| the primary structure of a fungal chitin deacetylase reveals the function for two bacterial gene products. | chitin deacetylase (ec 3.5.1.41) hydrolyzes the n-acetamido groups of n-acetyl-d-glucosamine residues in chitin. a cdna to the mucor rouxii mrna encoding chitin deacetylase was isolated, characterized, and sequenced. protein sequence comparisons revealed significant similarities of the fungal chitin deacetylase to rhizobial nodb proteins and to an uncharacterized protein encoded by a bacillus stearothermophilus open reading frame. these data suggest the functional homology of these evolutionaril ... | 1993 | 8367456 |
| cloning and sequence of the rhizobium leguminosarum biovar phaseoli fixa gene. | we report the identification and cloning of rhizobium leguminosarum biovar phaseoli fixabcx homologous genes and the complete nucleotide sequence of the fixa gene. the corresponding gene product is highly homologous to the rhizobium meliloti and azorhizobium caulinodans fixa proteins. putative ntra- and nifa-binding sites are identified in the fixa promoter region. | 1993 | 8369342 |
| uridylylation of the pii protein in rhizobium leguminosarum. | permeabilization with cetyl trimethyl ammonium bromide was used to study the post-translational modification of the pii protein in rhizobium leguminosarum. upon incubation with radioactive utp a single band was obtained after sds-page and autoradiography. rnase resistance and snake venom phosphodiesterase sensitivity showed that radioactivity was bound through a phosphodiester bond to a protein which was absorbed by an antiserum specific for the pii protein. uridylylation of the pii protein was ... | 1993 | 8370467 |
| a single missense mutation in the br1 movement protein alters the host range of the squash leaf curl geminivirus. | the bipartite geminiviruses causing squash leaf curl disease, sqlcv-e and sqlcv-r, have a broad host range that includes nicotiana benthamiana, pumpkin, squash, and beans. we have characterized a naturally occurring mutant of the sqlcv-r b component (brtd1) which has lost the ability to infect n. benthamiana, but still retains full infectivity for pumpkin and squash. the mutation responsible for this host range alteration was localized to the coding region of br1, a gene essential for viral move ... | 1993 | 8372442 |
| role of the rhizobium meliloti nodf and node genes in the biosynthesis of lipo-oligosaccharidic nodulation factors. | rhizobia nodulation (nod) genes are involved in the synthesis of symbiotic signals, the nod factors, which are mono-n-acylated chito-oligosaccharides. nod factors elicit, in a specific manner, various plant responses on legume roots. in this report we address the question of the role of nodfeg genes in the synthesis of the acyl moiety of rhizobium meliloti nod factors. in a nod factor-overproducing strain with the wild-type nod region, in addition to the delta 2,9-c16:2 and delta 2, 4,9-c16:3 ac ... | 1993 | 8376372 |
| [phenolic secondary metabolites as plant signals in interspecies interactions]. | | 1993 | 8378194 |
| organization and regulation of the mannopine cyclase-associated opine catabolism genes in agrobacterium tumefaciens 15955. | we have isolated and characterized tn3hoho1- and tn5-induced mutants of a cosmid clone, pydh208, which encodes the mannopine (mop) cyclase-associated catabolism of mop and agropine (agr). characterization of the transposon-induced lacz fusion mutants by beta-galactosidase activity and mannityl opine utilization patterns identified at least 6 genetic units associated with the catabolism of these opines. functions for the catabolism of mop and mannopinic acid are encoded by a 16.4-kb region, where ... | 1993 | 8380402 |
| genetic analysis of the vird operon of agrobacterium tumefaciens: a search for functions involved in transport of t-dna into the plant cell nucleus and in t-dna integration. | the transferred dna (t-dna) is transported from agrobacterium tumefaciens to the nucleus and is stably integrated into the genome of many plant species. it has been proposed that the vird2 protein, tightly attached to the t-dna, pilots the t-dna into the plant cell nucleus and that it is involved in integration. using agroinfection and beta-glucuronidase expression as two different very sensitive transient assays for t-dna transfer, together with assays for stable integration, we have shown that ... | 1993 | 8380800 |
| construction and characterization of tn5virb, a transposon that generates nonpolar mutations, and its use to define virb8 as an essential virulence gene in agrobacterium tumefaciens. | transfer of the t-dna from the ti plasmid of agrobacterium tumefaciens into plant cells involves movement of a single-stranded dna-protein intermediate across several membrane and cell wall barriers. the 11 virb proteins encoded by the ti plasmid are hypothesized to form at least part of a membrane-localized t-dna transport apparatus. although available genetic and biochemical analyses support this hypothesis, detailed study of this transport apparatus is hindered by the fact that most available ... | 1993 | 8380806 |
| effects of gene dosage and sequence modification on the frequency and timing of transposition of the maize element activator (ac) in tobacco. | the effect of ac copy number on the frequency and timing of germinal transposition in tobacco was investigated using the streptomycin phosphotransferase gene (spt) as an excision marker. the activity of one and two copies of the element was compared by selecting heterozygous and homozygous progeny of transformants carrying single spt::ac inserts. it was observed that increasing gene copy not only increases the transposition frequency, but also occasionally alters the timing of transposition such ... | 1993 | 8381038 |
| rapid and efficient techniques for detecting transgenic tobacco plants. | | 1993 | 8381653 |
| characterization of rfrs9, a second member of the rhizobium fredii repetitive sequence family from the nitrogen-fixing symbiont r. fredii usda257. | the genome of the nitrogen-fixing symbiont, rhizobium fredii usda257, contains nine copies of repetitive sequences known as the r. fredii repetitive sequence (rfrs) family. we previously sequenced rfrs3, which is linked to symbiosis plasmid-borne nodulation genes of this organism and has substantial homology to the t-dna of agrobacterium rhizogenes and lesser homology to reiterated sequences of bradyrhizobium japonicum. here we characterize a second family member, rfrs9. the ecori fragment conta ... | 1993 | 8382462 |
| expression of a foreign gene in chlamydomonas reinhardtii. | genomic transformation of chlamydomonas reinhardtii exposed to glass-bead abrasion was accomplished with a chimeric neomycin phosphotransferaseii (nptii)-encoding gene (nos::npt) flanked by the nopaline synthase promoter and polyadenylation sequences obtained from the ti plasmid of agrobacterium tumefaciens. these sequences were in a plasmid (pga482) which also contained gene nit1 encoding nitrate reductase of c. reinhardtii. transformants were selected by their ability to grow on medium contain ... | 1993 | 8382657 |
| autophosphorylation and phosphatase activities of the oxygen-sensing protein fixl of rhizobium meliloti are coordinately regulated by oxygen. | the fixl and fixj proteins of rhizobium meliloti control the expression of other nif and fix genes in response to oxygen levels. fixl is a hemoprotein kinase that senses oxygen availability and responds to the absence of oxygen by activation of its autophosphorylating activity followed by transfer of the phosphate to fixj. fixj in turn activates the nifa and fixk promoters. in vitro studies reported here with a soluble truncated version of fixl (fixl*) indicate that, while low oxygen tension spe ... | 1993 | 8382700 |
| the nitrogenase proteins of rhizobium meliloti: purification and properties of the mofe and fe components. | the alfalfa-rhizobium meliloti symbiosis contributes a major portion of biologically fixed nitrogen to temperate zone forage crop production. highly-purified molybdenum-iron (mofe) and iron (fe) nitrogenase components were obtained for the first time from extracts of r. meliloti bacteroids. intact bacteroid cells were isolated anaerobically from 100 g quantities of alfalfa nodules following storage in liquid nitrogen. centrifuged bacteroid extracts showed a marked reduction in specific activity ... | 1993 | 8386550 |
| transposition of the maize autonomous element activator in transgenic nicotiana plumbaginifolia plants. | the maize autonomous transposable element ac was introduced into haploid nicotiana plumbaginifolia via agrobacterium tumefaciens transformation of leaf disks. all the regenerated transformants (r0) were diploid and either homozygous or heterozygous for the hygromycin resistance gene used to select primary transformants. the ac excision frequency was determined using the phenotypic assay of restoration of neomycin phosphotransferase activity and expression of kanamycin resistance among progeny se ... | 1993 | 8386800 |
| nucleotide sequences of the sites involved in the integration of phage 16-3 of rhizobium meliloti 41. | | 1993 | 8386836 |
| nad(+)-dependent malic enzyme of rhizobium meliloti is required for symbiotic nitrogen fixation. | deae-cellulose chromatography of extracts of free-living rhizobium meliloti cells revealed separate nad(+)-dependent and nadp(+)-dependent malic enzyme activities. the nad+ malic enzyme exhibited more activity with nad+ as cofactor, but also showed some activity with nadp+. the nadp+ malic enzyme only showed activity when nadp+ was supplied as cofactor. three independent transposon-induced mutants of r. meliloti which lacked nad+ malic enzyme activity (dme-) but retained nadp+ malic enzyme activ ... | 1993 | 8387144 |
| is870 requires a 5'-ctag-3' target sequence to generate the stop codon for its large orf1. | the tb regions of the agrobacterium vitis octopine/cucumopine ti plasmids constitute a family of related structures. all contain a bacterial insertion element downstream of the tb-iaam gene, is870.1. whereas 43 isolates with octopine/cucumopine ti plasmids carry only one is870 copy, strain ag57 carries a second copy (is870.2) 3.9 kb to the right of is870.1 and part of the same tb region. two other octopine/cucumopine strains carry an is870 copy on their chromosome (is870.3). a study of the unmod ... | 1993 | 8387998 |
| rhizobium phaseoli cytochrome c-deficient mutant induces empty nodules on phaseolus vulgaris l. | a rhizobium phaseoli cytochrome mutant, unable to oxidize n,n,n',n'-tetramethyl-p-phenylenediamine (tmpd), was isolated after mu-dl (kan lac) mutagenesis of the wild-type strain ce-3. mutant strain cfn4202 had sixfold less haem-c but similar levels of b type, o and aa3 cytochromes than the wild-type strain. cfn4202 strain also showed reduced nadh- and tmpd-oxidase activity than the wild-type strain. succinate-oxidase activities were very similar. western blot experiments, using antiserum against ... | 1993 | 8388530 |
| a wound-induced promoter driving npt-ii expression limited to dedifferentiated cells at wound sites is sufficient to allow selection of transgenic shoots. | there is much data to indicate that only a small number of cells in plant explants are competent for stable transformation by agrobacterium. circumstantial evidence suggests that certain cells reentering cell division at wound sites are competent for transformation by agrobacterium. we have discovered a member of the intracellular pr gene family from asparagus (aopr1) which is strongly expressed upon wounding and during the reactivation of the cell cycle in cultured asparagus cells, but which sh ... | 1993 | 8388747 |
| a gene cluster for amylovoran synthesis in erwinia amylovora: characterization and relationship to cps genes in erwinia stewartii. | a large ams gene cluster required for production of the acidic extracellular polysaccharide (eps) amylovoran by the fire blight pathogen erwinia amylovora was cloned. tn5 mutagenesis and gene replacement were used to construct chromosomal ams mutants. five complementation groups, essential for amylovoran synthesis and virulence in e. amylovora, were identified and designated ams a-e. the ams gene cluster is about 7 kb in size and functionally equivalent to the cps gene cluster involved in eps sy ... | 1993 | 8389975 |
| the escherichia coli camp receptor protein (crp) represses the rhizobium meliloti dcta promoter in a camp-dependent fashion. | the expression of the rhizobium meliloti c4-dicarboxylic acid permease gene (dcta) is controlled by the sensor dctb and the transcriptional regulator, dctd. the r. meliloti dct system has been reconstituted in escherichia coli. expression of the dcta promoter is dctbd dependent and is induced in the presence of c4-dicarboxylic acids (dca). other carbon sources also influence dcta expression. we demonstrate that the camp receptor protein (crp) has a repressive effect on the dcta promoter. a mutat ... | 1993 | 8391103 |
| the vird2 protein of agrobacterium tumefaciens carries nuclear localization signals important for transfer of t-dna to plant. | agrobacterium tumefaciens is able to transfer a piece of dna, the t-dna, to the nucleus of the plant cell. the vird2 protein is required for the production of the t-dna, it is tightly linked to the t-dna and it is thought to direct it to the plant genome. two nuclear localization signals (nls), one in the n-terminal part and one in the c-terminal part of the vird2 protein, have been shown to be able to target marker proteins to the plant nucleus. here we analyze nuclear entry of the t-dna comple ... | 1993 | 8391110 |
| agrobacterium-mediated production of transgenic rice plants expressing a chimeric alpha-amylase promoter/beta-glucuronidase gene. | we have successfully transferred and expressed a reporter gene driven by an alpha-amylase promoter in a japonica type of rice (oryza sativa l. cv. tainung 62) using the agrobacterium-mediated gene transfer system. immature rice embryos (10-12 days after anthesis) were infected with an agrobacterium strain carrying a plasmid containing chimeric genes of beta-glucuronidase (uida) and neomycin phosphotransferase (nptii). co-incubation of potato suspension culture (psc) with the agrobacterium inocul ... | 1993 | 8392395 |
| a rhizobium meliloti homolog of the escherichia coli peptide-antibiotic transport protein sbma is essential for bacteroid development. | alfalfa nodules induced by a rhizobium meliloti strain carrying the baca386::tnphoa mutation (formerly fix386::tnphoa) were examined by light and electron microscopy. these ineffective nodules were found to contain bacteria within infection threads, but no mature bacteroids were observed. a closer examination revealed that there were undeveloped senescent bacteroids in the plant cells of the nodule invasion zone, strongly suggesting that the symbiotic defect of the baca386::tnphoa mutant is attr ... | 1993 | 8393417 |
| behaviour of modified ac elements in flax callus and regenerated plants. | the ac element of maize has been modified by deletion of 537 bases (delta naeac) from the untranslated leader of the transposase gene. in a second modification the cauliflower mosaic virus 35s promoter has been inserted into the truncated leader of delta naeac, 21 bases upstream of the natural translation start. the activity of these modified elements has been compared with that of the unmodified element in transgenic flax. deletion of sequences in the untranslated leader only marginally increas ... | 1993 | 8393718 |
| regulation of the kinase activity of heme protein fixl from the two-component system fixl/fixj of rhizobium meliloti. | the rhizobium meliloti two-component system fixl/fixj regulates nitrogen fixation in response to oxygen during symbiosis. fixj is a transcriptional activator of critical nif and fix promoters; its in vivo activity is enhanced by fixl in diminished oxygen (david, m., daveran, m.-l., batut, j., dedieu, a., domergue, o., ghai, j., hertig, c., boistard, p., and kahn, d. (1988) cell 54, 671-683; virts, e. l., stanfield, s. w., helinski, d. r., and ditta, g. s. (1988) proc. natl. acad. sci. u.s.a. 85, ... | 1993 | 8393856 |
| [testing transgenic plants using the polymerase chain reaction]. | a test system for selecting transgenic plants based on polymerase chain reaction (pcr) has been proposed. it is applicable to primary screening of transgenic plants obtained by cocultivation with agrobacterium which contains any vector carrying neomycin phosphotransferase genes from transposon tn5 and streptococcus (for example pbin19). these genes confer kanamycin resistance in plants and bacteria respectively. the absence of strong homology between these two genes allows one to perform two pcr ... | 1993 | 8395650 |
| transposition pattern of the maize element ds in arabidopsis thaliana. | as part of establishing an efficient transposon tagging system in arabidopsis using the maize elements ac and ds, we have analyzed the inheritance and pattern of ds transposition in four independent arabidopsis transformants. a low proportion (33%) of plants inheriting the marker used to monitor excision contained a transposed ds. selection for the transposed ds increased this to at least 49%. overall, 68% of ds transpositions inherited with the excision marker were to genetically linked sites; ... | 1993 | 8397137 |
| nodulation factors from rhizobium tropici are sulfated or nonsulfated chitopentasaccharides containing an n-methyl-n-acylglucosaminyl terminus. | phaseolus vulgaris (common bean) can be nodulated by several rhizobium species. among them, rhizobium tropici has a relatively broad host range, as it is able to infect beans, leucaena trees, and several other legumes. this work describes the isolation and the characterization of extracellular factors (nod factors) whose production from r. tropici was triggered by the transcriptional activation of its nod genes. these factors consist of a chitopentaose backbone in which the n-acetyl group of the ... | 1993 | 8399187 |
| replication of tomato yellow leaf curl virus (tylcv) dna in agroinoculated leaf discs from selected tomato genotypes. | the leaf disc agroinoculation system was applied to study tomato yellow leaf curl virus (tylcv) replication in explants from susceptible and resistant tomato genotypes. this system was also evaluated as a potential selection tool in breeding programmes for tylcv resistance. leaf discs were incubated with a head-to-tail dimer of the tylcv genome cloned into the ti plasmid of agrobacterium tumefaciens. in leaf discs from susceptible cultivars (lycopersicon esculentum) tylcv single-stranded genomic ... | 1993 | 8400142 |
| membrane location of the ti plasmid virb proteins involved in the biosynthesis of a pilin-like conjugative structure on agrobacterium tumefaciens. | the virb operon of the agrobacterium tumefaciens ti plasmid encodes 11 proteins. specific antisera to virb2, virb3 and virb9 were used to locate these virulence proteins in the a. tumefaciens cell. immunoblot analysis located virb2 protein to the inner and outer membranes; virb3 and virb9 were likewise associated with both membranes, but mainly in the outer membrane. virb2 is processed from a 12.3-kda protein into a 7.2-kda polypeptide. such sized protein results from cleavage at residue ala47, ... | 1993 | 8405938 |
| isolation and characterization of a dna replication origin from the 1,700-kilobase-pair symbiotic megaplasmid psym-b of rhizobium meliloti. | a 4-kb fragment active as an autonomously replicating sequence (ars) from the rhizobium meliloti symbiotic megaplasmid psym-b was isolated by selecting for sequences that allowed a normally nonreplicative pbr322 derivative to replicate in r. meliloti. the resulting escherichia coli-r. meliloti shuttle plasmid (mini-psym-b) containing the ars also replicated in the closely related agrobacterium tumefaciens, but only in strains carrying psym-b, suggesting that a megaplasmid-encoded trans-acting fa ... | 1993 | 8407832 |
| a chromosomally encoded two-component sensory transduction system is required for virulence of agrobacterium tumefaciens. | tnphoa mutagenesis of agrobacterium tumefaciens identified new extracytoplasmic protein-encoding virulence loci. mutations in these loci conferred increased sensitivity to detergents and several antibiotics. clones carrying these loci were isolated from an a. tumefaciens cosmid library by complementation of the detergent sensitivities of the mutants. the locus on one complementing clone was delineated by tn5 and tnphoa mutagenesis. dna sequence analysis of the delineated region revealed that thi ... | 1993 | 8407839 |
| the chromosomal response regulatory gene chvi of agrobacterium tumefaciens complements an escherichia coli phob mutation and is required for virulence. | in an effort to identify the agrobacterium tumefaciens phosphate regulatory gene(s), we isolated a clone from an a. tumefaciens cosmid library that restored regulated alkaline phosphatase activity to an escherichia coli phob mutant. the gene that complemented phob was localized by subcloning and deletion analysis, and the dna sequence was determined. an open reading frame, denoted chvi, was identified that encoded a predicted protein with amino acid similarity to the family of bacterial response ... | 1993 | 8407840 |
| effects of ribosome-inactivating proteins on escherichia coli and agrobacterium tumefaciens translation systems. | the effects of 30 type 1 and of 2 (ricin and volkensin) type 2 ribosome-inactivating proteins (rips) on escherichia coli and agrobacterium tumefaciens cell-free translation systems were compared with the effects on a rabbit reticulocyte translation system. the depurinating activity of rips on e. coli ribosomes was also evaluated. only six type 1 rips inhibited endogenous mrna-directed translational activity of e. coli lysates, with submicromolar 50% inhibitory concentrations. four rips had simil ... | 1993 | 8407849 |
| recovery of a strain of agrobacterium radiobacter with a mucoid phenotype from an immunocompromised child with bacteremia. | agrobacteria are associated more commonly with plant than with human disease. the isolation of agrobacterium radiobacter from blood cultures of an immunocompromised child with a transcutaneous catheter prompted a review of human infections caused by agrobacterium species. only 12 reports describing 19 cases of agrobacterium infections in humans have appeared in the literature. sixteen of the patients (84%) were equipped with implantable or transcutaneous medical devices at the time of infection, ... | 1993 | 8408587 |
| characterization of an is-like element from mycobacterium tuberculosis. | a dna sequence, present in members of the mycobacterium tuberculosis complex, has been identified and characterized. the distribution of this dna sequence among mycobacterial species was analysed by dna hybridization and pcr experiments. as the sequence was detected only in bacteria belonging to the m. tuberculosis complex, it may be useful for the rapid discrimination of mycobacteria. interestingly, the sequence has some characteristics of an insertion element (is) and codes for a hypothetical ... | 1993 | 8409920 |
| interactions of nodd at the nod box: nodd binds to two distinct sites on the same face of the helix and induces a bend in the dna. | the rhizobium meliloti nodd gene products are positive transcriptional activators of genes required for early stages of nodule morphogenesis in the r. meliloti-alfalfa symbiosis (nod genes). the regulatory activity of nodd, a member of the lysr family of activator proteins, is mediated in part through its binding to conserved dna sequences termed nod boxes which lie upstream of the inducible nod genes. here we use interference footprinting to identify two nodd binding sites in the noda, nodf and ... | 1993 | 8411148 |
| identification of nodsuij genes in nod locus 1 of azorhizobium caulinodans: evidence that nods encodes a methyltransferase involved in nod factor modification. | the azorhizobium caulinodans strain ors571 nodulation genes nodsuij were located downstream from nodabc. complementation data and transcriptional analysis suggest that nodabcsuij form a single operon. mutants with tn5 insertions in the genes nods, nodu, and nodj were delayed in nodulation of sesbania rostrata roots and stems. the nods amino acid sequences of ors571, bradyrhizobium japonicum, and rhizobium sp. strain ngr234, contain a consensus with similarity to s-adenosylmethionine (sam)-utiliz ... | 1993 | 8412659 |
| molecular cloning and characterization of a sym plasmid locus that regulates cultivar-specific nodulation of soybean by rhizobium fredii usda257. | rhizobium fredii strain usda257 produces nitrogen-fixing nodules on primitive soybean cultivars such as peking but fails to nodulate agronomically improved cultivars such as mccall. transposon-mutant 257dh4 has two new phenotypes: it nodulates mccall, and its ability to do so is sensitive to the presence of parental strain usda257, i.e. it is subject to competitive nodulation blocking. we have isolated a cosmid containing dna that corresponds to the site of transposon insertion in 257dh4 and hav ... | 1993 | 8412662 |
| the ntrbc genes of rhizobium leguminosarum are part of a complex operon subject to negative regulation. | we report here that ntrb and ntrc genes of rhizobium leguminosarum biovar phaseoli are cotranscribed with an open reading frame (called orf1) of unknown function. the promoter region of the orf1-ntrb-ntrc operon was mapped immediately upstream of orf1 and two in vivo transcription initiation sites were identified, both preceded by -35/-10 promoter consensus sequences. some major aspects differentiate r. leguminosarum from the enteric nitrogen regulatory system: the ntrbc genes are cotranscribed ... | 1993 | 8412703 |
| genes at different regulatory levels are required for the ammonia control of nodulation in rhizobium meliloti. | the expression of the nodulation genes nodabc of rhizobium meliloti, which determine early response functions to plant host signals, is regulated by the level of ammonia, the primary product of symbiotic nitrogen fixation. we show that the pathway that links the ammonia-induced signal to the transcriptional control of the nodabc genes involves at least two regulatory levels. the fluctuating nitrogen level is sensed and the signal is mediated by the members of the general nitrogen regulatory (ntr ... | 1993 | 8413194 |
| detection of a nitrous oxide reductase structural gene in rhizobium meliloti strains and its location on the nod megaplasmid of jj1c10 and su47. | the gene encoding a denitrification enzyme, nitrous oxide reductase (ec 1.7.99.6), in rhizobium meliloti and other gram-negative bacteria was detected by hybridization to an internal 1.2-kb psti fragment of the structural gene (nosz) cloned from pseudomonas stutzeri zobell (w.g. zumft, a. viebrock-sambale, and c. braun, eur. j. biochem. 192:591-599, 1990). homology to the probe was detected in the dnas of two n2-fixing strains of p. stutzeri, two denitrifying pseudomonas species, one alcaligenes ... | 1993 | 8416894 |
| siderophore-mediated iron transport correlates with the presence of specific iron-regulated proteins in the outer membrane of rhizobium meliloti. | a universal chemical assay used to detect the production of siderophores in a range of rhizobium strains showed that production is strain specific. iron nutrition bioassays carried out on rhizobium meliloti strains to determine cross-utilization of their siderophores showed that r. meliloti 2011, 220-5, and 220-3 could each use the siderophores produced by the other two but not the siderophore produced by r. meliloti dm4 (and vice versa). mutants of r. meliloti 2011 and 220-5 defective in sidero ... | 1993 | 8416915 |
| multiple copies of nodd in rhizobium tropici ciat899 and br816. | rhizobium tropici strains are able to nodulate a wide range of host plants: phaseolus vulgaris, leucaena spp., and macroptilium atropurpureum. we studied the nodd regulatory gene for nodulation of two r. tropici strains: ciat899, the reference r. tropici type iib strain, and br816, a heat-tolerant strain isolated from leucaena leucocephala. a survey revealed several nodd-hybridizing dna regions in both strains: five distinct regions in ciat899 and four distinct regions in br816. induction experi ... | 1993 | 8419293 |
| rhizobium nodb protein involved in nodulation signal synthesis is a chitooligosaccharide deacetylase. | the common nodulation genes nodabc are conserved in all rhizobia and are involved in synthesis of a lipooligosaccharide signal molecule. this bacterial signal consists of a chitooligosaccharide backbone, which carries at the nonreducing end a fatty acyl chain. the modified chitooligosaccharide molecule triggers development of nodules on the roots of the leguminous host plant. to elucidate the specific role of the nodb protein in nodulation factor synthesis, we have purified recombinant nodb and ... | 1993 | 8421697 |
| polysaccharide synthesis in relation to nodulation behavior of rhizobium leguminosarum. | in this study, we characterized four tn5 mutants derived from rhizobium leguminosarum rbl5515 with respect to synthesis and secretion of cellulose fibrils, extracellular polysaccharides (eps), capsular polysaccharides, and cyclic beta-(1,2)-glucans. one mutant, strain rbl5515 exo-344::tn5, synthesizes residual amounts of eps, the repeating unit of which lacks the terminal galactose molecule and the substituents attached to it. on basis of the polysaccharide production pattern of strain rbl5515 e ... | 1993 | 8423148 |
| biosynthesis of cyclic beta-(1-3),beta-(1-6) glucan in bradyrhizobium spp. | inner membranes of bradyrhizobium japonicum strain usda 110 produced in vitro soluble and insoluble beta-(1-3),beta-(1-6) glucans. the reaction proceeded through a 90 kda inner membrane intermediate protein; used udp-glucose as sugar donor and required mg2+. gel chromatography of soluble glucans resolved a cyclic beta-(1-3) glucan with a degree of polymerization of eleven from a family of beta-(1-3),beta-(1-6) glucans with variable degree of polymerization higher than eleven. bradyrhizobium stra ... | 1993 | 8427547 |
| nucleotide sequence and characterization of rhizobium meliloti nodulation competitiveness genes nfe. | rhizobium meliloti large plasmid prmegr4b carries the nodulation competitiveness locus nfe responsible for the nodulation efficiency and competitive ability of strain gr4 on alfalfa roots. we report here the nucleotide sequence and characterization of a 3345 base-pair dna section of the nfe region. sequence analysis revealed four open reading frames (orfs), two of them with rightward polarity, termed nfe1 and nfe2, are preceded by functional nif consensus sequences and nifa-binding motifs. an ad ... | 1993 | 8429568 |
| two functional soybean genes encoding p34cdc2 protein kinases are regulated by different plant developmental pathways. | we have isolated two cdna clones (cdc2-s5 and cdc2-s6) encoding p34cdc2 protein kinases, homologs of yeast cdc2/cdc28 genes, from a soybean nodule cdna library. the two sequences share 90% sequence homology in the coding regions. the 5' and 3' noncoding regions are distinct from each other, however, indicating that at least two genes encode p34cdc2 protein kinases in soybean. both sequences can rescue the cdc28 mutation in saccharomyces cerevisiae but rescue it with different efficiency. genomic ... | 1993 | 8430109 |
| regulation and function of rhizobial nodulation genes. | this review focuses on the functions of nodulation (nod) genes in the interaction between rhizobia and legumes. the nod genes are the key bacterial determinants of the signal exchange between the two symbiotic partners. the product of the nodd gene is a transcriptional activator protein that functions as receptor for a flavonoid plant compound. this signaling induces the expression of a set of nod genes that produces several related nod factors, substituted lipooligosaccharides. the nod factors ... | 1993 | 8431309 |
| the oxygen sensor fixl of rhizobium meliloti is a membrane protein containing four possible transmembrane segments. | regulation of nitrogen fixation genes in rhizobium meliloti is mediated by two proteins, fixl and fixj, in response to oxygen availability. fixl is an oxygen-binding hemoprotein with kinase and phosphatase activities that is thought to sense oxygen levels directly and to transmit this signal to fixj via phosphorylation-dephosphorylation reactions. fixj controls the expression of other regulatory genes, including nifa, that regulate the transcription of genes required for symbiotic nitrogen fixat ... | 1993 | 8432704 |
| roles of n-acetylglutaminylglutamine amide and glycine betaine in adaptation of pseudomonas aeruginosa to osmotic stress. | the mechanism of osmotic stress adaptation in pseudomonas aeruginosa pao1 was investigated. by using natural abundance 13c nuclear magnetic resonance spectroscopy, osmotically stressed cultures were found to accumulate glutamate, trehalose, and n-acetylglutaminylglutamine amide, an unusual dipeptide previously reported only in osmotically stressed rhizobium meliloti and pseudomonas fluorescens. the intracellular levels of these osmolytes were dependent on the chemical composition and the osmolal ... | 1993 | 8434912 |
| syntrophic interactions during degradation of 4-aminobenzenesulfonic acid by a two species bacterial culture. | during synthrophic growth of hydrogenophaga palleronii (strain s1) and agrobacterium radiobacter (strain s2) with 4-aminobenzene sulfonate (4abs) only strain s1 desaminates 4abs by regioselective 3,4-dioxygenation. the major part of the metabolite catechol-4-sulfonate (4cs) is excreted and further metabolized by strain s2. although both organisms harbour activities of protocatechuate pathways assimilation of the structural analog 4cs requires first of all enzyme activities with broader substrate ... | 1993 | 8439234 |
| psym nod gene influence on elicitation of peroxidase activity from white clover and pea roots by rhizobia and their cell-free supernatants. | the activities of salt-elutable peroxidases from roots of white clover and pea were examined during the early interaction of these legume hosts with strains of rhizobium leguminosarum in homologous and heterologous combination. peroxidase-specific activity from clover root hairs began to increase 6 hr after inoculation with r. l. bv. viciae rl300 and was localized over the entire area of their deformations. in contrast, the onset of elicitation of peroxidase activity from root hairs was delayed ... | 1993 | 8439669 |
| genetic analysis of the rhizobium meliloti exoyfq operon: exoy is homologous to sugar transferases and exoq represents a transmembrane protein. | the nucleotide sequence of a 4.8-kb clai-ecori dna fragment of megaplasmid 2 of rhizobium meliloti rm2011 involved in succinoglucan (eps i) synthesis and nodule infection was determined. four open reading frames (orfs) were identified on this fragment. a mutational analysis revealed that these orfs represent genes that were termed exox, exoy, exof, and exoq. the locations of transposon insertions in these exo genes were determined at the nucleotide level. plasmid integration mutagenesis revealed ... | 1993 | 8439670 |
| mserk1: a mitogen-activated protein kinase from a flowering plant. | the induction of proliferation and differentiation in cultured mammalian cells is mediated by a cascade of protein phosphorylations. a key enzyme in this signaling pathway is mitogen-activated protein (map) kinase (or erk, extracellular signal-regulated kinase). we report the recovery of a full-length cdna clone encoding a map kinase from alfalfa. we have named the 44-kd protein encoded by this clone mserk1. recombinant mserk1 (rmserk1), when overexpressed in escherichia coli, is recognized by a ... | 1993 | 8439746 |
| the virb operon of the agrobacterium tumefaciens virulence regulon has sequence similarities to b, c and d open reading frames downstream of the pertussis toxin-operon and to the dna transfer-operons of broad-host-range conjugative plasmids. | | 1993 | 8441642 |
| an ultraviolet-sensitive mutant of zymomonas mobilis affecting the stability of its natural plasmid pzmo2. | plasmid pzmo2, a 1.9-kb natural plasmid of zymomonas mobilis strain atcc 10988, was found to be absent from the extract of a mutant isolate sensitive to ultraviolet irradiation, methyl methanesulfonic acid, and mitomycin c. this mutant, named uvs51, also exhibited extremely high segregational instability of the recombinant plasmid pds212, whose maintenance in the parental strain is known to be due to pzmo2 sequences. helped conjugations, employing uvs51 as recipient with escherichia coli donors ... | 1993 | 8441765 |
| agrobacterium infections in humans: experience at one hospital and review. | agrobacteria are noted primarily for their phytopathogenicity and when isolated from human clinical specimens are often considered contaminants or organisms of low pathogenicity. we report six cases at one hospital over a 6 1/2-year period in which infection was accompanied by a compatible clinical syndrome and review 19 cases reported in the literature. fourteen of the 25 combined cases involved central venous catheter-associated infections. six cases involved peritonitis, five of which occurre ... | 1993 | 8448285 |
| supported pcr: an efficient procedure to amplify sequences flanking a known dna segment. | we describe a novel modification of the polymerase chain reaction for efficient in vitro amplification of genomic dna sequences flanking short stretches of known sequence. the technique utilizes a target enrichment step, based on the selective isolation of biotinylated fragments from the bulk of genomic dna on streptavidin-containing support. subsequently, following ligation with a second universal linker primer, the selected fragments can be amplified to amounts suitable for further molecular s ... | 1993 | 8448372 |
| measurement of inter-glycosidic 13c-1h coupling constants in a cyclic beta(1-->2)-glucan by 13c-filtered 2d (1h,1h)roesy. | a method for measuring three-bond 13c-1h scalar coupling constants across glycosidic bonds in a cyclic beta(1-->2)-glucan icosamer is presented. this oligosaccharide molecule, with its high degree of symmetry, represents a particular challenge for nmr spectroscopy to distinguish inter-residue from intra-residue heteronuclear coupling effects. chemically equivalent h2 protons in adjacent glucosyl residues are distinguished on the basis of their different through-space, dipolar interactions with t ... | 1993 | 8448437 |
| the agrobacterium tumefaciens virb4 gene product is an essential virulence protein requiring an intact nucleoside triphosphate-binding domain. | products of the approximately 9.5-kb virb operon are proposed to direct the export of t-dna/protein complexes across the agrobacterium tumefaciens envelope en route to plant cells. the presence of conserved nucleoside triphosphate (ntp)-binding domains in virb4 and virb11 suggests that one or both proteins couple energy, via ntp hydrolysis, to t-complex transport. to assess the importance of virb4 for virulence, a nonpolar virb4 null mutation was introduced into the ptia6nc plasmid of strain a34 ... | 1993 | 8449880 |
| precise deletions in large bacterial genomes by vector-mediated excision (vex). the trfa gene of promiscuous plasmid rk2 is essential for replication in several gram-negative hosts. | we have developed a simple and efficient method of vector-mediated excision (vex) for in vivo generation of precisely defined deletions in large bacterial genomes. the system uses homologous recombination with small cloned fragments on specialized pvex plasmids to insert directly repeated bacteriophage p1 loxp sites at positions flanking the region to be deleted. in the presence of cre recombinase, the loxp sites are efficiently recombined to produce the deletion. deletion endpoints can be direc ... | 1993 | 8450534 |
| simple and efficient method for directly electroporating agrobacterium plasmid dna into wheat callus cells. | | 1993 | 8451178 |
| n,n-(2,4-dinitrophenyl)octylamine derivatives for the isolation, purification, and mass spectrometric characterization of oligosaccharides. | a simple, sensitive method for the structural characterization of oligosaccharides by fast atom bombardment-mass spectrometry (fab-ms) has been designed. oligosaccharides are labeled with a uv chromophore (which also serves as a charge stabilizing group) and with a hydrophobic alkyl tail. the chromophore, a 2,4-dinitrophenyl group, aids uv detection during hplc and stabilizes negative ion species formed during analysis by fab-ms. the hydrophobic tail, provided by an octyl group, enhances the sur ... | 1993 | 8452234 |
| agrobacterium radiobacter: a recently recognized opportunistic pathogen. | over the past decade, an increasing number of infections due to agrobacterium radiobacter have been reported. observation of three cases of bacteremia due to this organism prompted a review of the english-language literature. nineteen cases of significant disease have previously been reported. in more than one-half of the cases, bacteremia was the primary manifestation, often associated with the presence of an intravascular catheter. other clinical syndromes (peritonitis, urinary tract infection ... | 1993 | 8452950 |
| molecular characterization of nadh-dependent glutamate synthase from alfalfa nodules. | alfalfa nadh-dependent glutamate synthase (nadh-gogat), together with glutamine synthetase, plays a central role in the assimilation of symbiotically fixed nitrogen into amino acids in root nodules. antibodies previously raised against purified nadh-gogat were employed to screen a cdna library prepared using rna isolated from nodules of 20-day-old alfalfa plants. a 7.2-kb cdna clone was obtained that contained the entire protein coding region of nadh-gogat. analysis of this cdna and determinatio ... | 1993 | 8453303 |
| biosynthesis of curdlan from culture media containing 13c-labeled glucose as the carbon source. | 13c-labeled curdlans were biosynthesized by agrobacterium sp. (atcc 31749) from culture media containing d-(1-13c)glucose, d-(6-13c)glucose, or d-(2-13c)glucose as the carbon source, and their structures were analyzed by 13c nmr spectroscopy. the labeling was mainly found in the original position, that is, c-1, c-6, or c-2, indicating direct polymerization of introduced glucose. in addition, c-3 in curdlan obtained from d-(1-13c)glucose, c-1 in curdlan obtained from d-(6-13c)glucose, and c-1 and ... | 1993 | 8458009 |
| structural characterization and rheological properties of an extracellular glucuronan produced by a rhizobium meliloti m5n1 mutant strain. | the mutant strain m5n1 c.s. (ncimb 40472) of rhizobium meliloti m5n1 is able to produce during fermentation a partially acetylated extracellular (1-->4)-beta-d-glucuronan. at low concentration (1 g.l-1), in the presence of monovalent cations, this new glucuronate behaves as a thickening agent, whereas at higher concentration a thermoreversible gel is obtained. with such divalent cations as ca2+, a thermally stable gel can be formed. | 1993 | 8458016 |
| characterization of a virg mutation that confers constitutive virulence gene expression in agrobacterium. | transformation of plants by agrobacterium tumefaciens is mediated by a set of virulence (vir) genes that are specifically induced by plant signal molecules through the vira/virg two-component regulatory system. the plant signal is transmitted from vira to virg by a cascade of phosphorylation reactions followed by the sequence-specific dna binding of the virg protein to the vir gene promoters which then activates their transcription. in this report, we describe a virg mutant which is able to acti ... | 1993 | 8459774 |
| genetic analysis of beet curly top virus: evidence for three virion sense genes involved in movement and regulation of single- and double-stranded dna levels. | the monopartite dna genome of beet curly top geminivirus (bctv, strain logan) contains four leftward, complementary sense open reading frames (orfs) designated l1, l2, l3, and l4 and three rightward, virion sense orfs designated r1, r2, and r3 (r1 encodes the coat protein). the r3 orf has not been reported previously in the bctv genome, and evidence for three functional virion sense genes on one genome component has not been presented before for any geminivirus. we investigated the functions of ... | 1993 | 8460493 |
| agrobacterium conjugation and gene regulation by n-acyl-l-homoserine lactones. | conjugal opines secreted by crown gall tumours induce strains of agrobacterium tumefaciens that are donors of ti plasmids to produce a diffusible conjugation factor. this enhances the conjugal transfer efficiency of the ti plasmid in other strains of a. tumefaciens. this factor behaves as a secondary messenger, transmitting the environmental information to tra genes. here we report the use of spectrometry to show that this factor is identical to synthetic n-(beta-oxo-octan-1-oyl)-l-homoserine la ... | 1993 | 8464475 |
| conjugation factor of agrobacterium tumefaciens regulates ti plasmid transfer by autoinduction. | conjugal transfer of ti plasmids from agrobacterium donors to bacterial recipients is controlled by two types of diffusible signal molecules. induction is mediated by novel compounds, called opines, that are secreted by crown gall tumours. these neoplasias result from infection of susceptible plants by virulent agrobacteria. the second diffusible signal, called conjugation factor, is synthesized by the donor bacteria themselves. production of this factor is induced by the opine. here we show tha ... | 1993 | 8464476 |
| molecular characterization of an operon required for pertussis toxin secretion. | mutants of bordetella pertussis which are defective in secretion of pertussis toxin were isolated and characterized. the region of the b. pertussis chromosome identified by mutagenesis as playing a role in transport of pertussis toxin was sequenced. analysis of this region revealed eight open reading frames, seven of which predict a protein exhibiting homology with one of the virb proteins of agrobacterium tumefaciens, which are involved in the transport of the t-dna molecule across bacterial an ... | 1993 | 8464913 |
| relationships between c4 dicarboxylic acid transport and chemotaxis in rhizobium meliloti. | the relationship between chemotaxis and transport of c4 dicarboxylic acids was analyzed with rhizobium meliloti dct mutants defective in one or all of the genes required for dicarboxylic acid transport. succinate, malate, and fumarate were moderately potent chemoattractants for wild-type r. meliloti and appeared to share a common chemoreceptor. while dicarboxylate transport is inducible, taxis to succinate was shown to be constitutive. mutations in the dcta and dctb genes both resulted in the re ... | 1993 | 8468289 |
| strategies in pathogenesis: mechanistic specificity in the detection of generic signals. | the virulence genes of the plant pathogen agrobacterium tumefaciens are induced by more than 40 low-molecular-weight phenolic compounds. the prevailing opinion is that (i) wound-derived phenols produced on breach of the integrity of the cell wall act as the initiating signal in a series of events which results in host cell transformation, and (ii) a classical membrane receptor, putatively vira, is responsible for the recognition of all such phenolic inducers. here, we argue that the discovery of ... | 1993 | 8469110 |
| the vira promoter is a host-range determinant in agrobacterium tumefaciens. | the limited host range (lhr) agrobacterium tumefaciens strain ag162 is an isolate with a narrow host range. introduction of the wide host range (whr) vira gene is essential for extending the host range to kalanchoë daigremontiana. in this report we show that the region upstream of the atg start codon is responsible for the lhr phenomenon and that this is probably due to the non-inducibility of the lhrvira promoter. by comparing the characteristics of the lhr and whr vira receptor proteins, it wa ... | 1993 | 8469115 |
| identification and growth characteristics of pink pigmented oxidative bacteria, methylobacterium mesophilicum and biovars isolated from chlorinated and raw water supplies. | pink pigmented bacteria were isolated from a blood bank water purification unit, a municipal town water supply (tap water), and an island (untreated) ground water source. a total of thirteen strains including two reference strains of pink pigmented bacteria were compared in a numerical phenotypic study using 119 binary characters. three clusters were derived, one major cluster of eleven strains was subdivided into two sub-clusters on the basis of methanol utilization. five strains were facultati ... | 1993 | 8469180 |
| the ti plasmid from the wide host range agrobacterium vitis strain tm4: map and homology with other ti plasmids. | the octopine/cucumopine (o/c) strains of agrobacterium vitis are divided into limited (lhr) and wide host range (whr) strains. we present here the first map of a ti plasmid from a whr o/c strain, tm4. ptitm4 (252 kb) has homology with the octopine ti plasmid ptiach5, the nopaline plasmid ptic58, and the ri plasmid prihri. approximately 155 kb of ptitm4 is homologous with the lhr o/c ti plasmids ptiab3 and ptiag57, the remaining part is ptitm4-specific. our data suggest that the evolution of the ... | 1993 | 8469721 |
| evaluation of a strategy for identifying nodulation competitiveness genes in rhizobium leguminosarum biovar phaseoli. | rhizobium leguminosarum biovar phaseoli strain kim5s is consistently much more competitive than strain ce3 in nodulation of beans (phaseolus vulgaris l.) in the laboratory and in the field. to identify genes that contribute to the competitiveness of kim5s, we transferred a cosmid library containing kim5s dna into ce3 and applied the transconjugants to bean plants to allow the plants to enrich for those with enhanced nodulation competitiveness. the nodule isolates were then applied to plants for ... | 1993 | 8473861 |
| agrobacterium gene transfer: progress on a "poor man's vector" for maize. | | 1993 | 8475049 |
| oxygen regulation of nifa transcription in vitro. | in rhizobium meliloti, transcription of the key nitrogen-fixation regulatory genes nifa and fixk is induced in response to microaerobiosis through the action of the fixl and fixj proteins. these two proteins are sensor and regulator homologues, respectively, of a large family of bacterial two-component systems involved in sensing and responding to environmental changes. a soluble, truncated form of the membrane protein fixl, fixl*, has been shown to be a hemoprotein that phosphorylates and depho ... | 1993 | 8475099 |
| vira, the plant-signal receptor, is responsible for the ti plasmid-specific transfer of dna to maize by agrobacterium. | agrobacteria exhibit marked ti (tumor-inducing)/ri (root-inducing) plasmid specificity in their interaction with the gramineae. in this study, we have used the technique of "agroinfection," in which agrobacterium-mediated delivery of viral genomes into plants is detected by the development of viral disease symptoms, to identify the region of the ti plasmid which is responsible for the major differences seen in the ability of nopaline- vs. octopine-type ti plasmids to transfer maize streak virus ... | 1993 | 8475103 |
| effect of pesticides on growth of rhizobia and their host plants during symbiosis. | effect of various pesticides (insecticides, fungicides and herbicides) has been studied on growth and efficiency of symbiotic properties of 3 fast growing rhizobium sp. under green house conditions. the results revealed adverse effects on plant growth and nitrogen fixing capacity as measured by dry weight and total nitrogen content of plants infected with pesticide treated rhizobium. of the pesticides tested, herbicides were found to be more effective on the above parameters than the insecticide ... | 1993 | 8476538 |
| symbiotic nitrogen fixation by a nifa deletion mutant of rhizobium meliloti: the role of an unusual ntrc allele. | in the n2-fixing alfalfa symbiont rhizobium meliloti, the three sigma 54 (ntra)-dependent positively acting regulatory proteins nifa, ntrc, and dctd are required for activation of promoters involved in n2 fixation (pnifhdke and pfixabcx), nitrogen assimilation (pglnii), and c4-dicarboxylate transport (pdcta), respectively. here, we describe an allele of ntrc which results in the constitutive activation of the above ntrc-, nifa-, and dctd-regulated promoters. the expression and activation of wild ... | 1993 | 8478331 |
| negative regulation of sigma 54-dependent dcta expression by the transcriptional activator dctd. | in rhizobium meliloti, the presence of the c4-dicarboxylate transport protein dcta is required for symbiotic n2 fixation in alfalfa root nodules. expression of dcta is inducible and is mediated by a sensor and activator gene pair encoded by dctb and dctd. in the presence of c4-dicarboxylates, the dctb sensor protein is believed to phosphorylate and activate dctd, which in turn activates transcription at the sigma 54-dependent dcta promoter. here, we present evidence that in addition to activatin ... | 1993 | 8478332 |
| analysis of the rhizobium meliloti exoh/exok/exol fragment: exok shows homology to excreted endo-beta-1,3-1,4-glucanases and exoh resembles membrane proteins. | nucleotide sequencing of a 4.15 kb dna fragment from megaplasmid 2 of rhizobium meliloti 2011 revealed the location of the genes exoh, exok and exol. the putative proteins encoded by these genes have molecular weights of 41, 30, and 44 kda, respectively. the hydrophobicity profile of the exoh amino acid sequence resembles that of transmembrane proteins. the predicted exol gene product does not contain hydrophobic regions, indicating a cytoplasmic localization. the exok gene product is characteri ... | 1993 | 8479421 |
| transgenic n. glauca plants expressing bacterial virulence gene virf are converted into hosts for nopaline strains of a. tumefaciens. | tumours are induced by agrobacterium tumefaciens on a variety of plants. the virulence determinants of a. tumefaciens reside on a large tumour-inducing (ti) plasmid. this plasmid carries two regions essential for tumour induction, namely the t region and the vir region. during infection the t region is transferred to the plant cell, where it becomes stably integrated in one of the host chromosomes as t-dna. expression of t-dna leads to the production of the plant hormones auxin and cytokinin, as ... | 1993 | 8479538 |
| purification, partial characterization, and subcellular localization of a 38 kilodalton, calcium-regulated protein of rhizobium fredii usda208. | calcium is essential for the growth of rhizobia and the formation of nitrogen-fixing root-nodules on legumes, but its precise role in these processes remains unknown. we have found that rhizobium fredii usda208 accumulates a major 38 kda protein when grown in media supplemented with 0.3-2 microm cacl2. we have purified this protein and raised polyclonal antibodies against it. the protein initially is synthesized as a 40 kda precursor which subsequently undergoes calcium-dependent processing to g ... | 1993 | 8481090 |
| versatile suicide vectors which allow direct selection for gene replacement in gram-negative bacteria. | a set of vector plasmids which greatly facilitate gene replacement and reverse genetics in many gram-negative bacteria was constructed. these vectors are based on the p15a origin of replication (ori) and incorporate sacb from bacillus subtilis, which is inducible by sucrose and is lethal when expressed in gram-negative bacteria. the vectors also have a convenient antibiotic-resistance marker (gentamicin resistance) and the lacz alpha system which allows blue/white selection of cloned fragments. ... | 1993 | 8486283 |
| levels and location of expression of the agrobacterium tumefaciens ptia6 ipt gene promoter in transgenic tobacco. | the location of gene expression of the agrobacterium tumefaciens ipt gene promoter in transgenic tobacco plants was examined using the beta-glucuronidase (gus) reporter gene. expression of gus was detected in every organ and most cell types examined. the highest levels of gus activity were found in roots. to further examine the transcriptional basis of this broad expression pattern, deletions in the 5' non-coding region of the gene were translationally fused to two promoterless reporter genes, e ... | 1993 | 8490124 |
| characterization and symbiotic importance of acidic extracellular polysaccharides of rhizobium sp. strain grh2 isolated from acacia nodules. | rhizobium sp. wild-type strain grh2 was originally isolated from root nodules of the leguminous tree acacia cyanophylla and has a broad host range which includes herbaceous legumes, e.g., trifolium spp. we examined the extracellular exopolysaccharides (epss) produced by strain grh2 and found three independent glycosidic structures: a high-molecular-weight acidic heteropolysaccharide which is very similar to the acidic eps produced by rhizobium leguminosarum biovar trifolii anu843, a low-molecula ... | 1993 | 8491702 |
| cloning, sequencing, and transcriptional analysis of the gene coding for the vegetative sigma factor of agrobacterium tumefaciens. | the siga gene of agrobacterium tumefaciens was cloned and sequenced. comparison with previously analyzed siga genes revealed a high degree of similarity in nucleotide and amino acid sequences of regions two, three, and four of vegetative sigma factors. however, the upstream regulatory region shows no sequence homology with the escherichia coli heat shock (sigma 32) promoters. it also does not contain the hairpin-loop structure (inverted repeat sequence) that was found in the upstream region of t ... | 1993 | 8491721 |
| isolation and characterization of a new chromosomal virulence gene of agrobacterium tumefaciens. | a mutant (strain b119) of agrobacterium tumefaciens with a chromosomal mutation was isolated by transposon (tn5) mutagenesis. the mutant exhibited growth rates on l agar and minimal medium (ab) plates similar to those of the parent strain (strain a208 harboring a nopaline-type ti plasmid). the mutant was avirulent on all host plants tested: daucus carota, cucumis sativus, and kalanchoe diagremontiana. the mutant was not impaired in attachment ability to carrot cells. the mutant had one insertion ... | 1993 | 8491736 |
| phylogenetic analysis of rhizobia and agrobacteria based on 16s rrna gene sequences. | the phylogenetic relationships of members of the genera rhizobium, agrobacterium, bradyrhizobium, and azorhizobium were studied by direct sequencing of their amplified 16s rrna genes. comparative analysis of the sequence data confirmed that the genera bradyrhizobium and azorhizobium belong to distinct phylogenetic lineages. the genera rhizobium and agrobacterium were found to be phylogenetically heterogeneous, and several subgroupings in which rhizobium and agrobacterium species were intermixed ... | 1993 | 8494742 |
| reclassification of american rhizobium leguminosarum biovar phaseoli type i strains as rhizobium etli sp. nov. | a new rhizobium species that nodulates phaseolus vulgaris l. is proposed on the basis of a sequence analysis of 16s ribosomal dna. this taxon, rhizobium etli sp. nov., was previously named rhizobium leguminosarum biovar phaseoli (type i strains) and is characterized by the capacity to establish an effective symbiosis with bean plants, the reiteration of the nitrogenase structural genes, the organization of the common nodulation genes into two separate transcriptional units bearing noda and nodbc ... | 1993 | 8494746 |
| organization of the genes necessary for hydrogenase expression in rhodobacter capsulatus. sequence analysis and identification of two hyp regulatory mutants. | a 25 kbp dna fragment from the chromosome of rhodobacter capsulatus b10 carrying hydrogenase (hup) determinants was completely sequenced. coding regions corresponding to 20 open reading frames were identified. the r. capsulatus hydrogenase-specific gene (hup and hyp) products bear significant structural identity to hydrogenase gene products from escherichia coli (13), from rhizobium leguminosarum (16), from azotobacter vinelandii (10) and from alcaligenes eutrophus (11). the sequential arrangeme ... | 1993 | 8497190 |