Roles of flavonoids and the transcriptional regulator TtsI in the activation of the type III secretion system of Bradyrhizobium elkanii SEMIA587

Campos, Samanta Bolzan de; Deakin, William J.; Broughton, W. J.; Passaglia, Luciane Maria Pereira

doi:10.1099/mic.0.040873-0

Cited by 20 publications

(15 citation statements)

References 31 publications

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“…Though not all rhizobia have T3SS, many genera have so far been described such as Sinorhizobium and Bradyrhizobium (Staehelin and Krishnan 2015). Nodulating outer proteins (Nops) are the effector proteins transported through T3SS and can be secreted from rhizobia in response to flavonoids (de Campos et al 2011).…”

Section: Nop Effectors Of Rhizobia Type III Secretion System (T3ss)mentioning

confidence: 99%

Defining plant growth promoting rhizobacteria molecular and biochemical networks in beneficial plant-microbe interactions

2018

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Background Our knowledge of plant beneficial bacteria in the rhizosphere is rapidly expanding due to intense interest in utilizing these types of microbes in agriculture. Laboratory and field studies consistently document the growth, health and protective benefits conferred to plants by applying plant growth promoting rhizobacteria (PGPR). PGPR exert their influence on other species, including plants, in the rhizosphere by producing a wide array of extracellular molecules for communication and defense. Scope The types of PGPR molecular products are characteristically diverse, and the mechanisms by which they are acting on the plant are only beginning to be understood. While plants may contribute to shape their microbiome, it is these bacterial products which induce beneficial responses in plants. PGPR extracellular products can directly stimulate plant genetic and molecular pathways, leading to increases in plant growth and induction of plant resistance and tolerance. This review will discuss known PGPR-derived molecules, and how these products are implicated in inducing plant beneficial outcomes through complex plant response mechanisms. Conclusions In order to move PGPR research to the next level, it will be important to describe and document the genetic and molecular mechanisms employed in these interactions. In this way, we will be able to restructure and harness these mechanisms in a way that allows for broad-based applications in agriculture. A greater depth of understanding of how these PGPR molecules are acting on the plant will allow more effective development of rhizobacterial applications in the field.

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Section: Nop Effectors Of Rhizobia Type III Secretion System (T3ss)mentioning

confidence: 99%

Defining plant growth promoting rhizobacteria molecular and biochemical networks in beneficial plant-microbe interactions

2018

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“…In rhizobia, the expression of the T3SS machinery and T3Es is under the control of the TtsI transcriptional regulator, which is in turn induced by the NodD transcriptional activator and plant-derived flavonoids [ 24 ]. TtsI is activated in strain ORS3257 by the flavonoid genistein [ 9 ].…”

Section: Resultsmentioning

confidence: 99%

The Type III Effectome of the Symbiotic Bradyrhizobium vignae Strain ORS3257

et al. 2021

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Many Bradyrhizobium strains are able to establish a Nod factor-independent symbiosis with the leguminous plant Aeschynomene indica by the use of a type III secretion system (T3SS). Recently, an important advance in the understanding of the molecular factors supporting this symbiosis has been achieved by the in silico identification and functional characterization of 27 putative T3SS effectors (T3Es) of Bradyrhizobium vignae ORS3257. In the present study, we experimentally extend this catalog of T3Es by using a multi-omics approach. Transcriptome analysis under non-inducing and inducing conditions in the ORS3257 wild-type strain and the ttsI mutant revealed that the expression of 18 out of the 27 putative effectors previously identified, is under the control of TtsI, the global transcriptional regulator of T3SS and T3Es. Quantitative shotgun proteome analysis of culture supernatant in the wild type and T3SS mutant strains confirmed that 15 of the previously determined candidate T3Es are secreted by the T3SS. Moreover, the combined approaches identified nine additional putative T3Es and one of them was experimentally validated as a novel effector. Our study underscores the power of combined proteome and transcriptome analyses to complement in silico predictions and produce nearly complete effector catalogs. The establishment of the ORS3257 effectome will form the basis for a full appraisal of the symbiotic properties of this strain during its interaction with various host legumes via different processes.

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“…Expression of most rhizobial T3SS genes usually depends on TtsI, a transcriptional regulator that controls expression of various flavonoid-inducible genes including those related to the T3SS. TtsI-regulated genes possess a promoter with a tts box, a conserved cis element required for TtsI-dependent gene expression [10,13,[45][46][47]. For strain S. fredii NGR234, direct binding of TtsI to the tts box promoter region of two TtsI-regulated genes has been demonstrated by electrophoretic mobility-shift and DNase I cleavage protection assays [47].…”

Section: Nops Are Secreted Through the T3ss Apparatus In Response To mentioning

confidence: 99%

“…For strain S. fredii NGR234, direct binding of TtsI to the tts box promoter region of two TtsI-regulated genes has been demonstrated by electrophoretic mobility-shift and DNase I cleavage protection assays [47]. In Bradyrhizobium elkanii SEMIA587, but not other strains, TtsI can also upregulate its own expression since the ttsI promoter region contains a functional tts box [13]. Like nod genes required for Nod factor synthesis, ttsI genes possess a nod box in their promoter.…”

Section: Nops Are Secreted Through the T3ss Apparatus In Response To mentioning

confidence: 99%

“…In a similar way, rhizobial T3 effectors have been found to play a role in certain symbiotic interactions between rhizobia and legumes. On the basis of mutant analysis and identification of secreted proteins, functional T3SSs have been reported for various nodule-inducing bacteria belonging to the genera Sinorhizobium (Ensifer) [7][8][9], Bradyrhizobium [10][11][12][13][14], Mesorhizobium [15][16][17] and Cupriavidus [18]. Furthermore, recent sequencing data revealed the presence of a T3SS gene cluster in the genome of a nodule-inducing Burkholderia strain [19].…”

Section: Introductionmentioning

confidence: 99%

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Nodulation outer proteins: double-edged swords of symbiotic rhizobia

Staehelin

Krishnan

2015

Biochemical Journal

115

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Rhizobia are nitrogen-fixing bacteria that establish a nodule symbiosis with legumes. Nodule formation depends on signals and surface determinants produced by both symbiotic partners. Among them, rhizobial Nops (nodulation outer proteins) play a crucial symbiotic role in many strain-host combinations. Nops are defined as proteins secreted via a rhizobial T3SS (type III secretion system). Functional T3SSs have been characterized in many rhizobial strains. Nops have been identified using various genetic, biochemical, proteomic, genomic and experimental approaches. Certain Nops represent extracellular components of the T3SS, which are visible in electron micrographs as bacterial surface appendages called T3 (type III) pili. Other Nops are T3 effector proteins that can be translocated into plant cells. Rhizobial T3 effectors manipulate cellular processes in host cells to suppress plant defence responses against rhizobia and to promote symbiosis-related processes. Accordingly, mutant strains deficient in synthesis or secretion of T3 effectors show reduced symbiotic properties on certain host plants. On the other hand, direct or indirect recognition of T3 effectors by plant cells expressing specific R (resistance) proteins can result in effector triggered defence responses that negatively affect rhizobial infection. Hence Nops are double-edged swords that may promote establishment of symbiosis with one legume (symbiotic factors) and impair symbiotic processes when bacteria are inoculated on another legume species (asymbiotic factors). In the present review, we provide an overview of our current understanding of Nops. We summarize their symbiotic effects, their biochemical properties and their possible modes of action. Finally, we discuss future perspectives in the field of T3 effector research.

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Roles of flavonoids and the transcriptional regulator TtsI in the activation of the type III secretion system of Bradyrhizobium elkanii SEMIA587

Cited by 20 publications

References 31 publications

Defining plant growth promoting rhizobacteria molecular and biochemical networks in beneficial plant-microbe interactions

Defining plant growth promoting rhizobacteria molecular and biochemical networks in beneficial plant-microbe interactions

The Type III Effectome of the Symbiotic Bradyrhizobium vignae Strain ORS3257

Nodulation outer proteins: double-edged swords of symbiotic rhizobia

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