Description du projet
Explorer des réactions dépendantes de la lumière qui maximisent la photosynthèse du phytoplancton
La photosynthèse, un processus biologique important sur notre planète, a permis la colonisation sur terre et mer par les plantes et le phytoplancton, respectivement. Les recherches se concentrent désormais sur l’élucidation de ce processus chez le phytoplancton. D’un point de vue énergétique, une microalgue est un «véhicule» contenant des mitochondries (un moteur à combustion utilisant du carbone pour produire de l’énergie et du CO2) et des chloroplastes (un panneau solaire utilisant la lumière pour produire de l’énergie et de l’O2). À l’aide d’approches optogénétiques et de l’imagerie cellulaire ou sous-cellulaire, le projet ChloroMito, financé par l’UE, examinera l’hypothèse selon laquelle l’efficacité photosynthétique des microalgues océaniques est provoquée par l’étroite liaison entre leur panneau solaire et leur moteur à combustion. Les recherches permettront de mieux comprendre la manière dont les interactions énergétiques sous-cellulaires optimisent la photosynthèse chez le phytoplancton marin.
Objectif
Photosynthesis emerged as an energy-harvesting process at least 3.5 billion years ago, first in anoxygenic bacteria and then in oxygen-producing organisms, which led to the evolution of complex life forms with oxygen-based metabolisms (e.g. humans). Oxygenic photosynthesis produces ATP and NADPH, and the correct balance between these energy-rich molecules allows assimilation of CO2 into organic matter. Although the mechanisms of ATP/NADPH synthesis are well understood, less is known about how CO2 assimilation was optimised. This process was essential to the successful phototrophic colonisation of land (by Plantae) and the oceans (by phytoplankton). Plants optimised CO2 assimilation using chloroplast-localised ATP-generating processes to control the ATP/NADPH ratio, but the strategies developed by phytoplankton are poorly understood. However, diatoms—ecologically successful ocean organisms—are known to control this ratio by exchanging energy between plastids and mitochondria. Is this mechanism a paradigm for optimisation of photosynthesis in the ocean? The ChloroMito project aims to first decipher the mechanism(s) behind plastid-mitochondria interactions. Thanks to a novel combination of whole-cell approaches, including (opto)genetics, cellular tomography and single-cell spectroscopy, we will identify the nature of the exchanges occurring in diatoms and assess their contribution to dynamic responses to environmental stimuli (light, temperature, nutrients). We will then assess conservation of this mechanism in ecologically relevant phytoplankton taxa, test its role in supporting different lifestyles (autotrophy, mixotrophy, photosymbiosis) encountered in the ocean, and track transitions between these different lifestyles as part of an unprecedented effort to visualise ocean dynamics. Overall, the ChloroMito project will alter our understanding of ocean photosynthesis, challenging textbook concepts which are often inferred from plant-based concepts
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ERC-ADG - Advanced GrantInstitution d’accueil
75794 Paris
France