More than 100 million genes from the marine world have been catalogued in a collaborative effort to deepen our understanding of ocean life.
The Tara Oceans expedition (2009-2013) enabled the collection of plankton samples in all of the world's oceans on board the schooner Tara. The teams from the CEA, French National Centre for Scientific Research (CNRS), European Molecular Biology Laboratory (EMBL) and the French graduate school ENS, have built on its work to analyse the expression of genes belonging to complex organisms, from microscopic algae to small planktonic animals.
The teams have demonstrated that very different genes express themselves depending on the water temperature or the concentration in nutrients of the oceanic areas studied.
Half of these genes are unknown, indicating that the ocean harbours an enormous potential of genetic functions awaiting discovery.
By using isolation and characterisation methods of isolated cells, the researchers have explored the role of the genes present in a little-studied and uncultivated compartment of the plankton – the first link in a long food chain. These results are the subject of two articles published in the journal Nature Communications 22 and 25 in January.
Comprising about 117 million different sequences, this catalogue has been created thanks to the isolation of the genes expressed in more than 400 samples collected during the expedition.
This massive DNA sequencing approach without the isolation of organisms is called metatranscriptomic.
"Thanks to this work, small organisms that are more complex than the bacteria that form most of oceanic plankton are beginning to be unveiled," a Tara Oceans spokesperson said.
"It opens up numerous opportunities to understand oceanic ecology with the help of sentinel genes. Among other things, it is becoming possible to study the major biogeochemical processes of the ocean based on the expression of these markers."
