	the use of the legume lupinus nootkatensis as a pioneer plant to fight soil erosion and to reclaim eroded soils in iceland has been under development for a few years. production of a robust, low-cost bacterial inoculant was therefore a prerequisite for the extended use of this plant. volcanic pumice is a naturally expanded mineral which is available in vast amounts in iceland. it was tested as a carrier for solid fermentation of rhizobium lupini. nutrient-supplemented pumice containing a small p ...	1993	16349083
sodium dodecyl sulfate-polyacrylamide gel electrophoresis protein banding patterns among rhizobium leguminosarum biovar phaseoli strains isolated from the mexican bean phaseolus coccineus.	several rhizobial strains were isolated from phaseolus coccineus root nodules and were determined to be rhizobium leguminosarum biovar phaseoli strains after reinfection of the same host plant. these strains were characterized by cultural procedures (growth on different carbon sources and intrinsic antibiotic resistance) and electrophoretic procedures (sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total proteins). our results showed that these rhizobia are very similar to each oth ...	1993	16349098
uptake hydrogenase (hup) in common bean (phaseolus vulgaris) symbioses.	strains of rhizobium forming nitrogen-fixing symbioses with common bean were systematically examined for the presence of the uptake hydrogenase (hup) structural genes and expression of uptake hydrogenase (hup) activity. dna with homology to the hup structural genes of bradyrhizobium japonicum was present in 100 of 248 strains examined. ecori fragments with molecular sizes of approximately 20.0 and 2.2 kb hybridized with an internal saci fragment, which contains part of both bradyrhizobial hup st ...	1993	16349115
the effect of heavy metals on dinitrogen fixation by rhizobium-white clover in a range of long-term sewage sludge amended and metal-contaminated soils.	an investigation was conducted to determine whether effective strains of rhizobium leguminosarum biovar. trifolii capable of symbiotic n2 fixation with white clover (trifolium repens) were present in a range of metal-contaminated soils. a number of historically sewage-amended sites (including experimental, pasture grassland and arable sites) were selected and compared with highly contaminated samples from abandoned heavy metal mines. many sites had metal concentrations above the limits establish ...	1993	15091894
rhizobium lipooligosaccharides rescue a carrot somatic embryo mutant.	at a nonpermissive temperature, somatic embryos of the temperature-sensitive (ts) carrot cell mutant ts11 only proceed beyond the globular embryo stage in the presence of medium conditioned by wild-type embryos. the causative component in the conditioned medium has previously been identified as a 32-kd acidic endochitinase. in search of a function for this enzyme in plant embryogenesis, several compounds that contain oligomers of n-acetylglucosamine were tested for their ability to promote ts11 ...	1993	12271077
alfalfa (medicago sativa l.) root exudates contain isoflavonoids in the presence of rhizobium meliloti.	root exudates of alfalfa (medicago sativa l.) inoculated with symbiotic rhizobium meliloti bacteria contained three isoflavonoids that were not found in exudates of uninoculated plants. data from proton nuclear magnetic resonance, mass spectrometry, and ultraviolet-visible absorbance analyses indicated that root exudates of inoculated plants contained aglycone and glycoside forms of the phytoalexin medicarpin and a formononetin-7-o-(6"-o-malonylglycoside), a conjugated form of the medicarpin pre ...	1993	12231731
five nodulation mutants of white sweetclover (melilotus alba desr.) exhibit distinct phenotypes blocked at root hair curling, infection thread development, and nodule organogenesis.	in an effort to obtain a developmental sequence of mutations in the rhizobium-legume interaction within a single legume species, we have characterized the early events of nodule development in 10 nodulation mutants of sweetclover, melilotus alba desr. cv u389, representing five genetic loci. both seed and root exudates from all of the sweetclover mutants induced expression of the nod genes of rhizobium meliloti. mutants in three loci were blocked in the early stages of root hair curling. of thes ...	1993	12231990
molecular mechanism of host specificity in legume-rhizobium symbiosis.	rhizobium - legume symbiosis is a highly specific interaction between the two partners. host specificity is evident at early stages of infection and results from multiple interactions involving signalling among bacteria and host plants. host specific plant signals (flavanoids) convert the nodd protein to an active form and its binding with nod box initiates the transcription of inducible nod operons. common nod genes (nodabc) code for an extracellular mitogenic nod factor which is required for n ...	1993	14538056
transgene copy number can be positively or negatively associated with transgene expression.	two different types of t-dna insert were found in tobacco plants transformed with agrobacterium tumefaciens. high-expressing (h) types had one copy of the t-dna at a locus and produced high expression of the transgene uida, as measured by uida rna levels and beta-glucuronidase activity; low-expressing (l) types had inverted repeats of the t-dna at a locus and produced low uida expression. h-types from different transformants acted additively, and cross-fertilization between two different homozyg ...	1993	7678759
identification of two alfalfa early nodulin genes with homology to members of the pea enod12 gene family.	in a search for plant genes expressed during early symbiotic interactions between medicago sativa and rhizobium meliloti, we have isolated and characterized two alfalfa genes which have strong sequence similarity to members of the enod12 gene family of pisum sativum. the m. sativa genes, msenod12a and b, encode putative protein products of 8066 da and 12849 da, respectively, each with a signal sequence at the n-terminus followed by a repetitive proline-rich region. based on their expression duri ...	1993	7678770
treatment of agrobacterium or leaf disks with 5-azacytidine increases transgene expression in tobacco.	we have studied the effect of the demethylating agent azacytidine (azac) on expression of a beta-glucuronidase (gus) gene transferred to tobacco leaf disks by agrobacterium-mediated transformation. in a system where no selection was performed, where shoot formation was partially repressed, and where agrobacterium does not express the gus gene, we were able to follow the early events of transient and stable expression. two days after inoculation, 8% of the cells expressed gus but this proportion ...	1993	7680239
phylogenetic analysis of the family rhizobiaceae and related bacteria by sequencing of 16s rrna gene using pcr and dna sequencer.	the 16s rrna gene sequences of 19 strains covering 97% of the molecules were determined for the members of the family rhizobiaceae and related bacteria by pcr and dna sequencer. the three biovars of agrobacterium were located separately, whereas agrobacterium rubi clustered with a. tumefaciens. phylogenetic locations for the species of the genera rhizobium, sinorhizobium, agrobacterium, phylobacterium, mycoplana (m. dimorpha), ochrobactrum, brucella and rochalimaea (a rickettsia) were intermingl ...	1993	7682191
diversity of retron elements in a population of rhizobia and other gram-negative bacteria.	genetic elements called retrons reside on the chromosome of escherichia coli and the myxobacteria and represent the first reverse transcriptase-encoding element to be found in a prokaryotic cell. all known retrons produce a functionally obscure rna-dna satellite molecule called multicopy single-stranded dna (msdna). we report here the presence of msdna-producing retron elements in a number of new bacterial groups, including strains of the genera proteus, klebsiella, salmonella, nannocystis, rhiz ...	1993	7686549
cloning and characterization of an ftsz homologue from a bacterial symbiont of drosophila melanogaster.	a 1194 bp open reading frame that codes for a 398 amino acid peptide was cloned from a lambda gt11 library of drosophila melanogaster genomic dna. the predicted peptide sequence is very similar to three previously characterized protein sequences that are encoded by the ftsz genes in escherichia coli, bacillus subtilis and rhizobium meliloti. the ftsz protein has a major role in the initiation of cell division in prokaryotic cells. using a tetracycline treatment that eradicates bacterial parasite ...	1993	7689140
the bacterial attachment site of the temperate rhizobium phage 16-3 overlaps the 3' end of a putative proline trna gene.	bacteriophage 16-3 inserts its genome into the chromosome of rhizobium meliloti strain 41 (rm41) by site-specific recombination. the dna regions around the bacterial attachment site (attb) and one of the hybrid attachment sites bordering the integrated prophage (attl) were cloned and their nucleotide sequences determined. we demonstrated that the 51 bp region, where the phage and bacterial dna sequences are identical, is active as a target site for phage integration. furthermore it overlaps the ...	1993	7689141
preparation, optimization and characterization of a polyphenylalanine synthetizing system from agrobacterium tumefaciens.	a very active cell-free translation system was prepared from agrobacterium tumefaciens, a bacterium broadly used to transfect plant cells to introduce foreign genes and one that produces tumours in plants. once optimized for mg2+, nh4+, high speed supernatant s 370, purified ribosomes and time, the system translates polyuridylic acid very efficiently. a. tumefaciens purified ribosomes were inhibited in vitro by several well-known translational inhibitors including some ribosome-inactivating prot ...	1993	7693097
rapid purification of ti plasmids from agrobacterium by ethidium bromide treatment and phenol extraction.	an efficient method is described for the purification of ti plasmid dna from agrobacterium. the procedure is based on the relative binding capacity of ethidium bromide to supercoiled plasmid dna and linear dna and on the high solubility of ethidium bromide in phenol. following treatment with ethidium bromide, more than 87% of linear chromosomal dna and most of the rna was present in the phenol phase, while 91% of ti plasmid dna was recovered from the aqueous phase. the ti plasmid dna was suffici ...	1993	7765300
cloning and expression of flavonol synthase from petunia hybrida.	flavonols are important co-pigments in flower colour and are also essential for pollen tube growth. in petunia, flavonol synthesis is controlled by the fl locus. flavonol synthase (fls) belongs to the 2-oxoglutarate-dependent dioxygenase family. dioxygenase gene fragments were amplified by pcr on cdna made from flfl and flfl flowers using degenerate primers designed from conserved dioxygenase sequences. a petunia petal cdna library was screened for clones that hybridized more strongly to the fl ...	1993	7904213
tn5-mob transposon mediated transfer of salt tolerance and symbiotic characteristics between rhizobia genera.	rhizobium meliloti 042b is a fast-growing, salt-tolerant and high efficiency nitrogen-fixing symbiont with alfalfa. bradyrhizobium japonicum usda110 grows slowly, and cannot grow in yma medium containing 0.1m nacl, but nodulates and fixed nitrogen efficiently with soybean. eighty-six transconjugants, called sr, were obtained by inserting tn5-mob randomly into genomes of 042b using psup5011 and helper plasmid rp4. selecting 4 sr strains randomly and introducing dna fragment of sr into usda110 wit ...	1993	8049344
resistance to nodulation of cv. afghanistan peas is overcome by nodx, which mediates an o-acetylation of the rhizobium leguminosarum lipo-oligosaccharide nodulation factor.	only some strains of rhizobium leguminosarum biovar viciae can efficiently nodulate varieties of peas such as cv. afghanistan, which carry a recessive allele that blocks efficient nodulation by most western isolates of r.i. viciae. one strain (tom) which can nodulate cv. afghanistan peas has a gene (nodx) that is required to overcome the nodulation resistance. strain tom makes significantly lower amounts of lipo-oligosaccharide nodulation factors than other strains of r.i. viciae and this effect ...	1993	7934826
processes at the nick region link conjugation, t-dna transfer and rolling circle replication.	data from prokaryotic replicative and conjugative systems, which interrelate dna processing events initiated by a site-specific nick, are reviewed. while the replicative systems have been established in accordance with the rolling circle replication model, the mechanism of conjugative replication has not been elucidated experimentally. we summarize data involving random point mutagenesis of the rk2 transfer origin (orit), which yielded relaxation-deficient and transfer-deficient derivatives havi ...	1993	7934927
a rhizobium tropici dna region carrying the amino-terminal half of a nodd gene and a nod-box-like sequence confers host-range extension.	rhizobium tropici ciat899 is a broad-host-range strain that, in addition to phaseolus, nodulates other plant legumes such as leucaena and macroptilium. the narrow-host-range of rhizobium leguminosarum biovars phaseoli (strain ce3) and trifolii (strain rs1051) can be extended to leucaena esculenta and phaseolus vulgaris plants, respectively, by the introduction of a dna fragment 521 bp long, which carries 128 amino acids of the amino-terminal region of a nodd gene from r. tropici, as well as a pu ...	1993	7934929
the orf1 of the gentamicin-resistance operon (aac) of pseudomonas aeruginosa encodes adenosine 5'-phosphosulphate kinase.	the gentamicin-resistance operon of pseudomonas aeruginosa (aac) contains two cistrons for which only the second gene product has an identified function. the 813bp second cistron (orf2) encodes a protein that confers gentamicin resistance by catalysis of the transfer of an acetyl group from acetyl coenzyme a to gentamicin. the first open reading frame (orf1) encodes a 23.9 kda protein that we have found, by enzyme activity and immunological reactivity, to be adenosine-5'-phosphosulphate (aps) ki ...	1993	7934935
hupk, a hydrogenase-ancillary protein from rhizobium leguminosarum, shares structural motifs with the large subunit of nife hydrogenases and could be a scaffolding protein for hydrogenase metal cofactor assembly.		1993	7934943
rhizobium meliloti adenylate cyclase: probing of a ntp-binding site common to cyclases and cation transporters.	alignments between amino acid sequences of eukaryotic adenylate (acase) and guanylate (gcase) cyclases and the prokaryotic rhizobium meliloti acase revealed four conserved regions. two were the target of site-directed mutagenesis. a positive charge at position 44 converted the enzyme to gcase, a negative charge at this position had no effect. a second modification indicated that residues 107 and 124 contribute to the nucleoside triphosphate binding pocket's conformation. this latter region was u ...	1993	7912636
restoration of attachment, virulence and nodulation of agrobacterium tumefaciens chvb mutants by rhicadhesin.	in contrast to wild-type agrobacterium tumefaciens strains, beta-1,2-glucan-deficient chvb mutants were found to be unable to attach to pea root hair tips. the mutants appeared to produce rhicadhesin, the protein that mediates the first step in attachment of rhizobiaceae cells to plant root hairs, but the protein was inactive. both attachment to root hairs and virulence of the chvb mutants could be restored by treatment of the plants with active rhicadhesin, whereas treatment of plants with beta ...	1993	7968537
insect tolerance of transgenic populus nigra plants transformed with bacillus thuringiensis toxin gene.	leaves and stem segments of populus nigra were transformed with a. tumefaciens lba4404 harboring a binary vector containing chimeric genes of npt and 35s-omega-b.t. toxin-nos. nineteen regenerated kanamycin resistant plants were analyzed by dna hybridization, out of which 10 were shown to be the candidates of transgenic plants. insect tolerance tests showed that the transgenic plants were toxic to two lepidopteran pests, lymantria dispar l. and apocheimia cinerarius erschoff. based on the result ...	1993	8061230
isolation and characterization of a novel glutamine synthetase from rhizobium meliloti.	two glutamine synthetases, gsi and gsii, are found in most rhizobia. however, wsu650, a rhizobium meliloti glna glnii mutant that lacks both enzymes, can grow without a glutamine supplement in minimal medium that contains both ammonium and glutamate. the bacteria contained a third glutamine synthetase, gsiii, which has been purified and partially characterized. gsiii had considerable glutamine synthetase activity when assayed using a semibiosynthetic (glutamate- and hydroxylamine-dependent) assa ...	1993	8093245
rhizobium meliloti mutants with decreased dahp synthase activity are sensitive to exogenous tryptophan and phenylalanine and form ineffective nodules.	we isolated two tn5-generated mutants of rhizobium meliloti whose growth was inhibited by rich medium or by exogenous tryptophan or phenylalanine. these mutants, rm7479 and rm7480, belonged to the same genetic complementation group. the mutant locus could not be found on either indigenous megaplasmid but was localized on the chromosome. the mutants formed ineffective nodules on alfalfa plants. they invaded nodules within infection threads and were released into plant cells enclosed within periba ...	1993	8094985
cloning and nucleotide sequencing of rhizobium meliloti aminotransferase genes: an aspartate aminotransferase required for symbiotic nitrogen fixation is atypical.	in rhizobium meliloti, an aspartate aminotransferase (aspat) encoded within a 7.3-kb hindiii fragment was previously shown to be required for symbiotic nitrogen fixation and aspartate catabolism (v. k. rastogi and r.j. watson, j. bacteriol. 173:2879-2887, 1991). a gene coding for an aromatic aminotransferase located within an 11-kb hindiii fragment was found to complement the aspat deficiency when overexpressed. the genes encoding these two aminotransferases, designated aata and tata, respective ...	1993	8096210
cloning and characterization of multiple groel chaperonin-encoding genes in rhizobium meliloti.	heat-shock treatment of rhizobium meliloti cells causes major enhancement in the synthesis of several proteins with apparent molecular weights in the range of 58-60 kda. using the polymerase chain reaction and degenerate oligodeoxyribonucleotide primers for conserved regions of the 60-kda heat-shock protein (hsp60) or groel protein family, a 0.6-kb probe for the r. meliloti hsp60 gene was prepared. southern blot analysis of r. meliloti dna digested with different restriction enzymes and hybridiz ...	1993	8097179
heat shock transcription of the groesl operon of agrobacterium tumefaciens may involve a hairpin-loop structure.	the groesl operon of agrobacterium tumefaciens was cloned and sequenced and found to be highly homologous to previously analyzed groe operons in nucleotides of the coding region and in amino acid sequence. transcription of this operon in a. tumefaciens was considerably stimulated by heat shock. primer extension analysis revealed that the groe transcripts from cells under heat shock were initiated from the same promoter (a sigma-70-like promoter) as transcripts from untreated cells, and no sequen ...	1993	8098329
how is leghemoglobin involved in peribacteroid membrane degradation during nodule senescence?	an increase in the rate of succinate and glutamate uptake by isolated symbiosomes from french bean nodules was observed in the presence of iron plus h2o2. the lipid bilayer, and not proteins involved in transport, seems to be the major target of radical attack. leghemoglobin in the presence of a 6-fold excess of h2o2 (where heme breakdown and iron release occurred) provoked also an increase in peribacteroid membrane permeability. in contrast, this hemoprotein in the presence of a 2-fold excess o ...	1993	8100785
rapid divergence of agrobacterium vitis octopine-cucumopine ti plasmids from a recent common ancestor.	the octopine/cucumopine (o/c) ti plasmids of the grapevine-associated agrobacterium vitis strains constitute a family of related dna molecules. restriction maps were established of two limited-host-range o/c ti plasmids, ptiag57 and ptiab3, and of the wide-host-range o/c ti plasmid ptihm1. together with the previously obtained map of the wide-host-range o/c ti plasmid ptitm4, about 1000 kb were mapped with a resolution of 0.2 kb, allowing a detailed comparison of the various structures. one regi ...	1993	8101965
enod8, a novel early nodule-specific gene, is expressed in empty alfalfa nodules.	the alfalfa enod8 nodule-specific gene is expressed in empty nodules elicited by exopolysaccharide-deficient rhizobium meliloti, and it is expressed early in nodule development. an enod8 cdna was sequenced and found to encode a novel product. its deduced polypeptide sequence was found to be similar to the nonproline-rich domains of the putative polypeptides encoded by a class of anther-specific genes from arabidopsis thaliana and brassica napus. the role of the enod8 gene product is predicted to ...	1993	8118054
analysis of the rhizobium meliloti genes exou, exov, exow, exot, and exoi involved in exopolysaccharide biosynthesis and nodule invasion: exou and exow probably encode glucosyltransferases.	sequence analysis of a 5.780-kb dna fragment originating from megaplasmid 2 of rhizobium meliloti 2011 involved in biosynthesis of exopolysaccharide i (eps i) and invasion of alfalfa nodules revealed the presence of five exo genes designated exou, exov, exow, exot, and exoi. exot resembled transmembrane proteins, whereas exoi displayed a characteristic signal peptide. sequence comparisons with several polysaccharide-polymerizing enzymes of both prokaryotic and eukaryotic origin indicated that ex ...	1993	8118055
biological activity of rhizobium sp. ngr234 nod-factors on macroptilium atropurpureum.	the broad host range of rhizobium sp. ngr234 is based mainly on its ability to secrete a family of lipooligosaccharide nod factors. to monitor nod-factor purification, we used the small seeded legume macroptilium atropurpureum, which responds evenly and consistently to nod factors. at concentrations between approximately equal to 10(-11) m and 10(-9) m, this response takes the form of deformation of the root hairs. higher concentrations (approximately equal to 10(-9) to 10(-7) m), provoked profo ...	1993	8118058
comparison of pathways for biodegradation of monomethyl sulphate in agrobacterium and hyphomicrobium species.	different mechanisms have been proposed previously for the biodegradation of monomethyl sulphate (mms) in agrobacterium sp. and hyphomicrobium sp. sulphate liberation from mms in agrobacterium sp. m3c was previously shown to be o2-dependent, whereas in several hyphomicrobium spp. the initiating step has been considered hitherto to be hydrolytic and catalysed by methyl sulphatase. in the present study, agrobacterium and hyphomicrobium strains were compared for their ability to oxidize mms and its ...	1993	8126419
new insights on t-dna transfer.		1993	8162420
a gene that encodes a proline-rich nodulin with limited homology to psenod12 is expressed in the invasion zone of rhizobium meliloti-induced alfalfa root nodules.	to define the early stages of the interaction between rhizobium and host legumes, we have cloned and characterized three early nodulin-encoding sequences from an alfalfa (medicago sativa l.) cdna library by probing with a fragment of a cdna clone for psenod12, an infection-related nodulin from pea (pisum sativum l.). although the coding regions of the three clones are 95 to 98% homologous to each other, they are only 43% homologous to the pea clone. however, the putative signal peptide encoded b ...	1993	8208847
identification of methyl jasmonate and salicylic acid response elements from the nopaline synthase (nos) promoter.	transgenic tobacco plants carrying a fusion between the nopaline synthase (nos) promoter and chloramphenicol acetyltransferase (cat) reporter gene (cat) were studied for their inducibility by salicylic acid (sa) or methyl jasmonate (mj) treatments. either chemical significantly increased cat activity to a level much higher than that achieved by wounding. northern blot analysis showed a corresponding increase in mrna levels. after 20 h of induction of flowering plants, the response to mj treatmen ...	1993	8208860
increased production of cadaverine and anabasine in hairy root cultures of nicotiana tabacum expressing a bacterial lysine decarboxylase gene.	several hairy root cultures of nicotiana tabacum varieties, carrying two direct repeats of a bacterial lysine decarboxylase (ldc) gene controlled by the cauliflower mosaic virus (camv) 35s promoter expressed ldc activity up to 1 pkat/mg protein. such activity was, for example, sufficient to increase cadaverine levels of the best line sr3/1-k1,2 from ca. 50 micrograms (control cultures) to about 700 micrograms/g dry mass. some of the overproduced cadaverine of this line was used for the formation ...	1993	8219043
does the ocs-element occur as a functional component of the promoters of plant genes?	the structural requirements of the ocs-element, a promoter element in several genes transferred to the host plant nucleus by agrobacterium tumefaciens and certain dna viruses, have been further characterized both in vitro and in vivo. two adjacent and functionally identical protein-binding sites separated by an exact number of nucleotides are required for in vivo activity of the ocs-element. plant pathogens have presumably recruited cellular transcription factors that interact with these binding ...	1993	8220489
tissue-specific and wound-inducible pattern of expression of the mannopine synthase promoter is determined by the interaction between positive and negative cis-regulatory elements.	in transgenic tobacco plants the regulatory region of the agrobacterium genes involved in mannopine synthesis (pmas) directs expression in vascular tissues and is induced upon wounding. to identify cis-acting sequences required for the cell-type-specific and wound-inducible expression of this regulatory region, the expression pattern of chimeric genes in which 5' upstream deletions of the pmas 1' promoter direct the expression of the beta-glucuronidase coding sequence, was analyzed in transgenic ...	1993	8220492
interaction between the tobacco dna-binding activity cbf and the cyt-1 promoter element of the agrobacterium tumefaciens t-dna gene t-cyt correlates with cyt-1 directed gene expression in multiple tobacco tissue types.	a novel dna-binding activity, designated cbf, has been identified in nuclear extracts from tobacco leaf, stem and root tissue. cbf interacts specifically with a 30 bp promoter fragment, referred to as cyt-1, of the agrobacterium tumefaciens t-dna cytokinin (t-cyt) gene. the t-cyt promoter, although of bacterial origin is active in planta and the 30 bp cyt-1 element is located within a region that is essential for t-cyt promotor activity in leaf, stem and root cells of tobacco plants. gel retarda ...	1993	8220494
roles of plant homologs of rab1p and rab7p in the biogenesis of the peribacteroid membrane, a subcellular compartment formed de novo during root nodule symbiosis.	the peribacteroid membrane (pbm) in legume root nodules is derived from plasma membrane following endocytosis of rhizobium by fusion of newly synthesized vesicles. we studied the roles of plant rab1p and rab7p homologs, the small gtp-binding proteins involved in vesicular transport, in the biogenesis of the pbm. three cdnas encoding legume homologs of mammalian rab1p and rab7p were isolated from soybean (srab1p, srab7p) and vigna aconitifolia (vrab7p). srab1p was confirmed to be a functional cou ...	1993	8223429
the regulatory vira protein of agrobacterium tumefaciens does not function at elevated temperatures.	previous studies have shown that agrobacterium tumefaciens causes tumors on plants only at temperatures below 32 degrees c, and virulence gene expression is specifically inhibited at temperatures above 32 degrees c. we show here that this effect persists even when the vira and virg loci are expressed under the control of a lac promoter whose activity is temperature independent. this finding suggests that one or more steps in the signal transduction process mediated by the vira and virg proteins ...	1993	8226624
oxygen-regulated in vitro transcription of rhizobium meliloti nifa and fixk genes.	oxygen concentration regulates the expression of nitrogen fixation genes in the symbiotic bacterium rhizobium meliloti. we demonstrate that two proteins, fixl and fixj, that belong to the two-component family of regulatory proteins are necessary and sufficient for oxygen-regulated in vitro transcription of the two key regulatory genes, nifa and fixk. we show directly that fixj is a transcriptional activator, working in conjunction with the rna polymerase sigma 70 holoenzyme. addition of fixl122, ...	1993	8226629
physical map of the genome of rhizobium meliloti 1021.	a physical map of the genome of rhizobium meliloti 1021 is presented. the physical sizes of the three replicons in this genome had previously been determined and are as follows: the chromosome, 3.4 mb; psym-b, 1.7 mb; and psym-a, 1.4 mb. the physical maps for this gc-rich genome contain at-rich restriction sites for swai (5'-taaattta-3'), paci (5'-ttaattaa-3'), pmei (5'-gtttaaac-3'), and, for psym-b, spei (5'-actagt-3'). in addition, the endonuclease i-ceui cleaved the 23s rrna genes in this gen ...	1993	8226638
family of glycosyl transferases needed for the synthesis of succinoglycan by rhizobium meliloti.	rhizobium meliloti produces an acidic exopolysaccharide, termed succinoglycan or eps i, that is important for invasion of the nodules that it elicits on its host, medicago sativa. succinoglycan is a high-molecular-weight polymer composed of repeating octasaccharide subunits. these subunits are synthesized on membrane-bound isoprenoid lipid carriers, beginning with a galactose residue followed by seven glucose residues, and modified by the addition of acetate, succinate, and pyruvate. biochemical ...	1993	8226645
genes needed for the modification, polymerization, export, and processing of succinoglycan by rhizobium meliloti: a model for succinoglycan biosynthesis.	the major acidic exopolysaccharide of rhizobium meliloti, termed succinoglycan, is required for nodule invasion and possibly nodule development. succinoglycan is a polymer of octasaccharide subunits composed of one galactose residue, seven glucose residues, and acetyl, succinyl, and pyruvyl modifications, which is synthesized on an isoprenoid lipid carrier. a cluster of exo genes in r. meliloti are required for succinoglycan production, and the biosynthetic roles of their gene products have rece ...	1993	8226646
polarized cells, polar actions.	the recognition of polar bacterial organization is just emerging. the examples of polar localization given here are from a variety of bacterial species and concern a disparate array of cellular functions. a number of well-characterized instances of polar localization of bacterial proteins, including the chemoreceptor complex in both c. crescentus and e. coli, the maltose-binding protein in e. coli, the b. japonicum surface attachment proteins, and the actin tail of l. monocytogenes within a mamm ...	1993	8226658
nucleotide sequence analysis of four genes, hupc, hupd, hupf and hupg, downstream of the hydrogenase structural genes in bradyrhizobium japonicum.	the nucleotide sequence of a 2.2 kb region downstream of the hydrogenase structural genes in bradyrhizobium japonicum was determined. four genes encoding predicted polypeptides of 27.8 (hupc), 21.4 (hupd), 10.6 (hupf) and 15.8 (hupg) kda were identified, of which the first three probably belong to the same operon as the hup structural genes, hups and hupl. hupc is homologous to the hydrophobic polypeptides with four potential transmembrane regions that are encoded by open reading frames followin ...	1993	8230232
the transcriptional activator hlyu of vibrio cholerae: nucleotide sequence and role in virulence gene expression.	hlyu upregulates expression of the haemolysin, hlya, of vibrio cholerae. dna sequence analysis indicates that hlyu is an 11.9 kda protein containing a putative helix-turn-helix motif and belonging to a family of small regulatory proteins, including noir (rhizobium meliloti), smtb (synechococcus pcc 7942) and arsr (plasmids r773, escherichia coli; pi258, staphylococcus aureus; and psx267, staphylococcus xylosus). an hlyu mutant was constructed by insertional inactivation, and found to be deficien ...	1993	8231807
the vird4 gene is required for virulence while vird3 and orf5 are not required for virulence of agrobacterium tumefaciens.	the vird operon of the resident ti plasmid of agrobacterium tumefaciens contains loci involved in t-dna processing and undefined virulence functions. nucleotide sequence of the entire vird operon of ptic58 revealed similarities to the vird operon of the root-inducing plasmid pria4b and to that of the octopine-type plasmid ptia6nc. however, comparative sequence data show that vird of ptic58 is more akin to that of the pria4b than to that of the ptia6nc. t7f10::vird gene fusions were used to gener ...	1993	8231811
sequence and molecular analysis of the nifl gene of azotobacter vinelandii.	in both klebsiella pneumoniae and azotobacter vinelandii the nifl gene, which encodes a negative regulator of nitrogen fixation, lies immediately upstream of nifa. we have sequenced the a. vinelandii nifl gene and found that it is more homologous in its c-terminal domain to the histidine protein kinases (hpks) than is k. pneumoniae nifl. in particular a. vinelandii nifl contains a conserved histidine at a position shown to be phosphorylated in other systems. both nifl proteins are homologous in ...	1993	8231815
the membrane topology of the rhizobium meliloti c4-dicarboxylate permease (dcta) as derived from protein fusions with escherichia coli k12 alkaline phosphatase (phoa) and beta-galactosidase (lacz).	the rhizobium meliloti dcta gene encodes the c4-dicarboxylate permease which mediates uptake of c4-dicarboxylates, both in free-living and symbiotic cells. based on the hydrophobicity of the dcta protein, 12 putative membrane spanning regions were predicted. the membrane topology was further analysed by isolating in vivo fusions of dcta to escherichia coli alkaline phosphatase (phoa) and e. coli beta-galactosidase (lacz). of 10 different fusions 7 indicated a periplasmic and 3 a cytoplasmic loca ...	1993	8232193
nopaline causes a conformational change in the nocr regulatory protein-nocr promoter complex of agrobacterium tumefaciens ti plasmid ptit37.	the nocr gene of agrobacterium tumefaciens ti plasmid ptit37 is the regulatory gene of the nopaline catabolism (noc) operon of ptit37. we have cloned and sequenced nocr, which encodes a dna-binding protein. the deduced amino acid sequence is similar to those of members of the lysr family of prokaryotic activator proteins. gel retardation experiments demonstrated that the nocr protein binds to the nocr promoter in both the presence and absence of nopaline. the increased mobility of the complex an ...	1993	8232213
preformed dimeric state of the sensor protein vira is involved in plant--agrobacterium signal transduction.	plant signal molecules such as acetosyringone and certain monosaccharides induce the expression of agrobacterium tumefaciens virulence (vir) genes, which are required for the processing, transfer, and possibly integration of a piece of the bacterial plasmid dna (t-dna) into the plant genome. two fo the vir genes, vira and virg, belonging to the bacterial two-component regulatory system family, control the induction of vir genes by plant signals. vira encodes a membrane-bound sensor kinase protei ...	1993	8234338
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 ...	1993	8240952
genomic heterogeneity among french rhizobium strains isolated from phaseolus vulgaris l.	levels of dna relatedness between strains isolated from root nodules of phaseolus vulgaris and reference strains of different rhizobium species were determined by performing dna-dna hybridization experiments (s1 nuclease method). the nine strains examined were members of three genomic groups previously delineated by a restriction fragment length polymorphism analysis among strains isolated from p. vulgaris at different sites in france. in agreement with the results of the restriction fragment le ...	1993	8240956
transcription in vitro promoted by the agrobacterium virg protein.	expression of the virulence genes (vir) on the hairy-root-inducing plasmid pria4 is induced by plant signals in agrobacterium cells through a two-component regulatory system, the vira-virg system. we constructed an in vitro transcription system that consisted of the purified virg protein and the agrobacterium rna polymerase holoenzyme. both versions of virg, the non-phosphorylated form and the vira-phosphorylated form, were active but showed different patterns of the ph-dependency for transcript ...	1993	8243632