scholarly journals Bacteroid Development in Legume Nodules: Evolution of Mutual Benefit or of Sacrificial Victims?

2011 ◽  
Vol 24 (11) ◽  
pp. 1300-1309 ◽  
Author(s):  
Attila Kereszt ◽  
Peter Mergaert ◽  
Eva Kondorosi
Keyword(s):  
Innate Immunity ◽  
Terminal Differentiation ◽  
Nodule Development ◽  
Mutual Benefit ◽  
Plant Origin ◽  
Peribacteroid Membrane ◽  
Effector Molecules ◽  
Plant Genes ◽  
Peribacteroid Space ◽  
Symbiotic Partner

Symbiosomes are organelle-like structures in the cytoplasm of legume nodule cells which are composed of the special, nitrogen-fixing forms of rhizobia called bacteroids, the peribacteroid space and the enveloping peribacteroid membrane of plant origin. The formation of these symbiosomes requires a complex and coordinated interaction between the two partners during all stages of nodule development as any failure in the differentiation of either symbiotic partner, the bacterium or the plant cell prevents the subsequent transcriptional and developmental steps resulting in early senescence of the nodules. Certain legume hosts impose irreversible terminal differentiation onto bacteria. In the inverted repeat–lacking clade (IRLC) of legumes, host dominance is achieved by nodule-specific cysteine-rich peptides that resemble defensin-like antimicrobial peptides, the known effector molecules of animal and plant innate immunity. This article provides an overview on the bacteroid and symbiosome development including the terminal differentiation of bacteria in IRLC legumes as well as the bacterial and plant genes and proteins participating in these processes.

scholarly journals Absence of Symbiotic Leghemoglobins Alters Bacteroid and Plant Cell Differentiation During Development of Lotus japonicus Root Nodules

2009 ◽  
Vol 22 (7) ◽  
pp. 800-808 ◽  
Author(s):  
Thomas Ott ◽  
John Sullivan ◽  
Euan K. James ◽  
Emmanouil Flemetakis ◽  
Catrin Günther ◽  
...  
Keyword(s):  
Gene Expression ◽  
Nitrogen Fixation ◽  
Cell Differentiation ◽  
Root Nodules ◽  
Lotus Japonicus ◽  
Nodule Development ◽  
Primary And Secondary Metabolism ◽  
Bacterial Differentiation ◽  
Plant Genes ◽  
Bacterial Genes

During development of legume root nodules, rhizobia and their host plant cells undergo profound differentiation, which is underpinned by massive changes in gene expression in both symbiotic partners. Oxygen concentrations in infected and surrounding uninfected cells drop precipitously during nodule development. To assess what effects this has on plant and bacterial cell differentiation and gene expression, we used a leghemoglobin-RNA-interference (LbRNAi) line of Lotus japonicus, which is devoid of leghemoglobins and has elevated levels of free-oxygen in its nodules. Bacteroids in LbRNAi nodules showed altered ultrastructure indicating changes in bacterial differentiation. Transcript analysis of 189 plant and 192 bacterial genes uncovered many genes in both the plant and bacteria that were differentially regulated during nodulation of LbRNAi plants compared with the wild type (containing Lb and able to fix nitrogen). These included fix and nif genes of the bacteria, which are involved in microaerobic respiration and nitrogen fixation, respectively, and plant genes involved in primary and secondary metabolism. Metabolite analysis revealed decreased levels of many amino acids in nodules of LbRNAi plants, consistent with the defect in symbiotic nitrogen fixation of this line.

Paneth cell defensins: key effector molecules of innate immunity

2006 ◽  
Vol 34 (2) ◽  
pp. 263-266 ◽  
Author(s):  
C.L. Bevins
Keyword(s):  
Innate Immunity ◽  
Paneth Cell ◽  
Intestinal Wall ◽  
Intestinal Lumen ◽  
Murine Models ◽  
Key Factors ◽  
Effector Molecules ◽  
Wide Range ◽  
Key Factor ◽  
Inflammatory Bowel

Antimicrobial peptides are fundamental effector molecules of innate immunity, utilized in host defence by virtually all organisms studied. These gene-encoded peptides have direct antibiotic activity against a wide range of bacteria and other microbes. In humans and other mammals, defensins are a predominant class of such peptides. In the mammalian small intestine, Paneth cells, specialized secretory epithelial cells located at the base of the crypt invaginations lining the intestinal wall, produce defensins and other antibiotic proteins. Recent investigations in murine models provide compelling support for the hypothesis that enteric defensins play a pivotal role in defence from food- and water-borne pathogens in the intestinal lumen. Investigations by others indicate that intestinal commensal bacteria are key factors in the pathogenesis of IBD (inflammatory bowel disease) in genetically susceptible humans. Recent studies provide evidence that reduced expression of Paneth cell defensins may be a key factor in the pathogenesis of ileal Crohn's disease, a subgroup of IBD. Future studies to further define the function and regulation of Paneth cell defensins will enhance our understanding of normal small bowel physiology, and probably contribute to a better understanding of the pathogenesis of inflammatory and infectious diseases of the bowel. Such knowledge may provide new therapeutic targets and strategies.

scholarly journals Rhizobium fix genes mediate at least two communication steps in symbiotic nodule development.

1988 ◽  
Vol 106 (3) ◽  
pp. 597-607 ◽  
Author(s):  
P Putnoky ◽  
E Grosskopf ◽  
D T Ha ◽  
G B Kiss ◽  
A Kondorosi
Keyword(s):  
Rhizobium Meliloti ◽  
Host Cells ◽  
Nodule Development ◽  
Peribacteroid Membrane ◽  
Symbiotic Gene ◽  
Morphological Studies ◽  
Group I ◽  
Infection Threads ◽  
Symbiotic Nodule ◽  
Bacterial Genes

To identify bacterial genes involved in symbiotic nodule development, ineffective nodules of alfalfa (Medicago sativa) induced by 64 different Fix-mutants of Rhizobium meliloti were characterized by assaying for symbiotic gene expression and by morphological studies. The expression of leghemoglobin and nodulin-25 genes from alfalfa and of the nifHD genes from R. meliloti were monitored by hybridizing the appropriate DNA probes to RNA samples prepared from nodules. The mutants were accordingly divided into three groups. In group I none of the genes were expressed, in group II only the plant genes were expressed and in group III all three genes were transcribed. Light and electron microscopical analysis of nodules revealed that nodule development was halted at different stages in nodules induced by different group I mutants. In most cases nodules were empty lacking infection threads and bacteroids or nodules contained infection threads and a few released bacteroids. In nodules induced by a third mutant class bacteria were released into the host cells, however the formation of the peribacteroid membrane was not normal. On this basis we suggest that peribacteroid membrane formation precedes leghemoglobin and nodulin-25 induction, moreover, after induction of nodulation by the nod genes at least two communication steps between the bacteria and the host plants are necessary for the development of the mature nodule. By complementing each mutant of group I with a genomic R. meliloti library made in pLAFRl, four new fix loci were identified, indicating that several bacterial genes are involved in late nodule development.

scholarly journals Identification of Novel Putative Regulatory Genes Induced During Alfalfa Nodule Development with a Cold-Plaque Screening Procedure

1998 ◽  
Vol 11 (5) ◽  
pp. 358-366 ◽  
Author(s):  
Florian Frugier ◽  
Adam Kondorosi ◽  
Martin Crespi
Keyword(s):  
Expression Patterns ◽  
Protein A ◽  
Screening Method ◽  
Screening Procedure ◽  
Nodule Development ◽  
Stage Of Development ◽  
Plant Genes ◽  
Gene Transcripts ◽  
And Function ◽  
Regulatory Functions

Until now very few plant genes with possible regulatory functions during nodule development have been isolated. We have used a modified cold-plaque screening method to identify new transcripts expressed at low levels that are induced during nodulation. Several clones were isolated and characterized by their mRNA expression patterns during nodule development and in spontaneous nodules. Sequence homology with known genes of other organisms indicated that transcripts corresponded to (i) “basic” genes probably required during the growth of the nodule organ (e.g., structural proteins), (ii) genes related to the metabolic adaptations taking place during nodule morphogenesis and function (e.g., carbonic anhydrase), and (iii) genes containing regulatory motifs and/or homologies (three clones out of the 20 identified). The latter genes encode a zinc-finger-containing protein, a putative protein kinase, and a Wilm's tumor (WT) suppressor homologue, respectively. Expression of the kinase and WT suppressor homologues was induced early in nodulation, although the latter was activated transiently. Accumulation of the Zn-finger gene transcripts was detected at a later stage of development and seems to be regulated in a complex manner. Hence, using a cold-plaque screening procedure, we could identify genes that may play regulatory roles in the signal transduction pathways activated during nodule development.

Membrane Interface of the Bradyrhizobium japonicum - Glycine max Symbiosis: Peribacteroid Units From Soyabean Nodules

1989 ◽  
Vol 16 (1) ◽  
pp. 69 ◽  
Author(s):  
DA Day ◽  
GD Price ◽  
MK Udvardi
Keyword(s):  
Glycine Max ◽  
Bradyrhizobium Japonicum ◽  
Recent Literature ◽  
Nitrogenase Activity ◽  
Membrane Interface ◽  
Peribacteroid Membrane ◽  
Literature Evidence ◽  
Peribacteroid Space ◽  
Ion Movements

A method for preparing intact peribacteroid units from soybean nodules is described in detail. The polypeptide compositions of the peribacteroid membrane and peribacteroid space contents are described, and the properties of these compartments are discussed In the hght of recent literature. Evidence is presented that the peribacteroid membrane is permeable to succinate and malate but not to sucrose and glutamate. A dicarboxylate transporter on the peribacteroid membrane, which is capable of transporting malate and succinate at rates sufficient to support measured nitrogenase activity, is described The properties of an ATPase found on the peribacteroid membrane are also described and compared to those described in other reports This ATPase is able to catalyse energisation of the peribacteroid membrane in an uncoupler and vanadate-sensitive manner and may play an important role in the regulation of ion movements across the membrane.

Defensins and cathelicidins in inflammatory lung disease: beyond antimicrobial activity

2006 ◽  
Vol 34 (2) ◽  
pp. 276-278 ◽  
Author(s):  
P.S. Hiemstra
Keyword(s):  
Innate Immunity ◽  
Immune Responses ◽  
Wound Repair ◽  
First Line ◽  
Gram Negative ◽  
Enveloped Viruses ◽  
Effector Molecules ◽  
Gram Positive Bacteria ◽  
Wide Range ◽  
Micro Organisms

Innate immunity provides an effective first line of defence against infections. This is of particular importance in the lung, an organ that is exposed to a large number of pathogens that are inhaled. Antimicrobial peptides play an important role in the defence against these pathogens as effector molecules of innate immunity. These peptides are mainly produced by phagocytes and epithelial cells, and kill a wide range of micro-organisms: Gram-negative and Gram-positive bacteria, fungi and (enveloped) viruses. However, it is increasingly evident that these peptides not only act as endogenous antibiotics, but also display a range of other functions, including activities that are involved in regulating immune responses and inflammation, and wound repair. In this review, these activities are highlighted and their role in inflammatory lung disorders is discussed.

scholarly journals Identifying effector molecules, cells, and cytokines of innate immunity in OA

2020 ◽  
Vol 28 (5) ◽  
pp. 532-543 ◽  
Author(s):  
M.H.J. van den Bosch ◽  
P.L.E.M. van Lent ◽  
P.M. van der Kraan
Keyword(s):  
Innate Immunity ◽  
Effector Molecules
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