Publications
936 views | +1 today
Follow
Your new post is loading...
Your new post is loading...
Rescooped by Nicolas Denancé from Xylella fastidiosa worldwide
Scoop.it!

Options Méditerranéennes: Xylella fastidiosa & the Olive Quick Decline Syndrome (OQDS). A serious worldwide challenge for the safeguard of olive trees (2017)

Options Méditerranéennes: Xylella fastidiosa & the Olive Quick Decline Syndrome (OQDS). A serious worldwide challenge for the safeguard of olive trees (2017) | Publications | Scoop.it
Over the last few years, olive trees (Olea europaea) have seriously been threatened by the bacterium Xylella fastidiosa, a devastating quarantine organism which affects about than 380 host plants worldwide including crop, ornamental, forestry and natural vegetation species. In 2013, the first outbreak of X. fastidiosa was reported in Puglia (Italy). It was a serious shock for the European and Mediterranean regions since it was associated with the olive quick decline syndrome (OQDS); furthermore, it was reported to infect more than 28 plant species (except grapevine and citrus), and to be rapidly vector-transmitted by the spittlebug Philaenus spumarius. After the finding in Italy of the subspecies pauca strain CoDiRO, several interceptions of Xylella occurred in Europe and new outbreaks of different subspecies of the pathogen were reported in France (2015), Germany (2015) and Spain (2016). Thanks to the support of CIHEAM, FAO, IPPC and IOC for the organization of two dedicated international workshops, this book represents a unique opportunity for the main national and international stakeholders to find the most updated information on X. fastidiosa and its vectors, with a focus on the latest experience and knowledge acquired in Europe. It includes short notes on the breakthrough of research, the current legislation and other initiatives at EU, Mediterranean and worldwide level on the pathogen, its vector(s), host plant species, surveillance, detection and control measures. In addition, a complete list of scientific publications of the last 10 years is also provided. The information and experiences reported in this book constitute a basis to build national phytosanitary capacity, awareness-raising and advocacy campaigns to combat X. fastidiosa.
more...
No comment yet.
Rescooped by Nicolas Denancé from Microbes, plant immunity, and crop science
Scoop.it!

Front. Plant Sci.: Editorial: Genomics and Effectomics of the crop killer Xanthomonas (2016)

Phytopathogenic bacteria of the Xanthomonas genus cause severe diseases on hundreds of host plants, including economically important crops, such as bean, cabbage, cassava, citrus, hemp, pepper, rice, sugarcane, tomato or wheat. Diseases occurring in nature comprise bacterial blight, canker, necrosis, rot, scald, spot, streak or wilt. Xanthomonas spp. are distributed worldwide and pathogenic and nonpathogenic strains are essentially found in association to plants. Some phytopathogenic strains are emergent or re-emergent and, consequently, dramatically impact agriculture, economy and food safety. During the last decades, massive efforts were undertaken to decipher Xanthomonas biology. So far, more than one hundred complete or draft genomes from diverse Xanthomonas species have been sequenced (http://www.xanthomonas.org), thus providing powerful tools to study genetic determinants triggering pathogenicity and adaptation to plant habitats. Xanthomonas spp. employ an arsenal of virulence factors to invade its host, including extracellular polysaccharides, plant cell wall-degrading enzymes, adhesins and secreted effectors. In most xanthomonads, type III secretion (T3S) system and secreted effectors (T3Es) are essential to bacterial pathogenicity through the inhibition of plant immunity or the induction of plant susceptibility (S) genes, as reported for Transcription Activation-Like (TAL) effectors. Yet, toxins can also be major virulence determinants in some xanthomonads while nonpathogenic Xanthomonas species do live in sympatry with plant without any T3S systems nor T3Es.
In a context of ever increasing international commercial exchanges and modifications of the climate, monitoring and regulating pathogens spread is of crucial importance for food security. A deep knowledge of the genomic diversity of Xanthomonas spp. is required for scientists to properly identify strains, to help preventing future disease outbreaks and to achieve knowledge informed sustainable disease resistance in crops.
This Research Topic published in the ‘Plant Biotic Interactions’ section of Frontiers in Plant Science and Frontiers in Microbiology aims at illustrating several of the recent achievements of the Xanthomonas community. We collected twelve manuscripts dealing with comparative genomics or T3E repertoires, including five focusing on TAL effectors which we hope will contribute to advance research on plant pathogenic bacteria.

 

Nicolas Denancé, Thomas Lahaye, Laurent D. Noël

Front. Plant Sci. (2016) 7:71.

more...
No comment yet.
Rescooped by Nicolas Denancé from Microbes, plant immunity, and crop science
Scoop.it!

BMC Genomics: Genomics and transcriptomics of Xanthomonas campestris species challenge the concept of core type III effectome (2015)

BMC Genomics: Genomics and transcriptomics of Xanthomonas campestris species challenge the concept of core type III effectome (2015) | Publications | Scoop.it
Background

The bacterial species Xanthomonas campestris infects a wide range of Brassicaceae. Specific pathovars of this species cause black rot (pv. campestris), bacterial blight of stock (pv. incanae) or bacterial leaf spot (pv. raphani).

Results

In this study, we extended the genomic coverage of the species by sequencing and annotating the genomes of strains from pathovar incanae (CFBP 1606R and CFBP 2527R), pathovar raphani (CFBP 5828R) and a pathovar formerly named barbareae (CFBP 5825R). While comparative analyses identified a large core ORFeome at the species level, the core type III effectome was limited to only three putative type III effectors (XopP, XopF1 and XopAL1). In Xanthomonas, these effector proteins are injected inside the plant cells by the type III secretion system and contribute collectively to virulence. A deep and strand-specific RNA sequencing strategy was adopted in order to experimentally refine genome annotation for strain CFBP 5828R. This approach also allowed the experimental definition of novel ORFs and non-coding RNA transcripts. Using a constitutively active allele of hrpG, a master regulator of the type III secretion system, a HrpG-dependent regulon of 141 genes co-regulated with the type III secretion system was identified. Importantly, all these genes but seven are positively regulated by HrpG and 56 of those encode components of the Hrp type III secretion system and putative effector proteins.

Conclusions

This dataset is an important resource to mine for novel type III effector proteins as well as for bacterial genes which could contribute to pathogenicity of X. campestris.

 

Roux  Brice, Bolot  Stéphanie, Guy  Endrick, Denancé  Nicolas, Lautier  Martine, Jardinaud  Marie-Françoise, Fischer-Le Saux  Marion, Portier  Perrine, Jacques  Marie-Agnès, Gagnevin  Lionel, Pruvost  Olivier, Lauber  Emmanuelle, Arlat  Matthieu, Carrère  Sébastien, Koebnik  Ralf, Noël  Laurent

 

BMC Genomics 2015, 16:975  doi:10.1186/s12864-015-2190-0

 

 

more...
No comment yet.
Rescooped by Nicolas Denancé from Plant-Microbe Symbiosis
Scoop.it!

Plant Cell Physiol.: Emerging Functions of Nodulin-Like Proteins in Non-Nodulating Plant Species (2014)

Plant Cell Physiol.: Emerging Functions of Nodulin-Like Proteins in Non-Nodulating Plant Species (2014) | Publications | Scoop.it

Plant genes whose expression is induced in legumes by Rhizobiumbacteria upon nodulation were initially referred to as nodulins. Several of them play a key role in the establishment of symbiosis. Yet, nodulin-like proteins are also found in non-nodulating plant species such as Arabidopsis, rice, maize or poplar. For instance, 132 are predicted in theArabidopsis thaliana Col-0 genome. Recent studies now highlight the importance of nodulin-like proteins for the transport of nutrients, solutes, amino acids or hormones and for major aspects of plant development. Interestingly, nodulin-like activities at the plant–microbe interface are also important for pathogens to enhance their fitness during host colonization. This work presents a genomic and functional overview of nodulin-like proteins in non-leguminous plant species, with a particular focus on Arabidopsis and rice.

 

Nicolas Denancé, Boris Szurek and Laurent D. Noël

Plant Cell Physiol. (2014) 55(3): 469-474.


Via Jean-Michel Ané
more...
Scooped by Nicolas Denancé
Scoop.it!

New Phytol.: Post mortem function of AtMC9 in xylem vessel elements (2013)

New Phytol.: Post mortem function of AtMC9 in xylem vessel elements (2013) | Publications | Scoop.it

Cell death of xylem elements is manifested by rupture of the tonoplast and subsequent autolysis of the cellular contents. Metacaspases have been implicated in various forms of plant cell death but regulation and execution of xylem cell death by metacaspases remains unknown. Analysis of the type II metacaspase gene family in Arabidopsis thaliana supported the function of METACASPASE 9 (AtMC9) in xylem cell death. Progression of xylem cell death was analysed in protoxylem vessel elements of 3-d-old atmc9 mutant roots using reporter gene analysis and electron microscopy. Protoxylem cell death was normally initiated in atmc9 mutant lines, but detailed electron microscopic analyses revealed a role for AtMC9 in clearance of the cell contents post mortem, that is after tonoplast rupture. Subcellular localization of fluorescent AtMC9 reporter fusions supported a post mortem role for AtMC9. Further, probe-based activity profiling suggested a function of AtMC9 on activities of papain-like cysteine proteases. Our data demonstrate that the function of AtMC9 in xylem cell death is to degrade vessel cell contents after vacuolar rupture. We further provide evidence on a proteolytic cascade in post mortem autolysis of xylem vessel elements and suggest that AtMC9 is part of this cascade.  

 

Benjamin Bollhöner, Bo Zhang, Simon Stael, Nicolas Denancé, Kirk Overmyer, Deborah Goffner, Frank Van Breusegem, Hannele Tuominen

 

New Phytol. (2013), 200(2):498-510.

more...
No comment yet.
Scooped by Nicolas Denancé
Scoop.it!

Plant J: Arabidopsis wat1-mediated resistance to the bacterial vascular pathogen, Ralstonia solanacearum, is accompanied by cross-regulation of salicylic acid and tryptophan metabolism (2013)

Plant J: Arabidopsis wat1-mediated resistance to the bacterial vascular pathogen, Ralstonia solanacearum, is accompanied by cross-regulation of salicylic acid and tryptophan metabolism (2013) | Publications | Scoop.it

The inactivation of Arabidopsis WAT1 (Walls Are Thin1), a gene required for secondary cell wall deposition, conferred a broad-spectrum resistance to vascular pathogens, including the bacteria Ralstonia solanacearum and Xanthomonas campestris pv. campestris, and the fungi, Verticillium dahliae and V. albo-atrum. The introduction of NahG, the bacterial salicylic acid (SA)-degrading salicylate hydroxylase gene, into wat1 restored full susceptibility to both R. solanacearum and X. campestris pv. campestris. Moreover, SA content was constitutively higher in wat1 roots, further supporting a role for SA in wat1-mediated resistance to vascular pathogens. By combining transcriptomic and metabolomic data, we demonstrated a general repression of indole metabolism in wat1-1 roots as shown by a constitutive down-regulation of several genes encoding proteins along the indole glucosinolate (IGS) biosynthetic pathway and reduced amounts of tryptophan (Trp), IAA and neoglucobrassicin, the major form of IGS in roots. Furthermore, wat1 susceptibility to R. solanacearum was partially restored when crossed with either trp5, an overaccumulator of Trp or Pro35S:AFB1-myc in which IAA signaling is constitutively activated. Our original hypothesis placed cell wall modifications at the heart of wat1 resistance phenotype. However, the results presented here point to a mechanism involving root-localized, metabolic channeling away from indole metabolites to SA as a central feature of wat1 resistance to R. solanacearum.

 

Nicolas Denancé*, Philippe Ranocha*, Nicolas Oria, Xavier Barlet, Marie-Pierre Rivière, Koste A. Yadeta, Laurent Hoffmann, François Perreau, Gilles Clément, Alessandra Maia-Grondard, Grardy C.M. van den Berg, Bruno Savelli, Sylvie Fournier, Yann Aubert, Sandra Pelletier, Bart P.H.J. Thomma, Antonio Molina, Lise Jouanin, Yves Marco, Deborah Goffner

 

Plant J (2013) 73(2):225-239

more...
No comment yet.
Scooped by Nicolas Denancé
Scoop.it!

Plant Sign. Behav. : Light-regulated compensation of wat1 (walls are thin1) growth and secondary cell wall phenotypes is auxin-independent (2010)

Plant Sign. Behav. : Light-regulated compensation of wat1 (walls are thin1) growth and secondary cell wall phenotypes is auxin-independent (2010) | Publications | Scoop.it

We previously reported the characterization of walls are thin1 (wat1), an Arabidopsis mutant that exhibits two developmental phenotypes in stems: (i) a severe decrease in fiber secondary cell wall thickness and (ii) a reduction in stem height. Auxin concentration and transport were also significantly reduced in the stem base of wat1 plants. In the original study, these characteristics were observed in plants grown under short day conditions (9h light /15h dark). Herein, we provide evidence for partial phenotypic complementation of both wat1 developmental phenotypes when grown under a continuous light regime. Interestingly, when auxin concentration and basipetal transport were measured in these plants, neither was restored to wild type levels. These results suggest that free auxin concentration is not responsible for the partial light–regulated complementation of wat1-mediated phenotypes.

 

Nicolas Denancé*, Philippe Ranocha*, Yves Martinez, Björn Sundberg, and Deborah Goffner.

 

Plant Sign. Behav. 5(10): 1302-1304.

more...
No comment yet.
Scooped by Nicolas Denancé
Scoop.it!

Plant J: Walls are thin 1 (WAT1), an Arabidopsis homolog of Medicago truncatula NODULIN21, is a tonoplast-localized protein required for secondary wall formation in fibers (2010)

Plant J: Walls are thin 1 (WAT1), an Arabidopsis homolog of Medicago truncatula NODULIN21, is a tonoplast-localized protein required for secondary wall formation in fibers (2010) | Publications | Scoop.it

By combining Zinnia elegans in vitro tracheary element genomics with reverse genetics in Arabidopsis, we have identified a new upstream component of secondary wall formation in xylary and interfascicular fibers. Walls are thin 1 (WAT1), an Arabidopsis thaliana homolog of Medicago truncatula NODULIN 21 (MtN21), encodes a plant-specific, predicted integral membrane protein, and is a member of the plant drug/metabolite exporter (P-DME) family (transporter classification number: TC 2.A.7.3). Although WAT1 is ubiquitously expressed throughout the plant, its expression is preferentially associated with vascular tissues, including developing xylem vessels and fibers. WAT1:GFP fusion protein analysis demonstrated that WAT1 is localized to the tonoplast. Analysis of wat1 mutants revealed two cell wall-related phenotypes in stems: a defect in cell elongation, resulting in a dwarfed habit and little to no secondary cell walls in fibers. Secondary walls of vessel elements were unaffected by the mutation. The secondary wall phenotype was supported by comparative transcriptomic and metabolomic analyses of wat1 and wild-type stems, as many transcripts and metabolites involved in secondary wall formation were reduced in abundance. Unexpectedly, these experiments also revealed a modification in tryptophan (Trp) and auxin metabolism that might contribute to the wat1 phenotype. Together, our data demonstrate an essential role for the WAT1 tonoplast protein in the control of secondary cell wall formation in fibers.

 

Philippe Ranocha , Nicolas Denancé, Ruben Vanholme, Amandine Freydier, Yves Martinez, Laurent Hoffmann, Lothar Köhler, Cécile Pouzet, Jean-Pierre Renou, Björn Sundberg, Wout Boerjan, and Deborah Goffner.

 

Plant J 63(3): 469-483.

more...
No comment yet.
Rescooped by Nicolas Denancé from Xylella fastidiosa worldwide
Scoop.it!

Plant Pathol.: Several subspecies and sequence types are associated with the emergence of Xylella fastidiosa in natural settings in France (2017)

Plant Pathol.: Several subspecies and sequence types are associated with the emergence of Xylella fastidiosa in natural settings in France (2017) | Publications | Scoop.it
Xylella fastidiosa is a plant pathogenic bacterium emerging in Europe. In France its emergence has been evidenced through interceptions of contaminated coffee plants and in 2015 by the survey of natural settings. The first French contaminated focus was detected in 2015 in Corsica; then almost 300 foci and nearly 30 plant species were declared contaminated, with Polygala myrtifolia remaining the principal host suffering from severe leaf scorches. We report on the diversity of X. fastidiosa identified in France in 2015. Multilocus sequence analysis/typing revealed the presence of mainly X. fastidiosa subsp. multiplex ST6 and ST7. A focus of subspecies pauca ST53 was identified in mainland France; one sample contaminated by X. fastidiosa subsp. sandyi ST76, one novel recombinant, and co-infections of different isolates in individual samples were also identified, but could not be confirmed by successive samplings indicating limited or transient contaminations. Koch's postulates were fulfilled for two isolates of X. fastidiosa subsp. multiplex on P. myrtifolia one being ST6 and the other ST7. Comparative genomics of the genome sequences of three French isolates (one ST6 and two ST7), with available sequences revealed that unlike the American Dixon strain, the French ST6 and ST7 strains are devoid of a plasmid encoding a complete type IV secretion system. Other differences regarding phage sequences were highlighted. Altogether, our results suggest that the emergence of X. fastidiosa in France is linked to several introduction events of diverse strains from different subspecies.
more...
No comment yet.
Scooped by Nicolas Denancé
Scoop.it!

App. Env. Microbiol.: New Coffee Plant-Infecting Xylella fastidiosa Variants Derived via Homologous Recombination (2016)

App. Env. Microbiol.: New Coffee Plant-Infecting Xylella fastidiosa Variants Derived via Homologous Recombination (2016) | Publications | Scoop.it

Xylella fastidiosa is a xylem-limited phytopathogenic bacterium endemic to the Americas that has recently emerged in Asia and Europe. Although classified as a quarantine organism in the European Union, importation of plant material from contaminated areas and latent infection in asymptomatic plants have engendered its inevitable introduction. In 2012, four coffee plants (Coffea arabica and C. canephora) with leaf scorch symptoms growing in a confined glasshouse were detected and intercepted in France. After identification of the causal agent, this outbreak was eradicated. Three X. fastidiosa strains were isolated from these plants, confirming a preliminary diagnostic based on immunology. The strains were characterized by multiplex PCR and by multilocus sequence analysis/typing (MLSA-MLST) based on seven housekeeping genes. One strain, CFBP 8073, isolated from C. canephora imported from Mexico, was assigned to X. fastidiosa subsp. fastidiosa/sandyi. This strain harbors a novel sequence type (ST) with novel alleles at two loci. The two other strains, CFBP 8072 and 8074, isolated from C. arabica imported from Ecuador, were allocated to X. fastidiosa subsp. pauca. These two strains shared a novel ST with novel alleles at two loci. These MLST profiles showed evidence of recombination events. We provided genome sequences for CFBP 8072 and CFBP 8073 strains. Comparative genomic analyses of these two genome sequences with publicly available X. fastidiosa genomes, including the Italian strain CoDiRO, confirmed these phylogenetic positions and provided candidate alleles for coffee adaptation. This study demonstrates the global diversity of X. fastidiosa and highlights the diversity of strains isolated from coffee.  

 

Jacques MA, Denancé N, Legendre B, Morel E, Briand M, Mississipi S, Durand K, Olivier V, Portier P, Poliakoff F, and Crouzillat D. (2016) Appl. Environ. Microbiol. 82(5):1556-1568.


Spotlight in Appl. Environ. Microbiol. 82(5):1361.

more...
No comment yet.
Scooped by Nicolas Denancé
Scoop.it!

Plant J.: PIRIN2 stabilizes cysteine protease XCP2 and increases susceptibility to the vascular pathogen Ralstonia solanacearum in Arabidopsis (2014)

Plant J.: PIRIN2 stabilizes cysteine protease XCP2 and increases susceptibility to the vascular pathogen Ralstonia solanacearum in Arabidopsis (2014) | Publications | Scoop.it

PIRIN (PRN) is a member of the functionally diverse cupin protein superfamily. There are four members of the Arabidopsis thaliana PRN family, but roles of these proteins are largely unknown. Here we describe a function of the Arabidopsis PIRIN2 (PRN2) that is related to susceptibility to the bacterial plant pathogen Ralstonia solanacearum. Two prn2 mutant alleles displayed decreased disease development and bacterial growth in response to R. solanacearum infection. We elucidated the underlying molecular mechanism by analyzing PRN2 interactions with the Papain-like cysteine proteases (PLCPs) XCP2, RD21A, and RD21B, all of which bound to PRN2 in yeast two-hybrid assays and in Arabidopsis protoplast co-immunoprecipitation assays. We show that XCP2 is stabilized by PRN2 through inhibition of its autolysis on the basis of PLCP activity profiling assays and enzymatic assays with recombinant protein. The stabilization of XCP2 by PRN2 was also confirmed in planta. Like prn2 mutants, an xcp2 single knockout mutant and xcp2 prn2 double knockout mutant displayed decreased susceptibility to R. solanacearum, suggesting that stabilization of XCP2 by PRN2 underlies susceptibility to R. solanacearum in Arabidopsis.

 

Bo Zhang, Dominique Tremousaygue, Nicolas Denancé, H. Peter van Esse, Anja C. Hörger, Patrick Dabos, Deborah Goffner, Bart P. H. J. Thomma, Renier A. L. van der Hoorn and Hannele Tuominen

 

Plant J (2014) 79(6): 1009–1019

more...
No comment yet.
Scooped by Nicolas Denancé
Scoop.it!

Front. Plant Sci.: Predicting promoters targeted by TAL effectors in plant genomes: from dream to reality (2013)

Front. Plant Sci.: Predicting promoters targeted by TAL effectors in plant genomes: from dream to reality (2013) | Publications | Scoop.it

Transcription Activator-Like (TAL) effectors from the plant pathogenic bacteria of the genus Xanthomonas are molecular weapons injected into eukaryotic cells to modulate the host transcriptome. Upon delivery, TAL effectors localize into the host cell nucleus and bind to the promoter of plant susceptibility (S) genes to activate their expression and thereby facilitate bacterial multiplication (Boch and Bonas, 2010; Schornack et al., 2013). In resistant plants, a few TAL effectors have been shown to bind to promoters of executor resistance (R) genes, resulting in localized cell death and preventing pathogen spread (reviewed in Doyle et al., 2013). Remarkably, TAL effectors harbor a novel type of DNA-binding domain with a unique modular architecture composed of 1.5 to 33.5 almost identical tandem repeats of 33-35 amino acids. Each repeat type specifies one or more bases through direct interaction with the second amino acid in a centrally located “Repeat Variable Diresidue” (RVD). The number and sequence of the RVDs across the whole repeat region of the TAL protein defines the DNA target. The code of DNA-binding specificity of Xanthomonas TAL effectors was inferred from experimental, computational and later on structural approaches (Boch et al., 2009; Moscou and Bogdanove, 2009; Deng et al., 2012; Mak et al., 2012). This new paradigm for protein-DNA interaction is now revolutionizing our perspectives for the understanding of TAL effectors roles during plant disease and defense since the identification of their plant targets is largely facilitated. A few algorithms are now available to predict in silico candidate genes of a given TAL effector. This Opinion gives an overview of the current tools and strategies that may be applied for finding targets of TAL effectors. We also raise limitations and pitfalls and emphasize what may be improved to gain in prediction accuracy. Finally, we also highlight several perspectives offered by these new tools.

 

Laurent D Noël, Nicolas Denancé, Boris Szurek

Front. Plant Sci. (2013) 4:333

 

more...
No comment yet.
Scooped by Nicolas Denancé
Scoop.it!

Front. Plant Sci.: Disease resistance or growth: the role of plant hormones in balancing immune responses and fitness costs (2013)

Front. Plant Sci.: Disease resistance or growth: the role of plant hormones in balancing immune responses and fitness costs (2013) | Publications | Scoop.it

Plant growth and response to environmental cues are largely governed by phytohormones. The plant hormones ethylene, jasmonic acid, and salicylic acid (SA) play a central role in the regulation of plant immune responses. In addition, other plant hormones, such as auxins, abscisic acid (ABA), cytokinins, gibberellins, and brassinosteroids, that have been thoroughly described to regulate plant development and growth, have recently emerged as key regulators of plant immunity. Plant hormones interact in complex networks to balance the response to developmental and environmental cues and thus limiting defense-associated fitness costs. The molecular mechanisms that govern these hormonal networks are largely unknown. Moreover, hormone signaling pathways are targeted by pathogens to disturb and evade plant defense responses. In this review, we address novel insights on the regulatory roles of the ABA, SA, and auxin in plant resistance to pathogens and we describe the complex interactions among their signal transduction pathways. The strategies developed by pathogens to evade hormone-mediated defensive responses are also described. Based on these data we discuss how hormone signaling could be manipulated to improve the resistance of crops to pathogens.

 

Nicolas Denancé, Andrea Sánchez-Vallet, Deborah Goffner, and Antonio Molina

 

Front. Plant Sci. (2013) 4:155

more...
fundoshi's curator insight, June 12, 2013 10:03 AM

TENGUがまんなかに!

Scooped by Nicolas Denancé
Scoop.it!

Planta: Deciphering the route of Ralstonia solanacearum colonization in Arabidopsis thaliana roots during a compatible interaction: focus at the plant cell wall (2012)

Planta: Deciphering the route of Ralstonia solanacearum colonization in Arabidopsis thaliana roots during a compatible interaction: focus at the plant cell wall (2012) | Publications | Scoop.it

The compatible interaction between the model plant, Arabidopsis thaliana, and the GMI1000 strain of the phytopathogenic bacterium, Ralstonia solanacearum, was investigated in an in vitro pathosystem. We describe the progression of the bacteria in the root from penetration at the root surface to the xylem vessels and the cell type-specific, cell wall-associated modifications that accompanies bacterial colonization. Within 6 days post inoculation, R. solanacearum provoked a rapid plasmolysis of the epidermal, cortical, and endodermal cells, including those not directly in contact with the bacteria. Plasmolysis was accompanied by a global degradation of pectic homogalacturonanes as shown by the loss of JIM7 and JIM5 antibody signal in the cell wall of these cell types. As indicated by immunolabeling with Rsol-I antibodies that specifically recognize R. solanacearum, the bacteria progresses through the root in a highly directed, centripetal manner to the xylem poles, without extensive multiplication in the intercellular spaces along its path. Entry into the vascular cylinder was facilitated by cell collapse of the two pericycle cells located at the xylem poles. Once the bacteria reached the xylem vessels, they multiplied abundantly and moved from vessel to vessel by digesting the pit membrane between adjacent vessels. The degradation of the secondary walls of xylem vessels was not a prerequisite for vessel colonization as LM10 antibodies strongly labeled xylem cell walls, even at very late stages in disease development. Finally, the capacity of R. solanacearum to specifically degrade certain cell wall components and not others could be correlated with the arsenal of cell wall hydrolytic enzymes identified in the bacterial genome.

 

Catherine Digonnet*, Yves Martinez*, Nicolas Denancé, Marine Chasseray, Patrick Dabos, Philippe Ranocha, Yves Marco, Alain Jauneau and Deborah Goffner

 

Planta 236(5):1419-1431

more...
No comment yet.
Scooped by Nicolas Denancé
Scoop.it!

Biology of Plant-Microbe Interactions (2008): Plant carbohydrate scavenging through TonB-dependent receptors by the phytopathogenic bacterium Xanthomonas campestris pv. campestris

Biology of Plant-Microbe Interactions (2008): Plant carbohydrate scavenging through TonB-dependent receptors by the phytopathogenic bacterium Xanthomonas campestris pv. campestris | Publications | Scoop.it

Phytopathogenic bacteria have in general a dual life: they are able to infect and colonize their host plants but they also have the ability to survive outside their hosts in various environments. This remarkable feature likely reflects a high degree of adaptability and the presence of specific genetic programs devoted to the exploitation of nutrients present in these diverse habitats. With the aim to study molecular mechanisms controlling adaptation of phytopathogenic bacteria to their host-plants, we undertook a global analysis of receptors and regulators of Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot of crucifers. This pathogen infects a wide range of Brassicaceae plants of economic interest, including cabbage, cauliflower and radish as well as the model plant Arabidopsis thaliana. Our analysis of the Xcc (ATCC33913) genome revealed an overrepresentation of a particular family of receptors, named TonB-dependent receptors (TBDRs) (Blanvillain et al. 2007).

 

Servane Blanvillain*, Damien Meyer*, Guillaume Déjean, Alice Boulanger, Martine Lautier, Catherine Guynet, Nicolas Denancé, Jacques Vasse, Emmanuelle Lauber*, and Matthieu Arlat*.

 

Biology of Plant-Microbe Interactions, Volume 6

Proceedings of the 13th International Congress on Molecular Plant‐Microbe Interactions, Sorrento (Naples), Italy, July 21–27, 2007

more...
No comment yet.
Scooped by Nicolas Denancé
Scoop.it!

PLoS ONE (2007): Plant Carbohydrate Scavenging through TonB-Dependent Receptors: A Feature Shared by Phytopathogenic and Aquatic Bacteria

PLoS ONE (2007): Plant Carbohydrate Scavenging through TonB-Dependent Receptors: A Feature Shared by Phytopathogenic and Aquatic Bacteria | Publications | Scoop.it

TonB-dependent receptors (TBDRs) are outer membrane proteins mainly known for the active transport of iron siderophore complexes in Gram-negative bacteria. Analysis of the genome of the phytopathogenic bacterium Xanthomonas campestris pv. campestris (Xcc), predicts 72 TBDRs. Such an overrepresentation is common in Xanthomonas species but is limited to only a small number of bacteria. Here, we show that one Xcc TBDR transports sucrose with a very high affinity, suggesting that it might be a sucrose scavenger. This TBDR acts with an inner membrane transporter, an amylosucrase and a regulator to utilize sucrose, thus defining a new type of carbohydrate utilization locus, named CUT locus, involving a TBDR for the transport of substrate across the outer membrane. This sucrose CUT locus is required for full pathogenicity on Arabidopsis, showing its importance for the adaptation to host plants. A systematic analysis of Xcc TBDR genes and a genome context survey suggested that several Xcc TBDRs belong to other CUT loci involved in the utilization of various plant carbohydrates. Interestingly, several Xcc TBDRs and CUT loci are conserved in aquatic bacteria such as Caulobacter crescentus, Colwellia psychrerythraea, Saccharophagus degradans, Shewanella spp., Sphingomonas spp. or Pseudoalteromonas spp., which share the ability to degrade a wide variety of complex carbohydrates and display TBDR overrepresentation. We therefore propose that TBDR overrepresentation and the presence of CUT loci designate the ability to scavenge carbohydrates. Thus CUT loci, which seem to participate to the adaptation of phytopathogenic bacteria to their host plants, might also play a very important role in the biogeochemical cycling of plant-derived nutrients in marine environments. Moreover, the TBDRs and CUT loci identified in this study are clearly different from those characterized in the human gut symbiont Bacteroides thetaiotaomicron, which allow glycan foraging, suggesting a convergent evolution of TBDRs in Proteobacteria and Bacteroidetes.

 

Servane Blanvillain*, Damien Meyer*, Alice Boulanger, Martine Lautier, Catherine Guynet, Nicolas Denancé, Jacques Vasse, Emmanuelle Lauber*, and Matthieu Arlat*.

 

PLoS ONE 2(2):e224.

more...
No comment yet.