Topic
Rhizobium
About: Rhizobium is a research topic. Over the lifetime, 7442 publications have been published within this topic receiving 234976 citations.
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TL;DR: Genetic manipulation of phosphate-solubilizing bacteria to improve their ability to improve plant growth may include cloning genes involved in both mineral and organic phosphate solubilization, followed by their expression in selected rhizobacterial strains.
2,761 citations
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TL;DR: In some areas of Latin America, inoculation which normally promotes nodulation and nitrogen fixation is hampered by the prevalence of native strains such as R. etli and R. giardinii as discussed by the authors.
Abstract: Common bean (Phaseolus vulgaris) has become a cosmopolitan crop, but was originally domesticated in the Americas and has been grown in Latin America for several thousand years. Consequently an enormous diversity of bean nodulating bacteria have developed and in the centers of origin the predominant species in bean nodules is R. etli. In some areas of Latin America, inoculation, which normally promotes nodulation and nitrogen fixation is hampered by the prevalence of native strains. Many other species in addition to R. etli have been found in bean nodules in regions where bean has been introduced. Some of these species such as R. leguminosarum bv. phaseoli, R. gallicum bv. phaseoli and R. giardinii bv. phaseoli might have arisen by acquiring the phaseoli plasmid from R. etli. Others, like R. tropici, are well adapted to acid soils and high temperatures and are good inoculants for bean under these conditions. The large number of rhizobia species capable of nodulating bean supports that bean is a promiscuous host and a diversity of bean-rhizobia interactions exists. Large ranges of dinitrogen fixing capabilities have been documented among bean cultivars and commercial beans have the lowest values among legume crops. Knowledge on bean symbiosis is still incipient but could help to improve bean biological nitrogen fixation.
1,641 citations
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University of Minnesota1, Centre national de la recherche scientifique2, Institut national de la recherche agronomique3, John Innes Centre4, Laboratory of Molecular Biology5, Iowa State University6, Agricultural Research Service7, West Virginia University8, University of Bonn9, Ghent University10, University of California, Davis11, Delaware Biotechnology Institute12, J. Craig Venter Institute13, University of Wisconsin-Madison14, National Center for Genome Resources15, King Saud University16, University of Oklahoma17, Cornell University18, Max Planck Society19, Wellcome Trust20, International Institute of Minnesota21, Rural Development Administration22, Carleton College23, Norwich Research Park24
TL;DR: The draft sequence of the M. truncatula genome sequence is described, a close relative of alfalfa (Medicago sativa), a widely cultivated crop with limited genomics tools and complex autotetraploid genetics, which provides significant opportunities to expand al falfa’s genomic toolbox.
Abstract: Legumes (Fabaceae or Leguminosae) are unique among cultivated plants for their ability to carry out endosymbiotic nitrogen fixation with rhizobial bacteria, a process that takes place in a specialized structure known as the nodule. Legumes belong to one of the two main groups of eurosids, the Fabidae, which includes most species capable of endosymbiotic nitrogen fixation. Legumes comprise several evolutionary lineages derived from a common ancestor 60 million years ago (Myr ago). Papilionoids are the largest clade, dating nearly to the origin of legumes and containing most cultivated species. Medicago truncatula is a long-established model for the study of legume biology. Here we describe the draft sequence of the M. truncatula euchromatin based on a recently completed BAC assembly supplemented with Illumina shotgun sequence, together capturing ∼94% of all M. truncatula genes. A whole-genome duplication (WGD) approximately 58 Myr ago had a major role in shaping the M. truncatula genome and thereby contributed to the evolution of endosymbiotic nitrogen fixation. Subsequent to the WGD, the M. truncatula genome experienced higher levels of rearrangement than two other sequenced legumes, Glycine max and Lotus japonicus. M. truncatula is a close relative of alfalfa (Medicago sativa), a widely cultivated crop with limited genomics tools and complex autotetraploid genetics. As such, the M. truncatula genome sequence provides significant opportunities to expand alfalfa's genomic toolbox.
1,153 citations
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TL;DR: Using R. meliloti strains overproducing symbiotic Nod factors, the major alfalfa-specific signal, NodRm-1, is purified by gel permeation, ion exchange and C18 reverse-phase high performance liquid chromatography and elicited root hair deformation on the homologous host when added in nanomolar concentration.
Abstract: Rhizobia are symbiotic bacteria that elicit the formation on leguminous plants of specialized organs, root nodules, in which they fix nitrogen. In various Rhizobium species, such as R. leguminosarum and R. meliloti, common and host-specific nodulation (nod) genes have been identified which determine infection and nodulation of specific hosts. Common nodABC genes as well as host-specific nodH and nodQ genes were shown recently, using bioassays, to be involved in the production of extracellular Nod signals. Using R. meliloti strains overproducing symbiotic Nod factors, we have purified the major alfalfa-specific signal, NodRm-1, by gel permeation, ion exchange and C18 reverse-phase high performance liquid chromatography. From mass spectrometry, nuclear magnetic resonance, (35)S-labelling and chemical modification studies, NodRm-1 was shown to be a sulphated beta-1,4-tetrasaccharide of D-glucosamine (Mr 1,102) in which three amino groups were acetylated and one was acylated with a C16 bis-unsaturated fatty acid. This purified Nod signal specifically elicited root hair deformation on the homologous host when added in nanomolar concentration.
1,086 citations
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TL;DR: The mechanisms by which the plant allows bacterial infection and promotes the formation of the nodule are reviewed, as well as the details of how a complex interchange of metabolites and regulatory peptides force the bacteria into a nitrogen-fixing organelle-like state are reviewed.
Abstract: Rhizobial bacteria enter a symbiotic association with leguminous plants, resulting in differentiated bacteria enclosed in intracellular compartments called symbiosomes within nodules on the root. The nodules and associated symbiosomes are structured for efficient nitrogen fixation. Although the interaction is beneficial to both partners, it comes with rigid rules that are strictly enforced by the plant. Entry into root cells requires appropriate recognition of the rhizobial Nod factor signaling molecule, and this recognition activates a series of events, including polarized root-hair tip growth, invagination associated with bacterial infection, and the promotion of cell division in the cortex leading to the nodule meristem. The plant's command of the infection process has been highlighted by its enforcement of terminal differentiation upon the bacteria within nodules of some legumes, and this can result in a loss of bacterial viability while permitting effective nitrogen fixation. Here, we review the mechanisms by which the plant allows bacterial infection and promotes the formation of the nodule, as well as the details of how this intimate association plays out inside the cells of the nodule where a complex interchange of metabolites and regulatory peptides force the bacteria into a nitrogen-fixing organelle-like state.
987 citations