Mutualism versus pathogenesis: the give-and-take in plant-bacteria interactions

Soto, Marı́a José; Domínguez-Ferreras, Ana; Pérez-Mendoza, Daniel; Sanjuán, Juan; Olivares, José

doi:10.1111/j.1462-5822.2009.01282.x

Cited by 130 publications

(93 citation statements)

References 67 publications

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“…Rhizobial surface polysaccharides, such as exopolysaccharides, lipopolysaccharides, and cyclic glucans, have been implicated in facilitating infection thread formation and nodule development (51). It has been proposed that surface polysaccharides play a role in the evasion or suppression of host defense responses, a feature that is shared by pathogenic and symbiotic bacteria (49)(50)(51). Thus, one can speculate that Rj4 might recognize rhizobial cell surface components, such as extracellular polysaccharides, or recognize effector proteins directly when coming into contact on the root surface with a strain incompatible with soybean plants carrying Rj4.…”

Section: Discussionmentioning

confidence: 99%

“…It remains unclear how the Rj4 protein restricts nodulation with strains incompatible with soybean plants carrying the Rj4 allele and how Rj4 interferes with the rhizobial genetic components identified in the current study. Host specificity is largely determined by NF, but rhizobial surface polysaccharides are also involved in the modulation of the host range (49)(50)(51). Rhizobial surface polysaccharides, such as exopolysaccharides, lipopolysaccharides, and cyclic glucans, have been implicated in facilitating infection thread formation and nodule development (51).…”

Section: Discussionmentioning

confidence: 99%

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Identification of Bradyrhizobium elkanii Genes Involved in Incompatibility with Soybean Plants Carrying the Rj4 Allele

Faruque

Miwa

Yasuda

et al. 2015

Appl Environ Microbiol

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c Symbioses between leguminous plants and soil bacteria known as rhizobia are of great importance to agricultural production and nitrogen cycling. While these mutualistic symbioses can involve a wide range of rhizobia, some legumes exhibit incompatibility with specific strains, resulting in ineffective nodulation. The formation of nodules in soybean plants (Glycine max) is controlled by several host genes, which are referred to as Rj genes. The soybean cultivar BARC2 carries the Rj4 gene, which restricts nodulation by specific strains, including Bradyrhizobium elkanii USDA61. Here we employed transposon mutagenesis to identify the genetic locus in USDA61 that determines incompatibility with soybean varieties carrying the Rj4 allele. Introduction of the Tn5 transposon into USDA61 resulted in the formation of nitrogen fixation nodules on the roots of soybean cultivar BARC2 (Rj4 Rj4). Sequencing analysis of the sequence flanking the Tn5 insertion revealed that six genes encoding a putative histidine kinase, transcriptional regulator, DNA-binding transcriptional activator, helix-turn-helix-type transcriptional regulator, phage shock protein, and cysteine protease were disrupted. The cysteine protease mutant had a high degree of similarity with the type 3 effector protein XopD of Xanthomonas campestris. Our findings shed light on the diverse and complicated mechanisms that underlie these highly host-specific interactions and indicate the involvement of a type 3 effector in Rj4 nodulation restriction, suggesting that Rj4 incompatibility is partly mediated by effector-triggered immunity. P lants of the legume family can effectively make their own fertilizers by forming symbioses with a diverse group of nitrogen-fixing soil bacteria known as rhizobia. This cross-kingdom collaboration is characterized by the formation of the root nodule, a specialized plant organ that provides an optimized environment in which the bacteria convert atmospheric nitrogen into ammonia. The symbiotic interactions between leguminous plants and Rhizobium bacteria show high species specificity, which is determined by the exchange of signal molecules. The best-known determinants of host specificity derived from rhizobia are the so-called Nod factors (NFs), which comprise a family of lipochitooligosaccharides with various strain-specific chemical decorations (1). Legume roots excrete flavonoid compounds that can interact specifically with the rhizobial transcriptional factor NodD. Activation of NodD induces the expression of nodulation genes in rhizobia, which are required for the synthesis of NFs (2, 3). NFs are received by host NF receptors (NFRs) and activate host signal transduction pathways that lead to root hair infection and nodule organogenesis (2, 3). A recent study showed that introduction of the putative NFRs NFR1 and NFR5 of Lotus japonicus into Medicago truncatula initiated nodulation of the transgenic roots by the L. japonicus symbiont Mesorhizobium loti (4, 5). Thus, NFs and their receptor proteins contribute significantly to the de...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Identification of Bradyrhizobium elkanii Genes Involved in Incompatibility with Soybean Plants Carrying the Rj4 Allele

Faruque

Miwa

Yasuda

et al. 2015

Appl Environ Microbiol

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“…The accumulation of reactive oxygen species leads to cell death and the necrosis of the area of infection, which prevents bacterial progression in the plant tissue. These observations suggest that Nod factors may also be important in the evasion of the plant immune response and the protection of cells from reactive oxygen species [10,15]. However, other components, such as receptor-like kinase with leucine-rich repeat (LRR) domains, have been identified to be essential for nodulation signalling in addition to the perception of pathogen signals [16,17].…”

Section: Introductionmentioning

confidence: 99%

“…Rhizobia should thus have co-opted ancient widespread mycorrhizal signalling pathways to enable the establishment of endosymbiotic interactions with legumes. Furthermore, Myc and Nod factors stimulate lateral root branching [4], suggesting that in the course of evolution, signals for modifying root system architecture were used to facilitate symbiotic infections or nodule organogenesis [6,10].…”

Section: Introductionmentioning

confidence: 99%

Complexity of miRNA-dependent regulation in root symbiosis

Bazin

Bustos-Sanmamed

Hartmann

et al. 2012

Phil. Trans. R. Soc. B

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The development of root systems may be strongly affected by the symbiotic interactions that plants establish with soil organisms. Legumes are able to develop symbiotic relationships with both rhizobial bacteria and arbuscular mycorrhizal fungi leading to the formation of nitrogen-fixing nodules and mycorrhizal arbuscules, respectively. Both of these symbiotic interactions involve complex cellular reprogramming and profound morphological and physiological changes in specific root cells. In addition, the repression of pathogenic defence responses seems to be required for successful symbiotic interactions. Apart from typical regulatory genes, such as transcription factors, microRNAs (miRNAs) are emerging as riboregulators that control gene networks in eukaryotic cells through interactions with specific target mRNAs. In recent years, the availability of deep-sequencing technologies and the development of in silico approaches have allowed for the identification of large sets of miRNAs and their targets in legumes. A number of conserved and legume-specific miRNAs were found to be associated with symbiotic interactions as shown by their expression patterns or actions on symbiosis-related targets. In this review, we combine data from recent literature and genomic and deep-sequencing data on miRNAs controlling nodule development or restricting defence reactions to address the diversity and specificity of miRNA-dependent regulation in legume root symbiosis. Phylogenetic analysis of miRNA isoforms and their potential targets suggests a role for miRNAs in the repression of plant defence during symbiosis and revealed the evolution of miRNA-dependent regulation in legumes to allow for the modification of root cell specification, such as the formation of mycorrhized roots and nitrogen-fixing nodules.

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“…However, the functions of these and other Nop proteins during nodulation are not well characterized. Some have hypothesized that Nops contribute to suppression of plant innate immune responses or modulate cytoskeletal rearrangements in root cells during nodule development (4,32,34). An important first step in determining the roles of Nops during symbiosis is the demonstration that these proteins are delivered into plant roots.…”

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confidence: 99%