Characterization of Astragalus sinicus Rhizobia by Restriction Fragment Length Polymorphism Analysis of Chromosomal and Nodulation Genes Regions

Guo, Xian-Wu

doi:10.1007/s002849900472

Cited by 14 publications

(12 citation statements)

References 13 publications

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“…Twenty-four representative strains were selected from a collection of field isolates isolated from six southern provinces of China. These strains had previously been characterized by restriction fragment length polymorphism (RFLP) analysis of PCR-amplified 16S rRNA genes and 16S-23S rDNA intergenic spacers (IGS) ( Table 1) (17,42). PCR amplification of each of the 24 strains, using primers DC1 and DC2, produced a single band of 2.0 kb.…”

Section: Resultsmentioning

confidence: 99%

“…This situation is equivalent to that known for the three biovars of R. leguminosarum, which have the same chromosomal type, but have different symbiotic genes and host ranges. Like R. leguminosarum, the nodulation genes of A. sinicus rhizobia are carried on a large plasmid, which could spread within field populations by horizontal plasmid transfer (17). Rapid horizontal transfer would explain why identical symbiotic genotypes are associated with different chromosomal backgrounds.…”

Section: Discussionmentioning

confidence: 99%

“…b Question marks indicate that more than one band was produced in the 16S-23S rDNA IGS PCR amplification (17). The number in parentheses is the 23S rDNA genotype (42).…”

Section: Methodsmentioning

confidence: 99%

“…On the basis of 16S ribosomal DNA (rDNA) sequence data and other taxonomic criteria, Jarvis et al (21) proposed a new genus, Mesorhizobium, to which R. huakuii was transferred. Our previous work has shown that A. sinicus rhizobia are diverse (17,42): of 204 strains analyzed, all are Mesorhizobium, but they belong to four different 16S rDNA genotypes. These four genotypes can be subdivided into seven genotypes when 16S and 23S rDNA data are combined.…”

Section: Astragalus Sinicus L (Chinese Milk Vetch)mentioning

confidence: 99%

“…The aims of this study were to isolate and characterize the nod genes of Mesorhizobium sp. (A. sinicus) strain 7653R, to compare the common nod genes with those from other species of rhizobia, and to look at nod gene variation among A. sinicus nodule isolates representing the different chromosome types (17,42).…”

Section: Astragalus Sinicus L (Chinese Milk Vetch)mentioning

confidence: 99%

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The Common Nodulation Genes of Astragalus sinicus Rhizobia Are Conserved despite Chromosomal Diversity

Zhang

Turner

Guo

et al. 2000

Appl Environ Microbiol

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The nodulation genes of Mesorhizobium sp. (Astragalus sinicus) strain 7653R were cloned by functional complementation of Sinorhizobium meliloti nod mutants. The common nod genes, nodD, nodA, and nodBC, were identified by heterologous hybridization and sequence analysis. The nodA gene was found to be separated from nodBC by approximately 22 kb and was divergently transcribed. The 2.0-kb nodDBC region was amplified by PCR from 24 rhizobial strains nodulating A. sinicus, which represented different chromosomal genotypes and geographic origins. No polymorphism was found in the size of PCR products, suggesting that the separation of nodA from nodBC is a common feature of A. sinicus rhizobia. Sequence analysis of the PCR-amplified nodA gene indicated that seven strains representing different 16S and 23S ribosomal DNA genotypes had identical nodA sequences. These data indicate that, whereas microsymbionts of A. sinicus exhibit chromosomal diversity, their nodulation genes are conserved, supporting the hypothesis of horizontal transfer of nod genes among diverse recipient bacteria.Rhizobia are soil bacteria that can form nodules, in which they fix nitrogen, on leguminous plants in a host-specific manner. Nodulation (nod) genes have been identified that control the specific infection and nodulation of the plant hosts. The initial infection event is regulated by a NodD protein or proteins which activate the transcription of other nod genes in the presence of host-produced flavonoids (12, 25, 37). The nod-ABC genes are called common nod genes because they are present in all rhizobia. Other nod genes, such as nodFE, nodH, nodSU, and nodZ (12,25,37), are present in various combinations in rhizobial species and are called host-specific nod genes.Expression of common and host-specific nod genes results in the production of lipochitooligosaccharides (Nod factors) that act as morphogenic signal molecules on specific legume hosts (12, 37). All Nod factors have a ␤-1,4-linked N-acetyl glucosamine oligosaccharide backbone ranging in length from 3 to 5 residues and substituted for by an N-acyl chain at the nonreducing end and other chemical groups on the glucosamine residues. The common nodABC gene products are involved in the synthesis of the N-acylated oligosaccharide core, while the host-specific nod gene products are involved in the decoration of this backbone with substitutions that confer plant specificity. The nodABC genes encode an acyltransferase, a chitin oligosaccharide deacetylase, and a chitin oligosaccharide synthase, respectively (3, 33). The common nod genes are also involved in determining host range specificity to some extent. For example, different NodA proteins recognize and transfer different fatty acid chains to the chitooligosaccharide chain, the length of which is determined by NodC (11, 27, 32). The common nodABC genes are essential for nodule formation. Mutation in any of them abolishes the ability to produce Nod factors and results in a nonnodulating (Nod Ϫ ) phenotype (12). Astragalus sinicus L. (Chinese ...

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…b Question marks indicate that more than one band was produced in the 16S-23S rDNA IGS PCR amplification (17). The number in parentheses is the 23S rDNA genotype (42).…”

Section: Methodsmentioning

confidence: 99%

Section: Astragalus Sinicus L (Chinese Milk Vetch)mentioning

confidence: 99%

Section: Astragalus Sinicus L (Chinese Milk Vetch)mentioning

confidence: 99%

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The Common Nodulation Genes of Astragalus sinicus Rhizobia Are Conserved despite Chromosomal Diversity

Zhang

Turner

Guo

et al. 2000

Appl Environ Microbiol

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The Diversity and Evolution of Rhizobia

Dresler-Nurmi

Fewer

Rásänen

et al. 2007

Microbiology Monographs

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Mesorhizobium amorphae , a rhizobial species that nodulates Amorpha fruticosa , is native to American soils

Wang¹,

Rogel²,

Sui

et al. 2002

Archives of Microbiology

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Amorpha fruticosa was inoculated with rhizosphere soil from Iowa, USA, and 140 rhizobia isolated from root nodules were compared with Mesorhizobium amorphae originating from Chinese soils. PCR-RFLP patterns of the 16S rRNA gene from the isolates and from M. amorphaewere the same. All isolates had a symbiotic plasmid of the same size with a single nifHgene. DNA:DNA hybridization values, DNA G+C content, and induced Nod factor patterns also were similar. We concluded that the four genotypes distinguished among 53 representative American isolates were M. amorphae. Since A. fruticosa is native to the Americas and is highly specific in its nodulation requirement, M. amorphae probably was transmitted to China.

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Characterization of Astragalus sinicus Rhizobia by Restriction Fragment Length Polymorphism Analysis of Chromosomal and Nodulation Genes Regions

Cited by 14 publications

References 13 publications

The Common Nodulation Genes of Astragalus sinicus Rhizobia Are Conserved despite Chromosomal Diversity

The Common Nodulation Genes of Astragalus sinicus Rhizobia Are Conserved despite Chromosomal Diversity

The Diversity and Evolution of Rhizobia

Mesorhizobium amorphae , a rhizobial species that nodulates Amorpha fruticosa , is native to American soils

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