<i>Azorhizobium caulinodans</i> ORS571 Colonizes the Xylem of <i>Arabidopsis thaliana</i>

Stone, Philip J.; O’Callaghan, K. J.; Davey, M. R.; Cocking, E. C.

doi:10.1094/mpmi.2001.14.1.93

Cited by 26 publications

(18 citation statements)

References 29 publications

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“…trifolii strain in the aforementioned study was isolated from soils in Egypt where rice has been rotated with berseem clover since antiquity. Our results on Arabidopsis also differ from those of Stone et al . (2001), who reported internal colonization of non‐legume roots.…”

Section: Resultscontrasting

confidence: 99%

“…(2001), who reported internal colonization of non‐legume roots. We did not detect GFP fluorescence inside any of the Arabidopsis roots inoculated with Rlv, using either light or confocal microscopy whereas Stone et al . (2001) performed their studies with A. caulinodans ORS571, which invades its host as well as non‐host roots by ‘crack entry’.…”

Section: Resultscontrasting

confidence: 76%

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A feeling for the micro-organism: structure on a small scale. Biofilms on plant roots

Fujishige

Kapadia

Hirsch

2006

Botanical Journal of the Linnean Society

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Biofilms are structured communities of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface; they have clinical, industrial and environmental impacts. Biofilms that are established by bacteria on plants are found on the surfaces of roots, leaves, seeds and internal vascular tissues where the microbes live in commensal, mutualistic or parasitic/pathogenic associations with their host. The study of the structure of plant-associated biofilms has been considerably helped by the development of techniques using fluorescent markers coupled with confocal scanning laser microscopy as well as scanning electron microscopy. We review several of these techniques as well as some of the research that has dealt with plant-associated biofilms. Our investigations focus on biofilm formation in the early stages of the Rhizobium -legume symbiosis, in which Gram-negative rhizobia provide fixed nitrogen to a host legume, and in return, the legume provides carbon-containing molecules. Because root colonization is an important early step in the establishment of the nitrogen-fixing symbiosis, we looked at Sinorhizobium meliloti attachment and biofilm establishment on the roots of its legume hosts, Medicago sativa L. and Melilotus alba Desr. We also examined biofilm formation by Rhizobium leguminosarum bv. viciae on the roots of Arabidopsis thaliana (L.) Heynh., a non-legume and non-host. Our ultimate goal is to characterize the rhizobial genes involved in aggregation and attachment to roots because several of these appear to be shared in biofilm formation and rhizobial entry of legume root cells.

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Section: Resultscontrasting

confidence: 99%

Section: Resultscontrasting

confidence: 76%

A feeling for the micro-organism: structure on a small scale. Biofilms on plant roots

Fujishige

Kapadia

Hirsch

2006

Botanical Journal of the Linnean Society

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“…Only gfp-tagged Azorhizobium caulinodans ORS571 was recovered from within surface-sterilized leaves (10 3.26 CFU/gfw) at 15 dpi, indicating that this test strain of rhizobia was efficient in endophytic ascending migration within rice, a finding consistent with its ability to infect other nonlegume plants (33). The second plating experiment conducted at 15 dpi indicated that a higher inoculum (10 8 cells/plant) of S. meliloti 1021 could compensate for its slower rate of endophytic ascending migration into rice leaf sheaths and leaves.…”

Section: Methodsmentioning

confidence: 61%

Ascending Migration of Endophytic Rhizobia, from Roots to Leaves, inside Rice Plants and Assessment of Benefits to Rice Growth Physiology

Chen

Shen

Cheng

et al. 2005

Appl Environ Microbiol

443

231

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Rhizobia, the root-nodule endosymbionts of leguminous plants, also form natural endophytic associations with roots of important cereal plants. Despite its widespread occurrence, much remains unknown about colonization of cereals by rhizobia. We examined the infection, dissemination, and colonization of healthy rice plant tissues by four species of gfp-tagged rhizobia and their influence on the growth physiology of rice. The results indicated a dynamic infection process beginning with surface colonization of the rhizoplane (especially at lateral root emergence), followed by endophytic colonization within roots, and then ascending endophytic migration into the stem base, leaf sheath, and leaves where they developed high populations. In situ CMEIAS image analysis indicated local endophytic population densities reaching as high as 9 ؋ 10 10 rhizobia per cm 3 of infected host tissues, whereas plating experiments indicated rapid, transient or persistent growth depending on the rhizobial strain and rice tissue examined. Rice plants inoculated with certain test strains of gfp-tagged rhizobia produced significantly higher root and shoot biomass; increased their photosynthetic rate, stomatal conductance, transpiration velocity, water utilization efficiency, and flag leaf area (considered to possess the highest photosynthetic activity); and accumulated higher levels of indoleacetic acid and gibberellin growthregulating phytohormones. Considered collectively, the results indicate that this endophytic plant-bacterium association is far more inclusive, invasive, and dynamic than previously thought, including dissemination in both below-ground and above-ground tissues and enhancement of growth physiology by several rhizobial species, therefore heightening its interest and potential value as a biofertilizer strategy for sustainable agriculture to produce the world's most important cereal crops.

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“…Furthermore, the expression patterns of genes involved in EPS biosynthesis indicate that EPS has an extra function in stem nodules. In addition, A. caulinodans has some distinctive features among the rhizobia: the ability to induce stem nodules after crack-entry infection; the ability to fix nitrogen both in the symbiotic and free-living states even at relatively high concentrations of dissolved oxygen (up to 12 M) (12); and the ability to colonize the xylem of wheat, rice, tomato, and Arabidopsis plants (11,28,29,66,75,76). These traits of A. caulinodans make this bacterium one of the most qualified candidates for the application of rhizobia to form nitrogen-fixing nodules on plants other than legumes.…”

Section: Resultsmentioning

confidence: 99%

Comparative Genome-Wide Transcriptional Profiling of Azorhizobium caulinodans ORS571 Grown under Free-Living and Symbiotic Conditions

Tsukada

Aono

Akiba

et al. 2009

Appl Environ Microbiol

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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 rich and minimal media and in bacteroids isolated from stem nodules. Transcriptional profiling showed that the genes involved in sulfur uptake and metabolism, acetone metabolism, and the biosynthesis of exopolysaccharide were highly expressed in bacteroids compared to the expression levels in free-living cells. Some mutants having Tn5 transposons within these genes with increased expression were obtained as nodule-deficient mutants in our previous study. A transcriptomic analysis was also performed on free-living cells grown in minimal medium supplemented with a flavonoid, naringenin, which is one of the most efficient inducers of A. caulinodans nod genes. Only 18 genes exhibited increased expression by the addition of naringenin, suggesting that the regulatory mechanism responding to the flavonoid could be simple in A. caulinodans. The combination of our genome-wide transcriptional profiling and our previous genome-wide mutagenesis study has revealed new aspects of nodule formation and maintenance.The symbiosis between rhizobia and legumes results in the formation of nitrogen-fixing nodules. The symbiotic interaction begins with the induction of bacterial nod genes by flavonoids secreted from the plant roots (8). The nod genes encode proteins that synthesize the nodulation (Nod) factor, which initiates many developmental changes, such as root hair curling and root cell division required for the formation of the nodule primordium in the host plant early during the nodulation process (8,24,50). Bacteria are entrapped in the curled root hair and subsequently infect the root hair through infection threads made of the plant cell wall. Upon release from the infection threads, bacteria invade the plant cell cytoplasm, where they differentiate into bacteroids and provide ammonium to the host plant by reducing atmospheric dinitrogen in exchange for carbon and amino acid compounds (16,49,53). It has been deduced that multiple stages exist in the establishment of nitrogen-fixing symbiosis. To identify novel genes involved in various stages of symbiosis, transcriptomic studies based on complete genome sequences were performed using Sinorhizobium (1, 2, 5, 9), Mesorhizobium (71), and Bradyrhizobium (10,42,54).Azorhizobium caulinodans ORS571 is a microsymbiont of Sesbania rostrata (18)(19)(20). Nitrogen-fixing nodules are formed by A. caulinodans on the stems as well as on the roots of S. rostrata. Stem nodules occur at the site of adventitious root primordia located on the stems after crack-entry invasion by A. caulinodans (70). During...

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Azorhizobium caulinodans ORS571 Colonizes the Xylem of Arabidopsis thaliana

Cited by 26 publications

References 29 publications

A feeling for the micro-organism: structure on a small scale. Biofilms on plant roots

A feeling for the micro-organism: structure on a small scale. Biofilms on plant roots

Ascending Migration of Endophytic Rhizobia, from Roots to Leaves, inside Rice Plants and Assessment of Benefits to Rice Growth Physiology

Comparative Genome-Wide Transcriptional Profiling of Azorhizobium caulinodans ORS571 Grown under Free-Living and Symbiotic Conditions

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