Soutenance de thèse de Shiri Moez (ECOBIO)



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Le vendredi 4 juillet 2014 à 9h30, dans l'amphi L de l'Université de Rennes 1 (Bât.

Le vendredi 4 juillet 2014 à 9h30, dans l'amphi L de l'Université de Rennes 1 (Bât. 42, campus de Beaulieu), Shiri Moez soutient sa thèse intitulée

Réponses physiologiques, antioxydantes et métabolomiques de Thellungiella salsuginea et Arabidopsis thaliana à l’interaction salinité modérée phénanthrène: application à la phytoremédiation des HAPs par les halophytes


Jury :
David MACHEREL - Professeur, Université d’Angers / rapporteur
Ferjani BEN ABDALLAH - Professeur, Faculté des Sciences de Sfax / rapporteur
Alain BOUCHEREAU - Professeur, UR 1 / examinateur
Mokded RABHI - Maître-assistant, CBBC / examinateur
Abdelhak EL AMRANI - Maître de conférences, UR1 / directeur de thèse
Chedly ABDELLY - Professeur, CBBC/ directeur de thèse


Résumé :
La pollution environnementale constitue un problème majeur pour les écosystèmes naturels et la santé publique. Récemment, la phytoremédiation a émergé comme une stratégie innovante, écologique et à faible coût. Elle consiste à utiliser les capacités des plantes à stocker ou/et à dégrader les polluants. Dans cette étude, des analyses physiologiques, biochimiques et métabolomiques, ont permis de montrer que les halophytes, une catégorie des plantes extrêmophiles, présentent une grande capacité à remédier la pollution engendrée par les Hydrocarbures Aromatiques Polycycliques (HAPs). D’autre part, la salinité modérée améliore leur capacité phytoremédiatrice. Ces résultats apportent de nouvelles données pouvant contribuer à l’amélioration de cette stratégie.

Abstract:
Halopytes, plants naturally adapted to high salt concentrations, have no clear definition, yet. Their cross-tolerance to abiotic stresses was reviewed in this work at the physiological, biochemical, and molecular levels, with a special emphasis on the mechanisms involved in their cross-tolerance to salinity and organic pollutants that could allow them a higher potential of xenobiotic phytoremediation as compared to glycophytes. In our experimental part, we compared in a first step some physiological and antioxidant responses to phenanthrene as well as its accumulation in the two related model plants Arabidopsis thaliana (glycophyte) and Thellungiella salsuginea (halophyte). We found more detrimental effects on biomass production, photosystem II (PSII) performance, and chlorophyll concentrations in the glycophyte than in the halophyte. Therefore, a more marked ROS accumulation was detected in A. thaliana, which induced higher increases in GR (+95%), GPX (+73%), and SOD (+36%) activities than in T. Salsuginea that exhibited an improvement of 34% in SOD activity only. In addition, a much higher capacity of recovery was recorded in the halophyte and was attributed to a preferential accumulation of phenanthrene in stomata suggesting its possible volatilization.

In a second step, we investigated the effects of moderate salinity on the responses of the two species to phenanthrene considered as model Polycyclic Aromatic Hydrocarbon (PAH) molecule. Obtained results showed an improvement of phenanthrene-induced responses in the two plants, the effect being more marked in the halophyte. This observation was particularly related to higher antioxidant activities and the induction of more adapted metabolism as several accumulated metabolites are known to be involved in signaling and osmotic adjustment processes.
In a final step, we studied the potential of the halophyte Cakile maritima to remediate an inert sand (to avoid the degradation of the pollutant by microorganisms or their interaction with the plant) highly contaminated with phenanthrene. T. salsuginea was used as a biomarker of phenanthrene stress severity: 0 (control), 125, 250, and 375 ppm. A test culture of T. salsuginea on the phytoremediated sand showed similar biomass production as plants subjected to 125 ppm phenanthrene. This indicates that C. maritima decreased pollutant concentration in the soil by 75% in 6 weeks only.
Taken together, these findings add new insight to the mechanisms developed by halophytes to tolerate abiotic stresses and suggest their potential use in phytoremediation of organic pollutants, in particular PAHs.
Keywords: antioxidant activity, cross-tolerance, halophyte, HAP, moderate salinity, phytoremediation.


Contact : @"+"@"+"";self.close();' onmouseover='window.status="mai"+"lto:"+"@"+"@"+""; return true;' onmouseout='window.status="";return true;'>Shiri Moez (ECOBIO)