Ammonia and amino acid transport across symbiotic membranes in nitrogen-fixing legume nodules

Day, David A.; Poole, Phillip; Tyerman, Stephen D.; Rosendahl, L.

doi:10.1007/pl00000778

Cited by 112 publications

(72 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…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 .…”

Section: Box 3 Host Invasion Parallels Between Rhizobia and Animal Pamentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

View full text Add to dashboard Cite

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...

show abstract

Section: Box 3 Host Invasion Parallels Between Rhizobia and Animal Pamentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

View full text Add to dashboard Cite

show abstract

“…The symbiosome membrane is highly specialized and participates in the exchange of metabolites (the efflux of fixed nitrogen and the uptake of a carbon source in the form of dicarboxylates) between the endosymbiont and the plant host as well as serving to protect the bacteroid from plant host defense responses (Udvardi and Day, 1997;Day et al, 2001). During the biogenesis of the symbiosome, a number of plant-encoded nodule-specific gene products (nodulins) are targeted to the symbiosome membrane, where they are presumed to aid in the establishment and maintenance of symbiosis (Fortin et al, 1985;Panter et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Phosphorylation of Soybean Nodulin 26 on Serine 262 Enhances Water Permeability and Is Regulated Developmentally and by Osmotic Signals

et al. 2003

View full text Add to dashboard Cite

Soybean nodulin 26 is expressed and targeted to the symbiosome membrane of nitrogen-fixing nodules, where it forms an aquaporin channel with a modest water transport rate. In this study, we show that the phosphorylation of nodulin 26 on Ser-262, which is catalyzed by a symbiosome membrane-associated calcium-dependent protein kinase, stimulates its intrinsic water transport rate. Furthermore, using a phosphospecific antibody, we have elucidated the developmental appearance and regulation of nodulin 26 phosphorylation in vivo. Although nodulin 26 protein is detected first in differentiating infected cells (16 days), phosphorylated nodulin 26 does not become pronounced until infected cell maturation (25 days). Phosphorylation is sustained at steady state levels until entry into senescence. Nodulin 26 phosphorylation is enhanced further by osmotic stresses (water deprivation and salinity). Thus, the phosphorylation of nodulin 26 coincides with the establishment of mature nitrogen-fixing symbiosomes, is regulated by osmotic stresses that induce calcium-signaling pathways, and appears to be part of the adaptive responses of infected cells to osmotic challenge.

show abstract

“…However, given its multifunctional transport activity, a role in infected cell metabolism cannot be excluded. In particular, work by Niemietz and Tyerman [11] with isolated SM vesicles provided support for a facilitated pathway of NH 3 transport that is inhibited by Hg 2+ . Since the aquaporin activity of nod26 is also blocked by Hg 2+ [8,9] and considering that a number of aquaporins show permeability to ammonia [12][13][14], a potential additional transport activity for nod26 may be the transport of fixed nitrogen in the form of NH 3 from the symbiosome [11].…”

Section: Introductionmentioning

confidence: 96%

“…The symbiosome membrane (SM), also referred to as the peribacteroid membrane, is the outer boundary of this organelle which controls the transport of metabolites between the symbiont and the plant host [2]. These transport activities include the efflux of the primary metabolic product of nitrogen fixation (NH 3 /NH 4 + ) and the uptake of dicarboxylates as an energy source to support bacterial N 2 fixation [2,3].…”

Section: Introductionmentioning

confidence: 99%

Ammonia permeability of the soybean nodulin 26 channel

2010

View full text Add to dashboard Cite

a b s t r a c tSoybean nodulin 26 (nod26), a member of the aquaporin superfamily, is the major protein component of the symbiosome membrane that encloses nitrogen-fixing bacteroids in root nodules. Previous work has demonstrated that nod26 facilitates the transport of water and glycerol, although a potential additional role as a channel for fixed ammonia efflux has been hypothesized. In the present study it is shown that recombinant nod26 reconstituted into proteoliposomes facilitates NH 3 transport in an Hg 2+ -sensitive manner with a reduced activation energy, hallmarks of proteinfacilitated transport characteristic of aquaporins. Comparison of the predicted single-channel transport rates of nod26 suggests a 4.9-fold preference for ammonia compared to water.

show abstract

Ammonia and amino acid transport across symbiotic membranes in nitrogen-fixing legume nodules

Cited by 112 publications

References 69 publications

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

Phosphorylation of Soybean Nodulin 26 on Serine 262 Enhances Water Permeability and Is Regulated Developmentally and by Osmotic Signals

Ammonia permeability of the soybean nodulin 26 channel

Contact Info

Product

Resources

About