Regulation of glycerolipids interconversion in plants in response to environmental variations – Reglisse

This project is based on the use of genetics and chemical genetics (this last one is used to circumvent the problems of genetic redundancy)

Identification of transcriptional control taking place very rapidly
Identification of key enzyme involved in glycerolipids remodeling
identification of link between Pi signaling and plant hormonal pathway.

Identification of plant compounds and enzymes triggering glycerolipids remodeling.

Arnaud et al (2014). Identification of phosphatin, a drug alleviating Pi starvation responses in Arabidopsis. Plant Physiol. 166 :1479-1491
Chevalier et al. « Chemical genetics in dissecting membrane glycerolipid functions. In Lipids in Plants and Algae development. Nakamura and Li-Beisson eds. Springer. Subcell Biochem 86, 159-75.
Chevalier et al (2015) Identification par deux criblages simultanés indépendants d’une famille d’inhibiteurs du métabolisme des glycérolipides. Med Sci Paris, 2015, 31(3): 320-327
Bonnot et al (2015). A chemical genetic strategy identify the PHOSTIN, a synthetic molecule that triggers phosphate starvation responses in Arabidopsis thaliana. New Phytol.
Kanno et al. 2016. Performance and Limitations of Phosphate Quantification: Guidelines for Plant Biologists. Plant Cell Physiol. 57, 690-706
Michaud et al. (2016) A tethering complex between mitochondrial membranes is involved in plant lipid trafficking. Curr. Biol. 26(5): 627-639
Botella et al. (2016) ALA10, a phospholipid flippase, controls FAD2/FAD3 desaturation of phosphatidylcholine in the ER, and affects chloroplast lipid composition in Arabidopsis thaliana. Plant Physiol. 170 (3):1300-1314
Rocha et al. (2016) Structural insights and membrane binding properties of MGD1, the major galactolipid synthase in plants. Plant J. 85 (5):622-633
Bastien et al. (2016) New insights on thylakoid biogenesis in plant cells. Int. Rev. Cell Mol. Biol. 323, 2016, 323, 1-30.

Phosphate (Pi) is an essential plant macro nutrient, present in limiting amounts in most soils worldwide. Pi fertilizers are therefore massively used to increase plant yield production. Pi is a non-renewable resource and its utilization promotes negative effects on environment (such as eutrophication of rivers and marine coasts). Improving the recovery and the use by plants of the Pi present in soils is therefore crucial. The REGLISSE project aims at gaining knowledge on the plant response to Pi changes in soils, focusing on the important lipid remodelling that Pi variations trigger in cell membranes. In plants, up to one third of Pi can be found in phospholipids. During Pi starvation, plants modulate the lipid balance to favor production of sulfo- and galactolipids, sparing thus Pi. This lipid remodelling implies a readjustment of the biosynthetic pathways generating each lipid class and also the induction of lipid conversions and trafficking within the cell. At the transcriptional level, a striking response of genes coding for phospholipid breakdown and plastid glycolipid syntheses is observed (induction of PLD?1, PLD?2, NPC4, NPC5, SQD2, MGD2, MGD3, PENMT1, DGD2 and repression of PENMT2, ATS1, ATS2). All these genes are involved in the tuning of the phospholipid vs glycolipid balance. They are far from covering all transcriptional and post-transcriptional mechanisms controlling this reorchestration, which remain mostly unknown despite their crucial physiological importance. We intend to identify missing actors involved in such process. We will define a referential temporal order of this reprogramming (for transcriptomic and lipidomic profiles), which has not been assessed to date, and look for additional missing and determining components. Our strategy will benefit from combination of classical genetics (mutant affecting Pi sensing) and chemical genetics with the use of small molecules to highlight responding genes and facilitate the dissection of the regulatory mechanisms. Available compounds patented by both partners used for this study are Phostin and Phosphatin, which induce or repress responses triggered by Pi variations and Galvestine-1, a drug inhibiting the synthesis of galactolipids (a main pathways induced by Pi starvation). Other new components inhibiting specific steps of glycerolipids synthesis will be searched.
Lipidome modifications are tightly associated with various additional traits promoted by Pi deficiency. It is therefore difficult to evaluate the real impact of lipidome modifications on plant physiology. This proposal thus circumvents such limitation by using various genetic tools (mutants or drugs identified by a chemical genetic strategy deployed by partners of this proposal) to uncouple glycerolipids remodeling from Pi supply. Understanding how plants regulate the glycerolipids in response to Pi supply in soil, identifying and validating novel actors involved in this process, studying physiological impact of these modifications and searching ways to control this phenomenon are the objectives of this research proposal. The REGLISSE project will therefore produce basic knowledge that should be useful for future agronomic exploitation of the plant lipid biomass and improvement of Pi management strategies.