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the early nodulin gene srenod2 from sesbania rostrata is inducible by cytokinin.the structure and expression of the early nodulin gene enod2 from the stem-nodulated tropical legume sesbania rostrata (srenod2) was examined. genomic clones carrying the single srenod2locus were isolated and the dna sequence of the gene was determined. the srenod2 gene was found to lack introns and to encode a protein consisting primarily of a 55-fold repeat of short proline-rich oligopeptides. a putative signal sequence, which may be responsible for targeting of the enod2 protein to the cell w ...19921303791
broad host range and promoter selection vectors for bacteria that interact with plants.a plasmid vector, pgv910, and a derived cosmid, prg930, have been constructed. both contain the cole1 and pvs1 origins of replication and are stably maintained in escherichia coli, agrobacterium tumefaciens, and azorhizobium caulinodans ors571. they are compatible with commonly used incp cloning vectors, although pvs1 was classified as an incp plasmid, unable to replicate in e. coli (y. itoh, j.m. watson, d. haas, and t. leisinger, plasmid 11:206-220, 1984). promoter selection vectors were deriv ...19921421510
identification of a new inducible nodulation gene in azorhizobium caulinodans.the narrow host range bacterial strain azorhizobium caulinodans ors571 induces the formation of nitrogen-fixing nodules on the root and stem of the tropical legume sesbania rostrata. here, a new flavonoid-inducible locus of ors571 is described, locus 4. the locus was identified and isolated via the occurrence of particular sequences, the gamma and delta elements. these elements are reiterated in the ors571 genome, linked to symbiotic loci. sequencing of locus 4 showed the presence of an open rea ...19921472718
nucleotide sequence of the fixabc region of azorhizobium caulinodans ors571: similarity of the fixb product with eukaryotic flavoproteins, characterization of fixx, and identification of nifw.the nucleotide sequence of a 4.1 kb dna fragment containing the fixabc region of azorhizobium caulinodans was established. the three gene products were very similar to the corresponding polypeptides of rhizobium meliloti. the c-terminal domains of both fixb products displayed a high degree of similarity with the alpha-subunits of rat and human electron transfer flavoproteins, suggesting a role for the fixb protein in a redox reaction. two open reading frames (orf) were found downstream of fixc. ...19911850088
functional analysis of the sesbania rostrata leghemoglobin glb3 gene 5'-upstream region in transgenic lotus corniculatus and nicotiana tabacum plants.expression of the sesbania rostrata leghemoglobin glb3 gene was analyzed in transgenic lotus corniculatus and tobacco plants harboring chimeric glb3-uida (gus) gene fusions to identify cis-acting elements involved in nodule-specific gene expression and general transcriptional control. a 1.9-kilobase fragment of the glb3 5'-upstream region was found to direct a high level of nodule-specific beta-glucuronidase (gus) activity in l. corniculatus, restricted to the rhizobium-infected cells of the nod ...19902136628
identification and characterization of a functional nodd gene in azorhizobium caulinodans ors571.azorhizobium caulinodans ors571, a bacterium capable of nodulating roots and stems of the tropical legume sesbania rostrata, has been shown to have no nodd-like gene located immediately upstream from its common nodabc locus. a clone carrying a functional nodd gene of strain ors571 has now been isolated from a plafr1 gene library by screening for naringenin-induced expression of the common nod genes in an agrobacterium background. tn5 mutagenesis of the cloned insert dna delimited the inducing ac ...19902158977
regulation of plant genes specifically induced in nitrogen-fixing nodules: role of cis-acting elements and trans-acting factors in leghemoglobin gene expression.transgenic alfalfa plants harboring a gene fusion between the soybean leghemoglobin (lbc3) promoter region and the chloramphenicol acetyl transferase (cat) gene were used to determine the influence of rhizobial mutants on lb gene expression in nodules. the promoter region of the sesbania rostrata glb3 (srglb3) leghemoglobin gene was examined for the presence of conserved motifs homologous to binding site 1 and 2 of the soybean lbc3 promoter region, found to interact with a trans-acting factor pr ...19892491659
common nodabc genes in nod locus 1 of azorhizobium caulinodans: nucleotide sequence and plant-inducible expression.azorhizobium caulinodans strain ors571 induces nitrogen-fixing nodules on roots and stem-located root primordia of sesbania rostrata. two essential nod loci have been previously identified in the bacterial genome, one of which (nod locus 1) shows weak homology with the common nodc gene of rhizobium meliloti. here we present the nucleotide sequence of this region and show that it contains three contiguous open reading frames (orfa, orfb and orfc) that are related to the nodabc genes of rhizobium ...19892615763
characterization of the fixabc region of azorhizobium caulinodans ors571 and identification of a new nitrogen fixation gene.the fast growing strain, azorhizobium caulinodans ors571, isolated from stem nodules of the tropical legume sesbania rostrata, can grow in the free-living state at the expense of molecular nitrogen. five point mutants impaired in nitrogen fixation in the free-living state have been complemented by a plasmid containing the cloned fix-abc region of strain ors571. genetic analysis of the mutants showed that one was impaired in fixc, one in fixa and the three others in a new gene, located upstream f ...19883216855
initial stages in the morphogenesis of nitrogen-fixing stem nodules of sesbania rostrata.morphogenesis of stem nodules in sesbania rostrata was studied over a period of 6 days after inoculation with an appropriate species of rhizobium. nodulation sites were initially slightly raised, circular areas 0.3 to 0.6 mm in diameter and 4 to 5 mm apart in vertical rows along the length of the stem. each site was underlaid by an adventitious root primordium. a site became susceptible to infection by a specific rhizobium sp. when the root primordium broke through the epidermis, leaving a fissu ...19836630154
an azorhizobium caulinodans ors571 locus involved in lipopolysaccharide production and nodule formation on sesbania rostrata stems and roots.azorhizobium caulinodans ors571 is able to nodulate roots and stems of the tropical legume sesbania rostrata. an ors571 tn5 insertion mutant, strain ors571-x15, had a rough colony morphology, was nonmotile, and showed clumping behavior on various media. when this pleiotropic mutant was inoculated on roots or stems of the host, no nodules developed (nod-). compared with the wild type, strain ors571-x15 produced lipopolysaccharides (lps) with an altered ladder pattern on sodium dodecyl sulfate-pol ...19947506708
cloning of an azorhizobium caulinodans endoglucanase gene and analysis of its role in symbiosis.azorhizobium caulinodans ors571, a symbiont of the tropical leguminous plant sesbania rostrata, showed low, constitutive levels of endoglucanase (egl) activity. a clone carrying the gene responsible for this phenotype was isolated via introduction of a genomic library into the wild-type strain and screening for transconjugants with enhanced egl activity. by subcloning and expression in escherichia coli, the egl phenotype was allocated to a 3-kb ecori-bamhi fragment. however, sequence analysis sh ...19957574641
the nodd locus from azorhizobium caulinodans is flanked by two repetitive elements.the sequence surrounding the azorhizobium caulinodans (ac) regulatory nodd gene was analyzed. upstream from nodd and in the opposite orientation, two small open reading frames were identified (orf1 and orf2). the dna sequence corresponding to orf1, termed epsilon 1, is similar to a part of the insertion element is51 from pseudomonas savastanoi. immediately downstream from nodd, a repeated element, delta 1, has been described [goethals et al., mol. plant-microbe interact. 5 (1992) 405-411]. the e ...19957590297
root nodulation of sesbania rostrata.the tropical legume sesbania rostrata can be nodulated by azorhizobium caulinodans on both its stem and its root system. here we investigate in detail the process of root nodulation and show that nodules develop exclusively at the base of secondary roots. intercellular infection leads to the formation of infection pockets, which then give rise to infection threads. concomitantly with infection, cortical cells of the secondary roots dedifferentiate, forming a meristem which has an "open-basket" c ...19948106317
site-specific mutagenesis of the nodule-infected cell expression (nice) element and the at-rich element atre-bs2* of the sesbania rostrata leghemoglobin glb3 promoter.sesbania rostrata leghemoglobin glb3 (srglb3) promoter sequences responsible for expression in infected cells of transgenic lotus corniculatus nodules were delimited to a 78-bp dral-hinfl fragment. this region, which is located between coordinates -194 to -116 relative to the start codon of the srglb3 gene, was named the nodule-infected cell expression (nice) element. insertion of the nice element into the truncated nopaline synthase promoter was found to confer a nodule-specific expression patt ...19948180496
interaction of a rhizobial dna-binding protein with the promoter region of a plant leghemoglobin gene.a nucleotide sequence was identified approximately 650 bp upstream of the sesbania rostrata leghemoglobin gene srglb3 start codon, which interacts specifically with a proteinaceous dna-binding factor found in nodule extracts but not in extracts from leaves or roots. the binding site for this factor was delimited using footprinting techniques. the dna-binding activity of this factor was found to be heat stable, dependent on divalent cations, and derived from the (infecting) azorhizobium caulinoda ...19938278541
azorhizobium caulinodans respires with at least four terminal oxidases.in culture, azorhizobium caulinodans used at least four terminal oxidases, cytochrome aa3 (cytaa3), cytd, cyto, and a second a-type cytochrome, which together mediated general, respiratory electron (e-) transport to o2. to genetically dissect physiological roles for these various terminal oxidases, corresponding azorhizobium apocytochrome genes were cloned, and three cytaa3 mutants, a cytd mutant, and a cytaa3, cytd double mutant were constructed by reverse genetics. these cytochrome oxidase mut ...19948300541
enzyme polymorphism of azorhizobium strains and other stem- and root-nodulating bacteria isolated from sesbania rostrata.relationships between bacterial groups nodulating sesbania rostrata were evaluated through examination of electrophoretic polymorphism of esterases and metabolic enzymes. the following conclusions were drawn: (i) the differentiation of two genomic species within azorhizobium strains and a group of non-identified strains (probably rhizobium) was strongly supported by enzyme electrophoresis; (ii) esterases were more electrophoretically polymorphic than metabolic enzymes, since 35 and 11 electropho ...19938327783
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 ...19938412659
three unusual modifications, a d-arabinosyl, an n-methyl, and a carbamoyl group, are present on the nod factors of azorhizobium caulinodans strain ors571.azorhizobium caulinodans strain ors571 is a symbiont of the tropical legume sesbania rostrata. upon nod gene induction with naringenin, strain ors571 secretes into the culture medium nod factors that morphologically change the host plant--in particular, deformed root hairs (hai/had) and meristematic foci are formed at the basis of lateral roots. the latter infrequently develop further into nodule-like structures. the azorhizobial nod factors are chitin tetramers or pentamers, n-acylated at the n ...19938434016
azorhizobium caulinodans nitrogen fixation (nif/fix) gene regulation: mutagenesis of the nifa -24/-12 promoter element, characterization of a ntra(rpon) gene, and derivation of a model.using site-directed mutagenesis, mutations were introduced in the -24/-12 promoter element of the azorhizobium caulinodans nifa gene, and chimeric nifa-lacz reporter gene fusions were constructed. single base-pair mutations in the conserved -25 or -13 g residues were found to reduce or abolish nifa promoter activity, respectively, demonstrating that the -24/-12 promoter element is important for nifa gene expression and suggesting the involvement of a sigma 54 (ntra/rpon)-type transcription facto ...19938471796
use of differential display to identify novel sesbania rostrata genes enhanced by azorhizobium caulinodans infection.upon infection of the tropical legume sesbania rostrata with azorhizobium caulinodans ors571, nodules are formed on the roots as well as on the stems. stem nodules appear at multiple predetermined sites consisting of dormant root primordia, which are positioned in vertical rows along the stem of the plant. we used the differential display method to isolate and characterize three cdna clones (differential display; didi-2, didi-13, and didi-20), corresponding to genes whose expression is enhanced ...19958664492
differential expression of the sesbania rostrata leghemoglobin glb3 gene promoter in transgenic legume and non-legume plants.the involvement of the sesbania rostrata glb3 gene promoter nice (nodule-infected cell expression) element in root-enhanced expression of 5'-srglb3-uida-3'nos chimeric gene was investigated in transgenic nicotiana tabacum plants. the full-length wild-type srglb3 promoter directed root meristem-enhanced expression in transgenic tobacco plants. the expression pattern of nine selected srglb3 promoter mutations in the nice element was examined in transgenic tobacco plants and compared with the patte ...19968806425
azorhizobium caulinodans uses both cytochrome bd (quinol) and cytochrome cbb3 (cytochrome c) terminal oxidases for symbiotic n2 fixation.azorhizobium caulinodans employs both cytochrome bd (cytbd; quinol oxidase) and cytcbb3 (cytc oxidase) as terminal oxidases in environments with very low o2 concentrations. to investigate physiological roles of these two terminal oxidases both in microaerobic culture and in symbiosis, knockout mutants were constructed. as evidenced by visible absorbance spectra taken from mutant bacteria carrying perfect gene replacements, both the cytbd- and cytcbb3- mutations were null alleles. in aerobic cult ...19968830696
expression of cell cycle genes during sesbania rostrata stem nodule development.upon infection of sesbania rostrata with azorhizobium caulinodans, nodules are formed on roots and stems. stem nodules develop from abundantly distributed dormant root primordia. to acquire more insight into the meristem organization during stem nodule development, the expression patterns of a mitotic b1-type cyclin gene (sesro; cycb1;1), a cyclin-dependent kinase gene (cdc-2-1sr), and a histone h4 gene (h4-1sr) of s. rostrata were followed by in situ hybridization. cdc2-1sr transcripts were fou ...19979100377
characterization of azorhizobium caulinodans glnb and glna genes: involvement of the p(ii) protein in symbiotic nitrogen fixation.the nucleotide sequence and transcriptional organization of azorhizobium caulinodans ors571 glna, the structural gene for glutamine synthetase (gs), and glnb, the structural gene for the p(ii) protein, have been determined. glnb and glna are organized as a single operon transcribed from the same start site, under conditions of both nitrogen limitation and nitrogen excess. this start site may be used by two different promoters since the expression of a glnb-lacz fusion was high in the presence of ...19979171403
germination, growth, and nodulation of sesbania rostrata grown in pb/zn mine tailings/ this study examined the possibility of growth, nodulation, and nitrogen accumulation of sesbania rostrata in pure and amended pb/zn tailings. about 90% of seeds of s. rostrata germinated in pure pb/zn tailings, which contained high concentrations of pb, zn, cu, and cd. although seedling growth suffered from the adverse environment of pb/zn tailings, they became established on tailings stands, in the greenhouse, as well as on the actual tailings dam, and completed their life cycle in 4 months. ...19979175548
nod factors of azorhizobium caulinodans strain ors571 can be glycosylated with an arabinosyl group, a fucosyl group, or both.in addition to the previously described arabinosylated nod factors, azorhizobium caulinodans can also produce fucosylated nod factors and nod factors that are both arabinosylated and fucosylated. the presence of a plasmid carrying extra copies of a subset of nod genes as well as bacterial growth conditions influence the relative proportion of carbamoylated, fucosylated, and arabinosylated nod factors. by using a root hair formation assay, we demonstrate that the nod factor glycosylations are imp ...19979204572
effect of nitrate on nitrogen fixation and nitrate assimilation in azorhizobium-sesbania rostrata symbiotic system.root nodule formation was inhibited by 30% and 50% respectively at low concentration of 1 mm and 2 mm nitrate, while stem nodule formation was enhanced by 50% only at 1 mm nitrate. the nodule specific nitrogenase activity decreased with the increasing concentration of nitrate. at 1 mm nitrate nitrogenase activity per plant stem nodule was not affected, but it was less than 50% in the root nodules as compared to control. increasing concentration of nitrate increased in vivo activity of nitrate re ...19979475064
the symbiotic interaction between azorhizobium caulinodans and sesbania rostrata molecular cross-talk in a beneficial plant-bacterium interaction. 19989594646
patterns of enod40 gene expression in stem-borne nodules of sesbania rostrata.at the base of adventitious root primordia, located on the stem of the tropical legume sesbania rostrata, nitrogen-fixing nodules are formed upon inoculation with the microsymbiont azorhizobium caulinodans. this pattern of nodule development presents features of indeterminate and determinate nodules in early and later stages, respectively. a s. rostrata cdna clone homologous to early nodulin enod40 genes was isolated from a cdna library of developing stem nodules. srenod40-1 contained the conser ...19989620265
srchi13, a novel early nodulin from sesbania rostrata, is related to acidic class iii chitinases.on the tropical legume sesbania rostrata, stem-borne nodules develop after inoculation of adventitious root primordia with the microsymbiont azorhizobium caulinodans. a cdna clone, srchi13, with homology to acidic class iii chitinase genes, corresponds to an early nodulin gene with transiently induced expression during nodule ontogeny. srchi13 transcripts accumulated strongly 2 days after inoculation, decreased from day 7 onward, and disappeared in mature nodules. induction was dependent on nod ...19989634579
poly-beta-hydroxybutyrate turnover in azorhizobium caulinodans is required for growth and affects nifa expression.azorhizobium caulinodans is able to fix nitrogen in the free-living state and in symbiosis with the tropical legume sesbania rostrata. the bacteria accumulate poly-beta-hydroxybutyrate (phb) under both conditions. the structural gene for phb synthase, phbc, was inactivated by insertion of an interposon. the mutant strains obtained were devoid of phb, impaired in their growth properties, totally devoid of nitrogenase activity ex planta (nif-), and affected in nucleotide pools and induced fix- nod ...19989748438
chalcone reductase-homologous transcripts accumulate during development of stem-borne nodules on the tropical legume sesbania rostrata.during a search for genes with induced or enhanced expression in the early stages of development of stem-borne nodules on sesbania rostrata, a cdna with homology to chalcone reductase (chr) genes was isolated. here, we describe the characterization of a full-length chr cdna (srchr1) and the pattern of chr transcript accumulation in stem-borne nodules. expression was correlated with both nodule development and bacterial invasion. in young nodules, chr transcripts were observed in cells of the par ...199910467030
nod factor requirements for efficient stem and root nodulation of the tropical legume sesbania rostrata.azorhizobium caulinodans ors571 synthesizes mainly pentameric nod factors with a household fatty acid, an n-methyl, and a 6-o-carbamoyl group at the nonreducing-terminal residue and with a d-arabinosyl, an l-fucosyl group, or both at the reducing-terminal residue. nodulation on sesbania rostrata was carried out with a set of bacterial mutants that produce well characterized nod factor populations. purified nod factors were tested for their capacity to induce root hair formation and for their sta ...200010821846
knockout of an azorhizobial dtdp-l-rhamnose synthase affects lipopolysaccharide and extracellular polysaccharide production and disables symbiosis with sesbania rostrata.a nonpolar mutation was made in the oac2 gene of azorhizobium caulinodans. oac2 is an ortholog of the salmonella typhimurium rfbd gene that encodes a dtdp-l-rhamnose synthase. the knockout of oac2 changed the lipopolysaccharide (lps) pattern and affected the extracellular polysaccharide production but had no effect on bacterial hydrophobicity. upon hot phenol extraction, the wild-type lps partitioned in the phenol phase. the lps fraction of ors571-oac2 partitioned in the water phase and had a re ...200111437259
azorhizobium caulinodans pyruvate dehydrogenase activity is dispensable for aerobic but required for microaerobic growth.azorhizobium caulinodans mutant 62004 carries a null allele of pdhb, encoding the e1beta subunit of pyruvate dehydrogenase, which converts pyruvate to acetyl-coa. this pdhb mutant completely lacks pyruvate oxidation activities yet grows aerobically on c(4) dicarboxylates (succinate, l-malate) as sole energy source, albeit slowly, and displays pleiotropic growth defects consistent with physiological acetyl-coa limitation. temperature-sensitive (ts), conditional-lethal derivatives of the pdhb muta ...200111496000
a critical evaluation of differential display as a tool to identify genes involved in legume nodulation: looking back and looking forward.screening for differentially expressed genes is a straightforward approach to study the molecular basis of a biological system. in the last 10 years, differential screening technology has evolved rapidly and currently high-throughput tools for genome-wide transcript profiling, such as expressed sequence tags and microarray analysis, are becoming widely available. here, an overview of this (r)evolution is given with emphasis on the differential display method, which for many years has been the pr ...200111522814
srchi24, a chitinase homolog lacking an essential glutamic acid residue for hydrolytic activity, is induced during nodule development on sesbania rostrata.the interaction between the tropical legume sesbania rostrata and the bacterium azorhizobium caulinodans results in the formation of nodules on both stem and roots. stem nodulation was used as a model system to isolate early markers by differential display. one of them, srchi24 is a novel early nodulin whose transcript level increased already 4 h after inoculation. this enhancement depended on nod factor-producing bacteria. srchi24 transcript levels were induced also by exogenous cytokinins. in ...200111553736
patterns of pectin methylesterase transcripts in developing stem nodules of sesbania rostrata.differential display was applied to the early stages of the interaction between the tropical legume sesbania rostrata and its microsymbiont azorhizobium caulinodans ors571. an upregulated clone that is similar to pectin methylesterase-encoding genes was isolated (srpmel). the full-length sequence of srpme1 was used to localize pme transcripts in situ during s. rostrata stem-nodule development. several expression patterns were distinguished, hinting at general roles in vascular tissue development ...200211876427
pmh11, a tool for gene disruption and expression analysis in azorhizobium caulinodans.tools for mutagenesis and expression analyses are needed to study the role of bacterial genes. here, we report the construction of pmh11, a small, mobilizable plasmid that replicates in escherichia coli, but not in azorhizobium caulinodans, a nodulating microsymbiont of sesbania rostrata, and that contains a unique bamhi restriction site upstream of a promoterless lacz gene. pmh11 and two derivatives with the multiple cloning site of pbluescript (ks(ii)) are useful for mutagenesis by gene disrup ...200211982330
nodule-enhanced protease inhibitor gene: emerging patterns of gene expression in nodule development on sesbania rostrata.a novel marker for the early stages of nodulation of sesbania rostrata was found to encode a putative member of the kunitz family of protease inhibitors (srpi1). its expression was enhanced during nodulation, and was not up-regulated by wounding or upon infection with wide host-range pathogens. in situ expression patterns resembled those previously described for functions that may be implicated in delimiting infected nodule tissues from the rest of the plant. thus, srpi1 may be a component of a ...200414676288
structural characterization of extracellular polysaccharides of azorhizobium caulinodans and importance for nodule initiation on sesbania rostrata.during lateral root base nodulation, the microsymbiont azorhizobium caulinodans enters its host plant, sesbania rostrata, via the formation of outer cortical infection pockets, a process that is characterized by a massive production of h(2)o(2). infection threads guide bacteria from infection pockets towards nodule primordia. previously, two mutants were constructed that produce lipopolysaccharides (lpss) similar to one another but different from the wild-type lps, and that are affected in extra ...200415066035
switch from intracellular to intercellular invasion during water stress-tolerant legume nodulation.rhizobia colonize their legume hosts by different modes of entry while initiating symbiotic nitrogen fixation. most legumes are invaded via growing root hairs by the root hair-curl mechanism, which involves epidermal cell responses. however, invasion of a number of tropical legumes happens through fissures at lateral root bases by cortical, intercellular crack entry. in the semiaquatic sesbania rostrata, the bacteria entered via root hair curls under nonflooding conditions. upon flooding, root h ...200415079070
a gfp reporter plasmid to visualize azorhizobium caulinodans during nodulation of sesbania rostrata.compared with other labeling techniques, the use of the green fluorescent protein (gfp) is advantageous to visualize bacteria because observations can be performed in real time. this feature is particularly interesting to study invasion events of rhizobia during nodule development on their legume host plant. to investigate the symbiotic interaction between azorhizobium caulinodans ors571 and sesbania rostrata, we constructed two plasmids, pmp220-hem-gfp5 and pbbr5-hem-gfp5-s65t, that carry a mod ...200415109825
[establishment and growth of lolium multiflorum for phyto-remediation of pb/zn tailings].following the cropping of sesbania rostrata, lolium multiflorum was cropped as the subsequent species on an acidified pb/zn tailings site. as the experimental treatments, s. rostrata issues harvested on the site were removed from the site or buried into the tailings as the green manure. changes of tailings chemical and physical properties, germination, growth and heavy metal accumulation of lolium multiflorum were investigated. the results showed that cropping of s. rostrata improved the chemica ...200415146634
molecular and functional characterization of the azorhizobium caulinodans ors571 hydrogenase gene cluster.in this work, we report the cloning and sequencing of the azorhizobium caulinodans ors571 hydrogenase gene cluster. sequence analysis revealed the presence of 20 open reading frames huptuvhypfhupslcdfghjk hypabhuprhypcdehupe. the physical and genetic organization of a. caulinodans ors571 hydrogenase system suggests a close relatedness to that of rhodobacter capsulatus. in contrast to the latter species, a gene homologous to rhizobium leguminosarum hupe was identified downstream of the hyp operon ...200415321689
lipopolysaccharides as a communication signal for progression of legume endosymbiosis.establishment of a successful symbiosis between rhizobia and legumes results from an elaborate molecular dialogue between both partners. bacterial nodulation (nod) factors are indispensable for initiating plant responses, whereas bacterial surface polysaccharides are important for infection progression and nodule development. the mutant ors571-oac2 of azorhizobium caulinodans, affected in its surface polysaccharides, provokes a defective interaction with its host sesbania rostrata. ors571-oac2 i ...200515699329
gibberellins are involved in nodulation of sesbania rostrata.upon submergence, azorhizobium caulinodans infects the semiaquatic legume sesbania rostrata via the intercellular crack entry process, resulting in lateral root-based nodules. a gene encoding a gibberellin (ga) 20-oxidase, srga20ox1, involved in ga biosynthesis, was transiently up-regulated during lateral root base nodulation. two srga20ox1 expression patterns were identified, one related to intercellular infection and a second observed in nodule meristem descendants. the infection-related expre ...200516258018
responses of azorhizobium caulinodans to cadmium stress.the symbiosis of azorhizobium caulinodans and an annul legume sesbania rostrata was recently found to be tolerant to cadmium pollution by an unknown mechanism. in this study, a. caulinodans ors571 and zy-20 showed much stronger tolerance to cadmium than a mutant ors571-x15 and a common rhizobium sp., with minimum inhibitory concentration values as high as 4 and 5 mm (versus 1 and 0.1 mm) on yeast extract mannitol agar medium, respectively. although cd uptake by all three strains of a. caulinodan ...200516332342
free-living rhizobium strain able to grow on n(2) as the sole nitrogen source.a rhizobium strain isolated from stem nodules of the legume sesbania rostrata was shown to grow on atmospheric nitrogen (n(2)) as the sole nitrogen source. non-n(2)-fixing mutants isolated directly on agar plates formed nodules that did not fix n(2) when inoculated into the host plant.198316346220
stem and root nodulation in aeschynomene spp.nodulation ability of 15 rhizobium strains isolated from root and stem nodules of tropical aeschynomene species was studied on 20 different aeschynomene species and four other legumes-arachis hypogaea, stylosanthes guianensis, macroptilium atropurpureum, and sesbania rostrata. the results of this investigation showed that aeschynomene species could be divided into three groups according to the cross-inoculation group concept.198516346895
survival of azorhizobium caulinodans in the soil and rhizosphere of wetland rice under sesbania rostrata-rice rotation.the survival of indigenous and introduced strains of azorhizobium caulinodans in flooded soil and in the rice rhizosphere, where in situ sesbania rostrata was incorporated before the rice crop, is reported. the azorhizobia studied were both root and stem nodulating. in a pot experiment, two crop cycles each of inoculated and noninoculated sesbania-rice were compared with two crop cycles of flooded fallow-rice. in a field experiment, the effect of repeated incorporation of in situ s. rostrata in ...198916347853
epiphytic occurrence of azorhizobium caulinodans and other rhizobia on host and nonhost legumes.a large population of azorhizobium caulinodans was present on sesbania rostrata; up to 5 x 10 cm were found on leaves and fewer were found on flowers. although a. caulinodans was also present on the leaves of sesbania aculeata (nonhost), the populations were much smaller than that observed on s. rostrata. the population of s. aculeata rhizobia on host leaves was less than 30 cm, and their presence on host flowers was sporadic. aeschynomene afraspera and aeschynomene aspera rhizobia, which are pr ...198916348019
genetic analysis of nitrogen fixation in a tropical fast-growing rhizobium.the rhizobium strain ors571, which is associated with the tropical legume sesbania rostrata, has the property of growing in the free-living state at the expense of ammonia or n(2) as sole nitrogen source. five mutants, isolated as unable to form colonies on plates under conditions of nitrogen fixation, were studied. all of them, which appear as fixin planta, are nif mutants. with mutant 5740, nitrogenase activity of the crude extract was restored by addition of pure mo-fe protein of klebsiella p ...198216453420
the sesbania root symbionts sinorhizobium saheli and s. teranga bv. sesbaniae can form stem nodules on sesbania rostrata, although they are less adapted to stem nodulation than azorhizobium caulinodans.sesbania species can establish symbiotic interactions with rhizobia from two taxonomically distant genera, including the sesbania rostrata stem-nodulating azorhizobium sp. and azorhizobium caulinodans and the newly described sinorhizobium saheli and sinorhizobium teranga bv. sesbaniae, isolated from the roots of various sesbania species. a collection of strains from both groups were analyzed for their symbiotic properties with different sesbania species. s. saheli and s. teranga bv. sesbaniae st ...199716535538
intercellular colonization and growth promoting effects of methylobacterium sp. with plant-growth regulators on rice (oryza sativa l. cv co-43).the methylobacterium sp. strain npfm-sb3, isolated from sesbania rostrata stem nodules possessed nitrogenase activity and noda genes. pure culture of npfm-sb3 strain produced indole-3-acetic acid, cytokinins and on inoculation to rice plants resulted in numerous lateral roots. inoculation of synthetic auxins 2,4-dichlorophenoxy acetic acid, naphthalene acetic acid or flavonoids naringenin and dihydroxy-4-methoxyisoflavone individually or to bacterial inoculated rice seedlings improved the plant ...200917207982
nod factor perception during infection thread growth fine-tunes nodulation.bacterial nodulation factors (nfs) are essential signaling molecules for the initiation of a nitrogen-fixing symbiosis in legumes. nfs are perceived by the plant and trigger both local and distant responses, such as curling of root hairs and cortical cell divisions. in addition to their requirement at the start, nfs are produced by bacteria that reside within infection threads. to analyze the role of nfs at later infection stages, several phases of nodulation were studied by detailed light and e ...200717313164
a symbiotic plant peroxidase involved in bacterial invasion of the tropical legume sesbania rostrata.aquatic nodulation on the tropical legume sesbania rostrata occurs at lateral root bases via intercellular crack-entry invasion. a gene was identified (srprx1) that is transiently up-regulated during the nodulation process and codes for a functional class iii plant peroxidase. the expression strictly depended on bacterial nodulation factors (nfs) and could be modulated by hydrogen peroxide, a downstream signal for crack-entry invasion. expression was not induced after wounding or pathogen attack ...200717384158
comparative transcriptome analysis reveals common and specific tags for root hair and crack-entry invasion in sesbania rostrata.the tropical legume sesbania rostrata provides its microsymbiont azorhizobium caulinodans with versatile invasion strategies to allow nodule formation in temporarily flooded habitats. in aerated soils, the bacteria enter via the root hair curling mechanism. submergence prevents this epidermal invasion by accumulation of inhibiting concentrations of ethylene and, under these conditions, the bacterial colonization occurs via intercellular cortical infection at lateral root bases. the transcriptome ...200717600136
rhizobial factors required for stem nodule maturation and maintenance in sesbania rostrata-azorhizobium caulinodans ors571 symbiosis.the molecular and physiological mechanisms behind the maturation and maintenance of n(2)-fixing nodules during development of symbiosis between rhizobia and legumes still remain unclear, although the early events of symbiosis are relatively well understood. azorhizobium caulinodans ors571 is a microsymbiont of the tropical legume sesbania rostrata, forming n(2)-fixing nodules not only on the roots but also on the stems. in this study, 10,080 transposon-inserted mutants of a. caulinodans ors571 w ...200717720818
3-hydroxy-3-methylglutaryl coenzyme a reductase 1 interacts with nork and is crucial for nodulation in medicago truncatula.nork in legumes encodes a receptor-like kinase that is required for nod factor signaling and root nodule development. using medicago truncatula nork as bait in a yeast two-hybrid assay, we identified 3-hydroxy-3-methylglutaryl coa reductase 1 (mt hmgr1) as a nork interacting partner. hmgr1 belongs to a multigene family in m. truncatula, and different hmgr isoforms are key enzymes in the mevalonate biosynthetic pathway leading to the production of a diverse array of isoprenoid compounds. testing ...200718156218
functional nodfe genes are present in sinorhizobium sp. strain mus10, a symbiont of the tropical legume sesbania rostrata.we have cloned the nodfe operon from sinorhizobium sp. strain mus10. mus10 nodf shows sequence homology to acyl carrier protein and enables an s. meliloti nodf mutant to effectively nodulate alfalfa. our results demonstrate the occurrence of nodfe in a symbiont that nodulates a legume host not belonging to the galegoid group.200818326678
the genome of the versatile nitrogen fixer azorhizobium caulinodans ors571.biological nitrogen fixation is a prokaryotic process that plays an essential role in the global nitrogen cycle. azorhizobium caulinodans ors571 has the dual capacity to fix nitrogen both as free-living organism and in a symbiotic interaction with sesbania rostrata. the host is a fast-growing, submergence-tolerant tropical legume on which a. caulinodans can efficiently induce nodule formation on the root system and on adventitious rootlets located on the stem.200818522759
an outer membrane autotransporter, aoaa, of azorhizobium caulinodans is required for sustaining high n2-fixing activity of stem nodules.in this study, we investigated the function of a putative high-molecular-weight outer membrane protein, azorhizobial outer membrane autotransporter a (aoaa), of azorhizobium caulinodans ors571. sequence analysis revealed that aoaa was an autotransporter protein belonging to the type v protein secretion system. azorhizobium caulinodans forms n(2)-fixing nodules on the stems and roots of sesbania rostrata. the sizes of stem nodules formed by an aoaa mutant having transposon insertion within this o ...200818557786
calcium spiking patterns and the role of the calcium/calmodulin-dependent kinase ccamk in lateral root base nodulation of sesbania rostrata.nodulation factor (nf) signal transduction in the legume-rhizobium symbiosis involves calcium oscillations that are instrumental in eliciting nodulation. to date, ca2+ spiking has been studied exclusively in the intracellular bacterial invasion of growing root hairs in zone i. this mechanism is not the only one by which rhizobia gain entry into their hosts; the tropical legume sesbania rostrata can be invaded intercellularly by rhizobia at cracks caused by lateral root emergence, and this proces ...200919470588
comparative genome-wide transcriptional profiling of azorhizobium caulinodans ors571 grown under free-living and symbiotic conditions.the whole-genome sequence of the endosymbiotic bacterium azorhizobium caulinodans ors571, which forms nitrogen-fixing nodules on the stems and roots of sesbania rostrata, was recently determined. the sizes of the genome and symbiosis island are 5.4 mb and 86.7 kb, respectively, and these sizes are the smallest among the sequenced rhizobia. in the present study, a whole-genome microarray of a. caulinodans was constructed, and transcriptomic analyses were performed on free-living cells grown in ri ...200919542345
enhanced adaptability of sesbania rostrata to pb/zn tailings via stem nodulation.sesbania rostrata is wellknown for its stem nodulation, but the roles of stem nodulation in root nodulation and adaptation of s. rostrata to pb/zn-enriched tailings environment has been poorly understood. we investigated the effects of inoculating (with stem nodule treatment) and non-inoculating (without stem nodule treatment) azorhizobium caulinodans on the growth, root nodulation, and n fixation of s. rostrata grown on three different types of soil substrata: pb/zn tailings, garden soil amende ...200919862929
characterization of the sesbania rostrata phytochelatin synthase gene: alternative splicing and function of four isoforms.phytochelatins (pcs) play an important role in detoxification of heavy metals in plants. pcs are synthesized from glutathione by phytochelatin synthase (pcs), a dipeptidyltransferase. sesbania rostrata is a tropical legume plant that can tolerate high concentrations of cd and zn. in this study, the s. rostrata pcs gene (srpcs) and cdnas were isolated and characterized. southern blot and sequence analysis revealed that a single copy of the srpcs gene occurs in the s. rostrata genome, and produces ...200920111680
phrr-like gene prar of azorhizobium caulinodans ors571 is essential for symbiosis with sesbania rostrata and is involved in expression of reb genes.this study focuses on the function of the gene prar that encodes a putative transcription factor in azorhizobium caulinodans ors571, a microsymbiont of sesbania rostrata. the prar gene is a homolog of the phrr gene of sinorhizobium medicae wsm419, and the prar and phrr homologs are distributed throughout the class alphaproteobacteria. the growth and nitrogen fixation activity of an a. caulinodans prar deletion mutant in the free-living state were not significantly different from those of the wil ...201020382809
symbiotic legume nodules employ both rhizobial exo- and endo-hydrogenases to recycle hydrogen produced by nitrogen fixation.in symbiotic legume nodules, endosymbiotic rhizobia (bacteroids) fix atmospheric n(2), an atp-dependent catalytic process yielding stoichiometric ammonium and hydrogen gas (h(2)). while in most legume nodules this h(2) is quantitatively evolved, which loss drains metabolic energy, certain bacteroid strains employ uptake hydrogenase activity and thus evolve little or no h(2). rather, endogenous h(2) is efficiently respired at the expense of o(2), driving oxidative phosphorylation, recouping atp u ...201020838423
azorhirobial chromosome partition gene (para) is involved in the onset of bacteroid differentiation in sesbania rostrata stem-nodule development.a para gene in-frame deletion mutant of azorhizobium caulinodans ors571 (ors571-δpara) was constructed to evaluate the roles of the chromosome partitioning gene on various bacterial traits and on the development of stem-positioned nodules. the δpara mutant showed a pleiomorphic cell shape phenotype, and was polyploidy with differences in nucleoid sizes due to dramatic defects in chromosome partitioning. upon inoculating the δpara mutant onto the stem of sesbania rostrata, three types of immature ...201121571889
variations in outer-membrane characteristics of two stem-nodulating bacteria of sesbania rostrata and its role in tolerance towards diverse stress.outer-membrane characteristics may determine the survivability of rhizobia under diverse abiotic and biotic stresses. therefore, the role of lipopolysaccharides (lps) and membrane proteins of two stem-nodulating bacteria of sesbania rostrata (azorhizobium caulinodans ors571 and rhizobium sp. we7) in determining tolerance towards abiotic and biotic stresses (hydrophobics and phages) was investigated. outer-membrane characteristics (lps and membrane-protein profiles) of ors571, we7 and thirteen st ...201121573832
respiratory membrane endo-hydrogenase activity in the microaerophile azorhizobium caulinodans is bidirectional.the microaerophilic bacterium azorhizobium caulinodans, when fixing n(2) both in pure cultures held at 20 µm dissolved o(2) tension and as endosymbiont of sesbania rostrata legume nodules, employs a novel, respiratory-membrane endo-hydrogenase to oxidize and recycle endogenous h(2) produced by soluble mo-dinitrogenase activity at the expense of o(2).201222662125
the sinorhizobium meliloti ntrx gene is involved in succinoglycan production, motility, and symbiotic nodulation on alfalfa.rhizobia establish a symbiotic relationship with their host legumes to induce the formation of nitrogen-fixing nodules. this process is regulated by many rhizobium regulators, including some two-component regulatory systems (tcss). ntry/ntrx, a tcs that was first identified in azorhizobium caulinodans, is required for free-living nitrogen metabolism and symbiotic nodulation on sesbania rostrata. however, its functions in a typical rhizobium such as sinorhizobium meliloti remain unclear. here we ...201324038694
a chemotaxis receptor modulates nodulation during the azorhizobium caulinodans-sesbania rostrata symbiosis.azorhizobium caulinodans ors571 is a free-living nitrogen-fixing bacterium which can induce nitrogen-fixing nodules both on the root and the stem of its legume host sesbania rostrata this bacterium, which is an obligate aerobe that moves by means of a polar flagellum, possesses a single chemotaxis signal transduction pathway. the objective of this work was to examine the role that chemotaxis and aerotaxis play in the lifestyle of the bacterium in free-living and symbiotic conditions. in bacteria ...201626994081
ethylene-mediated phenotypic plasticity in root nodule development on sesbania rostrata.leguminous plants in symbiosis with rhizobia form either indeterminate nodules with a persistent meristem or determinate nodules with a transient meristematic region. sesbania rostrata was thought to possess determinate stem and root nodules. however, the nature of nodule development is hybrid, and the early stages resemble those of indeterminate nodules. here we show that, depending on the environmental conditions, mature root nodules can be of the indeterminate type. in situ hybridizations wit ...19989770553
reactive oxygen species and ethylene play a positive role in lateral root base nodulation of a semiaquatic legume.lateral root base nodulation on the tropical, semiaquatic legume sesbania rostrata results from two coordinated, nod factor-dependent processes: formation of intercellular infection pockets and induction of cell division. infection pocket formation is associated with cell death and production of hydrogen peroxide. pharmacological experiments showed that ethylene and reactive oxygen species mediate nod factor responses and are required for nodule initiation, whereby induction of division and infe ...200312975522
srsymrk, a plant receptor essential for symbiosome formation.the symbiosis between legumes and rhizobia is essential for the nitrogen input into the life cycle on our planet. new root organs, the nodules, are established, which house n2-fixing bacteria internalized into the host cell cytoplasm as horizontally acquired organelles, the symbiosomes. the interaction is initiated by bacterial invasion via epidermal root hair curling and cell division in the cortex, both triggered by bacterial nodulation factors. of the several genes involved in nodule initiati ...200516006516
lon protease of azorhizobium caulinodans ors571 is required for suppression of reb gene expression.bacterial lon proteases play important roles in a variety of biological processes in addition to housekeeping functions. in this study, we focused on the lon protease of azorhizobium caulinodans, which can fix nitrogen both during free-living growth and in stem nodules of the legume sesbania rostrata. the nitrogen fixation activity of an a. caulinodans lon mutant in the free-living state was not significantly different from that of the wild-type strain. however, the stem nodules formed by the lo ...201222752172
nad(p)+-malic enzyme mutants of sinorhizobium sp. strain ngr234, but not azorhizobium caulinodans ors571, maintain symbiotic n2 fixation capabilities.c(4)-dicarboxylic acids appear to be metabolized via the tricarboxylic acid (tca) cycle in n(2)-fixing bacteria (bacteroids) within legume nodules. in sinorhizobium meliloti bacteroids from alfalfa, nad(+)-malic enzyme (dme) is required for n(2) fixation, and this activity is thought to be required for the anaplerotic synthesis of pyruvate. in contrast, in the pea symbiont rhizobium leguminosarum, pyruvate synthesis occurs via either dme or a pathway catalyzed by phosphoenolpyruvate carboxykinas ...201222307295
blue light does not inhibit nodulation in sesbania rostrata.earlier, we reported that root nodulation was inhibited by blue light irradiation of lotus japonicus. because some legumes do not establish nodules exclusively on underground roots, we investigated whether nodule formation in sesbania rostrata, which forms both root and "stem" nodules following inoculation with azorhizobium caulinodans, is inhibited by blue light as are l. japonicus nodules. we found that neither s. rostrata nodulation nor nitrogen fixation was inhibited by blue light exposure. ...201727935414
migration of endophytic diazotroph azorhizobium caulinodans ors571 inside wheat (triticum aestivum l) and its effect on micrornas.azorhizobium caulinodans ors571, a novel rhizobium, forms endosymbionts with its nature host sesbania rostrata, a semi-aquatic leguminous tree. recent studies showed that a. caulinodans ors571, as endophytic rhizobium, disseminated and colonized inside of cereal plants. however, how this rhizobium infects monocot plants and the regulatory mechanism remains unknown. micrornas (mirnas) are small, endogenous rnas that regulate gene expression at the post-transcriptional levels. in this study, we em ...201627858182
plant nodulation inducers enhance horizontal gene transfer of azorhizobium caulinodans symbiosis island.horizontal gene transfer (hgt) of genomic islands is a driving force of bacterial evolution. many pathogens and symbionts use this mechanism to spread mobile genetic elements that carry genes important for interaction with their eukaryotic hosts. however, the role of the host in this process remains unclear. here, we show that plant compounds inducing the nodulation process in the rhizobium-legume mutualistic symbiosis also enhance the transfer of symbiosis islands. we demonstrate that the symbi ...201627849579
effects of alteration in lps structure in azorhizobium caulinodans on nodule development.the lipopolysaccharide (lps) of azorhizobium caulinodans ors571, which forms n2-fixing nodules on the stems and roots of sesbania rostrata, is known to be a positive signal required for the progression of nodule formation. in this study, four a. caulinodans mutants producing a variety of defective lpss were compared. the lpss of the mutants having tn5 insertion in the rfaf, rfad, and rfae genes were more truncated than the modified lpss of the oac2 mutants. however, the nodule formation by the r ...201526782655
structure of lipid a from a stem-nodulating bacterium azorhizobium caulinodans.the structure of the lipid a of the lipopolysaccharide (lps) from azorhizobium caulinodans, a symbiont of the tropical legume sesbania rostrata, was investigated by chemical compositional analyses, mass spectrometry, as well as 1d and 2d nmr spectroscopy techniques. the lipid a backbone was composed of a β-(1→6)-linked 2,3-diamino-2,3-dideoxy-d-glucopyranose (glcpn3n) disaccharide and α-d-glucuronic acid (glcpa). nuclear magnetic resonance spectroscopy revealed that the glcpa was connected to th ...201222456102
plant gene expression during effective and ineffective nodule development of the tropical stem-nodulated legume sesbania rostrata.the expression of plant genes during symbiosis of sesbania rostrata with rhizobium sp. and azorhizobium caulinodans was studied by comparing two-dimensional page patterns of in vitro translation products of poly(a)(+) rna from uninfected roots and stems with that of root and stem nodules. both types of nodules are essentially similar, particularly when stem nodules are formed in the dark. we detected the specific expression of at least 16 genes in stem and root nodules and observed the stimulate ...198824277625
restoration of sodic soils involving chemical and biological amendments and phytoremediation by eucalyptus camaldulensis in a semiarid region.salt-affected soils in semiarid regions impede the agricultural productivity and degrade the ecosystem health. in south india, several hectares of land are salt-affected, where the evapotranspiration exceeds the annual precipitation. this study is an attempt to ameliorate sodic soils, by an experiment involving chemical treatment (addition of gypsum), organic amendments (decomposed bagasse pith and green manuring with sesbania rostrata) and phytoremediation by plantation of eucalyptus camaldulen ...201525547478
molecular characterisation of ltchi7, a gene encoding a class iii endochitinase induced by drought stress in lotus spp.chitinases are enzymes that digest chitin molecules, present principally in insects and fungi. in plants, these enzymes play an important role in defence against pathogen attack, although they have also been described as induced by mechanical damage, ozone, heavy metals, cold, salinity, etc. using an annealing control primer, we isolated a gene fragment whose translated sequence has high homology with a class iii endochitinase. the gene, named ltchi7, consisted of one orf of 1005 bp, which codes ...201121143727
primary structure and promoter analysis of leghemoglobin genes of the stem-nodulated tropical legume sesbania rostrata: conserved coding sequences, cis-elements and trans-acting factors.the primary structure of a leghemoglobin (lb) gene from the stem-nodulated, tropical legume sesbania rostrata and two lb gene promoter regions was analysed. the s. rostrata lb gene structure and lb amino acid composition were found to be highly conserved with previously described lb genes and lb proteins. distinct dna elements were identified in the s. rostrata lb promoter regions, which share a high degree of homology with cis-active regulatory elements found in the soybean (glycine max) lbc3 p ...19883237206
diffusion of gases through plant tissues : entry of acetylene into legume nodules.i have measured acetylene diffusion through plant tissues including nodules from several species of legume-vetch, peas, soybeans, and sesbania rostrata. the observed half-time for reequilibration of internal and external concentration is less than 1 minute for typical nodules. inward diffusion of acetylene in air is rapid relative to the use of acetylene by nitrogenase so that diffusion of acetylene would not be a significant limiting factor for nitrogenase activity in air. however, under an atm ...198416663958
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