Biology subjects

Albrieux, C.

Publications and source records attributed to Albrieux, C..

4 recordsLinked to original sources

bioRxiv2026

In vivo analyses reveal rapid and permissive lipid transport between the ER and mitochondria

Interorganelle lipid transport is essential for mitochondrial membrane biogenesis and function, yet its kinetics and substrate selectivity remain poorly understood in vivo. Here, we developed two complementary approaches to quantify lipid trafficking from the endoplasmic reticulum (ER) to mitochondria in yeast. Metabolic labeling combined with organelle fractionation revealed that newly synthesized phospholipids rapidly accumulate in mitochondria, with 20-35% of newly synthesized molecules detected in mitochondrial fractions within minutes of synthesis. To directly quantify lipid flux, we established a synthetic transport assay based on the production of heterologous galactolipids absent from yeast. This approach revealed an ER-to-mitochondria transport flux of approximately 2.6 x 105 lipid molecules per cell per minute. Remarkably, galactolipids were transported with high efficiency despite their absence from fungal membranes, indicating limited substrate selectivity of ER-mitochondria lipid transport pathways. Together, these complementary assays provide quantitative tools to investigate intracellular lipid transport and reveal the rapid and permissive nature of lipid exchange between the ER and mitochondria. SummaryUsing complementary metabolic labeling and synthetic lipid reporter assays, we quantitatively measured ER-mitochondria lipid transport in yeast. Our results reveal rapid lipid exchange, high transport fluxes and limited substrate selectivity, indicating that mitochondrial lipid trafficking efficiently accommodates structurally diverse membrane lipids.

Cell Biology↗

bioRxiv2024

Functional study of Phaeodactylum tricornutum Seipin homolog highlights unique features of lipid droplets biogenesis in diatoms.

Diatoms are a major phylum of microalgae, playing crucial ecological roles. They derive from secondary endosymbiosis of a red alga by an unknown heterotrophic eukaryote, leading to a complex intracellular organization. In response to unfavorable conditions (stress), diatoms store oil in lipid droplets (LD), raising interest for applications, in particular biofuels. In spite of numerous investigations aiming to increase their oil content, LD biogenesis mechanisms in these organisms remain poorly understood. In this study, we functionally characterized the homolog of Seipin, a major actor of LD biogenesis, in the diatom Phaeodactylum tricornutum. PtSeipin shares conserved structural features with other Seipins, yet presents unique characteristics, that appear common to diatoms and more broadly Stramenopiles. We provide evidence that Stramenopiles Seipins were inherited from the host during secondary endosymbiosis. The localization of PtSeipin highlights that LD biogenesis can arise simultaneously from the endoplasmic reticulum (ER) and the plastids most external membrane. Finally, the knock-out of PtSeipin leads to a strong increase of TAG accumulation, a feature that is not observed in other organisms and is greatly enhanced following high light exposure. Our results suggest a redirection of lipid fluxes towards TAG synthesis, reduced TAG recycling or a combination of both.

plant biology↗

bioRxiv2024

DGTS overproduced in seed plants is excluded from plastid membranes and promotes endomembrane expansion

Plants and algae must adapt to environmental changes, facing various stresses that negatively impact their growth and development. One common stress is phosphate (Pi) deficiency, which is often in limiting quantity in the environment. In response to Pi deficiency, these organisms increase Pi uptake and remobilize intracellular Pi. Phospholipids are degraded to provide Pi and replaced by non-phosphorous lipids, such as glycolipids or betaine lipids. During the evolution, seed plants lost their capacity to synthesize betaine lipid. By expressing BTA1 genes, involved in the synthesis of diacylglyceryl-N,N,N-trimethyl-homoserine (DGTS), from different species, our work shows that DGTS can be produced in seed plants. In Arabidopsis, expressing BTA1 under a phosphate starvation-inducible promoter resulted in limited DGTS production without having any impact on plant growth or lipid remodeling. In transient expression systems in Nicotiana benthamiana, leaves were able to accumulate DGTS up to 20 % of their glycerolipid content at a slight expense of galactolipid and phospholipid production. At the subcellular level, we showed that DGTS is absent from plastid and seems to be enriched in endomembrane, driving an ER membrane proliferation. Finally, DGTS synthesis pathway seems to compete with PC synthesis via the Kennedy pathway but does not seem to be derived from PC diacylglycerol backbone and therefore does not interfere with the eukaryotic pathway involved in galactolipid synthesis.

plant biology↗

bioRxiv2024

AtVPS13M1 is involved in lipid remodeling in low phosphate and is located at the mitochondria surface in plants

VPS13 are conserved lipid transporters with multiple subcellular localizations playing key roles in many fundamental cellular processes. While the localization and function of VPS13 have been extensively investigated in yeast and animals, little is known about their counterparts in plants, particularly regarding their role in stress response. In this study, we characterized AtVPS13M1, one of the four VPS13 paralogs of the flowering plant Arabidopsis thaliana. We show that AtVPS13M1 binds and transports glycerolipids with a low specificity in vitro. AtVPS13M1 interferes with phospholipids degradation in response to phosphate starvation, a nutrient stress that triggers a massive remodeling of membrane lipids. AtVPS13M1 is mainly expressed in young dividing and vascular tissues. Finally, we show that AtVPS13M1 is mainly located at the surface of mitochondria in leaves. Overall, our work highlights the conserved role in lipid transport of VPS13 in plants, reveals their importance in nutrient stress response and opens important perspectives for the understanding of lipid remodeling mechanisms and for the characterization of this protein family in plants.

cell biology↗