Rhizobium meliloti 1021 has three differentially regulated loci involved in glutamine biosynthesis, none of which is essential for symbiotic nitrogen fixation

Bruijn, Frans J. de; Rossbach, Silvia; Schneider, Maria Victoria; Ratet, Pascal; Messmer, Sylvia; Szeto, Wynne W.; Ausubel, F M; Schell, Jeff

doi:10.1128/jb.171.3.1673-1682.1989

Cited by 102 publications

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“…Once secreted, it is thought to be taken up by the plant through NH 4 + channels that have been detected in the peribacteroid membrane and then assimilated 88,102 . A complex amino-acid cycling system between plant cells and bacteroids might prevent the bacteroids from assimilating NH 4 + , and allow NH 4 + to be secreted for uptake by the plant 88,101,103,104 . Metabolite analysis and RNAi depletion experiments suggest that NH 4 + assimilation by plant cells occurs primarily through glutamine and asparagine synthetases [105][106][107] .…”

Section: Nih-pa Author Manuscriptmentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

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Nitrogen-fixing rhizobial bacteria and leguminous plants have evolved complex signal exchange mechanisms that allow a specific bacterial species to induce its host plant to form invasion structures through which the bacteria can enter the plant root. Once the bacteria have been endocytosed within a host-membrane-bound compartment by root cells, the bacteria differentiate into a new form that can convert atmospheric nitrogen into ammonia. Bacterial differentiation and nitrogen fixation are dependent on the microaerobic environment and other support factors provided by the plant. In return, the plant receives nitrogen from the bacteria, which allows it to grow in the absence of an external nitrogen source. Here, we review recent discoveries about the mutual recognition process that allows the model rhizobial symbiont Sinorhizobium meliloti to invade and differentiate inside its host plant alfalfa (Medicago sativa) and the model host plant barrel medic (Medicago truncatula).The recent completion of the Sinorhizobium meliloti genome sequence, and the progress towards the completion of the Medicago truncatula genome sequence, have led to a surge in the molecular characterization of the determinants that are involved in the development of the symbiosis between rhizobial bacteria and leguminous plants. Aromatic compounds from legumes called flavonoids first signal the rhizobial bacteria to produce lipochitooligosaccharide compounds called Nod factors 1 . Nod factors that are secreted by the bacteria activate multiple responses in the host plant that prepare the plant to receive the invading bacteria. Nod factors and symbiotic exopolysaccharides induce the plant to form infection threads, which are thin tubules filled with bacteria that penetrate into the plant cortical tissue and deliver the bacteria to their target cells. Plant cells in the inner cortex internalize the invading bacteria in host-membrane-bound compartments that mature into structures known Correspondence to G.C.W. gwalker@mit.edu. Competing interests statementThe authors declare no competing financial interests. DATABASES Invasion of plant rootsAlthough plant roots are exposed to various micro-organisms in the soil, their cell walls form a strong protective barrier against most harmful species. The early steps in the invasion of barrel medic (M. truncatula) and alfalfa (Medicago sativa) roots by S. meliloti are characterized by the reciprocal exchange of signals that allow the bacteria to use the plant root hair cells as a means of entry. Initial signal exchangeFlavonoid compounds (2-phenyl-1,4-benzopyrone derivatives) produced by leguminous plants are the first signals to be exchanged by host-rhizobial symbiont pairs 1 (FIG. 1). Flavonoids bind bacterial NodD proteins, which are members of the LysR family of transcriptional regulators, and activate these proteins to induce the transcription of rhizobial genes 1,2 . For example, the M. sativa-derived flavonoid luteolin stimulates binding of an active form of NodD1 to an S. meliloti 'nod-box' p...

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Section: Nih-pa Author Manuscriptmentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

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“…ADP1 are predicted enzymes depending on their genome similarity to other documented proteins in the database. Only GS III T of R. meliloti and R. leguminosarum was characterized, and it was described as having low glutamine-forming activity, [26][27][28] which suggested the question of Shatters et al about the primary role of the enzyme. 27) The higher reactivity to hydroxylamine of R. meliloti GS III T than to ammonia 27) was almost the same as that of M. mays No.…”

Section: Isolation Of Gmas Genementioning

confidence: 99%

“…23) GS III, encoded by the glnN, was recently discovered in a few obligate anaerobic bacteria and cyanobacteria. 18,24,25) Gln T (glnT) was isolated from Rhizobium meliloti 26,27) and R. leguminosarus. 28) Its molecular weight of subunit, number of subunits, and affinities to substrates are quite different from those of GS III (glnN), but most of Gln Ts are frequently described as ''GS III'' in the literature.…”

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“…28) Its molecular weight of subunit, number of subunits, and affinities to substrates are quite different from those of GS III (glnN), but most of Gln Ts are frequently described as ''GS III'' in the literature. 17,[26][27][28] In this paper, GS III encoded by glnN is indicated as GS III N , and Gln T (GS III) by glnT as GS III T , to prevent the confusion caused by the single description ''GS III.'' Detailed biochemical analysis has shown that GS I, GS II, and GS III N play a central role in nitrogen assimilation by catalyzing the condensation of ammonia and glutamate to form glutamine (Fig.…”

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confidence: 99%

“…Detailed biochemical analysis has shown that GS I, GS II, and GS III N play a central role in nitrogen assimilation by catalyzing the condensation of ammonia and glutamate to form glutamine (Fig. 1A), 19,23,24) but GS III T of Rhizobium has an extremely low glutamineforming activity, [26][27][28] though the gene of GS III T complemented an E. coli glutamine auxotroph, 26) which led Shatters et al to question whether the primary function of this enzyme is glutamine synthesis. 27) The GS III of Met.…”

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Cloning and Expression ofMethylovorus maysNo. 9 Gene Encoding γ-Glutamylmethylamide Synthetase: An Enzyme Usable in Theanine Formation by Coupling with the Alcoholic Fermentation System of Baker’s Yeast

Yamamoto

Wakayama

Tachiki

2008

Bioscience, Biotechnology, and Biochemistry

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Sinorhizobium meliloti metabolism in the root nodule: A proteomic perspective

Djordjevic¹

2004

Proteomics

111

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The proteome of the model symbiotic bacterium, Sinorhizobium meliloti was examined to determine the enzymatic reactions and cell processes that occur when S. meliloti occupies the root nodules of Medicago truncatula and Melilotus alba. The proteomes of the nodule bacteria were compared to that of S. meliloti grown under laboratory cultured conditions as an additional control. All the detectable protein spots on the two-dimensional (2-D) gels between pH 4-7 were analyzed. In total, the identity of proteins in 1545 spots from 2-D gels was determined using peptide mass fingerprinting. There were clear differences in the proteome of nodule bacteria and cultured bacteria and putative nodule-specific and nodule suppressed proteins were identified. The data were analyzed using metabolic pathway prediction programs and used to review the biochemical and genetic studies that had been done previously on S. meliloti over several decades. There was a broad congruency between the proteomic and biochemical data when the overall pathways of central carbon and nitrogen metabolism were considered. A selective suite of ABC-type transporters was present in nodule bacteria that were biased towards the transport of amino acids and inorganic ions (P and Fe) suggesting that a highly specialized nutrient exchange was occurring between the nodule bacteria and the host. Proteins prominent in nodule bacteria were those involved in the pathways for vitamin synthesis and stress-related processes (chaperoning, heat shock, detoxification of reactive oxygen species, regulation of stress and osmo-regulation). Some of these proteins were found only in nodule bacteria. These results show the extent of the shift in metabolism that occurs when S. meliloti invades legume plants and establishes a nitrogen fixing symbiosis.

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Rhizobium meliloti 1021 has three differentially regulated loci involved in glutamine biosynthesis, none of which is essential for symbiotic nitrogen fixation

Abstract: We have cloned and characterized three distinct Rhizobium meliloti loci involved in glutamine biosynthesis (ginA, glnlI, and glnT

Cited by 102 publications

References 60 publications

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

Cloning and Expression ofMethylovorus maysNo. 9 Gene Encoding γ-Glutamylmethylamide Synthetase: An Enzyme Usable in Theanine Formation by Coupling with the Alcoholic Fermentation System of Baker’s Yeast

Sinorhizobium meliloti metabolism in the root nodule: A proteomic perspective

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