Soil Biology of the Rhizobiaceae

Sadowsky, Michael J.; Graham, Peter

doi:10.1007/978-94-011-5060-6_8

Cited by 55 publications

(38 citation statements)

References 291 publications

(167 reference statements)

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“…Low-pH conditions can also negatively impact the growth of plants and rhizobia (Brockwell et al, 1991;Marschner, 1991;Smit et al, 1992;Hungria and Stacey, 1997;Sadowsky et al, 1998;Morón et al, 2005) and can decrease the synthesis of legume flavonoids and rhizobia Nod factor (McKay and Djordjevic, 1993;Hungria and Stacey, 1997). These factors may have also contributed to the down-regulation of early nodulation gene expression observed here (Figs.…”

Section: Discussionmentioning

confidence: 81%

“…This is especially important considering that nitrate acts through GmNARK in a root-localized fashion to suppress nodule development, and hence, a local mechanism is in place that could have been usurped by acid to exert nodulation control. Indeed, the debilitating effects of low pH on plant and rhizobia health (Brockwell et al, 1991;Marschner, 1991;Sadowsky et al, 1998) and on their symbiotic interactions (Smit et al, 1992;Hungria and Stacey, 1997;Morón et al, 2005) have long been considered local rhizosphere effects induced directly by H + ions. This now appears to be only one component of pH-regulated nodulation control.…”

Section: Discussionmentioning

confidence: 99%

“…Bradyrhizobium spp. are generally more acid tolerant than Rhizobium spp., but the cause for this remains unclear (Brockwell et al, 1991;Sadowsky et al, 1998). Moreover, certain strains that are less potent under neutral conditions can outcompete other strains under low-pH conditions (Triplett and Sadowsky, 1992;Hungria and Stacey, 1997).…”

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confidence: 99%

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Systemic Regulation of Soybean Nodulation by Acidic Growth Conditions

2012

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Mechanisms inhibiting legume nodulation by low soil pH, although highly prevalent and economically significant, are poorly understood. We addressed this in soybean (Glycine max) using a combination of physiological and genetic approaches. Split-root and grafting studies using an autoregulation-of-nodulation-deficient mutant line, altered in the autoregulation-of-nodulation receptor kinase GmNARK, determined that a systemic, shoot-controlled, and GmNARK-dependent mechanism was critical for facilitating the inhibitory effect. Acid inhibition was independent of aluminum ion concentration and occurred early in nodule development, between 12 and 96 h post inoculation with Bradyrhizobium japonicum. Biological effects were confirmed by measuring transcript numbers of known early nodulation genes. Transcripts decreased on both sides of split-root systems, where only one side was subjected to low-pH conditions. Our findings enhance the present understanding of the innate mechanisms regulating legume nodulation control under acidic conditions, which could benefit future attempts in agriculture to improve nodule development and biological nitrogen fixation in acid-stressed soils.

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Section: Discussionmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 99%

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Systemic Regulation of Soybean Nodulation by Acidic Growth Conditions

2012

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“…These conditions include the intrageneric differences to cope with desiccation stress which affect survival (5,6,9,10,13,18,21,22). These data suggest that no single gene affects the ability of rhizobia to survive desiccation but that several mechanisms are likely responsible.…”

mentioning

confidence: 91%

Identification and Characterization of a NaCl-Responsive Genetic Locus Involved in Survival during Desiccation in Sinorhizobium meliloti

Vriezen

Bruijn

Nüsslein

2013

Appl Environ Microbiol

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The Rhizobiaceae are a bacterial family of enormous agricultural importance due to the ability of its members to fix atmospheric nitrogen in an intimate relationship with plants. Their survival as naturally occurring soil bacteria in agricultural soils as well as popular seed inocula is affected directly by drought and salinity. Survival after desiccation in the presence of NaCl is enabled by underlying genetic mechanisms in the model organism Sinorhizobium meliloti 1021. Since salt stress parallels a loss in water activity, the identification of NaCl-responsive loci may identify loci involved in survival during desiccation. This approach enabled identification of the loci asnO and ngg by their reduced ability to grow on increased NaCl concentrations, likely due to their inability to produce the osmoprotectant N-acetylglutaminylglutamine (NAGGN). In addition, the mutant harboring ngg:: Tn5luxAB was affected in its ability to survive desiccation and responded to osmotic stress. The desiccation sensitivity may have been due to secondary functions of Ngg (N-acetylglutaminylglutamine synthetase)-like cell wall metabolism as suggested by the presence of a D-alanine-D-alanine ligase (dAla-dAla) domain and by sensitivity of the mutant to ␤-lactam antibiotics. asnO:: Tn5luxAB is expressed during the stationary phase under normal growth conditions. Amino acid sequence similarity to enzymes producing ␤-lactam inhibitors and increased resistance to ␤-lactam antibiotics may indicate that asnO is involved in the production of a ␤-lactam inhibitor. The Rhizobiaceae are a bacterial family of enormous agricultural importance due to their ability to fix atmospheric nitrogen in an intimate relationship with plants (1). They occur naturally in most agricultural soils, and their survival is affected directly by both drought and salinity (2). Unfortunately, changes in climate patterns are occurring and, as a direct consequence, salinification and desertification are some of the major threats to agricultural land use. It is estimated that over 40% of arable land will be affected by desiccation and salinity by 2025 (2). Furthermore, production of seed inocula often includes a drying phase negatively affecting CFU of added rhizobia (3, 4), potentially resulting in desiccation-induced viable but nonculturable cells (5).A multitude of conditions affecting survival during desiccation of agriculturally important Rhizobiaceae have been studied (6,7,8,9,10,11,12,13,14,15,16,17,18,19,20). These conditions include the intrageneric differences to cope with desiccation stress which affect survival (5,6,9,10,13,18,21,22). These data suggest that no single gene affects the ability of rhizobia to survive desiccation but that several mechanisms are likely responsible.One of the conditions affecting the ability of Sinorhizobium meliloti to survive desiccation is NaCl availability (10, 13); hence, we studied the response of S. meliloti 1021 to drought in conjunction with different salt stresses (13). We showed that survival of the strain in the presen...

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“…Rhizobial diversity is affected by abiotic factors such as temperature, soil pH, and salinity (Sadowsky and Graham 1998;Howieson and Ballard 2004), and biotic factors such as distribution of host trees within a forest (Hirsch 1996). The genetic diversity and spatial distribution of nodule-forming rhizobia should reflect the interaction and competition among soil bacteria within a rhizosphere.…”

Section: Introductionmentioning

confidence: 99%

Genetic diversity and spatial distribution of rhizobial bacteria nodulating on black locust (Robinia pseudoacacia) rhizospheres

Shiraishi

Komatsu

Matsushita

et al. 2011

Soil Science and Plant Nutrition

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Black locust (Robinia pseudoacacia L.) is an economically and ecologically important tree in Japan. The species is widely used for afforestation because of its symbiotic relationship with nitrogen-fixing rhizobia. In this study, genetic diversity of rhizobia isolated from black locust nodules and spatial distribution of their genotypes were examined. From a coastal forest, six black locust saplings including the whole root systems were collected and positions of nodules on the roots were recorded. Bacteria were isolated from each nodule and then genotyped by Polymerase Chain Reaction (PCR)-Restriction Fragment Length Polymorphism (RFLP) and sequencing analysis of the 16S rRNA gene. Dendrogram analysis based on PCR-RFLP and sequencing analysis indicated that Mesorhizobium species dominantly colonized black locust roots in this forest, occupying at least 77% of living nodules. Positions and PCR-RFLP genotypes of the nodules revealed that rhizobia isolated from neighbouring nodules tended to have the same genotype in some cases. Statistical analysis has supported this fact. The clustering distribution of nodules in the same RFLP groups should be considered to contribute to the large genetic diversity of rhizobia.

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Soil Biology of the Rhizobiaceae

Cited by 55 publications

References 291 publications

Systemic Regulation of Soybean Nodulation by Acidic Growth Conditions

Systemic Regulation of Soybean Nodulation by Acidic Growth Conditions

Identification and Characterization of a NaCl-Responsive Genetic Locus Involved in Survival during Desiccation in Sinorhizobium meliloti

Genetic diversity and spatial distribution of rhizobial bacteria nodulating on black locust (Robinia pseudoacacia) rhizospheres

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