The Symbiotic Interaction between Azorhizobium caulinodans and Sesbania rostrata

Goormachtig, Sofie; Mergaert, Peter; Montagu, Marc Van; Holsters, Marcelle

doi:10.1007/978-1-4899-1707-2_4

Cited by 15 publications

(12 citation statements)

References 190 publications

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“…For semithin sections, the tissues were embedded in Technovit 7100 (Heraeus), cut, and stained with toluidine blue (20,28). GFP analysis (28) and transmission EM (21) were performed as described.…”

Section: Light Microscopy and Transmission Emmentioning

confidence: 99%

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SrSymRK, a plant receptor essential for symbiosome formation

Capoen

Goormachtig²,

Rycke³

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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103

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The symbiosis between legumes and rhizobia is essential for the nitrogen input into the life cycle on our planet. New root organs, the nodules, are established, which house N 2-fixing bacteria internalized into the host cell cytoplasm as horizontally acquired organelles, the symbiosomes. The interaction is initiated by bacterial invasion via epidermal root hair curling and cell division in the cortex, both triggered by bacterial nodulation factors. Of the several genes involved in nodule initiation that have been identified, one encodes the leucine-rich repeat-type receptor kinase SymRK. In SymRK mutants of Lotus japonicus or its orthologs in Medicago sp. and Pisum sativum, nodule initiation is arrested at the level of the root hair interaction. Because of the epidermal block, the role of SymRK at later stages of nodule development remained enigmatic. To analyze the role of SymRK downstream of the epidermis, the water-tolerant legume Sesbania rostrata was used that has developed a nodulation strategy to circumvent root hair responses for bacterial invasion. Evidence is provided that SymRK plays an essential role during endosymbiotic uptake in plant cells.bacterial uptake ͉ endosymbiosis ͉ legume nodulation ͉ Sesbania rostrata ͉ infection thread structure

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Section: Light Microscopy and Transmission Emmentioning

confidence: 99%

“…However, on hydroponic roots, N 2 -fixing nodules develop at LRBs (19). Azorhizobia invade the cortex intercellularly via cracks, resulting from lateral root protrusion, thereby circumventing the epidermis (20). Cortical infection pockets (IPs) are formed by NF-dependent local cell death induction and subsequent colonization of bacteria.…”

mentioning

confidence: 99%

SrSymRK, a plant receptor essential for symbiosome formation

Capoen

Goormachtig²,

Rycke³

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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103

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“…The mechanism for deeper invasion varies. In Sesbania rostrata and in Neptunia sp., infection pockets narrow down to form intercellular infection threads, and subsequently intracellular infection threads intrude into the nodule primordium (9)(10)(11)(12). In Aeschynomene, Stylosanthes, and Arachis, invasion progresses by means of cell collapse, and bacteria enter the cells of the nodule primordia by direct uptake from the infection pockets (13-16).…”

mentioning

confidence: 99%

“…The process of intercellular invasion has been examined in most detail in the S. rostrata-Azorhizobium caulinodans interaction, which has become a model for the study of this type of entry (12,17). On S. rostrata, nodules arise not only on the root but also on the stem, at positions of adventitious root primordia (12).…”

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Switch from intracellular to intercellular invasion during water stress-tolerant legume nodulation

Goormachtig

Capoen

James

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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115

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Rhizobia colonize their legume hosts by different modes of entry while initiating symbiotic nitrogen fixation. Most legumes are invaded via growing root hairs by the root hair-curl mechanism, which involves epidermal cell responses. However, invasion of a number of tropical legumes happens through fissures at lateral root bases by cortical, intercellular crack entry. In the semiaquatic Sesbania rostrata, the bacteria entered via root hair curls under nonflooding conditions. Upon flooding, root hair growth was prevented, invasion on accessible root hairs was inhibited, and intercellular invasion was recruited. The plant hormone ethylene was involved in these processes. The occurrence of both invasion pathways on the same host plant enabled a comparison to be made of the structural requirements for the perception of nodulation factors, which were more stringent for the epidermal root hair invasion than for the cortical intercellular invasion at lateral root bases.ethylene ͉ host invasion ͉ nodulation factor ͉ symbiosis ͉ flooding-adapted growth L eguminous plants can engage in a symbiotic interaction with rhizobia (nitrogen-fixing bacterial symbionts), resulting in the formation of specialized root organs, the nodules. In the central nodule tissue, internalized bacteria fix dinitrogen to be used by the host. Many legumes are of agronomic importance as major food and feed crops, whereas others have a great potential as green manure. The legume-rhizobia interaction is initiated by a complex signal exchange during which recognition of bacterial nodulation (Nod) factors switches on the nodulation program in the plant. Nod factors are lipochitooligosaccharides that carry different substitutions. Recently, plant genes have been characterized that encode components of the Nod factor receptor͞ perception complexes (1-5).In legume symbiosis, bacterial invasion can follow different routes, the best known of which is via root hairs. Rhizobia induce the curling of growing root hairs, are entrapped in the curl, and enter the root hair by local hydrolysis of cell walls and invagination of the plasma membrane. Tip growth toward the base of the root hair results in an intracellular infection thread that proceeds through the cortical cells to reach the nodule primordia, where bacteria are released inside plant cells. The process takes place in the zone of developing root hairs (zone I, ref. 6), located just above the root meristem. Root hair invasion is used in pea, bean, soybean, vetch, and alfalfa, and in the model legumes Medicago truncatula and Lotus japonicus (7,8).Another mode of entry, via intercellular invasion at lateral root bases, has been observed in many tropical legumes. The bacteria enter via cracks formed by the protrusion of lateral roots and colonize large intercellular spaces called infection pockets. The mechanism for deeper invasion varies. In Sesbania rostrata and in Neptunia sp., infection pockets narrow down to form intercellular infection threads, and subsequently intracellular infection threads intrude in...

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