Plant acclimation to and recovery from drought stress, through autophagy.

Plant acclimation to and recovery from drought stress, through autophagy.

Sujet de thèse ouvert au concours de l’école doctorale SIE Université Paris-Est « Sciences, Ingénierie et Environnement ».

Context:

Global warming and climate change drive an increase in the frequency and intensity of abiotic stresses such as droughts. This stress strongly affects stomatal behaviour, photosynthesis, water relations and metabolic homeostasis, ultimately impairing plant growth, development, fitness and yield, thereby compromising global food security ¹. Key determinants of plant fitness and resilience to environmental stresses are (i) the ability to rapidly acclimate through metabolic and physiological adjustments that maintain cellular homeostasis, and (ii) the capacity to recover after stress release, enabling the restoration of nutrient assimilation, growth, development and seed filling ¹.

Macro-autophagy, hereafter referred to as “autophagy”, is a crucial process involved in cellular homeostasis and proteostasis through the degradation and recycling of damaged and dysfunctional cell components (such as proteins) and organelles. During autophagy, cell components destinated for degradation (collectively termed as “cargoes”) are engulfed within double membrane vesicles called autophagosomes, which are then delivered to the vacuole ². This process is tightly regulated by Autophagy-Related (ATG) Genes, which orchestrate each stage of autophagosome formation, expansion, and fusion ². Arabidospsi mutants impaired in autophagosome formation (atg) are hypersensitive to a wide range of abiotic stresses, including nutrient starvation ³, drought ⁴, heat, and high light. They display premature leaf senescence, decreased yield and decreased nitrogen (N) recycling to seeds ³, increased level of reactive oxygen species (ROS) and carbonylated proteins ⁵. These mutants also show altered chloroplast ultrastructure with reduced Photosystem II integrity ⁶, impaired stomatal regulation ⁷, higher leaf temperature, and delayed cellular reprogramming during stress recovery ⁸. In contrast, enhancing autophagy through the overexpression of ATG genes (ATG-OE) has been shown to improve plant growth, N recycling and seed yield under non-stressed conditions in Arabidopsis ⁹. Constitutive autophagy in cost1 Arabidopsis mutants conferred increased drought tolerance¹⁰, and the overexpression of MdATG8i-OE in apple improved photosynthesis, growth and water use efficiency (WUE) compared to WT under drought stress ¹¹.

Despite these advances, our understanding of autophagy’s role in plant resilience to drought stress remains limited. This is largely due to the absence of comprehensive eco-physiological characterizations of atg loss of function and ATG-OE plants exposed to drought

La thèse se séroulera au sein de l’équipe EcoPhyS du laboratoire iEES à l'Université Paris-Est Créteil. L'équipe s’attache à étudier les réponses des plantes aux contraintes abiotiques de l’environnement, selon une approche intégrative.

Desired profile:

• Master’s degree in plant physiology or equivalent,
• Experience in measuring physiological parameters and monitoring plant experiments,
• Experience in biochemistry (enzyme activity assays) and proteomics (SDS-PAGE, western blot) would be appreciated,
• Strong skills in data analysis and management, as well as statistics (R programming),
• Good English level.