Descrizione del progetto
Sulle tracce di un potenziale evento di evoluzione endosimbiotica
I plastidi, compresi i cloroplasti, sono organuli fotosintetici presenti negli organismi eucarioti. I cloroplasti sono nati come cianobatteri internalizzati dagli eucarioti in una relazione simbiotica (endosimbiosi). Con il sostegno del programma di azioni Marie Skłodowska-Curie, il progetto UCYN2PLAST verificherà l’ipotesi secondo cui staremmo assistendo ai preparativi evolutivi per un evento di internalizzazione analogo. Questa volta l’agente fotosintetico potrebbe essere l’internalizzatore, un’alga eucariotica unicellulare, che accoglierebbe il cianobatterio azotofissatore per la fornitura del suo indispensabile azoto in cambio della propria materia organica. Il progetto vaglierà questa ipotesi utilizzando metodi di analisi metatranscrittomica e microscopia elettronica combinati con sonde molecolari e tecniche isotopiche quantitative applicate a campioni marini e nell’ambito di esperimenti di incubazione in acqua marina.
Obiettivo
Symbioses are evident sources of innovation in nature, critical for the evolution of plastids and the success of eukaryotes on Earth. The mechanisms promoting such relationships, however, are difficult to identify, especially between single-celled organisms, and remain largely unknown. A widespread symbiosis was recently discovered in the ocean between an unicellular cyanobacterium (UCYN-A) and single-celled eukaryotic algae (prymnesiophyte). UCYN-A lacks typical cyanobacterial features such as the capacity to perform oxygenic photosynthesis, CO2 fixation or the tricarboxylic acid cycle, and must thus rely on the supply of organic matter from the algal host. In turn, UCYN-A shows a dramatic genome reduction with a high specialization in nitrogen fixation, providing fixed nitrogen to the alga. Given the importance of nitrogen for the algal productivity, it has been hypothesized that UCYN-A could eventually give rise to a nitrogen-fixing plastid in a process analogous to the origin of chloroplasts. This project aims to study the UCYN-A symbiosis both from an evolutionary and a functional point of view: First, the identification and characterization of new associations from marine samples at a global scale through molecular techniques will allow a deep comparison of closely-related symbiotic lineages that will help to understand the evolutionary underpinnings of this symbiosis. Second, nutrient incubation experiments of seawater samples over diel cycles will be performed to identify potential factors regulating the carbon and nitrogen exchange between partners to gain knowledge on the host-symbiont coupling mechanisms. For this purpose, metatranscriptomic analysis and electron microscopy combined with molecular probes and quantitative isotopic techniques (FISH-nanoSIMS) will be applied. Elucidating the mechanisms underlying this unusual nitrogen fixing symbiosis will provide valuable insight into previously unknown processes explaining the evolution of plastids
Campo scientifico
- natural sciencesbiological sciencesmicrobiologyphycology
- natural sciencesphysical sciencesopticsmicroscopyelectron microscopy
- natural sciencesbiological sciencesbiological behavioural sciencesethologybiological interactions
- natural sciencesbiological sciencesgeneticsgenomes
- natural sciencesbiological sciencesbotany
Parole chiave
Programma(i)
Argomento(i)
Meccanismo di finanziamento
MSCA-IF - Marie Skłodowska-Curie Individual Fellowships (IF)Coordinatore
75006 Paris
Francia