Plant isoprenoid biology

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.

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.

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.

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.

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.

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.

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.