Plant microbe symbiotic signals
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Rescooped by Olivier ANDRE from Plant-Microbe Symbiosis
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The potential roles of strigolactones and brassinosteroids in the autoregulation of nodulation pathway

The potential roles of strigolactones and brassinosteroids in the autoregulation of nodulation pathway | Plant microbe symbiotic signals | Scoop.it

Background and Aims The number of nodules formed on a legume root system is under the strict genetic control of the autoregulation of nodulation (AON) pathway. Plant hormones are thought to play a role in AON; however, the involvement of two hormones recently described as having a largely positive role in nodulation, strigolactones and brassinosteroids, has not been examined in the AON process.

Methods A genetic approach was used to examine if strigolactones or brassinosteroids interact with the AON system in pea (Pisum sativum). Double mutants between shoot-acting (Psclv2, Psnark) and root-acting (Psrdn1) mutants of the AON pathway and strigolactone-deficient (Psccd8) or brassinosteroid-deficient (lk) mutants were generated and assessed for various aspects of nodulation. Strigolactone production by AON mutant roots was also investigated.

Key Results Supernodulation of the roots was observed in both brassinosteroid- and strigolactone-deficient AON double-mutant plants. This is despite the fact that the shoots of these plants displayed classic strigolactone-deficient (increased shoot branching) or brassinosteroid-deficient (extreme dwarf) phenotypes. No consistent effect of disruption of the AON pathway on strigolactone production was found, but root-acting Psrdn1 mutants did produce significantly more strigolactones.

Conclusions No evidence was found that strigolactones or brassinosteroids act downstream of the AON genes examined. While in pea the AON mutants are epistatic to brassinosteroid and strigolactone synthesis genes, we argue that these hormones are likely to act independently of the AON system, having a role in the promotion of nodule formation.


Via Jean-Michel Ané
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Rescooped by Olivier ANDRE from Plant roots and rhizosphere
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Visualization of Highly Dynamic F-Actin Plus Ends in Growing Phaseolus vulgaris Root Hair Cells and Their Responses to Rhizobium etli Nod Factors

Visualization of Highly Dynamic F-Actin Plus Ends in Growing Phaseolus vulgaris Root Hair Cells and Their Responses to Rhizobium etli Nod Factors | Plant microbe symbiotic signals | Scoop.it

Legume plants secrete signaling molecules called flavonoids into the rhizosphere. These molecules activate the transcription of rhizobial nod genes, which encode proteins involved in the synthesis of signaling compounds named Nod factors (NFs). NFs, in turn, trigger changes in plant gene expression, cortical cell dedifferentiation and mitosis, depolarization of the root hair cell membrane potential and rearrangement of the actin cytoskeleton. Actin polymerization plays an important role in apical growth in hyphae and pollen tubes. Using sublethal concentrations of fluorescently labeled cytochalasin D (Cyt-Fl), we visualized the distribution of filamentous actin (F-actin) plus ends in living Phaseolus vulgaris and Arabidopsis root hairs during apical growth. We demonstrated that Cyt-Fl specifically labeled the newly available plus ends of actin microfilaments, which probably represent sites of polymerization. The addition of unlabeled competing cytochalasin reduced the signal, suggesting that the labeled and unlabeled forms of the drug bind to the same site on F-actin. Exposure to Rhizobium etli NFs resulted in a rapid increase in the number of F-actin plus ends in P. vulgaris root hairs and in the re-localization of F-actin plus ends to infection thread initiation sites. These data suggest that NFs promote the formation of F-actin plus ends, which results in actin cytoskeleton rearrangements that facilitate infection thread formation.


Via Christophe Jacquet
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Carlactone is an endogenous biosynthetic precursor for strigolactones

Carlactone is an endogenous biosynthetic precursor for strigolactones | Plant microbe symbiotic signals | Scoop.it

Strigolactones (SLs) were initially characterized as root-derived signals for parasitic and symbiotic interactions with root parasitic plants and arbuscular mycorrhizal fungi, respectively. SLs were later shown to act as endogenous hormones that regulate shoot branching. Carlactone (CL) was identified as a product of three SL biosynthetic enzymes in vitro, and therefore a putative biosynthetic precursor for SLs. However, it was neither detected from plant tissues, nor was the conversion of CL to SL demonstrated in vivo. In this paper, we show that 13C-labeled CL is converted to SLs in vivo, and that endogenous CL is successfully identified from rice and Arabidopsis. These results demonstrate that CL is a true biosynthetic precursor for SLs.

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Flavonoid-induced calcium signalling in Rhizobium leguminosarum bv. viciae

Flavonoid-induced calcium signalling in Rhizobium leguminosarum bv. viciae | Plant microbe symbiotic signals | Scoop.it

Legume–rhizobium symbiosis requires a complex dialogue based on the exchange of diffusible signals between the partners. Compatible rhizobia express key nodulation (nod) genes in response to plant signals – flavonoids – before infection. Host plants sense counterpart rhizobial signalling molecules – Nod factors – through transient changes in intracellular free-calcium. Here we investigate the potential involvement of Ca2+ in the symbiotic signalling pathway activated by flavonoids inRhizobium leguminosarum bv. viciae.•By using aequorin-expressing rhizobial strains, we monitored intracellular Ca2+ dynamics and the Ca2+ dependence of nodgene transcriptional activation.•Flavonoid inducers triggered, in R. leguminosarum, transient increases in the concentration of intracellular Ca2+ that were essential for the induction of nod genes. Signalling molecules not specifically related to rhizobia, such as strigolactones, were not perceived by rhizobia through Ca2+ variations. A Rhizobium strain cured of the symbiotic plasmid responded to inducers with an unchanged Ca2+ signature, showing that the transcriptional regulator NodD is not directly involved in this stage of flavonoid perception and plays its role downstream of the Ca2+ signalling event.•These findings demonstrate a key role played by Ca2+ in sensing and transducing plant-specific flavonoid signals in rhizobia and open up a new perspective in the flavonoid–NodD paradigm of nod gene regulation.


Via Jean-Michel Ané
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Automated analysis of calcium spiking profiles with CaSA software: two case studies from root-microbe symbioses

Automated analysis of calcium spiking profiles with CaSA software: two case studies from root-microbe symbioses | Plant microbe symbiotic signals | Scoop.it

Background

Repeated oscillations in intracellular calcium (Ca2+) concentration, known as Ca2+ spiking signals, have been described in plants for a limited number of cellular responses to biotic or abiotic stimuli and most notably the common symbiotic signaling pathway (CSSP) which mediates the recognition by their plant hosts of two endosymbiotic microbes, arbuscular mycorrhizal (AM) fungi and nitrogen fixing rhizobia. The detailed analysis of the complexity and variability of the Ca2+ spiking patterns which have been revealed in recent studies requires both extensive datasets and sophisticated statistical tools.

Results

As a contribution, we have developed automated Ca2+ spiking analysis (CaSA) software that performs i) automated peak detection, ii) statistical analyses based on the detected peaks, iii) autocorrelation analysis of peak-to-peak intervals to highlight major traits in the spiking pattern.

We have evaluated CaSA in two experimental studies. In the first, CaSA highlighted unpredicted differences in the spiking patterns induced in Medicago truncatula root epidermal cells by exudates of the AM fungus Gigaspora margarita as a function of the phosphate concentration in the growth medium of both host and fungus. In the second study we compared the spiking patterns triggered by either AM fungal or rhizobial symbiotic signals. CaSA revealed the existence of different patterns in signal periodicity, which are thought to contribute to the so-called Ca2+ signature.

Conclusions

We therefore propose CaSA as a useful tool for characterizing oscillatory biological phenomena such as Ca2+ spiking.

 

 


Via Christophe Jacquet
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D14-SCFD3-dependent degradation of D53 regulates strigolactone signalling

D14-SCFD3-dependent degradation of D53 regulates strigolactone signalling | Plant microbe symbiotic signals | Scoop.it

Strigolactones (SLs), a newly discovered class of carotenoid-derived phytohormones, are essential for developmental processes that shape plant architecture and interactions with parasitic weeds and symbiotic arbuscular mycorrhizal fungi. Despite the rapid progress in elucidating the SL biosynthetic pathway, the perception and signalling mechanisms of SL remain poorly understood. Here we show that DWARF 53 (D53) acts as a repressor of SL signalling and that SLs induce its degradation. We find that the rice (Oryza sativa) d53 mutant, which produces an exaggerated number of tillers compared to wild-type plants, is caused by a gain-of-function mutation and is insensitive to exogenous SL treatment. The D53 gene product shares predicted features with the class I Clp ATPase proteins and can form a complex with the α/β hydrolase protein DWARF 14 (D14) and the F-box protein DWARF 3 (D3), two previously identified signalling components potentially responsible for SL perception. We demonstrate that, in a D14- and D3-dependent manner, SLs induce D53 degradation by the proteasome and abrogate its activity in promoting axillary bud outgrowth. Our combined genetic and biochemical data reveal that D53 acts as a repressor of the SL signalling pathway, whose hormone-induced degradation represents a key molecular link between SL perception and responses.


Via Francis Martin
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Jean-Michel Ané's curator insight, December 12, 2013 10:34 AM

This one is for strigolactone fans!

Rescooped by Olivier ANDRE from GMOs & Sustainable agriculture
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Metabolic potential of endophytic bacteria

Metabolic potential of endophytic bacteria | Plant microbe symbiotic signals | Scoop.it

The bacterial endophytic microbiome promotes plant growth and health and beneficial effects are in many cases mediated and characterized by metabolic interactions. Recent advances have been made in regard to metabolite production by plant microsymbionts showing that they may produce a range of different types of metabolites. These substances play a role in defense and competition, but may also be needed for specific interaction and communication with the plant host. Furthermore, few examples of bilateral metabolite production are known and endophytes may modulate plant metabolite synthesis as well. We have just started to understand such metabolic interactions between plants and endophytes, however, further research is needed to more efficiently make use of beneficial plant-microbe interactions and to reduce pathogen infestation as well as to reveal novel bioactive substances of commercial interest.


Via Jean-Michel Ané, Christophe Jacquet
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Do strigolactones contribute to plant defence? - Torres-Vera - 2013 - Molecular Plant Pathology - Wiley Online Library

Do strigolactones contribute to plant defence? - Torres-Vera - 2013 - Molecular Plant Pathology - Wiley Online Library | Plant microbe symbiotic signals | Scoop.it

Strigolactones are multifunctional molecules involved in several processes outside and within the plant. As signalling molecules in the rhizosphere, they favour the establishment of arbuscular mycorrhizal symbiosis, but they also act as host detection cues for root parasitic plants. As phytohormones, they are involved in the regulation of plant architecture, adventitious rooting, secondary growth and reproductive development, and novel roles are emerging continuously. In the present study, the possible involvement of strigolactones in plant defence responses was investigated. For this purpose, the resistance/susceptibility of the strigolactone-deficient tomato mutant Slccd8 against the foliar fungal pathogens Botrytis cinerea and Alternaria alternata was assessed. Slccd8 was more susceptible to both pathogens, pointing to a new role for strigolactones in plant defence. A reduction in the content of the defence-related hormones jasmonic acid, salicylic acid and abscisic acid was detected by high-performance liquid chromatography coupled to tandem mass spectrometry in the Slccd8 mutant, suggesting that hormone homeostasis is altered in the mutant. Moreover, the expression level of the jasmonate-dependent gene PinII, involved in the resistance of tomato to B. cinerea, was lower than in the corresponding wild-type. We propose here that strigolactones play a role in the regulation of plant defences through their interaction with other defence-related hormones, especially with the jasmonic acid signalling pathway.

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When a repellent becomes an attractant: harmful saponins are kairomones attracting the symbiotic Harlequin crab : Scientific Reports : Nature Publishing Group

When a repellent becomes an attractant: harmful saponins are kairomones attracting the symbiotic Harlequin crab : Scientific Reports : Nature Publishing Group | Plant microbe symbiotic signals | Scoop.it
Marine organisms have developed a high diversity of chemical defences in order to avoid predators and parasites. In sea cucumbers, saponins function as repellents and many species produce these cytotoxic secondary metabolites.
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Cell Host and Microbe - Initial Symbiont Contact Orchestrates Host-Organ-wide Transcriptional Changes that Prime Tissue Colonization (2013)

Cell Host and Microbe - Initial Symbiont Contact Orchestrates Host-Organ-wide Transcriptional Changes that Prime Tissue Colonization (2013) | Plant microbe symbiotic signals | Scoop.it

Natacha Kremer, Eva E.R. Philipp, Marie-Christine Carpentier, Caitlin A. Brennan, Lars Kraemer, Melissa A. Altura, René Augustin, Robert Häsler, Elizabeth A.C. Heath-Heckman, Suzanne M. Peyer, Julia Schwartzman, Bethany A. Rader, Edward G. Ruby, Philip Rosenstiel, Margaret J. McFall-NgaiInitial

CEll Host & Microbe, Volume 14, Issue 2, 14 August 2013, Pages 183–194

http://dx.doi.org/10.1016/j.chom.2013.07.006

 

 

Upon transit to colonization sites, bacteria often experience critical priming that prepares them for subsequent, specific interactions with the host; however, the underlying mechanisms are poorly described. During initiation of the symbiosis between the bacterium Vibrio fischeri and its squid host, which can be observed directly and in real time, approximately five V. fischeri cells aggregate along the mucociliary membranes of a superficial epithelium prior to entering host tissues. Here, we show that these few early host-associated symbionts specifically induce robust changes in host gene expression that are critical to subsequent colonization steps. This exquisitely sensitive response to the host’s specific symbiotic partner includes the upregulation of a host endochitinase, whose activity hydrolyzes polymeric chitin in the mucus into chitobiose, thereby priming the symbiont and also producing a chemoattractant gradient that promotes V. fischeri migration into host tissues. Thus, the host responds transcriptionally upon initial symbiont contact, which facilitates subsequent colonization.

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Breaking the ice with your host (2013)

Breaking the ice with your host (2013) | Plant microbe symbiotic signals | Scoop.it

Christina Tobin Kåhrström

Nature Reviews Microbiology

doi:10.1038/nrmicro3114

27 August 2013

 

The early interactions between a bacterial symbiont and its host are crucial for establishing a long-lived association, but the molecular mechanisms underlying this initial dialogue are poorly understood. Using the well-established Vibrio fischeri–squid symbiosis as a model system, Kremer et al. now show that the few V. fischeri cells which initiate the association induce transcriptional changes in the host, and these changes prime the symbiont for subsequent colonization.

 

http://www.nature.com/nrmicro/journal/vaop/ncurrent/full/nrmicro3114.html

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Boreal feather mosses secrete chemical signals to gain nitrogen - Bay - 2013 - New Phytologist - Wiley Online Library

Boreal feather mosses secrete chemical signals to gain nitrogen - Bay - 2013 - New Phytologist - Wiley Online Library | Plant microbe symbiotic signals | Scoop.it
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Microbial signaling and plant growth promotion

Microbial signaling and plant growth promotion | Plant microbe symbiotic signals | Scoop.it

The rhizosphere offers a complex microhabitat where root exudates provide a diverse mixture of organic compounds that are used as nutrients or signals by the soil microbial population. On the other hand, these soil microorganisms produce compounds that directly or indirectly assist in plant growth promotion. The widely recognized mechanisms of plant growth promotion are biofertilization, production of phytohormones, suppression of diseases through biocontrol, induction of disease resistance and production of volatile signal compounds. During the past few decades our understanding of the interaction between rhizobacteria and plants has expanded enormously and this has resulted in application of microbial products used as crop inoculants (as biofertilizers), for increased crop biomass and disease suppression. However, this plant–microbe interaction is affected by adverse environmental conditions, and recent work has suggested that inoculants carrying plant-to-bacteria or bacteria-to-plant signals can overcome this and promote plant productivity under stressful environmental conditions. Very recent work has also shown that some plant growth-promoting rhizobacteria secrete novel signaling molecules that also promote plant growth. The use of rhizobacterial signaling in promoting plant growth offers a new window of opportunity, especially when we are looking at plants to provide biofuels and novel bioproducts. Developing technologies that can enhance plant growth and productivity is imperative.


Via Jean-Michel Ané, Nina Dombrowski
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Strigolactone Promotes Degradation of DWARF14, an α/β Hydrolase Essential for Strigolactone Signaling in Arabidopsis

Strigolactone Promotes Degradation of DWARF14, an α/β Hydrolase Essential for Strigolactone Signaling in Arabidopsis | Plant microbe symbiotic signals | Scoop.it

Strigolactones (SLs) are phytohormones that play a central role in regulating shoot branching. SL perception and signaling involves the F-box protein MAX2 and the hydrolase DWARF14 (D14), proposed to act as an SL receptor. We used strong loss-of-function alleles of the Arabidopsis thaliana D14 gene to characterize D14 function from early axillary bud development through to lateral shoot outgrowth and demonstrated a role of this gene in the control of flowering time. Our data show that D14 distribution in vivo overlaps with that reported for MAX2 at both the tissue and subcellular levels, allowing physical interactions between these proteins. Our grafting studies indicate that neither D14 mRNA nor the protein move over a long range upwards in the plant. Like MAX2, D14 is required locally in the aerial part of the plant to suppress shoot branching. We also identified a mechanism of SL-induced, MAX2-dependent proteasome-mediated degradation of D14. This negative feedback loop would cause a substantial drop in SL perception, which would effectively limit SL signaling duration and intensity.

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First indications for the involvement of strigolactones on nodule formation in alfalfa (Medicago sativa)

First indications for the involvement of strigolactones on nodule formation in alfalfa (Medicago sativa) | Plant microbe symbiotic signals | Scoop.it

Strigolactones have recently been suggested to be phytohormones that are present in all plants. Strigolactones are released by roots into the rhizosphere, stimulating the seed germination of parasitic plants such as Striga spp. and Orobanche spp. and play a crucial role in the interaction between plants and symbiotic arbuscular mycorrhizal fungi.

By applying different concentrations of the synthetic strigolactone analogue GR24 to alfalfa (Medicago sativa) inoculated with Sinorhizobium meliloti we could show that in alfalfa nodulation is positively affected by the presence of the strigolactone analogue GR24. Moreover, we could show that this increased nodulation cannot be linked with a stimulatory effect of GR24 on the growth or the expression of nod genes ofS. meliloti.

Putative mechanisms operating in the plant in response to the addition of GR24 and leading to increased nodule formation by rhizobia are discussed.


Via Jean-Michel Ané
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Strigolactones promote nodulation in pea

Strigolactones promote nodulation in pea | Plant microbe symbiotic signals | Scoop.it

Strigolactones are recently defined plant hormones with roles in mycorrhizal symbiosis and shoot and root architecture. Their potential role in controlling nodulation, the related symbiosis between legumes and Rhizobium bacteria, was explored using the strigolactone-deficient rms1 mutant in pea (Pisum sativum L.). This work indicates that endogenous strigolactones are positive regulators of nodulation in pea, required for optimal nodule number but not for nodule formation per se. rms1mutant root exudates and root tissue are almost completely deficient in strigolactones, and rms1mutant plants have approximately 40% fewer nodules than wild-type plants. Treatment with the synthetic strigolactone GR24 elevated nodule number in wild-type pea plants and also elevated nodule number in rms1 mutant plants to a level similar to that seen in untreated wild-type plants. Grafting studies revealed that nodule number and strigolactone levels in root tissue of rms1 roots were unaffected by grafting to wild-type scions indicating that strigolactones in the root, but not shoot-derived factors, regulate nodule number and provide the first direct evidence that the shoot does not make a major contribution to root strigolactone levels.


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Elicitors from the endophytic fungus Trichoderma atroviride promote Salvia miltiorrhiza hairy root growth and tanshinone biosynthesis

Elicitors from the endophytic fungus Trichoderma atroviride promote Salvia miltiorrhiza hairy root growth and tanshinone biosynthesis | Plant microbe symbiotic signals | Scoop.it

Biotic elicitors can be used to stimulate the production of secondary metabolites in plants. However, limited information is available on the effects of biotic elicitors from endophytic fungi on their host plant. Trichoderma atroviride D16 is an endophytic fungus isolated from the root of Salvia miltiorrhiza and previously reported to produce tanshinone I (T-I) and tanshinone IIA (T-IIA). Here, the effects of extract of mycelium (EM) and the polysaccharide fraction (PSF), produced by T. atroviride D16, on the growth and secondary metabolism of S. miltiorrhiza hairy roots are reported. The results indicated that both EM and PSF promoted hairy root growth and stimulated the biosynthesis of tanshinones in hairy roots. EM slightly suppressed the accumulation of phenolic acids, while PSF had no significant influence on the accumulation of these compounds. When comparing the effects of EM versus PSF, it was concluded that PSF is one of the main active constituents responsible for promoting hairy root growth, as well as stimulating biosynthesis of tanshinones in the hairy root cultures. Moreover, the transcriptional activity of genes involved in the tanshinone biosynthetic pathway increased significantly with PSF treatment. Thus, PSF from endophytic T. atroviride D16 affected the chemical composition of the host plant by influencing the expression of genes related to the secondary metabolite biosynthetic pathway. Furthermore, treatment with PSF can be effectively utilized for large-scale production of tanshinones in the S. miltiorrhiza hairy root culture system.

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DWARF 53 acts as a repressor of strigolactone signalling in rice

DWARF 53 acts as a repressor of strigolactone signalling in rice | Plant microbe symbiotic signals | Scoop.it

Strigolactones (SLs) are a group of newly identified plant hormones that control plant shoot branching. SL signalling requires the hormone-dependent interaction of DWARF 14 (D14), a probable candidate SL receptor, with DWARF 3 (D3), an F-box component of the Skp–Cullin–F-box (SCF) E3 ubiquitin ligase complex. Here we report the characterization of a dominant SL-insensitive rice (Oryza sativa) mutant dwarf 53 (d53) and the cloning of D53, which encodes a substrate of the SCFD3 ubiquitination complex and functions as a repressor of SL signalling. Treatments with GR24, a synthetic SL analogue, cause D53 degradation via the proteasome in a manner that requires D14 and the SCFD3 ubiquitin ligase, whereas the dominant form of D53 is resistant to SL-mediated degradation. Moreover, D53 can interact with transcriptional co-repressors known as TOPLESS-RELATED PROTEINS. Our results suggest a model of SL signalling that involves SL-dependent degradation of the D53 repressor mediated by the D14–D3 complex.


Via Francis Martin
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The Nod factor hydrolase of Medicago truncatula: Characterization of an enzyme specifically cleaving rhizobial nodulation signals

Nodule formation induced by nitrogen-fixing rhizobia depends on bacterial nodulation factors (NFs), modified chitin oligosaccharides with a fatty acid moiety. Certain NFs can be cleaved and inactivated by plant chitinases. However, the most abundant NF of Sinorhizobium meliloti, an O-acetylated and sulphated tetramer, is resistant to hydrolysis by all plant chitinases tested so far. Nevertheless, this NF is rapidly degraded in the host rhizosphere. Here, we identify and characterize MtNFH1 (Medicago truncatula Nod factor hydrolase 1), a legume enzyme structurally related to defense-related class V chitinases (glycoside hydrolase family 18). MtNFH1 lacks chitinase activity but efficiently hydrolyzes all tested NFs of S. meliloti. The enzyme shows a high cleavage preference, releasing exclusively lipo-disaccharides from NFs. Substrate specificity and kinetic properties of MtNFH1 were compared to those of class V chitinases from Arabidopsis thaliana and Nicotiana tabacum, which cannot hydrolyze tetrameric NFs of S. meliloti. The Michaelis-Menten constants of MtNFH1 for NFs are in the micromolar concentration range, whereas non-modified chitin oligosaccharides represent neither substrates nor inhibitors for MtNFH1. The three-dimensional structure of MtNFH1 was modeled on the basis of the known structure of class V chitinases. Docking simulation of NFs to MtNFH1 predicted a distinct binding cleft for the fatty acid moiety, which is absent in the class V chitinases. Point mutation analysis confirmed the modeled NF-MtNFH1 interaction. Silencing of MtNFH1 by RNA interference resulted in reduced NF degradation in the rhizosphere of M. truncatula. In conclusion, we have found a novel legume hydrolase that specifically inactivates NFs.


Via Jean-Michel Ané
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Evidence for a diffusible factor that induces susceptibility in the Colletotrichum–maize disease interaction

Evidence for a diffusible factor that induces susceptibility in the Colletotrichum–maize disease interaction | Plant microbe symbiotic signals | Scoop.it

Colletotrichum graminicola, the causal agent of maize anthracnose, is a hemibiotrophic fungus that initially infects living host cells via primary hyphae surrounded by a membrane. A nonpathogenic mutant disrupted in a gene encoding a component of the signal peptidase complex, and believed to be deficient in protein processing and secretion, regained pathogenicity when it was inoculated onto maize leaf sheaths close to the wild-type fungus. Evidence is presented suggesting that the wild-type produces a diffusible factor(s) that induces the localized susceptibility of host cells at the borders of expanding colonies, causing them to become receptive to biotrophic invasion. The induced susceptibility effect is limited to a distance of approximately eight cells from the edge of the wild-type colony, is dosage dependent and is specific to C. graminicola.


Via Bradford Condon
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Polyphony in the rhizosphere: presymbiotic communication in arbuscular mycorrhizal symbiosis

Polyphony in the rhizosphere: presymbiotic communication in arbuscular mycorrhizal symbiosis | Plant microbe symbiotic signals | Scoop.it
Publication date: Available online 5 July 2013 Source:Current Opinion in Plant Biology Author(s): Marina Nadal , Uta Paszkowski The Arbuscular Mycorrhizal (AM) symbiosis is a ubiquitous relationship established in terrestrial ecosystems...

Via IPM Lab, Olivier ANDRE
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ACS Chemical Biology: Lipo-chitooligosaccharidic Symbiotic Signals Are Recognized by LysM Receptor-Like Kinase LYR3 in the Legume Medicago truncatula (2013)

ACS Chemical Biology: Lipo-chitooligosaccharidic Symbiotic Signals Are Recognized by LysM Receptor-Like Kinase LYR3 in the Legume Medicago truncatula (2013) | Plant microbe symbiotic signals | Scoop.it

While chitooligosaccharides (COs) derived from fungal chitin are potent elicitors of defense reactions, structurally related signals produced by certain bacteria and fungi, called lipo-chitooligosaccharides (LCOs), play important roles in the establishment of symbioses with plants. Understanding how plants distinguish between friend and foe through the perception of these signals is a major challenge. We report the synthesis of a range of COs and LCOs, including photoactivatable probes, to characterize a membrane protein from the legumeMedicago truncatula. By coupling photoaffinity labeling experiments with proteomics and transcriptomics, we identified the likely LCO-binding protein as LYR3, a lysin motif receptor-like kinase (LysM-RLK). LYR3, expressed heterologously, exhibits high-affinity binding to LCOs but not COs. Homology modeling, based on the Arabidopsis CO-binding LysM-RLK AtCERK1, suggests that LYR3 could accommodate the LCO in a conserved binding site. The identification of LYR3 opens up ways for the molecular characterization of LCO/CO discrimination.


Via Jean-Michel Ané, Kamoun Lab @ TSL, Olivier ANDRE
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Nonlegumes Respond to Rhizobial Nod Factors by Suppressing the Innate Immune Response

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