Thesis defense: Vincent Salis
Monday, December 1st 2025 2 pm - INRAE, Versailles
Implication of Lipid Droplet in heat stress response and during recovery phase in Arabidopsis thaliana
Lipid Droplet (LDs) are organelles specialized in storing triacylglycerols (TGs). They are present at low levels in vegetative tissues but strongly accumulate in response to various stresses, particularly heat stress. Such stress triggers a rapid accumulation of TGs and proliferation of LDs. In vegetative tissues, LDs are associated with Lipid Droplet-Associated Proteins (LDAPs; LDAP1–3 in Arabidopsis thaliana). Among them, LDAP1 is specifically induced by heat, although its precise function remains unknown. The transient accumulation of LDs is accompanied by a remodeling of the lipidome, which is relatively well described during stress but gaps remain during the post-stress recovery phase. This gap limits our understanding of the role of LDs in membrane homeostasis and plant thermotolerance. Indeed, after heat stress relief, LDs are rapidly remobilized—possibly to provide the energy required for growth recovery or to rebuild functional membranes. The mechanisms underlying this remobilization, whether through lipolysis or autophagy, as well as the specific role of LDAP1, remain to be elucidated. In this context, the objectives of my PhD work were: (i) to characterize lipidome dynamics during heat stress and post-stress recovery ; (ii) to determine the involvement of LDAP1 in this lipid remodeling and LD dynamics; and (iii) to identify the degradation pathways activated during recovery, with a particular focus on the potential role of autophagy in this process. To address these objectives, we implemented an integrated approach combining lipidomic analyses, biochemical studies, and confocal microscopy observations on young Arabidopsis thaliana seedlings exposed to a short 3-hour heat stress at 37 °C, followed by a 24-hour recovery period at 22 °C.
We characterized in detail the evolution of the lipidome and identified specific lipid species showing distinct dynamics during stress and recovery phases, including the accumulation of galactolipids with a low degree of unsaturation during recovery. We also showed a very early and transient induction of LDAP1 expression in response to elevated temperature. LDAP1 accumulates and persists during the stress phase, before being degraded during recovery, following a kinetic pattern similar to that of TGs. Loss of LDAP1 function alters lipidome dynamics, notably leading to reduced TG accumulation during stress and overaccumulation of certain galactolipids during recovery. These observations suggest a role for LDAP1 in lipid fluxes between chloroplasts and LDs, a hypothesis further supported by the subcellular co-fractionation of LDAP1 with plastids. Regarding LD remobilization pathways, our preliminary data suggest a role for autophagy in TAG dynamics, though not in LDAP1 degradation—unlike LDAP3. Analysis of LDAP1 and LDAP3 interactions with ATG8 supports this conclusion. Moreover, interactomic analyses identified PUX10 as an LDAP interactor, revealing new potential regulators of LD dynamics in response to heat stress. In summary, our work identifies LDAP1 as an early marker of heat stress that influences lipidome dynamics, potentially by mediating interactions between LDs and chloroplasts. These findings contribute to a better understanding of the mechanisms underlying thermal resilience in plants.
Director: Sabine D'Andréa, "Dynamics and engineering of Lipidic Compartments" DECLIC team, INRAE, IJPB, Versailles
Co-direction: Céline Masclaux-Daubresse, "Senescence, Autophagy, Nutrient Recycling and Nitrogen Use Efficiency" SATURNE team, INRAE, IJPB, Versailles
Jury members
> Morgane Michaud (Rapportrice) - CNRS, LPCV, Lipid, Grenoble
> Sébastien Mongrand (Rapporteur) - CNRS, LBM, Villenave d’Ornon
> Arnould Savouré (Examinateur) - IEES Paris, APCE, Sorbonne Université, Paris
> Sébastien Baud (Examinateur) - CNRS, INRAE, IJPB, SEED-DREAM, Versailles
Research developed at the Institute Jean-Pierre Bourgin for Plant Sciences.
Lipid Droplet (LDs) are organelles specialized in storing triacylglycerols (TGs). They are present at low levels in vegetative tissues but strongly accumulate in response to various stresses, particularly heat stress. Such stress triggers a rapid accumulation of TGs and proliferation of LDs. In vegetative tissues, LDs are associated with Lipid Droplet-Associated Proteins (LDAPs; LDAP1–3 in Arabidopsis thaliana). Among them, LDAP1 is specifically induced by heat, although its precise function remains unknown. The transient accumulation of LDs is accompanied by a remodeling of the lipidome, which is relatively well described during stress but gaps remain during the post-stress recovery phase. This gap limits our understanding of the role of LDs in membrane homeostasis and plant thermotolerance. Indeed, after heat stress relief, LDs are rapidly remobilized—possibly to provide the energy required for growth recovery or to rebuild functional membranes. The mechanisms underlying this remobilization, whether through lipolysis or autophagy, as well as the specific role of LDAP1, remain to be elucidated. In this context, the objectives of my PhD work were: (i) to characterize lipidome dynamics during heat stress and post-stress recovery ; (ii) to determine the involvement of LDAP1 in this lipid remodeling and LD dynamics; and (iii) to identify the degradation pathways activated during recovery, with a particular focus on the potential role of autophagy in this process. To address these objectives, we implemented an integrated approach combining lipidomic analyses, biochemical studies, and confocal microscopy observations on young Arabidopsis thaliana seedlings exposed to a short 3-hour heat stress at 37 °C, followed by a 24-hour recovery period at 22 °C.
We characterized in detail the evolution of the lipidome and identified specific lipid species showing distinct dynamics during stress and recovery phases, including the accumulation of galactolipids with a low degree of unsaturation during recovery. We also showed a very early and transient induction of LDAP1 expression in response to elevated temperature. LDAP1 accumulates and persists during the stress phase, before being degraded during recovery, following a kinetic pattern similar to that of TGs. Loss of LDAP1 function alters lipidome dynamics, notably leading to reduced TG accumulation during stress and overaccumulation of certain galactolipids during recovery. These observations suggest a role for LDAP1 in lipid fluxes between chloroplasts and LDs, a hypothesis further supported by the subcellular co-fractionation of LDAP1 with plastids. Regarding LD remobilization pathways, our preliminary data suggest a role for autophagy in TAG dynamics, though not in LDAP1 degradation—unlike LDAP3. Analysis of LDAP1 and LDAP3 interactions with ATG8 supports this conclusion. Moreover, interactomic analyses identified PUX10 as an LDAP interactor, revealing new potential regulators of LD dynamics in response to heat stress. In summary, our work identifies LDAP1 as an early marker of heat stress that influences lipidome dynamics, potentially by mediating interactions between LDs and chloroplasts. These findings contribute to a better understanding of the mechanisms underlying thermal resilience in plants.
Director: Sabine D'Andréa, "Dynamics and engineering of Lipidic Compartments" DECLIC team, INRAE, IJPB, Versailles
Co-direction: Céline Masclaux-Daubresse, "Senescence, Autophagy, Nutrient Recycling and Nitrogen Use Efficiency" SATURNE team, INRAE, IJPB, Versailles
Jury members
> Morgane Michaud (Rapportrice) - CNRS, LPCV, Lipid, Grenoble
> Sébastien Mongrand (Rapporteur) - CNRS, LBM, Villenave d’Ornon
> Arnould Savouré (Examinateur) - IEES Paris, APCE, Sorbonne Université, Paris
> Sébastien Baud (Examinateur) - CNRS, INRAE, IJPB, SEED-DREAM, Versailles
Research developed at the Institute Jean-Pierre Bourgin for Plant Sciences.
Back
