Rapport final d'évaluation du projet APEFE "soutien au laboratoire du Commerce intérieur" de Dakar

Report (2011)

Etude du profil en oxylipines de plantes supérieures soumises à différents stress abiotiques et biotiques

Report (2011)

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 ▲]

The Resistance to Freeze-Drying and to Storage Was Determined as the Cellular Ability to Recover Its Survival Rate and Acidification Activity

in International Journal of Microbiology (2010), 2010(625239),

The protective effects of the fatty acid composition and membrane action of the acidification activity of two strains of Lactobacillus kept at 20◦C were studied. The addition of sorbitol, monosodium ... [more ▼]

The protective effects of the fatty acid composition and membrane action of the acidification activity of two strains of Lactobacillus kept at 20◦C were studied. The addition of sorbitol, monosodium glutamate and glycerol during storage is causing the decline of acidification and increased concentrations of unsaturated fatty acids observed in both strains. The addition of sorbitol and monosodium glutamate does not alter the fatty acid composition, whatever the strain, but increases the resistance to freeze-drying of L. plantarum CWBI-B1419 and improves survival during storage. The addition of these preservatives and decreased activity of acidification improves the ratio unsaturated. These results indicate that the survival during storage and freeze-drying resistance are closely related to the composition of membrane fatty acids. This behaviour can be interpreted as an adaptation of L. plantarum B1419-CWBI supplemented by cryoprotectant additives such as sorbitol or monosodium glutamate sorbitol and monosodium glutamate as an additive. L. plantarum CWBI-B1419 presents a greater adaptation to culture conditions than L. paracasei ssp. paracasei LMG9192T. [less ▲]

The lipoxygenase metabolic pathway in plants: potential for industrial production of natural green leaf volatiles

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(3), 451-460

Lipoxygenase enzymatic pathway is a widely studied mechanism in the plant kingdom. Combined actions of three enzymes: lipase, lipoxygenase (LOX) and hydroperoxide lyase (HPL) convert lipidic substrates ... [more ▼]

Lipoxygenase enzymatic pathway is a widely studied mechanism in the plant kingdom. Combined actions of three enzymes: lipase, lipoxygenase (LOX) and hydroperoxide lyase (HPL) convert lipidic substrates such as C18:2 and C18:3 fatty acids into short chain volatiles. These reactions, triggered by cell membrane disruptions, produce compounds known as Green Leaf Volatiles (GLVs) which are C6 or C9-aldehydes and alcohols. These GLVs are commonly used as flavors to confer a fresh green odor of vegetable to food products. Therefore, competitive biocatalytic productions have been developed to meet the high demand in these natural flavors. Vegetable oils, chosen for their lipidic acid profile, are converted by soybean LOX and plant HPL into natural GLVs. However this second step of the bioconversion presents low yield due to the HPL instability and the inhibition by its substrate. This paper will shortly describe the different enzymes involved in this bioconversion with regards to their chemical and enzymatic properties. Biotechnological techniques to enhance their production potentialities will be discussed along with their implication in a complete bioprocess, from the lipid substrate to the corresponding aldehydic or alcoholic flavors. [less ▲]

Volatile organic compounds of wheat roots as potential contributors to their communication with soil microorganisms

Poster (2010, January 26)

Development of a biotransformation process of hydroperoxides into green leaf volatiles using sugar beet leaves

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010)

Natural green leaf volatiles (GLVs) are commonly sole AS aldehydic and alcoholic flavors; their synthesis is a great challenge for industry. Especially, the bioconversion step of fatty acid hydroperoxides ... [more ▼]

Natural green leaf volatiles (GLVs) are commonly sole AS aldehydic and alcoholic flavors; their synthesis is a great challenge for industry. Especially, the bioconversion step of fatty acid hydroperoxides into aldehydes by the hydroperoxide lyase (HL). This widely studied enzyme is present in cell membranes of green organs from superior plants. Extracted from its natural condition, HL is subject to a suicidal behavior, being irreversibly inhibited by its own substrate. Furthermore, GLVs produced are highly volatile and quickly degraded by other plant enzymes. Thence, high GLVs levels in industrial production are very difficult to obtain, but several biotechnological tools could be developed to enhance this natural synthesis level more than hundred times. This paper will describe a new method for GLVs production in bioreactor using sugar beet leaves as source of HL. One step reaction, including hydroperoxide metabolisation and GLVs extraction, is performed during a short time process. Downstream processing to dispose of natural and pure GLVs molecule will also be discussed. [less ▲]

L'Ylang-Ylang (Cananga odorata (Lam.) Hook & Thoms.) : une plante à huile essentielle méconnue dans une filière en danger.

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14

Caractérisation et conservation de la diversité d’une espèce ligneuse tropicale : cas de l’Yalng ylang (Canaga odorata (Lam.) Hook et Thoms).

Report (2010)

Gene expression of the lipoxygenase pathway in a tomato species tolerant to salt stress

Poster (2010)