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See detailThe elicitation of a systemic resistance by Pseudomonas putida BTP1 in tomato involves the stimulation of two lipoxygenase isoforms
Mariutto, Martin ULg; Duby, Franceline ULg; Adam, Akram et al

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 ▲]

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See detailVitamin B6 deficient plants display increased sensitivity to high light and photo-oxidative stress
Havaux, Michel; Ksas, Brigitte; Szewczyk, Agnieszka et al

in BMC Plant Biology (2009), 9

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See detailSystemic resistance and lipoxygenase-related defence response induced in tomato by Pseudomonas putida strain BTP1.
Akram, Adam; Ongena, MARC ULg; Duby, Franceline et al

in BMC Plant Biology (2008), 8

BACKGROUND: Previous studies showed the ability of Pseudomonas putida strain BTP1 to promote induced systemic resistance (ISR) in different host plants. Since ISR is long-lasting and not conducive for ... [more ▼]

BACKGROUND: Previous studies showed the ability of Pseudomonas putida strain BTP1 to promote induced systemic resistance (ISR) in different host plants. Since ISR is long-lasting and not conducive for development of resistance of the targeted pathogen, this phenomenon can take part of disease control strategies. However, in spite of the numerous examples of ISR induced by PGPR in plants, only a few biochemical studies have associated the protective effect with specific host metabolic changes. RESULTS: In this study, we showed the protective effect of this bacterium in tomato against Botrytis cinerea. Following treatment by P. putida BTP1, analyses of acid-hydrolyzed leaf extracts showed an accumulation of antifungal material after pathogen infection. The fungitoxic compounds thus mainly accumulate as conjugates from which active aglycones may be liberated through the activity of hydrolytic enzymes. These results suggest that strain BTP1 can elicit systemic phytoalexin accumulation in tomato as one defence mechanism. On another hand, we have shown that key enzymes of the lipoxygenase pathway are stimulated in plants treated with the bacteria as compared with control plants. Interestingly, this stimulation is observed only after pathogen challenge in agreement with the priming concept almost invariably associated with the ISR phenomenon. CONCLUSION: Through the demonstration of phytoalexin accumulation and LOX pathway stimulation in tomato, this work provides new insights into the diversity of defence mechanisms that are inducible by non-pathogenic bacteria in the context of ISR. [less ▲]

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See detailCloning and Expression Analysis of Cdnas Corresponding to Genes Activated in Cucumber Showing Systemic Acquired Resistance after Bth Treatment
Bovie, C.; Ongena, MARC ULg; Thonart, Philippe ULg et al

in BMC Plant Biology (2004), 4

BACKGROUND: Infection of plants by necrotizing pathogens can lead to the rapid and localized induction of a complex set of defense responses resulting in a restriction of pathogen growth and spread ... [more ▼]

BACKGROUND: Infection of plants by necrotizing pathogens can lead to the rapid and localized induction of a complex set of defense responses resulting in a restriction of pathogen growth and spread. Subsequently, an increase of plant resistance against a broad spectrum of pathogens is observed systemically. This plant immunity is known as Systemic Acquired Resistance. To identify components of the transduction pathway, we cloned and analysed the expression pattern of several mRNAs accumulating in cucumber plants after induction of Systemic Acquired Resistance. RESULTS: We tested on cucumber different compounds known to induce systemic acquired resistance. Among these, BTH (benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester) proved to be very effective. mRNA RT-PCR differential display was used to identify mRNA sequences induced 24 hours after the application of 10 microM BTH to cucumber plants. A cDNA library constructed from cucumber plants sprayed with 10 microM BTH was screened to get corresponding full length cDNAs. Among the identified cDNAs were those coding for a putative ras-related GTP-binding protein, a putative beta-1,4-N-Acetylglucosaminyltranferase III and a putative pathogenesis related protein. The time course of accumulation of the three corresponding mRNAs was analysed by northern blotting in plants treated by BTH or in plants infected by Colletotrichum lagenarium. CONCLUSIONS: The mRNA RT-PCR differential display technique allowed the identification of three genes possibly involved in Systemic Acquired Resistance in cucumber. Pathogenesis-related proteins are known to be involved in plant defence against pathogens. GTP-binding protein and N-acetylglucosaminyltranferase III have been reported to be components of signal transduction pathways in mammals and plants. [less ▲]

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See detailA novel high efficiency, low maintenance, hydroponic system for synchronous growth and flowering of Arabidopsis thaliana.
Tocquin, Pierre ULg; Corbesier, Laurent; Havelange, Andrée ULg et al

in BMC Plant Biology (2003), 3(2), 302003

Background: Arabidopsis thaliana is now the model organism for genetic and molecular plant studies, but growing conditions may still impair the significance and reproducibility of the experimental ... [more ▼]

Background: Arabidopsis thaliana is now the model organism for genetic and molecular plant studies, but growing conditions may still impair the significance and reproducibility of the experimental strategies developed. Besides the use of phytotronic cabinets, controlling plant nutrition may be critical and could be achieved in hydroponics. The availability of such a system would also greatly facilitate studies dealing with root development. However, because of its small size and rosette growth habit, Arabidopsis is hardly grown in standard hydroponic devices and the systems described in the last years are still difficult to transpose at a large scale. Our aim was to design and optimize an up-scalable device that would be adaptable to any experimental conditions. Results: An hydroponic system was designed for Arabidopsis, which is based on two units: a seed-holder and a 1-L tank with its cover. The original agar-containing seed-holder allows the plants to grow from sowing to seed set, without transplanting step and with minimal waste. The optimum nitrate supply was determined for vegetative growth, and the flowering response to photoperiod and vernalization was characterized to show the feasibility and reproducibility of experiments extending over the whole life cycle. How this equipment allowed to overcome experimental problems is illustrated by the analysis of developmental effects of nitrate reductase deficiency in nia1nia2 mutants. Conclusion: The hydroponic device described in this paper allows to drive small and large scale cultures of homogeneously growing Arabidopsis plants. Its major advantages are its flexibility, easy handling, fast maintenance and low cost. It should be suitable for many experimental purposes. [less ▲]

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