ERC FUNDED PROJECTS

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

2 498 207 €

Start date: 2020-01-01, End date: 2024-12-31

Diatoms are major contributors of primary production in the ocean and participate in carbon sequestration over geologically relevant timescales. As key components of the Earth’s carbon cycle and marine food webs we need to understand the eco-evolutionary underpinnings of their ecological success to forecast their fate in a future ocean impacted by anthropogenic change. Genomes and epigenomes from model diatoms, as well as hundreds of transcriptomes from multiple species, have revealed genetic and epigenetic processes regulating gene expression in response to changing environments. The Tara Oceans survey has in parallel generated resources to explore diatom abundance, diversity and gene expression in the world’s ocean in widely contrasting conditions. DIATOMIC will build on these resources to understand how evolutionary and ecological processes combine to influence diatom adaptations to their environment at unprecedented spatiotemporal scales. To examine these processes over timescales relevant to current climate change, DIATOMIC includes the pioneering exploration of ancient diatom DNA from the sub-seafloor to reveal the genetic and epigenetic bases of speciation and adaptation that have impacted their ecological success during the last 100,000 years, when Earth experienced major climatological events and an increase in anthropogenic impacts. As a model for exploring eco-evolutionary processes in the past and contemporary ocean we will focus primarily on Chaetoceros because this diatom genus is ancient, ubiquitous, abundant and contributes significantly to carbon export. Key findings will be additionally supported by lab-based studies using the diatom Phaeodactylum for which exemplar molecular tools exist. Specifically, the project will address: 1. What molecular features characterize genome evolution in diatoms? 2. Which processes determine diatom metapopulation structure? 3. What can ancient DNA tell us about diatom adaptations to environmental change in the past?

2 495 753 €

Start date: 2019-11-01, End date: 2024-10-31

About 500 million years ago, the two sister groups of vertebrates independently evolved alternative forms of adaptive immunity, representing a striking example of convergent evolution. Whereas the components and functions of the immune system in jawed vertebrates (ranging from sharks to humans) are well characterized, much remains to be learned about adaptive immunity in jawless vertebrates (lampreys and hagfishes). Up to now, progress in understanding immunity in jawless fishes was hampered by their complex life-cycle, long generation time, and the difficulty of raising fish in the laboratory for extended periods, particularly after in vitro fertilization. Based on our recent methodological advances in aquatic husbandry and successful CRISPR/Cas9-mediated genetic modification, we propose to conduct a large-scale analysis of cellular immunity in lampreys laying the foundations for the identification of the unifying principles of vertebrate immunity. Our experiments will address the development and characteristics of different T cell subsets, the molecular basis of antigen receptor assembly, and the function of the two principal T cell lineages during the immune response. We will also examine the structure and function of the stromal microenvironment in the lamprey thymus equivalent, which is considered to be the site of T cell development. A particular focus will be on the functional analysis of a recently discovered MHC-like locus in the context of T cell development, and in the essential self/nonself discrimination mechanism(s) at play during the immune response. We expect that the identification of common design principles of adaptive immunity in vertebrates will provide us with an unprecedented view on immune functions in humans, potentially guiding the development of novel strategies for the treatment of failing immunity in patients with immunodeficiency and/or autoimmunity.

2 498 813 €

Start date: 2019-06-01, End date: 2024-05-31

Apicomplexan are obligatory intracellular parasites. The ability of these parasites (Plasmodium, Toxoplasma) to cause disease depends on the coordinated secretion of specialized secretory organelles. The rhoptries are particularly important, because they act as the apicomplexan equivalent of bacterial secretion systems. They inject parasite proteins directly in the cytoplasm of host cells not only for invasion but also to hijack host functions crucial to establish and maintain infection. However, in contrast to bacteria where the secretion machinery has been resolved to atomic detail, how eukaryotic parasites secrete and inject rhoptry effectors into cells is an enigma. This proposal aims to dissect the mechanistic steps and the molecular components that assemble the rhoptry secretion machine. Our aims are: 1- To explore the mechanisms that trigger rhoptry exocytosis upon binding of the parasite to the host cell. 2- To provide insights into fusion machinery of rhoptry with the parasite plasma membrane. Our model is based on the discovery that free-living Ciliates and intracellular Apicomplexa share an evolutionarily conserved blueprint for their fusion mechanism. 3- To test and expand our hypothesis that rhoptries deliver their content through a transient pore formed into the host cell membrane. We will employ powerful experimental systems in Toxoplasma, Plasmodium and the Ciliate Tetrahymena, taking full advantage of the relative strength of each model. This comprehensive project will bring together comparative genomics, targeted and global genetics, biochemistry, high resolution imaging and electrophysiology. This project answers a question of fundamental biological importance. How can a parasite sense the host cell and inject virulence factors to attain control? Understanding this mechanism will guide future efforts to disrupt parasite infection and will contribute to broader understanding of fascinating questions of membrane fusion and export processes.

2 496 210 €

Start date: 2020-10-01, End date: 2025-09-30