Description du sujet de thèse

Adaptation to fluctuating conditions is usually associated with a trade-off between growth and defense, a dynamic process that fine-tunes resources allocation for either plant growth or defense. This balance is tightly governed by plant hormones, which trigger adapted responses to the environment through transcriptional regulations impacting metabolic fluxes. Among phytohormones, gibberellins (GA) control major aspects of plant growth and development throughout the lifecycle. GA promote growth by stimulating the degradation of DELLA growth repressing proteins (DELLAs), a family of transcriptional regulators. In many cases it has been shown that changes in the environment restrain plant growth as a result of reduced GA content, which in turn enhances the function of the DELLAs. Interestingly, whereas the growth of multiple della mutants is less affected by adverse conditions, growth restraint conferred by DELLAs enhances survival to stress. Thus DELLA-dependent growth restraint is advantageous to flowering plants and permits flexible and appropriate modulation of growth in response to changes in natural environments. Strikingly, while much effort has been invested in the identification of signaling pathways by which GA/DELLA modulate plant growth, little is known about the regulatory networks that control stress tolerance. By using a combination of targeted and untargeted omics analyses, the DELLAdef project aims at identifying the DELLA-dependent defense pathways activated in response to drought, an important question in the actual context of global warming. To reach this goal, the project is structured in 4 highly complementary tasks: (1) map the spatiotemporal distribution of GA in response to drought; 2) obtain GA-dependent metabolomics profiles in a kinetic drought stress assay; 3) identify the gene networks; 4) reveal the DELLA-dependent defense networks associated with plant tolerance to drought stress by generating gene-metabolite correlation heatmap.

Contexte de travail

The PhD student will be affiliated with the Institut de Biologie Moléculaire des Plantes (IBMP) and the doctoral school 414 “Health and Life Sciences” of Strasbourg, France. The IBMP is the largest CNRS institute working on plant biology, located on the Esplanade campus of the University of Strasbourg, near the city's historic center. The IBMP provides a research of excellence aiming, through the study of fundamental processes of the life of plants, to answer social challenges in nutrition, health and environment. The institute hosts 16 teams and state of the art platforms in imaging, metabolomics, gene expression analyses and plant production. This doctoral thesis will be carried out in the "Gibberellins and plant adaptation" research team headed by Patrick Achard, in co-supervision with the partner laboratory “Evolution and diversity of plant metabolism” headed by Emmanuel Gaquerel (IBMP), as part of the nationally funded ANR DELLAdef project.