Title : Roles of lipolysis and autophagy in lipid droplet degradation and plant recovery from heat stress
Key words : Autophagy, lipolysis, stress response
Approaches : Functional genomics, biochemistry, molecular biology, cytology
Laboratory : Institut Jean-Pierre Bourgin (IJPB), UMR 1318, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France
PhD supervisor : Sabine D’Andréa, équipe Dynamique et Structure des Corps Lipidiques (DYSCOL)
PhD co-supervisor : Céline Masclaux, équipe Senescence, Autophagie, Recyclage nutritionnel et Efficacité d’utilisation de l’azote (SATURNE)
Starting date : between September and November 2022

PhD project summary
A PhD fellowship supported by ANR funding is available for 3 years at the ‘Institut Jean-Pierre Bourgin’ (Versailles, France). The candidate will explore the functions and dynamics of lipid droplets during post-stress recovery in the model plant Arabidopsis. In response to environmental stresses (including heat stress), neutral lipids accumulate in plants within dedicated intracellular structures called lipid droplets (LDs). Upon stress termination, the remobilization of these lipids is crucial to restore energy and provide lipids to rebuild membranes, and thus to support plant recovery.

Nevertheless, the mechanisms underlying such remobilization are unknown and the fate and cellular functions of these lipids remain elusive. The ANR funded project RecovOil aims to decipher these processes using a multidisciplinary approach combining biochemistry, lipidomics, proteomics, confocal microscopy as well as cell biology and plant genetics. The successful candidate will work on the RecovOil project alongside a consortium of researchers within the IJPB and in collaboration with 2 teams from the Laboratory of Membrane Biogenesis (LMB) in Bordeaux.

Within the frame of the RecovOil project, the thesis program aims to answer the following questions :
1) What adaptations in lipid metabolism and storage are associated with recovery from heat stress ?
The PhD project first aims to describe the lipidome changes (by LC-MS/MS ; lipidomics plateform of the LMB) and the lipid fluxes (fluxomics) after heat stress and during the recovery phase. Changes of the LD proteome will be explored by non-targeted (proteomics) and targeted (WB detection of candidates identified among known LD proteins ; tools already available in the laboratory). The PhD student will participate in the preparation of samples and the analysis of the results that will be provided by the lipidomic and proteomic platforms.
2) What is (are) the degradation pathway(s) involved in the remobilization of stress-accumulated lipids during stress recovery ?

LDs can be degraded by lipolysis or lipophagy (autophagic degradation of LD). The relative contribution of each pathway in post-stress remobilization will be assessed by comparing autophagy mutants and lipolysis mutants (genetic material available). Phenotypes will be characterized by lipidomics and biochemical analysis of LD proteins (WB). Pharmacological manipulation of these pathways will be an alternative and will confirm the results of the genetic approach.
3) What are the functions of a candidate protein identified as a putative player of LD dynamics in response to heat stress ?

PhD student opportunity in the field of plant resistance to environmental stress
The candidate protein, localized on LDs, was identified as being able to track LD dynamics during stress and post-stress recovery. Preliminary data suggest that this candidate may be involved in targeting LDs to one of the above-mentioned degradation pathways. Mutants deficient in this candidate (available) will be studied at different molecular and cellular levels. Their tolerance to heat stress will be evaluated.
Profile and skills required: The candidate must hold a master’s degree (or equivalent), and must have expertise in biochemistry and plant biology. Imaging skills and/or knowledge of lipid biochemistry will be appreciated.

Sabine D’Andréa (MCHC AgroParisTech), ✉ sabine.dandrea@inrae.fr, Tel. 01 30 83 32 20 / 07 81 31 99 18
Applications (by email) must contain (1) a cover letter with a short summary of past research activities, (2) a CV with contact details for 1-2 referees.
Deadline : The advertisement is valid until mid-July 2022

D’Andrea, S. (2016). Lipid droplet mobilization: The different ways to loosen the purse strings. Biochimie 120, 17-27.
Deruyffelaere, C., Bouchez, I., Morin, H., Guillot, A., Miquel, M., Froissard, M., Chardot, T., and D’Andrea, S. (2015). Ubiquitin-Mediated Proteasomal Degradation of Oleosins is Involved in Oil Body Mobilization During Post-Germinative Seedling Growth in Arabidopsis. Plant Cell Physiol. 56, 1374-1387.
Deruyffelaere, C., Purkrtova, Z., Bouchez, I., Collet, B., Cacas, J.L., Chardot, T., Gallois, J.L., and D’Andrea, S. (2018). PUX10 Is a CDC48A Adaptor Protein That Regulates the Extraction of Ubiquitinated Oleosins from Seed Lipid Droplets in Arabidopsis. Plant Cell 30, 2116-2136.
Have, M., Luo, J., Tellier, F., Balliau, T., Cueff, G., Chardon, F., Zivy, M., Rajjou, L., Cacas, J.L., and Masclaux-Daubresse, C. (2019). Proteomic and lipidomic analyses of the Arabidopsis atg5 autophagy mutant reveal major changes in endoplasmic reticulum and peroxisome metabolisms and in lipid composition. The New phytologist 223, 1461-1477.
Masclaux-Daubresse, C., d’Andrea, S., Bouchez, I., and Cacas, J.L. (2020). Reserve lipids and plant autophagy. J Exp Bot 71, 2854-2861.
Thirumalaikumar, V.P., Gorka, M., Schulz, K., Masclaux-Daubresse, C., Sampathkumar, A., Skirycz, A., Vierstra, R.D., and Balazadeh, S. (2020). Selective autophagy regulates heat stress memory in Arabidopsis by NBR1-mediated targeting of HSP90 and ROF1. Autophagy, 1-16.
Zienkiewicz, K., and Zienkiewicz, A. (2020). Degradation of Lipid Droplets in Plants and Algae—Right Time, Many Paths, One Goal. Frontiers in Plant Science 11.

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