Plant isoprenoid biology

Group leader : Hubert SCHALLER

Research area

The main research objective of the Plant Isoprenoid Biology team is the identification and characterization of regulators acting on cellular homeostasis of essential isoprenoids (sterols, steroids, terpenoid hormones, etc). We pursue cellular and genetic studies in Arabidopsis thaliana, Nicotiana tabacum, and Hordeum vulgare to provide a refined understanding of critical roles of specific compounds in biological processes and signaling. The team has an ongoing cooperation action with the Universidade Federal Do Para (UFPA), Belém, Brasil framed by an agreement of International Associated Laboratory « LIA – PALMHEAT ».

Isoprenoids (syn. Terpenoids) are produced by distinct cellular compartments and several different pathways. These pathways are largely characterized in terms of enzymes, metabolic intermediates and pathway end-products. However, regulatory mechanisms governing their production in an orchestrated manner with the cell metabolism are not fully described. In addition, the role of certain compounds such as sterols in the normal processes of growth and development is essential but this is not well understood. In fact, the complexity of a plant sterol profile (compared to mammals) may indicate multiple biological functions for these metabolites. Moreover, the molecular regulation of sterol lipid storage is not comprehensively documented. To identify these regulatory mechanisms, we are developing experimental approaches comprising genetic screens, biochemistry and analytical chemistry, the analysis of transcriptomes and proteomes of selected plant materials, and cell imaging to visualize via sensors the recruitment of cell compartments for the biogenesis of isoprenoid precursors. There is a considerable interest to understand the control of isoprenoid synthesis and accumulation in plant cells or organs since (i) these molecules are implicated in basic processes (membrane structure and biology, photosynthesis, respiration, and signaling) and in biotic interactions, and (ii) these molecules are bioactive compounds of medicinal and industrial value.



Plant growth and the isoprenoid pathway

Project manager: Hubert SCHALLER

Isoprenoids are hormones, photosynthetic pigments, vitamins, membrane lipids, and some other compounds essential for viability. The regulation of key biosynthetic segments (plastidial, cytosolic), and the integration of those in the cellular metabolism are yet poorly understood. Targeted modulations of gene expression and the implementation of genetic screens in Arabidopsis thaliana and Hordeum vulgare (barley) are approaches that currently provide us with novel sound material to further understand isoprenoid homeostasis and growth. This is of paramount interest to design a future strategy for crop improvement.

Regulation of protein prenylation

Project manager: Andréa HEMMERLIN

Protein prenylation is a posttranslational modification required in a variety of signaling pathways. In plants, protein prenyltransferases catalyzing this lipidation recruit prenyl diphosphates from different cellular compartments, this to guarantee a continuous prenylation of proteins with essential functions. This flexible metabolic modulation of protein prenylation in plants represents a perfect model to study the regulation of isoprenoid biosynthesis, the exchanges of isoprenoid precursors between cell compartments, but also for the screening of chemical compounds being able to interfere or deregulate this cellular process.

Triterpene metabolic diversity

Project manager: Hubert SCHALLER

Plants produce a wealth of triterpenes that may accumulate in specialized cells like for instance the laticifers from Euphorbia species. Other plants like Arabidopsis thaliana display a set of triterpene synthases of which some are essential for cell viability and some others are apparently dispensable. The thorough mass spectrometry analysis of chemical profiles and the elucidation of triterpene functions is a major goal of this project. The project is also linked to the valorization of valuable compounds as fine chemicals or raw materials in the frame of knowledge-based bio-economy.

Sterol biogenesis and functions in growth

Project managers: Hubert SCHALLER, Sylvain DARNET

Sterols are key membrane components and precursors of growth-regulators (brassinosteroids). Higher plants have evolved specific biosynthetic features that have no counterpart in metazoans. Our objective is to decipher the essential role of eg sitosterol and other plant-typical sterols at the cellular and molecular levels.

Heat stress response in a palm tree of the Amazon

Project managers: Sylvain DARNET, Hubert SCHALLER

The project is framed by a cooperation between the University Federal of Pará (UFPA, Belém, Brasil) and the IBMP (LIA CNRS “PALMHEAT”). Euterpe oleracea, a palm tree of the Amazon also known as “açai” displays an active specialized metabolism resulting in the accumulation of high amounts of isoprenoids. A prominent feature of that crop plant from a tropical agroforestry ecosystem or mangrove forest is its adaptation to heat stress episodes, high UV radiation, or long periods of flooding that cause root anoxia. The objective of this collaborative research is to identify key genetic elements responsible for such an adaptation.

Foliar lipid accumulation

Project manager: Anne BERNA

Oil storage is an important agricultural trait not only in seeds but also in leaves. Some crops like Nicotiana tabacum (tobacco) are currently evaluated for biomass and hydrocarbon production. We pursue the genetic, cellular and biochemical characterization of sterol acylation in several plant lines that display an hypercholesterolemic phenotype resulting in lipid droplet storage in photosynthetic organs.

Terpenoid metabolism of in microbiota-plant interactions

Project manager: Florence ARSÈNE-PLOETZE

Thanks to the recent development of the environmental microbial and genomic approaches, a precise inventory of the bacterial communities interacting with Arabidopsis thaliana, tobacco, or barley has been done. Many bacteria associated with these plants have been isolated. Using “omics” approaches, FISH, and classical microbiology, we examine the influence of microbial communities on the plant isoprenoids metabolism, on the one hand, and, on the other hand, the role that isoprenoids could have on the microbial community.