Thèse de Doctorat

Jeudi 13 septembre 2018
à 13h30 – salle 106, Coeur d’école, Campus La Gaillarde

Physiological responses to zinc excess in Arabidopsis non-extremophile and extremophile plant species: interaction with drought and role of plant defensins

Mohanad Alsulaiman
BPMP, équipe Adaptation des plantes aux métaux

Ecole Doctorale : GAIA – Biodiversité, Agriculture, Alimentation, Environnement, Terre, Eau
Spécialité : BIDAP – Biologie, Interactions, Diversité Adaptative des Plantes

Composition du jury
Dr Anna Kozhevnikova, CR, Russian Academy of Sciences, Fédération de Russie, Rapportrice
Dr Cécilia Vazquez-Roverre, CR, Argentinian National Agricultural Technology Institute, Argentine, Rapportrice
Dr Christian Dubos, DR, Institut National de la Recherche Agronomique, France, Examinateur
Dr Christine Granier, DR, Institut National de la Recherche Agronomique, France, Examinatrice
Dr Sébastien Thomine, DR, Centre National de la Recherche Scientifique, France, Examinateur
Dr Françoise Gosti, CR, Centre National de la Recherche Scientifique, France, Directrice de thèse
Dr Denis Vile, CR, Institut National de la Recherche Agronomique, France, Invité
Dr Hélène Frérot, MC, Université de Lille, France, Invitée

Résumé
Plants are continuously exposed to several biotic and abiotic stresses. Plant responses to these stresses are highly complex and involve changes at the transcriptome, cellular, as well as physiological levels. Among these stresses, drought is one of the most detrimental factors for plant growth and productivity and is considered a severe threat for sustainable crop production, especially under current changing climate. The aim of this study is to investigate traits and/or mechanisms involved in plants response to water deficit under zinc condition using plant material Arabidopsis halleri. A. halleri is a hypertolerant and hyperaccumulator plant species for zinc and cadmium; this evolutionary feature represents a valuable potential to investigate plant responses to multiple stresses. Here, we developed a comparative approach using this particular species and two closely related species, A. thaliana and A. lyrata, both sensitive to zinc excess. We characterized morpho-physiological traits of three Arabidopsis species in response to combinations of water deficit and zinc excess. The findings showed that, A. halleri plants has increased tolerance to water deficit compared to A. thaliana and A. lyrata when grown under high zinc concentration in the soil. A. halleri showed higher ability to control leaf water content by reduced water loss through transpiration due to reduction of stomatal conductance which ultimately positively increased water use efficiency. Our study shows that, zinc excess and water deficit have additive negative effects on the growth of A. thaliana species plants, whereas A. lyrata is less affected by the addition of Zn under conditions of WD compared to WW conditions. The combination of these stresses has a positive interactive effect on the growth of A. halleri plants. In other hand, plant defensins (PDF) are involved in plant responses to biotic and abiotic stresses. The purpose of this work was also to understand the contribution of PDF Type 1 (PDF1s) in the response of plants to zinc excess using comparatively wild-type A. thaliana plants and transgenic amiRNA plants targeting the reduction of transcripts PDF1s. We compared the physiological characteristics of mature plants grown in the presence of excess zinc in the soil, and under hydroponic conditions. Our results show that, under the effect of zinc, the decrease in AtPDF1s transcripts is associated with a lower zinc tolerance than that observed in wild-type A. thaliana plants without a change in zinc content.