Modulation of the lipopeptide pattern secreted by Bacillus subtilis upon colonization of different plant roots

in Bulletin OILB/SROP = IOBC/WPRS Bulletin (2012), 78

PAMPs, MAMPs, DAMPs and others: An update on the diversity of plant immunity elicitors [PAMPs, MAMPs, DAMPs et autres: Mise à jour de la diversité des éliciteurs de l'immunité des plantes]

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2012), 16(2), 257-268

Plants possess a broad array of defenses that could be actively expressed in response of pathogenic organisms or parasites but also following beneficial saprophytic microorganisms recognition ... [more ▼]

Plants possess a broad array of defenses that could be actively expressed in response of pathogenic organisms or parasites but also following beneficial saprophytic microorganisms recognition. Specifically, there are compounds derived from these organisms and called elicitors that are perceived by the plant to induce a locally or systemically expressed resistance. The understanding of the physiological and biological basis of these induced immunity mechanisms have greatly advanced over the past years but a deeper investigation of the mechanisms underlying the perception of elicitors is essential to develop novel strategies for pest control. The application of chemical and biological stimulators of plant immune defenses in conventional agriculture is expected to increase within the next years. Because of their organic origin and as they provide means for conferring plant protection in a non-transgenic manner, elicitors of plant immunity have a huge potential as biocontrol products. Through this review, we want to illustrate the diversity of compounds identified as stimulators of the plant immune system and describe the mechanisms by which they could be recognized at the plasma membrane level. [less ▲]

Unsuspected Control of Siderophore production by N-acetylglucosamine in Streptomycetes

in Environmental Microbiology (2012)

Assessment of aphid saliva role as plant defense elicitation by multiple approaches.

Poster (2011, July)

MALDI mass spectrometry imaging of secreted lipopeptides in a bacterial biofilm colonizing plant roots

Conference (2011, June 06)

During the aggression of a plant by a pathogen, different immune reactions may occur. "Induced Systemic Resistance” (ISR) is triggered by the specific interaction between plant and non-pathogenic ... [more ▼]

During the aggression of a plant by a pathogen, different immune reactions may occur. "Induced Systemic Resistance” (ISR) is triggered by the specific interaction between plant and non-pathogenic microorganism. The first step (of three) consists in the perception by plant cells of elicitors produced by the inducing agents that initiates the phenomenon. One class of known elicitors is antibiotics including surfactin- and fengycin-type lipopeptides. Recent studies in biology, genetics or biochemistry allowed a better understanding of the interactions between plants and microorganism but few has been done at the molecular level. MALDI MS imaging has been used to study the nature of the secreted lipopeptides, their relative quantity and their distribution in the root’s environment. Disinfected tomato seeds were first incubated at 28°C in sterile conditions for germination. Germinated seeds were then treated with freshly-grown cells of Bacillus amyloliquefaciens S499 and placed in Petri dish on ITO glass slide recovered with a thin layer of plant nutritive solution (Hoagland) containing 1,75% of agar. Petri dishes were finally incubated vertically in phytotron during 10 days (28°C, photoperiod 16h). For MALDI imaging experiments, the ITO slide was removed from the agar and dried in a dessiccator under vacuum. The matrix solution (9-aminoacridine) was applied with an ImagePrep automated sprayer (Bruker Daltonics). An UltraFlex II TOF/TOF mass spectrometer was used to record molecular cartographies. The average mass spectra recorded around the tomato root (2-3 mm on both sides of the root) showed that lipopeptides were major compounds detected on the agar. Only the surfactins have been detected when working with the S499 strain. The most abundant surfactins were those with longer fatty acyl chain lengths, such as C14- and C15-homologues. Such a surfactin signature is interesting since homologues with the longest acyl chains are also the more active biologically. The distribution of surfactins showed a gradient representing the diffusion of the molecules during the root growth. The more the fatty acyl chain is long, the more the surfactin is detected near the root. Other compounds detected during the analysis showed a clear anti-colocalization with the surfactins. Future work will be focused on the influence of the plant species (tobacco, salad, Arabidopsis thaliana) on the secretion of lipopeptides (type, concentration…) and the influence of the strain of Bacillus amyloliquefaciens regarding its ability to selectively produce specific lipopeptide families (overproducing or repressed mutants). This MS imaging technique thus appears to be a very powerful method to study in situ production of bioactive lipopeptides by bacteria developing on roots. This is crucial for a better understanding of the molecular dialogue governing perception of beneficial Bacillus strains by the host plant. This study provides a first analysis over a long root section of lipopeptides secreted by a bacterial biofilm colonizing plant. [less ▲]

The role of surfactins in plant immunization by Bacilli

Conference (2011, April)

The bacterial lipopeptide surfactin targets the lipid fraction of plasma membrane to trigger immune-related defense response in the host plant

in Cellular Microbiology (2011), 13

Beneficial effect of the rhizosphere microbial community for plant growth and health.

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(2), 327-337

The elicitation of a systemic resistance by Pseudomonas putida BTP1 in tomato involves the stimulation of two lipoxygenase isoforms

in BMC Plant Biology (2011), 11

Background Some non-pathogenic rhizobacteria called Plant Growth Promoting Rhizobacteria (PGPR) possess the capacity to induce in plant defense mechanisms effective against pathogens. Precedent studies ... [more ▼]

Background Some non-pathogenic rhizobacteria called Plant Growth Promoting Rhizobacteria (PGPR) possess the capacity to induce in plant defense mechanisms effective against pathogens. Precedent studies showed the ability of Pseudomonas putida BTP1 to induce PGPR-mediated resistance, termed ISR (Induced Systemic Resistance), in different plant species. Despite extensive works, molecular defense mechanisms involved in ISR are less well understood that in the case of pathogen induced systemic acquired resistance. Results We analyzed the activities of phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX), key enzymes of the phenylpropanoid and oxylipin pathways respectively, in tomato treated or not with P. putida BTP1. The bacterial treatment did not stimulate PAL activity and linoleate-consuming LOX activities. Linolenate-consuming LOX activity, on the contrary, was significantly stimulated in P. putida BTP1-inoculated plants before and two days after infection by B. cinerea. This stimulation is due to the increase of transcription level of two isoforms of LOX: TomLoxD and TomLoxF, a newly identified LOX gene. We showed that recombinant TomLOXF preferentially consumes linolenic acid and produces 13-derivative of fatty acids. After challenging with B. cinerea, the increase of transcription of these two LOX genes and higher linolenic acid-consuming LOX activity were associated with a more rapid accumulation of free 13-hydroperoxy-octadecatrienoic and 13-hydroxy-octadecatrienoic acids, two antifungal oxylipins, in bacterized plants. Conclusion In addition to the discovery of a new LOX gene in tomato, this work is the first to show differential induction of LOX isozymes and a more rapid accumulation of 13-hydroperoxy-octadecatrienoic and 13-hydroxy-octadecatrienoic acids in rhizobacteria mediated-induced systemic resistance. [less ▲]

Identification, characterization and expression profiling of the tomato gene TomLoxF

Poster (2010, January 26)