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  • symbiosis  (3)
  • nodD3  (2)
  • Agrobacterium  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Production of root hair deformation factors by Rhizobium meliloti nodulation genes in Escherichia coli: HsnD (NodH) is involved in the plant host-specific modification of the NodABC factor (1989)
    Springer
    Plant molecular biology 13 (1989), S. 1-12 
    Details
    ISSN: 1573-5028
    Keywords: host recognition ; hsnD (nodH) ; nod genes ; Rhizobium ; root hair deformation ; symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of the hsnD (nodH) gene in the determination of the host-specific nodulation ability of Rhizobium meliloti was studied by expressing the common nodulation genes (nodABC) with or without the hsnD gene in Escherichia coli and testing for biological activity on various leguminous plants. In this way, four categories of plants were established. Upon infection with E. coli carrying the nodABC construct, root hair deformation (Had) was detected on clovers while the hsnD gene was additionally needed for the elicitation of the same response on alfalfa and sweet clover. A weak root hair deformation was seen on siratro by inoculation with E. coli harbouring the nodABC genes and was highly increased when hsnD was also introduced. Cowpea and Desmodium did not respond to any of the E. coli strains constructed. Exudates or cytosolicfractions of the respective E. coli derivatives elicited the same root hair deformation as the intact bacteria. These data indicate that not only the nodABC gene products but also the hsnD product are involved in the synthesis of Had factors. Subclones expressing only the nodA, nodB, or nodC genes or the same genes in pairs (nodAB, nodBC, nodAC) did not provide a compound with activity comparable to the NodABC factor, suggesting that all three genes are required for the production of the Had factor which is active on clover. Coinoculation of alfalfa plants with two strains of E. coli, one carrying the nodABC genes and the other expressing only hsnD, or combining exudates or cytosolic fractions from these strains did not result in root hair deformation on alfalfa. These data indicate that the HsnD protein itself or its product is not an additional alfalfa-specific extracellular signal but more likely is enzymatically involved in the modification of the basic compound determined by the nodABC genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027330
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular characterization and expression of alfalfa (Medicago sativa L.) flavanone-3-hydroxylase and dihydroflavonol-4-reductase encoding genes (1995)
    Springer
    Plant molecular biology 29 (1995), S. 773-786 
    Details
    ISSN: 1573-5028
    Keywords: Key words ; alfalfa ; chalcone synthase ; dihydroflavonol-4 reductase ; flavanone-3 hydroxylase ; flavonoid ; symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Flavonoids are plant phenolic compounds involved in leguminous plant-microbe interactions. Genes implied in the central branch (chalcone synthase (CHS), chalcone isomerase (CHI)) or in the isoflavonoid branch of the flavonoid biosynthesis pathway have been characterized in Medicago sativa. No information is available to date, however, on genes whose products are involved in the synthesis of other types of flavonoids. In this paper we present the genomic organization as well as the nucleotide sequence of one flavanone-3-hydroxylase (F3H) encoding gene of M. sativa, containing two introns and exhibiting 82–89% similarity at the amino acid level to other F3H proteins. This is the first report on the gennomic organization of a f3h gene so far. We present also the sequence of a partial dihydroflavonol-4-reductase (DFR) M. sativa cDNA clone. Southern blot experiments indicated that f3h and dfr genes are each represented by a single gene within the tetraploid genome of M. sativa. By a combination of Northern blot and RT-PCR analysis, we showed that both f3h and dfr genes are expressed in flowers, nodules and roots, with a pattern distinct from chs expression. Finally, we show that dfr is expressed in M. sativa leaves whereas f3h is not. The role played by these two genes in organs other than flowers remains to be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041167
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  • 3
    Electronic Resource
    Electronic Resource
    New plant promoter and enhancer testing vectors (1995)
    Springer
    Molecular breeding 1 (1995), S. 419-423 
    Details
    ISSN: 1572-9788
    Keywords: binary vectors ; gus ; T-DNA ; Agrobacterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We describe here a set of binary vectors suitable forAgrobacterium-mediated gene transfer and specially designed for studying plant promoters. These vectors are based on the use of thegus reporter gene, contain multiple unique restriction sites upstream of thegus gene, and minimal promoters for testing the effect of enhancers or activator elements. In addition, an intron-containinggus (uidA) gene was introduced into one of these vectors in order to examine reporter gene activity in tissues whereAgrobacterium contamination may be a problem or in transient expression assays.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01248419
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  • 4
    Electronic Resource
    Electronic Resource
    The Rhizobium meliloti early nodulation genes (nodABC) are nitrogen-regulated: Isolation of a mutant strain with efficient nodulation capacity on alfalfa in the presence of ammonium (1989)
    Springer
    Molecular genetics and genomics 219 (1989), S. 89-96 
    Details
    ISSN: 1617-4623
    Keywords: Nitrogen regulation (ntr) ; nodABC ; nodD3 ; Nodulation ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The presence of combined nitrogen in the soil suppresses the formation of nitrogen-fixing root nodules by Rhizobium. We demonstrate that bacterial genes determining early nodulation functions (nodABC) as well as the regulatory gene nodD3 are under nitrogen (NH 4 + ) control. Our results suggest that the gene product of nodD3 has a role in mediating the ammonia regulation of early nod genes. The general nitrogen regulatory (ntr) system as well as a chromosomal locus mutated in Rhizobium meliloti were also found to be involved in the regulation of nod gene expression. A R. meliloti mutant with altered sensitivity to ammonia regulation was isolated, capable of more efficient nodulation of alfalfa than the wild-type strain in the presence of 2 mM ammonium sulfate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261162
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  • 5
    Electronic Resource
    Electronic Resource
    Genes at different regulatory levels are required for the ammonia control of nodulation in Rhizobium meliloti (1993)
    Springer
    Molecular genetics and genomics 240 (1993), S. 435-444 
    Details
    ISSN: 1617-4623
    Keywords: Nitrogen regulation ; nodD3 ; syrM ; Common nod genes ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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) system, then transmitted to the syrM-nodD3 genes representing the nod-specific level of ammonia regulation. At low ammonia concentration, the activator protein NtrC exerts its effect via nodD3. In conditions of nitrogen excess ntrR, involved in the repression of nod genes, may function in coordination with the syrM gene. Finally, the NodD3 protein may relay the nitrogen status signal to the transcriptional control of the nodABC genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280398
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  • 6
    Electronic Resource
    Electronic Resource
    Role of plant defence in alfalfa during symbiosis (1996)
    Springer
    World journal of microbiology and biotechnology 12 (1996), S. 175-188 
    Details
    ISSN: 1573-0972
    Keywords: Alfalfa ; defence mechanism ; flavonoids ; peroxidase ; PR protein ; symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract During effective symbiosis, rhizobia colonize their hosts, and avoid plant defence mechanisms. To determine whether the host defence responses can be elicited by the symbiotic bacteria, specific markers involved in incompatible pathogenic interactions are required. The available markers of alfalfa defence mechanisms are described and their use in the study of the symbiotic interaction discussed. As defence-related gene expression in roots is not always related to defence mechanisms, other model systems have been established allowing confirmation of an important role of bacterial surface components in alfalfa-Rhizobium meliloti interactions. Nod factors at high concentrations have been shown to elicit defence-like responses in Medicago cell suspensions and roots. Elicitation of defence mechanisms by high levels of Nod factors in Rhizobium-infected roots may be a part of the mechanism by which nodulation is feed-back regulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00364682
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