Commonalities and differences of T3SSs in rhizobia and plant pathogenic bacteria

Tampakaki, Anastasia P.

doi:10.3389/fpls.2014.00114

Cited by 81 publications

(85 citation statements)

References 163 publications

(261 reference statements)

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“…The ability to induce nodules on NF-independent Aeschynomene species is widespread among Bradyrhizobium species The increasing availability of genome sequences has revealed that the presence of a T3SS is frequent among rhizobia (Tampakaki, 2014). We therefore hypothesized that some strains could be able to exploit this T3SS machinery to develop a more compatible symbiotic relationship with Aeschynomene.…”

Section: Resultsmentioning

confidence: 99%

Rhizobium–legume symbiosis in the absence of Nod factors: two possible scenarios with or without the T3SS

et al. 2015

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The occurrence of alternative Nod factor (NF)-independent symbiosis between legumes and rhizobia was first demonstrated in some Aeschynomene species that are nodulated by photosynthetic bradyrhizobia lacking the canonical nodABC genes. In this study, we revealed that a large diversity of non-photosynthetic bradyrhizobia, including B. elkanii, was also able to induce nodules on the NFindependent Aeschynomene species, A. indica. Using cytological analysis of the nodules and the nitrogenase enzyme activity as markers, a gradient in the symbiotic interaction between bradyrhizobial strains and A. indica could be distinguished. This ranged from strains that induced nodules that were only infected intercellularly to rhizobial strains that formed nodules in which the host cells were invaded intracellularly and that displayed a weak nitrogenase activity. In all nonphotosynthetic bradyrhizobia, the type III secretion system (T3SS) appears required to trigger nodule organogenesis. In contrast, genome sequence analysis revealed that apart from a few exceptions, like the Bradyrhizobium ORS285 strain, photosynthetic bradyrhizobia strains lack a T3SS. Furthermore, analysis of the symbiotic properties of an ORS285 T3SS mutant revealed that the T3SS could have a positive or negative role for the interaction with NF-dependent Aeschynomene species, but that it is dispensable for the interaction with all NF-independent Aeschynomene species tested. Taken together, these data indicate that two NF-independent symbiotic processes are possible between legumes and rhizobia: one dependent on a T3SS and one using a so far unknown mechanism.

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Section: Resultsmentioning

confidence: 99%

Rhizobium–legume symbiosis in the absence of Nod factors: two possible scenarios with or without the T3SS

et al. 2015

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“…The symbiotic T3SS is responsible for the nodulation specificity phenotype shown by several Sinorhizobium fredii and Bradyrhizobium elkanii strains in their symbiosis with certain soybean cultivars (44,45). In these cases, the inactivation of the T3SS allows nodulation.…”

Section: Discussionmentioning

confidence: 99%

The Sinorhizobium (Ensifer) fredii HH103 Nodulation Outer Protein NopI Is a Determinant for Efficient Nodulation of Soybean and Cowpea Plants

Jiménez‐Guerrero

Pérez‐Montaño

Medina

et al. 2017

Appl Environ Microbiol

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The type III secretion system (T3SS) is a specialized secretion apparatus that is commonly used by many plant and animal pathogenic bacteria to deliver proteins, termed effectors, to the interior of the host cells. These effectors suppress host defenses and interfere with signal transduction pathways to promote infection. Some rhizobial strains possess a functional T3SS, which is involved in the suppression of host defense responses, host range determination, and symbiotic efficiency. The analysis of the genome of the broad-host-range rhizobial strain Sinorhizobium fredii HH103 identified eight genes that code for putative T3SS effectors. Three of these effectors, NopL, NopP, and NopI, are Rhizobium specific. In this work, we demonstrate that NopI, whose amino acid sequence shows a certain similarity with NopP, is secreted through the S. fredii HH103 T3SS in response to flavonoids. We also determined that NopL can be considered an effector since it is directly secreted to the interior of the host cell as demonstrated by adenylate cyclase assays. Finally, the symbiotic phenotype of single, double, and triple nopI, nopL, and nopP mutants in soybean and cowpea was assayed, showing that NopI plays an important role in determining the number of nodules formed in both legumes and that the absence of both NopL and NopP is highly detrimental for symbiosis.IMPORTANCE The paper is focused on three Rhizobium-specific T3SS effectors of Sinorhizobium fredii HH103, NopL, NopP, and NopI. We demonstrate that S. fredii HH103 is able to secrete through the T3SS in response to flavonoids the nodulation outer protein NopI. Additionally, we determined that NopL can be considered an effector since it is secreted to the interior of the host cell as demonstrated by adenylate cyclase assays. Finally, nodulation assays of soybean and cowpea indicated that NopI is important for the determination of the number of nodules formed and that the absence of both NopL and NopP negatively affected nodulation. KEYWORDS:Sinorhizobium fredii, cowpea, effector, nodulation, soybean, symbiosis, type III secretion S oil bacteria, collectively known as rhizobia, induce the formation of specialized structures, called nodules, on the roots or stems of host legumes. Within these nodules, rhizobia differentiate into bacteroids that are able to reduce atmospheric nitrogen to ammonia, which is assimilated by the plant. In exchange, rhizobia are provided with a carbon source and an appropriate environment to promote bacterial growth (1).

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“…T3S systems are present in plant- and animal-pathogenic bacteria as well as in several non-pathogenic bacteria and species (spp.) of the symbiotic bacterium Rhizobium , suggesting that T3S is not exclusively linked to pathogenicity (Troisfontaines and Cornelis 2005; Tampakaki 2014). According to phylogenetic analyses, T3S systems from plant-pathogenic bacteria have been grouped into different families including Hrp1 (hypersensitive response and pathogenicity 1; in spp.…”

Section: Introductionmentioning

confidence: 99%

Behind the lines–actions of bacterial type III effector proteins in plant cells

Büttner¹

2016

FEMS Microbiology Reviews

235

234

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Pathogenicity of most Gram-negative plant-pathogenic bacteria depends on the type III secretion (T3S) system, which translocates bacterial effector proteins into plant cells. Type III effectors modulate plant cellular pathways to the benefit of the pathogen and promote bacterial multiplication. One major virulence function of type III effectors is the suppression of plant innate immunity, which is triggered upon recognition of pathogen-derived molecular patterns by plant receptor proteins. Type III effectors also interfere with additional plant cellular processes including proteasome-dependent protein degradation, phytohormone signaling, the formation of the cytoskeleton, vesicle transport and gene expression. This review summarizes our current knowledge on the molecular functions of type III effector proteins with known plant target molecules. Furthermore, plant defense strategies for the detection of effector protein activities or effector-triggered alterations in plant targets are discussed.

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Commonalities and differences of T3SSs in rhizobia and plant pathogenic bacteria

Cited by 81 publications

References 163 publications

Rhizobium–legume symbiosis in the absence of Nod factors: two possible scenarios with or without the T3SS

Rhizobium–legume symbiosis in the absence of Nod factors: two possible scenarios with or without the T3SS

The Sinorhizobium (Ensifer) fredii HH103 Nodulation Outer Protein NopI Is a Determinant for Efficient Nodulation of Soybean and Cowpea Plants

Behind the lines–actions of bacterial type III effector proteins in plant cells

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